Aim To investigate the mechanism of demethylation on adenosine (ADO )and homocysteine (HCY)-induced apoptosis in human hepatoma HepG2 cells .Methods HepG 2 cells were treated with differ-ent concentrations of ADO (1.0、2.0、4.0 mol · L-1 ) alone or in combination with HCY for 6h,12h and 24h,5-aza-2-deoxycytidine (5-Aza-CdR)as a positive control.Cell viabilities were assessed by CCK8 assay. Cell apoptosis was observed by AnnexinV-FITC/PI staining.The mitochondrial membrane potentials(ΔΨ) were measured by flow cytometry.The mRNA and pro-tein expressions of caspase-3,caspase-8,caspase-9, MDM-2,p53,Cytochrome C,DNMT1,DNMT3a,DN-MT3 b were detected by RT-qPCR and Western blot re-spectively.Results ADO alone or in combination with HCY significantly reduced the viability of HepG2 cells in a dose and time-dependent manner.The apoptotic rates of HepG2 cells after combination treatment with ADO and HCY at 1 .0,2.0,4.0 mol · L-1 for 24 h were (1 8.63 ± 1.25 )%,(29.42 ±2.37 )% and (42.47 ±3.09 )%,compared with the control group (1.30 ±0.82 )%,P <0.01;and the mitochondrial membrane potentials were decreased from 674.15 ± 82.8%(black control group)to (428.38 ±54.5)%, (297.78 ±30.5)%,(74.45 ±5.73)%,P<0.01, respectively.The expressions of caspase-3,caspase-8, caspase-9,MDM-2,p53,Cytochrome C were up-regula-ted and MDM-2 were down-regulated after combination treatment of ADO and HCY.The mRNA expressions of DNMT1 ,DNMT3 a and DNMT3 b were down-regulated after combination treatment with ADO and HCY or 5-Aza-CdR alone.Conclusion Combination treatment of ADO and HCY can cause cellular methylation chan-ges.The effects of demethylation of ADO and HCY may activate p53 gene and mitochondrial pathway, which at last leads to HepG2 cell apoptosis.

BACKGROUND:Pulsed electromagnetic fields,as an important physical therapy,are exactly effective in the treatment of osteoarthritis,but the mechanism has not been fully clarified. OBJECTIVE:To observe the effect of pulsed electromagnetic field on the degeneration of knee joint cartilage in aged rats. METHODS:Eight 6-month-old Sprague-Dawley rats were selected as the young group and were subjected to normal diet with no treatment.Sixteen 22-month-old Sprague-Dawley rats were randomly divided into old group(n=8)and pulsed electromagnetic field group(n=8).The rats in the pulsed electromagnetic field group were subjected to a pulsed electromagnetic field intervention,once a day,5 days per week for continuous 8 weeks.The rats in the old group were given no treatment.All rats were anesthetized and executed after 8 weeks for the detection of relevant indexes. RESULTS AND CONCLUSION:Compared with the young group,serum type Ⅱ collagen C-terminal peptide level was increased in the old group(P<0.05);compared with the old group,serum type Ⅱ collagen C-terminal peptide level was decreased in the pulsed electromagnetic field group(P<0.05).Micro-CT showed that the bone volume fraction,bone mineral density,and number of bone trabeculae decreased(P<0.05)and the trabecular separation increased(P<0.05)in the tibia of rats in the aged group compared with the young group;and the bone volume fraction,bone density,and number of trabeculae increased(P<0.05)and the trabecular separation decreased(P<0.05)in the tibia of rats in the pulsed electromagnetic field group compared with the aged group.The tibial plateau Safranin O-fast green staining showed that the articular cartilage structure of rats in the aged group was disorganized,and the number of chondrocytes was obviously reduced,and the tidal line could not be distinguished.The above results were improved in the pulsed electromagnetic field group.RT-qPCR and western blot assay showed that the mRNA and protein expression levels of matrix metalloproteinase 1,matrix metalloproteinase 13,P53 and P21 in the articular cartilage and subchondral bone of rats were elevated in the aged group compared with the young group(P<0.05)and decreased in the pulsed electromagnetic field group compared with the old group(P<0.05).To conclude,pulsed electromagnetic fields may improve osteoarthritis in aged rats by inhibiting chondrocyte senescence,alleviating articular cartilage degradation and inhibiting subchondral bone osteoporosis through suppressing the expression of P53/P21.