STAT1 phosphorylation and cleavage is regulated by the histamine (H4) receptor in human atopic and non-atopic lymphocytes

Developmental trajectories of atopic dermatitis with multiomics approaches in the infant gut: COCOA birth cohort

BACKGROUND

An understanding of the phenotypes and endotypes of atopic dermatitis (AD) is essential for developing precision therapies. Recent studies have demonstrated evidence for the gut-skin axis in AD.

OBJECTIVE

We sought to determine the natural course and clinical characteristics of AD phenotypes and investigate their mechanisms on the basis of multiomics analyses.

METHODS

Latent class trajectory analysis was used to classify AD phenotypes in 2247 children who were followed until age 9 years from the COhort for Childhood Origin of Asthma and allergic diseases birth cohort study. Multiomics analyses (microbiome, metabolites, and gut epithelial cell transcriptome) using stool samples collected at age 6 months were performed to elucidate the underlying mechanisms of AD phenotypes.

RESULTS

Five AD phenotypes were classified as follows: never/infrequent, early-onset transient, intermediate transient, late-onset, and early-onset persistent. Early-onset persistent and late-onset phenotypes showed increased risks of food allergy and wheezing treatment ever, with bronchial hyperresponsiveness evident only in the early-onset persistent phenotype. Multiomics analyses revealed a significantly lower relative abundance of Ruminococcus gnavus and a decreased gut acetate level in the early-onset persistent phenotype, with potential associations to ACSS2, Janus kinase-signal transducer and activator of transcription signaling, and systemic TH2 inflammation. The early-onset transient phenotype was associated with adenosine monophosphate-activated protein kinase (AMPK) and/or chemokine signaling regulation, whereas the late-onset phenotype was linked with IL-17 and barrier dysfunction.

CONCLUSIONS

Multiomics profiling in early life may offer insights into different mechanisms underlying AD phenotypes in children.

Pharmacokinetics, pharmacodynamics, and safety of izuforant, an H4R inhibitor, in healthy subjects: A phase I single and multiple ascending dose study

Izuforant is a selective, and potent histamine H4 receptor (H4R) antagonist developed to treat atopic dermatitis (AD). There is an unmet medical need for therapeutic agents to control inflammation and pruritus. Izuforant is a strong candidate for this task based on the findings of non-clinical studies showing that inhibition of the histamine-mediated signaling pathway via H4R by izuforant results in decreased pruritus and inflammation. This study aimed to evaluate the clinical pharmacokinetic (PK) and pharmacodynamic (PD) profiles of izuforant. Dose-block-randomized, double-blind, placebo-controlled, single- and multiple ascending dose studies were conducted in 64 healthy volunteers. For the single ascending dose (SAD) study, 10-600 mg izuforant was administered to the designated groups. For the multiple ascending dose (MAD) study, 100-400 mg izuforant was administered to three groups. The clinical pharmacokinetic (PK) profile of izuforant was evaluated using plasma and urine concentrations. Blood sampling for the PD assay, which measured imetit-induced eosinophil shape changes (ESC), was also conducted. A one-compartment PK model described the distribution and elimination profiles of izuforant. An imetit-induced ESC inhibition test was established and validated for PD evaluation as a measure of the H4R antagonistic effect. ESC inhibition was observed even at doses as low as 10 mg; however, this inhibition became stronger and lasted longer as the dose increased. All izuforant doses were well tolerated, and no discontinuations due to adverse events (AE) or deaths were reported.

STAT signaling pathways in immune cells and their associated mechanisms in cancer pathogenesis

Introduction

Signal transducer and activator of transcriptions (STATs) factors as critical proteins in cell signaling regulate diverse biological processes such as differentiation and proliferation of cells. STATs have been shown to play distinct roles in modulating immune responses mediated by innate and adaptive immune cell subsets due to their significant roles in cytokine signaling.

Methods

In the current study, we review recent studies on the contribution of individual STAT proteins to cytokine signaling, development, and activity of diverse immune cells that constitute the whole immune system and help its performance against endogenous or exogenous agents with a particular focus on meaningful STAT factor in each of innate and adaptive immune cells' subsets to clarify their function in favor of the tumor or against it.

Results

Dysregulation of signaling pathways in the immune cells is associated with various immune disorders, such as the inability of immune system cells in the effective destruction of cancerous cells. Increase of knowledge about these pathways' functions is essential to understand how they can be effectively targeted to eliminate tumors.

