CRISTINA ALARCON VILA¹, Elisa GARCÍA VÁZQUEZ², PABLO PELEGRIN VIVANCOS³

(1)
(2) PATOLOGÍA INFECCIOSA, MICROBIOLOGÍA CLÍNICA Y MEDICINA TROPICAL, IMIB, España
(3) CIRUGÍA DIGESTIVA, ENDOCRINA Y TRASPLANTE DE ÓRGANOS ABDOMINALES, IMIB, España

Sepsis is a severe condition defined by systemic infection and inflammation that causes tissue damage and organ dysfunction. Cecal ligation and puncture (CLP) has become the gold-standard mouse model in sepsis research, where tissue disruption produces a strong release of ATP leading to the activation of the cation channel P2X7 receptor (P2X7R). Activated P2X7R is able to stimulate the NLRP3 inflammasome resulting in the release of proinflammatory cytokines, as well as NLRP3-independent release of lipid mediators and other cellular proteins, as the lipopolysaccharide co-receptor CD14.

In vivo CLP-induced sepsis procedure was performed in C57bl/6 (WT) and P2rx7-/- mice with or without a prior i.p. injection of human recombinant CD14 (rsCD14) or A438079, a pharmacologic inhibitor of P2X7R. Peritoneal lavage, blood serum and tissue samples were analyzed to assess bacterial load, proinflammatory markers, H&E staining and levels of soluble CD14. Mice survival was also evaluated.

P2rx7-/- showed a significant increase of bacterial load and proinflammatory cytokines in blood serum and peritoneal lavage, accompanied with decreased levels of soluble CD14 (sCD14) 24 or 48 hours after CLP. Besides, P2rx7-/- presented liver and spleen injury and a reduced median survival compared to WT. Administration of rsCD14 in P2rx7-/- remarkably decreased bacterial load and IL-6 levels both in blood serum and peritoneal lavage, in addition to enlarged life expectancy and improved liver and spleen tissues. Inhibition of P2X7R through A438079 further increased the susceptibility of WT to CLP-induced sepsis, shortening survival and compromising liver and spleen tissues. Beyond, WT displayed a significant rising of bacterial load along with a reduction of sCD14 in blood serum and peritoneal exudate.

The decrease of sCD14 could explain why P2rx7-/- mice are more susceptible to CLP given the fact that rsCD14 treatment improved the response to induced sepsis and the silencing of P2X7R by A438079 clearly exacerbated it. Overall, our study reveals that P2X7R as well as optimum levels of sCD14 are important to survive sepsis, probably by favoring an optimal immune response against the infection. The development of new strategies to early detect impaired P2X7R along with rsCD14 therapies could be key steps for the management of human sepsis.