Expression of HIV transgene aggravates kidney injury in diabetic mice

Comparable Short-Term Survival in HIV-Positive and HIV-Negative Dual Organ Heart Transplant Recipients: A Call for Increased Access to Organ Donation for People Living with HIV

Access to organ transplantation for HIV-positive individuals is expanding, yet the outcomes of HIV-positive patients requiring multiorgan transplant are not well-defined. Adult individuals in the United Network for Organ Sharing (UNOS) registry who were HIV-positive and received HT between 2010 and 2023 were included. The primary outcome was patient survival. During the study period, 175 HIV-positive patients were transplanted. Twenty-six (14.8%) underwent dual organ transplantation (20 heart/kidney, 4 heart/lung, and 2 heart/liver) at 23 centers. Median age at the time of HT was 56 years (IQR 47-60), majority were male (n=18, 69%), and 46% identified as Black (n= 12). Dilated cardiomyopathy was the most common etiology of heart failure (n=13, 50%). All patients received organs from HIV-negative donors. The probability of surviving at least one year was 87.6% (95% CI 81.0- 92.0) for single-organ recipients and 82.9% for dual organ recipients (95% CI 60.0-93.4). There was no difference in overall survival between HIV-positive and HIV-negative matched controls among dual organ recipients (log-rank p-value = 0.8). Over the last decade, only a small number of HIV-positive individuals with end-stage heart failure have undergone dual organ transplantation with encouraging short-term outcomes.

CD4+ T Cells Expressing Viral Proteins Induce HIV-Associated Endothelial Dysfunction and Hypertension Through Interleukin 1α-Mediated Increases in Endothelial NADPH Oxidase 1

BACKGROUND

Although combination antiretroviral therapy has increased life expectancy in people living with HIV, it has led to a marked increase in the prevalence of hypertension, the cause of which is unknown. Despite combination antiretroviral therapy, HIV-derived proteins remain expressed and produced by CD4+ T lymphocytes in people living with HIV. However, their contribution to HIV-associated hypertension and impaired endothelium-dependent relaxation remains ill defined.

METHODS

Here, we tested the hypothesis that CD4+ T cells expressing viral proteins contribute to endothelial dysfunction and hypertension using the Tg26 mouse model of HIV that expresses 7 of the 9 HIV proteins under the long terminal repeat promoter. We used male and female mice, bone marrow transplantation (BMT), adoptive transfer of CD4+ T cells, and aorta specimen discarded from people living with HIV.

RESULTS

We reported that intact Tg26 mice and mice receiving BMT (Tg26→WT) or CD4+ T cells from Tg26 mice display impaired endothelium-dependent relaxation and hypertension. Conversely, BMT from WT mice into Tg26 mice, inhibition of T cell activation, and CD4+ T cell depletion restored endothelial function and blood pressure in Tg26 mice. Cytokine profiling revealed that Tg26 mice, Tg26→WT, and Tg26 CD4+ T cells consistently exhibit high interleukin 1α (IL-1α) levels with no significant increase in other cytokines, whereas BMT from WT mice into Tg26 mice reduced IL-1α levels. IL-1α neutralization reduced blood pressure and restored endothelial function in Tg26 mice. To investigate the role of CD4+ T cells and IL-1α in endothelial dysfunction, we developed an aorta-immune cell coculture system. Exposure of WT aortas to Tg26 CD4+ T cells impaired endothelium-dependent relaxation, which was blocked by IL-1α-neutralizing antibody. While investigating the mechanisms of endothelial dysfunction, we reported that Tg26 mice, Tg26→WT aorta exhibit high NADPH oxidase (NOX) 1 expression. IL-1α exposure increased NOX1 in human microvascular endothelial cells, and NOX1 blockade restored endothelial function in Tg26 and Tg26→WT arteries, whereas NOX1 deficiency protected against Tg26 BMT-induced impaired endothelium-dependent relaxation and hypertension. Aortas from people living with HIV exhibit high NOX1 levels, and exposure of human aorta to Tg26 T cells increased NOX1 expression.

CONCLUSIONS

We provide the first evidence that CD4+ T cells expressing HIV viral proteins induced hypertension through IL-1α-mediated increases in vascular NOX1, which impairs endothelial function in males and females.

ATP dynamics as a predictor of future podocyte structure and function after acute ischemic kidney injury in female mice

Acute kidney injury (AKI), typically caused by ischemia, is a common clinical complication with a poor prognosis. Although proteinuria is an important prognostic indicator of AKI, the underlying causal mechanism remains unclear. In vitro studies suggest that podocytes have high ATP demands to maintain their structure and function, however, analyzing their ATP dynamics in living kidneys has been technically challenging. Here, using intravital imaging to visualize a FRET-based ATP biosensor expressed systemically in female mice due to their suitability for glomerular imaging, we monitor the in vivo ATP dynamics in podocytes during ischemia reperfusion injury. ATP levels decrease during ischemia, but recover after reperfusion in podocytes, exhibiting better recovery than in glomerular endothelial cells. However, prolonged ischemia results in insufficient ATP recovery in podocytes, which is inversely correlated with mitochondrial fragmentation and foot process effacement during the chronic phase. Furthermore, preventing mitochondrial fission via pharmacological inhibition ameliorates podocyte injury in vitro, ex vivo, and in vivo. Thus, these findings provide several insights into how ATP depletion and mitochondrial fragmentation contribute to podocyte injury after ischemic AKI and could potentially be therapeutic targets.

Podocyte-specific KLF6 primes proximal tubule CaMK1D signaling to attenuate diabetic kidney disease

Diabetic kidney disease (DKD) is the main cause of chronic kidney disease worldwide. While injury to the podocytes, visceral epithelial cells that comprise the glomerular filtration barrier, drives albuminuria, proximal tubule (PT) dysfunction is the critical mediator of DKD progression. Here, we report that the podocyte-specific induction of human KLF6, a zinc-finger binding transcription factor, attenuates podocyte loss, PT dysfunction, and eventual interstitial fibrosis in a male murine model of DKD. Utilizing combination of snRNA-seq, snATAC-seq, and tandem mass spectrometry, we demonstrate that podocyte-specific KLF6 triggers the release of secretory ApoJ to activate calcium/calmodulin dependent protein kinase 1D (CaMK1D) signaling in neighboring PT cells. CaMK1D is enriched in the first segment of the PT, proximal to the podocytes, and is critical to attenuating mitochondrial fission and restoring mitochondrial function under diabetic conditions. Targeting podocyte-PT signaling by enhancing ApoJ-CaMK1D might be a key therapeutic strategy in attenuating the progression of DKD.

Cardiac and Renal Comorbidities in Aging People Living With HIV

Contemporary World Health Organization data indicates that ≈39 million people are living with the human immunodeficiency virus. Of these, 24 million have been reported to have successfully accessed combination antiretroviral therapy. In 1996, the World Health Organization endorsed the widespread use of combination antiretroviral therapy, transforming human immunodeficiency virus infection from being a life-threatening disease to a chronic illness characterized by multiple comorbidities. The increased access to combination antiretroviral therapy has translated to people living with human immunodeficiency virus (PLWH) no longer having a reduced life expectancy. Although aging as a biological process increases exposure to oxidative stress and subsequent systemic inflammation, this effect is likely enhanced in PLWH as they age. This narrative review engages the intricate interplay between human immunodeficiency virus associated chronic inflammation, combination antiretroviral therapy, and cardiac and renal comorbidities development in aging PLWH. We examine the evolving demographic profile of PLWH, emphasizing the increasing prevalence of aging individuals within this population. A central focus of the review discusses the pathophysiological mechanisms that underpin the heightened susceptibility of PLWH to renal and cardiac diseases as they age.

The changing landscape of HIV-associated kidney disease

The HIV epidemic has devastated millions of people globally, with approximately 40 million deaths since its start. The availability of antiretroviral therapy (ART) has transformed the prognosis of millions of individuals infected with HIV such that a diagnosis of HIV infection no longer automatically confers death. However, morbidity and mortality remain substantial among people living with HIV. HIV can directly infect the kidney to cause HIV-associated nephropathy (HIVAN) - a disease characterized by podocyte and tubular damage and associated with an increased risk of kidney failure. The reports of HIVAN occurring primarily in those of African ancestry led to the discovery of its association with APOL1 risk alleles. The advent of ART has led to a substantial decrease in the prevalence of HIVAN; however, reports have emerged of an increase in the prevalence of other kidney pathology, such as focal segmental glomerulosclerosis and pathological conditions associated with co-morbidities of ageing, such as hypertension and diabetes mellitus. Early initiation of ART also results in a longer cumulative exposure to medications, increasing the likelihood of nephrotoxicity. A substantial body of literature supports the use of kidney transplantation in people living with HIV, demonstrating significant survival benefits compared with that of people undergoing chronic dialysis, and similar long-term allograft and patient survival compared with that of HIV-negative kidney transplant recipients.

