L-Arginine Supplementation Improves Vascular Endothelial Dysfunction Induced by High-Fat Diet in Rats Exposed to Hypoxia.

INTRODUCTION: Our previous study showed that high-fat diet inhibited the increase in nitric oxide and endothelial nitric oxide synthase expression in the aortic endothelium of rats exposed to hypoxia, and hypoxia plus a high-fat diet led to earlier and more severe vascular endothelial dysfunction (VED) than hypoxia alone. The purpose of the present study was to investigate the effects of L-arginine on high-fat diet-induced VED of rats in hypoxia. METHODS: Forty male Sprague-Dawley rats were randomly divided into 4 groups and treated with hypoxia (H group), hypoxia plus high-fat diet (H+HFD group), hypoxia plus L-arginine (H+L-Arg group), and hypoxia plus high-fat diet and L-arginine (H+HFD+L-Arg group) for 1 wk. Hypoxia was simulated in a hypobaric chamber with an altitude of 5000 m. Aortic morphology and endothelium-dependent vasorelaxation were used to assess VED. RESULTS: High-fat diet impaired vascular remodeling and reduced endothelium-dependent vasodilator response to acetylcholine in rats exposed to hypoxia, secondary to dysregulation of the nitric oxide pathway. L-arginine supplementation significantly increased plasma nitrates and nitrites and endothelial nitric oxide synthase mRNA levels and improved ultrastructural changes in aortic endothelium and endothelium-dependent vasodilator response. CONCLUSIONS: L-arginine prevents aortic ultrastructural changes and reverses VED induced by high-fat diet in rats exposed to hypoxia, which may have implications for VED induced by high-fat diet in high altitude dwellers.

A meta-analysis of the safety and efficacy of bosentan therapy combined with prostacyclin analogues or phosphodiesterase type-5 inhibitors for pulmonary arterial hypertension.

Bosentan is an effective drug for the treatment of pulmonary arterial hypertension (PAH). The aim of the present meta-analysis was to examine the evidence concerning the efficacy and safety of bosentan therapy combined with prostacyclin analogues or phosphodiesterase type 5 (PDE-5) inhibitors for treating PAH. Eligible published studies were collected from Embase, PubMed, The Cochrane Library and the www.clinicaltrials.gov website. Heterogeneity was assessed using the Cochran Q-statistic test. Results were presented as risk ratios or mean differences with 95% confidence intervals (CI). A total of five studies, comprising 310 patients were included for analysis. No significant improvements in six-minute walk distance (6MWD; mean difference, 16.43 m), clinical worsening (risk ratio, 0.54) and the World Health Organization functional classification (class I: risk ratio, 1.17; class II: risk ratio, 1.18) were observed in patients treated with bosentan in combination with prostacyclin analogues or PDE-5 inhibitors. However, a significant reduction in the mean pulmonary artery pressure (mPAP; 95% CI: -17.06, -6.83; P<0.0001) following bosentan combination therapy was observed. Comparisons of adverse event rates in the bosentan combination therapy (55.6%) and monotherapy (51.8%) suggested that there is no reduction in adverse events (risk ratio, 1.10). The results indicated that bosentan combined with prostacyclin analogues or PDE-5 inhibitors may not improve 6MWD, cardiac function, clinical worsening and adverse events. However, bosentan combined with prostacyclin analogues or PDE-5 inhibitor therapy was able to significantly reduce mPAP compared with the effect of bosentan monotherapy.

Crocin attenuates acute hypobaric hypoxia-induced cognitive deficits of rats.

