Calcium channel blocking activity of calycosin, a major active component of Astragali Radix, on rat aorta

Natural L-type calcium channels antagonists from Chinese medicine

L-type calcium channels (LTCCs), the largest subfamily of voltage-gated calcium channels (VGCCs), are the main channels for Ca2+ influx during extracellular excitation. LTCCs are widely present in excitable cells, especially cardiac and cardiovascular smooth muscle cells, and participate in various Ca2+-dependent processes. LTCCs have been considered as worthy drug target for cardiovascular, neurological and psychological diseases for decades. Natural products from Traditional Chinese medicine (TCM) have shown the potential as new drugs for the treatment of LTCCs related diseases. In this review, the basic structure, function of LTCCs, and the related human diseases caused by structural or functional abnormalities of LTCCs, and the natural LTCCs antagonist and their potential usages were summarized.

Effects of plant extracts and derivatives on cardiac K+, Nav, and Cav channels: a review

Natural products (NPs) are endless sources of compounds for fighting against several pathologies. Many dysfunctions, including cardiovascular disorders, such as cardiac arrhythmias have their modes of action regulation of the concentration of electrolytes inside and outside the cell targeting ion channels. Here, we highlight plant extracts and secondary metabolites' effects on the treatment of related cardiac pathologies on hERG, Nav, and Cav of cardiomyocytes. The natural product's pharmacology of expressed receptors like alpha-adrenergic receptors causes an influx of Ca2+ ions through receptor-operated Ca2+ ion channels. We also examine the NPs associated with cardiac contractions such as myocardial contractility by reducing the L-type calcium current and decreasing the intracellular calcium transient, inhibiting the K+ induced contractions, decreasing amplitude of myocyte shortening and showed negative ionotropic and chronotropic effects due to decreasing cytosolic Ca2+. We examine whether the NPs block potassium channels, particular the hERG channel and regulatory effects on Nav1.7.

Biosynthesis and Pharmacological Activities of Flavonoids, Triterpene Saponins and Polysaccharides Derived from Astragalus membranaceus

Astragalus membranaceus (A. membranaceus), a well-known traditional herbal medicine, has been widely used in ailments for more than 2000 years. The main bioactive compounds including flavonoids, triterpene saponins and polysaccharides obtained from A. membranaceus have shown a wide range of biological activities and pharmacological effects. These bioactive compounds have a significant role in protecting the liver, immunomodulation, anticancer, antidiabetic, antiviral, antiinflammatory, antioxidant and anti-cardiovascular activities. The flavonoids are initially synthesized through the phenylpropanoid pathway, followed by catalysis with corresponding enzymes, while the triterpenoid saponins, especially astragalosides, are synthesized through the universal upstream pathways of mevalonate (MVA) and methylerythritol phosphate (MEP), and the downstream pathway of triterpenoid skeleton formation and modification. Moreover, the Astragalus polysaccharide (APS) possesses multiple pharmacological activities. In this review, we comprehensively discussed the biosynthesis pathway of flavonoids and triterpenoid saponins, and the structural features of polysaccharides in A. membranaceus. We further systematically summarized the pharmacological effects of bioactive ingredients in A. membranaceus, which laid the foundation for the development of clinical candidate agents. Finally, we proposed potential strategies of heterologous biosynthesis to improve the industrialized production and sustainable supply of natural products with pharmacological activities from A. membranaceus, thereby providing an important guide for their future development trend.

In vitro effects of alcesefoliside and mauritianin, isolated from Astragalus monspessulanus subsp. monspessulanus, on the contractility of a. basilaris

Flavonoids are one of the most popular antioxidants in plants. Their varied pharmacological activities are important for these compounds in order to add and to complement conventional therapy. Alcesefoliside and mauritianin are rare flavonol triglycosides, isolated from the overground part of A. monspessulanus subsp. monspessulanus. The aim of the study was to examine the in vitro effects of the isolated flavonoids on the contractility of a. basilaris. Administered alone, at concentration 10 µM, alcesefoliside and mauritianin did not influence the vascular tone of segment of a. basilaris. The combination of both compounds, at 10 µM, revealed an increased response of the vascular tone of a. basilaris. These effects of the flavonoids suggest their possible beneficial effect as further candidates in the complex therapy of neurodegenerative disease.

Vasorelaxant and Antihypertensive Effects of Bergenin on Isolated Rat Aorta and High Salt-Induced Hypertensive Rats

Bergenin is a phenolic glycoside that has been reported to be present in some medicinal plants which are traditionally used for their antihypertensive actions. So, bergenin was investigated for antihypertensive and vasorelaxant experiments in a rat model. Bergenin produced a significant fall in the mean arterial pressure (MAP) of rats. To explore the involvement of NO and muscarinic receptors, rats were pretreated with L-NAME and atropine in-vivo. The L-NAME did not change significantly the effect of bergenin on MAP excluding the involvement of NO. Unlike the L-NAME, atropine pretreatment reduced the effect of bergenin on MAP, indicating the role of muscarinic receptors. In in-vitro study, the bergenin produced endothelium-dependent (at lower concentrations) and independent (at higher concentrations) vasorelaxation, which was attenuated significantly in the presence of atropine and indomethacin but not with L-NAME. While a partial response was observed against K⁺-induced contractions. This was further confirmed when bergenin partly shifted the CaCl₂-CRCs toward right. Bergenin also suppressed the PE peak formation, indicating the antagonist effect against the release of Ca²⁺. Moreover, the bergenin-induced vasorelaxant response was not markedly attenuated with TEA, while significantly ablated with 4-AP and BaCl₂. In conclusion, the antihypertensive effects of bergenin are due to Ca²⁺ channel blockade, K⁺ channels activation, and muscarinic receptor-linked vasodilation.

