The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
Leroy B. Townsend - One of the best experts on this subject based on the ideXlab platform.
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Toyocamycin specifically inhibits auxin signaling mediated by SCFTIR1 pathway
Phytochemistry, 2009Co-Authors: Shuichi Kamio, Yutaka Oono, Leroy B. Townsend, Hiroshi NozakiAbstract:Abstract The auxins, plant hormones, play a crucial role in many aspects of plant development by regulating cell division, elongation and differentiation. Toyocamycin, a nucleoside-type antibiotic, was identified as auxin signaling inhibitor in a screen of microbial extracts for inhibition of the auxin-inducible reporter gene assay. Toyocamycin specifically inhibited auxin-responsive gene expression, but did not affect other hormone-inducible gene expression. Toyocamycin also blocked auxin-enhanced degradation of the Aux/IAA repressor modulated by the SCF(TIR1) ubiquitin–proteasome pathway without inhibiting proteolytic activity of proteasome. Furthermore, Toyocamycin inhibited auxin-induced lateral root formation and epinastic growth of cotyledon in the Arabidopsis thaliana plant. This evidence suggested that Toyocamycin would act on the ubiquitination process regulated by SCF(TIR1) machineries. To address the structural requirements for the specific activity of Toyocamycin on auxin signaling, the structure-activity relationships of nine Toyocamycin-related compounds, including sangivamycin and tubercidin, were investigated.
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Total synthesis of the naturally occurring antibiotic Toyocamycin using new and improved synthetic procedures.
Nucleosides & nucleotides, 1999Co-Authors: Anthony R. Porcari, Leroy B. TownsendAbstract:Starting with commercially available tetracyanoethylene, we describe a more efficient and higher yielding synthesis of Toyocamycin with regards to convenience, overall yield, and total reaction time than those syntheses previously reported.
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Synthesis and evaluation of certain thiosangivamycin analogs as potential inhibitors of cell proliferation and human cytomegalovirus.
Journal of medicinal chemistry, 1995Co-Authors: Steven H. Krawczyk, Thomas E Renau, Linda L. Wotring, John C. Drach, M. Reza Nassiri, Allison C. Westerman, Leroy B. TownsendAbstract:A series of 7-substituted 4-aminopyrrolo[2,3-d]pyrimidines related to the nucleosides Toyocamycin and thiosangivamycin were prepared and tested for their activity against human cytomegalovirus (HCMV). The nucleosides 2'-deoxyToyocamycin (1), xylo-Toyocamycin (2), 3'-deoxyToyocamycin (3), 2',3'-dideoxy-2',3'-didehydroToyocamycin (4), 2',3'-dideoxyToyocamycin (5), ara-Toyocamycin (6), 2'-deoxy-2'-amino-ara-Toyocamycin (7), and 5'-deoxyToyocamycin (8) were treated with sodium hydrogen sulfide generated in situ to afford the corresponding thiosangivamycin analogs (9-16). The cyano derivatives 1-8 were synthesized by modifications of literature procedures. All of the thioamide derivatives (9-16) were active against HCMV with IC50's ranging from 0.5 to 6 microM. Most also were active against herpes simplex virus type 1 (HSV-1) but at higher concentrations. The antiviral activity was not completely separated from cytotoxicity in two human cell lines. The antiproliferative activity was strongly influenced by the position of the modification on the carbohydrate moiety. The xylosyl and 3'-deoxy derivatives were significantly more potent than those with modifications at the 2', 5', or 2',3' position(s). Interestingly, 5'-deoxythiosangivamycin (16) possessed both antiviral and antiproliferative activity suggesting that phosphorylation of the 5'-hydroxyl may not be required for these compounds to have biological activity.
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design synthesis and activity against human cytomegalovirus of non phosphorylatable analogs of Toyocamycin sangivamycin and thiosangivamycin
Bioorganic & Medicinal Chemistry Letters, 1992Co-Authors: Thomas E Renau, Mary S Ludwig, John C. Drach, Leroy B. TownsendAbstract:Abstract A number of 7-alkyl 4-aminopyrrolo[2,3- d pyrimidine derivatives related to Toyocamycin, sangivamycin and thiosangivamycin have been prepared and tested for their activity against human cytomegalovirus (HCMV). Only the thioamide substituted derivatives demonstrated biological activity.
