Lycium barbarum Polysaccharides and Capsaicin Inhibit Oxidative Stress, Inflammatory Responses, and Pain Signaling in Rats with Dextran Sulfate Sodium-Induced Colitis.

Ulcerative colitis (UC) is an inflammatory disease with chronic relapsing symptoms. This study investigated the effects of Lycium barbarum polysaccharides (LBP) and capsaicin (CAP) in dextran sulfate sodium (DSS)-induced UC rats. Rats were divided into normal, DSS-induced UC, and UC treated with 100 mg LBP/kg bw, 12 mg CAP/kg bw, or 50 mg LBP/kg bw and 6 mg CAP/kg bw. Rats were fed LBP or CAP orally by gavage for 4 weeks, and UC model was established by feeding 5% DSS in drinking water for 6 days during week 3. Oral CAP and mixture significantly reduced disease activity index. Oral LBP significantly decreased serum malondialdehyde, interleukin (IL)-6, colonic tumor necrosis factor (TNF)-α levels, and protein expression of transient receptor potential cation channel V1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1), but increased serum catalase activity. Oral CAP significantly suppressed serum IL-6, colonic TRPV1 and TRPA1 protein expression, but elevated IL-10 levels, serum superoxide dismutase and catalase activities. The mixture of LBP and CAP significantly reduced serum IL-6, colonic TNF-α and TRPA1 protein. In conclusion, administration of LBP and/or CAP attenuate DSS-induced UC symptoms through inhibiting oxidative stress, proinflammatory cytokines, and protein expression of TRPV1 and TRPA1.

Development and Validation of an HPLC Method for Simultaneous Determination of Capsaicinoids and Camphor in Over-the-Counter Medication for Topical Use.

A reverse-phase high-performance liquid chromatography method was developed to determine and quantify capsaicin (trans-8-methyl-N-vanillyl-6- nonenamid), dihydrocapsaicin (8-methyl-N-vanillylnonanamide), and camphor (trimethylbicyclo[2.2.1]heptan-2-one). It is applicable in analyses of over-the-counter (OTC) medications for topical use and raw materials such as chili pepper oleoresin. Chromatographic separation was carried out on a C18 column using an isocratic flow of the mobile phase containing acetonitrile and ultrapure water in a ratio of 2:3, with pH adjusted to 3.2 using glacial acetic acid, and a flow rate of 1.5 mL/min. The concentration of the eluting compounds was monitored by a diode-array detector at a wavelength of 281 nm. The method was evaluated for several validation parameters, including selectivity, accuracy (confidence intervals < 0.05%), repeatability, and intermediate precision. The limit of detection (LOD) was determined to be 0.070 µg/mL for capsaicin, 0.211 µg/mL for dihydrocapsaicin, and 0.060 µg/mL for camphor. The limit of quantification (LOQ) was determined to be 0.212 µg/mL for capsaicin, 0.640 µg/mL for dihydrocapsaicin, and 0.320 µg/mL for camphor. Linearity was set in the range of 2.5-200 µg/mL for capsaicin and dihydrocapsaicin and 25-2000 µg/mL for camphor. The suggested analytical method can be used for quality control of formulated pharmaceutical products containing capsaicinoids, camphor, and propolis.

Capsaicin and Its Effect on Exercise Performance, Fatigue and Inflammation after Exercise.

Capsaicin (CAP) activates the transient receptor potential vanilloid 1 (TRPV1) channel on sensory neurons, improving ATP production, vascular function, fatigue resistance, and thus exercise performance. However, the underlying mechanisms of CAP-induced ergogenic effects and fatigue-resistance, remain elusive. To evaluate the potential anti-fatigue effects of CAP, 10 young healthy males performed constant-load cycling exercise time to exhaustion (TTE) trials (85% maximal work rate) after ingestion of placebo (PL; fiber) or CAP capsules in a blinded, counterbalanced, crossover design, while cardiorespiratory responses were monitored. Fatigue was assessed with the interpolated twitch technique, pre-post exercise, during isometric maximal voluntary contractions (MVC). No significant differences (p > 0.05) were detected in cardiorespiratory responses and self-reported fatigue (RPE scale) during the time trial or in TTE (375 ± 26 and 327 ± 36 s, respectively). CAP attenuated the reduction in potentiated twitch (PL: -52 ± 6 vs. CAP: -42 ± 11%, p = 0.037), and tended to attenuate the decline in maximal relaxation rate (PL: -47 ± 33 vs. CAP: -29 ± 68%, p = 0.057), but not maximal rate of force development, MVC, or voluntary muscle activation. Thus, CAP might attenuate neuromuscular fatigue through alterations in afferent signaling or neuromuscular relaxation kinetics, perhaps mediated via the sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) pumps, thereby increasing the rate of Ca2+ reuptake and relaxation.

