WNT/β-catenin pathway is modulated in asthma patients and LPS-stimulated RAW264.7 macrophage cell line

Abstract

In the present study, we investigated the possibility that the WNT/β-catenin pathway plays a role in inflammatory responses both in an human inflammatory condition and in an in vitro inflammation model. First, we analyzed gene expression patterns of the peripheral blood cells from asthma patients compared with those from normal subjects using microarray analyses. We found that intracellular signaling molecules of the WNT/β-catenin pathway were significantly changed in asthma patients compared with the levels in the controls. Next, we determined whether major components of the WNT/β-catenin pathway were involved in the lipopolysaccharide (LPS)-induced inflammatory response of the RAW264.7 macrophage cell line. Among the members of WNT/β-catenin pathway, the protein levels of low-density lipoprotein receptor-related protein (LRP) 6, dishevelled (DVL) 2, and AXIN1, which were measured using western blotting, did not significantly change in the presence of LPS. In contrast, the LPS induced a rapid phosphorylation of glycogen synthase kinase (GSK) 3β and accumulation of β-catenin protein. It was found that β-catenin plays a significant role in the LPS-induced inflammatory response through the performance of small interfering RNA (siRNA) transfection experiments. The mRNA level of IL-6 was significantly elevated in β-catenin siRNA-transfected cells compared with that in control siRNA-transfected cells after LPS treatment. Furthermore, nuclear factor-κB (NF-κB) activity was also significantly increased in β-catenin siRNA-transfected cells compared with the level seen in control siRNA-transfected cells. Taken together, these results suggest that β-catenin plays a role as a negative regulator, preventing the overproduction of inflammatory cytokines such as IL-6 in LPS-induced inflammatory responses.

Platelet-derived Wnt antagonist Dickkopf-1 is implicated in ICAM-1/VCAM-1–mediated neutrophilic acute lung inflammation

“…19,20 Here, we observed that IL-6 in the BAL was markedly reduced after the administration of Wnt3a in LM-challenged lungs ( Figure 5D), and this reduction was due to attenuated IL-6 mRNA synthesis by Wnt3a ( Figure 5E). However, mRNA expression and the BAL level of TNFa showed no significant difference between Wnt3a-treated and control mice upon LM challenge (supplemental Figure 4C-D).…”

“…19 Knockdown of b-catenin in macrophages increases LPSinduced IL-6 expression. 20 Thus, macrophages may also contribute to the phenotypes we observed in our animal models. The interaction and relative contribution of macrophages and AECs to acute lung inflammation remain to be determined.…”

“…Our observations are consistent with the previous reports of suppression of Wnt/b-catenin signaling in inflammatory lung diseases. 20,[25][26][27][28][29] On the other hand, upregulation of Wnt/b-catenin signaling has been demonstrated in the resolution stage of ALI. 43,44 Wnt/b-catenin signaling is activated in AEC II and is essential for alveolar epithelial repair following acute injury.…”

“…[12][13][14][15] However, only limited evidence is available for a role of Wnt/b-catenin signaling in acute pulmonary inflammation. [16][17][18][19] Wnt/b-catenin signaling inhibits the endothelial and epithelial inflammatory responses by suppressing proinflammatory cytokines (tumor necrosis factor a [TNFa] and IL-6), 19,20 chemokines (IL-8 and CC chemokine ligand 2), 21 adhesion molecules (vascular cell adhesion molecule 1 [VCAM-1] and intercellular adhesion molecule 1 [ICAM-1]), 22 and other inflammatory regulators (nitric oxide synthase type 2, C8orf4 [TC1], and cyclooxygenase type 2) 23 through interacting with nuclear factor-kB (NF-kB) signaling and Toll-like receptor-mediated signaling. 21,23,24 In inflammatory lung diseases, suppression of Wnt/ b-catenin signaling is observed in COPD 25 and asthma patients, 20,26 contributing to their dysfunctional epithelial repair.…”

Anti-inflammatory effects of arbutin in lipopolysaccharide-stimulated BV2 microglial cells

“…Stimulation with LPS can induce the expression of iNOS, COX-2, proinflammatory cytokines, and chemokines in microglia/ macrophages [21]. Subsequently, activated microglia/ macrophages may secrete many pro-inflammatory cytokines, including IL-1b and TNF-a, which in turn can act on these cells in an autocrine manner [22].…”