Mechanisms responsible for the in vitro relaxation of ligustrazine on porcine left anterior descending coronary artery

Suxiao Jiuxin Pill attenuates acute myocardial ischemia via regulation of coronary artery tone

Suxiao Jiuxin Pill (SJP) is a well-known traditional Chinese medicine drug used to manage heart diseases. This study aimed at determining the pharmacological effects of SJP in acute myocardial infarction (AMI), and the molecular pathways its active compounds target to induce coronary artery vasorelaxation. Using the AMI rat model, SJP improved cardiac function and elevated ST segment. LC-MS and GC-MS detected twenty-eight non-volatile compounds and eleven volatile compounds in sera from SJP-treated rats. Network pharmacology analysis revealed eNOS and PTGS2 as the key drug targets. Indeed, SJP induced coronary artery relaxation via activation of the eNOS-NO pathway. Several of SJP's main compounds, like senkyunolide A, scopoletin, and borneol, caused concentration-dependent coronary artery relaxation. Senkyunolide A and scopoletin increased eNOS and Akt phosphorylation in human umbilical vein endothelial cells (HUVECs). Molecular docking and surface plasmon resonance (SPR) revealed an interaction between senkynolide A/scopoletin and Akt. Vasodilation caused by senkyunolide A and scopoletin was inhibited by uprosertib (Akt inhibitor) and eNOS/sGC/PKG axis inhibitors. This suggests that senkyunolide A and scopoletin relax coronary arteries through the Akt-eNOS-NO pathway. In addition, borneol induced endothelium-independent vasorelaxation of the coronary artery. The K_v channel inhibitor 4-AP, K_Ca2+ inhibitor TEA, and K_ir inhibitor BaCl₂ significantly inhibited the vasorelaxant effect of borneol in the coronary artery. In conclusion, the results show that Suxiao Jiuxin Pill protects the heart against acute myocardial infarction.

Tetramethylpyrazine: A Review of Its Antitumor Potential and Mechanisms

Cancer remains a major public health threat. The mitigation of the associated morbidity and mortality remains a major research focus. From a molecular biological perspective, cancer is defined as uncontrolled cell division and abnormal cell growth caused by various gene mutations. Therefore, there remains an urgent need to develop safe and effective antitumor drugs. The antitumor effect of plant extracts, which are characterized by relatively low toxicity and adverse effect, has attracted significant attention. For example, increasing attention has been paid to the antitumor effects of tetramethylpyrazine (TMP), the active component of the Chinese medicine Chuanqiong, which can affect tumor cell proliferation, apoptosis, invasion, metastasis, and angiogenesis, as well as reverse chemotherapeutic resistance in neoplasms, thereby triggering antitumor effects. Moreover, TMP can be used in combination with chemotherapeutic agents to enhance their effects and reduce the side effect associated with chemotherapy. Herein, we review the antitumor effects of TMP to provide a theoretical basis and foundation for the further exploration of its underlying antitumor mechanisms and promoting its clinical application.

A novel Danshensu/tetramethylpyrazine derivative induces vasorelaxation on rat aorta and exerts cardioprotection in dogs

ADTM, a previously reported novel Danshensu (DSS)/tetramethylpyrazine (TMP) derivative with cardioprotective and antiplatelet aggregative effects, is a promising therapeutic candidate for ischemic heart diseases. In the present study, ADTM increased coronary blood flow and protected myocardium against ischemic injury in dogs. In addition, the relaxing effect of ADTM on rat thoracic aorta and its underlying mechanisms were examined. ADTM relaxed KCl- and phenylephrine-precontracted arotic rings in a concentration-dependent manner. The relaxation by ADTM was greater than that by DSS, TMP and the mixture of DSS and TMP. ADTM induced endothelium-independent relaxation, which couldn't be abolished by removal of endothelium and the preincubation with inhibitors of nitric oxide synthase (L-NAME) and guanylate cyclase (ODQ). Potassium channel blockers including tetraethylammonium, BaCl₂ and glibenclamide failed to inhibit the relaxation by ADTM. In addition, cyclooxygenase (COX), muscarine receptor and β-adrenoceptor were not involved in ADTM-induced vasorelaxation. ADTM inhibited contraction induced by CaCl₂ and phenylephrine in Ca²⁺-free buffer, suggesting that ADTM inhibited both extracellular Ca²⁺ influx and intracellular Ca²⁺ release. Taken together, the vasorelaxation of ADTM may be possibly involved in its cardioprotection. ADTM may serve as a promising candidate for the treatment of ischemic heart diseases.

