Histamine H1 receptor antagonist blocks histamine-induced proinflammatory cytokine production through inhibition of Ca2+-dependent protein kinase C, Raf/MEK/ERK and IKK/IκB/NF-κB signal cascades

p62 Binding to Protein Kinase C Regulates HIV-1 gp120 V3 Loop Induced Microglial Inflammation

The main pathogenic mechanism of HIV-associated neurocognitive disorders (HAND) is neuronal apoptosis induced by inflammatory mediators, in which microglial inflammation plays a crucial role. However, the exact pathogenic mechanism remains unclear. Previous studies have shown that the HIV-1 gp120 V3 loop can trigger inflammation in CHME-5 microglia. p62 is a post-translational modified multidomain protein that is involved in the regulation of autophagy and is closely related to neuroinflammation. In this study, we found that p62 knockout down-regulated the expression of MCP-1, IL-6 and COX-2, and improved the inflammation of HIV-1 gp120 V3 loop induced microglia, while overexpression of p62 up-regulated the expression of MCP-1, IL-6 and COX-2, and promoted the inflammation of microglia. In addition, protein kinase C (PKC) knockout down-regulated the expression of MCP-1, IL-6 and COX-2 and inhibited the activation of IKK/ NF-κ B pathway, while tumor necrosis factor receptor-associated factor 6 (TRAF6) knockout had no significant effect on the expression of MCP-1, IL-6 and COX-2. Co-immunoprecipitation showed that p62 was bound and interacted with PKC. Inhibition of IKK/ NF-κ B pathway can down-regulate the expression of MCP-1, IL-6 and COX-2, and improve the inflammatory response of microglia. Our research further found that inhibition of IKK/ NF-κ B can decrease the expression of Caspase-3 and reduce the apoptosis of neurons in the co-culture of CHME-5 microglia and primary mouse neurons. The results of this study suggest that HIV-1 gp120 V3 loop induced CHME-5 microglial inflammation may be activated by the direct binding of p62 and PKC through the IKK/ NF-κ B signaling pathway, and these findings provide an important reference for the prevention and treatment of HAND.

The involvement of keratinocytes in pruritus of chronic inflammatory dermatosis

Frequent itching and incessant scratching are commonly observed in various chronic inflammatory skin conditions, including atopic dermatitis and psoriasis. The persistent and prolonged nature of pruritus can worsen one's quality of life. Keratinocytes (KCs), the predominant cells of the epidermis, have been confirmed to interact with sensory neurons and immune cells and be involved in chronic skin inflammatory diseases associated with pruritus. Initially, KCs and sensory neurons form a unique synapse-like connection within the epidermis, serving as the structural foundation for their interaction. Additionally, several receptors, including toll-like receptors and protease-activated receptor 2, expressed on KCs, become activated in an inflammatory milieu. On the one hand, activated KCs are sources of pro-inflammatory cytokines and neurotrophic factors, such as adenosine triphosphate, thymic stromal lymphopoietin, and nerve growth factor, which directly or indirectly participate in stimulating sensory neurons, thereby contributing to the itch sensations. On the other hand, KCs also function as primary transducers alongside intraepidermal nerve endings, directly initiating pruritic responses. This review summarizes the current literature and highlights the critical role of KCs in the development and persistence of chronic itch in inflammatory skin disorders.

Terfenadine, a histamine H1 receptor antagonist, induces apoptosis by suppressing STAT3 signaling in human colorectal cancer HCT116 cells

Introduction

Colorectal cancer is a highly aggressive and metastatic cancer with inadequate clinical outcomes. Given the crucial role of histamine and histamine receptors in colorectal carcinogenesis, this study aimed at exploring the anticancer effects of terfenadine against colorectal cancer HCT116 cells and elucidate its underlying mechanism.

Methods

Herein, we examined the effect of terfenadine on growth and proliferation of HCT116 cells in vitro and in vivo. Various experimental techniques such as flow cytometry, western blot, immunoprecipitation, luciferase assay were employed to unveil the mechanism of cell death triggered by terfenadine.

Results

Terfenadine markedly attenuated the viability of HCT116 cells by abrogating histamine H1 receptor (H1R) signaling. In addition, terfenadine modulated the balance of Bax and Bcl-2, triggering cytochrome c discharge in the cytoplasm, thereby stimulating the caspase cascade and poly-(ADP-ribose) polymerase (PARP) degradation. Moreover, terfenadine suppressed murine double minute-2 (Mdm2) expression, whereas p53 expression increased. Terfenadine suppressed STAT3 phosphorylation and expression of its gene products by inhibiting MEK/ERK and JAK2 activation in HCT116 cells. Furthermore, treatment with U0126, a MEK inhibitor, and AG490, a JAK2 inhibitor, dramatically diminished the phosphorylations of ERK1/2 and JAK2, respectively, leading to STAT3 downregulation. Likewise, terfenadine diminished the complex formation of MEK1/2 with β-arrestin 2. In addition, terfenadine dwindled the phosphorylation of PKC substrates. Terfenadine administration (10 mg/kg) substantially retarded the growth of HCT116 tumor xenografts in vivo.

Conclusion

Terfenadine induces the apoptosis of HCT116 cells by abrogating STAT3 signaling. Overall, this study supports terfenadine as a prominent anticancer therapy for colorectal cancer.

Exploration of the intestinal flora to reveal the important contribution of Radix Astragali to Huangqi Jianzhong Tang in treating chronic atrophic gastritis rats

Radix Astragali (Huangqi in Chinese, HQ) is a commonly used Chinese herbal medicine for thousands of years. In this study, A classic prescription Huangqi Jianzhong tang (HQJZ) was selected to evaluate the important effect of HQ on rats with chronic atrophic gastritis (CAG) from the perspective of intestinal flora in cecal contents samples. Traditional pharmacological indicators, including weight change, pathological examination and biochemical indicators showed that HQ exerted favorable contribution to HQJZ against CAG, where the efficiencies of HQ and HQJZ were better than HY (HQJZ prepared without HQ). An accurate strategy was adopted to screen out the differential metabolites in the metabolomis analysis of intestinal flora in cecal contents samples based on the optimal screening factors, including VIP (importance of variables in projection), FC (fold change), AUROC (area under the receiver operating characteristic curve) and -ln(p-value), which were evaluated based on their interpreting, grouping, and predicting abilities of the performed orthogonal partial least-squares-discriminate analysis (OPLS-DA) models. Ten altered differential metabolites were obtained and associated with the intestinal flora, which HQ exerted the important metabolic contributions to HQJZ. The efficacy on the diversity of intestinal flora and their correlations with the altered metabolites further showed the important role of HQ in HQJZ composition. This work provided valuable approach for looking for potential biomarkers associated with metabolomics research with more accuracy, and provided new insights into the mechanisms to explain the efficacy of HQ contributing to HQJZ formula.

Repurposing fexofenadine as a promising candidate for diabetic kidney disease: randomized clinical trial

PURPOSE

Diabetic kidney disease (DKD) is a devastating complication of diabetes mellitus. Inflammation and histamine are potentially involved in the disease progression. This study aimed to evaluate the role of fexofenadine in patients with DKD.

METHODS

From January 2020 to February 2022, out of 123 patients screened for eligibility, 61 patients completed the study. Patients were randomized into two groups, the fexofenadine group (n = 30): received ramipril plus fexofenadine, and the control group (n = 31): received ramipril only for six months. Changes in urinary albumin to creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) were considered primary outcomes. Measurements of urinary cyclophilin A, monocyte chemoattractant protein-1 (MCP-1), 8-hydroxy-2' deoxyguanosine (8-OHdG), and podocalyxin (PCX) were considered secondary outcomes. The study was prospectively registered on clinicaltrial.gov on January 13, 2020, with identification code NCT04224428.

RESULTS

At the end of the study, fexofenadine reduced UACR by 16% (95% CI, - 23.4% to - 9.3%) versus a noticeable rise of 11% (95% CI, 4.1% to 17.8%) in UACR in the control group, (p < 0.001). No significant difference in eGFR was revealed between the two groups. However, the control group showed a significant decrease of - 3.5% (95% CI, - 6.6% to - 0.3%) in eGFR, compared to its baseline value. This reduction was not reported in the fexofenadine group. Fexofenadine use was associated with a significant decline in MCP-1, 8-OHdG, and PCX compared to baseline values.

CONCLUSION

Fexofenadine is a possible promising adjuvant therapy in patients with DKD. Further large-scale trials are needed to confirm our preliminary results.

