title: Proton concentrations can be a major contributor to the modification of osteoclast and osteoblast differentiation, working independently of extracellular bicarbonate ions.
abstract: We established a system to separately analyze the role of protons and bicarbonate ions in vitro in which the pH of the medium was controlled by HEPES at various concentrations of sodium bicarbonate (NaHCO3) in the absence of carbon dioxide (CO2). Using this system, we demonstrated that acidosis promoted osteoclast formation independently of extracellular NaHCO3 in a short-term culture. Protons and bicarbonate ions acted on osteoclast differentiation with opposite effects, the former positively and the latter negatively. The HEPES-based system maintained pH in the absence of extracellular NaHCO3 without CO2. Therefore, we could demonstrate that osteoblast differentiation was promoted at higher pH in a long-term culture system without NaHCO3 in which ALP activity and nodule mineralization were enhanced. This finding indicates that protons negatively control osteoblast differentiation independently of extracellular bicarbonate ions. However, the difference in the concentration of NaHCO3 did not have any influence on nodule mineralization. The opposite effects of protons, the promotion of osteoclast formation and the inhibition of osteoblast differentiation, were suppressed in the presence of 5 mM N-acetyl cysteine, a reagent activating the scavenging of reactive oxygen species (ROS), implying that ROS act on both systems, the promotion of large osteoclast formation and the deterioration of osteoblast formation under acidosis.
authors.affiliation: Department of Cellular Physiological Chemistry, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan, suwakono-kaze9@ma.kitanet.ne.jp.
authors.forename: Kohtaro
authors.initials: K
authors.lastname: Kato
authors.forename: Misao
authors.initials: M
authors.lastname: Matsushita
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D003994:Bucladesine / Q000494:pharmacology; D002021:Buffers; D002113:Calcification, Physiologic / Q000187:drug effects; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D003470:Culture Media / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007477:Ions; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D011522:Protons; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D001639:Bicarbonates; D002021:Buffers; D003470:Culture Media; D007477:Ions; D011522:Protons; D012333:RNA, Messenger; D050916:TRPV Cation Channels; D003994:Bucladesine; D000111:Acetylcysteine