甲壳低聚糖对THP-1源性巨噬细胞脂质转运相关基因表达的影响

目的观察甲壳低聚糖(COS)对离体培养的THP-1源性巨噬细胞脂质转运相关基因表达的影响,以初步探讨COS降低血脂的可能分子机制。方法离体培养人THP-1单核细胞,诱导分化成巨噬细胞后,用100μg/mL的COS处理THP-1源性巨噬细胞6,12,24,48 h,运用半定量RT-PCR方法检测其LDL受体、SR-BⅠ、ABCA1和CD36mRNA表达水平的变化。结果COS处理THP-1源性巨噬细胞24和48 h后,LDL受体mRNA的表达与对照组比较分别下调了15.6%(P<0.05)和30.7%(P<0.01);处理6,12,24,48 h后,SR-BⅠmRNA的表达与对照组比较分别上调了14.7%,23.0%,14.6%(P<0.05)和33.9%(P<0.01);处理6和12 h后,ABCA1 mRNA的表达与对照组比较分别上调了12.6%和14.5%(P<0.05);处理6和12 h后,CD36 mRNA的表达与对照组比较分别下调了25.5%和10.2%(P<0.05)。结论通过细胞离体培养实验表明,COS具有的降低血脂作用可能与其能上调巨噬细胞中AB-CA1和SR-BⅠmRNA表达水平以及降低LDL受体和CD36 mRNA水平有关。     

Pleiotropic vascular effects of PPARgamma ligands

Peroxisome proliferator-activated receptor-gamma (PPARgamma) ligands have been used for several years as modulators of insulin sensitivity and glucose metabolism. Recent data from numerous studies have shown that PPARgamma ligands have numerous beneficial effects in the vasculature. They have been shown to regulate proliferation and migration of vascular smooth muscle cells as well as improving endothelial cell function. They improve blood pressure by actions at the resistance arteries and kidneys. Clinical trials have indicated that PPARgamma ligands can minimize the development of atherosclerosis as well as regulating other vascular inflammation. PPARgamma has been detected in all the cells found in the vessel wall as well as those cells associated with vascular pathophysiologies. In the monocyte/macrophage, PPARgamma ligands downregulate production of inflammatory cytokines and migration. Also, PPARgamma ligands regulate the expression of SR-A and CD36 receptors that take up lipids in the macrophage. PPARgamma has also been demonstrated to act through the liver X receptor alpha to increase the activity of reverse cholesterol transport in these cells. In dendritic cells and T-cells, PPARgamma ligands have been shown to inhibit activation and the initiation of inflammation. Inflammatory cytokines are downregulated in animal models administered PPARgamma ligands, leading to decreased atherosclerosis. While PPARgamma ligands have been useful in the treatment of type 2 diabetes, the important vasculoprotection elicited by these compounds could prove to be of greater benefit in the future.     

Berberine-induced inhibition of adipocyte enhancer-binding protein 1 attenuates oxidized low-density lipoprotein accumulation and foam cell formation in phorbol 12-myristate 13-acetate-induced macrophages

The phagocytosis of oxidized low-density lipoprotein (oxLDL) by monocyte-derived macrophages and the subsequent differentiation of macrophages into foam cells are the key steps in atherogenesis. Scavenger receptors, such as CD36 and lectin-like low-density lipoprotein receptor 1 (LOX-1), are responsible for the uptake of oxLDL. Adipocyte enhancer-binding protein 1 (AEBP1) regulates many key genes associated with intracellular cholesterol efflux. The present study investigated the function of berberine, a compound isolated from Rhizoma coptidis, on foam cell formation, and explored the possible underlying mechanism. We found that berberine inhibited the oxLDL uptake of macrophages and reduced foam cell formation in a dose-dependent manner. Moreover, AEBP1 expression in macrophages increased and decreased after oxLDL and berberine treatments in a dose-dependent manner, respectively. Berberine reduced the expression of scavenger receptors CD36 and LOX-1, but did not affect the expression of CD68 in oxLDL-stimulated macrophages. Overall, berberine reduced foam cell formation by a dual mechanism, which decreased oxLDL internalization via the suppression of CD36 and LOX-1, and increased cholesterol efflux by inhibiting AEBP1 expression in macrophages.     

The pharmacodynamic effects of sirolimus and sirolimus-calcineurin inhibitor combinations on macrophage scavenger and nuclear hormone receptors

BACKGROUND: Sirolimus (SIR) alone or in combination with cyclosporine (CsA) or tacrolimus (TAC) are used in solid organ transplantation, but uncertainty remains regarding their respective atherogenic potentials. METHODS: THP-1 cells were cultured as macrophages and then treated with plasma trough and peak concentration doses of SIR, SIR/CsA or SIR/TAC to assess the time- and dose-dependent mRNA or protein expression of selected atherogenic genes. The selected atherogenic genes included: the macrophage scavenger receptors (MSRs) CD36, CD68, scavenger receptor (SR)-A, SR-BII, and LOX-1; the nuclear hormone receptors peroxisome proliferator activated receptor gamma (PPARgamma) and liver-X-receptor alpha (LXRalpha); and the cholesterol efflux transporter (ABCA-1). RESULTS: SIR-mediated changes in mRNA included the upregulation of ABCA1, downregulation of CD68, SR-A and SR-BII, and concentration- and/or time-dependent effects on CD36, LOX-1, PPARgamma, and LXRalpha that did not translate into significant protein changes. With SIR/CsA, the protein expressions of PPARgamma and ABCA-1 were downregulated at 8 h. In contrast, with SIR/TAC, PPARgamma, and ABCA-1 protein expressions were upregulated at 8 h. CONCLUSIONS: Combination results differed from findings with SIR alone, supporting the observed clinical phenotype with calcineurin inhibitors. These findings may provide a rationale for the development of novel drug delivery strategies to mitigate adverse pharmacodynamic responses.     

