A Potential Route of Capsaicin to Its Binding Site in the TRPV1 Ion Channel

Investigation of the anti-inflammatory, anti-pruritic, and analgesic effects of sophocarpine inhibiting TRP channels in a mouse model of inflammatory itch and pain

ETHNOPHARMACOLOGICAL RELEVANCE

Sophocarpine is a bioactive compound extracted from the dried root of Sophorae Flavesentis Aiton, a plant that has been used for thousands of years for various conditions including skin itch and pain. Its antipruritic and analgesic effects are suggested in publications, while the molecular mechanisms underneath interacting with TRP channels are not understood.

AIM OF THE STUDY

We investigated the anti-inflammatory, antipruritic, and analgesic effects of sophocarpine in a murine inflammatory itch and pain model to elucidate the underlying mechanisms.

MATERIALS AND METHODS

We evaluated sophocarpine's anti-pruritic and analgesic effects by monitoring mice's scratching and wiping behaviors, and the anti-inflammatory effect by measuring psoriasis area and severity index (PASI) score. The mRNA and protein expression of TRPA1/TRPV1 was analyzed by real-time quantitative polymerase chain reaction and western blotting. We further investigated the relationship between sophocarpine and TRPA1/TRPV1 in mice administered allyl-isothiocyanate (AITC) or capsaicin and by molecular docking.

RESULTS

We found that sophocarpine decreased scratching bouts, wipes, and the PASI score, reduced the TNF-α and IL-1β in the skin and TRPA1 and TRPV1 in the trigeminal ganglion. Pretreatment of sophocarpine decreased AITC-induced scratching bouts and wipes and capsaicin-induced wipes. We also found potential competitive bindings between sophocarpine and AITC/capsaicin to TRPA1/TRPV1.

CONCLUSIONS

Sophocarpine is a potential competitive inhibitor of TRPA1 and TRPV1 channels eliciting strong anti-inflammatory, anti-pruritic, and analgesic effects, suggesting its significant therapeutic potential in treating diseases with inflammatory itch and pain.

Membrane Composition Allows the Optimization of Berberine Encapsulation in Liposomes

Berberine (BBR) is a natural molecule with noteworthy pharmacological properties, including the prevention of antibiotic resistance in Gram-negative bacteria. However, its oral bioavailability is poor, thus resulting in an impaired absorption and efficacy in humans. In combination with other drugs, liposomes have been shown to enhance the availability of the drug, representing a smart delivery system to target tissues and reduce negative side effects. To date, there is a lack of studies on BBR and liposomes that enable the rationalization and molecular-based design of such formulations for future use in humans. In this work, the encapsulation of BBR into liposomes is proposed to overcome current limitations using a combination of experimental and computational assays to rationalize the membrane composition of liposomes that maximizes BBR encapsulation. First, the encapsulation efficiency was measured for several membrane compositions, revealing that it is enhanced by cholesteryl hemisuccinate and, to a lesser extent, by cholesterol. The physical basis of the BBR encapsulation efficiency and permeability was clarified using molecular dynamics simulation: using the lipid composition, one can tune the capability of membranes to attract, i.e., to adsorb, the molecules onto their surface. Overall, these findings suggest a rational strategy to maximize the encapsulation efficiency of liposomes by using negatively charged lipids, thus representing the basis for designing delivery systems for BBR, useful to treat, e.g., antibiotic resistance.

