Effects of mast cell membrane stabilizing agents in a rat lung ischemia-reperfusion model

Background. The aim of this study was to test the hypothesis that agents which stabilize the mast cell membrane may modulate the phenotype of the vascular wall in a lung ischemia-reperfusion model, including altering expression of endothelial and leukocyte adhesion receptors and the inducible nitric oxide synthase (NOS-2). Methods. Three sets of rats were given either intravenous saline (group A), ketotifen (group B), or cromolyn (group C), respectively. The left pulmonary artery was ligated temporarily and reopened after 2 hours of ischemia. Then, after a 2-hour period of reperfusion, the left lung was excised. ICAM-1 and NOS-2 were measured at the protein level by Western blotting, and cGMP levels were measured by enzyme-linked immunosorbent assay in the lung tissue specimens for each drug group. Results. ICAM-1 expressions, determined as the intensity of a given band on the Western blot, were 197 ± 59 in group B and 195 ± 83 in group C versus 369 ± 114 in group A (p = 0.002 for analysis of variance). In contrast with ICAM-1, NOS-2 expression was increased by ketotifen or cromolyn treatment (464 ± 82 in group B and 507 ± 93 in group C, compared with 377 ± 44 for group A, p = 0.007). The finding of increased NOS-2 expression in groups B and C is consistent with the observed increase in tissue cGMP levels in the same groups (1.92 ± 0.9 pmol/mL for group A versus 7.8 ± 3.5 pmol/mL for group B, and 12.4 ± 5.8 pmol/mL for group C, p = 0.0004). Conclusions. These data establish that mast cell stabilizing agents modulate the vascular phenotype in the setting of pulmonary ischemia and reperfusion by decreasing ICAM-1 expression, augmenting expression of NOS-2, and increasing tissue cGMP levels. As decreasing ICAM-1 expression and increasing cGMP levels have proven useful to limit proinflammatory mechanisms of tissue injury, mast cell stabilizing agents may provide a new therapeutic option to improve organ function in the setting of reperfusion.