Modification of oestrogen signalling pathways influences cough induced by citric acid but not capsaicin in the animal model of both sexes.

To clarify the role of oestrogen signalling and the role of oestrogen receptor alpha (ERα) in the cough pathways we performed a study in which coughing was observed in both sexes animal models after the treatment by selective ERα degrader fulvestrant (ICI 182-780) and inhibitor of oestrogen synthesis danazol. Degradation of ERα with the normal plasma oestrogen levels induced by fulvestrant, significantly augments the cough response of female but not male guinea pigs. These changes were observed in citric acid-induced cough. Female guinea pigs responded with an increased count of cough expulsions per challenge time and we also detected shorter cough latency. The capsaicin-induced cough did not change. A similar response was observed after danazol treatment, which decreased the plasma oestrogen level. Our results indicate that the transient receptor potential vanilloid-1 (TRPV1) channel-mediated cough is resistant to the hypoestrous state, while the citric acid-mediated cough is oestrogen-dependent and hypersensitive during the hypoestrous state.

Evaluation of the systemic and spinal antinociceptive effect of a new hybrid NSAID tetrahydropyran derivative.

Pain is responsible for inducing physical and mental stress, interfering negatively in patients' quality of life. Classic analgesic drugs, such as opioids and non-steroidal anti-inflammatory drugs, are known for their wide range of adverse effects, making it important to develop new drugs. Thus, this study aimed to analyse the action of the hybrid compound cis- (±) -acetate of 4-chloro-6- (naphthalene-1-yl) -tetrahydro-2h-pyran -2-yl) methyl2- (2- [2,6-dichlorophenylamine] phenyl (LS19) under acute nociceptive conditions, and deepened the understanding of the responsible mechanisms. Male Swiss mice were evaluated in the acetic acid-induced abdominal writhing, formalin, tail flick, capsaicin- and glutamate-induced nociception, thermal stimulation in animals injected with capsaicin and rotarod tests besides the acute and subchronic toxicological evaluation. The compound showed effect on the acetic acid-induced abdominal writhing, formalin (both phases), tail flick, thermal stimulation in animals injected with capsaicin and capsaicin-induced nociception tests. In the study of the mechanism of action was observed reversion of the antihyperalgesic effect of the compound from the previous intraperitoneal and intrathecal administration of naloxone, nor-binaltorphimine, naltrindole, methylnaltrexone, 7-nitroindazole, L-NAME, ODQ, glibenclamide on the tail flick test. In the thermal stimulation in animals injected with capsaicin, the compound showed antinociceptive effect by oral and intraplantar routes, besides to reducing the levels of TNF-α, IL-1ß and PGE2 in the paws previously administered with capsaicin. There were no signs of acute and subchronic intoxication with the compound. In summary, the compound LS19 presented spinal and local antihyperalgesic effect, demonstrating participation of the opioid/NO/cGMP/K+ ATP pathway and TRPV1 receptors and it demonstrated safety in its use in mice.

Modulation of excitatory synaptic transmissions by TRPV1 in the spinal trigeminal subnucleus caudalis neurons of neuropathic pain rats.

The present study examined contribution of the transient receptor potential vanilloid 1 channel (TRPV1) to the chronic orofacial pain. Bilateral partial nerve ligation (PNL) of the mental nerve, a branch of trigeminal nerve, was performed to induce neuropathic pain. The withdrawal threshold in response to mechanical stimulation of the lower lip skin was substantially reduced after the surgery in the PNL rats while it remained unchanged in the sham rats. This reduction in the PNL rats was alleviated by pregabalin injected intraperitoneally (10 mg/kg) and intracisternally (10, 30, 100 µg). Furthermore, an intracisternal injection of AMG9810, an antagonist of TRPV1, (1.5, 5.0 µg) attenuated the reduction of withdrawal threshold. Spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs) were recorded from the spinal trigeminal subnucleus caudalis (Vc) neurons in the brainstem slice, which receive the orofacial nociceptive signals. In the PNL rats, superfusion of capsaicin (0.03, 0.1 µM) enhanced their frequency without effect on the amplitude and the highest concentration (0.3 µM) increased both the frequency and amplitude. In the sham rats, only 0.3 µM capsaicin increased their frequency. Thus, capsaicin-induced facilitation of sEPSCs and mEPSCs in the PNL rats was significantly stronger than that in the sham rats. AMG9810 (0.1 µM) attenuated the capsaicin's effect. Capsaicin was ineffective on the trigeminal tract-evoked EPSCs in the PNL and sham rats. These results suggest that the chronic orofacial pain in the PNL model results from facilitation of the spontaneous excitatory synaptic transmission in the Vc region through TRPV1 at least partly.

