Colony-stimulating factor-1 increases osteoclast intracellular pH and promotes survival via the electroneutral Na/HCO3 cotransporter NBCn1

Endocrinology. 2007 Feb;148(2):831-40. doi: 10.1210/en.2006-0547. Epub 2006 Oct 26.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / pharmacology
  • Alkalies / metabolism
  • Amiloride / analogs & derivatives
  • Amiloride / pharmacology
  • Animals
  • Bicarbonates / pharmacology
  • Carbon Dioxide / pharmacology
  • Caspase Inhibitors
  • Cell Separation
  • Cell Survival / drug effects
  • Cells, Cultured
  • Enzyme Inhibitors / pharmacology
  • Hydrogen-Ion Concentration
  • Intracellular Fluid / metabolism*
  • Macrolides / pharmacology
  • Macrophage Colony-Stimulating Factor / pharmacology*
  • Mice
  • Mice, Inbred Strains
  • Osteoclasts / metabolism
  • Osteoclasts / physiology*
  • Protons*
  • Rats
  • Sodium / pharmacology
  • Sodium-Bicarbonate Symporters / metabolism*

Substances

  • Alkalies
  • Bicarbonates
  • Caspase Inhibitors
  • Enzyme Inhibitors
  • Macrolides
  • Protons
  • Slc4a7 protein, rat
  • Sodium-Bicarbonate Symporters
  • Carbon Dioxide
  • Amiloride
  • concanamycin A
  • Macrophage Colony-Stimulating Factor
  • Sodium
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
  • ethylisopropylamiloride