Modifications of capsaicin-sensitive neurons in isolated guinea pig ileum by [6]-gingerol and lafutidine

Regional characterisation of TRPV1 and TRPA1 signalling in the mouse colon mucosa

Capsaicin and allyl isothiocyanate (AITC) activate transient receptor potential (TRP) vanilloid-1 (TRPV1) and TRP ankyrin-1 (TRPA1), respectively. TRPV1 and TRPA1 expression have been identified in the gastrointestinal (GI) tract. GI mucosal functions remain largely undefined for TRPV1 and TRPA1 with side-dependence and regional differences in signalling unclear. Here we investigated TRPV1- and TRPA1-induced vectorial ion transport as changes in short-circuit current (ΔIsc), in defined segments of mouse colon mucosa (ascending, transverse and descending) under voltage-clamp conditions in Ussing chambers. Drugs were applied basolaterally (bl) or apically (ap). Capsaicin responses were biphasic, with primary secretory and secondary anti-secretory phases, observed with bl application only, which predominated in descending colon. AITC responses were monophasic and secretory, with ΔIsc dependent on colonic region (ascending vs. descending) and sidedness (bl vs. ap). Aprepitant (neurokinin-1 (NK1) antagonist, bl) and tetrodotoxin (Na+ channel blocker, bl) significantly inhibited capsaicin primary responses in descending colon, while GW627368 (EP4 receptor antagonist, bl) and piroxicam (cyclooxygenase inhibitor, bl) inhibited AITC responses in ascending and descending colonic mucosae. Antagonism of the calcitonin gene-related peptide (CGRP) receptor had no effect on mucosal TRPV1 signalling, while tetrodotoxin and antagonists of the 5-hydroxytryptamine-3 and 4 receptors, CGRP receptor, and EP1/2/3 receptors had no effect on mucosal TRPA1 signalling. Our data demonstrates the regional-specificity and side-dependence of colonic TRPV1 and TRPA1 signalling, with involvement of submucosal neurons and mediation by epithelial NK1 receptor activation for TRPV1, and endogenous prostaglandins and EP4 receptor activation for TRPA1 mucosal responses.

The Effect of Dried Ginger (Gan Jiang) on Stomach Energy Metabolism and the Related Mechanism in Rats Based on Metabonomics

Dried ginger is a commonly used stomachic. Dried ginger is often used as a gastric protector to treat stomach-related diseases. However, the effect of dried ginger on energy metabolism in stomach tissue of rats under physiological condition has not been studied. In this study, different doses of water extract of dried ginger were given to rats for 4 weeks. The activity of Na+ -K+ -ATPase, Ca2+ -Mg2+ -ATPase, SDH (succinate dehydrogenase) enzyme, ATP content, mitochondrial metabolic rate and mitochondrial number in stomach tissue of rats were measured. Analysis of potential biomarkers related to the effect of dried ginger on energy metabolism in stomach tissue of rats by metabonomics, and their metabolic pathways were also analyzed. The results revealed that there was no significant difference in Na+ -K+ -ATPase in high-dose group (GJH), medium-dose group (GJM) and low-dose group (GJL) compared to the Control group. The Ca2+ -Mg2+ -ATPase activity was significantly increased in stomach tissue of GJH group and GJM group, but there were no significant changes in stomach tissue of GJL group. The SDH activity and the ATP levels were significantly increased in stomach tissue of GJH group, GJM group and GJL group. The mitochondrial metabolic rate was significantly increased in GJL group, but there was no significant change in GJM group and was inhibited in GJH group. These effects might be mediated by arginine biosynthesis, glutathione metabolism, arachidonic acid metabolism, glycerophospholipid metabolism, arginine and proline metabolism, purine metabolism pathway.

