Design,Synthesis And Bioactivity Exploration Of Organic Arsenicals

Since As2O3 was introduced to cure Acute Promyelocytic Leukemia(APL)patients successfully in 1970s,it has attracts more attention as a kind of anti-cancer drug.More and more research focuses on the biological activity and antitumor mechanism of arsenicals,especially inorganic arsenicals.Less attention is paid to organic arsenicals.It has been revealed that As2O3 can trigger the cell redifferentiation or apoptosis-inducing therapy for APL,which limits its therapeutic application in other leukemia subtypes or solid tumors.There are some advantages in organic arsenicals,such as the designable structure,the better biological efficacy and the higher affinity towards sulfydryl,which make them become a sort of promising anti-cancer precursors.Based on this,we design and synthesize a series of organic arsenicals with outstanding biological activity and specific targets,and study the effect mechanism systematically,which provides some novel structures with simplicity and antitumor mechanism for the research and development of new organic arsenical drugs.Furthermore,this thesis offers the suggestions and directions for the improvement and optimization of organic arsenical drugs based on the research findings.There are five chapters in this thesis:Chapter 1:The definition,characterization,classification and symptoms of leukemia are summarized briefly.Particularly,we elaborate the specific treatment methods for APL patients in clinic practice,including the therapies in different stages(induction,consolidation,maintenance,relapse,etc.)and for patients with different risk(high-risk,medium-risk and low-risk).Meanwhile it shows the both sides of arsenic,namely toxicity and activity,as well as the effect mechanism and research progress systematically and comprehensively.Chapter 2:The anti-cancer efficacy of Schif-base based organic arsenicals was investigated systematically in vitro.After analyzing the influences on cellular functions,it is displayed that compound 2a and 2b can induce the burst of ROS,the decrease of GSH level,the collapse of mitochondrial membrane potential and the release of cytochrome c,whereas the variations can be eliminated by the pre-culture of common exogenous antioxidants.So it is concluded that both organic arsenicals can trigger the oxidative stress-mediated intrinsic apoptosis in HL-60 cells.Chapter 3:Owing to the vital role of ROS in antitumor mechanism,it was considered to design and synthesize the organic arsenicals with the potential to target thioredoxin reductase(TrxR).Two organic arsenicals,PIM-PAO-PDT and PAM-PAO-PDT,bearing the S-As-S chemical scaffold and different linking groups have been synthesized,and both of them show the better inhibitory activity and selectivity towards HL-60 cells.Importantly,it is illustrated that they can target TrxR selectively and inhibit its activity by the disturbance of redox catalytic site.Afterwards,the cells suffer from the burst of ROS,consumption of antioxidants and high sensitivity for oxidants,which further lead to the mitochondria dysfunction including the collapse of membrane potential,ATP level decline,mitochondrial membrane swelling,MPTP opening,Ca2+ and cytochrome c release.Then the mitochondria-dependent apoptosis is triggered by PIM-PAO-PDT and PAM-PAO-PDT,which can also be deterred in the presence of NAC,DTT or LA.Although the organic arsenicals can suppress TrxR activity,the following oxidative stress and mitochondrial dysfunction are the main causes for apoptosis.Chapter 4:Considering the mitochondrion as the target organelle for organic arsenicals,we designed and synthesized the mitochondria-targeted compound PDT-PAO-TPP further.After making use of NMR and ESI-MS to assure the structure of PDT-PAO-TPP,the activity exploration was performed.The research has illustrated that the compound can decrease the membrane potential by accumulating in mitochondria after the short-time exposure.Meanwhile it can suppress the PDHC activity and PDHC E2 activity,followed by the generation of ROS and consumption of total thiols.Furthermore,the compound also influences the construction of proton gradient,the production of ATP and the respiratory process by inhibiting the activities of respiratory chain complexes.Exposing with PDT-PAO-TPP for a long time can damage the mitochondrial metabolic thermogenesis.Additionally,when mitochondrial membrane integrity is impaired by PDT-PAO-TPP resulting in the mitochondrial swelling,enhanced membrane permeability and even the membrane rupture,the cytochrome c located in mitochondrial intermembrane space can be released into the cytosol to activate the caspase family-dependent intrinsic apoptosis.Chapter 5:In order to display the intracellular distribution of organic arsenicals,we designed and synthesized the mitochondria-targeted fluorescent organic arsenical PDT-PAO-F16.The structure was confirmed by the NMR and ESI-MS,and the compound was characterized using the UV spectrophotometer and fluorescence spectrophotometer.Based on the research in vitro,we find maybe the compound is taken in according to the AQP membrane proteins to accumulate in the mitochondria and discharged through MRP proteins,which is tightly associated with the effective concentration and the retention time of intracellular organic arsenical.Similarly,compound PDT-PAO-F16 also shows the dual inhibitory activities towards PDHC and mitochondrial respiratory chain complexes,followed by the influences on cellular normal function,including the redox balance and energy state,and mitochondrial normal function,including the membrane integrity,biological thermogenesis and respiratory process.Finally,it can induce the caspase family-dependent apoptosis through mitochondrial pathway.