Histamine H1 Receptor-Mediated JNK Phosphorylation Is Regulated by Gq Protein-Dependent but Arrestin-Independent Pathways

Arrestins are known to be involved not only in the desensitization and internalization of G protein-coupled receptors but also in the G protein-independent activation of mitogen-activated protein (MAP) kinases, such as extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), to regulate cell proliferation and inflammation. Our previous study revealed that the histamine H1 receptor-mediated activation of ERK is dually regulated by Gq proteins and arrestins. In this study, we investigated the roles of Gq proteins and arrestins in the H1 receptor-mediated activation of JNK in Chinese hamster ovary (CHO) cells expressing wild-type (WT) human H1 receptors, the Gq protein-biased mutant S487TR, and the arrestin-biased mutant S487A. In these mutants, the Ser487 residue in the C-terminus region of the WT was truncated (S487TR) or mutated to alanine (S487A). Histamine significantly stimulated JNK phosphorylation in CHO cells expressing WT and S487TR but not S487A. Histamine-induced JNK phosphorylation in CHO cells expressing WT and S487TR was suppressed by inhibitors against H1 receptors (ketotifen and diphenhydramine), Gq proteins (YM-254890), and protein kinase C (PKC) (GF109203X) as well as an intracellular Ca2+ chelator (BAPTA-AM) but not by inhibitors against G protein-coupled receptor kinases (GRK2/3) (cmpd101), β-arrestin2 (β-arrestin2 siRNA), and clathrin (hypertonic sucrose). These results suggest that the H1 receptor-mediated phosphorylation of JNK is regulated by Gq-protein/Ca2+/PKC-dependent but GRK/arrestin/clathrin-independent pathways.

Pharmacological Characterization of the Zebrafish (Danio Rerio) Histamine H1 Receptor Reveals the Involvement of the Second Extracellular Loop in the Binding of Histamine

The zebrafish (Danio rerio) histamine H1 receptor gene (zfH1R) was cloned in 2007 and reported to be involved in fish locomotion. Yet, no detailed characterization of its pharmacology and signaling properties have so far been reported. In this study, we pharmacologically characterized the zfH1R expressed in HEK-293T cells by means of [3H]-mepyramine binding and G protein-signaling assays. The zfH1R [dissociation constant (KD), 0.7 nM] displayed similar affinity for the antagonist [3H]-mepyramine as the human histamine H1 receptor (hH1R) (KD, 1.5 nM), whereas the affinity for histamine is 100-fold higher than for the human H1R. The zfH1R couples to Gαq/11 proteins and activates several reporter genes, i.e., NFAT, NFϰB, CRE, VEGF, COX-2, SRE, and AP-1, and zfH1R-mediated signaling is prevented by the Gαq/11 inhibitor YM-254890 and the antagonist mepyramine. Molecular modeling of the zfH1R and human H1R shows that the binding pockets are identical, implying that variations along the ligand binding pathway could underly the differences in histamine affinity instead. Targeting differentially charged residues in extracellular loop 2 (ECL2) using site-directed mutagenesis revealed that Arg21045x55 is most likely involved in the binding process of histamine in zfH1R. This study aids the understanding of the pharmacological differences between H1R orthologs and the role of ECL2 in histamine binding and provides fundamental information for the understanding of the histaminergic system in the zebrafish. SIGNIFICANCE STATEMENT: The use of the zebrafish as in vivo models in neuroscience is growing exponentially, which asks for detailed characterization of the aminergic neurotransmitter systems in this model. This study is the first to pharmacologically characterize the zebrafish histamine H1 receptor after expression in HEK-293T cells. The results show a high pharmacological and functional resemblance with the human ortholog but also reveal interesting structural differences and unveils an important role of the second extracellular loop in histamine binding.

Carbon dioxide and MAPK signalling: towards therapy for inflammation

Inflammation, although necessary to fight infections, becomes a threat when it exceeds the capability of the immune system to control it. In addition, inflammation is a cause and/or symptom of many different disorders, including metabolic, neurodegenerative, autoimmune and cardiovascular diseases. Comorbidities and advanced age are typical predictors of more severe cases of seasonal viral infection, with COVID-19 a clear example. The primary importance of mitogen-activated protein kinases (MAPKs) in the course of COVID-19 is evident in the mechanisms by which cells are infected with SARS-CoV-2; the cytokine storm that profoundly worsens a patient's condition; the pathogenesis of diseases, such as diabetes, obesity, and hypertension, that contribute to a worsened prognosis; and post-COVID-19 complications, such as brain fog and thrombosis. An increasing number of reports have revealed that MAPKs are regulated by carbon dioxide (CO2); hence, we reviewed the literature to identify associations between CO2 and MAPKs and possible therapeutic benefits resulting from the elevation of CO2 levels. CO2 regulates key processes leading to and resulting from inflammation, and the therapeutic effects of CO2 (or bicarbonate, HCO3-) have been documented in all of the abovementioned comorbidities and complications of COVID-19 in which MAPKs play roles. The overlapping MAPK and CO2 signalling pathways in the contexts of allergy, apoptosis and cell survival, pulmonary oedema (alveolar fluid resorption), and mechanical ventilation-induced responses in lungs and related to mitochondria are also discussed. Video Abstract.

Differential regulation of histamine H1 receptor-mediated ERK phosphorylation by Gq proteins and arrestins

Gq protein-coupled histamine H1 receptors play crucial roles in allergic and inflammatory reactions, in which the phosphorylation of extracellular signal-regulated kinase (ERK) appears to mediate the production of inflammatory cytokines. ERK phosphorylation is regulated by G protein- and arrestin-mediated signal transduction pathways. Here, we aimed to explore how H1 receptor-mediated processes of ERK phosphorylation might be differentially regulated by Gq proteins and arrestins. For this purpose, we evaluated the regulatory mechanism(s) of H1 receptor-mediated ERK phosphorylation in Chinese hamster ovary cells expressing Gq protein- and arrestin-biased mutants of human H1 receptors, S487TR and S487A, in which the Ser487 residue in the C-terminal was truncated and mutated to alanine, respectively. Immunoblotting analysis indicated that histamine-induced ERK phosphorylation was prompt and transient in cells expressing Gq protein-biased S487TR, whereas it was slow and sustained in cells expressing arrestin-biased S487A. Inhibitors of Gq proteins (YM-254890) and protein kinase C (PKC) (GF109203X), and an intracellular Ca2+ chelator (BAPTA-AM) suppressed histamine-induced ERK phosphorylation in cells expressing S487TR, but not those expressing S487A. Conversely, inhibitors of G protein-coupled receptor kinases (GRK2/3) (cmpd101), β-arrestin2 (β-arrestin2 siRNA), clathrin (hypertonic sucrose), Raf (LY3009120), and MEK (U0126) suppressed histamine-induced ERK phosphorylation in cells expressing S487A, but not those expressing S487TR. These results suggest that H1 receptor-mediated ERK phosphorylation might be differentially regulated by the Gq protein/Ca2+/PKC and GRK/arrestin/clathrin/Raf/MEK pathways to potentially determine the early and late phases of histamine-induced allergic and inflammatory responses, respectively.

Effects of Histamine and the α-Tocopherol Metabolite α-13'-COOH in an Atopic Dermatitis Full-Thickness Skin Model

Atopic dermatitis is a T-cell mediated inflammatory skin disease with detected elevated levels of histamine in skin or plasma. In this study, the effects of histamine in a T_H2 cytokine environment on human keratinocytes and three-dimensional skin models were investigated. These models were used to explore the anti-inflammatory properties of the α-tocopherol-derived long-chain metabolite α-13'-carboxychromanol (α-13'-COOH). Histamine and T_H2 cytokine-induced proliferation of keratinocytes was studied using a scratch assay. The inflammatory marker interleukin-8 was significantly increased in healthy and T_H2 cytokine-stimulated keratinocytes and skin models after histamine treatment. The incubation of full-thickness skin models with T_H2 cytokines and histamine resulted in morphological changes in the epidermal layer, interpreted as hyperkeratosis. α-13'-COOH significantly decreased interleukin-8 in these disease-associated skin models. Histological staining of filaggrin showed skin-strengthening effects following α-13'-COOH treatment, without changes in mRNA expression. Cytokeratin 10 mRNA expression tended to be increased in response to α-13'-COOH. Anti-allergic properties of α-13'-COOH were studied by pre-incubation of human leukocytes with α-13'-COOH. This resulted in reduced sulfido-leukotriene synthesis. The hyperproliferation effect of histamine in atopic dermatitis skin models may be of further interest to the study of disease-associated morphological changes. Moreover, α-13'-COOH is a promising natural compound for the treatment of inflammatory skin diseases.

