TRPA1 channels as targets for resveratrol and related stilbenoids

Insights into Molecular Interactions and Biological Effect of Natural Stilbenoids at the TRPA1 Ion Channel

Natural stilbenoids, polyphenolic compounds notably found in Scots pine and Norway spruce, have been shown to exhibit analgesic and anti-inflammatory effects through the TRPA1 channel, making them promising hits for the development of novel agents to treat inflammatory diseases and pain. In this study, we computationally investigated the putative binding sites of natural stilbenoids at the TRPA1 channel. Specifically, we employed molecular docking and MD simulation approaches to explore three known ligand binding sites at TRPA1. Furthermore, the biological effect of the studied compounds on TRPA1 was assessed in vitro using a fluorescent imaging plate reader (FLIPR™) calcium assay. Our modeling results suggest the stilbenoids exhibit higher affinity to the two agonist binding sites than the antagonistic site. Consistent with this, the in vitro results showed that the stilbenoids act as moderate TRPA1 channel agonists and likely inhibit the channel through a desensitization mechanism rather than act as pure TRPA1 antagonists. Additionally, our bias-force pulling simulations proposed an additional binding pocket for the natural stilbenoids that is distinct from the known ligand binding sites at TRPA1. The results of the study give useful insights into structure-based design and development of novel therapeutic TRPA1 modulators.

Structure- and Ligand-Based Virtual Screening for Identification of Novel TRPV4 Antagonists

Transient receptor potential vanilloid (TRPV) 4 is involved in signaling pathways specifically mediating pain and inflammation, making it a promising target for the treatment of various painful and inflammatory conditions. However, only one drug candidate targeting TRPV4 has entered the clinical trials. To identify potential TRPV4 inhibitors for drug development, we screened a library of ion channel-modulating compounds using both structure- and ligand-based virtual screening approaches. Since a high-resolution experimental structure of the human TRPV4 (hTRPV4) was not available during this study, we used a comparative model of hTRPV4 for the structure-based screening by molecular docking. The ligand-based virtual screening was performed using the pharmacophoric features of two known TRPV4 antagonists. Five potential hits were selected based on either the binding stability or the pharmacophore match, and their effect on hTRPV4 was tested using a FLIPRtetra assay. All tested compounds inhibited hTRPV4 at 30 µM, with compound Z1213735368 showing an IC50 of 8 µM at a concentration of 10 µM. Furthermore, natural stilbenoids, known to modulate other TRP channels, were evaluated for their hTRPV4 binding and inhibitory potential. The findings provide insight into the structural determinants of hTRPV4 modulation and may facilitate further efforts in developing therapeutic hTRPV4 ligands.

Resveratrol and Other Natural Oligomeric Stilbenoid Compounds and Their Therapeutic Applications

The use of natural compounds as an alternative to synthetic molecules has become a significant subject of interest in recent decades. Stilbenoids are a group of phenolic compounds found in many plant species and they have recently gained the focus of a multitude of studies in medicine and chemistry, resveratrol being the most representative molecule. In this review, we focused on the research that illustrates the therapeutic potential of this class of natural molecules considering various diseases with higher incidence rates. PubChem database was searched for bioactivities of natural stilbenoids, while several keywords (i.e., "stilbenoids", "stilbenoid anticancer") were used to query PubMed database for relevant studies. The diversity and the simplicity of stilbenes' chemical structures together with the numerous biological sources are key elements that can simplify both the isolation of these compounds and the drug design of novel bioactive molecules. Resveratrol and other related compounds are heterogeneously distributed in plants and are mainly found in grapes and wine. Natural stilbenes were shown to possess a wide range of biological activities, such as antioxidant, anti-inflammatory, antihyperglycemic, cardioprotective, neuroprotective, and antineoplastic properties. While resveratrol is widely investigated for its benefits in various disorders, further studies are warranted to properly harness the therapeutic potential of less popular stilbenoid compounds.

Transient receptor potential ankyrin 1 (TRPA1) modulators: Recent update and future perspective

The transient receptor potential ankyrin 1 (TRPA1) channel is a non-selective cation channel that senses irritant chemicals. Its activation is closely associated with pain, inflammation, and pruritus. TRPA1 antagonists are promising treatments for these diseases, and there has been a recent upsurge in their application to new areas such as cancer, asthma, and Alzheimer's disease. However, due to the generally disappointing performance of TRPA1 antagonists in clinical studies, scientists must pursue the development of antagonists with higher selectivity, metabolic stability, and solubility. Moreover, TRPA1 agonists provide a deeper understanding of activation mechanisms and aid in antagonist screening. Therefore, we summarize the TRPA1 antagonists and agonists developed in recent years, with a particular focus on structure-activity relationships (SARs) and pharmacological activity. In this perspective, we endeavor to keep abreast of cutting-edge ideas and provide inspiration for the development of more effective TRPA1-modulating drugs.

