Tenofovir-induced kidney disease: an acquired renal tubular mitochondriopathy

Pyruvate dehydrogenase is a potential mitochondrial off-target for gentamicin based on in silico predictions and in vitro inhibition studies

During the drug development process, organ toxicity leads to an estimated failure of one-third of novel chemical entities. Drug-induced toxicity is increasingly associated with mitochondrial dysfunction, but identifying the underlying molecular mechanisms remains a challenge. Computational modeling techniques have proven to be a good tool in searching for drug off-targets. Here, we aimed to identify mitochondrial off-targets of the nephrotoxic drugs tenofovir and gentamicin using different in silico approaches (KRIPO, ProBis and PDID). Dihydroorotate dehydrogenase (DHODH) and pyruvate dehydrogenase (PDH) were predicted as potential novel off-target sites for tenofovir and gentamicin, respectively. The predicted targets were evaluated in vitro, using (colorimetric) enzymatic activity measurements. Tenofovir did not inhibit DHODH activity, while gentamicin potently reduced PDH activity. In conclusion, the use of in silico methods appeared a valuable approach in predicting PDH as a mitochondrial off-target of gentamicin. Further research is required to investigate the contribution of PDH inhibition to overall renal toxicity of gentamicin.

Methanol Crude Peel Extract of P. granatum Prevents Oxidative Damage in Kidneys of Rats Exposed to Highly Active Antiretroviral Therapy

Background

Highly Active Antiretroviral Therapy (HAART) has been linked to oxidative damage to kidney cells leading to renal disease in people living with HIV/AIDS on HAART treatment. The toxic effects of HAART affect the patients' quality of life leading to poor adherence to their regimen. Therefore, the purpose of this study was to investigate the nephron-protective activity of methanol crude peel extract of Punica granatum (MPEPG) in HAART-administered Wistar rats.

Methods

Thirty male albino Wistar rats weighing between 180-200g were randomly divided into six groups of five rats each. Group one served as normal control and was given distilled water only. Group two serves as a negative control and was given HAART at a dosage of 64 mg/kg. Groups 3 and 4 were given 100 and 400 mg/kg of MPEPG, respectively, while groups 5 and 6 were given MPEPG dosages of 100 and 400 mg/kg along with HAART, respectively, for 40 days. The rats were sacrificed under halothane anaesthesia, and the kidneys were removed for histological evaluation, while blood samples were analyzed for biochemical parameters.

Results

In the HAART (TLD) treated group, there was a significantly high amount of MDA and a lower level of the antioxidant enzymes SOD and CAT. Biochemical analysis revealed that animals treated with HAART (TLD) had significantly higher levels of urea and creatinine, which are biomarkers of kidney damage than the normal control animals. In contrast, all the kidney function markers were returned to normal levels in the HAART-treated group after administration of methanol crude peel extract of P. granatum. The kidney tissues of animals given HAART had considerable structural damage as revealed by histopathological studies. When HAART-exposed rats were treated with MPEPG, both the biochemical and histological results significantly improved.

Conclusion

Methanol crude peel extract of P. granatum provided effective protection against kidney oxidative injury brought on by HAART because of its anti-oxidant and free radical scavenging properties.

Renal and bone side effects of long-term use of entecavir, tenofovir disoproxil fumarate, and tenofovir alafenamide fumarate in patients with Hepatitis B: a network meta-analysis

BACKGROUND

Nucleoside analogues are currently applied as a first-line treatment for chronic hepatitis B (CHB) patients. However, the long-term effects of this type of treatment on kidney and bone tissue need to be further investigated.

METHODS

We conducted a search of entecavir (ETV), tenofovir disoproxil fumarate (TDF), and tenofovir alafenamide fumarate (TAF) for treatment of CHB patients through October 29, 2023. Side effects of the three drugs were compared. Standardized mean difference (SMD), 95% confidence interval (95%CI), and surface under the cumulative ranking curve (SUCRA) were reported for each outcome. Further subgroup analysis was conducted according to duration of administration.

RESULTS

ETV and TAF exhibited less effect on estimated glomerular filtration rate (eGFR) than TDF (SMD = -3.60 (95%CI: -1.94 ~ -5.26) and SMD = -4.27 (95%CI: -2.62 ~ -5.93)). ETV also exhibited less effect on creatinine rise than TAF and TDF (SMD = -0.55 (95%CI: -0.09 ~ -1.01) and SMD = -0.61 (95%CI: -0.15 ~ -1.06)). Moreover, the effect of TAF on bone mineral density (BMD) was less than that of TDF (SMD = -0.02 (95%CI: -0.01 ~ -0.02)). The probabilities of the three drugs changing relevant indicators exhibited similar patterns: eGFR (TDF (100.0%) > ETV (41.2%) > TAF (8.8%)), creatinine (TDF (94.7%) > TAF (54.7%) > ETV (0.6%)), BMD (TDF (79.7%) > ETV (50.6%) > TAF (19.6%)), and blood phosphorus (TDF (90.6%) > TAF (49.8%) > ETV (9.7%)). After 6 and 24 months of treatment, no statistically significant difference in renal function or bone tissue was observed between ETV and TDF. However, greater adverse effects on renal function were observed for TDF than ETV at 60 months compared to 12 months. TDF also exhibited greater adverse effects on bone tissue than ETV at 36 months than at 12 months.

CONCLUSIONS

Long-term administration of TDF has resulted in stronger adverse effects than TAF and ETV in regard to both renal function and bone tissue in CHB patients. The effect of TAF on creatinine increase was greater than ETV. The difference in side effects between ETV and TDF was independent of treatment duration.

Urine-HILIC: Automated Sample Preparation for Bottom-Up Urinary Proteome Profiling in Clinical Proteomics

Urine provides a diverse source of information related to a patient's health status and is ideal for clinical proteomics due to its ease of collection. To date, most methods for the preparation of urine samples lack the throughput required to analyze large clinical cohorts. To this end, we developed a novel workflow, urine-HILIC (uHLC), based on an on-bead protein capture, clean-up, and digestion without the need for bottleneck processing steps such as protein precipitation or centrifugation. The workflow was applied to an acute kidney injury (AKI) pilot study. Urine from clinical samples and a pooled sample was subjected to automated sample preparation in a KingFisher™ Flex magnetic handling station using the novel approach based on MagReSyn® HILIC microspheres. For benchmarking, the pooled sample was also prepared using a published protocol based on an on-membrane (OM) protein capture and digestion workflow. Peptides were analyzed by LCMS in data-independent acquisition (DIA) mode using a Dionex Ultimate 3000 UPLC coupled to a Sciex 5600 mass spectrometer. The data were searched in Spectronaut™ 17. Both workflows showed similar peptide and protein identifications in the pooled sample. The uHLC workflow was easier to set up and complete, having less hands-on time than the OM method, with fewer manual processing steps. Lower peptide and protein coefficient of variation was observed in the uHLC technical replicates. Following statistical analysis, candidate protein markers were filtered, at ≥8.35-fold change in abundance, ≥2 unique peptides and ≤1% false discovery rate, and revealed 121 significant, differentially abundant proteins, some of which have known associations with kidney injury. The pilot data derived using this novel workflow provide information on the urinary proteome of patients with AKI. Further exploration in a larger cohort using this novel high-throughput method is warranted.

Insights into the mechanisms of telbivudine-induced myopathy associated with mitochondrial dysfunction

As a nucleotide analogue (NA), telbivudine was widely used in the treatment for chronic hepatitis B (CHB) by interfering with reverse transcriptase of hepatitis B virus. However, the use of NAs for hepatitis B treatment has been accompanied by numerous reports highlighting the occurrence of neuromyopathy, particularly in the case of telbivudine. This study aimed to investigate the underlying mechanisms responsible for telbivudine-induced myopathy. We established animal and cell models of telbivudine-induced myopathy using C57BL/6 mice and C2C12 cells, respectively. Our findings revealed that telbivudine significantly reduced mitochondrial DNA (mtDNA) copy number and caused increase of oxidative stress. Telbivudine treatment significantly inhibited mitochondrial complex I and IV expression, impairing the oxidative phosphorylation function of the respiratory chain. Modified Gomori trichrome (MGT) staining of the muscle sections displayed an increase in ragged red fibers (RRFs), indicating abnormal mitochondrial accumulation. In conclusion, our study provides compelling evidence suggesting that telbivudine-induced myopathy is associated with mitochondrial toxicity and impaired energy metabolism. The observed muscle pathology, depletion of mtDNA, elevation of oxidative stress and altered mitochondrial function support the hypothesis that telbivudine disrupts mitochondrial homeostasis, ultimately leading to muscle damage. This may be also a common mechanism for NAs to cause neuromyopathy.