[6]-Gingerol Induces Amiloride-Sensitive Sodium Absorption in the Rat Colon via the Capsaicin Receptor TRPV1 in Colonic Mucosa

[6]-Gingerol possesses various beneficial pharmacological and therapeutic properties, including anti-carcinogenic and anti-inflammatory properties and the ability to regulate intestinal contraction. Recently, our group observed that the serosal administration of [6]-gingerol stimulated electrogenic sodium absorption in the rat colon via the capsaicin receptor, TRPV1. TRPV1 is known to be expressed in both the mucosal epithelium and the muscle layers in the colon. In the present study, we assessed whether [6]-gingerol stimulated sodium absorption via TRPV1 in the colonic mucosal epithelium. We compared the effect of [6]-gingerol on TRPV1-dependent colonic sodium absorption in the colon preparation with or without muscle layer. All experiments were performed by measuring the transmural potential difference (ΔPD) in an Ussing chamber system. [6]-Gingerol induced positive ΔPD when administered to the serosal side of the colon, and this effect was significantly larger in the colon preparation without muscle layer than in that with the muscle layer. In the colon preparation without muscle layer, the [6]-gingerol-dependent induction of ΔPD was markedly suppressed by mucosal addition of amiloride, a selective inhibitor of epithelial sodium channel. ΔPD induction by [6]-gingerol was considerably diminished by capsazepine, an inhibitor of the capsaicin receptor TRPV1, but not by AP-18, an inhibitor of TRPA1. These results suggest that [6]-gingerol induces amiloride-sensitive electrogenic sodium absorption in the rat colon via TRPV1 expressed in the colonic mucosal epithelium, and that this effect is independent of TRPV1 in the colonic muscle layer.

Extraoral Taste Receptor Discovery: New Light on Ayurvedic Pharmacology

More and more research studies are revealing unexpectedly important roles of taste for health and pathogenesis of various diseases. Only recently it has been shown that taste receptors have many extraoral locations (e.g., stomach, intestines, liver, pancreas, respiratory system, heart, brain, kidney, urinary bladder, pancreas, adipose tissue, testis, and ovary), being part of a large diffuse chemosensory system. The functional implications of these taste receptors widely dispersed in various organs or tissues shed a new light on several concepts used in ayurvedic pharmacology (dravyaguna vijnana), such as taste (rasa), postdigestive effect (vipaka), qualities (guna), and energetic nature (virya). This review summarizes the significance of extraoral taste receptors and transient receptor potential (TRP) channels for ayurvedic pharmacology, as well as the biological activities of various types of phytochemical tastants from an ayurvedic perspective. The relative importance of taste (rasa), postdigestive effect (vipaka), and energetic nature (virya) as ethnopharmacological descriptors within Ayurveda boundaries will also be discussed.

Prevention of allergic rhinitis by ginger and the molecular basis of immunosuppression by 6-gingerol through T cell inactivation

The incidence of allergies has recently been increasing worldwide. Immunoglobulin E (IgE)-mediated hypersensitivity is central to the pathogenesis of asthma, hay fever and other allergic diseases. Ginger (Zingiber officinale Roscoe) and its extracts have been valued for their medical properties including antinausea, antiinflammation, antipyresis and analgesia properties. In this study, we investigated the antiallergic effects of ginger and 6-gingerol, a major compound of ginger, using a mouse allergy model and primary/cell line culture system. In mice with ovalbumin (OVA)-induced allergic rhinitis, oral administration of 2% ginger diet reduced the severity of sneezing and nasal rubbing by nasal sensitization of OVA and suppressed infiltration of mast cells in nasal mucosa and secretion of OVA-specific IgE in serum. 6-Gingerol inhibited the expression of not only Th2 cytokines but also Th1 cytokines in OVA-sensitized spleen cells. Accordingly, 6-gingerol suppressed in vitro differentiation of both Th1 cells and Th2 cells from naïve T cells. In addition, 6-gingerol suppressed both superantigen staphylococcal enterotoxin B (SEB)- and anti-CD3-induced T cell proliferation. 6-Gingerol also abrogated PMA plus ionomycin- and SEB-induced IL-2 production in T cells, suggesting that 6-gingerol affected T cell receptor-mediated signal transduction rather than the antigen-presentation process. Indeed, 6-gingerol inhibited the phosphorylation of MAP kinases, calcium release and nuclear localization of c-fos and NF-κB by PMA and ionomycin stimulation. Thus, our results demonstrate that 6-gingerol suppresses cytokine production for T cell activation and proliferation, thereby not causing B cell and mast cell activation and resulting in prevention or alleviation of allergic rhinitis symptoms.

