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Zhengtao Wang - One of the best experts on this subject based on the ideXlab platform.
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comparative analysis of toxic components in different medicinal parts of gynura japonica and its toxicity assessment on mice
Phytomedicine, 2019Co-Authors: Aizhen Xiong, Li Yang, Xiao Yang, Wen-xing Ding, Lianxiang Fang, Youlin Shao, Suocai Zhang, Jian Zheng, Zhengtao WangAbstract:Abstract Background The roots of Gynura japonica are used as traditional medicine for treating blood stasis or traumatic injury even though hundreds of hepatic sinusoidal obstruction syndrome cases have been reported after consumption of the roots, which contain large amounts of hepatotoxic pyrrolizidine alkaloids (HPAs). However, no information is available about the toxic compounds in the aerial parts of G. japonica, which are also used as herbal medicines and even vegetables in several areas. Thus, the toxic chemicals in the aerial parts of G. japonica, i.e., HPAs, must be urgently identified. Purpose In this study, we aimed to 1) identify the toxic compounds in different medicinal parts and 2) examine the hepatotoxicity of G. japonica. Study design A total of 35 batches of the roots and aerial parts of G. japonica were collected from different sources and analyzed for HPAs. The hepatotoxicity of different extracts (i.e., total extracts [TE] and total alkaloids [TA]) and a single compound (i.e., Senecionine) was evaluated on mice. Methods Qualitative analysis of HPAs was performed using an ultra-performance liquid chromatography (UPLC)-mass spectrometry (MS)-parent ion scan approach, whereas a quantitative assay was performed by a UPLC-MS-selected ion monitoring approach. Male C57BL mice were orally administered the different extracts or the single compound at dosages equivalent to 50 mg HPAs/kg body weight. The sera and the livers were collected at 48 h after treatment and used to evaluate the hepatotoxicity through serum clinical biomarkers assay, liver histology, and bile acid profiling. Results A total of 21 HPAs were identified in the roots and the aerial parts. The roots contained higher levels of HPAs (4.90 mg/g) than did the aerial parts (2.21 mg/g). TE and TA induced similar acute liver injuries, but Senecionine was considerably more toxic than these extracts. Mice treated with TE showed significantly impaired bile acid homeostasis in the sera and the livers. Conclusion The roots and aerial parts of G. japonica contained large amounts of HPAs, including Senecionine, which were responsible for the hepatotoxicity of G. japonica. Bile acid homeostasis was uniquely impaired after exposure to the plant. Therefore, neither the roots nor the aerial parts of G. japonica should be consumed as medicines or vegetables.
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inhibition of drp1 protects against Senecionine induced mitochondria mediated apoptosis in primary hepatocytes and in mice
Redox biology, 2017Co-Authors: Xiao Yang, Aizhen Xiong, Zhengtao Wang, Hua Wang, Hiromi Sesaki, Wen-xing Ding, Li YangAbstract:Pyrrolizidine alkaloids (PAs) are a group of compounds found in various plants and some of them are widely consumed in the world as herbal medicines and food supplements. PAs are potent hepatotoxins that cause irreversible liver injury in animals and humans. However, the mechanisms by which PAs induce liver injury are not clear. In the present study, we determined the hepatotoxicity and molecular mechanisms of Senecionine, one of the most common toxic PAs, in primary cultured mouse and human hepatocytes as well as in mice. We found that Senecionine administration increased serum alanine aminotransferase levels in mice. H&E and TUNEL staining of liver tissues revealed increased hemorrhage and hepatocyte apoptosis in liver zone 2 areas. Mechanistically, Senecionine induced loss of mitochondrial membrane potential, release of mitochondrial cytochrome c as well as mitochondrial JNK translocation and activation prior to the increased DNA fragmentation and caspase-3 activation in primary cultured mouse and human hepatocytes. SP600125, a specific JNK inhibitor, and ZVAD-fmk, a general caspase inhibitor, alleviated Senecionine-induced apoptosis in primary hepatocytes. Interestingly, Senecionine also caused marked mitochondria fragmentation in hepatocytes. Pharmacological inhibition of dynamin-related protein1 (Drp1), a protein that is critical to regulate mitochondrial fission, blocked Senecionine-induced mitochondrial fragmentation and mitochondrial release of cytochrome c and apoptosis. More importantly, hepatocyte-specific Drp1 knockout mice were resistant to Senecionine-induced liver injury due to decreased mitochondrial damage and apoptosis. In conclusion, our results uncovered a novel mechanism of Drp1-mediated mitochondrial fragmentation in Senecionine-induced liver injury. Targeting Drp1-mediated mitochondrial fragmentation and apoptosis may be a potential avenue to prevent and treat hepatotoxicity induced by PAs.
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Inhibition of Drp1 protects against Senecionine-induced mitochondria-mediated apoptosis in primary hepatocytes and in mice
Elsevier, 2017Co-Authors: Xiao Yang, Aizhen Xiong, Zhengtao Wang, Hua Wang, Hiromi Sesaki, Wen-xing Ding, Li YangAbstract:Pyrrolizidine alkaloids (PAs) are a group of compounds found in various plants and some of them are widely consumed in the world as herbal medicines and food supplements. PAs are potent hepatotoxins that cause irreversible liver injury in animals and humans. However, the mechanisms by which PAs induce liver injury are not clear. In the present study, we determined the hepatotoxicity and molecular mechanisms of Senecionine, one of the most common toxic PAs, in primary cultured mouse and human hepatocytes as well as in mice. We found that Senecionine administration increased serum alanine aminotransferase levels in mice. H&E and TUNEL staining of liver tissues revealed increased hemorrhage and hepatocyte apoptosis in liver zone 2 areas. Mechanistically, Senecionine induced loss of mitochondrial membrane potential, release of mitochondrial cytochrome c as well as mitochondrial JNK translocation and activation prior to the increased DNA fragmentation and caspase-3 activation in primary cultured mouse and human hepatocytes. SP600125, a specific JNK inhibitor, and ZVAD-fmk, a general caspase inhibitor, alleviated Senecionine-induced apoptosis in primary hepatocytes. Interestingly, Senecionine also caused marked mitochondria fragmentation in hepatocytes. Pharmacological inhibition of dynamin-related protein1 (Drp1), a protein that is critical to regulate mitochondrial fission, blocked Senecionine-induced mitochondrial fragmentation and mitochondrial release of cytochrome c and apoptosis. More importantly, hepatocyte-specific Drp1 knockout mice were resistant to Senecionine-induced liver injury due to decreased mitochondrial damage and apoptosis. In conclusion, our results uncovered a novel mechanism of Drp1-mediated mitochondrial fragmentation in Senecionine-induced liver injury. Targeting Drp1-mediated mitochondrial fragmentation and apoptosis may be a potential avenue to prevent and treat hepatotoxicity induced by PAs. Keywords: Senecionine, Drp1, Mitochondria, Apoptosis, Liver injur
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metabolomic and genomic evidence for compromised bile acid homeostasis by Senecionine a hepatotoxic pyrrolizidine alkaloid
Chemical Research in Toxicology, 2014Co-Authors: Aizhen Xiong, Li Yang, Xiuli Wang, Fan Yang, Lianxiang Fang, Yujui Yvonne Wan, Karl Wah Keung Tsim, Zhengtao WangAbstract:Pyrrolizidine alkaloids (PAs) are among the most hepatotoxic natural products that produce irreversible injury to humans via the consumption of herbal medicine and honey, and through tea preparation. Toxicity and death caused by PA exposure have been reported worldwide. Metabolomics and genomics provide scientific and systematic views of a living organism and have become powerful techniques for toxicology research. In this study, Senecionine hepatotoxicity on rats was determined via a combination of metabolomic and genomic analyses. From the global analysis generated from two omics data, the compromised bile acid homeostasis in vivo was innovatively demonstrated and confirmed. Serum profiling of bile acids was altered with significantly elevated conjugated bile acids after Senecionine exposure, which was in accordance with toxicity. Similarly, the hepatic mRNA levels of several key genes associated with bile acid metabolism were significantly changed. This process included cholesterol 7-α hydroxylase, bile acid CoA-amino acid N-acetyltransferase, sodium taurocholate cotransporting polypeptide, organic anion-transporting polypeptides, and multidrug-resistance-associated protein 3. In conclusion, a cross-omics study provides a comprehensive analysis method for studying the toxicity caused by Senecionine, which is a hepatotoxic PA. Moreover, the change in bile acid metabolism and the respective transporters may provide a new PA toxicity mechanism.
