Remodeling of heterochromatin induced by heavy metals in extreme old age

The levels of chromosome instability and heat absorption of chromatin have been studied in cultured lymphocytes derived from blood of 80–93- and 18–30-year-old individuals, under the effect of heavy metal Cu(II) and Cd(II) salts. The analysis of the results obtained indicates that 50 μM Cu(II) induced a significantly higher level of cells with chromosome aberrations in old donors (13.8 ± 1.5% vs control, 3.8 ± 1.7%), whereas treatment with 100 μM Cd(II) did not induce any changes in the background index. Analysis of the lymphocyte melting curves showed that Cu(II) ions caused more effective condensation of heterochromatin in old healthy individuals compared with young donors, which was expressed by the increase of the Tm of elderly chromatin by ~3°C compared with the norm. Treatment of lymphocyte chromatin of old individuals with 100 μM Cd(II) caused decondensation (deheterochromatinization) of both the facultative and constitutive domains of heterochromatin. The deheterochromatinization Tm was decreased by ~3–3.5°C compared with the Tm observed for young individuals. Thus, the chromatin of cultured lymphocytes from the old-aged individuals underwent modification under the influence of copper and cadmium salts. Cu(II) caused additional heterochromatinization of heterochromatin, and Cd(II) caused deheterochromatinization of facultative and constitutive heterochromatin. Our data may be important as new information on the remodeling of constitutive and facultative heterochromatin induced by heavy metals in aging, aging pathology, and pathology linked with metal ions.