TNF-α‒Mediated Keratinocyte Expression and Release of Matrix Metalloproteinase 9: Putative Mechanism of Pathogenesis in Stevens‒Johnson Syndrome/Toxic Epidermal Necrolysis

Stevens‒Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are severe cutaneous adverse drug reactions characterized by widespread keratinocyte cell death and epidermal detachment. At present, there is little understanding of how the detachment occurs or how it is abrogated by the TNF-α inhibitor etanercept, an effective SJS/TEN treatment. RNA sequencing was used to identify upregulated transcripts in formalin-fixed paraffin-embedded SJS/TEN skin biopsies. Epidermal matrix metalloproteinase 9 (MMP9) expression was assessed by immunohistochemistry in skin biopsies and cultured human skin explants exposed to serum from patients with cutaneous adverse drug reactions. TNF-α‒induced MMP9 expression and activity and its abrogation by etanercept were determined using the HaCaT immortalized keratinocyte cell line. Epidermal MMP9 expression was significantly higher in SJS/TEN skin (70.6%) than in healthy control skin (0%) (P = 0.0098) and nonbullous skin reactions (10.7%) (P = 0.0002). SJS/TEN serum induced significant MMP9 expression and collagenase activity in healthy skin explants, which was reduced by etanercept. Etanercept was also able to negate the TNF-α‒induced MMP9 expression in the HaCaT cell line. Data suggest that elevated epidermal MMP9 expression and collagenase activity are a putative pathogenic mechanism in SJS/TEN, which is limited by etanercept. Modulation of MMP9 expression and activity represents, to our knowledge, a previously unreported therapeutic target for the treatment of SJS/TEN.

Regulation of gut microbiota of Astragali Radix in treating for chronic atrophic gastritis rats based on metabolomics coupled with 16S rRNA gene sequencing

Astragali Radix (HQ), a common traditional Chinese medicine (TCM), is widely used to treat chronic atrophic gastritis (CAG). However, its mechanism in treating CAG is still not clear. Accumulating evidence highlights the link between gut microbiota and CAG. We hypothesized that the gut microbiota might be involved in the effect of HQ. Ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry (UPLC-Q-TOF/MS) based metabolomics and 16S rRNA gene sequencing techniques of the cecal contents were applied to study its mechanisms. As a result, nine metabolites and fifteen gut microbiotas changed significantly in cecal contents samples between control group and model group. Among them, two metabolites (7-keto-3A ·12-α-hydroxyalkanoic acid and deoxycholic acid) and two gut microbiota genera (Acetobacter and Escherichia), had the most obvious callback effect after the administration of HQ. Sixty-seven correlated pairs exhibited the significant link between the involved metabolites and gut microbiotas through the correlation analysis, where two strong correlation pairs: Tetrahydrohydroxone ∼ Bacteroides (r = 0.895) and Deoxycholic acid ∼ Acetobacter (r = -0.843) were regulated by HQ. The results showed that HQ had the potential protection from metabolic perturbation involved into gut microbiotas induced by CAG. Two gut microbiotas, Acetobacter and Escherichia, and two metabolites, 7-keto-3A ·12-α-hydroxyalkanoic acid and deoxycholic acid were the potential targets of HQ.

Efficacy and safety of ebastine dose escalation in chronic urticaria: A prospective study

The second-generation antihistamines at licensed doses are first-line treatment in urticaria and up-dosing is recommended as second-line treatment. To assess the efficacy and safety of escalated doses of ebastine in patients with chronic urticaria (CU), we designed this study. Recruited patients with CU were treated with increasing doses of ebstine. Treatment started at the daily dose of 10 mg. The symptom is assessed weekly, and if there is no significant improvement, the dose is increased from 10 mg to 20 mg, and if still no significant improvement, up to 40 mg. Pruritus, number, diameter, duration and frequency of wheals, and adverse reactions were assessed. One hundred and forty (76.50%) patients achieved marked effect with ebastine 10 mg/day, 27 (14.75%) patients with ebastine 20 mg/day and 13 (7.10%) patients with ebastine 40 mg/day, while 3(1.64%) patients did not get marked effect. There was no significant difference of effect between factitious urticaria, CSU, cholinergic urticaria and CSU with factitious urticaria in different dose (all p > 0.05). Common adverse reactions of ebstine treatment, included dry mouth, somnolence, tiredness and headache, were mild or moderate. There was no significant difference between the degree score of dry mouth with different doses of ebastine, and the same to somnolence, tiredness and headache (all p > 0.05). Doses escalation of ebastine should be effective in treatment of factitious urticaria, CSU and cholinergic urticaria with poorly treated by standard of double doses. Increasing ebastine dose did not increase the incidence of adverse reactions.

A New Topical Candidate in Acne Treatment: Characterization of the Meclozine Hydrochloride as an Anti-Inflammatory Compound from In Vitro to a Preliminary Clinical Study

Acne is a chronic inflammatory multifactorial disease involving the anaerobic bacterium Cutibacterium acnes (C. acnes). Current acne treatments are associated with adverse effects, limiting treatment compliance and use. We showed that meclozine, an anti-histaminic H1 compound, has anti-inflammatory properties. In Vitro, meclozine reduced the production of CXCL8/IL-8 and IL-1β mRNA and protein by C. acnes-stimulated human keratinocytes and monocytes. No cell toxicity was observed at the IC50. Meclozine prevented the phosphorylation of ERK and JNK. In Vivo, 1% meclozine gel significantly decreased C. acnes-mouse ear induced inflammation by 26.7% (p = 0.021). Ex vivo experiments on human skin explants showed that meclozine decreased the production of GM-CSF, IL-1β and TNF-α at transcriptional and translational levels. In a randomized, double-blind, placebo-controlled proof-of-concept clinical trial on 60 volunteers, 2% meclozine pharmaceutical gel decreased by 20.1% (p < 0.001) the ASI score in the treated group after 12 weeks of treatment. No adverse event was reported. Together, these results indicate that meclozine is a potent topical anti-inflammatory compound of potential value for acne treatment.

Calcium Ions Aggravate Alzheimer's Disease Through the Aberrant Activation of Neuronal Networks, Leading to Synaptic and Cognitive Deficits

Alzheimer’s disease (AD) is a neurodegenerative disease that is characterized by the production and deposition of β-amyloid protein (Aβ) and hyperphosphorylated tau, leading to the formation of β-amyloid plaques (APs) and neurofibrillary tangles (NFTs). Although calcium ions (Ca²⁺) promote the formation of APs and NFTs, no systematic review of the mechanisms by which Ca²⁺ affects the development and progression of AD has been published. Therefore, the current review aimed to fill the gaps between elevated Ca²⁺ levels and the pathogenesis of AD. Specifically, we mainly focus on the molecular mechanisms by which Ca²⁺ affects the neuronal networks of neuroinflammation, neuronal injury, neurogenesis, neurotoxicity, neuroprotection, and autophagy. Furthermore, the roles of Ca²⁺ transporters located in the cell membrane, endoplasmic reticulum (ER), mitochondria and lysosome in mediating the effects of Ca²⁺ on activating neuronal networks that ultimately contribute to the development and progression of AD are discussed. Finally, the drug candidates derived from herbs used as food or seasoning in Chinese daily life are summarized to provide a theoretical basis for improving the clinical treatment of AD.

Signaling Pathway of Histamine H1 Receptor-Mediated Histamine H1 Receptor Gene Upregulation Induced by Histamine in U-373 MG Cells

Histamine H₁ receptor (H1R) is one of the targets of histamine in the nervous system and the peripheral tissues. Protein kinase Cδ (PKCδ) signaling is involved in histamine-induced upregulation of H1R gene expression in HeLa cells. Histamine also upregulates H1R gene expression in U-373 MG cells. However, the molecular signaling of this upregulation is still unclear. Here, we investigated the molecular mechanism of histamine-induced H1R gene upregulation in U-373 MG cells. Histamine-induced H1R gene upregulation was inhibited by H1R antagonist d-chlorpheniramine, but not by ranitidine, ciproxifan, or JNJ77777120, and H2R, H3R, or H4R antagonists, respectively. Ro-31-8220 and Go6976 also suppressed this upregulation, however, the PKCδ selective inhibitor rottlerin and the PKCβ selective inhibitor Ly333531 did not. Time-course studies showed distinct kinetics of H1R gene upregulation in U-373 MG cells from that in HeLa cells. A promoter assay revealed that the promoter region responsible for H1R gene upregulation in U-373 MG cells was different from that of HeLa cells. These data suggest that the H1R-activated H1R gene expression signaling pathway in U-373 MG cells is different from that in HeLa cells, possibly by using different promoters. The involvement of PKCα also suggests that compounds that target PKCδ could work as peripheral type H1R-selective inhibitors without a sedative effect.

The protective effect of isoflurane pretreatment on liver IRI by suppressing noncanonical pyroptosis of liver macrophages

BACKGROUND

Liver ischaemia-reperfusion injury (IRI) is a major complication in the perioperative period and often leads to liver failure and even systemic inflammation. Sufficient evidence has demonstrated that isoflurane has anti-inflammatory effects. We aimed to determine whether isoflurane pretreatment protects against liver IRI and to investigate the mechanisms involved in this protection.

METHODS

Male C57BL/6 mice were pretreated with or without isoflurane and subjected to 90 min of 70% liver ischaemia, followed by reperfusion for 6 h. Liver tissues and serum were analysed to assess liver IRI. To probe the mechanisms, liver macrophages isolated from C57BL/6 mice were pretreated with or without emulsified isoflurane for 30 min before incubation with 1 µg/ml lipopolysaccharide (LPS) for 24 h. Inflammatory cytokine production, intracellular Ca²⁺ levels, caspase-11 expression, NF-κB transcription, and NLRP3 inflammasome activation were assessed by ELISA, an intracellular Ca²⁺ concentration assay, immunohistochemistry, or Western blotting.

