MicroRNA-17-5p mediates hypoxia-induced autophagy and inhibits apoptosis by targeting signal transducer and activator of transcription 3 in vascular smooth muscle cells.

The aim of the present study was to investigate hypoxia-induced apoptosis and autophagy in vascular smooth muscle cells (VSMCs) and the underlying molecular mechanisms of microRNA (miR)-17-5p responses in an anaerobic environment. The results revealed that miR-17-5p expression was significantly upregulated in VSMCs subjected to hypoxic conditions (P<0.05) and lower miR-17-5p levels were observed in ethyl 3,4-dihydroxybenzoate-treated and hypoxia inducible factor-1 loss-of-function cells. Additionally, it was demonstrated that miR-17-5p is associated with hypoxia-induced autophagy, which was confirmed by upregulating the light chain 3-II/LC3-I ratio and downregulating nucleoporin p62. Cell apoptosis was inhibited in response to hypoxia, and levels of pro-apoptotic proteins B-cell lymphoma 2-associated X protein and p-caspase were markedly decreased when VSMCs were subjected to hypoxic conditions. Furthermore, expression of signal transducer and activator of transcription 3 (STAT3) decreased when cells were transfected with overexpressing miR-17-5p and subjected to hypoxic conditions, and the combination of miR-17-5p loss-of-function and hypoxia induced greater upregulation in the protein expression of STAT3 compared with a single treatment for hypoxia in VSMCs. In conclusion, miR-17-5p may be a novel hypoxia-responsive miR and hypoxia may induce protective autophagy and anti-apoptosis in VSMCs by targeting STAT3.

Rosiglitazone attenuates myocardial remodeling in spontaneously hypertensive rats.

Rosiglitazone, an important peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, improves left ventricular (LV) hypertrophy in diet-induced hypercholesterolemic rats. However, the effects and underlying mechanisms of rosiglitazone on myocardial remodeling in spontaneous hypertension rats (SHRs) are unclear. Twenty male 8-week-old SHRs were randomly divided into two groups: one treated with oral saline (n=10) and the other treated with rosiglitazone (5 mgkg(-1)day(-1), n=10). Ten age-matched Wistar-Kyoto rats were selected as a normal control group. Echocardiography, immunohistochemistry, real-time reverse transcriptase-PCR and western blot analysis were performed to assess the effects of rosiglitazone. After 16 weeks of treatment, LV hypertrophy was significantly attenuated by rosiglitazone (LV weight/body weight, 2.35±0.11 vs. 2.56±0.14 mgg(-1)). According to the echocardiography results, thickening of the LV wall was reduced, and mid-wall fractional shortening was improved by rosiglitazone. Similarly, the excessive collagen deposition and upregulation of collagen I and collagen III seen in SHRs receiving saline were significantly attenuated in SHRs receiving rosiglitazone. In addition, rosiglitazone treatment increased the activity of matrix metalloproteinase-9 (MMP-9) and normalized the MMP-9/tissue inhibitor of metalloproteinase-1 ratio. Furthermore, activator protein-1 (AP-1) activation and nuclear factor-kappa B (NF-κB) expression were suppressed in the rosiglitazone-treated group. These results demonstrate that the PPAR-γ agonist rosiglitazone had beneficial effects on myocardial remodeling in SHRs by way of decreasing AP-1 activation and NF-κB expression, which may help in further inhibiting transcription of the downstream genes involved in the pathogenesis of myocardial remodeling induced by hypertension.

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- alpha) 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- alpha secretion in murine macrophages; ii) oxLDL-induced TNF- alpha 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.

Effects and mechanisms of PPARalpha activator fenofibrate on myocardial remodelling in hypertension.

Although peroxisome proliferator-activated receptor alpha (PPARalpha) is highly expressed in the heart, the effects of PPARalpha on cardiac remodelling and the underlying mechanisms are unclear. The present study was undertaken to test the hypothesis that PPARalpha activator fenofibrate plays a key role in left ventricular hypertrophic remodelling via the formation of c-fos/c-jun heterodimers in spontaneous hypertensive rats (SHRs). Twenty-four male 8-week-old SHRs were randomly divided into two groups, one group treated with oral saline (n= 10) and another treated with oral fenofibrate (60 mg.kg-1.d-1, n= 14). Ten same-aged Wistar-Kyoto (WKY) rats were selected as a normal control group. Using echocardiography, immunohistochemistry, co-immunoprecipitation, Western blot analysis and real-time RT-PCR, we showed that the left ventricular wall thickness and significantly reduced and left ventricular diastolic function improved in SHRs treated with fenofibrate compared with SHRs treated with saline. Similarly, the excessive collagen deposition and the up-regulation of collagen I, collagen III, c-fos and c-jun seen in SHRs receiving saline were significantly attenuated in SHRs receiving fenofibrate. In addition, fenofibrate markedly decreased the expression of AP-1 and c-fos/c-jun heterodimers (P < 0.01). These results demonstrated that PPARalpha activator fenofibrate may exert a protective effect on cardiac remodelling in SHRs by decreasing the expression of c-fos and c-jun and suppressing the formation of c-fos/c-jun heterodimers, which may further inhibit transcription of the downstream genes involved in the pathogenesis of left ventricular hypertrophy induced by hypertension.