| Parkinson’s disease (PD) is the second most prevalent neurodegenerative diseasejust after Alzheimer’s disease. The major pathological features are the loss ofdopaminergic neurons in substantia nigra compact (SNc), the presence of Lewy’sbodies and the significant decrease of dopamine level in the striatum. However, wecannot prevent and treat effectively, all of the efforts used in the clinic today aims toalleviate the symptoms, mainly by L-DOPA administration; none halt or retarddopaminergic neuron degeneration, and result in serious adverse effect for long-termuse. So looking for new targets and researching new drug treatment for PD is urgentand necessary.So far, the exact etiology of the PD is unknown. However, lots of researchessuggest that multiple factors might be involved, such as heredity, environment,oxidative stress, inflammation and decline in growth factors levels. Oxidative stress isone of the important pathogenesis of the PD. In recent years a large number of studiesabroad indicate that oxidative stress induce the death of dopaminergic neuronsthrough various pathways in substantia nigra. Oxidative stress results from theimbalance of reactive oxygen species (ROS) generation and clearance. Astrocytesplay an important role in clearing production of ROS in the brain. Astrocytes mayhave a close relation with the selective vulnerability of neurons by scavenging ROSand releasing the precursor of γ-L-glutamyl-L-cysteinyglycine (GSH) synthesis in neurons, Furthermore, alteration in astrocyte GSH level may be an importantcontributor to the pathogenesis of neurodegenerative disease.Curcumin (Cur) is extracted from the rhizomes of the ginger family plantCurcuma longa(Cuma longa L.). Because of its color stability and low toxicity, it hasbeen widely used as food additives and dyes. Studies suggest that Cur may produceanti-inflammatory, anti-atherosclerosis, anti-tumor, anti-oxidation, scavengering freeradical and other pharmacological effects. Cur has a good protection for liver, kidneyand immuno system. However up to now, neuroprotection of Cur and its relatedmechanism has not been confirmed. Indeed, accumulating cell culture and animalmodel data show that dietary Cur is a strong candidate for use in the prevention ortreatment of major disabling age-related neurodegenerative diseases like Alzheimer’s,Parkinson’s, and stroke.The cytochrome P450enzymes are a superfamily of hemeproteins that serve asterminal oxidases in the mixed function oxidase system for metabolizing variousendogenous substrates (steroids, fatty acids) and xenobiotics (drugs and toxins).Multiple forms of CYPs are known to exist in hepatic and extrahepatic tissues,including brain. One of the isoforms that has received much attention during recentyears is the ethanol-inducible cytochrome P4502E1(CYP2E1), not only because ofthe capacity of this isoenzyme to metabolize ethanol to acetaldehyde, but alsobecause of its role in the metabolic activation of a large number of toxicologicalcompounds, including acetaminophen, various solvents, and nitrosamines. In addition,CYP2E1has an apparently high rate of oxidase activity that causes the formation ofreactive oxygen species (ROS) during its catalytic cycle, and these are able to initiatelipid peroxidation and damage cell membranes. In the brain, CYP2E1isconstitutively expressed, e.g. in hippocampal pyramid neurons, cortical astrocytes,and endothelial cells, and the enzyme has been found to be inducible and catalyticallyactive in the brain. It has been suggested that MPP+and LPS increase the expressionof CYP2E1and induce oxidative stress in astrocytes. And increasing evidence showsthat cytochrome P4502E1is involved the MPTP-induced mouse model of PD, but theexact mechanism remains unclear. In the present study, first we investigated the cytoprotective effect of Cur onastrocytes against MPP+and LPS neurotoxicity. Second, we explored the role of Curin oxidative stress via detecting the production of ROS and MDA. Eventually, weinquired into the effect of Cur on the expression and activity of CYP2E1.AIM: To investigate the impact of Cur on MPP+and LPS induced neurotoxicity inastrocyte, and the effect on drug-metabolizing enzyme in central nervous system.Further study the underlying mechanism of the neuroprotective effect.METHODS: Primary mesencephalic astrocyte cultures were prepared fromC57BL/6J mice. MTT analysis was used to assess the cell viability. Staining withHoechst33342and assay of LDH release in astrocytes supernatant liquid was used todetermine astroglia injury.2’7’-dichlorofluorescein diacetate (DCFH-DA) asfluorescence probe was used to detect ROS level by Flow Cytometry and Microplatefluorescence microplate reader. Biochemical experiment was used to detect thecontent of MDA, which was one of the oxidative stress indexes. Realtime PCR andimmunocytochemistry were taken for analysising the mRNA and protein level of theCYP2E1in astrocytes. CYP2E1activity was determined by the hydroxylation ofp-nitrophenol to4-nitrocatechol catalyzed by CYP2E1RESULTS:(1) Cur decreased the LDH release, enhanced the cell viability andlessened cytotoxicity that induced by MPP+and LPS in primary mesencephalicastrocytes.(2) Cur reduced the increase of ROS and MDA production caused byMPP+and LPS.(3) Cur inhibited the up-regulation of the CYP2E1expression,decreased the enhancement of CYP2E1activity after exposure to MPP+and LPS, butitself had no impact on CYP2E1.CONCLUSION: Cur had cytoprotective effect on astrocytes against MPP+and LPSneurotoxicity, lessened injury caused by oxidative stress. Cur possibly protectedagainst CYP2E1-dependent toxicity via inhibiting the up-regulation of the CYP2E1 expression and decreasing the enhancement of the CYP2E1activity that induced byMPP+and LPS.The major contributions of the present study lie in:We report for the first time the effect of Cur on drug-metabolizing enzyme(CYP2E1) in central nervous system. This research provides experimental evidenceto explore the possible use of Cur and its mechanism, new insight into developing avery low toxic natural compound as a therapeutic approach in PD. |
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