Inhibitory effects of lappaconitine on the neuronal isoforms of voltage-gated sodium channels

Therapeutic Potentials of Aconite-like Alkaloids: Bioinformatics and Experimental Approaches

Compounds from plants that are used in traditional medicine may have medicinal properties. It is well known that plants belonging to the genus Aconitum are highly poisonous. Utilizing substances derived from Aconitum sp. has been linked to negative effects. In addition to their toxicity, the natural substances derived from Aconitum species may have a range of biological effects on humans, such as analgesic, anti-inflammatory, and anti-cancer characteristics. Multiple in silico, in vitro, and in vivo studies have demonstrated the effectiveness of their therapeutic effects. In this review, the clinical effects of natural compounds extracted from Aconitum sp., focusing on aconitelike alkaloids, are investigated particularly by bioinformatics tools, such as the quantitative structure- activity relationship method, molecular docking, and predicted pharmacokinetic and pharmacodynamic profiles. The experimental and bioinformatics aspects of aconitine's pharmacogenomic profile are discussed. Our review could help shed light on the molecular mechanisms of Aconitum sp. compounds. The effects of several aconite-like alkaloids, such as aconitine, methyllycacintine, or hypaconitine, on specific molecular targets, including voltage-gated sodium channels, CAMK2A and CAMK2G during anesthesia, or BCL2, BCL-XP, and PARP-1 receptors during cancer therapy, are evaluated. According to the reviewed literature, aconite and aconite derivatives have a high affinity for the PARP-1 receptor. The toxicity estimations for aconitine indicate hepatotoxicity and hERG II inhibitor activity; however, this compound is not predicted to be AMES toxic or an hERG I inhibitor. The efficacy of aconitine and its derivatives in treating many illnesses has been proven experimentally. Toxicity occurs as a result of the high ingested dose; however, the usage of this drug in future research is based on the small quantity of an active compound that fulfills a therapeutic role.

Lappaconitine sulfate inhibits proliferation and induces mitochondrial-mediated apoptosis via regulating PI3K/AKT/GSK3β signaling pathway in HeLa cells

Lappaconitine (LA), a diterpenoid alkaloid extracted from the root of Aconitum sinomontanum Nakai, exhibits broad pharmacological effects, including anti-tumor activity. The inhibitory effect of lappaconitine hydrochloride (LH) on HepG2 and HCT-116 cells and the toxicity of lappaconitine sulfate (LS) on HT-29, A549, and HepG2 cells have been described. But the mechanisms of LA against human cervical cancer HeLa cells still need to be clarified. This study was designed to investigate the effects and molecular mechanisms of lappaconitine sulfate (LS) on the growth inhibition and apoptosis in HeLa cells. The cell viability and proliferation were evaluated using the Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2´-deoxyuridine (EdU) assay, respectively. The cell cycle distribution and apoptosis were detected by flow cytometry analysis and 4', 6-diamidino-2-phenylindole (DAPI) staining. The mitochondrial membrane potential (MMP) was determined through the 5, 5', 6, 6'-tetrachloro-1, 1', 3, 3'-tetraethylbenzimi-dazolyl carbocyanine iodide (JC-1) staining. The cell cycle arrest-, apoptosis-, and the phosphatidylinositol-3-kinase/protein kinase B/glycogen synthase kinase 3β (PI3K/AKT/GSK3β) pathway-related proteins were estimated by western blot analysis. LS markedly reduced the viability and suppressed the proliferation of HeLa cells. LS induced G0/G1 cell cycle arrest through the inhibition of Cyclin D1, p-Rb, and induction of p21 and p53. Furthermore, LS triggered apoptosis through the activation of mitochondrial-mediated pathway based on decrease of Bcl-2/Bax ratio and MMP and activation of caspase-9/7/3. Additionally, LS led to constitutive downregulation of the PI3K/AKT/GSK3β signaling pathway. Collectively, LS inhibited cell proliferation and induced apoptosis through mitochondrial-mediated pathway by suppression of the PI3K/AKT/GSK3β signaling pathway in HeLa cells.

