Effect of Dexamethasone on LC3 expression of neurons in cerebral cortex of juvenile rats with sepsis

Abstract

Objective To investigate the effect of Dexamethasone on microtubule-associated protein 1 light chain 3 (LC3)expression of cells and neurons in cerebral cortex of juvenile Wistar rats with sepsis. Methods Models of juvenile Wistar rats with sepsis were established through cecal ligation and puncture (CLP). Totally 60 cases of 30-day-old juvenile male Wistar rats were randomly divided into sham-operation group (10 cases), non-treated group (25 cases)and Dexamethasone group (25 cases). Twelve hours after CLP, rats in Dexamethasone group were injected with Dexamethasone (1 mg / kg)via tail vein every other day, with a total of 3 times.The same dose of saline was used in the non-treated group.All rats were killed at the age of 40 days.Expressions of LC3 and neuronal nuclei (NeuN)of cells in cerebral cortex of rats were detected by using immunofluorescence assay, and the number of positive cells was calculated by using image analysis system software.Expressions of LC3-Ⅰ and LC3-Ⅱ protein were measured by adopting Western blot. Results Three hours after CLP, rats appeared to be curled up and showed piloerection and shi-vering and the neurobehavioral score in non-treated group was significantly lower than that in sham-operation group (t=9.895, P=0.000). Twelve of 25 rats in Dexamethasone group died in 10 days after CLP (48%), while 8 of 25 rats in non-treated group died (32%), and the difference was not statistically significant between the 2 groups (χ2=1.333, P=0.248). The immunofluorescence staining and image analysis showed the percentage of LC3 positive cells in non-treated group was significantly increased (0.606 7±0.030 1 vs 0.353 3±0.025 8, t=15.644, P=0.000; 0.606 7±0.030 1 vs 0.270 3±0.019 4, t=22.450, P=0.000). In non-treated group, the LC3 expression of cells in the cerebral cortex of rats was up-regulated, and the LC3-Ⅱ/LC3-Ⅰ ratio was significantly higher than that in sham operation group and Dexamethasone group (0.413 3±0.022 5 vs 0.205 0±0.015 2, t=18.802, P=0.000; 0.413 3±0.022 5 vs 0.185 0±0.023 5, t=17.206, P=0.000). The LC3 positive neurons in the cerebral cortex of rats were less in sham operation group and Dexamethasone group.The LC3 positive neurons were more in non-treated group than that in sham operation group and Dexamethasone group (0.580 0±0.020 0 vs 0.298 3±0.014 7, t=27.783; P=0.000; 0.580 0±0.020 0 vs 0.261 7±0.017 2, t=28.614; P=0.000). Conclusions The LC3 expression of cells in the cerebral cortex of juvenile Wistar rats with sepsis was up-regulated, LC3-Ⅱ/LC3-Ⅰ ratio increased, and the number of LC3 positive neurons also increased, while Dexamethasone could have inhibitory effect on them. Key words: Sepsis; Neuron; Autophagy; Microtubule-associated protein 1 light chain 3; Rat