Mediation analysis of chronic kidney disease risk factors using kidney biomarkers in women living with HIV

OBJECTIVE

Novel urinary biomarkers reflecting kidney tubule health are associated with chronic kidney disease (CKD) risk in persons living with HIV. However, it is unknown whether these biomarkers provide mechanistic insight into the associations between clinical risk factors for CKD and subsequent CKD risk.

METHODS

Among 636 women living with HIV in the Women's Interagency HIV Study with estimated glomerular filtration rate (eGFR) >60 ml/min/1.73 m 2 , we used a counterfactual approach to causal mediation analysis to evaluate the extent to which systolic blood pressure (SBP), diastolic blood pressure (DBP), hemoglobin a1c (Hba1c) and serum albumin associations with incident CKD were mediated by eight urine proteins. These biomarkers reflect proximal tubular reabsorptive dysfunction (α1-microglobulin [a1m], β2-microglobulin, trefoil factor 3); tubular injury (interleukin 18 [IL-18], kidney injury molecule 1 [KIM-1]); kidney repair (epidermal growth factor); tubular reserve (uromodulin); and glomerular injury (urinary albumin). Incident CKD was defined as eGFR <60 ml/min/1.73 m 2 measured at two consecutive 6-month visits with an average annual eGFR decline ≥3% per year.

RESULTS

During a median follow-up of 7 years, 11% developed CKD. Urinary albumin and KIM-1 mediated 32% (95% CI: 13.4%, 76.6%) and 23% (6.9%, 60.7%) of the association between SBP and incident CKD, respectively; and 19% (5.1%, 42.3%) and 22% (8.1%, 45.7%) of the association between DBP and incident CKD, respectively. Urinary albumin, α1m, and IL-18 were significant mediators of the association between Hba1c and incident CKD. None of the eight biomarkers mediated the association between serum albumin and incident CKD.

CONCLUSIONS

Among women living with HIV, several urinary biomarkers reflecting distinct dimensions of kidney health may partially explain the associations between SBP, DBP, and Hba1c and subsequent CKD risk.

Additive renal protective effects between arctigenin and puerarin in diabetic kidney disease

Recent studies have shown that the combined use of renin angiotensin system inhibitor, SGLT2 inhibitors and/or mineralocorticoid receptor antagonist provides additional renal protection for patients with diabetic kidney disease (DKD). Similarly, in traditional Chinese medicine, the synergistic application of multiple herbs often brings more significant therapeutic effects. However, the synergistic or additive mechanisms of traditional Chinese medicine in combination therapy are not fully understood. In our previous studies, we show that arctigenin (ATG), a major component of Fructus Arctii, attenuates proteinuria and renal injury in diabetic mice by activating PP2A, and puerarin (a class of known isoflavones) can also reduce proteinuria and renal injury in diabetic mice via activation of Sirt1. Here, we further explored the potential additive renal protection of these two compounds in diabetic mice. Research has found that ATG and puerarin have a synergistic effect in reducing albuminuria in db/db mice. Mechanistically, we found that ATG reduced NF-κB p65 phosphorylation likely through activation of PP2A while puerarin reduced p65 acetylation via Sirt1 activation. Therefore, ATG and puerarin have additive inhibitory effects on the NF-κB activation, which is a key inflammatory pathway in DKD. RNA-sequencing analysis revealed distinct pathways activated by ATG and puerarin in the diabetic kidney, which may provide an additional mechanism for their additive effects in DKD. Our study suggests that ATG and puerarin could be a new combination therapy for DKD and reveals its underlined mechanisms.

Advancing the preclinical study of comorbid neuroHIV and substance use disorders: Current perspectives and future directions

Human immunodeficiency virus (HIV) remains a persistent public health concern throughout the world. Substance use disorders (SUDs) are a common comorbidity that can worsen treatment outcomes for people living with HIV. The relationship between HIV infection and SUD outcomes is likely bidirectional, making clear interrogation of neurobehavioral outcomes challenging in clinical populations. Importantly, the mechanisms through which HIV and addictive drugs disrupt homeostatic immune and CNS function appear to be highly overlapping and synergistic within HIV-susceptible reward and motivation circuitry in the central nervous system. Decades of animal research have revealed invaluable insights into mechanisms underlying the pathophysiology SUDs and HIV, although translational studies examining comorbid SUDs and HIV are very limited due to the technical challenges of modeling HIV infection preclinically. In this review, we discuss preclinical animal models of HIV and highlight key pathophysiological characteristics of each model, with a particular emphasis on rodent models of HIV. We then review the implementation of these models in preclinical SUD research and identify key gaps in knowledge in the field. Finally, we discuss how cutting-edge behavioral neuroscience tools, which have revealed key insights into the neurobehavioral mechanisms of SUDs, can be applied to preclinical animal models of HIV to reveal potential, novel treatment avenues for comorbid HIV and SUDs. Here, we argue that future preclinical SUD research would benefit from incorporating comorbidities such as HIV into animal models and would facilitate the discovery of more refined, subpopulation-specific mechanisms and effective SUD prevention and treatment targets.

HIV-1 infection of renal epithelial cells: 30 years of evidence from transgenic animal models, human studies and in vitro experiments

Although antiretroviral therapy (ART) has increased life expectancy in people with HIV-1 (PWH), acute and chronic kidney disease remain common in this population and are associated with poor outcomes. A broad spectrum of kidney disorders can be observed in PWH, some of which are directly related to intrarenal HIV infection and gene expression. HIV-associated nephropathy (HIVAN) was the most common kidney disease in PWH before ART became available. Animal models and human biopsy studies established the causal relationships between direct HIV-1 infection of renal epithelial cells and HIVAN, expression of viral genes in renal epithelial cells, and dysregulation of host genes involved in cell differentiation and cell cycle. In this review, we provide a summary of the body of work demonstrating HIV-1 infection of epithelial cells in the kidney and recent advancements in the understanding of viral entry mechanisms and consequences of HIV-1 gene expression in those cells.

Viral Glomerulopathy

Background

The association between viral infections and glomerular diseases, commonly known as "viral glomerulopathies," has been described in various clinical scenarios for decades. Despite advancements in diagnostic tools, it remains challenging to establish a causative link fully.

Summary

Data from mouse models have substantiated clinical observations and implicate direct viral infection in the pathogenesis of viral glomerulopathy, particularly in human immunodeficiency virus-associated nephropathy. In addition to the traditional concept of direct viral effects on kidneys, other factors such as APOL1 risk alleles can further modify the clinical outcomes or presentations of different viral glomerulopathies. Newly developed antiviral drugs are now applicable to a wider range of patients with lower kidney function and fewer side effects.

Key Message

Efforts focusing on vaccines and antiviral treatments have significantly reduced the incidence of viral glomerulopathies. However, the most recent pandemic caused by severe acute respiratory syndrome coronavirus 2 infection complicated by COVID-associated nephropathy illustrates our susceptibility to novel viruses. Ongoing research is pivotal to deciphering the mechanisms behind viral glomerulopathies and discovering therapeutics in a collaborative approach.

HIV at 40: kidney disease in HIV treatment, prevention, and cure

Four decades after the first cases of HIV were reported, kidney disease remains an important comorbidity in people with HIV (PWH). Both HIV-associated nephropathy and immune complex kidney disease were recognized as complications of HIV infection in the early years before treatment was available. Although the introduction of effective antiretroviral therapy in the late 1990s resulted in dramatic improvements in survival and health in PWH, several commonly used antiretroviral agents have been associated with kidney injury. HIV infection and treatment may also promote the progression of comorbid chronic kidney disease due to traditional risk factors such as diabetes, and HIV is one of the strongest "second hits" for the high-risk APOL1 genotype. Unique considerations in the management of chronic kidney disease in PWH are largely related to the need for lifelong antiretroviral therapy, with potential for toxicity, drug-drug interactions, and polypharmacy. PWH who develop progressive chronic kidney disease are candidates for all modalities of kidney replacement therapy, including kidney transplantation, and at some centers, PWH may be candidates to serve as donors for recipients with HIV. Transplantation of kidney allografts from donors with HIV also offers a unique opportunity to study viral dynamics in the kidney, with implications for kidney health and for research toward HIV cure. In addition, HIV-transgenic animal models have provided important insights into kidney disease pathogenesis beyond HIV, and experience with HIV and HIV-related kidney disease has provided important lessons for future pandemics.

