Hepatic Amiodarone Lipotoxicity Is Ameliorated by Genetic and Pharmacological Inhibition of Endoplasmatic Reticulum Stress

Association between Cardiovascular Disease and Liver Disease, from a Clinically Pragmatic Perspective as a Cardiologist

Cardiovascular diseases and liver diseases are closely related. Non-alcoholic fatty liver disease has the same risk factors as those for atherosclerotic cardiovascular disease and may also be a risk factor for atherosclerotic cardiovascular disease on its own. Heart failure causes liver fibrosis, and liver fibrosis results in worsened cardiac preload and congestion. Although some previous reports regard the association between cardiovascular diseases and liver disease, the management strategy for liver disease in patients with cardiovascular diseases is not still established. This review summarized the association between cardiovascular diseases and liver disease. In patients with non-alcoholic fatty liver disease, the degree of liver fibrosis progresses with worsening cardiovascular prognosis. In patients with heart failure, liver fibrosis could be a prognostic marker. Liver stiffness assessed with shear wave elastography, the fibrosis-4 index, and non-alcoholic fatty liver disease fibrosis score is associated with both liver fibrosis in patients with liver diseases and worse prognosis in patients with heart failure. With the current population ageing, the importance of management for cardiovascular diseases and liver disease has been increasing. However, whether management and interventions for liver disease improve the prognosis of cardiovascular diseases has not been fully understood. Future investigations are needed.

Detailed Molecular Mechanisms Involved in Drug-Induced Non-Alcoholic Fatty Liver Disease and Non-Alcoholic Steatohepatitis: An Update

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are some of the biggest public health challenges due to their spread and increasing incidence around the world. NAFLD is characterized by intrahepatic lipid deposition, accompanied by dyslipidemia, hypertension, and insulin resistance, leading to more serious complications. Among the various causes, drug administration for the treatment of numerous kinds of diseases, such as antiarrhythmic and antihypertensive drugs, promotes the onset and progression of steatosis, causing drug-induced hepatic steatosis (DIHS). Here, we reviewed in detail the major classes of drugs that cause DIHS and the specific molecular mechanisms involved in these processes. Eight classes of drugs, among the most used for the treatment of common pathologies, were considered. The most diffused mechanism whereby drugs can induce NAFLD/NASH is interfering with mitochondrial activity, inhibiting fatty acid oxidation, but other pathways involved in lipid homeostasis are also affected. PubMed research was performed to obtain significant papers published up to November 2021. The key words included the class of drugs, or the specific compound, combined with steatosis, nonalcoholic steatohepatitis, fibrosis, fatty liver and hepatic lipid deposition. Additional information was found in the citations listed in other papers, when they were not displayed in the original search.

Role of immune dysfunction in drug induced liver injury

Drug-induced liver injury (DILI) is one of the leading causes of liver failure and withdrawal of drugs from the market. A poor understanding of the precipitating event aetiology and mechanisms of disease progression has rendered the prediction and subsequent treatment intractable. Recent literature suggests that some drugs can alter the liver’s repair systems resulting in injury. The pathophysiology of DILI is complex, and immune dysfunction plays an important role in determining the course and severity of the disease. Immune dysfunction is influenced by the host response to drug toxicity. A deeper understanding of these processes may be beneficial in the management of DILI and aid in drug development. This review provides a structured framework presenting DILI in three progressive stages that summarize the interplay between drugs and the host defence networks.

Repetitive amiodarone administration causes liver damage via adipose tissue ER stress-dependent lipolysis, leading to hepatotoxic free fatty acid accumulation

