Histamine Receptor Research Articles

Histamine stimulates human microglia to alter cellular prion protein expression via the HRH2 histamine receptor

Although the cellular prion protein (PrPC) has been evolutionarily conserved, the role of this protein remains elusive. Recent evidence indicates that PrPC may be involved in neuroinflammation and the immune response in the brain, and its expression may be modified via various mechanisms. Histamine is a proinflammatory mediator and neurotransmitter that stimulates numerous cells via interactions with histamine receptors 1-4 (HRH1-4). Since microglia are the innate immune cells of the central nervous system, we hypothesized that histamine-induced stimulation regulates the expression of PrPC in human-derived microglia. The human microglial clone 3 (HMC3) cell line was treated with histamine, and intracellular calcium levels were measured via a calcium flux assay. Cytokine production was monitored by enzyme-linked immunosorbent assay (ELISA). Western blotting and quantitative reverse transcription-polymerase chain reaction were used to determine protein and gene expression of HRH1-4. Flow cytometry and western blotting were used to measure PrPC expression levels. Fluorescence microscopy was used to examine Iba-1 and PrPC localization. HMC3 cells stimulated by histamine exhibited increased intracellular calcium levels and increased release of IL-6 and IL-8, while also modifying PrPC localization. HMC3 stimulated with histamine for 6 and 24 hours exhibited increased surface PrPC expression. Specifically, we found that stimulation of the HRH2 receptor was responsible for changes in surface PrPC. Histamine-induced increases in surface PrPC were attenuated following inhibition of the HRH2 receptor via the HRH2 antagonist ranitidine. These changes were unique to HRH2 activation, as stimulation of HRH1, HRH3, or HRH4 did not alter surface PrPC. Prolonged stimulation of HMC3 decreased PrPC expression following 48 and 72 hours of histamine stimulation. HMC3 cells can be stimulated by histamine to undergo intracellular calcium influx. Surface expression levels of PrPC on HMC3 cells are altered by histamine exposure, primarily mediated by HRH2. While histamine exposure also increases release of IL-6 and IL-8 in these cells, this cytokine release is not fully dependent on PrPC levels, as IL-6 release is only partially reduced and IL-8 release is unchanged under the conditions of HRH2 blockade that prevent PrPC changes. Overall, this suggests that PrPC may play a role in modulating microglial responses.

Mucosal sugars delineate pyrazine vs pyrazinone autoinducer signaling in Klebsiella oxytoca

Virulent Klebsiella oxytoca strains are associated with gut and lung pathologies, yet our understanding of the molecular signals governing pathogenesis remains limited. Here, we characterized a family of K. oxytoca pyrazine and pyrazinone autoinducers and explored their roles in microbial and host signaling. We identified the human mucin capping sugar Neu5Ac as a selective elicitor of leupeptin, a protease inhibitor prevalent in clinical lung isolates of K. oxytoca, and leupeptin-derived pyrazinone biosynthesis. Additionally, we uncovered a separate pyrazine pathway, regulated by general carbohydrate metabolism, derived from a broadly conserved PLP-dependent enzyme. While both pyrazine and pyrazinone signaling induce iron acquisition responses, including enterobactin biosynthesis, pyrazinone signaling enhances yersiniabactin virulence factor production and selectively activates the proinflammatory human histamine receptor H4 (HRH4). Our findings suggest that the availability of specific carbohydrates delineates distinct autoinducer pathways in K. oxytoca that may have differential effects on bacterial virulence and host immune responses.

Effect of Aerobic Exercise with Blood Flow Restriction on Postexercise Hypotension in Young Adults: The Role of Histamine Receptors.

