Melatonin Attenuates Vascular Smooth Muscle Contraction Through the γ-Secretase/Notch Intracellular Domain/Myocardin Pathway.

ABSTRACT: Inositol 1, 4, 5-trisphosphate (IP3) signaling-mediated calcium release drives the contraction of vascular smooth muscles and hence regulates blood vessel volume and blood pressure. Melatonin supplementation has been suggested to be beneficial for hypertension. To determine whether the blood pressure-lowering effect of melatonin was accounted for by IP3 signaling, we evaluated the vasoconstriction response and IP3 signaling in isolated mouse thoracic aortic rings during melatonin incubation. C57BL/6 mice were given intraperitoneal injections daily with melatonin, and the systolic blood pressure and contractility of aortic rings from melatonin-treated mice were decreased, and the contraction suppression effect of melatonin was attributed to the impaired expression of contractile proteins in vascular smooth muscle cells rather than IP3 signaling. Our results further showed that melatonin increased the expression of γ-secretase, which could cleave and release the notch intracellular domain, and the notch intracellular domain prevented the transcription of contractile genes by interfering with the interaction between serum response factor and myocardin, the master regulator of contractile protein. In this article, we report a novel mechanism by which melatonin regulates smooth muscle contractility that does not depend on IP3 signaling.

Pyroptotic cell-derived microparticle: An atherogenic factor in infectious diseases.

Chronic infection is considered a risk factor for atherosclerosis. The link between infectious agents and atherosclerosis is manifested by the presence of infection-induced pyroptotic cells in atherosclerotic lesions. Pyroptosis is an inflammatory form of programmed cell death that occurs most frequently upon infection. However, inflammation is not the only cause by which pyroptosis involved in atherosclerosis. During pyroptosis, a large amount of microparticles are released from pyroptotic cells, which not only transfer inflammatory mediators to arterial vessel, but also mediate the interaction between a variety of cells, leading to endothelial injury, macrophage infiltration, vascular smooth muscle cell migration and proliferation, thereby accelerating atherosclerosis. Thus, we proposed hypothesis that pyroptotic cell-derived microparticle is an atherogenic factor in infectious diseases.

Direct Interaction of Daxx and Androgen Receptor Is Required for Their Regulatory Activity in Cholesterol Biosynthesis.

INTRODUCTION: Homeostasis of cholesterol is crucial for cellular function, and dysregulated cholesterol biosynthesis is a metabolic event that can lead to hepatic and cardiovascular abnormalities. OBJECTIVE: The aim of this study was to investigate the effects and mechanisms of domain-associated protein (Daxx) and androgen receptor (AR) on intracellular cholesterol synthesis. METHODS: HepG2 cells were transfected with pCDNA3.1(+)/Daxx plasmid or treated with testosterone propionate to observe the effects of Daxx and AR on intracellular cholesterol levels. Co-immunoprecipitation experiments were performed to identify the interaction between Daxx and AR and to explore the regulatory effects of this interaction on cholesterol synthesis. RESULTS: Our experiments showed that AR promoted cholesterol synthesis and accumulation by activating sterol-regulatory element-binding protein isoform 2. AR-induced cholesterol synthesis was inhibited by Daxx; however, the expression of AR was not affected. Further studies demonstrated the existence of direct binding between Daxx and AR and this interaction was required to suppress AR activity. CONCLUSIONS: The Daxx-mediated antagonism of AR depicts a more complete picture as to how Daxx regulates intracellular cholesterol level and provides a new target for treatment of atherosclerosis.

Curcumin enhances vascular contractility via induction of myocardin in mouse smooth muscle cells.

A variety of cardiovascular diseases is accompanied by the loss of vascular contractility. This study sought to investigate the effects of curcumin, a natural polyphenolic compound present in turmeric, on mouse vascular contractility and the underlying mechanisms. After mice were administered curcumin (100 mg·kg-1·d-1, ig) for 6 weeks, the contractile responses of the thoracic aorta to KCl and phenylephrine were significantly enhanced compared with the control group. Furthermore, the contractility of vascular smooth muscle (SM) was significantly enhanced after incubation in curcumin (25 µmol/L) for 4 days, which was accompanied by upregulated expression of SM marker contractile proteins SM22α and SM α-actin. In cultured vascular smooth muscle cells (VSMCs), curcumin (10, 25, 50 µmol/L) significantly increased the expression of myocardin, a "master regulator" of SM gene expression. Curcumin treatment also significantly increased the levels of caveolin-1 in VSMCs. We found that as a result of the upregulation of caveolin-1, curcumin blocked the activation of notch1 and thereby abolished Notch1-inhibited myocardin expression. Knockdown of caveolin-1 or activation of Notch1 signaling with Jagged1 (2 µg/mL) diminished these effects of curcumin in VSMCs. These findings suggest that curcumin induces the expression of myocardin in mouse smooth muscle cells via a variety of mechanisms, including caveolin-1-mediated inhibition of notch1 activation and Notch1-mediated repression of myocardin expression. This may represent a novel pathway, through which curcumin protects blood vessels via the beneficial regulation of SM contractility.

