PARP inhibition improves the effectiveness of neural stem cell transplantation in experimental brain trauma

Abstract

Abstract. Neural stem cell transplantation is a promising new treatment of ischemic or traumatic brain injury. We have now investigated the involvement of the peroxynitrite -poly(ADPribose) polymerase (ONOO --PARP) activation cascade in brain trauma and neural stem cell transplantation. The forelimb motor cortex of adult male rats was exposed to cold lesion (-60˚C) and motor function was monitored. Neural stem cells isolated from E14 rat embryos were labeled with brome deoxyuridine (BrDU) and injected into the injured cortex 6 days after the lesion. After another 6 days, the survival and differentiation of the grafted cells were investigated with immunohistochemistry. Increased production of ONOO -revealed by tyrosine nitration was seen in the lesion 2 days after transplantation. Animals treated with the ONOO -decomposition catalyst FP15 or the PARP inhibitor PJ34 had a significantly improved motor score, when compared to vehicle-treated controls. The neurological score further improved following stem cell grafting in the PJ34 treated, but not in the control animals. Six days after transplantation, differentiated BrDU positive cells were found in the cortical penumbra. The majority of these differentiated cells expressed an astrocyte marker and some of the cells expressed oligodendrocyte or neuronal markers. The number of surviving transplanted cells was significantly higher in the PJ34 treated group. Inhibition of the ONOO --PARP activation cascade significantly improves the effectiveness of neural stem cell transplantation and promotes rapid functional recovery. IntroductionStem cell transplantation is an emerging approach for the treatment of various diseases of the central nervous system. Naturally occurring stem cells can be found in the subventricular and hippocampal subgranular zones (1) and these cells respond to brain damage by proliferation and migration to the area of the injury (2,3). The number of these endogenous stem cells is very limited. Therefore, grafting of exogenous stem cells may accelerate the natural regeneration process. Recent findings indicated that neural stem cell transplantation can be a viable approach for the treatment of brain trauma (4-6) or stroke (7-10). However, it is still not completely understood how these cells, endogenous or exogenous, are involved in the brain repair process (11).Human trials with various neural stem cell transplantation strategies ended with both promising results and serious concerns (12-14). One major limitation of current approaches is the low number of surviving grafted cells (12,15). Thus, in most cases the survival rate of the cells is below 10% and this situation places severe constraints on ultimate beneficial results. Marginal improvements in cell survival can be achieved by limiting apoptosis (16,17), free radical production (18), or lipid peroxidation (19,20). Another approach for increasing the survival of grafted cells is the application of exogenous growth factors like GDNF (21,(22)(23)(24)(25). None of these methods can ensure the comple...

Poly (ADP-Ribose) Polymerase Inhibitors as Potential Therapeutic Agents in Stroke and Neurotrauma

“…The beneficial effects of PJ34 and INO-1001, two potent PARP inhibitors, on the neurological score have been seen despite no significant benefit on brain lesion volume, suggesting that the protective effect by PARP inhibition could not be attributed to salvaging significant amounts of lesioned tissue (unpublished data). This observation has been also noticed in both pharmacological inhibition and genetic intervention in models of TBI induced by controlled cortical impact [145,220] and cold injury [222], indicating that functional improvement does not always correlate with the extent of brain damage. In addition, more complete inhibition of PARP-1 with INH2BP impairs spatial memory acquisition independent of injury, and is associated with ribosylation of 14-3-3gamma, a protein implicated in learning and memory [220].…”

“…Indeed, it has been demonstrated in the traumatic spinal cord [177,182,183,217,218] and brain tissue [145,198,219,220]. Additionally, peroxynitrite is involved in neuronal cell death and neurological deficits following TBI [221,222] and SCI [223]. Treatment with L-NAME (N ω -nitro-L-argininemethylester), a NOS inhibitor, promotes neurological recovery, reduced nitrotyrosine formation and the number of nitrotyrosine-positive neurons after closed head injury in mice [198].…”

“…Indeed, treatment with the PARP inhibitor PJ34 improves the neurological score after cryogenic lesion, and increases it even further following stem cell transplantation. High peroxynitrite production coincides with the loss of the majority of the grafted cells, and inhibition of the PARP activation cascade increases the number of surviving cells [222]. This PARP inhibition approach may ultimately lead to an optimized grafting strategy.…”

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“…Systemic administration of the PARP inhibitor 5-iodo-6-amino-1,2-benzopyrone at moderate dosing improved functional outcome after TBI in mice; however, higher doses that further inhibited PARP activity worsened performance in a memory paradigm [65]. Other PARP inhibitors have also been shown to afford protection in experimental models of TBI [115,116]. None of these studies have directly assessed the affect of PARP inhibitors on apoptosis.…”

Original article Poly(ADP-ribose) polymerase-1 (PARP1) and p53 labelling index correlates with tumour grade in meningiomas

“…However, if there is a high level of DNA damage, necrotic cell death is triggered by activating a large number of PARP1, consuming NAD+ and the ensuing ATP depletion [3]. The role of PARP1 activation cascade has also been demonstrated in neuronal stem cell transplantation after brain injury in rats [27], as well as PARP1 is also activated in the ischemia-reperfusion injury [55], and the early activation of PARP1 after cold lesion that is -at least in part -related to neuronal NO synthetase (nNOS) induction [16]. The role of PARP1 has been revealed in the regulation of glycogen synthase kinase-3 (GSK3) that is responsible for the hyperphosphorylation of tau [54], and the amyloid peptide affected signal transduction to PARP1 in Alzheimer's disease [2].…”