A nonpungent component of steamed ginger--[10]-shogaol--increases adrenaline secretion via the activation of TRPV1

A journey from molecule to physiology and in silico tools for drug discovery targeting the transient receptor potential vanilloid type 1 (TRPV1) channel

The heat and capsaicin receptor TRPV1 channel is widely expressed in nerve terminals of dorsal root ganglia (DRGs) and trigeminal ganglia innervating the body and face, respectively, as well as in other tissues and organs including central nervous system. The TRPV1 channel is a versatile receptor that detects harmful heat, pain, and various internal and external ligands. Hence, it operates as a polymodal sensory channel. Many pathological conditions including neuroinflammation, cancer, psychiatric disorders, and pathological pain, are linked to the abnormal functioning of the TRPV1 in peripheral tissues. Intense biomedical research is underway to discover compounds that can modulate the channel and provide pain relief. The molecular mechanisms underlying temperature sensing remain largely unknown, although they are closely linked to pain transduction. Prolonged exposure to capsaicin generates analgesia, hence numerous capsaicin analogs have been developed to discover efficient analgesics for pain relief. The emergence of in silico tools offered significant techniques for molecular modeling and machine learning algorithms to indentify druggable sites in the channel and for repositioning of current drugs aimed at TRPV1. Here we recapitulate the physiological and pathophysiological functions of the TRPV1 channel, including structural models obtained through cryo-EM, pharmacological compounds tested on TRPV1, and the in silico tools for drug discovery and repositioning.

Do ginger footbaths improve symptoms of insomnia more than footbaths with warm water only? - A randomized controlled study

OBJECTIVES

To compare the effects between warm water (WW) and ginger footbaths (WW+ginger) on sleep quality and warmth regulation in adults with self-reported insomnia symptoms.

METHODS

A prospective randomized-controlled study in which 28 participants (mean age 50.9 years, 64.3% women, insomnia symptom duration 11.4 years) were randomized to receive WW (n = 13) or WW+ginger (n = 15) daily for 2 weeks. Treatment involved nightly footbaths (12 liters of 38-42 °C warm tap water, maximum duration 20 min) with and without topical ginger (80 g of powdered ginger rhizomes).

MAIN OUTCOME MEASURES

The primary outcome measure was self-reported sleep quality (global score from Pittsburgh Sleep Quality Index, PSQI) at 2 weeks. Secondary outcomes included measures of insomnia severity (Insomnia Severity Index, ISI) and warmth regulation (Herdecke Warmth Perception Questionnaire, HWPQ and 24-hour distal-proximal skin temperature gradient, DPG).

RESULTS

WW+ginger had no greater effect on PSQI (mean between-difference 0.0 [95% CI -3.0 to 2.9], Cohen's d=0.0) or ISI (-0.2 [-3.9 to 3.4], 0.0) than WW. Nor were there any significant differences in HWPQ perceived warmth (0.1 ≥d≥0.5) or DPG (0.1 ≥d≥0.4) between WW and WW+ginger. Both groups improved over time in PSQI (WW+ginger: d=0.7, WW: d=1.3) and ISI (WW+ginger: d=0.8, WW: d=1.0). Perceived warmth of the feet increased only in WW+ginger over time (d=0.6, WW: d=0.0).

CONCLUSIONS

This dose of ginger (6.67 g/liter) did not have greater effects on sleep quality, insomnia severity or warmth regulation than WW. Considering effect sizes, costs and risks, the use of WW would be recommended over WW+ginger in this patient population.

Do Chest Compresses with Mustard or Ginger Affect Warmth Regulation in Healthy Adults? A Randomized Controlled Trial

Background

Chest compresses with mustard (MU) or ginger (GI) are a complementary treatment option for respiratory tract infections. However, little is known about their specific thermogenic qualities. This study examines the short-term effects of MU, GI, and chest compresses with warm water only (WA) on measurable and self-perceived body warmth in healthy adults.

Methods

This was a single-center, randomized controlled trial with cross-over design (WA versus MU versus GI). 18 participants (23.7 ± 3.4 years; 66.7% female) received MU, GI, and WA in a random order on three different days with a mean washout period of 13.9 days. Chest compresses were applied to the thoracic back for a maximum of 20 minutes. The primary outcome measure was skin temperature of the posterior trunk (measured by infrared thermography) immediately following removal of the compresses (t1). Secondary outcome measures included skin temperature of the posterior trunk 10 minutes later (t2) and several parameters of self-perceived warmth at t1 and t2 (assessed with the Herdecke Warmth Perception Questionnaire).

Results

Skin temperature of the posterior trunk was significantly higher with MU compared to WA and GI at t1 (p < 0.001 for both, primary outcome measure) and t2 (WA versus MU: p=0.04, MU versus GI: p < 0.01). Self-perceived warmth of the posterior trunk was higher with MU and GI compared to WA at t1 (1.40 ≥ d ≥ 1.79) and remained higher with GI at t2 (WA versus GI: d = 0.74). The overall warmth perception increased significantly with GI (d = 0.69), tended to increase with MU (d = 0.54), and did not change with WA (d = 0.36) between t0 and t1.

Conclusions

Different effects on warmth regulation were observed when ginger and mustard were applied as chest compresses. Both substances induced self-perceived warming of the posterior trunk, but measurable skin temperature increased only with MU. Further research is needed to examine the duration of these thermogenic effects and how chest compresses with ginger or mustard might be incorporated into practice to influence clinical outcomes in respiratory tract infections.

Treatment of Gastrointestinal Disorders-Plants and Potential Mechanisms of Action of Their Constituents

The worldwide prevalence of gastrointestinal diseases is about 40%, with standard pharmacotherapy being long-lasting and economically challenging. Of the dozens of diseases listed by the Rome IV Foundation criteria, for five of them (heartburn, dyspepsia, nausea and vomiting disorder, constipation, and diarrhoea), treatment with herbals is an official alternative, legislatively supported by the European Medicines Agency (EMA). However, for most plants, the Directive does not require a description of the mechanisms of action, which should be related to the therapeutic effect of the European plant in question. This review article, therefore, summarizes the basic pharmacological knowledge of synthetic drugs used in selected functional gastrointestinal disorders (FGIDs) and correlates them with the constituents of medicinal plants. Therefore, the information presented here is intended as a starting point to support the claim that both empirical folk medicine and current and decades-old treatments with official herbal remedies have a rational basis in modern pharmacology.

