HIV associated nephropathy (HIVAN) is a major cause of HIV related morbidity and mortality. Pathogenesis involves direct infection of the glomerular and tubular epithelial cells leading to characteristic pathology. Recently, we have shown that HIV-1 Vpr causes hypertrophy, hyperploidy, and apoptosis. Here we report that Vpr activates the DNA damage response resulting in the observed renal phenotype. Renal sections from the HIVAN transgenic mouse model and human biopsies both show an abundant DNA damage response.
HIV Associated Nephropathy; Vpr; DNA Damage; gamma H2AX; Renal Epithelial Cell
HIV-associated nephropathy is the most common cause of end stage renal disease in persons with HIV/AIDS and is characterized by focal glomerulosclerosis and dysregulated renal tubular epithelial cell (RTEC) proliferation and apoptosis. HIV-1 viral protein r (Vpr) has been implicated in HIV-induced RTEC apoptosis but the mechanisms of Vpr-induced RTEC apoptosis are unknown. The aim of this study was therefore to determine the mechanisms of Vpr-induced apoptosis in RTEC.
Apoptosis and caspase activation were analyzed in human RTEC cells (HK2) after transduction with Vpr-expressing and control lentiviral vectors. Bax and BID were inhibited with lentiviral shRNA, and ERK activation was blocked with the MEK1,2 inhibitor, U0126.
Vpr induced apoptosis as indicated by caspase 3/7 activation, PARP-1 cleavage and mitochondrial injury. Vpr activated both caspases-8 and 9. Inhibition of Bax reduced Vpr-induced apoptosis, as reported in other cell types. Additionally, Vpr induced cleavage of BID to tBID and suppression of BID expression prevented Vpr-induced apoptosis. Since sustained ERK activation can activate caspase-8 in some cell types, we studied the role of ERK in Vpr-induced caspase-8 activation. Vpr induced sustained ERK activation in HK2 cells and incubation with U0126 reduced Vpr-induced caspase-8 activation, BID cleavage and apoptosis. We detected phosphorylated ERK in RTEC in HIVAN biopsy specimens by immunohistochemistry.
These studies delineate a novel pathway of Vpr-induced apoptosis in RTEC, which is mediated by sustained ERK activation, resulting in caspase 8-mediated cleavage of BID to tBID, thereby facilitating Bax-mediated mitochondrial injury and apoptosis.
vpr; apoptosis; caspases; AIDS-Associated Nephropathy; Extracellular Signal-Regulated MAP Kinases; kidney
Human immunodeficiency virus (HIV)-associated nephropathy is a significant cause of morbidity and mortality in HIV-infected persons. Vpr-induced cell cycle dysregulation and apoptosis of renal tubular epithelial cells are important components of the pathogenesis of HIV-associated nephropathy (HIVAN). FAT10 is a ubiquitin-like protein that is upregulated in renal tubular epithelial cells in HIVAN. In these studies, we report that Vpr induces increased expression of FAT10 in tubular cells and that inhibition of FAT10 expression prevents Vpr-induced apoptosis in human and murine tubular cells. Moreover, we found that Vpr interacts with FAT10 and that these proteins colocalize at mitochondria. These studies establish FAT10 as a novel mediator of Vpr-induced cell death.
SMC migration and proliferation critically influence the clinical course of vascular disease. We tested the effect of the novel small leucine-rich repeat protein podocan on SMC migration and proliferation using a podocan deficient mouse in combination with a model of arterial injury and aortic explant SMC culture. In addition, we examined the effect of overexpression of the human form of podocan on human SMC and tested for podocan expression in human atherosclerosis. In all these conditions we evaluated concomitantly the Wnt-TCF-pathway.
