Dual role for poly(ADP-ribose)polymerase-1 and -2 and poly(ADP-ribose)glycohydrolase as DNA-repair and pro-apoptotic factors in rat germinal cells exposed to nitric oxide donors.

We describe the involvement of poly(ADP-ribose)polymerase 1 and 2 (PARP-1 and -2) and poly(ADP-ribose)glycohydrolase (PARG) in the response of rat germinal cells to the action of the NO donors, 3-morpholino-sydnonimine (SIN-1) and spermine nonoate (SNO). Primary spermatocytes and round spermatids showed a differential sensitivity to DNA damage induced by acute exposure to SIN-1 and SNO. Spermatocytes were able to repair DNA damage caused by the release of NO from SNO but neither spermatocytes nor spermatids could recover from the release of NO and O2*- from SIN-1. Addition of the PARPs inhibitor, 3-aminobenzamide, and the PARG inhibitor, gallotannin (GT), to germ cell cultures impaired DNA repair significantly. Consistent with the DNA repair seen in primary spermatocytes, both SIN-1 and SNO induced PARPs activation in these cells. In the case of SIN-1, there was an immediate but transient response while SNO induced a delayed but more sustained increase in PARPs activity. Chronic exposure of spermatocytes to SIN-1 and SNO, however, committed the cells to apoptosis, which coincided with proteolysis of PARP-1. The data indicate a dual role for PARPs and PARG in germinal cells as key proteins in processes that sense and repair DNA damage as well as in the commitment to apoptosis following prolonged oxidative stress.