Vascular reactivity of doxycycline and hydrogen peroxide-induced oxidative stress in human saphenous vein

Objective: Increased level of reactive oxygen species (ROS) is an important clinical problem in cardiovascular surgery. ROS production and activation of matrix metalloprotienases (MMPs) which are proinflammatory enzymes are associated with many cardiovascular diseases. Doxycycline at subantimicrobial dose acts as a potent matrix metalloproteinase inhibitor and also ROS scavenger. In this study, we aimed to investigate the hypothesis that impaired vascular reactivity due to in vitro oxidative stress stimulated by hydrogen peroxide can be normalized with doxycyclin in human saphenous vein (HSV) segments. Methods: HSV segments were collected from patients who undergoing coronary artery bypass grafting operation. The endothelial layers were gently removed by scratching. Then, the segments were divided into 4 groups and incubated with 10 µM hydrogen peroxide and/or 10 µM doxycycline for 16 hs. Untreated HSV segments served as control. In order to evalute the changes in vascular reactivity, concentration-response curves for noradrenaline, potassium chloride, serotonin and papaverine were performed in vein rings which are confirmed not having functional endothelium. In parallel experiments, ROS levels in the vein rings were assessed by using lucigenin- and luminol-enhanced chemiluminescence method. In another experiment set, MMP-9 and MMP-13 expressions were examined immunohistochemically in parallel rings. Results: Incubation of HSVs with hydrogen peroxide caused 5-fold and 4-fold increases in the levels of ROS and superoxide anion, respectively. Doxycycline significantly reduced the increased levels of ROS and superoxide anion. Contractile responses to noradrenaline, potassium chloride and serotonin significantly decreased in HSV segments from hydrogen peroxide group. Treatment with doxycycline augmented the impaired contractile responses to noradrenaline and potassium chloride but not to serotonin. Sensitivity (pD2 values) to these contractile agents remained unchanged. Relaxant responses and pD2 to papaverine were not affected by either hydrogen peroxide or doxycycline treatment. MMP-9 and MMP-13 expressions increased in adventitia and media layers of vein segments respectively. Doxycycline did not affect the expressions of both MMPs. Conclusions: In our study, doxycycline improved impaired vascular reactivity induced by hydrogen peroxide-stimulated oxidative stress in HSV rings. These results may suggest that doxycycline may be useful as an antioxidant in the prevention of oxidative stress injury caused by ischemia during coronary artery bypass grafting operation. Keywords: Doxycycline, Matrix metalloproteinases, Oxidative stress, Reactive oxygen species, Coronary artery bypass graft, Hydrogen peroxide.