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Design, synthesis and activity against human cytomegalovirus of non-phosphorylatable analogs of Toyocamycin, sangivamycin and thiosangivamycin
Bioorganic & Medicinal Chemistry Letters, 1992Co-Authors: Thomas E Renau, Mary S Ludwig, John C. Drach, Leroy B. TownsendAbstract:A number of 7-alkyl 4-aminopyrrolo(2,3-glpyrimidine derivatives related to Toyocamycin, sangivamycin and thiosangivamycin have been prepared and tested for their activity against human cytomegalovirus (HCMV). Only the thioamide substituted derivatives demonstrated biological activity. Human cytomegalovirus (HCMV) infection is relatively benign in healthy individuals but can be debilitating or fatal to immunosuppressed individuals such as transplant recipients' and AIDS patients.2 The drugs currently approved for the treatment of HCMV are ganciclovir (GCV, DHPG)3 and foscarnet (PFA).4 The clinical use of these compounds is limited because of host toxicity. s-6 In addition, there have been recent report@ that strains of HCMV resistant to both drugs are emerging. Hence, there is a continued need to develop compounds which may circumvent the problems associated with the use of DHPG and PFA to treat HCMV infections. The naturally occurring pyrrolo(2,3-d)pyrimidine nucleosides Toyocamycin (I), sangivamycin (2) and a structurally related analog, thiosangivamycin (3), possess significant activity against HCMVg-lo
Ikuko Takahara - One of the best experts on this subject based on the ideXlab platform.
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Toyocamycin attenuates free fatty acid-induced hepatic steatosis and apoptosis in cultured hepatocytes and ameliorates nonalcoholic fatty liver disease in mice.
PLOS ONE, 2017Co-Authors: Ikuko Takahara, Naota Taura, Yuko Akazawa, Maiko Tabuchi, Katsuya Matsuda, Hisamitsu Miyaaki, Youko Kido, Yasuko Kanda, Ken Ohnita, Fuminao TakeshimaAbstract:Background and aims A high serum level of saturated free fatty acids (FFAs) is associated with the development of nonalcoholic fatty liver disease (NAFLD). X-box binding protein-1 (XBP-1) is activated by FFA treatment upon splicing. XBP-1 is a transcription factor induced by the endoplasmic reticulum (ER) stress sensor endoribonuclease inositol-requiring enzyme 1 alpha (IRE1α). However, the role of XBP-1 in NAFLD remains relatively unexplored. Toyocamycin was recently reported to attenuate the activation of XBP-1, possibly by inducing a conformational change in IRE1α. In this study, we examined the effect of Toyocamycin on hepatocyte lipoapoptosis and steatosis. We also explored the effects of Toyocamycin in a mouse model of NAFLD. Methods Huh-7 cells and isolated rat primary hepatocytes were treated with palmitic acid (PA), which is a saturated FFA, in the presence or absence of Toyocamycin. In addition, male C57BL/6J mice were fed a diet rich in saturated fat, fructose, and cholesterol (FFC) for 4 months, after which the effect of Toyocamycin was assessed. Results Toyocamycin attenuated FFA-induced steatosis. It also significantly reduced PA-induced hepatocyte lipoapoptosis. In addition, Toyocamycin reduced the expression of cytosine-cytosine-adenosine-adenosine-thymidine enhancer-binding protein homologous protein (CHOP), which is a key player in ER stress-mediated apoptosis, as well as its downstream cell death modulator, death receptor 5. In the in vivo study, Toyocamycin ameliorated the liver injury caused by FFC-induced NAFLD. It also reduced hepatic steatosis and the expression of lipogenic genes. Conclusions The data we obtained suggest that Toyocamycin attenuates hepatocyte lipogenesis and ameliorates NAFLD in vivo and may therefore be beneficial in the treatment of NAFLD in humans.