Ligustrazine for the Treatment of Unstable Angina: A Meta-Analysis of 16 Randomized Controlled Trials

Ligustrazine is a principal ingredient of chuanxiong. Concerns regarding the evaluation of the effectiveness of ligustrazine in the treatment of UA have resulted in a meta-analysis combined with recent clinical evidence. Seven computer databases that included the China hospital knowledge database (CHKD), Wanfang Med Online, the Chinese medical journal database (CMJD), PubMed, Cochrane, Embase (Ovid), and Medline (Ovid) were systematically searched. We included randomized controlled trials and quasi-randomized controlled trials. Our systematic review identified 16 RCTs that met our eligibility criteria. Ligustrazine combined with conventional medicine was associated with an increased rate of marked improvement in symptoms and an increased rate of marked improvement of ECG compared with conventional Western medicine alone. Additionally, the use of ligustrazine was associated with significant trends in the reduction of the consumption of nitroglycerin and the level of fibrinogen when compared with conventional Western medicine alone. No firm results were found between the intervention and the control method groups in the reduction of the time of onset or the frequency of acute attack angina due to the high level of heterogeneity. In conclusion, our meta-analysis found that ligustrazine was associated with some benefits for people with unstable angina.

The protective effect of tetramethylpyrazine on cartilage explants and chondrocytes

AIMS OF STUDY

Ligusticum wallichi Franchat (chuanxiong) is a very common traditional Chinese herbal medicine in China. Tetramethylpyrazine (TMP) is a major active ingredient extracted from Ligusticum wallichi Franchat. We investigated the protective effect of TMP on interleukin-1β (IL-1β) induced proteoglycan (PG) degradation and apoptosis in rabbit articular cartilage and chondrocytes.

MATERIALS AND METHODS

Rabbit articular cartilage explants and chondrocytes were cultured with 10 ng/ml IL-1β for 72 h in the absence or presence of various concentrations of TMP (50, 100 or 200 μM). Cartilage and chondroprotective effects of TMP were determined by evaluating (1) the degree of PG degradation by measuring the amount of glycosaminoglycan (GAG) released into the culture media with 1,9-dimethylmethylene blue (DMMB) assay in cartilage explants; (2) gene expression of MMP-3 and TIMP-1 by real-time quantitative reverse transcription-polymerase chain reaction analysis in cartilage explants; (3) chondrocytes viability with MTT assay; (4) the production of intracellular reactive oxygen species (ROS) with laser scanning confocal microscopy (LSCM). Anti-apoptotic effects of TMP were determined by measuring (1) apoptosis with flow cytometric analysis; (2) mitochondrial membrane potential assay with LSCM; (3) caspase-3 activity with special assay kit.

RESULTS

IL-1β treatment increased the level of GAG released into the culture media, and induced the gene expression of MMP-3 and inhibited the gene expression of TIMP-1 in cartilage explants. Moreover, IL-1β treatment decreased the cell viability and mitochondrial membrane potential, and enhanced the level of intracellular ROS, apoptosis rate, and caspase-3 activity in chondrocytes. However, simultaneous treatment with TMP attenuated the IL-1β-induced cartilage and chondrocyte destruction in a dose-dependent manner. TMP showed the decrease of GAG degradation and MMP-3 mRNA production, and the enhancement of TIMP-1 mRNA production in cartilage explants. TMP also increased the cell viability in chondrocytes. Furthermore, TMP inhibited the chondrocytes apoptosis through suppression of ROS production, maintaining of mitochondrial membrane potential and downregulation of caspase-3 activity.

CONCLUSION

These results demonstrate that TMP has the cartilage and chondroprotective effect, which suggest that TMP could act as an agent for pharmacological intervention in the progress of OA.

