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Avtar K. Singh - One of the best experts on this subject based on the ideXlab platform.
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Role of endogenous Psychosine accumulation in oligodendrocyte differentiation and survival: Implication for Krabbe disease
Brain research, 2013Co-Authors: Je-seong Won, Inderjit Singh, Jinsu Kim, Manjeet K. Paintlia, Avtar K. SinghAbstract:Krabbe disease is a lethal, demyelinating condition caused by genetic deficiency of galactocerebrosidase (GALC) and resultant accumulation of its cytotoxic substrate, Psychosine (galactosylsphingosine), primarily in oligodendrocytes (OLs). Psychosine is generated by galactosylation of sphingosine by UDP-galactose:ceramide galactosyltransferase (CGT), a galactosylceramide synthesizing enzyme which is primarily expressed in OLs. The expression of CGT and the synthesis of galactosyl-sphingolipids are associated with the terminal differentiation of OL, but little is known about the participation of endogenous Psychosine accumulation in OL differentiation under GALC deficient conditions. In this study, we report that accumulation of endogenous Psychosine under GALC deficient Krabbe conditions impedes OL differentiation process both by decreasing the expression of myelin lipids and protein and by inducing the cell death of maturating OLs. The Psychosine pathology under GALC deficient conditions involves participation of secretory phospholipase A2 (sPLA2) activation and increase in its metabolites, as evidenced by attenuation of Psychosine-induced pathology by treatment with pharmacological inhibitor of sPLA2 7,7-dimethyleicosadienoic acid (DEDA). These observations suggest for potential therapeutic efficacy of sPLA2 inhibitor in Krabbe disease.
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Inhibition of peroxisomal functions and production of excessive oxidative stress by Psychosine in rat C6 glial cells
Journal of Neurochemistry, 2008Co-Authors: M. A. Khan, Shailendra Giri, Inderjit Singh, Avtar K. SinghAbstract:The primary defect of abnormality in the metabolism of Psychosine in Krabbe disease results in the loss of oligodendrocytes, increased oxidative stress, inflammatory reactions and profound demyelination. To understand the basis of toxicity of Psychosine in the CNS of Krabbe disease, we examined the effects of Psychosine on the peroxisomal β-oxidation of very long chain fatty acids (VLCFA), plasmalogen biosynthesis and on the production of reactive oxygen/nitrogen species. Rat C6 glial cells were treated with Psychosine (2–10 mm) in absence and presence of cytokines (LPS + IFN-γ, or TNF-α + IL-1β) for 24 and 72 h. Psychosine inhibited peroxisomal b-oxidation of VLCFA (30–40% decrease compared to control) and induced the accumulation of VLCFA measured as levels of 26 : 0 (100% increase compared to control). Furthermore, Psychosine treatment decreased the levels of plasmalogens (35–50% decrease compared to control). Plasmalogens levels were also drastically low in Krabbe brain than normal control brain. Psychosine also potentiated the known cytokine-induced inhibition of peroxisomal β-oxidation, accumulation of VLCFA and NO production. We also measured overall oxidative stress using dichlorofluorescin diacetate in Psychosine-treated cells and found 1–2 fold increase in oxidative stress production. Both Psychosine-mediated loss of peroxisomal functions as well as ROS production could be inhibited by antioxidant, N-acetylcysteine. Our results suggest that inhibition of peroxisomal functions and increased free radical production by Psychosine may be responsible, at least in part, for the loss of oligodendrocytes and break down of myelin in Krabbe brain. Acknowledgements: Supported by NIH grants NS-40144, NS-40810, NS-22576, NS-34741 and NS-37766.
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Psychosine-induced alterations in peroxisomes of twitcher mouse liver.
Archives of biochemistry and biophysics, 2008Co-Authors: Ehtishamul Haq, Inderjit Singh, Miguel A. Contreras, Takuhiro Uto, Avtar K. SinghAbstract:Krabbe disease is a neuroinflammatory disorder in which galactosylsphingosine (Psychosine) accumulates in nervous tissue. To gain insight into whether the Psychosine-induced effects in nervous tissue extend to peripheral organs, we investigated the expression of cytokines and their effects on peroxisomal structure/functions in twitcher mouse liver (animal model of Krabbe disease). Immunofluorescence analysis demonstrated TNF-α and IL-6 expression, which was confirmed by mRNAs quantitation. Despite the presence of TNF-α, lipidomic analysis did not indicate a significant decrease in sphingomyelin or an increase in ceramide fractions. Ultrastructural analysis of catalase-dependent staining of liver sections showed reduced reactivity without significant changes in peroxisomal contents. This observation was confirmed by assaying catalase activity and quantitation of its mRNA, both of which were found significantly decreased in twitcher mouse liver. Western blot analysis demonstrated a generalized reduction of peroxisomal matrix and membrane proteins. These observations indicate that twitcher mouse pathobiology extends to the liver, where Psychosine-induced TNF-α and IL-6 compromise peroxisomal structure and functions.
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the role of ampk in Psychosine mediated effects on oligodendrocytes and astrocytes implication for krabbe disease
Journal of Neurochemistry, 2008Co-Authors: Shailendra Giri, Inderjit Singh, Avtar K. Singh, Mushfiquddin Khan, Narender NathAbstract:Krabbe disease (KD) is an inherited neurological disorder caused by the deficiency of galactocerebrosidase activity resulting in accumulation of Psychosine, which leads to energy depletion, loss of oligodendrocytes, induction of gliosis, and inflammation by astrocytes in CNS. In this study, for the first time, we report the regulation of 'cellular energy switch,' AMP-activated protein kinase (AMPK), by Psychosine in oligodendrocytes and astrocytes. Psychosine treatment significantly down-regulated AMPK activity, resulting in increased biosynthesis of lipids including cholesterol and free fatty acid in oligodendrocytes cell line (MO3.13) and primary astrocytes. Pharmacological activator of AMPK, 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR) attenuated the Psychosine-mediated down-regulation of AMPK and restored altered biosynthesis of lipids. AICAR treatment also down-regulated Psychosine induced expression of proinflammatory cytokines and inducible nitric oxide synthase in primary astrocytes. However, AICAR treatment had no effect on Psychosine induced-reactive oxygen species generation, arachidonic acid release, and death of oligodendrocytes; suggesting the specific role of AMPK in regulation of Psychosine-mediated inflammatory response of astrocytes but not in cell death of oligodendrocytes. This study delineates an explicit role for AMPK in Psychosine induced inflammation in astrocytes without directly affecting the cell death of oligodendrocytes. It also suggests that AMPK activating agents act as anti-inflammatory agents and can hold a therapeutic potential in Krabbe disease/twitcher disease, particularly when used in combination with drugs, which protect oligodendrocyte cell loss, such as sPLA2 inhibitor [Giri et al., J. Lipid Res. 47 (2006), 1478].
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The role of AMPK in Psychosine mediated effects on oligodendrocytes and astrocytes: Implication for Krabbe Disease
Journal of neurochemistry, 2008Co-Authors: Shailendra Giri, Inderjit Singh, Mushfiquddin Khan, Narender Nath, Avtar K. SinghAbstract:Krabbe disease (KD) is an inherited neurological disorder caused by the deficiency of galactocerebrosidase activity resulting in accumulation of Psychosine, which leads to energy depletion, loss of oligodendrocytes, induction of gliosis, and inflammation by astrocytes in CNS. In this study, for the first time, we report the regulation of ‘cellular energy switch,’ AMP-activated protein kinase (AMPK), by Psychosine in oligodendrocytes and astrocytes. Psychosine treatment significantly down-regulated AMPK activity, resulting in increased biosynthesis of lipids including cholesterol and free fatty acid in oligodendrocytes cell line (MO3.13) and primary astrocytes. Pharmacological activator of AMPK, 5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR) attenuated the Psychosine-mediated down-regulation of AMPK and restored altered biosynthesis of lipids. AICAR treatment also down-regulated Psychosine induced expression of proinflammatory cytokines and inducible nitric oxide synthase in primary astrocytes. However, AICAR treatment had no effect on Psychosine induced-reactive oxygen species generation, arachidonic acid release, and death of oligodendrocytes; suggesting the specific role of AMPK in regulation of Psychosine-mediated inflammatory response of astrocytes but not in cell death of oligodendrocytes. This study delineates an explicit role for AMPK in Psychosine induced inflammation in astrocytes without directly affecting the cell death of oligodendrocytes. It also suggests that AMPK activating agents act as anti-inflammatory agents and can hold a therapeutic potential in Krabbe disease/twitcher disease, particularly when used in combination with drugs, which protect oligodendrocyte cell loss, such as sPLA2 inhibitor [Giri et al., J. Lipid Res. 47 (2006), 1478].
Shailendra Giri - One of the best experts on this subject based on the ideXlab platform.
