Neary Joseph T, Kang Yuan, Willoughby Karen A, Ellis Earl F
Research Service, Veterans Affairs Medical Center, Department of Pathology, University of Miami School of Medicine, Miami, Florida 33125, USA.
J Neurosci. 2003 Mar 15;23(6):2348-56. doi: 10.1523/JNEUROSCI.23-06-02348.2003.
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.
胶质增生的特征是星形胶质细胞对脑损伤产生肥大和增生反应。为了确定脑外伤体外模型所产生的星形胶质细胞损伤是否会激活细胞增殖和分化的关键调节因子细胞外信号调节蛋白激酶（ERK），对培养在可变形硅橡胶膜上的星形胶质细胞施加快速、可逆的应变（拉伸）诱导损伤。损伤后1分钟观察到ERK激活，10至30分钟时达到最大值，并持续升高3小时。ERK激活取决于损伤的速率和程度；在20 - 60毫秒、7.5毫米膜位移后观察到最大ERK激活。ERK激活被抑制ERK的上游激活剂MEK所阻断。当钙内流减少时，ERK激活降低。当细胞外ATP被腺苷三磷酸双磷酸酶水解或ATP/P2受体被阻断时，损伤诱导的ERK激活显著降低。P2受体拮抗剂研究表明P2X2和P2Y1受体在损伤诱导的ERK激活中起作用，而P2X1、P2X3或P2X7受体不起作用。这些发现首次证明机械损伤释放的ATP是触发ERK激活的信号之一，并提示细胞外ATP、P2嘌呤能受体和钙依赖性ERK信号在星形胶质细胞对脑外伤的反应中起作用。
