Ac-SDKP Attenuates Osteoclasts Differentiation And Bone Loss In Rats Inhaled Of Silica

Objective To explore the effects of N-acetyl-serine-aspartyl-lysine-proline（Ac-SDKP）on activation of alveolar macrophages and osteoclast differentiation regulated by Receptor activator of nuclear Factor-κB Ligand（RANKL）and Toll-like receptors 4（TLR4）signaling pathways.Methods Silicosis model of rats was established by HOPE-MED8050 system and treated with Ac-SDKP.Raw 264.7 monocytes/macrophages and NR8383 alveolar macrophages were induced by SiO₂ or RANKL,and treated with Ac-SDKP,AC-ADKP,or TLR4-C34.Micro CT was used to detect the microstructure.The expression of lung elastin,osteoclasts,and osteoblasts were observed by elastin staining,tartrate resistant acid phosphatase（TRAP）,and alkaline phosphatase（ALP）staining,respectively.Osteo assay was used to detect the bone resorption activity of osteoclasts.The levels of RANKL and TLR4 related proteins were measured by immunohistochemistry staining,immunofluorescence staining,and western blot.The levels of TNF-αand RANKL in serum were detected by ELISA.Results 1 Ac-SDKP treatment inhibited reducing level of BMD and improved bone microarchitecture in femur of silicotic rats.And Ac-SDKP also increased osteoblasts and reduced ostroclast in tita and femur in rats exposed to silica.Ac-SDKP attenuated osteoclast differentiation,bone resorption,and RANKL signaling in RAW 264.7 cells induced by RANKL.2 Ac-SDKP reduced the increasing level of TRAP positive alveolar macrophages in lungs of silicostic rats.Positive expression of RANK,RANKL,TLR4,and TNF-αwere observed to be located in alveolar macrophages.And Ac-SDKP attenuated the high levels of RANKL,TLR4 signaling pathways and MMP-12 to maintain the elastin level in lung of rat exposed to silica.Furthermore,Ac-SDKP inhibited the increasing levels of RANKL and TLR4 in serum of silicotic rats.In vitro study showed that Ac-SDKP inhibited the activation of RANKL and TLR4 signaling pathways in NR8383 or RAW264.7 cells induced by silica.Conclusion Ac-SDKP inhibited activation of alveolar macrophages and osteoclast differentiation induced by inhalation of SiO₂ related inflammation.Figure28;Table17;Reference 157...