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uplc ms based metabolomics study on senecio scandens and s vulgaris an approach for the differentiation of two senecio herbs with similar morphology but different toxicity
Metabolomics, 2012Co-Authors: Aizhen Xiong, Li Yang, Xuejing Yang, Changhong Wang, Zhengtao Wang, Lili Ji, Z T Wang, Ying Chen, Xiuli WangAbstract:Pyrrolizidine alkaloids show significant hepatotoxicity as they can bind to DNA or proteins after being activated in liver. Senecio vulgaris L., like many Compositae herbs containing pyrrolizidine alkaloids, was reported to have great hepatotoxicity. However, Senicio scandens Buch.-Ham., from the same genus, which was also used as a herb and documented in China Pharmacopoeia published in 2010, hardly showed any side effects or relevant toxicity. In the present study, we conducted the metabolomics study using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) to obtain the different metabolic profiles of the two Senecio herbs. In addition, principle component analysis (PCA) and orthogonal projections to latent structures-discriminant analysis (OPLS-DA) were introduced for the multivariate analysis, and MS/MS was applied to the identification of target alkaloid markers which contributed most to the established models. As a result, ten pyrrolizidine alkaloids, including adonifoline, Senecionine, Senecionine N-oxide, retrorsine, retrorsine N-oxide and seneciphylline, were selected and identified. Among them, adonifoline was found to be a specific marker for S. scandens while Senecionine and its N-oxidative were characteristic markers for S. vulgaris. Furthermore, the hepatotoxicity studies in vivo and in vitro showed that Senecionine had more potent toxicity (LD50, 57.3 mg/kg; IC50, 5.41 μM) than that of adonifonine (LD50, 163.3 mg/kg; IC50, 49.91 μM). Taken together, the present study provides not only better understanding of the different toxicity between the two Senecio herbs containing pyrrolizidine alkaloids but also a reference method, which can be applied to other genetically closed species with similar morphology but different toxicity.
Aizhen Xiong - One of the best experts on this subject based on the ideXlab platform.
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comparative analysis of toxic components in different medicinal parts of gynura japonica and its toxicity assessment on mice
Phytomedicine, 2019Co-Authors: Aizhen Xiong, Li Yang, Xiao Yang, Wen-xing Ding, Lianxiang Fang, Youlin Shao, Suocai Zhang, Jian Zheng, Zhengtao WangAbstract:Abstract Background The roots of Gynura japonica are used as traditional medicine for treating blood stasis or traumatic injury even though hundreds of hepatic sinusoidal obstruction syndrome cases have been reported after consumption of the roots, which contain large amounts of hepatotoxic pyrrolizidine alkaloids (HPAs). However, no information is available about the toxic compounds in the aerial parts of G. japonica, which are also used as herbal medicines and even vegetables in several areas. Thus, the toxic chemicals in the aerial parts of G. japonica, i.e., HPAs, must be urgently identified. Purpose In this study, we aimed to 1) identify the toxic compounds in different medicinal parts and 2) examine the hepatotoxicity of G. japonica. Study design A total of 35 batches of the roots and aerial parts of G. japonica were collected from different sources and analyzed for HPAs. The hepatotoxicity of different extracts (i.e., total extracts [TE] and total alkaloids [TA]) and a single compound (i.e., Senecionine) was evaluated on mice. Methods Qualitative analysis of HPAs was performed using an ultra-performance liquid chromatography (UPLC)-mass spectrometry (MS)-parent ion scan approach, whereas a quantitative assay was performed by a UPLC-MS-selected ion monitoring approach. Male C57BL mice were orally administered the different extracts or the single compound at dosages equivalent to 50 mg HPAs/kg body weight. The sera and the livers were collected at 48 h after treatment and used to evaluate the hepatotoxicity through serum clinical biomarkers assay, liver histology, and bile acid profiling. Results A total of 21 HPAs were identified in the roots and the aerial parts. The roots contained higher levels of HPAs (4.90 mg/g) than did the aerial parts (2.21 mg/g). TE and TA induced similar acute liver injuries, but Senecionine was considerably more toxic than these extracts. Mice treated with TE showed significantly impaired bile acid homeostasis in the sera and the livers. Conclusion The roots and aerial parts of G. japonica contained large amounts of HPAs, including Senecionine, which were responsible for the hepatotoxicity of G. japonica. Bile acid homeostasis was uniquely impaired after exposure to the plant. Therefore, neither the roots nor the aerial parts of G. japonica should be consumed as medicines or vegetables.
