Role of CO-releasing molecules liberated CO in attenuating leukocytes sequestration and inflammatory responses in the lung of thermally injured mice

Abstract

Background: Acute lung injury and pulmonary inflammatory responses are important complications most frequently encountered in severely burned patients. Polymorphonuclear leukocyte (PMN) sequestration and the subsequent generation of oxidants and inflammatory mediators play the key roles in the pathogenesis of acute lung injury. In this study, we used CO-releasing molecules (CORM-2) to determine whether the CO-releasing molecules-liberated CO could attenuate leukocytes sequestration and the inflammatory response in the lung of thermally injured mice.

Materials and methods: Fifty-four mice were assigned to three groups in three respective experiments. In each experiment, mice in sham group (n=6) underwent sham thermal injury, whereas mice in the burn group (n=6) received 15% total body surface area (TBSA) full-thickness thermal injury and mice in CORM-2 group (n=6) underwent the same thermal injury with immediate administration of CORM-2 (8 mg/kg, i.v.). PMN accumulation (MPO assay) in mice lungs and tumor necrosis factor-alpha and interleukin-1beta in BAL fluid, pulmonary edema formation, and wet/dry weight ratios of lung were determined. Activation of NF-kappaB and expression level of ICAM-1 in the lung was assessed. In in vitro experiment, PMN adhesion to experimental mice serum-stimulated mouse lung endothelial cells (MLEC) was assessed.

Results: Treatment of thermally injured mice with CORM-2 attenuated PMN accumulation and prevented activation of NF-kappaB in the lung. This was accompanied by a decrease of the expression of ICAM-1. In parallel, PMN adhesion to MLEC stimulated by CORM-2-treated thermally injured mice serum was markedly decreased. Also, CORM-2 markedly decreased the production of inflammatory mediators in BAL fluid without suppressing the permeability of pulmonary microcirculation.

Conclusions: CORM-released CO attenuates the inflammatory response in the lung of thermally injured mice by decreasing leukocyte sequestration and interfering with NF-kappaB activation, protein expression of ICAM-1, and therefore, suppressing endothelial cells' pro-adhesive phenotype.