P2X7 Receptor Inhibition Increases CNTF in the Subventricular Zone, But Not Neurogenesis or Neuroprotection After Stroke
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ORIGINAL ARTICLE
P2X7 Receptor Inhibition Increases CNTF in the Subventricular Zone, But Not Neurogenesis or Neuroprotection After Stroke in Adult Mice Seong Su Kang & Matthew Phillip Keasey & Theo Hagg
Received: 4 February 2013 / Revised: 25 April 2013 / Accepted: 20 May 2013 # Springer Science+Business Media New York 2013
Abstract Increasing endogenous ciliary neurotrophic factor (CNTF) expression with a pharmacological agent might be beneficial after stroke as CNTF both promotes neurogenesis and, separately, is neuroprotective. P2X7 purinergic receptor inhibition is neuroprotective in rats and increases CNTF release in rat CMT1A Schwann cells. We, first, investigated the role of P2X7 in regulating CNTF and neurogenesis in adult mouse subventricular zone (SVZ). CNTF expression was increased by daily intravenous injections of the P2X7 antagonist Brilliant Blue G (BBG) in naïve C57BL/6 or Balb/c mice over 3 days. Despite the ~40–60 % increase or decrease in CNTF with BBG or the agonist BzATP, respectively, the number of proliferated BrdU+SVZ nuclei did not change. BBG failed to increase FGF2, which is involved in CNTF-regulated neurogenesis, but induced IL6, LIF, and EGF, which are known to reduce SVZ proliferation. Injections of IL-6 next to the SVZ induced CNTF and FGF2, but not proliferation, suggesting that IL-6 counteracts their neurogenesis-inducing effects. Following ischemic injury of the striatum by middle cerebral artery occlusion (MCAO), a 3-day BBG treatment increased CNTF in the medial penumbra containing the SVZ. BBG also induced CNTF and LIF, which are known to be protective following stroke, in the whole striatum after MCAO, but not GDNF or BDNF. However, BBG treatment did not reduce the lesion S. S. Kang : M. P. Keasey : T. Hagg (*) Kentucky Spinal Cord Injury Research Center, University of Louisville, 511 South Floyd Street, MDR Building, Room 616, Louisville, KY 40292, USA e-mail: [email protected] S. S. Kang : M. P. Keasey : T. Hagg Department of Neurological Surgery, University of Louisville, Louisville, KY 40292, USA T. Hagg Department of Pharmacology and Toxicology, University of Louisville, Louisville, KY 40292, USA
area or apoptosis in the penumbra. Even so, this study shows that P2X7 can be targeted with systemic drug treatments to differentially regulate neurotrophic factors in the brain following stroke. Keywords Ciliary neurotrophic factor . Mice . Neurogenesis . Neuroprotection . P2X7 purinergic receptor . Stroke
Introduction We are interested in upregulating CNTF expression in the CNS with systemic pharmacological small molecule treatments. CNTF is a good target because it is almost exclusively produced in the CNS and PNS by astrocytes and Schwann cells, respectively [1, 2]. CNTF is a potent survival-promoting factor for oligodendrocytes [3, 4] and a variety of neurons [5–9]. Exogenous [10] and endogenous [11] CNTF are protective following stroke in rodents, where it is increased in astrocytes [12]. In the adult CNS, CNTF promotes neurogenesis in the SVZ under normal [13,
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