Research on the antipruritic active ingredients of Mikania micrantha.

Mikania micrantha is a perennial liana of the genus Mikania of the Asteraceae family. It is a commonly used medicine in South America for treating fever, malaria, dysentery, snake bites, etc. Because of its strong adaptability and ability to inhibit the growth of its associated plants, Mikania micrantha is considered an invasive species in China and is known as a plant killer. Preliminary studies have shown that Mikania micrantha has an antipruritic effect, but the antipruritic active substance is not yet clear. In this study, a 4-aminopyridine-induced itching model in mice was used to determine the antipruritic effects of petroleum ether, ethyl acetate, ethanol extraction site, and Mikania micrantha volatile oil. GC-MS was used to analyze the components of the antipruritic fractions, combined with mice itch-causing models to study the antipruritic effects of ß-caryophyllene and humulene. The safety of ß-caryophyllene was preliminarily evaluated through the acute toxicity test of mice skin. The ethyl acetate and volatile oil of Mikania micrantha have apparent antipruritic effects. Humulene and ß-caryophyllene have a quantitative-effective relationship to inhibit itching in mice. The acute toxicity test of mouse skin showed that ß-caryophyllene has no acute toxicity. This study indicated that the main antipruritic active ingredients of Mikania micrantha are ß-caryophyllene and humulene.

Borneol exerts its antipruritic effects by inhibiting TRPA1 and activating TRPM8.

ETHNOPHARMACOLOGICAL RELEVANCE: Borneol is a long-established traditional Chinese medicine that has been found to be effective in treating pain and itchy skin. However, whether borneol has a therapeutic effect on chronic itch and its related mechanisms remain unclear. AIM OF THE STUDY: To investigate the antipruritic effect of borneol and its molecular mechanism. MATERIALS AND METHODS: DrugBAN framework and molecular docking were applied to predict the targets of borneol, and the calcium imaging or patch-clamp recording analysis were used to detect the effects of borneol on TRPA1, TRPM8 or TRPV3 channels in HEK293T cells. In addition, various mouse models of acute itch and chronic itch were established to evaluate the antipruritic effects of borneol on C57BL/6J mice. Then, the borneol-induced pruritic relief was further investigated in Trpa1-/-, Trpm8-/-, or Trpa1-/-/Trpm8-/- mice. The effects of borneol on the activation of TRPM8 and the inhibition of TRPA1 were also measured in dorsal root ganglia neurons of wild-type (WT), Trpm8-/- and Trpv1-/- mice. Lastly, a randomized, double-blind study of adult patients was conducted to evaluate the clinical antipruritic effect of borneol. RESULTS: TRPA1, TRPV3 and TRPM8 are the potential targets of borneol according to the results of DrugBAN algorithm and molecular docking. Calcium imaging and patch-clamp recording analysis demonstrated that borneol activates TRPM8 channel-induced cell excitability and inhibits TRPA1 channel-mediated cell excitability in transfected HEK293T cells. Animal behavior analysis showed that borneol can significantly reduce acute and chronic itch behavior in C57BL/6J mice, but this effect was eliminated in Trpa1-/-, Trpm8-/- mice, or at least in Trpa1-/-/Trpm8-/- mice. Borneol elicits TRPM8 channel induced [Ca2+]i responses but inhibits AITC or SADBE-induced activation of TRPA1 channels in dorsal root ganglia neurons of WT and Trpv1-/- mice, respectively. Furthermore, the clinical results indicated that borneol could reduce itching symptoms in patients and its efficacy is similar to that of menthol. CONCLUSION: Borneol has therapeutic effects on multiple pruritus models in mice and patients with chronic itch, and the mechanism may be through inhibiting TRPA1 and activating TRPM8.

Topical borneol relieves nonhistaminergic pruritus via targeting TRPA1 and TRPM8 channels in peripheral nerve terminals of mice.

