Blocking mPTP on Neural Stem Cells and Activating the Nicotinic Acetylcholine Receptor alpha 7 Subunit on Microglia Attenuate A beta-Induced Neurotoxicity on Neural Stem Cells

摘要

beta-Amyloid (A beta) can stimulate microglia to release a variety of proinflammatory cytokines and induce neurotoxicity. Nicotine has been reported to inhibit TNF-alpha, IL-1, and ROS production in microglia. Mitochondrial permeability transition pore (mPTP) plays an important role in neurotoxicity as well. Here, we investigated whether activating the microglial alpha 7-nAChR has a neuroprotective role on neural stem cells (NSCs) and the function of mPTP in NSCs in this process. The expression of alpha 7-nAChR in rat NSCs was detected by immunocytochemistry and RT-PCR. The viability of microglia and NSCs was examined by MTT assay. The mitochondrial membrane potential (Delta Im) and morphological characteristics of NSCs was measured by JC-1 staining and transmission electron microscopy respectively. The distribution of cytochrome c in the subcellular regions of NSCs was visualized by confocal laser scanning microscopy, and the expression levels of cyclophilin D and cleaved caspase-3 were assayed by western blot. The apoptotic rate of NSCs was measured by flow cytometry. The expression of alpha 7-nAChR was detected in microglial cells, but no expression was found in NSCs. The viability of rat microglial cells and NSCs was not affected by reagents or coculture itself. A beta(1-42)-mediated microglial activation impaired the morphology and the Delta Im of mitochondria of NSCs as well as increased cell apoptosis. However, the damage was attenuated when the alpha 7-nAChRs on microglial cells were activated or the mPTPs on NSCs were blocked. Blockade of mPTPs on NSCs and activation of alpha 7-nAChRs on microglia exhibit neuroprotective roles in A beta-induced neurotoxicity of NSCs.