HIV-associated nephropathy: pathogenesis

Role and Mechanisms of Tyro3 in Podocyte Biology and Glomerular Disease

Background

Podocyte loss occurs in both primary and secondary glomerular diseases, leading to the progression of kidney disease. A large body of evidence suggests that apoptosis and detachment are the mechanisms mediating the reduction in podocyte numbers in glomerular diseases. Recent studies demonstrate a renal protective effect of protein S (PS) through the activation of Tyro3, one of the TAM receptors. Tyro3 is predominantly expressed in podocytes within the kidney, and its expression increases in early diabetic kidney disease (DKD) but decreases in patients with progressive DKD and focal segmental glomerulosclerosis (FSGS). Glomerular expression of Tyro3 also correlates with the progression of DKD and predicts the progression of primary glomerular diseases. High glucose increases Tyro3 expression, while TNF-α suppresses the expression of PS and Tyro3. PS has anti-inflammatory and antiapoptotic effects in podocytes, likely via the activation of the Akt pathway and the inhibition of NF-kB activation. In vivo, the knockout of PS or Tyro3 exacerbates podocyte loss and glomerular disease, while the overexpression of PS and Tyro3 attenuates the injury in mice with DKD and FSGS. Tyro3 agonists have also been shown to protect podocytes from injury in these animal models.

Summary

Tyro3 plays a critical role in podocyte biology and glomerular disease. Tyro3 agonists could potentially be developed as a new therapy for glomerular disease.

Key Message

The aim of this review article was to summarize the role and mechanisms mediating the protective effects of Tyro3 in podocyte biology and glomerular disease. Additionally, we discuss the possibility of developing Tyro3 agonists as potential treatment for glomerular diseases.

Potential Advantages of a Well-balanced Nutrition Regimen for People Living with Human Immunodeficiency Virus Type -1

This review underscores the important role of nutrition in enhancing the management of Human Immunodeficiency Virus type 1 (HIV-1). Highlighting the efficacy of dietary interventions, including, the importance of omega-3 fatty acids, vitamins D and B-12, and the Mediterranean diet, we delineate how these beneficial nutritional strategies can improve the effectiveness of combined antiretroviral therapy (cART), mitigate its side effects, and ameliorate metabolic disorders in people living with HIV-1 (PLWH). Our review advocates for the integration and implementation of personalized nutritional assessments into the care plan for PLWH, proposing actionable strategies for healthcare providers in HIV-1 field. Summarizing the current standing of the relevance of the nutritional and well-planned diet recommended for the PLWH and emphasizing on the future research directions, this review establishes a foundation for nutrition as a cornerstone in comprehensive HIV-1 management. Our review aims to improve patients' health outcomes and overall quality of life for PLWH.

Focal Segmental Glomerulosclerosis Followed by Acute Hepatitis A Infection: Case Report

Background and Objectives: Chronic viral hepatitis such as hepatitis B or hepatitis C is frequently related to nephropathies, yet acute hepatitis A virus (HAV) infection is an exception. Materials and Methods: A 43-year-old male presented with jaundice accompanied by nausea and vomiting. The patient was diagnosed with acute HAV infection. Although the liver function improved after conservative treatment, various symptoms such as proteinuria, hypoalbuminemia, generalized edema and pleural effusion persisted. Due to nephrotic syndrome, the patient was referred to the clinic of the nephrology department and a renal biopsy was performed. Results: The result of the renal biopsy was focal segmental glomerulosclerosis (FSGS) based on histology, electron microscopy and immunohistochemistry. Therefore, based on the clinical history and biopsy results, the patient was diagnosed as having FSGS aggravated by acute HAV infection. Proteinuria, hypoalbuminemia and generalized edema were improved after prednisolone treatment. Conclusions: Although less common, acute HAV infection can also present with an extrahepatic manifestation, for example, FSGS. Hence, clinical attention is required if proteinuria or hypoalbuminemia persists in patients with acute HAV infection.

A Systematic Review Exploring the Range of Renal Complications of Human Immunodeficiency Virus

Human immunodeficiency virus (HIV) is a viral infection which progressively leads to acquired immunodeficiency syndrome (AIDS) in the absence of treatment. This happens through the destruction of crucial cells in the immune system, such as the helper T cells, dendritic cells, and macrophages. Since the first case was isolated in the 20th century, the disease has spread rapidly among humans, with significant renal, cardiovascular, respiratory, and neurological complications. It is predominantly sexually transmitted but non-sexual transmission. A relationship between HIV and renal diseases has been suggested for a long time, but only a few systematic studies have centered on this association. This systematic review aims to analyze the possible association between HIV and renal diseases as well as the range and pathogenesis of these renal diseases. HIV remains a critical infectious disease globally, inciting substantial morbidity and mortality. Studies have shown that people living with HIV (PLWH) are at increased risk of acute and chronic kidney disease. This review is based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Google Scholar, and Cochrane databases were searched exhaustively using the inclusion criteria of free full-text English papers that have exclusively studied humans in the last 20 years. Sixteen articles were selected including a systematic review, observational studies, and comprehensive narrative reviews on the role of HIV in the etiology of renal diseases, and were systemically reviewed and analyzed to elicit the wide range of possible renal complications resulting from HIV infection.

HIV-Associated Nephropathy in 2022

Background

HIV-associated nephropathy (HIVAN) is a renal parenchymal disease that occurs exclusively in people living with HIV. It is a serious kidney condition that may possibly lead to end-stage kidney disease, particularly in the HIV-1 seropositive patients.

Summary

The African-American population has increased susceptibility to this comorbidity due to a strong association found in the APOL1 gene, specifically two missense mutations in the G1 allele and a frameshift deletion in the G2 allele, although a "second-hit" event is postulated to have a role in the development of HIVAN. HIVAN presents with proteinuria, particularly in the nephrotic range, as with other kidney diseases. The diagnosis requires biopsy and typically presents with collapsing subtype focal segmental glomerulosclerosis and microcyst formation in the tubulointerstitial region. Gaps still exist in the definitive treatment of HIVAN - concurrent use of antiretroviral therapy and adjunctive management with like renal-angiotensin-aldosterone system inhibitors, steroids, or renal replacement therapy showed benefits.

Key Message

This study reviews the current understanding of HIVAN including its epidemiology, mechanism of disease, related genetic factors, clinical profile, and pathophysiologic effects of management options for patients.

PodoCount: A Robust, Fully Automated, Whole-Slide Podocyte Quantification Tool

Introduction

Podocyte depletion is a histomorphologic indicator of glomerular injury and predicts clinical outcomes. Podocyte estimation methods or podometrics are semiquantitative, technically involved, and laborious. Implementation of high-throughput podometrics in experimental and clinical workflows necessitates an automated podometrics pipeline. Recognizing that computational image analysis offers a robust approach to study cell and tissue structure, we developed and validated PodoCount (a computational tool for automated podocyte quantification in immunohistochemically labeled tissues) using a diverse data set.

Methods

Whole-slide images (WSIs) of tissues immunostained with a podocyte nuclear marker and periodic acid–Schiff counterstain were acquired. The data set consisted of murine whole kidney sections (n = 135) from 6 disease models and human kidney biopsy specimens from patients with diabetic nephropathy (DN) (n = 45). Within segmented glomeruli, podocytes were extracted and image analysis was applied to compute measures of podocyte depletion and nuclear morphometry. Computational performance evaluation and statistical testing were performed to validate podometric and associated image features. PodoCount was disbursed as an open-source, cloud-based computational tool.

Results

PodoCount produced highly accurate podocyte quantification when benchmarked against existing methods. Podocyte nuclear profiles were identified with 0.98 accuracy and segmented with 0.85 sensitivity and 0.99 specificity. Errors in podocyte count were bounded by 1 podocyte per glomerulus. Podocyte-specific image features were found to be significant predictors of disease state, proteinuria, and clinical outcome.

Conclusion

PodoCount offers high-performance podocyte quantitation in diverse murine disease models and in human kidney biopsy specimens. Resultant features offer significant correlation with associated metadata and outcome. Our cloud-based tool will provide end users with a standardized approach for automated podometrics from gigapixel-sized WSIs.

Microalbuminuria and Urinary Neutrophil Gelatinase-associated Lipocalin (uNGAL) in human immunodeficiency virus infected children

Introduction:

Renal dysfunction and progression to end stage renal disease is well known in human immunodeficiency virus (HIV) infection. We studied the role of microalbuminuria and urinary NGAL levels in children with HIV infection for the prediction of renal dysfunction.

Design and Methods:

A cross-sectional study was carried out and 60 HIV infected children, aged (18 months to 15 years) were screened for microalbuminuria by nephelometry and for uNGAL by ELISA. Thirty healthy children were screened for uNGAL for normative data in Indian children.

