Neutrophil NAD(P)H oxidase is required for hemorrhagic shock-enhanced TLR2 up-regulation in alveolar macrophages in response to LPS

Alveolar macrophages (AMs) play an important role in the development of posttrauma lung inflammation through initiating polymorphonuclear neutrophil (PMN) migration by direct interactions with PMN, which is in turn mediated by the expression of chemokines and cytokines. We have recently reported that hemorrhagic shock-activated PMN sensitize AM to bacteria LPS for the up-regulation of Toll-like receptor (TLR)2; in turn, this TLR2 up-regulation results in the amplification of expression of cytokines and chemokines in the AM in response to the bacterial products LPS and peptidoglycan, associated with enhanced PMN sequestration in the lung. We sought to address the mechanism underlying the augmentation of TLR2 in AM by shock-activated PMN. We found that hemorrhagic shock/resuscitation (shock) followed by a low dose of i.t. LPS markedly increased TLR2 mRNA expression in AM in wild-type (WT) mice. In contrast, in mice lacking the gp91(phox) subunit of nicotinamide adenine dinucleotide phosphate (reduced form) oxidase (gp91(Phox-/-)) or in neutropenic WT mice, the increase in TLR2 mRNA was attenuated. Coculture of AM with PMN derived from WT-shocked mice caused a significantly higher level of TLR2 expression in the AM in response to LPS. However, this increase in TLR2 expression was less evident when the AMs were cocultured with PMN derived from gp91(Phox-/-) mice subjected to shock. The antioxidant polyethylene glycol catalase markedly decreased MyD88-dependent activation of IL-1 receptor associated kinase 4 and TLR2 expression in the AM in response to LPS. Thus, PMN nicotinamide adenine dinucleotide phosphate (reduced form) oxidase sensitizes hemorrhagic shock-primed AM to LPS, at least in part via enhancing IL-1 receptor associated kinase 4 activity.