Sai Wang Seto

Angiogenic effect of saponin extract from Panax notoginseng on HUVECs in vitro and zebrafish in vivo

Angiogenesis plays an important role in a wide range of physiological processes such as wound healing and fetal development. In fact, many diseases are associated with imbalance in the regulation of angiogenesis in which there is either excessive or insufficient blood vessel formation. Panax notoginseng, a blood circulation invigorating herb, is commonly used in traditional Chinese medicine to treat circulation‐related diseases. However, the biological effects of saponin extract from Panax notoginseng (PNS) on angiogenesis and the underlying mechanisms are yet to be fully elucidated. This investigation describes the angiogenic effects of PNS on human umbilical vein endothelial cells (HUVECs) in vitro and zebrafish in vivo. The 2,3‐bis(2‐methoxy‐4‐nitro‐5‐sulfophenyl)5[(phenylamino)carbonyl]2H‐tetrazolium hydroxide (XTT) assay and microscopic cell counting demonstrated that the extract was able to stimulate the proliferation of HUVECs. Meanwhile, the numbers of invaded cells and tube branches were significantly increased in PNS treatment groups. PNS was also shown to promote changes in the subintestinal vessels, a feature of angiogenesis, in zebrafish. In addition, by using real‐time polymerase chain reaction (PCR), PNS was found to enhance vascular endothelial growth factor (VEGF) and kinase‐domain region/fetal liver kinase‐1 in mice (KDR/Flk‐1) mRNA expression, and the PNS‐induced HUVECs proliferation could be abolished by a KDR/Flk‐1 inhibitor. Furthermore, the proliferation of HUVECs induced by PNS was significantly attenuated by inhibitors of PI3K‐Akt‐eNOS. All the results suggest that PNS can promote angiogenesis, and that the proangiogenic effects involve the VEGF‐KDR/Flk‐1 and PI3K‐Akt‐eNOS signaling pathways. Copyright

Formononetin, an isoflavone, relaxes rat isolated aorta through endothelium-dependent and endothelium-independent pathways

We evaluated the vasorelaxation effects of formononetin, an isoflavone/phytoestrogen found abundantly in Astragalus mongholicus Bunge, on rat isolated aorta and the underlying mechanisms involved. Cumulative administration of formononetin, genistein, daidzein and biochanin A relaxed phenylephrine-preconstricted aorta. Formononetin and biochanin A caused a similar magnitude of relaxation whereas daidzein was least potent. Mechanical removal of endothelium, L-NAME (100 microM) and methylene blue (10 microM) suppressed formononetin-induced relaxation. Formononetin increased endothelial nitric oxide (NO) synthase (eNOS), but not inducible NO synthase, activity with an up-regulation of eNOS mRNA and p-eNOS(Ser1177) protein expression. In endothelium-denuded preparations, formononetin-induced vasorelaxation was significantly reduced by glibenclamide (3 microM) and iberiotoxin (100 nM), and a combination of glibenclamide (3 microM) plus iberiotoxin (100 nM) abolished the relaxation. In contrast, formononetin-elicited endothelium-independent relaxation was not altered by ICI 182,780 (10 microM, an estrogen receptor (ER alpha/ER beta) antagonist) or mifepristone (10 microM, a progesterone receptor antagonist). In single aortic smooth muscle cells, formononetin caused opening of iberiotoxin-sensitive Ca(2+)-activated K(+) (BK(Ca)) channels and glibenclamide-sensitive adenosine triphosphate (ATP)-dependent K(+) (K(ATP)) channels. Thus, our results suggest that formononetin caused vascular relaxation via endothelium/NO-dependent mechanism and endothelium-independent mechanism which involves the activation of BK(Ca) and K(ATP) channels.

