Linghong Shen

Statins for the Prevention of Contrast-Induced Nephropathy: A Systematic Review and Meta-Analysis

Background: Retrospective and prospective studies have demonstrated that statins have a protective effect in preventing contrast-induced nephropathy (CIN), but there are currently no established guidelines for statin timing or dosage. A systematic review and meta-analysis was performed to determine whether statin administration is protective and the magnitude of their effect. Methods: We searched MEDLINE, EMBASE, Cochrane Library, CNKI and ISI Proceedings for cohort studies comparing the CIN incidence in a chronic statin pretreatment group and a statin-naïve group, as well as for randomized controlled trials (RCTs) comparing short-term high-dose to short-term low-dose statin treatment or placebo. CIN was defined as an increase in serum creatinine >25% or 0.5 mg/dl (44.2 µmol/l). Qualitative analysis of cohort studies and quantitative analysis of RCTs to estimate pooled risk ratios were performed. Results: Among 6 cohort studies, 4 showed chronic statin pretreatment had a preventive effect against CIN. From 6 RCTs, 1,194 patients were included in the meta-analysis. Under the fixed-effects model, a nonsignificant protective trend toward decreased incidence of CIN with periprocedural short-term high-dose statin treatment was seen (RR: 0.70; 95% CI: 0.48–1.02). Conclusion: Current data are not conclusive to whether statins are protective for CIN due to the inherent limitations of the included studies. In the future, large well-designed studies are needed to address the effect of this drug and its longer-term clinical outcomes.

RXR agonists inhibit high-glucose-induced oxidative stress by repressing PKC activity in human endothelial cells

Activation of retinoid X receptor (RXR) is known to exert antiatherogenic effects. However, the underlying mechanism remains unclear. In this study, we examined the effects of the RXR agonists 9-cis-retinoic acid and SR11237 on high-glucose-induced oxidative stress in human endothelial cells. Our results demonstrated that high-glucose-induced oxidative stress in human umbilical vein endothelial cells (HUVECs) was mainly mediated through its activation of the Nox4, gp91phox, and p22phox components of nicotinamide adenine dinucleotide phosphate oxidase. Treatment of endothelial cells with RXR agonists resulted in significant inhibition of high-glucose-induced oxidative stress and expression of Nox4, gp91phox, and p22phox. The effect of RXR agonists was due to their inhibition of Rac-1 activation. Furthermore, RXR agonists rapidly inhibited high-glucose-induced activation of protein kinase C (PKC), an upstream activator of Rac-1. To study whether the rapid inhibitory effects of RXR agonists were mediated by RXR, we examined the effect of RXR downregulation by RXR siRNA. Our results showed that expression of RXR siRNA largely abrogated the effects of RXR agonists, suggesting the requirement of RXR expression. Interestingly, RXRalpha, which was diffusely distributed in HUVECs, accumulated mainly in the nucleus upon high glucose exposure. Treatment of cells with RXR agonists prevented the effect of high glucose. Thus, RXR ligands rapidly inhibit high-glucose-induced oxidative stress by antagonizing high-glucose-induced PKC activation, and cytoplasmic RXRalpha is implicated in this regulation.

Nuclear receptor Nur77 suppresses inflammatory response dependent on COX-2 in macrophages induced by oxLDL.

Oxidized low-density lipoprotein (oxLDL) cross-talks with macrophages, and both play a crucial role in the initiation and progression of atherosclerosis. Orphan nuclear receptor Nur77 is potently induced in macrophages by diverse stimuli, suggesting that it may be a key regulator of inflammation in vascular cells. The detailed mechanism of Nur77 activation and subsequent function in macrophages induced by oxLDL remains unclearly. In this study, we demonstrated that Nur77 is upregulated in a dose and time-dependent fashion by oxLDL stimulation in murine macrophages, as detected by real-time PCR and Western blotting. OxLDL activated the phosphorylation ERK1/2 and p38 MAPK, inhibition of p38 MAPK but not ERK1/2 attenuated Nur77 expression. Importantly, overexpression of Nur77 suppressed oxLDL-induced proinflammatory cytokines and chemokines secretion including tumor necrosis factor (TNF)alpha and monocyte chemoattractant protein-1(MCP-1). While knockdown Nur77 expression by specific small interfering RNA (siRNA) resulted in the enhancement of the secretion. Furthermore, exposure of macrophages to oxLDL significantly upregulated cyclooxygenase-2(COX-2) expression. However, this could be markedly inhibited by Nur77 overexpression. Also, Nur77 siRNA increased oxLDL-induced COX-2 expression and 6-mercaptopurine (6-MP) attenuated the increase. The results indicated that Nur77 is induced by oxLDL via p38 MAPK signal pathway and subsequently protects against inflammation by the inhibition of proinflammatory COX-2 pathway in activated macrophages. Specifically modifying transcription activity of Nur77 may represent a potential molecular target for the prevention and treatment of atherosclerosis.

