Autophagy defect and mitochondrial dysfunction in the pathogenesis of diabetic nephropathy in a high fat-diet fed and streptozotocin-treated mouse model
Hwajin Kim, Theodomir Dusabimana, Serok Jeong, So Ra Kim, Jihyun Je, Kyuho Jeong, and Sang Won Park*
Department of Pharmacology and Convergence Medical Science, Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju 52727, Republic of Korea
Diabetic nephropathy (DN) is a leading cause of end-stage renal disease and requires a high medical cost due to a life-long dialysis of >40% patients. A microvascular complication of type I and II diabetes are marked by albuminuria and a decline of glomerular filtration rate. Early stage of DN exhibits glomerular hypertrophy, mesangial matrix expansion, and basement membrane thickening. Advanced DN exhibits nodular glomerulosclerosis, mesangiolysis, and tubulointerstitial fibrosis. Here, we developed a DN animal model by a combined treatment of high fat-diet and streptozotocin for 2, 4, 6 weeks and analyzed pathological features and molecular mechanisms for early diagnosis and prevention of DN. We measured plasma creatinine and blood urea nitrogen levels and performed Periodic acid-Schiff and Sirus red staining. Apoptotic cell death in the kidney tissue was accessed by TUNEL and fragmentations of caspase-3 and Poly (ADP-ribose) polymerase-1. To investigate autophagy defects and mitochondrial dysfunction, the expression of autophagy-related proteins (ATGs, Becline-1, LC3II and p62), and mitochondrial biogenesis and fission/fusion factors (PGC-1a, Drp1, Opa1 and Mfn) was analyzed by Western blotting and RT-PCR. In this study, we first showed pathogenic mediators of early DN development and associated molecular changes in autophagy and mitochondrial dynamics. In addition, in vitro study using proximal tubular cell line, we examined the role of autophagy and mitochondria in hyperglycemic cell death by using chemical inhibitors and siRNA technology. Taken together, we conclude that autophagy and mitochondrial defects in proximal tubular cells causes kidney cell death and leads to tubulointerstitial fibrosis, so that increasing activities of autophagy and mitochondrial function would alleviates DN progression.
Keywords: autophagy, mitochondria, diabetic nephropathy, proximal tubular cell