Combination of TRP channel dietary agonists induces energy expending and glucose utilizing phenotype in HFD-fed mice.

BACKGROUND: Bioactive dietary constituents activating Transient receptor potential (TRP) channels have emerged as promising candidates for the prevention of metabolic disorders. OBJECTIVE: The present study is an attempt to evaluate anti-obesity potential of a dietary TRP-based tri-agonist, combination of sub-effective doses of capsaicin (TRPV1 agonist), menthol (TRPM8 agonist), and cinnamaldehyde (TRPA1 agonist) in high-fat diet (HFD)-fed mice. DESIGN: Male C57BL/6 J mice divided into three groups (n = 8), were fed on normal pellet diet (NPD), or high-fat diet (HFD) (60% energy by fat) and HFD + CB (combination of capsaicin 0.4 mg/Kg, menthol 20 mg/Kg, and cinnamaldehyde 2 mg/Kg; p.o) for 12 weeks. Effects on HFD-induced weight gain, biochemical, histological and genomic changes in the WAT, BAT, liver and hypothalamus tissues were studied. RESULTS: Administration of tri-agonist prevented HFD-induced increase in weight gain, improved altered morphometric parameters, glucose homeostasis, and adipose tissue hypertrophy. Tri-agonist supplementation was found to induce browning of white adipose tissue and promote brown adipose tissue activation. Enhanced glucose utilization and prevention of lipid accumulation and insulin resistance in the liver was observed in mice supplemented with a tri-agonist. CONCLUSION: The present work provides evidence that the new approach based on combination of sub-effective doses of TRP channel agonists (TRI-AGONIST) can be employed to develop concept-based functional food for therapeutic and preventive strategies against HFD-associated pathological complications.

Evidence for engagement of the nucleus of the solitary tract in processing intestinal chemonociceptive input irrespective of conscious pain response in healthy humans.

ABSTRACT: Neuroimaging studies have revealed important pathomechanisms related to disorders of brain-gut interactions, such as irritable bowel syndrome and functional dyspepsia. More detailed investigations aimed at neural processing in the brainstem, including the key relay station of the nucleus of the solitary tract (NTS), have hitherto been hampered by technical shortcomings. To ascertain these processes in more detail, we used multiecho multiband 7T functional magnetic resonance imaging and a novel translational experimental model based on a nutrient-derived intestinal chemonociceptive stimulus. In a randomized cross-over fashion, subjects received duodenal infusion of capsaicin (the pungent principle in red peppers) and placebo (saline). During infusion, functional magnetic resonance imaging data and concomitant symptom ratings were acquired. Of 26 healthy female volunteers included, 18 were included in the final analysis. Significantly increased brain activation over time during capsaicin infusion, as compared with placebo, was observed in brain regions implicated in pain processing, in particular the NTS. Brain activation in the thalamus, cingulate cortex, and insula was more pronounced in subjects who reported abdominal pain (visual analogue scale > 10 mm), as compared with subjects who experienced no pain. On the contrary, activations at the level of the NTS were independent of subjective pain ratings. The current experimental paradigm therefore allowed us to demonstrate activation of the principal relay station for visceral afferents in the brainstem, the NTS, which was engaged irrespective of the conscious pain response. These findings contribute to understanding the fundamental mechanism necessary for developing novel therapies aimed at correcting disturbances in visceral afferent pain processing.