Inhibition of the lncRNA MIAT prevents podocyte injury and mitotic catastrophe in diabetic nephropathy

Podocyte damage is strongly associated with the progression of diabetic nephropathy. Mitotic catastrophe plays an essential role in accelerating podocyte loss and detachment from the glomerular basement membrane. In the current study, we observed that the long non-coding RNA (lncRNA) MIAT was noticeably upregulated in the plasma and kidney tissues of patients with diabetic nephropathy, and this upregulation was accompanied by higher albumin/creatinine ratios and serum creatinine levels. By generating CRISPR-Cas9 Miat-knockout (KO) mice in vivo and employing vectors in vitro, we found that the depletion of Miat expression significantly restored slit-diaphragm integrity, attenuated foot process effacement, prevented dedifferentiation, and suppressed mitotic catastrophe in podocytes during hyperglycemia. The mechanistic investigation revealed that Miat increased Sox4 expression and subsequently regulated p53 ubiquitination and acetylation, thereby inhibiting the downstream factors CyclinB/cdc2 by enhancing p21^cip1/waf1 activity, and that Miat interacted with Sox4 by sponging miR-130b-3p. Additionally, the inhibition of miR-130b-3p with an antagomir in vivo effectively enhanced glomerular podocyte injury and mitotic dysfunction, eventually exacerbating proteinuria. Based on these findings, MIAT may represent a therapeutic target for diabetic nephropathy.

Mechanisms of Proteinuria in HIV

Proteinuria is common in the setting of HIV infection, and may reflect comorbid kidney disease, treatment-related nephrotoxicity, and HIV-related glomerular diseases. The mechanisms of podocyte and tubulointerstial injury in HIV-associated nephropathy (HIVAN) have been the subject of intense investigation over the past four decades. The pathologic contributions of viral gene expression, dysregulated innate immune signaling, and ancestry-driven genetic risk modifiers have been explored in sophisticated cellular and whole animal models of disease. These studies provide evidence that injury-induced podocyte dedifferentiation, hyperplasia, cytoskeletal dysregulation, and apoptosis may cause the loss of glomerular filtration barrier integrity and slit diaphragm performance that facilitates proteinuria and tuft collapse in HIVAN. Although the incidence of HIVAN has declined with the introduction of antiretroviral therapy, the collapsing FSGS lesion has been observed in the context of other viral infections and chronic autoimmune disorders, and with the use of interferon-based therapies in genetically susceptible populations. This highlights the fact that the lesion is not specific to HIVAN and that the role of the immune system in aggravating podocyte injury warrants further exploration. This review will summarize our progress in characterizing the molecular mechanisms of podocyte dysfunction in HIVAN and other forms of HIV-associated kidney disease.

Transforming growth factor β3 deficiency promotes defective lipid metabolism and fibrosis in murine kidney

Glomerulosclerosis and tubulointerstitial fibrosis are pathological features of chronic kidney disease. Transforming growth factor β (TGFβ) is a key player in the development of fibrosis. However, of the three known TGFβ isoforms, only TGFβ1 has an established role in fibrosis, and the pathophysiological relevance of TGFβ2 and TGFβ3 is unknown. Because Tgfb3 deficiency in mice results in early postnatal lethality, we analyzed the kidney phenotype of heterozygous Tgfb3-knockout mice (Tgfb3^+/−) and compared it with that of matched wild-type mice. Four-month-old Tgfb3^+/− mice exhibited incipient renal fibrosis with epithelial–mesenchymal transition, in addition to glomerular basement membrane thickening and podocyte foot process effacement associated with albuminuria. Also evident was insulin resistance and oxidative stress at the renal level, together with aberrant renal lipid metabolism and mitochondrial function. Omics analysis revealed toxic species, such as diacylglycerides and ceramides, and dysregulated mitochondrial metabolism in Tgfb3^+/− mice. Kidneys of Tgfb3^+/− mice showed morphological alterations of mitochondria and overactivation of non-canonical MAPK ERK1/2 and JNK cascades. Our study indicates that renal TGFβ3 might have antifibrotic and renoprotective properties, opposing or counteracting the activity of TGFβ1.

This article has an associated First Person interview with the first author of the paper.

Summary: Our study describes the renal abnormalities of heterozygous Tgfb3-targeted mice and suggests that TGFβ3 is renoprotective and may counteract the activity of TGFβ1.

Inflammation and kidney involvement in human viral diseases caused by SARS-CoV-2, HIV, HCV and HBV

Inflammation is closely related to renal diseases. This is particularly true for renal diseases caused by infections as in viral diseases. In this review, we highlight the inflammatory mechanisms that underlie kidney dysfunction in SARS-CoV-2, human immunodeficiency (HIV), hepatitis C (HCV), and hepatitis B (HBV) infections. The pathophysiology of renal involvement in COVID-19 is complex, but kidney damage is frequent, and the prognosis is worse when it happens. Virus-like particles were demonstrated mostly in renal tubular epithelial cells and podocytes, which suggest that SARS-CoV-2 directly affects the kidneys. SARS-CoV-2 uses the angiotensin-converting enzyme 2 receptor, which is found in endothelial cells, to infect the human host cells. Critical patients with SARS-CoV-2-associated acute kidney injury (AKI) show an increase in inflammatory cytokines (IL-1β, IL-8, IFN-γ, TNF-α), known as cytokine storm that favors renal dysfunction by causing intrarenal inflammation, increased vascular permeability, volume depletion, thromboembolic events in microvasculature and persistent local inflammation. Besides AKI, SARS-CoV-2 can also cause glomerular disease, as other viral infections such as in HIV, HBV and HCV. HIV-infected patients present chronic inflammation that can lead to a number of renal diseases. Proinflammatory cytokines and TNF-induced apoptosis are some of the underlying mechanisms that may explain the virus-induced renal diseases that are here reviewed.

Low expression of HIV genes in podocytes accelerates the progression of diabetic kidney disease in mice

With the widespread use combination antiretroviral therapy, there has been a dramatic decrease in HIV-associated nephropathy. However, although the patients living with HIV have low or undetectable viral load, the prevalence of chronic kidney disease (CKD) in this population remains high. Additionally, improved survival is associated with aging-related comorbidities such as diabetes and cardiovascular disease. A faster progression of CKD is associated with concurrent HIV infection and diabetes than with HIV infection or diabetes alone. To explore the potential pathogenic mechanisms that synergistically drive CKD progression by diabetes and HIV infection, we generated a new mouse model with a relatively low expression of HIV-1 proviral genes specifically in podocytes (pod-HIV mice) to better mimic the setting of kidney injury in patients living with HIV. While no apparent kidney phenotypes were observed at baseline in pod-HIV mice, the induction of mild diabetic kidney disease with streptozotocin led to significant worsening of albuminuria, glomerular injury, podocyte loss, and kidney dysfunction as compared to the mice with diabetes alone. Mechanistically, diabetes and HIV-1 synergistically increased the glomerular expression of microRNA-34a (miR-34a), thereby reducing the expression of Sirtuin-1 (SIRT1) deacetylase. These changes were also associated with increased acetylation and activation of p53 and p65 NF-κB and with enhanced expression of senescence and inflammatory markers. The treatment of diabetic pod-HIV mice with the specific Sirtuin-1 agonist BF175 significantly attenuated albuminuria and glomerulopathy. Thus, our study highlights the reduction in Sirtuin-1 as a major basis of CKD progression in diabetic patients living with HIV and suggests Sirtuin-1 agonists as a potential therapy.

Role of SIRT1 in HIV-associated kidney disease

Human immunodeficiency virus (HIV) infection of kidney cells can lead to HIV-associated nephropathy (HIVAN) and aggravate the progression of other chronic kidney diseases. Thus, a better understanding of the mechanisms of HIV-induced kidney cell injury is needed for effective therapy against HIV-induced kidney disease progression. We have previously shown that the acetylation and activation of key inflammatory regulators, NF-κB p65 and STAT3, were increased in HIVAN kidneys. Here, we demonstrate the key role of sirtuin 1 (SIRT1) deacetylase in the regulation of NF-κB and STAT3 activity in HIVAN. We found that SIRT1 expression was reduced in the glomeruli of human and mouse HIVAN kidneys and that HIV-1 gene expression was associated with reduced SIRT1 expression and increased acetylation of NF-κB p65 and STAT3 in cultured podocytes. Interestingly, SIRT1 overexpression, in turn, reduced the expression of negative regulatory factor in podocytes stably expressing HIV-1 proviral genes, which was associated with inactivation of NF-κB p65 and a reduction in HIV-1 long terminal repeat promoter activity. In vivo, the administration of the small-molecule SIRT1 agonist BF175 or inducible overexpression of SIRT1 specifically in podocytes markedly attenuated albuminuria, kidney lesions, and expression of inflammatory markers in Tg26 mice. Finally, we showed that the reduction in SIRT1 expression by HIV-1 is in part mediated through miR-34a expression. Together, our data provide a new mechanism of SIRT1 regulation and its downstream effects in HIV-1-infected kidney cells and indicate that SIRT1/miR-34a are potential drug targets to treat HIV-related kidney disease.