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inhibition of drp1 protects against Senecionine induced mitochondria mediated apoptosis in primary hepatocytes and in mice
Redox biology, 2017Co-Authors: Xiao Yang, Aizhen Xiong, Zhengtao Wang, Hua Wang, Hiromi Sesaki, Wen-xing Ding, Li YangAbstract:Pyrrolizidine alkaloids (PAs) are a group of compounds found in various plants and some of them are widely consumed in the world as herbal medicines and food supplements. PAs are potent hepatotoxins that cause irreversible liver injury in animals and humans. However, the mechanisms by which PAs induce liver injury are not clear. In the present study, we determined the hepatotoxicity and molecular mechanisms of Senecionine, one of the most common toxic PAs, in primary cultured mouse and human hepatocytes as well as in mice. We found that Senecionine administration increased serum alanine aminotransferase levels in mice. H&E and TUNEL staining of liver tissues revealed increased hemorrhage and hepatocyte apoptosis in liver zone 2 areas. Mechanistically, Senecionine induced loss of mitochondrial membrane potential, release of mitochondrial cytochrome c as well as mitochondrial JNK translocation and activation prior to the increased DNA fragmentation and caspase-3 activation in primary cultured mouse and human hepatocytes. SP600125, a specific JNK inhibitor, and ZVAD-fmk, a general caspase inhibitor, alleviated Senecionine-induced apoptosis in primary hepatocytes. Interestingly, Senecionine also caused marked mitochondria fragmentation in hepatocytes. Pharmacological inhibition of dynamin-related protein1 (Drp1), a protein that is critical to regulate mitochondrial fission, blocked Senecionine-induced mitochondrial fragmentation and mitochondrial release of cytochrome c and apoptosis. More importantly, hepatocyte-specific Drp1 knockout mice were resistant to Senecionine-induced liver injury due to decreased mitochondrial damage and apoptosis. In conclusion, our results uncovered a novel mechanism of Drp1-mediated mitochondrial fragmentation in Senecionine-induced liver injury. Targeting Drp1-mediated mitochondrial fragmentation and apoptosis may be a potential avenue to prevent and treat hepatotoxicity induced by PAs.
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Inhibition of Drp1 protects against Senecionine-induced mitochondria-mediated apoptosis in primary hepatocytes and in mice
Elsevier, 2017Co-Authors: Xiao Yang, Aizhen Xiong, Zhengtao Wang, Hua Wang, Hiromi Sesaki, Wen-xing Ding, Li YangAbstract:Pyrrolizidine alkaloids (PAs) are a group of compounds found in various plants and some of them are widely consumed in the world as herbal medicines and food supplements. PAs are potent hepatotoxins that cause irreversible liver injury in animals and humans. However, the mechanisms by which PAs induce liver injury are not clear. In the present study, we determined the hepatotoxicity and molecular mechanisms of Senecionine, one of the most common toxic PAs, in primary cultured mouse and human hepatocytes as well as in mice. We found that Senecionine administration increased serum alanine aminotransferase levels in mice. H&E and TUNEL staining of liver tissues revealed increased hemorrhage and hepatocyte apoptosis in liver zone 2 areas. Mechanistically, Senecionine induced loss of mitochondrial membrane potential, release of mitochondrial cytochrome c as well as mitochondrial JNK translocation and activation prior to the increased DNA fragmentation and caspase-3 activation in primary cultured mouse and human hepatocytes. SP600125, a specific JNK inhibitor, and ZVAD-fmk, a general caspase inhibitor, alleviated Senecionine-induced apoptosis in primary hepatocytes. Interestingly, Senecionine also caused marked mitochondria fragmentation in hepatocytes. Pharmacological inhibition of dynamin-related protein1 (Drp1), a protein that is critical to regulate mitochondrial fission, blocked Senecionine-induced mitochondrial fragmentation and mitochondrial release of cytochrome c and apoptosis. More importantly, hepatocyte-specific Drp1 knockout mice were resistant to Senecionine-induced liver injury due to decreased mitochondrial damage and apoptosis. In conclusion, our results uncovered a novel mechanism of Drp1-mediated mitochondrial fragmentation in Senecionine-induced liver injury. Targeting Drp1-mediated mitochondrial fragmentation and apoptosis may be a potential avenue to prevent and treat hepatotoxicity induced by PAs. Keywords: Senecionine, Drp1, Mitochondria, Apoptosis, Liver injur
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metabolomic and genomic evidence for compromised bile acid homeostasis by Senecionine a hepatotoxic pyrrolizidine alkaloid
Chemical Research in Toxicology, 2014Co-Authors: Aizhen Xiong, Li Yang, Xiuli Wang, Fan Yang, Lianxiang Fang, Yujui Yvonne Wan, Karl Wah Keung Tsim, Zhengtao WangAbstract:Pyrrolizidine alkaloids (PAs) are among the most hepatotoxic natural products that produce irreversible injury to humans via the consumption of herbal medicine and honey, and through tea preparation. Toxicity and death caused by PA exposure have been reported worldwide. Metabolomics and genomics provide scientific and systematic views of a living organism and have become powerful techniques for toxicology research. In this study, Senecionine hepatotoxicity on rats was determined via a combination of metabolomic and genomic analyses. From the global analysis generated from two omics data, the compromised bile acid homeostasis in vivo was innovatively demonstrated and confirmed. Serum profiling of bile acids was altered with significantly elevated conjugated bile acids after Senecionine exposure, which was in accordance with toxicity. Similarly, the hepatic mRNA levels of several key genes associated with bile acid metabolism were significantly changed. This process included cholesterol 7-α hydroxylase, bile acid CoA-amino acid N-acetyltransferase, sodium taurocholate cotransporting polypeptide, organic anion-transporting polypeptides, and multidrug-resistance-associated protein 3. In conclusion, a cross-omics study provides a comprehensive analysis method for studying the toxicity caused by Senecionine, which is a hepatotoxic PA. Moreover, the change in bile acid metabolism and the respective transporters may provide a new PA toxicity mechanism.
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Metabolomic and Genomic Evidence for Compromised Bile Acid Homeostasis by Senecionine, a Hepatotoxic Pyrrolizidine Alkaloid
2014Co-Authors: Aizhen Xiong, Li Yang, Fan Yang, Lianxiang Fang, Yvonne Yu-jui Wan, Xiuli WangAbstract:Pyrrolizidine alkaloids (PAs) are among the most hepatotoxic natural products that produce irreversible injury to humans via the consumption of herbal medicine and honey, and through tea preparation. Toxicity and death caused by PA exposure have been reported worldwide. Metabolomics and genomics provide scientific and systematic views of a living organism and have become powerful techniques for toxicology research. In this study, Senecionine hepatotoxicity on rats was determined via a combination of metabolomic and genomic analyses. From the global analysis generated from two omics data, the compromised bile acid homeostasis in vivo was innovatively demonstrated and confirmed. Serum profiling of bile acids was altered with significantly elevated conjugated bile acids after Senecionine exposure, which was in accordance with toxicity. Similarly, the hepatic mRNA levels of several key genes associated with bile acid metabolism were significantly changed. This process included cholesterol 7-α hydroxylase, bile acid CoA-amino acid N-acetyltransferase, sodium taurocholate cotransporting polypeptide, organic anion-transporting polypeptides, and multidrug-resistance-associated protein 3. In conclusion, a cross-omics study provides a comprehensive analysis method for studying the toxicity caused by Senecionine, which is a hepatotoxic PA. Moreover, the change in bile acid metabolism and the respective transporters may provide a new PA toxicity mechanism
Li Yang - One of the best experts on this subject based on the ideXlab platform.
