Integrated transcriptomic landscape of the effect of anti-steatotic treatments in high-fat diet mouse models of non-alcoholic fatty liver disease

High-fat diet (HFD) mouse models are widely used in research to develop medications to treat non-alcoholic fatty liver disease (NAFLD), as they mimic the steatosis, inflammation, and hepatic fibrosis typically found in this complex human disease. The aims of this study were to identify a complete transcriptomic signature of these mouse models and to characterize the transcriptional impact exerted by different experimental anti-steatotic treatments. For this reason, we conducted a systematic review and meta-analysis of liver transcriptomic studies performed in HFD-fed C57BL/6J mice, comparing them with control mice and HFD-fed mice receiving potential anti-steatotic treatments. Analyzing 21 studies broaching 24 different treatments, we obtained a robust HFD transcriptomic signature that included 2,670 differentially expressed genes and 2,567 modified gene ontology biological processes. Treated HFD mice generally showed a reversion of this HFD signature, although the extent varied depending on the treatment. The biological processes most frequently reversed were those related to lipid metabolism, response to stress, and immune system, whereas processes related to nitrogen compound metabolism were generally not reversed. When comparing this HFD signature with a signature of human NAFLD progression, we identified 62 genes that were common to both; 10 belonged to the group that were reversed by treatments. Altered expression of most of these 10 genes was confirmed in vitro in hepatocytes and hepatic stellate cells exposed to a lipotoxic or a profibrogenic stimulus, respectively. In conclusion, this study provides a vast amount of information about transcriptomic changes induced during the progression and regression of NAFLD and identifies some relevant targets. Our results may help in the assessment of treatment efficacy, the discovery of unmet therapeutic targets, and the search for novel biomarkers. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Resistance to apoptosis in complicated Crohn's disease: Relevance in ileal fibrosis

BACKGROUND AND AIMS

The stiffening of the extracellular matrix, and changes in its cellular and molecular composition, have been reported in the pathogenesis of fibrosis. We analyze the mechanisms that perpetuate ileal fibrosis in surgical resections of complicated Crohn's disease patients.

METHODS

Ileal resections were obtained from affected and non-affected tissue of stenotic or penetrating Crohn's disease behavior. Ilea from non-IBD patients were used as control tissue. All samples underwent RNA sequencing. Human small intestinal fibroblasts were treated for 48 h with IL-1β, TFGβ1, PDGFB or TNF-α. Resistance to apoptosis was analysed by RT-PCR, western blot and immunohistochemistry in ileal tissue and by RT-PCR and FACS in cultured cells.

RESULTS

Growth factor-driven signaling pathways and increased RAS GTPase activity were up-regulated in affected ilea in which we found expression of both the antiapoptotic molecule MCL1 and the transcription factor ETS1 in submucosal fibroblasts, and a senescence-associated secretory phenotype. In cultured intestinal fibroblasts, PDGFB induced an ETS1-mediated resistance to apoptosis that was associated with the induction of both of TGFB1 and IL1B, a cytokine that replicated the expression of SASP detected in ileal tissue. ETS1 drove fibroblast polarization between inflammatory and fibrogenic phenotypes in IL1β-treated cells.

CONCLUSIONS

Our data show resistance to apoptosis in complicated ileal CD, and demonstrate that PDGFB induce an ETS1-mediated resistance to apoptosis associated with an inflammatory and fibrogenic pattern of expression in intestinal fibroblasts. Results point to PDGFRB, IL1R1 or MCL1 as potential targets against ileal fibrosis.

Benefits of rilpivirine for liver stiffness in HIV/HCV-coinfected patients

BACKGROUND

Rilpivirine (RPV) is an antiretroviral drug characterized by good tolerability and a favorable liver safety profile. Recent research has shown that RPV ameliorates liver fibrosis in animal models of various chronic liver diseases. Our study aimed to analyze the effect of RPV on liver fibrosis by assessing changes in liver stiffness using transient elastography.

METHODS

Retrospective cohort study of HIV-infected patients who were exposed and not exposed to RPV. The change in liver stiffness during the period between two transient elastography measurements was analyzed and compared for patients exposed and not exposed to RPV.

RESULTS

We selected 118 RPV-exposed and 118 non-RPV-exposed HIV-infected patients. Median time between transient elastography (TE) measurements was 50 (29-68) months. A repeated-measures general linear model based on the main clinical characteristics revealed a significant decrease in the TE value of -0.8kPa in non-RPV-exposed patients (p=0.254) and -1.6kPa in the RPV-exposed group (p<0.001). The subgroup analysis showed a significant reduction in the TE value only patients cured of hepatitis C (RPV-exposed, -2.8kPa [p<0.001]; non-RPV-exposed, -1.1kPa [p=0.22]).

CONCLUSION

RPV-based antiretroviral regimens significantly reduced liver stiffness, as measured by TE, in patients cured of chronic hepatitis C.

Anti-inflammatory and immunomodulating effects of rilpivirine: Relevance for the therapeutics of chronic liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease (CLD) worldwide and inflammation is key to its progression/resolution. As we have previously described that rilpivirine (RPV) is hepatoprotective in murine models of CLD, here we determine the molecular mechanisms involved, focusing on its anti-inflammatory and immunomodulating properties. They were evaluated in vitro (human hepatic cell lines of the major hepatic cell types), in vivo (liver samples from a murine nutritional model of NAFLD) and ex vivo (peripheral blood mononuclear cells -PBMC- from patients with CLD). Transcriptomic analysis of liver samples from NAFLD mice showed RPV down-regulated biological processes associated with the inflammatory response (NF-κB/IκB signaling and mitogen-activated protein kinase -MAPK- activity) and leukocyte chemotaxis and migration. We observed a decrease in Adgre1 and Ccr2 expression and in the number of CCR2 + cells in the periportal areas of RPV-treated NAFLD mice. This RPV-induced effect on the CCL2/CCR2 axis was confirmed in vitro. A similar result was also obtained with CXCL10/IP10, one of the main chemokines in the liver. RPV also diminished activation of MAP kinases p38 and JNK. In addition, RPV inhibited the NLRP3 inflammasome pathway in vitro, decreasing NLRP3 protein expression, caspase-1 activation and IL-1β gene expression. RPV was also proven anti-inflammatory in PBMC from patients with CLD treated ex vivo. In conclusion, beyond its well-described role in antiretroviral therapy, RPV manifests anti-inflammatory and immunoregulatory effects, a finding that could be of great relevance for the search of novel targets or repositioning strategies for CLD.

Abacavir causes leukocyte/platelet crosstalk by activating neutrophil P2X7 receptors thus releasing soluble lectin-like oxidized low-density lipoprotein receptor-1

BACKGROUND AND PURPOSE

Abacavir, an antiretroviral drug used in HIV therapy associated with myocardial infarction, promotes thrombosis through P2X7 receptors. The role of platelets as pro-thrombotic cells is acknowledged whereas that of neutrophils-due to their secretory capacity-is gaining recognition. This study analyses the role of neutrophils-specifically the secretome of abacavir-treated neutrophils (SN_ABC )-in platelet activation that precedes thrombosis.

EXPERIMENTAL APPROACH

Effects of abacavir or SN_ABC on platelet activation and platelet-leukocyte interactions and expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) were analysed by flow cytometry. The secretome was analysed by proteomics. The role of leukocytes in the actions of abacavir was evaluated in a mouse model of thrombosis.

KEY RESULTS

Abacavir induced platelet-leukocyte interactions, not directly via effects of abacavir on platelets, but via activation of neutrophils, which triggered interactions between platelet P-selectin and neutrophil P-selectin glycoprotein ligand-1 (PSGL-1). SN_ABC stimulated platelet activation and platelet-leukocyte interactions through a process that was dependent on LOX-1, neutrophil P2X7 and platelet P2Y1, P2Y12 and P2X1 receptors. Abacavir induced the expression of LOX-1 on neutrophils and of the soluble form of LOX-1 (sLOX-1) in SN_ABC . Neutrophils, LOX-1, P2X7, P2Y1, P2Y12 and P2X1 receptors were required for the pro-thrombotic actions of abacavir in vivo.

CONCLUSION AND IMPLICATIONS

Neutrophils are target cells in abacavir-induced thrombosis. Abacavir released sLOX-1 from neutrophils via activation of their P2X7 receptors, which in turn activated platelets. Hence, sLOX-1 could be the missing link in the cardiovascular risk associated with abacavir.