Conclusion

The majority of immune cells use the Jak/STAT signaling pathway, which is one of the most important signaling pathways with a role in induction of proper immune responses. Since each of the STAT factors has a specific role in diverse immune cells' subsets, appropriate targeting of them can be a promising strategy for patients who suffer from immune system disorders; specifically it can be beneficial as an approach for cancer immunotherapy.

A Comprehensive Analysis and Anti-Cancer Activities of Quercetin in ROS-Mediated Cancer and Cancer Stem Cells

Reactive oxygen species (ROS) induce carcinogenesis by causing genetic mutations, activating oncogenes, and increasing oxidative stress, all of which affect cell proliferation, survival, and apoptosis. When compared to normal cells, cancer cells have higher levels of ROS, and they are responsible for the maintenance of the cancer phenotype; this unique feature in cancer cells may, therefore, be exploited for targeted therapy. Quercetin (QC), a plant-derived bioflavonoid, is known for its ROS scavenging properties and was recently discovered to have various antitumor properties in a variety of solid tumors. Adaptive stress responses may be induced by persistent ROS stress, allowing cancer cells to survive with high levels of ROS while maintaining cellular viability. However, large amounts of ROS make cancer cells extremely susceptible to quercetin, one of the most available dietary flavonoids. Because of the molecular and metabolic distinctions between malignant and normal cells, targeting ROS metabolism might help overcome medication resistance and achieve therapeutic selectivity while having little or no effect on normal cells. The powerful bioactivity and modulatory role of quercetin has prompted extensive research into the chemical, which has identified a number of pathways that potentially work together to prevent cancer, alongside, QC has a great number of evidences to use as a therapeutic agent in cancer stem cells. This current study has broadly demonstrated the function-mechanistic relationship of quercetin and how it regulates ROS generation to kill cancer and cancer stem cells. Here, we have revealed the regulation and production of ROS in normal cells and cancer cells with a certain signaling mechanism. We demonstrated the specific molecular mechanisms of quercetin including MAPK/ERK1/2, p53, JAK/STAT and TRAIL, AMPKα1/ASK1/p38, RAGE/PI3K/AKT/mTOR axis, HMGB1 and NF-κB, Nrf2-induced signaling pathways and certain cell cycle arrest in cancer cell death, and how they regulate the specific cancer signaling pathways as long-searched cancer therapeutics.

The Host CYP1A1-Microbiota Metabolic Axis Promotes Gut Barrier Disruption in Methicillin-Resistant Staphylococcus aureus-Induced Abdominal Sepsis

Background

Host-microbiota crosstalk has been implicated in multiple host metabolic pathway axes that regulate intestinal barrier function. Although constitutive cytochrome P4501A1 (CYP1A1) expression perturbs the microbiome-derived autoregulatory loop following enteric infection, little is known about the role of host CYP1A1 in modulating gut microbiome-mediated signaling during methicillin-resistant Staphylococcus aureus (MRSA)-induced abdominal sepsis and its effects on intestinal barrier integrity.

Methods

Abdominal sepsis was induced by the intraperitoneal injection of MRSA in mice. The effect of CYP1A1 deficiency on gut barrier integrity was investigated using RNA sequencing, microbiome analyses, and targeted metabolomics. The microbiota-produced metabolites were validated in patients with sepsis and persistent MRSA infection.

Results

Mice lacking CYP1A1 exhibited an altered gut microbiome, a reduced metabolic shift from lysine to cadaverine in the caecal contents and antimicrobial molecule production (Retnlb, Gbp7, and Gbp3), and they were protected against gut barrier disruption when subjected to MRSA challenge. These beneficial effects were validated in aryl hydrocarbon receptor (AHR) knockout (KO) mice by cohousing with CYP1A1 KO mice and abrogated after supplementation with cadaverine or Enterococcus faecalis, the primary microbiota genus for cadaverine synthesis. Antibiotic-driven gut dysbacteriosis impaired the survival benefit and disrupted the intestinal barrier integrity in CYP1A1 KO mice after MRSA infection. Furthermore, increased cadaverine levels in feces and serum were detected in critically ill patients with gut leakiness during persistent MRSA infection, whereas cadaverine was not detected in healthy controls. Additionally, microbiota-derived cadaverine induced enterocyte junction disruption by activating the histamine H4 receptor/nuclear factor-κB/myosin light-chain kinase signaling pathway.

