Blocking epidermal growth factor receptor attenuates reactive astrogliosis through inhibiting cell cycle progression and protects against ischemic brain injury in rats

Abstract

J. Neurochem. (2011) 119, 644–653. Abstract Excessive astrogliosis is a major impediment to axonal regeneration in CNS disorders. Overcoming this inhibitory barrier of reactive astrocytes might be crucial for CNS repair. Up‐regulation and activation of epidermal growth factor receptor (EGFR) has been shown to trigger quiescent astrocytes into reactive astrocytes in response to several neural injuries. In this study, we investigated the effects of EGFR blockade in cultured astrocytes exposure to oxygen–glucose deprivation/reoxygenation (OGD/R) and in the rat middle cerebral artery occlusion (MCAO) model. Astrocytes in primary culture were used for OGD/R model and adult male Sprague–Dawley rats were used for MCAO model. Cell cycle progression of astrocytes in vitro was studied by flow cytometric analysis. Expression of phosphorylated epidermal growth factor receptor (p‐EGFR), glial fibrillary acidic protein (GFAP), and cell proliferation‐related molecules in vitro and in vivo were evaluated by immunostaining and western blot analysis. Neuronal apoptosis after MCAO was determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method. Neurologic scores and infarct volumes post‐ischemia were assessed in the rat MCAO model. Astrocytes became activated in the cultured astrocytes exposure to OGD/R and in the rat brain after MCAO, accompanied with phosphorylation of EGFR. EGFR blockade significantly decreased expression of p‐EGFR, inhibited cell cycle progression of astrocytes, and reduced reactive astrogliosis in vitro and in vivo. EGFR inhibition also reduced infarct volumes and improved neurologic scores of rats after MCAO. Our findings indicated that blocking EGFR pathway might attenuate reactive astrogliosis through inhibiting cell cycle progression and protect against ischemic brain injury in rats.

Critical role of Ror2 receptor tyrosine kinase in regulating cell cycle progression of reactive astrocytes following brain injury

“…It has been reported that several signaling molecules, including bFGF, EGF, endothelin‐1, sonic hedgehog, and galectin‐1/3, are involved in proliferation of astrocytes in response to brain injury (Gadea et al, ; Kang et al, ; Pitter et al, ; Sirko et al, ; Sirko et al, ; Yang et al, ). However, these molecules also appear to affect other reactive responses such as induction of GFAP , and thus it remains to be elucidated how these molecules affect cell proliferation of reactive astrocytes.…”

Caveolin-1 is a checkpoint regulator in hypoxia-induced astrocyte apoptosis via Ras/Raf/ERK pathway

“…Primary astrocytes were obtained and purified as previously described (41) with minor modifications. Briefly, cerebral cortices from 1-day-old Sprague-Dawley rat pups were extracted and dissociated by mechanical trituration and 0.125% Trypsin-EDTA (Invitrogen) treatment.…”

Rapidly activated epidermal growth factor receptor mediates lipopolysaccharide-triggered migration of microglia

“…The activation of other membrane receptors, such as angiotensin II receptors and adrenergic receptors, were also reported to transactivate EGFR signaling pathway (Chen et al, 2012;Fischer et al, 2006;Flannery and Spurney, 2006). In addition, EGFR is also known to play a role other than the usual ligand-dependent one, especially after the onset of CNS disorders (Planas et al, 1998;Qu et al, 2012;Wong and Guillaud, 2004;Yang et al, 2011). Our recent published study showed that EGFR exerted an important effect on regulating microglia activation, however, blockade of EGFR phosphorylation could effectively inhibit the hypertrophy of LPS-exposed microglia, and attenuate the production of inflammatory mediators induced by either LPS stimulation in vitro or experimental spinal cord trauma (Qu et al, 2012).…”