Study on the calculation models of bus delay at bays using queueing theory and Markov chain.

Traffic congestion at bus bays has decreased the service efficiency of public transit seriously in China, so it is crucial to systematically study its theory and methods. However, the existing studies lack theoretical model on computing efficiency. Therefore, the calculation models of bus delay at bays are studied. Firstly, the process that buses are delayed at bays is analyzed, and it was found that the delay can be divided into entering delay and exiting delay. Secondly, the queueing models of bus bays are formed, and the equilibrium distribution functions are proposed by applying the embedded Markov chain to the traditional model of queuing theory in the steady state; then the calculation models of entering delay are derived at bays. Thirdly, the exiting delay is studied by using the queueing theory and the gap acceptance theory. Finally, the proposed models are validated using field-measured data, and then the influencing factors are discussed. With these models the delay is easily assessed knowing the characteristics of the dwell time distribution and traffic volume at the curb lane in different locations and different periods. It can provide basis for the efficiency evaluation of bus bays.

Ezetimibe-mediated protection of vascular smooth muscle cells from cholesterol accumulation through the regulation of lipid metabolism-related gene expression.

BACKGROUND: Ezetimibe is a potent inhibitor of Niemann-Pick type C1-Like 1 and has been approved for the treatment of hypercholesterolemia. Our preliminary study showed that ezetimibe promotes cholesterol efflux from vascular smooth muscle cells (VSMCs). Our aim was to investigate the cellular mechanisms underlying the ezetimibe actions. METHODS AND RESULTS: Rat VSMCs were converted to foam cells by incubation with cholesterol:methyl-ß-cyclodextrin. The intracellular free cholesterol, total cholesterol, and the ratio of cholesteryl ester to total cholesterol were decreased after the incubation of VSMCs with different concentrations of ezetimibe (3, 10, 30, and 30 µmol/l) or treated with 30 µmol/l of ezetimibe for different time periods (6, 12, 24, and 48 h). Our results also showed that the expression of caveolin-1, liver X receptor α, and ATP-binding cassette transporter ABCA1 was enhanced, but the expression of nSREBP-1c was decreased in a concentration- and time-dependent manner. RNA interference was used to determine the roles of caveolin-1 and SREBP-1 in the lipid-lowering effect of ezetimibe. The results showed that caveolin-1 was involved in the regulation of intracellular cholesterol content, and the expression of caveolin-1 was repressed by SREBP-1. CONCLUSION: The present study indicates that ezetimibe protects VSMCs from cholesterol accumulation by regulating the expression of lipid metabolism-related genes.

[Correlation of CpG methylation status of Runx3 with pathogenesis of gastric carcinoma].

OBJECTIVE: To investigate the role of Runx3 gene CpG island methylation in the development of human gastric carcinoma. METHODS: A total of 150 tumor specimens from patients with gastric carcinoma and 50 normal tissue specimens were selected. Methylation specific PCR (MSP) and pyrosequencing (PS) were used to detect the methylation status of Runx3 gene promoter. RESULTS: Compared to normal tissue samples, a significant increase of CpG island methylation status of Runx3 gene was observed in gastric carcinomas (MSP: 67.3% vs. 40.0%, P = 0.002; PS: 76.0% vs. 30.0%, P < 0.01). Runx3 gene methylation was only related to tumor size (P < 0.05) based on MSP analysis. PS test however showed that the extent of methylation of Runx3 gene was related to the tumor size (P = 0.004), Lauren's classification (P = 0.043), depth of invasion (P < 0.01), lymph node metastasis (P = 0.021) and TNM staging (P = 0.045). CONCLUSIONS: Methylation status of Runx3 gene detectable by PS is closely correlated with clinicopathological parameters of gastric carcinoma, including tumor size, Lauren's classification, depth of invasion, lymph node metastasis and TNM staging. PS is more sensitive than MSP in the detection of Runx3 gene methylation, which may serve as an important marker for early diagnosis and treatment of gastric carcinoma.