Tetracaine downregulates matrix metalloproteinase activity and inhibits invasiveness of strongly metastatic MDA-MB-231 human breast cancer cells

Tetracaine, a long-acting amino ester-type local anesthetic, prevents the initiation and propagation of action potentials by reversibly blocking voltage-gated sodium channels (VGSCs). These channels, which are highly expressed in several carcinomas (e.g. breast, prostate, colon and lung cancers) have been implicated in promoting metastatic behaviours. Recent evidence suggests that local anesthetics can suppress cancer progression. In this paper, we aimed to explore whether tetracaine would reduce the invasive characteristics of breast cancer cells. In a comparative approach, we used two cell lines of contracting metastatic potential: MDA-MB-231 (strongly metastatic) and MCF-7 (weakly metastatic). Tetracaine (50 μM and 75 μM) did not affect the proliferation of both MDA-MB-231 and MCF-7 cells. Importantly, tetracaine suppressed the migratory, invasive, and adhesive capacities of MDA-MB-231 cells; there was no effect on the motility of MCF-7 cells. Tetracaine treatment also significantly decreased the expression and activity levels of MMP-2 and MMP-9, whilst increasing TIMP-2 expression in MDA-MB-231 cells. On the other hand, VGSC α/Nav1.5 and VGSC-β1 mRNA and protein expression levels were not affected. We conclude that tetracaine has anti-invasive effects on breast cancer cells and may be exploited clinically, for example, in surgery and/or in combination therapies.

A review on efforts for improvement in medicinally important chemical constituents inAconitum through biotechnological interventions

The genus Aconitum belongs to the family Ranunculaceae, is endowed with more than 350 species on the earth. Medicinally important aconitine type of diterpenoid alkaloids are the characteristic compounds in most of the Aconitum species. The present review endeavored the major research carried out in the field of genetic resource characterization, pharmacological properties, phytochemistry, major factors influencing quantity, biosynthetic pathways and processing methods for recovery of active ingredients, variety improvement, propagation methods, and important metabolite production through cell/organ culture of various Aconitum species. More than 450 derivatives of aconitine-type C19 and C20-diterpenoid alkaloids along with a few other non-alkaloidal compounds, such as phenylpropanoids, flavonoids, terpenoids, and fatty acids, have been identified in the genus. A few Aconitum species and their common diterpenoid alkaloid compounds are also well characterized for analgesic, inflammatory and cytotoxic properties. However, the different isolated compound needs to be validated for supporting other traditional therapeutical uses of the plant species. Aconitine alkaloids shared common biosynthesis pathway, but their diversification mechanism remains unexplored in the genus. Furthermore, the process needs to be developed on secondary metabolite recovery, mass-scale propagation methods, and agro-technologies for maintaining the quality of products. Many species are losing their existence in nature due to over-exploitation or anthropogenic factors; thus, temporal monitoring of the population status in its habitat, and suitable management programs for ascertaining conservation needs to be developed.

Synthesis, Pharmacological Evaluation, and Molecular Modeling of Lappaconitine-1,5-Benzodiazepine Hybrids

Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, have long interested scientists due to their medicinal uses and infamous toxicity which has limited the clinical application of the native compound. Alkaloid lappaconitine extracted from various Aconitum and Delphinium species has displayed extensive bioactivities and active ongoing research to reduce its adverse effects. A convenient route to construct hybrid molecules containing diterpenoid alkaloid lappaconitine and 3H-1,5-benzodiazepine fragments was proposed. The key stage involved the formation of 5'-alkynone-lappaconitines in situ by acyl Sonogashira coupling of 5'-ethynyllappaconitine, followed by cyclocondensation with o-phenylenediamine. New hybrid compounds showed low toxicity and outstanding analgesic activity in experimental pain models, which depended on the nature of the substituent in the benzodiazepine nucleus. An analogous dependence was also shown for the antiarrhythmic activity in the epinephrine arrhythmia test in vivo. Studies on the isolated atrium have shown that the mechanism of action of the new compounds is included the blockade of beta-adrenergic receptors and potassium channels. Molecular docking analysis was conducted to determine the binding potential of target molecules with the voltage-gated sodium channel NaV1.5. All obtained results provide a basis for future rational modifications of lappaconitine, reducing side effects, while retaining its therapeutic effects.

