Retinoid X receptor agonists alleviate fibroblast activation and post-infarction cardiac remodeling via inhibition of TGF-ß1/Smad pathway.

Retinoid X receptor (RXR), particularly RXRα, has been implicated in cardiovascular diseases. However, the functional role of RXR activation in myocardial infarction (MI) remains unclear. This study aimed to determine the effects of RXR agonists on MI and to dissect the underlying mechanisms. Sprague-Dawley (SD) rats were subjected to MI and then treated (once daily for 4 weeks) with either RXR agonist bexarotene (10 or 30 mg/kg body weight) or vehicle. Heart function was determined using echocardiography and cardiac hemodynamic measurements. Four weeks post MI, myocardial tissues were collected to evaluate cardiac remodeling. Primary cardiac fibroblasts (CFs) were treated with or without RXR ligand 9-cis-RA followed by stimulation with TGF-ß1. Immunoblot, immunofluorescence, and co-immunoprecipitation were performed to elucidate the regulatory role of RXR agonists in TGF-ß1/Smad signaling. In vivo treatment with Bexarotene moderately affects systemic inflammation and apoptosis and ameliorated left ventricular dysfunction after MI in rat model. In contrast, bexarotene significantly inhibited post-MI myocardial fibrosis. Immunoblot analysis of heart tissue homogenates from MI rats revealed that bexarotene regulated the activation of the TGF-ß1/Smad signaling pathway. In vitro, 9-cis-RA inhibited the TGF-ß1-induced proliferation and collagen production of CFs. Importantly, upon activation by 9-cis-RA, RXRα interacted with p-Smad2 in cytoplasm, inhibiting the TGF-ß1-induced nuclear translocation of p-Smad2, thereby negatively regulating TGF-ß1/Smad signaling and attenuating the fibrotic response of CFs. These findings suggest that RXR agonists ameliorate post-infarction myocardial fibrosis, maladaptive remodeling, and heart dysfunction via attenuation of fibrotic response in CFs through inhibition of the TGF-ß1/Smad pathway activation.

Retinoid X receptor agonists inhibit hypertension-induced myocardial hypertrophy by modulating LKB1/AMPK/p70S6K signaling pathway.

BACKGROUND: Retinoid X receptor (RXR) has been demonstrated to play an important role in cardiac development and has been implicated in cardiovascular diseases. This study aimed to examine the effects of RXRα agonist bexarotene on pathological left ventricular hypertrophy (LVH) in a spontaneously hypertensive rat (SHR) model and the underlying mechanism. METHODS: WKY rats served as controls. SHRs were randomized into 3 groups at the age of 4 weeks and were treated (once daily for 12 weeks) with either bexarotene (30 or 100mg/kg body weight) or vehicle alone. Echocardiography was performed to determine cardiac structure and function. Neonatal cardiomyocytes were treated with AngII (10(-7) mmol/L) with or without the indicated concentration of RXRα ligand 9-cis-RA. The protein abundances of ß-actin, RXRα, LKB1, phospho-LKB1, AMPK, phospho-AMPK, P70S6K, phospho-P70S6K, ACE, and AT1 receptor were measured along with blood pressure, body weight and angiotensin II (Ang II) levels. The effects of LKB1 downregulation by LKB1 small, interfering RNA were examined. RESULTS: Treatment of SHRs with bexarotene resulted in significant inhibition of LVH without eliminating hypertension. Immunoblot with heart tissue homogenates from SHRs revealed that bexarotene activated the LKB1/AMPK signaling pathway and inhibited p70S6K. However, the increased Ang II levels in SHR serum and heart tissue were not reduced by bexarotene treatment. Treatment of cardiomyocytes with Ang II resulted in significantly reduced LKB1/AMPK activity and increased p70S6K activity. 9-cis-RA antagonized Ang II-induced LKB1/AMPK and p70S6K activation changes in vitro. CONCLUSIONS: RXR agonists prevent the inhibition of the LKB1/AMPK/p70S6K pathway and regulate protein synthesis to reduce LVH. This antihypertrophic effect of bexarotene is independent of blood pressure.

Metformin reduces vascular endothelial dysfunction caused by an acute glucose load in patients with hypertension.

BACKGROUND: To investigate the effects of a single dose of metformin (MF) on endothelium-dependent vasodilatation and serum antioxidant and free fatty acid levels in patients with primary hypertension (PH) after an acute glucose load. MATERIALS AND METHODS: Patients with untreated PH were randomized to a no-metformin group (PH, n = 34) and a metformin group (PH+ MF, n = 28) who received a single dose of 500 mg metformin before testing. Healthy volunteers (n = 31) served as a control group. Brachial artery endothelium-dependent flow-mediated vasodilatation (FMD) was determined at 0, 1, 2 and 3 h after glucose load. Levels of serum superoxide dismutase (SOD), total antioxidant capacity (T-AOC), anti-superoxide anion free radical (AntiO2) and free fatty acids (FFA) were measured. RESULTS: The FMD in the PH group decreased significantly 1 h after glucose load (PH: 10.9 ± 2.9% vs 13.67 ± 3.42% before glucose load). Metformin inhibited the effects of glucose load on FMD. At 1 h after acute glucose load, the concentrations of SOD, T-AOC and AntiO2 in the PH group decreased significantly compared with their fasting levels, and metformin inhibited the acute glucose load-induced decline in SOD and T-AOC levels. CONCLUSIONS: Metformin can prevent transient endothelial dysfunction caused by acute glucose load in patients with PH.

Effects of combined glucose and fat load on endothelium-dependent brachial artery vasodilatation in hypertensive patients.

