Granzyme A inhibition reduces inflammation and increases survival during abdominal sepsis.

Sepsis is a serious syndrome characterised by a dysregulated systemic inflammatory response. Here we have analysed the role and the therapeutic potential of Granzyme A (GzmA) in the pathogenesis of peritoneal sepsis using the Cecal Ligation and Puncture (CLP) polymicrobial sepsis model and samples from humans undergoing abdominal sepsis. Elevated GzmA was observed in serum from patients with abdominal sepsis suggesting that GzmA plays an important role in this pathology. In the CLP model GzmA deficient mice, or WT mice treated with an extracellular GzmA inhibitor, showed increased survival, which correlated with a reduction in proinflammatory markers in both serum and peritoneal lavage fluid. GzmA deficiency did not influence bacterial load in blood and spleen indicating that GzmA has no role in bacterial control. Mechanistically, we found that extracellular active GzmA acts as a proinflammatory mediator in macrophages by inducing the TLR4-dependent expression of IL-6 and TNFα. Our findings implicate GzmA as a key regulator of the inflammatory response during abdominal sepsis, and suggest that it could be targeted for treatment of this severe pathology.