Cigolini M, Tonoli M, Borgato L, Frigotto L, Manzato F, Zeminian S, Cardinale C, Camin M, Chiaramonte E, De Sandre G, Lunardi C
Institutes of Clinical Medicine, University of Verona, Italy.
Atherosclerosis. 1999 Mar;143(1):81-90. doi: 10.1016/s0021-9150(98)00281-0.
Elevated plasminogen activator inhibitor-1 (PAI-1) plasma levels, responsible for reduced fibrinolysis, are associated with animal and human obesity and with increased cardiovascular disease. The expression of PAI-1 has been found recently in animal and human adipose tissue. Factors and mechanisms regulating such an expression remain to be elucidated. In omental and/or subcutaneous biopsies from obese non-diabetic patients, incubated in Medium 199, we have confirmed that human adipose tissue expresses PAI-1 protein and mRNA; furthermore we have demonstrated that such an expression is clearly evident also in collagenase isolated human adipocytes and that it is stimulated by incubation itself and enhanced by exogenous human tumor necrosis factor-alpha (h-TNF-alpha). Since human adipose tissue produces TNF-alpha, to further characterize the relationship of PAI-1 to TNF-alpha, human fat biopsies were also incubated with Pentoxifylline (PTX) or Genistein, both known to inhibit endogenous TNF-alpha through different mechanisms. PTX caused a dose-dependent decrease of basal PAI-1 protein release, reaching 80% maximal inhibitory effect at 10(-3)M, the same inhibitory effect caused by Genistein at 100 microg/ml. This was associated to a marked inhibition of PAI-1 mRNA and of endogenous TNF-alpha production. Furthermore, when human fat biopsies were incubated in the presence of polyclonal rabbit neutralizing anti-human TNF-alpha antibody (at a concentration able to inhibit 100 UI/ml human TNF-alpha activity), a modest but significant decrease of the incubation induced expression of PAI-1 mRNA was observed (19.8+/-19.0% decrease, P = 0.04, n = 7). In conclusion, the results of this study demonstrate that PAI-I expression is present in human isolated adipocytes and that it is enhanced in human adipose tissue in vitro by exogenous TNF-alpha. Furthermore our data support the possibility of a main role of endogenous TNF-alpha on human adipose tissue PAI-1 expression. This cytokine, produced by human adipose tissue and causing insulin resistance, may be a link in the clinical relationship between insulin-resistance syndrome and increased PAI-1 plasma levels.
纤溶酶原激活物抑制剂-1（PAI-1）血浆水平升高会导致纤溶作用减弱，它与动物及人类的肥胖症以及心血管疾病风险增加有关。最近在动物和人类脂肪组织中发现了PAI-1的表达。调节这种表达的因素和机制仍有待阐明。在来自肥胖非糖尿病患者的网膜和/或皮下活检组织中，于199培养基中孵育后，我们证实人类脂肪组织表达PAI-1蛋白和mRNA；此外，我们还证明，在胶原酶分离的人类脂肪细胞中这种表达也很明显，并且它会受到孵育本身的刺激，并被外源性人类肿瘤坏死因子-α（h-TNF-α）增强。由于人类脂肪组织会产生TNF-α，为了进一步明确PAI-1与TNF-α之间的关系，人类脂肪活检组织还与己酮可可碱（PTX）或染料木黄酮一起孵育，已知这两种物质可通过不同机制抑制内源性TNF-α。PTX导致基础PAI-1蛋白释放呈剂量依赖性下降，在10⁻³M时达到80%的最大抑制效果，这与染料木黄酮在100μg/ml时产生的抑制效果相同。这与PAI-1 mRNA和内源性TNF-α产生的显著抑制有关。此外，当人类脂肪活检组织在多克隆兔中和抗人TNF-α抗体存在的情况下孵育时（浓度能够抑制100 UI/ml的人TNF-α活性），观察到孵育诱导的PAI-1 mRNA表达有适度但显著的下降（下降19.8±19.0%，P = 0.04，n = 7）。总之，本研究结果表明，PAI-1表达存在于人类分离的脂肪细胞中，并且在外源性TNF-α作用下在体外人类脂肪组织中会增强。此外，我们的数据支持内源性TNF-α在人类脂肪组织PAI-1表达中起主要作用的可能性。这种由人类脂肪组织产生并导致胰岛素抵抗的细胞因子，可能是胰岛素抵抗综合征与PAI-1血浆水平升高之间临床关系的一个环节。