Methods and Results
Podocan was strongly and selectively expressed in arteries of WT mice after injury. Podocan−/− mice showed increased arterial lesion formation as compared to WT littermates in response to injury (P<0.05). Also, SMC proliferation was increased in arteries of podocan −/− mice compared to WT (P<0.05). In vitro, migration and proliferation were increased in podocan−/− SMC and were normalized by transfection with the WT podocan gene (P<0.05). In addition, upregulation of the Wnt-TCF-pathway was found in SMC of podocan−/− mice both in vitro and in vivo. On the other hand, podocan overexpression in human SMC significantly reduced SMC migration and proliferation inhibiting the Wnt-TCF-pathway. Podocan and a Wnt-TCF-pathway marker were differently expressed in human coronary restenotic versus primary lesions.
Podocan appears to be a potent negative regulator of the migration and proliferation of both murine and human SMC. The lack of podocan results in excessive arterial repair and prolonged SMC proliferation, which likely is mediated by the Wnt-TCF-pathway.
Extracellular Matrix; Smooth Muscle Cells; Proliferation; Arteries
MYH9 encodes non-muscle myosin heavy chain IIA (NMMHCIIA), the predominant force-generating ATPase in non-muscle cells. Several lines of evidence implicate a role for MYH9 in podocytopathies. However, NMMHCIIA‘s function in podocytes remains unknown. To better understand this function, we performed immuno-precipitation followed by mass-spectrometry proteomics to identify proteins interacting with the NMMHCIIA-enriched actin-myosin complexes. Computational analyses revealed that these proteins belong to functional networks including regulators of cytoskeletal organization, metabolism and networks regulated by the HIV-1 gene nef. We further characterized the subcellular localization of NMMHCIIA within podocytes in vivo, and found it to be present within the podocyte major foot processes. Finally, we tested the effect of loss of MYH9 expression in podocytes in vitro, and found that it was necessary for cytoskeletal organization. Our results provide the first survey of NMMHCIIA-enriched actin-myosin-interacting proteins within the podocyte, demonstrating the important role of NMMHCIIA in organizing the elaborate cytoskeleton structure of podocytes. Our characterization of NMMHCIIA’s functions goes beyond the podocyte, providing important insights into its general molecular role.
HIV associated nephropathy (HIVAN) afflicts an estimated 1–3 million people worldwide and is a major cause of morbidity and mortality. Murine transgenic models have demonstrated that expression of HIV-1 genes in kidney cells results in characteristic HIVAN pathology: collapsing FSGS and microcystic tubular disease. While we have gained significant understanding of the podocyte disease, less is known about the tubular epithelial responses to infection.
HIV-1 vpr plays an important role in the FSGS of HIVAN particularly in association with nef expression in podocytes. In addition, Vpr is reported to exacerbate tubular pathology. Therefore, we explored the effect of vpr expression on renal tubular epithelial cell function.
Proximal tubule epithelial cells (PTEC) were transduced in vitro using a pseudotyped lentivirus vector carrying HIV-1 vpr and control genes. HIV-1 vpr expression in cultured PTECs impaired cytokinesis causing cell enlargement and multinucleation. Because the in vitro phenotype was so profound, we re-examined the HIVAN murine model and human HIVAN biopsies to see if similar changes could be seen in vivo.
Surprisingly, both the transgenic murine HIVAN model and human HIVAN biopsies showed abundant hypertrophic tubule cells consistent with the in vitro findings. The extent of the tubular cell hypertrophy was particularly impressive and represents a previously unappreciated aspect of the disease. Additionally, multinucleated tubular cells were identified in the murine HIVAN model and increased chromosome number was detected in tubular cells in HIVAN biopsies.
This study provides evidence of a new clinical phenotype in HIVAN that may result from Vpr’s ability to impair cytokinesis.