Implication of autophagy in the antifibrogenic effect of Rilpivirine: when more is less

As the main extracellular matrix-producing cells, activated hepatic stellate cells (HSC) are fundamental mediators of liver fibrosis (LF), and understanding their activation/inactivation mechanisms is paramount to the search for novel therapeutics. The antiretroviral drug Rilpivirine (RPV) has demonstrated a hepatoprotective effect in several animal models of chronic liver injury that is related to its antifibrogenic and apoptotic action in HSC. In the present study, we evaluated whether autophagy is implicated in the hepatoprotective action of RPV, as autophagy plays an important role in HSC transdifferentiation. We employed two standard mouse models of chronic liver injury - fatty liver disease and carbon tetrachloride (CCl₄)-induced hepatotoxicity -and cultured HSC activated with the profibrotic cytokine TGF-β. RPV enhanced autophagy in the whole liver of both mouse models and in activated HSC, evident in the protein expression of autophagy markers, increased autophagosome content and lysosomal mass. Moreover, increased autophagic flux was observed in RPV-exposed HSC as revealed by tandem fluorescence-tagged LC3 and p62 and analysis of LC3-II accumulation in cells exposed to the lysosomal inhibitor chloroquine. Importantly, autophagy was involved in the cytotoxic effect of RPV on HSC, though in a differential manner. Pharmacological inhibition of autophagy by 3-methyladenine (3-MA) did not affect the diminishing effect of RPV on viability, while treatment with wortmannin or depletion of specific autophagy proteins (ATG5, Beclin-1 and SQSTM1/p62) rescued the detrimental effect of high concentrations of RPV on the viability of activated HSC. Finally, we also provide evidence that RPV compromises the viability of TGF-β-induced HSC independently of its antifibrogenic effect, observed as reduced collagen 1A1 synthesis, and that this effect does not include RPV´s modulation of autophagy. In summary, as a contributor to the mechanisms involved in the hepatoprotective action of RPV, autophagy may be a good candidate to explore when developing novel therapeutics for LF.

Down-Regulation of the Longevity-Associated Protein SIRT1 in Peripheral Blood Mononuclear Cells of Treated HIV Patients

The activity of sirtuin 1 (SIRT1), a class III histone deacetylase with a critical role in several biological functions, decreases with age and its deficiency is associated with many inflammatory and age-related diseases. It also regulates the chronic immune activation and viral latency during an HIV infection. The life-span and particularly the health span of HIV patients are substantially shortened; however, the participation of SIRT1 in these effects is not clear. We performed a prospective cross-sectional monocentric study that included 70 HIV-infected patients and 43 BMI-, age- and sex-matched uninfected individuals. We found that in the PBMCs of the HIV patients, SIRT1 mRNA levels were significantly lower (p < 0.0001). This decrease, which was corroborated at the protein level, occurred irrespectively of the antiretroviral regimen these patients received and was not significantly related to the general, HIV-related or comorbidity-related parameters. The levels of the major mitochondrial sirtuin SIRT3 were not altered. Moreover, the strong correlations of SIRT1 with the leukocyte markers CD8A and CD19 present in the uninfected individuals were absent in the HIV patients. In conclusion, this study showed that the PBMCs of the HIV patients displayed diminished SIRT1 levels and altered correlations of SIRT1 with markers of CD8⁺ T cells and B cells, findings which may be relevant for understanding the complex pathogenic milieu in HIV patients.

Macrophages Modulate Hepatic Injury Involving NLRP3 Inflammasome: The Example of Efavirenz

Drug-induced liver injury (DILI) constitutes a clinical challenge due to the incomplete characterization of the mechanisms involved and potential risk factors. Efavirenz, an anti-HIV drug, induces deleterious actions in hepatocytes that could underlie induction of the NLRP3 inflammasome, an important regulator of inflammatory responses during liver injury. We assessed the potential of efavirenz to modulate the inflammatory and fibrogenic responses of major liver cell types involved in DILI. The effects of efavirenz were evaluated both in vitro and in vivo. Efavirenz triggered inflammation in hepatocytes, in a process that involved NF-κB and the NLRP3 inflammasome, and activated hepatic stellate cells (HSCs), thereby enhancing expression of inflammatory and fibrogenic markers. The NLRP3 inflammasome was not altered in efavirenz-treated macrophages, but these cells polarized towards the anti-inflammatory M2 phenotype and displayed upregulated anti-inflammatory mediators. Conversely, no evidence of damage was observed in efavirenz-treated animals, except when macrophages were depleted, which resulted in the in vivo manifestation of the deleterious effects detected in hepatocytes and HSCs. Efavirenz elicits a cell-specific activation of the NLRP3 inflammasome in hepatocytes and HSCs, but macrophages appear to counteract efavirenz-induced liver injury. Our results highlight the dynamic nature of the interaction among liver cell populations and emphasize the potential of targeting macrophage polarization as a strategy to treat NLRP3 inflammasome-induced liver injury.

NNRTI and Liver Damage: Evidence of Their Association and the Mechanisms Involved

Due to the improved effectiveness and safety of combined antiretroviral therapy, human immunodeficiency virus (HIV) infection has become a manageable, chronic condition rather than a mortal disease. However, HIV patients are at increased risk of experiencing non-AIDS-defining illnesses, with liver-related injury standing out as one of the leading causes of death among these patients. In addition to more HIV-specific processes, such as antiretroviral drug-related toxicity and direct injury to the liver by the virus itself, its pathogenesis is related to conditions that are also common in the general population, such as alcoholic and non-alcoholic fatty liver disease, viral hepatitis, and ageing. Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are essential components of combined anti-HIV treatment due to their unique antiviral activity, high specificity, and acceptable toxicity. While first-generation NNRTIs (nevirapine and efavirenz) have been related largely to liver toxicity, those belonging to the second generation (etravirine, rilpivirine and doravirine) seem to be generally safe for the liver. Indeed, there is preclinical evidence of rilpivirine being hepatoprotective in different models of liver injury, independently of the presence of HIV. The present study aims to review the mechanisms by which currently available anti-HIV drugs belonging to the NNRTI family may participate in the development of liver disease.

Understanding the implication of autophagy in the activation of hepatic stellate cells in liver fibrosis: are we there yet?

Liver fibrosis (LF) occurs as a result of persistent liver injury and can be defined as a pathologic, chronic, wound-healing process in which functional parenchyma is progressively replaced by fibrotic tissue. As a phenomenon involved in the majority of chronic liver diseases, and therefore prevalent, it exerts a significant impact on public health. This impact becomes even more patent given the lack of a specific pharmacological therapy, with LF only being ameliorated or prevented through the use of agents that alleviate the underlying causes. Hepatic stellate cells (HSCs) are fundamental mediators of LF, which, activated in response to pro-fibrotic stimuli, transdifferentiate from a quiescent phenotype into myofibroblasts that deposit large amounts of fibrotic tissue and mediate pro-inflammatory effects. In recent years, much effort has been devoted to understanding the mechanisms through which HSCs are activated or inactivated. Using cell culture and/or different animal models, numerous studies have shown that autophagy is enhanced during the fibrogenic process and have provided specific evidence to pinpoint the fundamental role of autophagy in HSC activation. This effect involves - though may not be limited to - the autophagic degradation of lipid droplets. Several hepatoprotective agents have been shown to reverse the autophagic alteration present in LF, but clinical confirmation of these effects is pending. On the other hand, there is evidence that implicates autophagy in several anti-fibrotic mechanisms in HSCs that stimulate HSC cell cycle arrest and cell death or prevent the generation of pro-fibrotic mediators, including excess collagen accumulation. The objective of this review is to offer a comprehensive analysis of published evidence of the role of autophagy in HSC activation and to provide hints for possible therapeutic targets for the treatment and/or prevention of LF related to autophagy. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Abacavir Increases Purinergic P2X7 Receptor Activation by ATP: Does a Pro-inflammatory Synergism Underlie Its Cardiovascular Toxicity?

