Mono-2-ethylhexylphthalate (MEHP) induces TNF-α release and macrophage differentiation through different signalling pathways in RAW264.7 cells

Epidemiological studies have associated indoor phthalate exposure with increased incidences and severity of asthma in children and adults, and inflammatory effects have been suggested as a possible mechanism. Recent studies report that phthalates may activate mitogen-activated protein (MAP) kinase p38 and various peroxisome proliferator-activated receptor (PPAR) isoforms. Here we confirm and extend these findings by investigating possible signalling pathways activated in the murine monocyte-macrophage cell line RAW264.7, using mono-2-ethylhexylphthalate (MEHP) as a model compound. MEHP exposure (0.3-1.0 mM) for 3h increased tumour necrosis factor (TNF)-alpha release and changed the cellular morphology into elongated spindle-like appearance, resembling more differentiated anti-inflammatory macrophages (M2). This was accompanied by increased expression of the macrophage differentiation marker CD163. Western analysis showed phosphorylation of p38 and Akt after 30 min exposure. Experiments using specific inhibitors suggested that MEHP-induced activation of both p38 and the phosphoinositide-3 (P13) kinase/Akt pathway were involved in the release of TNF-alpha; whereas only PI3kinase seemed to be involved in differentiation. In contrast, inhibitors of PPAR alpha and gamma reduced differentiation, but did not affect TNF-alpha release. In conclusion, MEHP induced cytokine release and triggered differentiation of RAW264.7 cells, possibly into M2-like macrophages, but different signalling pathways appear to be involved in these responses. (C) 2011 Elsevier Ireland Ltd. All rights reserved.