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696 XBP-1 Inhibitor Toyocamycin Attenuates Palmitate-Induced Hepatocyte Apoptosis and Steatosis
Gastroenterology, 2014Co-Authors: Ikuko Takahara, Fuminao Takeshima, Naota Taura, Tatsuki Ichikawa, Yuko Akazawa, Hajime Isomoto, Ken Ohnita, Kazuhiko NakaoAbstract:Background and Aim: Free fatty acid-induced hepatocyte cytotoxicity is deeply associated withmorbidity of Non-alcoholic fatty liver disease (NAFLD) (Malhi et al, 2008, Gastroenterology). Saturated free fatty acids induce hepatocyte lipoapoptosis via endoplasmic reticulum stress (ER) response, which leads to translational activation of DR5 and BH3 only protein Bim (Cazanave et al, JBC, 2011). We previously reported that X-box binding protein-1 (XBP-1) is activated downstream of IRE-1 arm of ER stress by free fatty acid treatment upon its splicing (Akazawa et al, 2009, J Hepatol). However, role of XBP-1 during hepatocyte lipoapoptosis remains relatively unexplored. We examined the impact of inhibiting XBP-1 on hepatocyte lipoapoptosis and steatosis employing Toyocamycin, which was recently reported to inhibit ER stress-mediated XBP-1 splicing (Ri M et al, Blood Cancer J. 2012). Methods: We employed hepatocellular carcinoma cell line, Huh-7 cells, for these studies. Cells were incubated with palmitate (200~800μM) in presence or absence of Toyocamycin (0.1~3μM). Apoptosis was assessed by DAPI staining and caspase 3/7 activity assay. Steatosis was assessed by Nile red staining. mRNA expression of Bim and DR5 was examined by real time PCR. Expression of Bim protein and phosphorylation of JNK was assessed by immunoblotting. Results: As expected, Toyocamycin inhibited palmitate-mediated XBP-1 splicing without affecting amount of total RNA. Toyocamycin significantly reduced palmitateinduced hepatocyte lipoapoptosis (p
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696 xbp 1 inhibitor Toyocamycin attenuates palmitate induced hepatocyte apoptosis and steatosis
Gastroenterology, 2014Co-Authors: Ikuko Takahara, Fuminao Takeshima, Naota Taura, Tatsuki Ichikawa, Yuko Akazawa, Hajime Isomoto, Ken Ohnita, Kazuhiko NakaoAbstract:Background and Aim: Free fatty acid-induced hepatocyte cytotoxicity is deeply associated withmorbidity of Non-alcoholic fatty liver disease (NAFLD) (Malhi et al, 2008, Gastroenterology). Saturated free fatty acids induce hepatocyte lipoapoptosis via endoplasmic reticulum stress (ER) response, which leads to translational activation of DR5 and BH3 only protein Bim (Cazanave et al, JBC, 2011). We previously reported that X-box binding protein-1 (XBP-1) is activated downstream of IRE-1 arm of ER stress by free fatty acid treatment upon its splicing (Akazawa et al, 2009, J Hepatol). However, role of XBP-1 during hepatocyte lipoapoptosis remains relatively unexplored. We examined the impact of inhibiting XBP-1 on hepatocyte lipoapoptosis and steatosis employing Toyocamycin, which was recently reported to inhibit ER stress-mediated XBP-1 splicing (Ri M et al, Blood Cancer J. 2012). Methods: We employed hepatocellular carcinoma cell line, Huh-7 cells, for these studies. Cells were incubated with palmitate (200~800μM) in presence or absence of Toyocamycin (0.1~3μM). Apoptosis was assessed by DAPI staining and caspase 3/7 activity assay. Steatosis was assessed by Nile red staining. mRNA expression of Bim and DR5 was examined by real time PCR. Expression of Bim protein and phosphorylation of JNK was assessed by immunoblotting. Results: As expected, Toyocamycin inhibited palmitate-mediated XBP-1 splicing without affecting amount of total RNA. Toyocamycin significantly reduced palmitateinduced hepatocyte lipoapoptosis (p<0.05) and caspase 3/7 activity (p<0.05) in dose dependent manner. Interestingly, Toyocamycin also attenuated free fatty acid-induced steatosis. In addition, Toyocamycin attenuated expression of Bim protein andmRNA (p<0.05) following palmitate treatment. Furthermore, PAmediated-transcriptional activation of DR5was reduced by Toyocamycin (p<0.05). In contrast, palmitate-induced JNK phosphorylation, which also occurs downstream of IRE-1 arm of ER stress, was not inhibited by Toyocamycin. Conclusions: These data imply that Toyocamycin attenuates hepatocyte lipotoxicity as well as steatosis, likely through inhibition of XBP-1 splicing. Toyocamycin might be beneficial for NASH treatment.