HIVAN; Proximal Tubule; HIV; Vpr; hypertrophy; multinucleation; cytokinesis; apoptosis
Injury to the specialized epithelial cells of the glomerulus (podocytes) underlies the pathogenesis of all forms of proteinuric kidney disease; however, the specific genetic changes that mediate podocyte dysfunction after injury are not fully understood. Here, we performed a large-scale insertional mutagenic screen of injury-resistant podocytes isolated from mice and found that increased expression of the gene Rap1gap, encoding a RAP1 activation inhibitor, ameliorated podocyte injury resistance. Furthermore, injured podocytes in murine models of disease and kidney biopsies from glomerulosclerosis patients exhibited increased RAP1GAP, resulting in diminished glomerular RAP1 activation. In mouse models, podocyte-specific inactivation of Rap1a and Rap1b induced massive glomerulosclerosis and premature death. Podocyte-specific Rap1a and Rap1b haploinsufficiency also resulted in severe podocyte damage, including features of podocyte detachment. Over-expression of RAP1GAP in cultured podocytes induced loss of activated β1 integrin, which was similarly observed in kidney biopsies from patients. Furthermore, preventing elevation of RAP1GAP levels in injured podocytes maintained β1 integrin–mediated adhesion and prevented cellular detachment. Taken together, our findings suggest that increased podocyte expression of RAP1GAP contributes directly to podocyte dysfunction by a mechanism that involves loss of RAP1-mediated activation of β1 integrin.
The continuing disease burden of HIV-associated nephropathy (HIVAN) warrants better elucidation of its pathogenic mechanisms. Given that loss of MYH9 function causes a Mendelian renal disease, we hypothesized that renal expression of MYH9 is downregulated by HIV-1 in HIVAN pathogenesis. Using immunofluorescence, we determined that glomerular expression of MYH9 was reduced in the kidneys of HIV-1 transgenic mice. We further determined that Myh9 expression was reduced in HIV-1 transgenic podocytes, statistically significantly at the protein level, and that MYH9 expression was significantly reduced at protein and message level in human podocytes transduced with HIV-1. In analyzing expression in human tissue, we confirmed that MYH9 is abundantly expressed in glomeruli, and podocytes specifically. Finally, we found that MYH9 expression was significantly reduced in human glomeruli in the setting of HIVAN. We conclude that the podocyte host response to HIV-1 includes downregulation of MYH9 expression, and hypothesize that this downregulation might play a role in the pathogenesis of HIVAN.
HIVAN; FSGS; MYH9; Podocyte; Glomerulus; HIV-1
Purpose of review
HIV-associated nephropathy (HIVAN) is characterized histologically by a collapsing form of FSGS, microcystic tubular dilation, interstitial inflammation and fibrosis. In this review, we provide a summary of the current state of knowledge about the mechanisms involved in the pathogenesis of HIVAN.
Two variants in the ApoL1 gene have been identified as the susceptibility alleles that account for a majority of the increased risk of FSGS and non-diabetic ESRD in Blacks. HIVAN1 and HIVAN 2 are the other host susceptibility genes that have been identified in animal models for HIVAN. HIV infects renal tubular epithelial cells likely through direct cell-cell transmission. Both in vivo and in vitro evidence suggests that nef and vpr are the key viral genes mediating HIVAN. Nef induces podocyte dysfunction whereas Vpr induces RTEC apoptosis.
HIVAN results from direct infection by HIV-1 and expression of viral genes, especially nef and vpr, in renal epithelial cells in a genetically susceptible host. The infected renal epithelium acts as a separate viral compartment from the blood and facilitates evolution of strains distant from blood. Dysregulation of several host cellular pathways, including those involved in cell cycle and apoptosis, ultimately results in the unique histopathological syndrome of HIVAN.