Zingiber officinale var. rubrum: Red Ginger's Medicinal Uses

Zingiber officinale var. rubrum (red ginger) is widely used in traditional medicine in Asia. Unlike other gingers, it is not used as a spice in cuisines. To date, a total of 169 chemical constituents have been reported from red ginger. The constituents include vanilloids, monoterpenes, sesquiterpenes, diterpenes, flavonoids, amino acids, etc. Red ginger has many therapeutic roles in various diseases, including inflammatory diseases, vomiting, rubella, atherosclerosis, tuberculosis, growth disorders, and cancer. Scientific evidence suggests that red ginger exhibits immunomodulatory, antihypertensive, antihyperlipidemic, antihyperuricemic, antimicrobial, and cytotoxic activities. These biological activities are the underlying causes of red ginger's therapeutic benefits. In addition, there have been few reports on adverse side effects of red ginger. This review aims to provide insights in terms the bioactive constituents and their biosynthesis, biological activities, molecular mechanisms, pharmacokinetics, and qualitative and quantitative analysis of red ginger.

The Effect of Ginger (Zingiber officinale) on Improving Blood Lipids and Body Weight; A Systematic Review and Multivariate Meta-analysis of Clinical Trials

BACKGROUND

Beneficial effects of ginger consumption on metabolic biomarkers has been reported previously. The current research aimed to investigate the effects of ginger supplementation on lipid profile and body weight using a meta-analysis of randomized, controlled trials.

METHODS

Online databases PubMed, Embase, Web of Science, and Science Direct were searched until December 2021 to identify eligible articles. Twenty-six trials were included.

RESULTS

The results showed that ginger consumption could significantly improve lipid profile including total triglyceride (-12.54 (-20.01 to -5.08)), cholesterol (-6.53 (-10.76 to -2.31)), LDL (-5.14 (-8.79 to -1.50)), and HDL (1.13 (0.35 to 1.91)). Moreover, ginger supplementation could significantly decrease body mass index (BMI) (-0.49 (-0.79 to -0.18)). However, the small number of sample studies that investigated reductions in body weight (-0.52 (-1.48 to 0.43)) were not statistically significant. Sub-group analysis of treatment dose and duration showed that in most of the analyzed lipid profiles, both ≤1500 and >1500 mg/d for both of ≤8 and >8 weeks could be effective; however, in the case of weight control dose of >1500 mg/d for more than 8 weeks was more effective. Besides, the results of multivariate meta-analysis revealed the effect of the intervention on all lipid profiles simultaneously.

CONCLUSION

The present meta-analysis and review revealed that ginger supplementation can improve lipid profile and body weight if used at the appropriate dose and duration. More studies are needed to fully evaluate the effect of ginger supplements' different doses and duration on lipid profile and BMI.

TRP Channels as Molecular Targets to Relieve Cancer Pain

Transient receptor potential (TRP) channels are critical receptors in the transduction of nociceptive stimuli. The microenvironment of diverse types of cancer releases substances, including growth factors, neurotransmitters, and inflammatory mediators, which modulate the activity of TRPs through the regulation of intracellular signaling pathways. The modulation of TRP channels is associated with the peripheral sensitization observed in patients with cancer, which results in mild noxious sensory stimuli being perceived as hyperalgesia and allodynia. Secondary metabolites derived from plant extracts can induce the activation, blocking, and desensitization of TRP channels. Thus, these compounds could act as potential therapeutic agents, as their antinociceptive properties could be beneficial in relieving cancer-derived pain. In this review, we will summarize the role of TRPV1 and TRPA1 in pain associated with cancer and discuss molecules that have been reported to modulate these channels, focusing particularly on the mechanisms of channel activation associated with molecules released in the tumor microenvironment.

Ginger from Farmyard to Town: Nutritional and Pharmacological Applications

Ginger (Zingiber officinale) is one of the most widely used natural products consumed as a spice and medicine for treating diabetes, flatulent intestinal colic, indigestion, infertility, inflammation, insomnia, a memory booster, nausea, rheumatism, stomach ache, and urinary tract infections. To date, over 400 bioactive components, such as diarylheptanoids, gingerol analogues, phenylalkanoids, sulfonates, monoterpenoid glycosides, steroids, and terpene compounds have been derived from ginger. Increasing evidence has revealed that ginger possesses a broad range of biological activities, especially protective effects against male infertility, nausea and vomiting, analgesic, anti-diabetic, anti-inflammatory, anti-obesity, and other effects. The pharmacological activities of ginger were mainly attributed to its active phytoconstituents such as 6-gingerol, gingerdiol, gingerol, gingerdione, paradols, shogaols, sesquiterpenes, zingerone, besides other phenolics and flavonoids. In recent years, in silico molecular docking studies revealed that gingerol (6-gingerol, 8-gingerol, and 10-gingerol) and Shogaol (6-shogaol, 8-shogaol, 10-shogaol) had the best binding affinities to the receptor protein in disease conditions such as diabetes, inflammation, obesity, and SARS-CoV-2. Furthermore, some clinical trials have indicated that ginger can be consumed for alleviation of nausea and vomiting induced by surgery, pain, diabetes, obesity, inflammation, male infertility. This review provides an updated understanding of the scientific evidence on the development of ginger and its active compounds as health beneficial agents in future clinical trials.

Surfactant cocamide monoethanolamide causes eye irritation by activating nociceptor TRPV1 channels

BACKGROUND AND PURPOSE

Cocamide monoethanolamide (CMEA) is commonly used as a surfactant-foam booster in cosmetic formulations. Upon contact with the eye or other sensitive skin areas, CMEA elicits stinging and lasting irritation. We hypothesized a specific molecular interaction with TRPV1 channels by which CMEA caused eye irritation.

EXPERIMENTAL APPROACH

Eye irritancy was evaluated using eye-wiping tests in rabbits and mice. Intracellular Ca2+ concentrations and action potentials were measured using Ca2+ imaging and current clamp respectively. Voltage clamp, site-direct mutagenesis and molecular modelling were used to identify binding pockets for CMEA on TRPV1 channels.

KEY RESULTS

CMEA-induced eye irritation is ameliorated by selective ablation of TRPV1 channels.Rodents exhibit much stronger responses to CMEA than rabbits. In trigeminal ganglion neurons, CMEA induced Ca2+ influx and neuronal excitability, effects mitigated by a TRPV1 channel inhibition and absent in TRPV1 knockout neurons. In HEK-293 cells expressing TRPV1 channels, CMEA increased whole-cell currents by increasing channel open probability (EC50  = 10.2 μM), without affecting TRPV2, TRPV3, TRPV4, and TRPA1 channel activities. Lauric acid monoethanolamide (LAMEA), the most abundant constituent of CMEA, was the most efficacious and potent TRPV1 channel activator, binding to the capsaicin-binding pocket of the channel. The T550I mutants of rabbit and human TRPV1 channels exhibit much lower sensitivity to LAMEA.

CONCLUSIONS AND IMPLICATION

CMEA directly activates TRPV1 channels to produce eye irritation. Rabbits, the standard animal used for eye irritancy tests are poor models for evaluating human eye irritants structurally related to CMEA. Our study identifies potential alternatives to CMEA as non-irritating surfactants.

