Expression of multidrug resistance 1 gene and C3435T genetic polymorphism in peripheral blood of patients with intractable epilepsy

BACKGROUND:Increased expression of multidrug resistance 1 (MDR1) mRNA in peripheral blood of pa-tients with intractable epilepsy is not due to epilepsy drugs,but epilepsy behavior. Monitoring MDR1 ex-pression in peripheral blood is a target for MDR1 gene evaluation. OBJECTIVE: To investigate the influence of antiepileptic drugs and seizures on MDR expression in intrac-table epilepsy,and to analyze the genetic polymorphisms of C3435T in the MDR1 gene. DESIGN,TIME AND SETTING: Factorial designs and comparativ...     

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.     

难治性癫痫与多药耐药基因1C3435T多态性的相关性

目的 探讨多药耐药基因1(MDR1)C3435T位点多态性与汉族难治性癫痫(RE)的关系. 方法 收集170例诊断明确、治疗合理的汉族癫痫患者,根据是否符合RE诊断标准将其分为RE组(91例)和非RE组(79例).RE定义为:至少观察2年,按患者发作类型正确使用≥2种对该发作类型有效的抗癫痫药物,单药前、后分别使用或联合使用,仍每月发作≥1次达2年及以上者.采用多聚酶链反应限制性片段长度多态性方法检测患者外周血MDR1基因C3435T多态性. 结果 RE组CC、CT、TT基因型分别占48.4%、40.7%、11.0%,非RE组分别占40.5%、38.0%、21.5%,总体差异无统计学意义(x2=3.615,P=0.164).RE组患者C3435T等位基因C、T频率分别为68.7%、31.3%,非RE组患者分别为59.5%、40.5%,差异也无统计学意义(x2=3.112,P=0.080).根据病因将患者分为原发性癫痫、症状性或隐源性癫痫2组,结果示2组患者中RE亚组和非RE亚组C3435T基因型分布、等位基因频率差异均无统计学意义(P＞0.05). 结论 本研究未发现MDR1基因C3435T多态性与汉族RE有关.

Abstract：

Objective To clarify the relation between the C3435T polymorphism of multidrug resistance 1 (MDR1) gene and human refractory epilepsy (RE) in ethnic Han Chinese. Methods We collected 170 patients with epilepsy, whose diagnoses were correct and treatments were reasonable. RE was defined as having uncontrolled seizures that occurred with an average frequency of at least once a month for a period of at least 2 years; during the 2-years period, at least 2 different antiepileptic drugs (AEDs) were used daily, either singly or in combination. According to the definition, 91 patients were classified into RE group and the other 79 patients into non-RE group. A 5-mL venous blood sample was taken from the patients for DNA extraction and genotyping. Genotype of C3435T polymorphism in MDR1 gene was determined by polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP). Results The distribution of CC, CT, TT genotypes was 48.4%, 40.7%,11.0% in RE group, and 40.5%, 38.0%, 21.5% in non-RE group, respectively; no significant differences of C3435T genotype were noted between the 2 groups (x2=3.615, P=0.164). The C and T allele frequencies were 68.7%, 31.3% in RE group, and 59.5%, 40.5% in non-RE group, respectively; no significant differences were found between 2 groups (x2=3.112, P=0.080). Patients were divided into primary epilepsy group and cryptogenic or symptomatic epilepsy group according to the etiology;analyses of the genotype and allele of C3435T in the sub-groups (RE and non-RE subgroups) of this 2 groups were similarly unremarkable. Conclusion No association between the C3435T polymorphism in MDR1 gene and RE in ethnic Han Chinese is noted.     

