Isolated cardiac myocytes are sensitized by hypoxia-reoxygenation to neutrophil-released mediators
Buerke, M.; Weyrich, A.S.; Lefer, A.M.
American Journal of Physiology 266(1 Pt 2): H128-H136
1994
ISSN/ISBN: 0002-9513 PMID: 8304493 Document Number: 436222
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 lt 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 (H-2O-2), elastase, and platelet-activating factor on H/R cardiac myocytes. Incubation of myocytes after hypoxia with 10, 50, and 100 mu-M H-2O-2 decreased viability in a concentration-dependent manner (from 83 +- 2 to 37 +- 2%; P lt 0.01). CK release of H/R myocytes was also significantly increased by 100 mu-M H-2O-2 (to 28 +- 5 from 12 +- 1% for H/R alone; P lt 0.01). Similarly, elastase (5 mu-g/ml) given after hypoxia significantly reduced cardiac myocyte viability during reoxygenation (viability 58 +- 1 vs. 85 +- 1% H/R alone; P lt 0.05) and increased CK release (to 29 +- 3 from 11 +- 1% for H/R alone; P lt 0.01), an effect that was abolished by L-680,833, an elastase inhibitor. Unlike H-2O-2 and elastase, platelet-activating factor had no significant effect on myocyte viability or CK release after H/R. These results indicate that neutrophil-released humoral substances enhance myocardial cell injury and death after hypoxia and reoxygenation without requiring direct contact between PMNs and cardiac myocytes.