Cytochrome P450 (CYP450) enzymes are the most important metabolizing enzyme family exists among all organs. Apart from their role in the deactivation of most endogenous compounds and xenobiotics, they also mediate most procarcinogens oxidation to ultimate carcinogens. There are several modes of CYP450s activation of procarcinogens. 1) Formation of epoxide and diol-epoxides intermediates, such as CYP1A1 and CYP1B1 mediates PAHs oxidation to epoxide intermediates; 2) Formation of diazonium ions, such as CYP2A6, CYP2A13 and CYP2E1 mediates activation of most nitrosamines to unstable metabolites, which can rearrange to give diazonium ions. 3) Formation of reactive semiquinones and quinines, such as CYP1A1 and CYP1B1 transformation of estradiol to catechol estrogens, subsequently formation semiquinones; 4) Formation of toxic O-esterification, such as CYP1A1 and CYP1A2 metabolizes PhIP to N(2)-acetoxy-PhIP and N(2)-sulfonyloxy-PhIP, which are carcinogenic metabolites. 5) Formation of free radical, such as CYP2E1 is involved in activation tetrachloromethane to free radicals. While for CYP2B6 and CYP2D6, only a minor role has been found in procarcinogens activation. In addition, as the gene polymorphisms reflected, the polymorphisms of CYP1A1 (-3801T/C and -4889A/G), CYP1A2 (- 163C/A and -2467T/delT), CYP1B1 (-48G/C, -119G/T and -432G/C), CYP2E1 (-1293G/C and -1053 C/T) have been associated with an increased risk of lung cancer. The polymorphisms CYP1A1 (-3801T/C and -4889A/G), and CYP2E1 (PstI/Rsa and 9-bp insertion) have an association with higher risk colon cancers, whereas CYP1A2 (-163C/A and -3860G/A) polymorphism is found to be among the protective factors. The polymorphisms CYP1A1 (-3801T/C and -4889A/G), CYP1B1 -432G/C, CYP2B6 (-516G/T and -785A/G) may increase the risk of breast cancer. In conclusion, CYP1A1, CYP1A2, CYP1B1, CYP2A6, and CYP2E1 are responsible for most of the procarcinogens activation, and their gene polymorphisms are associated with the risk of cancers.

Herbal medicines and their active ingredients are widely used worldwide, and they have become an important part of clinical medicine. The combined use of herbs and drugs has increased the possibility of pharmacokinetic and pharmacodynamic interactions. Clinical studies have demonstrated that the combined use of herbs and drugs can enhance or attenuate the drug efficacy and toxicity. The herb-drug combinations may reduce a drug efficacy and lead to treatment failure when long-term administration. Case reports detailing serious clinical adverse reactions have promoted studies on the interactions between herbs and drugs. This review highlights recent knowledge to discuss herb-drug interactions involving metabolizing enzymes and drug transporters. Drug transporters are widely present in body and play an important role in the absorption, distribution, excretion and metabolism, efficacy, and toxicity of drugs. Investigation of transporters has developed rapidly since 1990s, the effects of many transporters on the pharmacokinetics of drugs and herb-drug interactions have been reported. Some concepts on drug transporters issued experimentally and clinically drug-drug and herb-drug interactions have applied in many studies. Methodology studies are very important for understanding the mechanism, considerations and evaluation of experiments and clinical studies on drug metabolizing enzymes and transporters in drug-drug interactions.

Xenobiotics are converted by cytochrome P450 (CYP450) into highly reactive metabolites (RMs) that covalently bind to the catalytic site of the enzyme itself, subsequently causing mechanism-based inhibition. This phenomenon is one of the fates of RMs in the liver. Depending on their affinity to nucleophiles (high-electron density compounds), RMs also may act as hepatotoxic agents by binding to intracellular macromolecules. The present study summarized 29 mechanism-based inhibitors (drugs) with clinical hepatotoxicity. Eighteen of these drugs cause hepatotoxicity (7 through idiosyncratic drug-induced liver injury) via their RMs. The liver injury caused by remaining 11 drugs, namely, fluoxetine, verapamil, furan-containing compounds, and human immunodeficiency virus protease inhibitors, cannot be excluded via RMs because of limited data. A regular pattern for RM-induced hepatotoxicity is summarized: (a) formation of RM-protein adducts that trigger immune responses; (b) covalent binding of RMs to intracellular macromolecules (mitochondria is a commonly victim) may lead to reactive oxygen species (ROS) overproduction, respiratory chain dysfunction, cell stress, and so on; and (c) RM overproduction, which results in glutathione (GSH) depletion. The binding mechanism of RMs to CYP450s and the quantitative parameters (KI, Kinact, and Kinact/KI) of the mechanism-based inhibitors of CYP450s are weakly correlated with the occurrence of hepatotoxicity, while the induction of CYP450 expression (11/29 drugs) may contribute to hepatotoxicity via excessive ROS and RM generation. These results suggest that mechanism-based inhibition is an indicator of RM formation and may thus be used to identify drugs with RM-induced hepatotoxic potential (particularly idiosyncratic drug-induced liver injury).