Neuropharmacological Potential of Diterpenoid Alkaloids

This study provides a narrative review of diterpenoid alkaloids (DAs), a family of extremely important natural products found predominantly in some species of Aconitum and Delphinium (Ranunculaceae). DAs have long been a focus of research attention due to their numerous intricate structures and diverse biological activities, especially in the central nervous system (CNS). These alkaloids originate through the amination reaction of tetra or pentacyclic diterpenoids, which are classified into three categories and 46 types based on the number of carbon atoms in the backbone structure and structural differences. The main chemical characteristics of DAs are their heterocyclic systems containing β-aminoethanol, methylamine, or ethylamine functionality. Although the role of tertiary nitrogen in ring A and the polycyclic complex structure are of great importance in drug-receptor affinity, in silico studies have emphasized the role of certain sidechains in C13, C14, and C8. DAs showed antiepileptic effects in preclinical studies mostly through Na⁺ channels. Aconitine (1) and 3-acetyl aconitine (2) can desensitize Na⁺ channels after persistent activation. Lappaconitine (3), N-deacetyllapaconitine (4), 6-benzoylheteratisine (5), and 1-benzoylnapelline (6) deactivate these channels. Methyllycaconitine (16), mainly found in Delphinium species, possesses an extreme affinity for the binding sites of α7 nicotinic acetylcholine receptors (nAChR) and contributes to a wide range of neurologic functions and the release of neurotransmitters. Several DAs such as bulleyaconitine A (17), (3), and mesaconitine (8) from Aconitum species have a drastic analgesic effect. Among them, compound 17 has been used in China for decades. Their effect is explained by increasing the release of dynorphin A, activating the inhibitory noradrenergic neurons in the β-adrenergic system, and preventing the transmission of pain messages by inactivating the Na⁺ channels that have been stressed. Acetylcholinesterase inhibitory, neuroprotective, antidepressant, and anxiolytic activities are other CNS effects that have been investigated for certain DAs. However, despite various CNS effects, recent advances in developing new drugs from DAs were insignificant due to their neurotoxicity.

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].

Design, synthesis, and biological evaluation of low-toxic lappaconitine derivatives as potential analgesics

The C₁₈-diterpenoid alkaloid lappaconitine (LA) is a non-addictive analgesic used in China. The toxicity (LD₅₀ = 11.7 mg/kg) limits its application. Two series of LA derivatives, including amides and sulfonamides (1-93), were designed and synthesized by modification on their C4 acetamidobenzoate side chains in this work. In vivo analgesic activity and toxicity of all derivatives were evaluated, and the structure-activity relationship was summarized. Six lead compounds (35, 36, 39, 49, 70, and 89) exhibited approximate analgesic activity to LA but with significantly reduced toxicity. The therapeutic index of these compounds is 14-30 times that of LA. In vivo metabolism study of the lead compounds 39, 49, 70, and 89 were conducted by UPLC-MS^E, indicating the reason for the low toxicity of the potential derivatives might be they are difficult to metabolize to toxic metabolite N-deacetyllappaconitine compared to LA. The effects of lead compounds on sodium channels and hERG channels were also studied by ion channel reader (ICR) which further revealed their analgesic and toxicity-attenuating mechanisms. Sodium channel assay revealed that the analgesic mechanism of these lead compounds was inhibiting the Na_v 1.7 channels. Taken together, compound 39 was provided as a new analgesic lead compound with significantly low toxicity and comparable activity to LA.

