HIV-1 infection initiates an inflammatory cascade in human renal tubular epithelial cells

Acute kidney injury in HIV-infected patients

Acute kidney injury is common in human immunodeficiency virus (HIV)-infected patients, and has been associated with increased morbidity and mortality. Before the introduction of effective antiretroviral therapy, acute kidney injury in HIV-positive patients was most commonly the result of volume depletion, septicemia, or nephrotoxic medications. Acute kidney injury remains a significant problem in the antiretroviral era, and still commonly is attributed to infection or nephrotoxic medications. Less common causes such as direct infectious insults, immune restoration inflammatory syndrome, rhabdomyolysis, and obstruction should be considered when the underlying process is not obvious. In addition to advanced HIV disease, several other patient characteristics have emerged as potential risk factors for acute kidney injury in the antiretroviral era, including older age, diabetes, pre-existing chronic kidney disease, and hepatitis co-infection or liver disease.

Interruption of antiretroviral therapy is associated with increased plasma cystatin C

BACKGROUND

Cystatin C has been proposed as an alternative marker of renal function. We sought to determine whether participants randomized to episodic use of antiretroviral therapy guided by CD4 cell count (drug conservation) had altered cystatin C levels compared with those randomized to continuous antiretroviral therapy (viral suppression) in the Strategies for Management of Antiretroviral Therapy trial, and to identify factors associated with increased cystatin C.

METHODS

Cystatin C was measured in plasma collected at randomization, 1, 2, 4, 8 and 12 months after randomization in a random sample of 249 and 250 participants in the drug conservation and viral suppression groups, respectively. Logistic regression was used to model the odds of at least 0.15 mg/dl increase in cystatin C (1 SD) in the first month after randomization, adjusting for demographic and clinical characteristics.

RESULTS

At randomization, mean (SD) cystatin C level was 0.99 (0.26 mg/dl) and 1.01 (0.28 mg/dl) in the drug conservation and viral suppression arms, respectively (P = 0.29). In the first month after randomization, 21.8 and 10.6% had at least 0.15 mg/dl increase in cystatin C in the drug conservation and viral suppression arms, respectively (P = 0.0008). The difference in cystatin C between the treatment arms was maintained through 1 year after randomization. After adjustment, participants in the viral suppression arm had significantly reduced odds of at least 0.15 mg/dl increase in cystatin C in the first month (odds ratio 0.42; 95% confidence interval 0.23-0.74, P = 0.0023).

CONCLUSION

These results demonstrate that interruption of antiretroviral therapy is associated with an increase in cystatin C, which may reflect worsened renal function.

HIV-associated nephropathy: clinical presentation, pathology, and epidemiology in the era of antiretroviral therapy

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 shows 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 angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers, as well as corticosteroids in selected patients with significant interstitial inflammation or rapid progression.

Baseline renal insufficiency and risk of death among HIV-infected adults on antiretroviral therapy in Lusaka, Zambia

OBJECTIVE

To examine the association between baseline renal insufficiency and mortality among adults initiating antiretroviral therapy (ART) in an urban African setting.

DESIGN

Open cohort evaluation.

METHODS

We examined mortality according to baseline renal function among adults initiating ART in Lusaka, Zambia. Renal function was assessed by the Cockcroft-Gault method, the Modification of Diet in Renal Disease equation, and serum creatinine.

RESULTS

From April 2004 to September 2007, 25 779 individuals started ART with an available creatinine measurement at baseline. When creatinine clearance was calculated by the Cockcroft-Gault method, 8456 (33.5%) had renal insufficiency: 73.5% were mild (60-89 ml/min), 23.4% moderate (30-59 ml/min), and 3.1% severe (<30 ml/min). Risk for mortality at or before 90 days was elevated for those with mildly [adjusted hazard ratio (AHR)(1/4)1.7; 95% confidence interval (95% CI)(1/4)1.5-1.9], moderately (AHR(1/4)2.3; 95% CI(1/4)2.0-2.7), and severely (AHR(1/4)4.3; 95% CI(1/4)3.1-5.5) reduced creatinine clearance. Mild (AHR(1/4)1.4; 95% CI(1/4)1.2-1.6), moderate (AHR(1/4)1.9; 95% CI(1/4)1.5-2.3), and severe (AHR(1/4)3.6; 95% CI(1/4) 2.4-5.5) insufficiency were also associated with increased mortality after 90 days, when compared with those with normal renal function. Trends were similar when renal function was estimated with Modification of Diet in Renal Disease or serum creatinine.

