Ozone Exposure Initiates a Sequential Signaling Cascade in Airways Involving Interleukin-1Beta Release, Nerve Growth Factor Secretion, and Substance P Upregulation

Abstract

Previous studies demonstrated that interleukin-1β (IL-1β) and nerve growth factor (NGF) increase synthesis of substance P (SP) in airway neurons both after ozone (O₃) exposure and by direct application. It was postulated that NGF mediates O₃-induced IL-1β effects on SP. The current study specifically focused on the influence of O₃ on IL-1β, NGF, and SP levels in mice bronchoalveolar lavage fluid (BALF) and whether these mediators may be linked in an inflammatory-neuronal cascade in vivo. The findings showed that in vivo O₃ exposure induced an increase of all three proteins in mouse BALF and that O₃-induced elevations in both NGF and SP are mediated by the inflammatory cytokine IL-1β. Further, inhibition of NGF reduced O₃ induced increases of SP in both the lung BALF and lung tissue, demonstrating NGF serves as a mediator of IL-1β effects on SP. These data indicate that IL-1β is an early mediator of O₃-induced rise in NGF and subsequent SP release in mice in vivo.