Oxidized low-density lipoprotein induces differentiation of RAW264.7 murine macrophage cell line into dendritic-like cells

Dendtritic cells (DCs) are potent antigen-presenting cells and have an important role in the pathogenesis of atherosclerosis. Recent data suggests oxidized low-density lipoprotein (oxLDL) promotes the transition of a differentiating monocyte to a mature dendritic cell. In this study, we examined whether oxLDL could induce the differentiation of mature macrophages into DCs. After 48 h treatment with oxLDL, RAW264.7 cells increased in cell size and exhibited dendritic morphology. At the optimal oxLDL dose (10 microg/ml), approximately 74% of RAW264.7 cells differentiated into dendritic-like cells. Flow cytometric analysis detected dendritic cell surface markers (CD83, CD40, CD86, MHC Class II, and CD1d), and their expression increased in a dose- and time-dependent manner. Moreover, oxLDL-treated RAW264.7 cells showed functional changes including reduced endocytic activity, increased allostimulatory activity, and IL-12 production. The findings of the present work demonstrate that RAW264.7 cells, incubated with oxLDL, acquire some dendritic cell features.

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.

Endogenous Renovascular Hypertension Combined With Low Shear Stress Induces Plaque Rupture in Apolipoprotein E–Deficient Mice

Objective—The development of a murine model of spontaneous atherosclerotic plaque rupture with luminal thrombus. Methods and Results—Combined partial ligation of the left renal artery and left common carotid artery in 8-week-old apolipoprotein E–deficient mice induced endogenous renovascular hypertension and local low oscillatory shear stress in the left common carotid artery. After 8 weeks, a fresh left common carotid artery lumen thrombus associated with severe plaque burden was found in 50% (10/20) of the mice. Histological analyses indicated that all left common carotid artery lesions had vulnerable features, and 50% (5/10) of the mice showed plaque rupture with a lumen thrombus. Multiple layers with layering discontinuity and intraplaque hemorrhages were found in 80% (8/10) of the mice. Further experiments showed that both increased blood pressure, and angiotensin-II contributed to plaque progression and vulnerability. Decreased intimal collagen associated with increased collagenase activity and matrix metalloproteinase expression also resulted in plaque disruption. Conclusion—We demonstrate a murine model of spontaneous plaque rupture with a high incidence of luminal thrombus. The model not only nicely recapitulates the pathophysiological processes of human plaque rupture but it is also simple, fast, and highly efficient to generate.

The cannabinoid WIN55,212-2 protects against oxidized LDL-induced inflammatory response in murine macrophages

The endocannabinoid system has recently been attracted interest for its anti-inflammatory and anti-oxidative properties. In this study, we investigated the role of the endocannabinoid system in regulating the oxidized low-density lipoprotein (oxLDL)-induced inflammatory response in macrophages. RAW264.7 mouse macrophages and peritoneal macrophages isolated from Sprague-Dawley (SD) rats were exposed to oxLDL with or without the synthetic cannabinoid WIN55,212-2. To assess the inflammatory response, reactive oxygen species (ROS) and tumor necrosis factor alpha (TNF- α) levels were determined, and activation of the mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-kappa B signaling pathways were assessed. We observed that: i) oxLDL strongly induced ROS generation and TNF- α secretion in murine macrophages; ii) oxLDL-induced TNF- α and ROS levels could be lowered considerably by WIN55,212-2 via inhibition of MAPK (ERK1/2) signaling and NF-kappa B activity; and iii) the effects of WIN55212-2 were attenuated by the selective CB2 receptor antagonist AM630. These results demonstrate the involvement of the endocannabinoid system in regulating the oxLDL-induced inflammatory response in macrophages, and indicate that the CB2 receptor may offer a novel pharmaceutical target for treating atherosclerosis.

