Blood gene expression profiling of an early acetaminophen response

A Multi-Omic Mosaic Model of Acetaminophen Induced Alanine Aminotransferase Elevation

BACKGROUND

Acetaminophen (APAP) is the most common cause liver injury following alcohol in US patients. Predicting liver injury and subsequent hepatic regeneration in patients taking therapeutic doses of APAP may be possible using new 'omic methods such as metabolomics and genomics. Multi'omic techniques increase our ability to find new mechanisms of injury and regeneration.

METHODS

We used metabolomic and genomic data from a randomized controlled trial of patients administered 4 g of APAP per day for 14 days or longer with blood samples obtained at 0 (baseline), 4, 7, 10, 13 and 16 days. We used the highest ALT as the clinical outcome to be predicted in our integrated analysis. We used penalized regression to model the relationship between genetic variants and day 0 metabolite level, and then performed a metabolite-wide colocalization scan to associate the genetically regulated component of metabolite expression with ALT elevation. Genome-wide association study (GWAS) analyses were conducted for ALT elevation and metabolite level using linear regression, with age, sex, and the first five principal components included as covariates. Colocalization was tested via a weighted sum test.

RESULTS

Out of the 164 metabolites modeled, 120 met the criteria for predictive accuracy and were retained for genetic analyses. After genomic examination, eight metabolites were found to be under genetic control and predictive of ALT elevation due to therapeutic acetaminophen. The metabolites were: 3-oxalomalate, allantoate, diphosphate, L-carnitine, L-proline, maltose, and ornithine. These genes are important in the tricarboxylic acid cycle (TCA), urea breakdown pathway, glutathione production, mitochondrial energy production, and maltose metabolism.

CONCLUSIONS

This multi'omic approach can be used to integrate metabolomic and genomic data allowing identification of genes that control downstream metabolites. These findings confirm prior work that have identified mitochondrial energy production as critical to APAP induced liver injury and have confirmed our prior work that demonstrate the importance of the urea cycle in therapeutic APAP liver injury.

Identification of Genes Regulating Hepatocyte Injury by a Genome-Wide CRISPR-Cas9 Screen

Gene editing introduces stable mutations into the genome and has powerful applications extending from research to clinical gene therapy. CRISPR-Cas9 gene editing can be employed to study directly the functional impact of stable gene knockout, activation, and knockdown. Here, we describe the end-to-end methodology by which we employ genome-wide CRISPR-Cas9 knockout to study drug toxicity using acetaminophen (APAP) in a hepatocellular carcinoma liver model as an example. This methodology can be extended to other proliferative cell types and chemical metabolic and toxicity models. By employing a massively parallelized genome-wide knockout model, the genes responsible for cellular toxicity and proliferation may be assayed concurrently. Resultant data are interrogated in the context of existing gene expression data, pathway analysis, drug-gene interactions, and orthogonal confirmatory assays to better understand the metabolic mechanisms.

Transcriptomic Analysis of Polyhexamethyleneguanidine-Induced Lung Injury in Mice after a Long-Term Recovery

Polyhexamethyleneguanidine phosphate (PHMG-P) is one of the causative agents of humidifier disinfectant-induced lung injury. Direct exposure of the lungs to PHMG-P causes interstitial pneumonia with fibrosis. Epidemiological studies showed that patients with humidifier disinfectant-associated lung injuries have suffered from restrictive lung function five years after the onset of the lung injuries. We investigated whether lung damage was sustained after repeated exposure to PHMG-P followed by a long-term recovery and evaluated the adverse effects of PHMG-P on mice lungs. Mice were intranasally instilled with 0.3 mg/kg PHMG-P six times at two weeks intervals, followed by a recovery period of 292 days. Histopathological examination of the lungs showed the infiltration of inflammatory cells, the accumulation of extracellular matrix in the lung parenchyma, proteinaceous substances in the alveoli and bronchiolar–alveolar hyperplasia. From RNA-seq, the gene expression levels associated with the inflammatory response, leukocyte chemotaxis and fibrosis were significantly upregulated, whereas genes associated with epithelial/endothelial cells development, angiogenesis and smooth muscle contraction were markedly decreased. These results imply that persistent inflammation and fibrotic changes caused by repeated exposure to PHMG-P led to the downregulation of muscle and vascular development and lung dysfunction. Most importantly, this pathological structural remodeling induced by PHMG-P was not reversed even after long-term recovery.

