Substance P enhances the inhibition of osteoblastic cell differentiation induced by lipopolysaccharide from Porphyromonas gingivalis

Background: Substance P (SP) is a multifunctional neuropeptide that transmits pain signals, regulates the immune system, and may modulate emotional stress. SP stimulates bone resorption activity of osteoclasts, and SP level in gingival crevicular fluid is correlated with the degree of periodontal inflammation. However, the exact roles of SP in bone metabolism and periodontal diseases are poorly understood. To elucidate the effect of stress on bone metabolism, we investigated the effect of SP on osteoblastic cell differentiation in the presence of lipopolysaccharide from Porphyromonas gingivalis (P-LPS). Methods: The primary osteoblastic cells were isolated from fetal rat calvaria (RC) and cultured with SP, P-LPS, and an SP antagonist (Spa). The effects of SP on bone nodule (BN), alkaline phosphatase (ALPase) activity, mRNA expressions of SP receptor, bone matrix proteins, and Cbfa 1 were investigated. Results: SP stimulated the expression of SP receptor mRNA in RC cells and enhanced its expression in the presence of P-LPS (50 ng/ml). SP inhibited BN formation and ALPase activity in a dose-dependent manner ( 10(-7) to 10(-5) M) and further suppressed mRNA expression of bone sialoprotein, osteopontin, and osteocalcin but not of type I collagen mRNA. The inhibitory effects were enhanced in the presence of P-LPS and blocked by Spantide Ill. Furthermore, the expression of Cbfa 1 mRNA was also markedly suppressed in the presence of SP and P-LPS. Conclusion: These findings suggest that SP inhibits osteoblastic cell differentiation and may be related to bone metabolism in periodontal diseases under conditions of stress.