Utilization of Causal Reasoning of Hepatic Gene Expression in Rats to Identify Molecular Pathways of Idiosyncratic Drug-Induced Liver Injury

Abstract

Drug-induced liver injury (DILI) represents a leading cause of acute liver failure. Although DILI can be discovered in preclinical animal toxicology studies and/or early clinical trials, some human DILI reactions, termed idiosyncratic DILI (IDILI), are less predictable, occur in a small number of individuals, and do not follow a clear dose-response relationship. The emergence of IDILI poses a critical health challenge for patients and a financial challenge for the pharmaceutical industry. Understanding the cellular and molecular mechanisms underlying IDILI is key to the development of models that can assess potential IDILI risk. This study used Reverse Causal Reasoning (RCR), a method to assess activation of molecular signaling pathways, on gene expression data from rats treated with IDILI or pharmacologic/chemical comparators (NON-DILI) at the maximum tolerated dose to identify mechanistic pathways underlying IDILI. Detailed molecular networks involved in mitochondrial injury, inflammation, and endoplasmic reticulum (ER) stress were found in response to IDILI drugs but not negative controls (NON-DILI). In vitro assays assessing mitochondrial or ER function confirmed the effect of IDILI compounds on these systems. Together our work suggests that using gene expression data can aid in understanding mechanisms underlying IDILI and can guide in vitro screening for IDILI. Specifically, RCR should be considered for compounds that do not show evidence of DILI in preclinical animal studies positive for mitochondrial dysfunction and ER stress assays, especially when the therapeutic index toward projected human maximum drug plasma concentration is low.

Mitochondrial toxicity assessment in industry – a decade of technology development and insight

“…If compounds with potential mitochondrial liabilities are moved forward, projected exposure will determine a possible safety margin; a mitochondrial liability at 100 µM is a moot point for a compound with a 1-nM efficacy (unless bioaccumulation is afoot). The dilemma of preclinical species not revealing mitochondrial impairment as frank organ toxicity via histopathology requires more refined approaches such as gene expression analysis [34]. The data with diverse mice strains [29] cautions that mitochondrial susceptibility differs which would contribute to idiosyncratic responses.…”

Preventing Drug-Induced Liver Injury: How Useful Are Animal Models?

“…In a recent study by Laifenfeld et al [45], a single dose of one of nine IDILI-associated or eight non-DILI-associated drugs was administered to rats at the maximum tolerated dose and gene expression analysis was performed at 24 h. No signs of liver injury assessed by conventional markers were detected. Key molecular pathways involved in mitochondrial injury, inflammation or endoplasmic reticulum stress were identified based on specific gene expression profile signatures by reverse causal reasoning, with 8/9 IDILI-associated drugs but only 4/8 non-DILI-associated drugs.…”

High-Content Imaging in Human and Rat Hepatocytes Using the Fluorescent Dyes CLF and CMFDA Is Not Specific Enough to Assess BSEP/Bsep and/or MRP2/Mrp2 Inhibition by Cholestatic Drugs

“…One of those methods is described by Laifenfeld et al 54 The authors conducted gene expression studies in rats treated with idiosyncratic DILI compounds and causal reasoning identified fingerprints indicative of DILI, but were absent in compounds not known to cause DILI. 54 For DILI compounds inhibiting BSEP, the hunt for biomarkers suitable for rat and dog continues. Whether bile salt profiles can help identify potential human risk remains to be seen in the coming years.…”