Lactobacillus rhamnosus attenuates Thai chili extracts induced gut inflammation and dysbiosis despite capsaicin bactericidal effect against the probiotics, a possible toxicity of high dose capsaicin.

Because of a possible impact of capsaicin in the high concentrations on enterocyte injury (cytotoxicity) and bactericidal activity on probiotics, Lactobacillus rhamnosus L34 (L34) and Lactobacillus rhamnosus GG (LGG), the probiotics derived from Thai and Caucasian population, respectively, were tested in the chili-extract administered C57BL/6 mice and in vitro experiments. In comparison with placebo, 2 weeks administration of the extract from Thai chili in mice caused loose feces and induced intestinal permeability defect as indicated by FITC-dextran assay and the reduction in tight junction molecules (occludin and zona occludens-1) using fluorescent staining and gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, the chili extracts also induced the translocation of gut pathogen molecules; lipopolysaccharide (LPS) and (1→3)-ß-d-glucan (BG) and fecal dysbiosis (microbiome analysis), including reduced Firmicutes, increased Bacteroides, and enhanced total Gram-negative bacteria in feces. Both L34 and LGG attenuated gut barrier defect (FITC-dextran, the fluorescent staining and gene expression of tight junction molecules) but not improved fecal consistency. Additionally, high concentrations of capsaicin (0.02-2 mM) damage enterocytes (Caco-2 and HT-29) as indicated by cell viability test, supernatant cytokine (IL-8), transepithelial electrical resistance (TEER) and transepithelial FITC-dextran (4.4 kDa) but were attenuated by Lactobacillus condition media (LCM) from both probiotic-strains. The 24 h incubation with 2 mM capsaicin (but not the lower concentrations) reduced the abundance of LGG (but not L34) implying a higher capsaicin tolerance of L34. However, Lactobacillus rhamnosus fecal abundance, using qRT-PCR, of L34 or LGG after 3, 7, and 20 days of the administration in the Thai healthy volunteers demonstrated the similarity between both strains. In conclusion, high dose chili extracts impaired gut permeability and induced gut dysbiosis but were attenuated by probiotics. Despite a better capsaicin tolerance of L34 compared with LGG in vitro, L34 abundance in feces was not different to LGG in the healthy volunteers. More studies on probiotics with a higher intake of chili in human are interesting.

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.

How different experimental models of secondary hyperalgesia change the nociceptive flexion reflex.

OBJECTIVE: In this neurophysiological study in healthy humans, we assessed how central sensitization induced by either high-frequency stimulation (HFS) or topical capsaicin application modulates features of the RIII reflex response. The ability of these stimuli to engage the endogenous pain modulatory system was also tested. METHODS: In 26 healthy participants we elicited an RIII reflex using suprathreshold stimulation of the sural nerve. Subsequently HFS or capsaicin were applied to the foot and the RIII reflex repeated after 15 minutes. Contact heating of the volar forearm served as the heterotopic test stimulus to probe activation of the endogenous pain modulatory system. RESULTS: HFS significantly reduced the pain threshold by 29% and the RIII reflex threshold by 20%. Capsaicin significantly reduced the pain threshold by 17% and the RIII reflex threshold by 18%. Both HFS and capsaicin left RIII reflex size unaffected. Numerical Rating Scale (NRS) pain scores elicited by the heterotopic noxious heat stimulus were unaffected by capsaicin and slightly increased by HFS. CONCLUSIONS: HFS and capsaicin similarly modulated the pain threshold and RIII reflex threshold, without a concomitant inhibitory effect of the endogenous pain modulatory system. SIGNIFICANCE: Our neurophysiological study supports the use of the RIII reflex in investigating central sensitization in humans.

Role of nitric oxide, bradykinin B2 receptor, and TRPV1 in the airway alterations caused by simvastatin in rats.

