Tumor necrosis factor-α stimulates the expression of C-C chemokine ligand 2 gene in fibroblasts from the human nasal polyp through the pathways of mitogen-activated protein kinase

Background: Recruitment Of macrophages is crucial to the pathogenesis of the nasal polyp (NP) because this disease is believed to be inflammation related. Information regarding the expression of C-C chemokine ligand 2 (CCL2), an essential modulator of monocyte chemotaxis in nasal polyp fibroblasts (NPFs), remains unavailable. In this study, the effects of tumor necrosis factor (TNF)-alpha on CCL2 expression in NPFs and the signaling pathway involved were investigated. Methods: Primary cultures of NPFs were established from NPs. The, expressions of CCL2, c-Fos, and c-Jun mRNAs in NPF after TNF-alpha stimulation were detected by Northern blot. Western blot was used to examine the activation of mitogen-activated protein kinase (MAPK) signaling pathways. Activator protein (AP) 1/DNA interactions were evaluated by electrophoretic mobility shift assay (EMSA). Results: Northern blot showed that TNF-alpha stimulated CCL2 gene expression in NPFs. Significant increase of B-Raf, phosphorated MAPK including mitogen-activated ERK-activate kinase (MEK)1/2, extracellular signal-related kinase 112, and p38 were detected by Western blot. c-Fos and c-Jun mRNAs were induced by TNF-alpha, and PD98059 (MEK inhibitor) and SB203580 (p38 inhibitor) abolished the up-regulation of c-Fos. EMSA revealed that TNF-alpha increased AP-1/DNA binding, and PD98059 and SB203580 attenuated this reaction, possibly via reducing c-Fos synthesis. PD98059 and curcumin (AP-1 inhibitor) markedly suppressed the TNF-alpha-induced CCL2 expression, whereas the effect of SB203580 was less noted. Conclusion: TNF-alpha induces CCL2 transcription in NPFs. B-Raf/MEK/ERK signaling cascade and to a less extent the p38 pathway are responsible for c-Fos activation and the subsequent AP-1/DNA interaction leading to CCL2 expression.