Plasma fibrinogen beta-148C/T gene polymorphism in cerebral infarction patients

BACKGROUND： Plasma fibrinogen （Fg） β-148C/T gene polymorphism is a risk factor for ischemic angiopathy. OBJECTIVE： To explore the frequency distribution of Fg β- 148C/T gene polymorphism and its relationship with plasma Fg levels in patients with cerebral infarction. DESIGN, TIME AND SETTING： Case control experiment of gene polymorphism was performed at the Central Laboratory of Qingdao University Medical College from January 2003 to June 2004. PARTICIPANTS： A total of 88 patients with cerebral infarction were recruited from the Affiliated Hospital of Qingdao University Medical College, including 52 males and 36 females, averaging （61±14） years of age In addition, 80 healthy cases served as the control group, comprising 48 males and 32 females, with an average age of （58 ± 12） years. METHODS： Blood DNA was extracted, and electrophoresis results were observed using an ultraviolet single photon image system. The frequency distribution of Fg β -148C/T was analyzed by polymerase chain reaction-restriction fragment length polymorphism method. Plasma Fg levels were measured by cerebral infarction time. MAIN OUTCOME MEASURES： Plasma Fg β -148C/T gene polymorphism and plasma Fg levels in patients with cerebral infarction. RESULTS： The frequency of the T allele, and plasma Fg levels in CC, CT, and CC＋CT genotype subgroup, were significantly greater in the cerebral infraction group, compared with the control group （P 〈 0.05）. However, there was no significant difference between the TT genotype subgroup and the control group （P 〉 0.05）. The plasma Fg levels in the CT, TT, and CT＋TT genotype groups were significantly greater than the CC genotype group （P 〈 0.05）. However, in the control group, plasma Fg levels in the TT genotype subgroup were significantly greater than the remaining genotype subgroups （P 〈 0.05）. CONCLUSION： Plasma Fg β -148C/T gene polymorphism is an important hereditary factor for differences in plasma Fg levels. The T allele plays a crucial ro     

Genetic predisposition to essential hypertension in a Mongolian population——Detecting the C825T polymorphism of the G-protein beta 3 subunit gene

BACKGROUND： The prevalences of hypertension, cerebrovascular diseases, etc. are higher in Mongolian population because of the influence of various factors including genetics, geography, diet, etc. Therefore, it is helpful for prevention to develop researches on the genetics of various diseases including hypertension in Mongolian population. OBJECTIVE： To analyze the association between C825T polymorphisms of G-protein beta 3 subunit gene （GNB3）, the important candidate gene of various disease of cardiovascular system, and Mongolian patients with essential hypertension. DESIGN： A comparative observation. SETTINGS： Department of Neurology, the First Affiliated Hospital of Inner Mongolia Medical College; Wulate Houqi Red Cross Society. PARTICIPANTS： Totally 267 Mongolian residents, whose blood relations of 3 generations were all Mongolians, were selected from Wulate Houqi, Inner Mongolia. The patients were screened based on the diagnostic standard of hypertension set by WHO in 1999, and the enrolled subjects were divided into two groups according to the level of blood pressure： ① Normal blood pressure group （n =124）： 64 males and 60 females, systolic blood pressure （SBP） 〈 140 mm Hg （1 mm Hg=0.133 kPa）, diastolic blood pressure （DBP） 〈 90 mm Hg;②Essential hypertension group （n =143）： 71 males and 72 females, including 60 patients with simple high SBP （SBP ranged 145 to 195 mm Hg, whereas DBP 〈 90 mm Hg）. METHODS： Peripheral venous blood （5 mL） was drawn from all the subjects, the genome DNA was extracted, and the polymorphisms of the GNB3 C825T genotype were detected with the Sequenom system. Polyrnerase chain reaction （PCR） experiment and SNP detection were performed in Beijing Huada gene laboratory. Then the univariate analysis of variance was applied in the sample comparison among groups, and the chi-square test was used to compare the genotypes and allele frequencies. The odd ratio （OR） and 95% confidence interval （CI） were calculated. MAIN OUTCOME MEASURES： The distributions of GNB3 C825T genotypes and alleles were observed. RESULTS： All the 267 Mongolian subjects were involved in the analysis of results.① GNB3 C825T genotypes： In Mongolian population, the frequencies of CC, CT and TT genotypes at GNB3 C825T site in the essential hypertension group （48%, 41%, 11%） were not obvious different from those in the normal blood pressure group （43%, 47%, 10%, x^2 =0.162, P =0.688; OR：1.176, 95%CI： 0.533- 2.592）, whereas there were also no obvious differences between the simple high SBP group （57%, 35%, 8%） and the normal blood pressure group （x^2 =0.733, P =0.392; OR：1.957, 95%CI： 0.623- 6.143）. ②GNB3 C825T alleles： In Mongolian population, The frequencies of C and T alleles in the essential hypertension group （69%, 31%） were not obviously different from those in the normal blood pressure group （67%, 33%, x^2 =0.094, P = 0.759; OR：0.945, 95%CI：0.657 - 1.358）, whereas there were also no obvious differences between the simple high SBP group （74%, 26%） and the normal blood pressure group （ x^2 =2.133, P =0.144; OR：0.697, 95%CI： 0.428- 1.133）. CONCLUSION： GNB3 C825T site may be not a genetic marker of essential hypertension and simple high SBP in Mongolian population.     