Borneol has been used successfully for the treatment of itchy skin in traditional Chinese medicine. However, the antipruritic effect of borneol has rarely been studied, and the mechanism is unclear. Here, we showed that topical application of borneol on skin substantially suppressed pruritogen chloroquine- and compound 48/80-induced itching in mice. The potential targets of borneol, including transient receptor potential cation channel subfamily V member 3 (TRPV3), transient receptor potential cation channel subfamily A member 1 (TRPA1), transient receptor potential cation channel subfamily M member 8 (TRPM8), and gamma-aminobutyric acid type A (GABAA) receptor were pharmacologically inhibited or genetically knocked out one by one in mouse. Itching behavior studies demonstrated that the antipruritic effect of borneol is largely independent of TRPV3 and GABAA receptor, and TRPA1 and TRPM8 channels are responsible for a major portion of the effect of borneol on chloroquine-induced nonhistaminergic itching. Borneol activates TRPM8 and inhibits TRPA1 in sensory neurons of mice. Topical co-application of TRPA1 antagonist and TRPM8 agonist mimicked the effect of borneol on chloroquine-induced itching. Intrathecal injection of a group II metabotropic glutamate receptor antagonist partially attenuated the effect of borneol and completely abolished the effect of TRPM8 agonist on chloroquine-induced itching, suggesting that a spinal glutamatergic mechanism is involved. In contrast, the effect of borneol on compound 48/80-induced histaminergic itching occurs through TRPA1-and TRPM8-independent mechanisms. Our work demonstrates that borneol is an effective topical itch reliever, and TRPA1 inhibition and TRPM8 activation in peripheral nerve terminals account for its antipruritic effect.

Oxymatrine screened from Sophora flavescens by cell membrane immobilized chromatography relieves histamine-independent itch.

OBJECTIVES: This study aimed to discover the active compounds of Sophora flavescens Ait. (SF), the anti-itch effects and underlying mechanisms of oxymatrine (OMT), one of the bioactive compounds from SF. METHODS: Dorsal root ganglion cell membrane immobilized chromatography was used to screen potential anti-pruritic active compounds from SF. The scratching behaviour was analysed to systematically study the anti-pruritic effects of OMT in chloroquine- (CQ), peptide Ser-Leu-Ile-Gly-Arg-Leu- (SLIGRL), histamine- (HIS) and allyl-isothiocyanate-(AITC)-induced itch mice models. Real-time quantitative PCR, in-vivo study and molecular docking were employed to explore the underlying mechanisms. KEY FINDINGS: All in all, 21 compounds of SF were identified and 5 potential bioactive compounds were discovered. OMT significantly reduced scratching bouts in two HIS-independent itch models induced by CQ and SLIGRL but was not effective in the HIS-induced itch model. OMT reduced scratching bouts in a dose-dependent manner and decreased the messenger RNA (mRNA) expression of transient receptor potential ankyrin 1 (TRPA1) channel in two HIS-independent itch models; in addition, OMT reduced the wipes and scratching bouts induced by AITC. CONCLUSIONS: This study discovered five potential anti-pruritic compounds including OMT in the SF extract, and OMT has strong anti-pruritic effects in HIS-independent itch via TRPA1 channel.

[Effect of small dose capsaicin for treatment of pulmonary fibrosis in mice and its mechanism].

