Mechanisms of cardiac depression caused by lipoteichoic acids from Staphylococcus aureus in isolated rat hearts

Abstract

Background - Lipoteichoic acid (LTA) represents a major virulence factor in gram-positive sepsis. Methods and Results - In the present study we perfused isolated rat hearts for 180 minutes with highly purified LTA from Staphylococcus aureus. A progressive decline of left ventricular contractile function paralleled by the expression of myocardial tumor necrosis factor-α (TNF-α) mRNA and protein as well as the release of TNF-α into the perfusate was observed in LTA-perfused hearts. Employment of an anti-TNF-α antibody completely prevented the loss in contractile function. When CD14, a prominent pathogen recognition receptor, was blocked by a specific antibody, induction of TNF-α mRNA and protein release as well as the associated cardiodepression was diminished in response to LTA. Synthesis of TNF-α protein was located to interstitial cells of LTA-challenged hearts as detected by immunohistochemistry. Besides progressive cardiodepression, coronary perfusion pressure (CPP) was moderately increased in LTA-perfused hearts. This was accompanied by the release of thromboxane A2 (TXA2) into the perfusate and the induction of cyclooxygenase (Cox)-2 mRNA and protein in the myocardium. Blocking of TXA2 by the nonspecific Cox inhibitor indomethacin, the thromboxane receptor antagonist daltroban, or the selective Cox-2 inhibitor NS-398 prevented the increase in CPP. Conclusions - LTA causes cardiac depression by activating myocardial TNF-α synthesis via CD14 and induces coronary vascular disturbances by activating Cox-2-dependent TXA 2 synthesis. These phenomena may contribute to cardiac depression in gram-positive sepsis. © 2005 American Heart Association, Inc.