HIVAN; Glomerulosclerosis; Podocyte; ApoL1
With the widespread use of combination antiretroviral agents, the incidence of HIV-associated nephropathy has decreased. Currently, HIV-infected patients live much longer and often suffer from comorbidities such as diabetes mellitus. Recent epidemiological studies suggest that concurrent HIV infection and diabetes mellitus may have a synergistic effect on the incidence of chronic kidney disease. To address this, we determined whether HIV-1 transgene expression accelerates diabetic kidney injury using a diabetic HIV-1 transgenic (Tg26) murine model. Diabetes was initially induced with low-dose streptozotocin in both Tg26 and the wild-type mice on the C57BL/6 background, which is resistant to classic HIV-associated nephropathy. Although diabetic nephropathy is minimally observed on C57BL/6 background, diabetic Tg26 mice exhibited a significant increase in glomerular injury compared to non-diabetic Tg26 mice or diabetic wild type mice. Validation of microarray gene expression analysis from isolated glomeruli showed a significant up-regulation of pro-inflammatory pathways in the diabetic Tg26 mice. Thus, our study found that expression of HIV-1 genes aggravates diabetic kidney disease
More than two-thirds of the world's HIV-positive individuals live in sub-Saharan Africa, where genetic susceptibility to kidney disease is high and resources for kidney disease screening and antiretroviral therapy (ART) toxicity monitoring are limited. Equations to estimate glomerular filtration rate (GFR) from serum creatinine were derived in Western populations and may be less accurate in this population.
We compared results from published GFR estimating equations with a direct measure of GFR by iohexol clearance in 99 HIV-infected, ART-naïve Kenyan adults. Iohexol concentration was measured from dried blood spots on filter paper. The bias ratio (mean of the ratio of estimated to measured GFR) and accuracy (percentage of estimates within 30% of the measured GFR) were calculated.
The median age was 35 years, and 60% were women. The majority had asymptomatic HIV, with median CD4+ cell count of 355 cells/mm3. Median measured GFR was 115 mL/min/1.73 m2. Overall accuracy was highest for the Chronic Kidney Disease Epidemiology Consortium (CKD-EPI) equation. Consistent with a prior report, bias and accuracy were improved by eliminating the coefficient for black race (85% of estimates within 30% of measured GFR). Accuracy of all equations was poor in participants with GFR 60–90 mL/min/1.73 m2 (<65% of estimates within 30% of measured GFR), although this subgroup was too small to reach definitive conclusions.
Overall accuracy was highest for the CKD-EPI equation. Eliminating the coefficient for race further improved performance. Future studies are needed to determine the most accurate GFR estimate for use in individuals with GFR <90 mL/min/1.73 m2, in whom accurate estimation of kidney function is important to guide drug dosing. Direct measurement of GFR by iohexol clearance using a filter paper based assay is feasible for research purposes in resource-limited settings, and could be used to develop more accurate GFR estimates in African populations.
Despite intensive anti-hypertensive therapy there was a high incidence of renal end-points in participants of the African American Study of Kidney Disease and Hypertension (AASK) cohort. To better understand this, coding variants in the apolipoprotein L1 (APOL1) and the non-muscle myosin heavy chain 9 (MYH9) genes were evaluated for an association with hypertension-attributed nephropathy and clinical outcomes in a case-control study. Clinical data and DNA were available for 675 AASK participant cases and 618 African American non-nephropathy control individuals. APOL1 G1 and G2, and MYH9 E1 variants along with 44 ancestry informative markers were genotyped with allele frequency differences between cases and controls analyzed by logistic regression multivariable models adjusting for ancestry, age, and gender. In recessive models, APOL1 risk variants were significantly associated with kidney disease in all cases compared to controls with an odds ratio of 2.57. In AASK cases with more advanced disease, such as a baseline urine protein to creatinine ratio over 0.6 g/g or a serum creatinine over 3 mg/dL during follow-up, the association was strengthened with odds ratios of 6.29 and 4.61, respectively. APOL1 risk variants were consistently associated with renal disease progression across medication classes and blood pressure targets. Thus, kidney disease in AASK participants was strongly associated with APOL1 renal risk variants.
