The Design, Synthesis And Neuroprotective Effect Of PARP Inhibitors

The pathogenic mechanism of some elder neurodegenerative disease, such as Alzheimer's disease (AD) and Parkinson's disease (PD) is indefinite. So far, the interaction of polygene mutation and environment toxin including oxidative stress,mitochondria functional disorder,excitotoxicity,ionic concentration disturbance and inflammation can be considered as the factors of neurodegenerative disorder. However, neurodegenerative disorder can lead to the apoptosis and necrosis at the last. Hence, neuroprotective agents which can protect neuron and synapse or recover the function of neurotransmitter become a new alternative for elder neurodegenerative disease. Actually, the neuroprotective effect strategy can prevent or delay diseases'progress. The poly(ADP-ribose)polymerase(PARP), a nuclear enzyme relative to DNA repair, is a mediator of cell death by ATP depletion. It exists in brain extensively, and takes part in the pathology process of neurodegenerative disorder, cerebra ischemic damage and shock.Thus the PARP inhibitor was considered as a novel neuroprotective agent.The research methods and results in this paper included as follows:1. Constructing the pharmacophore model and designing the target compounds. The pharmacophore models of PARP-1 inhibitor were established from the training set of thirty-eight PARP-1 inhibitors with conformer analysis and pharmacophore mapping by using the catalyst software. To design multitarget neuroprotective agents, the combination of QSAR analysis and pharmacophore model analysis was applied. 2-aminothiazole derivatives which possessed neuroprotective effect were selected to be lead compounds and had good estimate activity to inhibit the PARP.2. Synthesizing and identifying the target compounds.The synthesis route mainly includes cyclization and acylation. At first, five 4, 5-substituted-2- aminothiazole were synthesized by iodine, sulfocarbamide and different ketones. General synthesis and microwave irradiation were both used. The method of double–time irradiation was applied, and it shorten the reaction time greatly. Then they were reacted with different aromatic acid or acyl chloride at RT. Finally, ten 4, 5-substituted-2- aminothiazole derivates were synthesized. The intermediate and product were analyzed by HPLC. The fifteen aminothiazole derivatives were all characterized by UV,IR and 1H-NMR.3. Biological activity test in vitroThe initial neuroprotective effect in vitro: The ability of all target compounds and PFT-α(positive control) to protect PC12 cells against hydrogen peroxide induced apoptosis was assessed through MTT methods. The result suggested that compoundⅠ-1,Ⅰ-3 andⅠ-4 possessed better cytotrophy activity, and compoundⅠ-1 andⅠ-3 also showed better anti-apoptosis activity against H2O2.Preliminary screening Caspase-3 inhibitory activity in vitro: Caspase-3 is a key protease on apoptosis of mammalian cell. The inhibition of compoundⅠ-1,Ⅰ-3 andⅡ-1 to Caspase-3 was tested by light absorption method. The result showed compoundⅠ-3 has potential inhibitory activity of Caspase-3 in the concentration of 65.3μmol·L-1.Preliminary screening PTP-sigma inhibitory activity in vitro: Protein tyrosine phosphatase sigma (PTP-sigma, encode by the Ptprs gene) plays an important role in the neural development. The inhibition of compoundⅠ-4 andⅠ-6 to PTP-sigma was detected by fluorescence signal. In the concertration of 272.9μmol·L-1, the inhibitory activity of compoundⅠ-4 was impoved greatly, which showed its potential intrinsic activity.Preliminary antibacterial activity in vitro: The value of MIC was tested by double dilution method. The result suggested compoundⅠ-2,Ⅰ-3 andⅡ-2 had the same inhibiton as AZM to streptococcus pneumoniae 8220 (MIC=32μg·ml-1). CompoundⅠ-6 has a litte inhibition to staphylococcus aureus ATCC25923 (MIC=32μg·ml-1). And compoundⅡ-2 also has inhibition to staphylococcus aureus ATCC25923 (MIC=64μg·ml-1) and streptococcus pneumoniae ATCC49619 (MIC=64μg·ml-1).4. Checking the pharmacophore modelComparing the results of biological activity test with the predictive values of pharmacophore model, it was discovered that the pharmacophore model showed excellent reliability and forecast ability. Conclusions:1. The pharmacophore models of PARP-1 inhibitor were constructed to further design. Combining structure optimization, QSAR analysis and pharmacophore model analysis, three new 4, 5-substituted-2- aminothiazole and seven new 4, 5-substituted-2- aminothiazole derivates were designed and sythsized, which showed neuronprotective effect. And the validity of the pharmacophore model was verified finally. It contributes to design the neuroprotective agents with undiscovered structure.2. It was the first time to find the 4, 5-substituted-2- aminothiazole derivate (as compoundⅠ-3 ) possessed both of the neurotrophic activity and anti-apoptosis activity against H2O2. And it may have multi-target neuroprotective effect.