Capsaicin--a literature survey

Beyond Neuronal Heat Sensing: Diversity of TRPV1 Heat-Capsaicin Receptor-Channel Functions

Transient receptor potential vanilloid 1 (TRPV1) is a calcium-permeable ion channel best known for its ability to be gated by the pungent constituent of red chili pepper, capsaicin, and related chemicals from the group of vanilloids as well as by noxious heat. As such, it is mostly expressed in sensory neurons to act as a detector of painful stimuli produced by pungent chemicals and high temperatures. Its activation is also sensitized by the numerous endogenous inflammatory mediators and second messengers, making it an important determinant of nociceptive signaling. Except for such signaling, though, neuronal TRPV1 activation may influence various organ functions by promoting the release of bioactive neuropeptides from sensory fiber innervation organs. However, TRPV1 is also found outside the sensory nervous system in which its activation and function is not that straightforward. Thus, TRPV1 expression is detected in skeletal muscle; in some types of smooth muscle; in epithelial and immune cells; and in adipocytes, where it can be activated by the combination of dietary vanilloids, endovanilloids, and pro-inflammatory factors while the intracellular calcium signaling that this initiates can regulate processes as diverse as muscle constriction, cell differentiation, and carcinogenesis. The purpose of the present review is to provide a clear-cut distinction between neurogenic TRPV1 effects in various tissues consequent to its activation in sensory nerve endings and non-neurogenic TRPV1 effects due to its expression in cell types other than sensory neurons.

Capsaicin enhances erlotinib-induced cytotoxicity via AKT inactivation and excision repair cross-complementary 1 (ERCC1) down-regulation in human lung cancer cells

Capsaicin, a natural active ingredient of green and red peppers, has been demonstrated to exhibit anti-cancer properties in several malignant cell lines. Excision repair cross-complementary 1 (ERCC1) has a leading role in the nucleotide excision repair (NER) process because of its involvement in the excision of DNA adducts. Erlotinib (Tarceva^R) is a selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that has demonstrated clinical activity in non-small cell lung cancer (NSCLC) cells. However, whether capsaicin and erlotinib could induce synergistic cytotoxicity in NSCLC cells through modulating ERCC1 expression is unknown. In this study, capsaicin decreased the ERCC1 expression in an AKT inactivation dependent manner in two human lung adenocarcinoma cells, namely, A549 and H1975. Enhancement of AKT activity by transfection with constitutive active AKT vectors increased the ERCC1 protein level as well as the cell survival by capsaicin. Moreover, capsaicin synergistically enhanced the cytotoxicity and cell growth inhibition of erlotinib in NSCLC cells, which were associated with the down-regulation of ERCC1 expression and inactivation of AKT in A549 and H1975 cells. Together, these results may provide a rationale to combine capsaicin with erlotinib for lung cancer treatment.

Mass Casualty Incident Involving Pepper Spray Exposure: Impact on the Emergency Department and Management of Casualties

Introduction

Exposure to pepper spray in an urban shopping complex resulted in 13 casualties being treated at a tertiary public hospital emergency department (ED). This report describes the ED's organisation in response to the disaster, and clinical management of those affected.

Results

Thirteen casualties – 11 acute, 2 delayed – presented with symptoms ranging from ocular, respiratory and skin irritation to nausea, vomiting and giddiness. The culprit agent was determined basing on the index patient's history and physical findings. All cases were decontaminated at the ED's on-site Hospital Decontamination Station. Nine adults were monitored overnight in the Emergency Observation Ward under the Toxic Inhalation Protocol and discharged well. The index case was treated symptomatically with improvement, but discharged against medical advice three hours later. No ED re-attendances were recorded.

Conclusions

The effects of pepper spray exposure are brief and self-limiting, but ED management can pose challenges in a mass casualty situation.

The impact of capsaicin intake on risk of developing gastric cancers: a meta-analysis

BACKGROUND

Reported associations of capsaicin with gastric cancer development have been conflicting. Here, we examine 10 published articles that explore these associations using 2,452 cases and 3,996 controls.

METHODS

We used multiple search strategies in MEDLINE through PubMed to seek for suitable articles that had case-control design with gastric cancer as outcome.

RESULTS

The outcomes of our study shows protection (odds ratio [OR] 0.55, P = 0.003) and susceptibility (OR 1.94, P = 0.0004), both significant with low and medium-high intake of capsaicin, respectively, although under relatively heterogeneous conditions (P(heterogeneity) = <0.0001). Outlier analysis resulted in loss of overall heterogeneity (P = 0.14) without affecting the pooled ORs. Among the subgroups, low intake elicited protection in both Korean (OR 0.37) and Mexican (OR 0.63) populations while high intake rendered these subgroups susceptible (OR 2.96 and OR 1.57, respectively). These subgroup values were highly significant (P = 0.0001-0.01) obtained in heterogeneous conditions (P(heterogeneity) < 0.0001-0.04). The homogeneous (P(heterogeneity) = 0.27-0.37) H. pylori (OR 0.60 and 1.69) effects were highly significant (P < 0.001) in the low and medium-high intake analyses, respectively. Given outcomes from the tests of interaction, high capsaicin intake is significantly different from the protection that low consumption offers.

CONCLUSIONS

This meta-analysis implies moderation in capsaicin consumption in order to derive its protective benefits.

