Atorvastatin suppresses oxidized LDL-induced dendritic cell-like differentiation of RAW264.7 cells regulated by the p38 MAPK pathway

Myeloid HMG-CoA (3-Hydroxy-3-Methylglutaryl-Coenzyme A) Reductase Determines Atherosclerosis by Modulating Migration of Macrophages

Objective- Inhibition of HMGCR (3-hydroxy-3-methylglutaryl-coenzyme A reductase) is atheroprotective primarily by decreasing plasma LDL (low-density lipoprotein)-cholesterol. However, it is unknown whether inhibition of HMGCR in myeloid cells contributes to this atheroprotection. We sought to determine the role of myeloid HMGCR in the development of atherosclerosis. Approach and Results- We generated mice with genetically reduced Hmgcr in myeloid cells ( Hmgcr ^{m- /m-}) using LysM (Cre) and compared various functions of their macrophages to those of Hmgcr ^fl/fl control mice. We further compared the extent of atherosclerosis in Hmgcr ^{m-/ m-} and Hmgcr ^fl/fl mice in the absence of Ldlr (LDL receptor). Hmgcr ^{m-/ m-} macrophages and granulocytes had significantly lower Hmgcr mRNA expression and cholesterol biosynthesis than Hmgcr ^fl/fl cells. In vitro, Hmgcr ^{m-/ m-} monocytes/macrophages had reduced ability to migrate, proliferate, and survive compared with Hmgcr ^fl/fl monocytes/macrophages. However, there was no difference in ability to adhere, phagocytose, store lipids, or polarize to M1 macrophages between the 2 types of macrophages. The amounts of plasma membrane-associated small GTPase proteins, such as RhoA (RAS homolog family member A), were increased in Hmgcr ^{m-/ m-} macrophages. In the setting of Ldlr deficiency, Hmgcr ^{m-/ m-} mice developed significantly smaller atherosclerotic lesions than Hmgcr ^fl/fl mice. However, there were no differences between the 2 types of mice either in plasma lipoprotein profiles or in the numbers of proliferating or apoptotic cells in the lesions in vivo. The in vivo migration of Hmgcr ^{m-/ m-} macrophages to the lesions was reduced compared with Hmgcr ^fl/fl macrophages. Conclusions- Genetic reduction of HMGCR in myeloid cells may exert atheroprotective effects primarily by decreasing the migratory activity of monocytes/macrophages to the lesions.

Atorvastatin inhibits cholesterol-induced caspase-3 cleavage through down-regulation of p38 and up-regulation of Bcl-2 in the rat carotid artery

AIM

Atherosclerotic lesions in the carotid arteries lead to a broad range of cerebrovascular disorders such as vascular dementia and ischaemic stroke. Recent studies have verified the beneficial role of atorvastatin (AV) in atherosclerosis. Despite a large body of studies, the mechanisms underlying this effect have not been completely explained. In this study, several experiments were performed on atherosclerotic rat models to investigate the anti-inflammatory and anti-apoptotic effect of AV in the carotid artery.

METHODS

In this experimental study, 40 male Wistar rats (250 ± 25 g) were randomly divided into four groups: rats on a normal diet (ND; n = 10); a high-cholesterol diet (HD; n = 10); a high-cholesterol diet plus AV (HD + AV; n = 10) ; and the AV control group (AV; n = 10). Cleavage of caspase-3 protein, expression of B-cell lymphoma 2 (Bcl-2) as well as phosphorylation of p38 mitogen-activated protein kinase (MAPK) were determined by immunoblotting assay in the carotid artery homogenate. Plasma atherogenic indices, including total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were measured by colorimetric assay at the end of the experiment. Plasma levels of oxidised LDL (oxLDL) were measured by sandwich enzyme-linked immunosorbent assay (ELISA).

RESULTS

After eight weeks of feeding with a high-cholesterol diet, an elevated level of oxLDL was observed in the plasma in the HD group compared with the ND group [214.42 ± 17.46 vs 69.13 ± 9.92 mg/dl (5.55 ± 0.45 vs 1.78 ± 0.26 mmol/l); p < 0.01]. AV administration significantly reduced oxLDL levels in the HD + AV compared to the HD group [126.52 ± 9.46 vs 214.42 ± 17.46 mg/dl (3.28 ± 0.25 vs 5.55 ± 0.45 mmol/l); p < 0.01]. Results also showed that compared with the HC group, the HC + AV group had lower levels of p38 phosphorylation (p < 0.05) and higher levels of Bcl-2 expression (p < 0.05). Lower levels of cleaved caspase-3 were observed in the HC + AV group in comparison with the HC group (p < 0.05).

CONCLUSIONS

The resultant data suggest that the anti-apoptotic effect of AV could be partially mediated by the pro-inflammatory protein p38 MAPK and the anti-apoptotic protein Bcl-2 in the rat carotid artery. Atorvastatin can therefore be considered a target drug in the prevention or development of atherosclerotic events.

