Identification, characterization, and gene expression profiling of endotoxin-induced myocarditis

Abstract

T he pathophysiology of the systemic inflammatory response syndrome (SIRS) and sepsis involves the CNS (1-3) and several peripheral systems that affect gastrointestinal, renal, and cardiovascular functions (4-6). In previous work we described temporal and spatial patterns of expression for genes encoding nitric oxide synthase type 2 (NOS2 or iNOS) and elements of the interleukin-1 system in the CNS (1, 2) during the course of lipopolysaccharide (LPS)-induced SIRS. Those data supported our hypothesis that a mechanism for immune system-brain communication could occur in brain vasculature through interleukin-1␤-NOS2 interactions. To learn more about bidirectional brain-periphery immune system communications, we have studied the effects of systemic inflammation on peripheral tissues; here we focus on the heart. Cardiac dysfunction generally starts during the first 24 h of the development of septic shock and it is reversible in survivors within 7-10 days (7,8). In those individuals, there appear to be simultaneous right (RV) and left (LV) ventricle systolic and diastolic dysfunctions (9, 10). These changes reflect both intrinsic cardiac dysfunction and hemodynamic alterations that are characteristic of septic shock. Global myocardial ischemia has been refuted as an etiological hypotheses to explain intrinsic cardiac dysfunction during SIRS because myocardial lactate production is not increased (11), coronary blood flow is not decreased (12), and diminished oxygen extraction is more consistent with the notion of abnormal myocyte metabolism than with inadequate oxygen delivery. Currently, there is a consensus that myocardial dysfunction seems to result from myocardial depressant factors. Candidate mediators for myocardial depressant factor include NO as well as a series of other factors (such as endotoxin, cytokines, platelet-activating factor, arachidonic acid derivatives, kinins, complement components, endothelial factors, and reactive oxygen molecules) (10,13,14).NO modulates both contraction and diastolic cardiac function in physiological states and in sepsis, and it may also limit the oxidative damage to cells by scavenging reactive molecules (15). Activation of constitutive NOS or NOS2 in the myocardium may play a role in the cardiac dysfunction complicating SIRS (16). We conducted studies to examine the effects of systemic inflammation in the heart, specifically to test the following three hypotheses: (i) NOS2 gene expression might be an element of the heart's response to systemic inflammation; (ii) myocardium tissue injury could be an element of the pathophysiology of SIRS; (iii) the extent of myocardium involvement could be assessed by characterization of differential patterns of gene expression. Materials and MethodsAnimals. Studies were carried out in accordance with protocols approved by the National Institutes of Health. Animals were treated as described before (1). Virus-and pathogen-free male Sprague-Dawley (200-250 g, Harlan, Indianapolis) rats were housed in a light-and temperature-controlled environme...

Selective Impairment of Nuclear Factor-κB-Dependent Gene Transcription in Adult Cardiomyocytes

“…The profile of genes altered in the heart after systemic administration of LPS is known, and a reversible cardiac dysfunction starting 24 hours after endotoxin administration has been reported. 24 These data show a spatial and temporal heterogeneity in the changes of the expression of genes that are important to understand the complexity of the sepsis in the whole organ, including the infiltration of inflammatory cells, 25,26 but most of these effects are lost when the organ is digested to prepare cardiomyocytic cultures, suggesting a major contribution of infiltrated nonmyocytic cells to the inflammatory response in the heart. 23 The role of TLR2 and TLR4 in the expression of inflammatory mediators in the cardiomyocyte is well documented.…”

Transcriptomic effects of adenosine 2A receptor deletion in healthy and endotoxemic murine myocardium

“…This entailed induction of membrane (Tlr2, Tlr3 and Tlr4), cytosolic (Ddx58, Ifih1, Eif2ak2 and Oas1) and extracellular (C1q, C3, C3a and Ptx3) receptors, and downstream mediators (Il6, Irf7 and Rantes). These shifts in TLR/CD14, MyD88-dependent and -independent and interferon/IRF signalling are relevant to temporal expansion of molecular changes [41,42] and injury progression in [67], inflammation and injury [68,69]. These profound responses diverge from in vitro data suggesting dampened/transient impacts of LPS on isolated myocyte NFκB and IκB kinase [43,63].…”

“…These mechanisms likely participate in heart, with evidence NFκB and IκB kinase promotes cardiac dysfunction in sepsis/endotoxemia [37,38], while JAK-STAT signalling mediates dysfunction and cell death in myocardial ischemia [39,40]. In vivo observations suggest marked expansion of this signalling in intact myocardium [41,42], contrasting in vitro evidence that cardiomyocyte NFκB and IκB kinase signalling is only transiently LPS responsive [43]. Importantly, these paths are inhibited by A 2A Rs in other cells, with exogenous agonism decreasing [44,45] and A 2A R KO increasing NFκB activity [6].…”

“…We thus undertook broad-scale transcriptomic profiling of hearts from WT and A 2A R KO mice, at baseline and following endotoxin challenge: shifts in gene expression can shed light on both functions of the A 2A R, and pathogenesis and modulation of endotoxemic myocarditis. There are no prior analyses of transcriptome-wide effects of A 2A R activity in myocardium, and relatively few of the in situ cardiac response to endotoxemia or sepsis [41,42,49].…”

“…While essential genesis of cardiac injury is studied and understood within the in situ organ, this entails experimental limitations inherent to in vivo studies of organ dysfunction in sepsis/ endotoxemia [15,16,20,21,24,41,42,49]. Organ injury in these settings not only involves intrinsic organ-specific mechanisms but also influenced by extrinsic factors, including shifts in systemic inflammation, haemodynamics and neuroendocrine influences (with relative impacts of these factors difficult to delineate).…”