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AK: Galactosylsphingosine (Psychosine)-induced expression of cytokinemediated inducible nitric oxide synthases via AP-1 and C/ EBP: implications for Krabbe disease
2013Co-Authors: Shailendra Giri, Inderjit Singh, Je-seong Won, Ramandeep Rattan, Manu Jatana, K. SinghAbstract:ABSTRACT Globoid cell leukodystrophy (Krabbe disease) is characterized by the accumulation of a toxic metabolite, Psychosine (galactosylsphingosine), which is a substrate for the deficient enzyme (galactocerebroside �-galactosidase). This study underscores the possible role of Psychosine in the effect of inducible nitric oxide synthase (iNOS)-derived NO in the pathophysiology of this demyelinating disease. For the first time, we provide evidence of the expression of iNOS in CNS of Krabbe patient and show that the iNOS-expressing cells in the CNS were astrocytes. Psychosine potentiated the LPS-induced production of proinflammatory cytokines (IL-1�, IL-6, and TNF-�) in primary rat astrocytes and regulated the cytokine-mediated production of NO in C6 glioma and primary rat astrocyte. Psychosine induced cytokine-mediated nuclear translocation of AP-1 and C/EBP by potentiating the expression of Fra-1 and C/EBP- � proteins. This suggests that Psychosine maintained or sustained the cytokineprimed expression of iNOS by further potentiating the nuclear translocation of AP-1 and C/EBP without modulating the cytokine-mediated transcription activity of NF-�B. This study hypothesizes that accumulated Psychosine leads to production of cytokines and iNOS expression. The ensuing excessive production of NO and ONOO � may play a role in pathogenesis of Krabb
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Inhibition of peroxisomal functions and production of excessive oxidative stress by Psychosine in rat C6 glial cells
Journal of Neurochemistry, 2008Co-Authors: M. A. Khan, Shailendra Giri, Inderjit Singh, Avtar K. SinghAbstract:The primary defect of abnormality in the metabolism of Psychosine in Krabbe disease results in the loss of oligodendrocytes, increased oxidative stress, inflammatory reactions and profound demyelination. To understand the basis of toxicity of Psychosine in the CNS of Krabbe disease, we examined the effects of Psychosine on the peroxisomal β-oxidation of very long chain fatty acids (VLCFA), plasmalogen biosynthesis and on the production of reactive oxygen/nitrogen species. Rat C6 glial cells were treated with Psychosine (2–10 mm) in absence and presence of cytokines (LPS + IFN-γ, or TNF-α + IL-1β) for 24 and 72 h. Psychosine inhibited peroxisomal b-oxidation of VLCFA (30–40% decrease compared to control) and induced the accumulation of VLCFA measured as levels of 26 : 0 (100% increase compared to control). Furthermore, Psychosine treatment decreased the levels of plasmalogens (35–50% decrease compared to control). Plasmalogens levels were also drastically low in Krabbe brain than normal control brain. Psychosine also potentiated the known cytokine-induced inhibition of peroxisomal β-oxidation, accumulation of VLCFA and NO production. We also measured overall oxidative stress using dichlorofluorescin diacetate in Psychosine-treated cells and found 1–2 fold increase in oxidative stress production. Both Psychosine-mediated loss of peroxisomal functions as well as ROS production could be inhibited by antioxidant, N-acetylcysteine. Our results suggest that inhibition of peroxisomal functions and increased free radical production by Psychosine may be responsible, at least in part, for the loss of oligodendrocytes and break down of myelin in Krabbe brain. Acknowledgements: Supported by NIH grants NS-40144, NS-40810, NS-22576, NS-34741 and NS-37766.
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the role of ampk in Psychosine mediated effects on oligodendrocytes and astrocytes implication for krabbe disease
Journal of Neurochemistry, 2008Co-Authors: Shailendra Giri, Inderjit Singh, Avtar K. Singh, Mushfiquddin Khan, Narender NathAbstract:Krabbe disease (KD) is an inherited neurological disorder caused by the deficiency of galactocerebrosidase activity resulting in accumulation of Psychosine, which leads to energy depletion, loss of oligodendrocytes, induction of gliosis, and inflammation by astrocytes in CNS. In this study, for the first time, we report the regulation of 'cellular energy switch,' AMP-activated protein kinase (AMPK), by Psychosine in oligodendrocytes and astrocytes. Psychosine treatment significantly down-regulated AMPK activity, resulting in increased biosynthesis of lipids including cholesterol and free fatty acid in oligodendrocytes cell line (MO3.13) and primary astrocytes. Pharmacological activator of AMPK, 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR) attenuated the Psychosine-mediated down-regulation of AMPK and restored altered biosynthesis of lipids. AICAR treatment also down-regulated Psychosine induced expression of proinflammatory cytokines and inducible nitric oxide synthase in primary astrocytes. However, AICAR treatment had no effect on Psychosine induced-reactive oxygen species generation, arachidonic acid release, and death of oligodendrocytes; suggesting the specific role of AMPK in regulation of Psychosine-mediated inflammatory response of astrocytes but not in cell death of oligodendrocytes. This study delineates an explicit role for AMPK in Psychosine induced inflammation in astrocytes without directly affecting the cell death of oligodendrocytes. It also suggests that AMPK activating agents act as anti-inflammatory agents and can hold a therapeutic potential in Krabbe disease/twitcher disease, particularly when used in combination with drugs, which protect oligodendrocyte cell loss, such as sPLA2 inhibitor [Giri et al., J. Lipid Res. 47 (2006), 1478].
