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Urate inhibits microglia activation to protect neurons in an LPS-induced model of Parkinson's disease.

ABSTRACT: Multiple risk factors contribute to the progression of Parkinson's disease, including oxidative stress and neuroinflammation. Epidemiological studies have revealed a link between higher urate level and a lower risk of developing PD. However, the mechanistic basis for this association remains unclear. Urate protects dopaminergic neurons from cell death induced by oxidative stress. Here, we investigated a novel role of urate in microglia activation in a lipopolysaccharide (LPS)-induced PD model.We utilized Griess, ELISA, real-time PCR, Western blot, immunohistochemistry, and immunofluorescence to detect the neuroinflammation. For Griess, ELISA, Western blot, and immunofluorescence assay, cells were seeded in 6-well plates pre-coated with poly-L-lysine (PLL) and incubated for 24 h with the indicated drugs. For real-time PCR assay, cells were seeded in 6-well plates pre-coated with PLL and incubated for 6 h with the indicated drugs. For animal experiments, rats were injected with urate or its vehicle twice daily for five consecutive days before and after stereotaxic surgery. Rats were killed and brain tissues were harvested after 4 weeks of LPS injection.In cultured BV2 cells and rat primary microglia, urate suppressed proinflammatory cytokine production and inducible cyclooxygenase 2 and nitric oxide synthase expression to protect dopaminergic neurons from the toxic effects of activated microglia. The neuroprotective effects of urate may also be associated with the stimulation of anti-inflammatory factors interleukin 10 and transforming growth factor ?1. Intracellular urate level was increased in a dose-dependent manner upon co-treatment with urate and LPS as compared with LPS alone, an effect that was abrogated by pretreatment with probenecid (PBN), an inhibitor of both glucose transporter 9 and urate transporter 1 (URAT1). PBN also abolished the anti-inflammatory effect of urate. Consistent with these in vitro observations, the number of tyrosine hydroxylase-positive neurons was decreased and the loss of motor coordination was reversed by urate administration in an LPS-induced rat model of PD. Additionally, increased plasma urate level abolished the reduction of URAT1 expression, the increase in the expression of interleukin-1?, and the number of ionized calcium-binding adaptor molecule 1-positive microglia along with changes in their morphology.Urate protects neurons against cytotoxicity induced by microglia activation via modulating urate transporter-mediated intracellular urate level.

SUBMITTER: Bao LH

PROVIDER: S-EPMC5932803 | biostudies-other | 2018 May

REPOSITORIES: biostudies-other

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Urate inhibits microglia activation to protect neurons in an LPS-induced model of Parkinson's disease.

Bao Li-Hui LH Zhang Ya-Nan YN Zhang Jian-Nan JN Gu Li L Yang Hui-Min HM Huang Yi-Ying YY Xia Ning N Zhang Hong H

Journal of neuroinflammation 20180502 1

<h4>Background</h4>Multiple risk factors contribute to the progression of Parkinson's disease, including oxidative stress and neuroinflammation. Epidemiological studies have revealed a link between higher urate level and a lower risk of developing PD. However, the mechanistic basis for this association remains unclear. Urate protects dopaminergic neurons from cell death induced by oxidative stress. Here, we investigated a novel role of urate in microglia activation in a lipopolysaccharide (LPS)- ...[more]

