Epidemiological, clinical and experimental evidence suggests that fatty acids have a modulatory effect on bone metabolism in animals and humans. To investigate this hypothesis, we evaluated the effects of three different fatty acids, arachidonic acid (AA), eicosapentaenoic acid (EPA) and oleic acid (OA), on the expression of cytokines involved in bone remodelling. Cytokine mRNAs in the human osteoblast-like cell line MG-63 were quantified by reverse transcription-PCR. AA induced increased expression of interleukin-1α, interleukin-1β, tumour necrosis factor-α and macrophage colony-stimulating factor mRNAs in a time- and dose-dependent manner. EPA and OA had no stimulatory effects, but instead caused a significant inhibition of AA-induced cytokine mRNA expression. Cell treatment with calphostin C, an inhibitor of protein kinase C (PKC), and cellular PKC down-regulation experiments independently resulted in significant inhibition of AA-induced cytokine expression, suggesting that a PKC-dependent mechanism accounts for the effects of AA on cytokine production. In conclusion, our study demonstrates specific effects of fatty acids on cytokine gene expression in human osteoblast-like cells. The clinical relevance of our findings requires further investigation.

We hypothesized that cytokine production following delayed in vitro cell stimulation (to reproduce physiological cellular status at baseline) may be related to outcome in patients with septic shock. A total of 20 patients were included in a prospective clinical study, conducted in a medico-surgical intensive care unit in a university hospital. Blood samples were obtained at the onset of septic shock; these were treated to retain the cells, but to wash out autologous plasma (containing potential inflammatory stimuli such as cytokines, bacterial products and drugs) and replace it with foetal calf serum. Each treated sample was divided into two sets of four aliquots, to be stimulated either immediately or after an overnight period of resting incubation at 37°C. The rest period was to allow recovery from potentially reversible endogenous or pharmacologically induced alterations in cellular response, in order to reproduce a near physiological state at baseline. In vitro cellular challenges used low-dose (0.2ng/ml) or high-dose (1ng/ml) CD14-dependent lipopolysaccharide and CD14-independent pokeweed mitogen to induce the production of tumour necrosis factor-α (TNF-α), and interleukins-1β and -10. Levels of TNF-α, interleukin-1β and interleukin-10 were significantly higher ( P < 0.05) when cell stimulation was delayed for 16h, indicating a functional down-regulation of cells during septic shock. Moreover, TNF-α responses obtained with high-dose lipopolysaccharide were significantly greater in cells from patients who subsequently survived septic shock ( n = 13; median value 1392pg/ml; range 592-2048pg/ml) than in cells from non-survivors ( n = 7; median value 708 pg/ml; range 520-1344pg/ml). These observations support the existence of individual differences in the inflammatory response that could influence patient outcome following septic shock.