Oral intake of encapsulated dried ginger root powder hardly affects human thermoregulatory function, but appears to facilitate fat utilization

The present study investigated the impact of a single oral ingestion of ginger on thermoregulatory function and fat oxidation in humans. Morning and afternoon oral intake of 1.0 g dried ginger root powder did not alter rectal temperature, skin blood flow, O2 consumption, CO2 production, and thermal sensation and comfort, or induce sweating at an ambient temperature of 28 °C. Ginger ingestion had no effect on threshold temperatures for skin blood flow or thermal sweating. Serum levels of free fatty acids were significantly elevated at 120 min after ginger ingestion in both the morning and afternoon. Morning ginger intake significantly reduced respiratory exchange ratios and elevated fat oxidation by 13.5 % at 120 min after ingestion. This was not the case in the afternoon. These results suggest that the effect of a single oral ginger administration on the peripheral and central thermoregulatory function is miniscule, but does facilitate fat utilization although the timing of the administration may be relevant.

Gingerols and shogaols: Important nutraceutical principles from ginger

Gingerols are the major pungent compounds present in the rhizomes of ginger (Zingiber officinale Roscoe) and are renowned for their contribution to human health and nutrition. Medicinal properties of ginger, including the alleviation of nausea, arthritis and pain, have been associated with the gingerols. Gingerol analogues are thermally labile and easily undergo dehydration reactions to form the corresponding shogaols, which impart the characteristic pungent taste to dried ginger. Both gingerols and shogaols exhibit a host of biological activities, ranging from anticancer, anti-oxidant, antimicrobial, anti-inflammatory and anti-allergic to various central nervous system activities. Shogaols are important biomarkers used for the quality control of many ginger-containing products, due to their diverse biological activities. In this review, a large body of available knowledge on the biosynthesis, chemical synthesis and pharmacological activities, as well as on the structure-activity relationships of various gingerols and shogaols, have been collated, coherently summarised and discussed. The manuscript highlights convincing evidence indicating that these phenolic compounds could serve as important lead molecules for the development of therapeutic agents to treat various life-threatening human diseases, particularly cancer. Inclusion of ginger or ginger extracts in nutraceutical formulations could provide valuable protection against diabetes, cardiac and hepatic disorders.

Control of biogenic amines in food--existing and emerging approaches

Biogenic amines have been reported in a variety of foods, such as fish, meat, cheese, vegetables, and wines. They are described as low molecular weight organic bases with aliphatic, aromatic, and heterocyclic structures. The most common biogenic amines found in foods are histamine, tyramine, cadaverine, 2-phenylethylamine, spermine, spermidine, putrescine, tryptamine, and agmatine. In addition octopamine and dopamine have been found in meat and meat products and fish. The formation of biogenic amines in food by the microbial decarboxylation of amino acids can result in consumers suffering allergic reactions, characterized by difficulty in breathing, itching, rash, vomiting, fever, and hypertension. Traditionally, biogenic amine formation in food has been prevented, primarily by limiting microbial growth through chilling and freezing. However, for many fishing based subsistence populations, such measures are not practical. Therefore, secondary control measures to prevent biogenic amine formation in foods or to reduce their levels once formed need to be considered as alternatives. Such approaches to limit microbial growth may include hydrostatic pressures, irradiation, controlled atmosphere packaging, or the use of food additives. Histamine may potentially be degraded by the use of bacterial amine oxidase or amine-negative bacteria. Only some will be cost-effective and practical for use in subsistence populations.

Localization of TRPV1 and contractile effect of capsaicin in mouse large intestine: high abundance and sensitivity in rectum and distal colon