(+/-)-Praeruptorin A enantiomers exert distinct relaxant effects on isolated rat aorta rings dependent on endothelium and nitric oxide synthesis

Praeruptorin A is a coumarin compound naturally occurring in the roots of Peucedanum praeruptorum Dunn., a commonly used traditional Chinese medicine for the treatment of certain respiratory diseases and hypertension. Although previous studies indicated the relaxant effects of (+/-)-praeruptorin A on tracheal and arterial preparations, little is known about the functional characteristics of the enantiomers. In the present study, the two enantiomers were successfully isolated and identified by using a preparative Daicel Chiralpak AD-H column, and their relaxant effects on aorta rings were observed and compared. (+)-Praeruptorin A showed more potent relaxation than (-)-praeruptorin A against KCl- and phenylephrine-induced contraction of rat isolated aortic rings with intact endothelium. Removal of the endothelium remarkably reduced the relaxant effect of (+)-praeruptorin A but not that of (-)-praeruptorin A. Pretreatment of aortic rings with N(omega)-nitro-L-arginine methyl ester (L-NAME, an inhibitor of nitric oxide synthase) or methylene blue (MB, a soluble guanylyl cyclase inhibitor) resulted in similar changes of the relaxant effects of the two enantiomers to endothelium removal. Molecular docking studies also demonstrated that (+)-praeruptorin A was in more agreement to nitric oxide synthase pharmacophores than (-)-praeruptorin A. On the other hand, the two enantiomers of praeruptorin A could slightly attenuate the contraction of rat aortic rings induced by internal Ca(2+) release from sarcoplasmic reticulum (SR). These findings indicated that (+)-praeruptorin A and (-)-praeruptorin A exerted distinct relaxant effects on isolated rat aorta rings, which might be mainly attributed to nitric oxide synthesis catalyzed by endothelial nitric oxide synthase.

Endothelium-derived nitric oxide inhibits the relaxation of the porcine coronary artery to natriuretic peptides by desensitizing big conductance calcium-activated potassium channels of vascular smooth muscle

The present experiments investigated whether endothelium-derived mediators modulate the effect of natriuretic peptides in porcine coronary arteries. Rings with and without endothelium were suspended in organ chambers for isometric tension recording. Concentration-relaxation curves to C-type natriuretic peptide (CNP) and atrial natriuretic peptide (ANP) were obtained during contractions to endothelin-1. Removal of the endothelium potentiated relaxations to both CNP and ANP. N(omega)-nitro-L-arginine methyl ester potentiated relaxations to natriuretic peptides only in arteries with endothelium. Sodium nitroprusside (SNP) inhibited the response to the natriuretic peptides only in the absence of the endothelium. In rings with endothelium, 1H-[1,2,4]oxadiazolo [4,3-a]quinoxalin-1-one (ODQ) and 4H-8-bromo-1,2,4-oxadiazolo[3,4-d]benz[b][1,4]oxazin-1-one (NS2028) potentiated CNP-mediated relaxations. Iberiotoxin (IBTX) reduced the response only in rings without endothelium. Glybenclamide inhibited the relaxations in both the presence and absence of endothelium. CNP-induced relaxations were reduced by 8-bromoguanosine 3',5'-cGMP (8-bromo-cGMP) to the same extent in rings with and without endothelium. There was no significant difference between the increased cGMP content caused by CNP in porcine coronary arteries with or without endothelium. In patch-clamp studies in porcine coronary arterial smooth muscle cells, the natriuretic peptide-mediated enhancement of the IBTX-sensitive big conductance calcium-activated potassium channel (BK(Ca)) amplitude was reversed by SNP and 8-bromo-cGMP. These findings demonstrate that, in the porcine coronary artery, the opening of BK(Ca) and ATP-dependent potassium channels of the vascular smooth muscle contributes to CNP-mediated relaxations. Endothelium-derived and exogenous NO inhibit the direct relaxing effect of natriuretic peptides by desensitizing the response of the BK(Ca)s of the vascular smooth muscle to the generation of cGMP.