Dry cough has been reported in patients receiving statin therapy. However, the underlying mechanism or other possible alterations in the airways induced by statins remain unknown. Thus, the aim of this study was to evaluate whether simvastatin promotes alterations in airways, such as bronchoconstriction and plasma extravasation, as well as the mechanism involved in these events. Using methods to detect alterations in airway resistance and plasma extravasation, we demonstrated that simvastatin [20 mg/kg, intravenous (i.v.)] caused plasma extravasation in the trachea (79.8 + 14.8 µg/g/tissue) and bronchi (73.3 + 8.8 µg/g/tissue) of rats, compared to the vehicle (34.2 + 3.6 µg/g/tissue and 29.3 + 5.3 µg/g/tissue, respectively). NG-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg, intraperitoneal), a nitric oxide (NO) synthase inhibitor, Icatibant [HOE 140, 10 nmol/50 µl, intratracheal (i.t.)], a bradykinin B2 antagonist, and capsazepine (100 nmol/50 µl, i.t.), a TRPV1 antagonist, attenuated simvastatin-induced plasma extravasation. Simvastatin (5, 10 and 20 mg/kg) did not cause bronchoconstriction per se, but exacerbated the bronchoconstrictive response to bradykinin (30 nmol/kg, i.v.), a B2 agonist (0.7 + 0.1 ml/H2O), or capsaicin (30 nmol/kg, i.v.), a TRPV1 agonist (0.8 + 0.1 ml/H2O), compared to the vehicle (0.1 + 0.04 ml/H2O and 0.04 + 0.01 ml/H2O, respectively). The bronchoconstriction elicited by bradykinin (100 nmol/kg, i.v.) in simvastatin non-treated rats was inhibited by L-NAME. The exacerbation of bronchoconstriction induced by bradykinin or capsaicin in simvastatin-treated rats was inhibited by L-NAME, HOE 140 or capsazepine. These results suggest that treatment with simvastatin promotes the release of bradykinin, which, via B2 receptors, releases NO that can then activate the TRPV1 to promote plasma extravasation and bronchoconstriction.

Estimation of Dietary Capsaicinoid Exposure in Korea and Assessment of Its Health Effects.

The consumption of capsaicinoids, the active components in chili peppers, has been associated with both positive and negative health effects, and the level of capsaicinoid exposure may be an important determinant. Dietary capsaicinoid exposure was estimated using a previously developed database for capsaicinoid content and a 24-h dietary recall dataset obtained from the Korea National Health and Nutrition Examination Survey. The estimated consumption level was evaluated to determine its potential effects on weight reduction and gastrointestinal distress. The estimated daily mean capsaicinoid intake was 3.25 mg (2.17 mg capsaicin), and most Koreans consumed 1-30 mg of capsaicinoids (0.67-20 mg capsaicin) in a day. No adverse effect of capsaicin consumption was reported other than abdominal pain. For long-term repeated consumption, 30 mg may be the maximum tolerable dose. However, the effects on body weight or energy balance were inconsistent in 4-12 week clinical studies conducted with various capsaicin doses (2-135 mg), which was likely due to the complex interplay between capsaicin dose, study length, and participant characteristics. Therefore, the capsaicin consumption of most Koreans was below the levels that may cause adverse effects. However, more long-term studies for the dose range of 2-20 mg are required to further characterize capsaicin's health benefits in Koreans.

In Vivo Calcium Imaging Visualizes Incision-Induced Primary Afferent Sensitization and Its Amelioration by Capsaicin Pretreatment.

Previous studies have shown that infiltration of capsaicin into the surgical site can prevent incision-induced spontaneous pain like behaviors and heat hyperalgesia. In the present study, we aimed to monitor primary sensory neuron Ca2+ activity in the intact dorsal root ganglia (DRG) using Pirt-GCaMP3 male and female mice pretreated with capsaicin or vehicle before the plantar incision. Intraplantar injection of capsaicin (0.05%) significantly attenuated spontaneous pain, mechanical, and heat hypersensitivity after plantar incision. The Ca2+ response in in vivo DRG and in in situ spinal cord was significantly enhanced in the ipsilateral side compared with contralateral side or naive control. Primary sensory nerve fiber length was significantly decreased in the incision skin area in capsaicin-pretreated animals detected by immunohistochemistry and placental alkaline phosphatase (PLAP) staining. Thus, capsaicin pretreatment attenuates incisional pain by suppressing Ca2+ response because of degeneration of primary sensory nerve fibers in the skin.SIGNIFICANCE STATEMENT Postoperative surgery pain is a major health and economic problem worldwide with ∼235 million major surgical procedures annually. Approximately 50% of these patients report uncontrolled or poorly controlled postoperative pain. However, mechanistic studies of postoperative surgery pain in primary sensory neurons have been limited to in vitro models or small numbers of neurons. Using an innovative, distinctive, and interdisciplinary in vivo populational dorsal root ganglia (DRG) imaging (>1800 neurons/DRG) approach, we revealed increased DRG neuronal Ca2+ activity from postoperative pain mouse model. This indicates widespread DRG primary sensory neuron plasticity. Increased neuronal Ca2+ activity occurs among various sizes of neurons but mostly in small-diameter and medium-diameter nociceptors. Capsaicin pretreatment as a therapeutic option significantly attenuates Ca2+ activity and postoperative pain.

