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

Long-term persistence of mitochondrial dysfunctions after viral infections and antiviral therapies: A review of mechanisms involved

Mitochondria are vital for most cells' functions. Viruses hijack mitochondria machinery for misappropriation of energy supply or to bypass defense mechanisms. Many of these mitochondrial dysfunctions persist after recovery from treated or untreated viral infections, particularly when mitochondrial DNA is permanently damaged. Quantitative defects and structural rearrangements of mitochondrial DNA accumulate in post-mitotic tissues as recently reported long after SARS-CoV-2 or HIV infection, or following antiviral therapy. These observations are consistent with the "hit-and-run" concept proposed decades ago to explain viro-induced cell transformation and it could apply to delayed post-viral onsets of symptoms and advocate for complementary supportive care. Thus, according to this concept, following exposure to viruses or antiviral agents, mitochondrial damage could evolve into an autonomous clinical condition. It also establishes a pathogenic link between communicable and non-communicable chronic diseases.

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.

MCT1-governed pyruvate metabolism is essential for antibody class-switch recombination through H3K27 acetylation

Monocarboxylate transporter 1 (MCT1) exhibits essential roles in cellular metabolism and energy supply. Although MCT1 is highly expressed in activated B cells, it is not clear how MCT1-governed monocarboxylates transportation is functionally coupled to antibody production during the glucose metabolism. Here, we report that B cell-lineage deficiency of MCT1 significantly influences the class-switch recombination (CSR), rendering impaired IgG antibody responses in Mct1f/fMb1Cre mice after immunization. Metabolic flux reveals that glucose metabolism is significantly reprogrammed from glycolysis to oxidative phosphorylation in Mct1-deficient B cells upon activation. Consistently, activation-induced cytidine deaminase (AID), is severely suppressed in Mct1-deficient B cells due to the decreased level of pyruvate metabolite. Mechanistically, MCT1 is required to maintain the optimal concentration of pyruvate to secure the sufficient acetylation of H3K27 for the elevated transcription of AID in activated B cells. Clinically, we found that MCT1 expression levels are significantly upregulated in systemic lupus erythematosus patients, and Mct1 deficiency can alleviate the symptoms of bm12-induced murine lupus model. Collectively, these results demonstrate that MCT1-mediated pyruvate metabolism is required for IgG antibody CSR through an epigenetic dependent AID transcription, revealing MCT1 as a potential target for vaccine development and SLE disease treatment.

Current drugs for HIV-1: from challenges to potential in HIV/AIDS

The human immunodeficiency virus (HIV) persists in latently infected CD4+T cells and integrates with the host genome until cell death. Acquired immunodeficiency syndrome (AIDS) is associated with HIV-1. Possibly, treating HIV/AIDS is an essential but challenging clinical goal. This review provides a detailed account of the types and mechanisms of monotherapy and combination therapy against HIV-1 and describes nanoparticle and hydrogel delivery systems. In particular, the recently developed capsid inhibitor (Lenacapavir) and the Ainuovirine/tenofovir disoproxil fumarate/lamivudine combination (ACC008) are described. It is interestingly to note that the lack of the multipass transmembrane proteins serine incorporator 3 (SERINC3) and the multipass transmembrane proteins serine incorporator 5 (SERINC5) may be one of the reasons for the enhanced infectivity of HIV-1. This discovery of SERINC3 and SERINC5 provides new ideas for HIV-1 medication development. Therefore, we believe that in treating AIDS, antiviral medications should be rationally selected for pre-exposure and post-exposure prophylaxis to avoid the emergence of drug resistance. Attention should be paid to the research and development of new drugs to predict HIV mutations as accurately as possible and to develop immune antibodies to provide multiple guarantees for the cure of AIDS.

Human immunodeficiency virus and antiretroviral therapy-mediated immune cell metabolic dysregulation in children born to HIV-infected women: potential clinical implications

