ABSTRACT
The aim of this study was to explore the molecular mechanisms of the effect of low intensity pulsed ultrasound (LIPUS) on human primary macrophage functions. Macrophage phagocytosis was analyzed using fluorescein isothiocyanate (FITC)-labelled Escherichia coli (E.Coli); focal complex and extracellular matrix metalloproteinase inducer (EMMPRIN) were observed by fluorescence microscopy; the secretion of metalloproteinases (MMPs) was examined by gelatin zymography, and the expressions of EMMPRIN and extracellular signal-regulated kinases (ERKs) were detected by Western blot. The results indicated that LIPUS accelerated macrophages to phagocytose E.Coli (29.81+/-0.36 vs 18.00+/-0.78), promoted the protein expressions of EMMPRIN and MMPs, increased the level of protein tyrosine phosphorylation, and induced the phosphorylation of ERKs. Furthermore, the above functions were only found in adherent macrophages, and were inhibited or decreased by mitogen activated protein kinase kinase (MAPK kinase, MEK) inhibitor PD98059 and RGD (Arg-Gly-Asp peptide), one of main integrin recognition sequences. It is concluded that the effect of LIPUS on macrophages depends on cell adhesion, and relates to integrin-MEK-ERK pathway.