The Genomics of Elevated ALT and Adducts in Therapeutic Acetaminophen Treatment: a Pilot Study

INTRODUCTION

Therapeutic acetaminophen (APAP) ingestion causes asymptomatic drug-induced liver injury in some patients. In most cases, elevations in alanine aminotransferase (ALT) are transient and return to the normal range, even with continued APAP ingestion, though ALT elevation persists in some patients unpredictably. The etiology of this liver injury or adaption is unclear. Our objective was to identify new pharmacogenomic variants associated with elevated ALT or elevated protein adduct concentrations in patients receiving therapeutic acetaminophen.

METHODS

We performed genome-wide sequencing analysis on eight patients using leftover blood samples from an observational study that administered four grams of acetaminophen for up to 16 days to all patients. Two patients with ALT elevations > two times the upper limit of normal, two patients with no adduct formation, and four control patients were sequenced. The genomes were aligned with the GRCh38 reference sequence, and variants with predicted low, moderate, or high impact on the subsequent proteins were first manually curated for biologic plausibility, then organized and examined in the REACTOME pathway analysis program.

RESULTS

We found 394 variants in 107 genes associated with elevated ALT. Variants associated with ALT elevation predominantly involved genes in the immune system (MHC class II complex genes), endoplasmic reticulum stress response (SEC23B and XBP1), oxidative phosphorylation (NDUFB9), and WNT/beta-catenin signaling (FZD5). Variants associated with elevated adducts were primarily in signal transduction (MUC20) and DNA repair mechanisms (P53).

CONCLUSIONS

While underpowered, genetic variants in immune system genes may be associated with drug-induced liver injury at therapeutic doses of acetaminophen.

A Meta-Analysis of the Performance of a Blood-Based Exposure Response Gene Signature Across Clinical Studies on the Tobacco Heating System 2.2 (THS 2.2)

As part of emerging tobacco harm reduction strategies, modified risk tobacco products (MRTP) are being developed to offer alternatives that have the potential to reduce the individual risk and population harm compared with smoking cigarettes for adult smokers who want to continue using tobacco and nicotine products. MRTPs are defined as any tobacco products that are distributed for use to reduce harm or the risk of tobacco-related disease associated with commercially marketed tobacco products. One such candidate MRTP is the Tobacco Heating System (THS) 2.2, which does not burn tobacco but instead heats it, thus producing significantly reduced levels of harmful and potentially harmful constituents compared with cigarettes. The clinical assessment of candidate MRTPs requires the development of exposure-response markers to distinguish current smokers from either nonsmokers or former smokers with high specificity and sensitivity. Toward this end, a whole blood-derived gene signature was previously developed and reported. Four randomized, controlled, open-label, three-arm parallel group reduced exposure clinical studies have been conducted with subjects randomized to three arms: switching from cigarettes to THS 2.2, continuous use of cigarettes, or smoking abstinence. These clinical studies had an investigational period of 5 days in confinement, which was followed by an 85-day ambulatory period in two studies. Here we tested the previously developed blood-derived signature on the samples derived from those clinical studies. We showed that in all four studies, the signature scores were reduced consistently in subjects who either stopped smoking or switched to THS 2.2 compared with subjects who continued smoking cigarettes.

Screening of acetaminophen-induced alterations in epithelial-to-mesenchymal transition-related expression of microRNAs in a model of stem-like triple-negative breast cancer cells: The possible functional impacts

Current protocols for therapy inefficiently targets triple negative breast cancer and barely eradicate cancer stem cells. Elucidation of the pleiotropic effect of clinically proven therapeutics on cancer cells shed light on novel application of old friends. The pleiotropic effect of acetaminophen (APAP) on breast cancer was previously reported. In a cell model of triple negative breast cancer with stem-like CD44^high/CD24^low phenotype, we screened the impacts of APAP (1 mM, 72 h) on the Epithelial to mesenchymal transition (EMT)-related expression of miRs. APAP significantly overexpressed hsa-miR-130a-3p, 192-5p, 214-3p, 101-3p, 30d-5p, 10a-5p, 99a-5p, 200c-3p, 143-3p, 30b-5p and let-7f-5p showed significant overexpression, but suppressed the expression of hsa-miR-7-5p, 149-3p, 215, 150-5p, 205-5p, 206, 10b-5p, 20b-5p, 145-5p, 26b-5p, 223-3p, 17-5p, 186-5p, 146a-5p and let-7c. It also altered on the expression of selected EMT-related genes, significantly upregulated the expression of KRT19, AKT2, CD24, and TIMP1; but downregulated the expression of MMP2, ALDH1, MMP9, TWIST, NOTCH1, and AKT1. Such shifts in expression profiles increased the population of the cells with CD44^high/CD24^high, and CD44^low/CD24^high phenotypes, significantly reduced the Twist protein and shifted the balance of E-cadherin and Vimentin proteins in favor of differentiation. Treated cells showed a significant reduction of in vitro migration and were significantly chemosensitized to Camptothecin. In conclusion, APAP, at a safe clinical dose, induced a set of targeted alterations in the EMT-related miRs which implicate, even in part, significant mitigation in chemoresistance and in vitro migration. Further studies should also be piloted to elucidate the most crucial miRs and to evaluate its clinical effectiveness.