Conclusion

This study revealed the unexpected function of host CYP1A1 in microbiota-mediated cadaverine metabolism, with crucial consequences for dysbacteriosis following MRSA-induced abdominal sepsis, indicating that inhibiting CYP1A1 or blocking cadaverine-histamine H4 receptor signaling could be a potential therapeutic target against abdominal sepsis.

Clinical Trial Registration

[http://www.chictr.org.cn/index.aspx], identifier [ChiCTR1800018646].

Human β-Defensin 2 Expression in Oral Epithelium: Potential Therapeutic Targets in Oral Lichen Planus

Human β-defensin 2 (hBD-2) is a potent antimicrobial peptide that participates in defense against invading bacteria. We recently showed that bacterial components and histamine, through histamine H4 receptor (H4R), are involved in the pathogenesis of the potentially malignant lesion, oral lichen planus (OLP). However, the underlying mechanisms remain unknown. We, therefore, investigated the role of hBD2–histamine crosstalk signaling in promoting OLP pathology. Biopsies from OLP and oral tongue squamous cell carcinoma (OTSCC) patients, and healthy controls were used. Two OTSCC cell lines and normal human oral keratinocytes (HOKs) were used. HBD-2 and other targets were mapped by immunostaining and analyzed by ImageJ2 software. The highly sensitive droplet-digital PCR technology and qRT-PCR were utilized to study the clinically derived and in vitro samples, respectively. H4R was challenged with the specific agonist HST-10 and inverse agonist ST-1007. HBD-2 was highly induced in OLP lesions. In contrast, hBD2 expression was attenuated in OTSCC tissues, while very low levels of hBD-2 messenger RNA (mRNA) were observed in OTSCC cells. Together with tumor necrosis factor-α (TNF-α), histamine upregulated hBD-2 mRNA expression in HOKs. Activation of H4R seems to modulate the expression of epithelial hBD-2. These findings suggest the involvement of hBD-2 in the pathogenesis of OLP and may, thus, be harnessed for therapeutic interventions in OLP.

pSTAT3 expression associated with survival and mammographic density of breast cancer patients

BACKGROUND

Constitutive activation of STAT3 have been shown in several tumor types including breast cancer. We investigate STAT3 expresion as possible molecular marker for breast cancer early detection, as well as prognostic factor for determination of tumor agressiveness.

METHODS

In this study we measure p(Y705)STAT3 expression in tumor and adjacent tissue of breast cancer patients by Western blot. For relapse-free survival (RFS) and overall survival (OS) we used Log-Rank test.

RESULTS

We show that average expression of p (Y705) STAT3 in tumor tissue is higher compared to adjacent tissue. Moreover, we found that patients with HER2 positive receptors had significantly higher pSTAT3 expression compared to HER2 negative patients. We showed that patients with high mammographic density had significantly higher tumor expression of pSTAT3 compared to patients with low mammographic density. Also, we show that pSTAT3 expression correlates with longer RFS in the entire group of patients, as well as in the group of ER positive, in lymph node positive and in older group of breast cancer patients (with age over 50). Furthermore, in the entire group of patients, in ER positive, in lymph node positive and in older group of patient, high expression of pSTAT3 showed a better survival than low expression of pSTAT3.

CONCLUSION

Considering that the expression of pSTAT3 is associated with longer RFS and survival, it can be used as prognostic tools for determination of group of breast cancer patients with low-risk.

The Role of Histamine and Histamine Receptors in Mast Cell-Mediated Allergy and Inflammation: The Hunt for New Therapeutic Targets

Histamine and its receptors (H1R–H4R) play a crucial and significant role in the development of various allergic diseases. Mast cells are multifunctional bone marrow-derived tissue-dwelling cells that are the major producer of histamine in the body. H1R are expressed in many cells, including mast cells, and are involved in Type 1 hypersensitivity reactions. H2R are involved in Th1 lymphocyte cytokine production. H3R are mainly involved in blood–brain barrier function. H4R are highly expressed on mast cells where their stimulation exacerbates histamine and cytokine generation. Both H1R and H4R have important roles in the progression and modulation of histamine-mediated allergic diseases. Antihistamines that target H1R alone are not entirely effective in the treatment of acute pruritus, atopic dermatitis, allergic asthma, and other allergic diseases. However, antagonists that target H4R have shown promising effects in preclinical and clinical studies in the treatment of several allergic diseases. In the present review, we examine the accumulating evidence suggesting novel therapeutic approaches that explore both H1R and H4R as therapeutic targets for histamine-mediated allergic diseases.

