Small Molecule Regulation Of Macrophage Alternative Activation And Macrophage Function

Macrophages play a central role in inflammation and resisting the invasion of foreign microbes. Macrophages have high plasticity. They can exhibit different activation when accepting various stimulis in different environments. In inflammatory response, macrophages have three functions:antigen presentation, phagocytosis and immunomodulatory function via secretion of various cytokines and growth factors. Active molecules secreted by macrophage can participate in a beneficial inflammatory response and also participate in a harmful inflammatory response. Therefore, interfering macrophages and their secretion product can open a new way to control inflammatory diseases.Extensive literature studies have shown that flavonoids in the diet have anti-inflammatory and antioxidant role. Moreover, in recent years, many studies have shown that these flavonoids had a strong killing effect on tumor cells, indicating that the flavonoids can inhibit the tumor cells. In our study, we selected two flavonoids, apigenin and chrysin, to study the macrophage activation regulation, and thus have a better understanding of the medicinal value of the flavonoids. Our results illustrated that:(1) The toxicity of the two compounds on the macrophages is concentration-dependent and time-dependent, and the toxicity of apigenin is higher than that of chrysin in the same circumstances.(2) LPS-activated macrophages increased the production of NO, MHCII expression and release of proinflammatory cytokines. Apigenin and chrysin can inhibit these effects of LPS, reducing the NO, MHCII expression and secretion of proinflammatory cytokines. These results suggested that apigenin and chrysin can regulate innate and acquired immune response, and had a potential therapeutic role in macrophage-mediated inflammation-related diseases.(3) Apigenin and chrysin can promote the alternative activation of macrophages induced by IL-4. They can increase arginase activity, Argl, CD206, Yml and Fizzl gene expression levels. Through detecting the IL-4signaling pathway, we found apigenin and chrysin also increased the phosphorylation levels of JAK1and STAT6. PPARy transcriptional level has no change, but the nucleus PPARy increased. The CD36, one PPARy downstream gene, its expression also increased, suggesting that apigenin and chrysin may have a moderating role in the transcriptional activity of PPARy.In summary, our experiments investigated the regulative effects of apigenin and chrysin on macrophage function and activation. Apigenin and chrysin can not only inhibit the LPS-induced macrophage classical activation, but also can promote IL-4induced macrophage alternative activation, and inhibit monocyte differentiation. These results showed that apigenin and chrysin can not only inhibit inflammation also help to eliminate inflammation, can not only alleviate the damage caused by the inflammation also help tissue repair.In animal level, our preliminary findings are not enough, but this study is continunig. In mouse peritoneal macrophages, the results showed that apigenin and chrysin can reduce the inflammation of obesity in peritoneal macrophages, and the morphology of peritoneal macrophages is also affected. Based on these early studies, we laid the foundation for apigenin and chrysin in obese mice. Macrophages in tumor microenvironment are called tumor-associated macrophages, TAM). By phenotype analysis, these cells have a high expression of mannose receptor, scanvenger receptor, typeⅠ arginase, chemokines such as CCL12and CCL17. These tams have a high secretion of IL-10, while a low production of IL-12, IL-23and TNF-a. They promote angiogenesis, tissue remodeling and facilitate Th2type immune response in an alternative activation form.Liver is a gender dimorphism organ with different gene expression and this lead to physiological, pathological variances. Hepatocarcinoma cancer (HCC) is one of the most malignant cancers in the world associated with gender disparity. The incidence of HCC in men is higher than in women. Epidemiological statistics show that the ratio of HCC incidence between men and women is about3-5. Clinical studies show that HCC has a poorer prognosis in men compared with women. The mechanisms accounting for the gender disparity in HCC especially in terms of the tumor microenvironment remain to be known. Our previous works have shown:(1) In vivo, we found gender disparity in HCC malignance in othotopic mouse models. Adminstration of17β-estradiol could eliminate this disparity. Histochemistry analysis showed that estrogen inhibited kupffer cell infiltration and alternative activation.(2) In vitro, we found that estrogen at physiological concentration could inhibit Arg I activity and CD206expression of M2. And we found estrogen at physiological concentration could inhibit IL-10secretion and reduce the ratio of IL-10to IL-12which is a macrophage activation parameter.(3) Estrogen at10nM could inhibit Tumor migration.(4) By using estrogen receptor α (ERα) specific agonist PPT, ERβ specific agonist DPN, we found DPN had a similar inhibitory effect on macrophage arginase activity which indicated that ERp-mediated estrogen inhibitory effect.Based on the results above, this study focused on the mechanisms of estrogen regulating macrophage alternative activation, and continues to uncover the mechanism of HCC gender disparity. The main work and results include:(1) Develop othotopic mouse models, test and verify the role of estrogen in HCC progression.(2)The signal transduction and molecular mechanism of estrogen-mediated macrophage alternative activation. Here we identify that17(3-estradiol (E2) could suppress tumor growth via regulating the polarization of macrophages. We show that E2re-administration reduces tumor growth in orthotopic and xenotopic mice HCC models. E2functions as a suppressor for macrophage alternative activation and tumor progression by keeping estrogen receptor beta (ERβ) away from interacting with ATP synthase-coupling factor6(ATP5J), an ATP synthetase, thus inhibiting JAK/STAT6signaling pathway. These studies introduce a novel mechanism for suppressing male-predominant HCC.