Drug-induced liver injury is an emerging form of acute and chronic liver disease that may manifest as fatty liver. Amiodarone (AMD), a widely used antiarrhythmic drug, can cause hepatic injury and steatosis by a variety of mechanisms, not all completely understood. We hypothesized that repetitive AMD administration may induce hepatic lipotoxicity not only via effects on the liver but also via effects on adipose tissue. Indeed, repetitive AMD administration induced endoplasmic reticulum (ER) stress in both liver and adipose tissue. In adipose tissue, AMD reduced lipogenesis and increased lipolysis. Moreover, AMD treatment induced ER stress and ER stress-dependent lipolysis in 3T3L1 adipocytes in vitro. In the liver, AMD caused increased expression of genes encoding proteins involved in fatty acid (FA) uptake and transfer (Cd36, Fabp1, and Fabp4), and resulted in increased hepatic accumulation of free FAs, but not of triacylglycerols. In line with this, there was increased expression of hepatic de novo FA synthesis genes. However, AMD significantly reduced the expression of the desaturase Scd1 and elongase Elovl6, detected at mRNA and protein levels. Accordingly, the FA profile of hepatic total lipids revealed increased accumulation of palmitate, an SCD1 and ELOVL6 substrate, and reduced levels of palmitoleate and cis-vaccenate, products of the enzymes. In addition, AMD-treated mice displayed increased hepatic apoptosis. The studies show that repetitive AMD induces ER stress and aggravates lipolysis in adipose tissue while inducing a lipotoxic hepatic lipid environment, suggesting that AMD-induced liver damage is due to compound insult to liver and adipose tissue.NEW & NOTEWORTHY AMD chronic administration induces hepatic lipid accumulation by several mechanisms, including induction of hepatic ER stress, impairment of β-oxidation, and inhibition of triacylglycerol secretion. Our study shows that repetitive AMD treatment induces not only hepatic ER stress but also adipose tissue ER stress and lipolysis and hepatic accumulation of free fatty acids and enrichment of palmitate in the total lipids. Understanding the toxicity mechanisms of AMD would help devise ways to limit liver damage.

New Avenues for Treatment and Prevention of Drug-Induced Steatosis and Steatohepatitis: Much More Than Antioxidants

Drug-induced lipid accumulation in the liver may induce two clinically relevant conditions, drug-induced steatosis (DIS) and drug-induced steatohepatitis (DISH). The list of drugs that may cause DIS or DISH is long and heterogeneous and includes therapeutically relevant molecules that cannot be easily replaced by less hepatotoxic medicines, therefore making specific strategies necessary for DIS/DISH prevention or treatment. For years, the only available tools to achieve these goals have been antioxidant drugs and free radical scavengers, which counteract drug-induced mitochondrial dysfunction but, unfortunately, have only limited efficacy. In the present review we illustrate how in vitro preclinical research unraveled new key players in the pathogenesis of specific forms of DISH, and how, in a few cases, proof of concept of the beneficial effects of their pharmacological modulation has been obtained in vivo in animal models of this condition. The key issue emerging from these studies is that, in selected cases, liver toxicity depends on mechanisms unrelated to those responsible for the desired, primary pharmacological effects of the toxic drug and, therefore, specific strategies can be designed to overcome steatogenicity without making the drug ineffective. In particular, the hepatotoxic drug could be given in combination with a second molecule intended to selectively antagonize its liver toxicity whilst, ideally, potentiating its desired pharmacological activity. Although most of the evidence that we discuss is from in vitro or animal models and will need to be further explored and validated in humans, it highlights new avenues to be pursued in order to improve the safety of steatogenic drugs.

Autophagy alleviates amiodarone-induced hepatotoxicity

Amiodarone is a widely used antiarrhythmic drug that can cause the development of steatohepatitis as well as liver fibrosis and cirrhosis. The molecular mechanisms of amiodarone-mediated liver injury remain largely unknown. We therefore analyzed amiodarone-mediated hepatocellular injury in patients with chronic heart failure, in primary hepatocytes and HepG2 cells. We found that amiodarone-treated patients with chronic heart failure revealed significantly higher serum levels of caspase-cleaved keratin-18, an apoptosis biomarker, compared to healthy individuals or patients not receiving amiodarone. Furthermore, amiodarone treatment of hepatocytes resulted in apoptosis associated with lipid accumulation and ER-stress induction. Liver cell steatosis was accompanied by enhanced de novo lipogenesis which, after reaching peak levels, declined together with decreased activation of ER stress. The decline of amiodarone-mediated lipotoxicity was associated with protective autophagy induction. In contrast, in hepatocytes treated with the autophagy inhibitor chloroquine as well as in autophagy gene (ATG5 or ATG7)-deficient hepatocytes, amiodarone-triggered toxicity was increased. In conclusion, we demonstrate that amiodarone induces lipid accumulation associated with ER stress and apoptosis in hepatocytes, which is mirrored by increased keratin-18 fragment serum levels in amiodarone-treated patients. Autophagy reduces amiodarone-mediated lipotoxicity and could provide a therapeutic strategy for protection from drug-induced liver injury.