Molecular Targets Underlying the Anticancer Effects of Quercetin: An Update

Quercetin, a medicinally important member of the flavonoid family, is one of the most prominent dietary antioxidants. It is present in a variety of foods-including fruits, vegetables, tea, wine, as well as other dietary supplements-and is responsible for various health benefits. Numerous pharmacological effects of quercetin include protection against diseases, such as osteoporosis, certain forms of malignant tumors, and pulmonary and cardiovascular disorders. Quercetin has the special ability of scavenging highly reactive species, such as hydrogen peroxide, superoxide anion, and hydroxyl radicals. These oxygen radicals are called reactive oxygen species, which can cause oxidative damage to cellular components, such as proteins, lipids, and deoxyribonucleic acid. Various oxygen radicals play important roles in pathophysiological and degenerative processes, such as aging. Subsequently, several studies have been performed to evaluate possible advantageous health effects of quercetin and to collect scientific evidence for these beneficial health claims. These studies also gather data in order to evaluate the exact mechanism(s) of action and toxicological effects of quercetin. The purpose of this review is to present and critically analyze molecular pathways underlying the anticancer effects of quercetin. Current limitations and future directions of research on this bioactive dietary polyphenol are also critically discussed.

Molecular targets of quercetin with anti-inflammatory properties in atopic dermatitis

Atopic dermatitis (AD) is an inflammatory skin disease. Over the past few decades, AD has become more prevalent worldwide. Quercetin, a naturally occurring polyphenol, shows antioxidant, anti-inflammatory, and antiallergic activities. Several recent clinical and preclinical findings suggest quercetin as a promising natural treatment for inflammatory skin diseases. Significant progress in elucidating the molecular mechanisms underlying the anti-AD properties of quercetin has been achieved in the recent years. Here, we discuss the use of quercetin as treatment for AD, with a particular focus on the molecular basis of its effect. We also briefly discuss the approaches to improve the bioavailability of quercetin.

Histamine and Skin Barrier: Are Histamine Antagonists Useful for the Prevention or Treatment of Atopic Dermatitis?

Atopic Dermatitis (AD), the most common chronic inflammatory skin disease, is characterized by an overactive immune response to a host of environmental allergens and dry, itchy skin. Over the past decade important discoveries have demonstrated that AD develops in part from genetic and/or acquired defects in the skin barrier. Histamine is an aminergic neurotransmitter involved in physiologic and pathologic processes such as pruritus, inflammation, and vascular leak. Enhanced histamine release has been observed in the skin of patients with AD and antihistamines are often prescribed for their sedating and anti-itch properties. Recent evidence suggests that histamine also inhibits the terminal differentiation of keratinocytes and impairs the skin barrier, raising the question whether histamine might play a role in AD barrier impairment. This, coupled with the notion that histamine’s effects mediated through the recently identified histamine receptor H4R, may be important in allergic inflammation, has renewed interest in this mediator in allergic diseases. In this paper we summarize the current knowledge on histamine and histamine receptor antagonists in AD and skin barrier function.

The role of histamine H1 and H4 receptors in atopic dermatitis: from basic research to clinical study

Histamine plays important roles in inflammation and nervous irritability in allergic disorders, including atopic dermatitis (AD). It has been shown to regulate the expression of pruritic factors, such as nerve growth factor and semaphorin 3A, in skin keratinocytes via histamine H1 receptor (H1R). Furthermore, H1R antagonist reduced the level of IL-31, a cytokine involving the skin barrier and pruritus, in chronic dermatitis lesions in NC/Nga mice and patients with AD. Histamine plays roles in the induction of allergic inflammation by activating eosinophils, mast cells, basophils, and Th2 cells via histamine H4 receptor (H4R). H4R, in addition to H1R, is expressed on sensory neurons, and a decrease in scratching behaviors was observed in H4R-deficient mice and mice treated with a H4R antagonist. We found that the combined administration of H1R and H4R antagonists inhibited the itch response and chronic allergic inflammation, and had a pharmacological effect similar to that of prednisolone. Although the oral administration of H1R antagonists is widely used to treat AD, it is not very effective. In contrast, JNJ39758979, a novel H4R antagonist, had marked effects against pruritus in Japanese patients with AD in a phase II clinical trial. Next generation antihistaminic agents possessing H1R and H4R antagonistic actions may be a potent therapeutic drug for AD.