We investigated immunohistochemical differences in the distribution of TRPV1 channels and the contractile effects of capsaicin on smooth muscle in the mouse rectum and distal, transverse, and proximal colon. In the immunohistochemical study, TRPV1 immunoreactivity was found in the mucosa, submucosal, and muscle layers and myenteric plexus. Large numbers of TRPV1-immunoreactive axons were observed in the rectum and distal colon. In contrast, TRPV1-positive axons were sparsely distributed in the transverse and proximal colon. The density of TRPV1-immunoreactive axons in the rectum and distal colon was much higher than those in the transverse and proximal colon. Axons double labeled with TRPV1 and protein gene product (PGP) 9.5 were detected in the myenteric plexus, but PGP 9.5-immunoreactive cell bodies did not colocalize with TRPV1. In motor function studies, capsaicin induced a fast transient contraction, followed by a large long-lasting contraction in the rectum and distal colon, whereas in the transverse and proximal colon only the transient contraction was observed. The capsaicin-induced transient contraction from the proximal colon to the rectum was moderately inhibited by an NK1 or NK2 receptor antagonist. The capsaicin-induced long-lasting contraction in the rectum and distal colon was markedly inhibited by an NK2 antagonist, but not by an NK1 antagonist. The present results suggest that TRPV1 channels located on the rectum and distal colon play a major role in the motor function in the large intestine.

Nicotine-induced neurogenic relaxation in the mouse colon: changes with dextran sodium sulfate-induced colitis

Nicotine has been shown to reduce both tone and muscular activity in the human colon by releasing nitric oxide (NO) from nerves. To our knowledge, however, the effect of nicotine on mouse colon has not been elucidated, and the response in tissue from ulcerative colitis (UC) has not been investigated. We examined nicotine-induced responses in colon from control mice and mice with dextran sodium sulfate (DSS)-induced UC. In controls, bath application of nicotine caused a transient relaxation in longitudinal preparations from the transverse and distal colons but not from the rectum. The response was observed in the presence of bethanechol, abolished by treatment with tetrodotoxin and hexamethonium, and mediated partially (>50%) by the NO pathway. In longitudinal preparations of the distal colon from DSS-treated mice, spontaneous contractions decreased markedly, and nicotine caused contraction without relaxation in half of the preparations tested. Nicotine-induced relaxation in the presence of bethanechol was significantly decreased in the DSS-treated distal colon without changing bethanechol-induced contractions. These data suggest that 1) responses to nicotine differ dependent on colon regions, 2) DSS treatment predominantly caused nicotine-sensitive neurogenic changes in distal colon, and 3) DSS treatment may reverse the direction of nicotine-evoked responses in the colon, in mice.

Mucosal acid causes gastric mucosal microcirculatory disturbance in nonsteroidal anti-inflammatory drug-treated rats

The mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) suppress gastric mucosal blood flow is not fully understood, although the depletion of mucosal prostaglandin E2 has been proposed as one possible explanation. We investigated the role of gastric acid on gastric mucosal blood flow in NSAID-treated rats. A rat stomach was mounted in an ex vivo chamber, and gastric mucosal blood flow was measured sequentially in a 5-mm2 area of the gastric corpus using a scanning laser Doppler perfusion image system. Results showed that diclofenac (5 mg/kg s.c.) and indomethacin (10 mg/kg s.c.) did not affect gastric mucosal blood flow, although both strongly decreased mucosal prostaglandin E2 when saline was instilled into the gastric chamber. On replacement of the saline in the chamber with 100 mM hydrochloric acid, these drugs caused a decrease in gastric mucosal blood flow levels within 30 min. The specific cyclooxygenase (COX)-2 inhibitors celecoxib (50 mg/kg s.c.) and rofecoxib (25 mg/kg s.c.) did not affect mucosal prostaglandin E2 level, nor did they decrease gastric mucosal blood flow, even when hydrochloric acid was added to the chamber. Furthermore, measurement of vasoconstrictive factors present in the mucosa showed that endothelin-1 levels increased after administration of diclofenac s.c. in the presence of intragastric hydrochloric acid. This indicates that the presence of mucosal hydrochloric acid plays an important role in the NSAID-induced decrease in gastric mucosal blood flow, while the COX-1-derived basal prostaglandin E2, which is unlikely to control gastric mucosal blood flow itself, protects microcirculatory systems from mucosal hydrochloric acid.

