Mechanisms of Cardiac Depression Caused by Lipoteichoic Acids From Staphylococcus aureus in Isolated Rat Hearts

Abstract

Lipoteichoic acid (LTA) represents a major virulence factor in gram-positive sepsis. 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-alpha (TNF-alpha) mRNA and protein as well as the release of TNF-alpha into the perfusate was observed in LTA-perfused hearts. Employment of an anti-TNF-alpha antibody completely prevented the loss in contractile function. When CD14, a prominent pathogen recognition receptor, was blocked by a specific antibody, induction of TNF-alpha mRNA and protein release as well as the associated cardiodepression was diminished in response to LTA. Synthesis of TNF-alpha 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. LTA causes cardiac depression by activating myocardial TNF-alpha synthesis via CD14 and induces coronary vascular disturbances by activating Cox-2-dependent TXA2 synthesis. These phenomena may contribute to cardiac depression in gram-positive sepsis.