Effect Of Plateau Hypoxia On Drug Transporters In Blood Brain Barrier

In the field of medcine,the plateau refers to the area with altitude above 2500 m.The total plateau area in China is approximately 3.1 million square kilometers,making it the largest country in the world.With the"the Belt and Road"economic strategy and the rapid development of modern transportation,the number of people entering the plateau from the plains gradually increases every year.After entering the plateau hypoxic environment,the functions and states of the central nervous system,blood circulation system and digestive system of the body have a certain influence,which affects the expression of drug transporters on the cells of the various tissues.In previous research,it was found that drug transporters under hypoxia focuses on the liver,kidney,small intestine and other tissues and organs,while there are few studies on the changes of drug transporters'expression in the blood brain barrier under hypoxia.Drug transporters in the blood brain barrier are crucial in limiting the entry of nutria ENTs,metabolites,and drugs into and out of the brain.Meanwhile,the existing studies mostly use whole brain tissue,which is difficult to reflect the differences in the expression of drug transporters in the blood brain barrier.Therefore,according to the relevant research,the blood brain barrier structure in the rat brain tissue was extracted,namely the cerebral microvascular segment.The following experim ENTs were designed to investigate the effects of plateau hypoxia on drug transporters in the blood brain barrier.First,the effect of simulated hypoxia on the changes of blood gas,biochemistry and brain tissue in rats was studied.?1?Blood gas results showed that with increased elevation above sea level,the body's pO₂ and sO₂ decreased significantly,and the body was in anoxic condition;?2?biochemical in dicators results showed that plateau hypoxia caused rat liver and kidney tissues to produce slight damage;?3?The results of brain pathology showed that the hippocampal pyramidal was arranged disorderly,with nuclear pyknosis,and brain tissue damage occurred with elevation;?4?The effects of hypoxia on blood brain barrier integrity were examined.The results showed that with the increase of altitude,the rat brain tissue was damaged,but the integrity of the blood brain barrier was not significantly changed.Second,the effect of hypoxia on the expression of drug transporters in the blood brain barrier was studied.Two different hypoxia states?hypoxia treatment at different altitudes and hypoxia time treatment at the same altitude?were designed.The effects of hypoxia on the expression of 10 drug transporters in the blood brain barrier were compared using Real Time-PCR and Western Blot.The results showed that:?1?With the increase of altitude,the expression of drug transporters P-gp,Mrp4,Bcrp,Pept2,Mct1,Oatp1c1,Oat3,Cnt2,and Glut1 in the blood brain barrier were all significant at the mRNA level.The expression of Octn2 at the mRNA level decreased with elevation,while the changes of P-gp,Mrp4,Bcrp,Pept2,Oat3 and Glut1 at the protein level were consistent with their mRNA levels.The results showed that the trend of differentdrug transporters in the blood brain barrier was inconsistent with the elevation of altitude;?2?Compared with the hypoxic 1d group,the same plateau area?4010 m above sea level?increased with time of hypoxia.The drug transporters Mrp4,Pept2,Glut1,Mct1,Oatp1c1,and Cnt2 in the blood brain barrier expressed the highest mRNA levels at 2days of hypoxia,and mRNA expression of P-gp,Bcrp,Oat3,and Octn2 at 3days of hypoxia.At the highest level,other trends were not positively correlated,and the changes in the levels of Mrp4,Pept2,Glut1,P-gp,Bcrp,and Oat3proteins were consistent with mRNA levels,while other trends were not positively correlated;the results indicated that they followed the same high altitude area.The trend of different drug transporters in the blood brain barrier is inconsistent with the increase of hypoxia time.Thirdly,the correlation between the change of the drug transporter expression and its transport capacity was verified.The pharmacokinetics of phenytoin,the specific substrate of the drug transporter P-gp in the blood brain barrier under hypoxia was investigated.The results showed that the AUC,MRT,and t_1/2 of phenytoin were significantly increased at the plateau hypoxia,and the CL was significantly decreased,indicating that the absorption and absorption rate of phenytoin increased rapidly and the excretion sloweddown after entering the plateau.That is,phenytoin sodium eliminated from the body at the plateau hypoxia environment slowed down,and the plasmadrug concentration was higher than that in the plain group.It is suggested that in order to maintain normal blood drug concentration,the dosage should be reduced in the hypoxic environment at the plateau.Fourth,the effect of hypoxia on the concentration of P-gp specific substrate phenytoin in cerebrospinal fluid was studied.The results showed that the concentration of P-gp specific substrate phenytoin sodium was significantly increased in cerebrospinal fluid of rats after hypoxia,and the expression of P-gp protein and mRNA was also significantly increased under hypoxia.It is thought that the expression change of P-gp may be positively correlated with the change of its substrate concentration in cerebrospinal fluid;thus,the P-gp inhibitor verapamil was added.The results showed that the concentration of phenytoin in cerebrospinal fluid was also suppressed after P-gp was inhibited,which shows that the change of P-gp expression in the blood brain barrier is consistent with the change trend of phenytoin sodium concentration in cerebrospinal fluid.In summary,this study has come to the following conclusions:the high altitude environment affects the expression of drug transporters in the blood brain barrier,which in turn influences the concentration of the drug transporter-mediated substrate in the brain and affects the efficacy of the drug.The study provided theoretical support and reference for the rational use of brain diseases in the plateau population.