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The role of AMPK in Psychosine mediated effects on oligodendrocytes and astrocytes: Implication for Krabbe Disease
Journal of neurochemistry, 2008Co-Authors: Shailendra Giri, Inderjit Singh, Mushfiquddin Khan, Narender Nath, Avtar K. SinghAbstract:Krabbe disease (KD) is an inherited neurological disorder caused by the deficiency of galactocerebrosidase activity resulting in accumulation of Psychosine, which leads to energy depletion, loss of oligodendrocytes, induction of gliosis, and inflammation by astrocytes in CNS. In this study, for the first time, we report the regulation of ‘cellular energy switch,’ AMP-activated protein kinase (AMPK), by Psychosine in oligodendrocytes and astrocytes. Psychosine treatment significantly down-regulated AMPK activity, resulting in increased biosynthesis of lipids including cholesterol and free fatty acid in oligodendrocytes cell line (MO3.13) and primary astrocytes. Pharmacological activator of AMPK, 5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR) attenuated the Psychosine-mediated down-regulation of AMPK and restored altered biosynthesis of lipids. AICAR treatment also down-regulated Psychosine induced expression of proinflammatory cytokines and inducible nitric oxide synthase in primary astrocytes. However, AICAR treatment had no effect on Psychosine induced-reactive oxygen species generation, arachidonic acid release, and death of oligodendrocytes; suggesting the specific role of AMPK in regulation of Psychosine-mediated inflammatory response of astrocytes but not in cell death of oligodendrocytes. This study delineates an explicit role for AMPK in Psychosine induced inflammation in astrocytes without directly affecting the cell death of oligodendrocytes. It also suggests that AMPK activating agents act as anti-inflammatory agents and can hold a therapeutic potential in Krabbe disease/twitcher disease, particularly when used in combination with drugs, which protect oligodendrocyte cell loss, such as sPLA2 inhibitor [Giri et al., J. Lipid Res. 47 (2006), 1478].
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Krabbe disease: Psychosine-mediated activation of phospholipase A2 in oligodendrocyte cell death.
Journal of lipid research, 2006Co-Authors: Shailendra Giri, Inderjit Singh, Mushfiquddin Khan, Ramandeep Rattan, Avtar K. SinghAbstract:Globoid cell leukodystrophy (Krabbe disease) is an inherited neurological disorder caused by the pathogenomic accumulation of Psychosine (galactosylsphingosine), a substrate for the deficient enzyme galactocerebroside β-galactosidase. This study underscores the mechanism of action of Psychosine in the regulation of oligodendrocyte cell death via the generation of lysophosphatidylcholine (LPC) and arachidonic acid (AA) by the activation of secretory phospholipase A2 (sPLA2). There was a significant increase in the level of LPC, indicating a phospholipase A2 (PLA2)-dependent pathobiology, in the brains of Krabbe disease patients and those of twitcher mice, an animal model of Krabbe disease. In vitro studies of the treatment of primary oligodendrocytes and the oligodendrocyte MO3.13 cell line with Psychosine also showed the generation of LPC and the release of AA in a dose- and time-dependent manner, indicating Psychosine-induced activation of PLA2. Studies with various pharmacological inhibitors of cytosolic phospholipase A2 and sPLA2 and Psychosine-mediated induction of sPLA2 enzymatic activity in media supernatant suggest that Psychosine-induced release of AA and generation of LPC is mainly contributed by sPLA2. An inhibitor of sPLA2, 7,7-dimethyl eicosadienoic acid, completely attenuated the Psychosine-mediated accumulation of LPC levels, release of AA, and generation of reactive oxygen species, and blocked oligodendroyte cell death, as evident from cell survival, DNA fragmentation, and caspase 3 activity assays. This study documents for the first time that Psychosine-induced cell death is mediated via the sPLA2 signaling pathway and that inhibitors of sPLA2 may hold a therapeutic potential for protection against oligodendrocyte cell death and resulting demyelination in Krabbe disease.
Inderjit Singh - One of the best experts on this subject based on the ideXlab platform.