Inhibitory effects of capsaicin on hepatic stellate cells and liver fibrosis

Hepatic stellate cells (HSCs) play an important role in the process of liver fibrosis. In this study, we investigated the inhibitory effects of capsaicin on HSCs and liver fibrosis. Cultured HSCs were incubated with various concentrations of capsaicin. Cell proliferation was examined using a cell counting kit. Production of hydrogen peroxide was determined using a 2′,7′-dichlorofluorescin diacetate (DCFH-DA) assay. The mRNA and protein expression of target genes was analyzed by reverse transcription PCR and Western blot analysis, respectively. Cell apoptosis was evaluated by annexin V-FITC and propidium iodide (PI) costaining followed by flow cytometric analysis. A CCl4 rat liver fibrosis model was used to assess in vivo effects of capsaicin by histological examination and measurement of liver fibrosis markers, including hydroxyproline content, serum type III collagen, and hyaluronic acid (HA) levels. Our results show that capsaicin dose-dependently inhibited cell proliferation, suppressed cell activation, and decreased hydrogen peroxide production in cultured HSCs. Capsaicin reduced the mRNA levels of tissue inhibitors of metalloproteinase 1 (TIMP-1) and transforming growth factor-β1 (TGF-β1) in HSCs. Moreover, capsaicin-induced cell apoptosis was associated with increased expression of Bax, cytochrome c (cyt c), and caspase-3, but reduced levels of Bcl-2. The animal studies further revealed that capsaicin efficiently reduced the extent of liver fibrosis, inhibited HSC proliferation, and promoted cell apoptosis. Our findings suggest that capsaicin might inhibit fibrogenesis by inhibiting the activities of HSCs.

Restoration of p53/miR-34a regulatory axis decreases survival advantage and ensures Bax-dependent apoptosis of non-small cell lung carcinoma cells

Tumor-suppressive miR-34a, a direct target of p53, has been shown to target several molecules of cell survival pathways. Here, we show that capsaicin-induced oxidative DNA damage culminates in p53 activation to up-regulate expression of miR-34a in non-small cell lung carcinoma (NSCLC) cells. Functional analyses further indicate that restoration of miR-34a inhibits B cell lymphoma-2 (Bcl-2) protein expression to withdraw the survival advantage of these resistant NSCLC cells. In such a proapoptotic cellular milieu, where drug resistance proteins are also down-regulated, p53-transactivated Bcl-2 associated X protein (Bax) induces apoptosis via the mitochondrial death cascade. Our results suggest that p53/miR-34a regulatory axis might be critical in sensitizing drug-resistant NSCLC cells.

Capsaicin induces apoptosis and modulates MAPK signaling in human gastric cancer cells

Capsaicin is known to have tumor suppressive effects. However, the molecular mechanisms and targets of capsaicin involved in exerting anticancer activity are complex and remain to be clarified. The aim of the current study was to investigate the effects of capsaicin on human gastric cancer cells (AGS cells) and demonstrate that capsaicin induced apoptosis in AGS cells. Results of the MTT assay and flow cytometry revealed that capsaicin potentially inhibited the proliferation of AGS cells and induced apoptosis in vitro in a dose-dependent manner. Cleaved caspase-3 was increased and Bcl-2 was reduced by treatment with capsaicin in AGS cells. Capsaicin treatment decreased the expression of phosphorylated ERK 1/2, p38 MAPK or JNK in AGS cells. The results of this study suggest that capsaicin may serve as an anti-tumorigenic agent in human gastric cancer.

Capsaicin pretreatment increased the bioavailability of cyclosporin in rats: involvement of P-glycoprotein and CYP 3A inhibition

Capsaicin (CAP), the main ingredient responsible for the hot pungent taste of chilli peppers. This study investigated the effect of CAP on the pharmacokinetics of Cyclosporin A (CyA) in rats and the mechanism of this food-drug interaction. The results indicated that after 7 days of low or middle dose of CAP (0.3 or 1.0 mg/kg), the blood concentration of CyA was not significantly changed compared with that of vehicle-treated rats, whereas the blood concentration of CyA in high dose group (3.0 mg/kg) was significantly increased. The total clearance (CL/F) of CyA was decreased, and the bioavailability was significantly increased to about 1.44-fold of that in vehicle-treated rats after 7 days of high dose CAP treatment. At this time, the P-gp and CYP3A1/2 in the liver and intestine were decreased at both the mRNA and protein levels. These results demonstrated that chronic ingestion of high doses of CAP will increase the bioavailability of CyA to a significant extent in rats and the food-drug interaction between CAP and CyA appears to be due to modulation of P-gp and CYP3A gene expression by CAP, with differential dose-dependence.

Design and evaluation of flexible membrane vesicles (FMVs) for enhanced topical delivery of capsaicin

Capsaicin, extracted from the fruits of Capsicum, is a powerful local stimulant with strong rubifacient action, devoid of vesication. Topical use of capsaicin is quite common in the treatment of various pain-associated musculo-skeletal disorders, itching and neuropathy. Despite its high pharmacodynamic potential, the patient compliance to the drug is reported to be poor owing to multiple skin problems like irritation, burning sensation, and erythma. The present study targets the encasement of drug in the interiors of flexible membrane vesicles (FMVs), as these are reported to have better penetration in the deeper layers of skin, thus leading to enhanced localization of drug and consequently, decreased skin irritation. Multilamellar drug-loaded FMVs, prepared by thin-film hydration were evaluated for their efficacy in vitro and in vivo. When compared with conventional liposomes, the formulated FMVs showed higher skin retention during ex vivo permeation studies employing LACA mice skin, higher analgesic potential using radiant tail-flick method in mice, and better flexibility in regaining their size. Being less of an irritant, these vesicular carriers were also found to be more comfortable on human skin. Thus, the capsaicin-loaded FMVs offer high potential as topical drug delivery technologies with improved patient acceptance and effectiveness.

Capsaicin causes cell-cycle arrest and apoptosis in ER-positive and -negative breast cancer cells by modulating the EGFR/HER-2 pathway

Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) is an ingredient of chili peppers with inhibitory effects against cancer cells of different origin. We examined the activity of capsaicin on breast cancer cells in vitro and in vivo. The drug potently inhibited growth of ER-positive (MCF-7, T47D, BT-474) and ER-negative (SKBR-3, MDA-MB231) breast cancer cell lines, which was associated with G(0)/G(1) cell-cycle arrest, increased levels of apoptosis and reduced protein expression of human epidermal growth factor receptor (EGFR), HER-2, activated extracellular-regulated kinase (ERK) and cyclin D1. In contrast, cell-cycle regulator p27(KIP1), caspase activity as well as poly-ADP ribose polymerase (PARP) cleavage were increased. Notably, capsaicin blocked breast cancer cell migration in vitro and decreased by 50% the size of MDA-MB231 breast cancer tumors growing orthotopically in immunodeficient mice without noticeable drug side effects. in vivo activation of ERK was clearly decreased, as well as expression of HER-2 and cyclin D1, whereas caspase activity and PARP cleavage products were increased in tumors of drug-treated mice. Besides, capsaicin potently inhibited the development of pre-neoplastic breast lesions by up to 80% without evidence of toxicity. Our data indicate that capsaicin is a novel modulator of the EGFR/HER-2 pathway in both ER-positive and -negative breast cancer cells with a potential role in the treatment and prevention of human breast cancer.

