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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

Post-injury treatment with INO-1001 reduces microglia and astrocyte activation. (A) Coronal rat brain sections showing microglial activation (CD11b immunostaining, brown) around the lesion sits. Rats were treated with vehicle or INO-1001 beginning 1 day after TBI, and brains were harvested at day 7. (B) Higher power confocal immunofluorescence staining of microglia (CD11b, red) and astrocytes (GFAP, green) in the peri-lesion cortex of rats treated with INO-1001 or vehicle. (C) Quantification of immunofluorescence. (D) Immunostaining in the ipsilateral hippocampal dentate gyrus of rats treated with INO-1001 or vehicle at day 7 post-TBI. (E) Quantifications of immunostaining in ipsilateral hippocampus. Scale bars are 20 μm. n = 3; *P < 0.05, **P < 0.01.
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Figure 3: Post-injury treatment with INO-1001 reduces microglia and astrocyte activation. (A) Coronal rat brain sections showing microglial activation (CD11b immunostaining, brown) around the lesion sits. Rats were treated with vehicle or INO-1001 beginning 1 day after TBI, and brains were harvested at day 7. (B) Higher power confocal immunofluorescence staining of microglia (CD11b, red) and astrocytes (GFAP, green) in the peri-lesion cortex of rats treated with INO-1001 or vehicle. (C) Quantification of immunofluorescence. (D) Immunostaining in the ipsilateral hippocampal dentate gyrus of rats treated with INO-1001 or vehicle at day 7 post-TBI. (E) Quantifications of immunostaining in ipsilateral hippocampus. Scale bars are 20 μm. n = 3; *P < 0.05, **P < 0.01.

Mentions: Separate groups of rats were then treated with INO-1001 (10 mg/kg) or vehicle for 7 days (encompassing the time of peak inflammation) to confirm that PARP inhibition can suppress TBI-induced brain inflammation. The drug was administered daily, with the first dose given 20 - 24 hours after injury. As expected, treatment initiated at this delayed time point did not affect the size of the necrotic lesion (not shown). However, rats receiving INO-1001 did exhibit reduced microglia activation in the peri-lesion cortex (Figure 3A,B,C). There was also a significant reduction in microglial activation in the ipsilateral hippocampus (Figure 3D,E). Reductions in astrocyte GFAP expression did not achieve statistical significance.


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)

Post-injury treatment with INO-1001 reduces microglia and astrocyte activation. (A) Coronal rat brain sections showing microglial activation (CD11b immunostaining, brown) around the lesion sits. Rats were treated with vehicle or INO-1001 beginning 1 day after TBI, and brains were harvested at day 7. (B) Higher power confocal immunofluorescence staining of microglia (CD11b, red) and astrocytes (GFAP, green) in the peri-lesion cortex of rats treated with INO-1001 or vehicle. (C) Quantification of immunofluorescence. (D) Immunostaining in the ipsilateral hippocampal dentate gyrus of rats treated with INO-1001 or vehicle at day 7 post-TBI. (E) Quantifications of immunostaining in ipsilateral hippocampus. Scale bars are 20 μm. n = 3; *P < 0.05, **P < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Post-injury treatment with INO-1001 reduces microglia and astrocyte activation. (A) Coronal rat brain sections showing microglial activation (CD11b immunostaining, brown) around the lesion sits. Rats were treated with vehicle or INO-1001 beginning 1 day after TBI, and brains were harvested at day 7. (B) Higher power confocal immunofluorescence staining of microglia (CD11b, red) and astrocytes (GFAP, green) in the peri-lesion cortex of rats treated with INO-1001 or vehicle. (C) Quantification of immunofluorescence. (D) Immunostaining in the ipsilateral hippocampal dentate gyrus of rats treated with INO-1001 or vehicle at day 7 post-TBI. (E) Quantifications of immunostaining in ipsilateral hippocampus. Scale bars are 20 μm. n = 3; *P < 0.05, **P < 0.01.
Mentions: Separate groups of rats were then treated with INO-1001 (10 mg/kg) or vehicle for 7 days (encompassing the time of peak inflammation) to confirm that PARP inhibition can suppress TBI-induced brain inflammation. The drug was administered daily, with the first dose given 20 - 24 hours after injury. As expected, treatment initiated at this delayed time point did not affect the size of the necrotic lesion (not shown). However, rats receiving INO-1001 did exhibit reduced microglia activation in the peri-lesion cortex (Figure 3A,B,C). There was also a significant reduction in microglial activation in the ipsilateral hippocampus (Figure 3D,E). Reductions in astrocyte GFAP expression did not achieve statistical significance.

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