TRP channels in COVID-19 disease: Potential targets for prevention and treatment

Coronavirus disease 2019 [COVID-19] is a global health threat caused by severe acute respiratory syndrome coronavirus 2 [SARS-CoV2] that requires two proteins for entry: angiotensin-converting enzyme 2 [ACE2] and -membrane protease serine 2 [TMPRSS2]. Many patients complain from pneumonia, cough, fever, and gastrointestinal (GI) problems. Notably, different TRP channels are expressed in various tissues infected by SARS-CoV-2. TRP channels are cation channels that show a common architecture with high permeability to calcium [Ca²⁺] in most sub-families. Literature review shed light on the possible role of TRP channels in COVID-19 disease. TRP channels may take part in inflammation, pain, fever, anosmia, ageusia, respiratory, cardiovascular, GI and neurological complications related to COVID-19. Also, TRP channels could be the targets for many active compounds that showed effectiveness against SARS-CoV-2. Desensitization or blocking TRP channels by antibodies, aptamers, small molecules or venoms can be an option for COVID-19 prevention and future treatment. This review provides insights into the involvement of TRP channels in different symptoms and mechanisms of SARS-CoV-2 , potential treatments targeting these channels and highlights missing gaps in literature.

Potential Interplay between Nrf2, TRPA1, and TRPV1 in Nutrients for the Control of COVID-19

In this article, we propose that differences in COVID-19 morbidity may be associated with transient receptor potential ankyrin 1 (TRPA1) and/or transient receptor potential vanilloid 1 (TRPV1) activation as well as desensitization. TRPA1 and TRPV1 induce inflammation and play a key role in the physiology of almost all organs. They may augment sensory or vagal nerve discharges to evoke pain and several symptoms of COVID-19, including cough, nasal obstruction, vomiting, diarrhea, and, at least partly, sudden and severe loss of smell and taste. TRPA1 can be activated by reactive oxygen species and may therefore be up-regulated in COVID-19. TRPA1 and TRPV1 channels can be activated by pungent compounds including many nuclear factor (erythroid-derived 2) (Nrf2)-interacting foods leading to channel desensitization. Interactions between Nrf2-associated nutrients and TRPA1/TRPV1 may be partly responsible for the severity of some of the COVID-19 symptoms. The regulation by Nrf2 of TRPA1/TRPV1 is still unclear, but suggested from very limited clinical evidence. In COVID-19, it is proposed that rapid desensitization of TRAP1/TRPV1 by some ingredients in foods could reduce symptom severity and provide new therapeutic strategies.

The Effects of Resveratrol on Prostate Cancer through Targeting the Tumor Microenvironment

Prostate cancer is one of the most common cancers diagnosed in men in the United States and the second leading cause of cancer-related deaths worldwide. Since over 60% of prostate cancer cases occur in men over 65 years of age, and this population will increase steadily in the coming years, prostate cancer will be a major cancer-related burden in the foreseeable future. Accumulating data from more recent research suggest that the tumor microenvironment (TME) plays a previously unrecognized role in every stage of cancer development, including initiation, proliferation, and metastasis. Prostate cancer is not only diagnosed in the late stages of life, but also progresses relatively slowly. This makes prostate cancer an ideal model system for exploring the potential of natural products as cancer prevention and/or treatment reagents because they usually act relatively slowly compared to most synthetic drugs. Resveratrol (RSV) is a naturally occurring stilbenoid and possesses strong anti-cancer properties with few adverse effects. Accumulating data from both in vitro and in vivo experiments indicate that RSV can interfere with prostate cancer initiation and progression by targeting the TME. Therefore, this review is aimed to summarize the recent advancement in RSV-inhibited prostate cancer initiation, proliferation, and metastasis as well as the underlying molecular mechanisms, with particular emphasis on the effect of RSV on TME. This will not only better our understanding of prostate cancer TMEs, but also pave the way for the development of RSV as a potential reagent for prostate cancer prevention and/or therapy.

Nrf2-interacting nutrients and COVID-19: time for research to develop adaptation strategies

There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPARγ:Peroxisome proliferator-activated receptor, NFκB: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2α:Elongation initiation factor 2α). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT1R axis (AT1R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity.

Mammalian Transient Receptor Potential TRPA1 Channels: From Structure to Disease

The transient receptor potential ankyrin (TRPA) channels are Ca²⁺-permeable nonselective cation channels remarkably conserved through the animal kingdom. Mammals have only one member, TRPA1, which is widely expressed in sensory neurons and in non-neuronal cells (such as epithelial cells and hair cells). TRPA1 owes its name to the presence of 14 ankyrin repeats located in the NH₂ terminus of the channel, an unusual structural feature that may be relevant to its interactions with intracellular components. TRPA1 is primarily involved in the detection of an extremely wide variety of exogenous stimuli that may produce cellular damage. This includes a plethora of electrophilic compounds that interact with nucleophilic amino acid residues in the channel and many other chemically unrelated compounds whose only common feature seems to be their ability to partition in the plasma membrane. TRPA1 has been reported to be activated by cold, heat, and mechanical stimuli, and its function is modulated by multiple factors, including Ca²⁺, trace metals, pH, and reactive oxygen, nitrogen, and carbonyl species. TRPA1 is involved in acute and chronic pain as well as inflammation, plays key roles in the pathophysiology of nearly all organ systems, and is an attractive target for the treatment of related diseases. Here we review the current knowledge about the mammalian TRPA1 channel, linking its unique structure, widely tuned sensory properties, and complex regulation to its roles in multiple pathophysiological conditions.

