title: Acute knockdown of uncoupling protein-2 increases uncoupling via the adenine nucleotide transporter and decreases oxidative stress in diabetic kidneys.
abstract: Increased O(2) metabolism resulting in chronic hypoxia is common in models of endstage renal disease. Mitochondrial uncoupling increases O(2) consumption but the ensuing reduction in mitochondrial membrane potential may limit excessive oxidative stress. The present study addressed the hypothesis that mitochondrial uncoupling regulates mitochondria function and oxidative stress in the diabetic kidney. Isolated mitochondria from kidney cortex of control and streptozotocin-induced diabetic rats were studied before and after siRNA knockdown of uncoupling protein-2 (UCP-2). Diabetes resulted in increased UCP-2 protein expression and UCP-2-mediated uncoupling, but normal mitochondria membrane potential. This uncoupling was inhibited by GDP, which also increased the membrane potential. siRNA reduced UCP-2 protein expression in controls and diabetics (-30-50%), but paradoxically further increased uncoupling and markedly reduced the membrane potential. This siRNA mediated uncoupling was unaffected by GDP but was blocked by ADP and carboxyatractylate (CAT). Mitochondria membrane potential after UCP-2 siRNA was unaffected by GDP but increased by CAT. This demonstrated that further increased mitochondria uncoupling after siRNA towards UCP-2 is mediated through the adenine nucleotide transporter (ANT). The increased oxidative stress in the diabetic kidney, manifested as increased thiobarbituric acids, was reduced by knocking down UCP-2 whereas whole-body oxidative stress, manifested as increased circulating malondialdehyde, remained unaffected. All parameters investigated were unaffected by scrambled siRNA. In conclusion, mitochondrial uncoupling via UCP-2 regulates mitochondria membrane potential in diabetes. However, blockade of the diabetes-induced upregulation of UCP- 2 results in excessive uncoupling and reduced oxidative stress in the kidney via activation of ANT.
authors: Division of Integrative Physiology, Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden. Malou.Friederich@mcb.uu.se
authors: Malou
authors: M
authors: Friederich-Persson
authors: Shakil
authors: S
authors: Aslam
authors: Lina
authors: L
authors: Nordquist
authors: William J
authors: WJ
authors: Welch
authors: Christopher S
authors: CS
authors: Wilcox
authors: Fredrik
authors: F
authors: Palm
mesh_terms: D000244:Adenosine Diphosphate / Q000235:genetics / Q000378:metabolism; D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D003928:Diabetic Nephropathies / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D055785:Gene Knockdown Techniques; D006153:Guanosine Diphosphate / Q000235:genetics / Q000378:metabolism; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000235:genetics; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000226:Mitochondrial ADP, ATP Translocases / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000071246:Uncoupling Protein 2
chemical_list: D007473:Ion Channels; D024101:Mitochondrial Proteins; C000604391:Ucp2 protein, rat; D000071246:Uncoupling Protein 2; D006153:Guanosine Diphosphate; D008315:Malondialdehyde; D000244:Adenosine Diphosphate; D000226:Mitochondrial ADP, ATP Translocases; D010100:Oxygen