[The Involvement of CRMP-2 on Axonal and Dendrictic Injury after Hypoxic-Ischemic Brain Injury in Neonatal Rat].

OBJECTIVE: To investigate the activity of collapsin response mediator protein 2 (CRMP-2) and its possible regulation for axonal and dendrictic injury under hypoxia-ischemia (HI).

METHODS: Postnatal day 10 SD rats were suffered the right common carotid artery ligation and 8% mixture of oxygen and nitrogen hypoxia 2.5 h to produce HI model. The expression of total and phosphorylated CRMP-2 and amyloid precursor protein (APP) were detected by Western blot after HI. After pretreatment of protein kinase B (Akt) inhibitor, wortmannin or LY294002, western blot and immunohistochemistry were applied to detect the expression of total and phosphorylated of CRMP-2 at 4 h and 24 h after HI. At 72 h after HI, APP was detected by Western blot and immunohistochemistry, axonal and dendrictic injury was determined by electron microscope.

RESULTS: Total CRMP-2 was not obviously changed after HI, compared with that of sham controls. However, the phosphorylated CRMP-2 (p-CRMP-2) protein transiently increased at 0.5 h, started to decrease at 2 h, remained at a low level at the rest of the time points, compared with that of sham controls. APP protein started to increase at 2 h, remained at a high level at 4, 8, 24 h, and then progressively increased at 48 and 72 h. In wortmannin and LY294002 group, CRMP-2 protein was not obviously changed at 4 h and 24 h after HI. However, p-CRMP-2 increased at 4 h and 24 h. At 72 h, wortmannin pretreatment increased APP expression, leading to more severe ultrastructure failure of axon and dendrite.

CONCLUSION: As a downstream effector of Akt pathway, CRMP-2 is involved in axonal and dendritic injury regulation after HI in neonatal rat.