Shireman P K, McCarthy W J, Pearce W H, Shively V P, Cipollone M, Kwaan H C
Department of Surgery, Northwestern University School of Medicine and the Veterans Administration Lakeside Medical Center, USA.
J Vasc Surg. 1997 Jan;25(1):157-64. doi: 10.1016/s0741-5214(97)70333-1.
Elevations of plasmin have been implicated in the pathogenesis of abdominal aortic aneurysms (AAA) because of its ability to digest extracellular matrix proteins. Plasminogen activators regulate the conversion of plasminogen to plasmin. Tissue-type plasminogen activator (tPA) is more important in modulation of fibrinolysis, and urokinase-type plasminogen activator (uPA) is predominant in tissue remodeling. The purpose of this study was to determine the levels of plasminogen activators in diseased aorta because they may be responsible for the increased plasmin levels previously described in AAA.
Levels of tPA and uPA in AAA, occlusive, and normal (organ donor) aorta were studied in tissue explant supernatants. Supernatant tPA and uPA levels were measured with an enzyme-linked immunosorbent assay. Northern analysis was used to quantitate uPA messenger RNA (mRNA) levels in aortic tissue.
Levels of tPA in the supernatants were similar in occlusive (20 +/- 4 ng/ml) and AAA (23 +/- 8) aorta, but threefold higher than in normal aorta (7 +/- 5; p < 0.005 for normal vs occlusive and p < 0.001 for normal vs AAA). In contrast, uPA supernatant levels were differentially expressed, with the highest level existing in AAA (9.7 +/- 2.7 ng/ml), followed by occlusive (4.9 +/- 3.5), and the lowest levels in normal aorta (1.2 +/- 0.7; p < 0.05 for normal vs occlusive, p < 0.001 for normal vs AAA, and p < 0.005 for occlusive vs AAA). Inhibition of protein or RNA synthesis by addition of cyclohexamide or actinomycin D, respectively, revealed no significant difference between treated and control supernatants, suggesting that the increases were caused by protein release rather than active synthesis. Levels of uPA mRNA followed the same trend as the supernatant uPA levels (AAA 1.07 +/- 0.54, occlusive 0.54 +/- 0.08, and normal aorta 0.01 +/- 0.01).
Levels of tPA were similar in aneurysmal and occlusive aorta, but exhibited a threefold increase over normal aorta, suggesting that the elevations of tPA are associated with the arteriosclerosis present in both aneurysmal and occlusive disease. Differences in uPA levels were significant between all three groups, with the highest levels in AAA and the lowest levels in normal specimens. Northern analysis of uPA mRNA followed the same trend, suggesting that the increase in uPA may be regulated at the level of transcription. As uPA plays an important role in tissue remodeling, our findings may also reflect the relative tissue repair activities in these three types of specimens and may explain the previously reported increased levels of plasmin seen in AAA.
纤溶酶水平升高与腹主动脉瘤（AAA）的发病机制有关，因为它能够消化细胞外基质蛋白。纤溶酶原激活剂调节纤溶酶原向纤溶酶的转化。组织型纤溶酶原激活剂（tPA）在纤维蛋白溶解调节中更为重要，而尿激酶型纤溶酶原激活剂（uPA）在组织重塑中占主导地位。本研究的目的是确定病变主动脉中纤溶酶原激活剂的水平，因为它们可能是先前报道的AAA中纤溶酶水平升高的原因。
在组织外植体上清液中研究AAA、闭塞性和正常（器官供体）主动脉中tPA和uPA的水平。用酶联免疫吸附测定法测量上清液中tPA和uPA的水平。用Northern印迹分析法定量主动脉组织中uPA信使核糖核酸（mRNA）的水平。
闭塞性主动脉（20±4 ng/ml）和AAA主动脉（23±8）上清液中tPA水平相似，但比正常主动脉（7±5；正常与闭塞性相比p<0.005，正常与AAA相比p<0.001）高三倍。相比之下，uPA上清液水平存在差异表达，AAA中水平最高（9.7±2.7 ng/ml），其次是闭塞性（4.9±3.5），正常主动脉中水平最低（1.2±0.7；正常与闭塞性相比p<0.05，正常与AAA相比p<0.001，闭塞性与AAA相比p<0.005）。分别加入环己酰亚胺或放线菌素D抑制蛋白质或RNA合成，结果显示处理后的上清液与对照上清液之间无显著差异，表明增加是由蛋白质释放而非活性合成引起的。uPA mRNA水平与上清液中uPA水平趋势相同（AAA 1.07±0.54，闭塞性0.54±0.08，正常主动脉为0.01±0.01）。
动脉瘤性和闭塞性主动脉中tPA水平相似，但比正常主动脉高两倍，表明tPA升高与动脉瘤性和闭塞性疾病中存在的动脉硬化有关。三组之间uPA水平差异显著，AAA中水平最高，正常标本中水平最低。uPA mRNA的Northern印迹分析呈现相同趋势，表明uPA的增加可能在转录水平受到调节。由于uPA在组织重塑中起重要作用，我们的发现也可能反映了这三种类型标本中相对的组织修复活动，并可能解释先前报道的AAA中纤溶酶水平升高的现象。