Identification of Novel Regulatory Genes in APAP Induced Hepatocyte Toxicity by a Genome-Wide CRISPR-Cas9 Screen

Acetaminophen (APAP) is a commonly used analgesic responsible for more than half of acute liver failure cases. Identification of previously unknown genetic risk factors would provide mechanistic insights and novel therapeutic targets for APAP-induced liver injury. This study used a genome-wide CRISPR-Cas9 screen to evaluate genes that are protective against, or cause susceptibility to, APAP-induced liver injury. HuH7 human hepatocellular carcinoma cells containing CRISPR-Cas9 gene knockouts were treated with 15 mM APAP for 30 minutes to 4 days. A gene expression profile was developed based on the 1) top screening hits, 2) overlap of expression data from APAP overdose studies, and 3) predicted affected biological pathways. We further demonstrated the implementation of intermediate time points for the identification of early and late response genes. This study illustrated the power of a genome-wide CRISPR-Cas9 screen to systematically identify novel genes involved in APAP-induced hepatotoxicity and to provide potential targets to develop novel therapeutic modalities.

Transcriptomics in toxicology

Xenobiotics, of which many are toxic, may enter the human body through multiple routes. Excessive human exposure to xenobiotics may exceed the body's capacity to defend against the xenobiotic-induced toxicity and result in potentially fatal adverse health effects. Prevention of the adverse health effects, potentially associated with human exposure to the xenobiotics, may be achieved by detecting the toxic effects at an early, reversible and, therefore, preventable stage. Additionally, an understanding of the molecular mechanisms underlying the toxicity may be helpful in preventing and/or managing the ensuing adverse health effects. Human exposures to a large number of xenobiotics are associated with hepatotoxicity or pulmonary toxicity. Global gene expression changes taking place in biological systems, in response to exposure to xenobiotics, may represent the early and mechanistically relevant cellular events contributing to the onset and progression of xenobiotic-induced adverse health outcomes. Hepatotoxicity and pulmonary toxicity resulting from exposure to xenobiotics are discussed as specific examples to demonstrate the potential application of transcriptomics or global gene expression analysis in the prevention of adverse health effects associated with exposure to xenobiotics.

The sbv IMPROVER Systems Toxicology Computational Challenge: Identification of Human and Species-Independent Blood Response Markers as Predictors of Smoking Exposure and Cessation Status

Cigarette smoking entails chronic exposure to a mixture of harmful chemicals that trigger molecular changes over time, and is known to increase the risk of developing diseases. Risk assessment in the context of 21^st century toxicology relies on the elucidation of mechanisms of toxicity and the identification of exposure response markers, usually from high-throughput data, using advanced computational methodologies. The sbv IMPROVER Systems Toxicology computational challenge (Fall 2015-Spring 2016) aimed to evaluate whether robust and sparse (≤40 genes) human (sub-challenge 1, SC1) and species-independent (sub-challenge 2, SC2) exposure response markers (so called gene signatures) could be extracted from human and mouse blood transcriptomics data of current (S), former (FS) and never (NS) smoke-exposed subjects as predictors of smoking and cessation status. Best-performing computational methods were identified by scoring anonymized participants' predictions. Worldwide participation resulted in 12 (SC1) and six (SC2) final submissions qualified for scoring. The results showed that blood gene expression data were informative to predict smoking exposure (i.e. discriminating smoker versus never or former smokers) status in human and across species with a high level of accuracy. By contrast, the prediction of cessation status (i.e. distinguishing FS from NS) remained challenging, as reflected by lower classification performances. Participants successfully developed inductive predictive models and extracted human and species-independent gene signatures, including genes with high consensus across teams. Post-challenge analyses highlighted "feature selection" as a key step in the process of building a classifier and confirmed the importance of testing a gene signature in independent cohorts to ensure the generalized applicability of a predictive model at a population-based level. In conclusion, the Systems Toxicology challenge demonstrated the feasibility of extracting a consistent blood-based smoke exposure response gene signature and further stressed the importance of independent and unbiased data and method evaluations to provide confidence in systems toxicology-based scientific conclusions.