A prospective cohort study of renal function and bone turnover in adults with hepatitis B virus (HBV)-HIV co-infection with high prevalence of tenofovir-based antiretroviral therapy use

OBJECTIVE

Tenofovir disoproxil fumarate (TDF) is a common component of antiretroviral therapy in hepatitis B virus (HBV)-HIV co-infected adults but few studies have evaluated worsening renal function and bone turnover, known effects of TDF.

METHODS

Adults from eight North American sites were enrolled in this cohort study. Research assessments were conducted at entry and every 24 weeks for ≤192 weeks. Bone markers were tested at baseline, week 96 and week 192 from stored serum. We evaluated changes in markers of renal function and bone turnover over time and potential contributing factors.

RESULTS

A total of 115 patients were prospectively followed; median age 49 years, 91% male and 52% non-Hispanic Black. Duration of HIV was 20.5 years. TDF use ranged from 80% to 92% throughout follow-up. Estimated glomerular filtration rate (eGFR) (ml/min/1.73m² ) decreased from 87.1 to 79.9 over 192 weeks (p < 0.001); however, the prevalence of eGFR <60 ml/min/1.73m² did not appear to differ over time (always <16%; p = 0.43). From baseline to week 192, procollagen type I N-terminal propeptide (P1NP) (146.7 to 130.5 ng/ml; p = 0.001), osteocalcin (14.4 to 10.2 ng/ml; p < 0.001) and C-terminal telopeptides of type I collagen (CTX-1) (373 to 273 pg/ml; p < 0.001) decreased. Younger age, male sex and overweight/obesity versus normal weight predicted a decrease in eGRF. Black race, healthy weight versus underweight, advanced fibrosis, undetectable HBV DNA, and lower parathyroid hormone level predicted worsening bone turnover.

CONCLUSION

In this HBV-HIV cohort with high prevalence of TDF use, several biomarkers of renal function and bone turnover indicated worsening status over approximately 4 years, highlighting the importance of clinical awareness in co-infected adults.

Altered Serum Uric Acid Levels in Kidney Disorders

Serum uric acid levels are altered by kidney disorders because the kidneys play a dominant role in uric acid excretion. Here, major kidney disorders which accompany hyperuricemia or hypouricemia, including their pathophysiology, are discussed. Chronic kidney disease (CKD) and hyperuricemia are frequently associated, but recent clinical trials have not supported the pathogenic roles of hyperuricemia in CKD incidence and progression. Diabetes mellitus (DM) is often associated with hyperuricemia, and hyperuricemia may be associated with an increased risk of diabetic kidney disease in patients with type 2 DM. Sodium-glucose cotransporter 2 inhibitors have a uricosuric effect and can relieve hyperuricemia in DM. Autosomal dominant tubulointerstitial kidney disease (ADTKD) is an important hereditary kidney disease, mainly caused by mutations of uromodulin (UMOD) or mucin-1 (MUC-1). Hyperuricemia and gout are the major clinical manifestations of ADTKD-UMOD and ADTKD-MUC1. Renal hypouricemia is caused by URAT1 or GLUT9 loss-of-function mutations and renders patients susceptible to exercise-induced acute kidney injury, probably because of excessive urinary uric acid excretion. Hypouricemia derived from renal uric acid wasting is a component of Fanconi syndrome, which can be hereditary or acquired. During treatment for human immunodeficiency virus, hepatitis B or cytomegalovirus, tenofovir, adefovir, and cidofovir may cause drug-induced renal Fanconi syndrome. In coronavirus disease 2019, hypouricemia due to proximal tubular injury is related to disease severity, including respiratory failure. Finally, serum uric acid and the fractional excretion of uric acid are indicative of plasma volume status; hyperuricemia caused by the enhanced uric acid reabsorption can be induced by volume depletion, and hypouricemia caused by an increased fractional excretion of uric acid is the characteristic finding in syndromes of inappropriate anti-diuresis, cerebral/renal salt wasting, and thiazide-induced hyponatremia. Molecular mechanisms by which uric acid transport is dysregulated in volume or water balance disorders need to be investigated.

Bibliometric and visual analysis of nephrotoxicity research worldwide

Background: Nephrotoxicity of drugs contributes to acute kidney injury with high mortality and morbidity, which crucially limits the application and development of drugs. Although many publications on nephrotoxicity have been conducted globally, there needs to be a scientometric study to systematically analyze the intellectual landscape and frontiers research trends in the future.

Methods: Publications on nephrotoxicity from 2011 to 2021 were collected to perform bibliometric visualization using VOSviewer, CiteSpace, and Scimago Graphica software based on the Web of Science Core Collection.

Results: A total of 9,342 documents were analyzed, which were primarily published in the United States (1,861), China (1,724), and Egypt (701). For institutions, King Saud University (166) had the most publications; Food and Chemical Toxicology, PLOS One, and Antimicrobial Agents and Chemotherapy were productive journals, primarily concentrating on the mechanisms of nephrotoxicity and renoprotective in cisplatin and antibiotics, especially in oxidative stress. Burst detection suggested that cisplatin, piperacillin-tazobactam, vancomycin-induced nephrotoxicity, antioxidants, and new biomaterials are frontiers of research.

Conclusion: This study first provides an updated perspective on nephrotoxicity and renoprotective strategies and mechanisms. This perspective may benefit researchers in choosing suitable journals and collaborators and assisting them in the deep understanding of the nephrotoxicity and renoprotective hotspots and frontiers.

Mapping Adverse Outcome Pathways for Kidney Injury as a Basis for the Development of Mechanism-Based Animal-Sparing Approaches to Assessment of Nephrotoxicity

In line with recent OECD activities on the use of AOPs in developing Integrated Approaches to Testing and Assessment (IATAs), it is expected that systematic mapping of AOPs leading to systemic toxicity may provide a mechanistic framework for the development and implementation of mechanism-based in vitro endpoints. These may form part of an integrated testing strategy to reduce the need for repeated dose toxicity studies. Focusing on kidney and in particular the proximal tubule epithelium as a key target site of chemical-induced injury, the overall aim of this work is to contribute to building a network of AOPs leading to nephrotoxicity. Current mechanistic understanding of kidney injury initiated by 1) inhibition of mitochondrial DNA polymerase γ (mtDNA Polγ), 2) receptor mediated endocytosis and lysosomal overload, and 3) covalent protein binding, which all present fairly well established, common mechanisms by which certain chemicals or drugs may cause nephrotoxicity, is presented and systematically captured in a formal description of AOPs in line with the OECD AOP development programme and in accordance with the harmonized terminology provided by the Collaborative Adverse Outcome Pathway Wiki. The relative level of confidence in the established AOPs is assessed based on evolved Bradford-Hill weight of evidence considerations of biological plausibility, essentiality and empirical support (temporal and dose-response concordance).

Urinary Epidermal Growth Factor: A Promising "Next Generation" Biomarker in Kidney Disease

BACKGROUND

The epidermal growth factor (EGF) is a globular protein that is generated in the kidney, especially in the loop of Henle and the distal convoluted tubule. While EGF is nonexistent or hardly detectable in plasma, it is present in normal people's urine. Until now, risk stratification and chronic kidney disease (CKD) diagnosis have relied on estimated glomerular filtration rate (eGFR) and urine albumin/creatinine ratio (uACR), both of which reflect glomerular function or impairment. Tubular dysfunction, on the other hand, may also be associated with renal failure.

SUMMARY

Because decreased urine EGF (uEGF) indicates tubular atrophy and interstitial fibrosis, this biomarker, together with eGFR and uACR, may be employed in the general population for risk assessment and diagnosis of CKD. uEGF levels have been shown to correlate with intrarenal EGF mRNA expression and have been found to decrease in a variety of glomerular and non-glomerular kidney disorders.

KEY MESSAGE

uEGF, uEGF/creatinine, or uEGF/monocyte chemotactic peptide-1 are possible "new generation" biomarkers linked to a variety of kidney diseases that deserve further investigation as a single biomarker or as part of a multi-biomarker panel.

Longitudinal renal changes in chronic hepatitis B patients treated with entecavir versus TDF: a REAL-B study

BACKGROUND AND AIMS

We aimed to compare the longitudinal changes in estimated glomerular filtration rate (eGFR) in chronic hepatitis B (CHB) patients treated with entecavir (ETV) vs. tenofovir disoproxil fumarate (TDF).

METHODS

This is a retrospective study of 6189 adult treatment-naïve CHB patients initiated therapy with TDF (n = 2482) or ETV (n = 3707) at 25 international centers using multivariable generalized linear modeling (GLM) to determine mean eGFR (mL/min/1.73 m²) and Kaplan-Meier method to estimate incidence of renal impairment (≥ 1 chronic kidney disease [CKD] stage worsening). We also examined above renal changes in matched ETV and TDF patients (via propensity score matching [PSM] on age, sex, diabetes mellitus [DM], hypertension [HTN], cirrhosis, baseline eGFR, and follow-up duration).