This study investigated whether crocin exerted neuroprotective effects against acute hypobaric hypoxia at high altitude in vivo and determined the underlying mechanisms. Male Sprague-Dawley rats were randomly assigned to a normoxic group，a hypoxic group, and three crocin groups at three different doses. The rats were transferred from 50m to 4200m for 3 days after treatment with crocin for 3 days. The learning and memory of the rat were evaluated with the Morris water maze test. Transmission electron microscope (TEM) was used to analyze the changes in the ultrastructure of hippocampal neurons. Peroxisome proliferator-activated receptor-γ co-activator 1α (PGC-1α) and sirtuin-1 (SIRT1) levels were determined using immunohistochemical staining and western blotting. The escape latency of the crocin group was shorter than that of the hypoxic group, while the frequency of the rats reaching the platform was significantly higher in the crocin group. The structures of nerve cells and mitochondria were destroyed in the hypoxic group, but were repaired in the crocin groups. The expressions of PGC-1α and SIRT1 were decreased in the hypoxic group, but were increased in the crocin group. All the effects improved by crocin were dose-dependent. Crocin attenuates acute hypobaric hypoxia-induced cognitive deficits in rats, accompanied by repairing the structures of hippocampal neurons and improving PGC-1α and SIRT1 levels.

Effects of the aqueous extract of a Tibetan herb, Rhodiola algida var. tangutica on proliferation and HIF-1α, HIF-2α expression in MCF-7 cells under hypoxic condition in vitro.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhodiola algida var. tangutica is a traditional Tibetan herb. Its root and rhizome have been successfully used as an effective clinical remedy for the prevention and treatment of cancer and high-altitude sickness. This study aimed to investigate the effect of Rhodiola algida var. tangutica on hypoxic MCF-7 breast cancer cells and the underlying mechanisms. MATERIALS AND METHODS: The antiproliferative effects of R. algida on MCF-7 breast cancer cells were compared in vitro under hypoxic and normal conditions by using MTT analysis. The influence of R. algida on cancer cell apoptosis was determined by flow cytometry. The expression levels of hypoxia-inducible factor (HIF)-1α and HIF-2α were evaluated by western blot analysis. RESULTS: R. algida inhibited the proliferation of MCF-7 breast cancer cells in a dose- and time-dependent manner. The results of flow cytometry indicated that the antiproliferative effect of R. algida was mediated by apoptosis induction. Pretreatment with R. algida significantly suppressed the hypoxia-induced proliferation and expression of HIF-1α and HIF-2α in MCF-7 breast cancer cells. CONCLUSIONS: R. algida might exert an anti-carcinogenic effect on MCF-7 breast cancer cells by decreasing the protein levels of HIF-1α and HIF-2α, which are overexpressed under hypoxic conditions. This effect might be elicited by inhibiting the hypoxia-induced proliferation of MCF-7 breast cancer cells.

Echinacoside induces rat pulmonary artery vasorelaxation by opening the NO-cGMP-PKG-BKCa channels and reducing intracellular Ca2+ levels.

AIM: Sustained pulmonary vasoconstriction as experienced at high altitude can lead to pulmonary hypertension (PH). The main purpose of this study is to investigate the vasorelaxant effect of echinacoside (ECH), a phenylethanoid glycoside from the Tibetan herb Lagotis brevituba Maxim and Cistanche tubulosa, on the pulmonary artery and its potential mechanism. METHODS: Pulmonary arterial rings obtained from male Wistar rats were suspended in organ chambers filled with Krebs-Henseleit solution, and isometric tension was measured using a force transducer. Intracellular Ca(2+) levels were measured in cultured rat pulmonary arterial smooth muscle cells (PASMCs) using Fluo 4-AM. RESULTS: ECH (30-300 µmol/L) relaxed rat pulmonary arteries precontracted by noradrenaline (NE) in a concentration-dependent manner, and this effect could be observed in both intact endothelium and endothelium-denuded rings, but with a significantly lower maximum response and a higher EC50 in endothelium-denuded rings. This effect was significantly blocked by L-NAME, TEA, and BaCl2. However, IMT, 4-AP, and Gli did not inhibit ECH-induced relaxation. Under extracellular Ca(2+)-free conditions, the maximum contraction was reduced to 24.54%±2.97% and 10.60%±2.07% in rings treated with 100 and 300 µmol/L of ECH, respectively. Under extracellular calcium influx conditions, the maximum contraction was reduced to 112.42%±7.30%, 100.29%±8.66%, and 74.74%±4.95% in rings treated with 30, 100, and 300 µmol/L of ECH, respectively. After cells were loaded with Fluo 4-AM, the mean fluorescence intensity was lower in cells treated with ECH (100 µmol/L) than with NE. CONCLUSION: ECH suppresses NE-induced contraction of rat pulmonary artery via reducing intracellular Ca(2+) levels, and induces its relaxation through the NO-cGMP pathway and opening of K(+) channels (BKCa and KIR).