[A 3-year-follow-up study on the prognosis of 'two-route chemotherapy' on liver cancer patients with portal vein tumor thrombus].

OBJECTIVE: To study the achievements and safety of Transcatheter arterial chemoembolization (TACE) associated Portal Vein Chemo-therapy (PVC) per-drug delivery system (DDS) program in preventing the recurrence of hepatic cell cancer (HCC) and Portal Vein Tumor Thrombus (PVTT). METHODS: 97 cases with HCC and PVTT were treated from January 2009 to January 2011. Patients with tumor or tumor thrombus were resected on all the cases and randomly divided into 3 groups. TACE, PVC per-DDS TACE and PVC per-DDS were given to group A, group B, and group C, respectively. Patients in the 3 groups were followed and compared on the Disease Free Survivals (DFS) and the accumulative survival rates, at 6 months, 1 year and 2 years after the operation. RESULTS: After the surgery was completed in June, the 1-year, 2-year, 3-year survival rates and cumulative survival rate in group C was higher than in group A or group. Significant differences did not appear in June but did show in 1 year after the surgery (P > 0.05) as well as in both 2 and 3 years, after the surgery (P < 0.01). CONCLUSION: Patients with HCC and PVTT, the TACE chemotherapy in association with PVC per-DDS could increase both the DFSs and accumulative survival rates, when compared to the either single TACE or PVC per-DDS, after the tumor or tumor thrombus were resected.

Angiopoietin-1 protects myocardial endothelial cell function blunted by angiopoietin-2 and high glucose condition.

AIM: To evaluate the effects of angiopoietin-1 (Ang-1) on myocardial endothelial cell function under high glucose (HG) condition. METHODS: Mouse heart myocardial endothelial cells (MHMECs) were cultured and incubated under HG (25 mmol/L) or normal glucose (NG, 5 mmol/L) conditions for 72 h. MTT was used to determine cellular viability, and TUNEL assay and caspase-3 enzyme linked immunosorbent assays were used to assay endothelial apoptosis induced by serum starvation. Immunoprecipitation and Western blot analysis were used to analyze protein phosphorylation and expression. Endothelial tube formation was used as an in vitro assay for angiogenesis. RESULTS: Exposure of MHMECs to HG resulted in dramatic decreases in phosphorylation of the Tie-2 receptor and its downstream signaling partners, Akt/eNOS, compared to that under NG conditions. Ang-1 (250 ng/mL) increased Tie-2 activation, inhibited cell apoptosis, and promoted angiogenesis. Ang-1-mediated protection of endothelial function was blunted by Ang-2 (25 ng/mL). CONCLUSION: Ang-1 activates the Tie-2 pathway and restores hyperglycemia-induced myocardial microvascular endothelial dysfunction. This suggests a protective role of Ang-1 in the ischemic myocardium, particularly in hearts affected by hyperglycemia or diabetes.

Caveolae and caveolin-1 mediate endocytosis and transcytosis of oxidized low density lipoprotein in endothelial cells.

AIM: To explore the mechanisms involved in ox-LDL transcytosis across endothelial cells and the role of caveolae in this process. METHODS: An in vitro model was established to investigate the passage of oxidized low density lipoprotein (ox-LDL) through a tight monolayer of human umbilical vein endothelial cells (HUVEC) cultured on a collagen-coated filter. Passage of DiI-labeled ox-LDL through the monolayer was measured using a fluorescence spectrophotometer. The uptake and efflux of ox-LDL by HUVEC were determined using fluorescence microscopy and HPLC. RESULTS: Caveolae inhibitors - carrageenan (250 µg/mL), filipin (5 µg/mL), and nocodazole (33 µmol/L)-decreased the transport of ox-LDL across the monolayer by 48.9%, 72.4%, and 79.8% as compared to the control group. In addition, they effectively decreased ox-LDL uptake and inhibited the efflux of ox-LDL. Caveolin-1 and LOX-1 were up-regulated by ox-LDL in a time-dependent manner and decreased gradually after depletion of ox-LDL (P<0.05). After treatment HUVEC with ox-LDL and silencing caveolin-1, NF-κB translocation to the nucleus was blocked and LOX-1 expression decreased (P<0.05). CONCLUSION: Caveolae can be a carrier for ox-LDL and may be involved in the uptake and transcytosis of ox-LDL by HUVEC.