Novel Polyhydroquinoline-Hydrazide-Linked Schiff's Base Derivatives: Multistep Synthesis, Antimicrobial, and Calcium-Channel-Blocking Activities

Polyhydroquinoline (PHQ) are the unsymmetrical Hantzsch derivatives of 1,4-dihydropyridines with several biological applications. In this work, twenty-five (3-27) new Schiff's base derivatives of polyhydroquinoline hydrazide were synthesized in excellent to good yields by a multi-component reaction. The structures of the synthesized products (1-27) were deduced with the help of spectroscopic techniques, such as 1H-, 13C -NMR, and HR-ESI-MS. The synthesized products (1-27) were tested for their antibacterial and in vitro calcium -channel-blocking (CCB) potentials using the agar-well diffusion method, and isolated rat aortic ring preparations, respectively. Among the series, sixteen compounds were found to inhibit the growth of Escherichia coli and Enterococcus faecalis. Among them, compound 17 was observed to be the most potent one at a dose 2 µg/mL, with an 18 mm zone of inhibition against both bacteria when it was compared with the standard drug amoxicillin. Eight compounds showed CCB activity of variable potency; in particular, compound 27 was more potent, with an EC50 value of 0.7 (0.3-1.1) µg/mL, indicating their CCB effect.

Investigation into the Antihypertensive Effects of Diosmetin and Its Underlying Vascular Mechanisms Using Rat Model

Objective: Diosmetin is a flavonoid that is found in many important medicinal plants that have antihypertensive therapeutic potential. Diosmetin has been shown to have antiplatelet, anti-inflammatory and antioxidant properties, which suggests that it could be a potential candidate for use in antihypertensive therapy. Methods: In vivo and in vitro methods were used for our investigation into the antihypertensive effects of diosmetin. Results: Diosmetin significantly decreased the mean arterial pressure (MAP). The effects of diosmetin on the MAP and heart rate were more pronounced in hypertensive rats. To explore the involvement of the muscarinic receptors-linked NO pathway, Nω-nitro-L-arginine methyl ester (L-NAME) and atropine were pre-administered in vivo. The pretreatment with L-NAME did not significantly change the effects of diosmetin on the MAP by excluding the involvement of NO. Unlike L-NAME, the atropine pretreatment reduced the effects of diosmetin on the MAP, which demonstrated the role of the muscarinic receptors. In the in vitro study, diosmetin at lower concentrations produced endothelium-dependent and -independent (at higher concentrations) vasorelaxation, which was attenuated significantly by the presence of atropine and indomethacin but not L-NAME. Diosmetin was also tested for high K+-induced contractions. Diosmetin induced significant relaxation (similar to verapamil), which indicated its Ca2+ antagonistic effects. This was further confirmed by diosmetin shifting the CaCl₂ CRCs toward the right due to its suppression of the maximum response. Diosmetin also suppressed phenylephrine peak formation, which indicated its antagonist effects on the release of Ca2+. Moreover, BaCl₂ significantly inhibited the effects of diosmetin, followed by 4-AP and TEA, which suggested that the K+ channels had a role as well. Conclusions: The obtained data showed the Ca2+ channel antagonism, potassium channel activation and antimuscarinic receptor-linked vasodilatory effects of diosmetin, which demonstrated its antihypertensive potential.

Biological active ingredients of Astragali Radix and its mechanisms in treating cardiovascular and cerebrovascular diseases

BACKGROUND

With the rising age of the global population, the incidence rate of cardiovascular and cerebrovascular diseases (CCVDs) is increasing, which causes serious public health burden. The efforts for new therapeutic approaches are still being sought since the treatment effects of existing therapies are not quite satisfactory. Chinese traditional medicine proved to be very efficient in the treatment of CCVDs. Well described and established in Chinese medicine, Astragali Radix, has been commonly administered in the prophylaxis and cure of CCVDs for thousands of years.

PURPOSE

This review summarized the action mode and mechanisms of Astragali Radix phytochemicals on CCVDs, hoping to provide valuable information for the future application, development and improvement of Astragali Radix as well as CCVDs treatment.

METHODS

A plenty of literature on biological active ingredients of Astragali Radix used for CCVDs treatment were retrieved from online electronic PubMed and Web of Science databases.

RESULTS

This review highlighted the effects of five main active components in Astragali Radix including astragaloside Ⅳ, cycloastragenol, astragalus polysaccharide, calycosin-7-O-β-d-glucoside, and calycosin on CCVDs. The mechanisms mainly involved anti-oxidative damage, anti-inflammatory, and antiapoptotic through signaling pathways such as PI3K/Akt, Nrf2/HO-1, and TLR4/NF-κB pathway. In addition, the majority active constituents in AR have no obvious toxic side effects.

CONCLUSION

The main active components of Astragali Radix, especially AS-IV, have been extensively summarized. It has been proved that Astragali Radix has obvious therapeutic effects on various CCVDs, including myocardial and cerebral ischemia, hypertension, atherosclerosis, cardiac hypertrophy, chronic heart failure. CAG possesses anti-ischemia activity without toxicity, indicating a worthy of further development. However, high-quality clinical and pharmacokinetic studies are required to validate the current studies.

Evaluation of processing mechanism in Astragali Radix by low-field nuclear magnetic resonance and magnetic resonance imaging

Astragali Radix (Huangqi) is an important herb medicine that is always processed into pieces for clinical use. Many operations need to be performed before use, among which drying of Astragali Radix (AR) pieces is a key step. Unfortunately, research on its drying mechanism is still limited. Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques were applied to study the moisture state and distribution during drying. The content of bioactive components and texture changes were measured by HPLC and texture analyzer, respectively. The moisture content of the AR pieces decreased significantly during drying, and the time to reach the drying equilibrium were different at different temperatures. The time when at 70°C, 80°C, and 90°C reach complete drying are 180 min, 150 min and 120 min, respectively. 80°C was determined as the optimum drying temperature, and it was observed that the four flavonoids and astragaloside IV have some thermal stability in AR pieces. When dried at 80°C, although the total water content decreased, the free water content decreased from 99.38% to 15.49%, in contrast to the increase in bound water content from 0.62% to 84.51%. The texture parameters such as hardness changed to some extent, with the hardness rising most significantly from 686.23 g to 2656.67 g. Correlation analysis revealed some connection between moisture content and LF-NMR and texture analyzer parameters, but the springiness did not show a clear correlation with most parameters. This study shows that HPLC, LF-NMR, MRI, and texture analyzers provide a scientific basis for elucidating the drying principles of AR pieces. The method is useful and shows potential for extension and application; therefore, it can be easily extended to other natural herb medicines.