Zingiberis rhizoma: a comprehensive review on the ginger effect and efficacy profiles

Zingiberis rhizoma is used as a broadspectrum antiemetic. We, therefore, conducted a comprehensive review of the literature to summarize the pharmacological and clinical effects of this popular plant material. Although clinical and experimental studies suggest that ginger has some antiemetic properties, clinical evidence beyond doubt is only available for pregnancy-related nausea and vomiting. Meta-analyses could not demonstrate the postoperative antiemetic effectiveness, and effect in motion sickness or nausea/vomiting of other ethiology. It also remains to be confirmed that proprietary ginger preparations are clinically useful to alleviate osteoarthritic or other pain, although there is no doubt that ginger constituents interfere with the inflammatory cascade and the vanilloid nociceptor. Ginger exerts in vitro antioxidative, antitumorigenic and immunomodulatory effects and is an effective antimicrobial and antiviral agent. Animal studies demonstrate effects on the gastrointestinal tract, the cardiovascular system, on experimental pain and fever, antioxidative, antilipidemic and antitumor effects, as well as central and other effects. The most relevant human pharmacological studies require a confirmatory study to exclude interaction of ginger preparations with platelet aggregation. Pharmacokinetic data are only available for [6]-gingerol and zingiberene. Preclinical safety data do not rule out potential toxicity, which should be monitored especially following ginger consumption over longer periods.

Lafutidine-induced increase in intracellular ca(2+) concentrations in PC12 and endothelial cells

Lafutidine, a histamine H(2) receptor antagonist, exerts gastroprotective effects in addition to gastric antisecretory activity. The gastrointestinal protective effects of lafutidine are mediated by capsaicin-sensitive neurons, where capsaicin excites neurons by opening a member of the transient receptor potential channel family (TRPV1). Since the effect of lafutidine on the intracellular Ca(2+) concentration ([Ca(2+)](i)) in cells has not been elucidated, we investigated the lafutidine response to [Ca(2+)](i) in rat pheochromocytoma PC12 and human endothelial cells. Lafutidine at pharmacological concentrations greater than 1 mM induced a sustained increase in [Ca(2+)](i) in the presence of extracellular CaCl(2) in PC12 cells, while capsaicin showed dual effects on [Ca(2+)](i) in PC12 cells, where it activated TRPV1 and inhibited store-operated Ca(2+) entry. The thapsigargin (an activator of store-operated Ca(2+) entry)-induced increase in [Ca(2+)](i) in PC12 cells was inhibited by capsaicin and SKF96365, an inhibitor of store-operated Ca(2+) entry, and the lafutidine response was inhibited by capsaicin but not by SKF96365. In endothelial cells, lafutidine induced an increase in [Ca(2+)](i) in a SKF96365-insensitive manner. These results suggest that lafutidine stimulates Ca(2+) entry via the capsaicin-sensitive pathway but not the SKF96365-sensitive pathway. The possible role of store-operated Ca(2+) entry induced by lafutidine on gastrointestinal function is also discussed.

Protective role of vanilloid receptor type 1 in HCl-induced gastric mucosal lesions in rats

BACKGROUND

Effects of vanilloid-receptor agonists and antagonists on HCl-induced gastric lesions in rats were investigated to elucidate the role of vanilloid receptor type 1 (VR1) in gastric mucosal defense mechanisms.

METHODS

Gastric lesions in rats were evaluated after intragastric administration of 0.6 N HCl. The localization of VR1 in the stomach was investigated immunohistochemically.

RESULTS

Intragastric administration of capsaicin inhibited the formation of gastric lesions in a dose-dependent manner (0.1-2.5 mg/kg). The functional VR1 antagonists ruthenium red and capsazepine markedly aggravated HCl-induced gastric lesions in rats. The gastroprotective effect of capsaicin was attenuated by ruthenium red or capsazepine. It is reported that resiniferatoxin, [6]-gingerol and lafutidine are compounds that activate VR1 and/or capsaicin-sensitive afferent neurons. These compounds significantly inhibited the formation of HCl-induced gastric lesions, and their gastroprotective effects were inhibited by treatment with ruthenium red. The immunohistochemical studies revealed that nerve fibers expressing VR1 exist along gastric glands in the mucosa, around blood vessels in the submucosa, in the myenteric plexus, and in the smooth muscle layers, especially the circular muscle layer.

CONCLUSION

The results of this study suggest that VR1 plays a protective role in the gastric defensive mechanism in rats.