Bioavailability of a Capsaicin Lipid Multi-particulate Formulation in Rats.

BACKGROUND AND OBJECTIVE: Because of the stomach-burning sensation it induces, capsaicin has been used at relatively low doses as a nutritional supplement, which has limited its bioavailability. The objective of this study was to investigate the serum bioavailability of capsaicin supplementation with or without a lipid multi-particulate (LMP) formulation. METHODS: Thirty-five rats were divided into five groups and administered capsaicin at either 0.2 or 1 mg/kg with or without the LMP formulation. Capsaicin bioavailability was assessed based on the area under the concentation-time curve (AUC), the time to peak concentration (Tmax), and the peak serum concentration (Cmax). RESULTS: For each formulation, the capsaicin Cmax was reached at 90 min and decreased thereafter. Serum capsaicin concentrations were greater in rats administered the higher dose of capsaicin (1 mg/kg) in the LMP formulation at all measurement times (P  ≤ 0.05). The AUC showed a significant increase, about 20%, when capsaicin was administered in the LMP formulation at the high dose (P = 0.002). The Tmax for oral capsaicin was similar whether or not administration was via the LMP formulation (P = 0.163). However, the Cmax of capsaicin increased in a dose-dependent manner (P < 0.05). Although the LMP formulation of the high dose of capsaicin resulted in a numerically higher Cmax, it was not statistically significantly higher (P = 0.068). CONCLUSIONS: The present work demonstrated that administration of capsaicin via the LMP formulation significantly impacted the pharmacokinetic parameters and the serum bioavailability of orally administered 1 mg/kg capsaicin in rats. The bioavailability of capsaicin in humans may also be increased by using the LMP formulation.

Efficacy of topical capsaicin for cannabinoid hyperemesis syndrome in a pediatric and adult emergency department.

INTRODUCTION: Cannabinoid hyperemesis syndrome (CHS) is a clinical diagnosis characterized by symptoms of recurrent nausea, vomiting, and severe abdominal pain in the setting of chronic cannabis use. Symptoms of CHS are frequently unresponsive to standard antiemetic therapy. Topical capsaicin applied to the abdomen has been cited as a potential effective agent for CHS however robust evidence is lacking. METHODS: This was a single-center retrospective cohort study to evaluate the efficacy of topical capsaicin in pediatric and adult patients presenting to the emergency department (ED) with suspected or confirmed CHS. The primary outcome assessed was if utilization of capsaicin for CHS resulted in more patients achieving an "efficacious" result, defined as only requiring ≤1 rescue medication for symptom relief after receiving capsaicin or after administration of the first agent in patients who did not receive capsaicin during their ED course. Secondary outcomes included total ED length of stay, time to discharge after administration of the reference agent (RA), proportion of patients requiring admission, total number of medication doses given for symptom relief, change in pain score and episodes of emesis, and proportion of patients returning to the ED within 24 h for the same complaint. Additional analyses were also performed to explore patient characteristics that may be predictive of capsaicin efficacy. RESULTS: 201 patients were included in the final analysis of which 25 were <21 years old and seen in the pediatric ED. A greater proportion of patients in the capsaicin group achieved the primary outcome of efficacy as compared to patients who did not receive capsaicin (55% vs 21%, p < 0.001, unadjusted OR 1.44 [95% CI 0.586-0.820]). There were no differences in secondary outcomes except for time to discharge after administration of the RA which was shorter in the capsaicin group (3.72 vs 6.11 h, p = 0.001). CONCLUSION: Significantly more patients in the capsaicin group experienced efficacy compared to patients who did not. Time to discharge after administration of the reference agent was shorter for those who received capsaicin compared to patients who did not. Administration of capsaicin did not influence patients' total number of medications received or total ED length of stay. Future research is needed to determine capsaicin's efficacy when utilized earlier in therapy, ideally upon initial diagnosis of CHS, and before additional adjunct medications are administered.