With the widespread use of combination antiretroviral agents, the incidence of HIV-associated nephropathy has decreased. Currently, HIV-infected patients live much longer and often suffer from comorbidities such as diabetes mellitus. Recent epidemiological studies suggest that concurrent HIV infection and diabetes mellitus may have a synergistic effect on the incidence of chronic kidney disease. To address this, we determined whether HIV-1 transgene expression accelerates diabetic kidney injury using a diabetic HIV-1 transgenic (Tg26) murine model. Diabetes was initially induced with low-dose streptozotocin in both Tg26 and wild-type mice on a C57BL/6 background, which is resistant to classic HIV-associated nephropathy. Although diabetic nephropathy is minimally observed on the C57BL/6 background, diabetic Tg26 mice exhibited a significant increase in glomerular injury compared with nondiabetic Tg26 mice and diabetic wild-type mice. Validation of microarray gene expression analysis from isolated glomeruli showed a significant upregulation of proinflammatory pathways in diabetic Tg26 mice. Thus, our study found that expression of HIV-1 genes aggravates diabetic kidney disease.
diabetic nephropathy; glomerulopathy; HIV
We previously reported an increased risk of all-cause and AIDS mortality among HIV-infected women with albuminuria (proteinuria or microalbuminuria) enrolled in the Women’s Interagency HIV Study (WIHS) prior to the introduction of highly active antiretroviral therapy (HAART).
The current analysis includes 1,073 WIHS participants who subsequently initiated HAART. Urinalysis for proteinuria and semi-quantitative testing for microalbuminuria from two consecutive study visits prior to HAART initiation were categorized as follows: confirmed proteinuria (both specimens positive for protein), confirmed microalbuminuria (both specimens positive with at least one microalbuminuria), unconfirmed albuminuria (one specimen positive for proteinuria or microalbuminuria), or negative (both specimens negative). Time from HAART initiation to death was modeled using proportional hazards analysis.
Compared to the reference group of women with two negative specimens, the hazard ratio (HR) for all-cause mortality was significantly elevated for women with confirmed microalbuminuria (HR 1.9; 95% CI 1.2–2.9). Confirmed microalbuminuria was also independently associated with AIDS death (HR 2.3; 95% CI 1.3–4.3), while women with confirmed proteinuria were at increased risk for non-AIDS death (HR 2.4; 95% CI 1.2–4.6).
In women initiating HAART, pre-existing microalbuminuria independently predicted increased AIDS mortality, while pre-existing proteinuria predicted increased risk of non-AIDS death. Urine testing may identify HIV-infected individuals at increased risk for mortality even after the initiation of HAART. Future studies should consider whether these widely available tests can identify individuals who would benefit from more aggressive management of HIV infection and comorbid conditions associated with mortality in this population.
HIV; microalbuminuria; proteinuria; mortality; non-AIDS death
HIV-associated nephropathy is characterized by renal podocyte proliferation and dedifferentiation. This study found that all-trans retinoic acid (atRA) reverses the effects of HIV-1 infection in podocytes. Treatment with atRA reduced cell proliferation rate by causing G1 arrest and restored the expression of the differentiation markers (synaptopodin, nephrin, podocin, and WT-1) in HIV-1–infected podocytes. It is interesting that both atRA and 9-cis RA increased intracellular cAMP levels in podocytes. Podocytes expressed most isoforms of retinoic acid receptors (RAR) and retinoid X receptors (RXR) with the exception of RXRγ. RARα antagonists blocked atRA-induced cAMP production and its antiproliferative and prodifferentiation effects on podocytes, suggesting that RARα is required. For determination of the effect of increased intracellular cAMP on HIV-infected podocytes, cells were stimulated with either forskolin or 8-bromo-cAMP. Both compounds inhibited cell proliferation significantly and restored synaptopodin expression in HIV-infected podocytes. The effects of atRA were abolished by Rp-cAMP, an inhibitor of the cAMP/protein kinase A pathway and were enhanced by rolipram, an inhibitor of phosphodiesterase 4, suggesting that the antiproliferative and prodifferentiation effects of atRA on HIV-infected podocytes are cAMP dependent. Furthermore, both atRA and forskolin suppressed HIV-induced mitogen-activated protein kinase 1 and 2 and Stat3 phosphorylation. In vivo, atRA reduced proteinuria, cell proliferation, and glomerulosclerosis in HIV-1–transgenic mice. These findings suggest that atRA reverses the abnormal phenotype in HIV-1–infected podocytes by stimulating RARα-mediated intracellular cAMP production. These results demonstrate the mechanism by which atRA reverses the proliferation of podocytes that is induced by HIV-1.
