Biphasic changes in the levels of poly(ADP‐ribose) polymerase‐1 and caspase 3 in the immature brain following hypoxia–ischemia

Abstract

Poly(ADP-ribose) polymerase-1 (PARP-1) is a DNA repair-associated enzyme that has multiple roles in cell death. This study examined the involvement of PARP-1 in ischemic brain injury in the 7-day old rat, 0.5-48 h after unilateral carotid artery ligation and 2 h of 7.8% oxygen. This experimental paradigm produced a mild to moderate injury; 40-67% of animals in the ligated groups had histological evidence of neuronal death. Ipsilateral cortical injury was seen at all survival times, while mild contralateral cortical injury was seen only at the 1h survival time. Hippocampal injury was delayed relative to the cortex and did not show a biphasic pattern. Immunohistochemical staining for PARP showed bilateral increased staining as early as 1 h post-hypoxia. PARP staining at early time periods was most intense in layer V of cortex, but did not demonstrate a pattern of cell clusters or columns. Ipsilateral PARP-1 levels quantified by western blotting showed a biphasic pattern of elevation with peaks at 0.5 and 12 h post-hypoxia. Contralateral PARP-1 levels were also elevated at 0.5 and 24 h. PARP activity as determined by immunoreactivity for poly(ADP-ribose) (PAR) was increased ipsilaterally at 0.5, 2 and 12 h survival times. Cortical caspase 3-activity was increased ipsilaterally at 6, 12, and 24 h and contralaterally at 0.5, 1, 2 and 6 h post-hypoxia. There are three main findings in this study. First, changes in the distribution and amount of cell death correlate well with measured PARP-1 levels after hypoxia-ischemia, and both display biphasic characteristics. Second, there are significant early, transient morphological and biochemical changes in the contralateral cortex after neonatal hypoxia-ischemia due to unilateral permanent occlusion of a carotid artery followed by 2 h of systemic hypoxia. Third, variability in the responses of individual pups to hypoxia-ischemia suggests the presence of unidentified confounding factors.

Hyperglycemia accentuates and ketonemia attenuates hypoglycemia-induced neuronal injury in the developing rat brain

“…Conversely, a biphasic PARP-1 and PAR expression in the cerebral cortex was demonstrated post HI in P7 rats, with an initial peak soon after the termination of hypoxia and a second peak 12 h later and lasting until 24 h (35). A biphasic pattern of neuronal injury slightly delayed in time, relative to the PARP-1 and PAR expression was present (35). Thus, persistent PARP-1 and AIF mRNA upregulation 24 h posthypoglycemia may portend the risk of additional neuronal injury.…”

Quantification of Poly(ADP-Ribose)-Modified Proteins in Cerebrospinal Fluid from Infants and Children after Traumatic Brain Injury

“…In whole-brain homogenates of late fetal rats, PARP activity was found to be 2.5 times that of postnatal day 4 rats, implicating a role for PARP in CNS cell differentiation, synaptogenesis, and development (Shambaugh et al, 1988). Although the effect of PARP activation on outcome after brain injuries sustained during development is less clear, the degree of PARP activation in neonatal rats after cerebral hypoxia-ischemia correlates with the degree of cerebral injury (Martin et al, 2005).…”

Hypoxia Ischemia-Mediated Cell Death in Neonatal Rat Brain

“…While in low abundance, many of these RS are used as signaling molecules (i.e. nitric oxide, NO • ), over-production of RS can promote cellular dysfunction and cell death through increased lipid peroxidation, protein oxidation and DNA damage [10,11]. A primary substrate in these RS-mediated reactions is superoxide (O 2…”