Decreased p66Shc promoter methylation in patients with end-stage renal disease

p66Shc is a stress response protein and partially regulated by epigenetic modifications. Mice lacking p66Shc have reduced atherosclerosis, increased resistance to oxidative stress and a prolonged life time. The aim of the present study was to compare promoter methylation of the p66Shc gene between healthy controls and patients with end-stage renal disease (ESRD). There are two reasons for studying patients with ESRD. First, patients with ESRD have a disturbed homocysteine metabolism, and second an increased risk of morbidity and mortality from cardiovascular disease is a constant finding in these patients.

In our study, we measured fasting levels of homocysteine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH) and 8-isoprostane in 22 patients and in 26 healthy, age- and sex-matched controls. The methylation of the p66Shc promoter and Line-1, as surrogate marker of whole genome methylation was quantified in peripheral blood mononuclear cells.

In comparison to the control group, homocysteine, SAM, SAH, 8-isoprostane and whole genome methylation were significantly elevated in ESRD patients, while the p66Shc promoter methylation was significantly reduced. A significant correlation was found between SAH and p66Shc promoter methylation in the patient group. This observation underlines the role of SAH as a potent inhibitor of methyltransferases. Using backward regression analysis, we demonstrated that 8-isoprostane has a significant influence on p66Shc promoter methylation. In the control group and in patients with ESRD, increasing 8-isoprostane levels were linked to an elevated promoter methylation.

Under physiological conditions, based on the results of the control group, the p66Shc expression is more silenced through epigenetic modifications. The atherosclerotic risk is dramatically increased in ESRD patients; therefore, our experimental results of methylation are in accordance with the clinical situation.