Cytogenotoxicity and protective effect of piperine and capsaicin on meristematic cells of Allium cepa L.

Piperine and capsaicin are important molecules with biological and pharmacological activities. This study aimed to evaluate the cytogenotoxic and protective effect of piperine and capsaicin on Allium cepa cells. A. cepa roots were exposed to negative (2% Dimethylsulfoxide) and positive (Methylmethanesulfonate, MMS, 10 µg/mL) controls, and four concentrations (25-200 µM) of piperine or capsaicin (alone) or associated before, simultaneously or after with the MMS. Only the lowest concentration of piperine (25 µM) showed a protective effect because it was not genotoxic. Piperine and capsaicin were cytotoxic (50, 100 and 200 µM). Piperine (50 to 200 µM) caused a significant increase in the total average of chromosomal alterations of in A. cepa cells. For capsaicin, the genotoxic effect was dose-dependent with a significant increase for all concentrations, highlighting the significant presence of micronuclei and nuclear buds for the two isolates. In general, bioactive compounds reduced the total average of chromosomal alterations against damage caused by MMS, mainly micronuclei and/or nuclear buds. Therefore, the two molecules were cytotoxic and genotoxic at the highest concentrations, and did not have cytoprotective action, and the lowest concentration of piperine demonstrated important chemopreventive activity.

Inflammasome Signaling Regulates the Microbial-Neuroimmune Axis and Visceral Pain in Mice.

Interactions between the intestinal microbiota, immune system and nervous system are essential for homeostasis in the gut. Inflammasomes contribute to innate immunity and brain-gut interactions, but their role in microbiota-neuro-immune interactions is not clear. Therefore, we investigated the effect of the inflammasome on visceral pain and local and systemic neuroimmune responses after antibiotic-induced changes to the microbiota. Wild-type (WT) and caspase-1/11 deficient (Casp1 KO) mice were orally treated for 2 weeks with an antibiotic cocktail (Abx, Bacitracin A and Neomycin), followed by quantification of representative fecal commensals (by qPCR), cecal short chain fatty acids (by HPLC), pathways implicated in the gut-neuro-immune axis (by RT-qPCR, immunofluorescence staining, and flow cytometry) in addition to capsaicin-induced visceral pain responses. Abx-treatment in WT-mice resulted in an increase in colonic macrophages, central neuro-immune interactions, colonic inflammasome and nociceptive receptor gene expression and a reduction in capsaicin-induced visceral pain. In contrast, these responses were attenuated in Abx-treated Casp1 KO mice. Collectively, the data indicate an important role for the inflammasome pathway in functional and inflammatory gastrointestinal conditions where pain and alterations in microbiota composition are prominent.

CGRP release in an experimental human trigeminal pain model.

BACKGROUND: Migraine and trigemino-autonomic cephalalgia attacks are associated with an increase of α-calcitonin-gene related peptide levels in the ipsilateral jugular vein. It is however unknown whether trigeminal pain stimulation in healthy subjects without headache disorders also induces increase of calcitonin-gene related peptide levels. FINDINGS: We measured α-calcitonin-gene related peptide levels in eight healthy subjects after subcutaneous injection of capsaicin in the forehead and in the mandibular region and after injection of sodium chloride in the forehead. We observed a significant increase of α-calcitonin-gene related peptide level only after injection of capsaicin in the forehead (i.e. first trigeminal branch). We also observed trigemino-autonomic activation (lacrimation, rhinorrhea etc.) only after injection of capsaicin in the forehead. CONCLUSION: Increase of α-calcitonin-gene related peptide levels do not only occur in primary headache attacks but also after experimental trigeminal pain of the first branch. This finding suggests that α-calcitonin-gene related peptide elevation is, at least an additional, unspecific effect of first trigeminal branch stimulation following pain activation and not a specific mechanism of idiopathic headache disorders.

