Regulation of rat pulmonary endothelial cell interleukin-6 production by bleomycin: effects of cellular fatty acid composition.

Previous studies have shown upregulation of lung cell interleukin-6 (IL-6) production in bleomycin-induced pulmonary fibrosis. To further elucidate the regulatory mechanisms governing this disease, the effects of bleomycin on the production of the pleiotropic cytokine, IL-6, were investigated in lung endothelial cells. Rat pulmonary artery endothelial cells were treated with bleomycin at doses previously shown to be effective in upregulating cytokine production in these cells, and the conditioned media was collected and assayed for IL-6 activity. The results show that these endothelial cells constitutively produced IL-6 and that bleomycin increased the production in a time- and dose-dependent manner. Feeding rats diets deficient in n-6 fatty acids is known to ameliorate bleomycin-induced lung fibrosis. In order to examine if fatty acids could modulate IL-6 production in vitro, cells were lipid depleted and then supplemented with 18:1n-9, 18:2n-6, or 18:3n-3 fatty acids, and the effects of bleomycin on IL-6 production reexamined. This regimen resulted in significant depletion of arachidonate in the 18:1n-9 and 18:3n-3 supplemented cells, which was associated with significantly reduced IL-6 production relative to the 18:2n-6-supplemented cells, both constitutively and when stimulated with bleomycin. Preincubation with indomethacin did not significantly inhibit the production of IL-6 by all three groups of cells, nor did supplementation with a stable prostacyclin analog increase IL-6 production. These results suggest that endothelial cell IL-6 production is not directly dependent on prostacyclin or other cyclooxygenase metabolites but may require or be upregulated by 18:2n-6 and/or metabolites derived from it.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of an association between cellular phospholipid triene: tetraene ratio and proliferation of human skin fibroblasts in culture.

Two experiments were performed in an attempt to establish an association between cellular phospholipid triene:tetraene ratio and proliferation of human neonatal skin fibroblasts in culture. In Experiment 1, a low lipid culture medium was developed that caused an accumulation of (n-9) eicosatrienoic acid in the phospholipids of human fibroblasts. This culture medium, when supplemented with a mixture of mitogens, supported growth of human fibroblasts at a level equivalent to that found under conditions of maximal growth using serum supplementation (8% fetal bovine serum). The triene:tetraene ratio of fibroblast phospholipids under the two conditions was 1.88 vs. 0.03, suggesting that the growth of these cells was not adversely affected by a high (greater than 0.4) triene: tetraene ratio. In Experiment 2, cells were cultured in a low lipid, mitogen-supplemented medium with 16:1(n-7), 18:1(n-9), 18:2(n-6) or 20:4(n-6) added as the albumin complex. All the fatty acids permitted an equivalent maximal growth stimulation in the assay system, although having different effects on the phospholipid triene:tetraene ratio. The results suggest that there is a lack of an association between cellular phospholipid triene:tetraene ratio (range, 0.03 to 3.4) and proliferation of human fibroblasts in this culture system.

The Na+K+ATPase activity in cultured human fibroblasts with an elevated phospholipid triene:tetraene ratio.

Human skin fibroblasts were cultured at low density for 11 days in MCDB 110, 0.4% fetal bovine serum, a mitogen mixture, and were supplemented with 18:2n-6 or 18:1n-9 as a fatty acid-albumin complex. The cells cultured with the 18:2n-6 supplement had a 20:3n-9/20:4n-6 ratio of 0.29 +/- 0.07; the 18:1n-9 supplemented cells had a ratio of 1.51 +/- 0.27. There was less than 4% difference in total growth of the cell population under the two culture conditions. The cells supplemented with 18:2n-9 had similar levels of protein/cell, K+/mg cell protein and functional Na+K+ATPase activity.