Pepper EST database: comprehensive in silico tool for analyzing the chili pepper (Capsicum annuum) transcriptome

BACKGROUND

There is no dedicated database available for Expressed Sequence Tags (EST) of the chili pepper (Capsicum annuum), although the interest in a chili pepper EST database is increasing internationally due to the nutritional, economic, and pharmaceutical value of the plant. Recent advances in high-throughput sequencing of the ESTs of chili pepper cv. Bukang have produced hundreds of thousands of complementary DNA (cDNA) sequences. Therefore, a chili pepper EST database was designed and constructed to enable comprehensive analysis of chili pepper gene expression in response to biotic and abiotic stresses.

RESULTS

We built the Pepper EST database to mine the complexity of chili pepper ESTs. The database was built on 122,582 sequenced ESTs and 116,412 refined ESTs from 21 pepper EST libraries. The ESTs were clustered and assembled into virtual consensus cDNAs and the cDNAs were assigned to metabolic pathway, Gene Ontology (GO), and MIPS Functional Catalogue (FunCat). The Pepper EST database is designed to provide a workbench for (i) identifying unigenes in pepper plants, (ii) analyzing expression patterns in different developmental tissues and under conditions of stress, and (iii) comparing the ESTs with those of other members of the Solanaceae family. The Pepper EST database is freely available at http://genepool.kribb.re.kr/pepper/.

CONCLUSION

The Pepper EST database is expected to provide a high-quality resource, which will contribute to gaining a systemic understanding of plant diseases and facilitate genetics-based population studies. The database is also expected to contribute to analysis of gene synteny as part of the chili pepper sequencing project by mapping ESTs to the genome.

Effect of HPbetaCD on solubility and transdermal delivery of capsaicin through rat skin

We evaluated the ability of hydroxypropyl-beta-cyclodextrin (HPbetaCD) to influence the percutaneous absorption of capsaicin (CP) through isolated rat skin. Phase solubility analysis and phase distribution studies suggested the potential of HPbetaCD as a solubilizer and permeation enhancer for CP. In vitro permeation studies showed the trend that, the penetration flux (J(s)) of CP increased with the increasing concentration of HPbetaCD from 0 to 2.20% (w/v), and then decreased dramatically when the concentration of HPbetaCD kept on increasing up to 15% (w/v). 2.20% (w/v) of HPbetaCD provided both just adequate solubilization and preferred J(s) for the permeation of CP (0.075%, w/v). Similar change patterns of the permeation parameters were also observed in the hydrogels, but the J(s) of CP was reduced significantly along with the increasing concentration of Carbopol U21. Histological analysis showed an invasive action of HPbetaCD on the stratum corneum (SC) of rat skin, which could only reduce the lag time (T(L)) but could not increase the J(s) of CP. On the other hand, the complexation of HPbetaCD with CP could attenuate this invasive action. It is inferred that excess of HPbetaCD could not only disturb the percutaneous absorption of CP but also disrupt the structure of SC.

Putative cancer chemopreventive agents of dietary origin-how safe are they?

As cancer chemopreventive agents are intended for use by healthy individuals as prophylactics to prevent or retard the development of cancer, they must be amenable to ingestion over prolonged periods without toxicity. Therefore, putative chemopreventive agents need to undergo stringent testing to ensure their safety with regard to chronic exposure in humans. The diet is thought to be a source of chemopreventive agents, and dietary compounds are generally considered to be of low hazard, albeit this notion has not often been put to the test. Here the safety information available for 5 dietary putative chemopreventive compounds, indole-3-carbinol (I3C), curcumin, quercetin, epigallocatechin gallate (EGCG), and capsaicin is reviewed. For these agents, normal dietary intake, doses used in clinical trials, efficacious doses in rodents, and where available, toxic doses are compared. For curcumin, quercetin and capsaicin, toxicological data is only available from studies in rodents. Information on long-term effects in animals beyond 28 or 90 days is lacking for EGCG. Capsaicin and quercetin are suspected carcinogens. I3C and quercetin can modulate the absorption of other drugs given concomitantly. Without further investigation of their toxicology, it is difficult to recommend any of these agents for long-term use in the healthy population.

Capsaicin induced cell cycle arrest and apoptosis in human esophagus epidermoid carcinoma CE 81T/VGH cells through the elevation of intracellular reactive oxygen species and Ca2+ productions and caspase-3 activation

Capsaicin (N-vanillyl-8-methyl-1-nonenamide) is found in pungent fruits, especially in red pepper. Many studies have focused on the anticarcinogenic, antimutagenic or chemopreventive activities of capsaicin. However, the effects of capsaicin on human esophagus epidermoid carcinoma cells have never been investigated. In this study, we investigated the effects of capsaicin on esophagus epidermoid carcinoma cells in vitro and further examined the molecular mechanisms of capsaicin-induced apoptosis in esophagus epidermoid carcinoma cells. Capsaicin decreased the percentage of viable cells of CE 81T/VGH cells, via induction of G0-G1 phase cell cycle arrest and apoptosis. Capsaicin induced G0-G1 phase arrest underwent the promotion of p53 and p21, which is an inhibitor of Cdk2 and cyclin E complex before leading to the inhibitions of both compounds. Capsaicin induced apoptosis in time-dependent manners. Capsaicin-induced apoptosis was in association with the elevation of intracellular reactive oxygen species and Ca2+ productions and BAPTA, an intracellular Ca2+ chelator, which significantly inhibited capsaicin-induced apoptosis. Collectively, these results suggest that the capsaicin-induced apoptosis in the CE 81T/VGH cells may result from the activation of caspase-3 and intracellular Ca2+ release pathway, and it is further suggested that capsaicin has potential as a novel therapeutic agent for the treatment of esophagus epidermoid carcinoma cells.