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comparative analysis of toxic components in different medicinal parts of gynura japonica and its toxicity assessment on mice
Phytomedicine, 2019Co-Authors: Aizhen Xiong, Li Yang, Xiao Yang, Wen-xing Ding, Lianxiang Fang, Youlin Shao, Suocai Zhang, Jian Zheng, Zhengtao WangAbstract:Abstract Background The roots of Gynura japonica are used as traditional medicine for treating blood stasis or traumatic injury even though hundreds of hepatic sinusoidal obstruction syndrome cases have been reported after consumption of the roots, which contain large amounts of hepatotoxic pyrrolizidine alkaloids (HPAs). However, no information is available about the toxic compounds in the aerial parts of G. japonica, which are also used as herbal medicines and even vegetables in several areas. Thus, the toxic chemicals in the aerial parts of G. japonica, i.e., HPAs, must be urgently identified. Purpose In this study, we aimed to 1) identify the toxic compounds in different medicinal parts and 2) examine the hepatotoxicity of G. japonica. Study design A total of 35 batches of the roots and aerial parts of G. japonica were collected from different sources and analyzed for HPAs. The hepatotoxicity of different extracts (i.e., total extracts [TE] and total alkaloids [TA]) and a single compound (i.e., Senecionine) was evaluated on mice. Methods Qualitative analysis of HPAs was performed using an ultra-performance liquid chromatography (UPLC)-mass spectrometry (MS)-parent ion scan approach, whereas a quantitative assay was performed by a UPLC-MS-selected ion monitoring approach. Male C57BL mice were orally administered the different extracts or the single compound at dosages equivalent to 50 mg HPAs/kg body weight. The sera and the livers were collected at 48 h after treatment and used to evaluate the hepatotoxicity through serum clinical biomarkers assay, liver histology, and bile acid profiling. Results A total of 21 HPAs were identified in the roots and the aerial parts. The roots contained higher levels of HPAs (4.90 mg/g) than did the aerial parts (2.21 mg/g). TE and TA induced similar acute liver injuries, but Senecionine was considerably more toxic than these extracts. Mice treated with TE showed significantly impaired bile acid homeostasis in the sera and the livers. Conclusion The roots and aerial parts of G. japonica contained large amounts of HPAs, including Senecionine, which were responsible for the hepatotoxicity of G. japonica. Bile acid homeostasis was uniquely impaired after exposure to the plant. Therefore, neither the roots nor the aerial parts of G. japonica should be consumed as medicines or vegetables.
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inhibition of drp1 protects against Senecionine induced mitochondria mediated apoptosis in primary hepatocytes and in mice
Redox biology, 2017Co-Authors: Xiao Yang, Aizhen Xiong, Zhengtao Wang, Hua Wang, Hiromi Sesaki, Wen-xing Ding, Li YangAbstract:Pyrrolizidine alkaloids (PAs) are a group of compounds found in various plants and some of them are widely consumed in the world as herbal medicines and food supplements. PAs are potent hepatotoxins that cause irreversible liver injury in animals and humans. However, the mechanisms by which PAs induce liver injury are not clear. In the present study, we determined the hepatotoxicity and molecular mechanisms of Senecionine, one of the most common toxic PAs, in primary cultured mouse and human hepatocytes as well as in mice. We found that Senecionine administration increased serum alanine aminotransferase levels in mice. H&E and TUNEL staining of liver tissues revealed increased hemorrhage and hepatocyte apoptosis in liver zone 2 areas. Mechanistically, Senecionine induced loss of mitochondrial membrane potential, release of mitochondrial cytochrome c as well as mitochondrial JNK translocation and activation prior to the increased DNA fragmentation and caspase-3 activation in primary cultured mouse and human hepatocytes. SP600125, a specific JNK inhibitor, and ZVAD-fmk, a general caspase inhibitor, alleviated Senecionine-induced apoptosis in primary hepatocytes. Interestingly, Senecionine also caused marked mitochondria fragmentation in hepatocytes. Pharmacological inhibition of dynamin-related protein1 (Drp1), a protein that is critical to regulate mitochondrial fission, blocked Senecionine-induced mitochondrial fragmentation and mitochondrial release of cytochrome c and apoptosis. More importantly, hepatocyte-specific Drp1 knockout mice were resistant to Senecionine-induced liver injury due to decreased mitochondrial damage and apoptosis. In conclusion, our results uncovered a novel mechanism of Drp1-mediated mitochondrial fragmentation in Senecionine-induced liver injury. Targeting Drp1-mediated mitochondrial fragmentation and apoptosis may be a potential avenue to prevent and treat hepatotoxicity induced by PAs.
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Inhibition of Drp1 protects against Senecionine-induced mitochondria-mediated apoptosis in primary hepatocytes and in mice
Elsevier, 2017Co-Authors: Xiao Yang, Aizhen Xiong, Zhengtao Wang, Hua Wang, Hiromi Sesaki, Wen-xing Ding, Li YangAbstract:Pyrrolizidine alkaloids (PAs) are a group of compounds found in various plants and some of them are widely consumed in the world as herbal medicines and food supplements. PAs are potent hepatotoxins that cause irreversible liver injury in animals and humans. However, the mechanisms by which PAs induce liver injury are not clear. In the present study, we determined the hepatotoxicity and molecular mechanisms of Senecionine, one of the most common toxic PAs, in primary cultured mouse and human hepatocytes as well as in mice. We found that Senecionine administration increased serum alanine aminotransferase levels in mice. H&E and TUNEL staining of liver tissues revealed increased hemorrhage and hepatocyte apoptosis in liver zone 2 areas. Mechanistically, Senecionine induced loss of mitochondrial membrane potential, release of mitochondrial cytochrome c as well as mitochondrial JNK translocation and activation prior to the increased DNA fragmentation and caspase-3 activation in primary cultured mouse and human hepatocytes. SP600125, a specific JNK inhibitor, and ZVAD-fmk, a general caspase inhibitor, alleviated Senecionine-induced apoptosis in primary hepatocytes. Interestingly, Senecionine also caused marked mitochondria fragmentation in hepatocytes. Pharmacological inhibition of dynamin-related protein1 (Drp1), a protein that is critical to regulate mitochondrial fission, blocked Senecionine-induced mitochondrial fragmentation and mitochondrial release of cytochrome c and apoptosis. More importantly, hepatocyte-specific Drp1 knockout mice were resistant to Senecionine-induced liver injury due to decreased mitochondrial damage and apoptosis. In conclusion, our results uncovered a novel mechanism of Drp1-mediated mitochondrial fragmentation in Senecionine-induced liver injury. Targeting Drp1-mediated mitochondrial fragmentation and apoptosis may be a potential avenue to prevent and treat hepatotoxicity induced by PAs. Keywords: Senecionine, Drp1, Mitochondria, Apoptosis, Liver injur
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metabolomic and genomic evidence for compromised bile acid homeostasis by Senecionine a hepatotoxic pyrrolizidine alkaloid
Chemical Research in Toxicology, 2014Co-Authors: Aizhen Xiong, Li Yang, Xiuli Wang, Fan Yang, Lianxiang Fang, Yujui Yvonne Wan, Karl Wah Keung Tsim, Zhengtao WangAbstract:Pyrrolizidine alkaloids (PAs) are among the most hepatotoxic natural products that produce irreversible injury to humans via the consumption of herbal medicine and honey, and through tea preparation. Toxicity and death caused by PA exposure have been reported worldwide. Metabolomics and genomics provide scientific and systematic views of a living organism and have become powerful techniques for toxicology research. In this study, Senecionine hepatotoxicity on rats was determined via a combination of metabolomic and genomic analyses. From the global analysis generated from two omics data, the compromised bile acid homeostasis in vivo was innovatively demonstrated and confirmed. Serum profiling of bile acids was altered with significantly elevated conjugated bile acids after Senecionine exposure, which was in accordance with toxicity. Similarly, the hepatic mRNA levels of several key genes associated with bile acid metabolism were significantly changed. This process included cholesterol 7-α hydroxylase, bile acid CoA-amino acid N-acetyltransferase, sodium taurocholate cotransporting polypeptide, organic anion-transporting polypeptides, and multidrug-resistance-associated protein 3. In conclusion, a cross-omics study provides a comprehensive analysis method for studying the toxicity caused by Senecionine, which is a hepatotoxic PA. Moreover, the change in bile acid metabolism and the respective transporters may provide a new PA toxicity mechanism.
