| Parkinson’s disease is one of the common neurodegenerative diseases among elder people. Loss of dopaminergic neurons leads to symptoms including resting tremor, rigidity, bradykinesia, and postural instability. The major pathological changes of Parkinson’s disease are characterized by the selective loss of DA neurons in the substantia nigra pars compacta region (SNpc) and the accumulation of the lewy in the survival neuron. The oxidative stress and mitochondrial dysfunction are involved in its molecular mechanism. Endoplasmic reticulum stress(ER Stress) play an important role in the pathogenesy of Parkinson’s disease.Endoplasmic reticulum is a large organelle that serves as storage for Ca2+ions, and is necessary for the balance of Ca2+ions in the cells. Transient receptor potential channel1(TRPC1) is a non-selective cation channel which locates in the cell membrane. TRPC1has been suggested as a mediator of Ca2+, Na2+and Fe2+enterring into cells. The expression level of TRPC1was high in the nigra pars compacta region. TRPC1is also critical for maintaining the ER Ca2+level. TRPC1plays an important role in regulating the homeostasis of the redox active oxygen. The calcium-actived neutral protease1(calpain1) is sensitive to the intracellular redox state, and its function is affected by the redox state, it can be activated by the disorder of the Ca2+. And then procaspase-12is induced, leads to endoplasmic reticulum stress apoptosis.Reactive oxygen species (ROS) are important molecules effecting cellular redox status, which play roles in cell contraction, migration, proliferation, differentiation and apoptosis by modulating the function of transient receptor potential (TRP) channels in the plasma membrane. Trx-1is conserved from bacteria to mammals, its molecular weight is12KDa, has the dithiol active site (-Cys-Gly-Pro-Cys-), which is essential for the redox-regulatory function. Trx-1has diverse functions, such as growth promotion, neuroprotection, antiapoptosis, and immune function modulation. Recent studies showed that TRPC1was activated by extracellular thioredoxin. Overexpression of functional TRPC1protected against neurotoxin-induced loss of SOCE, the associated decrease in ER Ca2+levels, and the resultant unfolded protein response (UPR). Over-expressing Trx-1transgenic mice showed increased resistance to oxidative stress and nerve system diseases by the endoplasmic reticulum stress.In this study,1-methyl-4-phenylpyridinum ion (MPP+)induced Parkinson’s disease cell model was used to explore the endoplasmic reticulum stress molecular mechanisms on Parkinson’s disease, and the interaction between Trx-1and TRPC1, calpain1. The main results are as follows:(1) Endoplasmic reticulum stress is associated with Parkinson’s disease. Calpainl was activated and TRPC1was reduced by MPP+in a time-dependent manner. MPP+significantly induced the expression of CHOP and procaspase-12activation, calpainl and TRPC1are involved in apoptosis of endoplasmic reticulum stress by MPP+.(2) The inhibitor of calpainl can inhibit MPP+induced neurotoxicity. PC12cells were pretreatment with calpainl inhibitor MDL28170for30min, and then treated with the MPP+for24hours, we found that MDL28170inhibited MPP+-induced activation of procaspase-12, but had no significant effect on the expression level of CHOP. The inhibition of calpainl restored the down-regulation of TRPC1and Trx-1expression levels induced by MPP+. This shows that calpainl is closely related with endoplasmic reticulum stress-induced apoptosis pathway and the expressions of TRPC1and Trx-1.(3) The TRPC1inhibitor further exacerbated the endoplasmic reticulum stress-induced apoptosis. PC12cells were pretreated with TRPC1inhibitor SKF96365for30min, and then were treated with the MPP+for24h. We found that SKF96365further increased the expressions of CHOP and BIP. Further, SKF96365treatment separately can reduce the expression of Trx-1. Trx-1may be the downstream of TRPC1.(4) After Trx-1expression was silenced, the expression of calpainl and TRPC1was unchanged, which further verified that Trx-1should under calpainl and TRPC1in the Signaling pathway. However, the overexpression of Trx-1recoverd MPP+-induced increase of calpainl in certain effects, indicating that Trx-1may affect the expression of calpainl through other signaling pathways.(5) The thioredoxinl inducer NGF protected PC12cells agansist neurotoxicity caused by MPP+through inducing the expressions of Trx-1and CDK5, and SKF96365restored the up-regulations of Trx-1induced by NGF. This result further suggests the correlation between Trx-1and TRPC1.(6) The supplement of Endoplasmic reticulum calcium can resist endoplasmic reticulum stress. The calcium channel blockers Verapamil and KN-62(the inhibitor of CaMKII) promoted the endoplasmic reticulum stress. KC1not only restored the cytoplasmic matrix calcium concentration and eased endoplasmic reticulum stress. At the same time, the expression of TRPC1was recovered by KC1at a certain degree. Interestingly, treating with KC1alone caused a significantly decreased on TRPC1expression. Supplement of the endoplasmic reticulum calcium stores is a key therapeutic target for Parkinson’s disease.Conclusion:TRPC1, Ca2+and calpainl played an important role in regulating the mechanism of the injury in the endoplasmic reticulum in Parkinson’s disease. Inhibition of calpainl partly blocked the endoplasmic reticulum stress-induced apoptosis. This is conducive for us to get a more comprehensive understanding of the pathogenesis of Parkinson’s disease. The activation of calpainl by calcium will become a new target for the prevention and treatment of Parkinson’s disease. Trx-1, TRPC1, ROS is closely related with the equilibrium of calcium ions in cytoplasmic matrix. Recovering the homeostasis of calcium ion by adjusting the levels of intracellular expressions of Trx-1and TRPC1can resistance to apoptosis induced by the endoplasmic reticulum stress in Parkinson’s disease. The thioredoxin-1inducer NGF plays neuroprotective roles by regulating expression of TRPC1. This study further provided theory basis with mechanism on Parkinson’s disease and new target for prevention and treatment of Parkinson’s disease. |