The effect and mechanism of dopamine D1 receptors on the proliferation of osteosarcoma cells

The physiological and pathological roles of dopamine D1 receptors (DR1) in the regulation of functions in tissues and organs have been recognized. However, whether DR1 are expressed in the osteosarcoma cells and inhibit the proliferation of these cells is unknown. In the present study, we found that DR1 were expressed in the osteosarcoma cells (OS732 cells). SKF-38393 (DR1 agonist) and the overexpression of DR1 decreased the proliferation of OS732 cells; SCH-23390 (DR1 antagonist) and the knockdown of DR1 increased the proliferation of OS732 cells, and both SCH-23390 and the knockdown of DR1 abolished the effect of SKF-38393 on the proliferation of OS732 cells. In addition, SKF-38393 down-regulated the phosphorylation of ERK1/2, PI3K, and Akt; SCH-23390 up-regulated the phosphorylation of ERK1/2, PI3K, and Akt, and SCH-23390 cancelled the effect of SKF-38393. The effect of SKF-38393 on the phosphorylation of ERK1/2, PI3K, and Akt and the proliferation of OS732 cells was similar to PD98059 (an ERK inhibitor) or LY294002 (a PI3K inhibitor), respectively. In conclusion, our results suggest that DR1 are expressed in the osteosarcoma cells and inhibit the proliferation of osteosarcoma cells by the down-regulation of the ERK1/2 and PI3K-Akt pathways. These findings provide a novel target for the treatment of the osteosarcoma.

β-Elemene reduces the progression of atherosclerosis in rabbits

The present study aimed at investigating the possible effects of β-elemene on the progression of atherosclerosis in a rabbit model. The rabbit atherosclerosis model was established by the combination of balloon angioplasty-induced endothelial injury and an atherogenic diet fed to the rabbits. New Zealand White rabbits were randomly divided into four groups (8/group): the normal control group (fed with normal chow diet), and three experimental groups, placebo group, atorvastatin group, and β-elemene group (received the atherogenic diet). After two weeks on the diet, the three experimental groups underwent balloon injury at right common carotid artery and were treated with drugs or placebo for five weeks. Serum lipids were measured. Carotid artery lesions were isolated for histological and immunohistochemical analysis. In vitro, RAW264.7 macrophages were pretreated with β-elemene and ox-LDL for 24 h and the viability of macrophages was assayed using the MTT method. TNF-α and IL-6 were also determined. Compared with the control group, the thickness of the atherosclerosis lesion in the placebo group was significantly increased; The thickness the drug treatment groups were significantly decreased, compared with that of the placebo group. The infiltration of macrophage was markedly reduced in the β-elemene group compared with that of the placebo group. β-elemene treatment also reduced the levels of TC, TG, and LDL-C, compared with the placebo group. β-elemene decreased the TNF-α and IL-6 levels in vitro. In conclusion, our results demonstrated that β-elemene retarded the progression of atherosclerosis in vivo and in vitro, which may be related to the capacity of β-elemene to reduce the infiltration of macrophages and suppress inflammatory factors.

Atorvastatin improves plaque stability in ApoE-knockout mice by regulating chemokines and chemokine receptors

It is well documented that statins protect atherosclerotic patients from inflammatory changes and plaque instability in coronary arteries. However, the underlying mechanisms are not fully understood. Using a previously established mouse model for vulnerable atherosclerotic plaque, we investigated the effect of atorvastatin (10 mg/kg/day) on plaque morphology. Atorvastatin did not lower plasma total cholesterol levels or affect plaque progression at this dosage; however, vulnerable plaque numbers were significantly reduced in the atorvastatin-treated group compared to control. Detailed examinations revealed that atorvastatin significantly decreased macrophage infiltration and subendothelial lipid deposition, reduced intimal collagen content, and elevated collagenase activity and expression of matrix metalloproteinases (MMPs). Because vascular inflammation is largely driven by changes in monocyte/macrophage numbers in the vessel wall, we speculated that the anti-inflammatory effect of atorvastatin may partially result from decreased monocyte recruitment to the endothelium. Further experiments showed that atorvastatin downregulated expression of the chemokines monocyte chemoattractant protein (MCP)-1, chemokine (C-X3-C motif) ligand 1 (CX3CL1) and their receptors CCR2 and, CX3CR1, which are mainly responsible for monocyte recruitment. In addition, levels of the plasma inflammatory markers C-reactive protein (CRP) and tumor necrosis factor (TNF)-α were also significantly decrease in atorvastatin-treated mice. Collectively, our results demonstrate that atorvastatin can improve plaque stability in mice independent of plasma cholesterol levels. Given the profound inhibition of macrophage infiltration into atherosclerotic plaques, we propose that statins may partly exert protective effects by modulating levels of chemokines and their receptors. These findings elucidate yet another atheroprotective mechanism of statins.

β-Glucan attenuates inflammatory responses in oxidized LDL-induced THP-1 cells via the p38 MAPK pathway

AIM

To investigate the immunomodulatory effects of β-(1,3/1,6)-d-glucan on atherosclerosis as well as on the molecular mechanisms of its transition.

METHODS AND RESULTS

Human monocytic leukemia (THP-1) cells were differentiated into the macrophage phenotype by incubation with oxLDL in the absence or presence of β-glucan. β-glucan attenuated CD86 and CD80 expression and simultaneously reduced secretion of the inflammatory cytokines IL-2, IL-8, IL-12, TNF-α and IFN-γ. Western blot analysis showed that oxLDL treatment induced phosphorylation of p38 MAPK and ERK1/2 in PMA-differentiated THP-1 cells. However, β-glucan inhibited p38 MAPK activation. In experiments with monocytes derived from healthy donors, β-glucan inhibited IL-8, IL-12 and TNF-α production. The anti-inflammatory effects of β-glucan were also observed in atherosclerotic plaque cells.

CONCLUSIONS

β-glucan inhibited oxLDL-induced pro-inflammatory effects in macrophages via regulation of p38 MAPK phosphorylation. This novel finding may provide insight for new therapeutic strategies.

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.