Highly expressed protein kinase A inhibitor α and suppression of protein kinase A may potentiate acetaminophen-induced hepatotoxicity

CREB is a potential marker associated with drug-induced liver injury: Identification and validation through transcriptome database analysis

Drug-induced liver injury (DILI) is the main cause of failure in drug development and postapproval withdrawal. Although toxicogenomic techniques provide an unprecedented opportunity for mechanistic assessment and biomarker discovery, they are not suitable for the screening of large numbers of exploratory compounds in early drug discovery. Using a comprehensive analysis of toxicogenomics (TGx) data, we aimed to find DILI-relevant transcription factors (TFs) that could be incorporated into a reporter gene assay system. Gene set enrichment analysis (GSEA) of the Open TG-GATEs dataset highlighted 4 DILI-relevant TFs, including CREB, NRF2, ELK-1, and E2F. Using ten drugs with already assigned idiosyncratic toxicity (IDT) risks, reporter gene assays were conducted in HepG2 cells in the presence of the S9 mix. There were weak correlations between NRF2 activity and IDT risk, whereas strong correlations were observed between CREB activity and IDT risk. In addition, CREB activation associated with 3 Withdrawn/Black box Warning drugs was reversed by pretreatment with a PKA inhibitor. Collectively, we suggest that CREB might be a sensitive biomarker for DILI prediction, and its response to stress induced by high-risk drugs might be primarily regulated by the PKA/CREB signaling pathway.

Glucose deprivation affects the expression of genes encoding cAMP-activated protein kinase and related proteins in U87 glioma cells in ERN1 dependent manner

Objective. The aim of this investigation was to study the expression of genes encoding cAMP-activated protein kinase catalytic and regulatory A subunits (PRKACA and PRKAR1A) and related proteins such as cAMP-dependent protein kinase inhibitors A and G (PKIA and PKIG), catalytic subunit A of protein phosphatase 3 (PPP3CA), A-kinase anchoring protein 12 (AKAP12), and praja ring finger ubiquitin ligase 2 (PJA2) in U87 glioma cells in response to glucose deprivation in both control U87 glioma cells and cells with ERN1 (endoplasmic reticulum to nucleus signaling 1) knockdown, the major pathway of the endoplasmic reticulum stress signaling, for evaluation of possible significance of glucose deprivation in ERN1 dependent regulation of glioma growth.Methods. The expression level of PRKA related genes was studied in control (transfected by vector) and ERN1 knockdown U87 glioma cells under glucose deprivation by real-time quantitative polymerase chain reaction.Results. It was shown that the expression level of PRKACA and PKIA genes was down-regulated in control glioma cells treated by glucose deprivation, but PJA2 gene was up-regulated. At the same time, the expression of four other genes (PRKAR1A, PKIG, AKAP12, and PPP3CA) was resistant to this experimental condition. Furthermore, ERN1 knockdown of glioma cells significantly modified the effect glucose deprivation on the expression almost all studied genes. Thus, treatment of glioma cells with inhibited ERN1 enzymatic activity by glucose deprivation lead to a more significant down-regulation of the expression level of PKIA and to suppression PRKAR1A gene expressions. Moreover, the ERN1 knockdown introduced up-regulation of PKIG and AKAP12 gene expressions in glioma cells treated by glucose deprivation and eliminated the sensitivity of PJA2 gene to this experimental condition.Conclusions. Results of this investigation demonstrated that ERN1 knockdown significantly modified the sensitivity of most studied PRKA related gene expressions to glucose deprivation and that these changes are a result of complex interactions of variable endoplasmic reticulum stress related and unrelated regulatory factors and contributed to the suppression of glioma cell proliferation and their possibly chemoresistance.

Glycyrrhetinic acid prevents acetaminophen-induced acute liver injury via the inhibition of CYP2E1 expression and HMGB1-TLR4 signal activation in mice

Acetaminophen (APAP) is a widely used antipyretic and analgesic drug, which is safe and effective at the therapeutic dose. Unfortunately, excessive dosage of APAP could cause severe liver injury due to lack of effective therapy. Successful therapeutic strategies are urgently requested in clinic. Glycyrrhetinic acid (GA), derived from a traditional medicine licorice, has been shown to exert anti-inflammatory and antioxidant actions. In this study, the effect and the underlying mechanism of GA on APAP-induced hepatotoxicity were explored. Our results showed that pretreatment with GA significantly reduced serum ALT and AST activities, alleviated hepatic pathological damages with hepatocellular apoptosis, down-regulated expression of CYP2E1 mRNA and protein, increased GSH levels, and reduced reactive oxygen species (ROS) productions in the liver of APAP-exposed mice. Furthermore, GA obviously inhibited APAP-induced HMGB1-TLR4 signal activation, as evaluated by reduced hepatic HMGB1 release, p-IRAK1, p-MAPK and p-IκB expression as well as the productions of TNF-α and IL-1β. In addition, GA attenuated hepatic neutrophils recruitment and macrophages infiltration caused by APAP. These findings reflected that GA could alleviate APAP-induced hepatotoxicity, the possible mechanism is associated with down-regulation of CYP2E1 expression and deactivation of HMGB1-TLR4 signal pathway.