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AK: Galactosylsphingosine (Psychosine)-induced expression of cytokinemediated inducible nitric oxide synthases via AP-1 and C/ EBP: implications for Krabbe disease
2013Co-Authors: Shailendra Giri, Inderjit Singh, Je-seong Won, Ramandeep Rattan, Manu Jatana, K. SinghAbstract:ABSTRACT Globoid cell leukodystrophy (Krabbe disease) is characterized by the accumulation of a toxic metabolite, Psychosine (galactosylsphingosine), which is a substrate for the deficient enzyme (galactocerebroside �-galactosidase). This study underscores the possible role of Psychosine in the effect of inducible nitric oxide synthase (iNOS)-derived NO in the pathophysiology of this demyelinating disease. For the first time, we provide evidence of the expression of iNOS in CNS of Krabbe patient and show that the iNOS-expressing cells in the CNS were astrocytes. Psychosine potentiated the LPS-induced production of proinflammatory cytokines (IL-1�, IL-6, and TNF-�) in primary rat astrocytes and regulated the cytokine-mediated production of NO in C6 glioma and primary rat astrocyte. Psychosine induced cytokine-mediated nuclear translocation of AP-1 and C/EBP by potentiating the expression of Fra-1 and C/EBP- � proteins. This suggests that Psychosine maintained or sustained the cytokineprimed expression of iNOS by further potentiating the nuclear translocation of AP-1 and C/EBP without modulating the cytokine-mediated transcription activity of NF-�B. This study hypothesizes that accumulated Psychosine leads to production of cytokines and iNOS expression. The ensuing excessive production of NO and ONOO � may play a role in pathogenesis of Krabb
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Role of endogenous Psychosine accumulation in oligodendrocyte differentiation and survival: Implication for Krabbe disease
Brain research, 2013Co-Authors: Je-seong Won, Inderjit Singh, Jinsu Kim, Manjeet K. Paintlia, Avtar K. SinghAbstract:Krabbe disease is a lethal, demyelinating condition caused by genetic deficiency of galactocerebrosidase (GALC) and resultant accumulation of its cytotoxic substrate, Psychosine (galactosylsphingosine), primarily in oligodendrocytes (OLs). Psychosine is generated by galactosylation of sphingosine by UDP-galactose:ceramide galactosyltransferase (CGT), a galactosylceramide synthesizing enzyme which is primarily expressed in OLs. The expression of CGT and the synthesis of galactosyl-sphingolipids are associated with the terminal differentiation of OL, but little is known about the participation of endogenous Psychosine accumulation in OL differentiation under GALC deficient conditions. In this study, we report that accumulation of endogenous Psychosine under GALC deficient Krabbe conditions impedes OL differentiation process both by decreasing the expression of myelin lipids and protein and by inducing the cell death of maturating OLs. The Psychosine pathology under GALC deficient conditions involves participation of secretory phospholipase A2 (sPLA2) activation and increase in its metabolites, as evidenced by attenuation of Psychosine-induced pathology by treatment with pharmacological inhibitor of sPLA2 7,7-dimethyleicosadienoic acid (DEDA). These observations suggest for potential therapeutic efficacy of sPLA2 inhibitor in Krabbe disease.
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Inhibition of peroxisomal functions and production of excessive oxidative stress by Psychosine in rat C6 glial cells
Journal of Neurochemistry, 2008Co-Authors: M. A. Khan, Shailendra Giri, Inderjit Singh, Avtar K. SinghAbstract:The primary defect of abnormality in the metabolism of Psychosine in Krabbe disease results in the loss of oligodendrocytes, increased oxidative stress, inflammatory reactions and profound demyelination. To understand the basis of toxicity of Psychosine in the CNS of Krabbe disease, we examined the effects of Psychosine on the peroxisomal β-oxidation of very long chain fatty acids (VLCFA), plasmalogen biosynthesis and on the production of reactive oxygen/nitrogen species. Rat C6 glial cells were treated with Psychosine (2–10 mm) in absence and presence of cytokines (LPS + IFN-γ, or TNF-α + IL-1β) for 24 and 72 h. Psychosine inhibited peroxisomal b-oxidation of VLCFA (30–40% decrease compared to control) and induced the accumulation of VLCFA measured as levels of 26 : 0 (100% increase compared to control). Furthermore, Psychosine treatment decreased the levels of plasmalogens (35–50% decrease compared to control). Plasmalogens levels were also drastically low in Krabbe brain than normal control brain. Psychosine also potentiated the known cytokine-induced inhibition of peroxisomal β-oxidation, accumulation of VLCFA and NO production. We also measured overall oxidative stress using dichlorofluorescin diacetate in Psychosine-treated cells and found 1–2 fold increase in oxidative stress production. Both Psychosine-mediated loss of peroxisomal functions as well as ROS production could be inhibited by antioxidant, N-acetylcysteine. Our results suggest that inhibition of peroxisomal functions and increased free radical production by Psychosine may be responsible, at least in part, for the loss of oligodendrocytes and break down of myelin in Krabbe brain. Acknowledgements: Supported by NIH grants NS-40144, NS-40810, NS-22576, NS-34741 and NS-37766.
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Psychosine-induced alterations in peroxisomes of twitcher mouse liver.