Results:

The prevalence of microalbuminuria in studied population was 3.3%. The mean uNGAL and uNGAL/creatinine in study population was higher than controls (26.94 ± 93.12 ng/ml vs. 88.94 ± 345.20 mcg/g, and 15.53 ± 37.52 ng/ml vs. 30.12 ± 78.66 ng/ml; P = 0.003, P = 0.002). Children with lower CD4 counts had significant higher mean Albumin Creatinine Ratio (ACR) and mean uNGAL; P = 0.03, P = 0.01.

Conclusions:

uNGAL and urine microalbumin are useful biomarkers of early tubular and glomerular injury in children with HIV infection.

A Case of Focal Segmental Glomerulosclerosis With Immune Complexes: Is HIV, Hepatitis B, or Crack the Culprit?

Human immunodeficiency virus (HIV)-positive individuals are at an increased risk for kidney diseases, including HIV-associated nephropathy (HIVAN), focal segmental glomerulosclerosis (FSGS), HIV immune complex disease of the kidney (HIVICK), and acute tubular necrosis (ATN). Non-modifiable factors such as age and genetics, as well as modifiable factors such as illicit drug use and compliance, define the progression to renal failure. The patient is a 64-year-old African American male with HIV, treated latent syphilis, chronic kidney disease stage 3a, and cocaine use disorder who presented with shortness of breath, bilateral lower extremities swelling, and fatigue with normal vitals and a physical exam remarkable for bibasilar inspiratory crackles with peripheral edema. Laboratory tests showed creatinine (Cr) of 2.23 mg/dL with a baseline of 1.5 mg/dL, albumin of 1.8, blood natriuretic peptide (BNP) of 667.88, and lipidemia. His urine was remarkable for proteinuria and microalbuminuria in the presence of cocaine. Immunofixation electrophoresis showed a marked increase in IgG and IgM, free lambda, and free kappa/free lambda ratio with HIV viral load of 39,400 copies/ml, absolute CD4 count of 56, and an acute hepatitis B panel. Renal biopsy confirmed HIVAN with FSGS accompanied by collapsing features, HIVICK, and ATN. The patient was subsequently started on highly active antiretroviral therapy (HAART) with prophylactic antibiotics and close monitoring.

COVID-19 Vaccines for HIV-Infected Patients

Nearly 40 years have passed since the initial cases of infection with the human mmunodeficiency virus (HIV) were identified as a new disease entity and the cause of acquired immunodeficiency disease (AIDS). This virus, unlike any other, is capable of causing severe suppression of our adaptive immune defense mechanisms by directly infecting and destroying helper T cells leading to increased susceptibility to a wide variety of microbial pathogens, especially those considered to be intracellular or opportunistic. After T cells are infected, HIV reproduces itself via a somewhat unique mechanism involving various metabolic steps, which includes the use of a reverse transcriptase enzyme that enables the viral RNA to produce copies of its complementary DNA. Subsequent physiologic steps lead to the production of new virus progeny and the eventual death of the invaded T cell. Fortunately, both serologic and molecular tests (such as PCR) can be used to confirm the diagnosis of an HIV infection. In the wake of the current COVID-19 pandemic, it appears that people living with HIV/AIDS are equally or slightly more susceptible to the etiologic agent, SARS-CoV-2, than the general population having intact immune systems, but they may have more serious outcomes. Limited clinical trials have also shown that the currently available COVID-19 vaccines are both safe and effective in affording protection to HIV/AIDS patients. In this review, we further explore the unique dynamic of HIV/AIDS in the context of the worldwide COVID-19 pandemic and the implementation of vaccines as a protective measure against COVID-19, as well as what immune parameters and safeguards should be monitored in this immunocompromised group following vaccination.

Viral Nephropathies, Adding SARS-CoV-2 to the List

Viral infections in the immunocompetent host can cause both acute and chronic kidney disease either as a direct damage to the infected kidney cells or as a consequence of systemic immune responses that impact kidney function. Since identifying these entities in the 1970s and 80s, major breakthroughs in the understanding of the viral mechanisms have occurred. Viruses have evolved mechanisms to hijack signaling pathways of infected cells to evade antiviral immune responses by the host. Over time, the clinical presentations and management of these diseases have evolved along with our in-depth understanding of the various pathophysiological mechanisms causing these conditions. Similarly, both at the cellular and systemic levels, the host has evolved mechanisms to counter viral subversion strategies for mutual survival. Since the start of the current COVID-19 pandemic, numerous cases of acute kidney injury have been reported in the literature with various possible pathophysiological mechanisms. In this review, we summarize lessons learned from prior viral pandemics related to viral mechanisms utilized in the pathogenesis of numerous renal manifestations to attempt to utilize this knowledge in predicting post-COVID-19 kidney disease.

Selected biochemical parameters in the urine of HIV-infected patients in monitoring of kidney function

Introduction

For years, there has been an increase in the number of cases of chronic kidney disease (CKD) in human immunodeficiency virus (HIV)-infected patients. Renal dysfunction can be caused by direct effects of HIV on the kidneys but also of applied combined antiretroviral therapy (cART). Therefore there is a need of renal function diagnosis to monitor the development of kidney disturbances. In this study the urinary levels of selected low molecular weight proteins (LMWP) in HIV-infected patients were measured and related to current CD4+ T lymphocyte (LT CD4+) count, the glomerular filtration rate (eGFR) value and the applied cART.

Material and methods

The levels of 5 LMWP - kidney injury molecule-1 (KIM-1), neutrophil gelatinase associated lipocalin (NGAL), glutathione S-transferase α (GST-α) and π (GST-π) isoenzymes and neopterin (NPT) - in urine were measured in HIV-infected patients and healthy controls by enzyme-linked immunosorbent assay.

Results

Taking into account the current LT CD4+ count, KIM-1, NGAL and GST-α showed statistically significant differences between groups with the CD4+ count < 500 and ≥ 500 cells (< 0.001). Depending on the eGFR, apart from KIM-1 and NGAL, NPT showed statistically significant differences in the investigated groups with normal and lower eGFR values (< 0.001). In terms of applied cART, the best parameters in the assessment of kidney damage were NGAL, GST-π and NPT (< 0.001).

Conclusions

This research shows that the analyzed LMWP parameters are useful in the assessment of kidney damage in HIV patients during cART, especially NPT, NGAL and GST-π. However, future studies should be conducted on larger groups.

Inhibition of apoptosis signal-regulating kinase 1 mitigates the pathogenesis of human immunodeficiency virus-associated nephropathy

BACKGROUND

Chronic kidney disease (CKD) is a common cause of morbidity and mortality in human immunodeficiency virus (HIV)-positive individuals. Among the HIV-related kidney diseases, HIV-associated nephropathy (HIVAN) is a rapidly progressive renal disease characterized by collapsing focal glomerulosclerosis (GS), microcystic tubular dilation, interstitial inflammation and fibrosis. Although the incidence of end-stage renal disease due to HIVAN has dramatically decreased with the widespread use of antiretroviral therapy, the prevalence of CKD continues to increase in HIV-positive individuals. Recent studies have highlighted the role of apoptosis signal-regulating kinase 1 (ASK1) in driving kidney disease progression through the activation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase and selective ASK-1 inhibitor GS-444217 was recently shown to reduce kidney injury and disease progression in various experimental models. Therefore we examined the efficacy of ASK1 antagonism by GS-444217 in the attenuation of HIVAN in Tg26 mice.

METHODS

GS-444217-supplemented rodent chow was administered in Tg26 mice at 4 weeks of age when mild GS and proteinuria were already established. After 6 weeks of treatment, the kidney function assessment and histological analyses were performed and compared between age- and gender-matched control Tg26 and GS-444217-treated Tg26 mice.

RESULTS

GS-444217 attenuated the development of GS, podocyte loss, tubular injury, interstitial inflammation and renal fibrosis in Tg26 mice. These improvements were accompanied by a marked reduction in albuminuria and improved renal function. Taken together, GS-4442217 attenuated the full spectrum of HIVAN pathology in Tg26 mice.

CONCLUSIONS

ASK1 signaling cascade is central to the development of HIVAN in Tg26 mice. Our results suggest that the select inhibition of ASK1 could be a potential adjunctive therapy for the treatment of HIVAN.

