MRP4/ABCC4 expression is regulated by histamine in acute myeloid leukemia cells, determining cAMP efflux.

Intracellular cAMP (i-cAMP) levels play an important role in acute myeloid leukemia (AML) cell proliferation and differentiation. Its levels are the result of cAMP production, degradation, and exclusion. We have previously described histamine H2 receptors and MRP4/ABCC4 as two potential targets for AML therapy. Acting through histamine H2 receptors, histamine increases cAMP production/synthesis, while MRP4/ABCC4 is responsible for the exclusion of this cyclic nucleotide. In this study, we show that histamine treatment induces MRP4/ABCC4 expression, augmenting cAMP efflux, and that histamine, in combination with MRP inhibitors, is able to reduce AML cell proliferation. Histamine, through histamine H2 receptor, increases i-cAMP levels and induces MRP4 transcript and protein levels in U937, KG1a, and HL-60 cells. Moreover, histamine induces MRP4 promoter activity in HEK293T cells transfected with histamine H2 receptor (HEK293T-H2 R). Our results support that the cAMP/Epac-PKA pathway, and not MEK/ERK nor PI3K/AKT signaling cascades, is involved in histamine-mediated upregulation of MRP4 levels. Finally, the addition of histamine potentiates the inhibition of U937, KG1a, and HL-60 cell proliferation induced by MRP4 inhibitors. Our data highlight that the use of a poly-pharmacological approach aimed at different molecular targets would be beneficial in AML treatment.

Identification of MRP4/ABCC4 as a Target for Reducing the Proliferation of Pancreatic Ductal Adenocarcinoma Cells by Modulating the cAMP Efflux.

Pancreatic cancer is one of the most lethal types of tumors with no effective therapy available; is currently the third leading cause of cancer in developed countries; and is predicted to become the second deadliest cancer in the United States by 2030. Due to the marginal benefits of current standard chemotherapy, the identification of new therapeutic targets is greatly required. Considering that cAMP pathway is commonly activated in pancreatic ductal adenocarcinoma (PDAC) and its premalignant lesions, we aim to investigate the multidrug resistance-associated protein 4 (MRP4)-dependent cAMP extrusion process as a cause of increased cell proliferation in human PDAC cell lines. Our results from in silico analysis indicate that MRP4 expression may influence PDAC patient outcome; thus, high MRP4 levels could be indicators of poor survival. In addition, we performed in vitro experiments and identified an association between higher MRP4 expression levels and more undifferentiated and malignant models of PDAC and cAMP extrusion capacity. We studied the antiproliferative effect and the overall cAMP response of three MRP4 inhibitors, probenecid, MK571, and ceefourin-1 in PDAC in vitro models. Moreover, MRP4-specific silencing in PANC-1 cells reduced cell proliferation (P < 0.05), whereas MRP4 overexpression in BxPC-3 cells significantly incremented their growth rate in culture (P < 0.05). MRP4 pharmacological inhibition or silencing abrogated cell proliferation through the activation of the cAMP/Epac/Rap1 signaling pathway. Also, extracellular cAMP reverted the antiproliferative effect of MRP4 blockade. Our data highlight the MRP4-dependent cAMP extrusion process as a key participant in cell proliferation, indicating that MRP4 could be an exploitable therapeutic target for PDAC. SIGNIFICANCE STATEMENT: ABCC4/MRP4 is the main transporter responsible for cAMP efflux. In this work, we show that MRP4 expression may influence PDAC patient outcome and identify an association between higher MRP4 expression levels and more undifferentiated and malignant in vitro models of PDAC. Findings prove the involvement of MRP4 in PDAC cell proliferation through a novel extracellular cAMP mitogenic pathway and further support MRP4 inhibition as a promising therapeutic strategy for PDAC treatment.

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.

Utilidad de los sellantes de fibrina en endoscopia terapéutica / Utility of fibrin glue in therapeutic endoscopy

Los sellantes de fibrina son agentes quirúrgicos hemostáticos y adhesivos, derivados principalmente de productos de plasma humano que han sido utilizados por más de veinte años y se han asociado con buena tolerabilidad a través de una variedad de aplicaciones que buscan reducir la incidencia de complicaciones quirúrgicas, tales como la hemorragia y dehiscencia. A pesar de llevar más de veinte años no se encuentra en la literatura una importante cantidad de trabajos acerca de su utilidad en los procedimientos endoscópicos. En el presente trabajo se presentan cuatro casos clínicos donde la utilización endoscópica de este agente mejoró la evolución y cambió la conducta terapéutica del paciente; de igual forma se presenta una breve revisión de la literatura acerca de estos productos y su empleo endoscópico.

The fibrin glues are surgical hemostatic and adhesive agents, derived principally from products of human plasma. that have been used for more than 20 years and have been associated a variety of applications that seek to reduce the incident of surgical, such complications as the hemorrhage and leak, in spite of going more of 20 years one does not find in the literature an important quantity of works brings over of his utility in the endoscopes procedures.In the present work present four clinical cases where the endoscopic use of this agent improve the evolution and change the therapeutic conduct of the patient, of equal form one presents a brief review of the literature brings over of these products and his endoscopic employment.