Efficiency of homocysteine plus copper in inducing apoptosis is inversely proportional to gamma-glutamyl transpeptidase activity

Hyperhomocysteinemia represents an independent risk factor for atherosclero sis, but the mechanisms leading to cellular dysfunctions remain unknown. Us ing ECV304 cells, we found that homocysteine (Hcy) plus copper (Cu2+) induc ed cytotoxic effects: loss of cell adhesion, increased permeability to PI, and the occurrence of morphologically apoptotic cells. This form of apoptos is, inhibited by Z-VAD-fmk, was associated with a loss of mitochondrial pot ential, a cytosolic release of cytochrome c, activation of caspase-3, degra dation of poly( ADP-ribose) polymerase, and internucleosomal DNA fragmentat ion. However, the ability of Hcy plus Cu2+ to induce apoptosis decreased wh en the pretreatment culture time increased. As a positive correlation was f ound between the length of time of culture before treatment and the enhance ment of gamma -glutamyl transpeptidase (gamma -GT) activity, we asked wheth er gamma -GT was involved in the control of Hcy plus Cu2+-induced apoptosis . Therefore, ECV304 cells were treated with either acivicin or dexamethason e, inhibiting and stimulating gamma -GT, respectively. In ECV304 cells and human umbilical venous endothelial cells, acivicin favored Hcy plus Cu2+-in duced apoptosis whereas dexamethasone counteracted the apoptotic process. A s acivicin and dexamethasone were also capable of modulating cell death in ECV304 cells treated with antitumoral drugs, our data emphasize that the in volvement of gamma -GT in the control of apoptosis is not restricted to Hcy but also concerns other chemical compounds.