Effect Of Rhy Research Articles

Rhynchophylline inhibits methamphetamine dependence via modulating the miR-181a-5p/GABRA1 axis

Ethnopharmacological relevanceUncaria rhynchophylla (Miq.) Miq. ex Havil. is a plant species that is routinely devoted in traditional Chinese medicine to treat central nervous system disorders. Rhynchophylline (Rhy), a predominant alkaloid isolated from Uncaria rhynchophylla (Miq.) Miq. ex Havil., has been demonstrated to reverse methamphetamine-induced (METH-induced) conditioned place preference (CPP) effects in mice, rats and zebrafish. The precise mechanism is still poorly understood, thus further research is necessary. Aim of studyThis study aimed to investigate the role of miRNAs in the inhibitory effect of Rhy on METH dependence. Materials and methodsA rat CPP paradigm and a PC12 cell addiction model were established. Microarray assays were used to screen and identify the candidate miRNA. Behavioral assessment, real-time PCR, dual-luciferase reporter assay, western blotting, stereotaxic injection of antagomir/agomir and cell transfection experiments were performed to elucidate the effect of the candidate miRNA and intervention mechanism of Rhy on METH dependence. ResultsRhy successfully reversed METH-induced CPP effect and the upregulated miR-181a-5p expression in METH-dependent rat hippocampus and PC12 cells. Moreover, suppression of miR-181a-5p by antagomir 181a reversed METH-induced CPP effect. Meanwhile, overexpression of miR-181a-5p by agomir 181a in combination with low-dose METH (0.5 mg/kg) elicited a significant CPP effect, which was blocked by Rhy through inhibiting miR-181a-5p. Finally, the result demonstrated that miR-181a-5p exerted its regulatory role by targeting γ-aminobutyric acid A receptor α1 (GABRA1) both in vivo and in vitro. ConclusionThis finding reveals that Rhy inhibits METH dependence via modulating the miR-181a-5p/GABRA1 axis, which may be a promising target for treatment of METH dependence.

Probing pathways by which rhynchophylline modifies sleep using spatial transcriptomics

BackgroundRhynchophylline (RHY) is an alkaloid component of Uncaria, which are plants extensively used in traditional Asian medicines. Uncaria treatments increase sleep time and quality in humans, and RHY induces sleep in rats. However, like many traditional natural treatments, the mechanisms of action of RHY and Uncaria remain evasive. Moreover, it is unknown whether RHY modifies key brain oscillations during sleep. We thus aimed at defining the effects of RHY on sleep architecture and oscillations throughout a 24-h cycle, as well as identifying the underlying molecular mechanisms. Mice received systemic RHY injections at two times of the day (beginning and end of the light period), and vigilance states were studied by electrocorticographic recordings.ResultsRHY enhanced slow wave sleep (SWS) after both injections, suppressed paradoxical sleep (PS) in the light but enhanced PS in the dark period. Furthermore, RHY modified brain oscillations during both wakefulness and SWS (including delta activity dynamics) in a time-dependent manner. Interestingly, most effects were larger in females. A brain spatial transcriptomic analysis showed that RHY modifies the expression of genes linked to cell movement, apoptosis/necrosis, and transcription/translation in a brain region-independent manner, and changes those linked to sleep regulation (e.g., Hcrt, Pmch) in a brain region-specific manner (e.g., in the hypothalamus).ConclusionsThe findings provide support to the sleep-inducing effect of RHY, expose the relevance to shape wake/sleep oscillations, and highlight its effects on the transcriptome with a high spatial resolution. The exposed molecular mechanisms underlying the effect of a natural compound should benefit sleep- and brain-related medicine.Graphical

Sleep-inducing effect of Rhynchophylline in EphA4 knockout mice.