We tested hypothesis that aerobic exercise with blood flow restriction (BFR) induced postexercise hypotension (PEH), and the reduction in blood pressure (BP) was due to peripheral vasodilation via the histamine receptors. Ten male subjects participated in this study. The subjects were randomly assigned to walk for 10 min at 6.4 km/h, 0% grade with or without BFR after taking histamine receptor blockade. Following exercise, BP was measured at 10 min interval for 60 min. Heart rate (HR), stroke volume (SV), cardiac output (CO), mean arterial pressure (MAP), and total peripheral resistance (TPR) were evaluated. Our results indicated that MAP was significantly lowered immediately after exercise at 20 min, 30 min, and 40 min before the blockade as opposed to after the blockade. A significant reduction in diastolic BP (DBP) occurred. There were no significant differences in HR, SV, CO, and TPR between before the blockade and after the blockade. MAP was substantially decreased at 20 min, 30 min, and 40 min before the blockade compared to resting (-3.2 ± 2.2, -3.3 ± 2.8, and -2.9 ± 2.5, respectively) while increasing MAP after the blockade. The current study demonstrated that low-intensity aerobic exercise with BFR lowered MAP via histamine receptor-induced peripheral vasodilation. In conclusion, BFR exercise training using short periods and low intensity would be greatly beneficial as a potential treatment to lower BP.

Pitolisant 40 mg for excessive daytime sleepiness in obstructive sleep apnea patients treated or not by CPAP: Randomised phase 3 study.

Obstructive sleep apnea (OSA) syndrome commonly leads to excessive daytime sleepiness (EDS). Pitolisant, a selective histamine-3 receptor antagonist, is efficacious at doses up to 20 mg once daily in OSA treated or not with continuous positive airway pressure (CPAP). We assessed the efficacy and safety of pitolisant at doses up to 40 mg once daily in patients with moderate to severe OSA treated or not with CPAP therapy. In this phase 3, multicentre, randomised, double-blind, placebo-controlled clinical trial, patients with OSA were assigned 2:1 to receive pitolisant (according to an individual up-titration scheme, 10, 20 or 40 mg once daily) or placebo for 12 weeks. The primary endpoint was a change in the Epworth Sleepiness Scale (ESS) score from baseline to week 12. Secondary endpoints included a change in reaction time using the Oxford Sleep Resistance test (OSleR), Clinical Global Impression of Change (CGI-C), and Patient's Global Opinion of the Effect (PGOE) of study treatment. Overall, 361 patients (mean age 52.4 years, 77.3% male; mean apnea-hypopnea index [AHI] 27.0 events/h) were randomised to receive pitolisant (n = 242; 50% received CPAP) or placebo (n = 119; 48.7% CPAP). After the dose-adjustment phase (week 3), 88.8% of patients received pitolisant 40 mg. Compared with placebo, pitolisant produced a significant reduction in the ESS score at week 12 (least square mean difference -2.6 (95% CI: -3.4; -1.8; p < 0.001)) irrespective of CPAP use; and improved the reaction time on OSleR, CGI-C, and PGOE at week 12. Pitolisant was well tolerated; no new safety signals were identified. In conclusion, pitolisant up to 40 mg once daily was an effective treatment for EDS in patients with moderate to severe OSA irrespective of CPAP use.

No Impact of Concomitant Medications on Efficacy and Safety of Biologics and Small Molecules for Ulcerative Colitis

