Abstract 10505: Antithrombin Protects Against Cardiac Ischemia/Reperfusion Injury via Inhibiting the NF-κB Pathway
Background- Antithrombin (AT) is a plasma serine protease inhibitor (serpin) which regulates proteolytic activity of coagulation proteases of both intrinsic and extrinsic coagulation pathways. In addition to its anticoagulant activity, AT also possesses potent anti-inflammatory properties. Recent studies have indicated that the protective effect of AT on sepsis requires supraphysiological concentrations of the serpin, thus the increased risk of bleeding remains a concern in AT-therapy. In this study, we evaluated the cardioprotective activity of wild-type AT and a reactive center loop mutant of AT (AT-RCL) which has lost its reactivity with thrombin in a murine myocardial ischemia/reperfusion (I/R) injury model.
Methods and Results- C57BL/6 mice were subjected to 20 min ischemia via left coronary artery occlusion followed by 3 hr reperfusion. Wild-type AT was injected via tail vein 5 min before reperfusion. Administration of AT decreased the myocardial infarct size in a dose-dependent manner (26.2% ± 3.1%, 0.1 mg/g; 21.6% ± 1.1%, 0.2 mg/g; and 16.9 ± 3.3%, 0.4 mg/g vs. 33.8 ± 1.06% vehicle, n=3-4 per group, all p<0.05 vs. vehicle). Interestingly, a similar decrease in the infarct size was observed with AT-RCL treatment (18.5 ± 3.1%, n=4, 0.4 mg/g, p<0.05 vs. vehicle). Further studies revealed that the interaction of the heparin-binding D-helix of AT with the cell surface heparan sulfate proteoglycans is required for its cardioprotective effect since AT (0.4 mg/g) co-injected with the equimolar concentration of the AT-binding pentasaccharide, fondaparinux, exhibited no discernable protective effect on the myocardial infarct size (26.1% ± 7.4%, n=4, p=NS vs. vehicle), suggesting that the cardioprotective effect of AT was primarily associated with its anti-inflammatory function. Furthermore, AT treatment did attenuate the activation of nuclear factor-κB (NF-κB) induced by I/R injury and significantly increased I-κB protein levels in the ischemic heart.
Conclusions- AT protects against myocardial I/R injury by inhibiting the NF- κB signaling pathway. Thus, the AT-RCL mutant, lacking inhibitory activity toward thrombin, may be developed as a potential therapeutic drug for treating ischemic heart diseases without increasing the risk of bleeding.
- © 2011 by American Heart Association, Inc.