RESULTS

In the overall cohort (mean age 49.7 years, 66.2% male), the baseline eGFR was higher for TDF vs. ETV group (75.9 vs. 74.0, p = 0.009). PSM yielded 1871 pairs of ETV or TDF patients with baseline eGFR ≥ 60 and 520 pairs for the eGFR < 60 group. GLM analysis of the overall (unmatched) cohort and PSM cohorts revealed lower adjusted mean eGFRs in TDF (vs. ETV) patients (all p < 0.01) during 10 years of follow-up. Among PSM eGFR ≥ 60 patients, the 5-year cumulative incidences of renal impairment were 42.64% for ETV and 48.03% for TDF (p = 0.0023). In multivariable Cox regression, TDF vs. ETV (adjusted HR 1.26, 95% CI 1.11-1.43) was associated with higher risk of worsening renal function.

CONCLUSION

Over the 10-year study follow-up, compared to ETV, TDF was associated with a lower mean eGFR and higher incidence of renal impairment.

Real-World Single-Center Comparison of the Safety and Efficacy of Entecavir, Tenofovir Disoproxil Fumarate, and Tenofovir Alafenamide in Patients with Chronic Hepatitis B

INTRODUCTION

Chronic hepatitis B (CHB) is a major cause of chronic liver diseases and tenofovir disoproxil fumarate (TDF), tenofovir alafenamide (TAF), and entecavir (ETV) are recommended as primary treatments. This study aimed to evaluate the efficacy and safety of ETV, TDF, and TAF in a real-world clinical setting.

METHODS

In this retrospective cohort study, a total of 363 CHB patients who were treated with ETV (n = 163), TDF (n = 154), or TAF (n = 46) from July 2007 to September 2019 were enrolled.

RESULTS

Median patient age was 51 years and 66.4% of patients were male. Median duration of treatment with ETV, TDF, or TAF was 49.0 months (interquartile range, 27.0-74.0 months). In terms of safety, cholesterol was mildly increased in the ETV and TAF groups and significantly lowered in the TDF group than baseline (p < 0.001). There was no significant difference in liver cirrhosis-related complications among the 3 groups at 48 weeks (p = 0.235). Hepatitis B e antigen seroconversion, complete virological response, and alanine aminotransferase normalization at 48 weeks as measures of treatment efficacy were not significantly different among the 3 groups (p = 0.142, 0.538, and 0.520, respectively). There was also no significant difference in cumulative incidence rate of hepatocellular carcinoma (HCC) between the ETV and TDF groups (p = 0.894).

CONCLUSIONS

ETV, TDF, and TAF were safe antiviral agents and showed similar antiviral effect for CHB at 48 weeks. Cirrhosis-related complications and annual HCC incidence rates did not differ significantly between the ETV and TDF groups over the 48 week follow-up period.

Urinary excretion of epidermal growth factor and rapid loss of kidney function

BACKGROUND

Lower urinary excretion of the kidney tubule-specific biomarker epidermal growth factor (uEGF) is associated with increased risk of renal function [glomerular filtration rate (GFR)] loss in diabetes and in patients with established chronic kidney disease (CKD). We investigated whether uEGF is associated with rapid GFR decline or incident CKD in the general population.

METHODS

Subjects without CKD or diabetes were recruited from the general population in Tromso, Norway [Renal Iohexol Clearance Survey (RENIS); N = 1249] and Groningen, the Netherlands [Prevention of REnal and Vascular END-stage disease (PREVEND); N = 4534], with a median follow-up of 5.6 and 7.4 years, respectively. GFR was measured by iohexol clearance in the RENIS and estimated using the CKD Epidemiology Collaboration creatinine-cystatin C equation in the PREVEND study. Rapid GFR decline was defined as an annual GFR loss >3.0 mL/min/1.73 m2 and in sensitivity analyses as subjects with the 10% steepest GFR slope within each cohort.

RESULTS

Lower baseline uEGF excretion was associated with rapid GFR loss in both cohorts {RENIS, odds ratio [OR] per 1 μg/mmol lower uEGF 1.42 [95% confidence interval (CI) 1.06-1.91], P = 0.02; PREVEND, OR 1.29 [95% CI 1.10-1.53], P < 0.01}, adjusted for baseline GFR, albumin:creatinine ratio and conventional CKD risk factors. Similar results were obtained using the outcome of the 10% steepest GFR slope in each cohort. Lower uEGF levels were associated with incident CKD in the combined analysis of both cohorts.

CONCLUSIONS

Lower uEGF levels are associated with increased risk of rapid GFR loss and incident CKD in the general population. This finding, together with previous findings in CKD and high-risk populations, supports that uEGF may serve as a broadly applicable biomarker representing the tubular component of the current glomerulus-centric clinical risk assessment system.

The Mechanism of Drug Nephrotoxicity and the Methods for Preventing Kidney Damage

Acute kidney injury (AKI) is a global health challenge of vast proportions, as approx. 13.3% of people worldwide are affected annually. The pathophysiology of AKI is very complex, but its main causes are sepsis, ischemia, and nephrotoxicity. Nephrotoxicity is mainly associated with the use of drugs. Drug-induced AKI accounts for 19-26% of all hospitalized cases. Drug-induced nephrotoxicity develops according to one of the three mechanisms: (1) proximal tubular injury and acute tubular necrosis (ATN) (a dose-dependent mechanism), where the cause is related to apical contact with drugs or their metabolites, the transport of drugs and their metabolites from the apical surface, and the secretion of drugs from the basolateral surface into the tubular lumen; (2) tubular obstruction by crystals or casts containing drugs and their metabolites (a dose-dependent mechanism); (3) interstitial nephritis induced by drugs and their metabolites (a dose-independent mechanism). In this article, the mechanisms of the individual types of injury will be described. Specific groups of drugs will be linked to specific injuries. Additionally, the risk factors for the development of AKI and the methods for preventing and/or treating the condition will be discussed.

Malformative Reno-Urinary Pathology in Patients with HIV Infection-Clinical and Therapeutic Implications

Chronic kidney disease is an important comorbidity of HIV infection causing real problems in the evolution and medical healthcare of HIV-positive patients. In recent years, a significant number of HIV-positive patients develop renal dysfunction, several mechanisms being incriminated: direct effect of the virus, toxic effect secondary to of antiretroviral medication, secondary to associated comorbidities, given that life expectancy has increased significantly in the last decade, thanks to the use of antiretroviral therapies. There are few studies in the literature to evaluate malformative renourinary pathology in patients with HIV infection. We present the case of a patient with HIV infection, horseshoe kidney, chronic kidney disease and incomplete Fanconi syndrome, secondary to the administration of tenofovir fumarate, a nucleoside reverse transcriptase inhibitor. Malformations, abnormalities or dysmorphysms of the renal tract should be considered in the HIV-positive patient with secondary renal dysfunction because they take a wide range of forms, are underdiagnosed and predispose to multiple complications, with varying degrees of severity, such as urinary tract infections, renal stones or progression of chronic kidney disease. Tenofovir fumarate and atazanavir must be avoided in patients with HIV infection and chronic renal dysfunction.

Diverse Roles of Mitochondria in Renal Injury from Environmental Toxicants and Therapeutic Drugs

Mitochondria are well-known to function as the primary sites of ATP synthesis in most mammalian cells, including the renal proximal tubule. Other functions have also been associated with different mitochondrial activities, including the regulation of redox status and the initiation of mitophagy and apoptosis. Mechanisms for the membrane transport of glutathione (GSH) and various GSH-derived metabolites across the mitochondrial inner membrane of renal proximal tubular cells are critical determinants of these functions and may serve as pharmacological targets for potential therapeutic approaches. Specific interactions of reactive intermediates, derived from drug metabolism, with molecular components in mitochondria have been identified as early steps in diverse forms of chemically-induced nephrotoxicity. Applying this key observation, we developed a novel hypothesis regarding the identification of early, sensitive, and specific biomarkers of exposure to nephrotoxicants. The underlying concept is that upon exposure to a diverse array of environmental contaminants, as well as therapeutic drugs whose efficacy is limited by nephrotoxicity, renal mitochondria will release both high- and low-molecular-weight components into the urine or the extracellular medium in an in vitro model. The detection of these components may then serve as indicators of exposure before irreversible renal injury has occurred.

Subclinical proximal tubulopathy in hepatitis B: The roles of nucleot(s)ide analogue treatment and the hepatitis B virus

BACKGROUND

The recommended monitoring tools for evaluating nucleot(s)ide analogue renal toxicity, such as estimated glomerular filtration rate (eGFR) and phosphatemia, are late markers of proximal tubulopathy. Multiple early markers are available, but no consensus exists on their use.