Kazuhiko Nakao - One of the best experts on this subject based on the ideXlab platform.
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696 XBP-1 Inhibitor Toyocamycin Attenuates Palmitate-Induced Hepatocyte Apoptosis and Steatosis
Gastroenterology, 2014Co-Authors: Ikuko Takahara, Fuminao Takeshima, Naota Taura, Tatsuki Ichikawa, Yuko Akazawa, Hajime Isomoto, Ken Ohnita, Kazuhiko NakaoAbstract:Background and Aim: Free fatty acid-induced hepatocyte cytotoxicity is deeply associated withmorbidity of Non-alcoholic fatty liver disease (NAFLD) (Malhi et al, 2008, Gastroenterology). Saturated free fatty acids induce hepatocyte lipoapoptosis via endoplasmic reticulum stress (ER) response, which leads to translational activation of DR5 and BH3 only protein Bim (Cazanave et al, JBC, 2011). We previously reported that X-box binding protein-1 (XBP-1) is activated downstream of IRE-1 arm of ER stress by free fatty acid treatment upon its splicing (Akazawa et al, 2009, J Hepatol). However, role of XBP-1 during hepatocyte lipoapoptosis remains relatively unexplored. We examined the impact of inhibiting XBP-1 on hepatocyte lipoapoptosis and steatosis employing Toyocamycin, which was recently reported to inhibit ER stress-mediated XBP-1 splicing (Ri M et al, Blood Cancer J. 2012). Methods: We employed hepatocellular carcinoma cell line, Huh-7 cells, for these studies. Cells were incubated with palmitate (200~800μM) in presence or absence of Toyocamycin (0.1~3μM). Apoptosis was assessed by DAPI staining and caspase 3/7 activity assay. Steatosis was assessed by Nile red staining. mRNA expression of Bim and DR5 was examined by real time PCR. Expression of Bim protein and phosphorylation of JNK was assessed by immunoblotting. Results: As expected, Toyocamycin inhibited palmitate-mediated XBP-1 splicing without affecting amount of total RNA. Toyocamycin significantly reduced palmitateinduced hepatocyte lipoapoptosis (p
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696 xbp 1 inhibitor Toyocamycin attenuates palmitate induced hepatocyte apoptosis and steatosis
Gastroenterology, 2014Co-Authors: Ikuko Takahara, Fuminao Takeshima, Naota Taura, Tatsuki Ichikawa, Yuko Akazawa, Hajime Isomoto, Ken Ohnita, Kazuhiko NakaoAbstract:Background and Aim: Free fatty acid-induced hepatocyte cytotoxicity is deeply associated withmorbidity of Non-alcoholic fatty liver disease (NAFLD) (Malhi et al, 2008, Gastroenterology). Saturated free fatty acids induce hepatocyte lipoapoptosis via endoplasmic reticulum stress (ER) response, which leads to translational activation of DR5 and BH3 only protein Bim (Cazanave et al, JBC, 2011). We previously reported that X-box binding protein-1 (XBP-1) is activated downstream of IRE-1 arm of ER stress by free fatty acid treatment upon its splicing (Akazawa et al, 2009, J Hepatol). However, role of XBP-1 during hepatocyte lipoapoptosis remains relatively unexplored. We examined the impact of inhibiting XBP-1 on hepatocyte lipoapoptosis and steatosis employing Toyocamycin, which was recently reported to inhibit ER stress-mediated XBP-1 splicing (Ri M et al, Blood Cancer J. 2012). Methods: We employed hepatocellular carcinoma cell line, Huh-7 cells, for these studies. Cells were incubated with palmitate (200~800μM) in presence or absence of Toyocamycin (0.1~3μM). Apoptosis was assessed by DAPI staining and caspase 3/7 activity