Discontinuation of Intermittent Hemodialysis in HIV-Associated Nephropathy Following Initiation of Antiretroviral Therapy

Human immunodeficiency virus (HIV) infection occurs due to the HIV virus. It results in an immunodeficient state and multi-organ system infections and malignancy known as AIDS. HIV-associated nephropathy (HIVAN) is the most common HIV kidney involvement and may present as acute kidney injury (AKI), as well as chronic kidney disease (CKD). HIVAN is a collapsing form of focal segmental glomerulosclerosis (FSGS). HIVAN treatment options include antiretroviral therapy (ART), steroids, angiotensin-converting enzyme inhibitors/angiotensin receptor blockers (ACEI/ARB), and hemodialysis (HD). We herein describe the case of a 40-year-old patient with an established diagnosis of HIVAN who has had partial recovery of end-stage renal failure following the initiation of ART.

APOL1 risk variants and the development of HIV-associated nephropathy

HIV-associated nephropathy (HIVAN) remains a concern among untreated HIV patients, notably of African descent, as patients can reach end-stage renal disease within 3 years. Two variants (G1 and G2) of the APOL1 gene, common in African populations to protect against African sleeping sickness, have been associated with an increased risk of several glomerular disorders including HIVAN, hypertension-attributed chronic kidney disease, and idiopathic focal segmental glomerulosclerosis and are accordingly named renal risk variants (RRVs). This review examines the mechanisms by which APOL1 RRVs drive glomerular injury in the setting of HIV infection and their potential application to patient management. Innate antiviral mechanisms activated by chronic HIV infection, especially those involving type 1 interferons, are of particular interest as they have been shown to upregulate APOL1 expression. Additionally, the downregulation of miRNA 193a (a repressor of APOL1) is also associated with the upregulation of APOL1. Interestingly, glomerular damage affected by APOL1 RRVs is caused by both loss- and gain-of-function changes in the protein, explicitly characterizing these effects. Their intracellular localization offers a further understanding of the nuances of APOL1 variant effects in promoting renal disease. Finally, although APOL1 variants have been recognized as a critical genetic player in mediating kidney disease, there are significant gaps in their application to patient management for screening, diagnosis, and treatment.

APOL1 polymorphism modulates sphingolipid profile of human podocytes

Apolipoprotein L1 (APOL1) wild type (G0) plays a role in the metabolism of sphingolipids, glycosphingolipids, sphingomyelin and ceramide, which constitute bioactive components of the lipid rafts (DRM). We asked whether APOL1 variants (APOL1-Vs) G1 and G2 carry the potential to alter the metabolism of sphingolipids in human podocytes. The sphingolipid pattern in HPs overexpressing either APOL1G0 or APOL1-Vs was analysed by using a thin mono- and bi-dimensional layer chromatography, mass-spectrometry and metabolic labelling with [1-³H]sphingosine. HP G0 and G1/G2-Vs exhibit a comparable decrease in lactosylceramide and an increase in the globotriaosylceramide content. An analysis of the main glycohydrolases activity involved in glycosphingolipid catabolism showed an overall decrease in the activeness of the tested enzymes, irrespective of the type of APOL1-Vs expression. Similarly, the high throughput cell live-based assay showed a comparable increased action of the plasma membrane glycosphingolipid-glycohydrolases in living cells independent of the genetic APOL1 expression profile. Importantly, the most significative modification of the sphingolipid pattern induced by APOL1-Vs occurred in DRM resulted with a drastic reduction of radioactivity associated with sphingolipids. G1/G2-Vs present a decrease amount of globotriaosylceramide and globopentaosylceramide compared to G0. Additionally, ceramide at the DRM site and lactosylceramide in general, showed a greatest fall in G1/G2 in comparison with G0. Additionally, the levels of glucosylceramide decreased only in the DRM of human podocytes overexpressing G1/G2-Vs. These findings suggest that altered sphingolipidsprofiles may contribute to the deranged functionality of the plasma membrane in APOL1 risk milieu.

Autophagy in kidney disease: Advances and therapeutic potential

Autophagy is a highly conserved intracellular catabolic process for the degradation of cytoplasmic components that has recently gained increasing attention for its importance in kidney diseases. It is indispensable for the maintenance of kidney homeostasis both in physiological and pathological conditions. Investigations utilizing various kidney cell-specific conditional autophagy-related gene knockouts have facilitated the advancement in understanding of the role of autophagy in the kidney. Recent findings are raising the possibility that defective autophagy exerts a critical role in different pathological conditions of the kidney. An emerging body of evidence reveals that autophagy exhibits cytoprotective functions in both glomerular and tubular compartments of the kidney, suggesting the upregulation of autophagy as an attractive therapeutic strategy. However, there is also accumulating evidence that autophagy could be deleterious, which presents a formidable challenge in developing therapeutic strategies targeting autophagy. Here, we review the recent advances in research on the role of autophagy during different pathological conditions, including acute kidney injury (AKI), focusing on sepsis, ischemia-reperfusion injury, cisplatin, and heavy metal-induced AKI. We also discuss the role of autophagy in chronic kidney disease (CKD) focusing on the pathogenesis of tubulointerstitial fibrosis, podocytopathies including focal segmental glomerulosclerosis, diabetic nephropathy, IgA nephropathy, membranous nephropathy, HIV-associated nephropathy, and polycystic kidney disease.

HIV-1 proteins gp120 and tat induce the epithelial-mesenchymal transition in oral and genital mucosal epithelial cells

The oral, cervical, and genital mucosa, covered by stratified squamous epithelia with polarized organization and strong tight and adherens junctions, play a critical role in preventing transmission of viral pathogens, including human immunodeficiency virus (HIV). HIV-1 interaction with mucosal epithelial cells may depolarize epithelia and disrupt their tight and adherens junctions; however, the molecular mechanism of HIV-induced epithelial disruption has not been completely understood. We showed that prolonged interaction of cell-free HIV-1 virions, and viral envelope and transactivator proteins gp120 and tat, respectively, with tonsil, cervical, and foreskin epithelial cells induces an epithelial-mesenchymal transition (EMT). EMT is an epigenetic process leading to the disruption of mucosal epithelia and allowing the paracellular spread of viral and other pathogens. Interaction of cell-free virions and gp120 and tat proteins with epithelial cells substantially reduced E-cadherin expression and activated vimentin and N-cadherin expression, which are well-known mesenchymal markers. HIV gp120- and tat-induced EMT was mediated by SMAD2 phosphorylation and activation of transcription factors Slug, Snail, Twist1 and ZEB1. Activation of TGF-β and MAPK signaling by gp120, tat, and cell-free HIV virions revealed the critical roles of these signaling pathways in EMT induction. gp120- and tat-induced EMT cells were highly migratory via collagen-coated membranes, which is one of the main features of mesenchymal cells. Inhibitors of TGF-β1 and MAPK signaling reduced HIV-induced EMT, suggesting that inactivation of these signaling pathways may restore the normal barrier function of mucosal epithelia.

Yes-associated protein regulates podocyte cell cycle re-entry and dedifferentiation in adriamycin-induced nephropathy

Podocytes are terminally differentiated cells with little proliferative capacity. The high expression levels of cell cycle inhibitory proteins, including p21, p27, and p57, play an important role in maintaining the low level of proliferation of mature podocytes. In the present study, we aimed to explore the role of yes-associated protein (YAP) signalling in adriamycin-induced podocyte re-entry into the cell cycle and dedifferentiation. Proliferating cell nuclear antigen (PCNA)-, cyclin-dependent kinase 4 (CDK4)-, and Cyclin D1-positive podocytes were found in mice with adriamycin-induced nephropathy. In vitro, adriamycin administration increased the percentage of cells in S phase and the upregulation of mesenchymal-related marker proteins. CDK4 and cyclin D1 were significantly up-regulated after incubation with adriamycin. Overexpression of YAP in podocytes promoted their entry into the cell cycle; up-regulated cyclin D1, desmin, and snail2 expression and down-regulated Wilms’ tumour 1 (WT1) and nephrin production. Recombinant murine FGF-basic induced podocytes to re-enter the cell cycle, inhibited WT1 and nephrin, and increased desmin and snail2 expression. Pretreating podocytes with verteporfin, an inhibitor of YAP/ TEA domain transcription factor (TEAD), decreased the adriamycin-induced overexpression of cyclin D1 and reduced the ratio of S-phase podocytes. This result was further verified by knocking down YAP expression using RNA interference. In conclusion, adriamycin induced podocytes to re-enter the cell cycle via upregulation of CDK4 and cyclin D1 expression, which was at least partly mediated by YAP signalling. Re-entry into the cell cycle induced the over-expression of mesenchymal markers in podocytes.

Proteinuria Is Associated With Increased Risk of Fragility Fracture in Men With or at Risk of HIV Infection

BACKGROUND

Proteinuria has been associated with bone loss and fractures in general population, but data in HIV-infected population are lacking.