Aripiprazole Cytotoxicity Coincides with Activation of the Unfolded Protein Response in Human Hepatic Cells

Schizophrenia is a mental disease that results in decreased life expectancy and well-being by promoting obesity and sedentary lifestyles. Schizophrenia is treated by antipsychotic drugs. Although the second-generation antipsychotics (SGA), Olanzapine and Aripiprazole, are more effective in treating schizophrenia, they display a higher risk of metabolic side effects, mostly by development of diabetes and insulin resistance, weight gain, and dyslipidemia. Endoplasmic reticulum (ER) stress is induced when ER homeostasis of lipid biosynthesis and protein folding is impaired. This leads to the activation of the unfolded protein response (UPR), a signaling cascade that aims to restore ER homeostasis or initiate cell death. Chronic conditions of ER stress in the liver are associated with diabetes and perturbed lipid metabolism. These metabolic dysfunctions resemble the pharmacological side effects of SGAs. We therefore investigated whether SGAs promote the UPR in human and mouse hepatocytes. We observed full-fledged activation of ER stress by Aripiprazole not by Olanzapine. This occurred at low micromolar concentrations and to variable intensities in different cell types, such as hepatocellular carcinoma, melanoma, and glioblastoma. Mechanistically, Aripiprazole caused depletion of ER calcium, leading to activation of inositol-requiring enzyme 1 (IRE1)and protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), two major transducers of the UPR. Cells underwent apoptosis with Aripiprazole treatment, which coincided with UPR induction, and this effect was reduced by adding glutathione without affecting UPR itself. Deletion of IRE1 from HepG2, a human liver cancer cell line, protected cells from Aripiprazole toxicity. Our study reveals for the first time a cytotoxic effect of Aripiprazole that involves the induction of ER stress. SIGNIFICANCE STATEMENT: The antischizophrenic drug Aripiprazole exerts cytotoxic properties at high concentrations. This study shows that this cytotoxicity is associated with the induction of endoplasmic reticulum (ER) stress and IRE1 activation, mechanisms involved in diet-induced obesity. Aripiprazole induced ER stress and calcium mobilization from the ER in human and mouse hepatocytes. Our study highlights a new mechanism of Aripiprazole that is not related to its effect on dopamine signaling.

Amiodarone Alters Cholesterol Biosynthesis through Tissue-Dependent Inhibition of Emopamil Binding Protein and Dehydrocholesterol Reductase 24

Amiodarone is prescribed for the treatment and prevention of irregular heartbeats. Although effective in clinical practice, the long-term use of amiodarone has many unwanted side effects, including cardiac, pulmonary, hepatic, and neurological toxicities. Our objective was to elucidate effects of amiodarone exposure on the cholesterol metabolism in cultured neuronal and non-neuronal cells and in individuals taking amiodarone. We observed that amiodarone increases distinct cholesterol precursors in different cell types in a dose-dependent manner. In liver and kidney cell lines, amiodarone causes increase in desmosterol levels, and in primary cortical neurons and astrocytes, amiodarone increases zymosterol, zymostenol, and 8-dehydrocholesterol (8-DHC). We conclude that amiodarone inhibits two enzymes in the pathway, emopamil binding protein (EBP) and dehydrocholesterol reductase 24 (DHCR24). Cortical neurons and astrocytes are more sensitive to amiodarone than liver and kidney cell lines. We confirmed the inhibition of EBP enzyme by analyzing the sterol intermediates in EBP-deficient Neuro2a cells versus amiodarone-treated control Neuro2a cells. To determine if the cell culture experiments have clinical relevance, we analyzed serum samples from amiodarone users. We found that in patient serum samples containing detectable amount of amiodarone there are elevated levels of the sterol precursors zymosterol, 8-DHC, and desmosterol. This study illustrates the need for close monitoring of blood biochemistry during prolonged amiodarone use to minimize the risk of side effects.