RESULTS

Isoflurane preconditioning significantly relieved liver IRI in mice and LPS-induced inflammation in liver macrophages. Additionally, isoflurane pretreatment inhibited caspase-11 expression and noncanonical pyroptosis-related production of cytokines (IL-1β and IL-18). Interestingly, isoflurane preconditioning reduced intracellular Ca²⁺ levels, NF-κB translocation, and NLRP3 inflammasome activation in LPS-induced macrophages. Our results indicated that isoflurane preconditioning ameliorated liver IRI by suppressing noncanonical pyroptosis in liver macrophages. These findings suggest that isoflurane could be a pharmacological agent for liver IRI prevention and thus deserves more attention and further investigation.

Could Histamine H1 Receptor Antagonists Be Used for Treating COVID-19?

COVID-19 has rapidly become a pandemic worldwide, causing extensive and long-term health issues. There is an urgent need to identify therapies that limit SARS-CoV-2 infection and improve the outcome of COVID-19 patients. Unbalanced lung inflammation is a common feature in severe COVID-19 patients; therefore, reducing lung inflammation can undoubtedly benefit the clinical manifestations. Histamine H1 receptor (H1 receptor) antagonists are widely prescribed medications to treat allergic diseases, while recently it has emerged that they show significant promise as anti-SARS-CoV-2 agents. Here, we briefly summarize the novel use of H1 receptor antagonists in combating SARS-CoV-2 infection. We also describe the potential antiviral mechanisms of H1 receptor antagonists on SARS-CoV-2. Finally, the opportunities and challenges of the use of H1 receptor antagonists in managing COVID-19 are discussed.

Biased agonism at histamine H1 receptor: Desensitization, internalization and MAPK activation triggered by antihistamines

Histamine H₁ receptor ligands used clinically as antiallergics rank among the most widely prescribed and over-the-counter drugs in the world. They exert the therapeutic actions by blocking the effects of histamine, due to null or negative efficacy towards Gα_q-phospholipase C (PLC)-inositol triphosphates (IP₃)-Ca²⁺ and nuclear factor-kappa B cascades. However, there is no information regarding their ability to modulate other receptor responses. The aim of the present study was to investigate whether histamine H₁ receptor ligands could display positive efficacy concerning receptor desensitization, internalization, signaling through Gα_q independent pathways or even transcriptional regulation of proinflammatory genes. While diphenhydramine, triprolidine and chlorpheniramine activate ERK1/2 (extracellular signal-regulated kinase 1/2) pathway in A549 cells, pre-treatment with chlorpheniramine or triprolidine completely desensitize histamine H₁ receptor mediated Ca²⁺ response, and both diphenhydramine and triprolidine lead to receptor internalization. Unlike histamine, histamine H₁ receptor desensitization and internalization induced by antihistamines prove to be independent of G protein-coupled receptor kinase 2 (GRK2) phosphorylation. Also, unlike the reference agonist, the recovery of the number of cell-surface histamine H₁ receptors is a consequence of de novo synthesis. On the other hand, all of the ligands lack efficacy regarding cyclooxygenase-2 (COX-2) and interleukin-8 (IL-8) mRNA regulation. However, a prolonged exposure with each of the antihistamines impaires the increase in COX-2 and IL-8 mRNA levels induced by histamine, even after ligand removal. Altogether, these findings demonstrate the biased nature of histamine H₁ receptor ligands contributing to a more accurate classification, and providing evidence for a more rational and safe use of them.

Amelioration of Compound 48/80-Mediated Itch and LL-37-Induced Inflammation by a Single-Stranded Oligonucleotide

Numerous inflammatory skin disorders display a high prevalence of itch. The Mas-related G protein coupled receptor X2 (MRGPRX2) has been shown to modulate itch by inducing non-IgE-mediated mast cell degranulation and the release of endogenous inducers of pruritus. Various substances collectively known as basic secretagogues, which include inflammatory peptides and certain drugs, can trigger MRGPRX2 and thereby induce pseudo-allergic reactions characterized by histamine and protease release as well as inflammation. Here, we investigated the capacity of an immunomodulatory single-stranded oligonucleotide (ssON) to modulate IgE-independent mast cell degranulation and, more specifically, its ability to inhibit the basic secretagogues compound 48/80 (C48/80)-and LL-37 in vitro and in vivo. We examined the effect of ssON on MRGPRX2 activation in vitro by measuring degranulation in a human mast cell line (LAD2) and calcium influx in MRGPRX2-transfected HEK293 cells. To determine the effect of ssON on itch, we performed behavioral studies in established mouse models and collected skin biopsies for histological analysis. Additionally, with the use of a rosacea mouse model and RT-qPCR, we investigated the effect on ssON on LL-37-induced inflammation. We reveal that both mast cell degranulation and calcium influx in MRGPRX2 transfected HEK293 cells, induced by the antimicrobial peptide LL-37 and the basic secretagogue C48/80, are effectively inhibited by ssON in a dose-dependent manner. Further, ssON demonstrates a capability to inhibit LL-37 and C48/80 activation in vivo in two mouse models. We show that intradermal injection of ssON in mice is able to block itch induced via C48/80 in a dose-dependent manner. Histological staining revealed that ssON inhibits acute mast cell degranulation in murine skin treated with C48/80. Lastly, we show that ssON treatment ameliorates LL-37-induced inflammation in a rosacea mouse model. Since there is a need for new therapeutics targeting non-IgE-mediated activation of mast cells, ssON could be used as a prospective drug candidate to resolve itch and inflammation in certain dermatoses.

Ca2+ release-activated Ca2+ channels are responsible for histamine-induced Ca2+ entry, permeability increase, and interleukin synthesis in lymphatic endothelial cells

The lymphatic functions in maintaining lymph transport, and immune surveillance can be impaired by infections and inflammation, thereby causing debilitating disorders, such as lymphedema and inflammatory bowel disease. Histamine is a key inflammatory mediator known to trigger vasodilation and vessel hyperpermeability upon binding to its receptors and evoking intracellular Ca²⁺ ([Ca²⁺]_i) dynamics for downstream signal transductions. However, the exact molecular mechanisms beneath the [Ca²⁺]_i dynamics and the downstream cellular effects have not been elucidated in the lymphatic system. Here, we show that Ca²⁺ release-activated Ca²⁺ (CRAC) channels, formed by Orai1 and stromal interaction molecule 1 (STIM1) proteins, are required for the histamine-elicited Ca²⁺ signaling in human dermal lymphatic endothelial cells (HDLECs). Blockers or antagonists against CRAC channels, phospholipase C, and H₁R receptors can all significantly diminish the histamine-evoked [Ca²⁺]_i dynamics in lymphatic endothelial cells (LECs), while short interfering RNA-mediated knockdown of endogenous Orai1 or STIM1 also abolished the Ca²⁺ entry upon histamine stimulation in LECs. Furthermore, we find that histamine compromises the lymphatic endothelial barrier function by increasing the intercellular permeability and disrupting vascular endothelial-cadherin integrity, which is remarkably attenuated by CRAC channel blockers. Additionally, the upregulated expression of inflammatory cytokines, IL-6 and IL-8, after histamine stimulation was abolished by silencing Orai1 or STIM1 with RNAi in LECs. Taken together, our data demonstrated the essential role of CRAC channels in mediating the [Ca²⁺]_i signaling and downstream endothelial barrier and inflammatory functions induced by histamine in the LECs, suggesting a promising potential to relieve histamine-triggered vascular leakage and inflammatory disorders in the lymphatics by targeting CRAC channel functions.

Cytosolic Ca2+ Modulates Golgi Structure Through PKCα-Mediated GRASP55 Phosphorylation

It has been well documented that the ER responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tm), and dithiothreitol (DTT), and found that only TG treatment resulted in Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, indicating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevating intracellular Ca²⁺ and protein kinase Cα (PKCα) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCα with other activating or inflammatory agents, including phorbol 12-myristate 13-acetate and histamine, modulates Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosolic Ca²⁺ modulates Golgi structure and function.

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Thapsigargin (TG) treatment leads to Golgi fragmentation independent of ER stress

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TG induces Golgi fragmentation through elevated cytosolic Ca²⁺

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TG-induced cytosolic Ca²⁺ spikes activate PKCα that phosphorylates GRASP55

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Histamine modulates the Golgi structure and function by a similar mechanism

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.