Warm Footbaths with Sinapis nigra or Zingiber officinale Enhance Self-Reported Vitality in Healthy Adults More than Footbaths with Warm Water Only: A Randomized, Controlled Trial

Objectives

To examine the effects of warm footbaths with thermogenic medicinal powders on vitality and heart rate variability in healthy adults. Intervention and Outcome. Seventeen healthy young adults (22.1 ± 2.4 years, 11 females) received three footbaths (WA: warm water only; GI: warm water and ginger; MU: warm water and mustard) in randomized order with a crossover design. We assessed vitality with the Basler Befindlichkeit questionnaire (BBS) and heart rate variability (HRV) before (t0), immediately after (t1), and 10 minutes following footbaths (t2). The primary outcome measure was self-reported vitality, measured via the BBS, at t1.

Results

The primary outcome measure, self-reported vitality, was higher after GI and tended to be higher after MU compared to WA with medium effect sizes (GI vs. WA, mean difference −2.47 (95% CI −5.28 to 0.34), p_adj=0.048, d_adj = 0.74), MU vs. WA, −2.35 (−5.32 to 0.61), p_adj=0.30, d_adj = 0.50). At t2, the standard deviation of beat-to-beat intervals (SDNN) of HRV increased, and the stress index tended to decrease after all three footbath conditions with small to medium effect sizes (0.42–0.66).

Conclusion

There is preliminary evidence that footbaths with thermogenic agents GI and MU may increase self-reported vitality during a short-time period with a more pronounced effect with GI. After a short follow-up, all three conditions tended to shift the autonomic balance towards relaxation. Future research should investigate these effects in clinical samples with a larger, more diverse sample size.

Involvement of TRP Channels in Adipocyte Thermogenesis: An Update

Obesity prevalence became a severe global health problem and it is caused by an imbalance between energy intake and expenditure. Brown adipose tissue (BAT) is a major site of mammalian non-shivering thermogenesis or energy dissipation. Thus, modulation of BAT thermogenesis might be a promising application for body weight control and obesity prevention. TRP channels are non-selective calcium-permeable cation channels mainly located on the plasma membrane. As a research focus, TRP channels have been reported to be involved in the thermogenesis of adipose tissue, energy metabolism and body weight regulation. In this review, we will summarize and update the recent progress of the pathological/physiological involvement of TRP channels in adipocyte thermogenesis. Moreover, we will discuss the potential of TRP channels as future therapeutic targets for preventing and combating human obesity and related-metabolic disorders.

The protective effects of steamed ginger on adipogenesis in 3T3-L1 cells and adiposity in diet-induced obese mice

BACKGROUND/OBJECTIVES

The steamed ginger has been shown to have antioxidative effects and a protective effect against obesity. In the present study, we investigated the effects of ethanolic extract of steamed ginger (SGE) on adipogenesis in 3T3-L1 preadipocytes and diet-induced obesity (DIO) mouse model.

MATERIALS/METHODS

The protective effects of SGE on adipogenesis were examined in 3T3-L1 adipocytes by measuring lipid accumulations and genes involved in adipogenesis. Male C57BL/6J mice were fed a normal diet (ND, 10% fat w/w), a high-fat diet (HFD, 60% fat w/w), and HFD supplemented with either 40 mg/kg or 80 mg/kg of SGE for 12 weeks. Serum chemistry was measured, and the expression of genes involved in lipid metabolism was determined in the adipose tissue. Histological analysis and micro-computed tomography were performed to identify lipid accumulations in epididymal fat pads.

RESULTS

In 3T3-L1 cells, SGE significantly decreased lipid accumulation, with concomitant decreases in the expression of adipogenesis-related genes. SGE significantly attenuated the increase in body, liver, and epididymal adipose tissue weights by HFD. Serum total cholesterol and triglyceride levels were significantly lower in SGE fed groups compared to HFD. In adipose tissue, SGE significantly decreased adipocyte size than that of HFD and altered adipogenesis-related genes.

CONCLUSIONS

In conclusion, steamed ginger exerted anti-obesity effects by regulating genes involved in adipogenesis and lipogenesis in 3T3-L1 cell and epididymal adipose tissue of DIO mice.

Efficacy of Ginger in the Treatment of Primary Dysmenorrhea: A Systematic Review and Meta-analysis

It has been evidenced that very few systematic reviews have examined the effectiveness of ginger for pain duration and its severity among women with primary dysmenorrhea. This meta-analysis was therefore performed to methodically incorporate and significantly evaluate randomized controlled ginger studies for the treatment of primary dysmenorrhea. The literature was searched using PubMed, Embase, Ovid, ClinicalKey, Medline, and electronic database. We have analyzed clinical trials by comparing ginger with placebo and non-steroidal anti-inflammatory drugs in women with primary dysmenorrhea. The primary outcomes assessed in our meta-analysis were pain severity and pain duration. Secondary outcomes were change in bleeding, side effects of the drug, and rate of satisfaction. We have screened a total of 638 studies, out of which narrative synthesis was formulated for eight studies. We have performed a meta-analysis of five trials examining ginger with placebo and other two randomized controlled trials comparing ginger with a non-steroidal anti-inflammatory drug (NSAID); it seems to be more helpful for relieving menstrual pain than a placebo (mean difference [MD] = 2.67, 95% CI = 3.51-1.84, P = 0.0001, I2 = 86%), although it was found that ginger and NSAIDs were equally effective in pain severity (risk ratios [RR] = 1.15, 95% CI = 0.53-2.52, P = 0.72, I2 =77%). We have not observed any significant difference between ginger and placebo on pain duration among primary dysmenorrheic women (MD = -2.22, 95% CI = -7.62-3.18, P = 0.42, I2 = 56%). Accessible information proposes that oral ginger can be a compelling treatment for primary dysmenorrhea. This meta-analysis strongly supports the requirement for high methodological quality consistency for upcoming trials.

A Luminescence-Based Human TRPV1 Assay System for Quantifying Pungency in Spicy Foods

The quantitation of pungency is difficult to achieve using sensory tests because of persistence, accumulation, and desensitization to the perception of pungency. Transient receptor vanilloid 1 (TRPV1), which is a chemosensory receptor, plays a pivotal role in the perception of many pungent compounds, suggesting that the activity of this receptor might be useful as an index for pungency evaluation. Although Ca²⁺-sensitive fluorescence dyes are commonly used for measuring human TRPV1 (hTRPV1) activity, their application is limited, as foods often contain fluorescent substances that interfere with the fluorescent signals. This study aims to design a new pungency evaluation system using hTRPV1. Instead of employing a fluorescent probe as the Ca²⁺ indicator, this assay system uses the luminescent protein aequorin. The luminescence assay successfully evaluated the hTRPV1 activity in foods without purification, even for those containing fluorescent substances. The hTRPV1 activity in food samples correlated strongly with the pungency intensity obtained by the human sensory test. This luminescence-based hTRPV1 assay system will be a powerful tool for objectively quantifying the pungency of spicy foods in both laboratory and industrial settings.