Objective: To observe whether the mechanism of small dose capsaicin (Cap) against pulmonary fibrosis in mouse is mediated by agitating transient receptor potential vanilloid 1 (TRPV1). Methods: A total of 60 BALB/c mice were randomly divided into control (CON) group, bleomycin (BLM)group, Cap (0.5, 1,2 mg/kg) groups and Cap (2 mg/kg) plus SB-452533 (2.5 mg/kg) group. C57BL/6 mice were intratracheally injected with 3.5 mg/kg BLM to induce pulmonary fibrosis model. Animals for drugs treatment received daily drug via subcutaneous injection for 21 days. The morphological changes and collagen deposition in lung tissues were analysed by HE staining, Masson staining and immunohistochemistry. The concentration of calcitonin gene-related peptide (CGRP) in plasma was determined by ELISA. The mRNA and (or) proteins levels of α-CGRP, ß-CGRP, collagen I, collagen III, E-Cadherin, zonula occludens-1 (ZO-1), vimentin, alpha smooth muscle actin (α-SMA), TRPV1, p-ERK1/2 and eukaryotic initiation factor 3a (eIF3a) were detected by qPCR and (or) Western blot. Results: Compared with the BLM group, small dose Cap significantly reduced bleomycin-induced pulmonary fibrosis in mice and obviously reversed alveolar epithelial cells epithelial-mesenchymal transition (EMT) (the expression of E-cadherin and ZO-1 were increased(P＜0.05 or P＜0.01)and the expression of α-SMA and Vimentin were decreased (P＜0.05 or P＜0.01) after drugs treatment for 21 day, concomitantly with the increase the expressions of TRPV1 and CGRP (P＜0.05 or P＜0.01), and inhibiting ERK1/2 phosphorylation and eIF3a expression (P＜0.05 or P＜0.01). These effects of small dose Cap were abolished in the presence of TRPV1 receptor antagonist SB-452533. Conclusion: The results suggest that small dose Cap can reverse alveolar epithelial cells EMT and alleviate bleomycin-induced pulmonary fibrosis in mice by inhibiting ERK1/2/eIF3asignaling pathway, which is related to agitating TRPV1 receptor and releasing of CGRP.

An overview of drug discovery efforts for eczema: why is this itch so difficult to scratch?

Introduction: Atopic dermatitis (AD) is a type of allergic/inflammatory dermatitis characterized by itch and an impairment in quality of life.Areas covered: Herein, the authors review drug discovery efforts for AD, highlighting the clinical efficacy of novel drugs, with a particular focus on the relief of pruritus. Topical agents include emollients, topical antihistamines, corticosteroids, calcineurin inhibitors and herbs. Recently, topical phosphodiesterase E4 (PDE4) inhibitors like crisaborole have become available and are efficacious for mild to moderate AD with few side effects. For more severe AD, monoclonal antibodies like dupilumab are considered as efficacious subcutaneous treatment options. In severe and recalcitrant AD, systemic treatment can ameliorate AD symptoms.Expert opinion: Many topical and systemic medications have demonstrated therapeutic benefits for AD. Indeed, randomized trials have shown that topical PDE4 inhibitors and subcutaneous dupilumab are safe and efficacious. Objective tools to evaluate itch and gauge treatment efficacy is important, but current methodology relies primarily on clinical scores. AD is a systemic atopic disease with a lot of complicated psychosocial issues. Suboptimal efficacy is often due to poor compliance and unrealistic expectation of curative treatment, rendering treatment difficult despite the existence of effective medications.

Extracts of the leaves of Pyrus ussuriensis Maxim. Alleviate itch sensation via TSLP-dependent manner in mouse models of atopic dermatitis.

Pyrus ussuriensis Maxim. commonly known as "Sandolbae" in Korean is a pear tree widely distributed across East Asia. Recent studies indicate that P. ussuriensis Maxim. leaves (PUL) have antipruritic effects. This study aimed to determine the effects of PUL extract and its fractions in decreasing the itch sensation and skin lesions in two distinct animal models of atopic dermatitis (AD) induced by dinitrofluorobenzene (DNFB) or house dust mite (HDM). Our results showed that the total ethanol extract of PUL decreased the scratching behavior in mice with DNFB- and HDM-induced AD. Moreover, the ethyl acetate fraction of PUL significantly improved the overall condition of the mice with AD induced by HDM. Further, we used HEK293T cells that express receptors and ion channels for thymic stromal lymphopoietin (TSLP), a potent pruritogen for AD, to determine the mechanisms underlying the antipruritic effects of PUL extract/fractions. Specific subfractions of the PUL strongly inhibited the increase in calcium levels induced by TSLP. In addition, the specific subfraction of PUL inhibited the TSLP-induced increase in calcium levels in cultured mouse dorsal root ganglia neurons. Thus, our results showed that the PUL extract could be effective for alleviating pruritus, and the antipruritic effects were exerted probably via the inhibition of the TSLP pathway in peripheral sensory neurons governing the itch sensation in AD.

