Poly(ADP-ribose) polymerase inhibitors attenuate necrotic but not apoptotic neuronal death in experimental models of cerebral ischemia

Abstract

An excessive activation of poly(ADP-ribose) polymerase (PARP) has been proposed to play a key role in postischemic neuronal death. We examined the neuroprotective effects of the PARP inhibitors benzamide, 6(5H)-phenanthridinone, and 3,4-dihydro-5-[4-1(1-piperidinyl)buthoxy]-1(2H)-isoquinolinone in three rodent models of cerebral ischemia. Increasing concentrations of the three PARP inhibitors attenuated neuronal injury induced by 60 min oxygen-glucose deprivation (OGD) in mixed cortical cell cultures, but were unable to reduce CA1 pyramidal cell loss in organotypic hippocampal slices exposed to 30 min OGD or in gerbils following 5 min bilateral carotid occlusion. We then examined the necrotic and apoptotic features of OGD-induced neurodegeneration in cortical cells and hippocampal slices using biochemical and morphological approaches. Cortical cells exposed to OGD released lactate dehydrogenase into the medium and displayed ultrastructural features of necrotic cell death, whereas no caspase-3 activation nor morphological characteristics of apoptosis were observed at any time point after OGD. In contrast, a marked increase in caspase-3 activity was observed in organotypic hippocampal slices after OGD, together with fluorescence and electron microscope evidence of apoptotic neuronal death in the CA1 subregion. Moreover, the caspase inhibitor Z-VAD-FMK reduced OGD-induced CA1 pyramidal cell loss. These findings suggest that PARP overactivation may be an important mechanism leading to post-ischemic neurodegeneration of the necrotic but not of the apoptotic type. Cell Death and Differentiation (2001) 8, 921 ± 932.

Group I metabotropic glutamate receptors stimulate the activity of poly(ADP-ribose) polymerase in mammalian mGlu1-transfected cells and in cortical cell cultures

“…In our model of sublethal OGD, the PARP inhibitor DPQ was not able to reduce in a significant manner the release of LDH induced by the pseudo-ischemic insult. This finding may appear to be in contrast with previous results from our laboratory showing that PARP inhibitors are neuroprotective in cortical cell cultures exposed to OGD (Moroni et al, 2001). It should be noted, however, that OGD exposure in the present study was much milder (40 vs. 60 min) and that PARP inhibitors are known to be efficacious only when excitotoxic or ischemic insults are particularly intense and presumably necrotic (Bonfoco et al, 1995;Meli et al, 2004).…”

“…A large body of evidence demonstrates that the increased neoformation of PAR plays a crucial role in neurodegeneration. In models of cerebral ischemia and excitotoxicity, it appears that intracellular depletion of ATP induced by PARP-1 leads to energy failure and necrotic neuronal death (Ha and Snyder, 1999;Meli et al, 2004;Moroni et al, 2001). In contrast, during the caspase-dependent apoptotic process, PARP-1 is proteolytically cleaved and inactivated by caspase-3, a process that is widely used as an apoptotic marker (Oliver et al, 1998).…”

“…A presumed cascade of glutamate activating NOS, leading to excessive formation of NO and DNA damage and then to overactivation of PARP-1, has been proposed to play a ''suicidal role'' due to the marked depletion of NAD and ATP tissue stores and the disruption of oxidative metabolism (Ha and Snyder, 2000;Herceg and Wang, 2001;Szabo´and Dawson, 1998). Accordingly, pharmacological PARP inhibition or targeted deletion of the PARP-1 gene provides impressive and unparalleled protection against neuronal damage in several animal models of excitotoxicity (Mandir et al, 2000;Moroni et al, 2001;Pieper et al, 1999). More recent findings also suggest a ''transcriptional hypothesis'' for the neurotoxic effects of PARP-1, in which the formation of PAR regulates the gene expression of neuroactive proteins such as iNOS, IL-1b, COX-2, TNFa and APP (Chiarugi, 2002).…”

Prokineticins are neuroprotective in models of cerebral ischemia and ischemic tolerance in vitro

“…To investigate the possible neuroprotective effects of Bv8 we carried out experiments in cultured murine cortical cells exposed to OGD, an in vitro model of focal cerebral ischemia routinely used in our lab (Pellegrini-Giampietro et al, 1999a). We have demonstrated that OGD induces necrotic neuronal death in this system, as detected by the appareance of necrotic ultrastructural features 24 h later and the lack of caspase-3 activation (Moroni et al, 2001). As previously shown, exposure to OGD for 60 min produced an intermediate level of neuronal damage in this system: the release of LDH was approximately 75% of that observed by exposing the cultures to a high concentration of glutamate (1 mM) for 24 h, which elicited complete neuronal cell death.…”

“…namely rat organotypic hippocampal slices exposed to 30 min OGD, which produces selective CA1 injury 24 h later and the appearance of morphological characteristics of apoptosis, caspase-3 activation and PARP-1 cleavage (Moroni et al, 2001;Gerace et al, 2012b). Fig.…”