Simplified tetrandrine congeners as possible antihypertensive agents with a dual mechanism of action

Non-volatile constituents from Monimiaceae, Siparunaceae and Atherospermataceae plant species and their bioactivities: An up-date covering 2000-2021

The Monimiaceae, Siparunaceae, and Atherospermataceae, formerly included in the broad ''old'' Monimiaceae family, have long been known for their uses in traditional medicine and have proven to be rich sources of chemically diverse specialized metabolites with numerous potent biological and therapeutical properties. The progress made recently has expanded their phytochemistry and pharmacology albeit to different extents. This review focuses on the non-volatile constituents isolated from the three plant families during the last two decades and their emerging therapeutic potential. Based on the data collected from multiple databases without statistical analysis, approximately 93 components, of which 35 undescribed compounds including γ-lactones, alkaloids, terpenoids, flavonoids, and homogentisic acid derivatives, have been reported. Moreover, diverse biological activities of pure isolated compounds such as anticancer, antioxidant, antiparasitic, antiviral, and antibacterial activities have been evidenced. Besides offering new important perspectives for different diseases' management, the chemical and biological diversities among the isolated compounds, open promising avenues of research and contribute to renewed interest in these families needing further studies. This review provides an updated overview of their potential as sources of leads for drug discovery, while also highlighting ongoing challenges and future research opportunities.

Tetrandrine Inhibits Epithelial-Mesenchymal Transition in IL-6-Induced HCT116 Human Colorectal Cancer Cells

Introduction

Patients with colorectal cancer (CRC) often develop distant metastases, which significantly reduces the 5-year survival rate. Epithelial-mesenchymal transition (EMT) is a crucial process for the invasion and metastasis of cancer cells. Tetrandrine has been reported to inhibit the viability and EMT of CRC cells; however, to the best of our knowledge, the molecular mechanism remains undetermined.

Methods

The MTT assay was used to determine HCT116 cell viability. Wound healing and Transwell assays were used to determine that cell migration and invasion, respectively. Western blotting analysis was performed to detect the expression of migration-related genes. Four different lengths of the E-cadherin gene promoter were constructed and cloned into pGL3 reporter plasmids to evaluate E-cadherin gene promoter activity.

Results

The results of the MTT assay revealed that tetrandrine inhibited HCT116 cell viability, with an IC₅₀ value of 7.2 μM following 24 h of treatment. Tetrandrine inhibited IL-6-induced cell migration and invasion, respectively. Tetrandrine regulates the expression of migration-related genes in IL-6-stimulated HCT116 cells. Tetrandrine significantly downregulated the expression and enzyme activity of MMP-2 in IL-6-stimulated HCT116 cells. In addition, tetrandrine restored E-cadherin gene promoter activity.

Conclusion

The findings of the present study suggested that tetrandrine may inhibit EMT in IL-6-stimulated HCT116 cells; therefore, it may represent a potential drug for CRC.

Gene editing and synthetically accessible inhibitors reveal role for TPC2 in HCC cell proliferation and tumor growth

The role of two-pore channel 2 (TPC2), one of the few cation channels localized on endolysosomal membranes, in cancer remains poorly understood. Here, we report that TPC2 knockout reduces proliferation of cancer cells in vitro, affects their energy metabolism, and successfully abrogates tumor growth in vivo. Concurrently, we have developed simplified analogs of the alkaloid tetrandrine as potent TPC2 inhibitors by screening a library of synthesized benzyltetrahydroisoquinoline derivatives. Removal of dispensable substructures of the lead molecule tetrandrine increases antiproliferative properties against cancer cells and impairs proangiogenic signaling of endothelial cells to a greater extent than tetrandrine. Simultaneously, toxic effects on non-cancerous cells are reduced, allowing in vivo administration and revealing a TPC2 inhibitor with antitumor efficacy in mice. Hence, our study unveils TPC2 as valid target for cancer therapy and provides easily accessible tetrandrine analogs as a promising option for effective pharmacological interference.

8-Oxo-9-Dihydromakomakine Isolated from Aristotelia chilensis Induces Vasodilation in Rat Aorta: Role of the Extracellular Calcium Influx