Liriodendrin, ameliorates hypertension by calcium channel blockade and enhancing enos expression in wistar rats

Introduction: Hypertension is found to be the prime cause ofdeath worldwide in spite of a number of available treatmentswhich suggests that there is a need of discovering new leadmolecules that would be more effective to treat cardiovasculardisease (CVD). Liriodendrin, the lignan phytoconstituent possessespotential pharmacological effects. Literature survey suggeststhat liriodendrin could be effective in mitigating hypertensionconsidering its structural similarity with reported cardiovascularprotective drugs. Hence liriodendrin is investigated to reveal itsmechanism of actions to support its antihypertensive property.Methods: Hypertension was induced in male wistar rats withDOCA salt. Hypertensive rats were treated with liriodendrin for4 weeks. Blood pressure, heart rate, body weight, lipid profile,serum nitrite levels, vascular reactivity to various catecholamines,in-vitro calcium channel blocking assays, antioxidantassay, determination of aortic calcium level, endothelial function,expression of eNOS analysis were studied.Result: Liriodendrin was found safe orally up to 2000 mg/kg. Itshowed a significant decrease in heart rate, blood pressure andmean arterial pressure. In-vitro study on the isolated rat aorta revealedthe calcium channel blocking potential of liriodendrin. Vascularreactivity to various catecholamines was normalized. Vascularendothelium was significantly protected by the enhancedrelease of nitric oxide and eNOS expression by the western blottechnique. Oxidative stress was also significantly reduced.Conclusion: Liriodendrin was found to be beneficial in hypertensionas it produced vasorelaxation by blocking calciumchannels, enhancing nitric oxide release, and reducing oxidativestress. Thus, liriodendrin may be useful to relieve hypertensionand cardiovascular complications.

Calycosin ameliorates atherosclerosis by enhancing autophagy via regulating the interaction between KLF2 and MLKL in apoE-/- mice

BACKGROUND AND PURPOSE

Atherosclerosis is one of the underlying causes of cardiovascular disease. Formation of foam cells and necrotic core in the plaque is a hallmark of atherosclerosis, which results from lipid deposition, apoptosis, and inflammation in macrophage. Macrophage autophagy is a critical anti-atherogenic process and defective autophagy aggravates atherosclerosis by enhancing foam cell formation, apoptosis, and inflammation. Hence, enhancing autophagy can be a strategy for atherosclerosis treatment. Calycosin, a flavonoid from Astragali Radix, displays antioxidant and anti-inflammatory activities, and therefore is potential to reduce the risk of cardiovascular disease. However, the antiatherogenic effect of calycosin and the involved mechanism remains unclear. In this study, we assessed the potential benefits of calycosin on autophagy and atherosclerosis, and revealed the underlying mechanism.

EXPERIMENTAL APPROACH

In this study, apoE^-/- mice were fed high-fat diet for 16 weeks in presence of calycosin and/or autophagy inhibitor chloroquine, which was followed by determination of atherosclerosis development, autophagy activity, and the involved mechanisms.

KEY RESULTS

Calycosin protected against atherosclerosis and enhanced plaque stability via promoting autophagy. Calycosin inhibited foam cells formation, inflammation, and apoptosis by enhancing autophagy. MLKL was demonstrated as a new autophagy regulator, which can be negatively regulated by KLF2. Mechanistically, inhibitory effects of calycosin on atherogenesis were via improving autophagy through modulating KLF2-MLKL signaling pathway.

CONCLUSIONS AND IMPLICATIONS

This study demonstrated the atheroprotective effect of calycosin was through upregulating KLF2-MLKL-mediated autophagy, which not only proposed novel mechanistic insights into the atherogenesis but also identified calycosin as a potential drug candidate for atherosclerosis treatment.

Long non-coding RNAs in nasopharyngeal carcinoma: biological functions and clinical applications

Nasopharyngeal carcinoma (NPC) is one of the most common head and neck malignancies. It has obvious ethnic and regional specificity. Long non-coding RNAs (LncRNAs) are a class of non-protein coding RNA molecules. Emerging research shows that lncRNAs play a key role in tumor development, prognosis, and treatment. With the deepening of sequence analysis, a large number of functional LncRNAs have been found in NPC, which interact with coding genes, miRNAs, and proteins to form a complex regulatory network. However, the specific role and mechanism of abnormally expressed lncRNAs in the pathogenesis of NPC is not fully understood. This article briefly introduced the concept, classification, and functional mechanism of lncRNAs and reviewed their biological functions and their clinical applications in NPC. Specifically, we described lncRNAs related to the occurrence, growth, invasion, metastasis, angiogenesis, and cancer stem cells of NPC; discussed lncRNAs related to Epstein-Barr virus infection; and summarized the role of lncRNAs in NPC treatment resistance. We have also sorted out lncRNAs related to Chinese medicine treatment. We believe that with the deepening of lncRNAs research, tumor-specific lncRNAs may become a new target for the treatment and a biomarker for predicting prognosis.

