Mechanisms of Neurotrophin Action on Human Airway Smooth Muscle

Abstract

Neurotrophins (NTs), which play an integral role in directing proper neuronal development and function, have been found in non‐neuronal tissue (including lung), but their role is still under investigation. We previously found NTs such as brain‐derived neurotrophic factor (BDNF) and neurotrophin‐3 (NT3) and their receptors to be expressed in human airway smooth muscle (ASM). In this study, we hypothesized that NTs contribute to regulation of ASM function via regulation of mechanisms that control intracellular Ca2+ ([Ca2+]i). Human ASM cells isolated from lung samples incidental to patient surgery were incubated for 24 or 48 h in medium (control), 10 nM BDNF or NT3 in the presence or absence of inhibitors of signaling pathways such as MAP kinases (PD98059), PI3/Akt (Wortmannin) and NFκB (SN50). In fluo‐4 loaded cells, [Ca2+]i responses to ACh and histamine were significantly higher following BDNF and NT3 exposure: effects that were blunted by SN50 and PD98059, but not Wortmannin. Western analysis of cell lysates showed higher expressions of Ca2+ regulatory proteins such as Orai1, TRPC3, and SERCA with 1 or 10nM BDNF exposure, but decreased expression by NT3. These data show that NTs activate signaling pathways in human ASM that lead to enhanced [Ca2+]i responses, and could thus contribute to airway hyperresponsiveness. Supported by NIH grants HL088029, HL090595 and FAMRI.