assay. Steatosis was assessed by Nile red staining. mRNA expression of Bim and DR5 was examined by real time PCR. Expression of Bim protein and phosphorylation of JNK was assessed by immunoblotting. Results: As expected, Toyocamycin inhibited palmitate-mediated XBP-1 splicing without affecting amount of total RNA. Toyocamycin significantly reduced palmitateinduced hepatocyte lipoapoptosis (p<0.05) and caspase 3/7 activity (p<0.05) in dose dependent manner. Interestingly, Toyocamycin also attenuated free fatty acid-induced steatosis. In addition, Toyocamycin attenuated expression of Bim protein andmRNA (p<0.05) following palmitate treatment. Furthermore, PAmediated-transcriptional activation of DR5was reduced by Toyocamycin (p<0.05). In contrast, palmitate-induced JNK phosphorylation, which also occurs downstream of IRE-1 arm of ER stress, was not inhibited by Toyocamycin. Conclusions: These data imply that Toyocamycin attenuates hepatocyte lipotoxicity as well as steatosis, likely through inhibition of XBP-1 splicing. Toyocamycin might be beneficial for NASH treatment.
Fuminao Takeshima - One of the best experts on this subject based on the ideXlab platform.
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Toyocamycin attenuates free fatty acid-induced hepatic steatosis and apoptosis in cultured hepatocytes and ameliorates nonalcoholic fatty liver disease in mice.
PLOS ONE, 2017Co-Authors: Ikuko Takahara, Naota Taura, Yuko Akazawa, Maiko Tabuchi, Katsuya Matsuda, Hisamitsu Miyaaki, Youko Kido, Yasuko Kanda, Ken Ohnita, Fuminao TakeshimaAbstract:Background and aims A high serum level of saturated free fatty acids (FFAs) is associated with the development of nonalcoholic fatty liver disease (NAFLD). X-box binding protein-1 (XBP-1) is activated by FFA treatment upon splicing. XBP-1 is a transcription factor induced by the endoplasmic reticulum (ER) stress sensor endoribonuclease inositol-requiring enzyme 1 alpha (IRE1α). However, the role of XBP-1 in NAFLD remains relatively unexplored. Toyocamycin was recently reported to attenuate the activation of XBP-1, possibly by inducing a conformational change in IRE1α. In this study, we examined the effect of Toyocamycin on hepatocyte lipoapoptosis and steatosis. We also explored the effects of Toyocamycin in a mouse model of NAFLD. Methods Huh-7 cells and isolated rat primary hepatocytes were treated with palmitic acid (PA), which is a saturated FFA, in the presence or absence of Toyocamycin. In addition, male C57BL/6J mice were fed a diet rich in saturated fat, fructose, and cholesterol (FFC) for 4 months, after which the effect of Toyocamycin was assessed. Results Toyocamycin attenuated FFA-induced steatosis. It also significantly reduced PA-induced hepatocyte lipoapoptosis. In addition, Toyocamycin reduced the expression of cytosine-cytosine-adenosine-adenosine-thymidine enhancer-binding protein homologous protein (CHOP), which is a key player in ER stress-mediated apoptosis, as well as its downstream cell death modulator, death receptor 5. In the in vivo study, Toyocamycin ameliorated the liver injury caused by FFC-induced NAFLD. It also reduced hepatic steatosis and the expression of lipogenic genes. Conclusions The data we obtained suggest that Toyocamycin attenuates hepatocyte lipogenesis and ameliorates NAFLD in vivo and may therefore be beneficial in the treatment of NAFLD in humans.