CONCLUSION

Renal insufficiency at time of ART initiation was prevalent and associated with increased mortality risk among adults in this population. These results have particular relevance for settings like Zambia, where tenofovir--a drug with known nephrotoxicity--has been adopted as part of first-line therapy. This emphasizes the need for resource-appropriate screening algorithms for renal disease, both as part of ART eligibility and pretreatment assessment.

Renal disease in patients with HIV infection: epidemiology, pathogenesis and management

With the introduction of highly active antiretroviral therapy, we have witnessed prolonged survival with the potential for normal life expectancy in HIV-infected individuals. With improved survival and increasing age, HIV-infected patients are increasingly likely to experience co-morbidities that affect the general population, including kidney disease. Although HIV-associated nephropathy, the most ominous kidney disease related to the direct effects of HIV, may be prevented and treated with antiretrovirals, kidney disease remains an important issue in this population. In addition to the common risk factors for kidney disease of diabetes mellitus and hypertension, HIV-infected individuals have a high prevalence of other risk factors, including hepatitis C, cigarette smoking and injection drug use. Furthermore, they have exposures unique to this population, including antiretrovirals and other medications. Therefore, the differential diagnosis is vast. Early identification (through efficient screening) and definitive diagnosis (by kidney biopsy when indicated) of kidney disease in HIV-infected individuals are critical to optimal management. Earlier interventions with disease-specific therapy, often with the help of a nephrologist, are likely to lead to better outcomes. In those with chronic kidney disease, interventions, such as aggressive blood pressure control with the use of ACE inhibitors or angiotensin receptor antagonists where tolerated, tight blood glucose control in those with diabetes, and avoidance of potentially nephrotoxic medications, can slow progression and prevent end-stage renal disease. Only with greater awareness of kidney-disease manifestations and their implications in this particularly vulnerable population will we be able to achieve success in confronting this growing problem.

Interaction of Chlamydia trachomatis serovar E with male genital tract epithelium results in secretion of proinflammatory cytokines

Although much has been reported on the in vitro interaction of Chlamydia trachomatis with cells derived from the female genital tract, little is known of its interaction with male genital tract epithelium. The aim of this work was to investigate the effect of C. trachomatis serovar E on immortalized normal human urethral epithelial cells and on immortalized normal adult human prostate epithelial cells with regard to chlamydial growth and secretion of cytokines. After infection, these epithelial cells were assessed for their support of chlamydial growth in comparison with HeLa cells, and cytokine levels in cell culture supernatants were determined by ELISA. Although the male-derived epithelial cells supported growth of chlamydiae, the best growth was seen in HeLa cells. In contrast to prostate epithelial cells, the urethral epithelial cells released much larger quantities of interleukin 1alpha (IL-1alpha) following infection, whereas both IL-6 and IL-8 were produced in larger quantities by infected prostate cells. At 7 days post-infection, HeLa cells consistently produced large quantities of all three cytokines. In conclusion, the male-derived cell lines were shown to support the invasion of C. trachomatis and initiate a proinflammatory response to infection. From in vitro studies the suggestion that high levels of IL-6 could be a possible marker for chlamydial prostatitis is confirmed. Although not as marked a change, it is also suggested that higher IL-8 levels could be associated more with infection of the prostate than the urethra. Differential cytokine production by different male-derived epithelial cells could help determine the site of chlamydial infection and help in the study of pathogenesis.

HIV-1 and HIV-Associated Nephropathy 25 Years Later

Twenty-five years after the first published description of AIDS, HIV-associated nephropathy (HIVAN) remains an important cause of kidney disease in HIV-infected patients. The pathogenesis of HIVAN involves direct HIV infection of the kidney, with both viral and host genetic factors playing an important role. The widespread use of antiretroviral therapy has influenced the epidemiology of HIV-related kidney disease, and the nephrology community should support efforts to improve access to therapy and limit HIV transmission in susceptible minority populations. This article reviews the history of HIV and HIVAN, focusing on advances in the understanding of pathogenesis, epidemiology, and treatment.

Infection and glomerulonephritis

Glomerular injury, occurring either as primary glomerular disease or as part of a systemic disease process, is usually a result of immune-mediated mechanisms. The morphologic reaction pattern has a diverse spectrum of appearance, ranging from normal by light microscopy in minimal change disease to crescentic forms of glomerulonephritis, with conspicuous disruption of the normal glomerular morphology. The mechanisms of glomerular immune deposit formation include trapping of circulating antigen-antibody complexes and the in situ formation of immune complexes within the glomerulus. While the majority of postinfectious immune-complex-mediated glomerulonephritides are believed to result from the deposition of circulating antigen-antibody complexes, preformed outside of the kidney and secondarily deposited in the kidney, the notion of forming in situ antigen-antibody complexes to either planted antigens or to integral structural components of the glomerulus, through "cross-reacting" autoimmune reactions, is gaining popularity in a variety of forms of glomerulonephritides. Patients with HIV infection may develop a spectrum of renal pathology, the glomerular manifestations of which include both antigen-antibody complex and nonimmune-complex-mediated pathogenetic mechanisms. Similarly, patients with Streptococcal infections, Hepatitis B virus, or Hepatitis C virus infection may develop a spectrum of glomerulonephritides, which are predominantly immune-complex-mediated. Therapy for glomerular diseases due to HIV, hepatitis B, or C virus infections remains a challenge.