Effect of a Blend of Zingiber officinale Roscoe and Bixa orellana L. Herbal Supplement on the Recovery of Delayed-Onset Muscle Soreness Induced by Unaccustomed Eccentric Resistance Training: A Randomized, Triple-Blind, Placebo-Controlled Trial

BACKGROUND

There is an increasing interest in the use of eccentric muscle exercise to improve physical condition, especially with regards to its health-related benefits. However, it is known that unaccustomed eccentric exercise causes muscle damage and delayed pain, commonly defined as "delayed onset muscle soreness" (DOMS). The efficacy of herbal preparations in subjects suffering from DOMS has been reported in a few previous studies with small or moderate outcome measures related to muscle recovery. The present study aimed to evaluate the effects of a polyherbal mixture containing whole Zingiber officinale Roscoe and Bixa orellana L., powders called ReWin(d), in young male athletes suffering from DOMS induced by a 1 h session of plyometric exercises.

METHODS

Thirty-three young male athletes participated in this randomized, Triple-blind, placebo-controlled trial: 17 of them assigned to the ReWin(d) group and 16 of them to the placebo group. Creatine kinase (CK) was measured as a muscle damage marker, pain was assessed using the Visual Analog Scale (VAS), muscle performance was measured through half-squat exercise (HS) monitored with an accelerometer (Encoder), and heart rate variability (HRV) was monitored for 5 min with the subjects in the supine position. All determinations were performed before and after the eccentric session and 24, 48, and 72 h after the session.

RESULTS

The eccentric exercise session caused an increase in CK at 24 and 48 h after exercise intervention in both groups (p < 0.001). There was no interaction between groups regarding muscle damage. The pain increased after the training session in both groups (p < 0.001), and a significant interaction was observed between groups at 48 h after exercise (p = 0.004). Lower limb muscular power showed a significant interaction between groups 24 h after exercise (p = 0.049); the placebo group showed a reduction in muscle power compared to the ReWin(d) group. The LF/HF ratio decreased significantly at 72 h after exercise in the herbal group but not in the placebo group.

CONCLUSION

The herbal supplement maintained the maximum power of the lower limbs and attenuated muscle pain.

CLINICAL TRIAL REGISTRATION

www.ClinicalTrials.gov, identifier NCT03961022.

Increasing Warmth in Adolescents with Anorexia Nervosa: A Randomized Controlled Crossover Trial Examining the Efficacy of Mustard and Ginger Footbaths

Objective

To analyze the thermogenic effects of footbaths with medicinal powders in adolescents with anorexia nervosa (AN) in comparison to healthy controls (HCs). Intervention and Outcomes. Forty-one female participants (21 AN, 20 HCs; 14.22 ± 1.54 years) received three footbaths-warm water and mustard (MU, Sinapis nigra), warm water and ginger (GI, Zingiber officinale), or warm water only (WA), in random order within a crossover design. Data were collected before (t1), immediately after foot immersion (maximum 20 minutes) (t2), and after 10 minutes subsequently (t3). Actual skin temperature (high resolution thermography) and perceived warmth (HeWEF questionnaire) were assessed at each time point for various body parts. The primary outcome measure was self-perceived warmth at the feet at t3. Secondary outcome measures were objective skin temperature and subjective warmth at the face, hands, and feet.

Results

Perceived warmth at the feet at t3 was significantly higher after GI compared to WA (mean difference -1.02) and MU (-1.07), with no differences between those with AN and HC (-0.29). For the secondary outcome measures, a craniocaudal temperature gradient for the skin temperature (thermography) was noted at t1 for patients with AN and HC (AN with colder feet). The craniocaudal gradient for subjective warmth was only seen for patients with AN.

Conclusion

Footbaths with ginger increased warmth perception at the feet longer than with mustard or warm water only for adolescents with AN as well as for HC. The impact of ginger footbaths on recovery of thermoregulatory disturbances in patients with AN repeated over extended periods merits further investigation.

A herbal premix containing Macrotyloma uniflorum, ginger, and whey curtails obesity in rats fed a high-fat diet by a novel mechanism

The present study designed and evaluated a polyherbal premix comprising Macrotyloma uniflorum, whey protein, Zingiber officinale, and Mentha piperita. Animals were fed a high-fat diet (HFD) for 30 days and were daily administered the premix (1.5 g/kg) in milk (PM) and water (PW), aerobic exercise (AE), premix in milk and water along with AE (PMAE and PWAE), ferulic acid (100 mg/kg), and the reference drug fluoxetine (6 mg/kg). All treatments showed significant reduction in food intake, weight gain, abdominal circumference, and body mass index compared with their initial values. All treatments generated a faster peak of the satiety marker cholecystokinin compared with the HFD group and control groups; PMAE and PWAE exhibited sustained satiety. The HFD-elevated blood glucose levels were significantly attenuated on the 30th day by all treatments when compared with their 15th day and basal values; PMAE exhibited the best results. All treatments significantly attenuated the HFD-elevated serum insulin, homeostasis model assessment of insulin resistance, C-reactive protein, triglycerides, total cholesterol, very-low-density lipoprotein, and low-density lipoprotein levels and significantly restored the HFD-depleted high-density lipoprotein and adiponectin levels. HFD-elevated thiobarbituric acid reactive substances values were attenuated successfully and the HFD-depleted reduced glutathione, superoxide dismutase, and catalase levels were significantly restored by all treatments. The histological findings corroborated the biochemical results. Novelty The polyherbal premix brought about appetite regulation and induction of satiety to control obesity in HFD-fed rats through homeostasis of energy metabolism. The premix along with exercise is a complete way to combat obesity.

