Albumin-bound lipids induce free cytoplasmic calcium oscillations in human osteoblast-like cells |
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Authors: | Tsai Jon A Lagumdzija Alena Stark André Kindmark Henrik |
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Institution: | CLINTEC, Division of Surgery, Department of Molecular Medicine and Surgery, Karolinska University Hospital and Institutet, Stockholm, Sweden. jon.tsai@cfss.ki.se |
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Abstract: | 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. |
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Keywords: | osteoblast [Ca2+]i oscillations lipids albumin |
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