Neuropeptide B (NPB) and neuropeptide W (NPW) system in cultured rat calvarial osteoblast-like (ROB) cells: NPW and NPB inhibit proliferative activity of ROB cells

Neuropeptides B (NPB) and W (NPW) have been identified as endogenous ligands of two G-protein-coupled receptors, neuropeptides B/W receptor 1 (NPBWR1, formerly known as GPR7) and neuropeptides B/W receptor 2 (NPBWR2, formerly known as GPR8). In rodents where NPBWR2 is absent, its counterpart is named the similar to neuropeptides B/W receptor 2 (similar to NPBWR2, formerly GPR8-like). Both NPB and NPW play a role in the control of feeding, neuroendocrine axis functions, memory and learning processes as well as in pain regulation. The present study aimed to investigate the expression of NPB, NPW, NPBWR1 and the similar to NPBWR2 genes in cultured rat calvarial osteoblast-like (ROB) cells and the effects of both peptides on proliferative activity and osteocalcin secretion by ROB cells. Classic RT-PCR technique revealed the presence of ppNPB mRNA, ppNPW mRNA, and NPBWR1 mRNA, but not similar to NPBWR2 mRNA in ROB cells. QPCR revealed gradual (days 7, 14 and 21 of culture) increase of the ppNPB gene expression, while expression of ppNPW gene was the highest at day 14 and was comparable to that seen in freshly isolated cells. In ROB cells, expression of NPBWR1 gene was notable at day 7 of culture, lower at day 21, and negligible at day 14. Neither NPB nor NPW changed osteocalcin secretion by cultured osteoblast-like cells while both neuropeptides inhibited their proliferative activity. Results of the present study suggest that the systems of NPW, NPB and NPBWR1 directly regulate proliferative activity of cultured rat calvaria osteoblast-like cells. The physiological significance of this osteoblastic system remains unclear, and requires further investigation.