While participants with inflammatory bowel diseases (IBD) in clinical trials of biologics and small molecule drugs (henceforth, advanced therapies) frequently receive several medications concomitantly, it is unclear how they modify treatment effect. Through an individual patient data pooled analysis of ten clinical trials of advanced therapies for moderate-to-severe ulcerative colitis (UC), we assessed whether concomitant exposure to corticosteroids, immunomodulators, 5-aminosalicylates, proton pump inhibitors (PPIs), histamine receptor antagonists (H2RA), opiates, antidepressants, and antibiotics modified the effect of the intervention on treatment efficacy and safety outcomes, using modified Poisson regression model. Of 6044 patients (4280 receiving intervention, 1764 receiving placebo), several received concomitant corticosteroids (47%), immunomodulators (28%), 5-aminosalicylates (68%), PPIs (14%), H2RAs (2%), opiates (7%), antidepressants (6%), and/or antibiotics (5%). After adjusting for confounders and examining treatment efficacy of intervention vs. placebo, we observed no impact of concomitant exposure to corticosteroids (ratio of relative risk of drug vs. placebo with vs. without concomitant exposure: RRR, 0.81 [95% CI,0.63-1.06], 5-aminosalicylates (RRR, 1.04[0.78-1.39]), PPIs (RRR, 0.87 [0.61-1.22]), H2RAs (RRR, 1.72[0.97-14.29]), opiates (RRR, 0.90[0.54-1.49]), antidepressants (RRR, 1.02[0.57-1.83]), and antibiotics (RRR, 0.72[0.44-1.16]) on likelihood of clinical remission. Concomitant exposure to immunomodulators was associated with lower likelihood of achieving clinical remission (RRR, 0.73[0.55-0.97]), particularly with non-TNF antagonists. In clinical trials of advanced therapies for UC, baseline concomitant exposure to multiple commonly used class of medications does not impact treatment efficacy or safety. These findings directly inform design of regulatory clinical trials with respect to managing concomitant medications at baseline.

Structural basis of ligand recognition and activation of the histamine receptor family

Histamine is a biogenic amine that is critical in various physiological and pathophysiological processes, including but not limited to allergic reactions, wakefulness, gastric acid secretion and neurotransmission. Here, we determine 9 cryo-electron microscopy (cryo-EM) structures of the 4 histamine receptors in complex with four different G protein subtypes, with endogenous or synthetic agonists bound. Inside the ligand pocket, we identify key motifs for the recognition of histamine, the distinct binding orientations of histamine and three subpockets that facilitate the design of specific ligands. In addition, we also identify key residues responsible for the selectivity of immethridine. Moreover, we reveal distinct structural features as determinants of Gq vs. Gs or Gs vs. Gi coupling differences among the histamine receptors. Our study provides a structural framework for understanding the ligand recognition and G protein coupling of all 4 histamine receptors, which may facilitate the rational design of ligands targeting these receptors.

Novel insights into famotidine as a GSK-3β inhibitor: An explorative study in aluminium chloride-induced Alzheimer’s disease rat model

Alzheimer's disease (AD), a chronic neurodegenerative disease, presents a substantial global health challenge. This study explored the potential therapeutic role of famotidine, a histamine (H2) receptor antagonist, as a glycogen synthase kinase-3β (GSK-3β) inhibitor in the context of AD induced by aluminium chloride (AlCl3) in a rat model. The intricate relationship between GSK-3β dysregulation and AD pathogenesis, particularly in amyloid-β (Aβ) production, formed the basis for investigating famotidine's efficacy. Molecular modelling revealed famotidine's efficient binding to GSK-3β, suggesting inhibitory potential. In behavioural assessments, famotidine-treated groups exhibited dose-dependent improvements in Morris Water Maze, Novel Object Recognition, and Y-Maze tests, comparable to the standard Rivastigmine tartrate group. Biochemical analyses showed that famotidine inhibits acetylcholinesterase, decreases lipid peroxidation, increases antioxidant activity, and mitigates oxidative stress. Moreover, famotidine significantly lowered the levels of GSK-3β, IL-6, and Aβ(1−42). The neuroprotective effects of famotidine were further supported by histopathological analysis. This comprehensive investigation underscores famotidine's potential as a GSK-3β inhibitor, providing insights into its therapeutic impact on AD induced by AlCl3. The study offers a promising avenue for repurposing famotidine due to its established safety profile and widespread availability, highlighting its potential in addressing the formidable challenge of AD.

Airways Relaxant and Antiasthmatic Activity of Aconitum heterophyllum Wall ex Royle. Roots: A Mechanistic Insight.

