Leveraging microphysiological systems to address challenges encountered during development of oligonucleotide therapeutics.

Oligonucleotide therapeutics (ONTs) encompass classes of medicines that selectively target and potentially ameliorate previously untreatable and often rare diseases. Several unique classes of ONTs provide versatility, enabling direct modu­lation of gene expression by virtue of Watson-Crick base pairing or modulation of cell signaling through structural mimicry or interference with protein-receptor interactions. Due to a lack of suitable in vitro models capable of recapitulating or predicting in vivo effects of ONTs, their discovery and optimization has relied heavily on animal studies for predicting efficacy and safety in humans.

Quantitative Characterization of Population-Wide Tissue- and Metabolite-Specific Variability in Perchloroethylene Toxicokinetics in Male Mice.

Quantification of interindividual variability is a continuing challenge in risk assessment, particularly for compounds with complex metabolism and multi-organ toxicity. Toxicokinetic variability for perchloroethylene (perc) was previously characterized across 3 mouse strains and in 1 mouse strain with various degrees of liver steatosis. To further characterize the role of genetic variability in toxicokinetics of perc, we applied Bayesian population physiologically based pharmacokinetic (PBPK) modeling to the data on perc and metabolites in blood/plasma and tissues of male mice from 45 inbred strains from the Collaborative Cross (CC) mouse population.

Cardiovascular microphysiological systems (CVMPS) for safety studies - a pharma perspective.

The integrative responses of the cardiovascular (CV) system are essential for maintaining blood flow to provide oxygenation, nutrients, and waste removal for the entire body. Progress has been made in independently developing simple in vitro models of two primary components of the CV system, namely the heart (using induced pluripotent stem-cell derived cardiomyocytes) and the vasculature (using endothelial cells and smooth muscle cells). These two in vitro biomimics are often described as immature and simplistic, and typically lack the structural complexity of native tissues.

PBPK modeling of impact of nonalcoholic fatty liver disease on toxicokinetics of perchloroethylene in mice.

Background: Nonalcoholic fatty liver disease (NAFLD), a major cause of chronic liver disease in the Western countries with increasing prevalence worldwide, may substantially affect chemical toxicokinetics and thereby modulate chemical toxicity.

Objectives: This study aims to use physiologically-based pharmacokinetic (PBPK) modeling to characterize the impact of NAFLD on toxicokinetics of perchloroethylene (perc).

Methods: Quantitative measures of physiological and biochemical changes associated with the presence of NAFLD induced by high-fat or methionine/choline-deficient diets in C57B1/6 J mice are incorporated into a previously developed PBPK model for perc and its oxidative and conjugative metabolites.

Using Collaborative Cross Mouse Population to Fill Data Gaps in Risk Assessment: A Case Study of Population-Based Analysis of Toxicokinetics and Kidney Toxicodynamics of Tetrachloroethylene.

Background: Interindividual variability in susceptibility remains poorly characterized for environmental chemicals such as tetrachloroethylene (PERC). Development of population-based experimental models provide a potential approach to fill this critical need in human health risk assessment.

Objectives: In this study, we aimed to better characterize the contribution of glutathione (GSH) conjugation to kidney toxicity of PERC and the degree of associated interindividual toxicokinetic (TK) and toxicodynamic (TD) variability by using the Collaborative Cross (CC) mouse population.

Histopathological and Molecular Signatures of a Mouse Model of Acute-on-Chronic Alcoholic Liver Injury Demonstrate Concordance With Human Alcoholic Hepatitis.

Human alcoholic hepatitis (AH) carries a high mortality rate. AH is an acute-on-chronic form of liver injury characterized by hepatic steatosis, ballooned hepatocytes, neutrophil infiltration, and pericellular fibrosis. We aimed to study the pathogenesis of AH in an animal model which combines chronic hepatic fibrosis with intragastric alcohol administration.

Modulation of Tetrachloroethylene-Associated Kidney Effects by Nonalcoholic Fatty Liver or Steatohepatitis in Male C57BL/6J Mice.

Accounting for genetic and other (eg, underlying disease states) factors that may lead to inter-individual variability in susceptibility to xenobiotic-induced injury is a challenge in human health assessments. A previous study demonstrated that nonalcoholic fatty liver disease (NAFLD), one of the common underlying disease states, enhances tetrachloroethylene (PERC)-associated hepatotoxicity in mice. Interestingly, NAFLD resulted in a decrease in metabolism of PERC to nephrotoxic glutathione conjugates; we therefore hypothesized that NAFLD would protect against PERC-associated nephrotoxicity.