Hepatoprotective and Renoprotective Properties of Lovastatin-Loaded Ginger and Garlic Oil Nanoemulsomes: Insights into Serum Biological Parameters

Background and Objectives: Dyslipidemia is gaining much attention among healthcare professionals because of its high association with the malfunctioning of a number of normal physiological and metabolic processes in the body. Obesity is directly interconnected with dyslipidemia and is said to be a denouement of hyperlipidemia and, if left untreated, may lead to intense damage to organs that are directly involved in fat metabolism. The objective of this study was to investigate the synergistic antiobesity and anti-hyperlipidemic activities along with hepato- and renoprotective potential of nanoemulsomes (NES) of lovastatin (LTN)-loaded ginger (GR) and garlic (GL) oils. Materials and Methods: LTN nanoemulsomes co-encapsulated with GR oil and GL oil were prepared by a thin hydration technique. Eight-week-old male Wistar rats weighing 200-250 g were induced with hyperlipidemia via a high-fat diet (HFD) comprising 40% beef tallow. Body weight, serum biochemical lipid parameters, and those for liver and kidney functions, serum TC, LDL-C, vLDL-C, HDL-C, TG, atherogenic index (AI), ALT, AFT, ALP, γ-GT, total protein (TP), serum albumin and globulin ratio (A/G), serum creatinine, blood urea nitrogen (BUN) and blood urea, and histopathology of hematoxylin and eosin (H&E) stained liver and kidney sections of all aforementioned groups were examined in the treated animals. Results: Nanoemulsomes of LTN-loaded GR and GL oils provided synergistic effects with LTN, exerted better ameliorative actions in reducing serum TC, LDL-C, vLDL-C, triglycerides, and AI, and improved serum HDL-C levels. Serum ALT, AST, ALP, and γ-GT levels were in the normal range for nanoemulsome groups. H&E stained liver and kidney sections of these animals confirmed better hepatoprotective and renoprotective effects than LTN alone. Serum biochemical parameters for renal functions also claimed to be in the moderate range for nanoemulsome-treated groups. Conclusion: This study demonstrated that nanoemulsomes of LTN-loaded GR and GL oils synergistically provided better antihyperlipidemic, hepatoprotective, and renoprotective effects as compared to LTN alone.

Structural mechanisms underlying activation of TRPV1 channels by pungent compounds in gingers

BACKGROUND AND PURPOSE

Like chili peppers, gingers produce pungent stimuli by a group of vanilloid compounds that activate the nociceptive transient receptor potential vanilloid 1 (TRPV1) ion channel. How these compounds interact with TRPV1 remains unclear.

EXPERIMENTAL APPROACH

We used computational structural modelling, functional tests (electrophysiology and calcium imaging), and mutagenesis to investigate the structural mechanisms underlying ligand-channel interactions.

KEY RESULTS

The potency of three principal pungent compounds from ginger -shogaol, gingerol, and zingerone-depends on the same two residues in the TRPV1 channel that form a hydrogen bond with the chili pepper pungent compound, capsaicin. Computational modelling revealed binding poses of these ginger compounds similar to those of capsaicin, including a "head-down tail-up" orientation, two specific hydrogen bonds, and important contributions of van der Waals interactions by the aliphatic tail. Our study also identified a novel horizontal binding pose of zingerone that allows it to directly interact with the channel pore when bound inside the ligand-binding pocket. These observations offer a molecular level explanation for how unique structures in the ginger compounds affect their channel activation potency.

CONCLUSIONS AND IMPLICATIONS

Mechanistic insights into the interactions of ginger compounds and the TRPV1 cation channel should help guide drug discovery efforts to modulate nociception.

Effects of Footbaths with Mustard, Ginger, or Warm Water Only on Objective and Subjective Warmth Distribution in Healthy Subjects: A Randomized Controlled Trial

OBJECTIVE

To analyze the short-term thermogenic effects of footbaths with warm water alone (WA) versus when combined with medicinal powders.

DESIGN

Randomized controlled trial with cross-over.

INTERVENTIONS AND OUTCOMES

Seventeen healthy volunteers (mean age 22.1 years, SD = 2.4; 11 female) received three footbaths with WA or WA combined with mustard (MU) or ginger (GI) in a randomized order. Self-perceived warmth (Herdecke warmth perception questionnaire) and actual skin temperatures (thermography) were assessed before (t0), immediately after footbaths (t1), and 10 minutes later (t2). The primary outcome was perceived warmth in the feet. Secondary outcomes were warmth perception in the face, hands and overall, as well as actual skin temperature in the feet, face, and hands.

RESULTS

Perceived warmth at the feet (primary outcome) increased significantly (all p's < .001) for MU and GI at t1 as well as for GI at t2 when compared to t0 with high effect sizes. At t2, GI differed significantly from WA (p < .001) and MU (p = .048). With regards to the secondary measures of outcome, no significant effects were seen for perceived warmth at the face or hands. Overall warmth was significantly higher at t1 compared to t0 (p = .01). Thermography assessments of skin temperature at the feet at t1 increased after all conditions (p < .001). No effects were seen in the face. At the hands, temperature decreased at t1 (p = .02) and t2 compared to t0 (p < .001).

CONCLUSION

The present study provides preliminary evidence that mustard and ginger increase warmth perception at the feet more than warm water alone, with only the effects for GI enduring at the brief follow-up.

Hyperthermic Effect of Ginger (Zingiber officinale) Extract-Containing Beverage on Peripheral Skin Surface Temperature in Women

Ginger is known to warm the body. Therefore, we conducted a placebo-controlled crossover trial to investigate the hyperthermic effect of a palatable ginger-containing beverage in healthy women with cold-sensitive extremities. Six women drank 280 mL of 0.07% ginger extract-containing or placebo beverage in a temperature-controlled room (21°C). Their palm temperatures were measured as measure of surface body temperature using a thermographic camera before intake and every 10 min after intake for 60 min. Palm temperature increased immediately following intake of the ginger and placebo beverages. However, palm temperature following intake of the ginger beverage increased for 20 min, while palm temperature following placebo intake decreased again after 10 min. The increased palm temperature following ginger intake was maintained significantly longer than after placebo intake (p < 0.05). In response to a questionnaire, some subjects answered that their increased body temperature was maintained after drinking the ginger beverage. Ginger extract-containing beverage may thus improve cold sensitivity.

A systematic review of the anti-obesity and weight lowering effect of ginger (Zingiber officinale Roscoe) and its mechanisms of action

Recently, the beneficial effects of ginger on obesity is taken into consideration. Albeit, it seems that the anti-obesity effect of ginger and its mechanism of action has not yet been reviewed. Therefore, the aim of this study was to systematically review the effect of Zingiber officinale Roscoe on obesity management. Databases including PubMed, Scopus, Google scholar, and Science Direct were searched from 1995 until May 2017 using the definitive keywords. Searching was limited to articles with English language. All of the relevant human and animal studies and also in vitro studies were included. Review articles, abstract in congress, and also other varieties of ginger were excluded. Eligibility of included articles were evaluated by 3 reviewers, which also extracted data. Articles were critically assessed individually for possible risk of bias. Twenty-seven articles (6 in vitro, 17 animal, and 4 human studies) were reviewed. Most of the experimental studies supported the weight lowering effect of ginger extract or powder in obese animal models, whereas the results of the available limited clinical studies showed no changes or slight changes of anthropometric measurements and body composition in subjects with obesity. Ginger could modulate obesity through various potential mechanisms including increasing thermogenesis, increasing lipolysis, suppression of lipogenesis, inhibition of intestinal fat absorption, and controlling appetite. This review article provides some convincing evidence to support the efficacy of ginger in obesity management and demonstrates the importance of future clinical trials.

