FGF8 Protects Against Polymicrobial Sepsis by Enhancing the Host's Anti-infective Immunity.

Background: Sepsis is characterized by a life-threatening syndrome caused by an unbalanced host response to infection. Fibroblast growth factor 8 (FGF8) has been newly identified to play important roles in inflammation and innate immunity, but its role in host response to sepsis is undefined.

Methods: A cecal ligation and puncture (CLP)-induced mouse sepsis model was established to evaluate the immunomodulatory function of FGF8 during sepsis. The underlying molecular mechanisms were elucidated by cell models using relevant molecular biology experiments. The clinical value of FGF8 in the adjuvant diagnosis of sepsis was evaluated using clinical samples.

Results: FGF8 protein concentrations were elevated in CLP-induced septic mice compared to controls. In vivo, FGF8 blockade using anti-FGF8 antibody significantly increased mortality and bacterial burden and was paralleled by significantly aggravated tissue injury after CLP. Therapeutic administration of recombinant FGF8 (rFGF8) improved the bacterial clearance and mortality of septic mice in a FGFR1-dependent manner. In vitro, FGF8 directly enhanced bacterial phagocytosis and killing of macrophages by enhancing the phosphorylation of the ERK1/2 signaling pathway, which could be abrogated with the ERK1/2 pathway inhibitor U0126. Clinically, serum FGF8 levels in both adult and pediatric patients with sepsis in an intensive care unit were significantly higher than those in healthy controls.

Conclusions: These results present a previously unrecognized role of FGF8 in improving survival of sepsis by enhancing host immune defense. Therefore, targeting FGF8 may provide new strategies for the diagnosis and immunotherapy of sepsis.