Subacute oral administration of folic acid elicits anti-inflammatory response in a mouse model of allergic dermatitis.

Folic acid (FA) deficiency is associated with several health problems, including megaloblastic anemia and fetal neural tube defects. Therefore, supplementation with FA is strongly recommended by governments worldwide. Recent published reports indicate that FA functions in immune system maintenance. The main objective of this study is to examine possible anti-inflammatory and antipruritic effects of FA using a mouse model of allergic dermatitis. The mouse model was developed by repetitive sensitization to the Th2-type hapten toluene-2,4-diisocyanate (TDI). During the development of allergic dermatitis, FA was orally administered to the mice at doses of 8, 160, 1000 or 10,000 µg/day for 5 weeks. The ear swelling response and scratching behavior were monitored after the TDI challenge. Serum, ear tissue and auricular lymph node samples were isolated for further analysis 24 h after the TDI challenge. The ear swelling response was reduced in a dose-dependent manner by FA administration, and a significant change was observed at a concentration of 10,000-µg/day group. Comparable results were obtained through histological evaluation and cytokine level measurement in the ear tissue samples. Oral administration of FA exhibited the inhibitory effect on T-cell infiltration and T-cell-related cytokine production in auricular lymph nodes. Scratching behavior was not altered by FA administration. The in vivo evidence was corroborated by in vitro results, which showed that FA treatment significantly interfered with T-cell proliferation in a dose-dependent manner. Our findings imply that subacute oral administration of FA elicits an anti-inflammatory response, mainly through inhibition of T-cell proliferation.

Antipruritic Effect of Natural Coumarin Osthole through Selective Inhibition of Thermosensitive TRPV3 Channel in the Skin.

Coumarin osthole is a dominant bioactive ingredient of the natural Cnidium monnieri plant commonly used for traditional Chinese herbal medicines for therapies and treatments including antipruritus and antidermatitis. However, the molecular mechanism underlying the action of osthole remains unclear. In this study, we report that osthole exerts an antipruritic effect through selective inhibition of Ca2+-permeable and thermosensitive transient receptor potential vanilloid 3 (TRPV3) cation channels that are primarily expressed in the keratinocytes of the skin. Coumarin osthole was identified as an inhibitor of TRPV3 channels transiently expressed in HEK293 cells in a calcium fluorescent assay. Inhibition of the TRPV3 current by osthole and its selectivity were further confirmed by whole-cell patch clamp recordings of TRPV3-expressing HEK293 cells and mouse primary cultured keratinocytes. Behavioral evaluation demonstrated that inhibition of TRPV3 by osthole or silencing by knockout of the TRPV3 gene significantly reduced the scratching induced by either acetone-ether-water or histamine in localized rostral neck skin in mice. Taken together, our findings provide a molecular basis for use of natural coumarin osthole from the C. monnieri plant in antipruritic or skin care therapy, thus establishing a significant role of the TRPV3 channel in chronic itch signaling or acute histamine-dependent itch sensation.

Modulation of Itch by Localized Skin Warming and Cooling.

Skin thermal changes modulate itch sensitivity. However, the mechanisms of this modulation are still unclear. Using mouse models of acute and chronic itch, we investigated whether local innocuous thermal stimulation of the skin alters itch sensitivity and if blockade of thermosensitive transient receptor potential (TRP) channels can reduce these changes. Localized thermal changes were achieved by placing a thermal probe in contact with the back skin for 30 s. Warming the skin significantly increased serotonin-evoked scratching and spontaneous scratching in the ovalbumin model of atopic dermatitis but decreased histamine-evoked scratching. These changes were blocked by a TRPV4 antagonist. Cooling the skin significantly increased serotonin-evoked scratching but reduced histamine-evoked scratching. The increase in serotonin-evoked scratching, but not the reduction of histamine-evoked scratching, was blocked by TRPM8 antagonism. Chloroquine-evoked scratching was unaffected by either warming or cooling. Our data indicate that different itch signaling pathways are differentially modulated by skin thermal changes.