Involvement of TRPV1 Channels in Energy Homeostasis

The ion channel TRPV1 is involved in a wide range of processes including nociception, thermosensation and, more recently discovered, energy homeostasis. Tightly controlling energy homeostasis is important to maintain a healthy body weight, or to aid in weight loss by expending more energy than energy intake. TRPV1 may be involved in energy homeostasis, both in the control of food intake and energy expenditure. In the periphery, it is possible that TRPV1 can impact on appetite through control of appetite hormone levels or via modulation of gastrointestinal vagal afferent signaling. Further, TRPV1 may increase energy expenditure via heat production. Dietary supplementation with TRPV1 agonists, such as capsaicin, has yielded conflicting results with some studies indicating a reduction in food intake and increase in energy expenditure, and other studies indicating the converse. Nonetheless, it is increasingly apparent that TRPV1 may be dysregulated in obesity and contributing to the development of this disease. The mechanisms behind this dysregulation are currently unknown but interactions with other systems, such as the endocannabinoid systems, could be altered and therefore play a role in this dysregulation. Further, TRPV1 channels appear to be involved in pancreatic insulin secretion. Therefore, given its plausible involvement in regulation of energy and glucose homeostasis and its dysregulation in obesity, TRPV1 may be a target for weight loss therapy and diabetes. However, further research is required too fully elucidate TRPV1s role in these processes. The review provides an overview of current knowledge in this field and potential areas for development.

Involvement of thermosensitive TRP channels in energy metabolism

To date, 11 thermosensitive transient receptor potential (thermo-TRP) channels have been identified. Recent studies have characterized the mechanism of thermosensing by thermo-TRPs and the physiological role of thermo-TRPs in energy metabolism. In this review, we highlight the role of various thermo-TRPs in energy metabolism and hormone secretion. In the pancreas, TRPM2 and other TRPs regulate insulin secretion. TRPV2 expressed in brown adipocytes contributes to differentiation and/or thermogenesis. Sensory nerves that express TRPV1 promote increased energy expenditure by activating sympathetic nerves and adrenaline secretion. Here, we first show that capsaicin-induced adrenaline secretion is completely impaired in TRPV1 knockout mice. The thermogenic effects of TRPV1 agonists are attributable to brown adipose tissue (BAT) activation in mice and humans. Moreover, TRPA1- and TRPM8-expressing sensory nerves also contribute to potentiation of BAT thermogenesis and energy expenditure in mice. Together, thermo-TRPs are promising targets for combating obesity and metabolic disorders.

Construction of Prediction Models for the Transient Receptor Potential Vanilloid Subtype 1 (TRPV1)-Stimulating Activity of Ginger and Processed Ginger Based on LC-HRMS Data and PLS Regression Analyses

To construct a model formula to evaluate the thermogenetic effect of ginger (Zingiber officinale Roscoe) from the ingredient information, we established transient receptor potential vanilloid subtype 1 (TRPV1)-stimulating activity prediction models by using a partial least-squares projections to latent structures (PLS) regression analysis in which the ingredient data from liquid chromatography-high-resolution mass spectrometry (LC-HRMS) and the stimulating activity values for TRPV1 receptor were used as explanatory and objective variables, respectively. By optimizing the peak extraction condition of the LC-HRMS data and the data preprocessing parameters of the PLS regression analysis, we succeeded in the construction of a TRPV1-stimulating activity prediction model with high precision ability. We then searched for the components responsible for the TRPV1-stimulating activity by analyzing the loading plot and s-plot of the model, and we identified [6]-gingerol (1) and hexahydrocurcumin (3) as TRPV1-stimulating activity components.

Changes of serum adipocytokines and body weight following Zingiber officinale supplementation in obese women: a RCT

PURPOSE

The present randomized, double-blind, placebo-controlled study aimed to evaluate the effect of Zingiber officinale (ginger) consumption on some metabolic and clinical features of obesity.

METHODS

Eighty eligible obese women (aged 18-45 years) were randomly assigned to either ginger or placebo groups (receiving 2 g/day of ginger powder or corn starch as two 1 g tablets) for 12 weeks. Body mass index (BMI) and body composition were assessed every 4 weeks, and serum levels of leptin, adiponectin, resistin, insulin and glucose were determined before and after intervention. The homeostasis model assessment of insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI) were also calculated.

RESULTS

Ginger consumption significantly decreased BMI, serum insulin and HOMA-IR index, along with increasing QUICKIs as compared to the placebo. Moreover, significant reductions in serum leptin, resistin and glucose were observed in both groups, especially in ginger group with nonsignificant differences between groups. The body composition and serum levels of adiponectin were not significantly changed in study groups.

CONCLUSION

In conclusion, our findings demonstrate a minor beneficial effect of 2 g ginger powder supplementation for 12 weeks on weight loss and some metabolic features of obesity. However, given the lack of data in this area, ongoing clinical trials are needed to further explore ginger's effectiveness.

Integrating TRPV1 Receptor Function with Capsaicin Psychophysics

Capsaicin is a naturally occurring vanilloid that causes a hot, pungent sensation in the human oral cavity. This trigeminal stimulus activates TRPV1 receptors and stimulates an influx of cations into sensory cells. TRPV1 receptors function as homotetramers that also respond to heat, proinflammatory substances, lipoxygenase products, resiniferatoxin, endocannabinoids, protons, and peptide toxins. Kinase-mediated phosphorylation of TRPV1 leads to increased sensitivity to both chemical and thermal stimuli. In contrast, desensitization occurs via a calcium-dependent mechanism that results in receptor dephosphorylation. Human psychophysical studies have shown that capsaicin is detected at nanomole amounts and causes desensitization in the oral cavity. Psychophysical studies further indicate that desensitization can be temporarily reversed in the oral cavity if stimulation with capsaicin is resumed at short interstimulus intervals. Pretreatment of lingual epithelium with capsaicin modulates the perception of several primary taste qualities. Also, sweet taste stimuli may decrease the intensity of capsaicin perception in the oral cavity. In addition, capsaicin perception and hedonic responses may be modified by diet. Psychophysical studies with capsaicin are consistent with recent findings that have identified TRPV1 channel modulation by phosphorylation and interactions with membrane inositol phospholipids. Future studies will further clarify the importance of capsaicin and its receptor in human health and nutrition.