Quantum chemical calculation and binding modes of H1R; a combined study of molecular docking and DFT for suggesting therapeutically potent H1R antagonist

Histamine-1 receptor (H1R) belongs to the family of rhodopsin-like G-protein-coupled receptors expressed in cells that mediates allergies and other pathophysiological diseases. For alleviation of allergic symptoms, H1R antagonists are therapeutic drugs; of which the most frequently prescribed are second generation drugs, such as; Cetirizine, Loratadine, Hydroxyzine, Desloratadine, Bepotastine, Acrivastine and Rupatadine. To understand their potency, binding affinity and interaction; we have employed molecular docking and quantum chemical study such as; Induced-fit docking and calculation of quantum chemical descriptors. This study also introduces the binding site characterization of H1R, with its known antagonists and Curcumin (our proposed alternative H1R antagonist); useful for future drug target site. The interactive binding site residues of H1R are found to be; Lys-191, Tyr-108, Asp-107, Tyr-100, Lys-179, Lys-191, Thr-194, Trp-428, Phe-432, Tyr-458, Hie-450, with most of these shown to be inhibited by naturally-occurring compound curcumin. Amongst the FDA approved drugs, Hydroxyzine showed best ligand binding affinity, calculated as - 141.491 kcal/mol and naturally occurring compound, Curcumin showed binding affinity of - 87.046 kcal/mol. The known antagonists of H1R has been used for hypothesizing curcumin as naturally occurring lead compound for the target using accurate molecular docking simulation study. Though the pharmacological action of known inhibitor is already established, they could differ from their reactivity, which we have also focused in our study for predicting drug reactivity.

Involvement of histamine H1 and H2 receptor inverse agonists in receptor's crossregulation

Histamine [2-(4-Imidazolyl)-ethylamine] modulates different biological processes, through histamine H₁ and H₂ receptors, and their respective blockers are widely used in treating allergic and gastric acid-related disorders. Histamine H₁ and H₂ receptor crossdesensitization and cointernalization induced by its agonists have been previously described. In this study, we show how this crosstalk determines the response to histamine H₁ and H₂ receptor inverse agonists and how histamine H₁ and H₂ receptor inverse agonists interfere with the other receptor's response to agonists. By desensitization assays we demonstrate that histamine H₁ and H₂ receptor inverse agonists induce a crossregulation between both receptors. In this sense, the histamine H₁ receptor inverse agonists desensitize the cAMP response to amthamine, a histamine H₂ receptor agonist. In turn, histamine H₂ receptor inverse agonists interfere with histamine H₁ receptor signaling. We also determine that the crossdesensitization induced by histamine H₁ or H₂ receptor agonists alters the histamine inverse agonists receptor response: activation of histamine H₁ receptor affects cAMP response induced by histamine H₂ receptor inverse agonists, whereas histamine H₂ receptor agonist induces a negative regulation on the anti-inflammatory response of histamine H₁ receptor inverse agonists. Binding studies revealed that histamine H₁ and H₂ receptors cointernalize after stimulus with histamine receptor inverse agonists. In addition, the inhibition of the internalization process prevents receptor crossregulation. Our study provides new insights in the mechanisms of action of histamine H₁ and H₂ receptors that explain the effect of histamine H₁ and H₂ receptor inverse agonists and opens up new venues for novel therapeutic applications.

Distinct roles of histamine H1- and H2-receptor signaling pathways in inflammation-associated colonic tumorigenesis

Inflammatory bowel disease (IBD) is a well-known risk factor for the development of colorectal cancer. Prior studies have demonstrated that microbial histamine can ameliorate intestinal inflammation in mice. We tested the hypothesis whether microbe-derived luminal histamine suppresses inflammation-associated colon cancer in Apc^min/+ mice. Mice were colonized with the human-derived Lactobacillus reuteri. Chronic inflammation was induced by repeated cycles of low-dose dextran sulfate sodium (DSS). Mice that were given histamine-producing L. reuteri via oral gavage developed fewer colonic tumors, despite the presence of a complex mouse gut microbiome. We further demonstrated that administration of a histamine H1-receptor (H1R) antagonist suppressed tumorigenesis, while administration of histamine H2-receptor (H2R) antagonist significantly increased both tumor number and size. The bimodal functions of histamine include protumorigenic effects through H1R and antitumorigenic effects via H2R, and these results were supported by gene expression profiling studies on tumor specimens of patients with colorectal cancer. Greater ratios of gene expression of H2R ( HRH2) vs. H1R ( HRH1) were correlated with improved overall survival outcomes in patients with colorectal cancer. Additionally, activation of H2R suppressed phosphorylation of mitogen-activated protein kinases (MAPKs) and inhibited chemokine gene expression induced by H1R activation in colorectal cancer cells. Moreover, the combination of a H1R antagonist and a H2R agonist yielded potent suppression of lipopolysaccharide-induced MAPK signaling in macrophages. Given the impact on intestinal epithelial and immune cells, simultaneous modulation of H1R and H2R signaling pathways may be a promising therapeutic target for the prevention and treatment of inflammation-associated colorectal cancer. NEW & NOTEWORTHY Histamine-producing Lactobacillus reuteri can suppress development of inflammation-associated colon cancer in an established mouse model. The net effects of histamine may depend on the relative activity of H1R and H2R signaling pathways in the intestinal mucosa. Our findings suggest that treatment with H1R or H2R antagonists could yield opposite effects. However, by harnessing the ability to block H1R signaling while stimulating H2R signaling, novel strategies for suppression of intestinal inflammation and colorectal neoplasia could be developed.

Effect of Royal Jelly and Brazilian Green Propolis on the Signaling for Histamine H1 Receptor and Interleukin-9 Gene Expressions Responsible for the Pathogenesis of the Allergic Rhinitis

The significant correlation between nasal symptom scores and level of histamine H₁ receptor (H1R) mRNA in nasal mucosa was observed in patients with pollinosis, suggesting that H1R gene is an allergic disease sensitive gene. We demonstrated that H1R and interleukin (IL)-9 gene are the allergic rhinitis (AR)-sensitive genes and protein kinase Cδ (PKCδ) signaling and nuclear factor of activated T-cells (NFAT) signaling are involved in their expressions, respectively. Honey bee products have been used to treat allergic diseases. However, their pathological mechanism remains to be elucidated. In the present study, we investigated the mechanism of the anti-allergic effect of royal jelly (RJ) and Brazilian green propolis (BGPP). Treatment with RJ and BGPP decreased in the number of sneezing on toluene 2,4-diissocyanate (TDI)-stimulated rats. The remarkable suppression of H1R mRNA in nasal mucosa was observed. RJ and BGPP also suppressed the expression of IL-9 gene. RJ and BGPP suppressed phorbol-12-myristate-13-acetate-induced Tyr³¹¹ phosphorylation of PKCδ in HeLa cells. In RBL-2H3 cells, RJ and BGPP also suppressed NFAT-mediated IL-9 gene expression. These results suggest that RJ and BGPP improve allergic symptoms by suppressing PKCδ and NFAT signaling pathways, two important signal pathways for the AR pathogenesis, and suggest that RJ and BGPP could be good therapeutics against AR.

Evodiamine Induces Apoptosis in SMMC-7721 and HepG2 Cells by Suppressing NOD1 Signal Pathway

Hepatocellular cancer (HCC) is a lethal malignancy with poor prognosis and easy recurrence. There are few agents with minor toxic side effects that can be used for treatment of HCC. Evodiamine (Evo), one of the major bioactive components derived from fructus Evodiae, has long been shown to exert anti-hepatocellular carcinoma activity by suppressing activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK). In addition, in the Nucleotide-Binding Oligomerization Domain 1 (NOD1) pathway, NOD1 could initiate NF-κB-dependent and MAPK-dependent gene transcription. Recent experimental studies reported that the NOD1 pathway was related to controlling development of various tumors. Here we hypothesize that Evo exerts anti-hepatocellular carcinoma activity by inhibiting NOD1 to suppress NF-κB and MAPK activation. Therefore, we proved the anti-hepatocellular carcinoma activity of Evo on HCC cells and detected the effect of Evo on the NOD1 pathway. We found that Evo significantly induced cell cycle arrest at the G2/M phase, upregulated P53 and Bcl-2 associated X proteins (Bax) proteins, and downregulated B-cell lymphoma-2 (Bcl-2), cyclinB1, and cdc2 proteins in HCC cells. In addition, Evo reduced levels of NOD1, p-P65, p-ERK, p-p38, and p-JNK, where the level of IκBα of HCC cells increased. Furthermore, NOD1 agonist γ-D-Glu-mDAP (IE-DAP) treatment weakened the effect of Evo on suppression of NF-κB and MAPK activation and cellular proliferation of HCC. In an in vivo subcutaneous xenograft model, Evo also exhibited excellent tumor inhibitory effects via the NOD1 signal pathway. Our results demonstrate that Evo could induce apoptosis remarkably and the inhibitory effect of Evo on HCC cells may be through suppressing the NOD1 signal pathway in vitro and in vivo.

