Denervation of capsaicin-sensitive C fibers increases pulmonary inflammation induced by ischemia-reperfusion in rabbits

BackgroundCapsaicin-sensitive C fibers (CapsCF) are abundantly distributed in the respiratory tract. Inflammation is one of the main contributors to lung ischemia-reperfusion (IR) injury. This study was designed to investigate the role of CapsCF in lung IR-induced inflammatory response.MethodsThirty-two male rabbits were randomized into four groups as follows: sham group (S), IR group (IR), large dose of capsaicin plus sham group (CS), and large dose of capsaicin plus IR group (CIR). The CS and CIR groups were pretreated with capsaicin (100 mg/kg) to induce functional ablation of CapsCF. The IR and CIR groups were subjected to 1 h lung ischemia and 3 h reperfusion. Thereafter, blood and lung tissue samples were obtained for blood gas and biochemical analyses. Levels of substance P and calcitonin gene-related peptide (CGRP), lung wet-to-dry weight ratio, and histopathologic changes as well as neutrophil counts in bronchoalveolar lavage fluids were also assessed.ResultsCapsaicin pretreatment in the CIR group resulted in increased lung wet-to-dry ratio, neutrophil counts in bronchoalveolar lavage fluids, and lung pathologic lesions, along with higher levels of plasma tumor necrosis factor α and interleukin 8 and lower level of interleukin 10 (P < 0.05 versus IR), although capsaicin did not alter the above variables in the CS group (P > 0.05 versus S). Lung tissue CGRP was elevated more than 2-fold in the IR group (P < 0.05 versus S), but it did not significantly change in the CIR group.ConclusionDenervation of CapsCF aggravated lung IR-induced inflammation, probably by depleting the CGRP content of CapsCF. CapsCF may protect against lung IR-induced inflammation and injury.