The cardiovascular toxicity of Abacavir is related to its purinergic structure. Purinergic P2X7-receptors (P2X7R), characterized by activation by high concentrations of ATP and with high plasticity, seem implicated. We appraise the nature of the interplay between Abacavir and P2X7R in generating vascular inflammation. The effects of Abacavir on leukocyte-endothelium interactions were compared with those of its metabolite carbovir triphosphate (CBV-TP) or ATP in the presence of apyrase (ATP-ase) or A804598 (P2X7R-antagonist). CBV-TP and ATP levels were evaluated by HPLC, while binding of Abacavir, CBV-TP and ATP to P2X7R was assessed by radioligand and docking studies. Hypersensitivity studies explored a potential allosteric action of Abacavir. Clinical concentrations of Abacavir (20 µmol/L) induced leukocyte-endothelial cell interactions by specifically activating P2X7R, but the drug did not show affinity for the P2X7R ATP-binding site (site 1). CBV-TP levels were undetectable in Abacavir-treated cells, while those of ATP were unaltered. The effects of Abacavir were Apyrase-dependent, implying dependence on endogenous ATP. Exogenous ATP induced a profile of proinflammatory actions similar to Abacavir, but was not entirely P2X7R-dependent. Docking calculations suggested ATP-binding to sites 1 and 2, and Abacavir-binding only to allosteric site 2. A combination of concentrations of Abacavir (1 µmol/L) and ATP (0.1 µmol/L) that had no effect when administered separately induced leukocyte-endothelium interactions mediated by P2X7R and involving Connexin43 channels. Therefore, Abacavir acts as a positive allosteric modulator of P2X7R, turning low concentrations of endogenous ATP themselves incapable of stimulating P2X7R into a functional proinflammatory agonist of the receptor.

Apoptosis of Hepatocytes: Relevance for HIV-Infected Patients under Treatment

Due to medical advances over the past few decades, human immunodeficiency virus (HIV) infection, once a devastatingly mortal pandemic, has become a manageable chronic condition. However, available antiretroviral treatments (cART) cannot fully restore immune health and, consequently, a number of inflammation-associated and/or immunodeficiency complications have manifested themselves in treated HIV-infected patients. Among these chronic, non-AIDS (acquired immune deficiency syndrome)-related conditions, liver disease is one of the deadliest, proving to be fatal for 15–17% of these individuals. Aside from the presence of liver-related comorbidities, including metabolic disturbances and co-infections, HIV itself and the adverse effects of cART are the main factors that contribute to hepatic cell injury, inflammation, and fibrosis. Among the molecular mechanisms that are activated in the liver during HIV infection, apoptotic cell death of hepatocytes stands out as a key pathogenic player. In this review, we will discuss the evidence and potential mechanisms involved in the apoptosis of hepatocytes induced by HIV, HIV-encoded proteins, or cART. Some antiretroviral drugs, especially the older generation, can induce apoptosis of hepatic cells, which occurs through a variety of mechanisms, such as mitochondrial dysfunction, increased production of reactive oxygen species (ROS), and induction of endoplasmic reticulum (ER) stress and unfolded protein response (UPR), all of which ultimately lead to caspase activation and cell death.

The vitamin D receptor Taq I polymorphism is associated with reduced VDR and increased PDIA3 protein levels in human intestinal fibroblasts

The synonymous single nucleotide polymorphism (SNP) rs731236, located in the vitamin D receptor (VDR) gene (Taq I) has been associated with both decreased levels of the protein in peripheral blood mononuclear cells and a fibrosis-related complication in Crohn´s disease (CD). Interactions between VDR and a protein-disulfide isomerase-associated 3 (PDIA3) in the regulation of extracellular matrix have been reported and we aim to analyze the relevance of the VDR genotypes and the effects of Vitamin D (VD) in the expression of VDR, PDIA3 and proliferation of intestinal fibroblasts. Human intestinal fibroblasts were isolated from the non-affected surgical resections of colorectal patients and classified according to the VDR genotype. In some cases, cells were transfected with specific PDIA3 siRNA. Basal and VD-stimulated expression of VDR, PDIA3 and Collagen 1A1 (COL1A1) as well as fibroblast migration/proliferation were analyzed. Our data show that intestinal fibroblasts homozygous for the C allele in the VDR gene exhibited lower VDR protein levels and higher proliferation than cells homozygous for the T allele. VD increased VDR and attenuated the accelerated proliferation of CC fibroblasts. The diminished VDR level detected in CC cells was associated with increased levels of both PDIA3 and COL1A1 expression and the transient silencing of PDIA3 significantly reduced COL1A1 expression. We conclude that intestinal fibroblasts homozygous for the C allele in the VDR gene exhibited: reduced VDR protein levels, increased proliferation and increased PDIA3/COL1A1 expression. Treatment with VD increased VDR and attenuated proliferation of these cells.

Pharmacology and safety of tofacitinib in ulcerative colitis

The use of Janus kinase (JAK) inhibitors is a new approach in the therapy of inflammatory diseases with immune base. Tofacitinib is one of these inhibitors targeting JAK1 and JAK3, and its efficacy has been demonstrated in the treatment of moderate to severe ulcerative colitis (UC). It is a small synthetic molecule administered orally, with a fast bioavailability and elimination rate, predictable pharmacokinetics and lack of immunogenicity, which are convenient characteristics for both efficacy and safety. This article reviews the pharmacological characteristics of tofacitinib and its safety profile.

Leukocyte-Endothelium Interaction Is Associated with Fat Mass in Children

OBJECTIVE

To study leukocyte-endothelium interaction, a measure of the initial phase of atheromatosis, in children with overweight or obesity.

STUDY DESIGN

A prospective study was conducted in 77 children aged 7-16 years; 47 were children with overweight/obesity and 30 were normal weight. Polymorphonuclear neutrophils (PMNs) and peripheral blood mononuclear cells were isolated from venous blood samples and the interaction of leukocytes over a monolayer of human umbilical vein endothelial cells was analyzed using flow chamber microscopy. The variables studied included leukocyte rolling velocity, rolling flux, and adhesion to endothelial cells. These were compared between children with overweight/obesity and control children. Correlation between the measures of leukocyte-endothelium interaction and anthropometric and biochemical variables was evaluated.

RESULTS

In comparison with normal weight children, the PMNs and peripheral blood mononuclear cells of the overweight/obesity group showed a reduction in rolling velocity (P = .000 and P = .001, respectively) and an increase in rolling flux (P = .001 and P = .004), and adhesion (P = .003 and P = .002). The homeostasis model of insulin resistance was correlated inversely with rolling velocity and positively with rolling flux in PMNs. C-reactive protein was correlated positively with rolling flux and adhesion in both types of leucocytes. Fat mass index was correlated with all measures of leukocyte-endothelial interaction and proved to be the main predictor of leukocyte adhesion in the multiple regression analysis (P = .001 for PMNs and P = .006 for peripheral blood mononuclear cells).

CONCLUSIONS

Excess fat mass in children is related to the activation of the leukocyte-endothelium interaction, potentially contributing to the development of atherosclerosis.

Rilpivirine attenuates liver fibrosis through selective STAT1-mediated apoptosis in hepatic stellate cells

OBJECTIVE

Liver fibrosis constitutes a major health problem worldwide due to its rapidly increasing prevalence and the lack of specific and effective treatments. Growing evidence suggests that signalling through cytokine-activated Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathways regulates liver fibrosis and regeneration. Rilpivirine (RPV) is a widely used anti-HIV drug not reported to produce hepatotoxicity. We aimed to describe the potential hepatoprotective effects of RPV in different models of chronic liver injury, focusing on JAK-STAT signalling regulation.

DESIGN

The effects of RPV on hepatic steatosis, inflammation and fibrogenesis were studied in a nutritional mouse model of non-alcoholic fatty liver disease, carbon tetrachloride-induced fibrosis and bile duct ligation-induced fibrosis. Primary human hepatic stellate cells (hHSC) and human cell lines LX-2 and Hep3B were used to investigate the underlying molecular mechanisms.

RESULTS

RPV exerted a clear anti-inflammatory and antifibrotic effect in all the in vivo models of liver injury employed, and enhanced STAT3-dependent proliferation in hepatocytes and apoptosis in HSC through selective STAT1 activation. These results were reproduced in vitro; RPV undermined STAT3 activation and triggered STAT1-mediated pathways and apoptosis in HSC. Interestingly, this selective pro-apoptotic effect completely disappeared when STAT1 was silenced. Conditioned medium experiments showed that HSC apoptosis activated STAT3 in hepatocytes in an interleukin-6-dependent mechanism.