Fenofibrate increases high-density lipoprotein and sphingosine 1 phosphate concentrations limiting abdominal aortic aneurysm progression in a mouse model

There are currently no acceptable treatments to limit progression of abdominal aortic aneurysm (AAA). Increased serum concentrations of high-density lipoprotein (HDL) are associated with reduced risk of developing an AAA. The present study aimed to assess the effects of fenofibrate on aortic dilatation in a mouse model of AAA. Male low-density lipoprotein receptor-deficient (Ldlr(-/-)) mice were maintained on a high-fat diet for 3 weeks followed by 6 weeks of oral administration of vehicle or fenofibrate. From 14 to 18 weeks of age, all mice were infused with angiotensin II (AngII). At 18 weeks of age, blood and aortas were collected for assessment of serum lipoproteins, aortic pathology, aortic Akt1 and endothelial nitric oxide synthase (eNOS) activities, immune cell infiltration, eNOS and inducible NOS (iNOS) expression, sphingosine 1 phosphate (S1P) receptor status, and apoptosis. Mice receiving fenofibrate had reduced suprarenal aortic diameter, reduced aortic arch Sudan IV staining, higher serum HDL levels, increased serum S1P concentrations, and increased aortic Akt1 and eNOS activities compared with control mice. Macrophages, T lymphocytes, and apoptotic cells were less evident and eNOS, iNOS, and S1P receptors 1 and 3 were up-regulated in aortas from mice receiving fenofibrate. The present findings suggest that fenofibrate antagonizes AngII-induced AAA and atherosclerosis by up-regulating serum HDL and S1P levels, with associated activation of NO-producing enzymes and reduction of aortic inflammation.

Radix Astragali extract promotes angiogenesis involving vascular endothelial growth factor receptor-related phosphatidylinositol 3-kinase/Akt-dependent pathway in human endothelial cells

Angiogenesis plays an important role in a wide range of physiological processes and many diseases are associated with dysregulation of angiogenesis. Radix Astragali, commonly used in traditional Chinese medicine, is a potential candidate for treating such diseases. However, the biological effects of Radix Astragali on angiogenesis and its underlying mechanisms are yet to be elucidated fully. This study describes the angiogenic effects of Radix Astragali extract (RAE) on human umbilical vein endothelial cells (HUVEC) in vitro. It was shown that RAE treatment stimulated HUVEC to proliferate. A significant increase in migration was observed in RAE‐treated HUVEC using the wound healing migration assay. In addition, a significant increase in the number of branching points was observed during endothelial cell capillary formation after RAE treatment. It was shown that RAE enhances vascular endothelial growth factor (VEGF) mRNA expression, and that a specific blocker of VEGF receptor 2 (KDR/Flk) inhibited the RAE‐induced HUVEC proliferation. In addition, a decrease in the RAE‐induced HUVEC proliferation was observed after treatment with inhibitors of phosphatidylinositol 3‐kinase (PI3K), Akt and endothelial nitric oxide synthase (eNOS). Taken together, these data suggest that RAE is a potent stimulator of angiogenesis and that its pro‐angiogenic effects involve the VEGF‐KDR/Flk and PI3K‐Akt‐eNOS pathways. Copyright

Synergistic Effects of Chinese Herbal Medicine: A Comprehensive Review of Methodology and Current Research.

Traditional Chinese medicine (TCM) is an important part of primary health care in Asian countries that has utilized complex herbal formulations (consisting 2 or more medicinal herbs) for treating diseases over thousands of years. There seems to be a general assumption that the synergistic therapeutic effects of Chinese herbal medicine (CHM) derive from the complex interactions between the multiple bioactive components within the herbs and/or herbal formulations. However, evidence to support these synergistic effects remains weak and controversial due to several reasons, including the very complex nature of CHM, misconceptions about synergy and methodological challenges to study design. In this review, we clarify the definition of synergy, identify common errors in synergy research and describe current methodological approaches to test for synergistic interaction. We discuss the strengths and weaknesses of these models in the context of CHM and summarize the current status of synergy research in CHM. Despite the availability of some scientific data to support the synergistic effects of multi-herbal and/or herb-drug combinations, the level of evidence remains low, and the clinical relevancy of most of these findings is undetermined. There remain significant challenges in the development of suitable methods for synergistic studies of complex herbal combinations.