An Evaluation of Baseline Kidney Function in the REPRIEVE Trial of Pitavastatin in Human Immunodeficiency Virus

BACKGROUND

Chronic kidney disease is a common comorbid condition among persons living with human immunodeficiency virus (PWH). We characterized baseline kidney function in the REPRIEVE (Randomized Trial to Prevent Vascular Events in HIV) trial cohort.

METHODS

REPRIEVE enrolled PWH with low to moderate cardiovascular risk based on traditional risk factors to evaluate the effect of statin therapy on cardiovascular events. We determined baseline estimated glomerular filtration rate (eGFR) with the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Modification of Diet in Renal Disease, and Cockcroft-Gault equations, and we evaluated baseline factors associated with eGFR <90 mL/min/1.73 m2 by logistic regression. We performed Bland-Altman plots and scatterplots to assess agreement between equations.

RESULTS

Among 7770 participants enrolled, the median age was 50 years, 31% were female (natal sex), 43% black or African American and 15% Asian, the median body mass index (calculated as calculated as weight in kilograms divided by height in meters squared) was 25.8, and the median CD4 cell count 620/µL. The median CKD-EPI eGFR was 97 mL/min/1.73 m2, and 38% had an eGFR <90 mL/min/1.73 m2. In the adjusted model, factors associated with eGFR <90 mL/min/1.73 m2 included white race, older age, higher body mass index, high-income region of enrollment, hypertension, and tenofovir disoproxil fumarate. The CKD-EPI and Modification of Diet in Renal Disease equations demonstrated strong agreement, particularly at lower eGFR values. Overall, there was 56% concordance between the 3 equations (categories <60, 60 to <90, ≥90 mL/min), improving to 73% after accounting for individual body surface area.

CONCLUSIONS

REPRIEVE enrolled a diverse cohort including a substantial number of PWH with reduced kidney function. Factors associated with reduced eGFR included traditional risk factors and tenofovir disoproxil fumarate exposure. Three commonly used equations have only fair agreement, with potential implications for both clinical care and epidemiologic studies.

CLINICAL TRIALS REGISTRATION

NCT02344290.

Contemporary issues and new challenges in chronic kidney disease amongst people living with HIV

Chronic kidney disease (CKD) is a comorbidity of major clinical significance amongst people living with HIV (PLWHIV) and is associated with significant morbidity and mortality. The prevalence of CKD is rising, despite the widespread use of antiretroviral therapy (ART) and is increasingly related to prevalent non-infectious comorbidities (NICMs) and antiretroviral toxicity. There are great disparities evident, with the highest prevalence of CKD among PLWHIV seen in the African continent. The aetiology of kidney disease amongst PLWHIV includes HIV-related diseases, such as classic HIV-associated nephropathy or immune complex disease, CKD related to NICMs and CKD from antiretroviral toxicity. CKD, once established, is often relentlessly progressive and can lead to end-stage renal disease (ESRD). Identifying patients with risk factors for CKD, and appropriate screening for the early detection of CKD are vital to improve patient outcomes. Adherence to screening guidelines is variable, and often poor. The progression of CKD may be slowed with certain clinical interventions; however, data derived from studies involving PLWHIV with CKD are sparse and this represent an important area for future research. The control of blood pressure using angiotensin converting enzyme inhibitors and angiotensin receptor blockers, in particular, in the setting of proteinuria, likely slows the progression of CKD among PLWHIV. The cohort of PLWHIV is facing new challenges in regards to polypharmacy, drug-drug interactions and adverse drug reactions. The potential nephrotoxicity of ART is important, particularly as cumulative ART exposure increases as the cohort of PLWHIV ages. The number of PLWHIV with ESRD is increasing. PLWHIV should not be denied access to renal replacement therapy, either dialysis or kidney transplantation, based on their HIV status. Kidney transplantation amongst PLWHIV is successful and associated with an improved prognosis compared to remaining on dialysis. As the cohort of PLWHIV ages, comorbidity increases and CKD becomes more prevalent; models of care need to evolve to meet the new and changing chronic healthcare needs of these patients.

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.

Kidney Disease in HIV Infection

Antiretroviral therapy (ART) has significantly improved life expectancy of infected subjects, generating a new epidemiological setting of people aging withHuman Immunodeficiency Virus (HIV). People living with HIV (PLWH), having longer life expectancy, now face several age-related conditions as well as side effects of long-term exposure of ART. Chronic kidney disease (CKD) is a common comorbidity in this population. CKD is a relentlessly progressive disease that may evolve toward end-stage renal disease (ESRD) and significantly affect quality of life and risk of death. Herein, we review current understanding of renal involvement in PLWH, mechanisms and risk factors for CKD as well as strategies for early recognition of renal dysfunction and best care of CKD.

Elevated indoleamine-2,3-dioxygenase enzyme activity in a novel mouse model of HIV-associated atherosclerosis

OBJECTIVE

HIV atherosclerosis and cardiovascular disease (CVD) represent a significant human health burden in the era of combination antiretroviral therapy (cART). The pathogenesis of HIV atherosclerosis is still poorly understood, due, in part, to the lack of a suitable small animal model. Indoleamine-2,3-dioxygenase (IDO) enzyme activity is the first and rate-limiting step in tryptophan catabolism and is measured by the kynurenine to tryptophan ratio (KTR). The serum KTR is a biomarker of inflammation and has recently been implicated as an important risk factor for CVD in patients living with HIV (PLWH) who are virologically suppressed under cART. However, IDO activity in HIV-associated CVD has not been studied in mouse model before.

DESIGN

A novel mouse model of HIV atherosclerosis (Tg26/ApoE) was generated and examined for IDO activity and atherogenesis throughout 8 weeks on a high-fat diet. Tg26/ApoE mice were compared with Tg26 and ApoE single transgenic mice, before and during a high-fat diet.

METHOD

Serum kynurenine, tryptophan and percentage of aortic plaque formation were measured. Additionally, levels of relevant cytokines were investigated in Tg26/ApoE and ApoE.

RESULTS

Tg26/ApoE developed an accelerated atherosclerosis with increasing levels of KTR that were associated with plaque progression. This accelerated plaque was potentially driven by elevated levels of circulating IL-6.

CONCLUSION

These results indicate that Tg26/ApoE serve as a new mouse model for HIV-induced atherogenesis, and aid in understanding the role of tryptophan catabolism in the pathogenesis of HIV atherosclerosis/CVD.

Sex-specific neurogenic deficits and neurocognitive disorders in middle-aged HIV-1 Tg26 transgenic mice

Varying degrees of cognitive deficits affect over half of all HIV-1 infected patients. Because of antiretroviral treatment (ART) regimens, the HIV-1 patient population is increasing in age. Very few epidemiological studies have focused on sex-specific differences in HIV-1-associated neurocognitive disorders (HAND). The purpose of this study is to examine any possible differences between male and female mice in the progression of cognitive dementia during persistent low-level HIV-1 protein exposure, mimicking the typical clinical setting in the post-ART era. Eight to ten-month old HIV-1 Tg26(+/-) transgenic mice were utilized to assess for specific learning and memory modalities. Initial physiological screening and fear conditioning assessments revealed that Tg26 mice exhibited no significant differences in general behavioral function, contextual fear conditioning, or cued fear conditioning responses when compared to their wild-type (WT) littermates, regardless of sex. However, Barnes maze testing revealed significantly impaired short and long-term spatial memory in males, while females had impaired spatial learning abilities and short-term spatial memory. The potential cellular mechanism underlying these sex-specific neurocognitive deficits was explored with hippocampal neurogenic analysis. Compared to WT mice, both male and female Tg26(+/-) mice had fewer quiescent neural stem cells and neuroblasts in their hippocampi. Male Tg26(+/-) mice had a more robust reduction of the quiescent neural stem cell pool than female Tg26(+/-) mice. While female WT mice had a higher number of neural progenitor cells than male WT mice, only female Tg26(+/-) mice exhibited a robust reduction in the number of neural progenitor cells. Altogether, these results suggest that middle-aged male and female Tg26(+/-) mice manifest differing impairments in cognitive functioning and hippocampal neurogenesis. This study emphasizes the importance of understanding sex related differences in HAND pathology, which would aid in designing more optimized therapeutic regimens for the treatment of HAND.

Changing concepts of HIV infection and renal disease

PURPOSE OF REVIEW

Human immunodeficiency virus (HIV)-associated nephropathy (HIVAN) was identified as the major renal manifestation of HIV infection early in the HIV epidemic. However, HIV infection now is associated with a different spectrum of renal lesions leading to chronic kidney disease. This review examines the changes in kidney injury occurring in the current HIV era and the factors involved in this transformation of disease expression.

