The adjuvant chemotherapy, such as cisplatin, doxorubicin, and methotrexate has significantly improved survival of osteosarcoma patients. However, the chemoresistance which arose with the chemotherapy blocks achieving favorable outcomes for some patients and finally led to relapse or metastatic disease. Studies have shown paradoxical functions of autophagy in tumor development, which has been demonstrated by microRNAs. In the present study, we determined the involvement of autophagy during the chemotherapy of osteosarcoma cell line, U-2 OS, and further determined the regulation of miR-101 on the autophagy in the U-2 OS cells. Results demonstrated that doxorubicin treatment of U-2 OS cells induced significantly high level of autophagy-characteristic acidic vesicular organelles (AVOs), and induced significant autophagy related protein expression in U-2 OS cells. While the miR-101 could significantly reduce the doxorubicin-induced AVOs and block the autophagy related protein expression in U-2 OS cells. Moreover, the autophagy blockage by miR-101 sensitized the U-2 OS cells to doxorubicin treatment. In summary, miR-101 blocks autophagy during the chemotherapy in osteosarcoma cells and enhances chemosensitivity in vitro.
Abstract. Oxidative stress is considered to be an important cause of dysfunction in chondrocytes and articular cartilage degradation, which leads to the pathogenesis of osteoarthritis (OA) and cartilage aging. The present study aimed to assess the effects of the widely applied antioxidant, ascorbic acid (AA), on human chondrocytes against hydrogen peroxide (H 2 O 2 ) in vitro. Using annexin V-fluorescein isothiocyanate, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and senescence-associated β-galactosidase assays, the present study identified that AA reduced apoptosis, reduced the loss of viability and markedly decreased H 2 O 2 -mediated senescence in cells treated with H 2 O 2 . Furthermore, AA not only stimulated the expression levels of collagens and proteoglycans, but also inhibited the differentiation of chondrocytes under conditions of oxidative stress. In addition, reverse transcription-quantitative polymerase chain reaction and western blotting demonstrated that AA decreased the activity of nrf2, NF-κB, AP1 and matrix metalloproteinase-3, which is stimulated by H 2 O 2 . In conclusion, AA efficiently protected human chondrocytes against damage induced by H 2 O 2 by regulating multiple regulatory pathways.
Hypoxia-inducible factor 1-alpha (HIF-1α) and some microRNA (miRNAs) play pivotal roles in response to hypoxia-related physiologic and pathophysiologic responses. Up to date, the regulatory mechanisms of these molecules were largely unknown in chondrocytes. In this study, to study the mechanisms of degradation and homeostasis of chondrocytes, the effects of miRNAs and HIF-1α on chondrocytes in physiologic environment were investigated. We found that the overexpression of miR-210 and HIF-1α was present on hypoxia in C28/I2 human chondrocytes significantly by qRT-PCR and western plot. Further study displayed that miR-210 played positive role as a promoter in regulation and its regulated molecules (bcl-xl and PHD-2) in C28/I2 cells on hypoxia by silenced miR-210, silenced HIF-1α, and adding miR-210. Moreover, downregulated miR-210 could significantly repress the viability and increase the apoptosis in C28/I2 cells on hypoxia, compared to those on normoxia. Furthermore, miR-210 could not modulate viability and apoptosis in C28/I2 cells with the HIF-1α knockdown on hypoxia and normoxia. Taken together, this study demonstrated that the MiR-210 was involved in an HIF-1α-dependent way in C28/I2 human chondrocytes for the first time. It also suggested that miR-210 downregulation decreased viability and induced apoptosis in hypoxic chondrocytes depending on HIF-1α.
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