Fonteh A N, Samet J M, Chilton F H
Department of Internal Medicine, Bowman Gray School of Medicine, Winston-Salem, North Carolina 27517, USA.
J Clin Invest. 1995 Sep;96(3):1432-9. doi: 10.1172/JCI118179.
The current study evaluates the capacity of recombinant rat stem cell factor (rrSCF) to regulate enzymes that control AA release and eicosanoid generation in mouse bone marrow-derived mast cells (BMMCs). Initial studies indicated that rrSCF provided for 24 h inhibited the release of AA into supernatant fluids of antigen- and ionophore A23187-stimulated BMMCs. Agonist-induced increases in cellular levels of AA were also inhibited, albeit to a lesser degree by rrSCF. To determine the inhibitory mechanism, several steps (e.g., mobilization of cytosolic calcium, release of BMMC granules, and regulation of phospholipase A2 [PLA2] activity) that could influence AA release were measured in rrSCF-treated cells. rrSCF did not alter the capacity of BMMCs to mobilize cytosolic calcium or release histamine in response to antigen and ionophore. BMMCs released large amounts of PLA2 with characteristics of the group II family in response to antigen and ionophore A23187. rrSCF treatment of BMMCs reduced the secretion of this PLA2 activity by BMMCs. Partial purification of acid-extractable PLA2 from rrSCF-treated and untreated BMMCs suggested that rrSCF decreased the quantity of acid-stable PLA2 within the cells. In contrast to group II PLA2, the quantity of cPLA2 (as determined by Western blot analysis) increased in response to rrSCF. To assess the ramifications of rrSCF-induced reductions in AA and group II PLA2, eicosanoid formation was measured in antigen- and ionophore-stimulated BMMCs, rrSCF-inhibited (100 ng/ml, 24 h) prostaglandin D2 (PGD2), thromboxane B2, and leukotriene B4 by 48.4 +/- 7.7%, 61.1 +/- 10.0% AND 38.1 +/- 3.6%, respectively, in antigen-stimulated cells. Similar patterns of inhibition were observed in ionophore-stimulated BMMCs. The addition of a group I PLA2 or exogenous AA to BMMCs reversed the inhibition of eicosanoid generation induced by rrSCF. Together, these data indicate that rrSCF differentially regulates group II and cytosolic PLA2 activities in BMMCs. The resultant reductions in eicosanoid generation suggest that group II PLA2 provides a portion of AA that is used for eicosanoid biosynthesis by BMMCs.
本研究评估重组大鼠干细胞因子（rrSCF）调节控制小鼠骨髓来源肥大细胞（BMMCs）中花生四烯酸（AA）释放和类花生酸生成的酶的能力。初步研究表明，给予24小时的rrSCF可抑制AA释放到抗原和离子载体A23187刺激的BMMCs的上清液中。rrSCF也抑制了激动剂诱导的细胞内AA水平的升高，尽管抑制程度较小。为了确定抑制机制，在rrSCF处理的细胞中测量了几个可能影响AA释放的步骤（例如，胞质钙的动员、BMMC颗粒的释放以及磷脂酶A2 [PLA2]活性的调节）。rrSCF不会改变BMMCs动员胞质钙或响应抗原和离子载体释放组胺的能力。BMMCs在响应抗原和离子载体A23187时释放大量具有II族特征的PLA2。rrSCF处理BMMCs可降低BMMCs分泌的这种PLA2活性。从rrSCF处理和未处理的BMMCs中对酸可提取的PLA2进行部分纯化表明，rrSCF降低了细胞内酸稳定PLA2的量。与II族PLA2相反，胞质型PLA2（通过蛋白质印迹分析确定）的量在rrSCF作用下增加。为了评估rrSCF诱导的AA和II族PLA2减少的影响，在抗原和离子载体刺激的BMMCs中测量类花生酸的形成，rrSCF（100 ng/ml，24小时）抑制抗原刺激细胞中前列腺素D2（PGD2）、血栓素B2和白三烯B4的生成，分别为48.4±7.7%、61.1±10.0%和38.1±3.6%。在离子载体刺激的BMMCs中观察到类似的抑制模式。向BMMCs中添加I族PLA2或外源性AA可逆转rrSCF诱导的类花生酸生成的抑制。总之，这些数据表明rrSCF在BMMCs中差异调节II族和胞质型PLA2的活性。类花生酸生成的减少表明II族PLA2提供了一部分用于BMMCs类花生酸生物合成的AA。