We have recently demonstrated that the alkaloid rhynchophylline (RHY; purified from Uncaria plants) induces sleep and modifies electrocorticographic (ECoG) activity throughout the 24-h day in a vigilance state-dependent manner in wild-type mice. We here asked whether this alkaloid impacts wake/sleep variables in the absence of the cell adhesion protein EPHA4, via ECoG recording in EphA4 knockout (KO) mice submitted to the same RHY treatment contemporaneously to the wild-type mice (littermates). We uncover that RHY decreases time spent awake and increases time spent in slow wave sleep in EphA4 KO mice and alters the 24-h time course of ECoG activity during wakefulness and sleep states. These observations are similar to the reported effects of RHY in wild-type littermate animals, which strongly supports that RHY-driven sleep alterations are not dependent on the presence of EPHA4.

Recent Advances in the Anti-Inflammatory Activity of Plant-Derived Alkaloid Rhynchophylline in Neurological and Cardiovascular Diseases.

Rhynchophylline (Rhy) is a plant-derived indole alkaloid isolated from Uncaria species. Both the plant and the alkaloid possess numerous protective properties such as anti-inflammatory, neuroprotective, anti-hypertensive, anti-rhythmic, and sedative effects. Several studies support the significance of the anti-inflammatory activity of the plant as an underlying mechanism for most of the pharmacological activities of the alkaloid. Rhy is effective in protecting both the central nervous system and cardiovascular system. Cerebro-cardiovascular disease primarily occurs due to changes in lifestyle habits. Many previous studies have highlighted the significance of Rhy in modulating calcium channels and potassium channels, thereby protecting the brain from neurodegenerative diseases and related effects. Rhy also has anticoagulation and anti-platelet aggregation activity. Although Rhy has displayed its role in protecting the cardiovascular system, very little is explored about its intervention in early atherosclerosis. Extensive studies are required to understand the cardioprotective effects of Rhye. This review summarized and discussed the various pharmacological effects of Rhy in neuro- and cardioprotection and in particular the relevance of Rhy in preventing early atherosclerosis using Rhy-loaded nanoparticles.

Neuroprotective Effects of Rhynchophylline Against Aβ1-42-Induced Oxidative Stress, Neurodegeneration, and Memory Impairment Via Nrf2-ARE Activation.

Extensive studies have shown that oxidative stress is a crucial pathogenic factor in Alzheimer's disease (AD). Nuclear factor E2-related factor 2 (Nrf2) is a master cytoprotective regulator against oxidative stress, and thus represents an attractive therapeutic target in AD. The goal of our study is to investigate the contribution of Nrf2 in Rhynchophylline (Rhy)-induced neuroprotection in AD. The data showed that intraperitoneal administration of Rhy (10 or 20mg/kg) could ameliorate Aβ1-42-induced cognitive impairment, evidenced by performance improvement in memory tests. The result of Antioxidant response element (ARE)-luciferase activity assay indicated that Rhy treatment improved ARE promoter activity. The results of reactive oxygen species (ROS), malondialdehyde (MDA) and glutathione (GSH) assessment in the frontal cortex and hippocampus showed that Rhy treatment could attenuate Aβ1-42-induced oxidative stress to some extent, evidenced by reversion of these cytokines compared to Aβ1-42 + Veh group. Rhy treatment also restored expression of Nrf2 and its downstream protein heme oxygenase-1 (HO-1), NAD(P)H/quinone oxidoreductase 1 (NOQ1), and recombinant glutamate cysteine ligase, modifier subunit (GCLM) in the frontal cortex and hippocampus of Aβ1-42-treated mice. In addition, to investigate whether activation of Nrf2-mediated pathway is responsible for the neuroprotection of Rhy, Nrf2 siRNA was used in human neuroblastoma cells (SH-SY5Y). Interestingly, the results showed that the protective effects of Rhy, including anti-oxidative, anti-apoptosis and elevation of Nrf2 and its downstream proteins, were abolished in Nrf2 siRNA-transfected cells. These findings indicate that Rhynchophylline is protective against Aβ1-42-induced neurotoxicity via Nrf2-ARE activation, and suggest that Rhy may serve as a potential candidate and promising Nrf2 activator for management of AD.