Association between apolipoprotein E promoter-219G/T polymorphism and total cholesterol level in patients with Alzheimer disease

BACKGROUND: Many researches have suggested that apolipoprotein E (APOE) and total cholesterol metabolism are closely related with dementia. In the supposed theory, 219 site of APOE promoter region is near gene coding region, so its polymorphism may result in the abnormality of APOE gene and protein expression, and finally lead to dementia. OBJECTIVE: To observe the association between APOE promoter-219G/T polymorphisms with serum total cholesterol in patients with Alzheimer disease, and compare it with non-dementia people. DESIGN: Case-control, comparative observation. SETTING: Department of Neurology, Fengtian Hospital of Shenyang Medical College. PARTICIPANTS: Fifty-five dementia patients including 27 males and 28 females aged (66±3) years and treated in the Department of Neurology, Fengtian Hospital were selected from January 2002 to December 2005 as the Alzheimer disease group. They all diagnosed according to the DSM-Ⅳdiagnostic criteria of Alzheimer disease instituted by American Psychiatry Association in 1994. Meanwhile, 44 none-dementia patients including 21 males and 23 females aged (66±3) years were selected from other clinical departments of Fengtian Hospital as control group. All the participants were informed the detection and agreed. METHODS: Genomic DNA was extracted from the peripheral blood of all subjects, then "NEST"PCR, DNA sequence and enzyme digestion were adopted to detect the expression of APOE promoter-219 polymorphism, following by biomedical statistics analysis based on the clinical total cholesterol level. MAIN OUTCOME MEASURES: Polymorphism of APOE promoter-219 G/T and total cholesterol level. RESULTS: All 55 dementia patients and 44 non-dementia ones were involved in the result analysis. ①Allele and genotype frequency: The T allele frequency of the Alzheimer disease group was significantly higher than that in the control group [88.2% (97/110), 54.5% (48/88)], while G allele frequency was remarkably lower than that in the control group [11.8%(13/110), 45.5%(40/88), χ2=8.2, P < 0.01]. The TT allele frequency of the Alzheimer disease group was significantly higher than that in the control group [76% (42/55), 48% (21/44)], while GT GG allele frequency was remarkably lower than that in the control group [24%(13/55), 52%(23/44), χ2=8.7, P < 0.01]. ②Total cholesterol level: The level of the TT genotype patients in the Alzheimer group was obviously higher than that in GT GG genotype patients (t =2.46, P < 0.05); the cholesterol level in the two genotypes of the control group was similar (P > 0.05). CONCLUSION: TT genotype and allele T in the APOE promoter-219 polymorphisms are the sensitive gene, and genotype TT has a relationship with the increase of total cholesterol level.     