Commencing lifelong antiretroviral therapy (ART) immediately following HIV diagnosis (Option B+) has dramatically improved the health of HIV-infected women and their children, with the majority being of HIV-exposed children born uninfected (HEU). This success has led to an increasing population of HIV-infected women receiving ART during pregnancy and children exposed to ART in utero. Nonetheless, a small proportion of children are still infected with HIV (HEI) each year. HEI children suffer from reduced immunocompetence and host-defence, due to CD4+ T lymphocyte depletion, but also dysregulation of other immune cells including CD8+ T lymphocytes, natural killer (NK) cells, macrophages including B lymphocytes. Furthermore, although HEU children are uninfected, altered immune responses are observed and associated with increased vulnerability to infections. The mechanisms underlying immune dysregulation in HEU children remain poorly described. Building on early studies, emerging data suggests that HIV/ART exposure early in life affects cell metabolic function of HEU children. Prenatal HIV/ART exposure has been associated with dysregulation of mitochondria, including impaired DNA polymerase activity. Furthermore, dysregulation of oxidative phosphorylation (OXPHOS) causes a decreased generation of adenosine triphosphate (ATP) and increased production of reactive oxygen species (ROS), resulting in oxidative stress. These altered metabolic processes can affect immune cell viability and immune responses. Recent studies have indicated that immune-metabolic dysregulation may contribute to HIV-associated pathogenesis and clinical observations associated with HIV and ART exposure in HEU/HEI children. Given the critical role metabolic processes in immune cell functioning, immune-metabolic dysregulation in HEU and HEI children may have implications in effective host-defence responses against pathogens, as well as efficacy of standard ART regimens and future novel HIV cure approaches in HEI children. At the same time, targeting metabolic pathways of immune cells may provide safer and novel approaches for HIV cure strategies. Here, we review the current literature investigating immune-metabolic dysregulation in paediatric HIV pathogenesis.

SIMULATED WEIGHTLESSNESS LED TO THE TRANSFORMATION OF GLYCOLIPID METABOLISM IN THE LIVERS OF MICE

ABSTRACT Objectives: The effects of weightlessness on the liver were studied using a tail suspension (TS) male mouse model. Methods: The effects of 0-, 2- and 4-week TS (CON, TS2 and TS4 groups) on glycogen and lipid content, as well as on the molecular processes of the synthesis and degradation pathways, were examined. Results: (1) The number of glycogenosomes under ultrastructure and the glycogen content were considerably larger in the TS4 group than in the other two groups. (2) In the TS4 group, glycogen synthase activity remained constant while glycogen phosphorylase activity dropped, indicating that glycogen breakdown was reduced. (3) The livers of the TS2 group had the highest lipid and triglyceride content, indicating lipid buildup in the liver at this time. (4) In the TS2 group, the activities of the fatty acid synthesis-related factors acetyl-CoA carboxylase and fatty acid synthase increased, while hepatic lipase decreased, indicating that lipid synthesis increased, while decomposition decreased. (5) In the TS2 group, the protein expression of glucose transporters 1 and 2 increased. Conclusions: From TS2 weeks to TS4 weeks, the main energy consumption mode in the livers of mice transitioned from glucose metabolism to lipid metabolism as glucose use decreased. Level of evidence II; Comparative prospective study.

ANTIGRAVIDADE SIMULADA LEVOU À TRANSFORMAÇÃO DO METABOLISMO DE GLICOLIPÍDIOS NO FÍGADO DE CAMUNDONGOS

RESUMO Objetivos: Os efeitos da antigravidade no fígado foram estudados usando um modelo de camundongo macho com a suspensão pela cauda (TS, tail suspension). Métodos: Foram examinados os efeitos da TS em 0, 2 e 4 semanas (grupos CON, TS2 e TS4) sobre o conteúdo de glicogênio e lipídios, bem como nos processos moleculares das vias de síntese e degradação. Resultados: (1) O número de glicogenossomos ultraestruturais e o teor de glicogênio foram expressivamente maiores no grupo TS4 do que nos outros dois grupos. (2) No grupo TS4, a atividade de glicogênio sintase permaneceu constante, enquanto a atividade de glicogênio fosforilase caiu, indicando que a degradação do glicogênio foi reduzida. (3) Os fígados do grupo TS2 tiveram o maior teor lipídico e de triglicérides, indicando acúmulo de lipídios no fígado no momento. (4) No grupo TS2, a atividade dos fatores relacionados com a síntese de ácidos graxos acetil-CoA carboxilase e ácido graxo sintase aumentaram, enquanto a lipase hepática diminuiu, indicando que a síntese de lipídios aumentou, enquanto a decomposição diminuiu. (5) No grupo TS2, a expressão proteica dos transportadores de glicose 1 e 2 aumentou. Conclusões: De TS2 semanas para TS4 semanas, o principal modo de consumo de energia no fígado de camundongos passou do metabolismo da glicose para o metabolismo lipídico, à medida que o uso de glicose diminuiu. Nível de evidência II, Estudo retrospectivo comparativo.