Screening an In-House Isoquinoline Alkaloids Library for New Blockers of Voltage-Gated Na+ Channels Using Voltage Sensor Fluorescent Probes: Hits and Biases

Voltage-gated Na⁺ (Na_V) channels are significant therapeutic targets for the treatment of cardiac and neurological disorders, thus promoting the search for novel Na_V channel ligands. With the objective of discovering new blockers of Na_V channel ligands, we screened an In-House vegetal alkaloid library using fluorescence cell-based assays. We screened 62 isoquinoline alkaloids (IA) for their ability to decrease the FRET signal of voltage sensor probes (VSP), which were induced by the activation of Na_V channels with batrachotoxin (BTX) in GH3b6 cells. This led to the selection of five IA: liriodenine, oxostephanine, thalmiculine, protopine, and bebeerine, inhibiting the BTX-induced VSP signal with micromolar IC₅₀. These five alkaloids were then assayed using the Na⁺ fluorescent probe ANG-2 and the patch-clamp technique. Only oxostephanine and liriodenine were able to inhibit the BTX-induced ANG-2 signal in HEK293-hNa_V1.3 cells. Indeed, liriodenine and oxostephanine decreased the effects of BTX on Na⁺ currents elicited by the hNa_V1.3 channel, suggesting that conformation change induced by BTX binding could induce a bias in fluorescent assays. However, among the five IA selected in the VSP assay, only bebeerine exhibited strong inhibitory effects against Na⁺ currents elicited by the hNav1.2 and hNav1.6 channels, with IC₅₀ values below 10 µM. So far, bebeerine is the first BBIQ to have been reported to block Na_V channels, with promising therapeutical applications.

Transdermal Enhancement Strategy of Lappaconitine: Alteration of Keratin Configuration by Counter-Ion

The objective of this study was to develop a lappaconitine (LA) transdermal patch with counter-ion to increase the transdermal permeability of the drug, and a theory of counter-ion altering the conformation of the skin keratin was put forward based on the in vitro skin permeation study and physicochemical properties of ion-pairs. Formulation factors including pressure sensitive adhesives (PSAs), drug-loading, counter-ions and molar ratios of counter-ion were screened by in vitro skin permeation study. The optimized formulation was composed of 7% LA, 1.5 mole cinnamic acid and AAOH (PSA containing hydroxyl group synthesized by our laboratory) as an adhesive matrix. The optimized patch was evaluated by the pharmacokinetic and analgesic pharmacodynamic studies. AUC_0-t and pain inhibition ratio of the optimized patch were 2450.40 ± 848.52 h ng/mL and 81.18%, which showed good absorption into the skin and excellent analgesic effect. The mechanism of facilitated transdermal drug permeation by counter-ion was investigated by ATR-FTIR, thermal analysis, FTIR, XPS and molecular docking. The results indicated that after the formation of ion-pairs, the excess counter-ions would alter the conformation of the skin keratin, thus increasing the transdermal penetration of LA. In conclusion, the LA patch was successfully optimized, and the effect of counter-ions on the skin was clarified at the molecular level. These findings provided additional references for the application of counter-ion in the transdermal drug delivery system.

C18-diterpenoid alkaloids in tribe Delphineae (Ranunculaceae): phytochemistry, chemotaxonomy, and bioactivities

This review systematically summarizes the C₁₈-diterpenoid alkaloid (DA) compositions isolated from the genera Aconitum and Delphinium in the Delphineae tribe (Ranunculaceae). A total of 117 distinct C₁₈-DA components have been reported, including 58 lappaconitine-type DAs, 54 ranaconitine-type DAs, and five rearranged-type DAs. These components mainly originated from plants from the subgenus Lycoctonum in the genus Aconitum or less frequently from plants within the genus Delphinium. Natural C₁₈-DAs have exhibited a wide range of bioactivities, including analgesic, antiarrhythmic, anti-inflammatory, anti-tumor, and insecticidal activities, which are closely related to their chemical structures. The high chemical and biological diversities among the reported C₁₈-DA constituents in Delphineae plants indicated their potential as a vast resource for drug discovery. Additionally, the Delphineae plant C₁₈-DAs exhibited chemotaxonomic values and showed a high regularity of distribution at different taxonomic levels; therefore, the Delphineae plant C₁₈-DAs can serve as good chemical molecular markers in the taxonomic treatment of plants within this tribe, especially in the infrageneric division.

