Coronaridine, an iboga type alkaloid from Tabernaemontana divaricata, inhibits the Wnt signaling pathway by decreasing β-catenin mRNA expression

Phytochemistry Profile, Antimicrobial and Antitumor Potential of the Methanolic Extract of Tabernaemontana catharinensis A DC and Eragrostis plana NEES

Natural compounds that have the potential to act as antimicrobials and antitumors are a constant search in the field of pharmacotherapy. Eragrostis plana NEES (Poaceae) is a grass with high allelopathic potential. Allelopathy is associated with compounds generated in the primary and secondary metabolism of the plant, which act to protect it from phytopathogens. Tabernaemontana catharinensis A DC (Apocynaceae), a tree in which its leaves and bark are used for the preparation of extracts and infusions that have anti-inflammatory and antinociceptive effects, is attributed to its phytochemical constitution. The objective of this study was to elucidate the phytochemical constitution, the antibacterial potential, the toxicity against immune system cells, hemolytic potential, and antitumor effect of methanolic extracts of E. plana and T. catharinensis. The phytochemical investigation was carried out using the UHPLC-QTOF MS equipment. The antibacterial activity was tested using the broth microdilution plate assay, against Gram-negative and Gram-positive strains, and cytotoxicity assays were performed on human peripheral blood mononuclear cells (PBMC) and in vitro hemolysis. Antitumor activity was performed against the colon cancer cell line (CT26). Results were expressed as mean and standard deviation and analyzed by ANOVA. p < 0.05 was considered significant. More than 19 possible phytochemical constituents were identified for each plant, with emphasis on phenolic compounds (acids: vanillic, caffeic, and quinic) and alkaloids (alstovenine, rhyncophylline, amezepine, voacangine, and coronaridine). Both extracts showed antibacterial activity at concentrations below 500 µg/mL and were able to decrease the viability of CT26 at concentrations below 2000 µg/mL, without showing cytotoxic effect on PBMCs and in vitro hemolysis at the highest concentration tested. This is the first report of the activity of E. plana and T. catharinensis extracts against colon cancer cell line (CT26). Studies should be carried out to verify possible molecular targets involved in the antitumor effect in vivo.

In vitro and in silico cholinesterase inhibitory potential of metabolites from Laurencia snackeyi (Weber-van Bosse) M. Masuda

Alzheimer's disease (AD) is a neurodegenerative disease that causes deterioration in intelligence and psychological activities. Yet, till today, no cure is available for AD. The marine environment is an important sink of bioactive compounds with neuroprotective potential with reduced adverse effects. Recently, we collected the red algae Laurencia snackeyi from Terumbu Island, Malaysia which is known to be rich in halogenated metabolites making it the most sought-after red algae for pharmaceutical studies. The red alga was identified based on basic morphological characteristics, microscopic observation and chemical data from literature. The purplish-brown algae was confirmed a new record. In Malaysia, this species is poorly documented in Peninsular Malaysia as compared to its eastern continent Borneo. Thus, this study intended to investigate the diversity of secondary metabolites present in the alga and its cholinesterase inhibiting potential for AD. The extract inhibited both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with IC50 values of  14.45 ± 0.34 μ g mL-1 and 39.59 ± 0.24 μ g mL-1, respectively. Subsequently, we isolated the synderanes, palisadin A (1), aplysistatin (2) and 5-acetoxypalisadin B (3) that was not exhibit potential. Mass spectrometry analysis detected at total of 33 additional metabolites. The computational aided molecular docking using the AChE and BChE receptors on all metabolites shortlisted 5,8,11,14-eicosatetraynoic acid (31) and 15-hydroxy-1-[2-(hydroxymethyl)-1-piperidinyl]prost-13-ene-1,9-dione (42) with best inhibitory properties, respectively with the lowest optimal combination of S-score and RMSD values. This study shows the unexplored potential of marine natural resources, however, obtaining sufficient biomass for detailed investigation is an uphill task. Regardless, there is a lot of potential for future prospects with a wide range of marine natural resources to study and the incorporation of synthetic chemistry, in vivo studies in experimental design.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03725-6.