Effect of different Thai traditional processing of various hot chili peppers on urethane-induced somatic mutation and recombination in Drosophila melanogaster: Assessment of the role of glutathione transferase activity

Four different Thai traditional chili peppers, namely bird pepper (Capsicum frutescens), red chili spur peppers (Capsicum annuum), green bell peppers and sweet pepper (C. annuum) were investigated for their antimutagenic properties. Each chili was prepared in three formulations commonly used for chili food processing; raw paste (chili ground in water), pickled in vinegar or stir-fried in palm oil. Each sample was tested for its antimutagenic effect against urethane by using the somatic mutation and recombination of wing hair of Drosophila melanogaster as an indicator. Three-day-old larvae, trans-heterozygous for two genetic markers, multiple wing hairs mwh and orrigon (ORR;flr3), were exposed to urethane alone or in combination with each chili formulation. The various processing methods for chilies differentially extracted the antimutagenic chili components. The specific chili as well as the method of processing influenced the observed antimutagenic properties against urethane. This suggested each chili contains a unique complex mixture of many antimutagens. Co-treatment and pre-treatment experiments showed that both direct and indirect protective mechanisms are involved in an 'activation' process to give antimutagenesis effects. An association between antigenotoxicity and glutathione transferase activity could not be established.

New Therapeutic Approach for Myeloid Leukemia: Induction of Apoptosis via Modulation of Reactive Oxygen Species Production by Natural Compounds

The therapeutic approach to acute myeloid leukemia is based on chemotherapy, but the side effects of the drugs used and various complications, including infections and bleedings, are sometimes fatal. Recently, imatinib mesylate has shown remarkable efficacy and less toxicity as a molecularly targeted therapy in patients with chronic myeloid leukemia. Natural products appear to be safer than the current chemotherapeutic drugs, and we have therefore sought out new potential agents from various natural compounds with the ability to induce the apoptosis of myeloid leukemic cells.

Induction of apoptosis in leukemic cells by homovanillic acid derivative, capsaicin, through oxidative stress: implication of phosphorylation of p53 at Ser-15 residue by reactive oxygen species

Capsaicin (N-vanillyl-8-methyl-1-nonenamide) is a homovanillic acid derivative found in pungent fruits. Several investigators have reported the ability of capsaicin to inhibit events associated with the promotion of cancer. However, the effects of capsaicin on human leukemic cells have never been investigated. We investigated the effects of capsaicin on leukemic cells in vitro and in vivo and further examined the molecular mechanisms of capsaicin-induced apoptosis in myeloid leukemic cells. Capsaicin suppressed the growth of leukemic cells, but not normal bone marrow mononuclear cells, via induction of G(0)-G(1) phase cell cycle arrest and apoptosis. Capsaicin-induced apoptosis was in association with the elevation of intracellular reactive oxygen species production. Interestingly, capsaicin-sensitive leukemic cells were possessed of wild-type p53, resulting in the phosphorylation of p53 at the Ser-15 residue by the treatment of capsaicin. Abrogation of p53 expression by the antisense oligonucleotides significantly attenuated capsaicin-induced cell cycle arrest and apoptosis. Pretreatment with the antioxidant N-acetyl-L-cystein and catalase, but not superoxide dismutase, completely inhibited capsaicin-induced apoptosis by inhibiting phosphorylation of Ser-15 residue of p53. Moreover, capsaicin effectively inhibited tumor growth and induced apoptosis in vivo using NOD/SCID mice with no toxic effects. We conclude that capsaicin has potential as a novel therapeutic agent for the treatment of leukemia.

Pharmacological effects of fermented red pepper

The pharmacological effects were investigated of fermented red pepper (HF-S), which consisted of 14.7% carbohydrate, 1.5% lipid, 4.9% protein, 0.3% ash, 78.2% moisture content, with 0.15% capsaicin and 0.06% dihydrocapsaicin. Oral administration of 0.25 mL HF-S for 3 weeks produced significant changes of the perirenal fat pad weight compared with the HF-control group, suggesting a suppressive effect on lipid accumulation and a significant decrease in the risk of arteriosclerosis. The HF-S (0.25 mL) group also showed a lower plasma TG, TC level and atherogenic index than that of the HF-control. In addition, the HF-S (0.25 mL) group showed a marked increase in the production of glutathione, which is the major endogenous antioxidant, and a decrease in the production of lipid peroxide as the product of chemical damage by oxygen free radicals. It is assumed that the effect of HF-S might relate to high glutathione production on the suppression of lipid peroxidation. HF-S stimulated not only the proliferation of macrophages (as high as the positive control, LPS at 1000 microg/mL) but also mitogenic activity (1.2-fold of LPS at 100 microg/mL).

Examination of the potential genotoxicity of pure capsaicin in bacterial mutation, chromosome aberration, and rodent micronucleus tests

There is widespread dietary exposure to capsaicin in the form of chili peppers, while capsaicin's analgesic qualities have led to increased use of a topical herbal remedy in various impure forms. Most recently, injection of pure capsaicin has been proposed as a means of relieving a variety of debilitating diseases, in which case tissues would receive relatively high and direct exposure. The purpose of the present study, where a series of standard assays were performed in accordance with the Organisation for Economic Cooperation and Development guidance, was to clarify earlier conflicting reports concerning potential genotoxicity of capsaicin prior to administering it to patients in an injectable form. The results confirm the absence of genotoxic activity of high-purity capsaicin in the bacterial mutation and chromosome aberration tests. In addition, no evidence of cytotoxicity or genotoxicity was seen in the rat bone marrow micronucleus test, where systemic exposure to pure capsaicin was achieved using the subcutaneous route and a rising dose toleration protocol. It is concluded that pure capsaicin is not active in the standard battery of genotoxicity assays recommended by the International Conference on Harmonisation for evaluation of new medicines; earlier reported in vitro genotoxic activity is probably associated with mutagenic impurities in commercial grades of the material.

