Russell D H, Buckley A R, Montgomery D W, Larson N A, Gout P W, Beer C T, Putnam C W, Zukoski C F, Kibler R
J Immunol. 1987 Jan 1;138(1):276-84.
Prolactin (PRL)-stimulated ornithine decarboxylase (ODC) activity and subsequent proliferation are inhibited by the cyclopeptides cyclosporine (CsA) and didemnin B (DB) in Nb 2 node lymphoma cells. Similar concentrations of these agents also inhibit 125I-PRL binding, suggesting that their inhibitory effects on these PRL-dependent physiologic responses are mediated at least in part at the level of PRL receptor interactions. The phorbol ester TPA stimulated ODC activity and [3H]thymidine incorporation to 54% and 31% that of a near-optimal mitogenic concentration of PRL (10 ng/ml), suggesting that mitogenesis in these cells is coupled to some degree to the activation of protein kinase C (PKC). The calcium ionophore A23187 increased ODC activity only slightly and actually decreased [3H]thymidine incorporation to a value below the "cells only" controls. The addition of TPA plus A23187 did not further enhance the effects of TPA to elevate ODC activity and [3H]thymidine incorporation. However, A23187 significantly elevated PRL-stimulated ODC activity with a subsequent inhibition of [3H]thymidine incorporation, suggesting a block of entry into S phase. Both cyclopeptides decreased the elevation of ODC activity in G1 phase of cell cycle in response to PRL, suggestive of a site of action for these agents in early G1, a conclusion compatible with their ability to inhibit PRL binding to these cells. Addition of CsA or DB 2 hr after PRL had no effect on PRL-stimulated ODC activity detectable at 6 hr, but addition of either as late as 6 hr still affected the extent of mitogenesis. This is in line with the requirement for PRL to be present in the culture medium for a minimum of 3 to 6 hr to invoke a maximal effect on mitogenesis. Addition of either cyclopeptide after the cells were in S phase had no effect on the extent of [3H]thymidine incorporation. An inhibitor of the cyclooxygenase pathway (indomethacin) enhanced both PRL-stimulated ODC activity and proliferation, whereas inhibition of the lipoxygenase pathway by NDGA attenuated only proliferation, suggesting that in Nb 2 cells, products of the lipoxygenase pathway may contribute to the mechanism of PRL-stimulated mitogenesis. Because Nb 2 lymphoma cells were derived from estrogenized rats, estrogen was tested as a mitogen. By itself it was not mitogenic, but in conjunction with PRL, estradiol-17 beta elevated the ODC response and inhibited proliferation. Inhibitors of PKC known to have minimal effects on RNA synthesis, quercetin and gossypol, totally inhibited both the elevations of ODC activity and [3H]thymidine incorporation in response to PRL in Nb 2 lymphoma cells.(ABSTRACT TRUNCATED AT 400 WORDS)
在Nb 2 淋巴瘤细胞中，催乳素（PRL）刺激的鸟氨酸脱羧酶（ODC）活性及随后的增殖受到环孢素（CsA）和苔藓抑素B（DB）这两种环肽的抑制。这些药物的相似浓度也抑制125I - PRL结合，表明它们对这些PRL依赖性生理反应的抑制作用至少部分是在PRL受体相互作用水平介导的。佛波酯TPA刺激的ODC活性和[3H]胸苷掺入量分别为接近最佳促有丝分裂浓度的PRL（10 ng/ml）的54%和31%，这表明这些细胞中的有丝分裂在一定程度上与蛋白激酶C（PKC）的激活相关。钙离子载体A23187仅轻微增加ODC活性，实际上却使[3H]胸苷掺入量降至“仅细胞”对照组以下的值。添加TPA加A23187并未进一步增强TPA升高ODC活性和[3H]胸苷掺入量的作用。然而，A23187显著提高PRL刺激的ODC活性，随后抑制[3H]胸苷掺入，提示细胞进入S期受阻。两种环肽均降低了细胞周期G1期PRL诱导的ODC活性升高，提示这些药物在G1早期存在作用位点，这一结论与其抑制PRL与这些细胞结合的能力相符。在PRL作用2小时后添加CsA或DB对6小时时可检测到的PRL刺激的ODC活性无影响，但直到6小时添加二者中的任何一种仍会影响有丝分裂程度。这与培养基中PRL至少存在3至6小时才能对有丝分裂产生最大效应的要求一致。在细胞进入S期后添加任何一种环肽对[3H]胸苷掺入程度均无影响。环氧化酶途径抑制剂（吲哚美辛）增强PRL刺激的ODC活性和增殖，而NDGA抑制脂氧合酶途径仅减弱增殖，提示在Nb 2 细胞中，脂氧合酶途径的产物可能参与PRL刺激的有丝分裂机制。由于Nb 2 淋巴瘤细胞源自雌激素化大鼠，因此对雌激素作为促有丝分裂原进行了测试。其本身无促有丝分裂作用，但与PRL联合时，17β - 雌二醇可提高ODC反应并抑制增殖。已知对RNA合成影响极小的PKC抑制剂槲皮素和棉酚，完全抑制了Nb 2 淋巴瘤细胞中PRL诱导的ODC活性升高和[3H]胸苷掺入。（摘要截短于400字）
