The Anti-Inflammatory and Anti-Pruritus Mechanisms of Huanglian Jiedu Decoction in the Treatment of Atopic Dermatitis

Atopic dermatitis (AD) is a common chronic skin disease driven by a T-cell-mediated immune response, with inflammation and pruritus being its main clinical manifestations. Huanglian Jiedu decoction (HLJDT), which is an ancient Chinese medicine herbal formula derived from Wai-Tai-Mi-Yao, is a potentially effective treatment for AD. We aimed to clarify the anti-inflammatory and anti-pruritus mechanisms of HLJDT in AD treatment. We performed immunohistochemistry, Western blotting, reverse transcriptase-polymerase chain reaction, Luminex-based direct multiplex immunoassay, enzyme-linked immunosorbent assays, and flow cytometry to address the abovementioned aims. HLJDT significantly reduced clinical symptoms and ear swelling in AD-like mice by inhibiting the production of cytokines [histamine, interleukin (IL)-3, IL-4, IL-5, IL-13, IL-17A, IL-31, and IL-33], substance P (SP), transient receptor potential cation channel subfamily V member 1 (TRPV-1), and gastrin-releasing peptide (GRP). Additionally, HLJDT significantly suppressed the protein expression levels and positive cell percentage of CD28, CD80, CD86, CD207, CD326, MHCII, and OX40 in the lymphoid nodes. Moreover, HLJDT significantly suppressed mRNA and protein expression of tyrosine–protein kinase (JAK1), histamine H4 receptor, and IL-4Rα, as well as the protein expression of GRP, SP, and TRPV-1 in the root ganglion. Our findings indicate that HLJDT can treat AD by regulating the antigen presentation function of dendritic cells, weakening T-lymphocyte activation, and subsequently exerting anti-inflammatory and anti-pruritus effects.

Evaluation of the Differences in the Expression of Biogenic Amine-Related mRNAs and Proteins in Endometrioid Endometrial Cancer

Biogenic amines, such as adrenaline, noradrenaline, histamine, dopamine, and serotonin are important neurotransmitters that also regulate cell viability. Their detection and analysis are helpful in the diagnosis of many diseases, including cancer. The aim of this study was to determine the expression profile of the biogenic amine-related genes and proteins in endometrioid endometrial cancer compared to the control group. The material consisted of endometrial tissue samples and whole blood collected from 30 endometrioid endometrial cancer patients and 30 cancer-free patients. The gene expression was determined by the mRNA microarrays and validated by qRT-PCR. Protein levels were determined in the serum by the enzyme-linked immunosorbent assay (ELISA). Overexpression of histamine H1–H3 receptors and early growth response 1 and silencing of calmodulin, the histamine H4 receptor, and the dopamine D5 receptor have been reported in endometrioid endometrial cancer. The obtained results indicate disturbances in the signaling activated by histamine and dopamine receptors, which could potentially contribute to the progression of endometrioid endometrial cancer.

Desensitization of TRPV1 Involved in the Antipruritic Effect of Osthole on Histamine-Induced Scratching Behavior in Mice

Osthole has been isolated from the fruits of Cnidium monnieri (L.) Cusson, which has been used in Chinese traditional medicine to treat pruritic disorders for a long time. However, the antipruritic mechanism of osthole is not fully understood. In the present study, using calcium imaging, molecular docking, and animal scratching behavior, we analyzed the pharmacological effects of osthole on transient receptor potential vanilloid 1 (TRPV1). The results showed that osthole significantly induced calcium influx in a dose-dependent manner in dorsal root ganglion (DRG) neurons. Osthole-induced calcium influx was inhibited by AMG9810, an antagonist of TRPV1. Osthole and the TRPV1 agonist capsaicin-induced calcium influx were desensitized by pretreatment with osthole. Furthermore, molecular docking results showed that osthole could bind to TRPV1 with a hydrogen bond by anchoring to the amino acid residue ARG557 in the binding pocket of TRPV1. In addition, TRPV1 is a downstream ion channel for the histamine H1 and H4 receptors to transmit itch signals. Osthole attenuated scratching behavior induced by histamine, HTMT (histamine H1 receptor agonist), and VUF8430 (histamine H4 receptor agonist) in mice. These results suggest that osthole inhibition of histamine-dependent itch may be due to the activation and subsequent desensitization of TRPV1 in DRG neurons.

The Histamine H4 Receptor Participates in the Anti-Neuropathic Effect of the Adenosine A3 Receptor Agonist IB-MECA: Role of CD4+ T Cells

A3 adenosine receptor (A3AR) agonists have emerged as potent relievers of neuropathic pain by a T cell-mediated production of IL-10. The H4 histamine receptor (H4R), also implicated in pain modulation, is expressed on T cells playing a preeminent role in its activation and release of IL-10. To improve the therapeutic opportunities, this study aimed to verify the hypothesis of a possible cross-talk between A3AR and H4R in the resolution of neuropathic pain. In the mouse model of Chronic Constriction Injury (CCI), the acute intraperitoneal co-administration of the A3AR agonist IB-MECA (0.5 mg/kg) and the H4R agonist VUF 8430 (10 mg/kg), were additive in counteracting mechano-allodynia increasing IL-10 plasma levels. In H4R−/− mice, IB-MECA activity was reduced, lower pain relief and lower modulation of plasma IL-1β, TNF-α, IL-6 and IL-10 were shown. The complete anti-allodynia effect of IB-MECA in H4R−/− mice was restored after intravenous administration of CD4+ T cells obtained from naïve wild type mice. In conclusion, a role of the histaminergic system in the mechanism of A3AR-mediated neuropathic pain relief was suggested highlighting the driving force evoked by CD4+ T cells throughout IL-10 up-regulation.