Capsaicin consumption, Helicobacter pylori positivity and gastric cancer in Mexico

Gastric cancer (GC) incidence has not declined in Mexico. We assessed whether the intake of capsaicin (CAP), the pungent compound of chili peppers, increases the risk of GC independently of H. pylori positivity (Hp). From 1994 to 1996, a hospital-based case-control study was performed in 3 areas of Mexico; 234 cases of GC and 468 matched controls were enrolled and their diet and other characteristics were inquired. Chili pepper intake was queried by interview and CAP content of chilies was determined in a separate analysis by gas chromatography to estimate CAP intake; IGg Hp serum antibodies were determined by ELISA. The risk of GC was increased (OR = 1.71; 95% CI = 0.76-3.88) among high-level consumers of CAP (90-250 mg of capsaicin per day, approximately 9-25 jalapeño peppers per day) as compared to low-level consumers (0-29.9 mg of capsaicin per day, approximately 0 to less than 3 jalapeño peppers per day; p for trend p = 0.026); this effect was independent of Hp status and other potential GC determinants and was higher among diffuse GC cases (OR = 3.64; 95% CI = 1.09-12.2; p for trend = 0.002) compared to intestinal GC cases (OR = 1.36; 95% CI = 0.31-5.89; p for trend = 0.493). No significant interaction was found between CAP intake and Hp on GC risk. Chili pepper consumption might be an independent determinant of GC in Mexico.

Riot control agents: pharmacology, toxicology, biochemistry and chemistry

The desired effect of all riot control agents is the temporary disablement of individuals by way of intense irritation of the mucous membranes and skin. Generally, riot control agents can produce acute site-specific toxicity where sensory irritation occurs. Early riot control agents, namely, chloroacetophenone (CN) and chlorodihydrophenarsazine (DM), have been replaced with 'safer' agents such as o-chlorobenzylidene malononitrile (CS) and oleoresin of capsicum (OC). Riot control agents are safe when used as intended: however, the widespread use of riot control agents raises questions and concerns regarding their health effects and safety. A large margin exists between dosages that produce harassment and dosages likely to cause adverse health effects for modern riot control agents such as CS and dibenz[b,f]1 : 4-oxazepine (CR). Yet, despite the low toxicity of modern riot control agents, these compounds are not entirely without risk. The risk of toxicity increases with higher exposure levels and prolonged exposure durations. Ocular, pulmonary and dermal injury may occur on exposure to high levels of these substances, and exposure to riot control agents in enclosed spaces may produce significant toxic effects. Reported deaths are few involving riot control agents, and then only under conditions of prolonged exposure and high concentrations. Recently, concern has focused on the deaths resulting from law enforcement use of OC, a riot control agent generally regarded as safe because it is a natural product. As with other xenobiotics, not enough is known concerning the long-term/chronic effects of riot control agents. Clearly, there is considerable need for additional research to define and delineate the biological and toxicological actions of riot control agents and to illuminate the full health consequences of these compounds as riot control agents.

Prevention of cerebral vasospasm by a capsaicin derivative, glyceryl nonivamide, in an experimental model of subarachnoid hemorrhage

BACKGROUND

Cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) remains a major complication in patients suffering from SAH. In our previous study, we reported that stimulating vascular K(+) channel activity prevented the development of cerebral vasospasm. Recent evidence indicates that glyceryl nonivamide (GLNVA), a capsaicin derivative, has a vasorelaxant effect on the aortic vascular smooth muscle due to the release of coronary calcitonin gene-related peptide, which in turn stimulates K(+) channel opening. The purpose of the present study was to examine the preventive effects of GLNVA on vasospasm.

METHODS

New Zealand white rabbits were subjected to experimental SAH by injecting autologous blood into the cisterna magna. GLNVA or vehicle was injected intrathecally immediately after the induction of SAH. All animals were killed by perfusion-fixation at 48 hours after SAH. The basilar arteries were removed and sectioned, and their cross-sectional areas were measured.

RESULTS

The average cross-sectional areas of basilar arteries were reduced by 69% and 71% in the SAH only and SAH plus vehicle groups, respectively, when compared with the healthy controls. After treatment with 0.35, 1.75, and 3.5 mg/kg GLNVA in rabbits subjected to SAH the average cross-sectional area was decreased by 46%, 12% and 2%, respectively, when compared with the healthy controls. The protective effect of GLNVA achieved statistical significance at all dosages. Morphologically, corrugation of the internal elastic lamina of vessels was often observed in the vehicle-treated group, but was not prominent in the GLNVA-treated groups or healthy controls.

CONCLUSION

The findings showed that GLNVA dose-dependently attenuated cerebral vasospasm after SAH in the rabbit. These results suggest that intrathecal administration of GLNVA could be an effective strategy for preventing cerebral vasospasm after SAH.

Capsaicin and nonivamide as novel skin permeation enhancers for indomethacin

The study was conducted in vitro to investigate the changes of indomethacin transdermal permeation pretreated by capsaicin and nonivamide, two compounds chemically similar to Azone. The combined effect of low frequency ultrasound (20 kHz) and enhancers on the indomethacin permeation was also evaluated. The experimental data demonstrated that capsaicin and nonivamide significantly enhanced the flux of indomethacin across nude mouse skin. Enhancement effects of both analogues were very similar and depended predominantly on the concentration tested. Histological examination coupled with visual scores indicated the safety of capsaicin and nonivamide on skin structure. Simultaneous application of ultrasound and enhancers significantly increased skin permeation of indomethacin compared with either ultrasound or enhancers alone. Better effect was obtained by the combination with capsaicin than nonivamide.