Genetic and Pharmacological Dissection of the Role of Spleen Tyrosine Kinase (Syk) in Intestinal Inflammation and Immune Dysfunction in Inflammatory Bowel Diseases.

Background: The DNAX adaptor protein 12 (DAP12) is a transmembrane adaptor molecule that signals through the activation of Syk (Spleen Tyrosine Kinase) in myeloid cells. The purpose of this study is to investigate the role of DAP12 and Syk pathways in inflammatory bowel diseases (IBDs). Methods: DAP12 deficient and DAP12 transgenic, overexpressing an increased amount of DAP12, mice and Syk deficient mice in the C57/BL6 background were used for these studies. Colitis was induced by administering mice with dextran sulfate sodium (DSS), in drinking water, or 2,4,6-trinitrobenzene sulfonic acid (TNBS), by intrarectal enema. Results: Abundant expression of DAP12 and Syk was detected in colon samples obtained from Crohn's disease patients with expression restricted to immune cells infiltrating the colonic wall. In rodents development of DSS colitis as measured by assessing severity of wasting diseases, global colitis score,and macroscopic and histology scores was robustly attenuated in DAP12-/- and Syk-/- mice. In contrast, DAP12 overexpression resulted in a striking exacerbation of colon damage caused by DSS. Induction of colon expression of proinflammatory cytokines and chemokines in response to DSS administration was attenuated in DAP12-/- and Syk-/- mice, whereas opposite results were observed in DAP12 transgenic mice. Treating wild-type mice with a DAP-12 inhibitor or a Syk inhibitor caused a robust attenuation of colitis induced by DSS and TNBS. Conclusions: DAP12 and Syk are essential mediators in inflammation-driven immune dysfunction in murine colitides. Because DAP12 and Syk expression is upregulated in patients with active disease, present findings suggest a beneficial role for DAP12 and Syk inhibitors in IBD.

Activités immunomodulatrice, anti-inflammatoire, antiprurigineuse et tolérogénique induites par I-modulia®, un extrait issu de culture d'Aquaphilus dolomiae, dans les modèles pharmacologiques de dermatite atopique: Immunomodulatory, anti-inflammatory, anti-pruritus and tolerogenic activities induced by I-modulia®, an Aquaphilus dolomiae culture extract, in atopic dermatitis pharmacology models.

Atopic dermatitis (AD) is an inflammatory and pruritic dermatosis of multifactorial origin. Topical steroids are the first line treatment for severe AD however alternatives treatment are increasingly needed. A biological concentrate was elaborated from culture of an Avène aquatic microflora isolate namely Aquaphilus dolomiae. Numerous extracts were evaluated in relevant AD in vitro models with human keratinocytes. Among these extracts, a particular one I-modulia® was found to be remarkable in terms of pharmacological activities: innate immunity modulating by agonizing Toll like receptor (TLR)2, TLR4 and TLR5, induction of anti-microbial peptides, inhibition of cytokines characteristics of T helper (Th)1, Th2 and Th17 responses, inhibition of Protease-activated-receptor (PAR) 2 and Thymic-stromal-lymphopoeitin (TSLP) both being known to be upregulated in pruritus. Additionally, when human dendritic cells (DC) were stimulated in vitro by Staphylococcus aureus secretomes from AD children lesions, I-modulia® was capable to induce IL-10 secretion to activate regular T lymphocytes and rendered DC tolerogenic. I-modulia®, extract of biotech origin incorporated in emollient, displays anti-inflammatory, anti-pruritus activities, restores homeostasis immune and ameliorates AD in young infant.

