Search

PGC1α‐Related Coactivator (PRC) is a transcriptional coactivator promoting cytokine expression in vitro in response to mitochondrial injury and oxidative stress, however, its physiological role has remained elusive. Herein we investigate aspects of the immune response function of PRC, first in an in vivo thioacetamide (TAA)‐induced mouse model of drug‐induced liver injury (DILI), and subsequently in vitro in human monocytes, HepG2, and dendritic (DC) cells. TAA treatment resulted in the dose‐dependent induction of PRC mRNA and protein, both of which were shown to correlate with liver injury markers. Conversely, an adenovirus‐mediated knockdown of PRC attenuated this response, thereby reducing hepatic cytokine mRNA expression and monocyte infiltration. Subsequent in vitro studies with conditioned media from HepG2 cells overexpressing PRC, activated human monocytes and monocyte‐derived DC, demonstrated up to 20% elevated expression of CD86, CD40, and HLA‐DR. Similarly, siRNA‐mediated knockdown of PRC abolished this response in oligomycin stressed HepG2 cells. A putative mechanism was suggested by the co‐immunoprecipitation of Signal Transducer and Activator of Transcription 1 (STAT1) with PRC, and induction of a STAT‐dependent reporter. Furthermore, PRC co‐activated an NF‐κB‐dependent reporter, indicating interaction with known major inflammatory factors. In summary, our study indicates PRC as a novel factor modulating inflammation in DILI. [ABSTRACT FROM AUTHOR]

Context:There is an ongoing search for specific and translational biomarkers of drug-induced liver injury (DILI). MicroRNA-122 (miR-122) has previously shown potential as a sensitive, specific, and translational biomarker of DILI in both rodent, and human studies. Objective:To build on previous work within the field, we examined biomarker kinetics in a rat model of acetaminophen (APAP)-induced liver injury to confirm the sensitivity, and specificity of miR-122 and glutamate dehydrogenase (GLDH). Materials and methods:qRT-PCR and a standard enzymatic assay were used for biomarker analysis. Results:Both miR-122 and GLDH were demonstrated to be more readily-detectable biomarkers of APAP-DILI than alanine aminotransferase (ALT). Peak levels for all biomarkers were detected at 2 days after APAP. At day 3, miR-122 had returned to baseline; however, other biomarkers remained elevated between 3 and 4 days. We were also able to demonstrate that, although miR-122 is present in greater quantities in exosome-free form, both exosome-bound and non-vesicle bound miR-122 are released in a similar profile throughout the course of DILI. Discussion and conclusions:Together, this study demonstrates that both GLDH and miR-122 could be used during preclinical drug-development as complementary biomarkers to ALT to increase the chance of early detection of hepatotoxicity. [ABSTRACT FROM AUTHOR]

Background & Aims There is a demand for more sensitive, specific and predictive biomarkers for drug-induced liver injury ( DILI) than the gold standard used today, alanine aminotransferase ( ALT). The aim of this study was to qualify novel DILI biomarkers (keratin-18 markers M65/M30, micro RNA-122, glutamate dehydrogenase and alpha-foetoprotein) in human DILI. Methods Levels of the novel biomarkers were measured by enzyme-linked immunosorbent assay or real-time quantitative reverse-transcription PCR ( qRT-PCR) in two human DILI cohorts: a human volunteer study with acetaminophen and a human immunodeficiency virus (HIV)/tuberculosis (TB) study. Results In the acetaminophen study, serum M65 and micro RNA-122 levels were significantly increased at an earlier time point than ALT. Furthermore, the maximal elevation of M65 and micro RNA-122 exceeded the increase in ALT. In the HIV/ TB study, all the analysed novel biomarkers increased after 1 week of treatment. In contrast to ALT, the novel biomarkers remained stable in a human cohort with exercise-induced muscular injury. Conclusions M65 and micro RNA-122 are potential biomarkers of DILI superior to ALT with respect to sensitivity and specificity. [ABSTRACT FROM AUTHOR]

Ximelagatran was developed for the prevention and treatment of thromboembolic conditions. However, in long-term clinical trials with ximelagatran, the liver injury marker, alanine aminotransferase (ALT) increased in some patients. Analysis of plasma samples from 134 patients was carried out using proteomic and metabolomic platforms, with the aim of finding predictive biomarkers to explain the ALT elevation. Analytes that were changed after ximelagatran treatment included 3-hydroxybutyrate, pyruvic acid, CSF1R, Gc-globulin, L-glutamine, protein S and alanine, etc. Two of these analytes (pyruvic acid and CSF1R) were studied further in human cell cultures in vitro with ximelagatran. A systems biology approach applied in this study proved to be successful in generating new hypotheses for an unknown mechanism of toxicity. [ABSTRACT FROM AUTHOR]

Abstract: Serum alanine aminotransferase (ALT) is used as a clinical marker of hepatotoxicity. Two forms of ALT have been identified, ALT1 and ALT2, encoded by separate genes. The cellular and tissue distribution of the different ALT proteins has not been characterized in humans, and their relative contribution to serum is unknown. Here, we describe the development of novel isoenzyme specific ALT1 and ALT2 antibodies and the expression of the enzymes in human cells and organs. In normal human tissue, high expression of ALT1 was found in liver, skeletal muscle and kidney and low levels in heart muscle and not detectable in pancreas. High ALT2 reactivity was detected in heart and skeletal muscle, while no ALT2 expression was found in liver or kidney. Using immunohistochemistry, strong ALT1 reactivity was found in hepatocytes, renaltubular epithelial cells and in salivary gland epithelial cells, while ALT2 was expressed in adrenal gland cortex, neuronal cell bodies, cardiac myocytes, skeletal muscle fibers and endocrine pancreas. Immunoprecipitation using ALT antibodies on normal human serums showed ALT1 to be mainly responsible for basal ALT activity. Together, the results points to a differential expression of ALT1 and ALT2 in human organs and substantiate a need for investigations regarding the possible impacts on ALT measurements. [Copyright &y& Elsevier]