CONCLUSION

RPV ameliorates liver fibrosis through selective STAT1-dependent induction of apoptosis in HSC, which exert paracrinal effects in hepatocytes, thus promoting liver regeneration. RPV's actions may represent an effective strategy to treat chronic liver diseases of different aetiologies and help identify novel therapeutic targets.

p53 and p53-related mediators PAI-1 and IGFBP-3 are downregulated in peripheral blood mononuclear cells of HIV-patients exposed to non-nucleoside reverse transcriptase inhibitors

The improved effectiveness and safety of the combined antiretroviral therapy (cART) has largely diminished mortality and AIDS-defining morbidity of HIV-patients. Nevertheless, chronic age-related diseases in these individuals are more common and their underlying pathogenic mechanisms of these actions seem to involve accelerated aging and enhanced inflammation. The present study explores markers of these processes in a heterogenous Spanish HIV cohort using peripheral blood samples of HIV-patients and matched uninfected controls. We isolated periheral blood mononuclear cells (PBMCs) and i) compared the expression of a panel of 14 genes related to inflammation and senescence in PBMCs of HIV-patients vs matched uninfected controls, ii) analyzed the expression in HIV-patients in association with a number of demographic, biochemical and immunological parameters and iii) in relation with the current cART they received. PBMCs of HIV-patients displayed significantly increased expression of general inflammatory genes (IL6, IL18 and CXCL10) and this occurs irrespectively of the antiviral therapy they have been receiving. Conversely, levels of senescence-associated genes TP53, SERPINE1andIGFBP3 were slightly but significantly reduced in patients compared to uninfected matched individuals and this effect is related to NNRTI-containing treatments. The expression of the inflammatory markers IL6, IL18, IL1B, TNFA, RELA, CCL2, CCL20 and CXCL10 displayed correlation with certain demographic, morbidity- and HIV infection-related parameters. The levels of TP53 mRNA were positively associated only with plasma LDL. Correlation analysis between the expressions of pairs of genes revealed a different pattern between HIV-patients and controls. The diminished expression of TP53 and SERPINE1 in HIV-patients was also observed at a protein level, and the correlation between the two proteins (p53 and PAI1) in patients and controls showed the opposite trend. In conclusion, HIV-patients show dysregulation of p53 and p53-related mediators, a phenomenon which may be of pathophysiological relevance and could be related to the shorter health- and/or life-span observed in these individuals.

WNT2b Activates Epithelial-mesenchymal Transition Through FZD4: Relevance in Penetrating Crohn´s Disease

BACKGROUND AND AIMS

Epithelial-mesenchymal transition [EMT] has been related to fibrosis and fistula formation, common complications associated with Crohn´s disease [CD]. The WNT signalling pathway mediates EMT, and specific WNT/FZD interactions have been related to the activation of this process in several diseases. We aim to analyse the relevance of EMT and WNT ligands and receptors in the penetrating behaviour of CD.

METHODS

Intestinal surgical resections were obtained from control and CD patients with a stenotic or penetrating behaviour. Fibrosis was determined by the histological analysis of collagen deposition and EMT by confocal microscopy. The expression of WNT ligands, inhibitors, and FZD receptors was analysed by RT-PCR, WB, IH, and IF studies. The effects of WNT2b and the role of FZD4 in EMT were analysed in HT29 epithelial cells.

RESULTS

Fibrosis and expression of EMT markers were detected in samples from CD patients irrespective of the clinical behaviour. However, an increased colocalisation of E-CADHERIN and VIMENTIN, an increased number of cells expressing WNT2b, and a higher expression of FZD4 and WNT2b/FZD4 interaction, were detected in intestinal tissue from the penetrating compared with the stenotic CD behaviour. WNT2b induced EMT in HT29 cells through FZD4 activation.

CONCLUSIONS

An increased EMT, associated with increased WNT2b/FZD4 interaction, was detected in intestinal tissue from CD patients with a penetrating behaviour. WNT2b, through FZD4 activation, induces EMT in vitro which points to a novel pharmacological target to prevent intestinal penetrating complications of CD.

Autophagy Stimulation as a Potential Strategy Against Intestinal Fibrosis

We recently observed reduced autophagy in Crohn’s disease patients and an anti-inflammatory effect of autophagy stimulation in murine colitis, but both anti- and pro-fibrotic effects are associated with autophagy stimulation in different tissues, and fibrosis is a frequent complication of Crohn’s disease. Thus, we analyzed the effects of pharmacological modulation of autophagy in a murine model of intestinal fibrosis and detected that autophagy inhibition aggravates, while autophagy stimulation prevents, fibrosis. These effects are associated with changes in inflammation and in collagen degradation in primary fibroblasts. Thus, pharmacological stimulation of autophagy may be useful against intestinal fibrosis.

Abacavir Induces Arterial Thrombosis in a Murine Model

Background

The purinergic system is known to underlie prothrombotic and proinflammatory vascular programs, making the profile of experimental actions demonstrated by abacavir compatible with thrombogenesis. However, direct evidence of a prothrombotic effect by the drug has been lacking.

Methods

The present study appraised the effects of abacavir in a well-validated animal model of arterial thrombosis. The role of ATP-P2X7 receptors in the actions of the drug was also assessed, and the actions of recognized vascular-damaging agents and other nucleoside reverse-transcriptase inhibitors (NRTIs) were evaluated and compared to those of abacavir.

Results

Abacavir dose-dependently promoted thrombus formation. This effect was reversed by a P2X7-receptor antagonist and was nonexistent in P2X7 knockout mice. The effects of abacavir were similar to those of diclofenac and rofecoxib. Other NRTIs had no thrombosis-related effects.

Conclusion

Abacavir promotes arterial thrombosis through interference with purinergic signaling, suggesting a possible biological mechanism for the clinical association of abacavir with cardiovascular diseases.

Role of p62/SQSTM1 beyond autophagy: a lesson learned from drug-induced toxicity in vitro

BACKGROUND AND PURPOSE

SQSTM1/p62 is a multifunctional, stress-induced, scaffold protein involved in multiple cellular processes including autophagic clearance, regulation of inflammatory responses and redox homeostasis. Its altered function has been associated with different human pathologies, such as neurodegenerative, metabolic and bone diseases (down-regulation), and cancerogenesis (up-regulation). However, its role in the off-target effects of clinically used drugs is still not understood.

EXPERIMENTAL APPROACH

We evaluated the expression of p62 in cultured Hep3B cells and their derived ρ° cells (lacking mitochondria), along with markers of autophagy and mitochondrial dysfunction. The effects of efavirenz were compared with those of known pharmacological stressors, rotenone, thapsigargin and CCCP, and we also used transient silencing with siRNA and p62 overexpression. Western blotting, quantRT-PCR and fluorescence microscopy were used to assay these effects and their underlying mechanisms.

KEY RESULTS

In Hep3B cells, efavirenz augmented p62 protein content, an effect not observed in the corresponding ρ° cells. p62 up-regulation followed enhanced SQSTM1 expression mediated through the transcription factor CHOP/DDIT3, while other well-known regulators (NF-kB and Nrf2) were not involved. Inhibition of autophagy with 3MA or with transient silencing of Atg5 did not affect SQSTM1 expression in efavirenz-treated cells while p62 overexpression ameliorated the deleterious effect of efavirenz on cell viability.

CONCLUSION AND IMPLICATIONS

In our model, p62 exerted a specific, autophagy-independent role and protected against efavirenz-induced mitochondrial ROS generation and activation of the NLRP3 inflammasome. These findings add to the multifunctional nature of p62 and may help to understand the off-target effects of clinically useful drugs.

Lon protease: a novel mitochondrial matrix protein in the interconnection between drug-induced mitochondrial dysfunction and endoplasmic reticulum stress

BACKGROUND AND PURPOSE

Mitochondria-associated membranes (MAMs) are specific endoplasmic reticulum (ER) domains that enable it to interact directly with mitochondria and mediate metabolic flow and Ca²⁺ transfer. A growing list of proteins have been identified as MAMs components, but how they are recruited and function during complex cell stress situations is still not understood, while the participation of mitochondrial matrix proteins is largely unrecognized.