Retinoid X receptor agonists inhibit phorbol-12-myristate-13-acetate (PMA)-induced differentiation of monocytic THP-1 cells into macrophages

Monocyte/macrophage differentiation is an essential process during atherosclerosis development. The retinoid X receptor (RXR) is a member of the nuclear hormone receptor superfamily, which plays an important regulatory role in many metabolic disorders, including atherosclerosis. The purpose of this study was to investigate the effect of RXR agonist on monocyte/macrophage differentiation in vitro. The THP-1 cell line was differentiated into a macrophage-like phenotype by incubation with phorbol-12-myristate-13-acetate (PMA) in the presence or absence of RXR agonist. The viability of adherent differentiated THP-1 cells was determined by MTT assay. Macrophage surface marker CD11b and CD36 was analyzed by flow cytometry. Phagocytosis was measured by fluorescence-labeled latex beads. The production of Cytokine Tunlornecrosisfactor-α (TNF-α), Interlaken-12p70 (IL-12p70), and Matrix metalloproteinase-9 (MMP-9), each of which was analyzed by ELISA. In the presence of the RXR agonists 9-cis retinoic acid or SR11237, PMA-induced THP-1 cells became less adherent, showed decreased macrophage-like morphological changes, decreased cell surface antigen CD11b and CD36 expression, and down regulated the phagocytosis of latex beads and the production of TNF-α and MMP-9. These data suggest that RXR agonists inhibit PMA-induced THP-1 cell differentiation into macrophage-like cells, which may be helpful in understanding the anti-atherosclerotic effect of RXR and its agonists.

Atorvastatin suppresses inflammatory response induced by oxLDL through inhibition of ERK phosphorylation, IκBα degradation, and COX-2 expression in murine macrophages

Macrophages crosstalk with oxidized low‐density lipoprotein (oxLDL), play a critical role in the initiation, progression, and subsequently stability of atherosclerotic plaques. Statins, inhibitors of HMG CoA (3‐hydroxy‐3‐methylglutaryl coenzyme A) reductase, reduce the expression of inflammatory proteins in addition to their lipid‐lowering action. However, the effect and detailed anti‐inflammation mechanisms of statins in macrophages induced by oxLDL remain unclearly. In the present study, we investigated the effect of atorvastatin on inflammatory response upon oxLDL stimulation in murine macrophages and analyzed the underlying mechanisms. Tumor necrosis factor (TNF)α and monocyte chemoattractant protein‐1 (MCP‐1) mRNA levels were assayed by real‐time PCR. The expression of cyclooxygenases‐2 (COX‐2) was detected by real‐time PCR and Western blotting. While mitogen‐activated protein kinase (MAPK) phosphorylation and IκBα degradation were determined by Western blotting. Our results showed that exposure of RAW264.7 cells to oxLDL, substantially changed the morphology of the cells and increased TNFα and MCP‐1 secretion. While pretreatment with atorvastatin resulted in a significant inhibition of oxLDL‐induced morphological alteration and inflammatory cytokines expression in a dose‐dependent fashion. Further investigation of the molecular mechanism revealed that oxLDL upregulated the transcription and protein expression of COX‐2 in a time‐dependent manner. Whereas, pretreatment with atorvastatin suppressed COX‐2 expression, MAPK activation and IκBα degradation. Thus, we conclude that the anti‐inflammatory effect of atorvastatin is mediated through the inhibition of proinflammatory COX‐2. Furthermore, suppression of ERK phosphorylation and IκBα degradation is involved in this regulation. Our findings provide a novel evidence that statins suppress inflammatory response, exert its anti‐atherogenic actions via against inflammation beyond cholesterol‐lowing effect. J. Cell. Biochem. 113: 611–618, 2012.

Optimal Duration of Dual‐Antiplatelet Therapy Following Drug‐Eluting Stent Implantation: A Meta‐Analysis

Optimal duration of dual‐antiplatelet therapy (DAPT) following drug‐eluting stent (DES) implantation remains uncertain. The aim of this study was to perform a meta‐analysis of trials evaluating the effect of DAPT duration on long‐term clinical outcomes after DES implantation. The authors searched OvidMEDLINE, EMBASE, and the Cochrane Library for both randomized controlled trials and nonrandomized studies that evaluated DAPT duration on long‐term clinical outcomes after DES implantation. The end point was the cumulative incidence of the composite of all‐cause death and nonfatal myocardial infarction (MI) at maximum follow‐up. Quantitative analysis was performed to estimate the pooled hazard ratios (HRs) for the effect of DAPT duration. The pooled effect of DAPT discontinuation before 6 months significantly increased risk of death and nonfatal MI (HR, 1.46; 95% confidence interval, 1.18‐1.80), but DAPT beyond 12 months did not reduce the incidence of the composite end point compared with drug discontinuation at 12 months (HR, 0.91; 95% confidence interval, 0.75‐1.10). In conclusion, the current evidence suggests that 6 to 12 months of DAPT may be optimal after DES implantation.