AIM

To determine the 24 mo prevalence of subclinical proximal tubulopathy (SPT), as defined with early biomarkers, in treated vs untreated hepatitis B virus (HBV)-monoinfected patients.

METHODS

A prospective, non-randomized, multicenter study of HBV-monoinfected patients with a low number of renal comorbidities was conducted. The patients were separated into three groups: Naïve, starting entecavir (ETV) treatment, or starting tenofovir disoproxil (TDF) treatment. Data on the early markers of SPT, the eGFR and phosphatemia, were collected quarterly. SPT was defined as a maximal tubular reabsorption of phosphate/eGFR below 0.8 mmoL/L and/or uric acid fractional excretion above 10%. The prevalence and cumulative incidence of SPT at month 24 (M24) were calculated. Quantitative data were analyzed using analyses of variance or Kruskal-Wallis tests, whereas chi-squared or Fisher’s exact tests were used to analyze qualitative data. Multivariate analyses were used to adjust for any potential confounding factors.

RESULTS

Of the 196 patients analyzed, 138 (84 naïve, 28 starting ETV, and 26 starting TDF) had no SPT at inclusion. At M24, the prevalence of SPT was not statistically different between naïve and either treated group (21.1% vs 30.7%, P < 0.42 and 50.0% vs 30.7%, P = 0.32 for ETV and TDF, respectively); no patient had an eGFR lower than 50 mL/min/1.73 m² or phosphatemia less than 0.48 mmoL/L. In the multivariate analysis, no explanatory variables were identified after adjustment. The cumulative incidence of SPT over 24 mo (25.5%, 13.3%, and 52.9% in the naïve, ETV, and TDF groups, respectively) tended to be higher in the TDF group vs the naïve group (hazard ratio: 2.283, P = 0.05). SPT-free survival at M24 was 57.6%, 68.8%, and 23.5% for the naïve, ETV, and TDF groups, respectively. The median survival time without SPT, evaluated only in the TDF group, was 5.9 mo.

CONCLUSION

The prevalence and incidence of SPT was higher in TDF-treated patients compared to naïve patients. SPT in the naïve population suggests that HBV can induce renal tubular toxicity.

Melatonin protects against tenofovir-induced nephrotoxicity in rats by targeting multiple cellular pathways

Nephrotoxicity is a dose-limiting side effect of long-term use of tenofovir, a reverse transcriptase inhibitor that is used for the treatment of HIV infection and chronic hepatitis B infection. Identifying an agent that prevents tenofovir disoproxil fumarate (TDF)-induced renal injury can lead to its better tolerance, and a more effective treatment can be achieved. The present study is aimed at investigating whether melatonin, a potent antioxidant and anti-inflammatory agent, protects against TDF nephrotoxicity in rats and to determine its cellular targets. Rats were divided into groups and treated as follows. Group I (control): Rats in this group (n = 6) received sterile water only by gavage for 35 days. Group II: Rats (n = 6) in this group received 600 mg/kg body weight TDF in sterile water by gavage for 35 days. Group III: Rats (n = 6) in this group received once daily 20 mg/kg bodyweight melatonin i.p. 2 h before the administration of 600 mg/kg body weight TDF in sterile water by gavage for 35 days. Group IV: Rats were pretreated daily with 20 mg/kg body weight melatonin i.p. 2 h before the administration of sterile water by gavage. All the rats were sacrificed on the 36th day, after overnight fast. Melatonin pretreatment protected the rats against TDF nephrotoxicity both histologically and biochemically. Biochemically, melatonin pretreatment attenuated TDF-induced, oxidative stress, nitrosative stress, mitochondrial pathway of apoptosis, PARP overactivation and preserved proximal tubular function (p < 0.01). This suggests that melatonin may be useful in ameliorating TDF nephrotoxicity.

HIV Prevalence and Morbidity in Older Inpatients in a High HIV Prevalence Setting

Understanding of the burden of HIV infection and comorbid conditions in older adults is limited, especially in low- and middle-income countries. Antiretroviral therapy (ART) has increased longevity of HIV-positive individuals, making age-related comorbidities more likely. This study aimed to compare the demographic and disease profiles, including chronic comorbid conditions of inpatients, at least 50 years of age, by HIV status, admitted to a regional hospital in South Africa. Adults, 50 years of age and older, admitted to internal medicine wards from November 2015 to February 2016 were approached to participate. Sociodemographic data, laboratory results, anthropometric data, discharge diagnoses, and HIV status were collected and compared by HIV serostatus. Overall, 151 participants were enrolled. Their median age was 61 years (IQR: 56-68 years); 89 (58.9%) were women. Overall, 47 (31.1%) were HIV positive, of whom 10 (6.6%) were first diagnosed during the admission. HIV-positive inpatients were younger than HIV-negative patients. The leading discharge diagnoses of all participants were acute gastroenteritis (11.5%) and community-acquired pneumonia (11.5%). Hypertension and type 2 diabetes mellitus (T2DM) were the leading comorbidities in both HIV-negative and HIV-positive participants. Prevalence of hypertension was 75.0% in seronegative, 59.5% in those with a prior diagnosis of HIV, and 40.0% in newly diagnosed; similarly, prevalence of T2DM was 22.1% in HIV-negative and 24.3% in known HIV-positive participants. Similar proportions died during admission; 11.3% of HIV-negative and 12.7% of HIV-positive admitted inpatients died. Almost one third of patients admitted were HIV positive. In HIV-positive older admitted to hospital, the leading cause for hospitalization was coinfections. In the ART era, irrespective of HIV status, older patients have similar age-related chronic illnesses and similar mortality rates, despite younger age at admission.

In Vitro and In Vivo Renoprotective Effects of Telbivudine in Chronic Hepatitis B Patients Receiving Nucleotide Analogue

AIM

Renal toxicity of adefovir disoproxil (ADV) and tenofovir disoproxil fumarate (TDF) is a significant concern in chronic hepatitis B (CHB) patients. Early observational clinical data suggested that telbivudine (LdT) might have renoprotective effects.

METHODS

In this prospective study, consecutive CHB patients on combined lamivudine (LAM) + ADV/TDF were switched to LdT + ADV/TDF at recruitment and were followed up for 24 months. Estimated glomerular filtration rate (eGFR) was calculated with the modification of diet in renal disease equation. The effects of LdT on cell viability and expression of kidney injury or apoptotic biomarkers were investigated in cultured renal tubular epithelial cell line HK-2.

RESULTS

Thirty-one patients (median age 55 years, 90.3% male) were recruited (54.8% TDF: 45.2% ADV). Serum HBV DNA was undetectable at all time points. Median eGFR was 70.2 (IQR 62.6-77.9) and 81.5 (IQR 63.6-99.1) mL/min/1.73 m² at baseline and 24 months, respectively (p < 0.001). Downstaging of chronic kidney disease was observed in eight (25.8%) patients and was more common in ADV-treated compared to TDF-treated patients (7/8 vs. 1/17, p = 0.011; OR 16, 95% CI 1.643-155.766, p = 0.017). In vitro data showed that adding LdT to ADV or TDF was associated with improved cell viability and lower expression of injury and apoptotic biomarkers compared with ADV or TDF alone. Treatment was prematurely discontinued in four(12.9%) patients due to myalgia.

CONCLUSIONS

Clinical and in vitro data suggest that LdT has renoprotective effects in patients on long-term ADV/TDF treatment. LdT may be considered as an adjuvant therapy in this special group of patients with renal impairment (NCT03778567).

Melatonin ameliorates the drug induced nephrotoxicity: Molecular insights

BACKGROUND

Drug-induced nephrotoxicity is a frequent adverse event that can lead to acute or chronic kidney disease and increase the healthcare expenditure. It has high morbidity and mortality incidence in 40-70% of renal injuries and accounts for 66% cases of renal failure in elderly population.

OBJECTIVE

Amelioration of drug-induced nephrotoxicity has been long soughed to improve the effectiveness of therapeutic drugs. This study was conducted to review the melatonin potential to prevent the pathogenesis of nephrotoxicity induced by important nephrotoxic drugs.

METHODS

We analyzed the relevant studies indexed in Pubmed, Medline, Scielo and Web of science to explain the molecular improvements following melatonin co-administration with special attention to oxidative stress, inflammation and apoptosis as key players of drug-induced nephrotoxicity.

RESULTS

A robust consensus among researchers of these studies suggested that melatonin efficiently eradicate the chain reaction of free radical production and induced the endogenous antioxidant enzymes which attenuate the lipid peroxidation of cellular membranes and subcellular oxidative stress in drug-induced nephrotoxicity. This agreement was further supported by the melatonin role in disintegration of inflammatory process through inhibition of principle pro-inflammatory or apoptotic cytokines such as TNF-α and NF-κB. These studies highlighted that alleviation of drug-induced renal toxicity is a function of melatonin potential to down regulate the cellular inflammatory and oxidative injury process and to stimulate the cellular repair or defensive mechanisms.

