| Objectives:To test the potential protective effects of L-triiodothyronine(L-T3) on a mouse model of excitotoxic brain injury induced by ibotenate (Ib). By detecting changes of the expressions of Fas/FasL and Caspase-8 in both transcriptional and translational level before and after L-T3 treatment to investigate the possible mechanisms of L-T3 on neuroprotection and provide theoretical bases for L-T3 as a future intervention in periventricular leukomalacia of premature infants.Methods:225 ICR mice of both sexes from different litters, weighing 3.0-3.6g, were selected for experiments on postnatal Day 5 (P5) and fed by their own mothers after operation. They were randomly and medially distributed into 5 groups:normal group (n=45), sham surgery group (n=45), PBS control group (n=45), Ib model group (n=45) and T3 treat group (n=45). The mice were sacrificed by decapitation at 24,48 and 168 hours after operation respectively. The paraffin slices of the injured brain were observed with H-E staining, and sizes of the lesions in the impaired hemispheres were measured. The mRNA expressions of Fas/FasL and Caspase-8 were detected via Q-PCR. Frozen sections of the injured hemispheres were observed with immunofluorescence histochemistry to detect the proteinic expressions of Fas/FasL and Caspase-8.Results:1. Pathological ChangesNo cystic lesions in brain tissue of mice were observed in norml group, sham surgery group and PBS control group in this experiment.Cystic lesions were observed at 24,48 and 168 hours after operation in Ib model group and the diameters of the cysts increased with time which were 180.00±42.42mm,435.00±49.74mm and 600.00±73.48mm, respectively. T3 treat group also showed cystic lesions at 24,48 and 168 hours after operation, which were 165.00±25.98mm,315.00±49.75mm and 180.00±42.43mm, respectively. No comparable lesion size was found between T3 treat group (165.00±25.98 mm) and Ib model group (180.00±42.42 mm) at postoperative Hour 24. Significant difference was observed between T3 treat group (315.00±49.75mm) and Ib model group (435.00±49.74 mm) at postoperative Hour 48 (p<0.01). At postoperative Hour 168, campared with Ib model group (600.00±73.48 mm), T3 treatment significantly reduced the lesion size (180.00±42.43 mm;p< 0.01).2.Q-PCR2.1 Expressions of Caspase-8The expression of Caspase-8 was not detected in all groups at postoperative Hour 24,48 and 168.2.2 Expressions of FasThe expression of Fas was not detected in normal group, sham surgery group and PBS control group at postoperative Hour 24,48 and 168. In Ib model group, the expression of Fas was not detected until postoperative Hour 168 (6.30+1.89 e*12). In T3 treat group, expressions of Fas were 2.18±0.93 e12,5.69±1.43 e-12 and 6.51±1.81 e-12 at postoperative Hour 24,48 and 168 respectively. Statistical differences between T3 treat group and Ib model group were found at postoperative Hour 24 and 48 (p<0.01) while not at postoperative Hour 168.2.3 Expressions of FasLIn normal group, sham surgery group and PBS control group, expression was not detected at postoperative Hour 24,48 and 168. In Ib model group, expressions of FasL were detected at postoperative Hour 24, and 48, which were respectively 2.02±0.50 e-12 and 2.92+1.12 e-12 while not at postoperative Hour 168. In comparison to Ib model group, FasL expressions in T3 treat group were significantly increased,which were respectively 5.96±1.13 e-12,7.33±1.38 e-12,3.87±1.10 e-12 at postoperative Hour 24,48 and 168 (p< 0.01).3. Immunofluorescence Histochemistry3.1 Expressions of Caspase-8Only small amounts of target proteins (Green fluorescence) were detected in all groups at different time.3.2 Expressions of FasFas expressions (Green fluorescence) were detected at postoperative Hour 24,48, and 168 in T3 treat group, while only at postoperative Hour 168 in Ib model group. No expression was detected in the other three groups.3.3 Expressions of FasLFasL expressions (Green fluorescence) were detected at postoperative Hour 24, 48 and 168 in T3 treat group, while only at postoperative Hour 24 and 48 in Ib model group. No expression was detected in the other three groups.Conclusions:1. L-T3 treatment could reduce the lesion size of PVL induced by ibotenate.2. Fas/FasL signaling pathway may participate in the neuropretection of L-T3.3. L-T3 treatment didn’t change the expression of caspase-8. |
PDF Full Text Request