Inhibition of the NLRP3-inflammasome as a potential approach for neuroprotection after stroke

Abstract

Activation of the NOD-like receptor protein (NLRP3)-inflammasome has been postulated to mediate inflammatory responses to brain damage during ischemic/reperfusion (I/R) injury. We therefore hypothesized that MCC950, a selective NLRP3-inflammasome inhibitor provides protection in mouse model of transient middle cerebral artery occlusion (tMCAO). Focal cerebral ischemia was induced by 60 min tMCAO followed by intraperitoneal administration of MCC950 (50 mg/kg) or saline at 1 h and 3 h post-occlusion. After 24 h of I/R, mice were tested for neurological outcome and were sacrificed for the analysis of infarct size and estimating NLRP3-inflammasome and apoptotic markers as well. Spectrophotometric method was used to determine hemoglobin (Hb) content as a marker of intracerebral hemorrhage. MCC950-treated mice showed a substantial reduction in infarction, edema and Hb content compared to saline controls in parallel with improved neurological deficits. MCC950 reduced expression of NLRP3-inflammasome cleavage products Caspase-1 and interlukin-1β (IL-1β) in penumbral region. These protective effects of MCC950 were associated with decreased TNF-α levels as well as poly (ADP-ribose) polymerase (PARP) and Caspase-3 cleavage and paralleled less phosphrylated NFκBp65 and IκBα levels. Taken together, these data indicate that inhibition of NLRP3-inflammasome with MCC950 has therapeutic potential in ischemic stroke models. Further investigations into the therapeutic efficacy and protocols are needed to confirm whether MCC950 treatment could be a promising candidate for clinical trials.

Inflammasomes in neuroinflammatory and neurodegenerative diseases

“…In agreement, mice deficient in both IL‐1α and IL‐1β exhibited dramatically reduced ischemic infarct volumes in transient MCAO (Boutin et al , ), whereas IL‐18‐deficient mice did not show protection in this model (Wheeler et al , ). NLRP3 deficiency in mice, treatment with the NLRP3 inflammasome inhibitor MCC950/CRID3, and intracerebroventricular injection of NLRP3 siRNAs all ameliorated clinical outcomes in experimental models of stroke (Ma et al , ; Yang et al , ; Yuan et al , ; Ismael et al , ). Also, NLRC4‐ and AIM2‐deficient mice were shown to have significantly smaller infarct volumes compared to wild‐type mice subjected to tMCAO, with was associated with strongly reduced microglia cell activation and leukocyte recruitment to the infarct site (Denes et al , ).…”

Neuromodulatory Effect of NLRP3 and ASC in Neonatal Hypoxic Ischemic Encephalopathy

“…We now report that 7 days after hypoxia-ischemia, there is significantly increased volume loss in the ipsilateral hemisphere of NLRP3-deficient mice, while ASC deficiency offers neuroprotection. In adult murine stroke models, NLRP3 deficiency and NLRP3 inhibition have previously shown neuroprotective effects 24 h after ischemia [11, 12]. Opposing results on the downstream mediators IL-1β [13] and IL-18 [14] also exist between neonatal and adult murine models, underscoring developmental differences recently reviewed [2].…”

Update of inflammasome activation in microglia/macrophage in aging and aging‐related disease

“…Accumulative evidences indicate that targeting inflammasome pharmacologically may salvage penumbral tissue in cerebral ischemia . Remarkably, the NLRP3 inhibitor MCC950 and the NLRP1 neutralizing antibodies have been proved to be curative in ischemic stroke . Besides, repressing inflammasome through enhancing autophagy has also been proved to offer protection in ischemic stroke .…”

“…Confronting the aging‐related CNS diseases, targeting inflammasome is a promising therapeutic strategy. A broad body of evidences suggest that inhibiting inflammasome activation displays favorable curative effects in neurodegenerative diseases as well as acute CNS injuries …”

“…68,69 Remarkably, the NLRP3 inhibitor MCC950 and the NLRP1 neutralizing antibodies have been proved to be curative in ischemic stroke. 70 Besides, repressing inflammasome through enhancing autophagy has also been proved to offer protection in ischemic stroke. 71 Inhibiting inflammasome to limit excessive neural inflammation in acute ischemic stroke should be a promising therapeutic strategy, which needs further efforts for clinical translation.…”