Sustained-Release Hydrogel-Based Rhynchophylline Delivery System Improved Injured Tendon Repair

During the injured flexor tendon healing process, tendon tissue is easy to form extremely dense adhesion with the surrounding tissue, which causes the serious influence of hand function recovery. Uncaria is widely used in clinic and its main composition, Rhynchophylline (Rhy), has been reported on its good therapeutic effect, which could effectively inhibit the intra-abdominal adhesion formation. However, the therapeutic effect of Rhy on tendon healing and adhesion formation is still unclear. Due to the short half-life of Rhy, hyaluronic acid (HA) sustained-release system for Rhy delivery was constructed and it could also avoid drug from the undesired loss during the transit. After Rhy delivery system was applied around the injured tendons, adhesion formation, gliding function and healing strength of tendons were evaluated. Our results showed that the gliding excursion and healing strength of repaired tendons were both significantly increased, as well as the adhesion was inhibited. From in vivo experiments, Rhy could be able to increase the expression of Col Ⅰ/Col Ⅲ and helped fibroblasts to ordered organization for tendon tissues. But for adhesion tissues, Rhy promoted the apoptosis and accelerated the degradation of extracellular matrix. In vitro study showed Rhy could help tenocytes stimulated with TGF-β1 to recover to normal cell functions involving cell proliferation and apoptosis level. Through high-throughput sequencing, we found that Rhy was involved in the regulation of Extracellular Matrix (ECM) signaling pathway. We draw a conclusion that Rhy enhanced the tendon healing and prevented adhesion formation through inhibiting the phosphorylation of Smad2. In a word, this sustained release system of Rhy may be a promising strategy for the treatment of injured tendons.

Rhynchophylline improves trophocyte mobility potential by upregulating ZEB1 level via the inhibition of miR-141-3p level.

Preeclampsia (PE) is characterized by the impaired invasive ability of trophocytes, which can be modulated by microRNAs (miRs). In the current study, the effects of rhynchophylline (Rhy) on the viability and invasive ability of trophocytes were explored by focusing on miR-141-3p/ZEB1 axis. The level of miR-141-3p was modulated in human trophocytes and the changes in cell viability, apoptosis, invasive ability, and ZEB1 level were detected. Then the trophocytes with miR-141-3p overexpression were treated with Rhy and the effects on trophocyte phenotypes were assessed. The induced miR-141-3p level suppressed cell viability, induced apoptosis, and inhibited invasion and ZEB1 level in trophocytes. The treatment of Rhy restored the viability and invasive ability of trophocytes under the overexpression of miR-141-3p, indicating the protective effects of Rhy on trophocytes. The findings in the current study highlighted the protective effects of Rhy on trophocytes during PE progression, which was associated with the inhibition of miR-141-3p.

Protection by rhynchophylline against MPTP/MPP+-induced neurotoxicity via regulating PI3K/Akt pathway

Ethnopharmacological relevanceIsolated from Uncaria rhynchophylla (U. rhynchophylla), rhynchophylline (Rhy) has been applied for treating diseases related to central nervous system such as Parkinson's disease. Nevertheless, the molecular mechanism of the neuroprotective effect has not been well interpreted.Aim of the study: To investigate the effects of Rhy on MPTP/MPP + -induced neurotoxicity in C57BL/6 mice or PC12 cells and study the mechanisms involved. Materials and methodsThe neuroprotective effect of Rhy on MPTP-induced neurotoxicity was evaluated by spontaneous motor activity test, as well as a test of rota-rod on a rat model of Parkinson's disease. The numbers of TH-positive neurons in the substantia nigra pars compacta (SNpc) was assessed by immunohistological. CCK-8, lactate dehydrogenase (LDH), reactive oxygen species (ROS), the concentration of intracellular calcium ([Ca2+]i) and flow cytometry analysis were performed to evaluate the pharmacological property of Rhy on 1-methyl-4-phenylpyridinium (MPP+) induced neurotoxicity in PC12 cells. Besides, LY294002, a PI3K inhibitor was employed to determine the underlying molecular signaling pathway revealing the effect of Rhy by western-blot analysis. ResultsThe results showed that Rhy exhibited a protective effect against the MPTP-induced decrease in tyrosine hydroxylase (TH)-positive fibers in the substantia nigra at 30 mg/kg, demonstrated by the immunohistological and behavioral outcomes. Furthermore, it has been indicated that cell viability was improved and the MPP+-induced apoptosis was inhibited after the treatment of Rhy at 20 μM, which were severally analyzed by the CCK-8 and the Annexin V/propidium iodide staining method. In addition, Rhy treatment attenuated MPP+-induced up-regulation of LDH, ([Ca2+]i), and the levels of ROS. Besides, it can be revealed from the Western blot assay that LY294002, as a selective Phosphatidylinositol 3-Kinase (PI3K) inhibitor, effectively inhibited the Akt phosphorylation caused by Rhy, which suggested that Rhy showed its protective property through the activated the PI3K/Akt signaling pathway. Moreover, the Rhy-induced decreases of Bax and caspase-3 as the proapoptotic markers and the increase of Bcl-2 as the antiapoptotic marker, were blocked by LY294002 in the MPP+-treated PC12 cells. ConclusionsRhy exerts a neuroprotective effect is partly mediated by activating the PI3K/Akt signaling pathway.

