Reynosin protects neuronal cells from microglial neuroinflammation by suppressing NLRP3 inflammasome activation mediated by NADPH oxidase

Neuroinflammation, driven by the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing-3 (NLRP3) inflammasome, significantly contributes to the pathogenesis of neurodegenerative disorders. The natural sesquiterpene lactone, reynosin, demonstrates a wide range of pharmacological activities with promising potential. However, the effects and mechanism of reynosin on neuroinflammation remain elusive. The present study aims to investigate the impact of reynosin on neuroinflammation in mice and BV-2 cells treated with lipopolysaccharide (LPS), along with elucidating the underlying mechanisms of action. Obtained data demonstrated that reynosin exhibited inhibitory effects on microglial inflammation in vitro, as indicated by the reduction in CD11b expression and the downregulation of pro-inflammatory cytokines interleukin 1β (IL-1β) and IL-18 mRNA and protein levels. In vivo, reynosin decreased the numbers of Iba-1 positive cells and mitigated morphological changes, accompanied by the decrease in the expressions of IL-1β and IL-18. Reynosin inhibited NLRP3 inflammasome activation as evidenced by reduced NLRP3 and caspase-1 transcription, inhibited NLRP3 protein expression and ASC oligomerization, and down-regulated caspase-1 self-cleavage. This effect was achieved through the inhibition of excessive generation of reactive oxygen species (ROS) both in vitro and in vivo, encompassing superoxide anions, hydrogen peroxide, and intracellular ROS. Moreover, reynosin suppressed the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase both in experimental models and cell cultures. The inhibition was proved by the reduction in NADP⁺ and NADPH levels, downregulation of gp91^phox mRNA and protein expression, and suppression of p47^phox expression and translocation to the membrane. Moreover, reynosin exhibited a neuroprotective effect against microglial inflammation both in vivo and in vitro.

Overall, reynosin exhibited neuroprotective effects by attenuating microglial inflammation mediated by the NLRP3 inflammasome, suggesting its potential as a therapeutic agent for inhibiting neuroinflammation.