The involvement of the JAK-STAT signaling pathway in chronic inflammatory skin disease atopic dermatitis

Atopic dermatitis (AD), a common chronic inflammatory skin disease, is characterized by inflammatory cell skin infiltration. The JAK-STAT pathway has been shown to play an essential role in the dysregulation of immune responses in AD, including the exaggeration of Th2 cell response, the activation of eosinophils, the maturation of B cells, and the suppression of regulatory T cells (Tregs). In addition, the JAK-STAT pathway, activated by IL-4, also plays a critical role in the pathogenesis of AD by upregulating epidermal chemokines, pro-inflammatroy cytokines, and pro-angiogenic factors as well as by downregulating antimicrobial peptides (AMPs) and factors responsible for skin barrier function. In this review, we will highlight the recent advances in our understanding of the JAK-STAT pathway in the pathogenesis of AD.

Effects of atopy and grass pollen season on histamine H₄ receptor expression in human leukocytes

BACKGROUND

The histamine H4 receptor (H4R) is a novel therapeutic target to treat allergic inflammation.

OBJECTIVE

To profile messenger RNA (mRNA) expression of H₄R isoforms in human cells and evaluate the effects of atopy and grass pollen season on H₄R expression in peripheral blood leukocytes ex vivo.

METHODS

H₄R isoform expression was assayed by quantitative polymerase chain reaction in human airway and peripheral RNA. During low and high grass pollen seasons, leukocytes were isolated from venous blood and fractionated into peripheral blood mononuclear cells and polymorphonuclear cells (PMN). H₄R expression was determined and related to atopy, defined by a level of specific IgE to Timothy grass pollen of ≥0.35 kU(A)/L (n = 7 atopic patients and 9 controls).

RESULTS

Expression of total and full length H₄R was at the limit of detection but predominant in peripheral blood leukocytes, where truncated H₄R was expressed exclusively (≤300-fold less). Suggestive evidence for total H₄R in airway cells and brain indicated an expression ≤260-fold lower than in peripheral blood mononuclear cells. Total H₄R mRNA expression was unaffected by atopy or grass pollen season, but truncated H₄R was significantly reduced during high grass pollen season in total leukocytes, independently of atopy (P < .01).

CONCLUSION

H₄R mRNA is predominantly expressed in peripheral blood leukocytes, and total H₄R expression levels are unrelated to atopy or grass pollen season. Atopy-independent seasonal variation in truncated H₄R expression might affect putative negative regulation of full length H4R during high grass pollen season. If verified, this should be considered during the design of drugs targeting H₄R to treat allergic inflammation, particularly for seasonal allergic rhinitis.

Reduced IFN-γ receptor expression and attenuated IFN-γ response by dendritic cells in patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is characterized by a predominance of T(H)2 immune reactions but weaker T(H)1 immune responses in acute skin lesions.

OBJECTIVES

To evaluate whether enhanced T(H)2 immunity in patients with AD might impair T(H)1 immune responses by affecting the IFN-γ responsiveness of antigen-presenting cells, we investigated IFN-γ receptor and IL-4 receptor α chain expression, IFN-γ signaling, and the expression of IFN-γ-responsive mediators in dendritic cells (DCs) and their precursors from patients with AD compared with those from healthy subjects.

METHODS

Skin biopsy specimens were obtained and both monocytes and monocyte-derived dendritic cells (MoDCs) from patients with AD (n = 86) and control subjects (n = 84) were analyzed by means of flow cytometry, real-time PCR, ELISA, and HPLC.

RESULTS

We observed lower IFN-γ receptor II expression combined with higher IL-4 receptor α chain expression on epidermal DCs, monocytes, and MoDCs from patients with AD. Induction of IFN-γ-inducible factors, such as interferon regulatory factor 1, interferon-inducible protein 10, and indoleamine 2,3-dioxygenase, was attenuated in IFN-γ-pulsed MoDCs from patients with AD. Weaker signal transducer and activator of transcription 1 activation mirrored by lower phosphorylated signal transducer and activator of transcription 1 levels in response to IFN-γ stimulation could be observed in epidermal DCs, monocytes, and MoDCs from patients with AD.

CONCLUSION

Impaired IFN-γ signaling together with attenuated IFN-γ responses in DCs and their precursor cells might contribute to the T(H)2 bias in patients with AD.