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696 XBP-1 Inhibitor Toyocamycin Attenuates Palmitate-Induced Hepatocyte Apoptosis and Steatosis
Gastroenterology, 2014Co-Authors: Ikuko Takahara, Fuminao Takeshima, Naota Taura, Tatsuki Ichikawa, Yuko Akazawa, Hajime Isomoto, Ken Ohnita, Kazuhiko NakaoAbstract:Background and Aim: Free fatty acid-induced hepatocyte cytotoxicity is deeply associated withmorbidity of Non-alcoholic fatty liver disease (NAFLD) (Malhi et al, 2008, Gastroenterology). Saturated free fatty acids induce hepatocyte lipoapoptosis via endoplasmic reticulum stress (ER) response, which leads to translational activation of DR5 and BH3 only protein Bim (Cazanave et al, JBC, 2011). We previously reported that X-box binding protein-1 (XBP-1) is activated downstream of IRE-1 arm of ER stress by free fatty acid treatment upon its splicing (Akazawa et al, 2009, J Hepatol). However, role of XBP-1 during hepatocyte lipoapoptosis remains relatively unexplored. We examined the impact of inhibiting XBP-1 on hepatocyte lipoapoptosis and steatosis employing Toyocamycin, which was recently reported to inhibit ER stress-mediated XBP-1 splicing (Ri M et al, Blood Cancer J. 2012). Methods: We employed hepatocellular carcinoma cell line, Huh-7 cells, for these studies. Cells were incubated with palmitate (200~800μM) in presence or absence of Toyocamycin (0.1~3μM). Apoptosis was assessed by DAPI staining and caspase 3/7 activity assay. Steatosis was assessed by Nile red staining. mRNA expression of Bim and DR5 was examined by real time PCR. Expression of Bim protein and phosphorylation of JNK was assessed by immunoblotting. Results: As expected, Toyocamycin inhibited palmitate-mediated XBP-1 splicing without affecting amount of total RNA. Toyocamycin significantly reduced palmitateinduced hepatocyte lipoapoptosis (p
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696 xbp 1 inhibitor Toyocamycin attenuates palmitate induced hepatocyte apoptosis and steatosis
Gastroenterology, 2014Co-Authors: Ikuko Takahara, Fuminao Takeshima, Naota Taura, Tatsuki Ichikawa, Yuko Akazawa, Hajime Isomoto, Ken Ohnita, Kazuhiko NakaoAbstract:Background and Aim: Free fatty acid-induced hepatocyte cytotoxicity is deeply associated withmorbidity of Non-alcoholic fatty liver disease (NAFLD) (Malhi et al, 2008, Gastroenterology). Saturated free fatty acids induce hepatocyte lipoapoptosis via endoplasmic reticulum stress (ER) response, which leads to translational activation of DR5 and BH3 only protein Bim (Cazanave et al, JBC, 2011). We previously reported that X-box binding protein-1 (XBP-1) is activated downstream of IRE-1 arm of ER stress by free fatty acid treatment upon its splicing (Akazawa et al, 2009, J Hepatol). However, role of XBP-1 during hepatocyte lipoapoptosis remains relatively unexplored. We examined the impact of inhibiting XBP-1 on hepatocyte lipoapoptosis and steatosis employing Toyocamycin, which was recently reported to inhibit ER stress-mediated XBP-1 splicing (Ri M et al, Blood Cancer J. 2012). Methods: We employed hepatocellular carcinoma cell line, Huh-7 cells, for these studies. Cells were incubated with palmitate (200~800μM) in presence or absence of Toyocamycin (0.1~3μM). Apoptosis was assessed by DAPI staining and caspase 3/7 activity assay. Steatosis was assessed by Nile red staining. mRNA expression of Bim and DR5 was examined by real time PCR. Expression of Bim protein and phosphorylation of JNK was assessed by immunoblotting. Results: As expected, Toyocamycin inhibited palmitate-mediated XBP-1 splicing without affecting amount of total RNA. Toyocamycin significantly reduced palmitateinduced hepatocyte lipoapoptosis (p<0.05) and caspase 3/7 activity (p<0.05) in dose dependent manner. Interestingly, Toyocamycin also attenuated free fatty acid-induced steatosis. In addition, Toyocamycin attenuated expression of Bim protein andmRNA (p<0.05) following palmitate treatment. Furthermore, PAmediated-transcriptional activation of DR5was reduced by Toyocamycin (p<0.05). In contrast, palmitate-induced JNK phosphorylation, which also occurs downstream of IRE-1 arm of ER stress, was not inhibited by Toyocamycin. Conclusions: These data imply that Toyocamycin attenuates hepatocyte lipotoxicity as well as steatosis, likely through inhibition of XBP-1 splicing. Toyocamycin might be beneficial for NASH treatment.