Fine-tuning pH sensor H98 by remote essential residues in the hydrogen-bond network of mTASK-3

TASK-3 generates a background K+ conductance which when inhibited by acidification depolarizes membrane potential and increases cell excitability. These channels sense pH by protonation of histidine residue H98, but recent evidence revealed that several other amino acid residues also contribute to TASK-3 pH sensitivity, suggesting that the pH sensitivity is determined by an intermolecular network. Here we use electrophysiology and molecular modeling to characterize the nature and requisite role(s) of multiple amino acids in pH sensing by TASK-3. Our results suggest that the pH sensor H98 and consequently pH sensitivity is influenced by remote amino acids that function as a hydrogen-bonding network to modulate ionic conductivity. Among the residues in the network, E30 and K79 are the most important for passing external signals near residue S31 to H98. The hydrogen-bond network plays a key role in selectivity or pH sensing in mTASK-3, and E30 and S31 in the network can modulate the conductive properties (E30) or reverse the pH sensitivity and selectivity of the channel (S31). Molecular dynamics simulations and pK1/2 calculation revealed that double mutants involving H98 + S31 primarily regulate the structure stability of the pore selectivity filter and pore loop regions, further strengthen the stability of the cradle suspension system, and alter the ionization state of E30 and K79, thereby preventing pore conformational change that normally occurs in response to varying extracellular pH. These results demonstrate that crucial residues in the hydrogen-bond network can remotely tune the pH sensing of mTASK-3 and may be a potential allosteric regulatory site for therapeutic molecule development.

The implications of lipid mobility, drug-enhancers (surfactants)-skin interaction, and TRPV1 activation on licorice flavonoid permeability

Licorice flavonoids (LFs) are derived from perennial herb licorice and have been attaining a considerable interest in cosmetic and skin ailment treatments. However, some LFs compounds exhibited poor permeation and retention capability, which restricted their application. In this paper, we systematically investigated and compared the enhancement efficacy and mechanisms of different penetration enhancers (surfactants) with distinct lipophilicity or "heat and cool" characteristics on ten LFs compounds. Herein, the aim was to unveil how seven different enhancers modified the stratum corneum (SC) surface and influence the drug-enhancers-skin interaction, and to relate these effects to permeation enhancing effects of ten LFs compounds. The enhancing efficacy was evaluated by enhancement ratio (ER)permeation, ERretention, and ERcom, which was conducted on the porcine skin. It was summarized that heat capsaicin (CaP) and lipophilic Plurol® Oleique CC 497 (POCC) caused the most significance of SC lipid fluidity, SC water loss, and surface structure alterations, thereby resulting in a higher permeation enhancing effects than other enhancers. CaP could completely occupied drug-skin interaction sites in the SC, while POCC only occupied most drug-skin interactions. Moreover, the enhancing efficacy of both POCC and CaP was dependent on the log P values of LFs. For impervious LFs with low drug solubility, enhancing their drug solubility could help them permeate into the SC. For high-permeation LFs, their permeation was inhibited ascribed to the strong drug-enhancer-skin strength in the SC. More importantly, drug-surfactant-skin energy possessed a good negative correlation with the LFs permeation amount for most LFs molecules. Additionally, the activation of transient receptor potential vanilloid 1 (TRPV1) could enhance LFs permeation by CaP. The study provided novel insights for drug permeation enhancement from the viewpoint of molecular pharmaceutics, as well as the scientific utilization of different enhancers in topical or transdermal formulations.

Identification and virtual screening of novel salty peptides from hydrolysate of tilapia by-product by batch molecular docking

Introduction

Tilapia produces a large number of by-products during processing, which contain potentially flavorful peptides.

Methods

The application of PyRx software enabled batch molecular docking andscreening of 16 potential salty peptides from 189 peptides identified in the enzymaticdigestion of tilapia by-products.

Results

According to sensory analysis, all 16 peptides werepredominantly salty with a threshold of 0.256 - 0.379 mmol/L with some sournessand astringency, among which HLDDALR had the highest salty intensity, followedby VIEPLDIGDDKVR, FPGIPDHL, and DFKSPDDPSRH. I addition, moleculardocking results showed these four core peptides with high salt intensity bound to thesalt receptor TRPV1 mainly via van der Waals interactions, hydrogen bonds, andhydrophobic forces; Arg491, Tyr487, VAL441, and Asp708 were the key sites for thebinding of salty peptides to TRPV1. Therefore, the application of batch moleculardocking using PyRx is effective and economical for the virtual screening of saltypeptides.

