Several drugs have been withdrawn from the market or restricted to avoid unexpected adverse outcomes. Drug-induced liver injury (DILI) is a serious issue for drug development. Among DILIs, idiosyncratic DILIs have been a serious problem in drug development and clinical uses. Idiosyncratic DILI is most often unrelated to pharmacological effects or the dosing amount of a drug. The number of drugs that cause idiosyncratic DILI continue to grow in part because no practical preclinical tests have emerged that can identify drug candidates with the potential for developing idiosyncratic DILIs. Nevertheless, the implications of drug metabolism-related factors and immune-related factors on idiosyncratic DILIs has not been fully clarified because this toxicity can not be reproduced in animals. Therefore, accumulated evidence for the mechanisms of the idiosyncratic toxicity has been limited to only in vitro studies. This review describes current knowledge of the effects of cytochrome P450 (CYP)-mediated metabolism and its detoxification abilities based on studies of idiosyncratic DILI animal models developed recently. This review also focused on antiepileptic drugs, phenytoin (diphenyl hydantoin, DPH) and carbamazepine (CBZ), which have rarely caused severe adverse reactions, such as fulminant hepatitis, and have been recognized as sources of idiosyncratic DILI. The studies of animal models of idiosyncratic DILIs have produced new knowledge of chronic administration, CYP inductions/inhibitions, glutathione contents, and immune-related factors for the initiation of idiosyncratic DILIs. Considering changes in the drug metabolic profile and detoxification abilities, idiosyncratic DILIs caused by antiepileptic drugs will lead to understanding the mechanisms of these DILIs.
Cadmium (Cd) is a common environmental pollutant with known toxic effects on the kidney. Urinary metabolomics is a promising approach to study mechanism by which Cd-induced nephrotoxicity. The aim of this study was to elucidate the mechanism of Cd toxicity and to develop specific biomarkers by identifying urinary metabolic changes after a long-term of Cd exposure and with the critical concentration of Cd in the kidney. Urine samples were collected from wild-type 129/Sv mice after 67 weeks of 300 ppm Cd exposure and analyzed by ultra performance liquid chromatography connected with quadrupole time of flight mass spectrometer (UPLC-QTOF-MS) based metabolomics approach. A total of 40 most differentiated metabolites (9 down-regulated and 31 up-regulated) between the control and Cd-exposed group were identified. The majority of the regulated metabolites are amino acids (glutamine, L-aspartic acid, phenylalanine, tryptophan, and D-proline) indicating that amino acid metabolism pathways are affected by long-term exposure of Cd. However, there are also some nucleotides (guanosine, guanosine monophosphate, cyclic AMP, uridine), amino acid derivatives (homoserine, N-acetyl-L-aspartate, N-acetylglutamine, acetyl-phenylalanine, carboxymethyllysine), and peptides. Results of pathway analysis showed that the arginine and proline metabolism, purine metabolism, alanine, aspartate and glutamate metabolism, and aminoacyl-tRNA biosynthesis were affected compared to the control. This study demonstrates that metabolomics is useful to elucidate the metabolic responses and biological effects induced by Cd-exposure.
Mitochondria can be used as important biomarkers of pollutants on human health, and fine particulate matter (PM2.5) has been documented to cause respiratory damage. However, current studies about the relationship between PM2.5 and mitochondria in respiratory tract are limited and warrant further detailed investigations. Hence, the study was aimed to evaluate effects of PM2.5 on mitochondrial structure, investigate the link between PM2.5-induced mitochondrial disorder and respiratory damage, and delineate the possible mechanisms using both in vitro and in vivo models. PM2.5 exposure resulted in damage of mitochondrial structure, including mitochondrial dynamic, DNA biogenesis and morphological alteration 16HBE cells. Furthermore, PM2.5 elevated ROS formation. However, DPI and NAC (inhibitor of ROS) in supplement restored PM2.5-induced mitochondrial disorder. PM2.5 also contributed to the 16HBE cells apoptosis via mitochondrial pathway. Additionally, the results coincided with the in vivo data which were obtained from bronchial tissues of SD rats exposed to PM2.5 for 30 days. Collectively, this study uncovers that PM2.5 leads to the disorder of mitochondrial structure via ROS generation, and then results in respiratory damage. It provides further understanding about the detrimental effect of PM2.5 on respiratory damage, and reveals a mechanistic basis for preventing outcomes in polluted environments.