Naota Taura - One of the best experts on this subject based on the ideXlab platform.
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Toyocamycin attenuates free fatty acid-induced hepatic steatosis and apoptosis in cultured hepatocytes and ameliorates nonalcoholic fatty liver disease in mice.
PLOS ONE, 2017Co-Authors: Ikuko Takahara, Naota Taura, Yuko Akazawa, Maiko Tabuchi, Katsuya Matsuda, Hisamitsu Miyaaki, Youko Kido, Yasuko Kanda, Ken Ohnita, Fuminao TakeshimaAbstract:Background and aims A high serum level of saturated free fatty acids (FFAs) is associated with the development of nonalcoholic fatty liver disease (NAFLD). X-box binding protein-1 (XBP-1) is activated by FFA treatment upon splicing. XBP-1 is a transcription factor induced by the endoplasmic reticulum (ER) stress sensor endoribonuclease inositol-requiring enzyme 1 alpha (IRE1α). However, the role of XBP-1 in NAFLD remains relatively unexplored. Toyocamycin was recently reported to attenuate the activation of XBP-1, possibly by inducing a conformational change in IRE1α. In this study, we examined the effect of Toyocamycin on hepatocyte lipoapoptosis and steatosis. We also explored the effects of Toyocamycin in a mouse model of NAFLD. Methods Huh-7 cells and isolated rat primary hepatocytes were treated with palmitic acid (PA), which is a saturated FFA, in the presence or absence of Toyocamycin. In addition, male C57BL/6J mice were fed a diet rich in saturated fat, fructose, and cholesterol (FFC) for 4 months, after which the effect of Toyocamycin was assessed. Results Toyocamycin attenuated FFA-induced steatosis. It also significantly reduced PA-induced hepatocyte lipoapoptosis. In addition, Toyocamycin reduced the expression of cytosine-cytosine-adenosine-adenosine-thymidine enhancer-binding protein homologous protein (CHOP), which is a key player in ER stress-mediated apoptosis, as well as its downstream cell death modulator, death receptor 5. In the in vivo study, Toyocamycin ameliorated the liver injury caused by FFC-induced NAFLD. It also reduced hepatic steatosis and the expression of lipogenic genes. Conclusions The data we obtained suggest that Toyocamycin attenuates hepatocyte lipogenesis and ameliorates NAFLD in vivo and may therefore be beneficial in the treatment of NAFLD in humans.
