The JNK Inhibitor D-JNKI1 Alleviates Dopaminergic Neurodegeneration In Parkinson’s Disease And Reduces Senile Plaque Deposition In Alzheimer’s Disease

Objective:Neurodegenerative disease is a kind of degenerative disease which is caused by the gradual loss of neurons in the brain and spinal cord,leading to dementia and other symptoms.It usually occurs in middle-aged and elderly people.They include Alzheimer’s disease,Parkinson’s disease,etc.The etiology is not fully understood.The c-Jun N-terminal kinase(JNK)pathway plays a crucial role in the pathogenesis of AD and PD and is increasingly recognized as an important part of its pathogenesis.Therefore,JNK inhibitors may provide a promising prevention and treatment strategy for neurodegenerative diseases.D-JNKI1 is a novel JNK inhibitor with many advantages and it is by far the most specific JNK inhibitor.In this study,mice and cell PD models as well as APPswe/PS1E9 double-transgenic mice were used to investigate the protective effect of D-JNKI1 on neurons and its mechanism by means of behavioral,morphological and molecular biological experiments,so as to provide a reliable experimental basis for the application of D-JNKI1 in neurodegenerative diseases.Methods:The subacute PD model of C57BL/6 mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)and the PD model of SH-SY5Y cells induced by1-methyl-4-phenylpyridiniumion(MPP~+)were used as research objects to investigate the effect of D-JNKI1 on the neurodegeneration of PD,and the APPswe/PS1E9 double-transgenic AD mice was used to investigate the effect of D-JNKI1 on the deposition of Amyloid beta(Aβ)in cerebral cortex and hippocampus.1.The open field test and traction test were used to detect the behavioral changes of PD mice.2. Immunohistochemistry and Western blotting were used to detect the protective effect of D-JNKI1 on dopaminergic neurons of MPTP/MPP~+induced PD model and its mechanism.3.Reactive oxygen species(ROS)levels and mitochondrial membrane potential(MMP)in SH-SY5Y cells were detected by the corresponding kits.4.CCK-8assay and TUNEL were used to detect SH-SY5Y cell viability and apoptosis.5. Immunohistochemistry was used to detect Aβdeposition in cerebral cortex and hippocampus of APPswe/PS1E9 double-transgenic AD mice.6.Western blotting was used to detect the effects of D-JNKI1 on amyloid precursor protein(APP)cleavage,apoptosis,as well as Tau protein phosphorylation in cerebral cortex and hippocampus and the related mechanisms.Results:Part Ⅰ Role of D-JNKI1 in PD:1.D-JNKI1 alleviated MPTP-induced behavioral changes in PD.2.D-JNKI1 alleviated the MPTP-induced decrease in the number of dopaminergic neurons and nerve fibers in the substantia nigra(SN)and striatum(CPU),and the MPTP-induced decrease in the expression of tyrosine hydroxylase and dopamine transporter;D-JNKI1 alleviated the decrease of TH expression in SH-SY5Y cells induced by MPP~+.3.D-JNK1 inhibited MPTP-induced JNK phosphorylation in mouse brain as well as JNK and c-Jun phosphorylations in SH-SY5Y cells,and inhibited MPTP-induced ERK phosphorylation,but did not affect p38phosphorylation.D-JNKI1 significantly inhibited the increase of p38 phosphorylation level induced by MPP~+,but did not alleviate the reduced ERK phosphorylation level.4.D-JNKI1 inhibited the production of ROS in MPP~+induced SH-SY5Y cells,and alleviated the reduction of MMP in MPP~+induced SH-SY5Y cells.5.D-JNKI1 inhibited the decrease of Bcl-2/Bax ratio and the increase of caspase-3 and cleaved-caspase-3 level induced by MPTP/MPP~+,and the TUNEL showed that D-JNKI1 alleviated MPP~+-induced cell apoptosis.Part II Role of D-JNKI1 in AD:1.D-JNKI1 reduced the area covered by Aβ-positive products in the cerebral cortex and hippocampus of APPswe/PS1E9 double-transgenic mice and decreased the phosphorylation level of APP and the ratio of s APPβ/s APPαin cerebral cortex and hippocampus.2.D-JNKI1 had no significant effect on the expression levels ofα-disintegrin and metalloproteinase-10 (ADAM10),β-site amyloid cleavage enzyme-1(BACE1)and presenilin 1(PS1)in the brain.3.D-JNKI1 inhibited the phosphorylation of JNK and c-Jun in the brain,and inhibited ERK and p38 phosphorylation as well.4.D-JNKI1 increased the Bcl-2/Bax ratio in cerebral cortex and decreased the Bcl-2/Bax ratio in hippocampus,but showed no significant effect on the expression level of caspase-3 in cerebral cortex and hippocampus.5.D-JNKI1 showed no significant effect on the phosphorylation of Tau protein in the brain.Conclusion:1.D-JNKI1 alleviates the degeneration of dopaminergic neurons induced by MPTP/MPP~+in PD model by inhibiting the JNK pathway.2.D-JNKI1 attenuates the deposition of Aβamyloid in the cerebral cortex and hippocampus of Appswe/PS1E9 double-transgenic AD mice by inhibiting the JNK pathway.The above studies provide a experimental basis for D-JNKI1 to be a potential prevention/treatment for PD and AD.