Carbon Monoxide-Induced Early Thrombolysis Contributes to Heme Oxygenase-1-Mediated Inhibition of Neointimal Growth after Vascular Injury in Hypercholesterolemic Mice

Abstract

Arterial thrombosis is a critical event in the pathogenesis of lesion development. In this study, we evaluated the effect of heme oxygenase-1 (HO-1), a stress-inducible enzyme with vasoprotective functions, on arterial thrombosis following vascular mechanical injury. The carotid arteries of apoE-deficient mice were subjected to angioplasty with a modified beaded-needle. Arterial thrombosis occurred at 12 h after injury. Treatment of the injured vessels with an adenovirus bearing HO-1 gene (Adv-HO-1) (1Â 10 8 pfu), but not saline or empty adenovirus (Adv), immediately after angioplasty resulted in earlier thrombolysis and restoration of blood flow detected at 24 h. Immunohistochemistry revealed that the arterial plasminogen activator inhibitor-1 (PAI-1) expression was markedly reduced in Adv-HO-1-treated injured arteries as compared to control counterparts. The thrombolytic effect was also observed by exposing animals with existing arterial thrombosis to carbon monoxide (CO) (250 ppm, 2 h), a byproduct derived from heme degradation by HO-1. In parallel with less fibrin(ogen) deposition, the macrophage infiltration, monocyte chemoattractant protein-1 expression and neointimal formation assessed at 2 weeks after angioplasty were substantially reduced in injured arteries treated with Adv-HO-1. These results support a role of early thrombolysis induced by CO in HO-1-mediated protection against intimal hyperplasia after vascular injury.

Carbon monoxide: Anticoagulant or procoagulant?

“…In other in vitro and in vivo investigations involving either mice or rats [24][25][26][27], COHb concentrations varied following CORM exposure, with little increase seen with CORMs that release CO quickly (e.g., CORM-3, tricarbonyldichloro(glycinato)ruthenium (II)), contrasted with COHb values between 8% to 17% after exposure to slow releasing CORMs (e.g., CORM-A1, sodium boranocarbonate, Na 2 [H 3 BCO 2 ]). In sum, when exposed to CO at low or high concentrations (based on COHb), platelet function and measures of intravascular thrombus formation were decreased in mice and rats [18][19][20][21][22][23].…”

“…While in vivo human investigation of the effect of CO is lacking, there are preclinical rodent models that demonstrate a profibrinolytic and/or antiplatelet effect in vitro and in vivo [18][19][20][21][22][23]. In hypercholesterolemic mice, upregulation with HO-1 with an adenovirus or exposure to inhaled CO (250 parts per million), decreased thrombus formation following carotid angioplasty, with a decrease in arterial tissue activity of plasminogen activator inhibitor-1, noted [18].…”

“…In hypercholesterolemic mice, upregulation with HO-1 with an adenovirus or exposure to inhaled CO (250 parts per million), decreased thrombus formation following carotid angioplasty, with a decrease in arterial tissue activity of plasminogen activator inhibitor-1, noted [18]. In a rat model of electrical carotid injury and thrombus formation, upregulation of HO-1 activity with hemin administration (an inducer of HO-1 activity)…”

“…There is evidence that excessive CO exposure may result in decreased in vivo and in vitro hemostasis in humans and rodents [4][5][6][7][8][18][19][20][21][22][23], potentially by inhibition of platelet aggregation [9][10][11][12][13]15,16,[20][21][22][23]. However, there is also evidence that increased CO exposure can enhance platelet activation [14,17] and cause enhanced coagulation/decreased fibrinolysis in humans and other mammalian species [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][67][68][69][70]…”

Antithrombotic Properties of Water-Soluble Carbon Monoxide-Releasing Molecules

“…Interestingly, all these pathological phenotypes were rescued by administration of CO gas. In another study by Chen et al, 15 it was shown that in carotid arteries injury model of apolipoprotein E-deficient mice a significant antithrombotic effect can be achieved by exposition to CO inhalation (250 ppm) for 2 hours or by treatment with an adenovirus bearing the HO-1 gene.…”