SETTING

Prospective, multicenter cohort study of men with or at risk of HIV infection.

METHODS

Between 2006 and 2015, urine protein measurements and bone fracture histories were ascertained semiannually in 947 HIV-infected (HIV+) and 969 HIV-uninfected (HIV-) men aged 40 years or older. Proteinuria was defined as protein-to-creatinine ratio ≥200 mg/g at ≥2 consecutive visits. Outcome measures (1) all fractures (excluding fractures of skull, face, and digits) and (2) fragility fractures (fractures of vertebral column, femur, wrist, and humerus). Multivariable Cox proportional hazards models assessed the association between proteinuria and fracture after adjusting for additional risk factors.

RESULTS

The overall period prevalence of proteinuria was higher among HIV+ than HIV- (29% vs 6%, P < 0.001). Men with proteinuria had a significantly higher risk of fragility fracture compared with men without proteinuria [adjusted hazard ratio (aHR) = 2.29 (1.12-4.66)] and did not differ by HIV serostatus (p-interaction = 0.83). The risk of all fractures was not statistically different between men with or without proteinuria [aHR = 1.31 (0.84-2.05)]. Among HIV+ men, the association between confirmed proteinuria and fragility fracture was attenuated [aHR = 2.12 (0.95-4.73)] after additional adjustment for CD4 T-cell count/mm, history of AIDS, the presence of detectable plasma HIV-1 RNA, and cumulative exposure to tenofovir disoproxil fumarate.

CONCLUSIONS

Proteinuria was more common in HIV+ than in HIV- men and was a strong independent risk factor for fragility fracture regardless of HIV serostatus. Proteinuria should prompt consideration of a thorough evaluation for bone disease among HIV+ persons.

The Changing Face of Human Immunodeficiency Virus-Mediated Kidney Disease

In nearly 40 years since human immunodeficiency virus (HIV) first emerged, much has changed. Our understanding of the pathogenesis of HIV infection and its effect on the cells within each kidney compartment has progressed, and the natural history of the disease has been transformed. What was once an acutely fatal illness is now a chronic disease managed with oral medications. This change is largely due to the advent of antiretroviral drugs, which have dramatically altered the prognosis and progression of HIV infection. However, the success of antiretroviral therapy has brought with it new challenges for the nephrologist caring for patients with HIV/acquired immune deficiency syndrome, including antiretroviral therapy-induced nephrotoxicity, development of non-HIV chronic kidney disease, and rising incidence of immune-mediated kidney injury. In this review, we discuss the pathogenesis of HIV infection and how it causes pathologic changes in the kidney, review the nephrotoxic effects of select antiretroviral medications, and touch upon other causes of kidney injury in HIV cases, including mechanisms of acute kidney injury, HIV-related immune complex glomerular disease, and thrombotic microangiopathy.

HIVAN associated tubular pathology with reference to ER stress, mitochondrial changes, and autophagy

Human immunodeficiency virus associated nephropathy (HIVAN) is a unique form of a renal parenchymal disorder. This disease and its characteristics can be accredited to incorporation of DNA and mRNA of human immunodeficiency virus type 1 into the renal parenchymal cells. A proper understanding of the intricacies of HIVAN and the underlying mechanisms associated with renal function and disorders is vital for the potential development of a reliable treatment for HIVAN. Specifically, the renal tubule segment of the kidney is characterized by its transport capabilities and its ability to reabsorb water and salts into the blood. However, the segment is also known for certain disorders, such as renal tubular epithelial cell infection and microcyst formation, which are also closely linked to HIVAN. Furthermore, certain organelles, like the endoplasmic reticulum (ER), mitochondria, and lysosome, are vital for certain underlying mechanisms in kidney cells. A paradigm of the importance of said organelles can be seen in documented cases of HIVAN where the renal disorder results increased ER stress due to HIV viral propagation. This balance can be restored through the synthesis of secretory proteins, but, in return, the secretion requires more energy; therefore, there is a noticeable increase in mitochondrial stress. The increased ER changes and mitochondrial stress will greatly upregulate the process of autophagy, which involves the cell's lysosomes. In conjunction, we found that ER stress and mitochondrial changes are associated in the Tg26 animal model of HIVAN. The aim of our review is to consolidate current knowledge of important mechanisms in HIVAN, specifically related to the renal tubules' association with ER stress, mitochondrial changes and autophagy. Although the specific regulatory mechanism detailing the cross-talk between the various organelles is unknown in HIVAN, the continued research in this field may potentially shed light on a possible improved treatment for HIVAN.

The role of exosomal transport of viral agents in persistent HIV pathogenesis

Human immunodeficiency virus (HIV) infection, despite great advances in antiretroviral therapy, remains a lifelong affliction. Though current treatment regimens can effectively suppress viral load to undetectable levels and preserve healthy immune function, they cannot fully alleviate all symptoms caused by the presence of the virus, such as HIV-associated neurocognitive disorders. Exosomes are small vesicles that transport cellular proteins, RNA, and small molecules between cells as a mechanism of intercellular communication. Recent research has shown that HIV proteins and RNA can be packaged into exosomes and transported between cells, to pathogenic effect. This review summarizes the current knowledge on the diverse mechanisms involved in the sorting of viral elements into exosomes and the damage those exosomal agents can inflict. In addition, potential therapeutic options to counteract exosome-mediated HIV pathogenesis are reviewed and considered.

Prevalence and outcomes of central venous catheter-related bacteraemia in HIV-infected versus non-HIV-infected patients undergoing haemodialysis treatment for end-stage kidney disease

Background

Central venous catheter (CVC) haemodialysis (HD) to implement renal replacement therapy is the preferred choice in the urgent setting. Unfortunately, CVC placement is associated with multiple complications including nosocomial bloodstream infections. There is a paucity of data on the prevalence and pattern of pathogenic organisms in haemodialysed HIV-infected versus non-HIV-infected patients with end-stage kidney disease.

Method and results

We undertook a retrospective study of 228 patients who were dialysed using a CVC at a tertiary referral hospital in KwaZulu-Natal, South Africa. Seventy-eight patients (34.2%) complicated with bacteraemia and sepsis requiring antibiotics. Removal of the catheter was necessary in 58 patients (74.0%). The most common organisms isolated were Staphylococcus aureus (30.8%), Staphylococcus epidermidis (24.4%) and Klebsiella pneumoniae (15.4%). There was no statistically significant difference between HIV-infected and non-infected patients with regards to infection rate, time interval from insertion of CVC to infection and final outcome. However, HIV-infected patients took longer to recover; 54.3% of non-infected patients versus 10.3% HIV-infected patients had their sepsis controlled within one week. Acidosis, hypotension, line malfunction and line discharge were infrequent signs of sepsis. Fever, rigors and raised white cell count occurred in over 80.0% of patients.

Conclusion

The infection rate in CVC HD is not more frequent in HIV-infected patients, provided that CD4+ count is ≥ 200 cells/µL and the patient is virologically suppressed. Outcomes following intravenous antibiotic and removal of the CVC are similar in HIV-infected and non-infected patients but response to treatment is slower in HIV-infected patients. A high index of suspicion is needed in detecting CVC-related bacteraemia.

Tyro3 is a podocyte protective factor in glomerular disease

Our previous work demonstrated a protective role of protein S in early diabetic kidney disease (DKD). Protein S exerts antiinflammatory and antiapoptotic effects through the activation of TYRO3, AXL, and MER (TAM) receptors. Among the 3 TAM receptors, we showed that the biological effects of protein S were mediated largely by TYRO3 in diabetic kidneys. Our data now show that TYRO3 mRNA expression is highly enriched in human glomeruli and that TYRO3 protein is expressed in podocytes. Interestingly, glomerular TYRO3 mRNA expression increased in mild DKD but was suppressed in progressive DKD, as well as in focal segmental glomerulosclerosis (FSGS). Functionally, morpholino-mediated knockdown of tyro3 altered glomerular filtration barrier development in zebrafish larvae, and genetic ablation of Tyro3 in murine models of DKD and Adriamycin-induced nephropathy (ADRN) worsened albuminuria and glomerular injury. Conversely, the induction of TYRO3 overexpression specifically in podocytes significantly attenuated albuminuria and kidney injury in mice with DKD, ADRN, and HIV-associated nephropathy (HIVAN). Mechanistically, TYRO3 expression was suppressed by activation of TNF-α/NF-κB pathway, which may contribute to decreased TYRO3 expression in progressive DKD and FSGS, and TYRO3 signaling conferred antiapoptotic effects through the activation of AKT in podocytes. In conclusion, TYRO3 plays a critical role in maintaining normal podocyte function and may be a potential new drug target to treat glomerular diseases.