Tetramethylpyrazine suppresses interleukin-8 expression in LPS-stimulated human umbilical vein endothelial cell by blocking ERK, p38 and nulear factor-kappaB signaling pathways

AIM OF THE STUDY

To determine the anti-inflammatory effects of Tetramethylpyrazine (TMP) and to investigate the inhibitory effect of TMP on IL-8 production in human umbilical vein endothelial cells (HUVECs) induced by LPS might be mediated by inhibiting p38, ERK and NF-kappaB signaling pathways.

MATERIALS AND METHODS

HUVECs were treated with or without TMP for 24h before exposure to LPS for 4h. IL-8 gene and protein expressions were determined by RT-PCR and ELISA. Cell viability was determined by methyl thiazoyltetrazolium (MTT) assay. Phosphorylation of ERK1/2 and p38 were examined by western blotting.

RESULTS

TMP inhibits LPS-induced IL-8 production in HUVECs at both the protein and mRNA levels, suggesting that TMP has an antiinflammatory effect on endothelial cells. TMP also inhibited U937 monocyte adhesion to HUVECs stimulated by LPS. LPS-induced phosphorylation of ERK1/2 and p38 were inhibited by TMP. The inhibitory effect of TMP on NF-kappaB (p65) activity was mediated by blocking the consequent translocation of p65 into the nucleus.

CONCLUSIONS

The inhibitory effect of TMP on the LPS-induced IL-8 production is mediated by the NF-kappaB-dependent pathway, and TMP also separately affects the ERK and p38 MAPK pathway. TMP may be beneficial in the treatment of cardiovascular disorders such as atherosclerosis.

Tetramethylpyrazine inhibits activities of glioma cells and glutamate neuro-excitotoxicity: potential therapeutic application for treatment of gliomas

We tested the herbal extract 2,3,5,6-tetramethylpyrazine (TMP) for possible therapeutic efficacy against a glioma cell line and against gliomas transplanted into rat brains. In the cultured glioma cells, 50 muM TMP significantly inhibited glutamate-induced increase in intracellular calcium. Significant cell damage (30%) and proliferation suppression (10%), however, occurred only at higher concentrations (200-400 microM). Gliomaneuronal co-culturing resulted in significant neuronal damage and higher proliferation of the glioma cells (140%) compared with single cultures. Low concentrations of TMP (< or =200 microM) attenuated the neuronal damage, suppressed glioma migration, and decreased glioma proliferation in the neuronal-glioma co-culture. Gliomas transplanted into the frontal cortical area exhibited high proliferation, with untreated rats dying 10-23 days later. TMP treatment inhibited tumor growth and significantly extended survival time. The results indicate that TMP can suppress glioma activity, including growth, and protect neurons against glioma-induced excitotoxicity, suggesting that TMP may have therapeutic potential in the treatment of malignant gliomas.

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

BACKGROUND AND PURPOSE

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(+) (BK(Ca)) channels.

EXPERIMENTAL APPROACHES

Expression of HMG CoA reductase in different cardiovascular preparations was measured. Effects of simvastatin on BK(Ca) channel gatings of porcine coronary artery smooth muscle cells were evaluated.

KEY RESULTS

Western immunoblots revealed the biochemical existence of HMG CoA reductase in human cardiovascular tissues and porcine coronary artery. In porcine coronary artery smooth muscle cells, extracellular simvastatin (1, 3 and 10 microM) (hydrophobic), but not simvastatin Na+ (hydrophilic), inhibited the BK(Ca) channels with a minimal recovery upon washout. Isopimaric acid (10 microM)-mediated enhancement of the BK(Ca) amplitude was reversed by external simvastatin. Simvastatin Na+ (10 microM, applied internally), markedly attenuated isopimaric acid (10 microM)-induced enhancement of the BK(Ca) amplitude. Reduced glutathione (5 mM; in the pipette solution) abolished simvastatin -elicited inhibition. Mevalonolactone (500 microM) and geranylgeranyl pyrophosphate (20 microM) only prevented simvastatin (1 and 3 microM)-induced responses. simvastatin (10 microM ) caused a rottlerin (1 microM)-sensitive (cycloheximide (10 microM)-insensitive) increase of PKC-delta protein expression.

