Icariin Regulates Glucocorticoid-induced Autophagy of Bone Microvascular Endothelial Cells Through PI3K/Akt/mTOR Pathway / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo investigate the impact of icariin （ICA） on autophagy in glucocorticoid-induced bone microvascular endothelial cells （BMECs） mediated by the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin （PI3K/Akt/mTOR） signaling pathway. MethodBMECs were isolated and cultured from femoral heads obtained during total hip arthroplasty and identified using immunofluorescence staining. The experimental cells were divided into four groups： A control group， a glucocorticoid group （100 mg·L-1 hydrocortisone）， an ICA group （100 mg·L-1 hydrocortisone+6.7×10-3 mg·L-1 ICA）， and a Rapamycin group （100 mg·L-1 hydrocortisone+6.7×10-3 mg·L-1 ICA+1 mg·L-1 rapamycin）. Autophagy in BMECs was induced using 100 mg·L-1 hydrocortisone. LC3 fluorescence staining was used to observe the peak of autophagy at different time points. Western blot analysis was employed to analyze the expression of autophagy-related proteins and PI3K/Akt/mTOR pathway proteins in each group. Electron microscopy was used to observe autophagosomes and autolysosomes in the cells. ResultHydrocortisone at 100 mg·L-1 induced autophagy in BMECs， reaching a peak at around 5 hours， which then declined with further intervention. Compared to the control group， the glucocorticoid group showed cell membrane damage， disordered organelle arrangement， and a large number of autophagosomes and autolysosomes. Compared to the glucocorticoid group， the ICA group had more intact cell membranes， sparser organelle arrangement， and fewer autophagosomes and autolysosomes. Compared to the ICA group， the Rapamycin group showed cell membrane damage， disordered organelle arrangement， and more autophagosomes and autolysosomes. Compared to the control group， the glucocorticoid group had significantly increased expression of light chain 3B （LC3B）， Atg4B， and p62 （P<0.01）. Compared to the glucocorticoid group， the ICA group showed significantly decreased expression of LC3B， Atg4B， p62， and Beclin-1 （P<0.01）. Compared to the ICA group， the Rapamycin group had significantly increased expression of Atg4B and p62 （P<0.01）. Compared to the control group， the glucocorticoid group had significantly decreased expression of p-PI3K/PI3K， p-Akt/Akt， and p-mTOR/mTOR （P<0.01）. Compared to the glucocorticoid group， the ICA group showed significantly increased expression of p-PI3K/PI3K， p-Akt/Akt， and p-mTOR/mTOR （P<0.01）. Compared to the ICA group， the Rapamycin group had significantly decreased expression of p-PI3K/PI3K， p-Akt/Akt， and p-mTOR/mTOR （P<0.01）. Ubiquitination levels were significantly decreased in the glucocorticoid group compared to the control group （P<0.01）. Compared to the glucocorticoid group， ubiquitination levels were significantly increased in the ICA group （P<0.01）， and significantly decreased in the Rapamycin group compared to the ICA group （P<0.01）. ConclusionThe glucocorticoid-induced autophagy in BMECs is time-dependent. ICA inhibits glucocorticoid-induced autophagy in BMECs， and this effect may be related to the regulation of the PI3K/Akt/mTOR pathway.