Background
Evidence shows that inflammatory responses play multiphasic roles in stroke pathogenesis. Ruxolitinib (Rux), a selective oral JAK 1/2 inhibitor, is efficacious in COVID-19 by reducing inflammation via the JAK2/STAT3 pathway.
Methods
Here, we investigated whether JAK2 inhibition has neuroprotective effects against ischemic stroke (IS) in MCAO mice in vivo and in vitro oxygen-glucose deprivation/reoxygenation (OGD/R) model, and explored the potential molecular mechanisms. Rux was applied to MCAO mice. Immunofluorescence staining, RT-qPCR, and western blots were used to measure the expression of NLRP3 inflammation components and proinflammatory cytokines as well as JAK2/STAT3 pathway. Local STAT3 deficiency in brain tissue was established to investigate the interplay between NLRP3 and STAT3 signaling.
Results
Rux treatment obviously improved neurological scores, decreased the infarct size and ameliorated cerebral edema 3 days after stroke. In addition, immunofluorescence staining and western blots showed that Rux application inhibited the expression of NLRP3 inflammasome components, proteins related to the NLRP3 inflammasome and phosphorylated STAT3 (p-STAT3) in neurons. Furthermore, Rux administration inhibited the expression of proinflammatory cytokines, including TNF-α, IFN-γ, HMBG1, IL-1β, IL-2, and IL-6 in middle cerebral artery occlusion (MCAO) model mice, suggesting that Rux may alleviate IS injury by inhibiting proinflammatory reactions via JAK2/STAT3 signaling pathway regulation. Local STAT3 deficiency decreased histone H3 and H4 acetylation on the NLRP3 promoter and the NLRP3 inflammasome component expression, indicating that the NLRP3 inflammasome may be directly regulated by STAT3 signaling. Finally, the effect of Rux on the NLRP3 inflammasome was further assessed in a HT22 cell OGD/R model in vitro. Rux application markedly suppressed lipopolysaccharide (LPS)-induced NLRP3 inflammasome secretion and JAK2/STAT3 pathway activation in vitro the in OGD/R HT22 cell model.
Conclusion
JAK2 inhibition by Rux in MCAO mice decreased STAT3 phosphorylation, thus inhibiting downstream proinflammatory cytokines and H3 and H4 acetylation on the NLRP3 promoter, resulting in downregulation of NLRP3 inflammasome component expression.