Rhynchophylline attenuates migraine in trigeminal nucleus caudalis in nitroglycerin-induced rat model by inhibiting MAPK/NF-кB signaling.

Migraine causes severe health and social issues worldwide. Rhynchophylline (Rhy) is one of the major active components of Uncaria rhynchophylla that is used for the treatment of headache in Traditional Chinese Medicine. In the current study, the effect of Rhy on nitroglycerin (NTG)-induced migraine was assessed and the associated mechanism was also explored to explain its function. Rats were pre-treated with Rhy of two doses (10mg/kg and 30mg/kg) and then subjected to NTG to induce migraine symptoms. Thereafter, the electroencephalogram (EEG) signaling, spontaneous behaviors, levels of indicators related to oxidative stress, and expression of calcitonin gene-related peptide (CGRP) were measured to assess the anti-migraine function of Rhy. Moreover, the activities of MAPK/NF-κB pathway under the administrations of Rhy were also detected. The results showed that NTG induced EEG and behavior disorders in rats, which was associated with the initiation of oxidative stress and increased expression of CGRP. Nevertheless, the pre-treatments with Rhy attenuated the damages induced by NTG by reversing the levels of all the above indicators. The results of western blotting demonstrated that the anti-migraine effect of Rhy was accompanied by the inhibition of MAPK/NF-кB pathway. The findings outlined in the current study revealed an alternative mechanism of Rhy in protecting brain tissues against migraine: the agent exerted its effect by suppressing MAPK/NF-кB pathway, which would ameliorate impairments associated with migraine.

Rhynchophylline attenuates allergic bronchial asthma by inhibiting transforming growth factor-β1-mediated Smad and mitogen-activated protein kinase signaling transductions in vivo and in vitro.

Rhynchophylline (Rhy) is a major active component of Uncaria rhynchophylla and exhibits the potential to inhibit the proliferation of airway smooth muscle cells (ASMCs). In the current study, it was hypothesized that Rhy serves a key role in the anti-asthma effect of Uncaria rhynchophylla by inhibiting transforming growth factor-β1 (TGF-β1)-mediated activation of Smad and mitogen-activated protein kinase (MAPK) signaling. Allergic asthma was induced in mice using ovalbumin (OVA), and the effect of Rhy treatment on inflammatory and allergic responses in the bronchoalveolar lavage fluid (BALF) and serum of mice was determined. Subsequently, the changes in TGF-β1-induced Smad and MAPK signaling following Rhy administration were detected to determine the mechanism associated with this treatment. In addition, TGF-β1 was employed to induce hyperplasia of ASMCs, and the effect of Rhy on proliferation of ASMCs, and Smad and MAPK signaling in vitro was also assessed. The administration of Rhy attenuated the recruitment of eosinophils in BALF induced by OVA, which was associated with the suppressed production of immunoglobulin E, interleukin (IL)-13, IL-4 and IL-5. At the molecular level, the administration of Rhy suppressed the expression levels of TGF-β1, Smad4, p-Smad2 and p-Smad3, while it induced the expression of Smad7, indicating the inhibitory effect of Rhy on TGF-β1-mediated Smad and MAPK signaling. Furthermore, Rhy inhibited the proliferation of ASMCs and, similar to the results of the in vivo assay, it blocked the pro-hyperplasia signaling transduction in vitro. In conclusion, the current study demonstrated the anti-asthma effect of Rhy, which depended on the inhibition of TGF-β1-mediated Smad and MAPK signaling.

