Albumin-bound lipids induce free cytoplasmic calcium oscillations in human osteoblast-like cells.
[Ca(2+)](i) oscillations were found in human osteoblast-like cells (hOB cells) exposed to high-lipid bovine serum albumin (BSA), but not when exposed to low-lipid BSA. These [Ca(2+)](i) oscillations were inhibited by heptanol and suramin, which implies that gap junctions and purinergic signalling may be important for these [Ca(2+)](i) oscillations. The high-lipid BSA preparation that was used contains arachidonic acid. [Ca(2+)](i) oscillations could be induced by low lipid albumin with arachidonic acid added. The albumin-bound lipids were also important for osteoblast growth since DNA synthesis and the total cell protein content was higher in hOB cells exposed to high-lipid BSA. The effect of arachidonic acid on hOB cell proliferation was bone-donor dependent; both stimulatory and inhibitory effects were observed. The physiological importance of albumin-bound lipids is unclear; given that albumin has only minimal contact with osteoblasts under normal conditions. Only when bone capillaries are disrupted, e.g. during a fracture, would significant amounts of albumin reach osteoblasts. Albumin-bound lipids could therefore contribute to stimulation of osteoblast proliferation during fracture healing.
Tsai
Jon A
JA
CLINTEC, Division of Surgery, Department of Molecular Medicine and Surgery, Karolinska University Hospital and Institutet, Stockholm, Sweden. jon.tsai@cfss.ki.se
Lagumdzija
Alena
A
Stark
André
A
Kindmark
Henrik
H
D016718:Arachidonic Acid / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003593:Cytoplasm / Q000187:drug effects* / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D019850:Heptanol / Q000494:pharmacology; D006801:Humans; D008055:Lipids / Q000494:pharmacology*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013498:Suramin / Q000494:pharmacology
D008055:Lipids; D012710:Serum Albumin, Bovine; D016718:Arachidonic Acid; D013498:Suramin; D019850:Heptanol; D004247:DNA; D002118:Calcium