INTRODUCTION: This study investigated the effects of combined glucose and fat load on glucose and lipid metabolism, as well as on vascular endothelial function, in hypertensive patients. METHODS AND RESULTS: A total of 98 hypertensive patients were randomly divided into 3 groups that received an oral fat tolerance test (OFTT), an oral glucose tolerance test (OGTT) or a combined oral glucose and fat tolerance test (OGFTT). Endothelium-dependent flow-mediated brachial artery dilation (FMD) was measured by vascular ultrasound and was used as an indicator of vascular endothelial function. There were no significant differences in demographics or clinical characteristics among the 3 groups before the study. Immediately after the OGFTT, the serum triglyceride levels and the area under the curve for serum glucose in the OGFTT group were not significantly different from those in the other 2 groups. However, the 1-hour FMD in the OGFTT group was significantly reduced compared with that of the OGTT group (5.45 ± 0.75 versus 9.46 ± 1.32, P < 0.05), and the 4-hour FMD in the OGFTT group was also significantly reduced compared with the OFTT group (8.56 ± 1.09 versus 9.76 ± 2.00, P < 0.05). CONCLUSION: A combined glucose and fat load has a cumulative effect on vascular endothelial dysfunction in hypertensive patients.

[Association between high sensitivity C-reactive protein and contrast induced acute kidney injury in patients with acute coronary syndrome undergoing percutaneous coronary intervention: impact of atorvastatin].

OBJECTIVE: To observe the association between preprocedural high sensitivity C-reactive protein (hs-CRP) level and incidence of contrast induced acute kidney injury (CI-AKI) in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) and the impact of atorvastatin pretreatment on CI-AKI. METHODS: According to the level of preprocedural hs-CRP, 270 ACS patients were divided into three groups: high hs-CRP group (hs-CRP ≥ 3 mg/L, n = 176), moderate hs-CRP group (hs-CRP 1-3 mg/L, n = 60) and normal hs-CRP group (hs-CRP < 1 mg/L, n = 34). According to the dosage of preprocedural atorvastatin, the high hs-CRP group was further divided into 10 mg group (n = 49), 20 mg group (n = 66) and 40 mg group (n = 61). Serum creatinine (Scr), blood urea nitrogen (BUN), cystatin C (Cys C), hs-CRP were measured at before and 24 hours, 48 hours after PCI. CCr and GFR were calculated according to Scr and Cys C. Risk factors for CI-AKI were determined by multivariate logistic regression analysis. RESULTS: (1) Cys C was significantly increased and GFR after PCI significantly reduced in high and moderate hs-CRP groups compared with normal hs-CRP group (P < 0.05). (2) Incidence of CI-AKI was 43.18%, 38.33%, 20.59% in high, moderate and normal hs-CRP groups, respectively (P < 0.05). (3) In high hs-CRP group, postprocedural GFR was significantly higher while postprocedural Cys C and hs-CRP were significantly lower in 40 mg statin subgroup than 10 mg and 20 mg statin subgroups (P < 0.05), similar trends were documented when comparing 20 mg statin subgroup with 10 mg statin subgroup (P < 0.05). (4) Multivariate logistic regression analysis showed that pretreatment with high dose atorvastatin was a protective factor for post CI-AKI (20 mg atorvastatin: OR = 0.15, 95%CI 0.06 - 0.33, P = 0.001; 40 mg atorvastatin: OR = 0.10, 95%CI 0.04 - 0.23, P = 0.001), while high levels of preprocedural hs-CRP (OR = 2.06, 95%CI 1.01 - 4.23, P = 0.048), diabetes mellitus (OR = 10.71, 95%CI 5.29 - 21.70, P = 0.001), advanced age (OR = 2.64, 95%CI 1.05 - 6.63, P = 0.038) and renal failure (OR = 5.14, 95%CI 1.13 - 23.39, P = 0.034) were independent risk factors of CI-AKI. CONCLUSION: High hs-CRP level is linked with the development of CI-AKI in ACS patients undergoing PCI and pretreatment with 40 mg atorvastatin is associated with lower incidence CI-AKI, possibly by reducing the postprocedural inflammation responses.

[Impact of acute glucose and fat loading on endothelium dependent vasodilation in patients with essential hypertension].

OBJECTIVE: To explore the influence of acute glucose and fat loading on endothelium dependent flow-mediated vasodilation (FMD) in patients with essential hypertension (EH). METHODS: Patients with EH were randomly divided into three groups: oral glucose loading alone (n = 26), oral standardized fat loading alone (n = 38), combined glucose and fat loading (n = 34). FMD of the brachial artery was assessed by high resolution ultrasound technique respectively. RESULTS: (1) Compared to control group, postprandial abnormal serum triglyceride metabolism was evidenced and FMD was significantly reduced and the lowest FMD occurred at 4 hours and returned to the baseline level at 8 hours post fat loading alone in EH patients. (2) GS-AUC and 1 hour glucose were significantly higher in EH patients than in controls (all P < 0.05), FMD was also significant decreased (-31.4%) at 1 hour and returned to baseline level at 2 hours post oral glucose loading. (3) After combined glucose and fat loading, FMD at 1 hour (5.45 ± 1.93 vs. 9.46 ± 3.33, P < 0.05) was significantly lower than that in glucose loading alone and FMD at 4 hours (7.98 ± 1.64 vs. 9.66 ± 2.26, P < 0.05), was also lower than that in fat loading alone in EH patients. (4) FMD was negatively correlated with SBP, GS-AUC, DBP, TG-AUC (γ = -0.46, -0.44, -0.41, -0.38, respectively, all P < 0.05). CONCLUSION: Combined glucose and fat loading additively reduced FMD in hypertensive patients.

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-alpha (TNF-alpha), 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-alpha 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.

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.