Emodin Regulates Macrophage Polarization: Application In Breast Cancer Treatment

Macrophages are pleiotropic cells capable of performing a broad spectrum of functions. Their phenotypes are classified along a continuum between the extremes of pro-inflammatory M1 macrophages and anti-inflammatory M2 macrophages. The seemingly opposing functions of M1 and M2 macrophages must be tightly regulated for an effective inflammatory response to foreign molecules or damaged tissue. Excessive activation of either M1 or M2 macrophages contributes to the pathology of many diseases. Infiltration of macrophages into breast tumors correlates with increased metastasis and decreased patient survival. Tumors recruit macrophages to the primary site as well as pre-metastatic niches, and educate them to adopt an M2-like phenotype, thereby creating a growth-promoting immunosuppressive microenvironment. Emodin is a Chinese herb-derived single compound and has shown potential to inhibit macrophage activation and to prevent tumor growth. In this study, the effects of emodin on macrophage response to M1 or M2 stimuli were investigated. Further, emodin was used to treat mice bearing breast tumors and its effect on tumor cell-macrophage interactions was examined. Emodin was found to bi-directionally tune the activation of macrophages induced by LPS/IFNγ or IL4 through inhibiting NFkB/IRF5/STAT1 or IRF4/STAT6 signaling pathways respectively. Furthermore, emodin inhibited the removal of H3K27m3 and the placement of H3K27ac histone modifications on genes associated with macrophage activation. In mice bearing breast cancer, emodin treatment attenuated tumor growth by reducing macrophage infiltration into the primary tumors and subsequent M2-like polarization. Reduced accumulation of M2-like macrophages in the tumors leads to increased T cell activation and decreased angiogenesis. Emodin was shown to suppress infiltration and M2-like polarization of TAMs by targeting the TAM-tumor interaction. Emodin inhibited macrophage M2-like polarization in response to tumor cell secreted molecules, inhibited tumor cell recruitment of macrophages through reducing CCL2 and CSF1 expression, and block tumor cell-macrophage adhesion. In conclusion, our data suggest that emodin is uniquely able to suppress excessive response of macrophages to both M1 and M2 stimuli, and that emodin has potential as a new anti-breast cancer therapy

Ursolic acid enhances macrophage autophagy and attenuates atherogenesis

Macrophage autophagy has been shown to be protective against atherosclerosis. We previously discovered that ursolic acid (UA) promoted cancer cell autophagy. In the present study, we aimed to examine whether UA enhances macrophage autophagy in the context of atherogenesis. Cell culture study showed that UA enhanced autophagy of macrophages by increasing the expression of Atg5 and Atg16l1, which led to altered macrophage function. UA reduced pro-interleukin (IL)-1β protein levels and mature IL-1β secretion in macrophages in response to lipopolysaccharide (LPS), without reducing IL-1β mRNA expression. Confocal microscopy showed that in LPS-treated macrophages, UA increased LC3 protein levels and LC3 appeared to colocalize with IL-1β. In cholesterol-loaded macrophages, UA increased cholesterol efflux to apoAI, although it did not alter mRNA or protein levels of ABCA1 and ABCG1. Electron microscopy showed that UA induced lipophagy in acetylated LDL-loaded macrophages, which may result in increased cholesterol ester hydrolysis in autophagolysosomes and presentation of free cholesterol to the cell membrane. In LDLR(−/−) mice fed a Western diet to induce atherogenesis, UA treatment significantly reduced atherosclerotic lesion size, accompanied by increased macrophage autophagy. In conclusion, the data suggest that UA promotes macrophage autophagy and, thereby, suppresses IL-1β secretion, promotes cholesterol efflux, and attenuates atherosclerosis in mice