Aconitum heterophyllum Wall ex Royle. (Ranunculaceae) is a traditional medicinal herb that has shown extensive pharmacological potential to treat cough, diarrhea, and infectious diseases but no scientific evidence is available to validate its antiasthmatic potential. In this study, we have investigated the tracheal relaxation and antiasthmatic activity of the selected bioactive fraction of A. heterophyllum. Chemical profiling of the most effective fraction obtained via bioassay-guided fractionation was done using LC-MS (Liquid chromatography-mass spectrometry, a technique utilized in the identification, separation, and quantification of known and unknown compounds). Molecular docking analysis of characterized constituents was performed to recognize the binding receptors, followed by an evaluation of the tracheal relaxation ability of active fraction. An acute oral toxicity study of the most effective fraction was done using OECD guidelines 423. Further, the therapeutic efficacy of the fraction was validated in asthma using a guinea pig model of ovalbumin (OVA) induced allergic asthma. The bio-guided activity revealed that hydro-methanolic extract of A. heterophyllum roots (F-1) was the most active fraction. LC-MS analysis of F-1 showed the presence of six major bioactive compounds in F-1. Molecular docking studies revealed strong binding affinities of identified constituents with histaminic receptor (H1) and muscarinic receptor (M3). The ex vivo study demonstrated smooth muscle relaxant activity of F-1 via dysregulating diverse signal transduction pathways viz. histaminic and muscarinic receptors antagonism (non-competitive), stimulation of β2-adrenergic receptor pathway, and soluble guanylyl cyclase activation. The findings of acute oral toxicity studies revealed that F-1 had no toxicity up to the dose of 2000 mg/Kg. The anti-asthmatic therapeutic efficacy of F-1 was further confirmed by the amelioration of respiratory hyperresponsiveness in asthmatic guinea pigs. This is the first evidence-based study showing the antiasthmatic therapeutic potential of the traditionally used herb A. heterophyllum through, computational and animal studies.

Effect of Switching the Histamine-1 Receptor Antagonist Clemastine to Cetirizine in Paclitaxel Premedication Regimens: The H1-Switch Study.

Premedication, including a histamine-1 receptor (H1) antagonist, is recommended to all patients treated with paclitaxel chemotherapy to reduce the incidence of hypersensitivity reactions (HSRs). However, the scientific basis for this premedication is not robust, which provides opportunities for optimization. Substitution of intravenously administered first-generation H1 antagonist for orally administered second-generation H1 antagonist could reduce side effects, and improve efficiency and sustainability. This study investigates the efficacy and safety of substituting intravenous clemastine for oral cetirizine as prophylaxis for paclitaxel-induced HSRs. This single-center, prospective, noninferiority study compares a historic cohort receiving a premedication regimen with intravenous clemastine to a prospective cohort receiving oral cetirizine. Primary end point of the study is HSR grade ≥3. The difference in incidence was calculated together with the 90% CI. We determined that the two-sided 90% CI of HSR grade ≥3 incidence in the oral cetirizine cohort should not be more than 4% higher (ie, the noninferiority margin) compared with the intravenous clemastine cohort. Two hundred and twelve patients were included in the oral cetirizine cohort (June 2022 and May 2023) and 183 in the intravenous clemastine cohort. HSR grade ≥3 incidence was 1.6% (n = 3) in the intravenous clemastine cohort and 0.5% (n = 1) in the oral cetirizine cohort, resulting in a difference of -1.2% (90% CI, -3.4 to 1.1). Premedication containing oral cetirizine is as safe as premedication containing intravenous clemastine in preventing paclitaxel-induced HSR grade ≥3. These findings could contribute to optimization of care for patients and improve efficiency and sustainability.

Targeting Histamine and Histamine Receptors for Memory Regulation: An Emotional Perspective.

