A Novel Compound Ligusticum Cycloprolactam Alleviates Neuroinflammation After Ischemic Stroke via the FPR1/NLRP3 Signaling Axis.

BACKGROUND

Microglia/macrophages, as pivotal immune cells in the central nervous system (CNS), play a critical role in neuroinflammation associated with ischemic brain injury. Targeting their activation through pharmacological interventions represents a promising strategy to alleviate neurological deficits, thereby harboring significant implications for the prevention and treatment of ischemic stroke. Ligusticum cycloprolactam (LIGc), a novel monomeric derivative of traditional Chinese medicine, has shown potential as a therapeutic agent; however, its specific role in cerebral ischemic injury remains unclear.

METHODS

In vitro experiments utilized lipopolysaccharide (LPS)-induced inflammation models of RAW264.7 cells and primary mouse microglia. In vivo studies employed LPS-induced neuroinflammation models in mice and a transient middle cerebral artery occlusion (tMCAO) mouse model to evaluate the impact of LIGc on neuroinflammation and microglia/macrophage phenotypic alterations. Further elucidation of the molecular mechanisms underlying these effects was achieved through RNA-Seq analyses.

RESULTS

LIGc exhibited the capacity to attenuate LPS-induced production of pro-inflammatory markers in macrophages and microglia, facilitating their transition to an anti-inflammatory phenotype. In models of LPS-induced neuroinflammation and tMCAO, LIGc ameliorated pathological behaviors and neurological deficits while mitigating brain inflammation. RNA-seq analyses revealed formyl peptide receptor 1 (FPR1) as a critical mediator of LIGc's effects. Specifically, FPR1 enhances the pro-inflammatory phenotype of microglia/macrophages and inhibits their anti-inflammatory response by upregulating NLR family pyrin domain protein 3 (NLRP3) inflammasomes, thus aggravating inflammatory processes. Conversely, LIGc exerts anti-inflammatory effects by downregulating the FPR1/NLRP3 signaling axis. Furthermore, FPR1 overexpression or NLRP3 agonists reversed the effects of LIGc observed in this study.

CONCLUSION

Our findings suggest that LIGc holds promise in improving ischemic brain injury and neuroinflammation through modulation of microglia/macrophage polarization. Mechanistically, LIGc attenuates the pro-inflammatory phenotype and promotes the anti-inflammatory phenotype by targeting the FPR1/NLRP3 signaling pathway, ultimately reducing inflammatory responses and mitigating neurological damage.