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Metabolomic and Genomic Evidence for Compromised Bile Acid Homeostasis by Senecionine, a Hepatotoxic Pyrrolizidine Alkaloid
2014Co-Authors: Aizhen Xiong, Li Yang, Fan Yang, Lianxiang Fang, Yvonne Yu-jui Wan, Xiuli WangAbstract:Pyrrolizidine alkaloids (PAs) are among the most hepatotoxic natural products that produce irreversible injury to humans via the consumption of herbal medicine and honey, and through tea preparation. Toxicity and death caused by PA exposure have been reported worldwide. Metabolomics and genomics provide scientific and systematic views of a living organism and have become powerful techniques for toxicology research. In this study, Senecionine hepatotoxicity on rats was determined via a combination of metabolomic and genomic analyses. From the global analysis generated from two omics data, the compromised bile acid homeostasis in vivo was innovatively demonstrated and confirmed. Serum profiling of bile acids was altered with significantly elevated conjugated bile acids after Senecionine exposure, which was in accordance with toxicity. Similarly, the hepatic mRNA levels of several key genes associated with bile acid metabolism were significantly changed. This process included cholesterol 7-α hydroxylase, bile acid CoA-amino acid N-acetyltransferase, sodium taurocholate cotransporting polypeptide, organic anion-transporting polypeptides, and multidrug-resistance-associated protein 3. In conclusion, a cross-omics study provides a comprehensive analysis method for studying the toxicity caused by Senecionine, which is a hepatotoxic PA. Moreover, the change in bile acid metabolism and the respective transporters may provide a new PA toxicity mechanism
Renata Rodrigues De Souza - One of the best experts on this subject based on the ideXlab platform.
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modulatory effect of senecio brasiliensis spreng less in a murine model of inflammation induced by carrageenan into the pleural cavity
Journal of Ethnopharmacology, 2015Co-Authors: Renata Rodrigues De Souza, Lizandra C Etanha, Eduardo Monguilho Dalmarco, Moacir Geraldo Pizzolatti, Tânia Silvia FrodeAbstract:Abstract Ethnopharmacological relevance Senecio brasiliensis (Spreng) Less ( S. brasiliensis ), known as “Flor-das-almas”, “Margaridinha” or “Maria mole”, is used in folk medicine as an anti-inflammatory and to treat gastric ulcers and stomach pain. While the Senecio genus has been widely studied for its pharmacological activities to support its use in traditional medicine, few studies focus on the anti-inflammatory activities of the species. Aim of the study To investigate the anti-inflammatory activities of S. brasiliensis , a specie native to Brazil, using a murine model of pleurisy induced by carrageenan. Material and methods The flowers of S. brasiliensis were air-dried for 3 days and subjected to ethanol (96%) extraction for 7 days to obtain the crude extract (CE). The CE was subjected to acid–base extraction to obtain the alkaloid fraction (AF). The hexane (HEX), dichloromethane (DCM) and ethyl acetate (EtOAc) fractions were obtained by extracting from CE with different solvents. The alkaloids Senecionine (Sen), integerrimine (Int) and Senecionine N-oxide were obtained from AF by chromatographic fractionation and a mixture of 1,4-, 3,4-, 3,5- and 4,5-dicaffeoylquinic acids (DCQs) were obtained from the EtOAc fraction. The isolated alkaloids were identified through spectroscopic analysis of IR, NMR and LC–MS coupled with electrospray ionization mass spectrometry (ESI-MS), and the dicaffeoylquinic acids through the hierarchical key method. Swiss mice were used in the in vivo experiments. We evaluated the effect of the CE, its derived fractions (AF, HEX, DCM and EtOAc), and the isolated compounds (Sen, Int, N-oxide Senecionine, and DCQs) on: leukocyte migration, exudate concentrations, myeloperoxidase (MPO) and adenosine-deaminase (ADA) activities, and tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β) and interleukin 17A levels in the fluid leakage from the pleural cavity using a mouse model of pleurisy induced by carrageenan. The effects of the isolated compounds, Sen, Int, N-oxide Senecionine and DCQs, were also analyzed for their ability to inhibit p65 phosphorylation (p-p65) in the nuclear factor-kappa B (NF-κB) pathway in the lung tissue. MPO and ADA were analyzed by colorimetric assays, and the cytokines and protein p65 levels were determined using an enzyme immunoassay (EIA). Results The CE, its EtOAc and AF fractions, and its isolated compounds (Sen, Int and DCQs), significantly reduced leukocyte migration ( P 0.05), MPO and ADA activities ( P 0.01), and TNF-α ( P 0.05), and IL-17A levels ( P 0.01). The CE, the EtOAc and AF fractions, and the DCQs also decreased IL-1β levels ( P 0.01). The isolated compounds, Sen, Int and the DCQs, inhibited p65 phosphorylation (NF-κB) ( P 0.05). Conclusion This study demonstrated that S. brasiliensis has important anti-inflammatory properties that are capable of inhibiting activated leukocytes by decreasing neutrophil migration. This effect may be attributed to the inhibition of pro-inflammatory cytokines and the reduction of the NF-κB pathway. The compounds Sen, Int, and DCQs may be responsible for the anti-inflammatory actions of S. brasiliensis .