EXPERIMENTAL APPROACH

This work compares mitochondrial/ER contact during combined ER stress/mitochondrial dysfunction using a model of human hepatoma cells (Hep3B cell line) treated for 24 h with classic pharmacological inducers of ER stress (thapsigargin), mitochondrial dysfunction (carbonyl cyanide m-chlorophenyl hydrazone or rotenone) or both (the antiretroviral drug efavirenz used at clinically relevant concentrations).

KEY RESULTS

Markers of mitochondrial dynamics (dynamin-related protein 1, optic atrophy 1 and mitofusin 2) were expressed differently with these stimuli, pointing to a specificity of combined ER/mitochondrial stress. Lon, a matrix protease involved in protein and mtDNA quality control, was up-regulated at mRNA and protein levels under all conditions. However, only efavirenz decreased the mitochondrial content of Lon while increasing its extramitochondrial presence and its localization to MAMs. This latter effect resulted in an enhanced mitochondria/ER interaction, as shown by co-immunoprecipitation experiments of MAMs protein partners and confocal microscopy imaging.

CONCLUSION AND IMPLICATIONS

A specific dual drug-induced mitochondria-ER effect enhances the MAMs content of Lon and its extramitochondrial expression. This is the first report of this phenomenon and suggests a novel MAMs-linked function of Lon protease.

Efavirenz: What is known about the cellular mechanisms responsible for its adverse effects

The HIV infection remains an important health problem worldwide. However, due to the efficacy of combined antiretroviral therapy (cART), it has ceased to be a mortal condition, becoming a chronic disease instead. Efavirenz, the most prescribed non-nucleoside analogue reverse transcriptase inhibitor (NNRTI), has been a key component of cART since its commercialization in 1998. Though still a drug of choice in many countries, its primacy has been challenged by the arrival of newer antiretroviral agents with better toxicity profiles and treatment adherence. The major side effects related to EFV have been widely described in clinical studies, however the mechanisms that participate in their pathogenesis remain largely ununderstood. This review provides an insight into the cellular and molecular mechanisms responsible for the development of the most significant undesired effects induced by efavirenz, both short- and long-term, revealed by in vitro and in vivo experimental pharmacological research. Growing evidence implicates the drug in energy metabolism, mitochondrial function, and other cellular processes involved in stress responses including oxidative stress, inflammation and autophagy.

Stimulation of autophagy prevents intestinal mucosal inflammation and ameliorates murine colitis

BACKGROUND AND PURPOSE

Defective autophagy contributes to the pathogenesis of inflammatory disorders such as inflammatory bowel disease and there are interactions between autophagy and inflammation. Here we have analysed the effects of autophagy stimulators on murine colitis.

EXPERIMENTAL APPROACH

Mice were treated with intrarectal administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) (3.5 mg·20 g^-1 ) and body weight was measured daily. Histological damage was scored 2 or 4 days after treatment. Some mice received trehalose (3% in drinking water 3 weeks before TNBS administration) or a daily administration of rapamycin (1.25 mg·kg^-1 , i.p.), betanin (1 g·kg^-1 , i.p.) or betanin + 3-methyladenine (3MA) (10 mg·kg^-1 , i.p.). Protein levels of p-mTOR, p62, LC3, BCL10, NFκB, IκBα and p-IκBα in mucosa were determined by Western blots and mRNA expression of TNFα, IL1β, IL6, IL10, COX2, CCR7, CD11c, inducible NOS and CD86 by qRT-PCR.

KEY RESULTS

Impaired autophagy associated with body weight loss and intestinal damage was detected in the mucosa of TNBS-treated mice. Administration of trehalose, rapamycin or betanin prevented the impaired autophagic flux induced by TNBS and decreased mucosal protein levels of BCL10, p-IκBα and NFκB-p65 and the expression of pro-inflammatory cytokines and M1 macrophage markers. Blockade of autophagosome formation by treatment with 3MA, prevented the reduction in protein levels of p62, BCL10, p-IκBα and NFκB-p65 induced by betanin in TNBS-treated mice and weakened the protective effects of betanin on murine colitis.

CONCLUSIONS AND IMPLICATIONS

Pharmacological stimulation of mucosal autophagy reduced intestinal inflammation and improved murine colitis.

Abacavir induces platelet-endothelium interactions by interfering with purinergic signalling: A step from inflammation to thrombosis

The controversy connecting Abacavir (ABC) with cardiovascular disease has been fuelled by the lack of a credible mechanism of action. ABC shares structural similarities with endogenous purines, signalling molecules capable of triggering prothrombotic/proinflammatory programmes. Platelets are leading actors in the process of thrombosis. Our study addresses the effects of ABC on interactions between platelets and other vascular cells, while exploring the adhesion molecules implicated and the potential interference with the purinergic signalling pathway. The effects of ABC on platelet aggregation and platelet-endothelium interactions were evaluated, respectively, with an aggregometer and a flow chamber system that reproduced conditions in vivo. The role of adhesion molecules and purinergic receptors in endothelial and platelet populations was assessed by selective pre-incubation with specific antagonists and antibodies. ABC and carbovir triphosphate (CBT) levels were evaluated by HPLC. The results showed that ABC promoted the adherence of platelets to endothelial cells, a crucial step for the formation of thrombi. This was not a consequence of a direct effect of ABC on platelets, but resulted from activation of the endothelium via purinergic ATP-P2X₇ receptors, which subsequently triggered an interplay between P-selectin and ICAM-1 on endothelial cells with constitutively expressed GPIIb/IIIa and GPIbα on platelets. ABC did not induce platelet activation (P-selectin expression or Ca²⁺ mobilization) or aggregation, even at high concentrations. CBT levels in endothelial cells were lower than those required to induce platelet-endothelium interactions. Thus, ABC interference with endothelial purinergic signalling leads to platelet recruitment. This highlights the endothelium as the main cell target of ABC in this interaction, which is in line with previous experimental evidence that ABC induces manifestations of vascular inflammation.

Proton Pump Inhibitors Display Antitumor Effects in Barrett's Adenocarcinoma Cells

Recent evidence has reported that proton pump inhibitors (PPIs) can exert antineoplastic effects through the disruption of pH homeostasis by inhibiting vacuolar ATPase (H⁺-VATPase), a proton pump overexpressed in several tumor cells, but this aspect has not been deeply investigated in EAC yet. In the present study, the expression of H⁺-VATPase was assessed through the metaplasia-dysplasia-adenocarcinoma sequence in Barrett's esophagus (BE) and the antineoplastic effects of PPIs and cellular mechanisms involved were evaluated in vitro. H⁺-VATPase expression was assessed by immunohistochemistry in paraffined-embedded samples or by immunofluorescence in cultured BE and EAC cell lines. Cells were treated with different concentrations of PPIs and parameters of citotoxicity, oxidative stress, and autophagy were evaluated. H⁺-VATPase expression was found in all biopsies and cell lines evaluated, showing differences in the location of the pump between the cell lines. Esomeprazole inhibited proliferation and cell invasion and induced apoptosis of EAC cells. Production of reactive oxygen species (ROS) seemed to be involved in the cytotoxic effects observed since the addition of N-acetylcysteine significantly reduced esomeprazole-induced apoptosis in EAC cells. Esomeprazole also reduced intracellular pH of tumor cells, whereas only disturbed the mitochondrial membrane potential in OE33 cells. Esomeprazole induced autophagy in both EAC cells, but also triggered a blockade in autophagic flux in the metastatic cell line. These data provide in vitro evidence supporting the potential use of PPIs as novel antineoplastic drugs for EAC and also shed some light on the mechanisms that trigger PPIs cytotoxic effects, which differ upon the cell line evaluated.

The activation of Wnt signaling by a STAT6-dependent macrophage phenotype promotes mucosal repair in murine IBD

The complete repair of the mucosa constitutes a key goal in inflammatory bowel disease (IBD) treatment. The Wnt signaling pathway mediates mucosal repair and M2 macrophages that coordinate efficient healing have been related to Wnt ligand expression. Signal transducer and activator of transcription 6 (STAT6) mediates M2 polarization in vitro and we hypothesize that a STAT6-dependent macrophage phenotype mediates mucosal repair in acute murine colitis by activating the Wnt signaling pathway. Our results reveal an impaired mucosal expression of M2 macrophage-associated genes and delayed wound healing in STAT6(-/-) mice treated with 2,4,6-trinitrobenzenesulfonic acid (TNBS). These mice also exhibited decreased mucosal expression of Wnt2b, Wnt7b, and Wnt10a, diminished protein levels of nuclear β-catenin that is mainly located in crypts adjacent to damage, and reduced mRNA expression of two Wnt/β-catenin target molecules Lgr5 and c-Myc when compared with wild-type (WT) mice. Murine peritoneal macrophages treated with interleukin-4 (IL-4) and polarized toward an M2a phenotype overexpressed Wnt2b, Wnt7b, and Wnt10a in a STAT6-dependent manner. Administration of a Wnt agonist as well as transfer of properly polarized M2a macrophages to STAT6(-/-) mice activated the Wnt signaling pathway in the damaged mucosa and accelerated wound healing. Our results demonstrate that a STAT6-dependent macrophage phenotype promotes mucosal repair in TNBS-treated mice through activation of the Wnt signaling pathway.

