CE: Alpana; MBC/201257; Total nos of Pages: 5; MBC 201257 In-vitro study of homocysteine and aspirin effects on fibrinolysis: measuring fibrinolysis parameters Javad Zavar-reza, Fahima Danesh Pouya, Beman Ali Jalali, Farangis Gholami and Naser Danesh Pouya Objectives Some studies suggest that increased homocysteine in blood leads to alterations in coagulation and fibrinolysis; however, the precise mechanism is not clear. The aim of this study was to compare different concentrations of homocysteine and aspirin on fibrinolysis in the plasma of healthy individuals in vitro. Materials and methods Different concentrations of homocysteine (200, 100, and 50 mmol/l) and aspirin (100, 10, and 1 mg/l) were added to the healthy people plasma citrate. They were incubated at 37-C for 24 h. Then, fibrinolysis parameters were analyzed by the turbidimetric procedure at 405 nm. The independent-samples t-test was utilized to compare them (P < 0.05). Results Findings revealed that homocysteine at 200 mmol/l with aspirin 100 ml/g had significant changes in the lysis maximum velocity (0.150 W 0.002), half-lysis time (218 W 5.77), the total lysis time (446 W 5.77), and lag time in lysis (119 W 3.60), compared to homocysteine at 200 mmol/l lysis maximum velocity (0.110 W 0.002), half-lysis time (278 W 7.63), the total lysis time (515 W 14.29), and lag time in lysis (176 W 3.60), respectively (P < 0.05). Homocysteine at 200 mmol/l with aspirin 1 ml/g did not significantly change in either parameter (P > 0.05). Homocysteine at 50 mmol/l with aspirin (100, 10, and 1 mg/l) had significant changes in all fibrinolysis parameters (P < 0.05), compared to homocysteine at 50 mmol/l. The other concentrations were compared in the same way. Conclusion Aspirin (more than 1 mg/l) had more effect on higher concentrations of homocysteine. Aspirin increased velocity of clot lysis and decreased lysis time of clot in the presence of homocysteine. Blood Coagul Fibrinolysis 24:000–000 ß 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins. Blood Coagulation and Fibrinolysis 2013, 24:000–000 Keywords: aspirin, fibrinolysis, homocysteine Shahid Sadoughi University of Medical Sciences and Health Services, Yazd, Iran Correspondence to Fahima Danesh Pouya, Shahid Sadoughi University of Medical Sciences and Health Services, Yazd, Iran Fax: +98 351 8202633; e-mail: f_daneshpouya@hotmail.com Received 13 February 2013 Revised 26 June 2013 Accepted 20 July 2013 Introduction Atherosclerosis is the major cause of coronary artery disease. It chiefly involves the large and middle muscular arteries, especially aorta, coronary, and cerebral arteries [1]. This process takes place in one’s lifetime, but the rapid formation depends on risk factors. When the lipid- rich plaques are separated from vessel walls, vessels will damage and thrombus formation will occur. Clotting disorders are the cause of many deaths. Clot formation is the most important cause of the onset of acute coronary syndromes (ACS) and sudden death caused by ischemia [2,3]. Among the risk factors for cardiovascular diseases is homocysteine (Hcys). It is a sulfur-containing amino acid which is produced in methionine metabolism pathway in the body [4]. Genetic defects such as enzymes involved in Hcys metabolism, and deficiency of vitamins such as folate, cobalamin, and B 6 increase levels of plasma Hcys [5]. Many studies have shown that increased Hcys levels in body fluids are associated with increased mortality due to cardiovascular diseases. Hcys may interfere in the blood coagulation and fibrinolysis system [6,7]. Studies have found that increased Hcys in blood is converted into Hcys thiolactone. Hcys thiolactone is a potent oxidant and leads to covalent oxidative modification of plasma proteins, such as fibrinogen; it changes fibrinogen func- tion, and then fibrin clots resistant to fibrinolysis are formed [4,8,9]. However, little information is available on the Hcys-precise mechanism on fibrinolysis [9,10]. To prevent this, several compounds have been studied, one of which is aspirin (NSAID), because aspirin inhibits platelet function used in the treatment of atherosclerotic cardiovascular disease [11]. Aspirin has anti-inflammatory property that inhibits cyclooxygenase-2 (COX-2) that prevents the synthesis of pro-inflammatory prostaglandins. It increases the endothelial nitric oxide synthesis. Nitric oxide is respon- sible for maintenance and repair of vascular endothelial function, and it has a vital role in preventing cardiovas- cular syndrome AQ2 (CVS) [12,13]. Another function of aspirin is acetylation of lysine resi- dues on the a-chain of fibrinogen, the functional group most susceptible to oxidative modification [14]. The structure of acetylated fibrinogen makes clot lysis easier AQ3 [11,15]. In-vitro studies showed an inverse relationship between the amount of acetylation and clot lysis time [16]. Original article 1 0957-5235 ß 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI:10.1097/MBC.0b013e3283657795