The effect of Daicong solution on hippocampal muscarinic receptors 1 and 3 gene expression in a rat model of Alzheimer’s disease*☆

BACKGROUND： It has been previously shown that the muscarinic （M） receptor is involved in brain arousal and selective attention, mood, and motor coordination.
OBJECTIVE： To explore the effects of various intragastric Daicong doses on hippocampal MI and M3 receptor gene expression in a rat model of Alzheimer＇s disease.
DESIGN, TIME AND SETTING： A randomized cellular and molecular biology experiment, conducted at the Molecular Immunology Laboratory in Shandong between October 2006 and April 2007.
MATERIALS： Fifty 22-month old Sprague Dawley rats, weighing 250-300 g were used for this experiment. Kainic acid was used to lesion the nucleus basalis to establish a rat model of Alzheimer＇s disease. The components of Daicong solution were as follows： ginseng, rehmannia dride rhizome, anemarrhena, and radix astragali. The solution was provided by the Affiliated Hospital to Weifang Medical College, according to preparation techniques of extracting liquid for traditional Chinese medicine （1 g crude drug/mL solution）. Kainic acid was provided by Professor Xiuyan Li at Weifang Medical College.
METHODS： The rats were randomly divided into 5 groups, 10 rats in each group. Four groups were used for model establishment, and the fifth group served as a normal control group. Three of the model groups were intragastrically administered 5, 10, and 20 g/kg/d Daicong solution, and an additional model group and normal control group received normal saline （10 mL/kg/d）. Drugs were administered over a time period of one month.
MAIN OUTCOME MEASURES： Four days after model establishment, Morris water maze was used to measure learning and memory capabilities. RT-PCR was used to detect the effect of Daicong solution on mRNA expression of M1 and M3 receptor in the hippocampus of all groups. RESULTS： Fifty rats were included in the final analysis, without any loss. M1 and M3 receptor mRNA expression was decreased in the model group, compared to the normal control group （P 〈 0.05）. Upon Daicong admin     

Gene expression in retinoic acid-induced neural tube defects

BACKGROUND： Neural tube defects can be induced by abnormal factors in vivo or in vitro during development. However, the molecular mechanisms of neural tube defect induction, and the related gene expression and regulation are still unknown. OBJECTIVE： To compare the differences in gene expression between normal embryos and those with neural tube defects. DESIGN, TIME AND SETTING： A neural development study was performed at the Department of Neurobiology, Third Military Medical University of Chinese PLA between January 2006 and October 2007. MATERIALS： Among 120 adult Kunming mice, 60 pregnant mice were randomly and evenly divided into a retinoic acid group （n = 30） and a normal control group （n =30）. The retinoic acid was produced by Sigma, USA, the gene microarray by the Amersham Pharmacia Company, Hong Kong, and the gene sequence was provided by the Incyte database, USA. METHODS： Retinoic acid was administered to prepare models of neural tube defects, and corn oil was similarly administered to the normal control group. Total RNA was extracted from embryonic tissue of the two groups using a Trizol kit, and a cDNA microarray containing 1 100 known genes was used to compare differences in gene expression between the normal control group and the retinoic acid group on embryonic （E） day 10.5 and 11.5. Several differentially expressed genes were randomly selected from the two groups for Northern blotting, to verify the results of the cDNA microarray. MAIN OUTCOME MEASURES： Morphological changes and differential gene expression between the normal control group and the retinoic acid group. RESULTS： Anatomical microscopy demonstrated that an intact closure of the brain was formed in the normal mouse embryos by days E10.5 and E11.5. The cerebral appearance was full and smooth, and the surface of the spine was intact. However, in the retinoic acid group on days E10.5 and E11.5, there were more dead embryos. Morphological malformations typically included non-closure at the top of the cranium and abnormal changes of the metencephalon and face. cDNA microarray analysis suggested that the changes in expression of seven different genes were similar on both days E10.5 and E11.5. These were downregulation of NekT, Igfbp5, Zw10, Csf3r, Psmc6 and Rb 1, and upregulation of Apoa-4. This study also indicated that Cdk5 expression was downregulated in the retinoic acid group on day E11.5. The results of the cDNA microarray analysis were partly confirmed by Northern blotting. CONCLUSION： Cdk5, Nek7, Igfbp5, Zw10, Csf3r, Psmc6, Rb1 and Apoa-4 may be key factors in retinoic acid-induced neural tube defects.     

