Staphylococcus aureus alpha-toxin and Escherichia coli hemolysin impair cardiac regional perfusion and contractile function by activating myocardial eicosanoid metabolism in isolated rat hearts.
OBJECTIVE
In sepsis, cardiac function is frequently depressed. Microcirculatory disturbances as evidenced in most organs may extend to the coronary circulation and may play a role in the occurrence of cardiac dysfunction. Staphylococcal alpha-toxin and Escherichia coli hemolysin (ECH), pore-forming exotoxins of clinically relevant bacteria, have recently been demonstrated to evoke cardiac dysfunction in isolated rat hearts by activating myocardial eicosanoid metabolism. alpha-Toxin activates synthesis of thromboxane (Tx) A2, ECH of cysteinyl-leukotrienes (Sibelius U, Grandel U, Buerke M, et al: Leukotriene-mediated coronary vasoconstriction and loss in myocardial contractility evoked by low doses of Escherichia coli hemolysin in perfused reat hearts. Crit Care Med 2003; 3:683-688, Sibelius U, Grandel U, Buerke M, et al: Staphylococcal alpha-toxin provokes coronary vasoconstriction and loss in myocardial contractility in perfused rat hearts-Role of Tx formation. Circulation 2000; 101:78-85). We now investigated whether cardiac dysfunction in response to alpha-toxin and ECH is caused by disturbances of regional cardiac perfusion.


METHODS
A prospective, experimental study.


METHODS
A research laboratory at a university hospital.


METHODS
Isolated hearts from male Wistar rats.


METHODS
Changes of regional perfusion were investigated by using colored microspheres in isolated rat hearts perfused with alpha-toxin or ECH either at constant coronary perfusion pressure or constant coronary flow rate. Significance of toxin-activated eicosanoid generation was evaluated by pharmacologic interventions.


RESULTS
By eliciting eicosanoid formation, both toxins caused an increase in coronary vascular resistance and a loss in contractile function. In ECH-perfused hearts, reduction of regional perfusion predominantly occurred in subendocardial sections in either perfusion mode (coronary perfusion pressure or coronary flow rate). When synthesis of cysteinyl-leukotrienes was blocked by the 5-lipooxygenase inhibitor MK-886, disturbances of regional perfusion and the associated cardiac dysfunction were largely prevented. Coronary perfusion of alpha-toxin caused a decrease of regional perfusion that was more pronounced in subepicardial layers. Inhibiting the release of TxA2 by blocking the cyclooxygenase with indomethacin attenuated the perfusion abnormalities and the cardiodepression in response to alpha-toxin.


CONCLUSIONS
Bacterial exotoxins of clinically relevant bacteria may impair cardiac function by eliciting distinct coronary perfusion abnormalities via release of vasoactive eicosanoids.
Grandel
Ulrich
U
Department of Internal Medicine , Justus-Liebig-University, Giessen, Germany.
Bennemann
Ulrich
U
Buerke
Michael
M
Hattar
Katja
K
Seeger
Werner
W
Grimminger
Friedrich
F
Sibelius
Ulf
U
D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects*; D015777:Eicosanoids / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D001427:Bacterial Toxins; D015777:Eicosanoids; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; C021091:staphylococcal alpha-toxin