Incorporation of the glutathione conjugation pathway in an updated physiologically-based pharmacokinetic model for perchloroethylene in mice.

Background: Perchloroethylene (perc) induced target organ toxicity has been associated with tissue-specific metabolic pathways. Previous physiologically-based pharmacokinetic (PBPK) modeling of perc accurately predicted oxidative metabolites but suggested the need to better characterize glutathione (GSH) conjugation as well as toxicokinetic uncertainty and variability.

Objectives: We updated the previously published "harmonized" perc PBPK model in mice to better characterize GSH conjugation metabolism as well as the uncertainty and variability of perc toxicokinetics.

Effects of pirfenidone in acute and sub-chronic liver fibrosis, and an initiation-promotion cancer model in the mouse.

Liver fibrosis results from chronic tissue damage and excessive regeneration with accumulation of extracellular matrix proteins; it is a precursor of liver cirrhosis and hepatocellular carcinoma. Liver fibrosis treatments are primarily directed at inflammation, with few options to combat fibrogenesis. Pirfenidone is a drug approved for idiopathic pulmonary fibrosis and this study was focused on anti-fibrotic and anti-cancer potential of pirfenidone in the liver of male B6C3F1/J mice.

Editor's Highlight: Comparative Dose-Response Analysis of Liver and Kidney Transcriptomic Effects of Trichloroethylene and Tetrachloroethylene in B6C3F1 Mouse.

Trichloroethylene (TCE) and tetrachloroethylene (PCE) are ubiquitous environmental contaminants and occupational health hazards. Recent health assessments of these agents identified several critical data gaps, including lack of comparative analysis of their effects. This study examined liver and kidney effects of TCE and PCE in a dose-response study design.

Nonalcoholic Fatty Liver Disease Is a Susceptibility Factor for Perchloroethylene-Induced Liver Effects in Mice.

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent pathological liver condition in developed countries. NAFLD results in severe alterations in liver function, including xenobiotic metabolism. Perchloroethylene (PERC) is a ubiquitous environmental pollutant, a known hepatotoxicant in rodents, and a probable human carcinogen.

Simultaneous detection of the tetrachloroethylene metabolites S-(1,2,2-trichlorovinyl) glutathione, S-(1,2,2-trichlorovinyl)-L-cysteine, and N-acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine in multiple mouse tissues via ultra-high performance liquid chromatography electrospray ionization tandem mass spectrometry.

Tetrachloroethylene (perchloroethylene; PERC) is a high-production volume chemical and ubiquitous environmental contaminant that is hazardous to human health. Toxicity attributed to PERC is mediated through oxidative and glutathione (GSH) conjugation metabolites. The conjugation of PERC by glutathione-s-transferase to generate S-(1,2,2-trichlorovinyl) glutathione (TCVG), which is subsequently metabolized to form S-(1,2,2-trichlorovinyl)-L-cysteine (TCVC) is of special importance to human health.

Characterization of Variability in Toxicokinetics and Toxicodynamics of Tetrachloroethylene Using the Collaborative Cross Mouse Population.

Background: Evaluation of interindividual variability is a challenging step in risk assessment. For most environmental pollutants, including perchloroethylene (PERC), experimental data are lacking, resulting in default assumptions being used to account for variability in toxicokinetics and toxicodynamics.

Objective: We quantitatively examined the relationship between PERC toxicokinetics and toxicodynamics at the population level to test whether individuals with increased oxidative metabolism are be more sensitive to hepatotoxicity following PERC exposure.

Impact of Nonalcoholic Fatty Liver Disease on Toxicokinetics of Tetrachloroethylene in Mice.

Lifestyle factors and chronic pathologic states are important contributors to interindividual variability in susceptibility to xenobiotic-induced toxicity. Nonalcoholic fatty liver disease (NAFLD) is an increasingly prevalent condition that can dramatically affect chemical metabolism. We examined the effect of NAFLD on toxicokinetics of tetrachloroethylene (PERC), a ubiquitous environmental contaminant that requires metabolic activation to induce adverse health effects.

Inhalation dosimetry modeling provides insights into regional respiratory tract toxicity of inhaled diacetyl.

Vapor dosimetry models provide a means of assessing the role of delivered dose in determining the regional airway response to inspired vapors. A validated hybrid computational fluid dynamics physiologically based pharmacokinetic model for inhaled diacetyl has been developed to describe inhaled diacetyl dosimetry in both the rat and human respiratory tracts. Comparison of the distribution of respiratory tract injury with dosimetry estimates provides strong evidence that regional delivered dose rather than regional airway tissue sensitivity to diacetyl-induced injury is the critical determinant of the regional respiratory tract response to this water soluble reactive vapor.