Pharmacological studies on aqueous extract of Launaea arborescens from southwest Algeria.

ETHNOPHARMACOLOGICAL RELEVANCE: Launaea arborescens, its vernacular name is Mol-albina belonging to asteracaea family origin of the southwest of Algeria. This plant is used in folk medicines to treat gastroenteritis, diabetes, child aliment and other diseases; it is taken macerated or boiled. AIM: This study aims to evaluate the anti-inflammation an analgesic activity of the aqueous extract of Launaea arborescens (AqELA) and its pathway of action. METHODS: the investigation of anti-inflammatory and analgesic effects were done using formalin test, acetic acid test. For mechanism investigation, it was used hot plate test to induce opioid receptors, a histamine and serotonin test to induce edema paw, finally, for the TRPV1 receptor, it was used the capsaicin test. RESULTS: The aqueous extract of Launaea arborescens showed a significant inhibition of abdominal writhing test 95% and 100% inhibition of licking paw using acid acetic test and formalin test respectively (EC: 47 mg/kg and 104 mg/kg). The analgesic effect of the aqueous extract of Launaea arborescens showed inhibition of sensation of pain after 120 min compared to morphine effect. The aqueous extract of Launaea arborescens reduced paw volume after 180 min and 120 min for histamine and serotonin respectively with dose-dependent. Concerning of TRPV1 receptors, the inhibition was showed at doses 100 mg and 300 mg. CONCLUSION: Our results contribute towards validation of the traditional use of Launaea arborescens for inflammation ailment.

Effects of R-flurbiprofen and the oxygenated metabolites of endocannabinoids in inflammatory pain mice models.

Pain is one of the cardinal signs accompanying inflammation. The prostaglandins (PGs), synthetized from arachidonic acid by cyclooxygenase (COX)-2, are major bioactive lipids implicated in inflammation and pain. However, COX-2 is also able to metabolize other lipids, including the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide (AEA), to give glycerol ester (PG-G) and ethanolamide (PG-EA) derivatives of the PGs. Consequently, COX-2 can be considered as a hub not only controlling PG synthesis, but also PG-G and PG-EA synthesis. As they were more recently characterized, these endocannabinoid metabolites are less studied in nociception compared to PGs. Interestingly R-profens, previously considered as inactive enantiomers of nonsteroidal anti-inflammatory drugs (NSAIDs), are substrate-selective COX inhibitors. Indeed, R-flurbiprofen can selectively block PG-G and PG-EA production, without affecting PG synthesis from COX-2. Therefore, we compared the effect of R-flurbiprofen and S-flurbiprofen in models of inflammatory pain triggered by local administration of lipopolysaccharides (LPS) and carrageenan in mice. Remarkably, the effects of flurbiprofen enantiomers on mechanical hyperalgesia seem to depend on (i) the inflammatory stimuli, (ii) the route of administration, and (iii) the timing of administration. We also assessed the effect of administration of the PG-Gs, PG-EAs, and PGs on LPS-induced mechanical hyperalgesia. Our data support the interest of studying the nonhydrolytic endocannabinoid metabolism in the context of inflammatory pain.

A neuroimaging biomarker for sustained experimental and clinical pain.

Sustained pain is a major characteristic of clinical pain disorders, but it is difficult to assess in isolation from co-occurring cognitive and emotional features in patients. In this study, we developed a functional magnetic resonance imaging signature based on whole-brain functional connectivity that tracks experimentally induced tonic pain intensity and tested its sensitivity, specificity and generalizability to clinical pain across six studies (total n = 334). The signature displayed high sensitivity and specificity to tonic pain across three independent studies of orofacial tonic pain and aversive taste. It also predicted clinical pain severity and classified patients versus controls in two independent studies of clinical low back pain. Tonic and clinical pain showed similar network-level representations, particularly in somatomotor, frontoparietal and dorsal attention networks. These patterns were distinct from representations of experimental phasic pain. This study identified a brain biomarker for sustained pain with high potential for clinical translation.