Prevalence of microalbuminuria is increased in patients with HIV. Microalbuminuria is associated with increased mortality in other populations, including diabetics, for whom microalbuminuria testing is standard of care. We investigated whether microalbuminuria is associated with mortality in HIV-infected women not receiving antiretroviral therapy.
Urinalysis for proteinuria and semi-quantitative testing for microalbuminuria were performed in specimens from two consecutive visits in 1,547 HIV-infected women enrolled in the Women’s Interagency HIV Study in 1994–1995. Time to death was modeled using proportional hazards analysis.
Compared to women without albuminuria, the hazard ratio (HR) for all-cause mortality was increased in women with one (HR 3.4; 95% CI 2.2–5.2) or two specimens positive for either proteinuria or microalbuminuria (HR 3.9; 95% CI 2.1–7.0). The highest risk was observed in women with both specimens positive for proteinuria (HR 5.8; 95% CI 3.4–9.8). The association between albuminuria and all-cause mortality risk remained significant after adjustment for demographics, HIV disease severity, and related comorbidities. Similar results were obtained for AIDS death.
We identified a graded relationship between albuminuria and the risk of all-cause and AIDS mortality.
HIV; microalbuminuria; proteinuria; mortality
All-trans retinoic acid protects against the development of HIV-associated nephropathy (HIVAN) in HIV-1 transgenic mice (Tg26). In vitro, all-trans retinoic acid inhibits HIV-induced podocyte proliferation and restores podocyte differentiation markers by activating its receptor-α (RARα). Here, we report that Am580, a water-soluble RARα-specific agonist, attenuated proteinuria, glomerosclerosis, and podocyte proliferation, and restored podocyte differentiation markers in kidneys of Tg26 mice. Furthermore, RARα−/− Tg26 mice developed more severe kidney and podocyte injury than did RARα+/− Tg26 mice. Am580 failed to ameliorate kidney injury in RARα−/− Tg26 mice, confirming our hypothesis that Am580 acts through RARα. Although the expression of RARα-target genes was suppressed in the kidneys of Tg26 mice and of patients with HIVAN, the expression of RARα in the kidney was not different between patients with HIVAN and minimal change disease. However, the tissue levels of retinoic acid were reduced in the kidney cortex and isolated glomeruli of Tg26 mice. Consistent with this, the expression of two key enzymes in the retinoic acid synthetic pathway, retinol dehydrogenase type 1 and 9, and the overall enzymatic activity for retinoic acid synthesis were significantly reduced in the glomeruli of Tg26 mice. Thus, a defect in the endogenous synthesis of retinoic acid contributes to loss of the protection by retinoic acid in HIVAN. Hence, RARα agonists may be potential agents for the treatment of HIVAN.
