The MC₄ receptor agonist RO27‐3225 inhibits NLRP1‐dependent neuronal pyroptosis via the ASK1/JNK/p38 MAPK pathway in a mouse model of intracerebral haemorrhage

Abstract

Background and Purpose: Inflammasome-mediated pyroptosis is an important neuronal cell death mechanism. Previous studies reported that activation of melanocortin MC 4 receptor exerted neuroprotection in several neurological diseases. Here, we have investigated the role of MC 4 receptor activation with RO27-3225 in suppressing neuronal pyroptosis after experimental intracerebral haemorrhage (ICH) and the underlying mechanism.Experimental Approach: One hundred and sixty-nine male CD1 mice were used. ICH was induced by injection of bacterial collagenase into the right-side basal ganglia.RO27-3225, a selective agonist of MC 4 receptor, was injected intraperitoneally at 1 hr after ICH. To elucidate the underlying mechanism, we used the specific MC 4 receptor antagonist HS024 and NQDI-1, a specific inhibitor of the apoptosis signalling-regulating kinase 1 (ASK1). Neurological tests, Western blot, Fluoro-Jade C, TUNEL, and immunofluorescence staining were conducted.Key Results: Expression of MC 4 receptor and the NOD-like receptor family, pyrin domain containing 1 (NLRP1) inflammasome in brain were increased after ICH. RO27-3225 treatment decreased neuronal pyroptosis and neurobehavioural deficits at 24 and 72 hr after ICH. RO27-3225 reduced the expression of p-ASK1, p-JNK, p-p38 MAPK, NLRP1 inflammasome, cleaved caspase-1, and IL-1β after ICH. HS024 pretreatment prevented the effects of RO27-3225. Similar to RO27-3225, NQDI-1 alone improved neurological functions and down-regulated ASK1/JNK/ p38MAPK expression after ICH. Conclusions and Implications: RO27-3225 suppressed NLRP1-dependent neuronal pyroptosis and improved neurological function, possibly mediated by activation of MC 4 receptor and inhibition of ASK1/JNK/p38 MAPK signalling pathways, after experimental ICH in mice. The MC 4 receptor may be a promising therapeutic target for the management of ICH. Abbreviations: ASK1, apoptosis signalling-regulating kinase 1; FJC, Fluoro-Jade C; ICH, intracerebral haemorrhage; MSH, melanocyte-stimulating hormones; NLRP1, NOD-like receptor (NLR) family, pyrin domain containing 1

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