Suppressive effects of an apoptotic mimicry prepared from jumbo-flying squid-skin phospholipids on the osteoclastogenesis in RANKL/M-CSF induced RAW 264.7 cells.

BACKGROUND Liposomes containing docosahexaenoic acid (DHA) and phosphatidylserine were claimed to inhibit osteoclast formation and bone resorption in the inflammatory status. Herein, we proposed that an apoptotic mimicry (SQ liposome) prepared from squid-skin phospholipids can explore the suppressive osteoclastogenesis. METHODS The intermolecular fatty-acid composition in the phospholipid of squid-skin extract was analyzed by GC-FID. SQ-liposome structure was characterized by size distribution and zeta potential (ζ). RAW 264.7 cell is used to study the effect of SQ liposomes on osteoclast differentiation. Secretion of prostaglandin E2 (PGE2) and transforming growth factor-β (TGF-β) from RAW 264.7 cells were assayed. Anti-osteoclastogenesis effects were performed via the tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cell counting, bone resorption pit assay and TRAP activity analysis. The specific gene expressions related to anti-osteoclastogenesis were also detected. RESULTS An apoptotic mimicry through the use of a single-layer liposome (SQ liposome) with phosphatidylserine exposure contains docosahexaenoic acid (DHA, 28.7%) and eicosapentaenoic acid (EPA, 11.8%). Co-treatment with RANKL/macrophage colony-stimulating factor (M-CSF) induced RAW 264.7-cell differentiation into mature osteoclasts, thus enhancing PGE2 and TGF-β secretion. However, co-treatment with one mg/mL of SQ liposome restored (p 0.05) influenced in SQ-liposome cotreatments. Co-treatments with 0.33∼1 mg/mL of SQ liposome suppressed (p < 0.05) the osteoclast maturation (such as decreased multinucleated cells [MNCs] and bone pit formation), inhibited TRAP activities, and down-regulated the osteoclastogenesis related gene expressions. CONCLUSION In summary, current data support that a possible prevention of our prepared SQ liposomes which are rich DHA and EPA on bone loss is through the suppression of osteoclastogenesis. Moreover, based on the results from this study an in vivo study warrants a further investigation.