Neuroanatomical effects of capsaicin on the primary afferent neurons

Studies by N. JANCSO and his associates in the 1970's established that capsaicin in paprika exerts selective damage on nociceptive primary sensory neurons. The physiological and pharmacological aspects of capsaicin's effect have been repeatedly reviewed, but no report seems available concerning the neuroanatomical changes caused by capsaicin. This paper first reviews the neuroanatomical aspect of the lesion caused by capsaicin. Special attention is paid to quantitative estimations made by our group and others on the loss of dorsal root ganglion (DRG) cells, dorsal root nerve fibers, the saphenous nerve, chorda tympani nerve, and pulp nerves after neonatal treatment with capsaicin. The degenerating process of DRG cells induced by capsaicin is discussed with respect to necrosis and apoptosis. The capsaicin receptors found recently are concisely introduced with reference to their action. A discrepancy between a marked loss of dorsal root C-fibers and an unexpectedly intact response to noxious heat in mice treated with capsaicin at neonate is discussed, and attension is given to nerves sprouting from capsaicin-resistant DRG cells in the superficial dorsal horn. In addition, the architecture of the synapses between the central endings of the capsaicin-sensitive primary afferent neurons and the intrinsic inhibitory interneurons is described and its possible significance considered in terms of the transmission of nociceptive information.

Update from Asia. Asian studies on cancer chemoprevention

In Asia, nontoxic dietary products are considered desirable primary prevention vehicles for conquering cancer. As early as 1978, investigators in Korea carried out extensive long-term anticarcinogenicity experiments using the mouse lung tumor model and observed an anticarcinogenic effect of Panax ginseng C.A. Meyer extract in 1980. The results showed that natural products can provide hope for human cancer prevention. A newly established nine-week medium-term model using mouse lung tumors (Yun's model) could confirm the anticarcinogenicity of ginseng that varies according to its type and age. Subsequently, the ginseng was shown by epidemiological studies to be a nonorgan-specific cancer preventive agent associated with a dose-response relationship. The anticarcinogenic effects of vegetarian foods common at every dining table in Korea and some synthetics were also studied using Yun's nine-week model. In brief, ascorbic acid, soybean lecithin, capsaicin, biochanin A, Ganoderma lucidum, caffeine, and a novel synthetic 2-(allylthio)pyrazine decrease the incidence of mouse lung tumors, whereas fresh ginseng (4 years old), carrot, spinach, Sesamum indicum, beta-carotene, and 13-cis retinoic acid do not. This result regarding beta-carotene is consistent with the ineffective findings of the ATBC trial, the CARET trial, and the Physicians' Health Study. In 1983, a cancer chemoprevention study group was first established in Japan. Subsequently, (-)-epigallocatechin gallate, cryptoporic acid E, and sarcophytol A from natural products, and synthetic acyclic retinoid and canventol were shown to be anticarcinogenic or chemopreventive in human subjects. Despite the frequent consumption of tea wordwide as a beverage and current experimental evidence of anticarcinogenesis, including controversial results of epidemiological studies, more systematic clinical trials for confirmation of preventive activity of tea against cancer are needed. Placebo-controlled intervention trials of dietary fiber are under study in Japan. In the past decade, new triterpenoids were isolated from various natural sources, and its biological activities were investigated in Asia. In the late 1970s a comprehensive chemoprevention program was established at the Institute of Materia Medica, Chinese Academy of Medical Sciences. Since then, many retinoid compounds have been synthesized and screened in the search for chemopreventive cancer agents. The National Cancer Institute (USA) and China are jointly engaged in the two-nutrition intervention in Linxian, China. The results of joint study of the general population and of dysplasia in China should stimulate further research to clarify the potential benefits of micronutrient supplements. We need to clarify if there is a connection between the lower rates of cancer mortality in Korea and the frequent consumption of anticarcinogenic vegetables or traditional foods, including ginseng and Ganoderma lucidum. The constituents of the nontoxic stable dietary products promise to be the future hope for conquering cancers in the coming years.

Antimicrobial properties of alkamides present in flavouring plants traditionally used in Mesoamerica: affinin and capsaicin

The bioactive amides affinin and capsaicin isolated respectively from Heliopsis longipes roots and Capsicum spp fruits, were assayed for activity against Escherichia coli, Pseudomonas solanacearum, Bacillus subtilis and Saccharomyces cerevisicae suspension cultures. The alkamide affinin inhibited growth of E. coli and S. cerevisiae at concentrations as low as 25 microg/ml. Higher concentrations of affinin were necessary to inhibit growth of P. solanacearum and B. subtilis. However. high concentrations of capsaicin only retarded the growth of E. coli and P. solanacearum, whereas growth of B. subtilis was strongly inhibited and that of S. cerevisiae was initially enhanced. Results are discussed in relation to previous reports concerning crude extract and to the molecular structures of the bioactive compounds.

Swimming capacity of mice is increased by oral administration of a nonpungent capsaicin analog, stearoyl vanillylamide

Intravenous injection of stearoyl vanillylamide (C18-VA), a nonpungent capsaicin (CAP) analog, enhances adrenaline secretion significantly and as effectively as CAP in rats. Because swimming capacity was enhanced by CAP in mice due to CAP-induced adrenal catecholamine secretion, we investigated the effects of oral administration of C18-VA on swimming capacity using an adjustable-current water pool. Male Std ddY 6-wk-old mice were fed a commercial diet for this study and one group was orally administered C18-VA via a stomach tube. Treated mice were able to swim longer before exhaustion than the control mice (62.9 +/- 5.6 vs. 49.6 +/- 7. 0 min, P < 0.05). The swimming capacity of two groups administered C18-VA (0.02 and 0.033 mmol/kg) was significantly greater than that of those administered vehicle alone, (P < 0.05). Substance P concentration in cerebrospinal fluid, which is involved in pain transmission and is the first direct measure of pungency, was not affected by C18-VA administration. In an experiment examining the effects of C18-VA on serum adrenaline concentration, adrenaline was significantly greater in C18-VA treated mice than in controls at 2-h post-dose (C18-VA group, 26.09 +/- 2.82; control group 13.29 +/- 0. 96 microg/L, P < 0.01). In a separate study free fatty acids in serum were elevated in treated mice at 2-h post-dose (P < 0.01). While serum glucose concentration was not affected. These results suggest that C18-VA increased swimming capacity of mice via adrenaline release, independent of pungency. In addition, the present study suggests the usefulness of its application to humans.

