Perturbations in mitochondrial dynamics by p66Shc lead to renal tubular oxidative injury in human diabetic nephropathy

Abstract

Renal tubular injury is increasingly being recognized as an early characteristic of diabetic nephropathy (DN). Mitochondrial dynamic alterations and redox protein p66Shc-mediated oxidative stress are both critical for ensuing diabetic tubular cell injury and apoptosis; whether these two processes are interlinked remains unclear. In the present study, we observed changes in mitochondrial morphology and expression of associated proteins in tubules of patients with DN. We demonstrated mitochondrial fragmentation as an important pathogenic feature of tubular cell injury that is linked to oxidative stress and p66Shc up-regulation. In renal proximal tubular cells, alterations in mitochondrial dynamics and expression of fission-fusion proteins were observed under high glucose (HG) ambience, along with p66Shc Ser36 phosphorylation. Gene ablation of p66Shc alleviated HG-induced mitochondrial fragmentation, down-regulated Fis1 and reduced p66Shc-Fis1 binding, increased Mfn1 expression, and disrupted interactions between Mfn1 and proapoptotic Bak. Overexpression of p66Shc exacerbated these changes, whereas overexpression of dominant-negative p66Shc Ser36 mutant had a marginal effect under HG, indicating that p66Shc phosphorylation as a prerequisite in the modulation of mitochondrial dynamics. Disrupted mitochondrial dynamics and enhanced Mfn1-Bak interactions modulated by p66Shc led to loss of mitochondrial voltage potential, cytochrome release, excessive ROS generation, and apoptosis. Taken together, these results link p66Shc to mitochondrial dynamic alterations in the pathogenesis of DN and unveil a novel mechanism by which p66Shc mediates HG-induced mitochondrial fragmentation and proapoptotic signaling that results in oxidative injury and apoptosis in the tubular compartment in human diabetic nephropathy.

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Targeting of miR-96-5p by catalpol ameliorates oxidative stress and hepatic steatosis in LDLr-/- mice via p66shc/cytochrome C cascade

“…It is well known that increased p66shc expression is closely associated with oxidative stress and recent study reported that oxidative stress is related to cytochrome C-mediated apoptosis. Consistent evidence demonstrated that high expression of p66shc in ischemia reperfusion [26], renal tubular oxidative injury [30], angiotensin II-induced mouse hippocampal HT22 cells apoptosis [31] could active cytochrome Cmediated apoptotic pathways. However, the relationship between p66shc and cytochrome C in NAFLD haven't been clearly demonstrated.…”

Lipotoxicity and Diabetic Nephropathy: Novel Mechanistic Insights and Therapeutic Opportunities

“…Alterations in mitochondria function determine the intracellular accumulation of lipids and further lipotoxic actions, as reported in both glomeruli and tubules [159][160][161]. The proximal tubule has highly specialized metabolic machinery, which needs a fine energy balance.…”

“…Recent studies have highlighted the renoprotective role of cardiolipin, a unique phospholipid present in the mitochondrial inner membrane, necessary for the formation and maintenance of mitochondrial cristae structure [158,159,165]. The prevention of cardiolipin peroxidation improves the efficiency of ATP production through the oxidative phosphorylation (OXPHOS) process, restoring mitochondrial bioenergetics [160,161]. Indeed, when phosphorylation capacity is exceeded, mitochondria are disturbed and, as a consequence, non-oxidized lipids are accumulated.…”