METHODS:ARPE-19 and HUVEC cells were cultured for 48 h in media containing various glucose concentrations(5.5, 25, 50, 75, 100 mmol/L)and cellular morphology was observed under an optical microscope.Cell viability was assessed using the CCK-8 assay. Flow cytometry was utilized to evaluate apoptosis levels, and Western blot analysis was conducted to measure the expression of Bcl-2 and SIRT6. ARPE-19/HUVEC cells were treated with 50 mmol/L glucose for 48 h, after which immunofluorescence staining was performed to determine the subcellular localization and expression level of SIRT6 protein. In parallel, cells receiving the same treatment were harvested at different time points(0, 6, 12, 24, 36, 48, and 72 h), and the temporal changes in SIRT6 protein expression were assessed by Western blot analysis. SIRT6 overexpressing stable ARPE-19/HUVEC cell lines were constructed. Western blot was performed to detect the effects of SIRT6 overexpression on the expression levels of glucose transporters in ARPE-19/HUVEC cells treated with high glucose(50 mmol/L glucose).

RESULTS:Compared with the 5.5 mmol/L glucose group, cell number was decreased and cell viability was significantly reduced in ARPE19/HUVEC cells with increasing glucose concentrations(all P<0.01). Meanwhile, the protein expression level of SIRT6 was markedly downregulated(P<0.05). Such inhibitory effects exhibited both concentration-and time-dependent patterns(all P<0.05). Furthermore, high glucose induced cell apoptosis and downregulated the protein expression of Bcl-2(P<0.05). Immunofluorescence staining revealed that SIRT6 protein was predominantly localized in the nucleus after 48 h of high-glucose treatment, accompanied by pyknosis and nuclear fragmentation. After incubation with highg-lucose medium(50 mmol/L glucose)for different durations, long-term high-glucose intervention was found to reduce SIRT6 protein expression in ARPE19/HUVEC cells. Successful construction of the SIRT6-overexpressing stable ARPE-19/HUVEC cell lines was confirmed via immunofluorescence and Western blotting. Western blot analysis revealed that, compared with the HG+LV-con group, the HG+LV-SIRT6 group exhibited no significant differences in GLUT1 or GLUT4 expression in ARPE-19 cells, whereas GLUT3 expression was elevated(P<0.05). Compared with the HG+LV-con group, the HG+LV-SIRT6 group showed no significant change in GLUT1 expression, while GLUT3 and GLUT4 levels were increased(both P<0.05).

CONCLUSION:High-concentration glucose-reduce the proliferative activity of ARPE-19/HUVEC cells, induce apoptosis, and downregulate SIRT6 expression. SIRT6 may alleviate high glucose-induced retinal cell damage by promoting the expression of glucose transporters.