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Cancer morbimortality is still a great concern despite advances in research and therapies. Histamine and its receptors' ligands can modulate different biological responses according to the cell type and the receptor subtype involved. Besides the wide variety of histamine functions in normal tissues, diverse roles in the acquisition of hallmarks of cancer such as sustained proliferative signaling, resistance to cell death, angiogenesis, metastasis, altered immunity and modified microenvironment have been described. This review summarizes the present knowledge of the various roles of histamine H2 receptor (H2R) ligands in neoplasias. A bioinformatic analysis of human tumors showed dissimilar results in the expression of the H2R gene according to tumor type when comparing malignant versus normal tissues. As well, the relationship between patients' survival parameters and H2R gene expression levels also varied, signaling important divergences in the role of H2R in neoplastic progression in different cancer types. Revised experimental evidence showed multiple effects of H2R antihistamines on several of the cited hallmarks of cancer. Interventional and retrospective clinical studies evaluated different H2R antihistamines in cancer patients with two main adjuvant uses: improving antitumor efficacy (which includes regulation of immune response) and preventing toxic adverse effects produced by chemo or radiotherapy. While there is a long path to go, research on H2R antihistamines may provide new opportunities for developing more refined combination therapeutic strategies for certain cancer types to improve patients' survival and health-related quality of life.

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OBJECTIVE: To examine the association between antibiotic and acid suppressant prescriptions in the first 2 years of life and subsequent treatment for childhood psychiatric disorders. STUDY DESIGN: This was a retrospective cohort study of children born between October 2001 and September 2012 in the Military Health System enrolled in TRICARE past age 2 years and within 35 days of birth, with an initial hospital stay <7 days, and without psychotropic agents dispensed during the first 2 years of life. Exposure was defined as a filled prescription for an antibiotic or acid suppressant before age 2 years, and the outcome was defined as a filled prescription for a psychotropic agent after age 2 years. RESULTS: For the 804 920 patients (51% males and 49% female) composing the study population, the mean age at first psychotropic prescription was 6.8 years. A total of 24 176 children (3%) were prescribed a proton pump inhibitor (PPI), 79 243 (10%) were prescribed a histamine-2 receptor antagonist (H2RA), and 607 348 (76%) were prescribed an antibiotic during the first 2 years of life. The adjusted hazard ratio (aHR) of a psychotropic prescription was significantly increased in children prescribed any H2RA (1.79; 95% CI, 1.63-1.96), PPI (1.47; 95% CI, 1.26-1.71), or antibiotic (1.71; 95% CI, 1.59-1.84). The aHR of psychotropic prescriptions increased commensurately with each additional antibiotic class added and with each additional class of medication (H2RA, PPI, or antibiotics) prescribed. CONCLUSIONS: Children prescribed antibiotic and acid suppressants in the first 2 years of life have a significant increase in future prescriptions for psychotropics, with a dose-related effect observed. This association represents a potential risk of early exposure to antibiotics and acid suppressants.

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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.

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Despite the pivotal role GPCRs play in cellular signaling, it is only in the recent years that structural biology has begun to elucidate how GPCRs function and to provide a platform for structure-based drug design. It is postulated that GPCR activation involves the movement of transmembrane helices. The finding that many residues, which have been shown to be critical for receptor activation and are highly conserved among different GPCRs, are clustered in particular positions of transmembrane helices suggests that activation of GPCRs may involve common molecular mechanisms. In particular, phenylalanine 6.44, located in the upper half of TMVI, is highly conserved among almost all GPCRs. We generated Phe 2436.44 Ala/Ser mutants of histamine H2 receptor and found that while the substitutions do not affect receptor expression or ligand signaling, are able to specifically alter cimetidine and ranitidine mechanisms of action from simply inactivating the receptor to produce a ligand-induced G-protein sequestering conformation, that interferes with the signaling of ß2-adrenoceptor. Taking advantage of the cubic ternary complex model, and mathematically modeling our results, we hypothesize that this alteration in ligand mechanism of action is consequence of a change in ligand-induced conformational rearrangement of receptor and its effect on G-protein coupling. Our results show that receptor point mutations can not only alter receptor behavior, as shown for activating/inactivating mutations, but also can have more subtle effects changing ligand mechanism of action.