Phytochemistry and cardiovascular protective effects of Huang-Qi (Astragali Radix)

Huang-Qi (Astragali Radix) is an herbal tonic widely used in China and many other countries. It is derived from the roots of Astragalus membranaceus and A. membranaceus var. mongholicus and shows potent cardiovascular protective effects. In this article, we comprehensively reviewed 189 small molecules isolated from the two Astragalus species and discussed the interspecies chemical differences. Moreover, we summarized the pharmacological activities and mechanisms of action of Huang-Qi and its major bioactive compounds for the treatment of cardiovascular diseases. This review covers 171 references published between February 1983 and March 2020.

Pharmacokinetic Analysis of Huangqi Guizhi Wuwu Decoction on Blood and Brain Tissue in Rats with Normal and Cerebral Ischemia-Reperfusion Injury by Microdialysis with HPLC-MS/MS

Objective

The aim of our research was to analyze and compare the pharmacokinetics of paeoniflorin, calycosin, calycosin-7-o-β-d-6-glucoside, and 6-gingerol in the blood and brain tissue of normal and cerebral ischemia-reperfusion injury rats by HPLC-MS/MS method.

Methods

The blood and brain tissue samples of normal and middle cerebral artery occlusion (MCAO) rats were compared. The blood and brain tissue samples were collected by using microdialysis technique. The concentrations of paeoniflorin, calycosin, calycosin-7-o-β-d-6-glucoside, and 6-gingerol in blood and brain tissues were determined by the HPLC-MS/MS internal standard method.

Results

Compared with the normal group, the model group after the administration of the Huangqi Guizhi Wuwu Decoction showed that C_{max blood}, AUC_{0-t blood}, and AUC_{0-inf blood} of paeoniflorin were increased, CL_blood, t_{1/2 brain}, and V_brain of paeoniflorin were decreased; C_maxblood, AUC_0-tblood, AUC_0-infblood, and average residence time (MRT_brain) of calycosin-7-o-β-d-6-glucoside were decreased and the CL_blood and C_{max brain} of calycosin-7-o-β-d-6-glucoside were increased; C_{max blood} of calycosin was decreased, V_blood and V_brain of calycosin were increased; C_{max blood}, AUC_{0-t blood}, AUC_{0-inf blood}, and MRT_brain of 6-gingerol were decreased, CL_blood of 6-gingerol was increased.

Conclusion

This method is simple, rapid, and sensitive. It is suitable for the pharmacokinetic study of Huangqi Guizhi Wuwu Decoction in the blood and brain tissue of rats. Cerebral ischemia-reperfusion injury increased the content of paeoniflorin, calycosin, calycosin-7-o-β-d-6-glucoside, and 6-gingerol in the blood, affecting the clearance rate of paeoniflorin in the brain, the detention time of calycosin-7-o-β-d-6-glucoside and the 6-gingerol in the brain. In normal and cerebral ischemia-reperfusion rats, the content of paeoniflorin and 6-gingerol in the blood was higher than that in brain tissue, while the content of calycosin, calycosin-7-o-β-d-6-glucoside in the brain tissue was higher than that in blood, suggesting that calycosin and calycosin-7-o-β-d-6-glucoside have brain targeting properties.

Juglone as antihypertensive agent acts through multiple vascular mechanisms

Background: Juglone, a natural phenolic compound obtained from the walnut tree, is known for its wide range of biological activities. However, it has yet to be tested for its effects on hypertension and vascular tone. This investigation was aimed to explore the antihypertensive effect and the nature of vascular reactivity of juglone in rat models.Methods: Juglone was tested in in vivo and in vitro experiments in rats. The responses were analyzed and recorded through a PowerLab data acquisition system.Results: Intravenous injection of juglone significantly decreased the mean arterial blood pressure (MAP) in normotensive and hypertensive rats (Max. fall, 43.50 ± 2.96 vs 49.66 ± 3.28 mmHg). In rats pretreated with Nω-Nitro l-arginine methyl ester (_L-NAME), the effect of juglone on MAP was reduced as compared to the control. However, in rats pretreated with atropine the fall in MAP by juglone was not altered. Juglone induced relaxation in the phenylephrine, K⁺ (80 mM), and angiotensin II pretreated isolated rat aortic rings. This vasorelaxant effect was reduced with _L-NAME pretreatment. Atropine pretreatment did not modify the vasorelaxant effect of juglone. Pre-incubation with juglone attenuated the intracellular Ca²⁺ release by suppressing phenylephrine peak formation and also shifted CaCl₂ concentration-response curves (CRCs) to the right. Of note, combined treatment with 4-aminopyridine and barium chloride also reduced juglone-mediated vasorelaxation suggesting a role of K⁺-channels as well.Conclusion: In conclusion, juglone exerts its antihypertensive effect through vasorelaxation, which is mediated by nitric oxide, inhibition of intracellular calcium release and opening of K⁺-channels.

New flavonoid-based compound synthesis strategy for antihypertensive drug development

Hypertension is one of the leading causes of mortality in relation to the cardiovascular conditions and easily the most overlooked and poorly managed disease in mankind. With well over 200 drugs available in the market globally, there is still an urgency to search for antihypertensive alternatives due to the subpar efficacy and unwarranted side effects of the current choices. Present studies reported over 250 types of plant-derived compounds were being investigated for potential pharmacological effects on the vasculature in the last 3 decades. There were numerous literatures that claimed various compounds exhibiting vasorelaxant properties to a certain extent with low numbers of these compounds being successfully adapted into the current medicinal practice for treatment of hypertension. The issue is the scarcity of reviews that summarizes the discovery of this field and the lack of thorough comparison of these compounds to identify which of these vasodilators should be the next face of hypertension management. Thus, this review is aiming towards identifying the relationship between a major class of plant-derived compounds, flavonoid's activity as a vasodilator with their signalling pathways and their structural characteristics according to their vasorelaxant properties. Interestingly, we found that both nitric oxide and voltage-operated calcium channels pathways, and two of the flavonoid's structural characteristics play crucial roles in eliciting strong vasorelaxant effects. We have faith that the insights of this review will serve as a reference for those researching similar topics in the future and potentially lead to the development of more promising antihypertensive alternative.

