Effects of hexosamines and omega-3/omega-6 fatty acids on pH regulation by interleukin 1-treated isolated bovine articular chondrocytes.
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.
Tattersall
Amanda L
AL
Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
Wilkins
Robert J
RJ
D009327:4-Chloro-7-nitrobenzofurazan / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D019587:Dietary Supplements; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015525:Fatty Acids, Omega-3 / Q000494:pharmacology*; D043371:Fatty Acids, Omega-6 / Q000494:pharmacology*; D005944:Glucosamine / Q000494:pharmacology; D006595:Hexosamines / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D053582:Interleukin-1alpha / Q000378:metabolism*; D019787:Linoleic Acid / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D017962:alpha-Linolenic Acid / Q000494:pharmacology
D004791:Enzyme Inhibitors; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D006595:Hexosamines; D053582:Interleukin-1alpha; D017923:Sodium-Hydrogen Exchangers; D017962:alpha-Linolenic Acid; C008322:mannosamine; D000584:Amiloride; D019787:Linoleic Acid; D006180:Proton-Translocating ATPases; D009327:4-Chloro-7-nitrobenzofurazan; D005944:Glucosamine