CONCLUSIONS AND IMPLICATIONS

Our results demonstrated the biochemical presence of HMG CoA reductase in different cardiovascular tissues, and that simvastatin inhibited the BK(Ca) channels of the arterial smooth muscle cells through multiple intracellular pathways.

Ligustrazine attenuates acute myocardium injury after thermal trauma

This study was designed to investigate the effects of ligustrazine on burn-induced myocardiac injury as well as TNF-alpha levels in severely burned rats. Sprague-Dawley rats were divided into four groups: (1) sham group, rats who underwent sham burn; (2) fluid-resuscitated sham group (FRsham), rats who underwent sham burn, and lactated Ringer's solution for resuscitation; (3) control group, rats given third-degree burns over 30% total body surface area (TBSA) and lactated Ringer's solution for resuscitation; (4) ligustrazine group, rats given burn and lactated Ringer's solution with ligustrazine inside for resuscitation. Myocardial injury was assessed at 6h after burn by detecting serum levels of creatine kinase MB fraction (CK-MB) and lactate dehydrogenase (LDH), as well as water content, histological score, and ultrastructure change of cardiac tissue. In addition, myocardium ATP content was analyzed. Enzyme-linked immunosorbent assay (ELISA) was used to examine cardiac tumor necrosis factor-alpha (TNF-alpha) levels. The results showed that burn trauma resulted in the increasing serum LDH and CK-MB, elevated myocardial water content, aggravated myocardial histological and ultrastructural lesions, increased myocardium ATP, and serum TNF-alpha. Ligustrazine 10mg/kg iv markedly inhibited increases in serum CK-MB and LDH, reduced myocardial water content from 76.91+/-0.19% in control group to 75.40+/-0.57%, significantly decreased the histologic scores of myocardium, and mollified the ultrastructural damage in cardiac myocytes. Ligustrazine significantly attenuated elevations in serum TNF-alpha level and myocardial ATP quantity. Therefore, our results demonstrate that ligustrazine exhibits significant protective effects on burn-induced myocardial injury via inhibiting the release of TNF-alpha and improving utilization of ATP.

Endothelium-independent relaxation to raloxifene in porcine coronary artery

Although the vascular action of raloxifene has been studied in several vascular beds, the underlying mechanisms are still incompletely understood. The role of endothelium in raloxifene-induced vascular responses was controversial. The present study was designed to examine endothelium-independent effects of raloxifene in isolated porcine left circumflex coronary arteries. Arterial rings were suspended in organ baths and changes in isometric tension were measured. The large-conductance Ca2+-activated K+(BK(Ca)) currents were recorded using a whole-cell patch-clamp technique. Treatment with raloxifene (1-10 micromol/l) reduced the contractions to 9,11-dideoxy-11alpha,9alpha-epoxy-methanoprostaglandin F2alpha (U46619), serotonin (5-HT), endothelin-1 in normal Krebs solution and to CaCl2 in a Ca2+-free, high K+-containing solution. In endothelin-1-contracted rings, raloxifene (0.3 to 50 micromol/l) caused relaxations which were comparable in rings with and without endothelium. The raloxifene-induced relaxation was reduced by putative K+ channel blockers, iberiotoxin and tetraethyl ammonium chloride (TEA+) in rings with and without endothelium, or by elevated extracellular K+ ions (30 mmol/l K+ and 60 mmol/l K+). 13-methyl-7-[9-(4,4,5,5,5-pentafluoropentylsulfinyl)nonyl]-7,8,9,11,12,13,14,15,16, 17-decahydro-6H-cyclopenta[a] phenanthrene-3,17-diol (ICI 182,780) did not affect raloxifene-induced relaxation. Raloxifene enhanced the outward BK(Ca) currents, which were sensitive to inhibition by iberiotoxin. In summary, the present study shows that raloxifene acutely relaxes porcine coronary arteries via an endothelium-independent mechanism without involving the ICI 182,780-sensitive estrogen receptors. Raloxifene mainly acts on the vascular smooth muscle cells to induce vasorelaxation by the inhibition of Ca2+ channels and the activation of BK(Ca) channels. The former mechanism appears to play a more significant role.

