Neuroprotective Effects Of Nimodipine And Catalpol

Glial cells,the most abundant cell types in the central nervous system(CNS),have been believed to provide support and nutrition,maintain homeostasis,form myelin,serve immune surveillance,and modulate neurotransmission.Recent studies suggest that glial cells also are implicated in a wide range of CNS disorders including ischemia and Parkinson's disease(PD) neurodegenerative disease,and play an important role in the progress of disorders.In this study,the protective effects of nimodipine and catalpol on neurodegenerative disease were investigated with LPS-induced degeneration of dopaminergic neurons in mesencephalic neuron-glia cultures as a PD model and primary cultured astrocytes exposed to oxygen-glucose deprivation followed by reperfusion as an in vitro ischemic model.1.Nimodipine protects dopaminergic neurons against inflammation-mediated degeneration through the inhibition of microglial activationInflammation in the brain has increasingly been recognized to play an important role in the pathogenesis of several neurodegenerative disorders,including Parkinson's disease and Alzheimer's disease.Inflammation-mediated neurodegeneration involves activation of the brain's resident immune cells,the microglia,which produce proinflammatory and neurotoxic factors,including cytokines,reactive oxygen intermediates,nitric oxide,and eicosanoids that impact on neurons to induce neurodegeneration.Hence,identification of compounds that prevent microglial activation may be highly desirable in the search for therapeutic agents for inflammation-mediated neurodegenerative diseases.In this study,nimodipine,a calcium channel blocker commonly-used in the therapy of cardiovascular diseases,was reported to significantly reduce lipopolysaccharide(LPS)-induced the degeneration of dopaminergic(DA) neurons in a dose-dependent manner in mesencephalic neuron-glia cultures.In addition,with reconstituted neuron and glia cultures,nimodipine was found to be neuroprotective only in the presence of microglia.Moreover,nimodipine was not neuroprotective to 1-methyi-4-phenylpyridinium (MPP⁺)-induced DA neurotoxitity in the absence of microglia.The neuroprotective effect of nimodipine was attributed to the inhibition of microglial activation, since nimodipine significantly inhibited the production of nitric oxide(NO),tumor necrosis factor-α(TNF-α),intedeukin-1β(IL-1β) and prostaglandin E₂(PGE₂) from LPS-stimulated microglia.Mechanistic study showed that nimodipine failed to protect the degeneration of neurons in neuron-glia cultures from mice lacking functional NADPH oxidase(PHOX),a key enzyme for extracellular superoxide production in immune cells,and significantly reduced LPS-induced PHOX cytosolic subunit p47phox translocation to the cell membrane in microglia from wild-type mice(PHOX^+/+).These results suggest that nimodipine is protective to DA neurodegeneration via inhibiting the microglial-mediated oxidative stress and inflammatory response.Furthermore,our study revealed that inhibition of PHOX is a novel site of action for the calcium channel blocker-independent effect of nimodipine.Thus, nimodipine may be a potential therapeutic agent for the treatment of inflammation-related neurodegenerative disorders such as Parkinson's disease.2.Catalpol protects primary cultured astrocytes from ischemia-induced damage in vitroBrain ischemia is an acute neurodegenerative disease caused by insufficiency bloods supply to a particular brain area and subsequent of irreversible brain damage.Studies on pathomechanism of brain ischemia have mainly focused neurons and,accordingly,therapeutic strategies have been designed to counteract neuronal dysfunction.However,recent data indicate that a decrease in neuronal survival during and after ischemia is also associated with astrocytic dysfunction.Thus,counteracting astrocytic dysfunction during ischemia and reperfusion provide a new option of the pharmacological intervention in prevention of brain damage.Catalpol,an iridoid glycoside abundant in the roots of Rehmannia glutinosa,has been previously found to prevent the loss of CA1 hippocampal neurons and to reduce working errors in gerbils after ischemia-reperfusion injury.In the present study,we investigated the effects of catalpol on astrocytes in an ischemic model to further characterize its neuroprotective mechanisms.Primary cultured astrocytes exposed to oxygen-glucose deprivation(OGD) followed by reperfusion(adding back oxygen and glucose,OGD-R),were used as an in vitro ischemic model.Treatment of the astrocytes with catalpol during ischemia-reperfusion increased astrocyte survival significantly in a concentration-dependent manner,as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay,lactate dehydrogenase(LDH) release and morphological observation.In addition,catalpol prevented the decrease in mitochondrial membrane potential,inhibited the formation of reactive oxygen species(ROS) and the production of nitric oxide(NO), decreased the level of lipid peroxide and the activity of inducible nitric oxide synthase(iNOS), and elevated the activities of superoxide dismutase(SOD),glutathione peroxidase(GSH-Px) and the content of glutathione(GSH).These results suggest that catalpol exerts the most significant cytoprotective effect on astrocytes by suppressing the production of free radicals and elevating antioxidant capacity.