Exposure of human lymphocytes and lymphoblastoid cells to simulated microgravity strongly affects energy metabolism and DNA repair

Exposure of freshly drawn lymphocytes and lymphoblastoid cells (LB and COR3) to simulated microgravity decreased the intracellular ATP concentration to 50%-40% of the value found in normal growth conditions. The decrease was reversible although recovery to normal values occurred only slowly both in lymphocytes and in lymphoblastoid cells. Poly(ADP-ribose) polymerase (PARP) activity was increased indicating that cells exposed to conditions of reduced gravitation experience stress. Exposure to microgravity forces cells into a condition of metabolic quiescence in which they appear to be particularly sensitive to subsequent exposures to a genotoxic agent. Thus, treatment of cells with the strong redox agent potassium bromate under microgravity conditions, indicated an impairment in repair of DNA 8-hydroxy-2'-deoxyguanosine (8-OHdG), an oxidized derivative of deoxyguanosine. We conclude that gravitational modulation of the kind routinely obtained under laboratory conditions and during spaceflights is a stressful process to which cells appear to be extremely sensitive. These effects may reflect the physiological alterations observed in astronauts and in animals following spaceflights or exposure to conditions of simulated microgravity.