ABSTRACT
Title
Alteration of the sodium/calcium exchanger 1 during LPS-induced hypertrophic response in adult cadiomyocytes
Authors
V. Lariccia1,A.A.Nasti1, S. Magi1, C.A. Violet1, F. Pettinari1, S. Amoroso1.
1Section of Pharmacology, Department of Neuroscience, University “Politecnica delle Marche”, Ancona, Itay
1Section of Pharmacology, Department of Neuroscience, University “Politecnica delle Marche”, Ancona, Itay
Abstract
In pathological conditions cardiac hypertrophy (CH) is a multi-steps maladaptive process triggered by a wide range of stimuli that impose a biomechanical stress. At cellular level, cardiomyocytes hypertrophy is typically characterized by an increase in cell size, sarcomere reorganization and enhanced protein synthesis. These changes are accompanied by the reinduction of the "fetal gene program", so-called because gene reprogramming mimics the patterns of gene expression seen during embryonic development.
The mechanisms underlying the maladaptive features of the hypertrophic response are under intense investigation and numerous remodeling processes develop with functional perturbation of cellular calcium homeostasis. Pathological calcium level can ultimately induce cell death, leading to dramatic loss of contractile units, dilation of the ventricles and, finally, loss of contractile force.
Bacterial infections can potentially provoke at least three changes in cardiac myocytes that are relevant to the process of heart remodeling, namely myocyte hypertrophy, progressive myocyte cell death and contractile defects. In experimental animals, the cardiovascular abnormalities can be mimicked by injecting either whole bacteria or purified structural components such as lipopolysaccharide (LPS). Thesechanges are triggered not only by hemodynamic alterations but also represent an intrinsic detrimental response of the heart. Many findings provide a link between the bacteria-induced responses and the Ca2+-dependent signaling pathways that mediate the development of CH. One of the key players for the maintenance of calcium homeostasis in the heart is the sodium/calcium exchanger 1 (NCX1). NCX1 is an integral membrane transporter that mediates the electrogenic countertransport of three Na+ ions for one Ca2+ working across its thermodynamic equilibrium during the cardiac excitation-contraction cycle. Over the last years several studies have shown a pivotal role of NCX1 in heart diseases, including CH.
This work has been undertaken to clarify the role of NCX1 in the development of bacteria-induced cardiac hypertrophy. The cardiac hypertrophic response were studied in adult rat ventricular cells that have been isolated by retrograde perfusion of the hearts using a Langendorff-type apparatus. The embryonic rat heart-derived H9c2 cell line were used as a parallel in vitro system. Perfused hearts or isolated cells were treated with LPS and several pharmacological blockers were used in order to prevent the hypertrophic response. More than 50 cells were analyzed for each experimental groups.
Myocytes exposed to different concentrations of LPS (0.3 and 1 ug/ml) clearly developed a time-dependent hypertrophic response as determined with real-time PCR analysis of hypertrophic markers (such as ANP and BNP) and with cell area measurements. In LPS-treated cells we found significant alterations in NCX1 expression and localization. Prevention of LPS-induced hypertrophy with pharmacological blockers (such as cyclosporin) significantly blunted the NCX1 alterations contributing to the development of the hypertrophic response.
The mechanisms underlying the maladaptive features of the hypertrophic response are under intense investigation and numerous remodeling processes develop with functional perturbation of cellular calcium homeostasis. Pathological calcium level can ultimately induce cell death, leading to dramatic loss of contractile units, dilation of the ventricles and, finally, loss of contractile force.
Bacterial infections can potentially provoke at least three changes in cardiac myocytes that are relevant to the process of heart remodeling, namely myocyte hypertrophy, progressive myocyte cell death and contractile defects. In experimental animals, the cardiovascular abnormalities can be mimicked by injecting either whole bacteria or purified structural components such as lipopolysaccharide (LPS). Thesechanges are triggered not only by hemodynamic alterations but also represent an intrinsic detrimental response of the heart. Many findings provide a link between the bacteria-induced responses and the Ca2+-dependent signaling pathways that mediate the development of CH. One of the key players for the maintenance of calcium homeostasis in the heart is the sodium/calcium exchanger 1 (NCX1). NCX1 is an integral membrane transporter that mediates the electrogenic countertransport of three Na+ ions for one Ca2+ working across its thermodynamic equilibrium during the cardiac excitation-contraction cycle. Over the last years several studies have shown a pivotal role of NCX1 in heart diseases, including CH.
This work has been undertaken to clarify the role of NCX1 in the development of bacteria-induced cardiac hypertrophy. The cardiac hypertrophic response were studied in adult rat ventricular cells that have been isolated by retrograde perfusion of the hearts using a Langendorff-type apparatus. The embryonic rat heart-derived H9c2 cell line were used as a parallel in vitro system. Perfused hearts or isolated cells were treated with LPS and several pharmacological blockers were used in order to prevent the hypertrophic response. More than 50 cells were analyzed for each experimental groups.
Myocytes exposed to different concentrations of LPS (0.3 and 1 ug/ml) clearly developed a time-dependent hypertrophic response as determined with real-time PCR analysis of hypertrophic markers (such as ANP and BNP) and with cell area measurements. In LPS-treated cells we found significant alterations in NCX1 expression and localization. Prevention of LPS-induced hypertrophy with pharmacological blockers (such as cyclosporin) significantly blunted the NCX1 alterations contributing to the development of the hypertrophic response.