PARP-1 may be involved in hydroquinone-induced apoptosis by poly ADP-ribosylation of ZO-2

Hydroquinone (HQ), a major reactive metabolite of benzene, contributes to benzene‑induced leukemia. The molecular mechanisms that underlie this activity remain to be elucidated. Poly ADP‑ribosylation (PARylation) is a type of reversible posttranslational modification that is performed by enzymes in the PAR polymerase (PARP) family and mediates different biological processes, including apoptosis. Zona occludens 2 (ZO‑2) is a tight junction scaffold protein, which is involved in cell proliferation and apoptosis. The present study investigated the activity and mechanisms regulated by PARP‑1 during HQ‑induced apoptosis using TK6 lymphoblastoid cells and PARP‑1‑silenced TK6 cells. The results revealed that exposure to 10 µM HQ for 72 h induced apoptosis in TK6 cells and that apoptosis was attenuated in PARP‑1‑silenced TK6 cells. In cells treated with HQ, inhibition of PARP‑1 increased the expression of B cell leukemia/lymphoma 2 (Bcl‑2), increased ATP production and reduced reactive oxygen species (ROS) production relative to the levels observed in cells treated with HQ alone. Co‑localization of ZO‑2 and PAR (or PARP‑1 protein) was determined using immunofluorescence confocal microscopy. The findings of the present study revealed that ZO‑2 was PARylated via an interaction with PARP‑1, which was consistent with an analysis of protein expression that was performed using western blot analysis, which determined that ZO‑2 protein expression was upregulated in HQ‑treated control cells and downregulated in HQ‑treated PARP‑1‑silenced TK6 cells. These findings indicated that prolonged exposure to a low dose of HQ induced TK6 cells to undergo apoptosis, whereas inhibiting PARP‑1 attenuates cellular apoptosis by activating Bcl‑2 and energy‑saving processes and reducing ROS. The present study determined that PARP‑1 was involved in HQ‑induced apoptosis by PARylation of ZO‑2.