Related Experiment Videos
Functional impairment in isolated rat hearts induced by activated leukocytes: protective effect of oxygen free
Abstract:
Ischemia-reperfusion activates polymorphonuclear leukocytes (PMN). Depletion of PMN has been shown to reduce the size of experimental myocardial infarction. We have studied whether PMN activated by phorbol myristate acetate (PMA) would depress function of the isolated rat heart, and if this effect was mediated by oxygen free radicals (OFR). Cells and/or drugs were added to the perfusate into the aortic cannula for 10 min, followed by a 30 min recovery period. Oxygen free radicals formation was verified by chemiluminescence (CL). PMA-activated PMN (n = 13) caused CL response of 27,493 +/- 5113 counts (mean +/- S.E.M.) and reduced left ventricular developed pressure (LVDP) to 30 +/- 9% and coronary flow (CF) to 49 +/- 7% of the baseline value at the end of the observation period. Addition of super-oxide dismutase (SOD) and catalase (CAT) (n = 11) reduced the CL response to 5623 +/- 806 counts, but did not influence either LVDP (36 +/- 15%) or CF (51 +/- 18%). Addition of thiourea (TU) to the activated cell suspension (n = 8) further reduced the CL response (3663 +/- 474 counts), and LVDP was 86 +/- 5% and CF was 87 +/- 3%. When TU + SOD + CAT was mixed with PMN + PMA (n = 11), the CL was almost abolished (117 +/- 21 counts) and LVDP was 73 +/- 8% and CF was 94 +/- 6%. When CF was reduced (n = 7) alike the CF reduction in the hearts receiving PMA + PMA, LVDP was not significantly changed at the end of the observation period (75 +/- 6%). Unactivated PMN (n = 8) caused minor response of LVDP and CF, similar to PMN + PMA + TU and PMN + PMA + SOD + CAT + TU. PMA alone (n = 8) was cardiotoxic and caused changes similar to PMN + PMA. This effect was not inhibited by scavengers (n = 6). The supernatant of the PMN + PMA suspension (n = 7) did not impair cardiac function, suggesting that no free PMA was available after mixing with PMN. We conclude that activated PMN in the coronary circulation depressed cardiac function and increased vascular resistance due to OFR production.
Insights
Activated polymorphonuclear leukocytes (PMN) depress heart function via oxygen free radicals (OFR). Scavenging OFR with thiourea, superoxide dismutase, and catalase protected the isolated rat heart from PMN-induced damage.
Area of Science:
- Cardiovascular Research
- Immunology
- Biochemistry
Background:
- Ischemia-reperfusion injury activates polymorphonuclear leukocytes (PMN).
- PMN depletion reduces myocardial infarction size in experimental models.
- The role of PMN-activated oxygen free radicals (OFR) in cardiac dysfunction requires further investigation.
Purpose of the Study:
- To investigate whether phorbol myristate acetate (PMA)-activated PMN depress isolated rat heart function.
- To determine if this depression is mediated by oxygen free radicals (OFR).
Main Methods:
- Isolated rat hearts were perfused with PMA-activated PMN.
- Oxygen free radical (OFR) formation was measured by chemiluminescence (CL).
- Cardiac function (left ventricular developed pressure - LVDP, coronary flow - CF) was assessed with and without OFR scavengers (super-oxide dismutase, catalase, thiourea).
Main Results:
- PMA-activated PMN significantly reduced LVDP and CF, accompanied by a high CL response.
- OFR scavengers partially or fully inhibited the CL response.
- Thiourea, alone or with SOD and catalase, significantly improved LVDP and CF, indicating OFR mediation.
- PMA alone was cardiotoxic, but this effect was not inhibited by scavengers.
Conclusions:
- Activated PMN in the coronary circulation depress cardiac function.
- This depression is mediated by the production of oxygen free radicals (OFR).
- OFR scavenging offers a potential therapeutic strategy against PMN-induced cardiac dysfunction.