Role Of Multidrug Resistance Gene And P-glycoprotein In Predicting Efficacy Of Antiepileptic Drugs In Children

PART ONE THE DYNAMIC EXPRESSION ANDSIGINIFICANCE OF MULTIDRUG RESISTANCE GENEAND P-GLYCOPROTEIN IN THE PERIPHERAL BLOODOF CHILDREN WITH EPILEPSYBackground:Epilepsy has a higher incidence in children and adolescence, which hasa great impact on children ’s growth and development and life andlearning. The main treatment of epilepsy still is long-term oralantiepileptic drugs (AEDs), approximately30%of children withepilepsy become refractory epilepsy(RE).Multidrug resistance is thedifficulty of clinical treatment. Previous studies have shown that theoverexpression of multidrug resistance gene1(MDR1) and its codedproduct P-glycoprotein (P-gp) reduced the ability of AEDs to enterbrain tissue and reduced blood concentration, and thus the seizurescouldn’t be effectively controlled. Currently, the studies on MDR1and P-gp as objective indicators of assessing AEDs efficacy and predictingrefractory epilepsy with children have fewer reported.Objective:To observe dynamic changes of the expression of multidrug resistancegene1and P-glycoprotein in peripheral blood in children withepilepsy，explore the relationship between it and epileptic resistanceand its value of predicting efficacy of AEDs.Methods:A total of70inpatients and outpatients in our department from January2011to December2o12were subjected in this study. These childrenwere divided into refractory epilepsy (n=30), and newly diagnosedepilepsy (n=40). Another30healthy children served as normal control.The expression of MDR1mRNA was analyzed by reverse transcriptionpolymerase chain reaction （RT-PCR） semi-quantitatively and P-gpwas detected by flow cytometry before entering group，6months，12months and18months after treatment， respectively. Therelationship of MDR1mRNA and P-gp level with epileptic frequencyand therapeutic effect of AEDs was analyzed.Results:(1) A positive correlation was found between the expression ofMDR1mRNA and P-gp in peripheral blood in children（r=0.86，P<0.05）. (2) The expression of MDR1mRNA and P-gp in refractory epilepsygroup and newly diagnosed epilepsy group at every time pointwere all significantly higher than that in healthy control group（P＜0.01）. The expression of MDR1mRNA and P-gp refractoryepilepsy group at every time point were all significantly higherthan that in newly diagnosed epilepsy（P＜0.01）. There was asignificant difference of the expression of the MDR1mRNA andP-gp in refractory epilepsy group at every time point（P＜0.01， P＜0.05）and not significantly different in newly diagnosed epilepsygroup.(3) In refractory epilepsy group before entering group，16out of19cases（84.2%）with over expression of MDR1mRNA and P-gpbecame invalid，3out of11cases（27.3%） without expression ofMDR1mRNA and P-gp became invalid，and there was a significantdifference between them（P＜0.01）. In newly diagnosed epilepsygroup before entering group，9out of13cases （69.2%）with overexpression of MDR1mRNA and P-gp became intractable epilepticpatients and2out of27（7.5%）without expression of MDR1mRNAand P-gp became intractable epileptic patients， there was asignificant difference between them（P＜0.01）.(4) MDR1mRNA and P-gp expression was more among patients withhigh frequent epilepsy than patients with low frequent epilepsy（P ＜0.01）. MDR1mRNAand P-gp expression was more in patientsadministered with four kinds of AEDs than those with two or threekinds of AEDs（P＜0.01）.Conclusion:(1) The expression of MDR1mRNA and P-gp increase in peripheralblood of children with epilepsy，especially in refractory epilepticchildren. The increased expression of MDR1mRNA and P-gp mayplay an important role in clinical drug resistance.(2) The expression of MDR1mRNA or P-gp may be a predictablemarker of evaluating efficacy of AEDs and occurring ofrefractory epilepsy.(3) The regular and quantitative detection of dynamic changes of theexpression of MDR1mRNA or P-gp in peripheral blood in childrenwith epilepsy, which can evaluate efficacy of AEDs and guidetreatment and minimize occurrence of refractory epilepsy. PART TWO EFFECT OF ANTIEPILEPTIC DRUGS ONEXPRESSION OF P-GLYCOPROTEIN OF CHILDRENBackground:Multidrug resistance is the difficulty of treatment of epilepsy, previousstudies have shown that the overexpression of P-gp encoded by MDR1had a close relationship with epilepsy drug resistance. But the specificreasons of its overexpression are still unclear, it maybe obtain fromhereditary or from induction of acquired factors including repeatedepileptic seizures or AEDs. Currently, the studies on objectiveindicators of assessing AEDs efficacy and predicting refractoryepilepsy with children have fewer reported.Objective:Fourty children of newly diagnosed epilepsy inpatients and outpatientsin our department were subjected in this study, to explore the effects ofvalproate acid, oxcarbazepine, levetiractam on expression ofP-glycoprotein(P-gp) in peripheral