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696 XBP-1 Inhibitor Toyocamycin Attenuates Palmitate-Induced Hepatocyte Apoptosis and Steatosis
Gastroenterology, 2014Co-Authors: Ikuko Takahara, Fuminao Takeshima, Naota Taura, Tatsuki Ichikawa, Yuko Akazawa, Hajime Isomoto, Ken Ohnita, Kazuhiko NakaoAbstract:Background and Aim: Free fatty acid-induced hepatocyte cytotoxicity is deeply associated withmorbidity of Non-alcoholic fatty liver disease (NAFLD) (Malhi et al, 2008, Gastroenterology). Saturated free fatty acids induce hepatocyte lipoapoptosis via endoplasmic reticulum stress (ER) response, which leads to translational activation of DR5 and BH3 only protein Bim (Cazanave et al, JBC, 2011). We previously reported that X-box binding protein-1 (XBP-1) is activated downstream of IRE-1 arm of ER stress by free fatty acid treatment upon its splicing (Akazawa et al, 2009, J Hepatol). However, role of XBP-1 during hepatocyte lipoapoptosis remains relatively unexplored. We examined the impact of inhibiting XBP-1 on hepatocyte lipoapoptosis and steatosis employing Toyocamycin, which was recently reported to inhibit ER stress-mediated XBP-1 splicing (Ri M et al, Blood Cancer J. 2012). Methods: We employed hepatocellular carcinoma cell line, Huh-7 cells, for these studies. Cells were incubated with palmitate (200~800μM) in presence or absence of Toyocamycin (0.1~3μM). Apoptosis was assessed by DAPI staining and caspase 3/7 activity assay. Steatosis was assessed by Nile red staining. mRNA expression of Bim and DR5 was examined by real time PCR. Expression of Bim protein and phosphorylation of JNK was assessed by immunoblotting. Results: As expected, Toyocamycin inhibited palmitate-mediated XBP-1 splicing without affecting amount of total RNA. Toyocamycin significantly reduced palmitateinduced hepatocyte lipoapoptosis (p
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696 xbp 1 inhibitor Toyocamycin attenuates palmitate induced hepatocyte apoptosis and steatosis
Gastroenterology, 2014Co-Authors: Ikuko Takahara, Fuminao Takeshima, Naota Taura, Tatsuki Ichikawa, Yuko Akazawa, Hajime Isomoto, Ken Ohnita, Kazuhiko NakaoAbstract:Background and Aim: Free fatty acid-induced hepatocyte cytotoxicity is deeply associated withmorbidity of Non-alcoholic fatty liver disease (NAFLD) (Malhi et al, 2008, Gastroenterology). Saturated free fatty acids induce hepatocyte lipoapoptosis via endoplasmic reticulum stress (ER) response, which leads to translational activation of DR5 and BH3 only protein Bim (Cazanave et al, JBC, 2011). We previously reported that X-box binding protein-1 (XBP-1) is activated downstream of IRE-1 arm of ER stress by free fatty acid treatment upon its splicing (Akazawa et al, 2009, J Hepatol). However, role of XBP-1 during hepatocyte lipoapoptosis remains relatively unexplored. We examined the impact of inhibiting XBP-1 on hepatocyte lipoapoptosis and steatosis employing Toyocamycin, which was recently reported to inhibit ER stress-mediated XBP-1 splicing (Ri M et al, Blood Cancer J. 2012). Methods: We employed hepatocellular carcinoma cell line, Huh-7 cells, for these studies. Cells were incubated with palmitate (200~800μM) in presence or absence of Toyocamycin (0.1~3μM). Apoptosis was assessed by DAPI staining and caspase 3/7 activity assay. Steatosis was assessed by Nile red staining. mRNA expression of Bim and DR5 was examined by real time PCR. Expression of Bim protein and phosphorylation of JNK was assessed by immunoblotting. Results: As expected, Toyocamycin inhibited palmitate-mediated XBP-1 splicing without affecting amount of total RNA. Toyocamycin significantly reduced palmitateinduced hepatocyte lipoapoptosis (p<0.05) and caspase 3/7 activity (p<0.05) in dose dependent manner. Interestingly, Toyocamycin also attenuated free fatty acid-induced steatosis. In addition, Toyocamycin attenuated expression of Bim protein andmRNA (p<0.05) following palmitate treatment. Furthermore, PAmediated-transcriptional activation of DR5was reduced by Toyocamycin (p<0.05). In contrast, palmitate-induced JNK phosphorylation, which also occurs downstream of IRE-1 arm of ER stress, was not inhibited by Toyocamycin. Conclusions: These data imply that Toyocamycin attenuates hepatocyte lipotoxicity as well as steatosis, likely through inhibition of XBP-1 splicing. Toyocamycin might be beneficial for NASH treatment.
