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Microglial activation induced by brain trauma is suppressed by post-injury treatment with a PARP inhibitor.

d'Avila JC, Lam TI, Bingham D, Shi J, Won SJ, Kauppinen TM, Massa S, Liu J, Swanson RA - J Neuroinflammation (2012)

Bottom Line: INO-1001 significantly reduced microglial activation in the peri-lesion cortex and ipsilateral hippocampus.The reduced inflammation was associated with increased neuronal survival in the peri-lesion cortex and improved performance on tests of forelimb dexterity conducted 8 weeks after TBI.Treatment with a PARP inhibitor for 12 days after TBI, with the first dose given as long as 20 hours after injury, can reduce inflammation and improve histological and functional outcomes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept. of Neurology, Veterans Affairs Medical Center, San Francisco, California 94121, USA.

ABSTRACT

Background: Traumatic brain injury (TBI) induces activation of microglia. Activated microglia can in turn increase secondary injury and impair recovery. This innate immune response requires hours to days to become fully manifest, thus providing a clinically relevant window of opportunity for therapeutic intervention. Microglial activation is regulated in part by poly(ADP-ribose) polymerase-1 (PARP-1). Inhibition of PARP-1 activity suppresses NF-kB-dependent gene transcription and thereby blocks several aspects of microglial activation. Here we evaluated the efficacy of a PARP inhibitor, INO-1001, in suppressing microglial activation after cortical impact in the rat.

Methods: Rats were subjected to controlled cortical impact and subsequently treated with 10 mg/kg of INO-1001 (or vehicle alone) beginning 20 - 24 hours after the TBI. Brains were harvested at several time points for histological evaluation of inflammation and neuronal survival, using markers for microglial activation (morphology and CD11b expression), astrocyte activation (GFAP), and neuronal survival (NeuN). Rats were also evaluated at 8 weeks after TBI using measures of forelimb dexterity: the sticky tape test, cylinder test, and vermicelli test.

Results: Peak microglial and astrocyte activation was observed 5 to 7 days after this injury. INO-1001 significantly reduced microglial activation in the peri-lesion cortex and ipsilateral hippocampus. No rebound inflammation was observed in rats that were treated with INO-1001 or vehicle for 12 days followed by 4 days without drug. The reduced inflammation was associated with increased neuronal survival in the peri-lesion cortex and improved performance on tests of forelimb dexterity conducted 8 weeks after TBI.

Conclusions: Treatment with a PARP inhibitor for 12 days after TBI, with the first dose given as long as 20 hours after injury, can reduce inflammation and improve histological and functional outcomes.

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Related in: MedlinePlus

Time course of microglia and astrocyte activation in cortex after controlled cortical impact. (A) Diagram of coronal rat brain section showing relationship of lesion cavity (red) to regions photographed (black squares). (B) Confocal fluorescence images of CD11b immunoreactivity (red) in peri-lesion cortex at designated time points after TBI. Panel '7d mag' is a magnified view showing amoeboid morphology of the activated microglia (arrows). (C) Quantification of microglial activation. (D) Astrocytes are immunostained for GFAP (green), and staining is quantified in (E). Scale bars are 20 μm. n = 3 at each time point; * p < 0.05, ** p < 0.01 vs. sham.
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Figure 1: Time course of microglia and astrocyte activation in cortex after controlled cortical impact. (A) Diagram of coronal rat brain section showing relationship of lesion cavity (red) to regions photographed (black squares). (B) Confocal fluorescence images of CD11b immunoreactivity (red) in peri-lesion cortex at designated time points after TBI. Panel '7d mag' is a magnified view showing amoeboid morphology of the activated microglia (arrows). (C) Quantification of microglial activation. (D) Astrocytes are immunostained for GFAP (green), and staining is quantified in (E). Scale bars are 20 μm. n = 3 at each time point; * p < 0.05, ** p < 0.01 vs. sham.

Mentions: Activation of microglia and astrocytes was evaluated in the lesioned and non-lesioned cortex and hippocampus on 4 coronal sections spaced 640 μm apart and centered on the lesion epicenter. Six 450 μm2 areas were photographed for later analysis: an area centered 625 um lateral to the lesion edge and midway through the cortical depth; the homologous contralateral cortex; and the hippocampal dentate gyrus ipsilateral and contralateral to the cortical lesion (Figure 1A). The edge of the lesion was defined by complete lack of Neu N staining. The regions analyzed were offset from the edge by 400 μM to avoid introducing error by edge irregularities. Microglial activation was scored by evaluating the density of CD11b - positive microglia and microglial morphology (modified from [25], as detailed in Table 1. Astrocyte activation was quantified by measuring expression of glial fibrillary acidic protein (GFAP). GFAP expression level in each photographed area was calculated by multiplying the net area of GFAP staining by the intensity of GFAP staining, using the NIH ImageJ program.