The role of the histamine H4 receptor in atopic dermatitis

The pathology of atopic dermatitis is orchestrated on the cellular level by several different cell types in the characteristic skin lesions. In such lesions, histamine as a mediator of many biological functions is also present in high concentrations. Most of the cells involved in the inflammatory responses express the histamine H1 and H2 receptors, but drugs targeting these receptors are not clinically effective. The discovery of the fourth histamine receptor, which is differentially expressed on immune and nonimmune cells, has shed new light on the actions of histamine in the complexity of atopic dermatitis. In this review, we describe a possible genetic impact on the expression level of the histamine H4 receptor and summarize the current data regarding the activity of the histamine H4 receptor on the key effector cells in atopic dermatitis. We do so in the context of whether the histamine H4 receptor offers a novel target for effective treatments of inflammatory skin diseases.

The expression of histamine H4 receptor mRNA in the skin and other tissues of normal dogs

The histamine 4 (H(4)) receptor was first cloned and characterized in 2000 using the human H(3) receptor DNA sequence. The H(4) receptor has been shown to participate in various aspects of inflammation, such as chemotaxis, upregulation of adhesion molecule expression and modulation of cytokine secretion. The primary goal of this study was to determine whether H(4) receptor mRNA is expressed in normal canine skin by performing an RT-PCR. An additional goal was to determine the expression of this receptor in the colon, liver, spleen and kidney. Tissues were collected from five healthy, young-adult pit bull dogs. Samples were immediately placed in RNAlater(®) solution and stored at -20°C until processed. The amplified products in all skin samples in addition to the colon, liver, spleen and kidney (variable expression) had the expected size of 400-500 bp. The sequenced amplicons matched the National Center for Biotechnology Information published sequence for the canine H(4) receptor. The study results showed that canine normal skin expresses the H(4) receptor mRNA. Further studies using immunohistochemistry should be conducted to demonstrate the expression of the H(4) receptor at the protein level and to localize the expression of this receptor in the skin.

Histamine and histamine receptors in pathogenesis and treatment of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease associated with chronic inflammatory demyelination of the central nervous system (CNS). Due to disease complexity and heterogeneity, its pathogenesis remains unknown and despite extensive studies, specific effective treatments have not yet been developed. The factors behind the initiation of the inflammatory reactions in CNS have not been identified until now. MS is considered as a complex disease depending on genetic as well as environmental factors. Experimental autoimmune encephalomyelitis (EAE) is the preferential experimental rodent model for MS. Histamine [2-(4-imidazole) ethylamine] is a ubiquitous inflammatory mediator of diverse physiological processes including neurotransmission, secretion of pituitary hormones, and regulation of the gastrointestinal and circulatory systems which can modulate immune responses. Histamine functions are mediated through four G-protein coupled receptors that are named H1-H4 receptor. Histamine is implicated as an important factor in pathophysiology of MS and EAE. It has been shown that histamine can change the permeability of blood brain barrier, which leads to elevation of infiltrated cells in CNS and neuroinflammation. In contrast, there are evidence that show the protective role of histamine in MS and its animal model, EAE. In this review, we try to clarify the role of histamine in pathogenesis of MS, as well as we evaluate the efficacy of histamine receptors agonists and antagonists in treatment of this disease.

Histamine induces human beta-defensin-3 production in human keratinocytes

BACKGROUND

The antimicrobial peptide human beta-defensin-3 (hBD-3) is produced by epidermal keratinocytes, and promotes cutaneous antimicrobial defense, inflammation, and wound repair. hBD-3 induces histamine release from mast cells. We previously showed that histamine enhanced transcriptional activity of activator protein-1 (AP-1) in human keratinocytes by inducing the expression of AP-1 component c-Fos via the activation of extracellular signal-regulated kinase (ERK) through H1 receptors.

OBJECTIVE

To examine in vitro effects of histamine on hBD-3 production in normal human keratinocytes.

METHODS

The hBD-3 production was examined by enzyme-linked immunosorbent assays and reverse transcription-polymerase chain reaction. The transcriptional activities were analyzed by dual luciferase assays. The phosphorylation of proteins was examined by Western blotting.

