The Study On The Expression And Regulation Of MDR1 Gene

Objective: To investigate the association of MDR1 C3435T polymorphism with its mRNA expression in peripheral blood mononuclear cells in healthy persons of Han populations. Furthermore, to investigate whether phenobarbital has effect on the expression of MDR1 in peripheral bloods mononuclear cells and try to demonstrate whether expression of MDR1 in PBMCs can be induced. After using phenobarbital the relationship between MDR1 and PXR mRNA expression levels in PBMCs was studied.Methods①163 (98males, 65females) blood samples were taken from unrelated Chinese Han healthy children. Genotypes of the MDR1 C3435T polymorphism were identified by PCR-RFLP. MDR1 mRNA expression levels in PBMCs were detected by SYBR green I real-time polymerase chain reaction.②The PBMCs were isolated and purified from 36 healthy children and then were divided into three groups for testing.The first group of PBMCs was not cultured and stimulated. The second group of PBMCs was cultured naturally.The third group of PBMC was stimulated by phenobarbital . After the PBMCs were cultured for 24 hours, the MDR1 and PXR mRNA expression levels were detected by SYBR green I real-time PCR.③Statistical methods: Hardy-Weinberg equilibrium testing was performed for the C3435T polymorphism using the chi-squared test. One way analysis of variance and t-test were used to compare the MDR1 or PXR mRNA expression levels among different groups.Spearman analysis was performed to investigate the correlation between MDR1 and PXR mRNA expression levels, accepting P<0.05 as being significant.Results①The CC, CT and TT genotype frequencies of C3435T polymorphism were 63(38.7%), 78(47.9%)and 22(13.5%), respectively. For C3435T polymorphism, the frequency of 3435C allele is 62.6%.The distribution of genotypes was consistent with Hardy-Weinberg equilibrium(P>0.05). The MDR1 mRNA expression levels of CC, CT and TT genotype groups were (4.562±3.383)×10-3, (4.673±3.710)×10-3and (4.489±2.928)×10-3, respectively.There were no significant differences were found among the three genotypes in PBMCs (P>0.05).②The MDR1 mRNA expression levels in uncultured PBMCs group, naturally cultured PBMCs group and the PBMCs group stimulated with PB were (4.475±2.980)×10-3,(4.991±4.165)×10-3and(7.265±5.067)×10-3,respectively.For PXR mRNA expression levels ,these were (2.073±1.335)×10-3, (1.836±1.467)×10-3 and (3.014±2.238)×10-3 in above groups,respectively. Compared with uncultured PBMCs group and naturally cultured PBMCs group,the MDR1 and PXR mRNA expression levels in the PBMCs group stimulated with PB were elevated significantly (P<0.05). There were no significant differences between the uncultured and naturally cultured PBMCs in MDR1 and PXR mRNA expression levels (P>0.05).The MDR1 mRNA expression levels were positively correlated with PXR expression after being stimulated by PB(r=0.517,P=0.0012).Conclusion①The results suggest that the MDR1 C3435T polymorphism does not appear to have a significant effect on its mRNA expression in PBMCs in Chinese Han populations. So that, the genotypes of C3435T polymorphism can not allow the predicting of the expression of MDR1 in Chinese Han children.②The phenobarbital can induce the expression of MDR1 in PBMCs ,which proved the expression of MDR1 in PBMCs can be induced. The MDR1 mRNA expression levels were positively correlated with PXR expression after being stimulated by Phenobarbital, which suggested that PXR may play some role in the regulation of MDR1 expression in PBMCs.