Drug-induced liver injury: what was new in 2013?

Perfused human hepatocyte microtissues identify reactive metabolite-forming and mitochondria-perturbing hepatotoxins

Hepatotoxins cause liver damage via many mechanisms but the formation of reactive metabolites and/or damage to liver mitochondria are commonly implicated. We assess 3D human primary hepatocyte microtissues as a platform for hepatotoxicity studies with reactive metabolite-forming and mitochondria-perturbing compounds. We show that microtissues formed from cryopreserved human hepatocytes had bile canaliculi, transcribed mRNA from genes associated with xenobiotic metabolism and expressed functional cytochrome P450 enzymes. Hierarchical clustering was used to distinguish dose-dependent hepatotoxicity elicited by clozapine, fialuridine and acetaminophen (APAP) from control cultures and less liver-damaging compounds, olanzapine and entecavir. The regio-isomer of acetaminophen, N-acetyl-meta-aminophenol (AMAP) clustered with the hepatotoxic compounds. The principal metabolites of APAP were formed and dose-dependent changes in metabolite profile similar to those seen in patient overdose was observed. The toxicological profile of APAP was indistinguishable from that of AMAP, confirming AMAP as a human hepatotoxin. Tissue oxygen consumption rate was significantly decreased within 2h of exposure to APAP or AMAP, concomitant with glutathione depletion. These data highlight the potential utility of perfused metabolically functional human liver microtissues in drug development and mechanistic toxicology.

Drug-induced liver injury: Do we know everything?

Interest in drug-induced liver injury (DILI) has dramatically increased over the past decade, and it has become a hot topic for clinicians, academics, pharmaceutical companies and regulatory bodies. By investigating the current state of the art, the latest scientific findings, controversies, and guidelines, this review will attempt to answer the question: Do we know everything? Since the first descriptions of hepatotoxicity over 70 years ago, more than 1000 drugs have been identified to date, however, much of our knowledge of diagnostic and pathophysiologic principles remains unchanged. Clinically ranging from asymptomatic transaminitis and acute or chronic hepatitis, to acute liver failure, DILI remains a leading causes of emergent liver transplant. The consumption of unregulated herbal and dietary supplements has introduced new challenges in epidemiological assessment and clinician management. As such, numerous registries have been created, including the United States Drug-Induced Liver Injury Network, to further our understanding of all aspects of DILI. The launch of LiverTox and other online hepatotoxicity resources has increased our awareness of DILI. In 2013, the first guidelines for the diagnosis and management of DILI, were offered by the Practice Parameters Committee of the American College of Gastroenterology, and along with the identification of risk factors and predictors of injury, novel mechanisms of injury, refined causality assessment tools, and targeted treatment options have come to define the current state of the art, however, gaps in our knowledge still undoubtedly remain.

A non-hepatotropic parasite infection increases mortality in the acetaminophen-induced acute liver failure murine model: possible roles for IL-5 and IL-6

We evaluated the effects of a non-hepatotropic parasite infection (Taenia crassiceps) on the outcome of acetaminophen-induced acute liver failure in mice. Uninfected and T. crassiceps infected mice orally received either 300 mg/kg acetaminophen or water as vehicle (n = 5 per group). Survival analysis, hepatocyte necrosis, alanine aminotransferase (ALT) levels, CYP2E1 protein, interleukin (IL-) 5, and IL-6 were assessed for all groups. All infected mice died within 16 h after exposure to acetaminophen (Tc+APAP group), whereas only one-third of uninfected animals exposed to acetaminophen (APAP group) died. Uninfected (Control group) and infected (Tc group) mice that received the vehicle showed no liver damage. Tc+APAP mice exhibited massive liver necrosis characterised by marked balloning degeneration of hepatocytes and higher serum ALT compared to Control, Tc, and APAP animals. Liver tissue from Tc+APAP mice also displayed increased expression of CYP2E1 protein and higher mRNA and protein levels of IL-5 and IL-6 compared to the other groups. These findings suggest that non-hepatotropic parasite infections may increase mortality following acute liver failure by promoting hepatocyte necrosis via IL-5 and IL-6-dependent CYP2E1 overproduction. This study identifies new potential risk factors associated with severe acute liver failure in patients.

The Art and Science of Diagnosing and Managing Drug-induced Liver Injury in 2015 and Beyond

Drug-induced liver injury (DILI) remains a leading reason why new compounds are dropped from further study or are the subject of product warnings and regulatory actions. Hy's Law of drug-induced hepatocellular jaundice causing a case-fatality rate or need for transplant of 10% or higher has been validated in several large national registries, including the ongoing, prospective U.S. Drug-Induced Liver Injury Network. It serves as the basis for stopping rules in clinical trials and in clinical practice. Because DILI can mimic all known causes of acute and chronic liver disease, establishing causality can be difficult. Histopathologic findings are often nonspecific and rarely, if ever, considered pathognomonic. A daily drug dose >50-100 mg is more likely to be hepatotoxic than does <10 mg, especially if the compound is highly lipophilic or undergoes extensive hepatic metabolism. The quest for a predictive biomarker to replace alanine aminotransferase is ongoing. Markers of necrosis and apoptosis such as microRNA-122 and keratin 18 may prove useful in identifying patients at risk for severe injury when they initially present with a suspected acetaminophen overdose. Although a number of drugs causing idiosyncratic DILI have HLA associations that may allow for pre-prescription testing to prevent hepatotoxicity, the cost and relatively low frequency of injury among affected patients limit the current usefulness of such genome-wide association studies. Alanine aminotransferase monitoring is often recommended but has rarely been shown to be an effective method to prevent serious DILI. Guidelines on the diagnosis and management of DILI have recently been published, although specific therapies remain limited. The LiverTox Web site has been introduced as an interactive online virtual textbook that makes the latest information on more than 650 agents available to clinicians, regulators, and drug developers alike.

Drug- and herb-induced liver injury: Progress, current challenges and emerging signals of post-marketing risk

Drug-induced liver injury (DILI) and herb-induced liver injury is a hot topic for clinicians, academia, drug companies and regulators, as shown by the steadily increasing number of publications in the past 15 years. This review will first provide clues for clinicians to suspect idiosyncratic (unpredictable) DILI and succeed in diagnosis. Causality assessment remains challenging and requires careful medical history as well as awareness of multifaceted aspects, especially for herbs. Drug discontinuation and therapy reconciliation remain the mainstay in patent’s management to minimize occurrence of acute liver failure. The second section will address novel agents associated with liver injury in 2014 (referred to as “signals”), especially in terms of clinical, research and drug development implications. Insights will be provided into recent trends by highlighting the contribution of different post-marketing data, especially registries and spontaneous reporting systems. This literature scrutiny suggests: (1) the importance of post-marketing databases as tools of clinical evidence to detect signals of DILI risk; and (2) the need for joining efforts in improving predictivity of pre-clinical assays, continuing post-marketing surveillance and design ad hoc post-authorization safety studies. In this context, ongoing European/United States research consortia and novel pharmaco-epidemiological tools (e.g., specialist prescription event monitoring) will support innovation in this field. Direct oral anticoagulants and herbal/dietary supplements appear as key research priorities.