Histamine H1 receptor gene polymorphism acts as a biological indicator of the prediction of therapeutic efficacy in patients with allergic rhinitis in the Chinese Han population

H1-antihistamine has been shown to be effective in treating patients with allergic rhinitis (AR), but its mechanism is still uncertain. We investigated effects of histamine H1 receptor (HRH1) gene polymorphisms on the efficacy of oral H1-antihistamine in perennial patients with AR caused by mites in the Chinese Han population for the first time. A total of 224 Han Chinese patients with AR and 165 Han Chinese healthy volunteers were selected. Genotype and allele frequency distribution of -17C/T in HRH1 gene in patients with AR, serum levels of eosinophil cationic protein (ECP), total immunoglobulin E (IgE), and specific IgE were detected. The clinical symptoms of patients with AR were evaluated with visual analogue scale (VAS). Direct counting method was applied to calculate genotype and allele frequencies. Higher levels of serum ECP and total IgE were shown in the AR group. Moreover, patients with CT, TT, or CT+TT genotype increased the risk of AR incidence in the in the -17C/T site of HRH1, and CC genotype and CT+TT genotype were associated with gender, asthma, VAS score, total IgE level, and specific IgE level in patients with AR. In addition, oral administration of H1-antihistamines improves clinical symptoms of patients with AR. At last, patients with the CC genotype showed the increased efficacy of H1-antihistamines in patients with AR. Our study provides evidence that HRH1 gene polymorphisms may correlate with oral H1-antihistamine efficacy for the treatment of patients with AR, which can be used as a biological indicator of the prediction of therapeutic efficacy of patients with AR.

Role of Histamine in Modulating the Immune Response and Inflammation

Inflammatory mediators, including cytokines, histamine, bradykinin, prostaglandins, and leukotrienes, impact the immune system, usually as proinflammatory factors. Other mediators act as regulatory components to establish homeostasis after injury or prevent the inflammatory process. Histamine, a biogenic vasoactive amine, causes symptoms such as allergies and has a pleiotropic effect that is dependent on its interaction with its four histamine receptors. In this review, we discuss the dualistic effects of histamine: how histamine affects inflammation of the immune system through the activation of intracellular pathways that induce the production of inflammatory mediators and cytokines in different immune cells and how histamine exerts regulatory functions in innate and adaptive immune responses. We also evaluate the interactions between these effects.

Curcumin derivative, 2,6-bis(2-fluorobenzylidene)cyclohexanone (MS65) inhibits interleukin-6 production through suppression of NF-κB and MAPK pathways in histamine-induced human keratinocytes cell (HaCaT)

Background

Histamine is a well-known mediator involved in skin allergic responses through up-regulation of pro-inflammatory cytokines. Antihistamines remain the mainstay of allergy treatment, but they were found limited in efficacy and associated with several common side effects. Therefore, alternative therapeutic preferences are derived from natural products in an effort to provide safe yet reliable anti-inflammatory agents. Curcumin and their derivatives are among compounds of interest in natural product research due to numerous pharmacological benefits including anti-inflammatory activities. Here, we investigate the effects of chemically synthesized curcumin derivative, 2,6-bis(2-fluorobenzylidene)cyclohexanone (MS65), in reducing cytokine production in histamine-induced HaCaT cells.

Methods

Interleukin (IL)-6 cytokine production in histamine-induced HaCaT cells were measured using enzyme-linked immunosorbent assay (ELISA) and cytotoxicity effects were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Real-time polymerase chain reaction (RT-qPCR) was carried out to determine the inhibitory effects of MS65 on nuclear factor-kappa B (NF-κB) and mitogen activated protein kinase (MAPK) pathways.

Results

Histamine enhanced IL-6 production in HaCaT cells, with the highest production of IL-6 at 97.41 ± 2.33 pg/mL after 24 h of exposure. MS65 demonstrated a promising anti-inflammatory activity by inhibiting IL-6 production with half maximal inhibitory concentration (IC₅₀) value of 4.91 ± 2.50 μM and median lethal concentration (LC₅₀) value of 28.82 ± 7.56 μM. In gene expression level, we found that MS65 inhibits NF-κB and MAPK pathways through suppression of IKK/IκB/NFκB and c-Raf/MEK/ERK inflammatory cascades.

Conclusion

Taken together, our results suggest that MS65 could be used as a lead compound on developing new medicinal agent for the treatment of allergic skin diseases.

H1-antihistamines are associated with lower prevalence of radiographic knee osteoarthritis: a cross-sectional analysis of the Osteoarthritis Initiative data

Background

There is growing evidence that mast cells (MCs) play a role in knee osteoarthritis (OA). H₁-antihistamines block H₁-receptors of histamine, which is an important mediator of MCs. There is a lack of data on whether H₁-antihistamines can influence OA. We hypothesized that the use of H₁-antihistamines may be linked to the reduced prevalence of knee OA.

Methods

Baseline data from the Osteoarthritis Initiative cohort were analysed cross-sectionally. Unadjusted and adjusted logistic regression models were performed to compare the prevalence of knee OA in H₁-antihistamine users and non-users. Generalized estimating equations were used to adjust for the correlation between knees. Knee OA was defined as (1) Kellgren-Lawrence (KL) grade ≥ 2 or total joint replacement or (2) KL grade ≥ 2 and joint space narrowing or total joint replacement.

Results

The analysed sample consisted of 8545 knees (664 knees of H₁-antihistamine users and 7881 knees of H₁-antihistamine non-users). The use of H₁-antihistamines was associated with reduced prevalence of knee OA in unadjusted and adjusted models using both the first (adjusted OR, 0.77; 95% CI, 0.62, 0.96; P < 0.02) and second (adjusted OR, 0.75; 95% CI, 0.62, 0.93; P < 0.008) definitions of knee OA.

Conclusions

H₁-antihistamines are associated with a reduced prevalence of knee OA. The findings indicate that this class of drugs should be further evaluated for possible structure-modifying properties in knee OA.

Synergistic mucus secretion by histamine and IL-4 through TMEM16A in airway epithelium

Histamine is an important mediator of allergic reactions, and mucus hypersecretion is a major allergic symptom. However, the direct effect of histamine on mucus secretion from airway mucosal epithelia has not been clearly demonstrated. TMEM16A is a Ca²⁺-activated chloride channel, and it is closely related to fluid secretion in airway mucosal epithelia. We investigated whether histamine directly induces fluid secretion from epithelial cells or submucosal glands (SMG) and mechanisms related, therewith, in allergic airway diseases. In pig airway tissues from the nose or trachea, histamine was a potent secretagogue that directly induced strong responses. However, gland secretion from human nasal tissue was not induced by histamine, even in allergic rhinitis patients. Histamine type 1 receptor (H1R) and histamine type 2 receptor (H2R) were not noted in SMG by in situ hybridization. Cultured primary human nasal epithelial (NHE) cells were used for the measurement of short-circuit current changes with the Ussing chamber. Histamine-induced slight responses of anion secretions under normal conditions. The response was enhanced by IL-4 stimulation through TMEM16A, which might be related to fluid hypersecretion in allergic rhinitis. Pretreatment with IL-4 augmented the histamine response that was suppressed by a TMEM16A inhibitor. TMEM16A expression was enhanced by 24-h treatment of IL-4 in human nasal epithelial cells. The expression of TMEM16A was significantly elevated in an allergic rhinitis group, compared with a control group. We elucidated histamine-induced fluid secretions in synergy with IL-4 through TMEM16A in the human airway epithelium. In addition, we observed species differences between pigs and humans in terms of gland secretion of histamine.

Apoptosis and surfactant protein-C expression inhibition induced by lipopolysaccharide in AEC II cell may associate with NF-κB pathway

Lipopolysaccharide (LPS), a Gram-negative bacterial outer membrane component, is one of the major causes of septic shock. Herein we investigate LPS-induced apoptosis of rat alveolar epithelial type II cells (AEC II) and the effects of LPS on surfactant protein-C (SP-C) expression in AEC II, along with the possible molecular mechanisms. LPS exposure impaired cell viability and increased apoptosis of AEC II significantly in concentration-dependent manner embodied in increased caspase-3 expression and the activity of caspase-3. Simultaneously, our results also indicated that LPS inhibited surfactant protein-C (SP-C) expression in AEC II. Mechanistic studies revealed that LPS treatment significantly increased the expression of NF-κB p50, NF-κB p65 and IKKβ proteins as well as induced IκB-α phosphorylation. Moreover, pretreatment with IKK inhibitor IKK-16 or NF-κB inhibitor PDTC ameliorated LPS-caused alterations in cleaved caspase-3 expression, the activity of caspase-3 and SP-C expression. Taken together, these results demonstrate that LPS can induce apoptosis of AEC II and decrease SP-C expression partly through activating the NF-κB pathway.

