Astrocyte-derived CCL7 promotes microglia-mediated inflammation following traumatic brain injury.

Microglia are immune cells of the central nervous system that mediate neuroinflammation. It is widely known that microglia-mediated inflammation in the brain contribute to the widespread tissue damage and neurological deficits in traumatic brain injury (TBI). However, the mechanisms responsible for this inflammatory response remain elusive. Here, we investigated the role of astrocyte-derived chemokine (C-C motif) ligand 7 (CCL7) in microglial-controlled inflammation following TBI. Our results demonstrated that astrocyte-derived CCL7 induced microglial activation and the release of proinflammatory mediators in the cortex and serum of rats that underwent experimental TBI. Furthermore, CCL7 knockout improved microglia-controlled inflammation, brain morphology and neurological dysfunction following TBI. In vitro, CCL7-siRNA attenuated the LPS-induced expression of pro-inflammatory markers in the co-culture of microglia and astrocytes. Collectively, our findings uncover an important role for astrocyte-derived CCL7 in promoting microglia-mediated inflammation after TBI and suggests CCL7 could serve as a potential therapeutic strategy for attenuating TBI by inhibiting microglial activation.