Scorpion venom heat-resistant protein decreases immunoreactivity of OX-42-positive microglia cells in MPTP-treated mice*☆

BACKGROUND： Microglia function as the immune surveyors of the brain under normal physiologica conditions. However, microglia become activated in response to brain injuries and immunological OBJECTIVE： To explore the influence of scorpion venom （SV） heat-resistant protein on frontal cortex and hippocampal microglia cells in a mice model of Parkinson＇s disease. DESIGN, TIME AND SETTING： Randomized, controlled, cellular immunity study. The experiment was performed at the Physiology Department Laboratory in Dalian Medical University between June 2005 and July 2008. MATERIALS： Ninety-six healthy, C57B1/6 mice; 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine （MPTP） from Sigma, USA; SV heat-resistant protein （Experimental Base Institute in Dalian Medical University）. The mice were randomly divided into four groups （n = 24）： normal control, negative control, model, and SV heat-resistant protein. METHODS： Mice in the model and SV heat-resistant protein groups were subcutaneously injected with MPTP （20 mg/kg） to model Parkinson＇s disease, while the normal control and negative control groups were injected with physiological saline in the neck for 8 successive days. In addition, mice in the model and normal control groups were intraperitoneally injected with physiological saline 2 hours following administration, while SV heat-resistant protein and negative control groups were injected SV heat-resistant protein （0.01 mg/kg）. MAIN OUTCOME MEASURES： lmmunoreactivity of microglia cells in MPTP-treated mice. RESULTS： Compared with normal control mice, MPTP-treated mice displayed increased OX-42 expression in the brain. However, in the SV heat-resistant protein-treated mice, OX-42 expression was decreased, compared to the model group. In the model mouse group, the number of OX-42-positive microglia was increased in the frontal cortex, caudatum, and hippocampal hilus, compared to the normal control mice （P 〈 0.01）. However, in the SV heat-resistant protein-treated mice, the number of O     

急性癫痫大鼠海马CA3区Bcl-2表达及线粒体改变

BACKGROUND： Previous studies have shown that the mitochondrial structure and function are damaged in animal models of epilepsy. In addition, the Bcl-2 protein is capable of regulating mitochondrial stability. OBJECTIVE： To observe and validate changes in mitochondrial structure and Bcl-2 expression, and to analyze these characteristics in the hippocampal CA3 region of rat models of epilepsy. DESIGN, TIME AND SETTING： This randomized, controlled, animal experiment was performed at the Laboratory of Electron Microscopy and Department of Histology and Embryology, Luzhou Medical College between 2007 and 2008. MATERIALS： Coriamyrtin was provided by the Pharmacy Factory of West China University of Medical Sciences. The primary and secondary antibodies were provided by Zhongshan Goldenbridge Biotechnology, Beijing. METHODS： A total of 44 adult, male, Sprague Dawley rats were randomly divided into control （n = 11） and epilepsy （n = 33） groups. Rats in the epilepsy group were induced by coriamyrtin （50 μ g/kg）, which was injected into the lateral ventricles. The rats were then observed at 3, 6, and 24 hours after epilepsy induction, with 11 rats at each time point. Epilepsy was not induced in rats from the control group. MAIN OUTCOME MEASURES： Pathological changes in the hippocampal CA3 region were observed by light microscopy; Bcl-2 expression was analyzed by immunohistochemistry; and mitochondrial changes in the hippocampus were observed under transmission electron microscopy. RESULTS： （1） The control group displayed very little Bcl-2 protein expression in the hippocampal CA3 region. However, after 3 hours of epilepsy, expression was visible. By 6 hours, expression peaked and then subsequently decreased after 24 hours, but remained higher than the control group （P 〈 0.05）. （2） Mitochondria were damaged to varying degrees in the epilepsy groups. For example, mitochondria edema, cristae space increase, and disappearance of mitochondria were apparent. Moreover, mitochondrial damage occurred prior to pathological changes in the neurons and nucleolus. CONCLUSION： Bcl-2 expression and mitochondrial damage increased in the hippocampal CA3 region in rats with epilepsy. Moreover, mitochondrial damage occurred prior to increased Bcl-2 expression and nucleolus damage.     