Mechanical loading attenuated negative effects of nucleotide analogue reverse-transcriptase inhibitor TDF on bone repair via Wnt/β-catenin pathway

The nucleotide analog reverse-transcriptase inhibitor, tenofovir disoproxil fumarate (TDF), is widely used to treat hepatitis B virus (HBV) and human immunodeficiency virus infection (HIV). However, long-term TDF usage is associated with an increased incidence of bone loss, osteoporosis, fractures, and other adverse reactions. We investigated the effect of chronic TDF use on bone homeostasis and defect repair in mice. In vitro, TDF inhibited osteogenic differentiation and mineralization in MC3T3-E1 cells. In vivo, 8-week-old C57BL/6 female mice were treated with TDF for 38 days to simulate chronic medication. Four-point bending test and μCT showed reduced bone biomechanical properties and microarchitecture in long bones. To investigate the effects of TDF on bone defect repair, we utilized a bilateral tibial monocortical defect model. μCT showed that TDF reduced new bone mineral tissue and bone mineral density (BMD) in the defect. To verify whether mechanical stimulation may be a useful treatment to counteract the negative bone effects of TDF, controlled dynamic mechanical loading was applied to the whole tibia during the matrix deposition phase on post-surgery days (PSDs) 5 to 8. Second harmonic generation (SHG) of collagen fibers and μCT showed that the reduction of new bone volume and bone mineral density caused by TDF was reversed by mechanical loading in the defect. Immunofluorescent deep tissue imaging showed that chronic TDF treatment reduced the number of osteogenic cells and the volume of new vessels. In addition, chronic TDF treatment inhibited the expressions of periostin and β-catenin, but increased the expression of sclerostin. Both negative effects were reversed by mechanical loading. Our study provides strong evidence that chronic use of TDF exerts direct and inhibitory impacts on bone repair, but appropriate mechanical loading could reverse these adverse effects.

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).

3D Spheroids of Human Primary Urine-Derived Stem Cells in the Assessment of Drug-Induced Mitochondrial Toxicity

Mitochondrial toxicity (Mito-Tox) risk has increased due to the administration of several classes of drugs, particularly some life-long antiretroviral drugs for HIV+ individuals. However, no suitable in vitro assays are available to test long-term Mito-Tox (≥4 weeks). The goal of this study is to develop a 3D spheroid system of human primary urine-derived stem cells (USC) for the prediction of drug-induced delayed Mito-Tox. The cytotoxicity and Mito-Tox were assessed in 3D USC spheroids 4 weeks after treatment with antiretroviral drugs: zalcitabine (ddC; 0.1, 1 and 10 µM), tenofovir (TFV; 3, 30 and 300 µM) or Raltegravir (RAL; 2, 20 and 200 µM). Rotenone (RTNN, 10 µM) and 0.1% DMSO served as positive and negative controls. Despite only mild cytotoxicity, ddC significantly inhibited the expression of oxidative phosphorylation enzyme Complexes I, III, and IV; and RAL transiently reduced the level of Complex IV. A significant increase in caspase 3 and ROS/RNS level but a decrease in total ATP were observed in USC treated with ddC, TFV, RAL, and RTNN. Levels of mtDNA content and mitochondrial mass were decreased in ddC but minimally or not in TFV- and RAL-treated spheroids. Thus, 3D USC spheroid using antiretroviral drugs as a model offers an alternative platform to assess drug-induced late Mito-Tox.

Tenofovir-induced osteopenia and hyperparathyroidism: A case report and literature review

Tenofovir disoproxil fumarate is the first-line antiviral therapy for chronic viral hepatitis B, but long-term use is associated with renal failure and hypophosphatemic osteomalacia. Tenofovir disoproxil fumarate-induced osteoporosis and secondary hyperparathyroidism are less commonly reported. Herein, we describe the case of a patient with bone and multijoint pain who was initially misdiagnosed as having normocalcemic primary hyperparathyroidism associated with prolonged exposure to tenofovir disoproxil fumarate. The patient's 24-h urinary calcium and phosphorus excretion levels and serum calcium levels were at the lower end of the normal range. After reviewing these findings, the diagnosis was amended to osteoporosis and secondary hyperparathyroidism caused by tenofovir disoproxil fumarate. In this report, we describe the differences in clinical and laboratory manifestations of hyperparathyroidism induced by tenofovir disoproxil fumarate and normocalcemic primary hyperparathyroidism. We also discuss relevant pathophysiological mechanisms and propose a feasible treatment strategy.

