Localization of the NO-cGMP Signaling Pathway Molecules, NOS III-Phosphorylation Sites, ERK1/2, and Akt/PKB in Osteoclasts

• Autores: Dr. Yüksel Korkmaz, Michael A. Baumann, Hannsjörg Schröder, Sönke Behrends, Klaus Addicks, Wolfgang H.-M. Raab, Wilhelm Bloch
• Localización: Journal of periodontology, ISSN 0022-3492, Vol. 75, Nº. 8, 2004, págs. 1119-1125
• Idioma: inglés
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  • Background: Nitric oxide (NO) mediates different cellular functions by activating soluble guanylate cyclase (sGC) that converts guanosine-5'- triphosphate (GTP) to cyclic guanosine-3' ,5'-monophosphate (cGMP). Membrane-bound GCs produce cGMP in response to natriuretic peptides in osteoblasts, but neither the NO-target enzyme sGC, nor the phosphorylation sites of NOS III, nor their regulation by extracellular signalregulated kinases 1 and 2 (ERK1/2) and Akt/protein kinase B (Akt/PKB) in osteoclasts have been established.

    Methods: Rat molars with periodontium were perfusion- and postfixed, decalcified, and frozen-sectioned. Free-floating sections were stained using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) and tartrate-resistant acid phosphatase (TRAP) histochemical techniques and immunoreacted with antisera against NOsynthase (NOS) I-III, NOS III phoshorylated at Thr495, NOS III phoshorylated at Serine1177 (Ser1177), ERK1/2, phosphorylated ERK1/2, Akt/PKB, phosphorylated Akt/PKB, sGC (α2/β1), and cGMP.

    Results: NADPH-d staining and immunostaining of NOS I-III, NOS III phosphorylated at Ser1177, ERK1/2, Akt/PKB, phosphorylated Akt/PKB, sGC (α2 and β1-subunits), and cGMP were detected in osteoclasts. Immunohistochemical reaction products for NOS III phosphorylated at threonine495 (Thr495) and phosphorylated ERK1/2 could not be identified in osteoclasts. Comparison of TRAP activity and immunostaining for sGC β1-subunit revealed that sGC β1-subunit is only expressed in a subpopulation of osteoclasts.

    Conclusions: NO is likely to be generated by NOS I and NOS III in osteoclasts. The inconstant expression of NOS II in some osteoclasts may be explained with inducible expression of NOS II upon physiological cell activation. Localization of the sGC α2 - and β1-subunits and cGMP in osteoclasts is compatible with an involvement of NO-sGC signaling in the homeostasis of osteoclasts. The phosphorylation site of NOS III at Ser1177 and phosphorylated Akt/PKB are involved in regulation of NO production by NOS III in osteoclasts under basal conditions. J Periodontol 2004;75:1119-1125.