ABSTRACT
BACKGROUND:The effect of advanced glycation end products (AGEs) on bone resorption is controversial. Our previous study has shown that bone resorption is significantly inhibited when AGEs present with pre-osteoclast cells RAW 264.7, while the effect of AGEs on osteoclastic acidification remains unknown. OBJECTIVE:To investigate the effect of AGEs on osteoclastic acidification and the underlying mechanism. METHODS:RAW 264.7 cells were induced by RANKL (15μg/L;normal group) to generate osteoclasts, and AGEs (50-400 mg/L;experimental group) or bovine serum albumin (100 mg/L;control group) were added at the beginning of the induction. The effect of AGEs on bone resorption was evaIuated by anaIyzing the area of bone resorption on the Osteo Assay Surface plates, and the effect of AGEs on osteoclastic acidification was evaluated by acridine orange staining. Furthermore, the expression levels of V-ATPase a3 and CIC-7 were detected to investigate the underlying mechanism. RESULTS AND CONCLUSION:The bone resorption area in the AGEs group was significantly decreased compared with the normal group (P<0.05). Acridine orange staining reveaIed that the red fluorescence (620 nm) intensity in the AGEs group was significantly decreased compared with the normal group (P<0.05), and this inhibitory effect became obvious with the increase of AGEs concentration. Immunocytochemistry, western blot assay and PCR findings showed that the expression levels of V-ATPase a3 and CIC-7 in the AGEs group were decreased significantly compared with the normal group (P<0.05). To conclude, AGEs exert inhibitory effect on osteoclastic acidification, probably by inhibiting the expression of V-ATPase a3 and CIC-7.
ABSTRACT
BACKGROUND:The effects of advanced glycation end products (AGEs) on osteoclast-induced bone resorption is controversial and the underlying mechanisms remain unclear. Most of the studies indicate that AGEs can enhance bone resorption, while some othersshowthe opposite effects. OBJECTIVE:To investigate the effects of AGEs on osteoclast-induced inorganicmatrixdissolution and organic componentdegradation and the underlying mechanisms. METHODS:RAW 264.7 cels were induced to generate osteoclasts,and AGEs (50-400 μg/mL) or control-bovine serum albumin (100 μg/mL) was added since the beginning of the induction. The effect of AGEs on bone resorption was evaluated by analyzing the area of resorption pits on the Osteo Assay Surface plates and the expression of cathepsin K. Furthermore, the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cels, nuclei per osteoclasts and the expression of integrinανβ3were detected. RESULTS AND CONCLUSION:The area of resorption pits and expression of cathepsin K in AGEs groups were significantly decreased compared withthecontrol group, and this inhibiting effect became more obvious with the increase of AGEs concentration. TRAP staining also showed that number of TRAP-positivemultinucleated celsand nuclei per osteoclast were significantly reduced in an AGE dose-dependent manner. Quantitative PCR revealed that the expression of integrin ανβ3decreased significantly with the extension of AGEs incubation time. These data indicate that AGEs can exert inhibitory effects on organic and inorganicmatrixdegradation induced by osteoclasts. The underlying mechanism may be involved in the inhibitory effects of AGEs on directed differentiation and cel fusion of osteoclast precursor cels, and migration and adhension of osteoclasts.