RESUMEN
Although increased levels of circulating interleukin (IL)-18 have been demonstrated in patients with cardiovascular diseases, the functional consequences of chronically increased circulating IL-18 with respect to myocardial function have not been defined. Thus we aimed to examine the effects of chronic IL-18 exposure on left ventricular (LV) function in healthy mice. Moreover, to clarify whether IL-18 has direct effects on the cardiomyocyte, we examined effects of IL-18 on cardiomyocytes in vitro. After 7 days of daily intraperitoneal injections of 0.5 microg IL-18 in healthy mice, a 40% (P < 0.05) reduction in the LV maximal positive derivative, a 25% (P < 0.05) reduction in the LV maximal rate of pressure decay, and a 2.8-fold (P < 0.001) increase in the LV end-diastolic pressure were measured, consistent with myocardial dysfunction. Furthermore, we measured a 75% (P < 0.05) reduction in beta-adrenergic responsiveness to isoproterenol. IL-18 induced myocardial hypertrophy, and there was a 2.9-fold increase (P < 0.05) in atrial natriuretic peptide mRNA expression in the LV myocardium. In vitro examinations of isolated adult rat cardiomyocytes being stimulated with IL-18 (0.1 microg/ml) exhibited an increase in peak Ca2+ transients (P < 0.05) and in diastolic Ca2+ concentrations (P < 0.05). In conclusion, this study shows that daily administration of IL-18 in healthy mice causes LV myocardial dysfunction and blunted beta-adrenergic responsiveness to isoproterenol. A direct effect of IL-18 on the cardiomyocyte in vitro was demonstrated, suggesting that IL-18 reduces the responsiveness of the myofilaments to Ca2+. Finally, induction of myocardial hypertrophy by IL-18 indicates a role for this cytokine in myocardial remodeling.
Asunto(s)
Cardiomiopatías/inducido químicamente , Interleucina-18/administración & dosificación , Agonistas Adrenérgicos beta/farmacología , Animales , Factor Natriurético Atrial/genética , Calcio/metabolismo , Proteínas de Unión al Calcio/metabolismo , ATPasas Transportadoras de Calcio/metabolismo , Cardiomegalia/inducido químicamente , Cardiomiopatías/metabolismo , Cardiomiopatías/patología , Cardiomiopatías/fisiopatología , Esquema de Medicación , Técnicas In Vitro , Molécula 1 de Adhesión Intercelular/metabolismo , Interleucina-18/farmacología , Isoproterenol/farmacología , Masculino , Ratones , Ratones Endogámicos BALB C , Miocardio/metabolismo , Miocardio/patología , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/metabolismo , ARN Mensajero/metabolismo , Ratas , Receptores Adrenérgicos beta/metabolismo , ATPasas Transportadoras de Calcio del Retículo Sarcoplásmico , Factor de Necrosis Tumoral alfa/genética , Función Ventricular Izquierda/efectos de los fármacosRESUMEN
We have tested a new fiber-optic pressure recording system, Samba, with a thin fiber [outer diameter (OD) = 0.25 mm] and a pressure sensor (length and OD = 0.42 mm) attached to the end. The accuracy of the system tested in vitro was good, with a coefficient of variation of 2.54% at 100 mmHg. The drift was <0.45 mmHg/h, and the temperature sensitivity was approximately 0.07 mmHg/1 degrees C between 22 and 37 degrees C. The frequency response characteristics were similar to a 1.4-Fr Millar catheter (0-200 Hz). Introduction of the Samba sensor from the right carotid artery into the left ventricle in six mice caused no drop in mean aortic pressure, whereas introduction of a 1.4-Fr Millar catheter (OD = 0.47 mm; n = 6) caused a pressure drop from 91.6 +/- 9.2 to 65.1 +/- 6.2 mmHg; P < 0.05. Thus the Samba sensor system may represent a new alternative to assess hemodynamic variables in the murine cardiovascular system.