linoleic-acid and mannosamine

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.

Topics: 4-Chloro-7-nitrobenzofurazan; alpha-Linolenic Acid; 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

Cytotoxic effects of mannosamine and free fatty acids on human malignant T-lymphoid cell lines derived from patients with T-cell leukemia were investigated. The combination of mannosamine and an unsaturated fatty acid (oleate or linoleate) produced more striking cytotoxic effects on malignant lymphoid cells than on normal human lymphocytes. The amino sugars glucosamine or mannosamine in the combination caused a synergistic cytotoxic effect, while the other carbohydrates (N-acetylmannosamine, N-acetylglucosamine, or mannose) had little effect. On the other hand, the effect of saturated fatty acids (palmitate or stearate) in the same system was nil. An unsaturated fatty acid (oleate) caused an increase in lipid fluidity of the surface membrane in MOLT-4 lymphoid cells, which possess higher lipid fluidity in combination with mannosamine, while saturated fatty acids had no effect on the fluidity properties of the membrane lipids (even in the presence of mannosamine). The relationship between mannosamine and unsaturated fatty acids in cytolysis was discussed.

Topics: Carbohydrates; Cell Line; Drug Combinations; Drug Synergism; Fatty Acids, Nonesterified; Hexosamines; Humans; Leukemia; Linoleic Acid; Linoleic Acids; Lymphocytes; Oleic Acid; Oleic Acids; T-Lymphocytes