Gallic acid Inhibits M1 Macrophage Polarization via Adenosine 5 '-Monophosphate-Activated Protein Kinase/Signal Transducers and Activators of Transcription 1 Pathway

To investigate the role of gallic acid in lipopolysaccharide/interferon-gamma induced macrophage polarization toward M1. Macrophages were isolated from peritoneal wash fluid and exposed to gallic acid prepared at the concentrations of control, 6.25, 12.5, 25 and 37.5 mu g/ml, in presence of lipopolysaccharide and interferon-gamma, for establishment of M1 polarization. Adenosine 5'-monophosphate-activated protein kinase inhibitor compound C was used to pre-treat the macrophages; cell viability was determined by flow cytometry with Annexin V-PE/7-amino actinomycin D staining, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and trypan blue assays; flow cytometry was applied to evaluate the expression of F4/80(+) inducible nitric oxide synthase(+) M1 macrophages; real-time polymerase chain reaction was used to assess the messenger ribonucleic acid expression level of inducible nitric oxide synthase, tumor necrosis factor-alpha and interleukin-1 beta. Protein expression levels of cyclooxygenase-2, adenosine 5'-monophosphate-activated protein kinase, signal transducers and activators of transcription 1 and phosphorylation levels of adenosine 5'-monophosphate-activated protein kinase and signal transducers and activators of transcription 1 were evaluated by Western blotting. Gallic acid at the concentrations of 6.25-37.5 mu g/ml showed no noticeable effects on macrophages viability, but significantly decreased F4/80+ inducible nitric oxide synthase+ M1 macrophages polarization and the expression levels of inducible nitric oxide synthase, tumor necrosis factor-alpha, interleukin-1 beta, cyclooxygenase-2 and phospho-signal transducers and activators of transcription 1, meanwhile increased the expression levels of p-adenosine 5'-monophosphate-activated protein kinase contents in a concentration-dependent manner. Adenosine 5'-monophosphate-activated protein kinase inhibitor compound C pre-treatment can reverse the effects of gallic acid on M1 macrophage polarization. Gallic acid may inhibit macrophage polarization toward M1 via adenosine 5'-monophosphate-activated protein kinase/signal transducers and activators of transcription 1 signaling pathway.