LXR (liver X receptor) is a ligand-activated transcription factor and plays an important role in regulation of lipid homoeostasis and inflammation. Several studies indicate that LXR inhibits IFN-γ (interferon γ)-induced biological responses; however, the influence of LXR on IFN-γ expression has not been fully elucidated. In the present study, we investigated the effects of LXR activation on IFN-γ expression at different levels. At the molecular level, we surprisingly observed that LXR ligand (T0901317) induced macrophage and T-cell IFN-γ protein expression which was associated with increased mRNA and secreted protein levels in culture medium. In contrast, selective inhibition of LXRα and/or LXRβ expression by siRNA reduced IFN-γ expression. Promoter analysis defined the multiple LXREs (LXR-responsive elements) in the proximal region of the IFN-γ promoter. EMSAs and ChIP indicated that LXR activation enhanced the binding of LXR protein to these LXREs. In vivo, T0901317 increased wild-type mouse serum IFN-γ levels and IFN-γ expression in the lung and lymph nodes. Functionally, we observed that administration of T0901317 to wild-type mice increased rates of survival and being tumour-free, and inhibited tumour growth when the animals were inoculated with LLC1 carcinoma. In contrast, these protective effects were substantially attenuated in IFN-γ-knockout (IFN-γ-/-) mice, suggesting that the induction of IFN-γ production plays a critical role in T0901317-inhibited tumour growth. Taken together, the results of the present study show that IFN-γ is another molecular target of LXR activation, and it suggests a new mechanism by which LXR inhibits tumour growth.

Background: LXR inhibits the development of atherosclerosis. It remains unknown whether LXR regulates IL-5 expression, an atheroprotective cytokine, in macrophages. Results: LXR induces macrophage IL-5 expression in an LXRE-dependent manner. It also induces IL-5 expression in aortic root area of LDLR Ϫ/Ϫ mice.

Macrophage CD36 binds and internalizes oxidized low density lipoprotein (oxLDL) to facilitate foam cell formation. CD36 expression is activated by peroxisome proliferator-activated receptor ␥ (PPAR␥). Tamoxifen, an anti-breast cancer medicine, has demonstrated pleiotropic functions including cardioprotection with unfully elucidated mechanisms. In this study, we determined that treatment of ApoE-deficient mice with tamoxifen reduced atherosclerosis, which was associated with decreased CD36 and PPAR␥ expression in lesion areas. At the cellular level, we observed that tamoxifen inhibited CD36 protein expression in human THP-1 monocytes, THP-1/PMA macrophages, and human blood monocyte-derived macrophages. Associated with decreased CD36 protein expression, tamoxifen reduced cellular oxLDL accumulation in a CD36-dependent manner. At the transcriptional level, tamoxifen decreased CD36 mRNA expression, promoter activity, and the binding of the PPAR␥ response element in CD36 promoter to PPAR␥ protein. Tamoxifen blocked ligand-induced PPAR␥ nuclear translocation and CD36 expression, but it increased PPAR␥ phosphorylation, which was due to that tamoxifen-activated ERK1/2. Furthermore, deficiency of PPAR␥ expression in macrophages abolished the inhibitory effect of tamoxifen on CD36 expression or cellular oxLDL accumulation both in vitro and in vivo. Taken together, our study demonstrates that tamoxifen inhibits CD36 expression and cellular oxLDL accumulation by inactivating the PPAR␥ signaling pathway, and the inhibition of macrophage CD36 expression can be attributed to the anti-atherogenic properties of tamoxifen.Tamoxifen (Nolvadex) and its immediate metabolite, 4-hydroxytamoxifen, belong to the class of drugs called selective estrogen receptor modulators (1). Dependent on target tissue/ molecules, tamoxifen can function either as an estrogen receptor (ER) 5 antagonist, such as in the mammary tissue, or as an ER agonist, such as in the endometrium (2). In the breast tissue, inactivation of ER by tamoxifen inhibits the growth of breast cancer cells. Therefore, tamoxifen is the most commonly used anti-hormonal drug for adjuvant treatment of patients with ERpositive breast cancer (2). In addition, tamoxifen has been determined to have a preventive function on breast cancer in the population of women with a high risk of developing this disease (3).Besides the effect on breast cancer, several lines of evidence have demonstrated the cardioprotective effects of tamoxifen. In animal models, tamoxifen reduces atherosclerosis in wild type mice and pro-atherogenic animal models, such as ApoE deficient (ApoE Ϫ/Ϫ ) mice and surgically postmenopausal monkeys (4 -6). In humans, tamoxifen lowers the incidence of fatal myocardial infarction, reduces the intima-media thickness of the common carotid artery in the postmenopausal women, and promotes the endothelium-dependent flow-mediated dilation in male patients with advanced atherosclerosis (7-9).Atherosclerosis is one of the major causes of coronary heart disease and a chronic patholo...

Activated macrophages play an important role in many inflammatory diseases including septic shock and atherosclerosis. However, the molecular mechanisms limiting macrophage activation are not completely understood. Members of the tripartite motif (TRIM) family have recently emerged as important players in innate immunity and antivirus. Here, we systematically analyzed mRNA expressions of representative TRIM molecules in human THP1-derived macrophages activated by different toll-like receptor (TLR) ligands. Twenty-nine TRIM members were highly induced (>3 fold) by one or more TLR ligands, among which 19 of them belong to TRIM C-IV subgroup. Besides TRIM21, TRIM22 and TRIM38 were shown to be upregulated by TLR3 and TLR4 ligands as previous reported, we identified a novel group of TRIM genes (TRIM14, 15, 31, 34, 43, 48, 49, 51 and 61) that were significantly up-regulated by TLR3 and TLR4 ligands. In contrast, the expression of TRIM59 was down-regulated by TLR3 and TLR4 ligands in both human and mouse macrophages. The alternations of the TRIM proteins were confirmed by Western blot. Finally, overexpression of TRIM59 significantly suppressed LPS-induced macrophage activation, whereas siRNA-mediated knockdown of TRIM59 enhanced LPS-induced macrophage activation. Taken together, the study provided an insight into the TLR ligands-induced expressions of TRIM family in macrophages.

No abstract