ABSTRACT
Cardiovascular morbidity is the leading cause of death of obstructive sleep apnea (OSA) syndrome patients. Nocturnal airway obstruction is associated with intermittent hypoxia (IH). In our previous work with cell lines, incubation with sera from OSA patients induced changes in cell morphology, NF-κB activation and decreased viability. A decrease in beating rate, contraction amplitude and a reduction in intracellular calcium signaling was also observed in human cardiomyocytes differentiated from human embryonic stem cells (hESC-CMs). We expanded these observations using a new controlled IH in vitro system on beating hESC-CMs. The Oxy-Cycler system was programed to generate IH cycles. Following IH, we detected the activation of Hif-1α as an indicator of hypoxia and nuclear NF-κB p65 and p50 subunits, representing pro-inflammatory activity. We also detected the secretion of inflammatory cytokines, such as MIF, PAI-1, MCP-1 and CXCL1, and demonstrated a decrease in beating rate of hESC-CMs following IH. IH induces the co-activation of inflammatory features together with cardiomyocyte alterations which are consistent with myocardial damage in OSA. This study provides an innovative approach for in vitro studies of OSA cardiovascular morbidity and supports the search for new pharmacological agents and molecular targets to improve diagnosis and treatment of patients.
Subject(s)
Cardiovascular Diseases , Sleep Apnea, Obstructive , Cardiovascular Diseases/metabolism , Cytokines/metabolism , Humans , Hypoxia/metabolism , Myocytes, Cardiac/metabolism , NF-kappa B/metabolism , Plasminogen Activator Inhibitor 1 , Sleep Apnea, Obstructive/metabolism , Stem Cells/metabolismABSTRACT
Obstructive sleep apnea syndrome (OSAS) patients suffer from cardiovascular morbidity, which is the leading cause of death in this disease. Based on our previous work with transformed cell lines and primary rat cardiomyocytes, we determined that upon incubation with sera from pediatric OSAS patients, the cell's morphology changes, NF-κB pathway is activated, and their beating rate and viability decreases. These results suggest an important link between OSAS, systemic inflammatory signals and end-organ cardiovascular diseases. In this work, we confirmed and expanded these observations on a new in vitro system of beating human cardiomyocytes (CM) differentiated from human embryonic stem cells (hES). Our results show that incubation with pediatric OSAS sera, in contrast to sera from healthy children, induces over-expression of NF-κB p50 and p65 subunits, marked reduction in CMs beating rate, contraction amplitude and a strong reduction in intracellular calcium signal. The use of human CM cells derived from embryonic stem cells has not been previously reported in OSAS research. The results further support the hypothesis that NF-κB dependent inflammatory pathways play an important role in the evolution of cardiovascular morbidity in OSAS. This study uncovers a new model to investigate molecular and functional aspects of cardiovascular pathology in OSAS.
Subject(s)
Cardiovascular Diseases/pathology , Heart Rate/drug effects , Myocardial Contraction/drug effects , Myocytes, Cardiac/metabolism , Sleep Apnea, Obstructive/blood , Calcium Signaling/drug effects , Cells, Cultured , Child , Human Embryonic Stem Cells/cytology , Humans , Myocytes, Cardiac/cytology , Myocytes, Cardiac/drug effects , NF-kappa B p50 Subunit/metabolism , Serum , Sleep Apnea, Obstructive/pathology , Transcription Factor RelA/metabolismABSTRACT
Obstructive sleep apnea syndrome (OSA) is associated with cardiovascular morbidity in adults and children. NFκB activity is enhanced in circulating monocytes of adults with OSA, that decreases following positive pressure therapy. OSA children's serum activates NFκB in a cell line. We hypothesized that OSA children's serum can activate NFκB in cardiomyocytes (CM) and effect their viability. In order to explore the role played by NFκB in OSA cardiovascular pathophysiology, rat, mouse and human immortalized CM were exposed to human serum drawn from OSA children and matched controls. Increased expression of NFκB classical subunits p65/p50 as well as major morphological changes occurred in cardiomyocytes following OSA's serum exposure. OSA children's serum induced NFκB activity as measured by p65 nuclear translocation in immortalized human CM and rat cardiomyocytes as well as dense immunostaining of the nucleus. Trypan blue and XTT assays showed that OSA sera induced CM apoptosis. We conclude that NFκB is systemically activated in cardiomyocytes, who also demonstrate decreased viability and contractility following exposure to OSA serum. It supports the hypothesis NFκB plays a role in the evolution of cardiovascular morbidity in OSA. It may support the search for new therapeutic interventions controlling NFκB activation in OSA.
