Inflammatory cellular influx follows capsaicin nasal challenge

Capsaicin is a specific activator of sensory nerve endings. In rodents, mucosal application of capsaicin causes cells to infiltrate the tissue. To examine whether inflammatory-cell influx follows sensory-nerve activation in human airways, we delivered capsaicin (200 microM) nasal spray into the nares of 20 subjects (10 with allergic rhinitis and 10 normal), and measured the total leukocyte content of nasal lavage fluid obtained from 10 min to 4 h after the capsaicin challenge. Vehicle spray (1% EtOH in 0.9% saline) served as a control. Capsaicin challenge caused significant increases from prechallenge leukocyte counts at 10 min (p<0.03), 30 min (p<0.01), and 4 h (p<0.03) after challenge, but not at 1 h after challenge (p = 0.68). Vehicle challenge did not increase leukocyte counts. Differential counts (performed on the 13 of 20 subjects from whom adequate specimens for differential counts were obtained) showed that neutrophils, eosinophils, and mononuclear cells increased at 10 min, 30 min, and 4 h (all p < 0.04), but not at 1 h after capsaicin challenge. Comparing the rhinitic to the normal subjects, we found no significant differences in the cellular response to capsaicin. These data support a nonspecific inflammatory effect of sensory nerve activation in the human nose. Consequently, this work provides evidence that neurogenic inflammation can be induced in the human airway in vivo.