Impaired Acetylcholine-Induced Endothelium-Dependent Aortic Relaxation by Caveolin-1 in Angiotensin II-Infused Apolipoprotein-E (ApoE−/−) Knockout Mice

Objective The angiotensin II (AngII)-infused apolipoprotein E-deficient (ApoE−/−) mouse model is widely used to study atherosclerosis and abdominal aortic aneurysm. An increase in blood pressure has been reported in this model however the underlying mechanism has not been fully explored. In this study, we investigated whether vasomotor dysfunction develops in AngII-infused ApoE−/− mice and the underlying mechanism involved. Methods ApoE−/− mice were infused with vehicle (distilled water) or AngII subcutaneously for 14 days. Blood pressure and heart rate were measured using the non-invasive tail cuff method. Aortic vascular reactivity and expression of key proteins (endothelial nitric oxide synthase (eNOS), phospho-eNOS and caveolin-1) were assessed using tension myography and Western blotting respectively. Plasma nitric oxide (NO) level was estimated using a colorimetric assay. Results AngII infusion caused a time-dependent increase in blood pressure (P<0.001). Aortas from AngII-infused mice were significantly less responsive to acetylcholine-induced endothelium-dependent relaxation when compared to aortas from mice infused with vehicle control (P<0.05). Contractile responses to phenylephrine (P<0.01) and potassium chloride (P<0.001) were significantly enhanced in aortas from AngII-infused mice. eNOS phosphorylation was significantly decreased in the aorta of AngII-infused mice (P<0.05). Aortic caveolin-1 protein expression was significantly increased in AngII-infused mice (P<0.05). Plasma nitrate/nitrite level was significantly reduced in AngII-infused mice (P<0.05). Pharmacological disruption of caveolae using methyl-β-cyclodextrin (MβCD) in isolated aortas from AngII-infused mice caused a significant leftward shift of the acetylcholine-induced relaxation concentration-response curve when compared to vehicle control (P<0.05). Conclusion Upregulation of caveolin-1 protein expression and reduced NO bioavailability contributes to aortic endothelial dysfunction in AngII-infused ApoE−/− mice.

Modulation by simvastatin of iberiotoxin-sensitive, Ca2+-activated K+ channels of porcine coronary artery smooth muscle cells

Statins (3‐hydroxy‐3‐methyl‐glutaryl coenzyme A (HMG CoA) reductase inhibitors) have been demonstrated to reduce cardiovascular mortality. It is unclear how the expression level of HMG CoA reductase in cardiovascular tissues compares with that in cells derived from the liver. We hypothesized that this enzyme exists in different cardiovascular tissues, and simvastatin modulates the vascular iberiotoxin‐sensitive Ca2+‐activated K+ (BKCa) channels.

A Peptide Antagonist of Thrombospondin-1 Promotes Abdominal Aortic Aneurysm Progression in the Angiotensin II–Infused Apolipoprotein-E–Deficient Mouse

Objective—Interaction of the activating sequence in thrombospondin-1 (TSP-1) with the conserved sequence (leucine-serine-lysine-leucine [LSKL]) in the latency-associated peptide region of latent transforming growth factor (TGF)-&bgr; complex is important in regulating TGF-&bgr;1 activity. We aimed to assess the effect of blocking peptide LSKL on the progression of pre-established abdominal aortic aneurysm in angiotensin II–infused apolipoprotein E-deficient (ApoE−/−) mice. Approach and Results—Abdominal aortic aneurysm was established in 3-month-old male ApoE−/− mice with subcutaneous infusion of angiotensin II for 28 days. After this, mice received LSKL peptide or control SLLK (serine–leucine–leucine–lysine) peptide (4 mg/kg) via daily intraperitoneal injection for an additional 2 weeks. Administration of LSKL peptide promoted larger suprarenal aortic diameter, as determined by ultrasound and morphometric analysis, and stimulated more severe atherosclerosis within the aortic arch. In addition, mice receiving LSKL peptide exhibited elevated circulating proinflammatory cytokine levels and greater inflammatory cells within the suprarenal aorta compared with controls. Mice receiving LSKL peptide showed low plasma TGF-&bgr;1 activity and low levels of aortic tissue phosphorylated to total Smad2/3. Aortic gene expression of TGF-&bgr; receptor 1 (TGFBRI) and receptor 2 (TGFBRII), but not TGF-&bgr;1 and thrombospondin-1, were lower in mice receiving LSKL peptide than controls. LSKL peptide administration was associated with greater aortic elastin fragmentation and lower expression and activity of the TGF-&bgr;1-target gene lysyl oxidase like 1 (LOXL1). Conclusions—Attenuation of thrombospondin-1-directed activation of TGF-&bgr;1 promotes abdominal aortic aneurysm and atherosclerosis progression in the angiotensin II–infused ApoE−/− mouse model.