Histamine has long been accepted as a pro-cognitive agent. However, lines of evidence have suggested that the roles of histamine in learning and memory processes are much more complex than previously thought. When explained by the spatial perspectives, there are many contradictory results. However, using emotional memory perspectives, we suspect that the histaminergic system may interplay with stress, reward inhibition, and attention to modulate emotional memory formation. The functional diversity of histamine makes it a viable target for clinical management of neuropsychiatric disorders. Here, we update the current knowledge about the functions of histamine in emotional memory and summarize the underlying molecular and neural circuit mechanisms. Finally, we review the main clinical studies about the impacts of histamine-related compounds on memory and discuss insights into future research on the roles of histamine in emotional memory. Despite the recent progress in histamine research, the histaminergic emotional memory circuits are poorly understood, and it is also worth verifying the functions of histamine receptors in a more spatiotemporally specific manner.

Diagnostic yield of bidirectional endoscopy for iron deficiency anemia in young patients

BackgroundWhile bidirectional endoscopy is recognized as the standard approach for investigating iron deficiency anemia (IDA) in men older than 45 and postmenopausal women, evidence supporting the application of this approach in younger men and premenopausal women is scarce in the absence of symptoms. Our primary aim is to identify the diagnostic yield of bidirectional endoscopy in men younger than 45 and premenopausal women, and describe the clinical characteristics of those with significant endoscopic and pathology-proven findings.MethodsWe performed a retrospective chart review including patients younger than age 45 with IDA who underwent esophagogastroduodenoscopy (EGD) and/or colonoscopy at the Brooklyn VA Hospital between 2009 and 2023. Demographic, clinical, and endoscopic patient data was all collected, stratified, analyzed, and interpreted.ResultsIn 143 patients younger than age 45 with IDA, 28.6% were found to have positive upper gastrointestinal (GI) findings, of which 70.3% were pathology-proven H. pylori cases. 57.9% of patients reported upper GI symptoms, while 42.9% of patients were asymptomatic. In total, 18.2% of symptomatic patients were found to have clinically significant findings on EGD as compared with 42.9% of asymptomatic patients. Additionally, 9.1% of symptomatic patients were found to have biopsy proven H. pylori-associated gastritis or duodenitis as compared with 33.9% of asymptomatic patients. Of the patients who underwent colonoscopy, 8.3% were found to have lower GI lesions.ConclusionsWe found the diagnostic yield of EGD to be significantly higher than that of colonoscopy in younger IDA patients. Our findings suggest current guidelines are clinically relevant to the young patient cohort. Our study also found asymptomatic IDA patients below age 45 to have a significantly higher diagnostic yield of EGD as compared to symptomatic IDA patients within the same age cohort. The differences in diagnostic yields may be a result of symptomatic patients being more likely to have been prescribed proton pump inhibitors or histamine receptor antagonists prior to endoscopy.

Liposomal nanocarriers of preassembled glycocalyx restore normal venular permeability and shear stress sensitivity in sepsis: assessed quantitatively with a novel microchamber system.

The endothelial glycocalyx (EG), covering the luminal side of endothelial cells, regulates vascular permeability and senses wall shear stress. In sepsis, EG undergoes degradation leading to increased permeability and edema formation. We hypothesized that restoring EG integrity using liposomal nanocarriers of preassembled glycocalyx (LNPG) will restore normal venular permeability in lipopolysaccharide (LPS)-induced sepsis model of mice. To test this hypothesis, we designed a unique perfusion microchamber in which the permeability of isolated venules could be assessed by measuring the concentration of Evans blue dye (EBD) in microliter samples of extravascular solution (ES). Histamine-induced time- and dose-dependent increases in EBD in the ES could be measured, confirming the sensitivity of the microchamber system. Notably, the histamine-induced increase in permeability was significantly attenuated by histamine receptor (H1) antagonist, triprolidine hydrochloride. Subsequently, mice were treated with LPS or LPS + LNPG. When compared with control mice, venules from LPS-treated mice showed a significant increased permeability, which was significantly reduced by LNPG administration. Moreover, in the presence of wall shear stress, intraluminal administration of LNPG significantly reduced the permeability in isolated venules from LPS-treated mice. We have found no sex differences. In conclusion, our newly developed microchamber system allows us to quantitatively measure the permeability of isolated venules. LPS-induced sepsis increases permeability of mesenteric venules that is attenuated by in vivo LNPG administration, which also reestablished endothelial responses to shear stress. Thus, LNPG presents a promising therapeutic potential for restoring EG function and thereby mitigating vasogenic edema due to increased permeability in sepsis.NEW & NOTEWORTHY In sepsis, the degradation of the endothelial glycocalyx leads to increased venular permeability. In this study, we developed a potentially new therapeutic approach by in vivo administration of liposomal nanocarriers of preassembled glycocalyx to mice, which restored venular sensitivity to wall shear stress and permeability in lipopolysaccharide-induced sepsis, likely by restoring the integrity of the endothelial glycocalyx. Using a new microchamber system, the permeability of Evans blue dye could be quantitatively determined.

