Pituitary adenylate cyclase‐activating polypeptide is up‐regulated in cortical pyramidal cells after focal ischemia and protects neurons from mild hypoxic/ischemic damage

Abstract

The protective effect of pituitary adenylate cyclase-activating polypeptide (PACAP) in stroke models is poorly understood. We studied patterns of PACAP, vasoactive intestinal peptide, and the PACAP-selective receptor PAC1 after middle cerebral artery occlusion and neuroprotection by PACAP in cortical cultures exposed to oxygen/glucose deprivation (OGD). Within hours, focal ischemia caused a massive, NMDA receptor (NMDAR)-dependent up-regulation of PACAP in cortical pyramidal cells. PACAP expression dropped below the control level after 2 days and was normalized after 4 days. Vasoactive intestinal peptide expression was regulated oppositely to that of PACAP. PAC1 mRNA showed ubiquitous expression in neurons and astrocytes with minor changes after ischemia. In cultured cortical neurons PACAP27 strongly activated Erk1/2 at low and p38 MAP kinase at higher nanomolar concentrations via PAC1. In astrocyte cultures, effects of PACAP27 on Erk1/2 and p38 were weak. During OGD, neurons showed severely reduced Erk1/2 activity and dephosphorylation of Erk1/2-regulated Ser112 of pro-apoptotic Bad. PACAP27 stimulation counteracted Erk1/2 inactivation and Bad dephosphorylation during short-term OGD but was ineffective after expanded OGD. Consistently, PACAP27 caused MEK-dependent neuroprotection during mild but not severe hypoxic/ischemic stress. While PACAP27 protected neurons at 1-5 nmol/L, full PAC1 activation by 100 nmol/L PACAP exaggerated hypoxic/ischemic damage. PACAP27 stimulation of astrocytes increased the production of Aktactivating factors and conferred ischemic tolerance to neurons. Thus, ischemia-induced PACAP may act via neuronal and astroglial PAC1. PACAP confers protection to ischemic neurons by maintaining Erk1/2 signaling via neuronal PAC1 and by increasing neuroprotective factor production via astroglial PAC1.

Pituitary Adenylate Cyclase-Activating Polypeptide and Its Receptors: 20 Years after the Discovery

“…The p53 and Zac proteins have been demonstrated to regulate the PAC1-R gene, which, in the presence of PACAP38, can attenuate the damages of ischemia. Consistent with this finding, PACAP and PAC1-R mRNA expressions are transiently increased in the cortex and the hippocampus after traumatic brain injury (Skoglösa et al, 1999a;Stumm et al, 2007). Besides its neuroprotective activity, PACAP reduces the number of damaged axons after traumatic injury (Farkas et al, 2004;Tamá s et al, 2006), favors dendrite outgrowth through the Rho PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE GTPase and PI3-K pathways in response to neuronal activity (Henle et al, 2006) and enhances NMDA receptor activity (Macdonald et al, 2005), which probably contribute to functional recovery.…”

Tonic Activation of CXC Chemokine Receptor 4 in Immature Granule Cells Supports Neurogenesis in the Adult Dentate Gyrus

“…Ser-473-phosphorylated Akt (pAkt) was detected by rabbit monoclonal antibody (1:1000; #193H12; Cell Signaling Technology, Danvers, MA). After stripping, phosphorylated and nonphosphorylated Akt were detected using anti-Akt rabbit polyclonal IgG (0.125 g/ml; #07-416; Biomol International, Hamburg, Germany) (Stumm et al, 2007a). The ratio of the pAkt and Akt signals was determined and normalized with the mean of the control group.…”

“…Hippocampal cultures from E17 Sprague Dawley rat embryos (Charles River, Margate, Kent, UK) were prepared and transfected by using the Nucleofector device (Amaxa, Köln, Germany) as described previously Stumm et al, 2007a).…”

Delayed Pituitary Adenylate Cyclase–Activating Polypeptide Delivery After Brain Stroke Improves Functional Recovery by Inducing M2 Microglia/Macrophage Polarization

“…Because the kinetics of expression of endogenous PACAP after stroke by pyramidal cortical neurons (PACAP expression increases as soon as 6 hours after middle cerebral artery occlusion and peaks at 24 hours before disappearing) parallels with the evolution of the microglial response, 34 the in vivo PACAP release can be part of an endogenous protective mechanism aimed at controlling the by guest on May 12, 2018 http://stroke.ahajournals.org/ Downloaded from differentiation process of microglial cells, the loss of PACAP favoring the acquisition of a neurotoxic phenotype.…”