KS370G對於腎臟纖維化保護作用之研究

Abstract

許多研究顯示腎小管間質纖維化是造成末期腎臟病的主因之一。但目前在臨床上仍然沒有一類藥物能夠有效地來治療腎小管間質纖維化。咖啡酸苯乙酯(caffeic acid phenylethyl ester)是蜂膠的主要成分，廣泛地分布在自然界中，並且已被證實具有抗糖尿病及抗纖維化等的保護作用。由於咖啡酸苯乙酯在生物體內很容易被酯酶(esterase)代謝而失去效用，因此它的生體可用率並不高。在本篇研究中，我們探討咖啡酸苯乙酯的結構類似物-咖啡酸苯乙醯胺(caffeic acid phenylethyl amide，KS370G)在動物腎臟纖維化模式(包括: 單側腎臟缺血再灌流以及單側輸尿管阻塞)以及利用轉化生長因子-β(TGF-β)誘導腎臟表皮細胞的模式下對於腎臟纖維化病變是否具有保護作用。 在動物的實驗模式下，我們在手術後的隔天開始給予一天一次口服10mg/kg 的KS370G，手術14天後對纖維化的腎臟進行研究。在單側腎動脈缺血再灌流的動物實驗中，我們發現到口服給予KS370G能夠降低腎臟膠原蛋白的沉積、減少fibronectin、α-SMA與vimentin的表現。KS370G也能夠去抑制缺血再灌流所增加的血漿中與腎臟組織中轉化生長因子-β的表現。而在單側輸尿管阻塞的動物實驗中，我們發現口服給予KS370G也可以降低腎臟膠原蛋白的沉積、降低輸尿管阻塞所增加的fibronectin、α-SMA與vimentin的表現。此外KS370G也會抑制發炎所引起的單核細胞趨化蛋白-1(monocyte chemoattractant protein-1; MCP-1)第一血管細胞黏附因子(vascular cell-adhesion molecule, VCAM-1),第一細胞間黏附分子(intercellular adhesion molecule 1, ICAM-1)以及單核細胞特徵蛋白CD-11b的表現。在抗氧化的部分，KS370G可以增加超氧歧化酶(superoxide dismutase; SOD)以及過氧化氫酶(catalase)的表現同時抑制脂質過氧化的發生。另外，KS370G也可以降低血漿中血管收縮素以及轉化生長因子-β的濃度，並抑制腎臟組織中轉化生長因子-β的表現與Smad3的磷酸化。 在細胞實驗中，我們利用轉化生長因子-β作為刺激，對人類與非人類兩種腎臟表皮細胞來進行研究。結果顯示，給予KS370G可以保護因轉化生長因子-β刺激所造成的E-cadherin下降和α-SMA的增加。KS370G同時可以抑制因轉化生長因子-β刺激所引起的fibronectin、collagen I與PAI-1等蛋白的表現。KS370G也抑制了轉化生長因子-β所引起的Smad2/3磷酸化。上述的研究結果顯示，KS370G不論在體內或是體外試驗中，對於腎臟纖維化的病變都具有保護的效果，而這些保護作用可能是與抑制了AngII，TGF-β，Smad2/3的訊息傳遞路徑有關。

Accumulating evidence suggests that renal tubulointerstitial fibrosis is a main cause of end-stage renal disease. Clinically, there are no beneficial treatments that can effectively reverse the progressive loss of renal functions. Caffeic acid phenethyl ester, a major component of propolis, is distributed wildly in nature and has anti-diabetic and anti-fibrotic effects. However, rapid decomposition by an esterase leads to its low bioavailability in vivo. In this study, we evaluated the effects of KS370G, a synthetic caffeamide derivative, on murine renal fibrosis induced by unilateral renal ischemia-reperfusion injury (IRI) and unilateral ureteral obstruction (UUO), and on TGF-β1 stimulated renal tubular epithelial cells (HK-2 and NRK52E) signaling. In the animal models, renal fibrosis was evaluated at 14 days post-operation. Immediately following the operation, KS370G (10 mg/kg) was administered by oral gavage once a day. In the IRI model, our results show that KS370G markedly attenuated collagen deposition and inhibits an IRI-induced increase of fibronectin, vimentin, α-SMA and TGF-β1 expression in the mouse kidney and plasma TGF-β1. In the UUO model, our results show that KS370G significantly attenuated collagen deposition in the obstructed kidney and inhibited UUO-induced renal fibrosis markers expression, including fibronectin, type I collagen, vimentin, and α-smooth muscle actin (α-SMA). KS370G significantly lowered the expression of renal inflammatory chemokines/adhesion molecules and monocyte cells marker (MCP-1, VCAM-1, ICAM-1 and CD11b). KS370G also reduced renal malondialdehyde (MDA) levels and reversed the expression of renal antioxidant enzymes (SOD and catalase) after UUO. Furthermore, KS370G significantly inhibited UUO-induced elevated plasma Ang II and TGF-β1 levels, TGF-β1 protein expression and Smad3 phosphorylation. In vitro study, we used human (HK-2) and non-human (NRK52E) renal epithelial cell lines. Our results showed that KS370G reverses TGF-β1-induced downregulation of E-cadherin and upregulation of α-SMA and also decreases the expression of fibronectin, collagen I and PAI-1 and inhibits TGF-β1-induced phosphorylation of Smad2/3. These findings show the beneficial effects of KS370G on renal fibrosis in vivo and in vitro with the possible mechanism through the inhibition of Ang II, TGF-β and Smad3 signaling pathways.