Mitochondrial changes associated with viral infectious diseases in the paediatric population

Infectious diseases occur worldwide with great frequency in both adults and children, causing 350,000 deaths in 2017, according to the latest World Health Organization reports. Both infections and their treatments trigger mitochondrial interactions at multiple levels: (i) incorporation of damaged or mutated proteins into the complexes of the electron transport chain; (ii) impact on mitochondrial genome (depletion, deletions and point mutations) and mitochondrial dynamics (fusion and fission); (iii) membrane potential impairment; (iv) apoptotic regulation; and (v) generation of reactive oxygen species, among others. Such alterations may result in serious adverse clinical events with considerable impact on the quality of life of the children and could even cause death. Herein, we use a systematic review to explore the association between mitochondrial alterations in paediatric infections including human immunodeficiency virus, cytomegalovirus, herpes viruses, various forms of hepatitis, adenovirus, T-cell lymphotropic virus and influenza. We analyse how these paediatric viral infectious processes may cause mitochondrial deterioration in this especially vulnerable population, with consideration for the principal aspects of research and diagnosis leading to improved disease understanding, management and surveillance.

The role of metabolic reprogramming in tubular epithelial cells during the progression of acute kidney injury

Acute kidney injury (AKI) is one of the most common clinical syndromes. AKI is associated with significant morbidity and subsequent chronic kidney disease (CKD) development. Thus, it is urgent to develop a strategy to hinder AKI progression. Renal tubules are responsible for the reabsorption and secretion of various solutes and the damage to this part of the nephron is a key mediator of AKI. As we know, many common renal insults primarily target the highly metabolically active proximal tubular cells (PTCs). PTCs are the most energy-demanding cells in the kidney. The ATP that they use is mostly produced in their mitochondria by fatty acid β-oxidation (FAO). But, when PTCs face various biological stresses, FAO will shut down for a time that outlives injury. Recent studies have suggested that surviving PTCs can adapt to FAO disruption by increasing glycolysis when facing metabolic constraints, although PTCs do not perform glycolysis in a normal physiological state. Enhanced glycolysis in a short period compensates for impaired energy production and exerts partial renal-protective effects, but its long-term effect on renal function and AKI progression is not promising. Deranged FAO and enhanced glycolysis may contribute to the AKI to CKD transition through different molecular biological mechanisms. In this review, we concentrate on the recent pathological findings of AKI with regards to the metabolic reprogramming in PTCs, confirming that targeting metabolic reprogramming represents a potentially effective therapeutic strategy for the progression of AKI.

FOSL2 Is Involved in the Regulation of Glycogen Content in Chicken Breast Muscle Tissue

The glycogen content in muscle of livestock and poultry animals affects the homeostasis of their body, growth performance, and meat quality after slaughter. FOS-like 2, AP-1 transcription factor subunit (FOSL2) was identified as a candidate gene related to muscle glycogen (MG) content in chicken in our previous study, but the role of FOSL2 in the regulation of MG content remains to be elucidated. Differential gene expression analysis and weighted gene coexpression network analysis (WGCNA) were performed on differentially expressed genes (DEGs) in breast muscle tissues from the high-MG-content (HMG) group and low-MG-content (LMG) group of Jingxing yellow chickens. Analysis of the 1,171 DEGs (LMG vs. HMG) identified, besides FOSL2, some additional genes related to MG metabolism pathway, namely PRKAG3, CEBPB, FOXO1, AMPK, and PIK3CB. Additionally, WGCNA revealed that FOSL2, CEBPB, MAP3K14, SLC2A14, PPP2CA, SLC38A2, PPP2R5E, and other genes related to the classical glycogen metabolism in the same coexpressed module are associated with MG content. Also, besides finding that FOSL2 expression is negatively correlated with MG content, a possible interaction between FOSL2 and CEBPB was predicted using the STRING (Search Tool for the Retrieval of Interacting Genes) database. Furthermore, we investigated the effects of lentiviral overexpression of FOSL2 on the regulation of the glycogen content in vitro, and the result indicated that FOSL2 decreases the glycogen content in DF1 cells. Collectively, our results confirm that FOSL2 has a key role in the regulation of the MG content in chicken. This finding is helpful to understand the mechanism of MG metabolism regulation in chicken and provides a new perspective for the production of high-quality broiler and the development of a comprehensive nutritional control strategy.

Mitochondrial quality control in kidney injury and repair

Mitochondria are essential for the activity, function and viability of eukaryotic cells and mitochondrial dysfunction is involved in the pathogenesis of acute kidney injury (AKI) and chronic kidney disease, as well as in abnormal kidney repair after AKI. Multiple quality control mechanisms, including antioxidant defence, protein quality control, mitochondrial DNA repair, mitochondrial dynamics, mitophagy and mitochondrial biogenesis, have evolved to preserve mitochondrial homeostasis under physiological and pathological conditions. Loss of these mechanisms may induce mitochondrial damage and dysfunction, leading to cell death, tissue injury and, potentially, organ failure. Accumulating evidence suggests a role of disturbances in mitochondrial quality control in the pathogenesis of AKI, incomplete or maladaptive kidney repair and chronic kidney disease. Moreover, specific interventions that target mitochondrial quality control mechanisms to preserve and restore mitochondrial function have emerged as promising therapeutic strategies to prevent and treat kidney injury and accelerate kidney repair. However, clinical translation of these findings is challenging owing to potential adverse effects, unclear mechanisms of action and a lack of knowledge of the specific roles and regulation of mitochondrial quality control mechanisms in kidney resident and circulating cell types during injury and repair of the kidney.