HIV-1 infection and the kidney: an evolving challenge in HIV medicine

With the advent of highly active antiretroviral therapy (HAART), the incidence of opportunistic infections has declined substantially, and cardiovascular, liver, and renal diseases have emerged as major causes of morbidity and mortality in individuals with human immunodeficiency virus (HIV). Acute renal failure is common in HIV-infected patients and is associated with acute infection and medication-related nephrotoxicity. HIV-associated nephropathy is the most common cause of chronic kidney disease in HIV-positive African American populations and may respond to HAART. Other important HIV-associated renal diseases include HIV immune complex kidney diseases and thrombotic microangiopathy. The increasing importance of non-HIV-associated diseases, such as diabetes mellitus, hypertension, and vascular disease, to the burden of chronic kidney disease has been recognized, focusing attention on prevention and control of these diseases in HIV-positive individuals. HIV-positive individuals who experience progression to end-stage renal disease and who have undetectable HIV-1 viral loads while receiving HAART should be evaluated for renal transplant. Emerging evidence suggests that HIV-positive individuals may have graft and patient survival comparable to HIV-negative individuals. Several studies suggest that HIV-1 can potentially infect renal cells, and HIV transgenic mice have clarified the roles of a number of HIV proteins in the pathogenesis of HIV-associated renal disease. Host factors may modify disease expression at the level of cytokine networks and the renal microvasculature and contribute to the pathogenic effects of HIV-1 infection on the kidney.

HIV-associated nephropathy in the era of antiretroviral therapy

With improved survival in the era of antiretroviral therapy, kidney disease has emerged as an important complication of Human Immunodeficiency Virus (HIV) infection and antiretroviral therapy. The classic kidney disease of HIV infection, HIV-associated nephropathy, occurs almost exclusively in patients of African descent. HIV-associated nephropathy is characterized by collapsing focal segmental glomerulosclerosis with associated tubular dilatation and interstitial inflammation, although the histology may be more subtle in patients receiving antiretroviral therapy. Renal epithelial cells are infected by HIV-1, which results in epithelial cell proliferation and induction of local inflammatory pathways. Even with appropriate therapy, the kidney is a reservoir for HIV-1. Although the widespread introduction of antiretroviral therapy has had a beneficial impact on the epidemiology of HIV-associated nephropathy, the burden of kidney disease is likely to increase as a result of antiretroviral toxicity, reduction in competing mortality risks, and the increasing prevalence of HIV-1 infection in patients at risk for kidney disease.

Role of Ubiquitin-Like Protein FAT10 in Epithelial Apoptosis in Renal Disease

Dysregulated apoptosis of renal tubular epithelial cells (RTEC) is an important component of the pathogenesis of several renal diseases, including HIV-associated nephropathy (HIVAN), the most common cause of chronic kidney failure in HIV-infected patients. In HIVAN, RTEC become infected by HIV-1 in a focal distribution, and HIV-1 infection has been shown to induce apoptosis in vitro. In microarray studies that used a novel renal tubular epithelial cell line from a patient with HIVAN, it was found that the ubiquitin-like protein FAT10 is one of the most upregulated genes in HIV-infected cells. Previously, FAT10 was shown to induce apoptosis in murine fibroblasts. The expression of FAT10 in HIVAN and the ability of FAT10 to induce apoptosis in human RTEC therefore were studied. This study revealed that FAT10 expression is induced after infection of RTEC by HIV-1 and that expression of FAT10 induces apoptosis in RTEC in vitro. Moreover, it was found that inhibition of endogenous FAT10 expression abrogated HIV-induced apoptosis of RTEC. Immunohistochemical studies demonstrated increased FAT10 expression in a murine model of HIVAN, in HIVAN biopsy samples, and in autosomal dominant polycystic kidney disease, another renal disease that is characterized by cystic tubular enlargement and epithelial apoptosis. These results suggest a novel role for FAT10 in epithelial apoptosis, which is an important component of the pathogenesis of many renal diseases.