Effects Of Treadmill Exercise On The Expression Of Netrin-1 And Its Receptors DCC,Unc5B In Rat Brain After Cerebral Ischemia

Object To investigate the effects of treadmill exercise on the expression of axonal guidance cue netrin-1 and its receptors DCC,Unc5B in rat brain after cerebral ischemia. We sought to determine potential mechanisms that are involved in treadmill exercise-induced neuroplasticity and functional rebuilding.Methods 1. Prior to the middle cerebral artery occlusion (MCAO) procedure, 108 male adult Sprague-dawley rats were placed on a motor driven treadmill and trained to run over a three-day adaptation period.2. Experimental animal and groups: rats were randomly divided into 3 groups: sham-operated group (S group, n=12), MCAO group (M group, n=48) and MCAO + treadmill exercise group (ME group, n = 48). Rats in M group and ME group were randomly divided into 4 subgroups according to time points after MCAO: 4d, 7d, 14d and 28d, 12 rats in every subgroup.3. A MCAO model was established with the modified Zea-Longa's method.4. From the 24 hours after MCAO, rats in ME group were forced to run on the treadmill for 30 min per day for 4 consecutive weeks. Rats in the S group and the M group were left on the treadmill for 30 min and were not made to run.5. Rats in M group and ME group underwent behavioral functional tests prior to the MCAO procedure and at 4, 7, 14 and 28 days after MCAO, and the modified neurologic severity scores (mNSS) was used to measure various aspects of neurologic function of rats.6. Rats were sacrificed after MCAO and the brains were removed. The tissue corresponding to the peri-infarct cortex was dissected for expression level of netrin-1, DCC and Unc5B by real-time PCR and Western blot, and localization of netrin-1, DCC and Unc5B by immunofluorescent staining.Results 1. Rats treated with the treadmill exercise had significantly lower mNSS scores at day 14 and 28 compared to the rats without exercise (P<0.05 and P<0.01).2. Realtime-PCR and Western blot analysis revealed that expressions of netrin-1, DCC and Unc5B were elevated and peaked at day 14 after MCAO, and decreased at day 28. Treadmill exercise significantly enhanced netrin-1 and DCC expression, while it suppressed Unc5B expression in rat peri-ischemic brain area.3. Immunofluorescent staining analysis showed that netrin-1 was mainly expressed in neurons in peri-ischemic brain area, DCC, however, was expressed in neural processes in peri-ischemic brain area, while Unc5B was expressed mostly in neuronal perikarya, and seldom in neuronal processes in peri-ischemic brain area.Conclusion We demonstrates that treadmill exercise has beneficial effects that may be attributed, at least in part, to the involvement of up-regulation of netrin-1, DCC and down-regulation of Unc5B in in rat peri-ischemic brain area.