Honokiol targets cyclophilin D and blocks mitochondrial DNA release to inhibit microglial NLRP3 inflammasome activation and alleviate neurodegeneration in Parkinson's disease models.

Parkinson's disease (PD) is linked to neuroinflammation, and the current focus of treating PD is to alleviate its pathological symptoms rather than neuroprotection. Honokiol (HNK), an active component of Magnolia officinalis, has been reported to be neuroprotective in PD models, but its mechanism remains unclear. In this study, we employed mouse and cellular PD models induced by lipopolysaccharide (LPS) combined with rotenone (ROT) to investigate molecular mechanisms and targets of HNK. We found that HNK alleviated microglial activation and decreased dopaminergic neurons loss. Transcriptomic profiling revealed that HNK markedly downregulated the activation of NLRP3 signaling pathway triggered by LPS + ROT. Functional analysis confirmed that HNK significantly suppressed the activation of the NLRP3 inflammasome, as reflected by decreased expression levels of NLRP3, ASC, cleaved caspase-1, and cleaved IL-1β, thereby attenuating neuronal cells injuries in vitro and in vivo. Knockdown of NLRP3 validated the anti-inflammatory effect of HNK and protected SH-SY5Y cells from damage mediated by activation of BV2 microglial cells. Additionally, we demonstrated that HNK protected mitochondrial function and inhibited the release of mitochondrial DNA (mtDNA). Blocking mtDNA release with cyclosporin A also suppressed NLRP3 activation, indicating that HNK acts through this mtDNA-NLRP3 axis. Notably, we observed that HNK markedly downregulated the expression of the cyclophilin D (CypD) in vivo. Combining molecular docking and cellular thermal shift assay, we identified CypD as the direct target of HNK. Molecular docking predicted that HNK binds to His70 of CypD, which may promote its destabilization and degradation, reducing mtDNA leakage and NLRP3 inflammasome activation. Collectively, these findings demonstrate that HNK targets CypD to disrupt the mtDNA-NLRP3 axis, thereby alleviating neurodegeneration and providing a potential therapeutic strategy for PD.