Activation of the iberiotoxin-sensitive BKCa channels by salvianolic acid B of the porcine coronary artery smooth muscle cells

In this study, we examined the effects of Salvia miltiorrhiza (Danshen) crude extract, some of its lipid-soluble components (tanshinone I, tanshinone II(A), cryptotanshinone, dihydroisotanshinone I) and the water-soluble compounds (danshensu and salvianolic acid B) on the K(+) channels such as the iberiotoxin-sensitive Ca(2+)-activated K(+) (BK(Ca)) channels and the glibenclamide-sensitive ATP-dependent K(+) (IK(ATP)) channels of the porcine left anterior descending coronary artery smooth muscle cells. Cumulative application of salvianolic acid B (30-300 microM) caused a l-NNA (100 microM)-insensitive, potentiation of the outward BK(Ca) current amplitude with no apparent effect on the IK(ATP) channels opening. Salvianolic acid B (300 microM) caused an ODQ (10 microM, a guanylate cyclase inhibitor)-sensitive enhancement of the outward BK(Ca) current amplitude. In contrast, none of the other isolated chemical constituents of S. miltiorrhiza modified the openings of the two types of K(+) channels studied. In conclusion, our results suggest that salvianolic acid B, a major hydrophilic constituent found in Radix S. miltiorrhiza, activated the opening of the BK(Ca) channels of the porcine coronary artery smooth muscle cells through the activation of guanylate cyclase without the involvement of the nitric oxide synthase activation.

Tetramethylpyrazine induces heme oxygenase-1 expression and attenuates myocardial ischemia/reperfusion injury in rats

The accumulation of oxygen free radicals and activation of neutrophils are strongly implicated as pathophysiological mechanisms mediating myocardial ischemia/reperfusion injury. Heme oxygenase-1 (HO-1) has been reported to play a protective role in oxidative tissue injuries. In this study, the cardioprotective activity of tetramethylpyrazine (TMP), an active ingredient of Chinese medicinal herb Ligusticum wallichii Franchat, was evaluated in an open-chest anesthetized rat model of myocardial ischemia/reperfusion injury. Pretreatment with TMP (5 and 10 mg/kg, i.v.) before left coronary artery occlusion significantly suppressed the occurrence of ventricular fibrillation. After 45 min of ischemia and 1 h of reperfusion, TMP (5 and 10 mg/kg) caused a significant reduction in infarct size and induced HO-1 expression in ischemic myocardium. The HO inhibitor ZnPP (50 microg/rat) markedly reversed the anti-infarct action of TMP. Superoxide anion production in ischemic myocardium after 10 min reperfusion was inhibited by TMP. Furthermore, TMP (200 and 500 microM) significantly suppressed fMLP (800 nM)-activated human neutrophil migration and respiratory burst. In conclusion, TMP suppresses ischemia-induced ventricular arrhythmias and reduces the infarct size resulting from ischemia/reperfusion injury in vivo. This cardioprotective activity of TMP may be associated with its antioxidant activity via induction of HO-1 and with its capacity for neutrophil inhibition.

