The role of poly (adp-ribose) metabolism in cell survival following various forms of stress

The role of poly(ADP-ribose) metabolism in cell survival following DNA damage and/or hyperthermia was examined. The effects of inhibitors of poly(ADP-ribose) polymerase on the recovery of cell division in C3H10T 1/2 cells following N-methyl-N'-nitro-N-nitroso-guanidine (MNNG) were examined. 3-methoxybenzamide (MBA), 3-aminobenzamide, and benzamide blocked recovery of cell division more effectively than did theophylline or caffeine. Three noninhibitory compounds, 3-methoxybenzoic acid, 3-aminobenzoic acid, and benzoic acid had no effect on the recovery of cell division. MBA synergistically enhanced the cytotoxicity of MNNG. In the presence of MBA, cells progressively lost the ability to resume cell division during the first 24 to 36 h following DNA damage. In the presence of MBA, the rates of RNA and protein synthesis following MNNG treatment were slightly higher than those in cells treated with MNNG alone while a dramatic decrease in the rate of DNA synthesis occurred approximately 16 h after MNNG treatment. These results suggested that poly(ADP-ribose) is required for subsequent rather than ongoing rounds of DNA synthesis following DNA damage.

The effect of MBA on the survival of quiescent cells following MNNG treatment was examined. Quiescent cells effected repair of potentially lethal damage (PLD) over a 48 h period following 68 (mu)M MNNG treatment. In contrast to observations made with dividing cells, MBA had no effect on PLD repair. These results suggest that poly(ADP-ribosylation) is required to coordinate DNA repair with cell cycle progression following DNA damage in dividing cells.

The effect of MBA following acute hyperthermia (45(DEGREES)C) was also examined. MBA synergistically potentiated the cytotoxicity of a 40 min, but not a 10 min, heat treatment. The time course of the development of thermotolerance was altered by the presence of MBA. When treatment with 34 (mu)M MNNG for 20 min was preceeded by a 10 min 45(DEGREES)C treatment, the cytotoxicity of MNNG was synergistically enhanced. The presence of MBA for 48 h following the combined heat and MNNG treatment further enhanced the observed cytotoxicity.