Department of Physiology, Section of Respiratory Disease, University of Manitoba, Winnipeg, MB, Canada.
Respir Res. 2011 Aug 24;12(1):113. doi: 10.1186/1465-9921-12-113.
Bronchial fibroblasts contribute to airway remodelling, including airway wall fibrosis. Transforming growth factor (TGF)-β1 plays a major role in this process. We previously revealed the importance of the mevalonate cascade in the fibrotic response of human airway smooth muscle cells. We now investigate mevalonate cascade-associated signaling in TGFβ1-induced fibronectin expression by bronchial fibroblasts from non-asthmatic and asthmatic subjects.
We used simvastatin (1-15 μM) to inhibit 3-hydroxy-3-methlyglutaryl-coenzyme A (HMG-CoA) reductase which converts HMG-CoA to mevalonate. Selective inhibitors of geranylgeranyl transferase-1 (GGT1; GGTI-286, 10 μM) and farnesyl transferase (FT; FTI-277, 10 μM) were used to determine whether GGT1 and FT contribute to TGFβ1-induced fibronectin expression. In addition, we studied the effects of co-incubation with simvastatin and mevalonate (1 mM), geranylgeranylpyrophosphate (30 μM) or farnesylpyrophosphate (30 μM).
Immunoblotting revealed concentration-dependent simvastatin inhibition of TGFβ1 (2.5 ng/ml, 48 h)-induced fibronectin. This was prevented by exogenous mevalonate, or isoprenoids (geranylgeranylpyrophosphate or farnesylpyrophosphate). The effects of simvastatin were mimicked by GGTI-286, but not FTI-277, suggesting fundamental involvement of GGT1 in TGFβ1-induced signaling. Asthmatic fibroblasts exhibited greater TGFβ1-induced fibronectin expression compared to non-asthmatic cells; this enhanced response was effectively reduced by simvastatin.
We conclude that TGFβ1-induced fibronectin expression in airway fibroblasts relies on activity of GGT1 and availability of isoprenoids. Our results suggest that targeting regulators of isoprenoid-dependent signaling holds promise for treating airway wall fibrosis.
支气管成纤维细胞参与气道重塑，包括气道壁纤维化。转化生长因子（TGF）-β1 在这个过程中起着重要作用。我们之前揭示了甲羟戊酸途径在人气道平滑肌细胞纤维化反应中的重要性。我们现在研究了甲羟戊酸途径相关信号在非哮喘和哮喘患者支气管成纤维细胞中 TGFβ1 诱导的纤维连接蛋白表达中的作用。
我们使用辛伐他汀（1-15 μM）抑制 3-羟-3-甲基戊二酰基辅酶 A（HMG-CoA）还原酶，该酶将 HMG-CoA 转化为甲羟戊酸。使用香叶基香叶基转移酶-1（GGT1；GGTI-286，10 μM）和法呢基转移酶（FT；FTI-277，10 μM）的选择性抑制剂来确定 GGT1 和 FT 是否有助于 TGFβ1 诱导的纤维连接蛋白表达。此外，我们研究了与辛伐他汀和甲羟戊酸（1 mM）、香叶基焦磷酸（30 μM）或法呢基焦磷酸（30 μM）共孵育的影响。
免疫印迹显示，辛伐他汀浓度依赖性抑制 TGFβ1（2.5 ng/ml，48 h）诱导的纤维连接蛋白。这可以通过外源性甲羟戊酸或异戊烯基（香叶基焦磷酸或法呢基焦磷酸）来预防。辛伐他汀的作用可以被 GGTI-286 模拟，但不能被 FTI-277 模拟，这表明 GGT1 基本参与了 TGFβ1 诱导的信号。与非哮喘细胞相比，哮喘成纤维细胞表现出更强的 TGFβ1 诱导的纤维连接蛋白表达；这种增强的反应可以被辛伐他汀有效降低。
我们得出结论，TGFβ1 诱导的气道成纤维细胞纤维连接蛋白表达依赖于 GGT1 的活性和异戊烯基的可用性。我们的结果表明，靶向异戊烯基依赖性信号调节因子有望治疗气道壁纤维化。