Enzymatically modified low-density lipoprotein upregulates CD36 in low-differentiated monocytic cells in a peroxisome proliferator-activated receptor-gamma-dependent way

Peroxisome proliferator-activated receptor-gamma (PPARgamma) has been suggested to upregulate CD36. Since free oxidized polyunsaturated fatty acids are PPARgamma ligands, we studied the effects of LDL modified by the simultaneous action of sPLA2 and 15-lipoxygenase (15LO) on CD36 expression and PPARgamma activation in monocytic cells. Exposure of MM6 cells, which do not express CD36 or other scavenger receptors, to such enzymatically modified LDL (enzLDL) resulted in upregulation of CD36 surface protein and mRNA expression. Similar effects were observed with free 13-hydroperoxyoctadecadienoic acid but not its esterified counterpart. Less pronounced effects were observed with LDL modified by 15LO alone. Upregulation of CD36 was inversely correlated to the state of cell differentiation, as showed by lower response to enzLDL of the scavenger receptor-expressing MM6-sr and THP1 cells. Importantly, LDL modified by sPLA2 and 15LO did not efficiently induce upregulation CD36 in PPARgamma-deficient macrophage-differentiated embryonic stem cells confirming a role of PPARgamma in CD36 expression in cells stimulated with enzLDL. Our data show that LDL modified with physiologically relevant enzymes stimulates CD36 expression in non-differentiated monocytes and that this process involves PPARgamma activation. These effects of enzLDL can be considered pro-atherogenic in the context of early atherosclerosis.     

Curcumin inhibits oxLDL-induced CD36 expression and foam cell formation through the inhibition of p38 MAPK phosphorylation

The uptake of oxidized low density lipoprotein (oxLDL) via scavenger receptors transforms macrophages into foam cells, which are a hallmark of atherosclerosis. OxLDL markedly increases the expression of the CD36 scavenger receptor. Here, we investigated whether curcumin modulate CD36 expression in oxLDL-treated RAW 264.7 murine macrophages. Our results showed that curcumin dramatically inhibits CD36 expression and foam cell formation. Furthermore, oxLDL-induced expression and activity of peroxisome proliferator-activated receptor-gamma (PPAR-γ), which is involved in CD36 expression, is also blocked in curcumin-treated cells. OxLDL activates the mitogen-activated protein kinase (MAPK) signaling transduction pathway, and p38 MAPK is associated with oxLDL-induced CD36 and PPAR-γ expression. Overexpression of dominant negative p38 MAPK blocks oxLDL-induced CD36 and PPAR-γ expression. Furthermore, curcumin markedly inhibits p38 MAPK phosphorylation. Taken together, our results suggest that curcumin modulates oxLDL-induced CD36 expression and foam cell formation via the inhibition of p38 MAPK phosphorylation in RAW 264.7 murine macrophages.     

Platonin modulates differentiation and maturation of human monocyte-derived dendritic cells

Platonin is a photosensitizer with NF-kappaB inhibitory activity that activates macrophages and suppresses lymphocyte response. In this study, we tested the effect of platonin on differentiation and maturation of human myeloid dendritic cells (DC) from CD14+ monocytes. Triggering of DC differentiation by GM-CSF and IL-4 resulted in typical immature DCs that were further stimulated to maturation by combination of cytokines. When platonin (2 to 50 ng/mL) was added to the culture, the resulting DCs had thicker and blunter protruding projections, lower CD83 expression, greater CD80 expression, and less stimulatory activity on allogeneic naive CD4+CD45RA+ T cells in terms of their proliferation and interferon-gamma production. This suggests that platonin redirects DC differentiation toward an intermediate stage of maturation, whereby the DCs have uniquely enhanced expression of CD80 which may confer some degree of immune tolerance.     

普罗布考在抗ox-LDL诱导THP-1巨噬细胞凋亡中对CD36、Caveolin-1表达的影响

目的研究普罗布考(Probucol)在抗ox-LDL诱导THP-1巨噬细胞凋亡中对CD36、Caveolin-1表达的影响。方法用流式细胞仪检测细胞凋亡;用RT-PCR、免疫荧光分别检测CD36、Caveolin-1mRNA水平和蛋白表达。结果普罗布考抗ox-LDL诱导THP-1巨噬细胞凋亡;RT-PCR检测发现普罗布考组与ox-LDL组CD36、Caveolin-1mRNA表达无明显差异;免疫荧光检测结果显示普罗布考下调Caveolin-1蛋白表达,但对CD36蛋白的表达没有影响。结论普罗布考在抗ox-LDL诱导THP-1巨噬细胞凋亡中下调Caveolin-1蛋白的表达。