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Previous work has shown that interleukin 1 (IL-1) increases the activity of acid extruders in articular chondrocytes, while the H+-adenosine triphosphatase (ATPase) inhibitor bafilomycin can prevent aggrecanase-mediated cartilage degradation. The H+ transport induced by IL-1 may therefore be required for proteinase activity. In the present study, the effects of hexosamines and fish oils on H+-ATPase activity have been characterised for isolated bovine articular chondrocytes. Cells isolated in the presence of IL-1 were acidified, and the fraction of acid extrusion mediated by Na+-H+ exchange and an H+-ATPase were determined using specific inhibitors. Exposure to IL-1 significantly enhanced both components of acid extrusion. Co-incubation with glucosamine or mannosamine attenuated the H+-ATPase fraction of efflux. The addition of glucosamine at 9 h after exposure to IL-1--when H+-ATPase activation is already apparent--was also able to abolish H+-ATPase activity, implying that hexosamines do not exert effects at the level of protein synthesis. Co-incubation with the glucose transport inhibitor phloretin elicited similar effects to the hexosamines, suggesting that modulation of adenosine triphosphate levels may underlie their effects on H+-ATPase function. The omega-3 fish oil linolenic acid but not the omega-6 fish oil linoleic acid reduced H+-ATPase activity to levels seen in IL-1-untreated cells, although total efflux remained elevated, as a result of an enhanced H+ leak. These observations support a model whereby IL-1 stimulates an H+-ATPase-dependent system, possibly involved in aggrecanase activation, which appears to be one of the target mechanisms interrupted by dietary supplements reported to have symptom-modifying effects on osteoarthritis.

Original publication




Journal article


Pflugers Arch

Publication Date





501 - 506


4-Chloro-7-nitrobenzofurazan, Amiloride, Animals, Cartilage, Articular, Cattle, Cells, Cultured, Chondrocytes, Dietary Supplements, Enzyme Inhibitors, Fatty Acids, Omega-3, Fatty Acids, Omega-6, Glucosamine, Hexosamines, Hydrogen-Ion Concentration, Interleukin-1alpha, Linoleic Acid, Proton-Translocating ATPases, Sodium-Hydrogen Exchangers, Spectrometry, Fluorescence, alpha-Linolenic Acid