A randomized double blinded placebo controlled study to evaluate motor unit abnormalities after experimentally induced sensitization using capsaicin.

Central sensitization is a condition that represents a cascade of neurological adaptations, resulting in an amplification of nociceptive responses from noxious and non-noxious stimuli. However, whether this abnormality translates into motor output and more specifically, ventral horn abnormalities, needs to be further explored. Twenty healthy participants aged 20-70 were randomly allocated to topical capsaicin or a placebo topical cream which was applied onto their left upper back to induce a transient state of sensitization. Visual analogue scale (VAS) ratings of pain intensity and brush allodynia score (BAS) were used to determine the presence of pain and secondary allodynia. Surface electromyography (sEMG) and intramuscular electromyography (iEMG) were used to record motor unit activity from the upper trapezius and infraspinatus muscles before and twenty minutes after application of capsaicin/placebo. Motor unit recruitment and variability were analyzed in the sEMG and iEMG, respectively. An independent t-test and Kruskal-Wallis H test were performed on the data. The sEMG results demonstrated a shift in the motor unit recruitment pattern in the upper trapezius muscle, while the iEMG showed a change in motor unit variability after application of capsaicin. These results suggest that capsaicin-induced central sensitization may cause changes in ventral horn excitability outside of the targeted spinal cord segment, affecting efferent pathway outputs. This preclinical evidence may provide some explanation for the influence of central sensitization on changes in movement patterns that occur in patients who have pain encouraging of further clinical investigation.Clinical Trials registration number: NCT04361149; date of registration: 24-Apr-2020.

Capsaicin attenuates imiquimod-induced epidermal hyperplasia and cutaneous inflammation in a murine model of psoriasis.

Psoriasis is one of the most common chronic inflammatory diseases that is characterized by well-defined erythematous plaques, with typical histopathological findings of lymphocytic infiltration and epidermal hyperplasia. Topical treatments of psoriasis are either associated with limited response or with side effects. Up to date, topicals targeting neuroimmune axis in psoriasis or psoriasiform dermatitis have not been explored. Here, we investigated whether percutaneous delivery of capsaicin could attenuate the pathological change of psoriasiform inflammation. Imiquimod-induced psoriasis-like murine model was used to evaluate therapeutic effects from topical application of capsaicin. An additional model of psoriasiform dermatitis induced by direct IL-23 injection was used to identify the level of action from capsaicin in this neuroimmune axis. Cutaneous inflammation was assessed by erythema level and ear thickness change. Key cytokines, infiltrating cells in the skin, and draining lymph node cells were investigated. The results showed that capsaicin administration obstructed the activation of IL-23/IL-17 pathway induced by imiquimod, presenting with significantly reduced psoriasiform dermatitis both in gross appearance and microscopic features. Tissue gene expression of psoriatic core cytokines induced by imiquimod (including IL-23, IL-17A, IL-22, TNF-α, and IL-6) were greatly decreased by capsaicin application. This protective effect from capsaicin could be hampered by direct intradermal injection of IL-23. CONCLUSION: Epicutaneous delivery of capsaicin on imiquimod-treated murine skin could significantly decrease expression of multiple inflammatory cytokines and the severity of prototypic change of psoriasiform inflammation. The beneficial effect imposed by capsaicin reinforces the neuroimmune contribution towards psoriasiform inflammation and provides a potential non-steroidal therapeutic alternative for topical treatment of psoriasiform dermatitis.

Chronic capsiate supplementation increases fat-free mass and upper body strength but not the inflammatory response to resistance exercise in young untrained men: a randomized, placebo-controlled and double-blind study.