This review systematically summarizes the C₁₈-diterpenoid alkaloid (DA) compositions isolated from the genera Aconitum and Delphinium in the Delphineae tribe (Ranunculaceae).

Quantitative Electrophysiological Evaluation of the Analgesic Efficacy of Two Lappaconitine Derivatives: A Window into Antinociceptive Drug Mechanisms

Quantitative evaluation of analgesic efficacy improves understanding of the antinociceptive mechanisms of new analgesics and provides important guidance for their development. Lappaconitine (LA), a potent analgesic drug extracted from the root of natural Aconitum species, has been clinically used for years because of its effective analgesic and non-addictive properties. However, being limited to ethological experiments, previous studies have mainly investigated the analgesic effect of LA at the behavioral level, and the associated antinociceptive mechanisms are still unclear. In this study, electrocorticogram (ECoG) technology was used to investigate the analgesic effects of two homologous derivatives of LA, Lappaconitine hydrobromide (LAH) and Lappaconitine trifluoroacetate (LAF), on Sprague-Dawley rats subjected to nociceptive laser stimuli, and to further explore their antinociceptive mechanisms. We found that both LAH and LAF were effective in reducing pain, as manifested in the remarkable reduction of nocifensive behaviors and laser-evoked potentials (LEPs) amplitudes (N2 and P2 waves, and gamma-band oscillations), and significantly prolonged latencies of the LEP-N2/P2. These changes in LEPs reflect the similar antinociceptive mechanism of LAF and LAH, i.e., inhibition of the fast signaling pathways. In addition, there were no changes in the auditory-evoked potential (AEP-N1 component) before and after LAF or LAH treatment, suggesting that neither drug had a central anesthetic effect. Importantly, compared with LAH, LAF was superior in its effects on the magnitudes of gamma-band oscillations and the resting-state spectra, which may be associated with their differences in the octanol/water partition coefficient, degree of dissociation, toxicity, and glycine receptor regulation. Altogether, jointly applying nociceptive laser stimuli and ECoG recordings in rats, we provide solid neural evidence for the analgesic efficacy and antinociceptive mechanisms of derivatives of LA.

The toxicology and detoxification of Aconitum: traditional and modern views

Aconitum carmichaeli Debx.-derived herbal medicine has been used for anti-inflammation and anti-arrhythmia purpose for more than two thousand years. It is processed into Chuanwu (Radix Aconiti praeparata) and Fuzi (Radix Aconiti lateralis praeparata) in Traditional Chinese Medicine, which are two useful drugs but with toxic properties. There have been patients poisoned by accidental ingestion of Aconitum plants or misuse of the herbal drug, and this is of great concern to study in-depth. In this review, we provided the traditional and contemporary practice of using Aconitum herbs as medicine, from functions, processing methods to toxicity in ethnomedicine aspects to discuss the underlying connections of traditional and modern understanding on the toxicity of Aconitum plants. We summarized the functions and toxicology of the herbal drugs are analyzed from chemical and clinical aspects, with the help of traditional and modern knowledge of medicine. The medicinal doses and lethal doses determined by researches are summarized, and the usage and processing methods are updated and reviewed in the modern view. In addition, clinical management of poisoned cases using western medicine is discussed. This review provides insights and awareness of safety when using Aconitum-derived herbal medicine, and the application of modern scientific knowledge to optimize the detoxification processes. We suggest the possibility to renew the current standard processing method from the official Pharmacopoeia all over the world.

The Analgesic Effect of Aconitum Sinomontanum Nakai Pharmacopuncture in Sprague-Dawley Rats

