Mechanism of Relaxant Action of Ethyl 6-amino-5-cyano-2-methyl- 4-(pyridin-4-yl)-4H-pyran-3-carboxylate Mainly Through Calcium Channel Blockade in Isolated Rat Trachea.

This study aims to investigate the mechanism of relaxant action of Ethyl 6-amino-5-cyano-2-methyl-4-(pyridin- 4-yl)- 4H-pyran-3-carboxylate (1) in in silico study and ex vivo tracheal rat rings pre-contracted with carbachol (1 µM). Compound 1 was more active than theophylline [a phosphodiesterases (PDE’s) inhibitor] used as positive control. Moreover, pretreatment with 1 significantly shifted to the right the carbachol-induced contraction and did not allow to reach the maximum effect (p< 0.001). In addition, compound 1 (96.30 µM) produces significant (100%) relaxant effect on the contraction induced by KCl (80mM), and the CaCl2-induced contraction was completely abolished by 1 as nifedipine does (a L-type calcium channel blocker), used as positive control (p< 0.001). Meanwhile, in the presence of isoproterenol (a β-adrenergic agonist), propranolol (a β-adrenergic antagonist), and K+ channel blocker 2-AP the relaxant curve was significantly modified (p< 0.05). Compound 1 was docked on an outer cavity located on the intracellular side of the human L-type calcium channel model and interacts in the following chains and residues: chain IP (G51, W52, T53, D54), IVP (R45, E50, A51, Q53, D54) and IS6 (W4, F7). In conclusion, ex vivo and in silico approaches suggest that compound 1 induces its relaxant effect mainly by calcium channel blockade, but other mechanisms like potassium channel and cAMP accumulation could be involved.

Neutrophilia induced by histamine challenge in guinea pig: The role of IL-5, IL-10 and IL-17A, but not CXCL8

Background: Histamine is widely used as a pharmacological tool for the evaluation of airway responsiveness. Nevertheless, undesirable and contradictory effects have been described after histamine provocation tests. In previous evaluations of airway responsiveness in a guinea pig asthma model, the control groups consistently showed high neutrophil counts in bronchoalveolar lavage fluid (BALF) immediately after the histamine challenge. The changes in cytokine and chemokine levels in guinea pig lung associated with histamine induced-neutrophilia are described in this paper. Methods: Immediately and 24 h after histamine challenge, airway wall and BALF eosinophil and neutrophil counts as well as lung cytokines (IL-5, IL-10, IL-17A, TNFα and TGFβ) and chemokines (CCL11 and CXCL8) levels were evaluated. Results: Histamine inhalation generated an all-or-none bronchial response, and the dose inducing airway obstruction was similar in all guinea pigs. Immediate increases in neutrophil counts in airway wall and BALF and in IL-5, IL-10 and IL-17A levels in the lung homogenate were observed after histamine challenge. Significant correlations were found between neutrophil counts from airway wall and IL-5, IL-10 and IL-17A levels in the lung homogenate. Conclusions: Histamine inhalation induced rapid neutrophil LBA and airway wall infiltration that was not associated with CXCL8 expression but with a Th2 and Th17 cytokines that probably are involved in the recruitment and activation of neutrophils.

Exposición aguda a diversas concentraciones de ozono en el cobayo: correlación entre inflamación e hiperreactividad de las vías aéreas / Acute exposure to several ozone concentrations in the guinea pig: correlation between inflammation and airway hyperresponsiveness

El ozono (O3) es uno de los principales contaminates atmosfericos en las grandes urbes como la Ciudad de México. Entre las alteraciones que ocasiona están la infiltración neutrofílica y la hiperreactividad de las vías aéreas, pero aún existe controversia de si ambos fenómenos son independientes o tienen una relación causa-efecto. Para evaluar esta última posibilidad, se realizaron curvas dosis-repuesta no acumulativas con histamina (0.01 a 1.8 µg/kg, i.v.) en cobayos machos con o sin exposición previa a O3 (0.15, 0.3, 0.6 ó 1.2 ppm por 4h, 16-18 h antes del estudio). En todos los cobayos se realizó lavado broncoalveolar (LBA) al final de la curva a histamina. La respuesta broncoconstrictora a la histamina se evaluó como incremento de la presión de insuflación pulmonar. Se observó que la exposición aguda a O3 aumentó significativamente la sensibilidad de las vías aéreas a la histamina en los cobayos expuestos a 1.2 ppm de O3 (p<0.01), existiendo correlación entre el grado de reactividad de todos los grupos y la concentración de O3 inhalada (p<0.0003). El número de células totales se incrementó en el grupo de 1.2 ppm de O3 (p<0.05) y en forma global tuvo correlación con la concentración de O3 (r=0.37, p<0.05) y con la reactividad a la histamina (r=0.35, p<0.05). Asimismo, la población de neutrófilos se incrementó en los grupos expuestos a 0.3 (p<0.01) y 1.2 ppm de O3 (p<0.05). Sin embargo, no existió correlación entre el número de neutrófilos y la reactividad a la histamina o la concentración de O3. Estos resultados sugieren que el O3 aumenta la sensibilidad de las vías aéreas a la histamina de manera proporcional a la concentración de O3 inhalada, y que dicha hiperreactividad se presenta como consecuencia de un proceso inflamatorio, sin que se haya podido determinar cuál es el principal tipo celular involucrado en este fenómeno