Heat Stress Induces Extended Plateau of Hsp70 Accumulation--A Possible Cytoprotection Mechanism in Hepatic Cells

The relevance of heat preconditioning resides in its ability to protect cells from different kinds of injury by induction of heat shock proteins, a process in which the intensity of heat stress (HS) and duration of subsequent recovery are vital. This study evaluates the effects of moderate HS (45 min/43°C) and the time-dependent changes during recovery period of HSP70, Bcl-2 and p53 gene and protein expression in HepG2 cells. We also evaluated the effects of 0.4 mM aspirin (ASA) as a potential pharmacological co-inducer of HSP, both alone and in a combination with HS (ASA + HS). HS alone and ASA + HS caused a major up-regulation of HSP70 mRNA in the first 2 h, while HSP70 protein increased gradually and was especially abundant from 2 h to 24 h. Regarding Bcl-2, all treatments rendered similar results: gene expression was down-regulated in the first 2 h, after which there was protein elevation (12-48 h after HS). mRNA expression of p53 in HS- and (ASA + HS)-cells was down-regulated in the first 12 h. The immediate decrease of p53 protein after HS was followed by a biphasic increase. In conclusion, 0.4 mM ASA + HS does not act as a co-inducer of HSP70 in HepG2 cells, but promotes Bcl-2 protein expression during prolonged treatment. Our suggestion is that hepatic cells are most vulnerable in the first 2-6 h, but may have a high capacity for combating stress 12-24 h after HS. Finally, short-term exposure HS might be a "physiological conditioner" for liver cells to accumulate HSP and Bcl-2 proteins and thus obtain cytoprotection against an additional stress.

The purine analogues abacavir and didanosine increase acetaminophen-induced hepatotoxicity by enhancing mitochondrial dysfunction

BACKGROUND

NRTIs are essential components of HIV therapy with well-documented, long-term mitochondrial toxicity in hepatic cells, but whose acute effects on mitochondria are unclear. As acetaminophen-induced hepatotoxicity also involves mitochondrial interference, we hypothesized that it would be exacerbated in the context of ART.

METHODS

We evaluated the acute effects of clinically relevant concentrations of the most widely used NRTIs, alone or combined with acetaminophen, on mitochondrial function and cellular viability.

RESULTS

The purine analogues abacavir and didanosine produced an immediate and concentration-dependent inhibition of oxygen consumption and complex I and III activity. This inhibition was accompanied by an undermining of mitochondrial function, with increased production of reactive oxygen species and reduction of mitochondrial membrane potential and intracellular ATP levels. However, this interference did not compromise cell survival. Co-administration with concentrations of acetaminophen below those considered hepatotoxic exacerbated the deleterious effects of both compounds on mitochondrial function and compromised cellular viability, showing a clear correlation with diminished glutathione levels.

CONCLUSIONS

The simultaneous presence of purine analogues and low concentrations of acetaminophen significantly potentiates mitochondrial dysfunction, increasing the risk of liver injury. This new mechanism is relevant given the liver's susceptibility to mitochondrial dysfunction-related toxicity and the tendency of the HIV infection to increase oxidative stress.

Differential effects of anti-TNF-α and anti-IL-12/23 agents on human leukocyte-endothelial cell interactions

Enhanced leukocyte recruitment is an inflammatory process that occurs during early phases of the vascular dysfunction that characterises atherosclerosis. We evaluated the impact of anti-TNF-α (adalimumab, infliximab and etanercept) and anti-IL-12/23 (ustekinumab) on interactions between human leukocytes and endothelial cells in a flow chamber that reproduced in vivo conditions. Clinical concentrations of anti-TNF-α were evaluated on the leukocyte recruitment induced by a variety of endothelial (TNF-α, interleukin-1β, lymphotoxin-α and angiotensin-II) and leukocyte (PAF, IL-12 and IL-23) stimuli related to inflammation and atherosclerosis. Treatment with anti-TNF-α, even before or after establishing the inflammatory situation induced by TNF-α, diminished leukocyte-endothelial cell interactions induced by this stimuli. Our results also implicated adhesion molecules (ICAM-1, VCAM-1 and E-selectin) in the actions of anti-TNF-α in terms of leukocyte adhesion to endothelium. However, anti-TNF-α drugs did not influence the actions of interleukin-1β, but prevented those of lymphotoxin-α and angiotensin-II. However, once established, inflammatory response elicited by the latter three stimuli could not be reversed. Pre-treatment with anti-TNF-α, also prevented leukocyte actions induced by IL-23 on PBMC rolling flux and rolling velocity and by IL-12 on PMN adhesion. Ustekinumab exhibited a more discreet profile, having no effect on leukocyte recruitment induced by any of the endothelial stimuli, while blocking the effects of IL-23 on leukocyte activation and those of IL-12 on PMN adhesion and PAF on PBMC rolling velocity. These findings endorse the idea that biological anti-inflammatory drugs, in particular anti-TNF-α, have the capacity to influence cardiovascular risk accompanying psoriasis and rheumatoid arthritis by ameliorating vascular inflammation.

Efavirenz and the CNS: what we already know and questions that need to be answered

The NNRTI efavirenz has long been one of the most frequently employed antiretroviral drugs in the multidrug regimens used to treat HIV infection, in accordance with its well-demonstrated antiretroviral efficacy and favourable pharmacokinetics. However, growing concern about its adverse effects has sometimes led to efavirenz being replaced by other drugs in the initial treatment selection or to switching of therapy to efavirenz-free regimens in experienced patients. Neurological and neuropsychiatric reactions are the manifestations most frequently experienced by efavirenz-treated patients and range from transitory effects, such as nightmares, dizziness, insomnia, nervousness and lack of concentration, to more severe symptoms including depression, suicidal ideation or even psychosis. In addition, efavirenz has recently been associated with mild/moderate neurocognitive impairment, which is of specific relevance given that half of the patients receiving ART eventually suffer some form of HIV-associated neurocognitive disorder. The mechanisms responsible for efavirenz-induced neurotoxicity are unclear, although growing evidence points to disturbances in brain mitochondrial function and bioenergetics. This review offers a comprehensive overview of the current evidence on the interaction that efavirenz displays with the CNS, including the penetration and concentration of the drug in the brain. We discuss the prevalence, types and specificities of its side effects and recently uncovered cellular mechanisms that may be involved in their development.

Efavirenz alters mitochondrial respiratory function in cultured neuron and glial cell lines

BACKGROUND

The NNRTI efavirenz is among the most widely employed antiretroviral drugs. Although it is considered safe, efavirenz has been linked with several adverse effects including neurological manifestations, which appear in the majority of the patients on efavirenz-containing regimens. The molecular mechanisms responsible for these manifestations are not understood, but mounting evidence points to altered brain bioenergetics.

METHODS

We evaluated the effect of short-term efavirenz treatment on the mitochondrial respiratory function of cultured glioblastoma and differentiated neuroblastoma cell lines using a Seahorse Extracellular Flux Analyzer.

RESULTS

Incubation with efavirenz provoked a significant and concentration-dependent decrease in basal respiration and specifically in ATP production-coupled O2 consumption in both SH-SY5Y and U-251MG cells, with the effect being more pronounced in the latter. In contrast, efavirenz did not alter mitochondrial proton leakage in either of the cell types. Efavirenz led to a decrease in the respiratory control ratio as well as to a reduction in the maximal respiration rate and spare respiratory capacity in both U-251MG and SH-SY5Y cells, the former cells being more susceptible.