Single nucleotide polymorphisms in the multidrug resistance 1 gene in Korean epileptics.

PURPOSE: P-glycoprotein 170 encoded by the multidrug resistance 1 (MDR1) gene exports various antiepileptic drugs out of the CNS, which leads to multidrug resistance. This study was performed to elucidate the relationship between single nucleotide polymorphisms (SNPs) in the MDR1 gene and drug resistance in Koreans with epilepsy. SUBJECTS AND METHODS: Three SNPs at nucleotide position 1236 in exon 12, 2677 in exon 21 and 3435 in exon 26 of the MDR1 gene were genotyped in 207 Korean epileptics. Subjects were classified according to whether they had drug-resistant (RS group; N=99) or drug-responsive epilepsy (RP group; N=108). The frequencies of genotype and haplotype were compared between the RS and RP groups. RESULTS: The frequencies of genotype and haplotype in the RS group were not statistically different from those in the RP group. CONCLUSIONS: In Korean epileptics, there was no significant relationship between three known SNPs in MDR1 and drug resistance. And there was no association of MDR1 haplotype based on above three sites with pharmacoresistance.     

Lack of association between C3435T nucleotide MDR1 genetic polymorphism and multidrug-resistant epilepsy.

The variability of P-glycoprotein expression in individuals is linked to a C3435T polymorphism of the multidrug-resistance 1 (MDR1) gene, and the CC genotype at the C3435T polymorphism was reported to be associated with multidrug resistance in epilepsy patients. Since population frequencies of polymorphic genes depend on ethnic specificity, we investigated functional significance of the C3435T polymorphism of the MDR1 gene in Korean epilepsy patients. One hundred and eight patients with drug-responsive epilepsy, 63 patients with drug-resistant epilepsy, and 219 control migraine subjects were studied, but the analysis for C3435T allele showed no significant association between the CC genotype and the multidrug-resistant epilepsy. We suggest that influence of the C3435T polymorphism in the multidrug-resistant epilepsy may not be significant in Korean populations and further investigations in various ethnic populations would be necessary to clarify the effect of C3435T polymorphism on the mutidrug resistance in epilepsy patients.     

Association of MDR1 gene C3435T polymorphism with childhood intractable epilepsy: a meta-analysis

Drug-resistant epilepsy is also referred to as intractable, medically refractory, or pharmacoresistant epilepsy. Approximately, one-third of patients with epilepsy have recurrent seizures despite therapy. Multidrug resistance 1 (MDR1) gene may play a role in drug-resistance in epilepsy. To assess the association between MDR1 C3435T polymorphism and the response to anticonvulsants in childhood intractable epilepsy, we conducted a systematic review and meta-analysis. Studies were obtained from the electronic database of PubMed, Medline, Embase and CNKI up to September 2013. All the case–control association researches evaluating the role of MDR1 C3435T polymorphism in childhood epilepsy to antiepileptic drugs were identified. The odds ratios (ORs) with 95 % confidence intervals (CIs) were calculated for comparisons of the alleles and genotypes with co-dominant (C/C vs. T/T, C/T vs. T/T), dominant (C/C + C/T vs. T/T), and recessive (C/C vs. C/T + T/T) models in overall and in ethnicity subgroups to measure the strength of genetic association. A total of 8 related studies, including 634 drug-resistant patients, 615 drug-responsive patients and 1,052 healthy controls were pooled in this meta-analysis. The allelic association of MDR1 C3435T with risk of drug-resistance was not significant (OR 1.03, 95 % CI 0.87–1.22, P = 0.73; OR 1.00, 95 % CI 0.86–1.16, P = 0.98) in overall and in the subgroup analysis by ethnicity (Asian: OR 0.95, 95 % CI 0.77–1.18, P = 0.67; Caucasian: OR 1.18, 95 % CI 0.89–1.57, P = 0.25). Neither association was found in other genetic models. Our results did not show a significant association between MDR1 C3435T polymorphism and response to anticonvulsant drugs, suggesting that this polymorphism may not be a risk factor to childhood intractable epilepsy.     

