Rossiello M R, Italia A, Stramaglia A M, Gesualdo L, Grandaliano G, Schena F P, Semeraro N, Colucci M
Dipartimento di Scienze Biomediche e Oncologia Umana, University of Bari, Italy.
Thromb Haemost. 2000 Sep;84(3):453-9.
Several studies indicate that fibrin may play a functional role in inflammation by modulating a variety of cellular functions. We investigated the effect of fibrin on tissue factor (TF) production by blood mononuclear cells (MNC). Citrated human blood was recalcified and incubated at 37 degrees C for 1-4 h. The resulting clot was lysed by the addition of tissue plasminogen activator (t-PA) and MNC were isolated by density gradient centrifugation. A control blood sample was processed in the same way but omitting calcium addition and clot formation. Clot- and blood-derived MNC did not express detectable TF activity and antigen whatever the incubation time. Clot-derived MNC, however, generated on average 5 fold less TF (activity and antigen) than control cells, when stimulated with lipopolysaccharide (LPS, I microg/ml) for 3 h at 37 degrees C. A reduced TF response of clot-derived cells was also observed at mRNA level as indicated by RT-PCR and in situ hybridization. The effect was dependent on the incubation time within the clot, could not be reversed by enhancing LPS concentration or by adding serum, and was maintained if LPS was replaced by the tumor promoter PMA. A reduced TF response was also found when washed MNC were incorporated for 1 h at 37 degrees C within purified fibrin but not when the cells were incubated with fibrinogen, thrombin or fibrin split products alone. indicating that contact with fibrin was responsible for the inhibition of TF production. Fibrin-induced down-regulation of TF response to LPS and PMA by MNC may represent a negative feed-back aimed at limiting excessive blood clotting activation in immunoinflammatory diseases.
多项研究表明，纤维蛋白可能通过调节多种细胞功能在炎症中发挥功能性作用。我们研究了纤维蛋白对血液单核细胞（MNC）产生组织因子（TF）的影响。将枸橼酸化的人血重新钙化并在37℃孵育1 - 4小时。通过添加组织纤溶酶原激活剂（t - PA）溶解形成的凝块，并通过密度梯度离心分离MNC。以相同方式处理对照血样，但不添加钙和不形成凝块。无论孵育时间如何，凝块来源和血液来源的MNC均未表达可检测到的TF活性和抗原。然而，当在37℃用脂多糖（LPS，1μg/ml）刺激3小时时，凝块来源的MNC产生的TF（活性和抗原）平均比对照细胞少5倍。如RT - PCR和原位杂交所示，在mRNA水平也观察到凝块来源细胞的TF反应降低。该效应取决于在凝块内的孵育时间，不能通过提高LPS浓度或添加血清来逆转，并且如果用肿瘤启动子PMA替代LPS则该效应得以维持。当洗涤后的MNC在37℃于纯化的纤维蛋白中孵育1小时时也发现TF反应降低，但当细胞仅与纤维蛋白原、凝血酶或纤维蛋白裂解产物孵育时则未发现该现象。这表明与纤维蛋白接触是抑制TF产生的原因。纤维蛋白诱导MNC对LPS和PMA的TF反应下调可能代表一种负反馈，旨在限制免疫炎症疾病中过度的血液凝固激活。
