TLR9 expression is required for the development of cigarette smoke-induced emphysema in mice

Abstract

The expression of Toll-like receptor (TLR)-9, a pathogen recognition receptor that recognizes unmethylated CpG sequences in microbial DNA molecules, is linked to the pathogenesis of several lung diseases. TLR9 expression and signaling was investigated in animal and cell models of chronic obstructive pulmonary disease (COPD). We observed enhanced TLR9 expression in mouse lungs following exposure to cigarette smoke. Tlr9(-/-) mice were resistant to cigarette smoke-induced loss of lung function as determined by mean linear intercept, total lung capacity, lung compliance, and tissue elastance analysis. Tlr9 expression also regulated smoke-mediated immune cell recruitment to the lung; apoptosis; expression of granulocyte-colony stimulating factor (G-CSF), the CXCL5 protein, and matrix metalloproteinase-2 (MMP-2); and protein tyrosine phosphatase 1B (PTP1B) activity in the lung. PTP1B, a phosphatase with anti-inflammatory abilities, was identified as binding to TLR9. In vivo delivery of a TLR9 agonist enhanced TLR9 binding to PTP1B, which inactivated PTP1B. Ptp1b(-/-) mice had elevated lung concentrations of G-CSF, CXCL5, and MMP-2, and tissue expression of type-1 interferon following TLR9 agonist administration, compared with wild-type mice. TLR9 responses were further determined in fully differentiated normal human bronchial epithelial (NHBE) cells isolated from nonsmoker, smoker, and COPD donors, and then cultured at air liquid interface. NHBE cells from smokers and patients with COPD expressed more TLR9 and secreted greater levels of G-CSF, IL-6, CXCL5, IL-1β, and MMP-2 upon TLR9 ligand stimulation compared with cells from nonsmoker donors. Although TLR9 combats infection, our results indicate that TLR9 induction can affect lung function by inactivating PTP1B and upregulating expression of proinflammatory cytokines.

Fibroblast growth factor 23 and Klotho contribute to airway inflammation

“…Since mice that were exposed to chronic cigarette smoke (27) did not show an upregulation of FGF23 serum levels (Suppl. Fig.…”

Glutathione Peroxidase-1 Suppresses the Unfolded Protein Response upon Cigarette Smoke Exposure

“…Repeat exposures were performed to maximize smoke stimuli without inducing apoptosis, determined by LDH release assays (Figure 1(a)). Gene expression of IL-6 was utilized as a positive control for sufficient exposure to smoke [20] (Figure 1(a)). CD45 and CD11C expressions were analyzed but detection was below significant amplification levels thereby confirming low levels of inflammatory-cell contamination (data not shown).…”

“…RNA and protein were collect 24 hours later. Human RSV strain A2 (ATCC, Manassas, VA; #VR-1540) was infected in NHBE cells as previously described [20]. RNA and protein were collect 24 hours later.…”

Oral feeding with probiotic Lactobacillus rhamnosus attenuates cigarette smoke-induced COPD in C57Bl/6 mice: Relevance to inflammatory markers in human bronchial epithelial cells

“…Exacerbated activity of metalloproteinases from neutrophils in COPD patients is responsible for destruction of alveolar parenchyma [9][10][11][12]. In COPD, neutrophils release proteinases into lung milieu, such as metalloproteases MMP-9 and MMP-12, result in emphysema [13] where the immune system switches to a Th17 response to promote the perpetuation of inflammation [14]. The effects of matrix metalloproteinase (MMP) can be inhibited by tissue inhibitors of metalloproteinase (TIMP) secreted by several cells [15].…”

“…Some airways structural cells, such as the bronchial epithelium, when exposed to cigarette smoke secrete pro-inflammatory mediators activating alveolar macrophages as well as attracting neutrophils and activated lymphocytes towards the injured tissue [13,30]. In fact, the airway epithelial cells are interface between innate and adaptive immunity.…”