Patsenker Eleonora, Popov Yury, Stickel Felix, Jonczyk Alfred, Goodman Simon L, Schuppan Detlef
Institute of Clinical Pharmacology, University of Bern, Bern, Switzerland.
Gastroenterology. 2008 Aug;135(2):660-70. doi: 10.1053/j.gastro.2008.04.009. Epub 2008 Apr 16.
BACKGROUND & AIMS: Integrin alphavbeta6 is highly expressed on certain activated epithelia, where it mediates attachment to fibronectin and serves as coreceptor for the activation of latent transforming growth factor (TGF)-beta1. Because its role in liver fibrosis is unknown, we studied alphavbeta6 function in vitro and explored the antifibrotic potential of the specific alphavbeta6 antagonist EMD527040.
Experimental liver fibrosis was studied in rats after bile duct ligation (BDL) and in Mdr2(abcb4)(-/-) mice. Different doses of EMD527040 were given to rats from week 2 to 6 after BDL and to Mdr2(-/-) mice from week 4 to 8. Liver collagen was quantified, and expression of alphavbeta6 and fibrosis-related transcripts was determined by quantitative reverse-transcription polymerase chain reaction. alphavbeta6-expressing cells, bile duct proliferation, and apoptosis were assessed histologically. The effect of EMD527040 on cholangiocyte adhesion, proliferation, apoptosis, and TGF-beta1 activation was studied in vitro.
alphavbeta6 was highly expressed on proliferating bile duct epithelia in fibrosis, with 100-fold increased transcript levels in advanced fibrosis. EMD527040 attenuated bile ductular proliferation and peribiliary collagen deposition by 40%-50%, induced down-regulation of fibrogenic and up-regulation of fibrolytic genes, and improved liver architecture and function. In vitro alphavbeta6 inhibition reduced activated cholangiocyte proliferation, their adhesion to fibronectin, and endogenous activation of TGF-beta1 by 50% but did not affect bile duct apoptosis.
Integrin alphavbeta6 is strongly up-regulated in proliferating bile duct epithelia and drives fibrogenesis via adhesion to fibronectin and auto/paracrine TGF-beta1 activation. Pharmacologic inhibition of alphavbeta6 potently inhibits the progression of primary and secondary biliary fibrosis.
整合素αvβ6在某些活化上皮细胞上高表达，在这些细胞中它介导与纤连蛋白的黏附，并作为激活潜伏转化生长因子（TGF）-β1的共受体。由于其在肝纤维化中的作用尚不清楚，我们在体外研究了αvβ6的功能，并探索了特异性αvβ6拮抗剂EMD527040的抗纤维化潜力。
在胆管结扎（BDL）后的大鼠和Mdr2（abcb4）基因敲除小鼠中研究实验性肝纤维化。从BDL后第2周开始至第6周，给大鼠给予不同剂量的EMD527040；从第4周开始至第8周，给Mdr2基因敲除小鼠给予不同剂量的EMD527040。对肝脏胶原蛋白进行定量，并通过定量逆转录聚合酶链反应测定αvβ6和纤维化相关转录本的表达。通过组织学评估表达αvβ6的细胞、胆管增殖和细胞凋亡。在体外研究EMD527040对胆管细胞黏附、增殖、凋亡和TGF-β1激活的影响。
在纤维化过程中，αvβ6在增殖的胆管上皮细胞上高表达，在晚期纤维化中转录水平增加100倍。EMD527040使胆管增生和胆管周围胶原沉积减少40%-50%，诱导促纤维化基因下调和纤溶基因上调，并改善肝脏结构和功能。在体外，抑制αvβ6可使活化胆管细胞增殖、它们与纤连蛋白的黏附以及TGF-β1的内源性激活减少50%，但不影响胆管细胞凋亡。
整合素αvβ6在增殖的胆管上皮细胞中强烈上调，并通过与纤连蛋白黏附及自分泌/旁分泌TGF-β1激活驱动纤维化形成。对αvβ6进行药物抑制可有效抑制原发性和继发性胆汁性纤维化的进展。