Up-Regulation of Glycogen Synthesis and Degradation Enzyme Level Maintained Myocardial Glycogen in Huddling Brandt's Voles Under Cool Environments

Small mammals exhibit limited glucose use and glycogen accumulation during hypothermia. Huddling is a highly evolved cooperative behavioral strategy in social mammals, allowing adaptation to environmental cooling. However, it is not clear whether this behavior affects the utilization of glycogen in cold environments. Here, we studied the effects of huddling on myocardial glycogen content in Brandt’s voles (Lasiopodomys brandtii) under a mild cold environment (15°C). Results showed that (1) Compared to the control (22°C) group (CON), the number of glycogenosomes more than tripled in the cool separated group (CS) in both males and females; whereas the number of glycogenosomes increased in females but was maintained in males in the cool huddling group (CH). (2) Glycogen synthase (GS) activity in the CS group remained unchanged, whereas glycogen phosphorylase (GYPL) activity decreased, which mediated the accumulation of glycogen content of the CS group. (3) Both GS and GYPL activity increased which may contribute to the stability of glycogen content in CH group. (4) The expression levels of glucose transporters GLUT1 and GLUT4 increased in the CS group, accompanied by an increase in glucose metabolism. These results indicate that the reduced glycogen degradation enzyme level and enhanced glucose transport may lead to an increase in myocardial glycogen content of the separated voles under cool environment; while the up-regulation of glycogen synthesis and degradation enzyme level maintained myocardial glycogen content in the huddling vole.

Dysfunctional Immunometabolism in HIV Infection: Contributing Factors and Implications for Age-Related Comorbid Diseases

PURPOSE OF REVIEW

An increasing body of evidence indicates that persons living with HIV (PLWH) display dysfunctional immunometabolism. Here, we provide an updated review of this topic and its relationship to HIV-associated immune stimuli and age-related disease.

RECENT FINDINGS

HIV infection alters immunometabolism by increasing reliance on aerobic glycolysis for energy and productive infection and repurposing oxidative phosphorylation machinery for immune cell proliferation and survival. Recent studies in PLWH with diabetes mellitus or cardiovascular disease have identified an association with elevated T cell and monocyte glucose metabolism, respectively. Immunometabolic dysfunction has also been observed in PLWH in frailty and additional studies suggest a role for immunometabolism in non-AIDS defining cancers and neurocognitive disease. There is a plethora of HIV-associated immune stimuli that could drive immunometabolic dysfunction and age-related disease in PLWH, but studies directly examining their relationship are lacking. Immunometabolic dysfunction is characteristic of HIV infection and is a potential link between HIV-associated stimuli and age-related comorbidities.

Gastrin Attenuates Renal Ischemia/Reperfusion Injury by a PI3K/Akt/Bad-Mediated Anti-apoptosis Signaling

Ischemic/reperfusion (I/R) injury is the primary cause of acute kidney injury (AKI). Gastrin, a gastrointestinal hormone, is involved in the regulation of kidney function of sodium excretion. However, whether gastrin has an effect on kidney I/R injury is unknown. Here we show that cholecystokinin B receptor (CCKBR), the gastrin receptor, was significantly up-regulated in I/R-injured mouse kidneys. While pre-administration of gastrin ameliorated I/R-induced renal pathological damage, as reflected by the levels of serum creatinine and blood urea nitrogen, hematoxylin and eosin staining and periodic acid-Schiff staining. The protective effect could be ascribed to the reduced apoptosis for gastrin reduced tubular cell apoptosis both in vivo and in vitro. In vitro studies also showed gastrin preserved the viability of hypoxia/reoxygenation (H/R)-treated human kidney 2 (HK-2) cells and reduced the lactate dehydrogenase release, which were blocked by CI-988, a specific CCKBR antagonist. Mechanistically, the PI3K/Akt/Bad pathway participates in the pathological process, because gastrin treatment increased phosphorylation of PI3K, Akt and Bad. While in the presence of wortmannin (1 μM), a PI3K inhibitor, the gastrin-induced phosphorylation of Akt after H/R treatment was blocked. Additionally, wortmannin and Akt inhibitor VIII blocked the protective effect of gastrin on viability of HK-2 cells subjected to H/R treatment. These studies reveals that gastrin attenuates kidney I/R injury via a PI3K/Akt/Bad-mediated anti-apoptosis signaling. Thus, gastrin can be considered as a promising drug candidate to prevent AKI.

