PARP1 activation/expression modulates regional-specific neuronal and glial responses to seizure in a hemodynamic-independent manner

Poly(ADP-ribose) polymerase-1 (PARP1) plays a regulatory role in apoptosis, necrosis and other cellular processes after injury. Status epilepticus (SE) induces neuronal and astroglial death that show regional-specific patterns in the rat hippocampus and piriform cortex (PC). Thus, we investigated whether PARP1 regulates the differential neuronal/glial responses to pilocarpine (PILO)-induced SE in the distinct brain regions. In the present study, both CA1 and CA3 neurons showed PARP1 hyperactivation-dependent neuronal death pathway, whereas PC neurons exhibited PARP1 degradation-mediated neurodegeneration following SE. PARP1 degradation was also observed in astrocytes within the molecular layer of the dentate gyrus. PARP1 induction was detected in CA1-3-reactive astrocytes, as well as in reactive microglia within the PC. Although PARP1 inhibitors attenuated CA1-3 neuronal death and reactive gliosis in the CA1 region, they deteriorated the astroglial death in the molecular layer of the dentate gyrus and in the stratum lucidum of the CA3 region. Ex vivo study showed the similar regional and cellular patterns of PARP1 activation/degradation. Taken together, our findings suggest that the cellular-specific PARP1 activation/degradation may distinctly involve regional-specific neuronal damage, astroglial death and reactive gliosis in response to SE independently of hemodynamics.