Apoptosis in a Neonatal Rat Model of Cerebral Hypoxia-Ischemia

Abstract

Background and Purpose-The mechanisms of excitotoxic cell death in cerebral ischemia are poorly understood. In addition to necrosis, apoptotic cell death may occur. The purpose of this study was to determine whether an established model of cerebral hypoxia-ischemia in the neonatal rat demonstrates any features of apoptosis. Methods-Seven-day-old neonatal rats underwent bilateral, permanent carotid ligation followed by 1 hour of hypoxia, and their brains were examined 1, 3, and 4 days after hypoxia-ischemia. The severity of ischemic damage was assessed in the dentate gyrus and frontotemporal cortex by light microscopy. Immunocytochemistry was performed to detect the cleavage of actin by caspases, a family of enzymes activated in apoptosis. Terminal deoxynucleotidyl transferasemediated dUTP-biotin nick end labeling (TUNEL) reactivity was examined in the cortical infarction bed and dentate gyrus. Neonatal rat brain DNA was run on agarose gel electrophoresis to detect DNA fragmentation. Ethidium bromide-staining and electron microscopy were used to determine whether apoptotic bodies, 1 of the hallmarks of apoptosis, were present. Results-The frontotemporal cortex displayed evidence of infarction, and in most rats the dentate gyrus showed selective, delayed neuronal death. Immunocytochemistry demonstrated caspase-related cleavage of actin. TUNEL and DNA electrophoresis provided evidence of DNA fragmentation. Ethidium bromide-staining and electron microscopy confirmed the presence of chromatin condensation and apoptotic bodies. Conclusions-Features of apoptosis are present in the described model of cerebral hypoxia-ischemia. Apoptosis may represent a mode of ischemic cell death that could be the target of novel treatments that could potentially expand the therapeutic window for stroke. (Stroke. 1998;29:2622-2630.)

BDNF Protects the Neonatal Brain from Hypoxic-Ischemic InjuryIn Vivovia the ERK Pathway

“…The injury resulting is similar to that seen in the term human infant that has been exposed to an H-I insult. We have found recently that BDNF markedly protects against the H-I injury in this model, a portion of which has features of apoptotic-like death (Ferrer et al, 1994;Mehmet et al, 1994;Hill et al, 1995;Sidhu et al, 1997;Silverstein et al, 1997;Hasegawa et al, 1998;Pulera et al, 1998) and is caspase dependent (Cheng et al, 1998;Han et al, 2000). Our results in the present study supporting the involvement of the ERK pathway in this protection may have important clinical implications.…”

Apoptotic Cell Death Following Traumatic Injury to the Central Nervous System

“…Recent studies have also provided additional evidence of caspase-3 activation in other models of cerebral ischemia following strokes in adults and neonates. This includes the mitochondrial release of cytochrome c and activation of caspase-9, a proximal caspase in the caspase-3 apoptotic cascade (Gillardon et al, 1997;Cheng et al, 1998;Namura et al, 1998;Pulera et al, 1998;Kiprianova et al, 1999;Krajewski et al, 1999;Ouyang et al, 1999;Velier et al, 1999;. Several recent studies using caspase inhibitors provide support of these original observations, and demonstrate that injury severity can affect the efficacy of caspase inhibitors in reducing cell death.…”

Nicotinamide mononucleotide adenylyl transferase 1 protects against acute neurodegeneration in developing CNS by inhibiting excitotoxic-necrotic cell death

“…Apoptosis and necrosis are the two distinctive cell-death pathways with distinct pathological hallmarks and molecular mechanisms prominent in neonatal animals that undergo H-I (Fig. 6) (3,10,23,42,43). Of all of the identified caspases, caspase-3 is a key player in neuronal apoptosis elicited by diverse stimuli (33).…”

“…Excitotoxicity after neonatal H-I initiates necrosis and apoptosis as well as cell death that has features of both necrosis and apoptosis (3,10,21,46,47). Pan-caspase and caspase-3-specific inhibitors as well as overexpression of Bcl-XL and knockout of Bax significantly protect against neonatal H-I in rats and mice by blocking caspase-dependent celldeath pathways (6,23,41,42). In the present study, cytNmnat1 protects against H-I-mediated damage largely by influencing the necrosis/necroptosis pathway but not the apoptosis pathway.…”