Epigenetic regulation of RCAN1 expression in kidney disease and its role in podocyte injury

Mounting evidence suggests that epigenetic modification is important in kidney disease pathogenesis. To determine whether epigenetic regulation is involved in HIV-induced kidney injury, we performed genome-wide methylation profiling and transcriptomic profiling of human primary podocytes infected with HIV-1. Comparison of DNA methylation and RNA sequencing profiles identified several genes that were hypomethylated with corresponding upregulated RNA expression in HIV-infected podocytes. Notably, we found only one hypermethylated gene with corresponding downregulated RNA expression, namely regulator of calcineurin 1 (RCAN1). Further, we found that RCAN1 RNA expression was suppressed in glomeruli in human diabetic nephropathy, IgA nephropathy, and lupus nephritis, and in mouse models of HIV-associated nephropathy and diabetic nephropathy. We confirmed that HIV infection or high glucose conditions suppressed RCAN1 expression in cultured podocytes. This suppression was alleviated upon pretreatment with DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine, suggesting that RCAN1 expression is epigenetically suppressed in the context of HIV infection and diabetic conditions. Mechanistically, increased expression of RCAN1 decreased HIV- or high glucose-induced nuclear factor of activated T cells (NFAT) transcriptional activity. Increased RCAN1 expression also stabilized actin cytoskeleton organization, consistent with the inhibition of the calcineurin pathway. In vivo, knockout of RCAN1 aggravated albuminuria and podocyte injury in mice with Adriamycin-induced nephropathy. Our findings suggest that epigenetic suppression of RCAN1 aggravates podocyte injury in the setting of HIV infection and diabetic nephropathy.

APOL1 risk variants cause podocytes injury through enhancing endoplasmic reticulum stress

Two coding sequence variants (G1 and G2) of Apolipoprotein L1 (APOL1) gene have been implicated as a higher risk factor for chronic kidney diseases (CKD) in African Americans when compared with European Americans. Previous studies have suggested that the APOL1 G1 and G2 variant proteins are more toxic to kidney cells than the wild-type APOL1 G0, but the underlying mechanisms are poorly understood. To determine whether endoplasmic reticulum (ER) stress contributes to podocyte toxicity, we generated human podocytes (HPs) that stably overexpressed APOL1 G0, G1, or G2 (Vec/HPs, G0/HPs, G1/HPs, and G2/HPs). Propidium iodide staining showed that HP overexpressing the APOL1 G1 or G2 variant exhibited a higher rate of necrosis when compared with those overexpressing the wild-type G0 counterpart. Consistently, the expression levels of nephrin and podocin proteins were significantly decreased in the G1- or G2-overexpressing cells despite the maintenance of their mRNA expressions levels. In contrast, the expression of the 78-kDa glucose-regulated protein ((GRP78), also known as the binding Ig protein, BiP) and the phosphorylation of the eukaryotic translation initiation factor 1 (eIF1) were significantly elevated in the G1/HPs and G2/HPs, suggesting a possible occurrence of ER stress in these cells. Furthermore, ER stress inhibitors not only restored nephrin protein expression, but also provided protection against necrosis in G1/HPs and G2/HPs, suggesting that APOL1 risk variants cause podocyte injury partly through enhancing ER stress.

Pharmacotherapy and treatment options for HIV-associated nephropathy

INTRODUCTION

Human immunodeficiency virus (HIV) remains a worldwide disease with significant mortality and morbidity. There are a multitude of HIV-related kidney diseases including HIV-associated nephropathy (HIVAN) most prominently. The risk of developing HIVAN increases with decreasing CD4 count, higher viral load, and based on genetic factors. The mortality rate for those with HIVAN-end stage renal disease (ESRD) remains 2.5-3 times higher than ESRD patients without HIVAN.

AREAS COVERED

The epidemiology of HIVAN, particularly risk assessment, will be explored in this review. Further, the pathogenesis of HIVAN, from viral-specific renal expression to the role of genetics as well as characteristic renal pathology will be described. Diagnosis and management of HIVAN will be addressed, with an emphasis on various treatment strategies including medication, dialysis, and kidney transplantation.

EXPERT OPINION

HIVAN is associated with a high risk for progression to ESRD and increased mortality. The backbone of HIVAN therapy remains combined anti-retroviral therapy (cART), while adjunctive therapies including RAAS blockade and prednisone, should be considered. In those who progress to ESRD, dialysis remains the mainstay of management, though increasing evidence has demonstrated that kidney transplantation can be effective in those with controlled HIV disease.

The Role of Transforming Growth Factor Beta-1 in the Progression of HIV/AIDS and Development of Non-AIDS-Defining Fibrotic Disorders

Even after attainment of sustained viral suppression following implementation of highly active antiretroviral therapy, HIV-infected persons continue to experience persistent, low-grade, systemic inflammation. Among other mechanisms, this appears to result from ongoing microbial translocation from a damaged gastrointestinal tract. This HIV-related chronic inflammatory response is paralleled by counteracting, but only partially effective, biological anti-inflammatory processes. Paradoxically, however, this anti-inflammatory response not only exacerbates immunosuppression but also predisposes for development of non-AIDS-related, non-communicable disorders. With respect to the pathogenesis of both sustained immunosuppression and the increased frequency of non-AIDS-related disorders, the anti-inflammatory/profibrotic cytokine, transforming growth factor-β1 (TGF-β1), which remains persistently elevated in both untreated and virally suppressed HIV-infected persons, may provide a common link. In this context, the current review is focused on two different, albeit related, harmful activities of TGF-β1 in HIV infection. First, on the spectrum of anti-inflammatory/immunosuppressive activities of TGF-β1 and the involvement of this cytokine, derived predominantly from T regulatory cells, in driving disease progression in HIV-infected persons via both non-fibrotic and profibrotic mechanisms. Second, the possible involvement of sustained elevations in circulating and tissue TGF-β1 in the pathogenesis of non-AIDS-defining cardiovascular, hepatic, pulmonary and renal disorders, together with a brief comment on potential TGF-β1-targeted therapeutic strategies.

HIV as a Cause of Immune Activation and Immunosenescence

Systemic immune activation has emerged as an essential component of the immunopathogenesis of HIV. It not only leads to faster disease progression, but also to accelerated decline of overall immune competence. HIV-associated immune activation is characterized by an increase in proinflammatory mediators, dysfunctional T regulatory cells, and a pattern of T-cell-senescent phenotypes similar to those seen in the elderly. These changes predispose HIV-infected persons to comorbid conditions that have been linked to immunosenescence and inflamm-ageing, such as atherosclerosis and cardiovascular disease, neurodegeneration, and cancer. In the antiretroviral treatment era, development of such non-AIDS-defining, age-related comorbidities is a major cause of morbidity and mortality. Treatment strategies aimed at curtailing persistent immune activation and inflammation may help prevent the development of these conditions. At present, the most effective strategy appears to be early antiretroviral treatment initiation. No other treatment interventions have been found effective in large-scale clinical trials, and no adjunctive treatment is currently recommended in international HIV treatment guidelines. This article reviews the role of systemic immune activation in the immunopathogenesis of HIV infection, its causes and the clinical implications linked to immunosenescence in adults, and the therapeutic interventions that have been investigated.

HIV Infection in the Native and Allograft Kidney: Implications for Management, Diagnosis, and Transplantation

The native kidney is a reservoir for human immunodeficiency virus (HIV)-1 and a site of viral replication, similar to lymphoid tissue, gut-associated lymphoid tissue or semen. The ability of the virus to persist may result from either a true latency or sequestration in an anatomic site that is not effectively exposed to antiretroviral therapy. The presence of HIV in kidney epithelial cells will lead progressively to end-stage renal disease. For decades, HIV-infected patients were excluded from consideration for kidney transplantation. Hemodialysis and peritoneal dialysis were the only forms of treatment available to these patients. The introduction of combined antiretroviral therapy has changed the overall prognosis of these patients and allowed them to benefit from kidney transplantation without an increased risk of opportunistic infections or cancer. However, we recently established that HIV-1 can infect kidney transplant epithelial cells in the absence of detectable viremia. The presence of HIV in kidney cells can manifest itself in multiple ways, ranging from indolent nephropathy and inflammation to proteinuria with glomerular abnormalities. Because the tools that are available to diagnose the presence of HIV in kidney cells are complex, the rate of infection is certainly underestimated. This finding will certainly have implications in the management of patients, particularly for HIV-positive donors. The purpose of this review is to highlight recent evidence that the allograft kidney can be infected by the virus after transplantation as well as the associated consequences.