RECENT FINDINGS

The incidence of HIVAN and opportunistic infections in HIV-infected individuals has declined in concert with the use of effective combination antiretroviral agents. Chronic kidney disease has become more prevalent as patients infected with HIV are living longer and developing non-HIV-associated diseases such as hypertension and diabetes. Additionally, noncollapsing focal and segmental glomerulosclerosis, co-infection with hepatitis C, HIV-associated immune complex kidney disease, HIV-related accelerated aging, and antiretroviral therapies contribute to progressive loss of renal function.

SUMMARY

HIV infection is now associated with a variety of renal lesions causing chronic kidney disease, not all of which are virally induced. It is important to determine the cause of renal functional decline in an HIV-infected patient, as this will impact patient management and prognosis.

Podocyte-Specific Loss of Krüppel-Like Factor 6 Increases Mitochondrial Injury in Diabetic Kidney Disease

Mitochondrial injury is uniformly observed in several murine models as well as in individuals with diabetic kidney disease (DKD). Although emerging evidence has highlighted the role of key transcriptional regulators in mitochondrial biogenesis, little is known about the regulation of mitochondrial cytochrome c oxidase assembly in the podocyte under diabetic conditions. We recently reported a critical role of the zinc finger Krüppel-like factor 6 (KLF6) in maintaining mitochondrial function and preventing apoptosis in a proteinuric murine model. In this study, we report that podocyte-specific knockdown of Klf6 increased the susceptibility to streptozotocin-induced DKD in the resistant C57BL/6 mouse strain. We observed that the loss of KLF6 in podocytes reduced the expression of synthesis of cytochrome c oxidase 2 with resultant increased mitochondrial injury, leading to activation of the intrinsic apoptotic pathway under diabetic conditions. Conversely, mitochondrial injury and apoptosis were significantly attenuated with overexpression of KLF6 in cultured human podocytes under hyperglycemic conditions. Finally, we observed a significant reduction in glomerular and podocyte-specific expression of KLF6 in human kidney biopsies with progression of DKD. Collectively, these data suggest that podocyte-specific KLF6 is critical to preventing mitochondrial injury and apoptosis under diabetic conditions.

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.

Adult neurogenic deficits in HIV-1 Tg26 transgenic mice

Background

Even in the antiretroviral treatment (ART) era, HIV-1-infected patients suffer from milder forms of HIV-1-associated neurocognitive disorders (HAND). While the viral proteins Tat and gp120 have been shown to individually inhibit the proliferation and neural differentiation of neural stem cells (NSCs), no studies have characterized the effects of all the combined viral proteins on adult neurogenesis.

Methods

The HIV-1 Tg26 transgenic mouse model was used due to its clinical relevance to ART-controlled HIV-1-infected patients who lack active viral replication but suffer from continuous stress from the viral proteins. Quantitative RT-PCR analysis was performed to validate the expression of viral genes in the neurogenic zones. In vitro stemness and lineage differentiation assays were performed in cultured NSCs from HIV-1 Tg26 transgenic mice and their wild-type littermates. Hippocampal neurogenic lineage analysis was performed to determine potential changes in initial and late differentiation of NSCs in the subgranular zone (SGZ). Finally, fluorescent retroviral labeling of mature dentate granule neurons was performed to assess dendritic complexity and dendritic spine densities.

Results

Varying copy numbers of partial gag (p17), tat (unspliced and spliced variants), env (gp120), vpu, and nef transcripts were detected in the neurogenic zones of Tg26 mice. Significantly fewer primary neurospheres and a higher percentage of larger sized primary neurospheres were generated from Tg26 NSCs than from littermated wild-type mouse NSCs, implying that Tg26 mouse NSCs exhibit deficits in initial differentiation. In vitro differentiation assays revealed that Tg26 mouse NSCs have reduced neuronal differentiation and increased astrocytic differentiation. In the SGZs of Tg26 mice, significantly higher amounts of quiescent NSCs, as well as significantly lower levels of active NSCs, proliferating neural progenitor cells, and neuroblasts, were observed. Finally, newborn mature granule neurons in the dentate gyri of Tg26 mice had deficiencies in dendritic arborization, dendritic length, and dendritic spine density.

Conclusions

Both in vitro and in vivo studies demonstrate that HIV-1 Tg26 mice have early- and late-stage neurogenesis deficits, which could possibly contribute to the progression of HAND. Future therapies should be targeting this process to ameliorate, if not eliminate HAND-like symptoms in HIV-1-infected patients.

Podocyte-Specific Induction of Krüppel-Like Factor 15 Restores Differentiation Markers and Attenuates Kidney Injury in Proteinuric Kidney Disease

BACKGROUND

Podocyte injury is the hallmark of proteinuric kidney diseases, such as FSGS and minimal change disease, and destabilization of the podocyte's actin cytoskeleton contributes to podocyte dysfunction in many of these conditions. Although agents, such as glucocorticoids and cyclosporin, stabilize the actin cytoskeleton, systemic toxicity hinders chronic use. We previously showed that loss of the kidney-enriched zinc finger transcription factor Krüppel-like factor 15 (KLF15) increases susceptibility to proteinuric kidney disease and attenuates the salutary effects of retinoic acid and glucocorticoids in the podocyte.

METHODS

We induced podocyte-specific KLF15 in two proteinuric murine models, HIV-1 transgenic (Tg26) mice and adriamycin (ADR)-induced nephropathy, and used RNA sequencing of isolated glomeruli and subsequent enrichment analysis to investigate pathways mediated by podocyte-specific KLF15 in Tg26 mice. We also explored in cultured human podocytes the potential mediating role of Wilms Tumor 1 (WT1), a transcription factor critical for podocyte differentiation.

RESULTS

In Tg26 mice, inducing podocyte-specific KLF15 attenuated podocyte injury, glomerulosclerosis, tubulointerstitial fibrosis, and inflammation, while improving renal function and overall survival; it also attenuated podocyte injury in ADR-treated mice. Enrichment analysis of RNA sequencing from the Tg26 mouse model shows that KLF15 induction activates pathways involved in stabilization of actin cytoskeleton, focal adhesion, and podocyte differentiation. Transcription factor enrichment analysis, with further experimental validation, suggests that KLF15 activity is in part mediated by WT1.

CONCLUSIONS

Inducing podocyte-specific KLF15 attenuates kidney injury by directly and indirectly upregulating genes critical for podocyte differentiation, suggesting that KLF15 induction might be a potential strategy for treating proteinuric kidney disease.

Cellular and molecular mechanisms of kidney fibrosis

Renal fibrosis is the final pathological process common to any ongoing, chronic kidney injury or maladaptive repair. It is considered as the underlying pathological process of chronic kidney disease (CKD), which affects more than 10% of world population and for which treatment options are limited. Renal fibrosis is defined by excessive deposition of extracellular matrix, which disrupts and replaces the functional parenchyma that leads to organ failure. Kidney's histological structure can be divided into three main compartments, all of which can be affected by fibrosis, specifically termed glomerulosclerosis in glomeruli, interstitial fibrosis in tubulointerstitium and arteriosclerosis and perivascular fibrosis in vasculature. In this review, we summarized the different appearance, cellular origin and major emerging processes and mediators of fibrosis in each compartment. We also depicted and discussed the challenges in translation of anti-fibrotic treatment to clinical practice and discuss possible solutions and future directions.

Increased podocyte Sirtuin-1 function attenuates diabetic kidney injury

Podocyte injury and loss contribute to the progression of glomerular diseases, including diabetic kidney disease. We previously found that the glomerular expression of Sirtuin-1 (SIRT1) is reduced in human diabetic glomeruli and that the podocyte-specific loss of SIRT1 aggravated albuminuria and worsened kidney disease progression in diabetic mice. SIRT1 encodes an NAD-dependent deacetylase that modifies the activity of key transcriptional regulators affected in diabetic kidneys, including NF-κB, STAT3, p53, FOXO4, and PGC1-α. However, whether the increased glomerular SIRT1 activity is sufficient to ameliorate the pathogenesis of diabetic kidney disease has not been explored. We addressed this by inducible podocyte-specific SIRT1 overexpression in diabetic OVE26 mice. The induction of SIRT1 overexpression in podocytes for six weeks in OVE26 mice with established albuminuria attenuated the progression of diabetic glomerulopathy. To further validate the therapeutic potential of increased SIRT1 activity against diabetic kidney disease, we developed a new, potent and selective SIRT1 agonist, BF175. In cultured podocytes BF175 increased SIRT1-mediated activation of PGC1-α and protected against high glucose-mediated mitochondrial injury. In vivo, administration of BF175 for six weeks in OVE26 mice resulted in a marked reduction in albuminuria and in glomerular injury in a manner similar to podocyte-specific SIRT1 overexpression. Both podocyte-specific SIRT1 overexpression and BT175 treatment attenuated diabetes-induced podocyte loss and reduced oxidative stress in glomeruli of OVE26 mice. Thus, increased SIRT1 activity protects against diabetes-induced podocyte injury and effectively mitigates the progression of diabetic kidney disease.