Can human allergy drug fexofenadine, an antagonist of histamine (H1) receptor, be used to treat dog and cat? Homology modeling, docking and molecular dynamic Simulation of three H1 receptors in complex with fexofenadine

Fexofenadine, a potent antagonist to human histamine 1 (H₁) receptor, is a non-sedative third generation antihistamine that is widely used to treat various human allergic conditions such as allergic rhinitis, conjunctivitis and atopic dermatitis. Encouragingly, it's been successfully used to treat canine atopic dermatitis, this supports the notion that it might have a great potential for treating other canine allergic conditions and other mammal pets such as dog. Regrettably, while there is a myriad of studies conducted on the interactions of antihistamines with human H₁ receptor, the similar studies on non-human pet H₁ are considerably scarce. The published studies using the first and second generation antihistamines drugs have shown that the antihistamine response is varied and unpredictable. Thus, to probe its efficacy on pet, the homology models of dog and cat H₁ receptors were built based on the crystal structure of human H₁ receptor bound to antagonist doxepin (PDB 3RZE) and fexofenadine was subsequently docked to human, dog and cat H₁ receptors. The docked complexes are then subjected to 1000ns molecular dynamics (MD) simulations with explicit membrane. Our calculated MM/GBSA binding energies indicated that fexofenadine binds comparably to the three receptors; and our MD data also showed the binding poses, structural and dynamic features among three receptors are very similar. Therefore, our data supported the application of fexofenadine to the H₁ related allergic conditions of dog and cat. Nonetheless, subtle systemic differences among human, dog and cat H₁ receptors were also identified. Clearly, there is still a space to develop a more selective, potent and safe antihistamine alternatives such as Fexofenadine for dog or cat based on these differences. Our computation approach might provide a fast and economic way to predict if human antihistamine drugs can also be safely and efficaciously administered to animals.

Changes in gene expression induced by histamine, fexofenadine and osthole: Expression of histamine H1 receptor, COX-2, NF-κB, CCR1, chemokine CCL5/RANTES and interleukin-1β in PBMC allergic and non-allergic patients

INTRODUCTION

Fexofenadine (FXF) is a third-generation antihistamine drug and osthole is assumed as a natural antihistamine alternative. This paper compares results of histamine, FXF and osthole impact on HRH-1, COX-2, NF-κB-p50, CCR1 mRNA expression. We also measured mRNA expression of IL-1β and CCL5/RANTES in incubated peripheral blood mononuclear cells (PBMC) to compared how histamine, FXF and osthole had influence on expression level and interacts on product secretion.

OBJECTIVE

The purpose was to investigate expression pattern in asthma PBMC.

METHODS

The cultures were treated 72h with FXF and osthole. We measured mRNA expression of histamine HRH-1, COX-2, NF-κB-p50, CCR1, IL-1β and CCL5/RANTES with Real-Time PCR (RT-PCR).

RESULTS

The present study suggest that osthole may be a potential inhibitor of histamine H₁ receptor activity. We also demonstrated that cells cultured with histamine increase COX-2 mRNA expression and osthole reduce it.

CONCLUSION

Allergy remains one of the most common chronic diseases in Europe and it is rapidly approaching epidemic proportions; with current predictions estimating that the number of allergy-afflicted will equal the healthy population by 2020. It is therefore paramount to find new pharmaceuticals which successfully combat allergic disease.

Histamine induces the production of matrix metalloproteinase-9 in human astrocytic cultures via H1-receptor subtype

Accumulation of β-amyloid (Aβ) protein within the brain is a neuropathological hallmark of Alzheimer's disease (AD). One strategy to facilitate Aβ clearance from the brain is to promote Aβ catabolism. Matrix metalloproteinase-9 (MMP-9), a member of the family of Zn(+2)-containing endoproteases, known to be expressed and secreted by astrocytes, is capable of degrading Aβ. Histamine, a major aminergic brain neurotransmitter, stimulates the production of MMP-9 in keratinocytes through the histamine H1 receptor (H1R). In the present study, we show that histamine evokes a concentration- and calcium-dependent release of MMP-9 from human astrocytic U373 cells and primary cultures of human and rat astrocytes through the H1R subtype. Activation of H1R on astrocytes elevated intracellular levels of Ca(2+) that was accompanied by time-dependent increases in MAP kinase p44/p42 and PKC. In-cell western blots revealed dose-dependent increases in both enzymes, confirming involvement of these signal transduction pathways. We next investigated the extent of recombinant human MMP-9 (rhMMP-9) proteolytic activity on soluble oligomeric Aβ (soAβ). Mass spectrometry demonstrated time-dependent cleavage of soAβ (20 μM), but not another amyloidogenic protein amylin, upon incubation with rhMMP-9 (100 nM) at 1, 4 and 17 h. Furthermore, Western blots showed a shift in soAβ equilibrium toward lower order, less toxic monomeric species. In conclusion, both MAPK p44/p42 and PKC pathways appear to be involved in histamine-upregulated MMP-9 release via H1Rs in astrocytes. Furthermore, MMP-9 appears to cleave soAβ into less toxic monomeric species. Given the key role of histamine in MMP-9 release, this neurotransmitter may serve as a potential therapeutic target for AD.

Regulation of mitogen-activated protein kinase by protein kinase C and mitogen-activated protein kinase phosphatase-1 in vascular smooth muscle

Vascular smooth muscle contraction is primarily regulated by phosphorylation of myosin light chain. There are also modulatory pathways that control the final level of force development. We tested the hypothesis that protein kinase C (PKC) and mitogen-activated protein (MAP) kinase modulate vascular smooth muscle activity via effects on MAP kinase phosphatase-1 (MKP-1). Swine carotid arteries were mounted for isometric force recording and subjected to histamine stimulation in the presence and absence of inhibitors of PKC [bisindolylmaleimide-1 (Bis)], MAP kinase kinase (MEK) (U0126), and MKP-1 (sanguinarine) and flash frozen for measurement of MAP kinase, PKC-potentiated myosin phosphatase inhibitor 17 (CPI-17), and caldesmon phosphorylation levels. CPI-17 was phosphorylated in response to histamine and was inhibited in the presence of Bis. Caldesmon phosphorylation levels increased in response to histamine stimulation and were decreased in response to MEK inhibition but were not affected by the addition of Bis. Inhibition of PKC significantly increased p42 MAP kinase, but not p44 MAP kinase. Inhibition of MEK with U0126 inhibited both p42 and p44 MAP kinase activity. Inhibition of MKP-1 with sanguinarine blocked the Bis-dependent increase of MAP kinase activity. Sanguinarine alone increased MAP kinase activity due to its effects on MKP-1. Sanguinarine increased MKP-1 phosphorylation, which was inhibited by inhibition of MAP kinase. This suggests that MAP kinase has a negative feedback role in inhibiting MKP-1 activity. Therefore, PKC catalyzes MKP-1 phosphorylation, which is reversed by MAP kinase. Thus the fine tuning of vascular contraction is due to the concerted effort of PKC, MAP kinase, and MKP-1.

Desloratadine citrate disodium injection, a potent histamine H(1) receptor antagonist, inhibits chemokine production in ovalbumin-induced allergic rhinitis guinea pig model and histamine-induced human nasal epithelial cells via inhibiting the ERK1/2 and NF-kappa B signal cascades

Chemokines have chemotactic properties on leukocyte subsets whose modulation plays a pivotal role in allergic inflammatory processes. Our present study was designed to investigate the anti-allergic and anti-inflammatory properties of desloratadine citrate disodium injection (DLC) and elucidate the molecular mechanisms of its anti-inflammatory properties. The anti-allergic effects of DLC were evaluated based on allergic symptoms, serological marker production and histological changes of the nasal mucosa in guinea pigs model of allergic rhinitis. The anti-inflammatory properties and molecular mechanisms of DLC were explored by studying the regulation of a set of chemokines and extracellular signal-regulated kinase (ERK)1/2 and nuclear factor-kappa B (NF-κB) pathways, after DLC treatment in guinea pigs model of allergic rhinitis in vivo and histamine-activated human nasal epithelial cells (HNECs) in vitro. In vivo model in guinea pigs, DLC alleviated the rhinitis symptoms, inhibited inflammatory cells infiltration in nasal lavage fluid (NLF) and histamine, monocyte chemotactic protein (MCP)-1, regulated on activation normal T cell expressed, and presumably secreted (RANTEs) and interleukin (IL)-8 release in sera and P-ERK1/2 and NF-κB activation in nasal mucosa. In vitro, DLC markedly inhibited histamine-induced production of MCP-1, RANTEs and IL-8 and suppressed c-Raf, mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) and ERK1/2 activation in HNECs. These results provide evidence that DLC possesses potent anti-allergic and anti-inflammatory properties. The mechanism of action underlying DLC in allergic inflammation appears to be inhibition of the phosphorylation of ERK1/2, in addition to blocking of the NF-κB pathway.