Histamine H3 receptor activation in the insular cortex during taste memory conditioning decreases appetitive response but accelerates aversive memory extinction under an ad libitum liquid regimen

Conditioned taste aversion (CTA) is a robust associative learning; liquid deprivation during this conditioning allows researchers to obtain readable measures of associative learning. Recent research suggests that thirst could be a crucial motivator that modulates conditioning and memory extinction processes, highlighting the importance of the body’s internal state during learning. Furthermore, the histaminergic system is one of the major modulatory systems controlling several behavioral and neurobiological functions, such as feeding, water intake, and nociception. Therefore, this research aimed to assess the effect of H3 histaminergic receptor activation in the insular cortex (IC) during CTA. For this, we conditioned adult male Wistar rats under two regimens: water deprivation and water ad libitum. A classical CTA protocol was used for water deprivation. Before CTA acquisition, 10 μM R-α-methylhistamine (RAMH), an H3 receptor agonist, was injected into the IC. Results showed that RAMH injections decreased CTA in water-deprived rats without affecting the significant aversion conditioning in rats that were given water ad libitum. Moreover, RAMH accelerated the process of aversive memory extinction under ad libitum water conditions. According to our findings, the degree of liquid satiety differentially affected taste-aversive memory formation, and H3 histamine receptors were more involved under water deprivation conditions during acquisition. However, these receptors modulated the strength of aversive conditioning by altering the rate of aversive memory extinction in the absence of deprivation. In conclusion, histaminergic activity in the IC may influence taste memory dynamics through different mechanisms depending on the degree of liquid satiety or deprivation during conditioning.

Mirtazapine in Primary Insomnia: Case report and Literature review

Introduction: Insomnia is a prevalent sleep disorder characterized by difficulty in falling asleep, maintaining sleep, or achieving restorative sleep, despite adequate opportunities. This condition often results in significant daytime impairments, including fatigue, concentration difficulties, and irritability. Insomnia can be primary or comorbid with other disorders such as anxiety or depression. Case Presentation: A 27-year-old woman presented with severe and chronic insomnia, persisting for 14 years with recent exacerbation. Her symptoms included significant difficulty in initiating and maintaining sleep, resulting in an average of only 3-4 hours of sleep per night and complete sleep deprivation for periods exceeding half an hour over the past 5 days. This sleep deficit led to pronounced emotional instability, physical discomfort, and reduced appetite, although suicidal ideation was absent. She had a past history of drug use for different psychiatric illnesses. She was started on mirtazipine 30mg and showed abrupt improvement in her symptoms. She was discharged afterwards. Discussion: The patient's chronic insomnia and its secondary effects necessitate a comprehensive treatment approach. Mirtazapine, an antidepressant with potent histamine receptor antagonism, has shown efficacy in improving sleep quality across diverse patient profiles. However, side effects like weight gain and sedation require careful monitoring. Combining mirtazapine with prolonged-release melatonin has demonstrated enhanced outcomes, particularly in perimenopausal women. Cognitive Behavioral Therapy for Insomnia (CBT-I) remains the first-line treatment due to its efficacy and long-term benefits. Conclusion: Mirtazapine can be a valuable option in the therapeutic arsenal for primary insomnia, but ongoing research is needed to refine treatment strategies. Personalized treatment plans considering patient history and response are crucial for effectively managing primary insomnia and improving patient outcomes.

