Preliminary And Clinical Studies On Positron Emission Tomography: The Preparation And Preliminary Biological Evaluation Of ¹¹C-HupA

Senile dementia of Alzheimer's disease(SDAT),or Alzheimer's disease(AD)is a common neurodegenerative disorder characterized by the progressive degeneration of memory,and finally threats the life of patients.The disease has been a great burden to patients and their families,also to the communities.It is estimated that the number of the dementia populalation in China aged 65 and over was more than 5,000,000,with the increasing of the proportion of the elderly in China,the problem will become more and more serious.The subject of the 21th propaganda day of AD in 2005 was "Take actation to change future",and it was "Focus on AD imminent" in 2006.With the prolong of patient's lifetime,AD has been the fourth disease to threat the life of the elderly followed by heart disease,tumor and stroke.So it has been concentrated by Chinese and foreign scholars and has become the important study about new medicine research,it was also the focus about new medicine exploitation.Some studies indicated that the nosogenesis of AD was relevant to cholinergic system.Some evidences shew that the relationship of the abnormal cholinergic system and the features of AD was the most closely,some previous researches have proved that the activity of choline acetylase in brain tissue of AD patients was decreased obviously,the activity of acetylcholine esterase was increased notably., so the content of acetylcholine in brain was not enough and result in functional impairment of central nervous system,degeneration of memory and cognitive ability,even the loss of intelligence.AD was mainly refer to the impairment of memory,it's impairment of cholinergic system proved that the cholinergic system was important to the memory ability.Many drugs for AD are based on the mechanism.Some progress about AD cured by traditional Chinese drug has made,Hup A is a kind of alkaloid extracted from serrate clubmoss herb,it was a reversible inhibitor of acetylcholine esterase,because its high selectivity and was easy to through blood-brain barrier,it has fortis inhibition to acetylcholine esterase,and can obviously increase the level of acetylcholine esterase in brain.Some animal experiments indicated that Hup A could improve the ability of study and memory of mouse,and it had the features of quick absorption,quick distribution and slow excretion.Clinical experiments also indicated that Hup A really had some therapeutic effects to improve memory function,especially to AD and normal elder of decreased memory.Normally it may cost about 15 years to develop a kind of new medicine successfully,and cost about 1～2 hundred million dollars.The activity in vitro can be proved by experiments,but the avtivity in vivo can not be proved by suitable methods,so a rational procedure which from discovery to use in human body,from animal experiments to clinic is needed urgly,it can shorten exploitation time of new medicine and decrease the costs largly.The appearance of micro PET,a kind of non-invaded dynamic imaging technology in living body will solve the problem effectively.Exploring and screening the medicine in living body,shortening the exploitation period can drive the process of medicine exploitation enormously.The documents about ¹¹C-labeled the effective elements of Chinese traditional herbs have not been reported before.Investigating the method of ¹¹C-labeled the effective elements of Chinese traditional herbs and undertaking the biological evaluation will be of significance and creativity,and it will be useful of investigating the mechanism of the effective elements of Chinese traditional herbs acting in vivo,in addition,it will be prepared for medicine exploitation by PET or micro PET.Considering the study is about AD and the factors of material selection, we choose Hup A to undertake the exploratory reresearch.Investigating the pharmacokinetics of Hup A by micro PET,exploring the mechanism of Hup A acting in brain,exploring a new pathway of investigating Chinese traditional herbs in vivo.The purposes of the study were to explore the feasible method of positron radionuclide radiolabeling the effective element of Chinese traditional;to explore the distribution in vivo of ¹¹C -labeled Hup A,provid references to the second exploitation of medicine;to do some preclinical jobs for PET or micro PET, observe the dynamic distribution and pharmacokinetics in vivo,explore a new pathway of investigating the pharmacokinetics in vivo of Chinese traditional herbs.Partâ… .Synthesis and quality control of ¹¹C-radiolabeled Hup AObjective:To expore the method and quality control of ¹¹C -radiolabeled Hup A. Methods:¹¹CO₂ was produced by CTI RDS 111 accelerator,converted ¹¹CO₂ to ¹¹C-CH₃I by CH₃I die-block,and then converted it to ¹C-Triflate-CH₄,imported ¹¹C-Triflate-CH₄ to Hup A which was dissolved in alocohol,reacted at common temperature and then obtained the product.Compared with ¹²C- HupA which was produced at the same condition.The labeled product was analyzed by HPLC on a reverse-phase C18 column,and eluted with 100%acetonitrile at a flow rate of 1.0 ml/min.Contents and analytical methods of quality control for ¹¹C- HupA were investigated and the main quality criteria were achieved through strict control of the determining parameters by standard procedures.Results:The Synthesis time of ¹¹C- HupA was 15 to 20 min with radiochemical purity＞98%,and average specific activity of 49.4GBq/mmol,the molecular weight of labeled product was 257, radiochemical purity＞90%in 2 hours.All quality criteria of ¹¹C- HupA met the requirements of the positron radio-pharmaceuticals.Conclusion:¹¹C- HupA injections can be used to further study in the animal or human study.Partâ…¡.Pharmacokinetics and biodistribution of ¹¹C-HupA in the normal animalObjective:To exolpre the pharmacokinetics and biodistribution of the new agent, ¹¹C-HupA in vivo.Methods:Take the sample of blood and organs in different time, 5min,15min,30min,60min,90min after injecting ¹¹C-HupA by vail in mice and measure the cpm,then the%ID/g was calculated.Analysed the pharmacokinetics by taking the blood sample from tail of rats and analysed the biodistribution in the different regions of brain,such as frontal lobe,apical lobe,temporal lobe,occipital lobe, cerebellum,hippocampus,striatum,thalamencephalon and brain stem in the rats.Results: ¹¹C-HupA was of the characteristic that quickly discharge from the blood,which half time was 14.608±1.773min,clearance rate was 0.12±0.009ml/min/kg, metabolism through the liver,kidney was the main eccrisis organ,which was 3.562±0.360%ID/g at 15 min and decreasing graduately,it was 2.547±0.337ID/g in liver at 15 min,Until 60 min the discharging of ¹¹C-HupA was keeping in a relative higher level.Pharmacokinetics of ¹¹C-HupA in the rats corresponded to one-compartment model.The half-time was 14.608±1.773min,apparent volume of distribution was 2.526±0.351ml/kg,clearance rate was 0.12±0.009ml/min/kg.Concisions:¹¹C-HupA could quickly discharge and decrease to the low level from background of issues in vivo.There was significant difference of ¹¹C-HupA that distribute in the different brain regions, there were more distribution in cerebral cortex,hippocampus,cerebral ganglion and brain stem.Conclusions(Partâ… -Partâ…¡):â‘ Synthesis of ¹¹C-HupA was of high radiochemical purity and good stability in vitro.All quality criteria of ¹¹C-HupA met the requirements of the positron radionuclide-radiolabeled pharmaceutical,and can be used to further study.â‘¡¹¹C-HupA could quickly discharge and decrease to the low level in vivo. Pharmacokinetics of ¹¹C-HupA in the rats corresponded to one-compartment model.The distribution and clearance in body corresponded to first order kinetics and there was significant difference of ¹¹C-HupA that distributed in the different brain regions of normal rats.The distribution and pharmacokinetics of ¹¹C-HupA in brain and body could offer references to second exploitation of drugs.