Total Synthesis of Gramistilbenoids A, B, and C

Stilbenes are biologically active metabolites of plants that have the potential to attenuate a broad range of human diseases. Gramistilbenoids are a class of natural products with a stilbene skeleton, isolated from the bamboo orchid ( Arundina graminifolia), and with significant cytotoxicity against cancer cell lines (NB4, A549, SHSY5Y, PC3, and MCF7). These are the first identified naturally occurring diphenylethylenes to possess a hydroxyethyl unit. However, some of these compounds are not abundant in nature, and thus, their synthesis is advantageous. This paper reports the first synthesis of gramistilbenoids A (1), B (2), and C (3), with overall yields of 10, 2, and 8% respectively. These natural products were synthesized using key reactions, such as Horner-Wadsworth-Emmons olefination, Stille coupling, and hydroboration-oxidation.

Schweinfurthins A–Q: isolation, synthesis, and biochemical properties

Stilbene analogues have shown remarkable structural diversity constituting simple or tangled structures, which have attracted the synthetic as well as the medicinal chemistry communities. Schweinfurthins are a family of prenylated/geranylated/farnesylated stilbenes that are isolated from an African plant belonging to the Macaranga species. These compounds have displayed potency towards central nervous system, renal and breast cancer cell lines. Specifically, these compounds have been found to be potent and selective inhibitors of cell growth in the National Cancer Institute's 60 cell-line screen. In this review article, we described the isolation, synthesis, and biochemical properties of schweinfurthins.

An overview of the isolation, synthesis, and biochemical properties of the stilbene-based natural products schweinfurthins A–Q (1999–2017).

Synthesis of resveratrol derivatives as new analgesic drugs through desensitization of the TRPA1 receptor

A series of 31 resveratrol derivatives was designed, synthesized and evaluated for activation and inhibition of the TRPA1 channel. Most acted as activators and desensitizers of TRPA1 channels like resveratrol or allyl isothiocyanate (AITC). Compound 4z (HUHS029) exhibited higher inhibitory activity than resveratrol with an IC₅₀ value of 16.1μM. The activity of 4z on TRPA1 was confirmed in TRPA1-expressing HEK293 cells, as well as in rat dorsal root ganglia neurons by a whole cell patch clamp recording. Furthermore, pretreatment with 4z exhibited an analgesic effect on AITC-evoked TRPA1-related pain behavior in vivo.

Activation of mutated TRPA1 ion channel by resveratrol in human prostate cancer associated fibroblasts (CAF)

Previous studies showed the effects of resveratrol (RES) on several cancer cells, including prostate cancer (PCa) cell apoptosis without taking into consideration the impact of the tumor microenvironment (TME). The TME is composed of cancer cells, endothelial cells, blood cells, and cancer-associated fibroblasts (CAF), the main source of growth factors. The latter cells might modify in the TME the impact of RES on tumor cells via secreted factors. Recent data clearly show the impact of CAF on cancer cells apoptosis resistance via secreted factors. However, the effects of RES on PCa CAF have not been studied so far. We have investigated here for the first time the effects of RES on the physiology of PCa CAF in the context of TME. Using a prostate cancer CAF cell line and primary cultures of CAF from prostate cancers, we show that RES activates the N-terminal mutated Transient Receptor Potential Ankyrin 1 (TRPA1) channel leading to an increase in intracellular calcium concentration and the expression and secretion of growth factors (HGF and VEGF) without inducing apoptosis in these cells. Interestingly, in the present work, we also show that when the prostate cancer cells were co-cultured with CAF, the RES-induced cancer cell apoptosis was reduced by 40%, an apoptosis reduction canceled in the presence of the TRPA1 channel inhibitors. The present work highlights CAF TRPA1 ion channels as a target for RES and the importance of the channel in the epithelial-stromal crosstalk in the TME leading to resistance to the RES-induced apoptosis.

The Structure-Activity Relationship of Pterostilbene Against Candida albicans Biofilms

Candida albicans biofilms contribute to invasive infections and dramatic drug resistance, and anti-biofilm agents are urgently needed in the clinic. Pterostilbene (PTE) is a natural plant product with potentials to be developed as an anti-biofilm agent. In this study, we evaluated the structure-activity relationship (SAR) of PTE analogues against C. albicans biofilms. XTT (Sodium 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt) reduction assay was used to evaluate the activity of the analogues against C. albicans biofilms. Knowing that hyphal formation is essential for C. albicans biofilms, anti-hyphal assay was further carried out. By comparing a series of compounds tested in this study, we found that compounds with para-hydroxy (–OH) in partition A exhibited better activity than those with other substituents in the para position, and the double bond in partition B and meta-dimethoxy (–OCH₃) in partition C both contributed to the best activity. Consistent results were obtained by anti-hyphal assay. Collectively, para-hydroxy (–OH), double bond and meta-dimethoxy (–OCH₃) are all needed for the best activity of PTE against C. albicans biofilms.