Peters-Golden M, Feyssa A
Division of Pulmonary and Critical Care Medicine, University of Michigan, Ann Arbor.
Am J Physiol. 1993 May;264(5 Pt 1):L438-47. doi: 10.1152/ajplung.1993.264.5.L438.
We have examined the importance of the relative capacities for arachidonic acid (AA) liberation and oxygenation as determinants of the magnitude of transcellular eicosanoid synthesis in cocultures of [3H]AA-prelabeled alveolar macrophages (AM) and [14C]AA-prelabeled alveolar epithelial cells (AEC). Taking advantage of our previous observation that over time in culture, AEC exhibit increases in AA release (plateau at day 4) that precede increases in cyclooxygenase capacity (maximal at day 7), we studied cocultures of freshly harvested AM together with AEC at culture days 2, 4, and 7. In this model, ionophore stimulation resulted in transcellular eicosanoid synthesis via the bidirectional transfer of free AA, with AM synthesizing their exclusive 5-lipoxygenase products leukotriene B4 and 5-hydroxyeicosatetraenoic from AEC-derived AA, and AEC synthesizing their exclusive cyclooxygenase metabolites prostaglandin E2 and prostacyclin from AM-derived AA. 14C-labeled 5-lipoxygenase products were synthesized by cocultures in the rank order: day 4 > day 2 > day 7, paralleling the relative amounts of unmetabolized AEC-derived [14C]AA. Transcellular flow of [14C]AA to the AM 5-lipoxygenase pathway was also favored when the AEC cyclooxygenase pathway was inhibited with indomethacin. Inhibition of the AM 5-lipoxygenase pathway with the compound MK 886 similarly resulted in the accumulation of unmetabolized AM-derived [3H]AA and greater synthesis of 3H-labeled prostanoids. We conclude that 1) the quantity of unmetabolized AA made available by one cell is an important determinant of the extent to which the fatty acid is utilized for transcellular eicosanoid synthesis by the second cell; 2) the fate of AA derived from a donor cell is influenced by the expression of AA oxygenation pathways in both the donor cell and the recipient cell; and 3) intercellular exchange of AA favors its shunting from an inhibited oxygenation pathway to an uninhibited one.
我们研究了花生四烯酸（AA）释放能力和氧化能力的相对大小作为[3H]AA预标记肺泡巨噬细胞（AM）与[14C]AA预标记肺泡上皮细胞（AEC）共培养中转细胞类花生酸合成量决定因素的重要性。利用我们之前的观察结果，即随着培养时间的延长，AEC的AA释放量（在第4天达到平台期）先于环氧化酶能力的增加（在第7天达到最大值），我们研究了新鲜收获的AM与培养第2天、第4天和第7天的AEC的共培养情况。在该模型中，离子载体刺激通过游离AA的双向转移导致转细胞类花生酸合成，AM从AEC来源的AA合成其特有的5-脂氧合酶产物白三烯B4和5-羟基二十碳四烯酸，而AEC从AM来源的AA合成其特有的环氧化酶代谢产物前列腺素E2和前列环素。共培养物合成14C标记的5-脂氧合酶产物的顺序为：第4天>第2天>第7天，这与未代谢的AEC来源的[14C]AA的相对量平行。当用吲哚美辛抑制AEC环氧化酶途径时，[14C]AA向AM 5-脂氧合酶途径的转细胞流动也更有利。用化合物MK 886抑制AM 5-脂氧合酶途径同样导致未代谢的AM来源的[3H]AA积累以及3H标记的前列腺素合成增加。我们得出结论：1）一个细胞提供的未代谢AA的量是脂肪酸被第二个细胞用于转细胞类花生酸合成程度的重要决定因素；2）供体细胞来源的AA的命运受供体细胞和受体细胞中AA氧化途径表达的影响；3）AA的细胞间交换有利于其从不被抑制的氧化途径转向被抑制的途径。