The TRPM3 ion channel mediates nociception but not itch evoked by endogenous pruritogenic mediators.

During the molecular transduction of itch, the stimulation of pruriceptors on sensory fibers leads to the activation or sensitization of ion channels, which results in a consequent depolarization of the neurons. These ion channels mostly belong to the transient receptor potential (TRP) channels, which are involved in nociception and thermosensation. In particular, TRPV1 and TRPA1 were described in the transduction of both thermal nociception as well as histaminergic and non-histaminergic itch. The thermosensitive TRPM3 plays an indispensable role in heat nociception together with TRPV1 and TRPA1. However, the role of TRPM3 in the development of pruritus has not been studied yet. Therefore, in this study we aimed at investigating the potential role of TRPM3 in the transduction of pruritus and pain by investigating itch- and nociception-related behavior of Trpm3+/+ and Trpm3-/- mice, and by studying the activation of somatosensory neurons isolated from trigeminal ganglia upon application of algogenic and pruritogenic substances. Activators of TRPM3 evoked only nocifensive responses, but not itch in Trpm3+/+ animals, and these nocifensive responses were abolished in the Trpm3-/- strain. Histamine and endogenous non-histaminergic pruritogens induced itch in both Trpm3+/+ and Trpm3-/- mice to a similar extent. Genetic deletion or pharmacological blockade diminished TRPM3 mediated Ca2+ responses of sensory neurons, but did not affect responses evoked by pruritogenic substances. Our results demonstrate that, in contrast to other thermosensitive TRP channels, TRPM3 selectively mediates nociception, but not itch sensation, and suggest that TRPM3 is a promising candidate to selectively target pain sensation.

Pharmacologycal activity of peperina (Minthostachys verticillata) on gastrointestinal tract.

ETHNOPHARMACOLOGICAL RELEVANCE: Minthostachys verticillata (Griseb.) Epling (Lamiaceae), known as Peperina is a medicinal native plant, with a traditional use as a digestive, antispasmodic and antidiarrheic. AIM OF THE STUDY: Despite its folkloric use, no scientific evaluation of this plant related to the gastrointestinal inflammatory process has been carried out to date. The present study aims to assess the effects of M. verticillata on gastrointestinal system in experimental models. MATERIALS AND METHODS: M. verticillata (250 and 500 mg/kg) was orally tested in a colitis model induced by acetic acid. Colon weight/length ratio, oxidative stress (oxidized and reduced glutathione), histological changes using Alcian blue and hematoxylin & eosin staining and expression of IL1ß, TNFα, iNOS, COX-2 were evaluated. The effect of the extract in three additional in vivo models were studied: intestinal motility and diarrhea induced by ricin oil, and visceral pain induced by intracolonic administration of capsaicin. Finally, the activity on concentration response curves of acetylcholine, calcium chloride, potassium and serotonin were achieved in isolated rat jejunum. RESULTS: In the colitis model, M. verticillata induced a significant reduction in the colon weight/length ratio, oxidative stress and expression levels of IL-1ß, iNOS and COX-2. Also, the extract diminished the severity of microscopic tissue damage and showed protective effect on goblet cells. Intestinal motility, diarrhea, visceral pain-related behaviors and referred hyperalgesia were significantly reduced when the animals were treated with the extract. Furthermore, in isolated jejunum, M. verticillata significantly reduced the contraction induced by serotonin and acetylcholine. Likewise, the extract non-competitively inhibited the response-concentration induced by CaCl2 and inhibited both low and high K+-induced contractions. CONCLUSIONS: This is the first study to validate traditional use of M. verticillata for digestive disorders and demonstrated that its aqueous extract could represent a promising strategy in targeting the multifactorial pathophysiology of inflammatory bowel disease.

Therapeutic effects and mechanisms study of Hanchuan Zupa Granule in a Guinea pig model of cough variant asthma.