Angiotensin II exerts glucose-dependent effects on Kv currents in mouse pancreatic β-cells via angiotensin II type 2 receptors

Hyperglycemia-associated glucotoxicity induces beta-cell apoptosis but the underlying mechanisms are unknown. Interestingly, prolonged exposure to high glucose upregulates the expression and function of the renin-angiotensin system (RAS). We hypothesize that the voltage-gated outward potassium (K(v)) current, which governs beta-cell membrane potential and insulin secretion, has a role in glucotoxicity. In this study, we investigated the effects of prolonged exposure to high glucose on mouse pancreatic beta-cells and concurrent effects on the RAS by examining changes in expression of angiotensin II (ANG II) receptors and changes in the expression and activity of K(v) channels. beta-Cells were incubated in high glucose medium for 1-7 days and then were examined with electrophysiological and molecular biology techniques. Prolonged exposure to high glucose produced a marked increase in beta-cell primary K(v) channel subunit, K(v)2.1, expression and K(v) current amplitude. Enhanced expression of ANG II type 1 receptor (AT(1)R) was also observed under high glucose conditions, whereas blockade of AT(1)R by losartan did not alter K(v) channel expression. External application of ANG II reduced K(v) current amplitude under normal, but not high, glucose conditions. The effect of ANG II on K(v) channel gating was abolished by ANG II type 2 receptor (AT(2)R) antagonism. These data suggest that hyperglycemia alters beta-cell function through modification of the K(v) channel which may be associated with the RAS.

Folic acid consumption reduces resistin level and restores blunted acetylcholine-induced aortic relaxation in obese/diabetic mice

Folic acid supplementation provides beneficial effects on endothelial functions in patients with hyperhomocysteinemia. However, its effects on vascular functions under diabetic conditions are largely unknown. Therefore, the effect(s) of folic acid (5.7 and 71 microg/kg/day for 4 weeks) on aortic relaxation was investigated using obese/diabetic (+db/+db) mice and lean littermate (+db/+m) mice. Acetylcholine-induced relaxation in +db/+db mice was less than that observed in +db/+m mice. The reduced relaxation in +db/+db mice was restored by consumption of 71 microg/kg folic acid. Acetylcholine-induced relaxation (with and without folic acid treatment) was sensitive to N(G)-nitro-L-arginine methyl ester, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one, geldanamycin and triciribine. In addition, acetylcholine-induced relaxation was attenuated by resistin. The plasma level of resistin in +db/+db mice was sevenfold higher than that measured in +db/+m mice, and the elevated plasma level of resistin in +db/+db mice was reduced by 25% after treatment with 71 microg/kg folic acid. Folic acid slightly increased the ratio of reduced glutathione to oxidized glutathione in +db/+db mice. Moreover, folic acid caused a reduction in PTEN (phosphatase and tensin homolog deleted on chromosome 10) expression, an increase in the phosphorylation of endothelial nitric oxide synthase (eNOS(Ser1177)) and Akt(Ser473), and an enhanced interaction of heat shock protein 90 (HSP90) with eNOS in both strains, with greater magnitude observed in +db/+db mice. In conclusion, folic acid consumption improved blunted acetylcholine-induced relaxation in +db/+db mice. The mechanism may be, at least partly, attributed to enhancement of PI3K/HSP90/eNOS/Akt cascade, reduction in plasma resistin level, down-regulation of PTEN and slight modification of oxidative state.