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Efeito modulatório da Senecio Brasiliensis (Spreng) Less. em um modelo murino de inflamação induzida pela carragenina na cavidade pleural
2015Co-Authors: Renata Rodrigues De SouzaAbstract:Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Programa de Pós-Graduação em Ciências Médicas, Florianópolis, 2015.Senecio Brasiliensis Less (S. brasiliensis) popularmente conhecida como "Flor-das-almas", "Margaridinha" ou "Maria mole" é utilizada na medicina popular como um anti-inflamatório, no tratamento de úlcera gástrica e dor de estômago. Embora o gênero Senecio já tenha sido amplamente estudado para avaliar as atividades farmacológicas que suportam seu uso na medicina tradicional, poucos estudos têm avaliado a atividade anti-inflamatória desta espécie. Portanto, objetivo deste estudo foi investigar a atividade anti-inflamatória da S. brasiliensis, uma espécie nativa no Brasil, usando um modelo murino de pleurisia induzida pela carragenina. As flores secas de S. brasiliensis foram maceradas e extraídas com etanol obtendo-se o extrato bruto (CE). As frações acetato de etila (AcOEt), fração rica em alcalóides (AF), hexano (HEX) e diclorometano (DCM) foram obtidas a partir do CE. Senecionina (Sen), integerrimina (Int) e N-óxido senecionina foram obtidas da fração FA, e uma mistura de ácidos x,y-dicafeiolquínicos (1,4-, 3,4-, 3,5- e 4,5-: DCQs) foi obtida da fração AcOEt. No protocolo para identificar e elucidar a estrutura dos compostos foram utilizadas técnicas de eletroforese capilar, infravermelho, ressonância magnética nuclear (RMN) e cromatografia líquida de alta eficiência acoplada a espectrometria de massa (HPLC/MS). Neste protocolo experimental utilizou-se o modelo da pleurisia induzida pela carragenina, em camundongos. Neste modelo foram estudados os efeitos da S. brasiliensis sobre: migração de leucócitos, atividades da mieloperoxidase (MPO) e adenosina desaminase (ADA) assim como as concentrações do fator de necrose tumoral alfa (TNF-a), interleucina 1-beta (IL-1ß) e interleucina 17A (IL-17A) . Todos estes parâmetros foram analisados no líquido da cavidade pleural, Além disso, foram analisados no tecido pulmonar, os efeitos dos compostos Sen, Int e DCQs, sobre a fosforilação da proteína p65 (p-p65) da via do fator de trancrição nuclear kappa B (NF-?B). Ensaios colorimétricos foram utilizados para analisar MPO e ADA e testes imunoenzimáticos (ELISA) para TNF-a, IL-1ß, IL-17A e a fosforilação da p65. O CE, as frações AcOEt e AF, e/ou os compostos Sen, Int e DCQs inibiram os leucócitos (p Abstract : Senecio Brasiliensis (Spreng) Less (S. brasiliensis), known as "Flor-das-almas", "Margaridinha" or "Maria mole", is used in folk medicine as an anti-inflammatory and to treat gastric ulcers and stomach pain. While the Senecio genus has been widely studied for its pharmacological activities to support its use in traditional medicine, few studies focus on the anti-inflammatory activities of the species. To investigate the anti-inflammatory activities of S. brasiliensis, a specie native to Brazil, using a murine model of pleurisy induced by carrageenan. The dried flowers of S. brasiliensis were macerated and subjected to ethanol (96%) extration to obtain the crude extract (CE). The ethyl acetate (AcOEt), alkaloid (AF), hexane (HEX) and dichloromethane (DCM) fractions were obtained by extracting the CE with different solvents. Senecionine (Sen), integerrimine (Int) and Senecionine N-oxide` and a mixture of dicaffeyoilquinic acids (1,4-, 3,4-, 3,5- and 4,5- dicaffeoylquinic acids, DCQs) were obtained from the AF and AcOEt fractions, respectively. The physical characteristics and column chromatography were used to extract and identify the compounds. Nuclear magnetic resonance (NMR), and gas chromatography?mass spectrometry (GC-MS), and high-performance liquid chromatography-diode array detector (HPLC-DAD) coupled with electrospray mass spectrometry (ESI-MS) (HPLC-DAD-MS/MS) and infrared (IR) spectroscopy were used to identify, elucidate and confirm the structures of the compounds. Swiss mice were used in the in vivo experiments. We evaluated the effect of the CE, its derived fractions (AcOEt, AF, HEX and DCM), and the isolated compounds (Sen, Int, N-oxide Senecionine) and DCQs on: leukocyte migration, exudate concentrations, myeloperoxidase (MPO) and adenosine-deaminase (ADA) activities, and tumour necrosis factor-a (TNF-a), interleukin 1ß (IL-1ß) and interleukin 17A levels in the fluid leakage from the pleural cavity using a mouse model of pleurisy induced by carrageenan. The effects of the isolated compounds, Sen, Int, N-oxide Senecionine and DCQs, were also analysed for their ability to inhibit p65 phosphorylation (p-p65) in the nuclear factor-kappa B (NF-?B) pathway in the lung tissue. MPO and ADA were analysed by colorimetric assays, and the cytokines and protein p65 levels were determined using an enzyme immunoassay (EIA). The CE, its AcOEt and AF fractions, and its compounds (Sen, Int and DCQs), significantly reduced leukocyte migration (P < 0.05), MPO and ADA activities (P < 0.01), and TNF-a (P < 0.05), and IL-17A levels (P < 0.01). The CE, the AcOEt and AF fractions, and the DCQs also decreased IL-1ß levels (P < 0.01). The isolated compounds, Sen, Int and the DCQs, inhibited p65 phosphorylation (NF-?B) (P < 0.05). This study demonstrated that S. brasiliensis has important anti-inflammatory properties that are capable of inhibiting activated leukocyte migration by decreasing neutrophil migration. This effect may be attributed to the inhibition of pro-inflammatory cytokines and the reduction of the NF-?B pathway. The compounds Sen Int, and DCQs may be responsible for the anti-inflammatory actions of S. brasiliensis
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Estudo modulatório da Senecio Brasiliensis (Spreng) Less. em um modelo murino de inflamação induzida pela carragenina na cavidade pleural