CONCLUSION

The comprehensive nephroprotection and safer profile suggests the melatonin to be a useful adjunct to improve the safety of nephrotoxic drugs.

Effects of long-term exposure to tenofovir disoproxil fumarate-containing antiretroviral therapy on renal function in HIV-positive Chinese patients

BACKGROUND

The regimen containing tenofovir disoproxil fumarate (TDF)+lamivudine or emtricitabine + efavirenz remains the recommended first-line antiretroviral therapy (ART) by the WHO. Limited studies, however, have been conducted on the incidence of renal impairment among Chinese patients with long-term exposure to TDF-containing ART regimens.

METHODS

We retrospectively analyzed 269 eligible patients who had no comorbidities and received TDF-containing ART from July 2014 to April 2015. TDF-related renal impairment was defined as a decrease of eGFR by >25% from baseline or eGFR <90 ml/min/1.73 m². Decreased renal function was defined as a decrease of eGFR by > 10 mL/min/1.73 m² from baseline.

RESULTS

97.0% of study patients were male (median age 29, eGFR 124.0 ml/min/1.73 m²). After 168-week of ART, renal impairment occurred in 7 patients (2.7%). The incidence of decreased renal function was significantly higher at Week 168 compared with that observed at Week 12 (24.8% vs 3.7%, p < 0.001). In generalized estimating equation analysis, patients receiving ART for 144-week (aOR4.1, 95%CI 2.0-8.4) and 168-week (aOR8.4, 95%CI 4.2-16.4) were more likely to develop decreased renal function compared with those receiving ART for 12-week, so were the patients with a weight <58 kg (aOR2.3, 95%CI 1.2-4.3) and 58-66 kg (aOR2.0, 95%CI 1.0-3.8) compared to those with a weight ≥67 kg. At 168-week, 41.0% of 100 patients examined had elevated urine β2-microglobulin levels, which were negatively correlated with eGFR (r = -0.22, p = 0.02).

CONCLUSIONS

TDF-related renal impairment remained rare in HIV-positive Chinese patients with a median age of 29 years who had no comorbidities. A lower weight and duration of ART were associated with decreased renal function.

Incidence and risk factors for tenofovir-associated nephrotoxicity among human immunodeficiency virus-infected patients in Korea

BACKGROUND/AIMS

Little is known about tenofovir disoproxil fumarate (TDF)-induced nephrotoxicity in human immunodeficiency virus (HIV)-infected patients in Korea. The objective of this study was to evaluate the incidence and risk factors of TDF-associated nephrotoxicity among HIV-infected patients in Korea.

METHODS

A single-center retrospective cohort study was conducted on HIVinfected patients in Korea. We included patients who had started TDF or abacavir (ABC)-based antiretroviral therapy (ART) between October 2006 and December 2014. Estimated glomerular filtration rate (eGFR) was estimated using the Chronic Kidney Disease-Epidemiology Collaboration equation. Renal dysfunction was defined as > 25% decrease of baseline eGFR. A propensity matched case-control study was conducted to compare renal dysfunction rates between the two groups. The risk factors of nephrotoxicity were analyzed by Cox regression analysis.

RESULTS

A total of 210 HIV-infected patients were included in the study, of which, 108 were TDF-based ART group and 102 were ABC-based ART group. Renal dysfunction occurred in 16 patients (14.8%) in the TDF group and 11 (10.8%) in the ABC group. Incidence of renal dysfunction of TDF and ABC group was 9.66 per 100 person-years (PYs) and 5.14 per 100 PYs, respectively (p = 0.176). In propensityscore-matched analysis, renal dysfunction rates were TDF 13.3% versus ABC 13.3% (p > 0.999). In multivariable analysis, Centers for Disease Control and Prevention clinical category C was a significant risk factor for renal dysfunction.

CONCLUSION

Approximately, 13% of HIV-infected patients treated with TDF had renal dysfunction. Advanced stage of HIV infection was a significant risk factor for renal dysfunction.

Pharmacology behind Common Drug Nephrotoxicities

Patients are exposed to numerous prescribed and over-the-counter medications. Unfortunately, drugs remain a relatively common cause of acute and chronic kidney injury. A combination of factors including the innate nephrotoxicity of drugs, underlying patient characteristics that increase their risk for kidney injury, and the metabolism and pathway of excretion by the kidneys of the various agents administered enhance risk for drug-induced nephrotoxicity. This paper will review these clinically relevant aspects of drug-induced nephrotoxicity for the clinical nephrologist.

Mitochondrial pathway of apoptosis and necrosis contribute to tenofovir disoproxil fumarate-induced renal damage in rats

Tenofovir disoproxil fumarate (TDF) is currently the only nucleotide analogue reverse-transcriptase inhibitor that is approved by the Food and Drug administration (FDA), USA, for the treatment of human immunodeficiency virus (HIV) infection. In recent days, renal toxicity is becoming common i HIV patients treated with TDF. However, the mechanism of tenofovir nephrotoxicity is not clear. We hypothesized that mitochondrial pathway of apoptosis, poly [ADP-ribose] polymerase (PARP) overactivation and neutrophil infiltration may contribute to tenofovir-induced renal damage. Renal damage was induced in adult male Wistar rats by the oral administration of 600 mg/kg body weight daily for five consecutive weeks. Kidneys were removed and used for histological and biochemical analyses. Apoptosis was detected by terminal deoxynucleotidyl transferase biotin-deoxyuridine triphosphate nick end-labelling (TUNEL) assay and caspase 3 activity and protein expression; mitochondrial pathway of apoptosis by cyt c release; and PARP activation by immunofluorescence, immunohistochemistry and Western blot techniques. Myeloperoxidase (MPO) activity was measured as a marker of neutrophil infiltration. TDF administration resulted in increased number of TUNEL-positive cells, activation of caspase 3 and release of cyt c from mitochondria into the cytosol in the kidneys. There was increased nuclear localization of PARP as well as increase in its protein level in the TDF-treated rat kidneys. In addition, renal MPO activity was increased ninefold as compared to controls. The results of the present study show that mitochondrial apoptotic pathway, PARP overactivation and neutrophil infiltration contribute to tenofovir-induced renal damage in rats.

Evaluation of Adverse Drug Reaction Profile of Drugs Used as First-Line Antiretroviral Therapy

Background and Objectives

The objective was to study the adverse drug reaction (ADR) profile in HIV patients receiving first-line antiretroviral therapy.

Methods

This was a prospective, observational study that included 171 HIV patients with a follow-up at six months. Demographic details, medical history, details of HIV infection including most recent CD4 count, details of antiretroviral therapy, and other concomitant medication were recorded. Adverse drug reactions were elicited by reviewing patient records and also by interviewing the patient/attendants directly.

Results

171 patients completed the study out of which 88 (51.5%) were males and 83 (48.5%) were females. The study subjects included HIV-positive, treatment naïve patients who were started on treatment regimens recommended by the NACO guidelines. The ADRs observed were a fall in haemoglobin or absolute anaemia in response to zidovudine, nonspecific symptoms like headache, and a nonspecific feeling of being unwell in response to tenofovir, stavudine, and efavirenz; dyslipidaemia, pancreatitis, peripheral neuropathy, and lactic acidosis in response to stavudine; generalised rash in response to nevirapine and one case of nephrotoxicity to efavirenz. Majority of the ADRs satisfied the ‘probable' category (60.1%), and the rest were “possible”. ADRs to zidovudine and nevirapine superseded all others.

Interpretation and Conclusion

Gastrointestinal effects were the most commonly observed group of ADRs, with nausea being the most common ADR, the others being gastritis and diarrhoea. The other ADRs included rash, hepatotoxicity, blood dyscrasias like anaemia, neutropenia, and thrombocytopenia, and fatigue. Few cases of lactic acidosis, peripheral neuropathy, headache, lipoatrophy, and pancreatitis were reported.

