Abstract
Recently we demonstrated that increased renal (Pro)renin receptor (PRR) expression in diabetes contributes to development of diabetic kidney disease. However, the exact mechanisms involving PRR activity and diabetic kidney dysfunction are unknown. We hypothesized that PRR is localized in renal mitochondria and contributes to renal fibrosis and apoptosis through oxidative stress-induced mitochondria dysfunction. Controls and streptozotocin-induced diabetic C57BL/6 mice were injected with scramble shRNA and PRR shRNA and followed for a period of eight weeks. At the end of study, diabetic mice showed increased expressions of PRR and NOX4 in both total kidney tissue and renal mitochondria fraction. In addition, renal mitochondria of diabetic mice showed reduced protein expression and activity of SOD2 and ATP production and increased UCP2 expression. In diabetic kidney, there was upregulation in the expressions of caspase3, phos-Foxo3a, phos-NF-κB, fibronectin, and collagen IV and reduced expressions of Sirt1 and total-FOXO3a. Renal immunostaining revealed increased deposition of PRR, collagen and fibronectin in diabetic kidney. In diabetic mice, PRR knockdown decreased urine albumin to creatinine ratio and the renal expressions of PRR, NOX4, UCP2, caspase3, phos-FOXO3a, phos-NF-κB, collagen, and fibronectin, while increased the renal mitochondria expression and activity of SOD2, ATP production, and the renal expressions of Sirt1 and total-FOXO3a. In conclusion, increased expression of PRR localized in renal mitochondria and diabetic kidney induced mitochondria dysfunction, and enhanced renal apoptosis and fibrosis in diabetes by upregulation of mitochondria NOX4/SOD2/UCP2 signaling pathway.
Highlights
(Pro)renin receptor (PRR) is a single transmembrane domain that is located in cell membrane and in some cell organelles such as endoplasmic reticulum and Golgi apparatus
We hypothesized that PRR localized in renal mitochondria contributes to development of renal fibrosis and apoptosis through oxidative stress-induced mitochondria dysfunction
We demonstrated that PRR is localized in the renal mitochondria and that this protein expression was upregulated in both total kidney tissue and renal mitochondria fraction in response to hyperglycemia
Summary
(Pro)renin receptor (PRR) is a single transmembrane domain that is located in cell membrane and in some cell organelles such as endoplasmic reticulum and Golgi apparatus. Previous studies showed increased renal oxidative stress and high level accumulation of reactive oxygen species (ROS) in diabetic kidney[10,11] This pathological process involves increased mitochondria NADPH oxidase 4 (NOX4) levels and reduced expression and activity of superoxide dismutase (SOD)[12,13,14]. Recent studies showed that PRR increased hydrogen peroxide production in collecting duct cells[22] and promoted fibrosis in human embryonic kidney cells[23] through a NOX4-dependent mechanism. It is unclear if hyperglycemia-induced PRR overexpression is linked to mitochondria derived oxidative stress and dysfunction. Enhanced PRR expression in renal mitochondria contributed to development of apoptosis and fibrosis in diabetic kidney through increased intra-mitochondria oxidative stress
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