Targeting complement C3/C3aR pathway restores rejuvenation factor PF4 and mitigates neurocognitive impairments in...

Perioperative neurocognitive disorders (PND), including postoperative delirium (POD), delayed neurocognitive recovery (dNCR) and postoperative neurocognitive disorder (PNCD), affect up to 10% of surgical patients older than 60 years, and currently there are no effective therapies to prevent PND. The gut microbiota is linked to PND through the gut-brain axis, promoting neuroinflammation via activation and proliferation of microglia and astrocytes in the central nervous system (CNS). In this study, we show that perioperative use of ceftriaxone, a long-acting β-lactam antibiotic, can prevent the development of PND in elderly surgical patients. This effect is associated with reduced serum complement C3 levels and increased levels of platelet factor 4 (PF4). Using an aged mouse model of PND, we found that C3/C3aR axis mediated the interaction of astroglia and microglia during the early stages of neuroinflammation. Genetic ablation or pharmacological blockade of C3/C3aR signaling pathway suppressed neuroinflammation and attenuated cognitive declines in PND. The C3/C3aR axis is essential for surgery-induced platelet count and circulating PF4 declines, and mice supplemented with recombinant PF4 exhibited reduced neuroinflammation and improved cognitive function. Together, our findings revealed the new roles of the C3/C3aR signaling pathway in platelet dysfunction and neuroinflammation in age-related PND, and these results highlight new potential therapeutic strategies for PND.