CSF1R and IL1R1 inhibitors synergistically attenuate the early pathogenesis of traumatic brain injury in mice

There is an unmet need in the treatment of traumatic brain injury (TBI), a leading cause of death and disability. Colony stimulating factor 1 receptor (CSF1R) and interleukin 1 receptor type 1 (IL1R1) are critical regulators of TBI-associated neuroinflammation. This study tested the hypothesis that early administration of CSF1R inhibitor PLX3397 plus IL1R1 inhibitor Anakinra alleviates TBI pathogenesis. Adult C57BL/6 mice were subjected to experimental TBI and treated with PLX3397 plus Anakinra, PLX3397 or Anakinra alone, or vehicle for up to five days post injury (5 dpi). Neurological deficits were attenuated by PLX3397 plus Anakinra in male and female mice. Combination therapy, as opposed to monotherapy, also reduced structural brain damage; however, this effect was observed exclusively in male mice. Bulk RNA-sequencing analysis of differentially expressed genes (DEGs) and gene set enrichment analysis (GSEA) revealed anti-neuroinflammatory effects in male mice treated with PLX3397 plus Anakinra, which exceeded the summed effects of monotherapies. Key DEGs included pro-neuroinflammatory markers such as Cd68 and Spp1/osteopontin, as well as genes associated with type I and II interferon responses. Immunofluorescence staining confirmed that PLX3397 plus Anakinra was more effective than monotherapy in attenuating CD68⁺ macrophages/microglia, CD45⁺/CD68^- leukocytes, and osteopontin. Again, these effects exceeded the summed effects of monotherapy. The findings demonstrate beneficial synergistic effects of FDA-approved CSF1R and IL1R1 inhibitors and offer novel insights into the mechanisms of early TBI pathogenesis and therapy in a clinically relevant model.