ETHNOPHARMACOLOGICAL RELEVANCE: Hanchuan Zupa Granule (HCZP), a traditional Chinese ethnodrug, has the functions of supressing a cough, resolving phlegm, warming the lungs, and relieving asthma. In clinical practice employing traditional Chinese medicine (TCM), HCZP is commonly used to treat acute colds, cough and abnormal mucous asthma caused by a cold, or "Nai-Zi-Lai" in the Uygur language. Studies have confirmed the use of HCZP to treat cough variant asthma (CVA) and other respiratory diseases. However, the pharmacological mechanisms of HCZP remain unrevealed. AIM OF THE STUDY: To investigate the anti-tussive and anti-asthmatic effects and the possible pharmacological mechanisms of HCZP in the treatment of CVA. MATERIALS AND METHODS: A guinea pig CVA animal model was established by intraperitoneal injection of ovalbumin (OVA) combined with intraperitoneal injection of aluminium hydroxide adjuvant and atomized OVA. Meanwhile, guinea pigs with CVA received oral HCZP (at dosages of 0.571, 0.285 and 0.143 g/kg bodyweight). The number of coughs induced by aerosol capsaicin was recorded, and the airway hyperresponsiveness (AHR) of CVA guinea pigs was detected with the FinePointe series RC system. H&E staining of lung tissues was performed to observe pathological changes. ELISA was used to detect inflammatory cytokines. qRT-PCR and western blotting analyses were used to detect the expression of Th1-specific transcription factor (T-bet), Th2-specific transcription factor (GATA3), and Toll-like receptor 4 (TLR4) signal transduction elements. These methods were performed to assess the protective effects and the potential mechanisms of HCZP on CVA. RESULTS: Great changes were found in the CVA guinea pig model after HCZP treatment. The number of coughs induced by capsaicin in guinea pigs decreased, the body weights of guinea pigs increased, and inflammation of the eosinophilic airway and AHR were reduced simultaneously. These results indicate that HCZP has a significant protective effect on CVA. A pharmacological study of HCZP showed that the levels of interleukin-4 (IL-4) and IL-5 and tumour necrosis factor-α (TNF-α) in serum decreased. The amount of interferon-γ (IFN-γ) increased, mRNA and protein expression of TLR4 and GATA3 weakened, and mRNA and protein expression of T-bet increased. CONCLUSIONS: HCZP ameliorated the symptoms of guinea pigs with CVA induced by OVA by regulating the Th1/Th2 imbalance and TLR4 receptors.

Resolvin D3 controls mouse and human TRPV1-positive neurons and preclinical progression of psoriasis.

Rationale: Psoriasis is a chronic inflammatory disease caused by a complex interplay between the immune and nervous systems with recurrent scaly skin plaques, thickened stratum corneum, infiltration and activation of inflammatory cells, and itch. Despite an increasing availability of immune therapies, they often have adverse effects, high costs, and dissociated effects on inflammation and itch. Activation of sensory neurons innervating the skin and TRPV1 (transient receptor potential vanilloid 1) are emerging as critical components in the pathogenesis of psoriasis, but little is known about their endogenous inhibitors. Recent studies have demonstrated that resolvins, endogenous lipid mediators derived from omega-3 fatty acids, are potent inhibitors of TRP channels and may offer new therapies for psoriasis without known adverse effects. Methods: We used behavioral, electrophysiological and biochemical approaches to investigate the therapeutic effects of resolvin D3 (RvD3), a novel family member of resolvins, in a preclinical model of psoriasis consisting of repeated topical applications of imiquimod (IMQ) to murine skin, which provokes inflammatory lesions that resemble human psoriasis. Results: We report that RvD3 specifically reduced TRPV1-dependent acute pain and itch in mice. Mechanistically, RvD3 inhibited capsaicin-induced TRPV1 currents in dissociated dorsal root ganglion (DRG) neurons via the N-formyl peptide receptor 2 (i.e. ALX/FPR2), a G-protein coupled receptor. Single systemic administration of RvD3 (2.8 mg/kg) reversed itch after IMQ, and repeated administration largely prevented the development of both psoriasiform itch and skin inflammation with concomitant decreased in calcitonin gene-related peptide (CGRP) expression in DRG neurons. Accordingly, specific knockdown of CGRP in DRG was sufficient to prevent both psoriasiform itch and skin inflammation similar to the effects following RvD3 administration. Finally, we elevated the translational potential of this study by showing that RvD3 significantly inhibited capsaicin-induced TRPV1 activity and CGRP release in human DRG neurons. Conclusions: Our findings demonstrate a novel role for RvD3 in regulating TRPV1/CGRP in mouse and human DRG neurons and identify RvD3 and its neuronal pathways as novel therapeutic targets to treat psoriasis.