Tubuloreticular Inclusions in the Absence of Systemic Lupus Erythematosus and HIV Infection: A Report of Three Pediatric Cases

Tubuloreticular inclusions (TRIs) are subcellular structures located within the cisternae of endoplasmic reticulum. Formation of TRIs has been linked to the exposure of excess interferon (IFN), either from endogenous or exogenous sources. In renal disease, TRIs have been most commonly associated with systemic lupus erythematosus (SLE), and human immunodeficiency virus-associated nephropathy (HIVAN). Case reports of patients with renal biopsies showing TRIs without underlying SLE or HIV are infrequent in adults, and to our knowledge none have been reported in children. We report 3 pediatric cases in which the renal biopsy showed TRIs on electron microscopy without underlying SLE or HIV infection. The first patient presented at 2 years of age with nephrotic syndrome and renal failure. His renal biopsy revealed focal segmental glomerulosclerosis and TRIs. The second patient presented at 6 months of age with infantile nephrotic syndrome, and his renal biopsy revealed membranous glomerulopathy and TRIs. The last patient presented at 4 years of age with acute kidney injury of unclear etiology leading to chronic kidney disease. Her biopsy revealed acute and chronic tubulointerstitial nephritis with TRIs. Despite extensive evaluation in all 3 patients, including testing for HIV infection and SLE, we could not identify an underlying etiology to explain the presence of TRIs. In conclusion, renal biopsy with TRIs in the absence of underling SLE and HIV remains obscure. We propose a possible role for excess IFN triggered by an abnormal immune response to common viral infections in the formation of TRIs and renal injury.

Nicotine Induces Podocyte Apoptosis through Increasing Oxidative Stress

Background

Cigarette smoking plays an important role in the progression of chronic kidney disease (CKD). Nicotine, one of the major components of cigarette smoking, has been demonstrated to increase proliferation of renal mesangial cells. In this study, we examined the effect of nicotine on podocyte injury.

Methods

To determine the expression of nicotinic acetylcholine receptors (nAChR subunits) in podocytes, cDNAs and cell lysate of cultured human podocytes were used for the expression of nAChR mRNAs and proteins, respectively; and mouse renal cortical sections were subjected to immunofluorescant staining. We also studied the effect of nicotine on podocyte nephrin expression, reactive oxygen species (ROS) generation (via DCFDA loading followed by fluorometric analysis), proliferation, and apoptosis (morphologic assays). We evaluated the effect of nicotine on podocyte downstream signaling including phosphorylation of ERK1/2, JNK, and p38 and established causal relationships by using respective inhibitors. We used nAChR antagonists to confirm the role of nicotine on podocyte injury.

Results

Human podocytes displayed robust mRNA and protein expression of nAChR in vitro studies. In vivo studies, mice renal cortical sections revealed co-localization of nAChRs along with synaptopodin. In vitro studies, nephrin expression in podocyte was decreased by nicotine. Nicotine stimulated podocyte ROS generation; nonetheless, antioxidants such as N-acetyl cysteine (NAC) and TEMPOL (superoxide dismutase mimetic agent) inhibited this effect of nicotine. Nicotine did not modulate proliferation but promoted apoptosis in podocytes. Nicotine enhanced podocyte phosphorylation of ERK1/2, JNK, and p38, and their specific inhibitors attenuated nicotine-induced apoptosis. nAChR antagonists significantly suppressed the effects of nicotine on podocyte.

Conclusions

Nicotine induces podocyte apoptosis through ROS generation and associated downstream MAPKs signaling. The present study provides insight into molecular mechanisms involved in smoking associated progression of chronic kidney disease.

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

BACKGROUND

Patients of African ancestry with untreated HIV-1 infection and carrying the G1 or G2 kidney disease risk variants (Vs) at the APOL1 gene have a tenfold higher risk of developing HIV-associated nephropathy (HIVAN) compared to those with the non-risk wild type (WT) G0 variant. However, the mechanistic contribution of the APOL1 allelic state to kidney injury in HIV-1 infection remains to be elucidated.

RESULTS

Non-risk WT APOL1 is associated with lower intracellular levels of HIV-1 in conditionally immortalized human podocytes, while the over expression of G1 or G2 risk Vs significantly increases viral accumulation. The priming of podocytes with exogenous IL-1β facilitates HIV-1 entry, via the up-regulation of DC-SIGN. The over expression of APOL1 G1 and G2 risk Vs in combination with an increase in IL-1β levels causes a greater increase in viral concentration than either condition alone. In turn, HIV-1 and exogenous IL-1β together induce a de novo secretion of endogenous IL-1β and an increase of APOL1 gene expression.

CONCLUSIONS

Our findings indicate that the presence of risk Vs of APOL1 is permissive of HIV-1 persistence in human podocytes in synergy with IL-1β, a cytokine that characterizes the inflammatory milieu of acute and chronic phases of HIV-1 infection. The elucidation of these molecular mechanisms explains, at least in part, the higher frequency of HIVAN in populations carrying the risk polymorphic genetic variant of APOL1 gene.

Interstitial nephritis caused by HIV infection by itself: a case report

Interstitial nephritis is a common cause of renal dysfunction. It is primarily caused by drugs, infections, or autoimmune disorders. Patients with human immunodeficiency virus (HIV) infection can develop interstitial nephritis, although it typically occurs because of the aforementioned etiologies and not as a direct consequence of HIV infection. Interstitial lesions may occur in patients with HIV-associated nephropathy (HIVAN). However, interstitial nephritis without the glomerular injuries characteristic of HIVAN, and without the risk factors described earlier, is very rare. Here, we describe a rare case of interstitial nephritis that was likely caused directly by HIV infection and not by other etiologies.

HIV infection-induced transcriptional program in renal tubular epithelial cells activates a CXCR2-driven CD4+ T-cell chemotactic response

OBJECTIVE

Viral replication and interstitial inflammation play important roles in the pathogenesis of HIV-associated nephropathy. Cell-cell interactions between renal tubule epithelial cells (RTECs) and HIV-infected T cells can trigger efficient virus internalization and viral gene expression by RTEC. To understand how HIV replication initiates HIV-associated nephropathy, we studied the cellular response of RTECs to HIV, examining the transcriptional profiles of primary RTECs exposed to cell-free HIV or HIV-infected T cells.

METHODS

HIV-induced gene expression in hRTECs was examined in vitro by Illumina RNA deep sequencing and revealed an innate response to HIV, which was subclassified by gene ontology biological process terms. Chemokine responses were examined by CD4 T-cell chemotaxis assays.

RESULTS

As compared with cell-free virus infection, exposure to HIV-infected T cells elicited a stronger upregulation of inflammatory and immune response genes. A major category of upregulated genes are chemokine/cytokine families involved in inflammation and immune response, including inflammatory cytokines CCL20, IL6 and IL8-related chemokines: IL8, CXCL1, CXCL2, CXCL3, CXCL5 and CXCL6. Supernatants from virus-exposed RTECs contained strong chemoattractant activity on primary CD4 T cells, which was potently blocked by a CXCR2 antagonist that antagonizes IL8-related chemokines. We observed a preferential migration of CXCR2-expressing, central memory CD4 T cells in response to HIV infection of RTECs.

CONCLUSION

Interactions between primary RTECs and HIV-infected T cells result in potent induction of inflammatory response genes and release of cytokines/chemokines from RTECs that can attract additional T cells. Activation of these genes reflects an innate response to HIV by nonimmune cells.

Current Understanding of the Pathogenesis of Progressive Chronic Kidney Disease in Cats

In cats with chronic kidney disease (CKD), the most common histopathologic finding is tubulointerstitial inflammation and fibrosis. However, these changes reflect a nonspecific response of the kidney to any inciting injury. The risk of developing CKD is likely to reflect the composite effects of genetic predisposition, aging, and environmental and individual factors that affect renal function over the course of a cat's life. However, there is still little information available to determine exactly which individual risk factors predispose a cat to develop CKD. Although many cats diagnosed with CKD have stable disease for years, some cats show overtly progressive disease.

Medium-grade tubular proteinuria is common in HIV-positive patients and specifically associated with exposure to tenofovir disoproxil Fumarate

OBJECTIVES

The aim of this cross-sectional study was to evaluate the prevalence and risk factors of medium-grade proteinuria (100-500 mg/g creatinine) among HIV-positive adults.

METHODS

Spot urine samples of HIV-positive adults without known renal disease were analyzed quantitatively between January 2009 and February 2011. Demographic and medical data were collected. Multivariate regression models for different patterns of proteinuria were constructed.

