Rapamycin improves circadian rhythm disorder induced by Aβ31-35 in mice

AIM:To observe the effect of rapamycin (Rapa) on the circadian rhythm disorder in C57BL/6 mice and the abnormal expression of Per2 in mouse hippocampal neuronal cell line HT22 induced by amyloid β-protein 31-35 (Aβ31-35).METHODS:The 6~8-week-old male C57BL/6 mice were selected for wheel-running behavior experiment. The effect of Rapa on the circadian rhythm disorder induced by Aβ31-35 was analyzed. The HT22 cells were randomly divided into control group, Aβ31-35 group, Rapa+Aβ31-35 group and Rapa group. The cell viability was measured by CCK-8 assay. Real-time PCR was used to detect the mRNA expression of Per2, and Western blot was applied to examine the expression of Per2 protein at circadian time (CT) 16. RESULTS:Compared with control group, Aβ31-35 disturbed the circadian rhythm which exhibited significantly longer free running period. However, the disruption was significantly relieved by pretreatment with Rapa compared with Aβ31-35 treatment, which manifested significantly decreased free running period (P<0.05). Aβ31-35 decreased the viability of HT22 cells compared with control group, and Rapa pretreatment reduced the toxicity of Aβ31-35 through up-regulating the cell viability. Abnormal mRNA expressions of Per2 was induced by Aβ31-35 in the HT22 cells. Rapa pretreatment reversed the abnormal expression of Per2 at mRNA level induced by Aβ31-35. Aβ31-35 significantly decreased the protein expression of Per2 at CT16. Pretreatment with Rapa significantly improved the protein expression of Per2. CONCLUSION:Rapa attenuates the circadian rhythm disorder induced by Aβ31-35 in C57BL/6 mice, and improves the abnormal expression of Per2 induced by Aβ31-35 in HT22 cells.