title: Neuroprotective signaling pathways are modulated by adenosine in the anoxia tolerant turtle.
abstract: Cumulative evidence shows a protective role for adenosine A1 receptors (A1R) in hypoxia/ischemia; A1R stimulation reduces neuronal damage, whereas blockade exacerbates damage. The signal transduction pathways may involve the mitogen-activated protein kinase (MAPK) pathways and serine/threonine kinase (AKT), with cell survival depending on the timing and degree of upregulation of these cascades as well as the balance between pro-survival and pro-death pathways. Here, we show in vitro that extracellular signal-regulated kinase (ERK1/2) and phosphatidylinositol 3-kinase (PI3-K/AKT) activation is dependent on A1R stimulation, with further downstream effects that promote neuronal survival. Phosphorylated ERK1/2 (p-ERK) and AKT (p-AKT) as well as Bcl-2 are upregulated in anoxic neuronally enriched primary cultures from turtle brain. This native upregulation is further increased by the selective A1R agonist 2-chloro-N-cyclopentyladenosine (CCPA), whereas the selective antagonist 8-cyclopentyl-1,3-dihydropylxanthine (DPCPX) decreases p-ERK and p-AKT expression. Conversely, A1R antagonism resulted in increases in phosphorylated JNK (p-JNK), p38 (p-p38), and Bax. As pathological and adaptive changes occur simultaneously during anoxia/ischemia in mammalian neurons, the turtle provides an alternative model to analyze protective mechanisms in the absence of evident pathologies.
authors.affiliation: Department of Biology, Boston University, Boston, Massachusetts 02215, USA. gnayak@bu.edu
authors.forename: Gauri H
authors.initials: GH
authors.lastname: Nayak
authors.forename: Howard M
authors.initials: HM
authors.lastname: Prentice
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Milton
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D058907:Adenosine A1 Receptor Agonists / Q000494:pharmacology; D058916:Adenosine A1 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D000860:Hypoxia / Q000503:physiopathology*; D007150:Immunohistochemistry; D053612:Janus Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D009474:Neurons / Q000502:physiology; D018696:Neuroprotective Agents; D010750:Phosphoproteins / Q000737:chemistry; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014426:Turtles / Q000502:physiology*; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D058907:Adenosine A1 Receptor Agonists; D058916:Adenosine A1 Receptor Antagonists; D018696:Neuroprotective Agents; D010750:Phosphoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D053612:Janus Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000241:Adenosine