Fig. 9: PARP inhibitors are neurotoxic in HR-deficient post-mitotic neurons and a potential mechanism of the opposite effects of cis-and trans-RSV on neuronal survival.

a PARP is required for cis-RSV-mediated neuroprotective effects. Rat cortical neurons (DIV 9) were treated with NMDA (50 µM for 5 min), AG-14361 (AG, 10 μM), olaparib (Ola, 10 μM) either alone or in combination with cis-RSV (50 μM) for 24 hr. Cells were then exposed to NMDA (500 µM for 5 min) and viability was assessed using MTT assay after 24 hr. b PARP1 inhibitors are neurotoxic and do not affect trans-RSV-mediated neurotoxicity. Rat cortical neurons (DIV 9) were treated with olaparib (10 μM), AG-14361 (10 μM) and talazoparib (2 μM) either alone or in combination with trans-RSV (50 μM) for 72 hr. c PARP1 inhibitors induce DNA damage in HR-deficient post-mitotic neurons. Immunostaining images (scale bar, 10 µm) for γ-H2AX foci (green; DAPI – nuclear marker, blue) in cortical neurons (DIV 10) after treatment with olaparib (10 μM), AG-14361 (10 μM) and talazoparib (2 μM) for 24 hr. The graph represents the average number of γ-H2AX foci per n ≥ 30 neurons per treatment condition for n = 3 experiments. d PARP1 inhibitors induce neurite degeneration. Representative images (scale bar, 20 µm) for cortical neurons following olaparib (10 μM), AG-14361 (10 μM) and talazoparib (1 μM) treatment for 24 hr (MAP2 – neurite marker, magenta and DAPI – nuclear marker, blue). Neurons were immunoassayed with anti-MAP2 antibody and quantified for neurite degeneration. e Proposed mechanism of cis-RSV-mediated neuroprotection and trans-RSV-mediated neurotoxicity. All data represent mean ± SEM with statistical significance calculated using ANOVA with Šídák’s test for multiple comparisons.