Deficiency in cold-inducible RNA-binding protein attenuates acute respiratory distress syndrome induced by intestinal ischemia-reperfusion

Abstract

Intestinal ischemia-reperfusion can occur in shock and mesenteric occlusive diseases, causing significant morbidity and mortality. Aside from local injury, intestinal ischemia-reperfusion can result in remote organ damage, particularly in the lungs. Cold-inducible RNA-binding protein (CIRP) was identified as a novel inflammatory mediator. We hypothesized that a deficiency in CIRP would protect the lungs during intestinal ischemia-reperfusion injury. Intestinal ischemia was induced in adult male C57BL/6 wild-type and CIRP knock-out (CIRP-/-) mice via clamping of the superior mesenteric artery for 60minutes. Reperfusion was allowed for 4hours or 20hours, and blood, gut, and lung tissues were harvested for various analyses. After intestinal ischemia-reperfusion, the elevated levels of serum lactate dehydrogenase and inflammatory cytokine interleukin-6 were reduced by 68% and 98%, respectively, at 20hours after ischemia-reperfusion in CIRP-/- mice compared with the wild-type mice. In the gut, mRNA levels of inflammatory cytokine interleukin-6 were reduced by 67% at 4hours after ischemia-reperfusion in CIRP-/- mice. In the lungs, inflammatory cytokine interleukin-6 protein and myeloperoxidase activity were reduced by 78% and 26% at 20hours and 4hours after ischemia-reperfusion, respectively, in CIRP-/- mice. Finally, the elevated lung caspase-3 was significantly decreased by 55%, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells decreased by 91%, and lung injury score decreased by 37% in CIRP-/- mice at 20hours after ischemia-reperfusion. Increased levels of proinflammatory cytokines, myeloperoxidase, and apoptosis are the hallmarks of acute respiratory distress syndrome. We noticed after intestinal ischemia-reperfusion the proinflammatory milieu in lungs was elevated significantly, while the CIRP-/- mice had significantly decreased levels of proinflammatory cytokine, myeloperoxidase, and apoptotic cells leading to decreased lung injury. These findings strongly established a causal link between CIRP and acute respiratory distress syndrome during intestinal ischemia-reperfusion injuries. Targeting CIRP may therefore be beneficial for treatment of intestinal ischemia-reperfusion-associated acute respiratory distress syndrome acute respiratory distress syndrome.