title: Colony-stimulating factor-1 increases osteoclast intracellular pH and promotes survival via the electroneutral Na/HCO3 cotransporter NBCn1.
abstract: Colony-stimulating factor-1 (CSF-1) promotes the survival of osteoclasts, short-lived cells that resorb bone. Although a rise in intracellular pH (pH(i)) has been linked to inhibition of apoptosis, the effect of CSF-1 on pH(i) in osteoclasts has not been reported. The present study shows that, in the absence of CO(2)/HCO(3)(-), CSF-1 causes little change in osteoclast pH(i). In contrast, exposing these cells to CSF-1 in the presence of CO(2)/HCO(3)(-) causes a rapid and sustained cellular alkalinization. The CSF-1-induced rise in pH(i) is not blocked by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid, an inhibitor of HCO(3)(-) transporters but is abolished by removing extracellular sodium. This inhibition profile is similar to that of the electroneutral Na/HCO(3) cotransporter NBCn1. By RT-PCR, NBCn1 transcripts are present in both osteoclasts and osteoclast-like cells (OCLs), and by immunoblotting, the protein is present in OCLs. Moreover, CSF-1 promotes osteoclast survival in the presence of CO(2)/HCO(3)(-) buffer but not in its absence. Preventing the activation of NBCn1 markedly attenuates the ability of CSF-1 to 1) block activation of caspase-8 and 2) prolong osteoclast survival. Inhibiting caspase-3 or caspase-8 in OCLs prolongs osteoclast survival to the same extent as does CSF-1. This study provides the first evidence that osteoclasts express a CSF-1-regulated Na/HCO(3) cotransporter, which may play a role in cell survival.
authors.affiliation: Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, POB 208026, New Haven, Connecticut 06520-8026, USA. Patrice.Bouyer@Yale.edu
authors.forename: Patrice
authors.initials: P
authors.lastname: Bouyer
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Sakai
authors.forename: Takashi
authors.initials: T
authors.lastname: Itokawa
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kawano
authors.forename: Christiaan M
authors.initials: CM
authors.lastname: Fulton
authors.forename: Walter F
authors.initials: WF
authors.lastname: Boron
authors.forename: Karl L
authors.initials: KL
authors.lastname: Insogna
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000468:Alkalies / Q000378:metabolism; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D002245:Carbon Dioxide / Q000494:pharmacology; D061945:Caspase Inhibitors; D002469:Cell Separation; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism*; D018942:Macrolides / Q000494:pharmacology; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D051379:Mice; D008815:Mice, Inbred Strains; D010010:Osteoclasts / Q000378:metabolism / Q000502:physiology*; D011522:Protons; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D027982:Sodium-Bicarbonate Symporters / Q000378:metabolism*
chemical_list: D000468:Alkalies; D001639:Bicarbonates; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D018942:Macrolides; D011522:Protons; C498902:Slc4a7 protein, rat; D027982:Sodium-Bicarbonate Symporters; D002245:Carbon Dioxide; D000584:Amiloride; C036978:concanamycin A; D016173:Macrophage Colony-Stimulating Factor; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C039614:ethylisopropylamiloride