Association of single nucleotide polymorphisms of brain-derived neurotrophic factor gene and multidrug resistance 1 gene to refractory epilepsy in Chinese Han children

BACKGROUND： There are two hypotheses for the underlying cause of refractory epilepsy： ＂target＂ and ＂transport＂. Studies have shown that brain-derived neurotrophic factor （BDNF） is over-expressed in refractory epilepsy. Multidrug resistance 1 （MDR1） gene encodes for P-glycoprotein, the primary ATP-binding cassette transporter in the human body. Some single nucleotide polymorphisms of the MDR1 gene have been associated with refractory epilepsy. OBJECTIVE： To investigate the association between BDNF gene C270T polymorphism and MDR1 T-129C polymorphism with refractory epilepsy in Chinese Han children through the use of polymerase chain reaction （PCR）-restriction fragment length polymorphism analysis. DESIGN, TIME AND SETTING： A case-control, genetic association study was performed at the Central Laboratory, Third Xiangya Hospital of Central South University from June 2005 to November 2007. PARTICIPANTS： A total of 84 cases of unrelated children with epilepsy, including 41 cases of refractory epilepsy and 43 cases of drug-responsive epilepsy, were enrolled. An additional 30 healthy, Chinese Han children, whose ages and gender matched the refractory epilepsy patients, were selected as normal controls. METHODS： Venous blood was collected and genomic DNA was extracted from the blood specimens. C270T polymorphism in BDNF gene and T-129C polymorphism in MDR1 gene were genotyped using PCR-restriction fragment length polymorphism analysis. Association analysis using the Ftest and Chi-square test was statistically performed between C270T polymorphism in BDNF gene and T-129C polymorphism in MDR1 gene and refractory epilepsy. MAIN OUTCOME MEASURES： The distribution of genotypes and allele frequencies of C270T polymorphism in BDNF gene and T-129C polymorphism in MDR1 gene. RESULTS： The distribution of CC, CT, and TT genotypes, as well as C and T allele frequencies, in the BDNF gene was not significantly different between the refractory epilepsy group, drug-responsive epilepsy group, or the normal control group （P 〉 0.05）. The distribution of TT genotype and T allele frequencies of the MDR1 gene was significantly different in the refractory epilepsy group compared with the drug-responsive epilepsy and normal control groups （P 〈 0.05）. Comparison of haplotype combinations demonstrated that there were no significant differences in combinations of TT＋CC, -FI-＋CT, TC＋CC, and TC＋CT among the three groups （P 〉 0.05）. CONCLUSION： C270T polymorphism of the BDNF gene was not associated with refractory epilepsy in Chinese Han children, but T-129C polymorphism in the MDR1 gene was associated with refractory epilepsy in Chinese Han children. The TT genotype and T allele frequencies could serve as susceptibility loci for refractory epilepsy. Interactions between C270T in BDNF gene and T-129C in MDR1 gene were not observed in refractory epilepsy in Chinese Han children.

Ursolic acid sensitized colon cancer cells to chemotherapy under hypoxia by inhibiting MDR1 through HIF-1α

Objective： To explore the efficacy of ursolic acid in sensitizing colon cancer cells to chemotherapy under hypoxia and its underlying mechanisms. Methods： Three colon cancer cell lines （RKO, LoVo, and SW480） were used as in vitro models. 5-Fluorouracil （5-FU） and oxaliplatin were used as chemotherapeutic drugs. Cell viability and apoptosis were tested to evaluate the sensitivity of colon cancer cells to chemotherapy. The transcription and ex- pression levels of hypoxia-inducible factor-1α （HIF-1α）, multidrug resistance gene 1 （MDR1）, and vascular endothelial growth factors （VEGF） were assessed by quantitative real-time polymerase chain reaction （qRT-PCR） and im- munoblotting. Cycloheximide and MG132 were used to inhibit protein synthesis and degradation, respectively. In vitro tube formation assay was used to evaluate angiogenesis. Results： We demonstrated the chemosensitizing effects of ursolic acid with 5-FU and oxaliplatin in three colon cancer cell lines under hypoxia. This effect was correlated to its inhibition of MDR1 through HIF-la. Moreover, ursolic acid was capable of inhibiting HIF-1α accumulation with little effects on its constitutional expression in normoxia. In addition, ursolic acid also down-regulated VEGF and inhibited tumor angiogenesis. Conclusions： Ursolic acid exerted chemosensitizing effects in colon cancer cells under hypoxia by inhibiting HIF-la accumulation and the subsequent expression of the MDR1 and VEGF.