Amphiregulin may be a new biomarker of classically activated macrophages.

Amphiregulin (Areg) participates in tissue repair and inflammation regulation. As important effector cells in inflammation, macrophages can be polarized to classically (M1) or alternatively (M2) activated phenotype with diverse functions in immunity. However, the relationship between Areg expression and macrophage activation is poorly understood. Here we report that Areg was significantly expressed in M1 but not in M2 macrophages. This was confirmed by analyses of RT-PCR and ELISA in peritoneal macrophages, and by evaluating protein expression in alveolar macrophages and RAW264.7 cells. Selective inhibitors of TLR4 (CLI-095) and MAP kinase, including Erk1/2 (PD98059), JNK (SP600125) and p38 (SB203580), significantly reduced Areg expression in M1 macrophages, suggesting that M1 macrophages produce Areg mainly through the TLR4-MAPK pathway, which is involved in the mechanism of M1 activation. When compared with productions of classical biomarkers of M1 macrophages, Areg expression was highly consistent in time series. Taken together, Areg may be an effective new biomarker of M1 macrophages.