Activation of extracellular signal-regulated kinase by stretch-induced injury in astrocytes involves extracellular ATP and P2 purinergic receptors.
Gliosis is characterized by hypertrophic and hyperplastic responses of astrocytes to brain injury. To determine whether injury of astrocytes produced by an in vitro model of brain trauma activates extracellular signal-regulated protein kinase (ERK), a key regulator of cellular proliferation and differentiation, astrocytes cultured on deformable SILASTIC membranes were subjected to rapid, reversible strain (stretch)-induced injury. Activation of ERK was observed 1 min after injury, was maximal from 10 to 30 min, and remained elevated for 3 hr. Activation of ERK was dependent on the rate and magnitude of injury; maximum ERK activation was observed after a 20-60 msec, 7.5 mm membrane displacement. ERK activation was blocked by inhibiting MEK, the upstream activator of ERK. Activation of ERK was reduced when calcium influx was diminished. When extracellular ATP was hydrolyzed by apyrase or ATP/P2 receptors were blocked, injury-induced ERK activation was significantly reduced. P2 receptor antagonist studies indicated a role for P2X2 and P2Y1, but not P2X1, P2X3, or P2X7, receptors in injury-induced ERK activation. These findings demonstrate for the first time that ATP released by mechanical injury is one of the signals that triggers ERK activation and suggest a role for extracellular ATP, P2 purinergic receptors, and calcium-dependent ERK signaling in the astrocytic response to brain trauma.
Neary
Joseph T
JT
Research Service, Veterans Affairs Medical Center, Department of Pathology, University of Miami School of Medicine, Miami, Florida 33125, USA. jneary@med.miami.edu
Kang
Yuan
Y
Willoughby
Karen A
KA
Ellis
Earl F
EF
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D001930:Brain Injuries / Q000150:complications / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism*; D005911:Gliosis / Q000209:etiology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058476:Receptors, Purinergic P2X2; D058472:Receptors, Purinergic P2Y1; D015398:Signal Transduction / Q000502:physiology; D013314:Stress, Mechanical
D004791:Enzyme Inhibitors; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D058472:Receptors, Purinergic P2Y1; D000255:Adenosine Triphosphate; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D002118:Calcium