Nakada M T, Tam S H, Woulfe D S, Casper K A, Swerlick R A, Ghrayeb J
Department of Molecular Biology, Centocor, Inc., Malvern, PA 19355, USA.
Cell Adhes Commun. 1998 Sep;5(6):491-503. doi: 10.3109/15419069809005606.
Upregulation of adhesion proteins plays an important role in mediating inflammation. The induction of adhesive molecules has been well studied, but the reversibility of their expression has not been well characterized. A neutralizing anti-TNF monoclonal antibody (cA2) was used to study the down regulation of TNF-induced E-selectin, vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) on cultured human umbilical vein endothelial cells (HUVECs). Addition of cA2 following TNF stimulation of HUVECs enhanced the rate of E-selectin and VCAM-1 down-regulation from the cell surface and also reduced steady state E-selectin and VCAM-1 mRNA levels. The cA2-mediated disappearance of E-selectin, but not VCAM-1 protein was microtubule and not microfilament dependent. Neutralization of TNF only slightly reduced ICAM-1 cell surface levels following initial TNF stimulation, suggesting a slower turnover of ICAM-1 compared to E-selectin and VCAM-1. Microtubule inhibition during TNF stimulation partially inhibited E-selectin, VCAM-1 and ICAM-1 mRNA upregulation. VCAM-1 and ICAM-1 cell surface expression were similarly partially inhibited, however, E-selectin levels were unaffected, presumably due to the dual, opposing effect of inhibiting protein expression and inhibiting internalization. Microfilament inhibition during protein induction specifically inhibited the maximal expression of VCAM-1 protein and mRNA, without affecting E-selectin or ICAM-1. These data support the notion that E-selectin, VCAM-1, and ICAM-1 expression are differentially regulated on HUVECs and suggest that TNF neutralizing therapies may be effective because of their ability to reduce the levels of pre-existing adhesion proteins.
黏附蛋白的上调在介导炎症过程中起重要作用。黏附分子的诱导已得到充分研究，但其表达的可逆性尚未得到很好的表征。使用一种中和抗TNF单克隆抗体（cA2）来研究TNF诱导的人脐静脉内皮细胞（HUVECs）上E-选择素、血管细胞黏附分子-1（VCAM-1）和细胞间黏附分子-1（ICAM-1）的下调。在TNF刺激HUVECs后添加cA2可提高E-选择素和VCAM-1从细胞表面下调的速率，并降低稳态E-选择素和VCAM-1 mRNA水平。cA2介导的E-选择素消失，但VCAM-1蛋白消失不依赖微管而依赖微丝。在最初的TNF刺激后，中和TNF仅略微降低ICAM-1细胞表面水平，表明与E-选择素和VCAM-1相比，ICAM-1的周转较慢。TNF刺激期间微管抑制部分抑制E-选择素、VCAM-1和ICAM-1 mRNA上调。VCAM-1和ICAM-1细胞表面表达同样受到部分抑制，然而，E-选择素水平未受影响，推测是由于抑制蛋白表达和抑制内化的双重相反作用。蛋白诱导期间微丝抑制特异性抑制VCAM-1蛋白和mRNA的最大表达，而不影响E-选择素或ICAM-1。这些数据支持这样的观点，即E-选择素、VCAM-1和ICAM-1在HUVECs上的表达受到不同调节，并表明TNF中和疗法可能有效，因为它们能够降低预先存在的黏附蛋白水平。
