Attenuation of Atherosclerosis by Protocatechuic Acid via Inhibition of M1 and Promotion of M2 Macrophage Polarization (P04-063-19)

Macrophage polarization has a vital impact on the progression of atherosclerosis (AS). Protocatechuic acid (PCA), a flavonol, displays notable atheroprotective effects, but its mechanisms have not been clearly defined. Therefore, we investigated whether PCA attenuated AS by regulating macrophage polarization. Male apolipoprotein E-deficient (ApoE−/−) mice fed a normal chow diet (NCD), a high-cholesterol diet (HCD) or a high-cholesterol diet with PCA (PCA, 15 mg/kg body weight) for 14 weeks. In in vitro studies, mouse-macrophage cell line (J774 cells) and mouse-bone-marrow-derived macrophages (BMDMs) were stimulated with interferon γ (IFN γ) plus lipopolysaccharide (LPS) or interleukin 4 (IL-4) with or without pretreated with PCA for 24 h. Flow cytometry analysis, immunofluorescence, real-time quantitative reverse transcriptase and western blotting were performed for the next measurement. PCA consumption inhibited HCD-induced plaque formation (17.84% and 8.21% in the HCD and HCD with PCA groups, respectively; P < 0.05) and inflammatory responses in apolipoprotein E-deficient (ApoE−/−) mice (Fig. 1). Moreover, PCA suppressed the classically activated macrophage (M1) polarization, which decreased the secretion of synthesis of nitric oxide synthase (54.63% and 32.86% in the HCD and HCD with PCA group, respectively; P < 0.05) and proinflammatory factors (Fig. 2). PCA promoted alternatively activated macrophage (M2) activation, which increased the expression of arginine I (6.97% and 26.19% in the HCD and HCD + PCA group, respectively; P < 0.001) and anti-inflammatory factors (Fig. 2). PCA also regulated M1-M2 polarization in J774 cells and mouse-bone-marrow-derived macrophages. Finally, PCA reduced PI3K-Akt-mediated nuclear-factor-κB activation, thereby suppressing M1 polarization, and provoked signal-transducers-and-activators-of-transcription-6 phosphorylation and peroxisome-proliferator-activated-receptor-γ activation, leading to enhanced M2 activation. Our data revealed that PCA alleviated AS progression by suppressing M1 polarization and promoting M2 activation. This work was received funding from the Major Projects of Guangzhou Health Collaborative Innovation, the State Key Program of National Natural Science Foundation of China and the Guangdong Science and Technology Project.