HIV; kidney disease; podocytes; proteinuria; retinoic acid receptor
The classic kidney disease of Human Immunodeficiency Virus (HIV) infection, HIV-associated nephropathy, is characterized by progressive acute renal failure, often accompanied by proteinuria and ultrasound findings of enlarged, echogenic kidneys. Definitive diagnosis requires kidney biopsy, which demonstrates collapsing focal segmental glomerulosclerosis with associated microcystic tubular dilatation and interstitial inflammation. Podocyte proliferation is a hallmark of HIV-associated nephropathy, although this classic pathology is observed less frequently in antiretroviral-treated patients. The pathogenesis of HIV-associated nephropathy involves direct HIV infection of renal epithelial cells, and the widespread introduction of combination antiretroviral therapy has had a significant impact on the natural history and epidemiology of this unique disease. These observations have established antiretroviral therapy as the cornerstone of treatment for HIV-associated nephropathy, in the absence of prospective clinical trials. Adjunctive therapy for HIV-associated nephropathy includes ACE inhibitors or angiotensin receptor blockers, as well as corticosteroids in selected patients with significant interstitial inflammation or rapid progression.
HIV-associated nephropathy; focal segmental glomerulosclerosis; HIV; kidney
HIV-1 transgenic mice on the FVB/NJ background (TgFVB) represent a well-validated model of HIV-associated nephropathy (HIVAN). A mapping study between TgFVB and CAST/EiJ (CAST) strains previously demonstrated that this trait is influenced by a major susceptibility locus on Chr. 3A1-A3 (called HIVAN1), with CAST alleles associated with increased risk of disease. We introgressed a 50 Mb interval, encompassing the HIVAN1 locus from CAST into the TgFVB genome (TgFVB-HIVAN1CAST congenic mice). Compared to the TgFVB strain, TgFVB-HIVAN1CAST mice develop earlier onset of proteinuria, rapid progression to kidney failure and increased mortality. Prospective analysis of TgFVB-HIVAN1CAST mice demonstrated significantly greater histologic and biochemical evidence of glomerulopathy with one-third of mice developing global glomerulosclerosis by 6 weeks of age. An F2 cross between TgFVB and FVB-HIVAN1CAST demonstrated significant linkage (lod= 3.7, empiric p=0.001) to a 10 cM interval within the HIVAN1 region between D3Mit167 and D3Mit67, resulting in a 60% reduction of the original interval. These data independently confirm that a gene on chr3A1-A3 increases susceptibility to HIVAN, resulting in early onset and rapid progression of kidney disease. These mice represent a novel model for studying the development and progression of collapsing glomerulopathy.
In the era of antiretroviral therapy, non-AIDS complications such as kidney disease are important contributors to morbidity and mortality.
To estimate the impact of hepatitis C co-infection on the risk of kidney disease in HIV patients.
Two investigators identified English-language citations in MEDLINE and Web of Science from 1989 through July 1, 2007. References of selected articles were reviewed. Observational studies and clinical trials of HIV-related kidney disease and antiretroviral nephrotoxicity were eligible if they included at least 50 participants and reported hepatitis C status. Data on study characteristics, population, and kidney disease outcomes were abstracted by two independent reviewers.
After screening 2,516 articles, twenty-seven studies were eligible and 24 authors confirmed or provided data. Separate meta-analyses were performed for chronic kidney disease outcomes (n=10), proteinuria (n=4), acute renal failure (n=2), and indinavir toxicity (n=5). The pooled incidence of chronic kidney disease was higher in patients with hepatitis C co-infection (6.2% versus 4.0%; RR 1.49, 95% CI 1.08–2.06). In meta-regression, prevalence of black race and the proportion of patients with documented hepatitis C status were independently associated with the risk of chronic kidney disease. The relative risk associated with hepatitis C co-infection was significantly increased for proteinuria (1.15; 95% CI 1.02–1.30) and acute renal failure (1.64; 95% CI 1.21–2.23), with no significant statistical heterogeneity. The relative risk of indinavir toxicity was 1.59 (95% CI 0.99–2.54) with Hepatitis C co-infection.
Hepatitis C co-infection is associated with a significant increase in the risk of HIV-related kidney disease.
