Shikonin alleviates rotenone-induced Parkinson's disease neuroinflammation by targeting PKM2-mediated glycolytic MG-Hs production.

BACKGROUND: In Parkinson's disease (PD), microglial activation is driven by metabolic reprogramming toward aerobic glycolysis, a shift regulated by pyruvate kinase M2 (PKM2). While the environmental toxin rotenone is a recognized PD risk factor, the precise glycolytic mechanism linking it to microglial neuroinflammation remains unclear, and the therapeutic potential of targeting this axis is largely unexplored. PURPOSE: We sought to elucidate the specific glycolytic pathway by which rotenone induces microglial activation and to investigate whether shikonin, a natural PKM2 inhibitor, could attenuate neuroinflammation by targeting this metabolic mechanism. METHODS: Using rotenone (250 nM)-treated BV2 microglia, we assessed glycolytic function (lactate production, glucose consumption) and quantified the formation of methylglyoxal-derived hydroimidazolones (MG-Hs), key pro-inflammatory glycation adducts. NF-κB pathway activation and inflammatory cytokine release were evaluated. The inhibitory effects of shikonin on this cascade were systematically examined. RESULTS: We identified a novel mechanistic pathway: rotenone promotes PKM2-mediated glycolytic flux, leading to accumulation of the cytotoxic metabolite methylglyoxal (MG) and its derived MG-Hs. These MG-Hs function as critical signaling mediators that directly activate the NF-κB pathway, fueling neuroinflammation. Shikonin effectively disrupted this cascade at its source by inhibiting PKM2, thereby normalizing glycolytic activity, reducing MG-Hs formation, and subsequently suppressing NF-κB activation and the release of pro-inflammatory factors. CONCLUSION: This study delineates a complete PKM2-glycolysis-MG-Hs-NF-κB axis as a fundamental mechanism in rotenone-induced neuroinflammation. Our results provide compelling preclinical evidence that shikonin exerts its neuroprotective effects by specifically targeting this metabolic-inflammatory pathway, positioning it as a highly promising disease-modifying therapeutic candidate for PD.