Identification of TSPAN4 as Novel Histamine H4 Receptor Interactor

The histamine H4 receptor (H4R) is a G protein-coupled receptor that is predominantly expressed on immune cells and considered to be an important drug target for various inflammatory disorders. Like most GPCRs, the H4R activates G proteins and recruits -arrestins upon phosphorylation by GPCR kinases to induce cellular signaling in response to agonist stimulation. However, in the last decade, novel GPCR-interacting proteins have been identified that may regulate GPCR functioning. In this study, a split-ubiquitin membrane yeast two-hybrid assay was used to identify H4R interactors in a Jurkat T cell line cDNA library. Forty-three novel H4R interactors were identified, of which 17 have also been previously observed in MYTH screens to interact with other GPCR subtypes. The interaction of H4R with the tetraspanin TSPAN4 was confirmed in transfected cells using bioluminescence resonance energy transfer, bimolecular fluorescence complementation, and co-immunoprecipitation. Histamine stimulation reduced the interaction between H4R and TSPAN4, but TSPAN4 did not affect H4R-mediated G protein signaling. Nonetheless, the identification of novel GPCR interactors by MYTH is a starting point to further investigate the regulation of GPCR signaling.

The Function of the Histamine H4 Receptor in Inflammatory and Inflammation-Associated Diseases of the Gut

Histamine is a pleiotropic mediator involved in a broad spectrum of (patho)-physiological processes, one of which is the regulation of inflammation. Compounds acting on three out of the four known histamine receptors are approved for clinical use. These approved compounds comprise histamine H1-receptor (H1R) antagonists, which are used to control allergic inflammation, antagonists at H2R, which therapeutically decrease gastric acid release, and an antagonist at H3R, which is indicated to treat narcolepsy. Ligands at H4R are still being tested pre-clinically and in clinical trials of inflammatory diseases, including rheumatoid arthritis, asthma, dermatitis, and psoriasis. These trials, however, documented only moderate beneficial effects of H4R ligands so far. Nevertheless, pre-clinically, H4R still is subject of ongoing research, analyzing various inflammatory, allergic, and autoimmune diseases. During inflammatory reactions in gut tissues, histamine concentrations rise in affected areas, indicating its possible biological effect. Indeed, in histamine-deficient mice experimentally induced inflammation of the gut is reduced in comparison to that in histamine-competent mice. However, antagonists at H1R, H2R, and H3R do not provide an effect on inflammation, supporting the idea that H4R is responsible for the histamine effects. In the present review, we discuss the involvement of histamine and H4R in inflammatory and inflammation-associated diseases of the gut.

The Novel H4R Antagonist 1-[(5-Chloro-2,3-Dihydro-1-Benzofuran-2-Yl)Methyl]-4-Methyl-Piperazine (LINS01007) Attenuates Several Symptoms in Murine Allergic Asthma

BACKGROUND/AIMS: Histamine is an important chemical transmitter involved in inflammatory processes, including asthma and other chronic inflammatory diseases. Its inflammatory effects involve mainly the histamine H4 receptor (H4R), whose role in several studies has already been demonstrated. Our group have explored the effects of 1-[(2,3-dihydro-1-benzofuran-2-yl)methyl]piperazines as antagonists of H4R, and herein the compounds LINS01005 and LINS01007 were studied with more details, considering the different affinity profile on H4R and the anti-inflammatory potential of both compounds. METHODS: We carried out a more focused evaluation of the modulatory effects of LINS01005 and LINS01007 in a murine asthma model. The compounds were given i.p. (1-7 mg/kg) to ovalbumin sensitized BALB/c male mice (12 weeks old) 30 min before the antigen challenging, and after 24 h the cell analysis from the bronchoalveolar lavage fluid (BALF) was performed. The lung tissue was used for evaluation by western blot (COX-2, 5-LO, NF-κB and STAT3 expressions) and histological analysis. RESULTS: Treatment with the more potent H4R antagonist LINS01007 significantly decreased the total cell count and eosinophils in BALF at lower doses when compared to LINS01005. The expression of COX-2, 5-LO, NF-κB and STAT3 in lung tissue was significantly reduced after treatment with LINS01007. Morphophysiological changes such as mucus and collagen production and airway wall thickening were significantly reduced after treatment with LINS01007. CONCLUSION: These results show important down regulatory effect of novel H4R antagonist (LINS01007) on allergic lung inflammation.