Acute lung injury (ALI) is a major cause of mortality in
burn patients, even without direct inhalational injury. Identification of early mediators that instigate ALI after
burn and of the molecular mechanisms by which they work are of high importance but remain poorly understood. We previously reported that an endogenous
neuropeptide,
substance P (SP), via binding
neurokinin-1 receptor (NK1R), heightens remote ALI early after severe local
burn. In this study, we examined the downstream signaling pathway following SP-NK1R coupling that leads to remote ALI after
burn. A 30% total body surface area full-thickness
burn was induced in male BALB/c wild-type (WT) mice,
preprotachykinin-A (PPT-A) gene-deficient mice, which encode for SP, and PPT-A(-/-) mice challenged with exogenous SP. Local
burn injury induced excessive SP-NK1R signaling, which activated ERK1/2 and NF-κB, leading to significant upregulation of
cyclooxygenase (COX)-2,
PGE metabolite, and remote ALI. Notably, lung COX-2 levels were abrogated in
burn-injured WT mice by
L703606,
PD98059, and
Bay 11-7082, which are specific NK1R, MEK-1, and NF-κB antagonists, respectively. Additionally,
burn-injured PPT-A(-/-) mice showed suppressed lung COX-2 levels, whereas PPT-A(-/-) mice injected with SP showed augmented COX-2 levels postburn, and administration of
PD98059 and
Bay 11-7082 to
burn-injured PPT-A(-/-) mice injected with SP abolished the COX-2 levels. Furthermore, treatment with
parecoxib, a selective
COX-2 inhibitor, attenuated proinflammatory
cytokines,
chemokines, and ALI in
burn-injured WT mice and PPT-A(-/-) mice injected with SP. To our knowledge, we show for the first time that SP-NK1R signaling markedly elevates COX-2 activity via ERK1/2 and NF-κB, leading to remote ALI after
burn.