BACKGROUND: Acute capsaicinoid and capsinoid supplementation has endurance and resistance exercise benefits; however, if these short-term performance benefits translate into chronic benefits when combined with resistance training is currently unknown. This study investigated changes of chronic Capsiate supplementation on muscular adaptations, inflammatory response and performance in untrained men. METHODS: Twenty untrained men were randomized to ingest 12 mg Capsiate (CAP) or placebo in a parallel, double-blind design. Body composition and performance were measured at pre-training and after 6 weeks of resistance training. An acute resistance exercise session test was performed pre and post-intervention. Blood samples were collected at rest and post-resistance exercise to analyze Tumor necrosis factor- (TNF-), Soluble TNF- receptor (sTNF-r), Interleukin-6 (IL-6) and Interleukin-10 (IL-10). RESULTS: Exercise and CAP supplementation increased fat-free mass in comparison to baseline by 1.5 kg (P < 0.001), however, the majority of the increase (1.0 kg) resulted from an increase in total body water. The CAP change scores for fat-free mass were significantly greater in comparison to the placebo (CAP ∆%= 2.1 ± 1.8 %, PLA ∆%= 0.7 ± 1.3 %, P = 0.043) and there was a significant difference between groups in the bench press exercise (P = 0.034) with greater upper body strength change score for CAP (∆%= 13.4 ± 9.1 %) compared to placebo (∆%= 5.8 ± 5.2 %), P = 0.041. CAP had no effect on lower body strength and no supplementation interactions were observed for all cytokines in response to acute resistance exercise (P > 0.05). CONCLUSION: Chronic Capsiate supplementation combined with resistance training during short period (6 weeks) increased fat-free mass and upper body strength but not inflammatory response and performance in young untrained men.

Interest of a standardized hypnotic message for the reduction of pain and anxiety in cancer patients treated by capsaicin patch for neuropathic pain: a randomized controlled trial.

BACKGROUND: Neuropathic pain is characterized by spontaneous painful symptoms. Medical therapies include the use of a capsaicin 8% patch (Qutenza®, Grünenthal Gmbh, Germany), and patients may experience a sharp burning sensation at application and removal of the patch. This study aimed to evaluate the impact of playing a standardized hypnosis recording during application, on the pain and anxiety induced by capsaicin treatment. METHODS: In a randomized, controlled trial, we assessed the benefits of the intervention firstly on pain and secondly on anxiety, as measured using numerical rating scales. All patients had application of the capsaicin patch, including the possibility for the patient to apply a cold patch. Participants were randomly assigned to one of 3 groups, namely the "Standard group" (no intervention), "Hypnosis group", in which a standardized hypnotic message was played during application, or the "Music group" in which relaxing music was played during application of the patch. RESULTS: Sixty-nine patients were included. Overall, there was no significant difference in pain scores between groups (p = 0.355). Compared to standard application, anxiety was significantly lower in the hypnosis group after application (p = 0.007), with no significant difference between the standard and music arms (p = 0.271), or between the hypnosis and music arms (p = 0.423). CONCLUSIONS: Listening to a standardized hypnotic message during application of a capsaicin patch was found to significantly lower anxiety. These findings indicate that the use of a hypnotic message can reduce discomfort and warrant its evaluation in other indications of pain or anxiety during treatment procedures. TRIAL REGISTRATION: NCT02822625 .

Dose Escalation and Safety of Capsaicin for Cerebral Perfusion Augmentation: A Pilot Study.