CONCLUSIONS

These findings reveal that efavirenz specifically alters mitochondrial respiration, which is of relevance for a better understanding of the molecular mechanisms responsible for the efavirenz-associated neurological effects that have been recorded in clinical situations.

Mitochondrial (dys)function - a factor underlying the variability of efavirenz-induced hepatotoxicity?

BACKGROUND AND PURPOSE

The non-nucleoside analogue reverse transcriptase inhibitor efavirenz is associated with hepatic toxicity and metabolic disturbances. Although the mechanisms involved are not clear, recent evidence has pinpointed a specific mitochondrial action of efavirenz accompanied by the induction of an endoplasmic reticulum (ER) stress/unfolded protein response in human hepatic cells. The aim of this study was to further investigate the involvement of this organelle by evaluating efavirenz's effects in cells lacking functional mitochondria (rho°) and comparing them with those of the typical mitotoxic agent rotenone, a standard complex I inhibitor, and the ER stress inducer thapsigargin.

EXPERIMENTAL APPROACH

Hep3B rho(+) and rho° cells were treated with clinically relevant concentrations of efavirenz, then mitochondrial function and cytotoxicity were studied using standard cell biology techniques.

KEY RESULTS

Efavirenz-treated rho° cells exhibited a substantial reduction in parameters indicative of mitochondrial interference, such as increased superoxide production, mitochondrial mass/morphology alterations and enhanced expression of LONP, a highly conserved mitochondrial protease. In line with these results, the cytotoxic effect (cell number, chromatin condensation, cell cycle alterations and induction of apoptosis) of efavirenz was less pronounced in Hep3B respiration-depleted cells than in wild-type cells. The effect of efavirenz was both similar and different from those of two distinct mitochondrial stressors, thapsigargin and rotenone.

CONCLUSIONS AND IMPLICATIONS

Cells lacking normal mitochondria (rho°) are less vulnerable to efavirenz. Our results provide further evidence that the hepatic damage induced by efavirenz involves acute interference with mitochondria and extend our knowledge of the response of mitochondria/ER to a stress stimulus.

Involvement of nitric oxide in the mitochondrial action of efavirenz: a differential effect on neurons and glial cells

The anti-human immunodeficiency virus (HIV) drug efavirenz (EFV) alters mitochondrial function in cultured neurons and glial cells. Nitric oxide (NO) is a mediator of mitochondrial dysfunction associated with HIV central nervous system symptoms. We show that EFV promotes inducible nitric oxide synthase (iNOS) expression in cultured glial cells and generated NO undermines their mitochondrial function, as inhibition of NOS partially reverses this effect. EFV inhibits mitochondrial Complex I in both neurons and glia; however, when the latter cells are treated for longer periods, other mitochondrial complexes are also affected in accordance with the increased NO production. These findings shed light on the mechanisms responsible for the frequent EFV-associated neurotoxicity.

Lack of mitochondrial toxicity of darunavir, raltegravir and rilpivirine in neurons and hepatocytes: a comparison with efavirenz

OBJECTIVES

Growing evidence associates the non-nucleoside reverse transcriptase inhibitor efavirenz with several adverse events. Newer antiretrovirals, such as the integrase inhibitor raltegravir, the non-nucleoside reverse transcriptase inhibitor rilpivirine and the protease inhibitor darunavir, claim to have a better toxicological profile than efavirenz while producing similar levels of efficacy and virological suppression. The objective of this study was to determine the in vitro toxicological profile of these three new antiretrovirals by evaluating their effects on the mitochondrial and cellular parameters altered by efavirenz in hepatocytes and neurons.

METHODS

Hep3B cells and primary rat neurons were treated with clinically relevant concentrations of efavirenz, darunavir, rilpivirine or raltegravir. Parameters of mitochondrial function, cytotoxicity and oxidative and endoplasmic reticulum stress were assessed using standard cell biology techniques.

RESULTS

None of the new compounds altered the mitochondrial function of hepatic cells or neurons, while efavirenz decreased mitochondrial membrane potential and enhanced superoxide production in both cell types, effects that are known to significantly compromise the functioning of mitochondria, cell viability and, ultimately, cell number. Of the four drugs assayed, efavirenz was the only one to alter the protein expression of LC3-II, an indicator of autophagy, and CHOP, a marker of endoplasmic reticulum stress and the unfolded protein response.

CONCLUSIONS

Darunavir, rilpivirine and raltegravir do not induce toxic effects on Hep3B cells and primary rat neurons, which suggests a safer hepatic and neurological profile than that of efavirenz.

Neuronal bioenergetics and acute mitochondrial dysfunction: a clue to understanding the central nervous system side effects of efavirenz

BACKGROUND

Neurological pathogenesis is associated with mitochondrial dysfunction and differences in neuronal/glial handling of oxygen and glucose. The main side effects attributed to efavirenz involve the CNS, but the underlying mechanisms are unclear.

METHODS

Human cell lines and rat primary cultures of neurons and astrocytes were treated with clinically relevant efavirenz concentration.

RESULTS

Efavirenz alters mitochondrial respiration, enhances reactive oxygen species generation, undermines mitochondrial membrane potential, and reduces adenosine triphosphate (ATP) levels in a concentration-dependent fashion in both neurons and glial cells. However, it activates adenosine monophosphate-activated protein kinase only in glial cells, upregulating glycolysis and increasing intracellular ATP levels, which do not occur in neurons. To reproduce the conditions that often exist in human immunodeficiency virus-related neuroinflammatory disorders, the effects of efavirenz were evaluated in the presence of exogenous nitric oxide, an inflammatory mediator and mitochondrial inhibitor. The combination potentiated the effects on mitochondrial parameters in both neurons and glial cells, but ATP generation and lactate production were enhanced only in glial cells.

CONCLUSIONS

Efavirenz affects the bioenergetics of neurons through a mechanism involving acute mitochondrial inhibition, an action exacerbated in neuroinflammatory conditions. A similar scenario of glial cells survival and degeneration of neurons with signs of mitochondrial dysfunction and oxidative stress has been associated with neurocognitive disorders.

Efavirenz induces interactions between leucocytes and endothelium through the activation of Mac-1 and gp150,95

OBJECTIVES

The potential cardiovascular (CV) toxicity associated with combined antiretroviral therapy (cART) has been attributed mainly to the nucleoside reverse transcriptase inhibitors abacavir and didanosine. However, the other two components of cART--non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs)--may also be implicated, either directly or by influencing the action of the other drugs. This study evaluates the acute direct effects of the NNRTIs efavirenz and nevirapine and one of the most widely employed PIs, lopinavir, on leucocyte-endothelium interactions, a hallmark of CV disease.

METHODS

Drugs were analysed in vitro in human cells (interactions of peripheral blood polymorphonuclear or mononuclear cells with human umbilical vein endothelial cells) using a flow chamber system, and in vivo in rat mesenteric vessels by means of intravital microscopy. The expression of adhesion molecules in leucocytes and endothelial cells was studied by flow cytometry, and the role of these molecules in white cell recruitment was evaluated by pre-treating human cells or rats with blocking antibodies.

RESULTS

Efavirenz and nevirapine, but not lopinavir, increased the rolling flux and adhesion of leucocytes in vitro and in vivo while inducing emigration in rat venules. Efavirenz, but not nevirapine, augmented the levels of CD11b, CD11c and CD18 in neutrophils and monocytes. The actions of efavirenz, but not of nevirapine, were reversed by antibodies against Mac-1 (CD11b/CD18), gp150,95 (CD11c/CD18) or ICAM-1 (CD54).

CONCLUSIONS

NNRTIs, but not PIs, interfere with leucocyte-endothelial interactions. However, differences between efavirenz and nevirapine suggest a specific CV profile for each compound.