Patchouli alcohol isolated from Pogostemon cablin mediates endothelium-independent vasorelaxation by blockade of Ca2+ channels in rat isolated thoracic aorta

ETHNOPHARMACOLOGICAL RELEVANCE

The aerial parts of Pogostemon cablin (Blanco) Benth. for the treatment of cardiodynia have been documented in Mingyi Bielu of late Han Dynasty, in addition to that the Ca²⁺ antagonized activities of P. cablin and its critically pharmacological ingredient patchouli alcohol (PA) were reported previously.

AIM OF THE STUDY

To investigate the relaxant effects of PA on rat isolated thoracic aortas and further explore its potential mechanisms of actions.

MATERIALS AND METHODS

The aortas with endothelium and without endothelium were prepared and suspended in the organ bath for isometric tension recordings. The responses to accumulative concentrations of PA in endothelium-intact (E + ) aortas with basal tension and in different treated aortas pre-contracted with potassium chloride (KCl) or phenylephrine (PHE) were observed; the effects of L-NAME and indomethacin in aortas with intact endothelium, and of L-NAME, propranolol, tetraethtylamine (TEA), 4-aminopyridine (4-AP), barium chloride (BaCl₂), glyburide in aortas with endothelial denudation on PA-produced vasorelaxation were assessed; the influences of PA on extracellular Ca²⁺ influx and intracellular Ca²⁺ release were measured in Ca²⁺-free medium. Finally, the abilities of PA to inhibit KCl- and PHE-induced contractions were compared to that of verapamil in E- aortas.

RESULTS

PA produced vasorelaxant effects in KCl- and PHE-precontracted E + aortas in a concentration-dependent manner, which had no statistically different from that in KCl- and PHE-precontracted E- aortas. PA (10 μM) significantly reduced KCl-induced contractions while PHE-induced contractions were significantly reduced by 100 μM of PA instead of 10 μM and 30 μM in aortas with endothelium. Pre-incubation of E + aortas with L-NAME as well as indomethacin and of E- aortas with L-NAME, propranolol, TEA, 4-AP, BaCl₂ and glyburide had no obvious effects on vasorelaxation of PA. In endothelium-removed aortas around Ca²⁺-free solution, PA remarkably lowered the contractions stimulated with Ca²⁺ and PHE, and application of ruthenium red and heparin further enhanced the abilities of PA to reduce PHE-caused contractions. In aortas without endothelium, 100 μM of PA markedly attenuated KCl-induced contractions but not affect PHE-induced contractions. Verapamil at the equal dose markedly attenuated KCl- and PHE-induced contractions, and the inhibitory effects on KCl-induced contractions were more forceful than that on PHE-induced contractions. In combined usage, the inhibitory effects on the contractions elicited by KCl were evidently weaker than that of verapamil alone and indifferently stronger than that of PA alone, and the inhibitory effects on the contractions elicited by PHE were evidently weaker than that of single verapamil but stronger than that of single PA.

CONCLUSION

PA may act as a Ca²⁺ antagonist to exert an intensively vasorelaxant effects through endothelium-independent pathway, and its mechanisms underlying the vasoactivities seem to be associated with the blockade of extracellular Ca²⁺ influx through VDCCs and ROCCs in vascular smooth muscle cells (VSMCs) membrane and intracellular Ca²⁺ releases through IP₃R- and RYR-mediated Ca²⁺ channels in sarcolemma.

Targeting RNS/caveolin-1/MMP signaling cascades to protect against cerebral ischemia-reperfusion injuries: potential application for drug discovery

Reactive nitrogen species (RNS) play important roles in mediating cerebral ischemia-reperfusion injury. RNS activate multiple signaling pathways and participate in different cellular events in cerebral ischemia-reperfusion injury. Recent studies have indicated that caveolin-1 and matrix metalloproteinase (MMP) are important signaling molecules in the pathological process of ischemic brain injury. During cerebral ischemia-reperfusion, the production of nitric oxide (NO) and peroxynitrite (ONOO⁻), two representative RNS, down-regulates the expression of caveolin-1 (Cav-1) and, in turn, further activates nitric oxide synthase (NOS) to promote RNS generation. The increased RNS further induce MMP activation and mediate disruption of the blood-brain barrier (BBB), aggravating the brain damage in cerebral ischemia-reperfusion injury. Therefore, the feedback interaction among RNS/Cav-1/MMPs provides an amplified mechanism for aggravating ischemic brain damage during cerebral ischemia-reperfusion injury. Targeting the RNS/Cav-1/MMP pathway could be a promising therapeutic strategy for protecting against cerebral ischemia-reperfusion injury. In this mini-review article, we highlight the important role of the RNS/Cav-1/MMP signaling cascades in ischemic stroke injury and review the current progress of studies seeking therapeutic compounds targeting the RNS/Cav-1/MMP signaling cascades to attenuate cerebral ischemia-reperfusion injury. Several representative natural compounds, including calycosin-7-O-β-D-glucoside, baicalin, Momordica charantia polysaccharide (MCP), chlorogenic acid, lutein and lycopene, have shown potential for targeting the RNS/Cav-1/MMP signaling pathway to protect the brain in ischemic stroke. Therefore, the RNS/Cav-1/MMP pathway is an important therapeutic target in ischemic stroke treatment.

Metabolic profiling of the traditional Chinese medicine formulation Yu Ping Feng San for the identification of constituents relevant for effects on expression of TNF-α, IFN-γ, IL-1β and IL-4 in U937 cells

Yu Ping Feng San (YPFS) is a classical TCM formulation which has been traditionally used for treatment of immune system related diseases such as chronic bronchitis, allergic rhinitis and asthma. The formula is a mixture of Radix Saposhnikoviae (Fangfeng), Radix Astragali (Huangqi), and Rhizoma Atractylodis macrocephalae (Baizhu). TLC- and LC-DAD-ESI-MS/MS methods have been developed for the analysis of the metabolic profiles of the single herbs and of the formula. Decoctions and ASE extracts were analyzed in order to trace components of the individual herbs in YPFS. Nine constituents of Radix Saposhnikoviae, ten constituents of Radix Astragali and five constituents of Rhizoma Atractylodis macrocephalae have been assigned in the chemical profiles of the formula, which now allow the standardisation of YPFS. The pharmacological testing showed that all extracts significantly inhibited expression of TNF-α, IFN-γ, and IL-1β in U937 cells, while the inhibition of IL-4 was consistently low. Compared to conventional analyses which are focused on a limited set of compounds, metabolomics approaches, together with novel data processing tools, enable a more holistic comparison of the herbal extracts. In order to identify the constituents which are relevant for the immunomodulatory effects of the formula, metabolomics studies (PCA, OPLS-DA) have been performed using UPLC/QTOF MS data.

The Role of TRPC6 in the Neuroprotection of Calycosin Against Cerebral Ischemic Injury

Our previous studies have provided evidences that calycosin can protect the brain from ischemia/reperfusion injury, but its mechanisms is not fully understand. Transient receptor potential canonical 6 (TRPC6) has a critical role in promoting neuronal survival against cerebral ischemic injury. The aim of the present study is to test whether calycosin protects against cerebral ischemic injury through TRPC6-CREB pathway. In vivo, rats were subjected to transient middle cerebral artery occlusion (MCAO) for 2 h and then treated with different doses of calycosin at the onset of reperfusion. In vitro, primary cultured neurons were treated by calycosin, then exposed to 2 h oxygen glucose deprivation (OGD) followed by 24 h reoxygenation. Our results showed that treatment with calycosin protected against ischemia-induced damages by increasing TRPC6 and P-CREB expression and inhibiting calpain activation. The neuroprotection effect of calycosin was diminished by inhibition or knockdown of TRPC6 and CREB. These findings indicated that the potential neuroprotection mechanism of calycosin was involved with TRPC6-CREB pathway.

Calycosin and Formononetin Induce Endothelium-Dependent Vasodilation by the Activation of Large-Conductance Ca2+-Activated K+ Channels (BKCa)

Calycosin and formononetin are two structurally similar isoflavonoids that have been shown to induce vasodilation in aorta and conduit arteries, but study of their actions on endothelial functions is lacking. Here, we demonstrated that both isoflavonoids relaxed rat mesenteric resistance arteries in a concentration-dependent manner, which was reduced by endothelial disruption and nitric oxide synthase (NOS) inhibition, indicating the involvement of both endothelium and vascular smooth muscle. In addition, the endothelium-dependent vasodilation, but not the endothelium-independent vasodilation, was blocked by BK_Ca inhibitor iberiotoxin (IbTX). Using human umbilical vein endothelial cells (HUVECs) as a model, we showed calycosin and formononetin induced dose-dependent outwardly rectifying K⁺ currents using whole cell patch clamp. These currents were blocked by tetraethylammonium chloride (TEACl), charybdotoxin (ChTX), or IbTX, but not apamin. We further demonstrated that both isoflavonoids significantly increased nitric oxide (NO) production and upregulated the activities and expressions of endothelial NOS (eNOS) and neuronal NOS (nNOS). These results suggested that calycosin and formononetin act as endothelial BK_Ca activators for mediating endothelium-dependent vasodilation through enhancing endothelium hyperpolarization and NO production. Since activation of BK_Ca plays a role in improving behavioral and cognitive disorders, we suggested that these two isoflavonoids could provide beneficial effects to cognitive disorders through vascular regulation.

Flavonoids from the Genus Astragalus: Phytochemistry and Biological Activity

Flavonoids, the most common plant polyphenols are widely distributed in every species and possess a broad range of pharmacological activities. The genus Astragalus is the largest in the Fabaceae family with more than 2,500 species spread. They are known to contain different metabolites such as flavonoids, saponins, and polysaccharides. Plants from the genus have been used in the traditional medicine of many countries for centuries. This paper is focused on the large group of flavonoid compounds. Details on structure as well as information about the pharmacological properties of flavonoids, isolated from Astragalus species have been discussed. This review is based on publications until the first half of 2014 and includes also the results from our phytochemical investigations of the genus.

Effects of total flavones from Acanthopanax senticosus on L-type calcium channels, calcium transient and contractility in rat ventricular myocytes

Acanthopanax senticosus (Rupr. et Maxim.) Harms (AS), a traditional herbal medicine, has been widely used to treat ischemic heart disease. However, the underlying cellular mechanisms of its benefits to cardiac function remain unclear. The present study examined the effects of total flavones from AS (TFAS) on L-type Ca(2+) channel currents (ICa-L ) using the whole cell patch-clamp technique and on intracellular calcium ([Ca(2+) ]i ) handling and cell contractility in rat ventricular myocytes with the aid of a video-based edge-detection system. Exposure to TFAS resulted in a concentration- and voltage-dependent blockade of ICa-L , with the half-maximal inhibitory concentration (IC50 ) of 283.12 µg/mL and the maximal inhibitory effect of 36.49 ± 1.95%. Moreover, TFAS not only increased the maximum current in the current-voltage relationship but also shifted the activation and inactivation curves of ICa-L toward the hyperpolarizing direction. Meanwhile, TFAS significantly reduced amplitudes of myocyte shortening and [Ca(2+) ]i with an increase in the time to 10% of the peak (Tp) and a decrease in the time to 10% of the baseline (Tr). Thus, the cardioprotective effects of TFAS may be attributed mainly to the attenuation of [Ca(2+) ]i through the direct inhibition of ICa-L in rat ventricular myocytes and consequent negative effect on myocardial contractility.

Pharmaceutical properties of calycosin, the major bioactive isoflavonoid in the dry root extract of Radix astragali

CONTEXT

Radix astragali (Fabaceae astragalus propinquus Schischkin) is a Chinese medicinal herb traditionally used for the treatment of several diseases. Calycosin is the major bioactive chemical in the dry root extract of this medical plant.

OBJECTIVE

This work presents a brief overview of recent reports on the potential effects of calycosin on several diseases and the possible mechanisms of action of this chemical.

MATERIALS AND METHODS

This review gathers information from the scientific literature (before 1 June 2013) that was compiled from various databases, such as Science Direct, PubMed, Google Scholar, and Scopus.

RESULTS

The potential pharmaceutical properties of calycosin in the treatment of tumors, inflammation, stroke, and cardiovascular diseases have gained increasing attention in the recent years. The literature survey showed that calycosin exhibits promising effects for the treatment of several diseases and that these effects may be due to its isoflavonoid and phytoestrogenic properties. The effects of calycosin most likely result from its interaction with the ER receptors on the cell membrane and the modulation of the MAPK signaling pathway.

CONCLUSION

Calycosin exhibits great potential as a therapeutic drug and may be a successful example of the standardization and modernization of traditional Chinese herbal medicine.

Hypotensive and vasorelaxant effects of sericin-derived oligopeptides in rats

Sericin-derived oligopeptides obtained from silk cocoons were investigated for the in vivo hypotensive effect and investigated for the underlying mechanism involved in vasodilation in isolated rat thoracic aorta. In normotensive anesthetized rats, oligopeptides induced an immediate and transient hypotensive activity. In rat aortic rings, oligopeptides induced a concentration-dependent vasorelaxation in vessels precontracted with both KCl and phenylephrine (PE) with endothelium-intact or endothelium-denuded rings. In endothelium-intact rings, pretreatment with Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME, 100 µM), an inhibitor of the NO synthase (NOS) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 1 µM), a selective inhibitor of the guanylyl cyclase enzyme, significantly reduced the relaxant effect of oligopeptides. However, indomethacin, an inhibitor of the cyclooxygenase, had no effect on oligopeptides-induced relaxation. In addition, pretreatment with tetraethylammonium (TEA, 5 mM) reduced the maximal relaxant effect induced by oligopeptides. By contrast, relaxation was not affected by 4-aminopyridine (4-AP, 1 mM), glibenclamide (10 µM), or barium chloride (BaCl₂, 1 mM). In depolarization Ca²⁺-free solution, oligopeptides inhibited calcium chloride- (CaCl₂-) induced contraction in endothelium-denuded rings in a concentration-dependent manner. Nevertheless, oligopeptides attenuated transient contractions in Ca²⁺-free medium containing EGTA (1 mM) induced by 1 µM PE, but they were not affected by 20 mM caffeine. It is obvious that potent vasodilation effect of oligopeptides is mediated through both the endothelium and the vascular smooth muscle.

Vasodilator compounds derived from plants and their mechanisms of action

The present paper reviews vasodilator compounds isolated from plants that were reported in the past 22 years (1990 to 2012) and the different mechanisms of action involved in their vasodilator effects. The search for reports was conducted in a comprehensive manner, intending to encompass those metabolites with a vasodilator effect whose mechanism of action involved both vascular endothelium and arterial smooth muscle. The results obtained from our bibliographic search showed that over half of the isolated compounds have a mechanism of action involving the endothelium. Most of these bioactive metabolites cause vasodilation either by activating the nitric oxide/cGMP pathway or by blocking voltage-dependent calcium channels. Moreover, it was found that many compounds induced vasodilation by more than one mechanism. This review confirms that secondary metabolites, which include a significant group of compounds with extensive chemical diversity, are a valuable source of new pharmaceuticals useful for the treatment and prevention of cardiovascular diseases.

Study of the relationship between genetics and geography in determining the quality of Astragali Radix

Astragali Radix (AR), prepared from the roots of Astragalus membranaceus (FISCH. ex LINK) BUNGE or its variey, A. membranaceus (FISCH. ex LINK) BUNGE var. mongholicus (BUNGE) HSIAO., is one of the most used and valuable traditional Chinese medicines (TCMs). Historically, Hunyuan, Shanxi Province in China is the geo-authentic producing area of AR and crude AR from here called "geo-authentic." According to tradition, geo-authentic TCMs define both authenticity and quality. However, no scientific investigation has ever determined whether the superior quality of Hunyuan AR is due to the genetic characteristics or to the local environment. In our study, seeds of 30 AR samples representing the two varieties from different regions were cultivated in Hunyuan under the same conditions. A method, using ultra-performance liquid chromatography coupled with photodiode array detector and evaporative light scattering detectors, was developed to evaluate the quality through a simultaneous determination of four major isoflavonoids and four major saponins. The two AR varieties were successfully distinguished by principal component analysis while samples of the same species with different seeds origins could not be distinguished. A genetic study demonstrated that the internal transcribed spacer sequences of the nuclear ribosomal DNA in A. membranaceus var. mongholicus samples from different geographical regions were highly conservative. These results indicate that the content of active components in AR depends on the interaction of genotype and environment. At the varietal level, genetic properties appear to be more important for pharmaceutical quality than environmental factors, while on the intraspecific level environmental factors might be more important than genetic properties.

Vasorelaxant Effect of a Newly Synthesized Dihydropyridine Ethyl Ester (DHPEE) on Rat Thoracic Aorta: Dual Mechanism of Action

INTRODUCTION

DHPEE is a newly synthesized compound by merging the key structural elements in an angiotensin receptor blocker (Telmisartan) with key structural elements in 1,4- dihydropyridine calcium channel blocker (Nifedipine). In this study, we examined dual calcium channel blocking and AT1 antagonist activity for DHPEE.

METHODS

The functional inhibitory characteristics of DHPEE were studied in vitro in rat thoracic aorta preparations precontracted by phenylephrine (1μM) or KCl (80μM) or Ang II in normal or calcium-free solutions.

RESULTS

Concentration-dependent significant relaxation was observed in aortic rings precontracted with phenylephrine, KCl or Ang II. The tension increment produced by increasing external calcium was also reduced by DHPEE. DHPEE caused a marked decrease in the maximal contractile response of the vasoactive agents and shifted their concentration-response curves to the right.

CONCLUSION

DHPEE possesses dual characteristics and cause vasorelaxation by blocking the L-type calcium channels and blocking Ang II receptors (AT1) in rat aortic smooth muscle.

Cardiovascular ion channels as a molecular target of flavonoids

Flavonoids are a class of naturally occurring polyphenols abundant in edibles and beverages of plant origin. Epidemiological studies consistently associate high flavonoid intake with a reduced risk for the development of cardiovascular diseases. So far these beneficial effects have been mainly attributed to nonspecific antioxidant and antiinflammatory properties. However, there is an increasing body of evidence that flavonoids specifically target molecular structures including cardiovascular ion channels. Playing a pivotal role in the regulation of vascular tone and cardiac electric activity, ion channels represent a major target for the induction of antihypertensive and cardioprotective effects. Thus, pharmacological properties of flavonoids on cardiovascular ion channels, ion currents and tissue preparations are being increasingly addressed in experimental studies. Whereas it has become clear that cardiovascular ion channels represent an important molecular target of flavonoids, the published data have not yet been systematically reviewed.

Comparison of the immunoregulatory function of different constituents in radix astragali and radix hedysari

Radix Astragali (RA), known as “Huangqi” in China, is one of the most popular herbal medicines known worldwide to reinforce “Qi”. RA is traditionally prepared from the dried roots of Astragalus membranaceus (MJHQ) and A. membranaceus var. mongholicus (MGHQ). Radix Hedysari is named “Hongqi” (HQ), which is similar to RA. We assessed and compared the chemical constituents and bioactivity of RA and HQ. Different constituents were extracted into five major parts and were analyzed using different methods. Comparison of the immunological effects of extracts was done by using two immunological models. Results showed that flavonoids and saponins present in RA and HQ were not only structurally significantly different but also different in their immunological effect. Amino acids extract (AE) in MGHQ shows immunological effect while AE in MJHQ and HQ did not. Polysaccharides comprised the major constituents in RA and HQ. All polysaccharides extract (PE) of the three herbs showed similar levels of immunological effect in both immunological assays.

Combined effects of fangchinoline from Stephania tetrandra Radix and formononetin and calycosin from Astragalus membranaceus Radix on hyperglycemia and hypoinsulinemia in streptozotocin-diabetic mice

The anti-hyperglycemic action of Stephania tetrandra Radix (Stephania) is potentiated by Astragalus membranaceus BUNGE Radix (Astragali) in streptozotocin (STZ)-diabetic ddY mice (Tsutsumi et al., Biol. Pharm. Bull., 26, 313 (2003)). Fangchinoline (0.3-3 mg/kg), a main constituent of Stephania, decreased the high level of blood glucose and increased the low level of blood insulin in STZ-diabetic mice. Here, we investigated the combined effects of fangchinoline with isoflavone or isoflavonoid components (formononetin, calycosin and ononin) of Astragali on the hyperglycemia and hypoinsulinemia of STZ-diabetic mice. Formononetin, calycosin and ononin (0.03-0.1 mg/kg) alone did not affect the blood glucose or blood insulin level of the diabetic mice. Formononetin and calycosin (0.03-0.1 mg/kg) potentiated the anti-hyperglycemic action of fangchinoline (0.3 mg/kg), but ononin did not. Formononetin (0.1 mg/kg) facilitated the fangchinoline-induced insulin release, and calycosin (0.1 mg/kg) also facilitated it, though without statistical significance. In conclusion, the combined effect of fangchinoline with formononetin and calycosin on hyperglycemia in the diabetic mice accounted well for the therapeutic effect of the combination of Stephania with Astragali in Boi-ogi-to. The anti-hyperglycemic action of formononetin appeared to be due to its potentiating action on insulin release. Our strategy for studying combinations of crude drugs and their components in Kampo medicine has uncovered new potentiating effects of formononetin and calycosin on the anti-hyperglycemic action of fangchinoline in STZ-diabetic mice.

Hypertonic and isotonic potassium solutions have different effects on vessel contractility resulting in differences in optimal resting tension in rat aorta

AIM

To compare high K(+ )-induced contraction and optimal resting tension measured by two commonly used techniques of hypertonic and isotonic K(+ ) in aortas with and without adventitial fat from various age rats.

METHODS

Three age groups of rats (15, 25, and 62 weeks) were used to prepare thoracic aortic rings in which adventitial fat was either removed or left intact. High K(+ ) (30 mmol/L)-induced contractions were observed under increasing resting tensions of 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 g. Optimal resting tension was the resting tension at which the aorta showed a maximal contraction.

RESULTS

The contractions induced by 2 kinds of high K(+ ) were significantly different. Hypertonic and isotonic K(+ ) induced a different style of contraction, and the pattern varied with different ages. At the age of 15 weeks, isotonic K(+ )-induced contractions were greater than hypertonic K+-induced contractions. However, at the age of 62 weeks, isotonic K(+ )-induced contractions were smaller than hypertonic K(+ )-induced contractions. Optimal resting tensions measured by 2 kinds of high K(+ ) were inconsistent. Optimal resting tensions in different kinds of aortic preparations from various age rats were almost a constant of 2 g, determined by isotonic K(+ ), but a variable, determined by hypertonic K(+ ). The adventitial fat could delay the development of high K(+ )-induced contractions at different resting tensions, but had little effect on the maximal contractions.

CONCLUSION

Hypertonic and isotonic K(+ ) may produce different contractions resulting in differences in optimal resting tension in rat aorta.