Flare Size but Not Intensity Reflects Histamine-Induced Itch.

INTRODUCTION: Flare reactions arise due to the release of vasodilators from sensory nerves caused by antidromic transmission of action potentials after the induction of itch. OBJECTIVE: We investigated the link between flare and itch using 3 models of itch. METHODS: Skin provocations with histamine, capsaicin, and cowhage were performed in 31 subjects. Itch was quantified using the visual analog scale. Flare was assessed using laser speckle contrast imaging (LSCI) and digital photography. RESULTS: The duration, intensity, and area under the curve of histamine-induced itch correlated with the area of increased blood flow measured with LSCI (r = 0.545, p = 0.002; r = 0.575, p = 0.001; and r = 0.649, p < 0.001, respectively). Itch and skin blood flow in response to capsaicin or cowhage did not correlate. CONCLUSION: In histamine-induced skin inflammation, itch and increased blood flow are linked. Thus, the area of histamine-induced flare may be used as a surrogate marker for histamine-induced itch.

Resilience to capsaicin-induced mitochondrial damage in trigeminal ganglion neurons.

Capsaicin is an agonist of transient receptor potential cation channel subfamily V member 1 (TRPV1). Strong TRPV1 stimulation with capsaicin causes mitochondrial damage in primary sensory neurons. However, the effect of repetitive and moderate exposure to capsaicin on the integrity of neuronal mitochondria remains largely unknown. Our electron microscopic analysis revealed that repetitive stimulation of the facial skin of mice with 10 mM capsaicin induced short-term damage to the mitochondria in small-sized trigeminal ganglion neurons. Further, capsaicin-treated mice exhibited decreased sensitivity to noxious heat stimulation, indicating TRPV1 dysfunction, in parallel with the mitochondrial damage in the trigeminal ganglion neurons. To analyze the capsaicin-induced mitochondrial damage and its relevant cellular events in detail, we performed cell-based assays using TRPV1-expressing PC12 cells. Dose-dependent capsaicin-mediated mitochondrial toxicity was observed. High doses of capsaicin caused rapid destruction of mitochondrial internal structure, while low doses induced mitochondrial swelling. Further, capsaicin induced a dose-dependent loss of mitochondria and autophagy-mediated degradation of mitochondria (mitophagy). Concomitantly, transcriptional upregulation of mitochondrial proteins, cytochrome c oxidase subunit IV, Mic60/Mitofilin, and voltage-dependent anion channel 1 was observed, which implied induction of mitochondrial biogenesis to compensate for the loss of mitochondria. Collectively, although trigeminal ganglion neurons transiently exhibit mitochondrial damage and TRPV1 dysfunction following moderate capsaicin exposure, they appear to be resilient to such a challenge. Our in vitro data show a dose-response relationship in capsaicin-mediated mitochondrial toxicity. We postulate that induction of mitophagy and mitochondrial biogenesis in response to capsaicin stimulation play important roles in repairing the damaged mitochondrial system.

Amelioration from the ocular irritant Capsaicin: development and assessment of a Capsazepine in situ gel system for ocular delivery.