EMX1 functions as a tumor inhibitor in spinal cord glioma through transcriptional suppression of WASF2 and inactivation of the Wnt/β-catenin axis

BACKGROUND

Gliomas are the most frequent and aggressive cancers in the central nervous system, and spinal cord glioma (SCG) is a rare class of the gliomas. Empty spiracles homobox genes (EMXs) have shown potential tumor suppressing roles in glioma, but the biological function of EMX1 in SCG is unclear.

METHODS

The EMX1 expression in clinical tissues of patients with SCG was examined. SCG cells were extracted from the tissues, and altered expression of EMX1 was then introduced to examine the role of EMX1 in cell growth and invasiveness in vitro. Xenograft tumors were induced in nude mice for in vivo validation. The targets of EXM1 were predicted via bioinformatic analysis and validated by luciferase and ChIP-qPCR assays. Rescue experiments were conducted to validate the involvements of the downstream molecules.

RESULTS

EMX1 was poorly expressed in glioma, which was linked to decreased survival rate of patients according to the bioinformatics prediction. In clinical tissues, EMX1 was poorly expressed in SCG, especially in the high-grade tissues. EMX1 upregulation significantly suppressed growth and metastasis of SCG cells in vitro and in vivo. EMX1 bound to the promoter of WASP family member 2 (WASF2) to suppress its transcription. Restoration of WASF2 blocked the tumor-suppressing effect of EMX1. EMX1 suppressed Wnt/β-catenin signaling activity by inhibiting WASF2. Coronaridine, a Wnt/β-catenin-specific antagonist, blocked SCG cell growth and metastasis induced by WASF2.

CONCLUSION

This study elucidates that EMX1 functions as a tumor inhibitor in SCG by suppressing WASF2-dependent activation of the Wnt/β-catenin axis.

Major Bioactive Alkaloids and Biological Activities of Tabernaemontana Species (Apocynaceae)

Several species belonging to the genus Tabernaemontana have been well researched and utilized for their wide-ranging biological activities. A few of the most prominent species include Tabernaemontana divaricata, Tabernaemontana catharinensis, Tabernaemontana crassa, and Tabernaemontana elegans. These species and many others within the genus often display pharmacological importance, which is habitually related to their chemical constituents. The secondary metabolites within the genus have demonstrated huge medicinal potential for the treatment of infections, pain, injuries, and various diseases. Regardless of the indispensable reports and properties displayed by Tabernaemontana spp., there remains a wide variety of plants that are yet to be considered or examined. Thus, an additional inclusive study on species within this genus is essential. The current review aimed to extensively analyze, collate, and describe an updated report of the current literature related to the major alkaloidal components and biological activities of species within the genus Tabernaemontana.

Small Molecule Wnt Pathway Modulators from Natural Sources: History, State of the Art and Perspectives

The Wnt signaling is one of the major pathways known to regulate embryonic development, tissue renewal and regeneration in multicellular organisms. Dysregulations of the pathway are a common cause of several types of cancer and other diseases, such as osteoporosis and rheumatoid arthritis. This makes Wnt signaling an important therapeutic target. Small molecule activators and inhibitors of signaling pathways are important biomedical tools which allow one to harness signaling processes in the organism for therapeutic purposes in affordable and specific ways. Natural products are a well known source of biologically active small molecules with therapeutic potential. In this article, we provide an up-to-date overview of existing small molecule modulators of the Wnt pathway derived from natural products. In the first part of the review, we focus on Wnt pathway activators, which can be used for regenerative therapy in various tissues such as skin, bone, cartilage and the nervous system. The second part describes inhibitors of the pathway, which are desired agents for targeted therapies against different cancers. In each part, we pay specific attention to the mechanisms of action of the natural products, to the models on which they were investigated, and to the potential of different taxa to yield bioactive molecules capable of regulating the Wnt signaling.