Associations between <Emphasis Type="Italic">MDR1</Emphasis> C3435T polymorphism and drug-resistant epilepsy in the Polish population

Epilepsy is a common neurological disorder. About one-third of epileptic patients demonstrate multidrug resistance (MDR) phenotype and develop drug-resistant epilepsy (DRE). Single nucleotide polymorphism (SNP) C3435T (rs1045642), identified in the MDR1 gene, is associated with an increased intestinal expression of P-glycoprotein (P-gp) which affects the levels of anti-epileptic drugs in plasma. The reported study was designed to explore associations between the MDR1-C3435T gene SNP and the risk of DRE in the Polish population. The C3435T polymorphism of MDR1 gene was investigated by the PCR-RFLP technique in 74 patients with DRE and 70 age- and sex-matched non-DRE controls. Blood samples were obtained from patients with drug-resistant epilepsy, treated at the Department of Neurological Surgery, Medical University in Warsaw between the years 2011 and 2012. Odds ratios (ORs) and 95 % confidence intervals (CIs) were calculated for each genotype and allele. Genotype distribution of C3435T polymorphism of MDR1 gene was compared between the DRE patients and controls with significant differences (p < 0.05) between the two investigated groups. A possible association was observed between DRE and the presence of 3435C allele. The 3435C allele was found in 69 % of DRE cases and in 48 % of the used controls. The variant 3435T allele of MDR1 decreased the risk of drug-resistant epilepsy [odds ratio (OR) 0.41; 95 % confidence interval (CI) 0.26–0.67]. The results indicate that the C3435T polymorphism of MDR1 gene may be associated with the incidence of DRE observed in the Polish population.     

Multidrug resistance 1 (MDR1) 3435C/T genotyping in childhood drug-resistant epilepsy

Introduction

A mutation at nucleotide position 3435 in exon 26 of the multidrug resistance 1 (MDR1) gene is the most frequently studied polymorphism in relation to multidrug resistance. However, there are conflicting data as to whether the CC or TT genotype of the 3435C>T polymorphism is associated with drug resistance. Methods and results: We investigated the association between this polymorphism in drug-resistant childhood epilepsy by comparison with drug-responsive patients. In total, 59 patients with drug-resistant epilepsy, defined as having four or more seizures within a 12-month period while using three or more AEDs, 60 children with drug-responsive epilepsy who had remained seizure-free for 12 months on their current AED regimen and 76 healthy children were involved in this study. Genotype frequencies in drug-resistant patients were as follows: 32.2% CC, 44.1% CT, 23.7% TT; in the drug-responsive group: 20.0% CC, 50.0% CT, 30.0% TT; in the control group: 24.3% CC, 50.0% CT, 25.7% TT. Comparison of drug-resistant and drug-responsive patients revealed no significant difference in genotype frequency. The findings of the epilepsy patients were not significantly different from those of the healthy control subjects. Conclusions: Our study does not support any significant association between the MDR1 polymorphism and drug-resistant childhood epilepsy.     