Microglial activation induced by brain trauma is suppressed by post-injury treatment with a PARP inhibitor.

d'Avila JC, Lam TI, Bingham D, Shi J, Won SJ, Kauppinen TM, Massa S, Liu J, Swanson RA - J Neuroinflammation (2012)

Time course of microglia and astrocyte activation in cortex after controlled cortical impact. (A) Diagram of coronal rat brain section showing relationship of lesion cavity (red) to regions photographed (black squares). (B) Confocal fluorescence images of CD11b immunoreactivity (red) in peri-lesion cortex at designated time points after TBI. Panel '7d mag' is a magnified view showing amoeboid morphology of the activated microglia (arrows). (C) Quantification of microglial activation. (D) Astrocytes are immunostained for GFAP (green), and staining is quantified in (E). Scale bars are 20 μm. n = 3 at each time point; * p < 0.05, ** p < 0.01 vs. sham.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3298794&req=5

Figure 1: Time course of microglia and astrocyte activation in cortex after controlled cortical impact. (A) Diagram of coronal rat brain section showing relationship of lesion cavity (red) to regions photographed (black squares). (B) Confocal fluorescence images of CD11b immunoreactivity (red) in peri-lesion cortex at designated time points after TBI. Panel '7d mag' is a magnified view showing amoeboid morphology of the activated microglia (arrows). (C) Quantification of microglial activation. (D) Astrocytes are immunostained for GFAP (green), and staining is quantified in (E). Scale bars are 20 μm. n = 3 at each time point; * p < 0.05, ** p < 0.01 vs. sham.
Mentions: Activation of microglia and astrocytes was evaluated in the lesioned and non-lesioned cortex and hippocampus on 4 coronal sections spaced 640 μm apart and centered on the lesion epicenter. Six 450 μm2 areas were photographed for later analysis: an area centered 625 um lateral to the lesion edge and midway through the cortical depth; the homologous contralateral cortex; and the hippocampal dentate gyrus ipsilateral and contralateral to the cortical lesion (Figure 1A). The edge of the lesion was defined by complete lack of Neu N staining. The regions analyzed were offset from the edge by 400 μM to avoid introducing error by edge irregularities. Microglial activation was scored by evaluating the density of CD11b - positive microglia and microglial morphology (modified from [25], as detailed in Table 1. Astrocyte activation was quantified by measuring expression of glial fibrillary acidic protein (GFAP). GFAP expression level in each photographed area was calculated by multiplying the net area of GFAP staining by the intensity of GFAP staining, using the NIH ImageJ program.

Bottom Line: INO-1001 significantly reduced microglial activation in the peri-lesion cortex and ipsilateral hippocampus.The reduced inflammation was associated with increased neuronal survival in the peri-lesion cortex and improved performance on tests of forelimb dexterity conducted 8 weeks after TBI.Treatment with a PARP inhibitor for 12 days after TBI, with the first dose given as long as 20 hours after injury, can reduce inflammation and improve histological and functional outcomes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept. of Neurology, Veterans Affairs Medical Center, San Francisco, California 94121, USA.

ABSTRACT

Background: Traumatic brain injury (TBI) induces activation of microglia. Activated microglia can in turn increase secondary injury and impair recovery. This innate immune response requires hours to days to become fully manifest, thus providing a clinically relevant window of opportunity for therapeutic intervention. Microglial activation is regulated in part by poly(ADP-ribose) polymerase-1 (PARP-1). Inhibition of PARP-1 activity suppresses NF-kB-dependent gene transcription and thereby blocks several aspects of microglial activation. Here we evaluated the efficacy of a PARP inhibitor, INO-1001, in suppressing microglial activation after cortical impact in the rat.

Methods: Rats were subjected to controlled cortical impact and subsequently treated with 10 mg/kg of INO-1001 (or vehicle alone) beginning 20 - 24 hours after the TBI. Brains were harvested at several time points for histological evaluation of inflammation and neuronal survival, using markers for microglial activation (morphology and CD11b expression), astrocyte activation (GFAP), and neuronal survival (NeuN). Rats were also evaluated at 8 weeks after TBI using measures of forelimb dexterity: the sticky tape test, cylinder test, and vermicelli test.

Results: Peak microglial and astrocyte activation was observed 5 to 7 days after this injury. INO-1001 significantly reduced microglial activation in the peri-lesion cortex and ipsilateral hippocampus. No rebound inflammation was observed in rats that were treated with INO-1001 or vehicle for 12 days followed by 4 days without drug. The reduced inflammation was associated with increased neuronal survival in the peri-lesion cortex and improved performance on tests of forelimb dexterity conducted 8 weeks after TBI.

Conclusions: Treatment with a PARP inhibitor for 12 days after TBI, with the first dose given as long as 20 hours after injury, can reduce inflammation and improve histological and functional outcomes.

Show MeSH
Related in: MedlinePlus