Astrocyte-derived CCL2 participates in surgery-induced cognitive dysfunction and neuroinflammation via evoking microglia activation.

Neuroinflammation induced by peripheral trauma plays a key role in the development of postoperative cognitive dysfunction (POCD). Substantial evidence points to reactive glia as a pivotal factor during the inflammation process. However, little is known about the functional interactions between astrocytes and microglia. Recent evidence suggests the involvement of the CCL2-CCR2 pathway in CNS inflammation-related diseases. Our previous studies have suggested that astrocyte-derived CCL2 can induce microglial activation in vitro. Within this context, we sought to determine if the CCL2/CCR2 axis is involved in the crosstalk between astrocytes and microglia, contributing to increased neuroinflammation. Here, we show that tibial fracture surgery promoted CCL2 upregulation in activated astrocytes, increased CCR2 expression in activated microglia, and induced deficits in learning and memory. Site-directed pre-injection of RS504393, a CCR2 antagonist, inhibited this effect by reducing microglial activation, M1 polarization, inflammatory cytokines, and neuronal injury and death and improving cognitive function. Taken together, these data implicate CCL2-CCR2 signaling in astrocyte-mediated microglial activation in central nervous system (CNS) inflammation and suggest that interference with CCL2 signaling could constitute another potential therapeutic target for POCD.