SIRT3-KLF15 signaling ameliorates kidney injury induced by hypertension

Renal fibrosis participates in the progression of hypertension-induced kidney injury. The effect of SIRT3, a member of the NAD⁺-dependent deacetylase family, in hypertensive nephropathy remains unclear. In this study, we found that SIRT3 was reduced after angiotensin II (AngII) treatment both in vivo and in vitro. Furthermore, SIRT3-knockout mice aggravated hypertension-induced renal dysfunction and renal fibrosis via chronic AngII infusion (2000 ng/kg per minute for 42 days). On the contrary, SIRT3-overexpression mice attenuated AngII-induced kidney injury compared with wild-type mice. Remarkably, a co-localization of SIRT3 and KLF15, a kidney-enriched nuclear transcription factor, led to SIRT3 directly deacetylating KLF15, followed by decreased expression of fibronectin and collagen type IV in cultured MPC-5 podocytes. In addition, honokiol (HKL), a major bioactive compound isolated from Magnolia officinalis (Houpo), suppressed AngII-induced renal fibrosis through activating SIRT3-KLF15 signaling. Taken together, our findings implicate that a novel SIRT3-KLF15 signaling may prevent kidney injury from hypertension and HKL can act as a SIRT3-KLF15 signaling activator to protect against hypertensive nephropathy.

The loss of Krüppel-like factor 15 in Foxd1+ stromal cells exacerbates kidney fibrosis

Large epidemiological studies clearly demonstrate that multiple episodes of acute kidney injury contribute to the development and progression of kidney fibrosis. Although our understanding of kidney fibrosis has improved in the past two decades, we have limited therapeutic strategies to halt its progression. Myofibroblast differentiation and proliferation remain critical to the progression of kidney fibrosis. Although canonical Wnt signaling can trigger the activation of myofibroblasts in the kidney, mediators of Wnt inhibition in the resident progenitor cells are unclear. Recent studies demonstrate that the loss of a Krüppel-like factor 15 (KLF15), a kidney-enriched zinc-finger transcription factor, exacerbates kidney fibrosis in murine models. Here, we tested whether Klf15 mRNA and protein expression are reduced in late stages of fibrosis in mice that underwent unilateral ureteric obstruction, a model of progressive renal fibrosis. Knockdown of Klf15 in Foxd1-expressing cells (Foxd1-Cre Klf15fl/fl) increased extracellular matrix deposition and myofibroblast proliferation as compared to wildtype (Foxd1-Cre Klf15+/+) mice after three and seven days of ureteral obstruction. This was validated in mice receiving angiotensin II treatment for six weeks. In both these murine models, the increase in renal fibrosis was found in Foxd1-Cre Klf15fl/fl mice and accompanied by the activation of Wnt/β-catenin signaling. Furthermore, knockdown of Klf15 in cultured mouse embryonic fibroblasts activated canonical Wnt/β-catenin signaling, increased profibrotic transcripts, and increased proliferation after treatment with a Wnt1 ligand. Conversely, the overexpression of KLF15 inhibited phospho-β-catenin (Ser552) expression in Wnt1-treated cells. Thus, KLF15 has a critical role in attenuating kidney fibrosis by inhibiting the canonical Wnt/β-catenin pathway.

HIV-1-Associated Atherosclerosis: Unraveling the Missing Link

Cardiovascular disease, including atherosclerosis and atherosclerosis-associated complications, is an increasing cause of morbidity and mortality in human immunodeficiency virus (HIV) patients in the post-antiretroviral therapy era. HIV alone accelerates atherosclerosis. Antiretroviral therapy; HIV-associated comorbidities, such as dyslipidemia, drug abuse, and opportunistic infections; and lifestyle are risk factors for HIV-associated atherosclerosis. However, our current understanding of HIV-associated atherogenesis is very limited and has largely been obtained from clinical observation. There is a pressing need to experimentally unravel the missing link between HIV and atherosclerosis. Understanding these mechanisms will help to better develop and design novel therapeutic interventions for the treatment of HIV-associated cardiovascular disease. HIV mainly infects T cells and macrophages resulting in the induction of oxidative and endoplasmic reticulum stress, the formation of the inflammasome, and the dysregulation of autophagy. These mechanisms may contribute to HIV-associated atherogenesis. In this review, we will summarize our current understanding and propose potential mechanisms of HIV-associated atherosclerosis.

Rtn1a-Mediated Endoplasmic Reticulum Stress in Podocyte Injury and Diabetic Nephropathy

We previously reported a critical role of reticulon (RTN) 1A in mediating endoplasmic reticulum (ER) stress in kidney tubular cells and the expression of RTN1A correlates with the renal function and the severity of kidney injury in patients with diabetic nephropathy (DN). Here, we determined the roles of RTN1A and ER stress in podocyte injury and DN. We used db/db mice with early unilateral nephrectomy (Unx) as a murine model of progressive DN and treated mice with tauroursodeoxycholic acid (TUDCA), a specific inhibitor of ER stress. We found increased expression of RTN1A and ER stress markers in the kidney of db/db-Unx mice. Treatment of TUDCA not only attenuated proteinuria and kidney histological changes, but also ameliorated podocyte and glomeruli injury in diabetic mice, which were associated with reduction of RTN1A and ER stress marker expression in the podocytes of TUDCA-treated mice. In vitro, we showed RTN1A mediates albumin-induced ER stress and apoptosis in human podocytes. A positive feedback loop between RTN1A and CHOP was found leading to an enhanced ER stress in podocytes. Our data suggest that ER stress plays a major role in podocyte injury in DN and RTN1A might be a key regulator of ER stress in podocytes.

Kidney Disease and HIV Infection

The risk of acute and chronic kidney disease remains higher in HIV-infected persons than in the general population, and kidney disease in HIV-infected persons is associated with poor outcomes, including increased mortality. HIV-associated nephropathy occurs less frequently in the era of antiretroviral therapy. HIV immune complex kidney disease is being diagnosed more frequently, but the term is currently used to refer to a heterogeneous group of kidney diseases. Comorbid chronic kidney disease poses a growing burden in HIV-infected persons due to an overrepresentation of risk factors such as black race, diabetes, hypertension, and coinfection with hepatitis C virus. Drug-induced kidney toxicity also remains a concern. This article summarizes a presentation by Christina M. Wyatt, MD, at the Ryan White HIV/AIDS Program Clinical Care Conference held in New Orleans, Louisiana, in December 2015.

Greater efficacy of atorvastatin versus a non-statin lipid-lowering agent against renal injury: potential role as a histone deacetylase inhibitor

Statins, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors have been shown to improve diabetic nephropathy. However, whether they provide protection via Histone deacetylases (HDAC) inhibition is not clear. We conducted a comparative evaluation of Atorvastatin (AT) versus the non-statin cholesterol-lowering drug, Ezetimibe (EZT) on severity of diabetic nephropathy. Streptozotocin-treated male Wistar rats were fed a cholesterol-supplemented diet and gavaged daily with vehicle, AT or EZT. Control rats received normal diet and gavaged vehicle (n = 8-9/group). Diabetes increased blood glucose, urine albumin-to-creatinine ratio (ACR), kidney pathology and HDAC activity, and reduced renal E-cadherin levels. Both AT and EZT reduced circulating cholesterol, attenuated renal pathology, and did not lower blood glucose. However, AT was significantly more effective than EZT at reducing kidney pathology and HDAC activity. Chromatin immunoprecipitation revealed a significantly higher association of acetylated H3 and H4 with the E-cadherin promoter in kidneys from AT-, relative to EZT- or vehicle-treated rats. Moreover, we demonstrated a direct effect of AT, but not EZT, on HDAC-inhibition and, H3 and H4- acetylation in primary glomerular mesangial cells. Overall, both AT and EZT attenuated diabetic nephropathy; however, AT exhibited greater efficacy despite a similar reduction in circulating cholesterol. HDAC-inhibition may underlie greater efficacy of statins in attenuating kidney injury.

HIV and kidney diseases: 35 years of history and consequences

Kidney diseases in human immunodeficiency virus (HIV)-infected patients are often misdiagnosed. Despite reductions in morbidity and mortality owing to widespread use of highly effective combination antiretroviral therapy (cART), acute kidney injury (AKI) and chronic kidney disease (CKD) are still more common in these patients than in the general population, and are associated with poor health outcomes. HIV-associated nephropathy and HIV immune complex kidney diseases are the more recognizable HIV-related kidney diseases. However, a broad spectrum of kidney disorders related or not directly related with HIV infection can be observed, including cART-induced AKI, CKD, proximal tubular dysfunction, crystalluria and urolithiasis, among others. This review summarizes the major epidemiologic studies of kidney diseases in HIV-infected patients, discusses novel approaches that may potentially limit nephrotoxicity such as the use of tenofovir alafenamide, and outlines current screening measures for early diagnosis of kidney dysfunction or tubular damage, and for accurate detection of increased risk for acute or chronic kidney diseases.