Antiproliferative effect of echinacoside on rat pulmonary artery smooth muscle cells under hypoxia.

The main purpose of this study is to evaluate the effect of echinacoside (ECH) on hypoxia-induced proliferation of rat pulmonary artery smooth muscle cells (PASMCs) and the underlying mechanism. PASMCs were incubated under normoxia (nor), hypoxia (hyp), hypoxia + 0.35 mM ECH (hyp + ECH0.35), or hypoxia + 0.4 mM ECH (hyp + ECH0.4) for 24 h. Cell viability was assessed by MTS assays. The morphology of apoptosis was observed by DAPI staining, and apoptosis was quantified by flow cytometric analysis. Caspase-3 activity was determined by immunohistochemistry and real-time PCR, and the expressions of HIF-1α, Bax, Bcl-2, and Fas were determined by real-time PCR. Hypoxia induced significant proliferation of PASMCs, which could be inhibited by ECH in a concentration-dependent manner. This was associated with apoptosis of PASMCs. Z-DEVD-FMK could partly reduce the suppression effect of ECH; protein and gene expression of caspase-3 were significantly higher in the hyp + ECH0.4 and hyp + ECH0.35 groups. ECH significantly increased the expressions of Bax and Fas, but decreased the expressions of Bcl-2 and HIF-1α. ECH could inhibit hypoxia-induced proliferation of rat PASMCs, which is associated with apoptosis of PASMCs and improvement of hypoxia. ECH might be a potential agent for prevention and treatment of hypoxia-induced PAH.

[Legionella pneumophila lvgA and Hsp60 gene splicing and the fusion gene expression in E.coli].

OBJECTIVE: To fuse Legionella virulence gene (lvgA) with heat shock protein 60 gene (Hsp60) by PCR and detect the fusion gene expression in E.coli. METHODS: The fragments of lvgA and Hsp60 genes having matching sequences at their ends to be fused were amplified from the genomic DNA of Legionella pneumophila by PCR, and the PCR products were mixed, denatured, reannealed, so that the strands with matching sequences at their 3' ends overlapped to serve as primers for each other. Extension of this overlap by DNA polymerase produced recombinant products. After amplification with outer primers, sufficient product of the fusion gene was harvested, which was inserted into the prokaryotic expression vector pGEX-4T-1 to construct the prokaryotic expression recombinant plasmid. After identification with restriction enzyme analysis, polymerase chain reaction and nucleotide sequence analysis, the E.coli BL21 containing the recombinant plasmid pGlvgA/Hsp60 was induced with IPTG and the expression of lvgA/Hsp60 was detected by SDS-PAGE and Western blot analysis. RESULTS: The lvgA/Hsp60 fusion gene of 2,292 bp was amplified and the recombinant plasmid pGlvgA/Hsp60 was constructed successfully. A 117-kD GST-lvgA-Hsp60 fusion protein was detected in the E.coli containing the recombinant plasmid. CONCLUSION: The recombinant plasmid for Legionella pneumophila lvgA/Hsp60 fusion gene is constructed successfully and this fusion protein can be expressed in prokaryotic cells efficiently, which make possible the immunological characterization of this fusion gene.