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BACKGROUND: Histamine, through histamine H2 receptor (H2R), modulates different biological processes, involving the modulation of PI3K/AKT/mTOR and RAS/RAF/MEK/ERK pathways. Many evidences have demonstrated the existence and importance of the crossregulation between these two signaling pathways. The aim of the present work was to determine the molecular mechanisms leading to PI3K and ERK pathways modulation induced by the H2R agonist amthamine and to evaluate the possible interplay between them. METHODS: Phosphorylation levels of ERK and Akt were examined by Western blot in HEK293T cells expressing the human H2R, in the presence of H2R agonist and dominant negative mutants or pharmacological inhibitors of different proteins/pathways. Transcriptional activity assays were assessed to determine SRE activity. Amthamine-mediated cellular proliferation was investigated in MA-10A cells in the presence of PI3K inhibitor. RESULTS: H2R agonist inhibits PI3K/Akt/mTOR and stimulates Ras/MEK/ERK pathways. Moreover, PI3K/Akt/mTOR signaling inhibition is necessary to achieve H2R mediated ERK activation. In the presence of a constitutive active mutant of Akt, amthamine is not able to mediate ERK activation. This crosstalk affects classical ERK downstream targets such as Elk1 phosphorylation and the transcriptional activity of the SRE, classically associated to proliferation. We further demonstrate that amthamine-induced proliferation in Leydig MA-10 tumor cells, is enhanced by LY294002, a PI3K inhibitor. CONCLUSIONS: These results describe a crosstalk between PI3K/AKT/mTOR and Ras/MEK/ERK pathways induced by H2R stimulation with implications in cell proliferation. GENERAL SIGNIFICANCE: This work indicates that the modulation of PI3K/AKT/mTOR pathway by H2R in turn regulates Ras/MEK/ERK activation conditioning the proliferative capacity of the cells.

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JUSTIFICATIVA E OBJETIVOS: O sangramento gastrintestinal agudo é uma condição comum que, geralmente, demanda admissão em unidades de emergência, além de representar também complicação frequente naqueles pacientes previamente internados em unidades de terapia intensiva (UTI). A hemorragia digestiva alta (HDA) possui incidência anual de 50 a 150 para cada 100.000 habitantes, ocorrendo duas vezes mais em homens e aumenta com a idade; a hemorragia digestiva baixa (HDB) apresenta incidência de 20,5 a 27 para cada 100.000 habitantes e a úlcera por estresse é clinicamente evidente em 15% dos casos sem profilaxia e em 1,5% a 8% daqueles com profilaxia. Neste cenário, este estudo teve como objetivo apresentar os métodos profiláticos primários e secundários utilizados nos sangramentos gastrintestinais em Medicina de urgência, bem como suas indicações atuais baseadas em evidências. CONTEÚDO: Revisão narrativa com período delimitado entre os anos de 1970 a 2010, com busca de artigos disponíveis e resumos em bases de dados como Scielo, LILACS, Medline, Pubmed, Sumsearch, National Guideline Clearinghouse, assim como livros relacionados à área de Medicina intensiva e emergência. CONCLUSÃO: No manuseio das úlceras por estresse são utilizados os antagonistas do receptor H2 (AR2H) como método de escolha, seguidos do sucralfato, antiácidos e inibidores da bomba de prótons (IBP). Nos sangramentos gastrintestinais utilizam-se preferencialmente os IBP e nas roturas de varizes esofágicas, escleroterapia e ligaduras elásticas. Nestes casos, o ressangramento pode ser prevenido com betabloqueadores e nitrato.

BACKGROUND AND OBJECTIVES: Acute gastrointestinal bleeding is a common condition that usually requires admission to the emergency room and also represents a complication in patients previously hospitalized in intensive care units (ICU). The upper gastrointestinal bleeding (UGIB) has an annual incidence of 50-150 per 100,000 inhabitants, occurring twice as often in men and increases with age, the lower gastrointestinal bleeding presents incidence from 20.5 to 27 per 100,000 and the stress ulcer is clinically evident in 15% of cases without prophylaxis and 1.5% to 8% of those with prophylaxis. In this scenario, this paper had as objective to present the primary and secondary prophylactic methods to control gastrointestinal bleedings in Emergency Medicine, as well as your indications based on the best actual evidences. CONTENTS: Narrative bounded between the years 1970 to 2010, with search articles and abstracts available on databases such as Scielo, LILACS, Medline, Pubmed, Sumsearch, National Guideline Clearinghouse, as well as books related to area of critical care medicine and emergency. CONCLUSION: In the management of stress ulcers are used H2 receptor antagonists (AR2H) as a method of choice, followed by sucralfate, antacids and proton pump inhibitors (PPIs). In gastrointestinal bleeding are used preferentially IBPs and in ruptures of esophageal varices, sclerotherapy and elastic bandages. In these cases, rebleeding can be prevented with beta-blockers and nitrates.

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