Homocysteine thiolactone induces apoptosis in cultured human trophoblasts: a mechanism for homocysteine-mediated placental dysfunction?

Objective Hyperhomocystinemia is a thrombophilic condition associated with placental dysfunction. We tested the hypothesis that homocysteine-thiolactone, a metabolite of homocysteine, induces apoptosis in cultured trophoblasts. Study design Cytotrophoblasts from term human placentas were cultured for 72 hours or less in the presence or absence of 50 to 400 μmol/L homocysteine-thiolactone or 400 μmol/L cysteine (control), with or without vitamin C, vitamin E, folate, or N-acetylcysteine. Cell death was assessed by cellular adenosine triphosphate concentration, medium lactate dehydrogenase level, and immunocytochemical staining for the cleavage products of cytokeratin 18 and poly(adenosine diphosphate ribose) polymerase. Changes in expression of p53, Bcl-2, Bax, and Bak were quantified by Western immunoblotting. Results Homocysteine-thiolactone induced a concentration dependent increase in total cell death and death by apoptosis, compared with control. Vitamin C ameliorated apoptosis in cytotrophoblasts, whereas N-acetylcysteine mitigated cell death in syncytiotrophoblasts. Apoptosis in both phenotypes occurred with increased expression of p53 and Bak, but no change in Bcl-2 or Bax. Conclusion Homocysteine-thiolactone enhances apoptosis in cultured human trophoblast, and the effect can be limited by antioxidants.