Screening for natural products that affect Wnt signaling activity

Wnt signaling has been implicated in numerous aspects of development, cell biology, and physiology. When aberrantly activated, Wnt signaling can also lead to the formation of tumors. Thus, Wnt signaling is an attractive target for cancer therapy. Based on our screening program targeting Wnt signaling activity using a cell-based luciferase screening system assessing TCF/β-catenin transcriptional activity, we isolated a series of terpenoids and heterocyclic aromatic compounds that affect the Wnt signaling pathway at different points. Here, we describe our recent results in screening for natural products that inhibit or activate Wnt signaling.

Apoptosis induction in K562 human myelogenous leukaemia cells is connected to the modulation of Wnt/β-catenin signalling by BHX, a novel pyrazoline derivative

OBJECTIVES

The goal of this study was to explore the effects of BHX on human chronic myeloid leukaemia (CML) cells and to elucidate the underlying molecular mechanism.

MATERIALS AND METHODS

CML cell line K562 cells were treated with BHX. The effects of BHX on cell proliferation, apoptosis and cell cycle were detected. Subsequently, the caspase, ATP activity, Ca²⁺ , ROS and mitochondrial membrane potential (MMP) levels treated with various concentrations of BHX were analysed. The variation of relevant proteins and genes was detected. Further, toxicity of BHX on peripheral blood cells, bone marrow-nucleated cells (BMNC) and organ index were investigated on mice.

RESULTS

Results showed that BHX suppressed K562 cell proliferation in a dose-dependent manner and induced apoptosis and G0/G1 phase arrest. BHX induced mitochondria-mediated apoptosis, which was associated with downregulation of MMP, activation of caspase-3 and caspase-9, generation of intracellular ROS and elevation of Ca²⁺ in K562 cells. In treated cells, ATP levels were decreased, expression of total β-catenin, phosphorylated β-catenin and β-catenin in the nucleus was decreased, and expression of cell cycle-related proteins was decreased. Further analysis revealed that BHX lowered the transcriptional level of β-catenin. Lastly, BHX treatment significantly reduced the number of white blood cells, but had no effect on BMNC and organ index.

CONCLUSIONS

These findings provide further insight into the potential use of BHX as an anti-cancer agent against human leukaemia.

Nymphaeol-C, a prenylflavonoid from Macaranga tanarius, suppresses the expression of fibroblast growth factor 18

BACKGROUND

Fibroblast growth factor 18 (FGF18) is one of the key factors in human signaling pathways and has been reported to be associated with the formation of various tissues. Additionally, FGF18 has been reported to maintain the telogen stage of the hair cycle, and its over-expression has also been observed in cancer cells.

HYPOTHESIS/PURPOSE

We searched for natural compounds that inhibit the expression of FGF18 expression in vitro and evaluated their inhibitory mechanisms.

STUDY DESIGN

Various plant samples were screened using a luciferase assay targeting FGF18. One active compound was selected by the screening, isolated and identified.

METHODS

The active compound was isolated using chromatographic techniques and identified by specific rotation measurements, LC-MS and NMR. Additionally, its inhibitory mechanism was evaluated using real-time RT-PCR and Western blotting.

RESULTS

As a result of screening various plant leaf samples, Macaranga tanarius was identified as the most active plant and a prenylflavonoid nymphaeol-C was isolated as the active compound. Using real-time RT-PCR and Western blotting analysis, this compound was confirmed to strongly suppress the expression of FGF18. The compound lowered the β-catenin level in the Wnt/β-catenin pathway. Thus, it was suggested that nymphaeol-C suppresses the expression of FGF18 by suppressing β-catenin expression. Additionally, the compound lowered the extracellular signal-regulated kinase1/2 (ERK1/2) phosphorylation level in the mitogen-activated protein kinase cascade (MAPK cascade). Therefore, nymphaeol-C suppressed downstream signals of FGF18 by suppressing the expression of FGF18.

CONCLUSION

We isolated and identified prenylflavonoid nymphaeol-C from M. tanarius. The compound suppresses the expression of FGF18 and affects FGF18 related signals.