Progress in the development of TRPV1 small-molecule antagonists: Novel Strategies for pain management

Transient receptor potential vanilloid 1 (TRPV1) channels are widely distributed in sensory nerve endings, the central nervous system, and other tissues, functioning as ion channel proteins responsive to thermal pain and chemical stimuli. In recent years, the TRPV1 receptor has garnered significant interest as a potential therapeutic approach for various pain-related disorders, particularly TRPV1 antagonists. The present review offers a comprehensive, systematic exploration of both first- and second-generation TRPV1 antagonists in the context of pain management. Antagonists are categorized and explicated according to their structural characteristics. Detailed examination of binding modes, structural features, and pharmacological activities, alongside a critical appraisal of the advantages and limitations inherent to typical compounds within each structural category, are undertaken. Detailed discussions of the binding modes, structural features, pharmacological activities, advantages, and limitations of typical compounds within each structural category offer valuable insights and guidance for the future research and development of safer, more effective, and more targeted TRPV1 antagonists.

Insights from molecular dynamics simulations of TRPV1 channel modulators in pain

TRPV1 is a nonselective cation channel vital for detecting noxious stimuli (heat, acid, capsaicin). Its role in pain makes it a potential drug target for chronic pain management, migraines, and related disorders. This review updates molecular dynamics (MD) simulation studies on the TRPV1 channel, focusing on its gating mechanism, ligand-binding sites, and implications for drug design. The article also explores challenges in developing modulators, SAR optimization, and clinical trial studies. Efforts have been undertaken to concisely present MD simulation findings, with a focus on their relevance to drug discovery.

Multidisciplinary Advances Address the Challenges in Developing Drugs against Transient Receptor Potential Channels to Treat Metabolic Disorders

Transient receptor potential (TRP) channels are cation channels that regulate key physiological and pathological processes in response to a broad range of stimuli. Moreover, they systemically regulate the release of hormones, metabolic homeostasis, and complications of diabetes, which positions them as promising therapeutic targets to combat metabolic disorders. Nevertheless, there are significant challenges in the design of TRP ligands with high potency and durability. Herein we summarize the four challenges as hydrophobicity, selectivity, mono-target therapy, and interspecies discrepancy. We present 1134 TRP ligands with diversified modes of TRP-ligand interaction and provide a detailed discussion of the latest strategies, especially cryogenic electron microscopy (cryo-EM) and computational methods. We propose solutions to address the challenges with a critical analysis of advances in membrane partitioning, polypharmacology, biased agonism, and biochemical screening of transcriptional modulators. They are fueled by the breakthrough from cryo-EM, chemoinformatics and bioinformatics. The discussion is aimed to shed new light on designing next-generation drugs to treat obesity, diabetes and its complications, with optimal hydrophobicity, higher mode selectivity, multi-targeting and consistent activities between human and rodents.

Highly Efficient Real-Time TRPV1 Screening Methodology for Effective Drug Candidates

Transient receptor potential vanilloid 1 (TRPV1) agonists that bind to the vanilloid pocket are being actively studied in the pharmaceutical industry to develop novel treatments for chronic pain and cancer. To discover synthetic vanilloids without the side effect of capsaicin, a time-consuming process of drug candidate selection is essential to a myriad of chemical compounds. Herein, we propose a novel approach to field-effect transistors for the fast and facile screening of lead vanilloid compounds for the development of TRPV1-targeting medications. The graphene field-effect transistor was fabricated with human TRPV1 receptor protein as the bioprobe, and various analyses (SEM, Raman, and FT-IR) were utilized to verify successful manufacture. Simulations of TRPV1 with capsaicin, olvanil, and arvanil were conducted using AutoDock Vina/PyMOL to confirm the binding affinity. The interaction of the ligands with TRPV1 was detected via the fabricated platform, and the collected responses corresponded to the simulation analysis.