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Caspase-1 inhibition prevents glial inflammasome activation and pyroptosis in models of multiple sclerosis.

ABSTRACT: Multiple sclerosis (MS) is a progressive inflammatory demyelinating disease of the CNS of unknown cause that remains incurable. Inflammasome-associated caspases mediate the maturation and release of the proinflammatory cytokines IL-1? and IL-18 and activate the pore-forming protein gasdermin D (GSDMD). Inflammatory programmed cell death, pyroptosis, was recently shown to be mediated by GSDMD. Here, we report molecular evidence for GSDMD-mediated inflammasome activation and pyroptosis in both myeloid cells (macrophages/microglia) and, unexpectedly, in myelin-forming oligodendrocytes (ODCs) in the CNS of patients with MS and in the MS animal model, experimental autoimmune encephalomyelitis (EAE). We observed inflammasome activation and pyroptosis in human microglia and ODCs in vitro after exposure to inflammatory stimuli and demonstrate caspase-1 inhibition by the small-molecule inhibitor VX-765 in both cell types. GSDMD inhibition by siRNA transduction suppressed pyroptosis in human microglia. VX-765 treatment of EAE animals reduced the expression of inflammasome- and pyroptosis-associated proteins in the CNS, prevented axonal injury, and improved neurobehavioral performance. Thus, GSDMD-mediated pyroptosis in select glia cells is a previously unrecognized mechanism of inflammatory demyelination and represents a unique therapeutic opportunity for mitigating the disease process in MS and other CNS inflammatory diseases.

SUBMITTER: McKenzie BA

PROVIDER: S-EPMC6042136 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Caspase-1 inhibition prevents glial inflammasome activation and pyroptosis in models of multiple sclerosis.

McKenzie Brienne A BA Mamik Manmeet K MK Saito Leina B LB Boghozian Roobina R Monaco Maria Chiara MC Major Eugene O EO Lu Jian-Qiang JQ Branton William G WG Power Christopher C

Proceedings of the National Academy of Sciences of the United States of America 20180612 26

Multiple sclerosis (MS) is a progressive inflammatory demyelinating disease of the CNS of unknown cause that remains incurable. Inflammasome-associated caspases mediate the maturation and release of the proinflammatory cytokines IL-1β and IL-18 and activate the pore-forming protein gasdermin D (GSDMD). Inflammatory programmed cell death, pyroptosis, was recently shown to be mediated by GSDMD. Here, we report molecular evidence for GSDMD-mediated inflammasome activation and pyroptosis in both mye ...[more]

PMID: 29895691

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Project description:AimsThe involvement of pyroptosis in ischemic stroke remains to be established. Therefore, we used the specific pyroptosis inhibitor Vx765 as an experimental intervention target in a murine model of stroke.MethodsA total of 564 C57BL/6 mice were subjected to photothrombotic procedures and treated via gavage with Vx765 at 1-hour post-ischemia. We subsequently assessed the expression of Gasdermin D (GSDMD), inflammasomes, caspase-1, and interleukin-1β (IL-1β) using immunofluorescence (IF) and Western blot (WB) analyses. We also examined ultrastructural changes of cortical neurons with transmission electron microscopy (TEM) and measured infarct volumes dynamically by magnetic resonance imaging (MRI). Moreover, we evaluated the neurologic deficits by modified neurological severity scores, the rotarod test, and Treadscan.ResultsElevated expression of GSDMD and GSDMD p30, the pore-forming subunit, was evident in the peri-ischemic region on days one and three post-ischemia. The neuronal plasma, nuclear, and mitochondrial membranes showed ultrastructural damage at day three post-stroke. Elevated expression of inflammasomes, caspase-1, and IL-1β was also present on days one and three post-injury. There were significant differences between Vx765-treated and vehicle groups in mean infarct volumes (14.36 vs 21.52 mm3 ; 12.34 vs 18.56 mm3 ; 4.13 vs 10.06 mm3 ; P < .05 at day one, three, and seven post-surgery, respectively). Mice treated with Vx765 showed better motor recovery as assessed by serial behavior tests and had better neuronal survival, which was attributable to pyroptosis inhibition, as illustrated by downregulated expression of the effector protein GSDMD, inflammasomes, caspase-1, and IL-1β. Besides, treatment with Vx765 preserved neuronal membrane structures after the ischemic injury.ConclusionsPyroptosis emerges as an important pathway for neuronal death in an acute ischemic stroke. Vx765, a low molecular weight drug that has proven safe in clinical epilepsy trials, has potential therapeutic value for cerebral ischemia by targeting the canonical inflammasome pathway of pyroptosis.

Project description:BackgroundPyroptosis is a type of proinflammatory regulated cell death (RCD) in which caspase-1 proteolytically cleaves gasdermin D (GSDMD) to yield a cytotoxic pore-forming protein. Recent studies have suggested that additional cell death pathways may interact with GSDMD under certain circumstances to execute pyroptosis. Microglia/macrophages in the central nervous system (CNS) undergo GSDMD-associated pyroptosis in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) but the contribution of other cell death pathways to this phenomenon is unknown. Herein, we tested the hypothesis that multiple RCD pathways underlie microglial pyroptosis in the context of neuroinflammation.MethodsA siRNA screen of genes with known RCD functions was performed in primary human microglia to evaluate their role in nigericin-induced pyroptosis using supernatant lactate dehydrogenase activity as a read-out of cell lysis. Activation of apoptotic executioner proteins and their contribution to pyroptosis was assessed using semi-quantitative confocal microscopy, high-sensitivity ELISA, immunoblot, cell lysis assays, and activity-based fluorescent probes. Quantification of pyroptosis-related protein expression was performed in CNS lesions from patients with progressive MS and mice with MOG35-55-induced EAE, and in matched controls.ResultsAmong progressive MS patients, activated caspase-3 was detected in GSDMD immunopositive pyroptotic microglia/macrophages within demyelinating lesions. In the siRNA screen, suppression of caspase-3/7, caspase-1, or GSDMD expression prevented plasma membrane rupture during pyroptosis. Upon exposure to pyroptotic stimuli (ATP or nigericin), human microglia displayed caspase-3/7 activation and cleavage of caspase-3/7-specific substrates (e.g., DFF45, ROCK1, and PARP), with accompanying features of pyroptosis including GSDMD immunopositive pyroptotic bodies, IL-1β release, and membrane rupture. Pyroptosis-associated nuclear condensation and pyroptotic body formation were suppressed by caspase-3/7 inhibition. Pharmacological and siRNA-mediated inhibition of caspase-1 diminished caspase-3/7 activation during pyroptosis. In mice with EAE-associated neurological deficits, activated caspase-3 colocalized with GSDMD immunopositivity in lesion-associated macrophages/microglia.ConclusionsActivation of executioner caspases-3/7, widely considered key mediators of apoptosis, contributed to GSDMD-associated microglial pyroptosis under neuroinflammatory conditions. Collectively, these observations highlight the convergence of different cell death pathways during neuroinflammation and offer new therapeutic opportunities in neuroinflammatory disease.

Dataset Information

Caspase-1 inhibition prevents glial inflammasome activation and pyroptosis in models of multiple sclerosis.

Publications

Caspase-1 inhibition prevents glial inflammasome activation and pyroptosis in models of multiple sclerosis.

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