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

We evaluated the acute effect of homocysteine on the iberiotoxin-sensitive, Ca(2+)-activated K(+) (BK(Ca)) channels of the porcine coronary artery smooth muscle cells. NS 1619 (1 to 30 microM) caused a concentration-dependent enhancement of the BK(Ca) amplitude (recorded using the whole-cell, membrane-rupture configuration) only with an elevated [Ca(2+)](i) of approximately 444 nM, but not with [Ca(2+)](i) of approximately 100 nM. Homocysteine (30 microM) caused a small inhibition ( approximately 16%) of the BK(Ca) amplitude ([Ca(2+)](i)= approximately 444 nM), and a greater inhibition ( approximately 77%) was observed with 100 microM NADH present in the pipette solution. The inhibition persisted after washing. With NADPH (100 microM), a smaller magnitude of inhibition ( approximately 34%) of the BK(Ca) amplitude was recorded. The NS 1619-mediated enhancement of the BK(Ca) amplitude (with elevated [Ca(2+)](i) plus NADH in the pipette) was attenuated by homocysteine. The homocysteine-mediated inhibition of the BK(Ca) amplitude was suppressed by Tiron (10 mM) or diphenylene iodonium (30 nM), applied alone, but not by superoxide dismutase (500 U/ml) and catalase (500 U/ml). Generation of superoxide (O(2)(-)) of the smooth muscle cells (with NADH presence), measured using the lucigenin-enhanced chemiluminescence, was markedly increased by angiotensin II (100 nM) and homocysteine (30 microM). The chemiluminescence signal was sensitive to apocynin (300 microM) or Tiron, applied alone, but not to superoxide dismutase and catalase. In conclusion, our results demonstrate that acute homocysteine application inhibits the iberiotoxin-sensitive BK(Ca) channels (with elevated [Ca(2+)](i) and NADH present) which is probably caused by the NADH oxidase activation and the concomitant generation of intracellular superoxide.

Calcium channel blockade as a target for the cardiovascular effects induced by the 8 (17), 12E, 14-labdatrien-18-oic acid (labdane-302)

The cardiovascular effects induced by labdane-302, a diterpene isolated from the stems of Xylopia langsdorffianna St. Hill and Tull, were evaluated in male Wistar rats. In normotensive, conscious animals, labdane-302 produced dose-dependent hypotension and tachycardia. These effects were significantly attenuated after pre-treatment with L-NAME (20 mg/kg, i.v.). In isolated mesenteric artery rings, labdane-302 (10(-10)-10(-4)M) elicited concentration-dependent relaxation of phenylephrine-induced contractions (IC50 = 5.4 +/- 1.4 microM). Endothelium removal, and pre-treatment with L-NAME (100 microM) or indomethacin (10 microM) caused significant reductions in sensitivity. Labdane-302 also caused concentration-dependent relaxation in arterial rings pre-contracted with high extracellular KCl (80 mM). In Ca2+-free depolarized preparations, labdane-302 inhibited contractions produced by cumulative increases in extracellular Ca2+ concentration. In GH3 cells, labdane-302 (100 microM) inhibited whole-cell L-type Ca2+ currents by approximately 50%. These results demonstrate that labdane-302 causes hypotension through peripheral vasodilation, mediated in part by NO and PGI2 and by blockade of Ca2+ entry through L-type Ca2+ channels.

Modulatory effect of interleukin-1β on rat isolated basilar artery contraction

An increased level of cytokine interleukin-1 (IL-1) has been detected around the site of stroke. However, the effect of IL-1beta on the basilar artery has received little attention. We evaluated the effects of IL-1beta on the contractile response of rat isolated basilar artery by measuring isometric tension change. IL-1beta (10 ng/ml) and phenylephrine (0.1 nM) markedly enhanced U46619 (30 and 100 nM)-induced basilar artery contraction. The IL-1beta-mediated potentiation was partly suppressed by zinc protoporphyrin (3 microM) and was abolished by tetrodotoxin (TTX, 100 nM), (-)-perillic acid (1 microM), PD98059 (0.3 microM), SB203580 (1 microM) and prazosin (1 microM). Our data suggest that IL-1beta (10 ng/ml) causes an enhancement of U46619-mediated basilar artery contraction that probably involves TTX-sensitive neuronal release of an alpha1-adrenoceptor agonist and activation of p42/p44 and p38 mitogen-activated protein kinases/p21(ras) pathways.