Tenofovir alafenamide does not inhibit mitochondrial function and cholesterol biosynthesis in human T lymphoblastoid cell line

In clinical trials, the concentration of tenofovir diphosphate (TFV-DP) in peripheral mononuclear cells was 4 to 5-fold higher in individuals treated with tenofovir alafenamide (TAF) compared to individuals treated with tenofovir disoproxil fumarate (TDF). We hypothesized that the higher intracellular accumulation of TFV-DP could cause mitochondrial toxicity from either polymerase gamma (Pol-γ)-dependent or Pol-γ-independent mechanism(s). To test this hypothesis, we cultured human T lymphoblastoid cell line (CEM cells) for up to 12 days with TAF or TDF (multiplicities of C_max) to investigate the effects on mitochondrial function and respiration, and cholesterol biosynthesis. Both TAF and TDF treatments had no significant effect on cell growth, mitochondrial potential (ΔΨ), production of reactive oxygen species (ROS), and mitochondrial respiratory parameters. TAF had no statistically significant effect on expression of Pol-γ mRNA, mitochondria DNA (mtDNA) content, expression of proteins of the electron transport chain (ETC), and key genes of cholesterol biosynthesis. TDF had significant reduction in mtDNA content at 8xC_max, and statistically significant reduction in mRNA expression of squalene epoxidase (SQLE). Our findings do not support our hypothesis that the higher intracellular accumulation of TFV-DP in cells treated with TAF could cause mitochondrial dysfunction. In conclusion, our findings add to the emerging data that TAF may have a low potential for causing mitochondrial toxicity in HIV-infected individuals on TAF-containing regimens.

Immunometabolism and HIV-1 pathogenesis: food for thought

Antiretroviral therapies efficiently block HIV-1 replication but need to be maintained for life. Moreover, chronic inflammation is a hallmark of HIV-1 infection that persists despite treatment. There is, therefore, an urgent need to better understand the mechanisms driving HIV-1 pathogenesis and to identify new targets for therapeutic intervention. In the past few years, the decisive role of cellular metabolism in the fate and activity of immune cells has been uncovered, as well as its impact on the outcome of infectious diseases. Emerging evidence suggests that immunometabolism has a key role in HIV-1 pathogenesis. The metabolic pathways of CD4⁺ T cells and macrophages determine their susceptibility to infection, the persistence of infected cells and the establishment of latency. Immunometabolism also shapes immune responses against HIV-1, and cell metabolic products are key drivers of inflammation during infection. In this Review, we summarize current knowledge of the links between HIV-1 infection and immunometabolism, and we discuss the potential opportunities and challenges for therapeutic interventions.

Identifying the role of PrimPol in TDF-induced toxicity and implications of its loss of function mutation in an HIV+ patient

A key component of antiretroviral therapy (ART) for HIV patients is the nucleoside reverse transcriptase inhibitor (NRTI) is tenofovir. Recent reports of tenofovir toxicity in patients taking ART for HIV cannot be explained solely on the basis of off-target inhibition of mitochondrial DNA polymerase gamma (Polγ). PrimPol was discovered as a primase-polymerase localized to the mitochondria with repriming and translesion synthesis capabilities and, therefore, a potential contributor to mitochondrial toxicity. We established a possible role of PrimPol in tenofovir-induced toxicity in vitro and show that tenofovir-diphosphate incorporation by PrimPol is dependent on the n-1 nucleotide. We identified and characterized a PrimPol mutation, D114N, in an HIV+ patient on tenofovir-based ART with mitochondrial toxicity. This mutant form of PrimPol, targeting a catalytic metal ligand, was unable to synthesize primers, likely due to protein instability and weakened DNA binding. We performed cellular respiration and toxicity assays using PrimPol overexpression and shRNA knockdown strains in renal proximal tubular epithelial cells. The PrimPol-knockdown strain was hypersensitive to tenofovir treatment, indicating that PrimPol protects against tenofovir-induced mitochondrial toxicity. We show that a major cellular role of PrimPol is protecting against toxicity caused by ART and individuals with inactivating mutations may be predisposed to these effects.