Rhynchophylline Downregulates Phosphorylated cAMP Response Element Binding Protein, Nuclear Receptor-related-1, and Brain-derived Neurotrophic Factor Expression in the Hippocampus of Ketamine-induced Conditioned Place Preference Rats.

Background:Addiction to ketamine is becoming a serious public health issues, for which there exists no effective treatment. Rhynchophylline (Rhy) is an alkaloid extracted from certain Uncaria species that is well known for both its potent anti-addictive and neuroprotective properties. Increasing evidence supports the contributions of cAMP response element binding protein (CREB), nuclear receptor-related-1 (Nurr1), and brain-derived neurotrophic factor (BDNF) in modulating neural and behavioral plasticity which was induced by addictive drugs.Objective:To investigate the effects of Rhy on the behavior and the levels of phosphorylated CREB (p-CREB), Nurr1, and BDNF in the hippocampus of ketamine-induced conditioned place preference (CPP) rats.Materials and Methods:CPP paradigm was used to establish the model of ketamine-dependent rats and to evaluate the effect of Rhy on ketamine dependence. The expressions of p-CREB, Nurr1, and BDNF were tested by Western blotting and immunohistochemistry.Results:We observed that Rhy can reverse the behavior preference induced by ketamine CPP training. At the same time, expression of p-CREB, Nurr1, and BDNF, which was significantly increased by ketamine, was restored in the Rhy -treated group.Conclusion:This study indicates that Rhy can reverse the reward effect induced by ketamine in rats and the mechanism can probably be related to regulate the hippocampal protein expression of p-CREB, Nurr1, and BDNF.SUMMARY P-CREB, Nurr1 and BDNF play an important role in the formation of ketamine-induced place preference in ratsRhynchophylline reversed the expression of p-CREB, Nurr1 and BDNF which was activated by ketamine in the hippocampusRhynchophylline demonstrates the potential effect of mediates ketamine induced rewarding effect. Abbreviations used: Rhy: Rhynchophylline; CREB: cAMP response element binding protein; Nurr1: Nuclear receptor-related-1; BDNF: Brain-derived neurotrophic factor; CPP: Conditioned place preference; NMDA: N-methyl-D-aspartic acid; METH: Methamphetamine; CNS: Central nervous system; PFA: Paraformaldehyde; GAPDH: Glyceraldehyde-3-phosphate dehydrogenase; LTP: long-term potentiation.

Isorhynchophylline, a Potent Plant Alkaloid, Induces Apoptotic and Anti-Metastatic Effects in Human Hepatocellular Carcinoma Cells through the Modulation of Diverse Cell Signaling Cascades.

Isorhynchophylline (Rhy) is an active pharmacological component of Uncaria rhynchophylla that has been reported previously to exert significant antihypertensive and neuroprotective effects. However, very little is known about its potential anti-cancer activities. This study was carried out to evaluate the anticancer effects of Rhy against various human carcinoma cell lines. We found that Rhy exhibited substantial cytotoxic effect against human hepatocellular carcinoma HepG2 cells when compared with other human carcinoma cell lines including those of lung, pancreas, prostate, head and neck, breast, multiple myeloma, brain and renal cell carcinoma. Rhy induced apoptosis as characterized by accumulation of cells in sub G1 phase; positive Annexin V binding; activation of caspase-8, -9, and -3; and cleavage of PARP (poly-ADP ribose polymerase). This effect of Rhy correlated with the down-regulation of various proteins that mediated cell proliferation, cell survival, metastasis, and angiogenesis. Moreover, cell proliferation, migration, and constitutive CXCR4 (C-X-C chemokine receptor type 4), MMP-9 (Matrix metallopeptidase-9), and MMP-2 expression were inhibited upon Rhy treatment. We further investigated the effect of Rhy on the oncogenic cell signaling cascades through phospho-kinase array profiling assay. Rhy was found to abrogate phospho-p38, ERK, JNK, CREB, c-Jun, Akt, and STAT3 signals, but interestingly enhanced phospho-p53 signal. Overall, our results indicate, for the first time, that Rhy could exert anticancer and anti-metastatic effects through regulation of multiple signaling cascades in hepatocellular carcinoma cells.