The pungent substances piperine, capsaicin, 6-gingerol and polygodial inhibit the human two-pore domain potassium channels TASK-1, TASK-3 and TRESK

For a long time, the focus of trigeminal chemoperception has rested almost exclusively on TRP channels. However, two-pore domain (K_2P) potassium channels have recently been identified as targets for substances associated with typical trigeminal sensations, such as numbing and tingling. In addition, they have been shown to be modulated by several TRP agonists. We investigated whether the pungent substances piperine, capsaicin, 6-gingerol and polygodial have an effect on human K_2P channels. For this purpose, we evaluated the effects of these pungent substances on both wild-type and mutant K_2P channels by means of two-electrode voltage-clamp experiments using Xenopus laevis oocytes. All four pungent substances were found to inhibit the basal activity of TASK-1 (K_2P 3.1), TASK-3 (K_2P 9.1), and TRESK (K_2P 18.1) channels. This inhibitory effect was dose-dependent and, with the exception of polygodial on TASK-1, fully reversible. However, only piperine exhibited an IC₅₀ similar to its reported EC₅₀ on TRP channels. Finally, we observed for TASK-3 that mutating H98 to E markedly decreased the inhibition induced by piperine, capsaicin, and 6-gingerol, but not by polygodial. Our data contribute to the relatively sparse knowledge concerning the pharmacology of K_2P channels and also raise the question of whether K_2P channels could be involved in the pungency perception of piperine.

Functionally important amino acid residues in the transient receptor potential vanilloid 1 (TRPV1) ion channel--an overview of the current mutational data

This review aims to create an overview of the currently available results of site-directed mutagenesis studies on transient receptor potential vanilloid type 1 (TRPV1) receptor. Systematization of the vast number of data on the functionally important amino acid mutations of TRPV1 may provide a clearer picture of this field, and may promote a better understanding of the relationship between the structure and function of TRPV1. The review summarizes information on 112 unique mutated sites along the TRPV1, exchanged to multiple different residues in many cases. These mutations influence the effect or binding of different agonists, antagonists, and channel blockers, alter the responsiveness to heat, acid, and voltage dependence, affect the channel pore characteristics, and influence the regulation of the receptor function by phosphorylation, glycosylation, calmodulin, PIP2, ATP, and lipid binding. The main goal of this paper is to publish the above mentioned data in a form that facilitates in silico molecular modelling of the receptor by promoting easier establishment of boundary conditions. The better understanding of the structure-function relationship of TRPV1 may promote discovery of new, promising, more effective and safe drugs for treatment of neurogenic inflammation and pain-related diseases and may offer new opportunities for therapeutic interventions.

Tibetan herbal formula Padma Digestin modulates gastrointestinal motility in vitro

AIM: To examine the effects of Padma Digestin on the smooth muscle motility of different gastrointestinal segments in vitro.

METHODS: The effects of the ethanolic extract of Padma Digestin (at 8.16 mg/mL or 81.6 mg/mL) on the contractility and susceptibility to acetylcholine (ACh) of muscle strips from the cardia, antrum, pylorus, duodenum, jejunum, ileum and colon of male Wistar rats were analyzed.

RESULTS: Compared with the control treatment, the Padma Digestin extract had a procontractile effect on the antral smooth muscle strips. Padma Digestin decreased ACh sensitivity in cardia muscle strips and increased it in those from the antrum and pylorus. In the intestinal segments, spontaneous contractility was inhibited in both the duodenal and jejunal strips, whereas reactivity to ACh was inhibited in the jejunal strips only. In the colonic samples, Padma Digestin inhibited spontaneous and ACh-stimulated contractility at a low dose but seems to have increasing effects at a high dose.

CONCLUSION: Padma Digestin extract has region-specific effects on the contractility and excitability of gastrointestinal smooth muscle. Our results support the traditional use of Padma Digestin for maldigestion and functional gastrointestinal disorders.

Cellular mechanism underlying formaldehyde-stimulated Cl- secretion in rat airway epithelium

BACKGROUND

Recent studies suggest that formaldehyde (FA) could be synthesized endogeneously and transient receptor potential (TRP) channel might be the sensor of FA. However, the physiological significance is still unclear.

METHODOLOGY/PRINCIPAL FINDINGS

The present study investigated the FA induced epithelial Cl(-) secretion by activation of TRPV-1 channel located in the nerve ending fiber. Exogenously applied FA induced an increase of I(SC) in intact rat trachea tissue but not in the primary cultured epithelial cells. Western blot and immunofluorescence analysis identified TRPV-1 expression in rat tracheal nerve ending. Capsazepine (CAZ), a TRPV-1 specific antagonist significantly blocked the I(SC) induced by FA. The TRPV-1 agonist capsaicin (Cap) induced an increase of I(SC), which was similar to the I(SC) induced by FA. L-703606, an NK-1 specific inhibitor and propranolol, an adrenalin β receptor inhibitor significantly abolished the I(SC) induced by FA or Cap. In the ion substitute analysis, FA could not induce I(SC) in the absence of extracelluar Cl(-). The I(SC) induced by FA could be blocked by the non-specific Cl(-) channel inhibitor DPC and the CFTR specific inhibitor CFTR(i-172), but not by the Ca(2+)-activated Cl(-) channel inhibitor DIDS. Furthermore, both forskolin, an agonist of adenylate cyclase (AC) and MDL-12330A, an antagonist of AC could block FA-induced I(SC).

CONCLUSION

Our results suggest that FA-induced epithelial I(SC) response is mediated by nerve, involving the activation of TRPV-1 and release of adrenalin as well as substance P.

Ginger consumption enhances the thermic effect of food and promotes feelings of satiety without affecting metabolic and hormonal parameters in overweight men: a pilot study

Evidence suggests that ginger consumption has anti-inflammatory, anti-hypertensive, glucose-sensitizing, and stimulatory effects on the gastrointestinal tract. This study assessed the effects of a hot ginger beverage on energy expenditure, feelings of appetite and satiety and metabolic risk factors in overweight men. Ten men, age 39.1±3.3 y and body mass index (BMI) 27.2±0.3 kg/m(2), participated in this randomized crossover study. Resting state energy expenditure was measured using indirect calorimetry and for 6h after consumption of a breakfast meal with or without 2 g ginger powder dissolved in a hot water beverage. Subjective feelings of satiety were assessed hourly using visual analog scales (VAS) and blood samples were taken fasted and for 3 h after breakfast consumption. There was no significant effect of ginger on total resting energy expenditure (P=.43) or respiratory quotient (P=.41). There was a significant effect of ginger on thermic effect of food (ginger vs control=42.7±21.4 kcal/d, P=.049) but the area under the curve was not different (P=.43). VAS ratings showed lower hunger (P=.002), lower prospective food intake (P=.004) and greater fullness (P=.064) with ginger consumption versus control. There were no effects of ginger on glucose, insulin, lipids, or inflammatory markers. The results, showing enhanced thermogenesis and reduced feelings of hunger with ginger consumption, suggest a potential role of ginger in weight management. Additional studies are necessary to confirm these findings.

