Renal aquaporin-4 associated pathology in TG-26 mice

Human immunodeficiency virus-associated nephropathy (HIVAN) is a leading cause of end-stage renal disease in HIV patients, which is characterized by glomerulosclerosis and renal tubular dysfunction. Aquaporin-4 (AQP-4) is a membrane bound water channel protein that plays a distinct role in water reabsorption from renal tubular fluid. It has been proven that failure of AQP-4 insertion into the renal tubular membrane leads to renal dysfunction. However, the role of AQP-4 in HIVAN is unclear. We hypothesize that impaired water reabsorption leads to renal injury in HIVAN, where AQP-4 plays a crucial role. Renal function is assessed by urinary protein and serum blood urea nitrogen (BUN). Kidneys from HIV Transgenic (TG26) mice (HIVAN animal model) were compared to wild type mice by immunostaining, immunoblotting and quantitative RT-PCR. TG26 mice had increased proteinuria and BUN. We found decreased AQP-4 levels in the renal medulla, increased endothelin-1, endothelin receptor A and reduced Sirtuin1 (SIRT-1) levels in TG26 mice. Also, oxidative and endoplasmic reticulum stress was enhanced in kidneys of TG26 mice. We provide the first evidence that AQP-4 is inhibited due to induction of HIV associated stress in the kidneys of TG26 mice which limits water reabsorption in the kidney which may be one of the cause associated with HIVAN, impairing kidney physiology. AQP-4 dysregulation in TG26 mice suggests that similar changes may occur in HIVAN patients. This work may identify new therapeutic targets to be evaluated in HIVAN.

Glomerular mitochondrial changes in HIV associated renal injury

HIV-associated nephropathy (HIVAN) is an AIDs-related disease of the kidney. HIVAN is characterized by severe proteinuria, podocyte hyperplasia, collapse, glomerular, and tubulointerstitial damage. HIV-1 transgenic (Tg26) mouse is the most popular model to study the HIV manifestations that develop similar renal presentations as HIVAN. Viral proteins, including Tat, Nef, and Vpr play a significant role in renal cell damage. It has been shown that mitochondrial changes are involved in several kidney diseases, and therefore, mitochondrial dysfunction may be implicated in the pathology of HIVAN. In the present study, we investigated the changes of mitochondrial homeostasis, biogenesis, dynamics, mitophagy, and examined the role of reactive oxygen species (ROS) generation and apoptosis in the Tg26 mouse model. The Tg26 mice showed significant impairment of kidney function, which was accompanied by increased blood urea nitrogen (BUN), creatinine and protein urea level. In addition, histological, western blot and PCR analysis of the Tg26 mice kidneys showed a downregulation of NAMPT, SIRT1, and SIRT3 expressions levels. Furthermore, the kidney of the Tg26 mice showed a downregulation of PGC1α, MFN2, and PARKIN, which are coupled with decrease of mitochondrial biogenesis, imbalance of mitochondrial dynamics, and downregulation of mitophagy, respectively. Furthermore, our results indicate that mitochondrial dysfunction were associated with ER stress, ROS generation and apoptosis. These results strongly suggest that the impaired mitochondrial morphology, homeostasis, and function associated with HIVAN. These findings indicated that a new insight on pathological mechanism associated with mitochondrial changes in HIVAN and a potential therapeutic target.