RESULTS

Among 411 patients, 18 (4.4 %) presented albuminuria >300 mg/g creatinine and/or proteinuria >500 mg/g creatinine and were excluded from further analyses. Among the study population of 393 patients, 181 (46.1 %) had no significant proteinuria or albuminuria (<100 and <30 mg/g creatinine, respectively), 60 (15.3 %) had moderate albuminuria, while 152 (38.7 %) had proteinuria without albuminuria, suggesting tubular proteinuria. Independent predictors for medium-grade tubular proteinuria in multivariate analysis were exposure to tenofovir (DF), a CD4 nadir <500/µl, older age, and anti-HCV-antibodies. There was no association with classic renal risk factors like diabetes mellitus and arterial hypertension, or with estimated glomerular filtration rate (eGFR).

CONCLUSIONS

We detected significant proteinuria in 230 (56.0 %) of 411 HIV-positive patients. Among this group, 152 (66.1 %) had medium-grade proteinuria without albuminuria, which was significantly associated with exposure to tenofovir, older age, a lower CD4 nadir and Hepatitis C. Nephrologic or HIV treatment guidelines fail to detect most of these patients but rather identify patients with high cardiovascular risk. In the absence of an association with eGFR the role of medium-grade tubular proteinuria as a potential early marker of chronic kidney disease remains unclear. Prospective studies are needed.

Key data from the 17th International Workshop on Co-morbidities and Adverse Drug Reactions in HIV

Combination antiretroviral therapy (cART) has significantly reduced HIV-related morbidity and mortality; however, residual inflammation often persists in the absence of detectable viral load. In addition, chronic use of cART and an ageing HIV-positive population present new challenges to treating physicians who must balance the need for good virological control with risk of treatment-related toxicities. Discussions at the 17th International Workshop on Co-morbidities and Adverse Drug Reactions in HIV once again sought a better understanding of the complex relationship between HIV-, treatment- and age-related factors in the development of comorbidities in those infected with HIV. Key data from the meeting pertaining to inflammatory pathways in HIV, adipose tissue metabolism, cardiovascular disease, bone health, ageing and frailty, neurocognitive dysfunction, pulmonary disease and HCV coinfection are the focus of this report.

Podocytes

Podocytes are highly specialized cells of the kidney glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule. When it comes to glomerular filtration, podocytes play an active role in preventing plasma proteins from entering the urinary ultrafiltrate by providing a barrier comprising filtration slits between foot processes, which in aggregate represent a dynamic network of cellular extensions. Foot processes interdigitate with foot processes from adjacent podocytes and form a network of narrow and rather uniform gaps. The fenestrated endothelial cells retain blood cells but permit passage of small solutes and an overlying basement membrane less permeable to macromolecules, in particular to albumin. The cytoskeletal dynamics and structural plasticity of podocytes as well as the signaling between each of these distinct layers are essential for an efficient glomerular filtration and thus for proper renal function. The genetic or acquired impairment of podocytes may lead to foot process effacement (podocyte fusion or retraction), a morphological hallmark of proteinuric renal diseases. Here, we briefly discuss aspects of a contemporary view of podocytes in glomerular filtration, the patterns of structural changes in podocytes associated with common glomerular diseases, and the current state of basic and clinical research.

Infectious Diseases and the Kidney in Children

The kidney is involved in a wide range of bacterial, viral, fungal, and parasitic diseases. In most systemic infections, renal involvement is a minor component of the illness, but in some, renal failure may be the presenting feature and the major problem in management. Although individual infectious processes may have a predilection to involve the renal vasculature, glomeruli, interstitium, or collecting systems, a purely anatomic approach to the classification of infectious diseases affecting the kidney is rarely helpful because most infections may involve several different aspects of renal function. In this chapter, a microbiological classification of the organisms affecting the kidney is adopted. Although they are important causes of renal dysfunction in infectious diseases, urinary tract infections and hemolytic uremic syndrome (HUS) are not discussed in detail because they are considered separately in chapters XX and XX, respectively.

APOL1 Risk Alleles Are Associated with Exaggerated Age-Related Changes in Glomerular Number and Volume in African-American Adults: An Autopsy Study

APOL1 genetic variants contribute to kidney disease in African Americans. We assessed correlations between APOL1 profiles and renal histological features in subjects without renal disease. Glomerular number (N glom) and mean glomerular volume (V glom) were measured by the dissector/fractionator method in kidneys of African-American and non-African-American adults without renal disease, undergoing autopsies in Jackson, Mississippi. APOL1 risk alleles were genotyped and the kidney findings were evaluated in the context of those profiles. The proportions of African Americans with none, one, and two APOL1 risk alleles were 38%, 43%, and 19%, respectively; 38% of African Americans had G1 allele variants and 31% of African Americans had G2 allele variants. Only APOL1-positive African Americans had significant reductions in N glom and increases in V glom with increasing age. Regression analysis predicted an annual average loss of 8834 (P=0.03, sex adjusted) glomeruli per single kidney over the first 38 years of adult life in African Americans with two risk alleles. Body mass index above the group medians, but below the obesity definition of ≥ 30 kg/m(2), enhanced the expression of age-related changes in N glom in African Americans with either one or two APOL1 risk alleles. These findings indicate that APOL1 risk alleles are associated with exaggerated age-related nephron loss, probably decaying from a larger pool of smaller glomeruli in early adult life, along with enlargement of the remaining glomeruli. These phenomena might mark mechanisms of accentuated susceptibility to kidney disease in APOL1-positive African Americans.

Epigenetic Modulation of Human Podocyte Vitamin D Receptor in HIV Milieu

HIV (human immunodeficiency virus) has been reported to induce podocyte injury through down regulation of vitamin D receptor (VDR) and activation of renin angiotensin system; however, the involved mechanism is not clear. Since HIV has been reported to modulate gene expression via epigenetic phenomena, we asked whether epigenetic factors contribute to down regulation of VDR. Kidney cells in HIV transgenic mice and HIV-infected podocytes (HIV/HPs) displayed enhanced expression of SNAIL, a repressor of VDR. To elucidate the mechanism, we studied the effect of HIV on expression of molecules involved in SNAIL repressor complex formation and demonstrated that HIV enhances expression of the histone deacetylase HDAC1 and DNA methyl transferases DNMT3b and DNMT1. 293T cells, when stably transfected with SNAIL (SNAIL/293T), displayed suppressed transcription and translation of VDR. In SNAIL/293T cells, co-immunoprecipitation studies revealed the association of HDAC1, DNMT3b, DNMT1, and mSin3A with SNAIL. Chromatin immunoprecipitation experiments confirmed the presence of the SNAIL repressor complex at the VDR promoter. Consistent with the enhanced DNA methyl transferase expression in HIV/HPs, there was an increased CpG methylation at the VDR promoter. Chromatin immunoprecipitation assay confirmed occurrence of H3K4 trimethylation on SNAIL promoter. Neither a VDR agonist (VDA) nor an HDAC inhibitor (HDACI) nor a demethylating agent (DAC) individually could optimally up regulate VDR in HIV milieu. However, VDA and HDACI when combined were successful in de-repressing VDR expression. Our findings demonstrate that SNAIL recruits multiple chromatin enzymes to form a repressor complex in HIV milieu that down regulates VDR expression.

A Rare Mechanism of Hyponatremia in HIV Disease

Patient: Male, 25

Final Diagnosis: Corticosteroid reistance

Symptoms: Weakness

Medication: —

Clinical Procedure: Diagnosis

Specialty: Nephrology

Vascular smooth muscle cells contribute to APOL1-induced podocyte injury in HIV milieu

Clinical reports have demonstrated that higher rates of non-diabetic glomerulosclerosis in African Americans can be attributed to two coding sequence variants (G1 and G2) in the APOL1 gene; however, the underlying mechanism is still unknown. Kidney biopsy data suggest enhanced expression of APOL1/APOL1 variants (Vs) in smooth muscle cells (SMCs) of renal vasculature. Since APOL1 is a secretory protein of relatively low molecular weight (41kDa), SMCs may be a contributory endocrine/paracrine source of APOL1 wild type (WT)/APOL1Vs in the glomerular capillary perfusate percolating podocytes. In the present study, we tested the hypothesis that an HIV milieu stimulated secretion of APOL1 and its risk variants by arterial SMCs contributes to podocyte injury. Human umbilical artery smooth muscle cells (HSMCs)-treated with conditioned media (CM) of HIV-infected peripheral mononuclear cells (PBMC/HIV-CM), CM of HIV-infected U939 cells, or recombinant IFN-γ displayed enhanced expression of APOL1. Podocytes co-cultured in trans-wells with HSMCs-over expressing APOL1WT showed induction of injury; however, podocytes co-cultured with HSMC-over expressing either APOL1G1 or APOL1G2 showed several folds greater injury when compared to HSMC-over expressing APOL1WT. Conditioned media collected from HSMC-over-expressing APOL1G1/APOL1G2 (HSMC/APOL1G1-CM or HSMC/APOL1G2-CM) also displayed higher percentages of injured podocytes in the form of swollen cells, leaky lysosomes, loss of viability, and enhanced sensitivity to adverse host factors when compared to HSMC/APOL1WT-CM. Notably, HSMC/APOL1WT-CM promoted podocyte injury only at a significantly higher concentrations compared to HSMC/APOL1G1/G2-CM. We conclude that HSMCs could serve as an endocrine/paracrine source of APOL1Vs, which mediate accelerated podocyte injury in HIV milieu.

