Novel Compounds Inhibit PMA-induced Monocyte Differentiation And LPS-triggered Macrophage Activation

Inflammation is a physiologic process mediated by the innate immune system to protect organisms against pathogen infections, environmental insults and wounding. However, prolonged or deregulated immune responses may lead to constant overproduction of pro-inflammatory cytokines, which are the major factors in chronic inflammation damage. It has been associated with the development of several chronic diseases, including atherosclerosis, ischemic heart disease, cancer, obesity, diabetes, cancer and autoimmune diseases. Rudolf Virchow who discovered the presence of leukocytes within tumors first put forward the hypothesis about the relations between cancer and inflammation in the19th century. More recently, the importance of inflammation in tumor initiation and malignant progression has become the focus of attention.Multiple cell types are involved in mounting the inflammatory response by producing pro-inflammatory cytokines, chemokines, nitric oxide, cyclooxygenase-2and cell adhesion molecules. For instance, circulating monocytes are versatile precursors differentiating into the various forms of specialized macrophages. The cytokine milieu profoundly affects the differentiation and function of tissue macrophages. There is an increasing interest in defining new therapies in order to inhibit the persistent activation of macrophages or their synthesis and production of inflammatory molecules.One anti-inflammatory therapeutic target that has received more and more attention is the nuclear hormone receptor, peroxisome proliferator-activated receptor gamma (PPARy). Activation of PPARy has been demonstrated to inhibit select inflammatory responses both in vitro and in vivo. However, there are also reports demonstrated that a significant reduction in TNF-α secretion when cells were pre-treated with the irreversible PPAR y antagonist, GW9662. All the above results suggest that the anti-inflammatory benefit of PPARγ ligands may be independent of its molecular target. In this study we investigated the effect of a range of completely new compounds, which were modified from GW9662.(1) The differentiation of THP-1cells into macrophages was induced by phorbol-12-myristate-13-acetate (PMA), a well-accepted model system utilized to explore molecular events in monocytic differentiation. We found that#26slowed down the differentiation of THP-1cells induced by PMA.(2) The cells were differentiated maturely after treated with PMA overnight. Then LPS was added into the media with the preincubation of#26. We found that#26inhibited the production of cytokines from LPS-activated PMA-differentiated THP-1macrophages, including MCP-1and IL-6.(3) The acute inflammation triggered by LPS. In this study, mice were injected with DMSO, GW9662and#26before challenged with LPS. A pretreatment of GW9662and#26mice displayed longer survival time compared with DMSO-pretreated animals after LPS challenge. We also exploited a mouse cytokine array to determine how#26treatments affected the plasma levels of several different cytokines following the treatment of mice with LPS. Different from the cytokine profile in the supernatants of the LPS-activated PMA-differentiated THP-1,#26significantly inhibited the expression level of pro-inflammatory cytokine TNF-α instead of IL-6. However, the anti-inflammatory IL-10was still down-regulated in this acute inflammatory animal model.(4)4T1is a mammary carcinoma cell line that has been studied extensively. In vivo generation of tumors was accomplished by injection of4T1cells into the mammary fat pad. Four days later, mice were treated by intraperitoneal injection of#26and Paclitaxel everyday. The results indicated that#26could regulate the growth of tumor, the release of cytokines and the phenotype of macrophages compared with the positive control.All the above data lead to the conclusion that#26could inhibit the differentiation of monocytes to macrophages and the inflammatory state of macrophages.#26was functional in the experiments of the acute inflammation triggered by LPS and mouse4T1breast tumor model, which provied strong evidence to investigate the mechanism. Due to the important roles of#26in differentiation, imflammation and tumor, we could regarded#26as a tool to study molecule target or a prodrug to do further study.