Synergic Anti-Pruritus Mechanisms of Action for the Radix Sophorae Flavescentis and Fructus Cnidii Herbal Pair.

Radix Sophorae Flavescentis (RSF) and Fructus Cnidii (FC) compose a typical herbal synergic pair in traditional Chinese medicine (TCM) for pruritus symptom treatments. The mechanisms of action for the synergy are not understood. This paper aims at predicting the anti-pruritus targets and the main active ingredients for the RSF and FC herbal pair. We demonstrate that the RSF-FC herbal pair can be elucidated by mining the chemical structures of compounds derived from RSF and FC. Based on chemical structure data, the putative targets for RSF and FC were predicted. Additional putative targets that interact with the anti-pruritus targets were derived by mapping the putative targets onto a PPI network. By examining the annotations of these proteins, we conclude that (1) RSF's active compounds are mainly alkaloids and flavonoids. The representative putative targets of the alkaloids are inflammation-related proteins (MAPK14, PTGS2, PTGS2, and F2) and pruritus-related proteins (HRH1, TRPA1, HTR3A, and HTR6). The representative putative targets of the flavonoids are inflammation-related proteins (TNF, NF-κB, F2, PTGS2, and PTGS2) and pruritus-related proteins (NR3C1 and IL2). (2) FC's active compounds are mainly coumarins. Their representative putative targets are CNS-related proteins (AChE and OPRK1) and inflammation-related proteins (PDE4D, TLR9, and NF-κB). (3) Both RSF and FC display anti-inflammatory effects, though they exhibit their anti-pruritus effects in different ways. Their synergy shows that RSF regulates inflammation-related pruritus and FC regulates CNS-related pruritus.

Echinacea purpurea-derived alkylamides exhibit potent anti-inflammatory effects and alleviate clinical symptoms of atopic eczema.

BACKGROUND: Atopic eczema (AE) is a chronic inflammatory and pruritic skin disease. There is still an unmet need for topical anti-inflammatory and anti-pruritic substances exhibiting an excellent safety profile. The endocannabinoid system is known to regulate various aspects of cutaneous barrier and immune functions, thus targeting it may be a valid approach for alleviating the symptoms of AE. OBJECTIVE: To assess the putative efficacy of Echinacea purpurea-derived alkylamides (Ec. extract) activating cannabinoid (CB)-2 receptors in exerting anti-inflammatory effects and alleviating symptoms of AE. METHODS: In vitro anti-inflammatory efficiency was investigated by monitoring the effects of Ec. extract on poly-(I:C)-induced pro-inflammatory cytokine expression (Q-PCR) and release (ELISA) of HaCaT keratinocytes. Irritancy and sensitization potential (assessed by Human Repeat Insult Patch Test; Clinical trial 1); clinical efficiency in alleviating symptoms of AE (Clinical trial 2) as well as effects on human skin structure and lipid content (Clinical trial 3 followed by transmission electron microscopy and HPTLC) were investigated in randomized double blind clinical trials. RESULTS: Ec. extract significantly reduced mRNA expression as well as release of poly-(I:C)-induced pro-inflammatory cytokines (IL-6 and IL-8) in keratinocytes. Thus, not surprisingly, the well-tolerated (Clinical trial 1) Ec. extract-based cream reduced local SCORAD statistically significantly, not only compared to baseline, but also compared to the comparator (Clinical trial 2). Of great importance, besides the in vitro anti-inflammatory effects, administration of the Ec. extract-based cream also resulted in significantly higher levels of overall epidermal lipids, ceramide EOS (ω-esterified fatty acid+sphingosine sphingoid base), and cholesterol at Day 15 compared to baseline as well as significantly greater numbers of intercellular lipid lamellae in the intercellular space (Clinical trial 3). CONCLUSION: The investigated Ec. extract shows great potential in alleviating cutaneous symptoms of AE, and by exerting remarkable anti-inflammatory actions and restoring the epidermal lipid barrier, it will be very likely a well-tolerated, powerful novel ingredient for the adjuvant therapy of AE.