10-Shogaol, an antioxidant from Zingiber officinale for skin cell proliferation and migration enhancer

In this work, one of Zingiber officinale components, 10-shogaol, was tested with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, metal chelating ability, and reducing power to show antioxidant activity. 10-Shogaol promoted human normal epidermal keratinocytes and dermal fibroblasts cell growths. 10-Shogaol enhanced growth factor production in transforming growth factor-β (TGF-β), platelet derived growth factor-αβ (PDGF-αβ) and vascular endothelial growth factors (VEGF) of both cells. In the in vitro wound healing assay for 12 or 24 h, with 10-shogaol, the fibroblasts and keratinocytes migrated more rapidly than the vehicle control group. Thus, this study substantiates the target compound, 10-shogaol, as an antioxidant for human skin cell growth and a migration enhancer with potential to be a novel wound repair agent.

Functional foods with digestion-enhancing properties

On analyzing the traditional societies' plant lore by treatment and plant categories, one cannot but notice the greater weight given to treatment of digestive disturbances and ailments compared to modern Western pharmacopoeias, and the blurred boundaries between medicines and foods, in contrast to the clear-cut distinction made in contemporary industrialized societies. Hence, there is an interest in exploring the issue of multifunctional food and traditional ingredients with digestive properties. In this paper, I examine the coevolutionary foundations for digestive activities, the problems and ambiguities that emerge in the analysis of traditional data, and the possible biological mechanisms underlying the actions of bitter, aromatic and pungent compounds. After these premises, this paper presents a short review of those plants with a significant body of research supporting the claims that they have a digestive action, with particular emphasis on clinical data. The plants that have a substantial body of data in support of their digestion-enhancing activities mainly belong to one of three groups: bitter, aromatic and pungent plants. Amongst the most important we can find ginger, peppermint, aniseed and fennel, citrus fruits, dandelion and artichoke, melissa and chamomile, but many more have a significant body of experimental data available.

Moving towards supraspinal TRPV1 receptors for chronic pain relief

Transient receptor potential vanilloid type 1 (TRPV1) receptor is a non selective ligand-gated cation channel activated by capsaicin, heat, protons and endogenous lipids termed endovanilloids. As well as peripheral primary afferent neurons and dorsal root ganglia, TRPV1 receptor is also expressed in spinal and supraspinal structures such as those belonging to the endogenous antinociceptive descending pathway which is a circuitry of the supraspinal central nervous system whose task is to counteract pain. It includes periaqueductal grey (PAG) and rostral ventromedial medulla (RVM) whose activation leads to analgesia. Such an effect is associated with a glutamate increase and the activation of OFF and inhibition of ON cell population in the rostral ventromedial medulla (RVM). Activation of the antinociceptive descending pathway via TPRV1 receptor stimulation in the PAG may be a novel strategy for producing analgesia in chronic pain. This review will summarize the more recent insights into the role of TRPV1 receptor within the antinociceptive descending pathway and its possible exploitation as a target for new pain-killer agents in chronic pain conditions, with particular emphasis on the most untreatable pain state: neuropathic pain.

Herbal compounds and toxins modulating TRP channels

Although the benefits are sometimes obvious, traditional or herbal medicine is regarded with skepticism, because the mechanism through which plant compounds exert their powers are largely elusive. Recent studies have shown however that many of these plant compounds interact with specific ion channels and thereby modulate the sensing mechanism of the human body. Especially members of the Transient Receptor Potential (TRP) channels have drawn large attention lately as the receptors for plant-derived compounds such as capsaicin and menthol. TRP channels constitute a large and diverse family of channel proteins that can serve as versatile sensors that allow individual cells and entire organisms to detect changes in their environment. For this family, a striking number of empirical views have turned into mechanism-based actions of natural compounds. In this review we will give an overview of herbal compounds and toxins, which modulate TRP channels.

TRPV1: on the road to pain relief

Historically, drug research targeted to pain treatment has focused on trying to prevent the propagation of action potentials in the periphery from reaching the brain rather than pinpointing the molecular basis underlying the initial detection of the nociceptive stimulus: the receptor itself. This has now changed, given that many receptors of nociceptive stimuli have been identified and/or cloned. Transient Receptor Potential (TRP) channels have been implicated in several physiological processes such as mechanical, chemical and thermal stimuli detection. Ten years after the cloning of TRPV1, compelling data has been gathered on the role of this channel in inflammatory and neuropathic states. TRPV1 activation in nociceptive neurons, where it is normally expressed, triggers the release of neuropeptides and transmitters resulting in the generation of action potentials that will be sent to higher CNS areas where they will often be perceived as pain. Its activation also will evoke the peripheral release of pro-inflammatory compounds that may sensitize other neurons to physical, thermal or chemical stimuli. For these reasons as well as because its continuous activation causes analgesia, TRPV1 has become a viable drug target for clinical use in the management of pain. This review will provide a general picture of the physiological and pathophysiological roles of the TRPV1 channel and of its structural, pharmacological and biophysical properties. Finally, it will provide the reader with an overall view of the status of the discovery of potential therapeutic agents for the management of chronic and neuropathic pain.

Compounds from Sichuan and Melegueta peppers activate, covalently and non-covalently, TRPA1 and TRPV1 channels

BACKGROUND AND PURPOSE

Oily extracts of Sichuan and Melegueta peppers evoke pungent sensations mediated by different alkylamides [mainly hydroxy-alpha-sanshool (alpha-SOH)] and hydroxyarylalkanones (6-shogaol and 6-paradol). We assessed how transient receptor potential ankyrin 1 (TRPA1) and TRP vanilloid 1 (TRPV1), two chemosensory ion channels, participate in these pungent sensations.

EXPERIMENTAL APPROACH

The structure-activity relationships of these molecules on TRPA1 and TRPV1 was measured by testing natural and synthetic analogues using calcium and voltage imaging on dissociated dorsal root ganglia neurons and human embryonic kidney 293 cells expressing the wild-type channels or specific cysteine mutants using glutathione trapping as a model to probe TRPA1 activation. In addition, using Trpv1 knockout mice, the compounds' aversive responses were measured in a taste brief-access test.

KEY RESULTS

For TRPA1 activation, the cis C6 double bond in the polyenic chain of alpha-SOH was critical, whereas no structural specificity was required for activation of TRPV1. Both 6-shogaol and 6-paradol were found to activate TRPV1 and TRPA1 channels, whereas linalool, an abundant terpene in Sichuan pepper, activated TRPA1 but not TRPV1 channels. Alkylamides and 6-shogaol act on TRPA1 by covalent bonding whereas none of these compounds activated TRPV1 through such interactions. Finally, TRPV1 mutant mice retained sensitivity to 6-shogaol but were not responsive to alpha-SOH.

CONCLUSIONS AND IMPLICATIONS

The pungent nature of components of Sichuan and Melegueta peppers was mediated via interactions with TRPA1 and TRPV1 channels and may explain the aversive properties of these compounds.