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NLRP6 Inflammasome Ameliorates Brain Injury after Intracerebral Hemorrhage.

ABSTRACT: NLRP6 inflammasome, one of the important intracellular innate immune sensors, has been shown to regulate immune responses. However, its roles in the intracerebral hemorrhage (ICH) are completely not clear. In the present study, we investigated the expression profile and biological roles of NLRP6 inflammasome in perihematomal brain tissues of mice subjected to ICH. In this study, we investigated the expression profile of NLRP6 inflammasome in the perihematomal brain tissues and explored the biological role of NLRP6 inflammasome upon acute brain injury in mice subjected to ICH. Increased expression of NLRP6 inflammasome was found in perihematomal brain tissues ranging from 6 h to 3 days, with a peak level at 1 day after ICH. Immunohistochemistry staining also showed that NLRP6 inflammasome was significantly increased in the perihematomal brain tissues at 1 day after ICH. Moreover, immunofluorescence staining showed that NLRP6 inflammasome was mainly colocalized in glial fibrillary acidic protein (GFAP)-positive astrocytes, while with little colocalized expression in NeuN-positive neurons and without expression in CD11b-positive microglia and CD31-positive endothelial cell in the perihematomal brain tissue of mice after ICH. Furthermore, NLRP6^-/- ICH mice exhibited significantly higher brain water contents (BMCs), proinflammatory cytokines, NF-?B activity and neurological deficit scores when compared with the wild type (WT) ICH mice. In addition, we found that Toll-like receptor 4 (TLR4)^-/- mice, as well as the TAK242 treated mice, had markedly lower expression of NLRP6 inflammasome expression in the perihematomal brain tissue at 1 day after ICH. Our data suggest that the upregulated NLRP6 inflammasome in perihematomal brain tissues attenuates ICH-induced brain injury.

SUBMITTER: Wang PF

PROVIDER: S-EPMC5527702 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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NLRP6 Inflammasome Ameliorates Brain Injury after Intracerebral Hemorrhage.

Wang Peng-Fei PF Li Zhen-Guang ZG Zhang Yong Y Ju Xiao-Hua XH Liu Xin-Wu XW Zhou Ai-Ming AM Chen Jing J

Frontiers in cellular neuroscience 20170714

NLRP6 inflammasome, one of the important intracellular innate immune sensors, has been shown to regulate immune responses. However, its roles in the intracerebral hemorrhage (ICH) are completely not clear. In the present study, we investigated the expression profile and biological roles of NLRP6 inflammasome in perihematomal brain tissues of mice subjected to ICH. In this study, we investigated the expression profile of NLRP6 inflammasome in the perihematomal brain tissues and explored the biolo ...[more]

PMID: 28798666

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Project description:BackgroundThe NLRP3 inflammasome is a multiprotein complex that regulates the innate immune inflammatory response by activating caspase-1 and subsequent IL-1β and IL-18. Fluoxetine has been shown to have the anti-inflammatory properties in many disease models. However, the effects and mechanisms of these effects of fluoxetine in early brain injury after subarachnoid hemorrhage (SAH) have not been defined.MethodsThe SAH model was induced by an endovascular perforation in adult male Sprague-Dawley (SD) rats weighing 300-320 g. N-Ac-Tyr-Val-Ala-Asp-chloromethyl ketone (AC-YVAD-CMK) was injected intraperitoneally (5 mg/kg) 1 h after SAH. Fluoxetine was administered via intravenous route 6 h after SAH. 3-Methyladenine (3-MA) was intracerebroventricularly injected 20 min before SAH. SAH grade, neurological function, brain water content, propidium iodide (PI) staining, western blot, double immunostaining, and transmission electron microscopy were performed.ResultsExpression of caspase-1 increased and peaked at 24 h after SAH. Caspase activation was along with the increased necrotic cells, which occurred mainly in neurons. Necrotic cell death of microglia and astrocyte were also found. Administration of AC-YVAD-CMK, a caspase-1 inhibitor, reduced the expression of IL-1β and IL-18 and the number of PI-positive cells, attenuated brain edema, and improved neurological function, which was also observed in fluoxetine-treated rats. Furthermore, fluoxetine treatment significantly decreased the expression of NLRP3 and cleaved caspase-1 and upregulated the expression of beclin-1, a marker for autophagy. Finally, the effects of fluoxetine in NLRP3 inflammasome activation were reversed by additional 3-MA administration.ConclusionsTogether, our present study indicated that NLRP3 inflammasome and caspase-1 activation play a deleterious role in early brain injury and fluoxetine mitigates NLRP3 inflammasome and caspase-1 activation through autophagy activation after SAH, providing a potential therapeutic agent for SAH treatment.

Project description:The NLRP3 (NALP3, cryopyrin) inflammasome, a key component of the innate immune system, facilitates caspase-1 and interleukin (IL)-1? processing, which amplifies the inflammatory response. Here, we investigated whether NLRP3 knockdown decreases neutrophil infiltration, reduces brain edema, and improves neurological function in an intracerebral hemorrhage (ICH) mouse model. We also determined whether mitochondrial reactive oxygen species (ROS) governed by mitochondrial permeability transition pores (mPTPs) would trigger NLRP3 inflammasome activation following ICH.ICH was induced by injecting autologous arterial blood (30?l) into a mouse brain. NLRP3 small interfering RNAs were administered 24 hours before ICH. A mPTP inhibitor (TRO-19622) or a specific mitochondria ROS scavenger (Mito-TEMPO) was coinjected with the blood. In naive animals, rotenone, which is a respiration chain complex I inhibitor, was applied to induce mitochondrial ROS production, and followed by TRO-19622 or Mito-TEMPO treatment. Neurological deficits, brain edema, enzyme-linked immunosorbent assay, Western blot, in vivo chemical cross-linking, ROS assay, and immunofluorescence were evaluated.ICH activated the NLRP3 inflammasome. NLRP3 knockdown reduced brain edema and decreased myeloperoxidase (MPO) levels at 24 hours, and improved neurological functions from 24 to 72 hours following ICH. TRO-19622 or Mito-TEMPO reduced ROS, NLRP3 inflammasome components, and MPO levels following ICH. In naive animals, rotenone administration induced mPTP formation, ROS generation, and NLRP3 inflammasome activation, which were then reduced by TRO-19622 or Mito-TEMPO.The NLRP3 inflammasome amplified the inflammatory response by releasing IL-1? and promoting neutrophil infiltration following ICH. Mitochondria ROS may be a major trigger of NLRP3 inflammasome activation. The results of our study suggest that the inhibition of the NLRP3 inflammasome may effectively reduce the inflammatory response following ICH.ANN NEUROL 2014;75:209-219.

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NLRP6 Inflammasome Ameliorates Brain Injury after Intracerebral Hemorrhage.

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NLRP6 Inflammasome Ameliorates Brain Injury after Intracerebral Hemorrhage.

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