In vivo and in vitro evaluation for nutraceutical purposes of capsaicin, capsanthin, lutein and four pepper varieties.

The purpose of this study is to determine the nutraceutic potential of different Capsicum sp, capsaicin, capsanthin and lutein and provide data in order to clarify the conflicting results obtained for capsaicin by different authors. To achieve these objectives, in vivo (geno/antigenotoxicity and lifespan assays in the animal model Drosophila) and in vitro (cytotoxicity and DNA-fragmentation assays in HL60 promyelocytic cell line) assays were carried out. Results showed that i) none of the tested substances were genotoxic except green hot pepper and capsaicin at the highest tested concentration (5 mg/mL and 11.5 µM respectively), ii) all tested substances except green hot pepper are antimutagenic against H2O2-induced damage, iii) only red sweet pepper significantly extend the lifespan and healthspan of D. melanogaster at 1.25 and 2.5 mg/mL, iv) all pepper varieties induce dose-depended cytotoxic effect in HL60 cells with different IC50, and v) all pepper varieties and capsaicin exerted proapoptotic effect on HL60 cells. IN CONCLUSION: (i) sweet peppers could be suggested as nutraceutical food, (ii) hot peppers should be moderately consumed, and (iii) supplementary studies are necessary to clarify the synergic effect of the carotenoids and capsaicinoids in the hot pepper food matrix.

Effects of Viola yedoensis Makino anti-itching compound on degranulation and cytokine generation in RBL-2H3 mast cells.

ETHNOPHARMACOLOGICAL RELEVANCE: The Chinese herb compound prescription Viola yedoensis Makino Anti-itching Compound (VYAC), which consists of Viola yedoensis Makino, herb, Sophora flavescens Aiton, root, and Dictamnus dasycarpus Turcz, root and rhizome, has been traditionally used to treat various skin allergic inflammatory diseases in clinic. AIM OF THE STUDY: The aim of this study is to investigate the effects of VYAC on degranulation and to determine its anti-inflammatory mechanism in RBL-2H3 mast cells. MATERIALS AND METHODS: VYAC was extracted with water-coction extraction (Shufen et al., 2012). The aqueous extracts were concentrated in vacuum under reduced pressure and lyophilized using a freeze dryer, and lyophilized powder was obtained. MTT was used to evaluate the cytotoxic of VYAC on RBL-2H3 cells. Degranulation was carried out with RBL-2H3 cell model, which was stimulated with A23187 plus PMA. ß-Hexosaminidase and histamine were measured to evaluate degranulation. The mRNA levels of inflammation cytokines (IL-1ß, TNF-α, IL-6, and iNOS) were investigated by RT-PCR to explain the anti-inflammatory mechanism of VYAC. RESULTS: VYAC did not show cytotoxic effect on RBL-2H3 cells in the range of 25-400µg/mL. A higher dose of VYAC (800µg/mL) showed significant cytotoxicity (P<0.05). VYAC could significantly inhibit ß-hexosaminidase and histamine release when treated with 100, 200, and 400µg/mL (P<0.05), but could not significantly inhibit ß-Hexosaminidase and histamine release when treated with 25 and 50µg/mL (p>0.05). The mRNA levels of inflammatory cytokines (TNF-α, IL-1ß, IL-6, and iNOS) could significantly decrease when treated with 200 and 400µg/mL (P<0.05) of VYAC, which were associated with the development of inflammation. CONCLUSIONS: Results showed that VYAC inhibited ß-hexosaminidase and histamine release, which was inhibit A23187 plus PMA stimulated RBL-2H3 cell degranulation and downregulated inflammatory cytokines (IL-1ß, TNF-α, IL-6, and iNOS) expression to block inflammatory development.

Osthole inhibits histamine-dependent itch via modulating TRPV1 activity.