Prevalence of chronic kidney disease in patients with chronic hepatitis B: A cross-sectional survey

Renal safety is a major concern during long-term antiviral treatment for chronic hepatitis B (CHB). This study aimed to investigate the prevalence of chronic kidney disease (CKD) in patients with CHB that had been treated with antiviral therapy. This was a single-centre, cross-sectional study in a real-life cohort in which all patients received antiviral treatment. Serum creatinine-based equations from the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) were used to estimate the glomerular filtration rate (GFR). CKD was defined as an eGFR <60 mL/min/1.73 m² or a urinary albumin to creatinine ratio ≥ 3 mg/mmol (defined as albuminuria). Univariate and multivariate analyses were conducted to determine the risk factors of CKD. A total of 1985 patients were included in the analysis from February 2015 to December 2015. The mean age and median duration of antiviral treatment was 42.20 years and 17.05 months, respectively. The overall prevalence of CKD was 7.9% (157/1985), with 44 patients experiencing decreased renal function (eGFR less than 60 mL/min/1.73 m²) and 129 patients with albuminuria. Patients with cirrhosis had a higher prevalence of a decreased GFR (4.3% vs 1.6%, P<.001) and albuminuria (11.1% vs 5.2%, P<.001) than those without cirrhosis. In the multivariate analysis, hypertension (Odds Ratio [OR] 4.564, P<.001), diabetes mellitus (OR 2.688, P<.001) and cirrhosis (OR 1.918, P<.001) were independent factors associated with the presence of CKD. CKD was a clinically significant comorbidity in patients with CHB. Special attention should be paid to cirrhotic patients and patients with the metabolic syndrome.

HIV associated kidney diseases: Clarifying concordance between renal failure in HIV infection and histopathologic manifestations at kidney biopsy

Patients with HIV infection have a wide spectrum of renal diseases. Some are known to be the direct effect of the viral infection while others are renal diseases that also occur in uninfected populations. HIV associated nephropathy (HIVAN) is considered to be a subtype of primary focal and segmental glomerulosclerosis that is distinct in HIV infected patients. It is more frequent in the African-American population and associated with mutations of the apolipoprotein L1 (APOL1) gene. HIV associated immune complex kidney disease (HIVICD) encompasses a spectrum of HIV associated renal diseases characterized by the presence of immune complex deposition within glomeruli. Thrombotic microangiopathy (TMA) is a complication of HIV infection that presents with hemolytic anemia, thrombocytopenia, and renal failure. TMA in HIV patients is associated with very high mortality. Lastly, the multitude of antiretroviral drugs used for treatment of HIV infections can result in nephrotoxicity. Although a kidney biopsy may not be the first line study for renal disease, knowledge of the different histopathologic features of HIV-associated and unassociated diseases is of paramount importance in the treatment and subsequent outcome of renal function in HIV infected patients. In this review we will describe the histopathologic features and discuss the pathophysiology of the entities previously named.

Tenofovir and adefovir down-regulate mitochondrial chaperone TRAP1 and succinate dehydrogenase subunit B to metabolically reprogram glucose metabolism and induce nephrotoxicity

Despite the therapeutic success of tenofovir (TFV) for treatment of HIV-1 infection, numerous cases of nephrotoxicity have been reported. Mitochondrial toxicity has been purported as the major target of TFV-associated renal tubulopathy but the underlying molecular mechanism remains unclear. In this report, we use metabolomics and proteomics with HK-2 cells and animal models to dissect the molecular pathways underlying nephropathy caused by TFV and its more toxic analog, adefovir (ADV). Proteomic analysis shows that mitochondrial chaperone TRAP1 and mtDNA replicating protein SSBP1 were significantly down-regulated in TFV and ADV treated HK-2 cells compared with controls. Transmission electron microscopy (TEM) revealed that TFV and ADV-treated HK-2 cells had accumulated glycogen, a phenotype that was also observed in mice treated with TFV and ADV. Analysis of the proteins in TCA cycle showed succinate dehydrogenase subunit B (SDHB) was nearly depleted in glucose oxidative phosphorylation pathway however certain enzymes in the glycolysis and glycogen synthesis pathway had elevated expression in TFV and ADV-treated HK-2 cells. These results suggest that TFV and ADV may cause mitochondrial dysfunction in renal tubular cells and reprogramming of glucose metabolism. The resulting glycogen accumulation may partially contribute to TFV and ADV induced renal dysfunction.

Prospective Study to Assess Progression of Renal Markers after Interruption of Tenofovir due to Nephrotoxicity

Background. Prospective studies about the reversibility of tenofovir disoproxil fumarate- (TDF-) related renal impairment remain scarce. Methods. This is an observational prospective study including all patients that presented at our HIV Unit who interrupted TDF owing to nephrotoxicity. We assessed the evolution of renal parameters after discontinuation of this drug. Results. We included 59 patients, who were followed up for 72 weeks. Most were male (41, 69.5%), median (IQR) age was 53 (44; 58) years, and median time receiving TDF-containing regimens was 55.4 (28; 87.7) months. Most patients were receiving PI-based treatments (67%). At the final visit, most of the subjects showed complete recovery (35, 59.3%) or improvement (13 subjects, 22%). Significant improvements were observed in creatinine levels (from 84.9 [73.8; 97.5] to 78 [69.6; 91] μmol/L, p = 0.013), estimated glomerular filtration rate (eGFR, CKD EPI equation, from 87.7 [67; 99] to 89.9 [73.6; 99.3] mL/min/1.73 m², p = 0.017), and number of patients with eGFR <60 mL/min/1.73 m² (from 9 [15.3%] to 1 [1.7%], p = 0.031). A trend toward significance was observed in abnormal urine proteinuria/creatinine ratio (from 22 [37%] to 8 [13.6%], p = 0.057). Conclusions. Our results corroborate the high frequency of complete or partial renal recovery in patients receiving TDF-containing regimens who discontinued therapy owing to nephrotoxicity.

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.

Brief Report: Effects of Tenofovir and Amphotericin B Deoxycholate Coadministration on Kidney Function in Patients Treated for Cryptococcal Meningitis

The effect of tenofovir and amphotericin coadministration on kidney function is poorly characterized. We measured creatinine during induction therapy and at 4 weeks after diagnosis in Ugandans undergoing cryptococcal meningitis therapy and classified as not receiving antiretroviral therapy (ART), receiving nontenofovir ART or receiving tenofovir-based ART. Longitudinal creatinine changes and grade 2-4 creatinine adverse events were evaluated across groups. Creatinine concentrations were similar across ART groups. At 4 weeks after diagnosis, creatinine was 0.25 mg/dL higher than at diagnosis, but similar across groups. Adverse event incidence was also similar across ART groups. Tenofovir and amphotericin coadministration did not increase the risk of kidney dysfunction.

Cellular and Molecular Mechanisms of AKI

In this article, we review the current evidence for the cellular and molecular mechanisms of AKI, focusing on epithelial cell pathobiology and related cell-cell interactions, using ischemic AKI as a model. Highlighted are the clinical relevance of cellular and molecular targets that have been investigated in experimental models of ischemic AKI and how such models might be improved to optimize translation into successful clinical trials. In particular, development of more context-specific animal models with greater relevance to human AKI is urgently needed. Comorbidities that could alter patient susceptibility to AKI, such as underlying diabetes, aging, obesity, cancer, and CKD, should also be considered in developing these models. Finally, harmonization between academia and industry for more clinically relevant preclinical testing of potential therapeutic targets and better translational clinical trial design is also needed to achieve the goal of developing effective interventions for AKI.

A Single-Nucleotide Polymorphism in ABCC4 Is Associated with Tenofovir-Related Beta2-Microglobulinuria in Thai Patients with HIV-1 Infection

Background

In Thailand, the combined generic anti-retroviral drug stavudine/lamivudine/nevirapine (d4T/3TC/NVP) has been used to treat human immunodeficiency virus (HIV)-infected individuals since 2001. Due to relatively frequent adverse effects, d4T gradually has been replaced with tenofovir disoproxil fumarate (TDF). Although the frequency of adverse drug effects with TDF is lower than that with d4T, TDF is known to induce kidney dysfunction, especially in the proximal tubules. It has been reported that renal tubular transporters, including members of the multi-drug resistant (MDR) protein family, are implicated in tenofovir extrusion and may, therefore, confer susceptibility to TDF-induced kidney tubular dysfunction (KTD). We have explored the association between KTD and polymorphisms in genes that encode adenosine triphosphate-binding cassette (ABC)-type MDRs.

Methods

HIV-infected patients receiving TDF-containing antiretroviral regimens for at least one year were enrolled in the study. The levels of beta2-microglobulin in urine and creatinine (Cr) were measured. Three single-nucleotide polymorphisms, ABCC2 C-24T (rs717620), ABCC2 G1429A (rs2273697), and ABCC4 T4976C (rs1059751), were analyzed using TaqMan SNP genotyping assays.

Results

A total of 273 HIV-infected patients were recruited. The median number of years of TDF treatment was 5.04 with interquartile range (IQR) of 3.9–6.7. Despite the length of treatment with TDF, 98.5% patients maintained an estimated glomerular filtration rate (eGFR) of >60 mL/min as calculated by the CKD-EPI formula. Fifty-four patients (19.8%) showed beta2-microglobulinuria (median 2636 μg/g Cr with IQR of 1519–13197 μg/g Cr). The allele frequency of ABCC4 T4976C among those 54 patients was 0.602, compared to 0.475 among the 219 remaining patients (p = 0.018).