A Non-Targeted Capillary Electrophoresis-Mass Spectrometry Strategy to Study Metabolic Differences in an In vitro Model of High-Glucose Induced Changes in Human Proximal Tubular HK-2 Cells

Diabetic nephropathy is characterized by the chronic loss of kidney function due to high glucose renal levels. HK-2 proximal tubular cells are good candidates to study this disease. The aim of this work was to study an in vitro model of high glucose-induced metabolic alterations in HK-2 cells to contribute to the pathogenesis of this diabetic complication. An untargeted metabolomics strategy based on CE-MS was developed to find metabolites affected under high glucose conditions. Intracellular and extracellular fluids from HK-2 cells treated with 25 mM glucose (high glucose group), with 5.5 mM glucose (normal glucose group), and with 5.5 mM glucose and 19.5 mM mannitol (osmotic control group) were analyzed. The main changes induced by high glucose were found in the extracellular medium where increased levels of four amino acids were detected. Three of them (alanine, proline, and glutamic acid) were exported from HK-2 cells to the extracellular medium. Other affected metabolites include Amadori products and cysteine, which are more likely cause and consequence, respectively, of the oxidative stress induced by high glucose in HK-2 cells. The developed CE-MS platform provides valuable insight into high glucose-induced metabolic alterations in proximal tubular cells and allows identifying discriminative molecules of diabetic nephropathy.

Synthesis, pharmacological evaluation, and mechanistic study of adefovir mixed phosphonate derivatives bearing cholic acid and l-amino acid moieties for the treatment of HBV

The deficiency of nucleos(t)ide analogues (NAs) as anti-hepatitis B virus (HBV) drugs in clinical use is attributable to their insufficient enrichment in liver and non-target organ toxicity. We aimed to develop potent anti-HBV adefovir derivatives with hepatotrophic properties and reduced nephrotoxicity. A series of adefovir mono l-amino acids, mono cholic acid-drug conjugates were designed and synthesized, and their antiviral activity and uptake in rat primary hepatocytes and Na⁺-dependent taurocholate co-transporting polypeptide (NTCP)-HEK293 cells were evaluated. We isolated compound 6c as the optimal molecular candidate, with the highest antiviral activity (EC₅₀ 0.42 μmol/L, SI 1063.07) and highest cellular uptake in primary hepatocytes and NTCP-HEK293 cells. In-depth mechanistic studies demonstrated that 6c exhibited a lower toxicity in HK-2 cells when compared to adefovir dipivoxil (ADV). This is because 6c cannot be transported by the human renal organic anion transporter 1 (hOAT1). Furthermore, pharmacokinetic characterization and tissue distribution of 6c indicates it has favorable druggability and pharmacokinetic properties. Further docking studies suggested compounds with ursodeoxycholic acid and l-amino acid groups are better at binding to NTCP due to their hydrophilic properties, indicating that 6c is a potential candidate as an anti-HBV therapy and therefore merits further investigation.

An untargeted metabolomic strategy based on liquid chromatography-mass spectrometry to study high glucose-induced changes in HK-2 cells

Diabetes mellitus is a major health concern nowadays. It is estimated that 40% of diabetics are affected by diabetic nephropathy, one of the complications derived from high glucose blood levels which can lead to chronic loss of kidney function. It is now clear that the renal proximal tubule plays a critical role in the progression of diabetic nephropathy but research focused on studying the molecular mechanisms involved is still needed. The aim of this work was to develop a liquid chromatography-mass spectrometry platform to carry out, for the first time, the untargeted metabolomic analysis of high glucose-induced changes in cultured human proximal tubular HK-2 cells. In order to find the metabolites which were affected by high glucose and to expand the metabolite coverage, intra- and extracellular fluid from HK-2 cells exposed to high glucose (25 mM), normal glucose (5.5 mM) or osmotic control (5.5 mM glucose +19.5 mM mannitol) were analyzed by two complementary chromatographic modes: hydrophilic interaction and reversed-phase liquid chromatography. Non-supervised principal components analysis showed a good separation among the three groups of samples. Statistically significant variables were chosen for further metabolite identification. Different metabolic pathways were affected mainly those derived from amino acidic, polyol, and nitrogenous bases metabolism.

Organic cation transporter 3 (Oct3) is a distinct catecholamines clearance route in adipocytes mediating the beiging of white adipose tissue