2015Co-Authors: Renata Rodrigues De SouzaAbstract:Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Programa de Pós-Graduação em Ciências Médicas, Florianópolis, 2015.Senecio Brasiliensis Less (S. brasiliensis) popularmente conhecida como "Flor-das-almas", "Margaridinha" ou "Maria mole" é utilizada na medicina popular como um anti-inflamatório, no tratamento de úlcera gástrica e dor de estômago. Embora o gênero Senecio já tenha sido amplamente estudado para avaliar as atividades farmacológicas que suportam seu uso na medicina tradicional, poucos estudos têm avaliado a atividade anti-inflamatória desta espécie. Portanto, objetivo deste estudo foi investigar a atividade anti-inflamatória da S. brasiliensis, uma espécie nativa no Brasil, usando um modelo murino de pleurisia induzida pela carragenina. As flores secas de S. brasiliensis foram maceradas e extraídas com etanol obtendo-se o extrato bruto (CE). As frações acetato de etila (AcOEt), fração rica em alcalóides (AF), hexano (HEX) e diclorometano (DCM) foram obtidas a partir do CE. Senecionina (Sen), integerrimina (Int) e N-óxido senecionina foram obtidas da fração FA, e uma mistura de ácidos x,y-dicafeiolquínicos (1,4-, 3,4-, 3,5- e 4,5-: DCQs) foi obtida da fração AcOEt. No protocolo para identificar e elucidar a estrutura dos compostos foram utilizadas técnicas de eletroforese capilar, infravermelho, ressonância magnética nuclear (RMN) e cromatografia líquida de alta eficiência acoplada a espectrometria de massa (HPLC/MS). Neste protocolo experimental utilizou-se o modelo da pleurisia induzida pela carragenina, em camundongos. Neste modelo foram estudados os efeitos da S. brasiliensis sobre: migração de leucócitos, atividades da mieloperoxidase (MPO) e adenosina desaminase (ADA) assim como as concentrações do fator de necrose tumoral alfa (TNF-a), interleucina 1-beta (IL-1ß) e interleucina 17A (IL-17A) . Todos estes parâmetros foram analisados no líquido da cavidade pleural, Além disso, foram analisados no tecido pulmonar, os efeitos dos compostos Sen, Int e DCQs, sobre a fosforilação da proteína p65 (p-p65) da via do fator de trancrição nuclear kappa B (NF-?B). Ensaios colorimétricos foram utilizados para analisar MPO e ADA e testes imunoenzimáticos (ELISA) para TNF-a, IL-1ß, IL-17A e a fosforilação da p65. O CE, as frações AcOEt e AF, e/ou os compostos Sen, Int e DCQs inibiram os leucócitos (p < 0.05), a atividade de MPO e ADA (p < 0.01), as concentrações de TNF-a(p < 0.05) e IL-17A (p < 0.01), O CE, as frações AcOEt e AF, e DCQs, também diminuíram as concentrações de IL-1ß (p < 0.01). Os compostos isolados Sen, Int e DCQs inibiram fosforilação da p-65 (NF-?B) (p < 0.05). Este estudo demonstrou que a S. brasiliensis tem uma importante atividade anti-inflamatória pela inibição da migração de leucócitos ativados devido a diminuição de neutrófilos no sítio da inflamação. Este efeito pode ser atribuído a inibição de citocinas pró-inflamatórias e também da ativação da via do NF-?B. Os compostos Sen, Int, e DCQs pode ser, pelo menos em parte, responsáveis pela ação anti-inflamatória da S. brasiliensis.Abstract : Senecio Brasiliensis (Spreng) Less (S. brasiliensis), known as "Flor-das-almas", "Margaridinha" or "Maria mole", is used in folk medicine as an anti-inflammatory and to treat gastric ulcers and stomach pain. While the Senecio genus has been widely studied for its pharmacological activities to support its use in traditional medicine, few studies focus on the anti-inflammatory activities of the species. To investigate the anti-inflammatory activities of S. brasiliensis, a specie native to Brazil, using a murine model of pleurisy induced by carrageenan. The dried flowers of S. brasiliensis were macerated and subjected to ethanol (96%) extration to obtain the crude extract (CE). The ethyl acetate (AcOEt), alkaloid (AF), hexane (HEX) and dichloromethane (DCM) fractions were obtained by extracting the CE with different solvents. Senecionine (Sen), integerrimine (Int) and Senecionine N-oxide` and a mixture of dicaffeyoilquinic acids (1,4-, 3,4-, 3,5- and 4,5- dicaffeoylquinic acids, DCQs) were obtained from the AF and AcOEt fractions, respectively. The physical characteristics and column chromatography were used to extract and identify the compounds. Nuclear magnetic resonance (NMR), and gas chromatography?mass spectrometry (GC-MS), and high-performance liquid chromatography-diode array detector (HPLC-DAD) coupled with electrospray mass spectrometry (ESI-MS) (HPLC-DAD-MS/MS) and infrared (IR) spectroscopy were used to identify, elucidate and confirm the structures of the compounds. Swiss mice were used in the in vivo experiments. We evaluated the effect of the CE, its derived fractions (AcOEt, AF, HEX and DCM), and the isolated compounds (Sen, Int, N-oxide Senecionine) and DCQs on: leukocyte migration, exudate concentrations, myeloperoxidase (MPO) and adenosine-deaminase (ADA) activities, and tumour necrosis factor-a (TNF-a), interleukin 1ß (IL-1ß) and interleukin 17A levels in the fluid leakage from the pleural cavity using a mouse model of pleurisy induced by carrageenan. The effects of the isolated compounds, Sen, Int, N-oxide Senecionine and DCQs, were also analysed for their ability to inhibit p65 phosphorylation (p-p65) in the nuclear factor-kappa B (NF-?B) pathway in the lung tissue. MPO and ADA were analysed by colorimetric assays, and the cytokines and protein p65 levels were determined using an enzyme immunoassay (EIA). The CE, its AcOEt and AF fractions, and its compounds (Sen, Int and DCQs), significantly reduced leukocyte migration (P < 0.05), MPO and ADA activities (P < 0.01), and TNF-a (P < 0.05), and IL-17A levels (P < 0.01). The CE, the AcOEt and AF fractions, and the DCQs also decreased IL-1ß levels (P < 0.01). The isolated compounds, Sen, Int and the DCQs, inhibited p65 phosphorylation (NF-?B) (P < 0.05). This study demonstrated that S. brasiliensis has important anti-inflammatory properties that are capable of inhibiting activated leukocyte migration by decreasing neutrophil migration. This effect may be attributed to the inhibition of pro-inflammatory cytokines and the reduction of the NF-?B pathway. The compounds Sen Int, and DCQs may be responsible for the anti-inflammatory actions of S. brasiliensis
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comparison of hepatic in vitro metabolism of the pyrrolizidine alkaloid Senecionine in sheep and cattle
American Journal of Veterinary Research, 2004Co-Authors: Jennifer M Duringer, Donald R Buhler, Morrie A CraigAbstract:Objective—To compare hepatic metabolism of pyrrolizidine alkaloids (PAs) between sheep and cattle and elucidate the protective mechanism of sheep. Sample Population—Liver microsomes and cytosol from 8 sheep and 8 cattle. Procedure—The PA Senecionine, Senecionine N-oxide (nontoxic metabolite) and 6,7-dihydro-7-hydroxy- 1-hydroxymethyl-5H-pyrrolizine (DHP; toxic metabolite) were measured in microsomal incubations. The kcat (turnover number) was determined for DHP and N-oxide formation. Chemical and immunochemical inhibitors were used to assess the role of cytochrome P450s, flavin-containing monooxygenases (FMOs), and carboxylesterases in Senecionine metabolism. The CYP3A, CYP2B, and FMO concentrations and activities were determined, in addition to the role of glutathione (GSH) in Senecionine metabolism. Results—DHP concentration did not differ between species. Sheep formed more N-oxide, had higher N-oxide kcat, and metabolized Senecionine faster than cattle. The P450 concentrations and isoforms had a large ...