PMID: 29720230

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Project description:BackgroundMicroglia activation induced by ?-synuclein (?-syn) is one of the most important factors in Parkinson's disease (PD) pathogenesis. However, the molecular mechanisms by which ?-syn exerts neuroinflammation and neurotoxicity remain largely elusive. Targeting metabotropic glutamate receptor 5 (mGluR5) has been an attractive strategy to mediate microglia activation for neuroprotection, which might be an essential regulator to modulate ?-syn-induced neuroinflammation for the treatment of PD. Here, we showed that mGluR5 inhibited ?-syn-induced microglia inflammation to protect from neurotoxicity in vitro and in vivo.MethodsCo-immunoprecipitation assays were utilized to detect the interaction between mGluR5 and ?-syn in microglia. Griess, ELISA, real-time PCR, western blotting, and immunofluorescence assays were used to detect the regulation of ?-syn-induced inflammatory signaling, cytokine secretion, and lysosome-dependent degradation.Results?-syn selectively interacted with mGluR5 but not mGluR3, and ?-syn N terminal deletion region was essential for binding to mGluR5 in co-transfected HEK293T cells. The interaction between these two proteins was further detected in BV2 microglia, which was inhibited by the mGluR5 specific agonist CHPG without effect by its selective antagonist MTEP. Moreover, in both BV2 cells and primary microglia, activation of mGluR5 by CHPG partially inhibited ?-syn-induced inflammatory signaling and cytokine secretion and also inhibited the microglia activation to protect from neurotoxicity. We further found that ?-syn overexpression decreased mGluR5 expression via a lysosomal pathway, as evidenced by the lysosomal inhibitor, NH4Cl, by blocking mGluR5 degradation, which was not evident with the proteasome inhibitor, MG132. Additionally, co-localization of mGluR5 with ?-syn was detected in lysosomes as merging with its marker, LAMP-1. Consistently, in vivo experiments with LPS- or AAV-?-syn-induced rat PD model also confirmed that ?-syn accelerated lysosome-dependent degradation of mGluR5 involving a complex, to regulate neuroinflammation. Importantly, the binding is strengthened with LPS or ?-syn overexpression but alleviated by urate, a potential clinical biomarker for PD.ConclusionsThese findings provided evidence for a novel mechanism by which the association of ?-syn with mGluR5 was attributed to ?-syn-induced microglia activation via modulation of mGluR5 degradation and its intracellular signaling. This may be a new molecular target for an effective therapeutic strategy for PD pathology.

Project description:AimIncreasing evidence suggests that probucol, a lipid-lowering agent with anti-oxidant activities, may be useful for the treatment of ischemic stroke with hyperlipidemia via reduction in cholesterol and neuroinflammation. In this study we examined whether probucol could protect against brain ischemic injury via anti-neuroinflammatory action in normal and hyperlipidemic mice.MethodsPrimary mouse microglia and murine BV2 microglia were exposed to lipopolysaccharide (LPS) for 3 h, and the release NO, PGE2, IL-1? and IL-6, as well as the changes in NF-?B, MAPK and AP-1 signaling pathways were assessed. ApoE KO mice were fed a high-fat diet containing 0.004%, 0.02%, 0.1% (wt/wt) probucol for 10 weeks, whereas normal C57BL/6J mice received probucol (3, 10, 30 mg·kg(-1)·d(-1), po) for 4 d. Then all the mice were subjected to focal cerebral ischemia through middle cerebral artery occlusion (MCAO). The neurological deficits were scored 24 h after the surgery, and then brains were removed for measuring the cerebral infarct size and the production of pro-inflammatory mediators.ResultsIn LPS-treated BV2 cells and primary microglial cells, pretreatment with probucol (1, 5, 10 ?mol/L) dose-dependently inhibited the release of NO, PGE2, IL-1? and IL-6, which occurred at the transcription levels. Furthermore, the inhibitory actions of probucol were associated with the downregulation of the NF-?B, MAPK and AP-1 signaling pathways. In the normal mice with MCAO, pre-administration of probucol dose-dependently decreased the infarct volume and improved neurological function. These effects were accompanied by the decreased production of pro-inflammatory mediators (iNOS, COX-2, IL-1, IL-6). In ApoE KO mice fed a high-fat diet, pre-administration of 0.1% probucol significantly reduced the infarct volume, improved the neurological deficits following MCAO, and decreased the total- and LDL-cholesterol levels.ConclusionProbucol inhibits LPS-induced microglia activation and ameliorates cerebral ischemic injury in normal and hyperlipidemic mice via its anti-neuroinflammatory actions, suggesting that probucol has potential for the treatment of patients with or at risk for ischemic stroke and hyperlipidemia.

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Urate inhibits microglia activation to protect neurons in an LPS-induced model of Parkinson's disease.

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Urate inhibits microglia activation to protect neurons in an LPS-induced model of Parkinson's disease.

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