Conclusions

Approximately 20% of HIV-infected patients receiving TDF showed beta2-microglobulinuria. The C allele at position 4976 of the ABCC4 gene was associated with beta2-microglobulinuria in this population. This polymorphism may help to identify patients at greater risk for developing TDF-associated KTD.

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.

Renal tubular disease in the era of combination antiretroviral therapy

OBJECTIVES

To describe the spectrum of renal tubular disease (RTD) in HIV-positive patients and its association with exposure to antiretroviral therapy (ART).

DESIGN

Review of 265 consecutive renal biopsies from HIV-positive patients attending eight clinics in the United Kingdom between 2000 and 2012.

METHODS

We described the clinical characteristics of patients with RTD and compared current/recent exposure (at the time of, or up to 3 months prior to the date of biopsy) to potentially nephrotoxic ART [tenofovir (TDF), atazanavir (ATV), indinavir (IDV) and lopinavir/ritonavir (LPV/r)]. We also analysed the incidence of RTD in the UK CHIC cohort. Kruskall-Wallis, analysis of variance and Fisher's exact tests were used to evaluate between-group differences.

RESULTS

Of the 60 RTD cases, 54 (90%) were included in the analyses. RTD comprised of three distinct patterns: acute tubular injury (ATI, n = 22), tubulo-interstitial nephritis (TIN, n = 20) and interstitial fibrosis and tubular atrophy (IFTA, n = 12). Compared with TIN and IFTA, ATI cases were less likely to be of black ethnicity (10 vs. 42-55%; P = 0.006), more likely to be on ART (100 vs. 55-68%; P = 0.001), with HIV-RNA below 200 copies/ml (100 vs. 54-58%; P < 0.001), and more likely to have current/recent exposure to TDF (P < 0.001). We did not find evidence for an association between exposure to TDF, ATV/r or LPV/r and either TIN or IFTA.

CONCLUSION

RTD was present in approximately 20% of renal biopsies and comprised three distinct injury patterns with considerable clinical overlap. ATI was associated with TDF exposure, although the overall incidence of biopsy-defined ATI was low.

Current Management of Chronic Hepatitis B and C in Chronic Kidney Disease

The landscape of therapeutic options for hepatitis B and C has changed drastically over the course of 2 decades. There are now novel, effective, well-tolerated, oral antiviral agents being used to successfully control chronic hepatitis B (HBV) infections and cure chronic hepatitis C (HCV) infections. However, patients with CKD were rarely included in the Phase II and III randomized trials for these medications. This paucity of data and the high prevalence of comorbidities associated with CKD pose distinct challenges to physicians treating chronic hepatitis B virus and hepatitis C virus infections in the setting of kidney insufficiency/failure. Thus, this review will attempt to summarize the current data regarding novel antiviral therapies for HBV and HCV in the CKD population.

Proximal tubular dysfunction and kidney injury associated with tenofovir in HIV patients: a case series

Background

Tenofovir disoproxil fumarate (TDF) may cause acute kidney injury and proximal tubular dysfunction. However, no detailed studies document urinary phosphate wasting as a marker of TDF-induced tubulopathy.

Methods

Records of HIV-infected patients with presumed TDF toxicity were reviewed. We describe the characteristics and clinical course of 15 patients who had documented elevated (>20%) fractional excretion of phosphate (FEphos).

Results

Patients were predominantly Caucasian and male (73 and 80%, respectively), with a mean age of 56 years (range 38–76). Of the 15 patients, 11 had a estimated glomerular filtration rate (eGFR) of >90 mL/min/1.73² at time of TDF initiation. The mean duration of TDF therapy prior to diagnosis of TDF toxicity was 64 months. Mean FEphos was 34% (range 20–62). The mean eGFR at TDF initiation was 104 mL/min/1.73 m² [standard deviation (SD) 17.0] with a gradual decline to 69 mL/min/1.73 m² (SD 19.0) by the time of TDF discontinuation. Of 10 patients with repeated FEphos after TDF discontinuation, 9 had improvement of their FEphos. Of these individuals, 6 had normalization of their FEphos. Estimated GFR improved in 12 patients after discontinuation of TDF, though importantly, none returned to their baseline eGFR.

Conclusions

Urinary phosphate wasting is a sensitive marker for TDF-induced proximal tubulopathy and is associated with unrecognized and permanent renal function decline. Tubular dysfunction can develop after years of TDF therapy in those with normal kidney function at the time of drug initiation. This suggests that continuing vigilance be maintained in all those on TDF.

Monitoring of kidney function in HIV-positive patients

HIV-positive patients are at increased risk of developing chronic kidney disease. Although guidelines recommend regular monitoring of renal function in individuals living with HIV, the optimal frequency remains to be defined. In this review, we discuss the renal syndromes that may be identified at an earlier stage via routine assessment of kidney function, and provide guidance in terms of the frequency of monitoring, the most useful tests to perform, and their clinical significance. Specifically, we address whether annual monitoring of kidney function is appropriate for the majority of HIV-positive patients.

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.

Mucosal effects of tenofovir 1% gel

Tenofovir gel is being evaluated for vaginal and rectal pre-exposure prophylaxis against HIV transmission. Because this is a new prevention strategy, we broadly assessed its effects on the mucosa. In MTN-007, a phase-1, randomized, double-blinded rectal microbicide trial, we used systems genomics/proteomics to determine the effect of tenofovir 1% gel, nonoxynol-9 2% gel, placebo gel or no treatment on rectal biopsies (15 subjects/arm). We also treated primary vaginal epithelial cells from four healthy women with tenofovir in vitro. After seven days of administration, tenofovir 1% gel had broad-ranging effects on the rectal mucosa, which were more pronounced than, but different from, those of the detergent nonoxynol-9. Tenofovir suppressed anti-inflammatory mediators, increased T cell densities, caused mitochondrial dysfunction, altered regulatory pathways of cell differentiation and survival, and stimulated epithelial cell proliferation. The breadth of mucosal changes induced by tenofovir indicates that its safety over longer-term topical use should be carefully monitored.

A consensus statement on the renal monitoring of Australian patients receiving tenofovir based antiviral therapy for HIV/HBV infection

A number of antiviral agents used against Human Immunodeficiency Virus (HIV) infection and hepatitis B virus (HBV) mono or co-infection have been associated with real nephrotoxicity (including tenofovir disoproxil fumarate (TDF), atazanavir, indinavir and lopinavir) or apparent changes in renal function (e.g. cobicistat, ritonavir, rilpivirine and dolutegravir). Patients with HIV are at higher risk of acute and chronic renal dysfunction, so baseline assessment and ongoing monitoring of renal function is an important part of routine management of patients with HIV.

Given the paucity of evidence in this area, we sought to establish a consensus view on how routine monitoring could be performed in Australian patients on ART regimens, especially those involving TDF. A group of nephrologists and prescribers (an HIV physician and a hepatologist) were assembled by Gilead to discuss practical and reasonable renal management strategies for patients particularly those on TDF-based combination regimens (in the case of those with HIV-infection) or on TDF-monotherapy (in the case of HBV-mono infection). The group considered which investigations should be performed as part of routine practice, their frequency, and when specialist renal referral is warranted. The algorithm presented suggests testing for serum creatinine along with plasma phosphate and an assessment of urinary protein (rather than albumin) and glucose.

Here we advocate baseline tests of renal function at initiation of therapy. If creatinine excretion inhibitors (e.g. cobicistat or rilpivirine) are used as part of the ART regimen, we suggest creatinine is rechecked at 4 weeks and this value used as the new baseline. Repeat testing is suggested at 3-monthly intervals for a year and then at least yearly thereafter if no abnormalities are detected. In patients with abnormal baseline results, renal function assessment should be performed at least 6 monthly. In HBV mono-infected patients advocate that a similar testing protocol may be logical.

Antiretrovirals and the kidney in current clinical practice: renal pharmacokinetics, alterations of renal function and renal toxicity

Assessment of renal function in HIV-positive patients is of increasing importance in the context of ageing and associated comorbidities. Exposure to nephrotoxic medications is widespread, and several commonly used antiretroviral drugs have nephrotoxic potential. Moreover, specific antiretrovirals inhibit renal tubular transporters resulting in the potential for drug-drug interactions as well as increases in serum creatinine concentrations, which affect estimates of glomerular filtration rate in the absence of changes in actual glomerular filtration rate. This review explores the effects of antiretroviral therapy on the kidney and offers an understanding of mechanisms that lead to apparent and real changes in renal function.

Long-term treatment with tenofovir: prevalence of kidney tubular dysfunction and its association with tenofovir plasma concentration

BACKGROUND

Monitoring of side effects of long-term HIV treatment has become increasingly important. Tenofovir disoproxil fumarate (TDF), a first-line treatment option, is associated with kidney tubular dysfunction (KTD). Our objective was to further investigate the prevalence and risk factors of KTD, in particular its association with TDF plasma concentration in HIV-infected patients treated with TDF for at least one year.

METHODS

An observational cross-sectional single-centre study was conducted. KTD was defined as the presence of at least two of the following criteria: urinary α1-microglobulin/creatinine ratio >15 mg/10 mmol; fractional excretion (FE) of phosphate >20% in the presence of hypophosphataemia; FE of uric acid >10% in the presence of hypouricaemia and glucosuria. Multivariate logistic regression was used to study which variable was associated with KTD.

RESULTS

A total of 161 HIV patients were included. Abnormalities in tubular function were observed in 101 patients (62.7%), while 17 patients (10.6%) fulfilled the definition of KTD. Urinary α1-microglobulin/creatinine ratio was the most sensitive parameter to detect KTD. Multivariate logistic regression showed TDF plasma concentration to be the only variable associated with KTD. Post hoc analysis showed a stronger association between the product of TDF plasma concentration and TDF exposure and KTD.

CONCLUSIONS

Parameters of KTD are frequently observed in patients on long-term TDF-containing combination antiretroviral therapy. KTD is associated with higher TDF plasma concentrations. A stronger association between the product of TDF plasma concentration and TDF exposure and KTD could suggest cumulative toxicity. A causative role for elevated TDF plasma concentration in development of KTD cannot be demonstrated in this cross-sectional analysis. Longitudinal research is needed to investigate the development and clinical relevance of KTD.

Effects of switching from stavudine to raltegravir on subcutaneous adipose tissue in HIV-infected patients with HIV/HAART-associated lipodystrophy syndrome (HALS). A clinical and molecular study

HIV-1/HAART-associated lipodystrophy syndrome (HALS) has been associated with exposure to stavudine (d4T) through mitochondrial dysfunction. We performed a 48-week study to assess the effects of switching from d4T to raltegravir (RAL) on metabolic and fat molecular parameters of patients with HALS. Forty-two patients with HALS and a median exposure to d4T > 7 years were switched to RAL and followed for 48 weeks. Fasting metabolic tests, HIV RNA, CD4 cell count, and fat measured by DEXA were obtained at baseline and week 48. mtDNA and gene transcripts for PPAR gamma, adiponectin, cytochrome b, Cox IV, TNF alpha, MCP-1 and CD68 were assessed in paired subcutaneous fat tissue biopsies. Lipid parameters, fasting glucose, insulin, and HOMA-IR did not change significantly. Whole body fat (P = 0.0027) and limb fat mass (P<0.0001) increased from baseline. Trunk/limb fat ratio (P = 0.0022), fat mass ratio (P = 0.0020), fat mass index (P = 0.0011) and percent leg fat normalized to BMI (P<0.0001) improved after 48 weeks. Relative abundance of mtDNA, expression of PPAR gamma, adiponectin, Cyt b, and MCP-1 genes increased, whereas Cox IV, TNF alpha, and CD68 did not change significantly from baseline. Switching from d4T to RAL in patients with HALS is associated with an increase in limb fat mass and an improvement in markers of adipocyte differentiation and mitochondrial function in SAT.

Preclinical efficacy of melatonin in the amelioration of tenofovir nephrotoxicity by the attenuation of oxidative stress, nitrosative stress, and inflammation in rats

Abstract Background: Nephrotoxicity is a dose-limiting side effect of long-term use of tenofovir, a reverse transcriptase inhibitor that is used for the treatment of human immunodeficiency virus (HIV) infection. Identifying an agent that prevents tenofovir disoproxil fumarate (TDF)-induced renal injury can lead to better tolerance to TDF, and a more effective treatment can be achieved in HIV infected patients. Recent studies show that oxidative stress, nitrosative stress, and inflammation play a role in TDF nephrotoxicity. The present study is aimed at investigating whether melatonin, a potent antioxidant and anti-inflammatory agent, protects against TDF nephrotoxicity in rats. Methods: Adult male rats were used for the study. Some rats received 600 mg/kg body weight TDF by gavage for 35 days, while others received once daily 20 mg/kg body weight melatonin i.p. 2 h before TDF administration. All the rats were sacrificed on the 36th day, after overnight fast. Results: Melatonin pretreatment protected the rats against TDF nephrotoxicity both histologically and biochemically. Biochemically, melatonin pretreatment attenuated TDF-induced renal oxidative stress, nitrosative stress, and inflammation and preserved proximal tubular function. Histologically, melatonin pretreatment prevented TDF-induced proximal tubular injury and mitochondrial injury such as swelling, disruption of cristae, and deposition of amorphous material in the matrix. It restored the lysosomal and mitochondrial numbers in the proximal tubules also. Conclusions: Melatonin pretreatment protects rats from tenofovir-induced damage to proximal tubular mitochondria by attenuating oxidative stress, nitrosative stress, and inflammation. This suggests that it may be useful in ameliorating TDF nephrotoxicity in humans.

Does an increase in serum creatinine always reflect renal injury? The case of Stribild®

Single tablet, once-daily HIV treatment regimens offer patient convenience, the potential for increased adherence, and fewer patient-related dosing errors[1] . Stribild® (manufactured and marketed by Gilead Sciences; referred to as "applicant" in this report), a 4-drug fixed-dose combination (FDC) tablet, is approved for the treatment of HIV-1 infection in treatment-naïve adult patients. Stribild® contains elvitegravir (an integrase strand transfer inhibitor), cobicistat (an inhibitor of cytochrome P450 enzymes), and the nucleoside/nucleotide reverse transcriptase inhibitors emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF).

Depletion of the cellular antioxidant system contributes to tenofovir disoproxil fumarate - induced mitochondrial damage and increased oxido-nitrosative stress in the kidney

BACKGROUND

Nephrotoxicity is a dose limiting side effect of tenofovir, a reverse transcriptase inhibitor that is used for the treatment of HIV infection. The mechanism of tenofovir nephrotoxicity is not clear. Tenofovir is specifically toxic to the proximal convoluted tubules and proximal tubular mitochondria are the targets of tenofovir cytotoxicity. Damaged mitochondria are major sources of reactive oxygen species and cellular damage is reported to occur after the antioxidants are depleted. The purpose of the study is to investigate the alterations in cellular antioxidant system in tenofovir induced renal damage using a rat model.

RESULTS

Chronic tenofovir administration to adult Wistar rats resulted in proximal tubular damage (as evidenced by light microscopy), proximal tubular dysfunction (as shown by Fanconi syndrome and tubular proteinuria), and extensive proximal tubular mitochondrial injury (as revealed by electron microscopy). A 50% increase in protein carbonyl content was observed in the kidneys of TDF treated rats as compared with the control. Reduced glutathione was decreased by 50%. The activity of superoxide dismutase was decreased by 57%, glutathione peroxidase by 45%, and glutathione reductase by 150% as compared with control. Carbonic Anhydrase activity was decreased by 45% in the TDF treated rat kidneys as compared with control. Succinate dehydrogenase activity, an indicator of mitochondrial activity was decreased by 29% in the TDF treated rat kidneys as compared with controls, suggesting mitochondrial dysfunction.

CONCLUSION

Tenofovir- induced mitochondrial damage and increased oxidative stress in the rat kidneys may be due to depletion of the antioxidant system particularly, the glutathione dependent system and MnSOD.

Update on tenofovir toxicity in the kidney

Tenofovir (TFV) is a widely used and effective treatment for HIV infection. Numerous studies have shown that TFV exposure is associated with small but significant declines in estimated glomerular filtration rate (eGFR). However, TFV toxicity is targeted mainly at the proximal tubule (PT), and in severe cases can cause the renal Fanconi syndrome or acute kidney injury. Severe toxicity occurs in a minority of patients, but milder PT dysfunction is more common; the long-term significance of this on kidney and bone health is uncertain. Recent work suggests that changes in eGFR on TFV therapy might be explained by inhibition of PT creatinine secretion rather than actual alterations in glomerular function. Risk factors for nephrotoxicity include pre-existing kidney disease, increased age, and low body mass. Mitochondria in the PT are the targets of TFV toxicity, but the exact mechanisms remain unclear. Substantial improvement of renal function occurs in many patients with TFV toxicity upon stopping therapy, but function does not always return to baseline. In recent years, TFV usage has been extended to new clinical spheres, including pediatrics, resource-poor settings and treatment of hepatitis B infection; theoretical reasons exist as to why some of these patients might be at higher or lower risk of TFV toxicity. Finally, strategies have been proposed to prevent TFV toxicity or enhance recovery.