BACKGROUND: Defense personnel utilize capsaicin-based ocular sprays as non-lethal agents for law implementation during instances of mob violence. This study involves the capsaicin antagonist Capsazepine and the investigation of whether Capsazepine's antagonistic approach can be favorably utilized for defense utilization to block capsaicin-initiated pain and inflammation via the ocular pathway. RESEARCH DESIGN AND METHODS: Ocular capsazepine in situ gels were prepared with polymers Pluronic F-127 and Chitosan; optimized formulation was quantified in ocular tissues chromatographically and by in vivo live ocular imaging; anti-inflammatory efficacy was determined by eye irritation testing, corneal and retinal imaging, ocular prostaglandin estimation, and by viability and proliferation testing using human ocular cell lines, etc. RESULTS: A physicochemically stable Capsazepine in situ gel was formulated which showed little ocular irritation, considerable transcorneal permeation; was precisely quantified in ocular tissues by gas chromatography and in vivo live ocular imaging; showed anti-inflammatory properties against capsaicin by eye imaging experiments, prostaglandin declination and showed acceptable cytocompatibility when studied using human ocular cell lines. CONCLUSIONS: The fabricated in situ Capsazepine gel system might be promising for ocular delivery as it appears a pharmacologically potent and safe development, suitable for utilization in the ocular clinical therapy, provided there is additional research to substantiate it.

Female Guinea Pig Model for Cough Studies and Its Response to Most Common Tussive Substances.

Laboratory research of cough reflex utilizes almost exclusively male guinea pigs - a practice that represents a significant obstacle in the successful translation of results into clinical practice. Chronic hypersensitivity cough syndrome affects mostly postmenopausal women and it represents significant decrease in patient's quality of life. No cause for such exaggerated cough can be found, therefore this condition cannot be treated appropriately. One of the reasons leading to the lack of relevant data about mechanisms responsible for hypersensitivity of cough related pathways is nowadays widely discussed gender bias, which is present in nearly all branches of biomedical research. Since gender differences in cough reflex physiology do exist in humans, it would be reasonable to study cough-related phenomena on both sexes of laboratory animals. In this study, we focused on detailed characterization of cough response of female guinea pigs to aerosols of commonly used tussive agents (capsaicin, distilled water, allyl isothiocyanate, cinnamaldehyde, citric acid). In pooled data from multiple challenges we found no statistical difference in number of cough and cough latency between sexes. Based on our results we conclude that the utilization of female guinea pigs model does not lead to messy data and can be used in basic cough research.

Capsaicinoids from hot pepper (Capsicum annuum L.) and their phytotoxic effect on seedling growth of lettuce (Lactuca sativa L.).

One new capsaicinoid, N-vanillyl-4E,6E-dien-8-methylnonanamide (4), along with nine known capsaicinoids, capsaicin (1), dihydrocapsaicin (2), N-vanillyloctanamide (3), nordihydrocapsaicin (5), N-vanillyldecanamide (6), homocapsaicin (7), N-vanillyl-4,8-dimethylnonanamide (8), homodihydrocapsaicin II (9), and homodihydrocapsaicin I (10) were isolated from the fruits of Capsicum annuum using semi-preparative high-performance liquid chromatography. The structural characterizations of the isolated compounds were elucidated by spectroscopic data and comparison with the literatures. Bioassays showed that the isolated capsaicinoids significantly reduced the radical length of Lactuca sativa seedling, this inhibition being dose-dependent.

Toxicokinetic Study of a Gastroprotective Dose of Capsaicin by HPLC-FLD Method.

BACKGROUND: A low dose of capsaicin and its natural homologs and analogs (capsaicinoids) have shown to prevent development of gastric mucosal damage of alcohol and non-steroid anti-inflammatory drugs. Based on this experimental observation, a drug development program has been initiated to develop per os applicable capsaicin containing drugs to eliminate gastrointestinal damage caused by non-steroid anti-inflammatory drugs. METHODS: As a part of this program, a sensitive and selective reverse-phase high-performance liquid chromatography-based method with fluorescence detection has been developed for quantification of capsaicin and dihydrocapsaicin in experimental dog's plasma. RESULTS: The method was evaluated for a number of validation characteristics (selectivity, repeatability, and intermediate precision, LOD, LOQ, and calibration range). The limit of detection (LOD) was 2 ng/mL and the limit of quantification (LOQ) was 10 ng/mL for both capsaicin and dihydrocapsaicin. The method was used for analysis of capsaicin and dihydrocapsaicin in the plasma samples obtained after per os administration of low doses (0.1, 0.3, and 0.9 mg/kg bw) of Capsaicin Natural (USP 29) to the experimental animals. CONCLUSIONS: The obtained results indicated that the administered capsaicinoids did not reach the general circulation.