Quinocetone induces mitochondrial apoptosis in HepG2 cells through ROS-dependent promotion of VDAC1 oligomerization and suppression of Wnt1/β-catenin signaling pathway

Quinocetone (QCT) has been used as an animal feed additive in China since 2003. However, investigations indicate that QCT has potential toxicity due to the fact that it shows cytotoxicity, genotoxicity, hepatotoxicity, nephrotoxicity and immunotoxicity in vitro and animal models. Although QCT-induced mitochondrial apoptosis has been established, the molecular mechanism remains unclear. This study was aimed to investigate the role of voltage-dependent anion channel 1 (VDAC1) oligomerization and Wnt/β-catenin pathway in QCT-induced mitochondrial apoptosis. The results showed VDAC inhibitor 4, 4-diisothiocyano stilbene-2, 2-disulfonic acid (DIDS) partly compromised QCT-induced cell viability decrease (from 34.1% to 68.5%) and mitochondrial apoptosis accompanied by abating VDAC1 oligomerization, cytochrome c (Cyt c) release and the expression levels of cleaved caspase-9, -3 and poly (ADP-ribose) polymerase (PARP). Meanwhile, overexpression VDAC1 exacerbated QCT-induced VDAC1 oligomerization and Cyt c release. In addition, lithium chloride (LiCl), an activator of Wnt/β-catenin pathway, markedly attenuated QCT-induced mitochondrial apoptosis by partly restoring the expression levels of Wnt1 and β-catenin. Finally, reactive oxygen species (ROS) scavenger N-acetyl-l-cysteine (NAC) obviously blocked QCT-induced VDAC1 oligomerization and the inhibition of Wnt1/β-catenin pathway. Taken together, our results reveal that QCT induces mitochondrial apoptosis by ROS-dependent promotion of VDAC1 oligomerization and suppression of Wnt1/β-catenin pathway.

The Iboga Alkaloids

Iboga alkaloids are a particular class of indolomonoterpenes most often characterized by an isoquinuclidine nucleus. Their first occurrence was detected in the roots of Tabernanthe iboga, a sacred plant to the people of Gabon, which made it cult object. Ibogaine is the main representative of this class of alkaloids and its psychoactive properties are well documented. It has been proposed as a drug cessation treatment and has a wide range of activities in targeting opioids, cocaine, and alcohol. The purpose of this chapter is to provide a background on this molecule and related compounds and to update knowledge on the most recent advances made. Difficulties linked to the status of ibogaine as a drug in several countries have hampered its development, but 18-methoxycoronaridine is currently under evaluation for the same purposes and for the treatment of leishmaniasis. The chapter is divided into six parts: an introduction aiming at defining what is called an iboga alkaloid, and this is followed by current knowledge on their biosynthesis, which unfortunately remains a "black box" as far as the key construction step is concerned. Many of these alkaloids are still being discovered and the third and fourth parts of the chapter discuss the analytical tools in use for this purpose and give lists of new monomeric and dimeric alkaloids belonging to this class. When necessary, the structures are discussed especially with regard to absolute configuration determinations, which remain a point of weakness in their assignments. Part V gives an account of progress made in the synthesis, partial and total, which the authors believe is key to providing solid solutions to the industrial development of the most promising molecules. The last part of the chapter is devoted to the biological properties of iboga alkaloids, with particular emphasis on ibogaine and 18-methoxycoronaridine.

BHX Inhibits the Wnt Signaling Pathway by Suppressing β-catenin Transcription in the Nucleus

BHX (N-(4-hydroxybenzyl)-1,3,4-triphenyl-4,5-dihydro-1H-pyrazole-5-carboxamide), a Wnt signaling pathway inhibitor, effectively inhibits tumor cell growth, but the underlying mechanism is unclear. Thus, we aim to investigate the effects and associated mechanism of BHX action on A549 and MCF-7 cell lines. In our study, MTT(3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide) and xenograft model assay indicated that cell growth was inhibited by BHX at a range of concentrations in vitro and in vivo. The expression of β-catenin and Wnt signaling pathway downstream target genes were decreased evidently under BHX treatment. Flow cytometry also revealed that BHX treatment significantly induced G1 arrest. Further analysis showed that BHX lowered the transcriptional level of β-catenin. In conclusion, BHX inhibited the nuclear synthesis of β-catenin, thereby suppressing the Wnt signaling pathway and further inhibiting tumor growth and proliferation.