Neurological deficit following
cerebral infarction correlates with not only primary injury, but also secondary neuronal apoptosis in remote loci connected to the
infarction.
Netrin-1 is crucial for axonal guidance by interacting with its receptors, deleted in
colorectal cancer (DCC) and uncoordinated gene 5H (UNC5H). DCC and UNC5H are also dependence receptors inducing cell apoptosis when unbound by
netrin-1. The present study is to investigate the role of
netrin-1 and its receptors in ipsilateral ventroposterior thalamic nucleus (VPN) injury secondary to
stroke in hypertensive rats. Renovascular hypertensive Sprague-Dawley rats underwent
middle cerebral artery occlusion (MCAO). Continuous
intracerebroventricular infusion of
netrin-1 (600 ng/d for 7 days) or vehicle (
IgG/Fc) was given 24h after MCAO. Neurological function was evaluated by postural reflex 8 and 14 days after MCAO. Then, immunoreactivity was determined in the ipsilateral VPN for NeuN,
glial fibrillary acidic protein,
netrin-1 and its receptors (DCC and UNC5H2), apoptosis was detected with
Terminal deoxynucleotidyl transferase-mediated
digoxigenin-dUTP-
biotin nick-end labeling (TUNEL) assay, and the expressions of
caspase-3,
netrin-1, DCC, and UNC5H2 were quantified by western blot analysis. MCAO resulted in the impaired postural reflex after 8 and 14 days, with decreased NeuN marked neurons and increased TUNEL-positive cells, as well as an up-regulation in the levels of cleaved
caspase-3 and UNC5H2
protein in the ipsilateral VPN, without significant change in DCC or
netrin-1 expression. By exogenous
netrin-1 infusion, the number of neurons was increased in the ipsilateral VPN, and both TUNEL-positive cell number and
caspase-3 protein level were reduced, while UNC5H2 expression remained unaffected, simultaneously, the impairment of postural reflex was improved. Taken together, the present study indicates that exogenous
netrin-1 could rescue neuron loss by attenuating secondary apoptosis in the ipsilateral VPN after focal
cerebral infarction, possibly via its receptor UNC5H2, suggesting that relative insufficiency of endogenous
netrin-1 be an underlying mechanism of secondary injury in the VPN post
stroke.