Stawowy Philipp, Margeta Christian, Blaschke Florian, Lindschau Carsten, Spencer-Hänsch Chantel, Leitges Michael, Biagini Giuseppe, Fleck Eckart, Graf Kristof
Department of Medicine-Cardiology, Deutsches Herzzentrum Berlin, Augustenburger Platz 1, D-13353 Berlin, Germany.
Cardiovasc Res. 2005 Jul 1;67(1):50-9. doi: 10.1016/j.cardiores.2005.03.002. Epub 2005 Apr 7.
Angiotensin II (AII) promotes cardiac fibrosis by increased extracellular matrix production and enhanced interaction of matrix proteins with their cellular receptors, including integrins. AII and other growth factors augment beta(1)-integrin-dependent adhesion and spreading by "inside-out signaling" without affecting the total number of integrin receptors. "Inside-out signaling" involves specific signaling pathways, including protein kinase C (PKC), leading to activation of beta1-integrins. In the present study we investigated the mechanisms involved in AII-increased adhesion of adult rat cardiac fibroblasts (CFBs), obtained from Sprague-Dawley rats, to collagen I mediated by beta1-integrin.
Treatment of CFBs with AII induced a concentration-dependent increase in adhesion to collagen I (2.2-fold, p<0.01) within 3-6 h of treatment. This effect was mediated by beta1-integrin via the angiotensin AT1 receptor and was significantly reduced by protein kinase C inhibition. AII significantly induced phosphorylation of PKC epsilon (PKCepsilon), which is involved in beta1-integrin-dependent adhesion and motility, and phosphorylation of the cytoplasmatic tail of beta1-integrin at threonine 788/789, required for adhesion. Phosphorylation of beta1-integrin and an increase in adhesion was also induced by l-alpha-phosphatidylinositol-3,4,5-triphosphate (l-alpha-PIP3), an activator of endogenous PKCepsilon. AII failed to increase adhesion in myofibroblasts obtained from PKCepsilon (-/-) mice, but not in cells obtained from control mice. Co-immunoprecipitation and double immunofluorescence demonstrated that AII induced a close association of PKCepsilon with beta1-integrin in CFBs.
The present study demonstrates that AII increased beta1-integrin-dependent adhesion to collagen I in cardiac fibroblasts by inside-out signaling via PKCepsilon and phosphorylation of the cytoplasmatic tail of the beta1-integrin.
血管紧张素II（AII）通过增加细胞外基质生成以及增强基质蛋白与其细胞受体（包括整合素）之间的相互作用来促进心脏纤维化。AII和其他生长因子通过“由内向外信号转导”增强β1整合素依赖性黏附与铺展，而不影响整合素受体的总数。“由内向外信号转导 ”涉及特定的信号通路，包括蛋白激酶C（PKC），从而导致β1整合素的激活。在本研究中，我们探究了AII增加成年大鼠心脏成纤维细胞（CFB，取自Sprague-Dawley大鼠）与I型胶原黏附（由β1整合素介导）的相关机制。
用AII处理CFB，在处理3 - 6小时内可诱导其与I型胶原的黏附呈浓度依赖性增加（2.2倍，p<0.01）。这种效应由β1整合素通过血管紧张素AT1受体介导，并且蛋白激酶C抑制可使其显著降低。AII显著诱导PKCε（参与β1整合素依赖性黏附与运动）的磷酸化，以及黏附所需β1整合素细胞质尾部苏氨酸788/789位点的磷酸化。内源性PKCε的激活剂l-α-磷脂酰肌醇-3,4,5-三磷酸（l-α-PIP3）也可诱导β1整合素的磷酸化及黏附增加。AII未能增加取自PKCε（-/-）小鼠的肌成纤维细胞的黏附，但对取自对照小鼠的细胞无此影响。免疫共沉淀和双重免疫荧光显示，AII可诱导CFB中PKCε与β1整合素紧密结合。
本研究表明，AII通过PKCε介导的由内向外信号转导以及β1整合素细胞质尾部的磷酸化，增加了心脏成纤维细胞中β1整合素依赖性与I型胶原的黏附。
