Hypertension and Collagen: Effect of Ac-SDKP

描述(申请人提供)：高血压导致左心室肥厚(LVH)和左心室间质和血管周围胶原沉积增加。心肌胶原蛋白的增加可能改变肥厚心脏的功能。血管紧张素转换酶抑制剂(ACEI)可逆转高血压患者的左心室肥厚。这种作用归因于抑制血管紧张素II(Ang II)的形成和激动素的降解。我们已经证明，ACE的另一种天然底物N-乙酰-丝氨酰-天冬氨酰-赖氨酰-脯氨酸(Ac-SDKP)在不改变高血压患者血压(BP)或左心室肥厚的情况下，可以防止左室单核/巨噬细胞的浸润和纤维化。我们认为这是Ac-SDKP影响心肌纤维化的第一个证据；然而，Ac-SDKP提供心脏保护的机制(S)或受体(S)尚不清楚，也不知道ACEI是否参与ACEI的心脏保护作用。我们推测：(1)Ac-SDKP对高血压大鼠心脏具有抗炎和抗纤维化作用，其作用机制可能与Ac-SDKP介导的一系列信号转导通路有关，包括MAP、蛋白激酶C、核因子-kB和转化生长因子-β。本研究的目的是合成和测试Ac-SDKP和SDK片段的新类似物，以鉴定(1)具有与Ac-SDKP相似抑制作用的Ac-SDKP类似物，并可放射性标记并用于表征Ac-SDKP受体(S)；(2)特异性阻断Ac-SDKP的抑制作用的拮抗剂。在AIM II中，我们将确定(1)Ac-SDKP的作用是否与抑制TGF-β、CTGF和Smad的表达有关，以及(2)Ac-SDKP是否影响转化生长因子-β对I型和/或III型胶原表达的影响。我们还将检测Ac-SDKP是否抑制成纤维细胞中p38和PKC的激活。在第四章中，我们将确定Ac-SDKP(1)是否抑制慢性高血压大鼠左室炎症细胞的浸润、p42/p44、p38和/或PKC活性、核因子-kB、转化生长因子-β、CTGF和Smads，(2)逆转心肌成纤维细胞的增殖、胶原表达和合成，(3)提高基质金属蛋白酶活性，(4)减少心肌I和III型胶原的表达。在Aim IV中，我们将研究ACE对LV胶原沉积的抑制作用是否通过Ac-SDKP介导。本项目将为研究ACEI在高血压中的心脏保护作用和Ac-SDKP的作用机制提供重要的新信息。

DESCRIPTION (provided by applicant): Hypertension causes left ventricular hypertrophy (LVH) and increased LV interstitial and perivascular collagen deposition. Increased cardiac collagen may alter function in hypertrophied hearts. Angiotensin converting enzyme inhibition(ACEi) has been shown to reverse LVH in hypertension. This effect has been attributed to blockade of angiotensin II (Ang II) formation and kinin degradation. We have shown that N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), another natural substrate for ACE, prevents LV monocyte/macrophage infiltration and fibrosis without altering blood pressure (BP) or LVH in hypertension. We believe this is the first demonstration that Ac-SDKP affects cardiac fibrosis; however, the mechanism(s) or receptor(s) by which Ac-SDKP affords cardioprotection are not known, nor whether Ac-SDKP contributes to the cardioprotective effects of ACEi. We hypothesize that (1) Ac-SDKP has an anti-inflammatory and antifibrotic effect on the heart in hypertension via specific receptor(s) linked to a cascade of signal transduction, including MAP kinase, protein kinase C (PKC), NF-kB and TGF-beta, and (2) the effect of ACEi on the heart is mediated in part by Ac-SDKP. In aim new analogues of Ac-SDKP and SDK fragments will be synthesized and tested to identify (1) an ACE-resistant analogue with an inhibitory effect similar to Ac-SDKP that can be radiolabeled and used to characterize Ac-SDKP receptor(s), and (2) an antagonist that specifically blocks the inhibitory effect of Ac-SDKP. In aim II we will determine whether (1) the effect of Ac- SDKP is linked to suppression of TGF-beta, CTGF and Smad expression, and (2) the effect of TGF-beta on collagen type I and/or III expression is affected by Ac-SDKP. We will also examine whether Ac-SDKP inhibits p38 and PKC activation in fibroblasts. In aim IV we will determine whether in vivo Ac-SDKP (1) inhibits inflammatory cell infiltration in the LV, p42/p44, p38 and/or PKC activity, NF-kB,TGF-beta, CTGF and Smads, (2) regresses cardiac fibroblast proliferation, collagen expression and synthesis, (3) increases matrix metalloproteinase activity, and (4) decreases cardiac expression of collagen I and III in rats with long-term hypertension. In aim IV we will examine whether the effect of ACE inhibitionon LV collagen deposition is mediated by Ac-SDKP. This project will provide important new information on the on the cardioprotective effect of ACEi in hypertension and the mechanism of action of Ac-SDKP.