Carbon monoxide and nitric oxide modulate α₂-antiplasmin and plasmin activity: role of heme.

Cigarette smoke and carbon monoxide (CO) released from tricarbonyldichlororuthenium (II) dimer (CORM-2) attenuate fibrinolysis. The purpose of the present study was to determine whether CO diminished fibrinolysis by enhancement of α₂-antiplasmin via a putative heme group. Plasma, isolated α₂-antiplasmin and isolated plasmin were exposed to CO released from CORM-2 and nitric oxide (NO) via a NO donor to induce carboxyheme and metheme states, respectively. Exposed, isolated enzymes were placed in either α₂-antiplasmin-deficient or normal plasma. Effects of CO and NO on tissue-type plasminogen activator initiated fibrinolysis were determined by thrombelastography. Liquid chromatography-mass spectrometry (LC-MS/MS) was used to identify heme released from α₂-antiplasmin and plasmin. CO significantly enhanced α₂-antiplasmin activity, but decreased plasmin activity. NO decreased both α₂-antiplasmin and plasmin activity. Although inadequate LC-MS/MS data were obtained with α₂-antiplasmin (secondary to glycosylation), a putative plasmin-associated heme was identified. CO elicits hypofibrinolysis by enhancing α₂-antiplasmin activity and decreasing plasmin activity. On the basis of the responses to NO and LC-MS/MS data, it is highly likely that both enzymes are modulated by attached heme groups. Efforts to develop methods to detect CO-mediated hypercoagulability are ongoing, with the goal of identifying populations at risk of thrombotic morbidity secondary to cigarette smoking.