Evidence for cytochrome P450 2B1/2B2 isoenzymes in freshly prepared peripheral blood lymphocytes

The Novel Atypical Antipsychotic Lurasidone Affects Cytochrome P450 Expression in the Liver and Peripheral Blood Lymphocytes

Lurasidone is a novel atypical antipsychotic drug acting on dopaminergic, serotonergic and noradrenergic receptors; it is applied for the long-term treatment of schizophrenia and depression in patients with bipolar disorders. We aimed at performing a comparative study on the influence of chronic treatment with lurasidone on the expression of cytochrome P450 enzymes in the liver and in peripheral blood lymphocytes, and to evaluate the relationship between changes in the expression of CYP enzymes in the two experimental models. The obtained results show a fairly similar expression pattern of the main CYP enzymes in the rat livers and lymphocytes, and they indicate that in the liver, lurasidone exerts an inhibitory effect on the activity, protein and mRNA levels of CYP2B1/2 (not CYP2B2 mRNA), CYP2C11 and CYP2E1, while in the case of CYP3A1 and CYP3A2, it causes enzyme induction. At the same time, lurasidone decreases the expression of CYP2B, CYP2C11 (CYP2C11 protein only) and CYP2E1 but increases that of CYP3A2 (not CYP3A1) in lymphocyte cells. In conclusion, chronic treatment with lurasidone simultaneously and in the same way influences the expression and activity of CYP2B, CYP2C11, CYP2E1 and CYP3A2 in the liver and peripheral blood lymphocytes of rats. Thus, the lymphocyte cytochrome P450 profile may be utilized as an indicator of the hepatic cytochrome P450 profile in further clinical studies with lurasidone, and lymphocytes may serve as easily available surrogates for examining the impact of new drugs and chronic in vivo treatments on CYP enzyme expression, as well as to estimate drug-drug interactions and toxicity risk.

Microsomal reductase activity in patients with thyroid neoplasms

OBJECTIVE

Cytochrome b5-reductase (CYB5R) and cytochrome P450 reductase (CYPOR) are important for cell metabolism; however, their role in thyroid hormonogenesis and carcinogenesis has not been elucidated yet. The activity of CYB5R correlates with the metastasis in breast cancer, but there are no similar studies for CYB5R and CYPOR for thyroid tumors. The aim of this study was to elucidate the activity of CYB5R and CYPOR changes in benign euthyroid and hyperthyroid neoplasms and in papillary thyroid cancer for their potential application as biomarkers for diagnosis and prognosis prediction of thyroid cancer.

METHODS

Thirty-six patients with thyroid diseases participated in the study. The control euthyroid nodular goiter group included ten patients; the thyrotoxic nodular or diffuse goiter group included 14 patients; the papillary thyroid cancer T1-2N0-1M0 (PTC) group included 12 patients. The activity of CYB5R and CYPOR was assessed with lucigenin-enhanced chemiluminescence stimulated by NADH and NADPH, respectively.

RESULTS

Compared to the control euthyroid nodular goiter group, activity of CYB5R and CYPOR increased ~5 and 10 times, respectively, in toxic goiter, and 15 and 30 times, respectively, in half of cases of PTC. The change in activity of CYPOR was more pronounced compared to CYB5R. Within the PTC group, the subgroups with low and high activities of microsomal reductases were identified. Microsomal reductases in follicular adenoma was 2-4-fold less active compared to the euthyroid nodular goiter and the low-activity PTC group.

CONCLUSIONS

Activity of tissue microsomal reductases varies in thyroid pathology and can be considered as a promising biomarker for differential diagnostics of benign and malignant thyroid tumors.

A comprehensive survey of the mutagenic impact of common cancer cytotoxics

BACKGROUND

Genomic mutations caused by cytotoxic agents used in cancer chemotherapy may cause secondary malignancies as well as contribute to the evolution of treatment-resistant tumour cells. The stable diploid genome of the chicken DT40 lymphoblast cell line, an established DNA repair model system, is well suited to accurately assay genomic mutations.

RESULTS

We use whole genome sequencing of multiple DT40 clones to determine the mutagenic effect of eight common cytotoxics used for the treatment of millions of patients worldwide. We determine the spontaneous mutagenesis rate at 2.3 × 10(-10) per base per cell division and find that cisplatin, cyclophosphamide and etoposide induce extra base substitutions with distinct spectra. After four cycles of exposure, cisplatin induces 0.8 mutations per Mb, equivalent to the median mutational burden in common leukaemias. Cisplatin-induced mutations, including short insertions and deletions, are mainly located at sites of putative intrastrand crosslinks. We find two of the newly defined cisplatin-specific mutation types as causes of the reversion of BRCA2 mutations in emerging cisplatin-resistant tumours or cell clones. Gemcitabine, 5-fluorouracil, hydroxyurea, doxorubicin and paclitaxel have no measurable mutagenic effect. The cisplatin-induced mutation spectrum shows good correlation with cancer mutation signatures attributed to smoking and other sources of guanine-directed base damage.

CONCLUSION

This study provides support for the use of cell line mutagenesis assays to validate or predict the mutagenic effect of environmental and iatrogenic exposures. Our results suggest genetic reversion due to cisplatin-induced mutations as a distinct mechanism for developing resistance.

Similarities in lindane induced alteration in cytochrome P450s and associated signaling events in peripheral blood lymphocytes and brain

Studies were initiated to investigate the similarities in alterations in cytochrome P450s (CYPs) and associated signaling events in brain and peripheral blood lymphocytes (PBL) induced by lindane, an organochlorine pesticide. Adult male albino wistar rats were treated orally with different doses (2.5- or 5.0- or 10- or 15 mg/kg/body weight) of lindane daily for 4 days. In another experiment, the treatment of low dose (2.5mg/kg) of lindane was continued for 15- and 21 days. A dose- and time-dependent increase was observed in the activity of CYP dependent enzymes in brain microsomes and PBL isolated from the treated rats. However, the magnitude of induction was several folds less in PBL. As observed in brain, RT-PCR and Western immunoblotting demonstrated that increase in CYP enzymes in PBL is due to the increase in the mRNA expression of specific CYP isoenzymes. Similarities were also observed in activation of ERK and JNK MAP kinases and c-jun in PBL or brain isolated from rats treated with lindane. Similarities in the induction of CYPs and activation of MAP kinases in PBL and brain suggest that CYP expression profiles in PBL could be used for monitoring the exposure and toxicity of environmental chemicals.