Effect of methyl gallate on polarized macrophages: evaluation of inflammatory and metabolic mechanisms

Rodrigues, da Silva. Carolina ; Noboru, Seito. Leonardo.; Costa, M, M, E. Thadeu; Cruz, Rosas. Elaine.; Barbosa, Correa. Luana.

Introduction: Macrophages play a central role in inflammation by acquiring different phenotypes in response to microenvironmental stimuli. Polarization toward the M1 phenotype is associated with pro-inflammatory mediators, while the M2 phenotype promotes inflammatory resolution and tissue repair (1). An imbalance between these phenotypes contributes to chronic inflammatory diseases, in which the M1 profile predominates (2,3). Thus, modulation of macrophage polarization is a promising therapeutic strategy. Methyl gallate (GM), a natural phenolic compound with antioxidant and anti-inflammatory properties, has been investigated for macrophage polarization (4). Objective: To investigate the immunomodulatory potential of GM in in vitro macrophage polarization. Methods: Bone marrow-derived macrophages (BMDMs) were stimulated with LPS and IFN-γ (M1), IL-4 and IL-13 (M2). Cells were pretreated with GM (1 h before stimulation); dexamethasone was the reference inhibitor. Cell viability was assessed by MTT, NO by Griess assay, cytokines by ELISA, and protein expression by western blot. Experimental procedures were approved by the Ethics Committee on the Use of Animals (CEUA), protocol LW-15/23. Results: GM showed no cytotoxicity. Pre-treatment reduced NO production, iNOS expression, IL-6, IL-12, TNF-α, CCL2 and CCL5 levels, without affecting COX-2 or M2a markers (arginase-1 and 15-lipooxygenase). GM also reduced STAT1 and STAT3 expression, with no effect on STAT6. Discussion: GM reduced inflammatory mediators without affecting cell viability. STAT1 and STAT3 reduction suggests their involvement. Absence of M2a marker changes indicates inhibition of the pro-inflammatory phenotype over M2. Conclusion: GM reduced inflammatory mediators and proteins associated with the M1 phenotype, supporting its therapeutic potential in chronic inflammatory diseases.