With prolonged survival and aging of the HIV-infected population in the era of antiretroviral therapy, biopsy series have found a broad spectrum of HIV-related and co-morbid kidney disease in these patients. Our study describes the variety of renal pathology found in a prospective cohort of antiretroviral-experienced patients (the Manhattan HIV Brain Bank) who had consented to postmortem organ donation. Nearly one-third of 89 kidney tissue donors had chronic kidney disease, and evidence of some renal pathology was found in 75. The most common diagnoses were arterionephrosclerosis, HIV-associated nephropathy and glomerulonephritis. Other diagnoses included pyelonephritis, interstitial nephritis, diabetic nephropathy, fungal infection and amyloidosis. Excluding 2 instances of acute tubular necrosis, slightly over one-third of the cases would have been predicted using current diagnostic criteria for chronic kidney disease. Based on semi-quantitative analysis of stored specimens, pre-mortem microalbuminuria testing could have identified an additional 12 cases. Future studies are needed to evaluate the cost-effectiveness of more sensitive methods for defining chronic kidney disease, in order to identify HIV-infected patients with early kidney disease who may benefit from antiretroviral therapy and other interventions known to delay disease progression and prevent complications.
AIDS; histopathology; HIV-associated nephropathy; kidney disease
Multiple studies have linked podocyte gene variants to diverse sporadic nephropathies, including HIV-1–associated nephropathy (HIVAN). We previously used linkage analysis to identify a major HIVAN susceptibility locus in mouse, HIVAN1. We performed expression quantitative trait locus (eQTL) analysis of podocyte genes in HIV-1 transgenic mice to gain further insight into genetic susceptibility to HIVAN. In 2 independent crosses, we found that transcript levels of the podocyte gene nephrosis 2 homolog (Nphs2), were heritable and controlled by an ancestral cis-eQTL that conferred a 3-fold variation in expression and produced reactive changes in other podocyte genes. In addition, Nphs2 expression was controlled by 2 trans-eQTLs that localized to the nephropathy susceptibility intervals HIVAN1 and HIVAN2. Transregulation of podocyte genes was observed in the absence of HIV-1 or glomerulosclerosis, indicating that nephropathy susceptibility alleles induce latent perturbations in the podocyte expression network. Presence of the HIV-1 transgene interfered with transregulation, demonstrating effects of gene-environment interactions on disease. These data demonstrate that transcript levels of Nphs2 and related podocyte-expressed genes are networked and suggest that the genetic lesions introduced by HIVAN susceptibility alleles perturb this regulatory pathway and transcriptional responses to HIV-1, increasing susceptibility to nephropathy.
Nef-induced podocyte proliferation and dedifferentiation via mitogen-activated protein kinase 1,2 (MAPK1,2) activation plays a role in human immunodeficiency virus (HIV) nephropathy pathogenesis. All-trans retinoic acid (atRA) reverses the HIV-induced podocyte phenotype by activating cyclic AMP (cAMP)/protein kinase A (PKA) and inhibiting MAPK1,2. Here we show that atRA, through cAMP and PKA, triggers a feed-forward loop involving CREB and USF1 to induce biphasic stimulation of MKP1. atRA stimulated CREB and USF1 binding to the MKP1 gene promoter, as shown by gel shifting and chromatin immunoprecipitation assays. CREB directly mediated the early phase of atRA-induced MKP1 stimulation; whereas the later phase was mediated by CREB indirectly through induction of USF1. These findings were confirmed by a reporter gene assay using the MKP1 promoter with mutation of CRE or Ebox binding sites. Consistent with these findings, the biological effects of atRA on podocytes were inhibited by silencing either MKP1, CREB, or USF1 with small interfering RNA. atRA also induced CREB phosphorylation and MKP1 expression and reduced MAPK1,2 phosphorylation in kidneys of HIV type 1-infected transgenic mice. We conclude that atRA induces sustained activation of MKP1 to suppress Nef-induced activation of the Src-MAPK1,2 pathway, thus returning the podocyte to a more differentiated state. The mechanism involves a feed-forward loop where activation of one transcription factor (TF) (CREB) leads to induction of a second TF (USF1).