Differential function and regulation of orphan nuclear receptor TR3 isoforms in endothelial cells

TR3 has been reported to be an excellent target for angiogenesis therapies. We reported three TR3 transcript variant messenger RNAs (mRNAs) are expressed in human umbilical vein endothelial cell (HUVEC) and are differentially regulated by vascular endothelial growth factor (VEGF). TR3 transcript variant 1 (TR3-TV1) and variant 2 (TR3-TV2) encoding the same TR3 isoform 1 protein (TR3-iso1) that was named TR3 has been extensively studied. However, the function of TR3 isoform 2 protein (TR3-iso2) encoded by TR3 transcript variant 3 (TR3-TV3) is still not known. Here, we clone and express the novel TR3-iso2 protein and find that expression of TR3-iso2, in contrast to TR3-iso1, inhibits endothelial cell proliferation induced by VEGF-A, histamine, and phorbol-12-myristate-13-acetate (PMA). The differential function of TR3-iso2 correlates with the down-regulation of cyclin D1. However, TR3-iso2 plays similar roles in endothelial cell migration and monolayer permeability as TR3-iso1. We further demonstrate that several intracellular signaling pathways are involved in histamine-induced TR3 transcript variants, including histamine receptor H1-mediated phospholipase C (PLC)/calcium /calcineurin/protein kinase C (PKC)/protein kinase D (PKD) pathway and ERK pathway, as well as histamine receptor H3-mediated PKC-ERK pathway. Further, expressions of TR3-TV1, TR3-TV2, and TR3-TV3 by VEGF and histamine are regulated by different promoters, but not by their mRNA stability.

Altered esophageal histamine receptor expression in Eosinophilic Esophagitis (EoE): implications on disease pathogenesis

Eosinophilic Esophagitis (EoE) is a chronic allergic disorder, whose pathobiology is incompletely understood. Histamine-producing cells including mast cells and basophils have been implicated in EoE. However, very little is currently known about the role of histamine and histamine receptor (HR) expression and signaling in the esophageal epithelium. Herein, we characterized HR (H1R, H2R, H3R, and H4R) expression in human esophageal biopsies and investigate the role of histamine signaling in inducible cytokine expression in human esophageal epithelial cells in vitro. HR expression was quantified in esophageal biopsies from non-EoE control (N = 23), inactive EoE (<15 eos/hpf, N = 26) and active EoE (>15 eos/hpf, N = 22) subjects using qRT-PCR and immunofluorescent localization. HR expression and histamine-mediated cytokine secretion were evaluated in human primary and telomerase-immortalized esophageal epithelial cells. H1R, H2R, and H4R expression were increased in active EoE biopsies compared to inactive EoE and controls. H2R was the most abundantly expressed receptor, and H3R expression was negligible in all 3 cohorts. Infiltrating eosinophils expressed H1R, H2R, and H4R, which contributed to the observed increase in HR in active subjects. H1R and H2R, but not H3R or H4R, were constitutively expressed by primary and immortalized cells, and epithelial histamine stimulation induced GM-CSF, TNFα, and IL-8, but not TSLP or eotaxin-3 secretion. Epithelial priming with the TLR3 ligand poly (I:C) induced H1R and H2R expression, and enhanced histamine-induced GM-CSF, TNFα, and IL-8 secretion. These effects were primarily suppressed by H1R antagonists, but unaffected by H2R antagonism. Histamine directly activates esophageal epithelial cytokine secretion in vitro in an H1R dependent fashion. However, H1R, H2R and H4R are induced in active inflammation in EoE in vivo. While systemic antihistamine (anti-H1R) therapy may not induce clinical remission in EoE, our study suggests that further study of histamine receptor signaling in EoE is warranted and that targeting of additional histamine receptors may lead to novel treatment strategies for this important disease.

Anti-allergic and anti-inflammatory properties of a potent histamine H1 receptor antagonist, desloratadine citrate disodium injection, and its anti-inflammatory mechanism on EA.hy926 endothelial cells

The present study, demonstrates that, desloratadine citrate disodium injection (DLC) possesses antihistaminic, anti-allergic and anti-inflammatory properties and elucidates its molecular mechanisms of anti-inflammatory properties. In vitro antihistamine activity of DLC was determined in guinea pig isolated tissues. In vivo antihistamine effects were evaluated after following intravenous administration of DLC in mice with histamine- induced paw edema and in rats with increased capillary permeability. Anti-allergic effects were assessed through passive cutaneous anaphylactic (PCA) reactions in sensitized rodents and ovalbumin-induced allergic rhinitis in rats. Anti-inflammatory properties and molecular mechanisms of DLC were determined on histamine- and lipopolysaccharide (LPS)-induced EA.hy926 endothelial cells. DLC exhibited significant and reversible inhibition of histamine-induced contractions of isolated guinea pig ileum with pA2 value of 8.88. Histamine-induced paw edema and increased capillary permeability were notably inhibited by DLC intravenous administration. In the model of PCA reactions, DLC showed significant activity in a dose-dependent nd potently inhibited both the early-phase and late-phase allergic reaction of ovalbumin-induced allergic rhinitis in rats. DLC alleviated the rhinitis symptoms and inhibited inflammatory cell infiltration, IL-4 and protein leakage in nasal lavage fluid (NLF). In EA.hy926 cells, DLC significantly inhibited the histamine- and LPS- induced IL-6 and IL-8 production and P-selectin and intercellular cell adhesion molecule-1 (ICAM-1) expression. Moreover, DLC reduced translocation of nuclear factor-kappaB (NF-κB) to the nucleus in activated EA.hy926 cells. These results provide evidence that DLC possesses potent antihistaminic, anti-allergic and, anti-inflammatory properties via suppressing IL-6, IL-8, P-selectin and ICAM-1 expression.

Histamine H4 receptor in oral lichen planus

OBJECTIVES

Oral lichen planus (OLP) is an autoimmune disease characterized by a band-like T-cell infiltrate below the apoptotic epithelial cells and degenerated basement membrane. We tested the hypothesis that the high-affinity histamine H4 receptors (H4 Rs) are downregulated in OLP by high histamine concentrations and proinflammatory T-cell cytokines.

MATERIALS AND METHODS

Immunohistochemistry and immunofluorescence staining, image analysis and quantitative real-time polymerase chain reaction of tissue samples and cytokine-stimulated cultured SCC-25 and primary human oral keratinocytes.

RESULTS

H4 R immunoreactivity was weak in OLP and characterized by mast cell (MC) hyperplasia and degranulation. In contrast to controls, H4 R immunostaining and MC counts were negatively correlated in OLP (P = 0.003). H4 R agonist at nanomolar levels led to a rapid internalization of H4 Rs, whereas high histamine concentration and interferon-γ decreased HRH4 -gene transcripts.

CONCLUSION

Healthy oral epithelial cells are equipped with H4 R, which displays a uniform staining pattern in a MC-independent fashion. In contrast, in OLP, increased numbers of activated MCs associate with increasing loss of epithelial H4 R. Cell culture experiments suggest a rapid H4 R stimulation-dependent receptor internalization and a slow cytokine-driven decrease in H4 R synthesis. H4 R may be involved in the maintenance of healthy oral mucosa. In OLP, this maintenance might be impaired by MC degranulation and inflammatory cytokines.

Efficacy of olopatadine versus epinastine for treating allergic conjunctivitis caused by Japanese cedar pollen: a double-blind randomized controlled trial

Introduction

The objective of this study was to compare the efficacy and safety of olopatadine versus epinastine in healthy Japanese adults with a history of allergic conjunctivitis to Japanese cedar pollen.

Methods

This Phase IV double-blind randomized controlled clinical trial comprised three clinical visits over 30 days. Screening tests were performed to identify subjects with a history of allergic conjunctivitis to Japanese cedar pollen in terms of skin sensitivity and positive bilateral reactions to a conjunctival allergen challenge (CAC) with Japanese cedar pollen at Visit 1, and confirmation by a positive bilateral CAC reaction at Visit 2. At Visit 3, the subjects were randomized to receive one drop of olopatadine HCl ophthalmic solution 0.1% (olopatadine) in the left or right eye (1:1 ratio). All subjects received one drop of epinastine HCl ophthalmic solution 0.05% (epinastine) in the contralateral eye as an active control. Five min later, the subjects underwent bilateral CAC tests with one drop of the allergen solution at the concentration that elicited positive reactions at Visits 1 and 2. Efficacy outcomes included the severity of ocular itching at 5, 7, and 15 min and the severity of conjunctival hyperemia at 7, 15, and 20 min after the CAC test, as graded by the investigator by biomicroscopy.

Results

Fifty people participated in this study (25 per group). Olopatadine significantly reduced ocular itching at 7 and 15 min (both p < 0.05) and conjunctival hyperemia at 7 and 20 min (p = 0.0010 and p < 0.05, respectively) after allergen exposure compared with epinastine. There were no adverse events for either treatment.

Conclusion

The results of this single-dose study suggest that olopatadine is superior to epinastine in terms of suppressing ocular itching and hyperemia induced by Japanese cedar pollen during CAC tests. Further studies are needed to confirm these findings in real-life settings.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-014-0156-2) contains supplementary material, which is available to authorized users.