Expression Levels of GABA-A Receptor Subunit Alpha 3, Gabra3 and Lipoprotein Lipase, Lpl Are Associated with the Susceptibility to Acetaminophen-Induced Hepatotoxicity

Drug-induced liver injury (DILI) is the serious and fatal drug-associated adverse effect, but its incidence is very low and individual variation in severity is substantial. Acetaminophen (APAP)-induced liver injury accounts for >50% of reported DILI cases but little is known for the cause of individual variations in the severity. Intrinsic genetic variation is considered a key element but the identity of the genes was not well-established. Here, pre-biopsy method and microarray technique was applied to uncover the key genes for APAP-induced liver injury in mice, and a cause and effect experiment employing quantitative real-time PCR was conducted to confirm the correlation between the uncovered genes and APAP-induced hepatotoxicity. We identified the innately and differentially expressed genes of mice susceptible to APAP-induced hepatotoxicity in the pre-biopsied liver tissue before APAP treatment through microarray analysis of the global gene expression profiles (Affymetrix GeneChip® Mouse Gene 1.0 ST for 28,853 genes). Expression of 16 genes including Gdap10, Lpl, Gabra3 and Ccrn4l were significantly different (t-test: FDR <10%) more than 1.5 fold in the susceptible animals than resistant. To confirm the association with the susceptibility to APAP-induced hepatotoxicity, another set of animals were measured for the expression level of selected 4 genes (higher two and lower two genes) in the liver pre-biopsy and their sensitivity to APAP-induced hepatotoxicity was evaluated by post hoc. Notably, the expressions of Gabra3 and Lpl were significantly correlated with the severity of liver injury (p<0.05) demonstrating that these genes may be linked to the susceptibility to APAP-induced hepatotoxicity.

Rhododenol and raspberry ketone impair the normal proliferation of melanocytes through reactive oxygen species-dependent activation of GADD45

Rhododenol or rhododendrol (RD, 4-(4-hydroxyphenyl)-2-butanol) occurs naturally in many plants along with raspberry ketone (RK, 4-(4-hydroxyphenyl)-2-butanone), a ketone derivative, which include Nikko maple tree (Acer nikoense) and white birch (Betula platyphylla). De-pigmenting activity of RD was discovered and it was used as a brightening ingredient for the skin whitening cosmetics. Recently, cosmetics containing RD were withdrawn from the market because a number of consumers developed leukoderma, inflammation and erythema on their face, neck and hands. Here, we explored the mechanism underlying the toxicity of RD and RK against melanocytes using B16F10 murine melanoma cells and human primary epidermal melanocytes. Treatment with RD or RK resulted in the decreased cell viability in a dose-dependent manner which appeared from cell growth arrest. Consistently, ROS generation was significantly increased by RD or RK as determined by DCF-enhanced fluorescence. An antioxidant enzyme, glutathione peroxidase was depleted as well. In line with ROS generation, oxidative damages and the arrest of normal cell proliferation, GADD genes (Growth Arrest and DNA Damage) that include GADD45 and GADD153, were significantly up-regulated. Prevention of ROS generation with an anti-oxidant, N-acetylcysteine (NAC) significantly rescued RD and RK-suppressed melanocyte proliferation. Consistently, up-regulation of GADD45 and GADD153 was significantly attenuated by NAC, suggesting that increased ROS and the resultant growth arrest of melanocytes may contribute to RD and RK-induced leukoderma.

Predose and Postdose Blood Gene Expression Profiles Identify the Individuals Susceptible to Acetaminophen-Induced Liver Injury in Rats

The extent of drug-induced liver injury (DILI) can vary greatly between different individuals. Thus, it is crucial to identify susceptible population to DILI. The aim of this study was to determine whether transcriptomics analysis of predose and postdose rat blood would allow prediction of susceptible individuals to DILI using the widely applied analgesic acetaminophen (APAP) as a model drug. Based on ranking in alanine aminotransferase levels, five most susceptible and five most resistant rats were identified as two sub-groups after APAP treatment. Predose and postdose gene expression profiles of blood samples from these rats were determined by microarray analysis. The expression of 158 genes innately differed in the susceptible rats from the resistant rats in predose data. In order to identify more reliable biomarkers related to drug responses for detecting individuals susceptibility to APAP-induced liver injury (AILI), the changes of these genes' expression posterior to APAP treatment were detected. Through the further screening method based on the trends of gene expression between the two sub-groups before and after drug treatment, 10 genes were identified as potential predose biomarkers to distinguish between the susceptible and resistant rats. Among them, four genes, Incenp, Rpgrip1, Sbf1, and Mmp12, were found to be reproducibly in real-time PCR with an independent set of animals. They were all innately higher expressed in resistant rats to AILI, which are closely related to cell proliferation and tissue repair functions. It indicated that rats with higher ability of cell proliferation and tissue repair prior to drug treatment might be more resistant to AILI. In this study, we demonstrated that combination of predose and postdose gene expression profiles in blood might identify the drug related inter-individual variation in DILI, which is a novel and important methodology for identifying susceptible population to DILI.

Circulating mitochondrial biomarkers for drug-induced liver injury

Liver mitochondria affected by drugs can be released into circulation and serve as biomarkers for drug-induced liver injury (DILI). The tissue specificity of ALT was improved by differentiating cytosolic ALT1 and mitochondrial ALT2 isoforms released in circulation. Prior to ALT elevation, mitochondrial cytochrome c, OCT, GLDH, CPS1 and DNA were increased in circulation following DILI. The baseline expression of mt-Nd6 was predictive of individual DILI susceptibility in animals. As mitochondrial DILI biomarkers appeared to be drug or species dependent, they might have value in clinical scenarios when culprit drugs are established, but may not be ideal tools to assess DILI potentials of new drugs.