Bystander effect in human lymphocytes incubated with irradiated mitochondrial DNA deficient yeast cells

The comparison of strength of bystander effect induction in human lymphocytes by rho0 (complete loss of mitochondrial DNA) and rho+ (with fully functional mtDNA) strains of Saccharomyces cerevisiaewas carried out. The cultures of human peripheral blood were experimentally contaminated with nonirradiated or X-ray irradiated yeast cells (haploid rho0 and rho+ strains of S. cerevisiae). The doses of irradiation were 1 and 10 Gy. Well spread human metaphases were scored for chromosomal aberrations (CA). It was found that nonirradiated yeast cells (no matter rho0 or rho+) had no effect on lymphocytes chromosomal stability. Statistically significant increased level of CA was observed in lymphocytes incubated with irradiated rho+ yeast cells. The increasing of the CA was dose independent. However, after cocultivation with irradiated rho0 cells the bystander effect was revealed for dose 10 Gy only and his manifestation was mild in comparison with rho+ data. Thus, our findings suggest that strength of bystander effect depends on existence of mitochondrial DNA and normally functioning mitochondria