Update on current management of chronic kidney disease in patients with HIV infection

The prevalence of HIV-associated chronic kidney disease (CKD) varies geographically and depends on the definition of CKD used, ranging from 4.7% to 38% globally. The incidence, however, has decreased with the use of effective combined antiretroviral therapy (cART). A wide variety of histological patterns are seen in HIV-associated kidney diseases that include glomerular and tubulointerstitial pathology. In resource-rich settings, there has been a plateau in the incidence of end-stage renal disease secondary to HIV-associated nephropathy (HIVAN). However, the prevalence of end-stage renal disease in HIV-positive individuals has risen, mainly due to increased longevity on cART. There is a disparity in the occurrence of HIVAN among HIV-positive individuals such that there is an 18- to 50-fold increased risk of developing kidney disease among HIV-positive individuals of African descent aged between 20 and 64 years and who have a poorer prognosis compared with their European descent counterparts, suggesting that genetic factors play a vital role. Other risk factors include male sex, low CD4 counts, and high viral load. Improvement in renal function has been observed after initiation of cART in patients with HIV-associated CKD. Treatment with an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker is recommended, when clinically indicated in patients with confirmed or suspected HIVAN or clinically significant albuminuria. Other standard management approaches for patients with CKD are recommended. These include addressing other cardiovascular risk factors (appropriate use of statins and aspirin, weight loss, cessation of smoking), avoidance of nephrotoxins, and management of serum bicarbonate and uric acid, anemia, calcium, and phosphate abnormalities. Early diagnosis of kidney disease by screening of HIV-positive individuals for the presence of kidney disease is critical for the optimal management of these patients. Screening for the presence of kidney disease upon detection of HIV infection and annually thereafter in high-risk populations is recommended.

Krüppel-Like Factor 15 Mediates Glucocorticoid-Induced Restoration of Podocyte Differentiation Markers

Podocyte injury is the inciting event in primary glomerulopathies, such as minimal change disease and primary FSGS, and glucocorticoids remain the initial and often, the primary treatment of choice for these glomerulopathies. Because inflammation is not readily apparent in these diseases, understanding the direct effects of glucocorticoids on the podocyte, independent of the immunomodulatory effects, may lead to the identification of targets downstream of glucocorticoids that minimize toxicity without compromising efficacy. Several studies showed that treatment with glucocorticoids restores podocyte differentiation markers and normal ultrastructure and improves cell survival in murine podocytes. We previously determined that Krüppel-like factor 15 (KLF15), a kidney-enriched zinc finger transcription factor, is required for restoring podocyte differentiation markers in mice and human podocytes under cell stress. Here, we show that in vitro treatment with dexamethasone induced a rapid increase of KLF15 expression in human and murine podocytes and enhanced the affinity of glucocorticoid receptor binding to the promoter region of KLF15 In three independent proteinuric murine models, podocyte-specific loss of Klf15 abrogated dexamethasone-induced podocyte recovery. Furthermore, knockdown of KLF15 reduced cell survival and destabilized the actin cytoskeleton in differentiated human podocytes. Conversely, overexpression of KLF15 stabilized the actin cytoskeleton under cell stress in human podocytes. Finally, the level of KLF15 expression in the podocytes and glomeruli from human biopsy specimens correlated with glucocorticoid responsiveness in 35 patients with minimal change disease or primary FSGS. Thus, these studies identify the critical role of KLF15 in mediating the salutary effects of glucocorticoids in the podocyte.

The roles of oxidative stress, endoplasmic reticulum stress, and autophagy in aldosterone/mineralocorticoid receptor-induced podocyte injury

Podocytes play an important role in the pathogenesis and progression of glomerulosclerosis. Recent studies indicate that aldosterone/mineralocorticoid receptor (MR) is a major contributor of chronic kidney disease (CKD) progression. Aldosterone/MR induces glomerular podocyte injury, causing the disruption of the glomerular filtration barrier and proteinuria. The present study investigated the mechanisms by which aldosterone/MR mediated podocyte injury, focusing on the involvement of oxidative stress, endoplasmic reticulum (ER) stress, and autophagy. We observed that aldosterone/MR induced ER stress and podocyte injury both in vivo and in vitro. Blockade of ER stress significantly reduced aldosterone/MR-induced podocyte injury. In addition, we found that ER stress-induced podocyte injury was mediated by CCAAT/enhancer-binding protein (C/EBP) homologous protein (Chop). Interestingly, autophagy was also enhanced by aldosterone/MR. Pharmacological inhibition of autophagy resulted in increased apoptosis. Inhibition of ER stress significantly reduced aldosterone/MR-induced autophagy. In addition, the activation of ER stress increased the formation of autophagy, which protected podocytes from apoptosis. Moreover, we observed that the addition of ROS scavenger, N-acetyl cystein (NAC), blocked both ER stress and autophagy by aldosterone/MR. Collectively, these results suggest that oxidant stress-mediated aldosterone/MR-induced podocyte injury via activating ER stress, which then triggers both Chop-dependent apoptosis and autophagy to cope with the injury. These findings may guide us to therapeutic strategies for glomerular diseases.

Comparison of Glomerular and Podocyte mRNA Profiles in Streptozotocin-Induced Diabetes

Evaluating the mRNA profile of podocytes in the diabetic kidney may indicate genes involved in the pathogenesis of diabetic nephropathy. To determine if the podocyte-specific gene information contained in mRNA profiles of the whole glomerulus of the diabetic kidney accurately reflects gene expression in the isolated podocytes, we crossed Nos3(-/-) IRG mice with podocin-rtTA and TetON-Cre mice for enhanced green fluorescent protein labeling of podocytes before diabetic injury. Diabetes was induced by streptozotocin, and mRNA profiles of isolated glomeruli and sorted podocytes from diabetic and control mice were examined 10 weeks later. Expression of podocyte-specific markers in glomeruli was downregulated in diabetic mice compared with controls. However, expression of these markers was not altered in sorted podocytes from diabetic mice. When mRNA levels of glomeruli were corrected for podocyte number per glomerulus, the differences in podocyte marker expression disappeared. Analysis of the differentially expressed genes in diabetic mice also revealed distinct upregulated pathways in the glomeruli (mitochondrial function, oxidative stress) and in podocytes (actin organization). In conclusion, our data suggest reduced expression of podocyte markers in glomeruli is a secondary effect of reduced podocyte number, thus podocyte-specific gene expression detected in the whole glomerulus may not represent that in podocytes in the diabetic kidney.

RTN1 mediates progression of kidney disease by inducing ER stress

Identification of new biomarkers and drug targets for chronic kidney disease (CKD) is required for the development of more effective therapy. Here we report an association between expression of reticulon 1 (RTN1) and severity of CKD. An isoform-specific increase in the expression of RTN1A is detected in the diseased kidneys from mice and humans, and correlates inversely with renal function in patients with diabetic nephropathy. RTN1 overexpression in renal cells induces ER stress and apoptosis, whereas RTN1 knockdown attenuates tunicamycin-induced and hyperglycaemia-induced ER stress and apoptosis. RTN1A interacts with PERK through its N-terminal and C-terminal domains, and mutation of these domains prevents this effect on ER stress. Knockdown of Rtn1a expression in vivo attenuates ER stress and renal fibrosis in mice with unilateral ureteral obstruction, and also attenuates ER stress, proteinuria, glomerular hypertrophy and mesangial expansion in diabetic mice. Together, these data indicate that RTN1A contributes to progression of kidney disease by inducing ER stress.

ER stress is associated with the pathogenesis of chronic kidney disease (CKD) and new CKD therapies are needed. Here the authors show that expression of Rtn1 can control severity of renal disease and that inhibition of its expression can attenuate ER stress and CKD.

