title: A self-propelling cycle mediated by reactive oxide species and nitric oxide exists in LPS-activated microglia.
abstract: It has been widely accepted that microglia, the innate immune cells in the brain, can be chronically activated in response to neuron death, fuelling a self-renewing cycle of microglial activation followed by further neuron damage (reactive microgliosis), which has been considered as the main reason responsible for the progressive nature of neurodegenerative diseases. In the present study, it was found that LPS (lipopolysaccharide) significantly induced the activation of N9 microglia, and the increase of NO level induced by pretreatment of LPS could last after the removal of LPS. The culture medium of activated microglia significantly decreased the viability of rat primary cortical neuron. These results can be blocked by the antioxidant N-acetylcysteine (NAC) and nicotinamide adenine dinucleotide phosphate reduced (NADPH) oxidase inhibitor diphenyleneiodonium sulfate (DPI), suggesting that intracellular reactive oxide species (iROS) released from the activated microglial cells may continue to further activate microglia. Next, it was shown that the iROS level increased rapidly after the LPS treatment in microglia cells followed by the NO production through the regulation of iNOS (inducible nitric oxide synthase) expression. The increase of iROS could be reversed by gp91phox (the critical and catalytic subunit of NADPH oxidase) siRNA. Moreover, NO released from sodium nitroprusside (SNP) was able to increase the iROS production of N9 microglia by regulating of the activity and the expression of NADPH oxidase. In conclusion, our research suggests for the first time that there may exist a self-propelling cycle in microglial cells possibly mediated by iROS and NO when they become activated by LPS. It may be responsible partially for the ongoing microglial activation and the progressive nature of neurodegenerative diseases.
authors.affiliation: Department of Pharmacology, Shenyang Pharmaceutical University, Shenyang, People's Republic of China.
authors.forename: Zhang
authors.initials: Z
authors.lastname: Lijia
authors.forename: Siqi
authors.initials: S
authors.lastname: Zhao
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Wang
authors.forename: Chunfu
authors.initials: C
authors.lastname: Wu
authors.forename: Jingyu
authors.initials: J
authors.lastname: Yang
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D017077:Culture Media, Conditioned; D017931:DNA Primers; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D017077:Culture Media, Conditioned; D017931:DNA Primers; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D020030:Nitric Oxide Donors; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D009599:Nitroprusside; D009569:Nitric Oxide; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases