The hypotensive agent dodoneine inhibits L-type Ca2+ current with negative inotropic effect on rat heart

Purification, Structural Analysis and Cardio-Protective Activity of Polysaccharides from Radix Astragali

Two polysaccharides, named APS2-I and APS3-I, were purified from the water extract of Radix Astragali. The average molecular weight of APS2-I was 1.96 × 10⁶ Da and composed of Man, Rha, GlcA, GalA, Glc, Gal, Xyl, and Ara in a molar ratio of 2.3:4.8:1.7:14.0:5.8:11.7:2.8:12.6, while the average molecular weight of APS3-I was 3.91 × 10⁶ Da and composed of Rha, GalA, Glc, Gal, and Ara in a molar ratio of 0.8:2.3:0.8:2.3:4.1. Biological evaluation showed APS2-I and APS3-I had significant antioxidant activity and myocardial protection activity. Furthermore, total polysaccharide treatment could significantly enhance hemodynamic parameters and improve cardiac function in rat ischemia and reperfusion isolated heart models. These results provided important information for the clinical application of APS in the field of cardiovascular disease and implied that Astragalus polysaccharides (APS) could be considered as a reference for the quality control of Radix Astragali.

Plant and fungi derived analgesic natural products targeting voltage-gated sodium and calcium channels

Voltage-gated sodium and calcium channels (VGSCs and VGCCs) play an important role in the modulation of physiologically relevant processes in excitable cells that range from action potential generation to neurotransmission. Once their expression and/or function is altered in disease, specific pharmacological approaches become necessary to mitigate the negative consequences of such dysregulation. Several classes of small molecules have been developed with demonstrated effectiveness on VGSCs and VGCCs; however, off-target effects have also been described, limiting their use and spurring efforts to find more specific and safer molecules to target these channels. There are a great number of plants and herbal preparations that have been empirically used for the treatment of diseases in which VGSCs and VGCCs are involved. Some of these natural products have progressed to clinical trials, while others are under investigation for their action mechanisms on signaling pathways, including channels. In this review, we synthesize information from ~30 compounds derived from natural sources like plants and fungi and delineate their effects on VGSCs and VGCCs in human disease, particularly pain. [Figure: see text].

Pharmacological Effects of Hydrocotyle bonariensis Comm. ex Lam (Araliaceae) Extract on Cardiac Activity

Hydrocotyle bonariensis is one of the medicinal plants used in traditional medicine for the management of hypertension in Africa, Asia, and Latin America. However, the real impact of the traditional use of this plant on arterial hypertension has not yet been the subject of conclusive scientific information in the literature. This study aimed essentially to evaluate the potential cardiomodulatory effect of the hydroethanolic extract of Hydrocotyle bonariensis. In other to do so, the hydroethanolic extract of H. bonariensis was studied in vivo on the Wistar rat ECG and then in vitro on the isolated perfused Wistar rat heart using the Langendorff system. The extract was also tested on isolated guinea pig atria kept alive in the organ-specific vessel under physiological conditions similar to those of a living organism. At the cellular level, the effects of the extract were evaluated on the human cardiac sodium current INav1.5 and on the human cardiac pacemaker current If. We noted that the extract caused a decrease in P wave and T wave amplitudes and heart rate and an increase in the duration of the RR interval on the in vivo rat ECG. On the isolated perfused Langendorff heart as well as on the isolated atria, a decrease in the RR interval and in the heart rate was noted. The extract had no effect on human cardiac sodium current, but it did reduce human cardiac pacemaker current. In conclusion, the present study demonstrated that Hydrocotyle bonariensis, a medicinal plant traditionally used to prevent and treat hypertension, has an overall cardiomoderating effect. This effect would contribute to the reduction of blood pressure.

Production of lactones for flavoring and pharmacological purposes from unsaturated lipids: an industrial perspective

The enantiomeric pure and natural (+)-Lactones (C ≤ 14) with aromas obtained from fruits and milk are considered flavoring compounds. The flavoring value is related to the lactones' ring size and chain length, which blend in varying concentrations to produce different stone-fruit flavors. The nature-identical and enantiomeric pure (+)-lactones are only produced through whole-cell biotransformation of yeast. The industrially important γ-decalactone and δ-decalactone are produced by a four-step aerobic-oxidation of ricinoleic acid (RA) following the lactonization mechanism. Recently, metabolic engineering strategies have opened up new possibilities for increasing productivity. Another strategy for increasing yield is to immobilize the RA and remove lactones from the broth regularly. Besides flavor impact, γ-, δ-, ε-, ω-lactones of the carbon chain (C8-C12), the macro-lactones and their derivatives are vital in pharmaceuticals and healthcare. These analogues are isolated from natural sources or commercially produced via biotransformation and chemical synthesis processes for medicinal use or as active pharmaceutical ingredients. The various approaches to biotransformation have been discussed in this review to generate more prospects from a commercial point of view. Finally, this work will be regarded as a magical brick capable of containing both traditional and genetic engineering technology while contributing to a wide range of commercial applications.

Influence of Crocetin, a Natural Carotenoid Dicarboxylic Acid in Saffron, on L-Type Ca2+ Current, Intracellular Ca2+ Handling and Contraction of Isolated Rat Cardiomyocytes

Crocetin is a major bioactive ingredient in saffron (Crocus sativus L.) and has favorable cardiovascular effects. Here, the effects of crocetin on L-type Ca²⁺ current (I_Ca-L), contractility, and the Ca²⁺ transients of rat cardiomyocytes, were investigated via patch-clamp technique and the Ion Optix system. A 600 µg/mL dose of crocetin decreased I_Ca-L 31.50 ± 2.53% in normal myocytes and 35.56 ± 2.42% in ischemic myocytes, respectively. The current voltage nexus of the calcium current, the reversal of the calcium current, and the activation/deactivation of the calcium current was not changed. At 600 µg/mL, crocetin abated cell shortening by 28.6 ± 2.31%, with a decrease in the time to 50% of the peak and a decrease in the time to 50% of the baseline. At 600 µg/mL, crocetin abated the crest value of the ephemeral Ca²⁺ by 31.87 ± 2.57%. The time to half maximal of Ca²⁺ peak and the time constant of decay of Ca²⁺ transient were both reduced. Our results suggest that crocetin inhibits L-type Ca²⁺ channels, causing decreased intracellular Ca²⁺ concentration and contractility in adult rat ventricular myocytes. These findings reveal crocetin's potential use as a calcium channel antagonist for the treatment of cardiovascular disease.

Chenodeoxycholic and deoxycholic acids induced positive inotropic and negative chronotropic effects on rat heart

Bile acids are endogenous amphiphilic steroids from the metabolites of cholesterol. Studies showed that they might contribute to the pathogenesis of cardiopathy in cholestatic liver diseases. Chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA) is associated with colon cancer, gallstones, and gastrointestinal disorders. However, little information is available regarding their cardiac effects. Here, we reported that CDCA (100 μM) and DCA (100 μM) significantly increased the left ventricular developed pressure of the isolated rat hearts to 122.3 ± 5.6% and 145.1 ± 13.7%, and the maximal rate of the pressure development rising and descending (± dP/dtmax) to 103.4 ± 17.6% and 124.4 ± 37.7% of the basal levels, respectively. They decreased the heart rate and prolonged the RR, QRS, and QT intervals of Langendorff-perfused hearts in a concentration-dependent manner. Moreover, CDCA and DCA increased the developed tension of left ventricular muscle and the cytosolic Ca2+ concentrations in left ventricular myocytes; these functions positively coordinated with their inotropic effects on hearts. Additionally, CDCA (150 μM) and DCA (100 μM) decreased the sinoatrial node beating rate to 80.6 ± 3.0% and 79.7 ± 0.9% of the basal rate (334.2 ± 10.7 bpm), respectively. These results were consistent with their chronotropic effects. In conclusion, CDCA and DCA induced positive inotropic effects by elevating the Ca2+ in left ventricular myocytes. They exerted negative chronotropic effects by lowering the pace of the sinoatrial node in rat heart. These results indicated that the potential role of bile acids in cardiopathy related to cholestasis.

Protective effect of quercetin against myocardial ischemia as a Ca2+ channel inhibitor: involvement of inhibiting contractility and Ca2+ influx via L-type Ca2+ channels

Many studies describe the stimulating effect of quercetin on Ca²⁺ channels and the treatment of cardiovascular diseases such as myocardial ischemia and hypertension. However, these studies are scattered and contradictory. The aim of this study is to elucidate the protective effects of quercetin against isoproterenol (ISO)-induced myocardial ischemia and verify the cellular mechanisms based on the L-type Ca²⁺ channel (LTCC), Ca²⁺ transients, and myocardial contractility. An animal model of myocardial ischemia was established by subcutaneous injection of ISO for 2 days. Quercetin significantly reduced J-point elevation, heart rate, reactive oxygen species, serum levels of myocardial enzymes, superoxide dismutase, catalase, glutathione, glutathione peroxidase, glutathione S-transferase and improved heart pathologic morphology. L-type Ca²⁺ current (I_Ca-L) was tested in an experiment with isolated rat myocardial cells by using the whole-cell patch-clamp recording technique and IonOptix Myocam detection system. Quercetin reduced I_Ca-L in a concentration-dependent fashion with a half-maximal inhibitory concentration of 4.67 × 10^-4 M. Quercetin also shifted the current-voltage curve upwards, moved the activation and inactivation curves to the left and inhibited the amplitude of the cell shortening and Ca²⁺ transients. The results showed that quercetin acts as a LTCC inhibitor and exerts a cardioprotective effect by inhibiting Ca²⁺ influx and contractility in rats.

Berberine Mediated Positive Inotropic Effects on Rat Hearts via a Ca2+-Dependent Mechanism

Previous studies showed that berberine, an alkaloid from Coptis Chinensis Franch, might exert a positive inotropic effect on the heart. However, the underlying mechanisms were unclear. Here, we reported that berberine at 10–20 µM increased the left ventricular (LV) developed pressure and the maximal rate of the pressure rising, and it increased the maximal rate of the pressure descending at 20 µM in Langendorff-perfused isolated rat hearts. These effects diminished with the concentration of berberine increasing to 50 µM. In the concentration range of 50–300 µM, berberine increased the isometric tension of isolated left ventricular muscle (LVM) strips with or without electrical stimulations, and it (30–300 µM) also increased the intracellular Ca²⁺ level in the isolated LV myocytes. The removal of extracellular Ca²⁺ hindered the berberine-induced increases in the tension of LVM strips and the intracellular Ca²⁺ level of LV myocytes. These suggested that berberine might exert its positive inotropic effects via enhancing Ca²⁺ influx. The blockade of L-type Ca²⁺ channels (LTCCs) with nifedipine significantly attenuated 300 μM berberine-induced tension increase in LVM strips but not the increase in the intracellular Ca²⁺ level. Berberine (300 μM) further increased the LVM tension following the treatment with the LTCC opener FPL-64716 (10 μM), indicating an LTCC-independent effect of berberine. Lowering extracellular Na⁺ attenuated the berberine-induced increases in both the tension of LVM strips and the intracellular Ca²⁺ level of LV myocytes. In conclusion, berberine might exert a positive inotropic effect on the isolated rat heart by enhancing the Ca²⁺ influx in LV myocytes; these were extracellular Na⁺-dependent.

Recent Advances in the Stereoselective Total Synthesis of Natural Pyranones Having Long Side Chains

Pyranone natural products have attracted great attention in recent years from chemists and biologists due to their fascinating stereoisomeric structural features and impressive bioactivities. A large number of stereoselective total syntheses of these compounds have been described in the literature. The natural pyranones with long side chains have recently received significant importance in the synthetic field. In the present article, we aim to review the modern progress of the stereoselective total syntheses of these natural pyranones containing long-chain substituents.

Bioactive Natural Product and Superacid Chemistry for Lead Compound Identification: A Case Study of Selective hCA III and L-Type Ca2+ Current Inhibitors for Hypotensive Agent Discovery

Dodoneine (Ddn) is one of the active compounds identified from Agelanthusdodoneifolius, which is a medicinal plant used in African pharmacopeia and traditional medicine for the treatment of hypertension. In the context of a scientific program aiming at discovering new hypotensive agents through the original combination of natural product discovery and superacid chemistry diversification, and after evidencing dodoneine's vasorelaxant effect on rat aorta, superacid modifications allowed us to generate original analogues which showed selective human carbonic anhydrase III (hCA III) and L-type Ca²⁺ current inhibition. These derivatives can now be considered as new lead compounds for vasorelaxant therapeutics targeting these two proteins.

Anti-Hypertensive Herbs and Their Mechanisms of Action: Part II

Traditional medicine has a history extending back to thousands of years, and during the intervening time, man has identified the healing properties of a very broad range of plants. Globally, the use of herbal therapies to treat and manage cardiovascular disease (CVD) is on the rise. This is the second part of our comprehensive review where we discuss the mechanisms of plants and herbs used for the treatment and management of high blood pressure. Similar to the first part, PubMed and ScienceDirect databases were utilized, and the following keywords and phrases were used as inclusion criteria: hypertension, high blood pressure, herbal medicine, complementary and alternative medicine, endothelial cells, nitric oxide (NO), vascular smooth muscle cell (VSMC) proliferation, hydrogen sulfide, nuclear factor kappa-B (NF-κB), oxidative stress, and epigenetics/epigenomics. Each of the aforementioned keywords was co-joined with plant or herb in question, and where possible with its constituent molecule(s). This part deals in particular with plants that are used, albeit less frequently, for the treatment and management of hypertension. We then discuss the interplay between herbs/prescription drugs and herbs/epigenetics in the context of this disease. The review then concludes with a recommendation for more rigorous, well-developed clinical trials to concretely determine the beneficial impact of herbs and plants on hypertension and a disease-free living.

New Findings on the Effects of Tannic Acid: Inhibition of L-Type Calcium Channels, Calcium Transient and Contractility in Rat Ventricular Myocytes

Tannic acid (TA) is a group of water-soluble polyphenolic compounds that occur mainly in plant-derived feeds, food grains and fruits. Many studies have explored its biomedical properties, such as anticancer, antibacterial, antimutagenic, antioxidant, antidiabetic, antiinflammatory and antihypertensive activities. However, the effects of TA on the L-type Ca(2+) current (ICa-L) of cardiomyocytes remain undefined. The present study examined the effects of TA on ICa-L using the whole-cell patch-clamp technique and on intracellular Ca(2+) handling and cell contractility in rat ventricular myocytes with the aid of a video-based edge detection system. Exposure to TA resulted in a concentration- and voltage-dependent blockade of ICa-L, with the half maximal inhibitory concentration of 1.69 μM and the maximal inhibitory effect of 46.15%. Moreover, TA significantly inhibited the amplitude of myocyte shortening and peak value of Ca(2+) transient and increased the time to 10% of the peak. These findings provide new experimental evidence for the cellular mechanism of action of TA and may help to expand clinical treatments for cardiovascular disease.

Crocin, a carotenoid component of Crocus cativus, exerts inhibitory effects on L-type Ca(2+) current, Ca(2+) transient, and contractility in rat ventricular myocytes

Crocin, a carotenoid component of Crocus sativus L. belonging to the Iridaceae family, has demonstrated cardioprotective effects. To investigate the cellular mechanisms of these cardioprotective effects, here we studied the influence of crocin on L-type Ca(2+)current (I(Ca-L)), intracellular Ca(2+) ([Ca(2+)]i), and contraction of isolated rat cardiomyocytes by using the whole-cell patch-clamp technique and video-based edge detection and dual excitation fluorescence photomultiplier systems. Crocin inhibited I(Ca-L) in a concentration-dependent manner with the half-maximal inhibitory concentration (IC50) of 45 μmol/L and the maximal inhibitory effect of 72.195% ± 1.54%. Neither current-voltage relationship of I(Ca-L), reversal potential of I(Ca-L), nor the activation/inactivation of I(Ca-L) was significantly changed. Crocin at 1 μmol/L reduced cell shortening by 44.64% ± 2.12% and the peak value of the Ca(2+) transient by 23.66% ± 4.52%. Crocin significantly reduced amplitudes of myocyte shortening and [Ca(2+)]i with an increase in the time to reach 10% of the peak (Tp) and a decrease in the time to 10% of the baseline (Tr). Thus, the cardioprotective effects of crocin may be attributed to the attenuation of [Ca(2+)]i through the inhibition of I(Ca-L) in rat cardiomyocytes and negative inotropic effects on myocardial contractility.

Vasorelaxation induced by dodoneine is mediated by calcium channels blockade and carbonic anhydrase inhibition on vascular smooth muscle cells

ETHNOPHARMACOLOGICAL RELEVANCE

Dodoneine (Ddn) is one of the active compounds identified from Agelanthus dodoneifolius (DC.) Polhill and Wiens, a medicinal plant used in traditional medicine for the treatment of hypertension. This dihydropyranone exerts hypotensive and vasorelaxant effects on rats, and two molecular targets have been characterized: the carbonic anhydrase and the L-type calcium channel in cardiomyocytes with biochemical and electrophysiological techniques, respectively. To further evaluate the involvement of these two molecular targets in vasorelaxation, the effect of Ddn on rat vascular smooth muscle was investigated.

MATERIAL AND METHODS

The effects of Ddn on L-type calcium current and on resting membrane potential were characterized in A7r5 cell line using the whole-cell patch-clamp configuration. The molecular identities of carbonic anhydrase isozymes in smooth muscle cells were examined with RT-PCR. Vascular response was measured on rat aortic rings in an organ bath apparatus and the effect of Ddn on intracellular pH was determined by flow cytometry using the pH-sensitive fluorescent probe BCECF-AM [2,7-Bis-(2-Carboxyethyl)-5-(and-6)-Carboxyfluorescein, Acetoxymethyl Ester].

RESULTS

100µM Ddn reduced calcium current density of about 30%. In addition, carbonic anhydrase II, III, XIII and XIV were shown to be expressed in rat aorta and inhibited in smooth muscle cells by Ddn. This inhibition resulted in a rise in pHi of about 0.31, leading to KCa channel activation, thereby inducing membrane hyperpolarization and vasorelaxation. The results of vascular reactivity experiments obtained with pharmacological tools acting on the L-type calcium current and carbonic anhydrase suggest that Ddn produces its vasorelaxant effect via the inhibition of these two molecular targets.

CONCLUSION

This study demonstrates that Ddn induced vasorelaxation by targeting two proteins involved in the modulation of excitation-contraction coupling: L-type calcium channels and carbonic anhydrase.