Chemical activators of sensory neurons

Chemical activation of sensory neurons plays an important role in the somatosensory system. The actions of both endogenous mediators such as excitatory amino acids, acetylcholine, bradykinin, and ATP, as well as selective exogenous activators of nociceptive sensory neurons are reviewed. The physiological significance of these mediators in both nociception and other types of sensation are discussed.

Vanilloid receptors: new insights enhance potential as a therapeutic target

Compounds related to capsaicin and its ultrapotent analog, resiniferatoxin (RTX), collectively referred to as vanilloids, interact at a specific membrane recognition site (vanilloid receptor), expressed almost exclusively by primary sensory neurons involved in nociception and neurogenic inflammation. Desensitization to vanilloids is a promising therapeutic approach to mitigate neuropathic pain and pathological conditions (e.g. vasomotor rhinitis) in which neuropeptides released from primary sensory neurons play a major role. Capsaicin-containing preparations are already commercially available for these purposes. The use of capsaicin, however, is severely limited by its irritancy, and the synthesis of novel vanilloids with an improved pungency/desensitization ratio is an on-going objective. This review highlights the emerging evidence that the vanilloid receptor is not a single receptor but a family of receptors, and that these receptors recognize not simply RTX and capsaicin structural analogs but are broader in their ligand-binding selectivity. We further focus on ligand-induced messenger plasticity, a recently discovered mechanism underlying the analgesic actions of vanilloids. Lastly, we give a brief overview of the current clinical uses of vanilloids and their future therapeutic potential. The possibility is raised that vanilloid receptor subtype-specific drugs may be synthesized, devoid of the undesirable side-effects of capsaicin.

The antimicrobial properties of chile peppers (Capsicum species) and their uses in Mayan medicine

A survey of the Mayan pharmacopoeia revealed that tissues of Capsicum species (Solanaceae) are included in a number of herbal remedies for a variety of ailments of probable microbial origin. Using a filter disk assay, plain and heated aqueous extracts from fresh Capsicum annuum, Capsicum baccatum, Capsicum chinese, Capsicum frutescens, and Capsicum pubescens varieties were tested for their antimicrobial effects with fifteen bacterial species and one yeast species. Two pungent compounds found in Capsicum species (capsaicin and dihydrocapsaicin) were also tested for their anti-microbial effects. The plain and heated extracts were found to exhibit varying degrees of inhibition against Bacillus cereus, Bacillus subtilis, Clostridium sporogenes, Clostridium tetani, and Streptococcus pyogenes.

Capsaicin in hot chili pepper: carcinogen, co-carcinogen or anticarcinogen?

Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) is a major pungent ingredient of the Capsicum fruits such as hot green and red peppers. Besides its use as a food additive in various spicy cuisines, capsaicin is currently utilized for therapeutic purposes to treat various peripheral painful conditions such as rheumatoid arthritis and diabetic neuropathy. Considering consumption of capsaicin as a food additive and its current medicinal application in humans, correct evaluation and precise assessment of any harmful effects of this compound are essential from the public health standpoint. Numerous investigations have been conducted to determine the potential mutagenic and carcinogenic activity of capsaicin and chili pepper, but results are discordant. This review briefly examines findings in the literature of studies testing mutagenicity and tumorigenicity of capsaicin and presents a possible mechanistic basis for the dual effects exerted by the compound.

Genotoxic effects produced by capsaicin in mouse during subchronic treatment

Capsaicin is the chemical responsible for the pungent, hot properties of Capsicum, a vegetable widely consumed in the diet of many countries in the world. In this work, the genotoxic capacity of capsaicin was studied in mouse during a 32-day treatment. We used the dosages of 1.46 and 1.94 mg/kg given by the i.p. route. Each week, the frequency of micronucleated normochromatic erythrocytes (MN-NE) and the ratio polychromatic/normochromatic erythrocytes (PE/NE) were scored. At the end of the experiment we also scored the frequency of sister chromatid exchanges (SCE). The results in the MN-NE analysis showed a genotoxic response with 1.94 mg/kg starting from day 16, while the 1.46 mg/kg dose produced a significant increase of MN-NE only at the 32nd day. The ratio PE/NE was only affected at the 32nd day with the high dose. Concerning the SCE frequency, the genotoxic effect was only observed with the highest dose. These results indicated that capsaicin is a genotoxicant, and due to the probable relation between an excessive consumption of Capsacum and an increase in gastric cancer, it is suggested that its consumption could be moderated until a definitive risk for humans is established.

Capsaicin, a double-edged sword: toxicity, metabolism, and chemopreventive potential

Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is a primary pungent and irritating principle present in chilies and red peppers which are widely used as spices. Because of its selective effects on the functions of a defined subpopulation of sensory neurons, capsaicin is currently used as a versatile tool for the study of pain mechanisms and also for pharmacotherapy to treat several pain disorders. Considering the frequent consumption of capsaicin as a food additive and its current medicinal use, correct assessment of hazardous effects of this compound is important. Mutagenic and carcinogenic activities of capsaicin and chili extracts have been studied, but results are conflicting. Mammalian metabolism of capsaicin has been also reported. Capsaicin appears to interact with xenobiotic metabolizing enzymes, particularly microsomal cytochrome P450-dependent monooxygenases which are involved in activation as well as detoxification of various chemical carcinogens and mutagens. Recent studies have shown that hepatic cytochrome P450 2E1 catalyzes the conversion of capsaicin to reactive species such as the phenoxy radical intermediate capable of covalently binding to the active site of the enzyme as well as tissue macromolecules. While covalent modification of protein and nucleic acids leads to toxicity including necrosis, mutagenesis, and carcinogenesis, suicidal inhibition of microsomal cytochrome P450 may prohibit further activation of capsaicin and also of other toxic xenobiotics. Results from recent studies indicate that capsaicin possesses the chemoprotective activity against some chemical carcinogens and mutagens.

