H1R mediates local anesthetic-induced vascular permeability in angioedema

Construction and application of H1R ligand screening materials based on SMA stabilization and his-tag covalent immobilization of membrane proteins

The histamine H1 receptor (H1R) plays a pivotal role in allergy initiation and undergoes the necessity of devising a high-throughput screening approach centered on H1R to screen novel ligands effectively. This study suggests a method employing styrene maleic acid (SMA) extraction and His-tag covalent bonding to immobilize H1R membrane proteins, minimizing the interference of nonspecific proteins interference while preserving native protein structure and maximizing target exposure. This approach was utilized to develop a novel material for high-throughput ligand screening and implemented in cell membrane chromatography (CMC). An H1R-His-SMALPs/CMC model was established and its chromatographic performance (selectivity, specificity and lifespan) validated, demonstrating a significant enhancement in lifespan compared to previous CMC models. Subsequently, this model facilitated high-throughput screening of H1R ligands in the compound library and preliminary activity verification of potential H1R antagonists. Identification of a novel H1R antagonist laid the foundation for further development in this area.

Clinical commentary about foreign body complications over 20 years after polymethyl-methacrylate face implants and control of late sequelae with Polynucleotides Highly Purified Technology (PN-HPT® )

INTRODUCTION

Mainly in the past, foreign body complications, including granuloma, were pretty frequent after semi-permanent polymethyl-methacrylate (PMMA) implants.

RESULTS

The authors describe a twenty-year history of recurring post-PMMA complications interspersed by long uneventful years, with acute edematous side effects evolving into unpleasant skin dystrophia with persistent cutis laxa. The case report also discusses a simple clinical algorithm to discriminate among foreign body complications with particular attention to granulomas.

CONCLUSIONS

The authors conclude by discussing the benefits of the anti-dystrophic treatment with natural-origin remodeling PN-HPT^® (Polynucleotides Highly Purified Technology).

p-Phenylenediamine induces immediate contact allergy and non-histaminergic itch via MRGPRX2

p-phenylenediamine (PPD) is a common component of hair dye known to induce immediate allergy, even acute dermatitis and contact dermatitis. MAS-related G protein coupled receptor-X2 (MRGPRX2) in mast cells (MCs) mediates small molecular substances-induced pseudo-allergic reactions. However, the role of MRGPRX2 in PPD-induced immediate contact allergy needs further exploration. The aim of this study was to investigate whether PPD activates MCs via MRGPRX2 and induces immediate allergies that contribute to contact dermatitis. Wild-type (WT) and kitw-sh/w-sh mice (MUT) were treated with PPD to observe local inflammation and MC degranulation in vivo. The release of inflammatory mediators was measured in vitro. Histamine 1 receptor (H1R)-/- mice were used to analyze itch type. PPD caused immediate contact allergy in WT mice, induced scratching, and local inflammatory reactions, while exhibiting minimal effects on MUT mice. PPD did not induce histamine release, but induced significant tryptase release in vivo and in vitro. PPD activated MRGPRX2 to induce MC degranulation in vitro. PPD caused immediate contact allergy in WT mice, induced scratching and local inflammatory reactions, while exhibited minimal effect on MUT mice. PPD did not induce histamine release, while induced significant tryptase release in vivo and in vitro. PPD induced immediate contact allergy by MCs activation via MRGPRX2 and lead to tryptase release. The scratching times showed no significant difference in WT mice or H1R-/- mice, which indicated PPD caused non-histaminergic itch. The results showed that PPD activated MCs via MRGPRX2 and induced immediate contact allergy, leading to the release of tryptase without monoamine release, which might induce non-histaminergic itch.

Angioedema and Fatty Acids

Angioedema is a life-threatening emergency event that is associated with bradykinin and histamine-mediated cascades. Although bradykinin-mediated angioedema currently has specific therapeutic options, angioedema is sometimes intractable with current treatments, especially histamine-mediated angioedema, suggesting that some other mediators might contribute to the development of angioedema. Fatty acids are an essential fuel and cell component, and act as a mediator in physiological and pathological human diseases. Recent updates of studies revealed that these fatty acids are involved in vascular permeability and vasodilation, in addition to bradykinin and histamine-mediated reactions. This review summarizes each fatty acid’s function and the specific receptor signaling responses in blood vessels, and focuses on the possible pathogenetic role of fatty acids in angioedema.

Resveratrol inhibits MRGPRX2-mediated mast cell activation via Nrf2 pathway

Mast cells (MCs) are crucial effectors in inflammation and allergic reactions. The Mas-related G-protein-coupled receptor X2 (MRGPRX2) was the MC-specific receptor and play a key role in IgE-independent allergic reactions. The activation of the Nuclear factor erythroid derived 2-related factor 2 (Nrf2) is involved in IgE-mediated MC degranulation. Resveratrol (Res) is a polyphenolic compound in red wine and has been reported to exert a variety of pharmacological effects. In the current study, we investigated the effect of Res in regulating MRGPRX2-mediated MC activation and its underlyingmechanism. We demonstrated that Res reduced compound 48/80 (C48/80)-induced calcium flux in MCs and inhibited MCs degranulation in vitro. Res also suppressed C48/80-induced hind paw extravasation, active systemic anaphylaxis, and MCs degranulation in mouse models of pseudo-allergy in vivo. Furthermore, PCR and immunohistochemistry assay suggest that Res up-regulates Nrf2 expression and Nrf2 inhibitor attenuates the protective effects of Res. In conclusion, Res exerts an inhibitory effect on MRGPRX2-mediated MCs activation by targeting Nrf2 pathway and may present a promising new therapeutic agent for the treatment of MRGPRX2-dependent anaphylactoid reactions.

Characterization of interactions between local anesthetics and histamine H1 receptor by cell membrane chromatography model

Local anesthetic has a wide application in clinical practice. However, angioedema, an adverse reaction caused by local anesthetics, has been reported to be related to histamine H₁ receptor (H₁R). Hence, an effective and practical method for investigating the interaction characteristics between local anesthetics and H₁R is needed. In this work, the competition binding assay and the relative standard method based on H₁R-HEK293/cell membrane chromatography (CMC) were developed to analyze the equilibrium dissociation constant (K_D) values of local anesthetics with H₁R. The activity of drugs toward H₁R was evaluated by intracellular Ca²⁺ imaging assay. Molecular docking was used to verify the interaction modes that occurred at the activate pocket of H₁R protein. Results showed that the local anesthetics can directly occupy histamine binding sites on H₁R, and the K_D values obtained from different CMC methods exhibited positive correlations with each other (p < 0.01). The K_D values of tetracaine, procaine, and lidocaine were much closer to that of histamine than bupivacaine and ropivacaine. This was not only in line with the Ca²⁺ responses in activating H₁R, but also consistent with the same amino acid residues shared with histamine in the H₁R active site. In conclusion, this study provided new insight into the interactions between local anesthetics and H₁R. The H₁R-HEK293/CMC methods developed in this study could be used to evaluate the interaction characteristics of those compounds acting on H₁R.