Background and Purpose: Sphenopalatine ganglion (SPG) electrical stimulation has been studied in the setting of acute ischemic stroke to enhance collateral flow. Capsaicin poses an alternative to chemically stimulate the sphenopalatine ganglion. Therefore, the objective of this study was to determine the safety and effect of increasing doses of capsaicin upon serial transcranial Doppler markers of cerebral blood flow. Methods: We performed serial transcranial Doppler testing in 30 healthy volunteers divided into 5 equal groups. Capsaicin doses ranged from 33 to 165 µMol. We recorded peak systolic and end-diastolic velocities in the middle cerebral artery, arterial pressure, and perceived pungency in 5-minute intervals up to 20 minutes. We then calculated the mean velocity, the pulsatility index, and the cerebral blood flow index. Results: The participants' median age was 21 years (range, 5 years); all reported consumption of capsaicin in their diets. After and during the study, none reported side effects. Perceived pungency peaked at 5 minutes, and by the 20-minute mark, none perceived any pungency. All the tested doses produced the same pattern, consisting of augmentation of the middle cerebral artery mean velocity with the pulsatility index's diminution. The effects peaked between the 5- and the 10-minute measurements and then returned to basal levels except for the 66-µMol doses, which produced a sustained effect. We found no correlation between perceived pungency and dose, but the middle cerebral artery mean velocity was strongly correlated with the dose administered. Conclusions: This study provides evidence supporting the safety and tolerability of oral capsaicin in a population of healthy volunteers. Capsaicin appears to produce effects similar to those of sphenopalatine ganglion electrical stimulation. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04545892.

A novel computational technique for the quantification of temporal summation in healthy individuals.

BACKGROUND: The pathophysiology of chronic musculoskeletal pain is linked to the neurophysiologic condition known as central sensitization. Developing reliable, sensitive and clinically feasible techniques for quantifying central sensitization is a timely priority for advancing the field of chronic pain diagnosis and management. OBJECTIVE: To compare the sensitivity of the Windup Ratio, a commonly employed Quantitative Sensory Testing (QST) technique, to a novel approach, the Sumsquare method, for detecting changes in experimentally induced central sensitization. DESIGN: Individual, randomized, controlled experimental study. METHODS: A total of 37 subjects assigned to experimental (N = 18) and control (N = 19) groups. Central sensitization was experimentally induced in the C5-C6 spinal segments using topical capsaicin (0.075%); controls received a non-sensitizing placebo (Lubriderm). Windup (temporal summation) was assessed using weighted pinpricks (MRC Systems, Heidelberg, Germany) applied within regions of secondary hyperalgesia surrounding the topical capsaicin. A train of 10 stimuli was applied at baseline, 10, 20 and 30 min post-topical application and participants provided numeric pain ratings after each pinprick application. Sumsquare and Windup Ratio outcomes were calculated using the pain rating data. RESULTS: Sumsquare outcome was significantly increased at all time points (10, 20, 30 min) post-sensitization (p < 0.05); in contrast, no differences in Windup Ratio from baseline were observed at any time point post-sensitization (p > 0.05). CONCLUSIONS: Sumsquare outcome offers greater sensitivity than Windup Ratio for detecting changes in experimentally induced central sensitization. These findings introduce a novel method for assessing changes in central sensitization in patients presenting with chronic musculoskeletal pain hypersensitivity.

No Influence of Nonivamide-nicoboxil on the Peak Power Output in Competitive Sportsmen.

Recent studies have shown that the oxygenated hemoglobin level can be enhanced during rest through the application of nonivamide-nicoboxil cream. However, the effect of nonivamide-nicoboxil cream on oxygenation and endurance performance under hypoxic conditions is unknown. Therefore, the purpose of this study was to investigate the effects of nonivamide-nicoboxil cream on local muscle oxygenation and endurance performance under normoxic and hypoxic conditions. In a cross-over design, 13 athletes (experienced cyclists or triathletes [age: 25.2±3.5 years; VO2max 62.1±7.3 mL·min-1·kg-1]) performed four incremental exercise tests on the cycle ergometer under normoxic or hypoxic conditions, either with nonivamide-nicoboxil or placebo cream. Muscle oxygenation was recorded with near-infrared spectroscopy. Capillary blood samples were taken after each step, and spirometric data were recorded continuously. The application of nonivamide-nicoboxil cream increased muscle oxygenation at rest and during different submaximal workloads as well as during physical exhaustion, irrespective of normoxic or hypoxic conditions. Overall, there were no significant effects of nonivamide-nicoboxil on peak power output, maximal oxygen uptake or lactate concentrations. Muscle oxygenation is significantly higher with the application of nonivamide-nicoboxil cream. However, its application does not increase endurance performance.