Novel therapeutic receptor agonists and antagonists in allergic conjunctivitis.

Allergic conjunctivitis is characterized by the development of pathophysiological changes to the ocular surface, which occurs when pro-allergic and pro-inflammatory mediators interact with their cognate receptors expressed on immune and nonimmune cells. Traditional treatments with antihistamines and corticosteroids provide relief, but there is a need for more efficacious and tolerable long-term therapy with a better safety profile. This article aims to provide an overview of the mode of action and clinical application of agonist therapies targeting glucocorticoid, melanocortin, and toll-like receptors, as well as antagonist therapies targeting cytokine, chemokine, integrin, and histamine receptors. There has been considerable advancement in immunology and pharmacology, as well as a greater understanding of the cellular and molecular mechanisms of allergic conjunctivitis. Recent research advancing therapy for allergic conjunctivitis has focused on developing synthetic molecules and biologics that can interfere with the process of the allergic immune reaction. This review discusses novel therapeutic receptors being explored agonistically or antagonistically to develop alternative treatment options for allergic conjunctivitis. These novel approaches hold promise for improving the management of allergic eye diseases, offering patients hope for more effective and safer treatment options in the future.

Evaluating the efficacy of a premedication regimen including high-dose cetirizine in reduction of hypersensitivity reactions to paclitaxel: A retrospective cohort study.

Hypersensitivity reactions (HSR) are a known adverse effect of paclitaxel, occurring in approximately 10% of patients, typically during the first or second infusion of the medication. Corticosteroids, histamine-1 and histamine-2 receptor antagonists are given prior to paclitaxel infusions to reduce the incidence of HSR. There are limited data that suggest administration of cetirizine given prior to a platinum infusion as secondary prophylaxis may reduce HSR rates. The objective of this study was to assess the impact of a novel paclitaxel hypersensitivity prevention protocol including high-dose cetirizine administered 12 and 6 h prior to paclitaxel infusion on the rate of HSR compared to a historical control. The primary objective was the rate of HSR of any grade after the first cycle of paclitaxel. Secondary outcomes included grade of infusion reaction and incidence of severe HSR. A total of 104 patients were included for analysis in the cetirizine group and 124 in the control group. Hypersensitivity reactions occurred in 37 (16.2%) patients in the overall population, and no statistical difference was observed between groups. (13.46% vs 18.55%; p = 0.23). Numerically more grade 3-4 HSRs occurred in the control group than the treatment group (30.77% vs 69.23; p = 0.51). The addition of cetirizine to paclitaxel infusions resulted in numerically lower rates of HSR and a reduction in severity of grade 3-4 HSRs. Future studies with more robust compliance data and a larger patient population would be needed to appropriately assess the efficacy of our novel treatment regimen.

Identification of HRH1 as an alternative receptor for SARS-CoV-2: insights from viral inhibition by repurposable antihistamines.

Numerous coreceptors have been shown to facilitate hACE2-dependent or hACE2-independent infection by SARS-CoV-2. A recent study published in mBio by Yu et al. showed that the histamine receptor H1 (HRH1) functions as an alternative receptor for SARS-CoV-2 via direct binding to viral spike proteins (F. Yu, X. Liu, H. Ou, X. Li, et al., mBio e01088-24, 2024, https://doi.org/10.1128/mbio.01088-24). Furthermore, they present compelling evidence that antihistamine drugs targeting HRH1 potently inhibit SARS-CoV-2 entry. This study highlights the therapeutic potential of repurposable antihistamines against COVID-19.

Molecular mechanism of bitter taste receptor agonist-mediated relaxation of airway smooth muscle.