RESULTS

Histamine enhanced hBD-3 secretion and mRNA expression in keratinocytes. The histamine-induced hBD-3 production was suppressed by H1 antagonist pyrilamine and antisense oligonucleotides against signal transducer and activator of transcription 3 (STAT3) and AP-1 components c-Jun and c-Fos. Histamine enhanced STAT3 transcriptional activity and induced tyrosine and serine phosphorylation of STAT3. The former was suppressed by Janus kinase 2 (JAK2) inhibitor AG490, while the latter was suppressed by mitogen-activated protein kinase kinase (MEK) inhibitor PD98059; both were suppressed by pyrilamine. AG490 and PD98059 suppressed histamine-induced hBD-3 production and STAT3 activity. Histamine induced tyrosine phosphorylation of JAK2, and pyrilamine suppressed the phosphorylation.

CONCLUSION

It is suggested that histamine induces hBD-3 production in human keratinocytes through H1 receptors by activating STAT3 and AP-1 via JAK2 and MEK/ERK. Histamine may promote cutaneous antimicrobial defense, inflammation, and wound repair through hBD-3.

The role of histamine H4 receptor in immune and inflammatory disorders

Since its discovery at the beginning of the 20th century, histamine has been established to play a pathophysiological regulatory role in cellular events through binding to four types of G-protein-coupled histamine receptors that are differentially expressed in various cell types. The discovery, at the turn of the millennium, that the histamine H4 receptor is largely expressed in haemopoietic cells as well as its chemotactic properties designate its regulatory role in the immune system. H4 receptors modulate eosinophil migration and selective recruitment of mast cells leading to amplification of histamine-mediated immune responses and eventually to chronic inflammation. H4 receptor involvement in dendritic cell activation and T cell differentiation documents its immunomodulatory function. The characterization of the H4 as the immune system histamine receptor directed growing attention towards its therapeutic exploitation in inflammatory disorders, such as allergy, asthma, chronic pruritus and autoimmune diseases. The efficacy of a number of H4 receptor ligands has been evaluated in in vivo and in vitro animal models of disease and in human biological samples. However, before reaching decisive conclusions on H4 receptor pathophysiological functions and therapeutic exploitation, identification of genetic polymorphisms and interspecies differences in its relative actions and pharmacological profile need to be addressed and taken into consideration. Despite certain variations in the reported findings, the available data strongly point to the H4 receptor as a novel target for the pharmacological modulation of histamine-transferred immune signals and offer an optimistic perspective for the therapeutic exploitation of this promising new drug target in inflammatory disorders.

Histamine enhances the production of human beta-defensin-2 in human keratinocytes

The anti-microbial peptide human beta-defensin-2 (hBD-2), produced by epidermal keratinocytes, plays pivotal roles in anti-microbial defense, inflammatory dermatoses, and wound repair. hBD-2 induces histamine release from mast cells. We examined the in vitro effects of histamine on hBD-2 production in normal human keratinocytes. Histamine enhanced TNF-alpha- or IFN-gamma-induced hBD-2 secretion and mRNA expression. Histamine alone enhanced transcriptional activities of NF-kappaB and activator protein-1 (AP-1) and potentiated TNF-alpha-induced NF-kappaB and AP-1 activities or IFN-gamma-induced NF-kappaB and STAT1 activities. Antisense oligonucleotides against NF-kappaB components p50 and p65, AP-1 components c-Jun and c-Fos, or H1 antagonist pyrilamine suppressed hBD-2 production induced by histamine plus TNF-alpha or IFN-gamma. Antisense oligonucleotide against STAT1 only suppressed hBD-2 production induced by histamine plus IFN-gamma. Histamine induced serine phosphorylation of inhibitory NF-kappaBalpha (IkappaBalpha) alone or together with TNF-alpha or IFN-gamma. Histamine induced c-Fos mRNA expression alone or together with TNF-alpha, whereas it did not further increase c-Jun mRNA levels enhanced by TNF-alpha. Histamine induced serine phosphorylation of STAT1 alone or together with IFN-gamma, whereas it did not further enhance IFN-gamma-induced tyrosine phosphorylation of STAT1. The histamine-induced serine phosphorylation of STAT1 was suppressed by MAPKK (MEK) inhibitor PD98059. These results suggest that histamine stimulates H1 receptor and potentiates TNF-alpha- or IFN-gamma-induced hBD-2 production dependent on NF-kappaB, AP-1, or STAT1 in human keratinocytes. Histamine may potentiate anti-microbial defense, skin inflammation, and wound repair via the induction of hBD-2.