Restoring the expression of GHS-R
specifically in osteoblasts, and not in osteoclasts or the central nervous system, ameliorated bone abnormalities in GHS-R-null mice, which indicates that the osteoblastic expression of GHS-R
is necessary and sufficient for the bone anabolic actions of GHRL.
Furthermore, as analyzed by immunohistochemistry, the GHS-R protein was also reduced in gingiva from periodontitis patients, which paralleled our findings at transcriptional level.
Rossi Fanelli, "The growth hormone secretagogue receptor (Ghs-R)," Current Pharmaceutical Design, vol.
(c) GHS-R protein synthesis in PDL cells stimulated with F.
(b) GHS-R protein immunostaining in human gingival biopsies from periodontally healthy control and periodontitis sites, as visualized by immunohistochemistry.
After heating (90[degrees]C for 5 min) and recooling on ice, proteins were separated on Tris-tricine gradient gels (10-20%; Bio-Rad), transferred to nitrocellulose membranes (Roth), blocked with 50 g/L nonfat powdered milk in Tris-buffered saline (TBS) overnight (4[degrees]C), and incubated for 2 h at room temperature with specific rabbit antibodies against human ghrelin (Phoenix) and GHS-R (Alpha Diagnostic) diluted 1:500 or 1:200, respectively, in blocking buffer.
NOX-B11 binds to the octanoylated NH, terminus of ghrelin and prevents binding to the GHS-R (30).
Ghrelin and GHS-R mRNA expression was detected in the 3 major salivary glands as well as in oral keratino-cytes.
These findings are consistent with the use of the ghrelin inhibitor NOX-B11, which specifically binds to the active form of ghrelin and neutralizes its binding to the GHS-R. A sevenfold molar excess of NOX-B11 (50 nmol/L) completely blocked ghrelin-induced (25 [micro]g/L) cell proliferation (P <0.001), whereas the inhibitor itself had no statistically significant effect on cell growth.
In the present study, we could show that ghrelin and the two receptor isoforms, GHS-R 1a and GHS-R 1b, are produced by the human salivary glands, with subsequent secretion of the hormone into saliva.
Moreover, the increase in CAMP supports the functionality of the GHS-R because cAMP has been shown to be involved in ghrelin signaling (38, 39).