G-protein-coupled receptors (GPCRs) belonging to the type 2 taste receptors (TAS2Rs) family are predominantly present in taste cells to allow the perception of bitter-tasting compounds. TAS2Rs have also been shown to be expressed in human airway smooth muscle (ASM), and TAS2R agonists relax ASM cells and bronchodilate airways despite elevating intracellular calcium. This calcium "paradox" (calcium mediates contraction by pro-contractile Gq-coupled GPCRs) and the mechanisms by which TAS2R agonists relax ASM remain poorly understood. To gain insight into pro-relaxant mechanisms effected by TAS2Rs, we employed an unbiased phosphoproteomic approach involving dual-mass spectrometry to determine differences in the phosphorylation of contractile-related proteins in ASM following the stimulation of cells with TAS2R agonists, histamine (an agonist of the Gq-coupled H1 histamine receptor) or isoproterenol (an agonist of the Gs-coupled β2-adrenoceptor) alone or in combination. Our study identified differential phosphorylation of proteins regulating contraction, including A-kinase anchoring protein (AKAP)2, AKAP12, and RhoA guanine nucleotide exchange factor (ARHGEF)12. Subsequent signaling analyses revealed RhoA and the T853 residue on myosin light chain phosphatase (MYPT)1 as points of mechanistic divergence between TAS2R and Gs-coupled GPCR pathways. Unlike Gs-coupled receptor signaling, which inhibits histamine-induced myosin light chain (MLC)20 phosphorylation via protein kinase A (PKA)-dependent inhibition of intracellular calcium mobilization, HSP20 and ERK1/2 activity, TAS2Rs are shown to inhibit histamine-induced pMLC20 via inhibition of RhoA activity and MYPT1 phosphorylation at the T853 residue. These findings provide insight into the TAS2R signaling in ASM by defining a distinct signaling mechanism modulating inhibition of pMLC20 to relax contracted ASM.

Function of mast cell and bile-cholangiocarcinoma interplay in cholangiocarcinoma microenvironment

ObjectiveThe correlation between cholangiocarcinoma (CCA) progression and bile is rarely studied. Here, we aimed to identify differential metabolites in benign and malignant bile ducts and elucidate the generation, function and...

Histamine deficiency exacerbates cisplatin-induced ferroptosis in cochlea hair cells of HDC knockout mice

Cisplatin (CDDP) is extensively utilized in the management of diverse types of cancers, but its ototoxicity cannot be ignored, and clinical interventions are not ideal. Histidine decarboxylase (HDC) is the exclusive enzyme for histamine synthesis. Anti-histamine receptor drugs are ubiquitously employed in the therapeutics of allergies and gastrointestinal diseases. Yet, the specific role of histamine and its signaling in the inner ear is not fully understood. This study utilized cisplatin treated mice and HEI-OC1 auditory hair cell line to establish a cisplatin-induced ototoxicity (CIO) model. Histidine decarboxylase knockout (HDC−/−) mice and histamine receptor 1 (H1R) antagonist were utilized to investigate the influence of HDC/histamine/H1R signaling on ototoxicity. The results identified HDC and H1R expression in mouse hair cells. Transcriptomics indicated that the expression levels of oxidative stress-related genes in the cochlea of HDC−/− mice increased. Furthermore, histamine deficiency or suppression of H1R signaling accelerated HC ferroptosis, a pivotal factor underlying the aggravation of CIO in vivo and in vitro, conversely, the supplementation of exogenous histamine reversed these deleterious effects. Mechanistically, this study revealed that the malfunction of HDC/histamine/H1R signaling induced upregulation of NRF2 expression, accompanied by the upregulation of ACSL4 and downregulation of GPX4 expression, which are major regulatory factors of ferroptosis. In summary, histamine deficiency may induce hair cell death by regulating the H1R pathway and exacerbate CIO. Our findings have indicated a potential therapeutic target for CIO.