Identification of nitrophenols as nitrosation products from capsaicin and red chillies

The in vitro nitrosation of sun-dried red chillies (Capsicum annuum) and of its constituents capsaicin and dihydrocapsaicin was studied. The nitrophenols 4-nitroguaiacol, 4,6-dinitroguaiacol, nitrocapsaicin and nitrodihydrocapsaicin were detected as final products, whereas no formation of nitrosamides was observed though this is expected from the amide precursors capsaicin and dihydrocapsaicin. The nitrosation occurs readily with remarkable yields of nitrophenols even at physiological pH and at nitrite concentrations which are within the range of those found in the human stomach. Due to their toxicity, nitrophenols need to be included in total risk assessment through potential endogenous nitrosation of foodstuffs.

The vanilloid (capsaicin) receptor: receptor types and species differences

1. Capsaicin was postulated to exert its pharmacological actions by interacting at a specific recognition site (receptor) expressed predominantly by primary afferent neurons. 2. The actual existence of this long-sought "capsaicin-receptor" has recently been demonstrated by the specific binding of [3H]resiniferatoxin (RTX), an ultrapotent capsaicin analog with a unique spectra of actions. 3. Since homovanillic acid is the key structural motif shared by capsaicin and RTX, their recognition site appears to be best termed the vanilloid receptor. 4. Central (sensory ganglia and spinal cord) vanilloid receptors of the rat bind RTX with high affinity in a cooperative fashion; moreover, they recognize capsaicin with higher affinity than the competp6ive antagonist, capsazepine. Peripheral (urinary bladder, urethra, airways, colon) vanilloid receptors, by contrast, bind RTX with lower affinity in a noncooperative manner. An opposite affinity for capsazepine relative to capsaicin appears to distinguish vanilloid receptors in the urinary bladder from those present in the airways or colon. These findings imply heterogeneity in the properties of vanilloid receptors. 5. The affinity of [3H]RTX binding in vitro is influenced by reducing agents, suggesting an in vivo modulatory role for endogenous reducing agents in vanilloid receptor functions. 6. The size of central vanilloid receptors (270 kDa) as measured by radiation inactivation and the cooperative binding both suggest a receptor cluster with cooperating subunits. 7. RTX binds to vanilloid receptors with orders of magnitude higher affinity than capsaicin; its ability to induce cooperative binding is also more pronounced. These differences in receptor binding along with the pharmacokinetical differences in tissue equilibration and in plasma binding may form a rational basis to explain the peculiar spectrum of actions of RTX. 8. Guinea pig spinal cord and airway membranes bind RTX with lower affinity than rat tissues. The receptor density is, however, higher in the guinea pig in keeping with the marked sensitivity of this species to vanilloid actions. 9. The apparently low level of specific [3H]RTX binding sites in the hamster and rabbit is in accord with the resistance of these species to vanilloid actions. 10. In post-mortem human spinal cord specific [3H]RTX binding sites can be detected; their binding parameters are similar to those determined in guinea pig spinal cord. 11. The vanilloid receptor appears to display both intraspecies heterogeneity and marked interspecies differences. 12. As yet, it is known whether the vanilloid receptor is operated by endogenous ligands. It is not known either which receptor superfamily (if any) it belongs to. The [3H]RTX binding assay has, however, the potential of answering these questions.(ABSTRACT TRUNCATED AT 400 WORDS)

Autonomic and sensory cardiovascular activities of nonivamide: intrathecal administration of clonidine

The effects of nonivamide on the cardiovascular system were examined and compared with the effects of substance P (SP) in rats. Intravenous (i.v.) injection (10 micrograms/kg) of nonivamide produced triphasic pressure responses (A; depressor, B; pressor, and C; depressor) and biphasic bradycardia responses (f; fast bradycardia and s; slow bradycardia). IA injection (10 micrograms/kg) into the epigastric artery caused hypotension and mild tachycardia. The effects of atropine, vagotomy, SP antagonist, propranolol, and clonidine on these responses were examined and mechanisms responsible for the nonivamide-induced responses are postulated as follows. A and f are due to vagal reflex resulting from the excitation of afferent sensory neurons in the heart and are parasympathetic efferent effects from the nucleus solitarius. B is involved in sympathetic activation, partly caused by the release of SP in the spinal cord. C is due to the vasodilatory effect of SP released from perivascular stores. s was diminished by vagotomy and is due to the bradycardiac effect of acetylcholine, released by SP, from cardiac stores. The activation of the autonomic system is inhibited by clonidine and involved in the wide spectrum of nonivamide-induced cardiovascular effects.

The effect of chilli and its pungent ingredient capsaicin on gastrointestinal transit in the rat

The effect of chilli powder and its pungent ingredient capsaicin on gastrointestinal transit in the rat was studied. Fasted unanaesthetized male Sprague-Dawley rats (n = 144) received by gavage a test meal containing charcoal and cellulose in water or capsaicin solvent plus 51Cr as a radioactive marker. Either 100 or 200 mg of chilli powder (containing 0.13 and 0.26 mg of capsaicin, respectively) or 0.5 or 1 mg of capsaicin were added, the final volume of each meal being 1.5 mL. At 10 and 20 min, animals were killed and the amount of isotope that had left the stomach was measured, together with the distance the charcoal column had travelled along the small intestine. Compared to controls, animals given chilli powder emptied less of their gastric content at 10 and 20 min, an effect partly reproduced by capsaicin. However overall gastric-small intestinal transit was unaffected by chilli powder or capsaicin. Another 12 male Sprague-Dawley rats received, under light ether anaesthesia, on six occasions at 1-2 week intervals, the same six test meals as used in the previous experiment except that charcoal was not used. Total gut transit as measured by the amount of radioactive marker excreted in the stools at 18 and 24 h was unaffected by the use of chilli or capsaicin.