8-Oxo-9-dihydromakomakine is a tetracyclic indole alkaloid extracted from leaves of the Chilean tree Aristotelia chilensis. The present study investigated the effects of this alkaloid on vascular response in tissues isolated from aortic segments obtained from normotensive rats. Our results showed that 8-oxo-9-dihydromakomakine induced a dose-dependent relaxation of aortic rings pre-contracted with phenylephrine (PE; 10⁻⁶ M). The vasorelaxation induced by 8-oxo-9-dihydromakomakine in rat aortic rings is independent of endothelium. The pre-incubation of aortic rings with 8-oxo-9-dehydromakomakine (10⁻⁴ M) significantly reduced the contractile response to KCl (p < 0.001) more than PE (p < 0.05). The highest dose of 8-oxo-9-dehydromakomakine (10⁻⁴ M) drastically reduced the contraction to KCl (6·10⁻² M), but after that, PE (10⁻⁶ M) caused contraction (p < 0.05) in the same aortic rings. The addition of 8-oxo-9-dihydromakomakine (10⁻⁵ M) decreased the contractile response to tetraethylammonium (a voltage-dependent potassium channels blocker; TEA; 5 × 10⁻³ M; p < 0.01) and BaCl₂ (a non-selective inward rectifier potassium channel blocker; 5 × 10⁻³ M; p < 0.001) in rat aorta. 8-oxo-9-dihydromakomakine (10⁻⁵ M) decreased the contractile response to PE in rat aorta in the presence or absence of ouabain (an inhibitor of Na,K-ATPase; 10⁻³ M; p < 0.05). These results could indicate that 8-oxo-9-dihydromakomakine partially reduces plasma membrane depolarization-induced contraction. In aortic rings depolarized by PE, 8-oxo-9-dihydromakomakine inhibited the contraction induced by the influx of extracellular Ca²⁺ in a Ca²⁺ free solution (p < 0.01). 8-oxo-9-dihydromakomakine reduced the contractile response to agonists of voltage-dependent calcium channels type L (Bay K6844; 10⁻⁸ M; p < 0.01), likely decreasing the influx of extracellular Ca²⁺ through the voltage-dependent calcium channels. This study provides the first qualitative analysis indicating that traditional folk medicine Aristotelia chilensis may be protective in the treatment of cardiovascular pathologies.

Current natural products with antihypertensive activity

Natural products have been an important source of new drugs, which also played a dominant role in the discovery and research of new drugs for the treatment of hypertension. This review article reviews the recent progress in the research and development of natural lead compounds with antihypertensive activity, including alkaloids, diterpenes, coumarins, flavonoids, and peptides. We summarized their structures, sources, as well as the antihypertensive mechanisms. These information provides instructive reference for the following structural modifications and optimization.

Antinociceptive effect of tetrandrine on LPS-induced hyperalgesia via the inhibition of IKKβ phosphorylation and the COX-2/PGE₂ pathway in mice

Tetrandrine (TET) is a bisbenzylisoquinoline alkaloid that is isolated from the Stephania Tetrandra. It is known to possess anti-inflammatory and immunomodulatory effects. We have shown that TET can effectively suppress the production of bacterial lipopolysaccharide (LPS)-induced inflammatory mediators, including cyclooxygenases (COXs), in macrophages. However, whether TET has an antinociceptive effect on LPS-induced hyperalgesia is unknown. In the present study, we investigated the potential antinociceptive effects of TET and the mechanisms by which it elicits its effects on LPS-induced hyperalgesia. LPS effectively evoked hyperalgesia and induced the production of PGE2 in the sera, brain tissues, and cultured astroglia. TET pretreatment attenuated all of these effects. LPS also activated inhibitor of κB (IκB) kinase β (IKKβ) and its downstream components in the IκB/nuclear factor (NF)-κB signaling pathway, including COX-2; the increase in expression levels of these components was significantly abolished by TET. Furthermore, in primary astroglia, knockdown of IKKβ, but not IKKα, reversed the effects of TET on the LPS-induced increase in IκB phosphorylation, P65 phosphorylation, and COX-2. Our results suggest that TET can effectively exert antinociceptive effects on LPS-induced hyperalgesia in mice by inhibiting IKKβ phosphorylation, which leads to the reduction in the production of important pain mediators, such as PGE2 and COX-2, via the IKKβ/IκB/NF-κB pathway.

Central Nicotinic Receptors: Structure, Function, Ligands, and Therapeutic Potential

The growing interest in nicotinic receptors, because of their wide expression in neuronal and non-neuronal tissues and their involvement in several important CNS pathologies, has stimulated the synthesis of a high number of ligands able to modulate their function. These membrane proteins appear to be highly heterogeneous, and still only incomplete information is available on their structure, subunit composition, and stoichiometry. This is due to the lack of selective ligands to study the role of nAChR under physiological or pathological conditions; so far, only compounds showing selectivity between alpha4beta2 and alpha7 receptors have been obtained. The nicotinic receptor ligands have been designed starting from lead compounds from natural sources such as nicotine, cytisine, or epibatidine, and, more recently, through the high-throughput screening of chemical libraries. This review focuses on the structure of the new agonists, antagonists, and allosteric ligands of nicotinic receptors, it highlights the current knowledge on the binding site models as a molecular modeling approach to design new compounds, and it discusses the nAChR modulators which have entered clinical trials.

