Treadmill exercise alleviates STING-mediated microglia pyroptosis and polarization via activating mitophagy post-TBI

Moderate-intensity treadmill exercise has emerged as a promising therapeutic intervention for traumatic brain injury (TBI), yet its precise mechanisms remain unclear. Emerging evidence suggests that STING-mediated microglial pyroptosis and polarization might exacerbate TBI-induced pathological damage. Our previous work demonstrated treadmill exercise's inhibitory effects on the STING level, and mitophagy has been recognized as a crucial regulator of STING activity. Therefore, we aimed to test the possibility that treadmill exercise alleviates STING-mediated microglia pyroptosis and polarization partially through activating mitophagy post-TBI. First, we found that TBI-induced pyroptosis primarily occurred in neurons and microglia, along with pro-inflammatory M1 microglial polarization in the injured cortex. Remarkably, treadmill exercise could effectively reverse those pathological changes, demonstrating its anti-pyroptotic and anti-inflammatory potential. Then, we explored the dynamic expression of STING post-TBI, and found a progressively increased trend of STING in neurons, astrocytes, and microglia from 6 hours to 35 days after TBI, with the most prominent rise in microglia. Notably, STING knockdown markedly diminished TBI-induced pyroptosis and prompted a shift in microglial polarization from M1 to M2. Furthermore, STING overexpression could partly abolish the treadmill exercise's neuroprotective effects against pyroptosis and inflammation post-TBI, suggesting that the anti-pyroptosis and anti-inflammatory effects of treadmill exercise were partly established via inhibiting the STING pathway. Crucially, pharmacological inhibition of mitophagy using mdivi-1 could partly reverse the treadmill exercise's suppressive effects on STING signaling, establishing mitophagy as the likely regulatory mechanism through which treadmill exercise regulates the STING pathway. To conclude, these findings demonstrated that treadmill exercise ameliorates STING-mediated microglial pyroptosis and M1 polarization, at least partially through enhancing mitophagy following TBI.