Contribution of glibenclamide-sensitive, ATP-dependent K+ channel activation to acetophenone analogues-mediated in vitro pulmonary artery relaxation of rat

Compared to the currently available therapeutic drugs for peripheral vascular diseases, agents that are selective for relaxing pulmonary circulation are scarce. The present study was undertaken, using isometric tension change measurement and whole-cell patch-clamp electrophysiology methods, to evaluate the vascular relaxation effect and the underlying mechanisms involved of two naturally found alkaloids: paeonol (2-hydroxy-4-methoxy-acetophenone), acetovanillone (4-hydroxy-3-methoxy-acetophenone) and the non-substituted analogue acetophenone on pulmonary artery of Sprague-Dawley rats. Cumulative administration (3 microM-1 mM) of acetophenone analogues resulted in a concentration-dependent relaxation of phenylephrine (1 microM) pre-contracted pulmonary artery. A relative order of inhibitory potency, estimated by comparing the concentration at which a 50% relaxation of phenylephrine-induced contraction observed was: acetovanillone > paeonol > acetophenone. Endothelial denudation and inhibition of nitric oxide synthase (with 20 microM N(G)-nitro-L-arginine methyl-ester) only moderately suppressed (17.6 +/- 4.2%) acetovanillone- but not paeonol- or acetophenone-mediated maximum relaxation. Glibenclamide (3 microM, an ATP-sensitive K(+) (IK(ATP)) channel blocker) markedly attenuated all acetophenone analogues-mediated endothelium-independent relaxation. Neither cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine (MDL 12330A, 10 microM), iberiotoxin (300 nM), 4-aminopyridine (3 mM), (+/-)-propranolol (1 microM, a non-selective beta-adrenoceptor blocker) nor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (3 microM, a guanylate cyclase inhibitor) altered endothelium-independent relaxation. In electrophysiological experiments using single pulmonary artery smooth muscle cells, acetovanillone, paeonol, acetophenone and cromakalim activated glibenclamide-sensitive, IK(ATP) channels. In conclusion, our results demonstrate that acetophenone analogues caused pulmonary artery relaxation through opening of IK(ATP) channels. In addition, acetovanillone-mediated pulmonary artery relaxation is partly depended on nitric oxide released from endothelium.

Activation of iberiotoxin-sensitive, Ca2+-activated K+ channels of porcine isolated left anterior descending coronary artery by diosgenin

The objective of this study was to determine the vasodilating effect of 3beta-hydroxy-5-spirostene (diosgenin), a phytoestrogen found in wild yams, using porcine resistance left anterior descending coronary artery. In 5-hydroxytryptamine (3 microM) pre-contracted preparation, diosgenin caused a concentration-dependent (0.01 to 1 microM), endothelium-independent relaxation, with a maximum relaxation of approximately 72% at 1 microM. No apparent effect was observed with 17beta-oestradiol and progesterone with concentrations < or =0.3 microM, and a relaxation of approximately 15% and approximately 23% caused by 17beta-oestradiol (1 microM) and progesterone (1 microM), respectively. Diosgenin-elicited relaxation was not altered by 7alpha,17beta-[9[(4,4,5,5,5-pentafluoropentyl)sulfinyl]nonyl]estra-1,3,5(10)-triene-3,17-diol (ICI 182,780), mifepristone, (+)-bicuculline, cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine (MDL 12330A), glibenclamide and scavengers of reactive oxygen species. The iberiotoxin-sensitive, Ca2+-activated K+ (BK(Ca)) current of single vascular myocytes recorded, using patch-clamp techniques, was markedly enhanced by diosgenin, 17beta-oestradiol and progesterone. Application of (9S, 10R, 12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid methyl ester (KT 5823, 300 nM) eradicated the enhancement of BK(Ca) amplitude. Diosgenin, 17beta-oestradiol and progesterone did not affect whereas phloretin, biochanin A and zearalanone (1 microM each) significantly suppressed [Ca2+]o-induced contraction. In oestrogen competition essay using human breast cancer cell (MCF-7 cells), diosgenin (0.001 nM to 10 microM) did not interact with oestrogen receptor-alpha, and no displacement of [3H]17beta-oestradiol was observed. In oestrogen receptor alpha- and beta-fluorescence polarization competitor assay, diosgenin (100 microM) demonstrated a greater competition with the beta-isoform of oestrogen receptor. These results suggest that diosgenin caused an acute, endothelium-independent coronary artery relaxation via protein kinase G signalling cascade and an activation of BK(Ca) channel of arterial smooth muscle cells. The oestrogen receptor (alpha and beta-isoforms) and progesterone receptor are probably not involved.