Substance P Of Mpp ~ + Induced Mes23.5 Protective Effect And Mechanism Of Apoptosis

Parkinson’s disease (PD) is a progressive neurodegenerative disorder associated with the loss of dopaminergic neurons originating in the substantia nigra pars compacta (SNc). The degeneration of nigrostriatal pathways produces the depletion of dopamine (DA) in the striatum and the motor function is therefore disrupted in PD. Although the exact pathogenesis of PD has not being revealed, multiple factors might be involved, such as heredity, environmental factors, oxidative stress, excitotoxin, autoimmunity, iron accumulation and cell apoptosis. Previous studies showed that concentration of chromatin and apoptotic bodies could be observed in dopaminergic neurons of SNc of PD patients, which demonstrated that apoptosis plays an important role in PD.Substance P, a neuropeptide first discovered in1931, is a member of neurokinin family. Being a neurotransmitter, neuromodulator or neurotrophins, substance P plays important roles in central nervous system by acting its high-affinity neurokinin receptors, NK-1receptor. Previous studies have shown that substance P is involved in the modulation of nigrostriatal pathways. In order to study the possible neuroprotective effects of substance P on dopaminergic neurons, as well as the underlying mechanisms, we performed the in vitro experiments in MPP+-treated MES23.5cells by using immunohistochemistry, cell viability assay, flow cytometry and other molecular biological methods. The results are as follows:1. NK-1receptors expressed abundantly in MES23.5cells.2. MPP+treatment resulted in a significant reduction in cell viability (P<0.01). SMSP (10-9-10"5mol/L) pretreatment significantly attenuated MPP+-induced reduction in cell viability (P<0.01). The peak effect of SMSP was observed at the concentration of10-7mol/L, which was chosen for the following experiments. Co-treatment with SR140333B and SMSP significantly blocked SMSP-induced neuroprotective effects on MES23.5cells (P<0.01compared to SMSP alone).3. The nuclei of MPP+treated MES23.5cells appeared some morphological changes such as condensation (brightly stained) and fragmentation of chromatin (P<0.05compared to control). However, pretreatment with SMSP significantly attenuated MPP+-induced morphological changes in nuclei (P<0.05compared to MPP+alone). While co-treatment with SR140333B and SMSP significantly blocked SMSP-induced protective effects (P<0.05compared to SMSP alone).4. MPP+treatment significantly increased the production of ROS in MES23.5cells (P<0.05compared to control). SMSP pretreatment significantly decreased the production of ROS in MES23.5cells (P<0.05compared to MPP+alone). Co-treatment with SR140333B and SMSP significantly blocked SMSP-induced effects (P<0.05compared to SMSP alone).5. MPP+treatment significantly increased the activated caspase-3in MES23.5cells (P<0.05compared to control). SMSP pretreatment significantly attenuated MPP+-induced increase in caspase-3(P<0.05compared to MPP+alone). Co-treatment with SR140333B and SMSP significantly blocked SMSP-induced effects in caspase-3level (P<0.05compared to SMSP alone).6. MPP+treatment significantly decreased the mitochondrial transmembrane potential in MES23.5cells (P<0.05compared to control). SMSP pretreatment significantly attenuated MPP+-induced change in mitochondrial transmembrane potential (P<0.05compared to MPP+alone). Co-treatment with SR140333B and SMSP significantly blocked SMSP-induced effects in mitochondrial transmembrane potential (P<0.05compared to SMSP alone).7. MPP+treatment significantly increased the calcium influx in MES23.5cells (P<0.05compared to control). SMSP pretreatment significantly attenuated MPP+-induced increase in calcium influx (P<0.05compared to MPP+alone). Co-treatment with SR140333B and SMSP significantly blocked SMSP-induced effects in calcium influx (P<0.05compared to SMSP alone).In conclusion, the present results suggest that NK-1receptor expressed abundantly in MES23.5cells. SMSP pretreatment could significantly antagonize MPP+-induced neurotoxicity in MES23.5cells by multiple pathways, including antiapoptosis, inhibition of ROS production, reduction of caspses-3activity, reduction of mitochondrial transmembrane potential as well as inhibition of calcium influx. Furthermore, SR140333B blocked SMSP-induced effects confirming the involvement of NK-1receptor. The present study on substance P may provide a rationale for further investigations into its potential in the treatment of Parkinson’s disease.