RESUMEN
OBJECTIVE To investigate the protective effect of artesunate(Art)against apoptosis and mitophagy induced by NaF in osteocytes MLO-Y4,and to explore the molecular mechanism.METHODS MLO-Y4 cells were treated with NaF(2 mmol·L-1)for 48 h to establish an in vitro model of osteocytes injuries,and the cells were divided into the cell control group,NaF(2 mmol·L-1)group and NaF+Art 0.25,0.50 and 1.00 μmol·L-1 groups.The cells were pretreated for 2 h and NaF was added for 48 h.The cell survival of MLO-Y4 cells was detected by MTT assay.The cell viability of MLO-Y4 cells was measured by Calcein-AM staining.The lactate dehydrogenase(LDH)content in the supernatant was examined by the LDH detection kit.The level of intracellular reactive oxygen species(ROS)was examined by DCFH-DA staining.The malondialdehyde(MDA)content and superoxide dismutase(SOD)activity were detected by chemical colorimetry.Apoptosis was measured by Hoechst33342 staining and Annexin-V/PI staining.The level of mitochondrial membrane potential(MMP)was measured by JC-1 staining.The formation of autophagic vacuoles and morphological mitochondrial changes were observed via Lyso-tracker staining and Mito-Tracker staining.The ATP content was detected with the luciferase method.The expression of microtubule-associated protein light chain 3(LC-3)in mitochon-dria was examined by immunofluorescence staining.Protein expressions of LC-3,P62,E3 ubiquitin-ligase(Parkin)and PTEN-induced putative kinase 1(PINK1)were detected by Western blotting.RESULTS Compared with the cell control group,the cell survival rate and cell viability were significantly reduced in the NaF group(P<0.01),LDH content in the supernatant,the level of intracellular ROS,the MDA content,apoptosis rate and autophagic vesicle formation were remarkably increased(P<0.01),protein levels of Parkin and PINK1,and the conversion of LC-3Ⅱ from LC-3Ⅰ were markedly upregulated along with the elevation of LC-3 in damaged mitochondria(P<0.01),while P62 levels,SOD activity,MMP and ATP contents were reduced in NaF cells(P<0.05,P<0.01).Compared with NaF group,the cell viability and survival rate of MLO-Y4 cells in NaF+Art 0.25,0.50 and 1.00 μmol·L-1 groups were significantly increased(P<0.01);the content of LDH in supernatants was decreased obviously(P<0.01);the levels of intracellular ROS and MDA content were markedly reduced(P<0.05,P<0.01);the apoptosis rate and autophagic vesicle formation were remarkably decreased(P<0.05,P<0.01);protein levels of Parkin and PINK1,and the conversion of LC-3Ⅱ from LC-3Ⅰ were markedly down-regulated along with the accumulation of LC-3 in damaged mitochondria(P<0.01);MMP and ATP content were also reduced(P<0.05,P<0.01);while SOD activityand P62 levelwere significantly increased(P<0.05,P<0.01).CONCLU-SION Art has a protective effect against oxidative damage induced by NaF in MLO-Y4 cells,which might be related to the inhibition of apoptosis and mitophagy.