Poly(ADP ribose) polymerase cleavage precedes neuronal death in the hippocampus and cerebellum following injury to the developing rat forebrain

Abstract

Transient unilateral forebrain hypoxia-ischaemia (HI) in 14-day-old rats produces infarction and delayed neuronal death in the frontal cortex. Cell death can also be observed in regions distant from the primary injury, a phenomenon known as diaschisis. While apoptosis is involved in selective neuronal death, its role in infarction and diaschisis remains poorly understood. Here, we have investigated the proteolytic cleavage of poly(ADP ribose) polymerase (PARP) and the occurrence of apoptosis in the hippocampus and the cerebellum following either HI or traumatic brain injury. We demonstrate that: (i) in vitro, PARP is cleaved during apoptosis but not necrosis in cultured neuronal (N1E) cells and Swiss 3T3 fibroblasts; (ii) following HI, apoptotic cells can be detected by 4 h after injury in the hippocampus; (iii) in the ipsilateral hippocampus the appearance of cells with apoptotic morphology is preceded by a dramatic increase in PARP cleavage in the same region, starting immediately following HI and persisting for 24 h; (iv) HI also induces apoptosis in the cerebellum and, as in the hippocampus, the appearance of cells with apoptotic morphology is preceded by PARP cleavage that is greater on the side ipsilateral to forebrain injury; and (v) similarly, traumatic brain injury to the forebrain leads to PARP cleavage and apoptosis in the cerebellum. We conclude that HI injury or traumatic injury to the developing rat forebrain leads to PARP cleavage in directly affected areas and in sites distant from the primary injury that precedes the appearance of cells with apoptotic morphology. Our results are consistent with a role for apoptotic cell death in infarction and in diaschisis resulting from forebrain injury to the developing brain.

Reduction in Cerebellar Volumes in Preterm Infants: Relationship to White Matter Injury and Neurodevelopment at Two Years of Age

“…One would anticipate that, with significant WMI altering fiber tract integrity into the corticospinal tracts, a secondary reduction in CV could result from axonal loss, Wallerian degeneration (24), and/or cerebellar neuronal deafferentation (25). Thus, it was not surprising to us to find an association between significant WMI and a reduction in CV.…”

Mechanisms Underlying Neuronal Death Induced by Chromogranin A-activated Microglia

“…Treatment of neuron/microglial co-cultures with CGA triggers two features characteristic of apoptotic death (1,36): the translocation of phosphatidylserine from the inner to the outer face of the plasma membrane and intranucleosomal cleavage of DNA in neurons. Culture medium conditioned by CGA-activated microglia induces apoptosis in neurons after a delay of 22 h, an observation that is consistent with the release of diffusable neurotoxins from CGA-treated microglia and the subsequent activation of a death program in neurons.…”

“…Thus, cortical neurons were exposed to cell-free conditioned medium (CM) collected from either resting microglia or microglia treated for 24 h with 10 nM CGA, and the rate of apoptosis and necrosis was determined. In the early stages of apoptosis, the plasma membrane remains intact and impermeable to inert dyes such as trypan blue (36). In contrast, necrosis is accompanied by a rapid loss of membrane integrity, and the cell membrane becomes permeable.…”

Activation of Poly(ADP‐Ribose) Polymerase in the Rat Hippocampus May Contribute to Cellular Recovery Following Sublethal Transient Global Ischemia

“…ance of cells with apoptotic morphology (Joashi et al, 1999). Therefore, it is plausible that caspase-3 activation by ischemia may mediate apoptosis by means of PARP cleavage.…”