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the effect of spironolactone treatment on the cytochrome p450 mediated metabolism of the pyrrolizidine alkaloid Senecionine by hepatic microsomes from rats and guinea pigs
Toxicology and Applied Pharmacology, 1994Co-Authors: Woongye Chung, Donald R BuhlerAbstract:Spironolactone (SPL), a known inducer of cytochrome P4503A, was injected into rats and guinea pigs in order to investigate species differences in pyrrolizidine alkaloid (PA) metabolism. Liver microsomes from treated male rats showed an increased (+/-)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP) formation of 47% from the PA Senecionine, coincident with the induction of P4503A1, whereas Senecionine N-oxidation was decreased by 49%, probably due to a reduction in hepatic P4502C11 concentrations. By contrast, liver microsomes from SPL-treated female rats exhibited almost a 500% increase in both DHP and Senecionine N-oxide production, coincident with the marked induction of P4503A1. In guinea pigs of both sexes, oral treatment with SPL caused an approximately 50% increased formation of both DHP and Senecionine N-oxide by liver microsomes. Only a slight increase in hepatic concentrations of P4503A1 occurred in the treated guinea pigs. SPL treatment increased testosterone 16 beta-hydroxylase activity by 100% in both sexes of guinea pigs. Use of the P4503A1 specific inhibitor triacetyloleandomycin showed that the P4503A sub-family played an important role in Senecionine bioactivation in untreated or SPL-treated rats but not in both untreated and SPL-treated guinea pigs. This study demonstrated that P4503A was not the major enzyme for Senecionine metabolism in guinea pigs.
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microsomal formation of a pyrrolic alcohol glutathione conjugate of the pyrrolizidine alkaloid Senecionine
Xenobiotica, 1992Co-Authors: Ralph L Reed, Cristobal L Miranda, Marilyn C Henderson, Bogdan Kedzierski, Donald R BuhlerAbstract:1. Pyrrolizidine alkaloids (PAs) are metabolized primarily to putative dehydroalkaloid (PA pyrrole) metabolites and to PA N-oxide by rat liver microsomal monooxygenases. 2. The dehydroalkaloids are highly reactive and either bind covalentely to tissue nucleophiles or are hydrolysed to the more stable pyrrole, (R,S)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP), and the corresponding necic acid. 3. Addition of glutathione (GSH 1 mM) to incubation mixtures containing rat liver microsomes and the PA Senecionine (SN), resulted in the formation of a conjugate of DHP with GSH. 5. The mass spectrum of this DHP-GSH conjugate was identical to that of the chemically-synthesized dehydroretronecine (the R enantiomer of the racemic DHP) and GSH. 6. Only negligible amounts of DHP-GSH conjugate were formed when DHP itself was incubated with GSH at physiological pH. 7. These findings provide strong evidence for the microsomal conversion of SN to a highly reactive metabolite, presumably dehydroSenecionine, which then reacts with GSH to form the DHP-GSH conjugate. 8. It is likely that a similar mechanism is responsible in vivo for the formation of GSH conjugates of DHP from SN and other PAs.
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flavin containing monooxygenase a major detoxifying enzyme for the pyrrolizidine alkaloid Senecionine in guinea pig tissues
Biochemical and Biophysical Research Communications, 1991Co-Authors: Cristobal L Miranda, Woongye Chung, Ralph E Reed, Xine Zhao, Marilyn C Henderson, Junlan Wang, David E Williams, Donald R BuhlerAbstract:Abstract Evidence based on optimal pH, thermal stability, and enzyme inhibition data suggests that the NADPH-dependent microsomal N -oxidation of the pyrrolizidine alkaloid Senecionine is carried out largely by flavin-containing monooxygenase in guinea pig liver, lung, and kidney. In contrast, the hepatic microsomal conversion of Senecionine to the pyrrole metabolite (±)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP) is catalyzed largely by cytochrome P450. However, the rate of Senecionine N -oxide formation (detoxication) far exceeded the rate of DHP formation (activation) in guinea pig liver microsomes over a range of pHs (pH 6.8 to 9.8). In guinea pig lung and kidney microsomes, N -oxide was the major metabolite formed from Senecionine with little or no production of DHP. The high rate of detoxication coupled with the low level of activation of Senecionine in liver, lung, and kidney may help explain the apparent resistance of the guinea pig to intoxication by Senecionine and other pyrrolizidine alkaloids.
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role of cytochrome p450iiia4 in the metabolism of the pyrrolizidine alkaloid Senecionine in human liver
Carcinogenesis, 1991Co-Authors: Cristobal L Miranda, Ralph L Reed, Peter F Guengerich, Donald R BuhlerAbstract:Studies were carried out to investigate the metabolism of Senecionine by human liver microsomes and the role of human cytochrome P450IIIA4 in this process. Human liver microsomes metabolized Senecionine to two major products, (+/-)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP) and Senecionine N-oxide. The rates of product formation (DHP and Senecionine N-oxide) varied widely with the microsomal samples tested. There was a 30-fold difference in DHP formation and a 25-fold difference in N-oxidation between the poorest metabolizer and the highest metabolizer of Senecionine. The conversion of Senecionine to DHP and Senecionine N-oxide in human liver microsomes was markedly inhibited by the mechanism-based inactivators of P450IIIA4, gestodene and triacetyloleandomycin. Anti-P450IIIA4 IgG, at a concentration of 1 mg/nmol of P450, was found to inhibit completely the formation of DHP and Senecionine N-oxide in human liver microsomes (HL101) having low activity toward Senecionine. At 5 mg IgG/nmol P450, anti-P450IIIA4 inhibited 90 and 84% respectively of the formation of DHP and Senecionine N-oxide in liver microsomes (HL110) with the highest activity toward Senecionine. The formation of DHP or Senecionine N-oxide was highly correlated with the amount of P450IIIA4 measured in the microsomes using polyclonal anti-P450IIIA4 IgG. The rate of DHP production also had a strong correlation with the rate of Senecionine N-oxide formation (r = 0.999) and with the rate of nifedipine oxidation (r = 0.998). Our present studies provide evidence that P450IIIA4 is the major enzyme catalyzing the bioactivation (DHP formation) and detoxication (Senecionine N-oxide formation) of Senecionine in human liver.