Archives of biochemistry and biophysics, 2008Co-Authors: Ehtishamul Haq, Inderjit Singh, Miguel A. Contreras, Takuhiro Uto, Avtar K. SinghAbstract:Krabbe disease is a neuroinflammatory disorder in which galactosylsphingosine (Psychosine) accumulates in nervous tissue. To gain insight into whether the Psychosine-induced effects in nervous tissue extend to peripheral organs, we investigated the expression of cytokines and their effects on peroxisomal structure/functions in twitcher mouse liver (animal model of Krabbe disease). Immunofluorescence analysis demonstrated TNF-α and IL-6 expression, which was confirmed by mRNAs quantitation. Despite the presence of TNF-α, lipidomic analysis did not indicate a significant decrease in sphingomyelin or an increase in ceramide fractions. Ultrastructural analysis of catalase-dependent staining of liver sections showed reduced reactivity without significant changes in peroxisomal contents. This observation was confirmed by assaying catalase activity and quantitation of its mRNA, both of which were found significantly decreased in twitcher mouse liver. Western blot analysis demonstrated a generalized reduction of peroxisomal matrix and membrane proteins. These observations indicate that twitcher mouse pathobiology extends to the liver, where Psychosine-induced TNF-α and IL-6 compromise peroxisomal structure and functions.
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the role of ampk in Psychosine mediated effects on oligodendrocytes and astrocytes implication for krabbe disease
Journal of Neurochemistry, 2008Co-Authors: Shailendra Giri, Inderjit Singh, Avtar K. Singh, Mushfiquddin Khan, Narender NathAbstract:Krabbe disease (KD) is an inherited neurological disorder caused by the deficiency of galactocerebrosidase activity resulting in accumulation of Psychosine, which leads to energy depletion, loss of oligodendrocytes, induction of gliosis, and inflammation by astrocytes in CNS. In this study, for the first time, we report the regulation of 'cellular energy switch,' AMP-activated protein kinase (AMPK), by Psychosine in oligodendrocytes and astrocytes. Psychosine treatment significantly down-regulated AMPK activity, resulting in increased biosynthesis of lipids including cholesterol and free fatty acid in oligodendrocytes cell line (MO3.13) and primary astrocytes. Pharmacological activator of AMPK, 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR) attenuated the Psychosine-mediated down-regulation of AMPK and restored altered biosynthesis of lipids. AICAR treatment also down-regulated Psychosine induced expression of proinflammatory cytokines and inducible nitric oxide synthase in primary astrocytes. However, AICAR treatment had no effect on Psychosine induced-reactive oxygen species generation, arachidonic acid release, and death of oligodendrocytes; suggesting the specific role of AMPK in regulation of Psychosine-mediated inflammatory response of astrocytes but not in cell death of oligodendrocytes. This study delineates an explicit role for AMPK in Psychosine induced inflammation in astrocytes without directly affecting the cell death of oligodendrocytes. It also suggests that AMPK activating agents act as anti-inflammatory agents and can hold a therapeutic potential in Krabbe disease/twitcher disease, particularly when used in combination with drugs, which protect oligodendrocyte cell loss, such as sPLA2 inhibitor [Giri et al., J. Lipid Res. 47 (2006), 1478].
Xuntian Jiang - One of the best experts on this subject based on the ideXlab platform.
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cerebrospinal fluid and serum glycosphingolipid biomarkers in canine globoid cell leukodystrophy krabbe disease
Molecular and Cellular Neuroscience, 2020Co-Authors: Carley R Corado, Jessica H. Bagel, Xuntian Jiang, Jason Pinkstaff, Evelyn M Galban, Samantha J Fisher, Oriane Scholler, Chris B Russell, Patricia Odonnell, Daniel S. OryAbstract:Abstract Globoid cell leukodystrophy (GLD, Krabbe disease, Krabbe's disease) is caused by genetic mutations in the gene encoding, galactosylceramidase (GALC). Deficiency of this enzyme results in central and peripheral nervous system pathology, and is characterized by loss of myelin and an infiltration of globoid cells. The canine model of GLD provides a translational model which faithfully recapitulates much of the human disease pathology. Targeted lipidomic analysis was conducted in serum and cerebrospinal fluid (CSF) over the lifetime of GLD affected and normal canines, and in brain tissue at humane endpoint to better understand disease progression and identify potential biomarkers of disease. Psychosine, a substrate of GALC and primary contributor to the pathology in GLD, was observed to be significantly elevated in the serum and CSF by 2 or 4 weeks of age, respectively, and steadily increased over the lifetime of affected animals. Importantly, Psychosine concentration strongly correlated with disease severity. Galactosylceramide, glucosylceramide, and lactosylceramide were also found to be elevated in the CSF of affected animals and increased with age. Psychosine and galactosylceramide were found to be significantly increased in brain tissue at humane endpoint. This study identified several biomarkers which may be useful in the development of therapeutics for GLD.
