Isolated cardiac myocytes are sensitized by hypoxia-reoxygenation to neutrophil-released mediators.
We exposed isolated rat cardiac myocytes to 20 min of hypoxia followed by 20 min of reoxygenation and observed the effect of supernatants of stimulated neutrophils [polymorphonuclear leukocytes (PMNs)] given at the beginning of reoxygenation. PMN supernatants induced cardiac myocyte injury, which was characterized by a significant (P < 0.01) reduction in cell viability to 53 +/- 3%, vs. 84 +/- 3% in rat myocytes subjected to hypoxia-reoxygenation (H/R) alone. The PMN supernatants also resulted in elevated creatine kinase (CK) activities in the myocyte medium. To examine specific PMN-released mediators that may contribute to this cell death, we studied the effects of hydrogen peroxide (H2O2), elastase, and platelet-activating factor on H/R cardiac myocytes. Incubation of myocytes after hypoxia with 10, 50, and 100 microM H2O2 decreased viability in a concentration-dependent manner (from 83 +/- 2 to 37 +/- 2%; P < 0.01). CK release of H/R myocytes was also significantly increased by 100 microM H2O2 (to 28 +/- 5 from 12 +/- 1% for H/R alone; P < 0.01). Similarly, elastase (5 micrograms/ml) given after hypoxia significantly reduced cardiac myocyte viability during reoxygenation (viability 58 +/- 1 vs. 85 +/- 1% H/R alone; P < 0.05) and increased CK release (to 29 +/- 3 from 11 +/- 1% for H/R alone; P < 0.01), an effect that was abolished by L-680,833, an elastase inhibitor. Unlike H2O2 and elastase, platelet-activating factor had no significant effect on myocyte viability or CK release after H/R.(ABSTRACT TRUNCATED AT 250 WORDS)
Buerke
M
M
Department of Physiology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Weyrich
A S
AS
Lefer
A M
AM
D000818:Animals; D002469:Cell Separation; D002470:Cell Survival; D002478:Cells, Cultured; D006321:Heart / Q000187:drug effects / Q000503:physiopathology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009206:Myocardium / Q000473:pathology*; D009504:Neutrophils / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology*; D010196:Pancreatic Elastase / Q000502:physiology; D010972:Platelet Activating Factor / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D010972:Platelet Activating Factor; D006861:Hydrogen Peroxide; D010196:Pancreatic Elastase; D010100:Oxygen