Acetaminophen overdose causes a breach of the blood-bile barrier in mice but not in rats.

Acetaminophen (APAP) is known to cause a breach of the blood-bile barrier in mice that, via a mechanism called futile bile acid (BA) cycling, increases BA concentrations in hepatocytes above cytotoxic thresholds. Here, we compared this mechanism in mice and rats, because both species differ massively in their susceptibility to APAP and compared the results to available human data. Dose and time-dependent APAP experiments were performed in male C57BL6/N mice and Wistar rats. The time course of BA concentrations in liver tissue and in blood was analyzed by MALDI-MSI and LC-MS/MS. APAP and its derivatives were measured in the blood by LC-MS. APAP-induced liver damage was analyzed by histopathology, immunohistochemistry, and by clinical chemistry. In mice, a transient increase of BA in blood and in peri-central hepatocytes preceded hepatocyte death. The BA increase coincided with oxidative stress in liver tissue and a compromised morphology of bile canaliculi and immunohistochemically visualized tight junction proteins. Rats showed a reduced metabolic activation of APAP compared to mice. However, even at very high doses that caused cell death of hepatocytes, no increase of BA concentrations was observed neither in liver tissue nor in the blood. Correspondingly, no oxidative stress was detectable, and the morphology of bile canaliculi and tight junction proteins remained unaltered. In conclusion, different mechanisms cause cell death in rats and mice, whereby oxidative stress and a breach of the blood-bile barrier are seen only in mice. Since transient cholestasis also occurs in human patients with APAP overdose, mice are a clinically relevant species to study APAP hepatotoxicity but not rats.

Inhibition of the renal apical sodium dependent bile acid transporter prevents cholemic nephropathy in mice with obstructive cholestasis.

BACKGROUND & AIMS: Cholemic nephropathy (CN) is a severe complication of cholestatic liver diseases for which there is no specific treatment. We revisited its pathophysiology with the aim of identifying novel therapeutic strategies. METHODS: Cholestasis was induced by bile duct ligation (BDL) in mice. Bile flux in kidneys and livers was visualized by intravital imaging, supported by MALDI mass spectrometry imaging and liquid chromatography-tandem mass spectrometry. The effect of AS0369, a systemically bioavailable apical sodium-dependent bile acid transporter (ASBT) inhibitor, was evaluated by intravital imaging, RNA-sequencing, histological, blood, and urine analyses. Translational relevance was assessed in kidney biopsies from patients with CN, mice with a humanized bile acid (BA) spectrum, and via analysis of serum BAs and KIM-1 (kidney injury molecule 1) in patients with liver disease and hyperbilirubinemia. RESULTS: Proximal tubular epithelial cells (TECs) reabsorbed and enriched BAs, leading to oxidative stress and death of proximal TECs, casts in distal tubules and collecting ducts, peritubular capillary leakiness, and glomerular cysts. Renal ASBT inhibition by AS0369 blocked BA uptake into TECs and prevented kidney injury up to 6 weeks after BDL. Similar results were obtained in mice with humanized BA composition. In patients with advanced liver disease, serum BAs were the main determinant of KIM-1 levels. ASBT expression in TECs was preserved in biopsies from patients with CN, further highlighting the translational potential of targeting ASBT to treat CN. CONCLUSIONS: BA enrichment in proximal TECs followed by oxidative stress and cell death is a key early event in CN. Inhibiting renal ASBT and consequently BA enrichment in TECs prevents CN and systemically decreases BA concentrations. IMPACT AND IMPLICATIONS: Cholemic nephropathy (CN) is a severe complication of cholestasis and an unmet clinical need. We demonstrate that CN is triggered by the renal accumulation of bile acids (BAs) that are considerably increased in the systemic blood. Specifically, the proximal tubular epithelial cells of the kidney take up BAs via the apical sodium-dependent bile acid transporter (ASBT). We developed a therapeutic compound that blocks ASBT in the kidneys, prevents BA overload in tubular epithelial cells, and almost completely abolished all disease hallmarks in a CN mouse model. Renal ASBT inhibition represents a potential therapeutic strategy for patients with CN.

Vinpocetine protects against chloroquine-induced cardiotoxicity by mitigating oxidative stress.

Chloroquine (CQ) and hydroxychloroquine (HCQ) are classical antimalarial drugs, and recently have been used for other applications including coronavirus disease 2019 (COVID-19). Although they are considered safe, cardiomyopathy may associate CQ and HCQ applications particularly at overdoses. The goal of the present study was to evaluate the potential protective effect of the nootropic agent vinpocetine against CQ and HCQ adverse effects with a specific focus on the heart. For this purpose, a mouse model of CQ (0.5 up to 2.5 g/kg)/HCQ (1 up to 2 g/kg) toxicity was used, and the effect of vinpocetine was evaluated by survival, biochemical, as well as histopathological analyses. Survival analysis revealed that CQ and HCQ caused dose-dependent lethality, which was prevented by co-treatment with vinpocetine (100 mg/kg, oral or intraperitoneal). To gain deeper understanding, a dose of 1 g/kg CQ-which did not cause death within the first 24 h after administration-was applied with and without vinpocetine administration (100 mg/kg, intraperitoneal). The CQ vehicle group showed marked cardiotoxicity as evidenced by significant alterations of blood biomarkers including troponione-1, creatine phosphokinase (CPK), creatine kinase-myocardial band (CK-MB), ferritin, and potassium levels. This was confirmed at the tissue level by massive alteration of the heart tissue morphology and coincided with massive oxidative stress. Interestingly, co-administration of vinpocetine strongly ameliorated CQ-induced alterations and restored the antioxidant-defense system of the heart. These data suggest that vinpocetine could be used as an adjuvant therapy together with CQ/HCQ applications.