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genetic ablation of acid ceramidase in krabbe disease confirms the Psychosine hypothesis and identifies a new therapeutic target
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Bruno A Benitez, Murtaza S Nagree, Joshua T Dearborn, Xuntian Jiang, Miguel Guzman, Josh C Woloszynek, Alex Giaramita, Bryan K Yip, Joseph Elsbernd, Michael C BabcockAbstract:Infantile globoid cell leukodystrophy (GLD, Krabbe disease) is a fatal demyelinating disorder caused by a deficiency in the lysosomal enzyme galactosylceramidase (GALC). GALC deficiency leads to the accumulation of the cytotoxic glycolipid, galactosylsphingosine (Psychosine). Complementary evidence suggested that Psychosine is synthesized via an anabolic pathway. Here, we show instead that Psychosine is generated catabolically through the deacylation of galactosylceramide by acid ceramidase (ACDase). This reaction uncouples GALC deficiency from Psychosine accumulation, allowing us to test the long-standing "Psychosine hypothesis." We demonstrate that genetic loss of ACDase activity (Farber disease) in the GALC-deficient mouse model of human GLD (twitcher) eliminates Psychosine accumulation and cures GLD. These data suggest that ACDase could be a target for substrate reduction therapy (SRT) in Krabbe patients. We show that pharmacological inhibition of ACDase activity with carmofur significantly decreases Psychosine accumulation in cells from a Krabbe patient and prolongs the life span of the twitcher (Twi) mouse. Previous SRT experiments in the Twi mouse utilized l-cycloserine, which inhibits an enzyme several steps upstream of Psychosine synthesis, thus altering the balance of other important lipids. Drugs that directly inhibit ACDase may have a more acceptable safety profile due to their mechanistic proximity to Psychosine biogenesis. In total, these data clarify our understanding of Psychosine synthesis, confirm the long-held Psychosine hypothesis, and provide the impetus to discover safe and effective inhibitors of ACDase to treat Krabbe disease.
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Mechanism-Based Combination Treatment Dramatically Increases Therapeutic Efficacy in Murine Globoid Cell Leukodystrophy
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2015Co-Authors: Jacqueline A. Hawkins-salsbury, Xuntian Jiang, Lauren Shea, Daniel A. Hunter, A. Miguel Guzman, Adarsh S. Reddy, Elizabeth Y. Qin, Steven J. Gray, Daniel S. OryAbstract:Globoid cell leukodystrophy (GLD, Krabbe disease) is a lysosomal storage disease (LSD) caused by a deficiency in galactocerebrosidase (GALC) activity. In the absence of GALC activity, the cytotoxic lipid, galactosylsphingosine (Psychosine), accumulates in the CNS and peripheral nervous system. Oligodendrocytes and Schwann cells are particularly sensitive to Psychosine, thus leading to a demyelinating phenotype. Although hematopoietic stem-cell transplantation provides modest benefit in both presymptomatic children and the murine model (Twitcher), there is no cure for GLD. In addition, GLD has been relatively refractory to virtually every experimental therapy attempted. Here, Twitcher mice were simultaneously treated with CNS-directed gene therapy, substrate reduction therapy, and bone marrow transplantation to target the primary pathogenic mechanism (GALC deficiency) and two secondary consequences of GALC deficiency (Psychosine accumulation and neuroinflammation). Simultaneously treating multiple pathogenic targets resulted in an unprecedented increase in life span with improved motor function, persistent GALC expression, nearly normal Psychosine levels, and decreased neuroinflammation. Treating the primary pathogenic mechanism and secondary targets will likely improve therapeutic efficacy for other LSDs with complex pathological and clinical presentations.
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lipid extracts with a semi-synthetic internal standard
2013Co-Authors: Xuntian Jiang, Kui Yang, Xianlin HanAbstract:Direct quantitation of Psychosine from alkaline-treate
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Direct quantitation of Psychosine from alkaline-treated lipid extracts with a semi-synthetic internal standard.
Journal of lipid research, 2008Co-Authors: Xuntian Jiang, Kui Yang, Xianlin HanAbstract:Psychosine is an important bioactive sphingolipid metabolite and plays an essential role in the pathogenesis of Krabbe's disease. Herein, we extended shotgun lipidomics for the characterization and quantitation of Psychosine in alkaline-treated crude lipid extracts by using neutral loss scan of 180 amicro (i.e., galactose) in the positive-ion mode. Specifically, we semi-synthesized N,N-dimethyl Psychosine and used it as an internal standard for quantitation of Psychosine. After characterization of the fragmentation patterns of Psychosine and the selected internal standard and optimization of the experimental conditions, we demonstrated that a broad linear dynamic range for the quantitation of Psychosine and a limit of detection at a concentration of low fmol/microl were achieved using this approach. The developed method is generally simpler and more efficient than other previously reported methods. Multiple factors influencing quantitation of Psychosine were extensively examined and/or discussed. The levels of Psychosine in diabetic mouse nerve tissue samples were determined by the developed methodology. Collectively, the developed approach, as a new addition to the shotgun lipidomics technology, will be extremely useful for understanding the pathways/networks of sphingolipid metabolism and for exploring the important roles of Psychosine in a variety of physiological and pathological conditions.