Evaluation of benzyltetrahydroisoquinolines as ligands for neuronal nicotinic acetylcholine receptors

Effects of derivatives of coclaurine (C), which mimic the 'eastern' or the nonquaternary halves of the alkaloids tetrandrine or d-tubocurarine, respectively, both of which are inhibitors of nicotinic acetylcholine receptors (nACh), were examined on recombinant, human alpha7, alpha4beta2 and alpha4beta4 nACh receptors expressed in Xenopus oocytes and clonal cell lines using two-electrode voltage clamping and radioligand binding techniques. In this limited series, Cs have higher affinity and are most potent at alpha4 subunit-containing-nACh receptors and least potent at homomeric alpha7 receptors, and this trend is very marked for the N-unsubstituted C and its O,O'-bisbenzyl derivative. 7-O-Benzyl-N-methylcoclaurine (BBCM) and its 12-O-methyl derivative showed the highest affinities and potencies at all three receptor subtypes, and this suggests that lipophilicity at C7 and/or C12 increases potency. Laudanosine and armepavine (A) were noncompetitive and voltage-dependent inhibitors of alpha7, alpha4beta2 or alpha4beta4 receptors, but the bulkier C7-benzylated 7BNMC (7-O-benzyl-N-methylcoclaurine) and 7B12MNMC (7-O-benzyl-N,12-O-dimethyl coclaurine) were voltage-independent, noncompetitive inhibitors of nACh receptors. Voltage-dependence was also lost on going from A to its N-ethyl analogue. These studies suggest that C derivatives may be useful tools for studies characterising the antagonist and ion channel sites on human alpha7, alpha4beta2 or alpha4beta4 nACh receptors and for revealing structure-function relationships for nACh receptor antagonists.

Effect of Tetrandrine on Calcium-Dependent Tumour Necrosis Factor-alpha Production in Glia-Neurone Mixed Cultures

Tumour necrosis factor-alpha is believed to have a deleterious role in the pathophysiology of brain injury. Tetrandrine has protective effect on neuronal cells, however, the mechanisms involved in its action have not been clearly established. The aim of this study was to investigate the role of tetrandrine on calcium-dependent tumour necrosis factor-alpha production in glia-neurone mixed cultures. Glia-neurone mixed cultures were treated by addition of Ca2+ regulating agents for a period of 6 hr. Tetrandrine or/and TMB-8 were added 30 min. before the stimulation. The supernatant tumour necrosis factor-alpha levels were quantified by enzyme-linked immunosorbent assay. Exposure of lipopolysaccharide 10 and 100 ng/ml caused significant increase in tumour necrosis factor-alpha production respectively, with no alteration in cultures treated with 1 ng/ml lipopolysaccharide. Glia-neurone mixed cultures exhibited a marked elevation in tumour necrosis factor-alpha production after exposure to CaCl2, KCl, thapsigargin, BHQ and norepinephrine in the presence of lipopolysaccharide at 1 ng/ml respectively. Tetrandrine 0.3, 1, and 3 microM concentration-dependently reduced tumour necrosis factor-alpha production evoked by CaCl2 or KCl. Tetrandrine preincubation had no significant effect on the response to Ca2+-ATPase inhibitor thapsigargin or BHQ. Norepinephrine-induced tumour necrosis factor-alpha production was significantly reduced by tetrandrine and almost abolished by combination of tetrandrine and intracellular Ca2+ release inhibitor TMB-8. These results suggested that tetrandrine at a concentration of 0.3, 1, or 3 microM inhibited tumour necrosis factor-alpha production induced by Ca2+ entry in glia-neurone mixed cultures.

β-Phenylethylamines and the isoquinoline alkaloids

This review covers beta-phenylethylamines and isoquinoline alkaloids derived from them, including further products of oxidation, condensation with formaldehyde and rearrangement, some of which do not contain as isoquinoline system, together with napthylisoquinoline alkaloids, which have a different biogenetic origin. The occurrence of the alkaloids with the structures of new bases, together with their reactions and syntheses, are reported. The literature from July 2003 to June 2004 is reviewed, with 145 references cited.

NMR spectroscopic, mass spectroscopic, X-ray crystallographic, and theoretical studies of molecular mechanics of natural products: farformolide B and sesamin

Two natural products, farformolide B and sesamin were isolated from Farfugium japonicum and Cinnamomum kanehirae, respectively. The structures of the two natural products, including their relative stereochemistry, were elucidated using spectroscopic data and theoretical calculations. The molecule 1 (farformolide B) is newly recognized by X-ray crystallography. The two compounds were also investigated by a theoretical analysis using the B3LYP/6-31G* method of the Gaussian 03 package program. The theoretical results were supplemented by experimental data to determine the optimal geometric structures of the two compounds. The calculated molecular mechanics were found to compare well with the experimental data. Several important thermodynamic properties of the two products, including ionization potentials, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies, energy gaps, heat of formation, atomization energies, and vibration frequencies, were also calculated. The study also provided a good understanding of the stereochemical structure and thermodynamic properties of the two molecules.