Background: Aconitum sinomontanum Nakai (ASN) has been reported to have analgesic effects. In this study an animal model of pharmacopuncture using ASN (100-500 mg/kg) was examined.Methods: Sprague-Dawley (SD) rats (<i>n</i> = 40) were randomly assigned to ASN-Low (1 mg/mL, 1.8 mL, ASN-L), ASN-Intermediate (5 mg/mL, 1.8 mL, ASN-M), ASN-High (10 mg/mL, 1.8 mL, ASN-H), negative control (0.2 mL normal saline), and positive control (0.2 mL 0.5% lidocaine) groups. All experiments were administered to the rats’ left hind leg. The analgesic response was assessed by monitoring the physical (hot plate, and von Frey test) and chemical (formalin) responses to pain.Results: All ASN pharmacopuncture groups demonstrated significant differences in pain response to the hot plate test, von Frey test, and formalin test, compared to the control group (<i>p</i> < 0.05). The response of the ASN-M group and ASN-H groups to the hot plate, the formalin, and the von Frey tests were significantly different, compared to the lidocaine group (<i>p</i> < 0.05).Conclusion: ASN pharmacopuncture had a significant analgesic effect on SD rats in response to physical and chemical models of pain.

Hybrides of Alkaloid Lappaconitine with Pyrimidine Motif on the Anthranilic Acid Moiety: Design, Synthesis, and Investigation of Antinociceptive Potency

Convenient and efficient routes to construct hybrid molecules containing diterpene alkaloid lappaconitine and pyrimidine fragments are reported. One route takes place via first converting of lappaconitine to 1-ethynyl-lappaconitine, followed by the Sonogashira cross-coupling-cyclocondensation sequences. The other involves the palladium-catalyzed carbonylative Sonogashira reaction of 5'-iodolappaconitine with aryl acetylene and Mo (CO)6 as the CO source in acetonitrile and subsequent cyclocondensation reaction of the generated alkynone with amidines. The reaction proceeded cleanly in the presence of the PdCl2-(1-Ad)2PBn∙HBr catalytic system. The protocol provides mild reaction conditions, high yields, and high atom and step-economy. Pharmacological screening of lappaconitine-pyrimidine hybrids for antinociceptive activity in vivo revealed that these compounds possessed high activity in experimental pain models, which was dependent on the nature of the substituent in the 2 and 6 positions of the pyrimidine nucleus. Docking studies were undertaken to gain insight into the possible binding mode of these compounds with the voltage-gated sodium channel 1.7. The moderate toxicity of the leading compound 12 (50% lethal dose (LD50) value was more than 600 mg/kg in vivo) and cytotoxicity to cancer cell lines in vitro encouraged the further design of therapeutically relevant analogues based on this novel type of lappaconitine-pyrimidine hybrids.

Quantification of Lappaconitine in Mouse Blood by UPLC-MS/MS and Its Application to a Pharmacokinetic Study

Lappaconitine is extracted from Aconitum sinomontanum Nakai, which belongs to the Ranunculaceae. Lappaconitine is as a diterpenoid alkaloid used as a nonaddictive analgesic. To assure the rational use of the drug, ultrahigh-pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was conducted to determine lappaconitine in mouse blood and its application to pharmacokinetics. In this study, khasianine was used as internet standard (IS). A UPLC BEH C18 column was used for chromatographic separation and the mobile phase consisted of acetonitrile and 10 mmol/L ammonium acetate (0.1% formic acid). The flow rate of was 0.4 mL/min. Quantitative detection was performed in a multiple reaction monitoring (MRM) mode using an electrospray ionization source in positive mode. Twenty-four mice were randomly divided into four groups, three of which received 2, 4, and 8 mg/kg lappaconitine by intragastric administration, while the other group received 1 mg/kg lappaconitine by intravenous administration. After 0.0833, 0.5, 1, 1.5, 2, 3, 4, and 8 h, blood samples were collected and acetonitrile was used for protein precipitation. A linear calibration relationship (R² = 0.9979) in the range of 0.1-500 ng/mL in mouse blood indicated good results. The lower limit of quantitation was 0.1 ng/mL and the limit of detection was 0.04 ng/mL. The intra-day and inter-day precision were below 13% and 14%, respectively. The accuracy was 90.1-107.2%, and the recovery exceeded 81.1%. The matrix effect ranged between 102.1 and 108.8%. The absolute bioavailability of lappaconitine was 2.0%. UPLC-MS/MS achieved high sensitivity, speed, and selectivity. Methodological verification indicated this method as suitable for determination of lappaconitine in mouse blood.