The role of rhynchophylline in alleviating early brain injury following subarachnoid hemorrhage in rats

Rhynchophylline (Rhy) has been demonstrated protective effects on some neurological diseases. However, the roles of Rhy in the subarachnoid hemorrhage (SAH) are still to be cleared. In the present study, the effects of Rhy on attenuation of early brain injury (EBI) after SAH have been evaluated. The adult male Sprague-Dawley rats (280–300g) were used to establish the SAH models using endovascular perforation method. Rhy was administered by intraperitoneal injection immediately following SAH. Brain edema was assessed by magnetic resonance imaging (MRI) at 24h after SAH. Neurological deficits, brain water content, malondialdehyde (MDA) concentration, myeloperoxidase (MPO) activity and reactive oxygen species (ROS) content in hippocampus were also evaluated. Immunofluorescence and western blot were used to explore the underlying protective mechanism of Rhy. The results showed that, following 10mg/kg Rhy treatment, the brain edema and neurological deficits, and blood-brain barrier (BBB) disruption were significantly attenuated at 24h after SAH. Additionally, in hippocampus, MDA concentration, MPO activity and ROS content were markedly decreased. Meanwhile, the levels of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase (NQO-1) were increased, while the expressions of p-p53, cleaved-caspase-3 and tumor necrosis factor-α (TNF-α) were significantly decreased. Our results indicated that Rhy could attenuate early brain injury by reducing inflammation and apoptosis in hippocampus after SAH.

Neuroprotective effects of rhynchophylline against ischemic brain injury via regulation of the Akt/mTOR and TLRs signaling pathways.

Rhynchophylline (Rhy) is an alkaloid isolated from Uncaria which has long been recommended for the treatment of central nervous diseases. In our study, the neuroprotective effect of Rhy was investigated in a stroke model, namely permanent middle cerebral artery occlusion (pMCAO). Rats were injected intraperitoneally once daily for four consecutive days before surgery and then received one more injection after surgery. The protein and mRNA levels of p-Akt, p-mTOR, apoptosis-related proteins (p-BAD and cleaved caspase-3), TLR2/4/9, NF-κB, MyD88, BDNF and claudin-5 were examined. Following pMCAO, Rhy treatment not only ameliorated neurological deficits, infarct volume and brain edema, but also increased claudin-5 and BDNF expressions (p < 0.05). Moreover, Rhy could activate PI3K/Akt/mTOR signaling while inhibiting TLRs/NF-κB pathway. Wortmannin, a selective PI3K inhibitor, could abolish the neuroprotective effect of Rhy and reverse the increment in p-Akt, p-mTOR and p-BAD levels. In conclusion, we hypothesize that Rhy protected against ischemic damage, probably via regulating the Akt/mTOR pathway.

Inhibitory effect of rhynchophylline on contraction of cerebral arterioles to endothelin 1: Role of rho kinase

