TY - JOUR
T1 - myo-inositol oxygenase overexpression accentuates generation of reactive oxygen species and exacerbates cellular injury following high glucose ambience
T2 - A new mechanism relevant to the pathogenesis of diabetic nephropathy
AU - Sun, Lin
AU - Dutta, Rajesh K.
AU - Xie, Ping
AU - Kanwar, Yashpal S.
N1 - Funding Information:
This work was supported by National Institutes of Health Grant DK60635 and National Natural Science Foundation of China Grants 81270812 and 81470960. The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Publisher Copyright:
© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.
PY - 2016/3/11
Y1 - 2016/3/11
N2 - Diabetic nephropathy (DN) is characterized by perturbations in metabolic/cellular signaling pathways with generation of reactive oxygen species (ROS). The ROS are regarded as a common denominator of various pathways, and they inflict injury on renal glomerular cells. Recent studies indicate that tubular pathobiology also plays a role in the progression of DN. However, the mechanism(s) for how high (25 mM) glucose (HG) ambience induces tubular damage remains enigmatic. myo-Inositol oxygenase (MIOX) is a tubular enzyme that catabolizes myo-inositol to D-glucuronate via the glucuronate-xylulose (G-X) pathway. In this study, we demonstrated that G-X pathway enzymes are expressed in the kidney, and MIOX expression/bioactivity was up-regulated under HG ambience in LLC-PK1 cells, a tubular cell line. We further investigated whether MIOX overexpression leads to accentuation of tubulo-interstitial injury, as gauged by some of the parameters relevant to the progression of DN. Under HG ambience, MIOX overexpression accentuated redox imbalance, perturbed NAD+/NADH ratios, increased ROS generation, depleted reduced glutathione, reduced GSH/GSSG ratio, and enhanced adaptive changes in the profile of the antioxidant defense system. These changes were also accompanied by mitochondrial dysfunctions, DNA damage and induction of apoptosis, accentuated activity of profibrogenic cytokine, and expression of fibronectin, the latter two being the major hallmarks of DN. These perturbations were largely blocked by various ROS inhibitors (Mito Q, diphenyleneiodonium chloride, and N-acetylcysteine) and MIOX/NOX4 siRNA. In conclusion, this study highlights a novel mechanism where MIOX under HG ambience exacerbates renal injury during the progression of diabetic nephropathy following the generation of excessive ROS via an unexplored G-X pathway.
AB - Diabetic nephropathy (DN) is characterized by perturbations in metabolic/cellular signaling pathways with generation of reactive oxygen species (ROS). The ROS are regarded as a common denominator of various pathways, and they inflict injury on renal glomerular cells. Recent studies indicate that tubular pathobiology also plays a role in the progression of DN. However, the mechanism(s) for how high (25 mM) glucose (HG) ambience induces tubular damage remains enigmatic. myo-Inositol oxygenase (MIOX) is a tubular enzyme that catabolizes myo-inositol to D-glucuronate via the glucuronate-xylulose (G-X) pathway. In this study, we demonstrated that G-X pathway enzymes are expressed in the kidney, and MIOX expression/bioactivity was up-regulated under HG ambience in LLC-PK1 cells, a tubular cell line. We further investigated whether MIOX overexpression leads to accentuation of tubulo-interstitial injury, as gauged by some of the parameters relevant to the progression of DN. Under HG ambience, MIOX overexpression accentuated redox imbalance, perturbed NAD+/NADH ratios, increased ROS generation, depleted reduced glutathione, reduced GSH/GSSG ratio, and enhanced adaptive changes in the profile of the antioxidant defense system. These changes were also accompanied by mitochondrial dysfunctions, DNA damage and induction of apoptosis, accentuated activity of profibrogenic cytokine, and expression of fibronectin, the latter two being the major hallmarks of DN. These perturbations were largely blocked by various ROS inhibitors (Mito Q, diphenyleneiodonium chloride, and N-acetylcysteine) and MIOX/NOX4 siRNA. In conclusion, this study highlights a novel mechanism where MIOX under HG ambience exacerbates renal injury during the progression of diabetic nephropathy following the generation of excessive ROS via an unexplored G-X pathway.
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U2 - 10.1074/jbc.M115.669952
DO - 10.1074/jbc.M115.669952
M3 - Article
C2 - 26792859
AN - SCOPUS:84966817832
SN - 0021-9258
VL - 291
SP - 5688
EP - 5707
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 11
ER -
