Therapeutic Approach for Diabetic Nephropathy Using Gene Delivery of Translocase of Inner Mitochondrial Membrane 44 by Reducing Mitochondrial Superoxide Production

Abstract

Hyperglycemia-induced overproduction of mitochondrial reactive oxygen species has emerged as a major player in diabetic vascular complications. Mammalian translocase of inner mitochondrial membrane 44 (TIM44) was identified by upregulation in diabetic mouse kidneys. TIM44 functions as a membrane anchor of mitochondrial heat-shock protein 70 (mtHsp70) to TIM23 complex and is involved in the import of mitochondria-targeted preproteins into mitochondrial matrix. The process is dependent on inner membrane potential and ATP hydrolysis on ATPase domain of mitochondrial heat-shock protein 70. Hemagglutination virus of Japan-envelope vector that carries pcDNA3.1 plasmid that contains the full-length cDNA of TIM44 and control plasmid were injected weekly into the tail vein of uninephrectomized streptozotocin-induced diabetic CD-1 mice. The gene delivery alleviated proteinuria and renal hypertrophy at 8 wk after the injection, inhibited renal cell proliferation and apoptosis, and suppressed superoxide production. In vitro experiments, using human proximal tubular (HK2) cells, revealed that the gene delivery of TIM44 reversed high glucose-induced metabolic and cellular abnormalities such as enhanced reactive oxygen species production, increased ATP contents, alterations in inner membrane potential, increased cell proliferation, and apoptosis. Transfection with siRNA and expressing vector of TIM44 revealed that TIM44 facilitates import of antioxidative enzymes such as superoxide dismutase and glutathione peroxidase into mitochondria. The gene delivery of TIM44 therefore seems to be beneficial for the maintenance of mitochondrial function and is a novel therapeutic approach for diabetic nephropathy.

High Glucose-Induced Thioredoxin-Interacting Protein in Renal Proximal Tubule Cells Is Independent of Transforming Growth Factor-β1

“…6,17,18 The present in vitro studies confirm that this up-regulation is attributable to high glucose, either directly or via downstream metabolic derangements. Furthermore our studies in an in vivo model of diabetic nephropathy localize Txnip up-regulation and associated oxidative stress to the dilated tubules.…”

siRNA-Based Therapy Ameliorates Glomerulonephritis

“…Our nanocarriers may be clinically advantageous, especially compared with liposomes that are too large to pass through the intact endothelium. [13][14][15][16][17][18] Conjugated siRNAs, mostly bound to albumin, are also unfavorable for the treatment of nephrotic diseases because of their filtration through the injured GBM.…”

“…HVJ-E is one of the most available vehicles for the delivery to the kidney, 14,48 and we used it for comparison.…”

Attenuation of Interstitial Fibrosis and Tubular Apoptosis in db/db Transgenic Mice Overexpressing Catalase in Renal Proximal Tubular Cells

“…Indeed, apoptotic cell death was detected in a number of renal diseases (18 -21). For instance, renal proximal tubular cells (RPTCs) exhibit apoptosis in streptozotocin-induced diabetic mice (22)(23)(24) and rats (25,26), as well as in diabetic patients (27,28), suggesting that tubular apoptosis might precede tubular atrophy in atubular glomeruli.…”