Beiging of white adipose tissue (WAT) is a particularly appealing target for therapeutics in the treatment of metabolic diseases through norepinephrine (NE)-mediated signaling pathways. Although previous studies report NE clearance mechanisms via SLC6A2 on sympathetic neurons or proinflammatory macrophages in adipose tissues (ATs), the low catecholamine clearance capacity of SLC6A2 may limit the cleaning efficiency. Here, we report that mouse organic cation transporter 3 (Oct3; Slc22a3) is highly expressed in WAT and displays the greatest uptake rate of NE as a selective non-neural route of NE clearance in white adipocytes, which differs from other known routes such as adjacent neurons or macrophages. We further show that adipocytes express high levels of NE degradation enzymes Maoa, Maob, and Comt, providing the molecular basis on NE clearance by adipocytes together with its reuptake transporter Oct3. Under NE administration, ablation of Oct3 induces higher body temperature, thermogenesis, and lipolysis compared with littermate controls. After prolonged cold challenge, inguinal WAT (ingWAT) in adipose-specific Oct3-deficient mice shows much stronger browning characteristics and significantly elevated expression of thermogenic and mitochondrial biogenesis genes than in littermate controls, and this response involves enhanced β-adrenergic receptor (β-AR)/protein kinase A (PKA)/cyclic adenosine monophosphate (cAMP)-responsive element binding protein (Creb) pathway activation. Glycolytic genes are reprogrammed to significantly higher levels to compensate for the loss of ATP production in adipose-specific Oct3 knockout (KO) mice, indicating the fundamental role of glucose metabolism during beiging. Inhibition of β-AR largely abolishes the higher lipolytic and thermogenic activities in Oct3-deficient ingWAT, indicating the NE overload in the vicinity of adipocytes in Oct3 KO adipocytes. Of note, reduced functional alleles in human OCT3 are also identified to be associated with increased basal metabolic rate (BMR). Collectively, our results demonstrate that Oct3 governs β-AR activity as a NE recycling transporter in white adipocytes, offering potential therapeutic applications for metabolic disorders.

Tenofovir disoproxil fumarate induces pheochromocytoma cells apoptosis

Despite the triumph of highly active antiretroviral therapy (HAART) in anti-HIV infection, more than half of the HIV infection individuals receiving antiretroviral therapy acquire HIV-associated neurocognitive disorder (HAND). Previously researches had reported that the HAART neurotoxicity is implicated in HAND-related morbidity. The molecular mechanism of HAND is not clear. Tenofovir disoproxil fumarate (TDF) is a novel nucleotide reverse transcriptase inhibitor (NRTI), which was recommended as first-line therapeutic schedule for free AIDS antiviral drugs. Whether the neurotoxicity of TDF is associated with HAND is not well known. In this study, the cell viability of TDF-treated pheochromocytoma cells (PC-12) line was detected using MTT assay, while apoptosis was evaluated by Hoechst 33342 staining, TUNEL assay, as well as flow cytometry. In addition, the level of reactive oxygen species and BAX protein expression were evaluated using DCFH-DA staining and western blotting. The results showed that the proliferation of PC-12 cells was significantly inhibited by TDF. The morphological assay, TUNEL assay and flow cytometry showed that TDF efficiently triggered apoptosis in PC-12 cells. The reactive oxygen species levels were BAX expression was markedly up-regulated in PC-12 cells after treatment with TDF. These findings indicated that TDF may induce PC-12 cell apoptosis. TDF has neural toxicity effect that is relevant to the cell apoptosis, which may be related to the increasing prevalence of HAND.

Zoledronate dysregulates fatty acid metabolism in renal tubular epithelial cells to induce nephrotoxicity

Zoledronate is a bisphosphonate that is widely used in the treatment of metabolic bone diseases. However, zoledronate induces significant nephrotoxicity associated with acute tubular necrosis and renal fibrosis when administered intravenously. There is speculation that zoledronate-induced nephrotoxicity may result from its pharmacological activity as an inhibitor of the mevalonate pathway but the molecular mechanisms are not fully understood. In this report, human proximal tubular HK-2 cells and mouse models were combined to dissect the molecular pathways underlying nephropathy caused by zoledronate treatments. Metabolomic and proteomic assays revealed that multiple cellular processes were significantly disrupted, including the TGFβ pathway, fatty acid metabolism and small GTPase signaling in zoledronate-treated HK-2 cells (50 μM) as compared with those in controls. Zoledronate treatments in cells (50 μM) and mice (3 mg/kg) increased TGFβ/Smad3 pathway activation to induce fibrosis and kidney injury, and specifically elevated lipid accumulation and expression of fibrotic proteins. Conversely, fatty acid transport protein Slc27a2 deficiency or co-administration of PPARA agonist fenofibrate (20 mg/kg) prevented zoledronate-induced lipid accumulation and kidney fibrosis in mice, indicating that over-expression of fatty acid transporter SLC27A2 and defective fatty acid β-oxidation following zoledronate treatments were significant factors contributing to its nephrotoxicity. These pharmacological and genetic studies provide an important mechanistic insight into zoledronate-associated kidney toxicity that will aid in development of therapeutic prevention and treatment options for this nephropathy.