CGRP inhibits osteoprotegerin production in human osteoblast-like cells via cAMP/PKA-dependent pathway

Abstract

The osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL)/receptor activator of nuclear factor-κB (RANK) system was evaluated as a potential target of CGRP anabolic activity on bone. Primary cultures of human osteoblast-like cells (hOB) express calcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1, and, because CGRP stimulates cAMP (one of the modulators of OPG production in osteoblasts), it was investigated whether it affects OPG secretion and expression in hOB. CGRP treatment of hOB (10−11 M–10−7 M) dose-dependently inhibited OPG secretion with an EC50 of 1.08 × 10−10 M, and also decreased its expression. This action was blocked by the antagonist CGRP8–37. Forskolin, a stimulator of cAMP production, and dibutyryl cAMP also reduced the production of OPG. CGRP (10−8 M) enhanced protein kinase A (PKA) activity in hOB, and hOB exposure to the PKA inhibitor, H89 (2 × 10−6 M), abolished the inhibitory effect of CGRP on OPG secretion. Conditioned media from CGRP-treated hOB increased the number of multinucleated tartrate-resistant acid phosphatase-positive cells and the secretion of cathepsin K in human peripheral blood mononuclear cells compared with the conditioned media of untreated hOB. These results show that the cAMP/PKA pathway is involved in the CGRP inhibition of OPG mRNA and protein secretion in hOB and that this effect favors osteoclastogenesis. CGRP could thus modulate the balance between osteoblast and osteoclast activity, participating in the fine tuning of all of the bone remodeling phases necessary for the subsequent anabolic effect.

Calcitonin gene-related peptide stimulates BMP-2 expression and the differentiation of human osteoblast-like cells in vitro

“…BMP-2 promotes the proliferation of pre-osteoblast cells, induces the osteogenic or chondrogenic differentiation of mesenchymal cells [17,18] , and improves the osteogenic phenotype and capacity of stem cells through increased ALP activity and osteocalcin mRNA expression. Signal transduction studies have revealed that the Smad and P38MAPK pathways are immediately downstream of BMP receptors and that they play central roles in BMP signal transduction [4,[19][20][21] .…”

“…In vitro studies have demonstrated that CGRP stimulates osteoblast proliferation, differentiation and maturation in both osteoblast cell lines and bone marrow mesenchyme stromal cells. CGRP and its receptors have been identified in the [Ca 2+ ] i (intracellular Ca2 + ) [3] , cAMP (cyclic adenosine monophosphate) [4] , PKC (protein kinase C) [5] , MAPK (mitogen-activated protein kinase) [2,6] , and ERK (extracellular signal-regulated protein kinase) signal transduction pathways [7] .…”

Calcitonin Gene-related Peptide Inhibits Tumor Cell Proliferation of Hepatocellular Carcinoma Cells Through the Ras/MEK/ERK Pathway

“…CRE is essential for the response of the calcitonin/CGRP gene promoter 12), 13) . Villa et al reported that CGRP enhances PKA activity in human osteoblast-like cells and inhibits osteoprotegrin production through the CGRP receptor 28) . To examine whether CREB activation in cells cultured with CGRP mediates the CGRP receptor, Huh7 cells were precultured with the CGRP receptor antagonist CGRP .…”

Medial arterial calcification in diabetes and its relationship to neuropathy

“…Both calcitonin and CGRP have been shown to inhibit the maturation of osteoclasts induced by RANKL [77]. Nevertheless, CGRP can also inhibit the synthesis of osteoprotegerin by osteoblasts, suggesting a bimodal, autoregulatory, action [78]. This is echoed by the finding that CGRP (as well as substance P) can induce in vitro formation of the pro-inflammatory cytokines, IL-1, IL-6 and TNF-α, in human dental pulp cells [79].…”