Kunihiko Suzuki - One of the best experts on this subject based on the ideXlab platform.
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Evolving perspective of the pathogenesis of globoid cell leukodystrophy (Krabbe disease)
2003Co-Authors: Kunihiko SuzukiAbstract:Clinical, pathological and biochemical phenotype of globoid cell leukodystrophy (Krabbe disease) has several unique characteristics that are sometimes contrary to the conventional concept of genetic lysosomal disease. It was demonstrated early that galactosylceramide has unusual capacity to elicit a globoid cell-like reaction when implanted into the brain. Then, thirty years ago a hypothesis was introduced to explain the pathogenetic mechanism underlying the rapid and complete loss of myelin and myelinating cells. It postulated that galactosylsphingosine (Psychosine), which is highly cytotoxic and also cannot be degraded due to the underlying genetic defect, is responsible for the very rapid loss of the oligoden-drocytes and the consequent paradoxical analytical finding - lack of accumulation of the primary substrate, galactosylceramide, in patients'brain. It took nearly ten years before the actual accumulation of Psychosine was demonstrated in human Krabbe patients and also in the brain of mouse and dog models of the disease. During the intervening years, the Psychosine hypothesis has been generally accepted as a critical pathogenetic mechanism in classical infantile globoid cell leukodystrophy. However, a more recent experimental mouse model due to genetic defect in saposin A, an in vivo galactosylceramidase activator protein, introduced new elements in our understanding of the disease process. Not only has it established the second gene, genetic defect of which can cause globoid cell leukodystrophy but it has indicated potential decoupling of the two previously postulated pathogenetic mechanisms, galactosylceramide for the globoid cell reaction and Psychosine for loss of myelinating cells. Pathogenetic significance of participation of the major histocompatibility complexes and other immune mechanisms, inflammatory processes as suggested by activation of many cytokines, and possible interactions with sex hormones remain to be further explored.
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Psychosine Is as Potent an Inducer of Cell Death as C6-Ceramide in Cultured Fibroblasts and in MOCH-1 Cells
Neurochemical Research, 2001Co-Authors: Jun Tohyama, Junko Matsuda, Kunihiko SuzukiAbstract:Cytotoxic capacity of Psychosine (galactosylsphingosine) was evaluated in comparison with C6-ceramide in cultured fibroblasts and the glia-derived MOCH-1 cells that have characteristics of myelinating cells (1). Psychosine caused cytotoxic cell death and DNA fragmentation at concentrations similar to C6-ceramide and MOCH-1 cells were substantially more sensitive to their cytotoxic effects than fibroblasts. In this system, pretreatment with GM1-ganglioside failed to protect the cells from the deleterious effects of these compounds. These findings are consistent with the hypothesis that Psychosine is the cytotoxic metabolite that causes apoptotic death of the oligodendrocyte in globoid cell leukodystrophy (Krabbe disease). They further suggest that the protective capacity of GM1-ganglioside is unlikely to be the explanation for the paradoxical improvement of the phenotype of globoid cell leukodystrophy in the mouse simultaneously deficient in two lysosomal β-galactosidases, galactosylceramidase and GM1-ganglioside β-galactosidase.
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Twenty Five Years of the “Psychosine Hypothesis”: A Personal Perspective of its History and Present Status
Neurochemical Research, 1998Co-Authors: Kunihiko SuzukiAbstract:Twenty five years ago in 1972, a hypothesis was introduced to explain the pathogenetic mechanism underlying the unusual cellular and biochemical characteristics of globoid cell leukodystrophy (Krabbe disease). It postulated that galactosylsphingosine (Psychosine), which cannot be degraded due to the underlying genetic defect, is responsible for the very rapid loss of the oligodendrocytes and the consequent paradoxical analytical finding, the lack of accumulation of the primary substrate, galactosylceramide, in patients' brain. It took nearly ten years before the actual accumulation of Psychosine was demonstrated in human Krabbe patients and also in the brain of twitcher mice, an equivalent murine mutant. Meanwhile this “Psychosine hypothesis” has been extended to Gaucher disease and then to a more general hypothesis encompassing all sphingolipidoses that the “lyso-derivatives” of the primary sphingolipid substrates of the defective enzymes in respective disorders play a key role in their pathogenesis. Some of these extensions not only remain speculative without conclusive factual evidence but may eventually turn out to be an overstretching. This article attempts, from my personal perspective, at tracing historical development of the “Psychosine hypothesis” and examining its current status and possible future directions.