BAMBI elimination enhances alternative TGF-β signaling and glomerular dysfunction in diabetic mice

BMP, activin, membrane-bound inhibitor (BAMBI) acts as a pseudo-receptor for the transforming growth factor (TGF)-β type I receptor family and a negative modulator of TGF-β kinase signaling, and BAMBI(-/-) mice show mild endothelial dysfunction. Because diabetic glomerular disease is associated with TGF-β overexpression and microvascular alterations, we examined the effect of diabetes on glomerular BAMBI mRNA levels. In isolated glomeruli from biopsies of patients with diabetic nephropathy and in glomeruli from mice with type 2 diabetes, BAMBI was downregulated. We then examined the effects of BAMBI deletion on streptozotocin-induced diabetic glomerulopathy in mice. BAMBI(-/-) mice developed more albuminuria, with a widening of foot processes, than BAMBI(+/+) mice, along with increased activation of alternative TGF-β pathways such as extracellular signal-related kinase (ERK)1/2 and Smad1/5 in glomeruli and cortices of BAMBI(-/-) mice. Vegfr2 and Angpt1, genes controlling glomerular endothelial stability, were downmodulated in glomeruli from BAMBI(-/-) mice with diabetes. Incubation of glomeruli from nondiabetic BAMBI(+/+) or BAMBI(-/-) mice with TGF-β resulted in the downregulation of Vegfr2 and Angpt1, effects that were more pronounced in BAMBI(-/-) mice and were prevented by a MEK inhibitor. The downregulation of Vegfr2 in diabetes was localized to glomerular endothelial cells using a histone yellow reporter under the Vegfr2 promoter. Thus, BAMBI modulates the effects of diabetes on glomerular permselectivity in association with altered ERK1/2 and Smad1/5 signaling. Future therapeutic interventions with inhibitors of alternative TGF-β signaling may therefore be of interest in diabetic nephropathy.

Thioredoxin-Interacting Protein Deficiency Protects against Diabetic Nephropathy

Expression of thioredoxin-interacting protein (TxNIP), an endogenous inhibitor of the thiol oxidoreductase thioredoxin, is augmented by high glucose (HG) and promotes oxidative stress. We previously reported that TxNIP-deficient mesangial cells showed protection from HG-induced reactive oxygen species, mitogen-activated protein kinase phosphorylation, and collagen expression. Here, we investigated the potential role of TxNIP in the pathogenesis of diabetic nephropathy (DN) in vivo. Wild-type (WT) control, TxNIP(-/-), and TxNIP(+/-) mice were rendered equally diabetic with low-dose streptozotocin. In contrast to effects in WT mice, diabetes did not increase albuminuria, proteinuria, serum cystatin C, or serum creatinine levels in TxNIP(-/-) mice. Whereas morphometric studies of kidneys revealed a thickened glomerular basement membrane and effaced podocytes in the diabetic WT mice, these changes were absent in the diabetic TxNIP(-/-) mice. Immunohistochemical analysis revealed significant increases in the levels of glomerular TGF-β1, collagen IV, and fibrosis only in WT diabetic mice. Additionally, only WT diabetic mice showed significant increases in oxidative stress (nitrotyrosine, urinary 8-hydroxy-2-deoxy-guanosine) and inflammation (IL-1β mRNA, F4/80 immunohistochemistry). Expression levels of Nox4-encoded mRNA and protein increased only in the diabetic WT animals. A significant loss of podocytes, assessed by Wilms' tumor 1 and nephrin staining and urinary nephrin concentration, was found in diabetic WT but not TxNIP(-/-) mice. Furthermore, in cultured human podocytes exposed to HG, TxNIP knockdown with siRNA abolished the increased mitochondrial O2 (-) generation and apoptosis. These data indicate that TxNIP has a critical role in the progression of DN and may be a promising therapeutic target.

In vivo RNA interference models of inducible and reversible Sirt1 knockdown in kidney cells

The silent mating type information regulation 2 homolog 1 gene (Sirt1) encodes an NAD-dependent deacetylase that modifies the activity of well-known transcriptional regulators affected in kidney diseases. Sirt1 is expressed in the kidney podocyte, but its function in the podocyte is not clear. Genetically engineered mice with inducible and reversible Sirt1 knockdown in widespread, podocyte-specific, or tubular-specific patterns were generated. We found that mice with 80% knockdown of renal Sirt1 expression have normal glomerular function under the basal condition. When challenged with doxorubicin (Adriamycin), these mice develop marked albuminuria, glomerulosclerosis, mitochondrial injury, and impaired autophagy of damaged mitochondria. Reversal of Sirt1 knockdown during the early phase of Adriamycin-induced nephropathy prevented the progression of glomerular injury and reduced the accumulation of dysmorphic mitochondria in podocytes but did not reverse the progression of albuminuria and glomerulosclerosis. Sirt1 knockdown mice with diabetes mellitus, which is known to cause mitochondrial dysfunction in the kidney, developed more albuminuria and mitochondrial dysfunction compared with diabetic mice without Sirt1 knockdown. In conclusion, these results demonstrate that our RNA interference-mediated Sirt1 knockdown models are valid and versatile tools for characterizing the function of Sirt1 in the kidney; Sirt1 plays a role in homeostatic maintenance of podocytes under the condition of mitochondrial stress/injury.

Krüppel-like factor 6 regulates mitochondrial function in the kidney

Maintenance of mitochondrial structure and function is critical for preventing podocyte apoptosis and eventual glomerulosclerosis in the kidney; however, the transcription factors that regulate mitochondrial function in podocyte injury remain to be identified. Here, we identified Krüppel-like factor 6 (KLF6), a zinc finger domain transcription factor, as an essential regulator of mitochondrial function in podocyte apoptosis. We observed that podocyte-specific deletion of Klf6 increased the susceptibility of a resistant mouse strain to adriamycin-induced (ADR-induced) focal segmental glomerulosclerosis (FSGS). KLF6 expression was induced early in response to ADR in mice and cultured human podocytes, and prevented mitochondrial dysfunction and activation of intrinsic apoptotic pathways in these podocytes. Promoter analysis and chromatin immunoprecipitation studies revealed that putative KLF6 transcriptional binding sites are present in the promoter of the mitochondrial cytochrome c oxidase assembly gene (SCO2), which is critical for preventing cytochrome c release and activation of the intrinsic apoptotic pathway. Additionally, KLF6 expression was reduced in podocytes from HIV-1 transgenic mice as well as in renal biopsies from patients with HIV-associated nephropathy (HIVAN) and FSGS. Together, these findings indicate that KLF6-dependent regulation of the cytochrome c oxidase assembly gene is critical for maintaining mitochondrial function and preventing podocyte apoptosis.

HIV and the aging kidney

PURPOSE OF REVIEW

To review unique considerations in the epidemiology, diagnosis, and management of kidney disease in older adults with HIV.

RECENT FINDINGS

HIV infection may accelerate the course of kidney disease associated with traditional risk factors, such as diabetes, which are more common in older adults. The risks of acute and chronic kidney disease are increased both with HIV infection and with older age. Although the prevalence of chronic kidney disease is higher among HIV-infected adults than among HIV-negative adults, the mean age at diagnosis of end-stage renal disease is similar. Recent studies have supported the use of newer creatinine-based kidney function estimates in HIV-infected adults, although data in older adults are limited. These estimates are susceptible to artifact in the setting of newer medications that interfere with the secretion of creatinine, including cobicistat and dolutegravir. The management of kidney disease in older adults with HIV infection may be complicated by polypharmacy and increased risk for medication toxicity.

SUMMARY

With aging of the HIV-infected population, age-related comorbid conditions such as kidney disease are increasingly important causes of morbidity and mortality. Although recent data do not support premature aging of HIV-infected individuals with respect to kidney disease, the risk of acute and chronic kidney disease is increased by HIV infection and its treatment.

Hyperglycemia enhances kidney cell injury in HIVAN through down-regulation of vitamin D receptors

In the present study, we evaluated the effect of short term hyperglycemia on renal lesions in a mouse model (Tg26) of HIV-associated nephropathy (HIVAN). Control and Tg26 mice in groups (n=6) were administered either normal saline (FVBN or Tg) or streptozotocin (FVBN+STZ or Tg26+STZ). After two weeks, biomarkers were collected and kidneys were harvested. FVBN+ STZ and Tg26+STZ displayed elevated serum glucose levels when compared to FVBN and Tg26 respectively. Tg26+STZ displayed elevated (P<0.05) blood urea nitrogen (BUN) levels (P<0.05) and enhanced (P<0.01) proteinuria when compared to Tg26. Tg26+STZ displayed enhanced (P<0.001) number of sclerotic glomeruli and microcysts vs. Tg26. Renal tissues of Tg26 displayed down regulation of vitamin D receptor (VDR) expression and enhanced Ang II production when compared to FVBN mice. Hyperglycemia exacerbated down regulation of VDR and production of Ang II in FVBN and Tg mice. Hyperglycemia increased kidney cell reactive oxygen species (ROS) production and oxidative DNA damage in both FVBN and Tg26 mice. In in vitro studies, HIV down regulated podocyte VDR expression and also enhanced renin angiotensin system activation. In addition, both glucose and HIV stimulated kidney cell ROS generation and DNA damage and compromised DNA repair; however, tempol (superoxide dismutase mimetic), losartan (Ang II blocker) and EB1089 (VDR agonist) provided protection against DNA damaging effects of glucose and HIV. These findings indicated that glucose activated the RAS and inflicted oxidative stress-mediated DNA damage via down regulation of kidney cell VDR expression in HIV milieu both in vivo and in vitro.