Phillips W A, Croatto M, Hamilton J A
Department of Medicine, University of Melbourne, Royal Melbourne Hospital, Victoria, Australia.
J Immunol. 1992 Aug 1;149(3):1016-22.
The biochemical mechanism(s) underlying the priming of the macrophage for an enhanced PMA-induced respiratory burst is not understood. Because the cellular receptor for PMA is thought to be protein kinase C (PKC), we have investigated the effects of priming agents on cellular PKC levels. Sonicates from unprimed bone marrow-derived macrophages (BMM) were found to contain PKC activity (309 +/- 51 pmol 32P-incorporated/mg/min; mean +/- SE, n = 17) as measured by the phospholipid-, diacylglycerol-, and calcium-dependent phosphorylation of histone. Exposure of BMM to priming agents such as TNF-alpha, LPS, and granulocyte/macrophage-CSF resulted in a significant increase in both histone-phosphorylating activity and levels of immunoreactive PKC protein in these cells. A minimum of 6-h exposure, with an increasing effect up to 48 h, was required for a detectable increase in PKC level. The activity from primed BMM, like that of the untreated cells, was predominantly cytosolic. The kinetics and concentration dependence of the priming agent-induced increase in the PKC content of BMM closely paralleled the enhancing effects of these agents on the PMA-stimulated respiratory burst. Furthermore, CSF-1, a cytokine that does not prime BMM, failed to increase PKC activity. We propose that the exposure of BMM to priming agents leads to an increase in the expression of a stimulatory isozyme(s) of PKC, resulting in an enhanced ability to mount a respiratory burst in response to stimulation with PMA.
巨噬细胞因引发作用而增强佛波酯（PMA）诱导的呼吸爆发的生化机制尚不清楚。由于PMA的细胞受体被认为是蛋白激酶C（PKC），我们研究了引发剂对细胞PKC水平的影响。通过组蛋白的磷脂、二酰基甘油和钙依赖性磷酸化来测量，发现未引发的骨髓来源巨噬细胞（BMM）的超声裂解物含有PKC活性（309±51 pmol 32P掺入/毫克/分钟；平均值±标准误，n = 17）。将BMM暴露于引发剂如肿瘤坏死因子-α（TNF-α）、脂多糖（LPS）和粒细胞/巨噬细胞集落刺激因子（GM-CSF）中，导致这些细胞中组蛋白磷酸化活性和免疫反应性PKC蛋白水平显著增加。PKC水平要有可检测到的增加，至少需要暴露6小时，最长可达48小时，且效果逐渐增强。引发后的BMM的活性，与未处理细胞的活性一样，主要存在于细胞质中。引发剂诱导BMM的PKC含量增加的动力学和浓度依赖性与这些试剂对PMA刺激的呼吸爆发的增强作用密切平行。此外，集落刺激因子-1（CSF-1），一种不会引发BMM的细胞因子，未能增加PKC活性。我们提出，BMM暴露于引发剂会导致PKC的一种刺激性同工酶的表达增加，从而增强对PMA刺激产生呼吸爆发的能力。
