RESUMO
Objective The aim of this study was to elucidate the effects of homocysteine (Hcy) on the expression and secretion of tissue factor pathway inhibitor (TFPI) in endothelial cells (Ecs). Methods Cultured human umbilical vein endothelial cells (HUVECs) (ECV-304 strain) were incubated with homocysteine (Hcy) in different concentrations of 0, 25, 50, 100?mol/L, and 1,5,10mmol/L, respectively, for 24 hours. Cell viability was then determined by MTT assay, and lactate dehydrogenase (LDH) released into the culture medium was measured to assess cell damage. Antigen levels of the free form of TFPI after Hcy exposure were measured in culture media with ELISA (Diagnostica Stago, France). Furthermore, the total content of TFPI was assessed with cellular ELISA. Results Hcy in concentrations of 0～1mmol/L did not produce cell toxicity as shown by cell viability and LDH determination in culture media after 24 hours of incubation. When the endothelial cells were exposed to concentrations up to 5mmol/L, cell viability decreased, and a higher concentration of Hcy (10mmol/L) elicited a significant cytotoxic effect, as shown by a decreased cell viability and a higher amount of LDH in culture supernatants compared with the control cells. All the TFPI absorbance values in Hcy-treated cells and the free TFPI levels in culture supernatants were significantly increased, especially in the 50?mol/L group. Conclusion A lower concentration of Hcy did not show signs of cell toxicity but it could promote the expression and secretion of TFPI. The results can help us partly explain why the TFPI level was increased in some patients with hyperhomocysteinemia. They also suggested that Hcy could play an important role in the modulation of coagulation processes in blood circulation.