Homocysteine contribution to DNA damage in cystathionine β-synthase-deficient patients

• Homocystinuria leads to accumulation of Hcy and its metabolites in the plasma.
• Homocystinuric patients present increase in DNA damage when compared to controls.
• Homocystinuric patients present a higher number of cells with high damage classes.
• Homocysteine has an in vitro concentration-dependent effect of on DNA damage.
• New therapeutic approaches should be considered to homocystinuric patients.

High blood levels of homocysteine (Hcy) are found in patients affected by homocystinuria, a genetic disorder caused by deficiency of cystathionine β-synthase (CBS) activity, as well as in nutritional deficiencies (vitamin B12 or folate) and in abnormal renal function. We previously demonstrated that lipid and protein oxidative damage is increased and the antioxidant defenses diminished in plasma of CBS-deficient patients, indicating that oxidative stress is involved in the pathophysiology of this disease. In the present work, we extended these investigations by evaluating DNA damage through the comet assay in peripheral leukocytes from CBS-deficient patients, as well as by analyzing of the in vitro effect of Hcy on DNA damage in white blood cells. We verified that DNA damage was significantly higher in the CBS-deficient patients under treatment based on a protein-restricted diet and pyridoxine, folic acid, betaine and vitamin B12 supplementation, when compared to controls. Furthermore, the in vitro study showed a concentration-dependent effect of Hcy inducing DNA damage. Taken together, the present data indicate that DNA damage occurs in treated CBS-deficient patients, possibly due to high Hcy levels.