HIV Promotes NLRP3 Inflammasome Complex Activation in Murine HIV-Associated Nephropathy

Abstract

Dysregulated growth and loss of podocytes are important features of HIV-associated nephropathy. Recently, HIV was reported to induce a new type of programed cell death, pyroptosis, in T lymphocytes through induction of Nod-like receptor protein 3 (NLRP3) inflammasome complexes. We evaluated the role of HIV in podocyte NLRP3 inflammasome formation both in vivo and in vitro. Renal cortical sections of HIV-transgenic mice (Tg26) displayed increased expression of NLRP3, ASC (a CARD protein), caspase-1, and IL-1b proteins, confirming NLRP3 inflammasome complex formation in podocytes of Tg26 mice. Renal tissues of Tg26 mice also displayed enhanced mRNA levels and protein expressions of inflammasome markers (NLRP3, ASC, and caspase-1, and IL-1b). Serum of Tg26 mice also showed elevated concentrations of IL-1b cytokine compared with FVBN mice. HIV induced pyroptosis in a dose-and time-dependent manner within podocytes, a phenotype of inflammasome activation. Caspase-1 inhibitor not only attenuated podocyte expression of caspase-1 and IL-1b but also provided protection against pyroptosis, suggesting that HIV-induced podocyte injury was mediated by caspase-1 activation. Interestingly, HIV-induced podocyte pyroptosis could be partially inhibited by Tempol (a superoxide dismutase-mimetic agent) and by glyburide (an inhibitor of potassium efflux). These findings suggest that generation of reactive oxygen species and potassium efflux contribute to HIV-induced pyroptosis and NLRP3 inflammasome activation in podocytes.

Impact of APOL1 polymorphism and IL-1β priming in the entry and persistence of HIV-1 in human podocytes

“…Although the harmful effect of this potent cytokine in increasing viral replication and in directly damaging several immune and not immune cells both in blood and tissue have been extensively reported [46, 59, 60, 64–66], little is known about the pathogenic role of IL-1β in HIV-1 targeted podocytes. Recently, it has been shown in a murine HIVAN model (Tg26) that HIV-1 induces the activation of the inflammasome in podocytes [53]. We show here that the stimulation of podocytes with exogenous rhIL-1β induces a de novo IL-1β gene transcription.…”

Live or Let Die: Is There any Cell Death in Podocytes?

“…47 Other groups have shown the association of human immunodeficiency virus (HIV) infection with podocyte loss. 50,51 HIVassociated nephropathy with its characteristic feature of collapsing focal segmental glomerulonephritis was linked to vascular endothelial growth factor signaling, showing that HIV-infected podocytes in vitro and in vivo showed increased levels of vascular endothelial growth factor, hypoxia-inducible factor 2α, and vascular endothelial growth factor receptor 2. This was stimulated by the viral protein Nef.…”

“…The experimental design mostly relied on the labeling of DNA double-strand breaks terminal deoxy-nucleotidyl transferase-mediated deoxy-uridine triphosphate nick-end labeling (TUNEL) assay as a sign for chromatin degradation during the apoptotic process ( Figure 1). [45][46][47][48][49][50][51][52] To add specificity, additional stainings for activated (cleaved) caspase-3 45 or commercial assays 47 oftentimes have been performed. Another addition to terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling were the examination of chromatin condensation and fragmentation via 4 0 ,6-diamidino-2-phenylindole stainings 47,53 or enzyme-linked immunosorbent assays for DNA fragments.…”

Oxalate, inflammasome, and progression of kidney disease

“…A wide variety of immune cells, such as dendritic cells (DCs) and macrophages, have been shown to use the inflammasome machinery to release cytokines [74]. Several studies suggest an additional role in tubular epithelial cells (TECs) [75, 76, 77] and podocytes [78, 79]. The NLRP3 inflammasome is the most extensively studied so far.…”