Abstract:

Objective To investigate the autophagic changes in the brain and spinal cord of mice with Alzheimer's disease(AD). Methods The brain and spinal cord of AD mice aged 3 months, 8 months and 11 months and normal controls (n=6) of the corresponding ages were isolated. The left side of brain and the lumbar segment of spinal cord were used for histological sections, and the right side of brain and the remaining part of spinal cord were used for protein extraction. Immunohistochemistry was employed to detect the amyloid plaque in the brain and spinal cord, confocal microscopy was performed to observe the distribution of LC3-positive autophagic vesicles in the brain and motor neuron in the spinal cord, the expression of LC3-II and Beclin 1 protein in the brain and spinal cord of mice aged 8 months was determined by Western blotting, and Nissl staining was adopted to quantify the motor neuron in the spinal cord. Results The immunohistochemistry revealed that there was no amyloid plaque in the brain of AD mice aged 3 months, a large number of plaques emerged in the cortex and hippocampus in mice aged 8 months, and the quantity of plaques increased significantly in mice aged 11 months. There was intraneuronal amyloid in the lumbar spinal cord of AD mice, while no extracellular plaque was detected. The confocal microscopy revealed that the quantity of LC3-positive autophagic vesicles in the brain cortex of AD mice aged 8 months was significantly larger than that in control group, there were LC3-positive autophagic vesicles in motor neuron in the spinal cord of AD mice aged 3 months, and the quantities of autophagic vesicles significantly increased in mice aged 8 months and 11 months. Western blotting indicated that compared with the corresponding controls, the expression of LC3-II protein in brain tissues of AD mice aged 8 months was significantly higher (P<0.01), the expression of Beclin 1 protein in brain tissues was significantly lower (P<0.05), the expression of LC3-II protein in spinal cord was significantly higher (P<0.05), and the expression of Beclin 1 protein in spinal cord was not significantly changed (P>0.05). Nissl staining demonstrated that there was no significant difference in the quantity of motor neuron of lumbar segment of spinal cord between AD mice aged 8 months and corresponding controls (P>0.05). Conclusion There are significant autophagic changes in the brain and spinal cord of AD mice, and the change of autophagy may be associated with the change of intraneuronal amyloid levels.

Key words: Alzheimer´s disease, spinal cord, amyloid plaque, autophagy