blood and its value of predictingefficacy of AEDs in children.MethodsFourty children of newly diagnosed epilepsy were divided intovalproate acid group(n=19), oxcarbazepine group(n=16), levetiractamgroup(n=15), another20healthy children served as normal control. The expression of P-gp was detected by flow cytometry beforetreatment，6months，12months and18months after treatment，respectively. The relationship of P-gp level with therapeutic effect ofAEDs was analyzed.Results:(1) The expression of P-gp in valproate acid group, oxcarbazepinegroup and levetiractam group at every time point were allsignificantly higher than that in healthy control group（P＜0.01）;there was no significant difference of the expression of P-gp invalproate acid group, oxcarbazepine group and levetiractam groupat every time point.(2) The expression of P-gp was higher of patients with invalidtreatment than that in patients with valid treatment and healthycontrol group（P＜0.01）.(3) In50paitents, before treatment，9out of15cases（69.2%）withover expression of P-gp became invalid，3out of35cases（7.5%）without expression of P-gp became invalid，and there was asignificant difference between them （P＜0.01）.Conclusion:(1) The expression of P-gp increase in peripheral blood of childrenwith epilepsy， especially in refractory epileptic children. Theincreased expression of P-gp may play an important role in clinical drug resistance.(2) The expression of P-gp may be a predictable marker of evaluatingefficacy of AEDs and occurring of refractory epilepsy.(3) There was no influence on the expression of P-gp in peripheralblood of mere use of valproate acid, oxcarbazepine andlevetiractam, the increased expression of P-gp may be theconsequence of uncontrolled recurrent seizures. PART THREE EFFECT OF ANTIEPILEPTIC DRUGS ONEXPRESSION OF MULTIDRUG RESISTANCE GENEAND P-GLYCOPROTEIN OF RATSBackground:The abnormally overexpression of multidrug resistance gene1(MDR1)and its coded product P-glycoprotein (P-gp) in epileptic focus havebeen considered to be an important mechanism of the epilepsy drug.But the specific reasons of their overexpression are still unclear, theymaybe obtain from hereditary or from induction of acquired factors.Many scholars regard that repeated seizures can induce overexpressionof MDR1and P-gp, but there is still controversial for the AEDswhether it will lead to overexpression. Previous studies have shownthat the expression of MDR1and P-gp in peripheral blood are alsoactive except that overexpression in Lesions brain tissue of patientswith epilepsy. But whether there is a relationship between theexpression in peripheral blood and brain tissue, whether the expressionin peripheral blood can instead brain tissue, the related study is stillless.Objective:Chronic and spontaneous epileptic rats induced by lithium-pilocarpineand normal rats were used to be study objects, and animal model of long-term antiepileptic drugs treatment was established to explore theeffects of valproate acid (VPA), oxcarbazepine (OXC), levetiractam(LEV) on expression of multidrug resistance gene1（MDR1）inperipheral blood and P-glycoprotein(P-gp) in brain.Methods:75male rats of4-5weeks were randomly divided into chronic epilepsymodel group （n=43） induced by lithium-pilocarpine and controlgroup(n=32). When epilepsy model was developed，the32survivedrats were divided into VPA group (EP+VPA）, OXC group (EP+OXC）,LEV group (EP+LEV）and EP group. Rats of control group weredivided into normal saline(NS) group, VPA group (NS+VPA）, OXCgroup (NS+OXC）and LEV group (NS+LEV）. Gavage twice daily for4weeks, the expression of MDR1mRNA in peripheral blood wasanalyzed by reverse transcription polymerase chain reaction （RT-PCR） semi-quantitatively and P-gp was detected byimmunohistochemical method.Results:(1) A positive correlation was found between the expression ofMDR1mRNA in peripheral blood and P-gp in brain in rats（r=0.71， P <0.05）.(2) The expression of MDR1mRNA in peripheral blood and P-gp inbrain in EP group, EP+VPA group, EP+OXC group and EP+LEV group were all significantly higher than that in NS group（P＜0.01）.There was not significantly different in NS+VPA group,NS+OXC group and NS+LEV group（P＞0.05）.(3) Compared with EP group, there was not significantly different inEP+VPA group, EP+OXC group and EP+LEV group of theexpression of MDR1mRNA in peripheral blood and P-gp in brain（P＞0.05）.Conclusion:(1) The expression of MDR1mRNA in peripheral blood and P-gp inbrain increase of rats with epilepsy，their overexpression may playan important role in the drug resistance of epilepsy.(2) The expression of MDR1mRNA in peripheral blood can be used asa credible and simple indicator of the expression of P-gp in braintissue of epileptic rats.(3) There was no influence on the expression of MDR1mRNA inperipheral blood and P-gp in brain of mere use of VPA or OXC orLEV, the increased expression of MDR1mRNA and P-gp may bethe consequence of uncontrolled recurrent seizures.