Abstract
The expression of proinflammatory and immunoregulatory cytokines rapidly increases in the lungs after hemorrhage, and such alterations contribute to the frequent development of acute inflammatory lung injury in this setting. Blood loss also produces elevations in catecholamine concentrations in the pulmonary and systemic circulation. In the present experiments, we used alpha- and beta-adrenergic receptor blockade to examine in vivo interactions between hemorrhage-induced adrenergic stimulation and pulmonary cytokine expression. Treatment of mice with the alpha-adrenergic receptor antagonist phentolamine prevented not only the elevation in mRNA levels of IL-1beta, TNF-alpha, and TGF-beta1, the increase in IL-1beta protein, but also the activation of nuclear factor (NF)-KB and cyclic AMP response element binding protein, which occurred in lung cells of untreated animals during the first hour after hemorrhage. In contrast, treatment before hemorrhage with the beta-adrenergic receptor antagonist propranolol was associated with increases in mRNA levels for IL-1beta, TNF-alpha, and TGF-beta1, which were greater than those present in untreated hemorrhaged mice, and did not prevent hemorrhage-associated increases in lung IL-1beta protein. Treatment with propranolol prevented hemorrhage-induced phosphorylation of cyclic AMP response element binding protein, but increased hemorrhage-associated activation of NF-KB. These results demonstrate that hemorrhage initially increases pulmonary cytokine expression through alpha- but not beta-adrenergic stimulation, and suggest that such alpha-adrenergic-mediated effects occur through activation of the transcriptional regulatory factor NF-kappaB.