Osthole, an active coumarin isolated from Cnidium monnieri (L.) Cusson, has long been used in China as an antipruritic herbal medicine; however, the antipruitic mechanism of osthole is unknown. We studied the molecular mechanism of osthole in histamine-dependent itch by behavioral test, Ca(2+) imaging, and electrophysiological experiments. First, osthole clearly remitted the scratching behaviors of mice induced with histamine, HTMT, and VUF8430. Second, in cultured dorsal root ganglion (DRG) neurons, osthole showed a dose-dependent inhibitory effect to histamine. On the same neurons, osthole also decreased the response to capsaicin and histamine. In further tests, the capsaicin-induced inward currents were inhibited by osthole. These results revealed that osthole inhibited histamine-dependent itch by modulating TRPV1 activity. This study will be helpful in understanding how osthole exerts anti-pruritus effects and suggests that osthole may be a useful treatment medicine for histamine-dependent itch.

Anatomical evidence of pruriceptive trigeminothalamic and trigeminoparabrachial projection neurons in mice.

Itch is relayed to higher centers by projection neurons in the spinal and medullary dorsal horn. We employed a double-label method to map the ascending projections of pruriceptive and nociceptive trigeminal and spinal neurons. The retrograde tracer fluorogold (FG) was stereotaxically injected into the right thalamus or lateral parabrachial area (LPb) in mice. Seven days later, mice received intradermal (id) microinjection of histamine, chloroquine, capsaicin, or vehicle into the left cheek. Histamine, chloroquine, and capsaicin intradermally elicited similar distributions of Fos-positive neurons in the medial aspect of the superficial medullary and spinal dorsal horn from the trigeminal subnucleus caudalis to C2. Among neurons retrogradely labeled from the thalamus, 43%, 8%, and 22% were Fos-positive following id histamine, chloroquine, or capsaicin. Among the Fos-positive neurons following pruritic or capsaicin stimuli, ∼1-2% were retrogradely labeled with FG. Trigeminoparabrachial projection neurons exhibited a higher incidence of double labeling in the superficial dorsal horn. Among the neurons retrogradely labeled from LPb, 36%, 29%, and 33% were Fos positive following id injection of histamine, chloroquine, and capsaicin, respectively. Among Fos-positive neurons elicited by id histamine, chloroquine, and capsaicin, respectively, 3.7%, 4.3%, and 4.1% were retrogradely labeled from LPb. The present results indicate that, overall, relatively small subpopulations of pruriceptive and/or nociceptive neurons innervating the cheek project to thalamus or LPb. These results imply that the vast majority of pruritogen- and algogen-responsive spinal neurons are likely to function as interneurons relaying information to projection neurons and/or participating in segmental nocifensive circuits.

Methods for preclinical assessment of antipruritic agents and itch mechanisms independent of mast-cell histamine.

Itch is a sensation that provokes a desire to scratch. Mast-cell histamine was thought to be a key itch mediator. However, histamine and mast-cell degranulation were reported not to elicit scratching in animals. It was difficult to investigate the pathophysiology of itching and to evaluate the antipruritic efficacy of chemical agents in the early 1990 s. We showed that hind-paw scratching and biting were elicited by stimulation with pruritogenic agents in mice. Those results demonstrated for the first time that cutaneous itching could be evaluated behaviorally in animals. We established various animal models of pathological itch of the skin (dry skin, mosquito allergy, surfactant-induced pruritus, and herpes zoster) and mucus membranes (pollen allergy). Mast-cell histamine did not play a key role in itching in any animal model examined except for the pollen allergy model. Histamine is not an exclusive itch mediator of mast cells; tryptase and leukotriene B4 released from mast cells also act as itch mediators. Epidermal keratinocytes release several itch mediators, such as leukotriene B4, sphingosylphosphorylcholine, thromboxane A2, nociceptin, nitric oxide, and histamine, which may play important roles in pathological itching. Appropriate animal models of pathological itching are needed for pharmacological evaluation of the antipruritic efficacy of chemical agents.