Background Inflammation induced by intracerebral hemorrhage (ICH) is one of the main causes of the high mortality and poor prognosis of patients with ICH. A1 astrocytes are closely associated with neuroinflammation and neurotoxicity, whereas A2 astrocytes are neuroprotective. Homer scaffolding protein 1 (Homer1) plays a protective role in ischemic encephalopathy and neurodegenerative diseases. However, the role of Homer1 in ICH-induced inflammation and the effect of Homer1 on the phenotypic conversion of astrocytes remain unknown. Methods Femoral artery autologous blood from C57BL/6 mice was used to create an ICH model. We use the A1 phenotype marker C3 and A2 phenotype marker S100A10 to detect astrocyte conversion after ICH. Homer1 overexpression/knock-down mice were constructed by adeno-associated virus (AAV) infection to explore the role of Homer1 and its mechanism of action after ICH. Finally, Homer1 protein and selumetinib were injected into in situ hemorrhage sites in the brains of Homer1flox/flox/Nestin-Cre+/− mice to study the efficacy of Homer1 in the treatment of ICH by using a mouse cytokine array to explore the potential mechanism. Results The expression of Homer1 peaked on the third day after ICH and colocalized with astrocytes. Homer1 promotes A1 phenotypic conversion in astrocytes in vivo and in vitro. Overexpression of Homer1 inhibits the activation of MAPK signaling, whereas Homer1 knock-down increases the expression of pathway-related proteins. The Homer1 protein and selumetinib, a non-ATP competitive MEK1/2 inhibitor, improved the outcome in ICH in Homer1flox/flox/Nestin-Cre+/− mice. The efficacy of Homer1 in the treatment of ICH is associated with reduced expression of the inflammatory factor TNFSF10 and increased expression of the anti-inflammatory factors activin A, persephin, and TWEAK. Conclusions Homer1 plays an important role in inhibiting inflammation after ICH by suppressing the A1 phenotype conversion in astrocytes. In situ injection of Homer1 protein may be a novel and effective method for the treatment of inflammation after ICH.

ObjectivesTo investigate the relationship between tumour budding, clinicopathological characteristics of patients and prognosis in non-small cell lung cancer.Study designA retrospective study was used.ParticipantsWe selected 532 patients with non-small cell lung cancer from China, including 380 patients with adenocarcinoma and 152 with squamous cell carcinoma.Primary and secondary outcome measuresTumour budding was visible using H&E staining as well as pancytokeratin staining. The count data and measurement data were compared using the χ2 test and the t-test, respectively. The overall survival rate was the follow-up result. The survival curves were drawn using the Kaplan-Meier method, and the differences between groups were analysed using the log-rank method. The independent prognostic factor of patients with lung cancer was determined using a multivariate Cox proportional hazard model.ResultsIn patients with lung adenocarcinoma, there was a correlation between tumour budding and spread through air spaces (OR 36.698; 95% CI 13.925 to 96.715; p<0.001), and in patients with squamous cell carcinoma, tumour budding state was closely related to the peritumoural space (OR 11.667; 95% CI 4.041 to 33.683; p<0.001). On Cox regression analysis, multivariate analysis showed that tumour budding, pleural and vascular invasion, spread through air spaces, tumour size, lymph node metastasis, and tumour node metastasis stage were independent risk factors of prognosis for patients with non-small cell lung cancer.ConclusionsAs an effective and simple pathological diagnostic index, it is necessary to establish an effective grading system in the clinical diagnosis of lung cancer to verify the value of tumour budding as a prognostic indicator. We hope that this analysis of Chinese patients with non-small cell lung cancer can provide useful reference material for the continued study of tumour budding.