Polymorphism of the MDR1/ABCB1 C3435T drug-transporter and resistance to anticonvulsant drugs: A meta-analysis

Background:   Approximately one-third of patients with epilepsy patients have recurrent seizures despite therapy. It has been suggested that therapeutic failure is associated with high expression of the multidrug efflux ABCB1 (MDR1) drug-transporter; specifically, that patients with the 3435CC genotype have higher efflux of anticonvulsants out of brain tissue, with correspondingly lower concentrations in the central nervous system.
Methods:   We conducted a meta-analysis to examine the association between MDR1 polymorphisms and the response to anticonvulsants. We included all published studies until September 2007, in which patients with responsive and unresponsive seizure disorders underwent genotyping for ABCB1 C3435T. Individual and summary odds ratios were calculated using a random effects model. A secondary analysis was also performed, stratifying the studies by their ethnic distribution to account for genetic heterogeneity. We also performed a cumulative analysis by date of publication for the included studies using a random effects model.
Results:   We identified 11 case-control studies involving 3,371 patients (1,646 patients with drug-resistant epilepsy and 1,725 controls). We identified no significant association between anticonvulsant drug resistance and MDR1 polymorphism [odds ratio 1.15; 95% confidence interval (CI) 0.78–1.70; p = 0.48). Subanalysis of studies according to ethnicity yielded similar findings [European cohort: OR = 1.31; 95% CI 0.89–1.94, p = 0.18; Asian cohort: OR = 0.99; 95% CI 0.51–1.89, p = 0.96).
Conclusions:   We found no association between ABCB1 genotype and response to anticonvulsant drugs. At the present time, genetic typing for MDR1 polymorphism is not warranted for patients with drug-resistant epilepsy.     

Failure to confirm association of a polymorphism in ABCB1 with multidrug-resistant epilepsy

Alteration of ATP-binding cassette subfamily B member 1 transporter (ABCB1) can plausibly cause drug-resistant epilepsy as it influences brain penetration of drugs. The CC genotype at the ABCB1 C3435T polymorphism was reported to be associated with multidrug resistance. A replication study in 401 drug-resistant and 208 drug-responsive subjects with epilepsy showed no significant association between the CC genotype and drug-resistant epilepsy. The authors suggest the initial association may have arisen by chance.     

Lack of association between the C3435T polymorphism in the human multidrug resistance (MDR1) gene and response to antiepileptic drug treatment

PURPOSE: P-glycoprotein (P-gp) has been implicated in the causation of refractory epilepsy. The expression and efflux efficiency of P-gp is influenced by a polymorphism (C3435T) in the encoding gene (MDR1). Recent evidence suggests that the homozygous C-variant, which is associated with higher expression and increased activity of P-gp, is more common in patients with pharmacoresistant epilepsy. We have investigated the prevalence of this polymorphism in a series of patients attending a specialist epilepsy clinic. METHODS: DNA samples were obtained from 400 patients, irrespective of seizure type or drug treatment. Genotype of the C3435T polymorphism was determined by traditional polymerase chain reaction (PCR) followed by restriction digest. Classification of response to treatment was determined in a blinded fashion by an independent physician. Results were expressed as genotype and allele frequencies per response group and compared by logistic regression analysis. RESULTS: In total, 170 patients were classified as responders, with > or =12 months seizure freedom on current treatment. The remaining 230 patients were classified as nonresponders. Comparison of responders and nonresponders revealed no significant difference in allele frequency (C vs. T; odds ratio, 1.03; 95% CI, 0.78-1.37; p = 0.83) or genotype frequency (CC vs TT; odds ratio, 1.07; 95% CI, 0.60-1.91; p = 0.81). Subanalyses of individual seizure types were similarly unremarkable. CONCLUSIONS: This study failed to corroborate a previously reported association between the C3435T polymorphism in the human MDR1 gene and pharmacoresistant epilepsy. Whether the C3435T polymorphism can act as a marker for the natural history of treated epilepsy remains to be determined.