The carcinogenicity of quinoline was examined by administrating quinoline in the drinking water to groups of 50 F344/DuCrj rats and 50 Crj: BDF1 mice of each sex. In rats, the doses of quinoline were 0, 200, 400, and 800 ppm for males and 0, 150, 300, and 600 ppm for females. In male rats, administration of quinoline was terminated at week 96 due to high mortality caused by tumors. There were significant increases of hepatocellular adenomas, hepatocellular carcinomas, hepatocellular adenomas and/or carcinomas (combined), and liver hemangiomas, hemangiosarcomas, hemangiomas and/or hemangiosarcomas (combined) in both male and female rats, and nasal esthesioneuroepitheliomas and sarcoma NOS (not otherwise specified) in males. In mice, doses of quinoline were 0, 150, 300 and 600 ppm for both males and females. Administration of quinoline was terminated at week 65 in males and at week 50 in females due to high mortality caused by tumors. There were marked increases of hemangiomas, hemangiosarcomas, and hemangiomas and/or hemangiosarcomas (combined) in the retroperitoneum, mesenterium, and liver in males, and in the retroperitoneum, mesenterium, peritoneum, and subcutis in females. Additionally, histiocytic sarcomas were statistically increased in the livers of female mice. Thus the present studies provided clear evidence of carcinogenic activity of quinoline administered in the drinking water in both rats and mice.
The aim of the present study is to investigate the “chronotoxicity” of seven metal compounds (Hg, Pb, Ni, Cr, Cu, Zn, or Fe) by assessing how their toxicity varies with circadian periodicity. Male ICR mice were injected with each metal compound intraperitoneally at 6 different time points over the course of a day (zeitgeber time [ZT]: ZT2, ZT6, ZT10, ZT14, ZT18 and ZT22). Mortality was then monitored until 14 days after the injection. Our investigation demonstrated that mice were tolerant against Ni toxicity during dark phase, on the other hand, they were tolerant against Cr toxicity during light phase. The chronotoxicity of Hg and Pb seemed to be biphasic. Further, mice were susceptible to toxicities against Cu and Zn in the time zone during which light and dark were reversed. Interestingly, no significant differences were observed for Fe exposure at any time of the day. Our results propose that the chronotoxicology may provide valuable information regarding the importance of injection timing for not only toxicity evaluation tests but also the reproducibility of animal experiments. Furthermore, our data suggests that chronotoxicology may be an important consideration when evaluating the quality of risk assessments for night shift workers who may be exposed to toxic substances at various times of the day.
Acyl CoA: diacylglycerol acyltransferase (DGAT) 1 is an enzyme that catalyzes the re-synthesis of triglycerides (TG) from free fatty acids and diacylglycerol. JTT-553 is a DGAT1 inhibitor and exhibits its pharmacological action (inhibition of re-synthesis of TG) in the enterocytes of the small intestine leading to suppression of a postprandial elevation of plasma lipids. After repeated oral dosing JTT-553 in rats and monkeys, plasma transaminase levels were increased but there were neither changes in other hepatic function parameters nor histopathological findings suggestive of hepatotoxicity. Based on the results of exploratory studies for investigation of the mechanism of the increase in transaminase levels, plasma transaminase levels were increased after dosing JTT-553 only when animals were fed after dosing and a main factor in the diet contributing to the increase in plasma transaminase levels was lipids. After dosing JTT-553, transaminase levels were increased in the small intestine but not in the liver, indicating that the origin of transaminase increased in the plasma was not the liver but the small intestine where JTT-553 exhibits its pharmacological action. The increase in small intestinal transaminase levels was due to increased enzyme protein synthesis and was suppressed by inhibiting fatty acid-transport to the enterocytes. In conclusion, the JTT-553-related increase in plasma transaminase levels is considered not to be due to release of the enzymes from injured cells into the circulation but to be phenomena resulting from enhancement of enzyme protein synthesis in the small intestine due to the pharmacological action of JTT-553 in this organ.
Tumor necrosis factor-alpha (TNF-α) is a proinflammatory cytokine released by immune cells during inflammation process. Sodium arsenite (NaAsO2) is an environmental toxic metal. The effects of excess NaAsO2 on TNF-α response and its intracellular signaling are not well understood. We hypothesized that NaAsO2 exposure might affect cellular response to TNF-α. Using HeLa cell model, we found that the combination of NaAsO2 and TNF-α clearly decreased cell viability and mitochondrial membrane potential, but increased percentage of early and late apoptotic cells and cleaved-poly (ADP-ribose) polymerase (PARP). Moreover, the combination prolonged the phosphorylation of mitogen-activated protein kinase (MAPK) members, including c-Jun-N-terminal kinase (JNK), p38, and extracellular signal related kinases (ERK), and increased intracellular reactive oxygen species (ROS), in comparison to treatment of NaAsO2 or TNF-α alone. We further investigated the role of ROS and MAPK signaling on this event by inhibiting ROS production and MAPK. An antioxidant N-acetylcysteine pretreatment diminished the apoptosis-inducing effect of NaAsO2 and TNF-α combination and also inhibited MAPK signaling. Using specific inhibitor of p38 (SB203580) and siRNA-p38 surprisingly increased cell apoptosis and this effect was not observed by JNK and ERK inhibition. This study suggests that p38 may possibly be a survival mediator in response to environmental toxicant-related inflammation. In conclusion, NaAsO2 exposure might amplify inflammation-related tissue injury by potentiating the apoptosis-inducing effect of TNF-α through ROS-dependent mechanism.