Differentiating HIV-associated nephropathy from antiretroviral drug-induced nephropathy: a clinical challenge

With the introduction of potent combination antiretroviral therapy (cART) into clinical practice, HIV-infected patients have garnered much benefit. However, kidney disease continues to be a potential complication in this group. Whereas HIV-associated nephropathy (HIVAN) was the major renal complication prior to cART, co-morbid diseases and adverse renal effects of various drugs, in particular cART, now complicate the landscape. Clinicians now must differentiate HIVAN from cART nephrotoxicity. While sometimes this is easy and relatively straightforward, often the clinician faces a difficult challenge distinguishing these two etiologies of kidney disease. This review will discuss HIVAN and cART-related kidney disease and review the clinical and laboratory data that may be useful in differentiating these processes. Often, however, kidney biopsy may be required to differentiate HIVAN from cART nephrotoxicity as well as other kidney lesions associated with concurrent co-morbidities, both infectious and non-infectious.

Causes and pathogenesis of focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) describes both a common lesion in progressive kidney disease, and a disease characterized by marked proteinuria and podocyte injury. The initial injuries vary widely. Monogenetic forms of FSGS are largely due to alterations in structural genes of the podocyte, many of which result in early onset of disease. Genetic risk alleles in apolipoprotein L1 are especially prevalent in African Americans, and are linked not only to adult-onset FSGS but also to progression of some other kidney diseases. The recurrence of FSGS in some transplant recipients whose end-stage renal disease was caused by FSGS points to circulating factors in disease pathogenesis, which remain incompletely understood. In addition, infection, drug use, and secondary maladaptive responses after loss of nephrons from any cause may also cause FSGS. Varying phenotypes of the sclerosis are also manifest, with varying prognosis. The so-called tip lesion has the best prognosis, whereas the collapsing type of FSGS has the worst prognosis. New insights into glomerular cell injury response and repair may pave the way for possible therapeutic strategies.

Low-grade proteinuria is highly prevalent in HIV-positive patients on antiretroviral treatment

OBJECTIVES

HIV-positive patients are at an increased risk for chronic kidney disease. However, these data mainly derive from cohorts with a high percentage of African-American patients, representing a specific ethnical risk group for chronic kidney disease. The aim of this study was to estimate the prevalence and risk factors specifically for early signs of kidney dysfunction in a large, predominantly white cohort of HIV patients.

DESIGN

Cross-sectional study.

METHODS

Prevalence of low-grade proteinuria was measured by quantitative analysis of urinary protein-to-creatinine ratio (cutoff >70 mg/g) and further differentiated by assessing α1-microglobulin (tubular proteinuria) and albumin-to-creatinine ratio (glomerular proteinuria) of HIV patients attending the University Hospital in Cologne, Germany. Together with standard and HIV-related laboratory findings and medical history, risk factors for each form of proteinuria were identified using multivariate forward selection.

RESULTS

Of 945 enrolled patients, 55% were identified with low-grade proteinuria, 41% with tubular proteinuria, and 20% with glomerular proteinuria. Older age was a risk factor for all forms of proteinuria in multivariate analysis. Low-grade proteinuria was also associated with concomitant diabetes and exposure to nucleoside reverse transcriptase inhibitor [anytime during HIV infection, not tenofovir (TDF)-specific], whereas tubular proteinuria was linked to current and any exposure to nucleoside reverse transcriptase inhibitor (TDF-specific). Further risk factors for glomerular proteinuria were hypertension and diabetes in this cohort.

CONCLUSION

Low-grade, glomerular and tubular proteinuria are highly prevalent in this large white HIV cohort. Older age represents a nonmodifiable risk factor for all forms of proteinuria. Glomerular proteinuria is associated with modifiable cardiovascular, but not HIV-related risk factors, whereas tubular proteinuria is linked to TDF exposure.

APOL1 risk variants enhance podocyte necrosis through compromising lysosomal membrane permeability

Development of higher rates of nondiabetic glomerulosclerosis (GS) in African Americans has been attributed to two coding sequence variants (G1 and G2) in the APOL1 gene. To date, the cellular function and the role of APOL1 variants (Vs) in GS are still unknown. In this study, we examined the effects of overexpressing wild-type (G0) and kidney disease risk variants (G1 and G2) of APOL1 in human podocytes using a lentivirus expression system. Interestingly, G0 inflicted podocyte injury only at a higher concentration; however, G1 and G2 promoted moderate podocyte injury at lower and higher concentrations. APOL1Vs expressing podocytes displayed diffuse distribution of both Lucifer yellow dye and cathepsin L as manifestations of enhanced lysosomal membrane permeability (LMP). Chloroquine attenuated the APOL1Vs-induced increase in podocyte injury, consistent with targeting lysosomes. The chloride channel blocker DIDS prevented APOL1Vs- induced injury, indicating a role for chloride influx in osmotic swelling of lysosomes. Direct exposure of noninfected podocytes with conditioned media from G1- and G2-expressing podocytes also induced injury, suggesting a contributory role of the secreted component of G1 and G2 as well. Adverse host factors (AHFs) such as hydrogen peroxide, hypoxia, TNF-α, and puromycin aminonucleoside augmented APOL1- and APOL1Vs-induced podocyte injury, while the effect of human immunodeficiency virus (HIV) on podocyte injury was overwhelming under conditions of APOLVs expression. We conclude that G0 and G1 and G2 APOL1 variants have the potential to induce podocyte injury in a manner which is further augmented by AHFs, with HIV infection being especially prominent.

An Unusual Case of Anti-GBM Antibody Elevation in HIV-Associated Nephropathy

Introduction. The most commonly seen glomerular disease in HIV infected patients is HIV-associated nephropathy (HIVAN); however, a multitude of other nephropathies can occur in HIV infection with an almost equal cumulative frequency. We report an unusual case of a patient with clinical and histological evidence of HIVAN in which the diagnosis was initially confounded by the finding of an elevated serum anti-glomerular basement membrane (anti-GBM) antibody. Case Presentation. We present a case of a 27-year-old African American female with a history of schizophrenia, cocaine abuse, and HIV infection who upon admission to our hospital was found to have severe acute kidney injury requiring hemodialysis. Urine studies revealed nephrotic range proteinuria and a serological workup was positive for anti-GBM antibody elevation with a value of 91 units (normal: 0–20 units). A renal biopsy revealed HIVAN with no evidence of crescentic glomerulonephritis or anti-GBM disease. Conclusion. This case highlights the need for careful interpretation of anti-GBM antibody tests in HIV infected patients with kidney disease and, in particular, the need for biopsy confirmation of the diagnosis prior to starting therapy. More research is needed to study the prognostic correlation between the degree of anti-GBM antibody elevation in HIVAN and disease severity.

Lipid biology of the podocyte--new perspectives offer new opportunities

In the past 15 years, major advances have been made in understanding the role of lipids in podocyte biology. First, susceptibility to focal segmental glomerulosclerosis (FSGS) and glomerular disease is associated with an APOL1 sequence variant, is expressed in podocytes and encodes apolipoprotein L1, an important component of HDL. Second, acid sphingomyelinase-like phosphodiesterase 3b encoded by SMPDL3b has a role in the conversion of sphingomyelin to ceramide and its levels are reduced in renal biopsy samples from patients with recurrent FSGS. Furthermore, decreased SMPDL3b expression is associated with increased susceptibility of podocytes to injury after exposure to sera from these patients. Third, in many individuals with membranous nephropathy, autoantibodies against the phospholipase A2 (PLA2) receptor, which is expressed in podocytes, have been identified. Whether these autoantibodies affect the activity of PLA2, which liberates arachidonic acid from glycerophospholipids and modulates podocyte function, is unknown. Fourth, clinical and experimental evidence support a role for ATP-binding cassette sub-family A member 1-dependent cholesterol efflux, free fatty acids and glycerophospolipids in the pathogenesis of diabetic kidney disease. An improved understanding of lipid biology in podocytes might provide insights to develop therapeutic targets for primary and secondary glomerulopathies.