M2 macrophages activate WNT signaling pathway in epithelial cells: relevance in ulcerative colitis

Macrophages, which exhibit great plasticity, are important components of the inflamed tissue and constitute an essential element of regenerative responses. Epithelial Wnt signalling is involved in mechanisms of proliferation and differentiation and expression of Wnt ligands by macrophages has been reported. We aim to determine whether the macrophage phenotype determines the expression of Wnt ligands, the influence of the macrophage phenotype in epithelial activation of Wnt signalling and the relevance of this pathway in ulcerative colitis. Human monocyte-derived macrophages and U937-derived macrophages were polarized towards M1 or M2 phenotypes and the expression of Wnt1 and Wnt3a was analyzed by qPCR. The effects of macrophages and the role of Wnt1 were analyzed on the expression of β-catenin, Tcf-4, c-Myc and markers of cell differentiation in a co-culture system with Caco-2 cells. Immunohistochemical staining of CD68, CD206, CD86, Wnt1, β-catenin and c-Myc were evaluated in the damaged and non-damaged mucosa of patients with UC. We also determined the mRNA expression of Lgr5 and c-Myc by qPCR and protein levels of β-catenin by western blot. Results show that M2, and no M1, activated the Wnt signaling pathway in co-culture epithelial cells through Wnt1 which impaired enterocyte differentiation. A significant increase in the number of CD206+ macrophages was observed in the damaged mucosa of chronic vs newly diagnosed patients. CD206 immunostaining co-localized with Wnt1 in the mucosa and these cells were associated with activation of canonical Wnt signalling pathway in epithelial cells and diminution of alkaline phosphatase activity. Our results show that M2 macrophages, and not M1, activate Wnt signalling pathways and decrease enterocyte differentiation in co-cultured epithelial cells. In the mucosa of UC patients, M2 macrophages increase with chronicity and are associated with activation of epithelial Wnt signalling and diminution in enterocyte differentiation.

Profile of leukocyte-endothelial cell interactions induced in venules and arterioles by nucleoside reverse-transcriptase inhibitors in vivo

BACKGROUND

There is controversy regarding cardiovascular (CV) toxicity of the nucleoside reverse-transcriptase inhibitors used to treat human immunodeficiency virus infection.

METHODS

We evaluated the effects of nucleoside reverse-transcriptase inhibitors on leukocyte-endothelium interactions, a hallmark of CV diseases, in rat mesenteric vessels using intravital microscopy and in human arterial cells using a flow chamber system.

RESULTS

Abacavir and didanosine increased rolling, adhesion and emigration in rat vessels. These effects were reversed with antibodies against Macrophage-1 antigen (Mac-1) or intercellular adhesion molecule 1 and were reproduced in human cells. Lamivudine, zidovudine, emtricitabine, and tenofovir had no effects.

CONCLUSIONS

Our results support the association of abacavir and didanosine with CV diseases.

Induction of CD36 and thrombospondin-1 in macrophages by hypoxia-inducible factor 1 and its relevance in the inflammatory process

Inflammation is part of a complex biological response of vascular tissue to pathogens or damaged cells. First inflammatory cells attempt to remove the injurious stimuli and this is followed by a healing process mediated principally by phagocytosis of senescent cells. Hypoxia and p38-MAPK are associated with inflammation, and hypoxia inducible factor 1 (HIF-1) has been detected in inflamed tissues. We aimed to analyse the role of p38-MAPK and HIF-1 in the transcriptional regulation of CD36, a class B scavenger receptor, and its ligand thrombospondin (TSP-1) in macrophages and to evaluate the involvement of this pathway in phagocytosis of apoptotic neutrophils. We have also assessed HIF-1α, p38-MAPK and CD36 immunostaining in the mucosa of patients with inflammatory bowel disease. Results show that hypoxia increases neutrophil phagocytosis by macrophages and induces the expression of CD36 and TSP-1. Addition of a p38-MAPK inhibitor significantly reduced the increase in CD36 and TSP-1 expression provoked by hypoxia and decreased HIF-1α stabilization in macrophages. Transient transfection of macrophages with a miHIF-1α-targeting vector blocked the increase in mRNA expression of CD36 and TSP-1 during hypoxia and reduced phagocytosis, thus highlighting a role for the transcriptional activity of HIF-1. CD36 and TSP-1 were necessary for the phagocytosis of neutrophils induced by hypoxic macrophages, since functional blockade of these proteins undermined this process. Immunohistochemical studies revealed CD36, HIF-1α and p38-MAPK expression in the mucosa of patients with inflammatory bowel disease. A positive and significant correlation between HIF-1α and CD36 expression and CD36 and p38-MAPK expression was observed in cells of the lamina propria of the damaged mucosa. Our results demonstrate a HIF-1-dependent up-regulation of CD36 and TSP-1 that mediates the increased phagocytosis of neutrophils by macrophages during hypoxia. Moreover, they suggest that CD36 expression in the damaged mucosa of patients with inflammatory bowel disease depends on p38-MAPK and HIF-1 activity.

Differential effects of tenofovir/emtricitabine and abacavir/lamivudine on human leukocyte recruitment

BACKGROUND

The association of abacavir (ABC) with cardiovascular disease has led to HIV treatment guidelines favouring the combination of tenofovir/emtricitabine (TDF/FTC) over that of ABC/lamivudine (ABC/3TC). We have analysed the effects of plasma-relevant concentrations of TDF, FTC, ABC and 3TC, individually and in clinically employed combinations, on human leukocyte accumulation. The effects of ABC, 3TC, TDF and FTC on the expression of adhesion molecules were also evaluated.

METHODS

Interactions between human leukocytes - specifically peripheral blood polymorphonuclear or mononuclear cells - and human umbilical vein endothelial cells were evaluated in a flow chamber reproducing in vivo conditions. The expression of adhesion molecules was analysed by flow cytometry.

RESULTS

Concentrations of TDF, FTC or 3TC mimicking those in the plasma of patients did not have any effect on human leukocyte-endothelial cell interactions, while contrasting results were obtained with ABC. This distinct pattern was reproduced when the drugs were administered in combination; namely, ABC/3TC had a significant influence on rolling and adhesion while TDF/FTC did not. However, the effects produced by ABC alone did not differ when it was combined with 3TC, which suggests the former drug was responsible for the effects observed. ABC, 3TC, TDF and FTC did not modify the expression of endothelial adhesion molecules. Conversely, only ABC enhanced the expression of leukocyte CD11b/CD18 in neutrophils and monocytes.

CONCLUSIONS

Our results provide evidence that the combination TDF/FTC has a better vascular profile than ABC/3TC.

Mitochondria sentencing about cellular life and death: a matter of oxidative stress

Mitochondria are crucial, multifunctional organelles which actively regulate cellular homeostasis. Their complex and diverse role includes maintenance of the cellular energetic balance through hosting several catabolic pathways which result in the process of oxidative phosphorylation, as well as enabling various fundamental anabolic processes and controlling Ca2+ distribution. Moreover, mitochondria are the main cellular generator of reactive oxygen species, which act as second messengers and when over-produced provoke a state of oxidative stress, a condition implicated in many pathologies. Importantly, mitochondria are directly involved in triggering different and complexly interconnected programs promoting cell survival or death. The aim of this review is to summarize the current understanding regarding mitochondrial implication in the main cellular pathways controlling cell "fate" such as apoptosis, autophagy (mitophagy), mitoptosis and necrosis with particular emphasis on the role that reactive oxygen species and oxidative stress may play in these phenomena. The literature extensively covers the topic of reactive oxygen species and apoptosis, fewer articles however deal with mitophagy or mitochondrial dynamics and very few mention the implication oxidative stress and redox modifications have for mitoptosis or necrosis. This review offers a global picture of the complex role of mitochondria in the regulation of cell "fate", referring specifically to the interconnection and balance between different cellular pathways of death and survival. Current knowledge regarding the involvement of these processes in particular human pathologies, specifically with respect to the implication of reactive oxygen species and oxidative stress, is also discussed.

Oxidative stress and mitochondrial impairment after treatment with anti-HIV drugs: clinical implications

Thirty years after the discovery of HIV infection, there are numerous antiretroviral drugs that control the disease when administered in a potent combination referred to as Highly Active Antiretroviral Therapy (HAART). This therapy reduces the viral load and improves immune system reconstitution, leading to a significant reduction of HIV-related morbidity and mortality. However, HAART does not completely eliminate HIV, so treatment must continue throughout the patient's life. Prolonged use of HAART has been related to long-term adverse events that can compromise patient health. These deleterious effects have been reported for the majority of antiretroviral drugs and are the most common causes for therapy discontinuation. In most of these adverse events, such as diabetes, cardiovascular diseases, neurological disorders and metabolic alterations, oxidative stress and mitochondrial impairment play important roles. This review covers the implication of antiretroviral drugs in the overproduction of reactive oxygen species and the reduction of antioxidant defences, and in the consequent mitochondrial dysfunction, focusing on the molecular mechanisms involved and the clinical implications for HIV-infected patients.