Target Organ Metabolism, Toxicity, and Mechanisms of Trichloroethylene and Perchloroethylene: Key Similarities, Differences, and Data Gaps.

Trichloroethylene (TCE) and perchloroethylene or tetrachloroethylene (PCE) are high-production volume chemicals with numerous industrial applications. As a consequence of their widespread use, these chemicals are ubiquitous environmental contaminants to which the general population is commonly exposed. It is widely assumed that TCE and PCE are toxicologically similar; both are simple olefins with three (TCE) or four (PCE) chlorines.

Effects of Acetaminophen on Oxidant and Irritant Respiratory Tract Responses to Environmental Tobacco Smoke in Female Mice.

Background: Although it is known that acetaminophen causes oxidative injury in the liver, it is not known whether it causes oxidative stress in the respiratory tract. If so, this widely used analgesic may potentiate the adverse effects of oxidant air pollutants.

Objectives: The goal of this study was to determine if acetaminophen induces respiratory tract oxidative stress and/or potentiates the oxidative stress and irritant responses to an inhaled oxidant: environmental tobacco smoke (ETS).

The Contribution of Peroxisome Proliferator-Activated Receptor Alpha to the Relationship Between Toxicokinetics and Toxicodynamics of Trichloroethylene.

Exposure to the ubiquitous environmental contaminant trichloroethylene (TCE) is associated with cancer and non-cancer toxicity in both humans and rodents. Peroxisome proliferator-activated receptor-alpha (PPARα) is thought to be playing a role in liver toxicity in rodents through activation of the receptor by the TCE metabolite trichloroacetic acid (TCA). However, most studies using genetically altered mice have not assessed the potential for PPARα to alter TCE toxicokinetics, which may lead to differences in TCA internal doses and hence confound inferences as to the role of PPARα in TCE toxicity.

Menthol attenuates respiratory irritation and elevates blood cotinine in cigarette smoke exposed mice.

Addition of menthol to cigarettes may be associated with increased initiation of smoking. The potential mechanisms underlying this association are not known. Menthol, likely due to its effects on cold-sensing peripheral sensory neurons, is known to inhibit the sensation of irritation elicited by respiratory irritants.

Tissue sensitivity of the rat upper and lower extrapulmonary airways to the inhaled electrophilic air pollutants diacetyl and acrolein.

The target site for inhaled vapor-induced injury often differs in mouth-breathing humans compared with nose-breathing rats, thus complicating the use of rat inhalation toxicity data for assessment of human risk. We sought to examine sensitivity of respiratory/transitional nasal (RTM) and tracheobronchial (TBM) mucosa to two electrophilic irritant vapors: diacetyl and acrolein. Computational fluid dynamic physiologically based pharmacokinetic modeling was coupled with biomarker assessment to establish delivered dose-response relationships in RTM and TBM in male F344 rats following 6 h exposure to diacetyl or acrolein.

Sex differences in the acute nasal antioxidant/antielectrophilic response of the rat to inhaled naphthalene.

Naphthalene is a nasal carcinogen, inducing respiratory adenomas in male and olfactory neuroblastomas in female rats, respectively. The reasons for the site and sex-specific tumorigenic response are unknown. Naphthalene is bioactivated to electrophilic metabolites; cytotoxicity followed by regenerative cell proliferation is likely involved in the tumorigenic response.

In situ measurement of vapor uptake in the rodent upper respiratory tract.

The response of respiratory tract tissue target sites to inhaled vapors depends on the amount of inhaled vapor that is delivered to those sites. Direct measurement of vapor absorption within a specific airway of the living animal requires that the airway be isolated, which currently can only be performed on the upper airways. Towards this end, the upper respiratory tract (all airways anterior to the larynx) is surgically isolated in the anesthetized rat by tracheostomy and insertion of two endotracheal tubes, one leading anteriorly and the other posteriorly.

A validated hybrid computational fluid dynamics-physiologically based pharmacokinetic model for respiratory tract vapor absorption in the human and rat and its application to inhalation dosimetry of diacetyl.

Diacetyl vapor is associated with bronchiolar injury in man but primarily large airway injury in the rat. The goal of this study was to develop a physiologically based pharmacokinetic model for inspired vapor dosimetry and to apply the model to diacetyl. The respiratory tract was modeled as a series of airways: nose, trachea, main bronchi, large bronchi, small bronchi, bronchioles, and alveoli with tissue dimensions obtained from the literature.