Chronic high glucose downregulates mitochondrial calpain 10 and contributes to renal cell death and diabetes-induced renal injury.
Whereas most calpains are cytosolic proteases, calpain 10 is resident in mitochondria and is important in mitochondrial homeostasis. Because calpain 10 has been implicated in type 2 diabetes, we studied its possible role in diabetes-induced renal dysfunction. We treated renal proximal tubular cells with high glucose (17 mmol/l) and found decreased mitochondrial calpain 10 mRNA and protein at 96 h compared with cells incubated with 0 or 5 mmol/l glucose or 17 mmol/l D-mannitol. High glucose increased mitochondrial calpain 10 substrates (NDUFB8 and ATP synthase β), decreased basal and uncoupled respiration, and initiated cell apoptosis as indicated by cleaved caspase 3 and nuclear condensation. Renal calpain 10 protein and mRNA were specifically decreased in streptozotocin-induced diabetic rats with kidney dysfunction, and in diabetic ob/ob mice. In agreement with our in vitro data, the kidneys of streptozotocin-induced diabetic rats had elevated calpain 10 substrates and cleaved caspase 3. Finally, specific siRNA-induced knockdown of calpain 10 in the proximal tubules of control rats resulted in decreased renal function as evidenced by increased serum creatinine, and increased caspase 3 cleavage compared with rats receiving scrambled siRNA. Thus, the glucose-induced loss of calpain 10 in vivo results in renal cell apoptosis and organ failure through accumulation of mitochondrial calpain 10 substrates and mitochondrial dysfunction. Whether this is a major cause of the decreased renal function in diabetic nephropathy will require further studies.
Center for Cell Death, Injury and Regeneration, Department of Pharmaceutical and Biomedical Sciences, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Marisa D
MD
Covington
Rick G
RG
Schnellmann
D000818:Animals; D017209:Apoptosis; D002154:Calpain / Q000187:drug effects / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D003920:Diabetes Mellitus / Q000139:chemically induced; D003928:Diabetic Nephropathies / Q000201:enzymology / Q000378:metabolism*; D015536:Down-Regulation; D005260:Female; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000201:enzymology* / Q000503:physiopathology; D008297:Male; D051379:Mice; D008820:Mice, Obese; D008928:Mitochondria / Q000201:enzymology* / Q000502:physiology; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D013311:Streptozocin
D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013311:Streptozocin; D002154:Calpain; D053148:Caspase 3; C415197:calpain 10; C497342:ATP synthase beta subunit, rat; D025261:Mitochondrial Proton-Translocating ATPases; D005947:Glucose