Ethnopharmacological relevanceRhynchophylline (Rhy) is a major ingredient of Uncaria rhynchophylla (UR) used to reduce blood pressure and ameliorate brain ailments. This study was to examine the role of Rho kinase (ROCK) in the inhibition of Rhy on contraction of cerebral arterioles caused by endothelin 1 (ET-1). Materials and methodsCerebral arterioles of male Wistar rats were constricted with ET-1 for 10min followed by perfusion of Rhy for 20min. Changes in the diameters of the arterioles were recorded. The effects of Rhy on contraction of middle cerebral arteries (MCAs) were determined by a Multi-Myograph. Western blotting and immunofluorescent staining were used to examine the effects of Rhy on RhoA translocation and myosin phosphatase target subunit 1 (MYPT1) phosphorylation. ResultsIn vivo, Rhy (30–300µM) relaxed cerebral arterioles constricted with ET-1 dose-dependently. In vitro, Rhy at lower concentrations (1–100µM) caused relaxation of rat MCAs constricted with KCl and Bay-K8644 (an agonist of L-type voltage-dependent calcium channels (L-VDCCs)). Rhy at higher concentrations (>100µM) caused relaxation of rat MCAs constricted with ET-1, which was inhibited by Y27632, a ROCK׳s inhibitor. Western blotting of rat aortas showed that Rhy inhibited RhoA translocation and MYPT1 phosphorylation. Immunofluorescent staining of MCAs confirmed that phosphorylation of MYPT1 caused by ET-1 was inhibited by Rhy. ConclusionsThese results demonstrate that Rhy is a potent inhibitor of contraction of cerebral arteries caused by ET-1 in vivo and in vitro. The effect of Rhy was in part mediated by inhibiting RhoA–ROCK signaling.

Rhynchophylline-induced vasodilation in human mesenteric artery is mainly due to blockage of L-type calcium channels in vascular smooth muscle cells

Rhynchophylline (Rhy) is a pharmacologically active substance isolated from Uncaria rhynchophylla which has been used to treat cardiovascular diseases and has drawn considerable attention in recent years for its antihypertensive activities. We investigated the actions of Rhy on endothelium-denuded human mesenteric artery by tension measurement and its actions on high conductance Ca(2+)-activated K(+) channels (BKCa) currents and calcium currents (ICa) in freshly isolated smooth muscle cells using perforated patch clamp technique. Intracellular Ca(2+) level was measured in Fura-2-loaded cells. Rhy inhibited both the KCl and BayK-evoked mesenteric artery constrictions in a dose-dependent manner. K(+) channel blockers (TEA, glibenclamide, IbTX, and 4-AP) did not affect the vasorelaxing effect of Rhy. Rhy inhibited L-type voltage-gated Ca(2+) current (ICa,L) but had no significant effect on macroscopic BKCa current. Rhy preincubation markedly reduced the elevation of [Ca(2+)]i level induced by KCl depolarization. Caffeine-stimulated [Ca(2+)]i elevation was also decreased to some extent by pretreatment with Rhy for 20min. Our results show that Rhy relaxes smooth muscles of human mesenteric resistance arteries, mainly due to inhibition of Ca(2+) influx by blockage of L-type Ca(2+) channels and thereby the decrease in [Ca(2+)]i.

Rhynchophylline Protects Cultured Rat Neurons against Methamphetamine Cytotoxicity

Rhynchophylline (Rhy) is an active component isolated from species of the genus Uncaria which has been used for the treatment of ailments to the central nervous system in traditional Chinese medicine. Besides acting as a calcium channel blocker, Rhy was also reported to be able to protect against glutamate-induced neuronal death. We thus hypothesize that Rhy may have neuroprotective activity against methamphetamine (MA). The primary neurons were cultured directly from the cerebral cortex of neonatal rats, acting as in vitro model in the present study. The neurotoxicity of MA and the protective effect of Rhy were evaluated by MTT assay. The effects of MA, Rhy or their combination on intracellular free calcium concentration ([Ca2+]i) were determined in individual neocortical neurons by the Fluo-3/AM tracing method. The MTT assay demonstrated that MA has a dose-dependent neurotoxicity in neuronal cultures. The addition of Rhy prior to the exposure to MA prevented neuronal death. Time course studies with the Fluo-3/AM probe showed that Rhy significantly decreased neuronal [Ca2+]i which was elevated by the exposure to MA. Our results suggested that Rhy can protect the neuronal cultures against MA exposure and promptly attenuate intracellular calcium overload triggered by MA challenge. This is the first report demonstrating an inhibitory effect of Rhy against MA impairment in cultured neurons in vitro.