強心?哇巴因是一種具有毒性的天然化合物，但在醫學上以低劑量可以用於治療心力衰竭。它的主要生物作用是通過與鈉鉀泵阿爾法亞基結合後直接抑制鈉鉀泵的?促活性及誘發伴隨的哇巴因相關的信號傳導。我們實驗室先前利用纖維細胞生長因子受體1(FGFR1)抑製劑SU5402和哇巴因處理A549細胞後，發現哇巴因通過FGF2/FGFR1信號傳導促使A549細胞分泌FGF2和活化FGFR1。為了深入闡明強心?調節FGF2釋放的分子機制，我們首先依據可能之相關訊息傳遞，篩選了幾種訊息傳遞分子之抑制劑對哇巴因誘導的纖維細胞生長因子2釋放之影響，並使用HSA模型和Chou-Talalay來分析對A549細胞代謝活性有互相拮抗作用的信號傳導路徑。利用這些方法後發現ERK1/2抑製劑U0126強烈拮抗哇巴因誘導的細胞生長抑制，並且隨後的ELISA和Western blot分析顯示U0126減少了哇巴因促使的FGF2釋放和FGFR1磷酸化。另外，接著使用EGFR抑製劑吉非替尼和MKP1抑製劑NSC95397進一步證明了EGFR激活和MKP1減少各自部分地促使ERK1/2磷酸化。總而言之，強心?哇巴因通過上游的EGFR磷酸化和MKP1減少來激活ERK1/2，從而促進FGF2釋放、FGF2/FGFR1信號傳導。;Cardiac glycoside ouabain is a nature occurring toxic compound but used medically in small doses to treat heart failure. Its primary biological action is to directly inhibit Na+/K+-ATPase enzymatic activity with concomitant ouabain-related signaling induction through binding to Na+/K+-ATPase α subunit. Our laboratory had previously utilized FGFR1 inhibitor SU5402 and ouabain to treat A549 cells and found ouabain promoted FGF2 secretion and FGFR1 activation in A549 cells via FGF2/FGFR1 signaling. To further elucidate the molecular mechanisms underlying cardiac glycoside-mediated FGF2 release, we first screened several compounds to identify small molecular inhibitors of signaling effectors that were able to antagonize to the ouabain effect in A549 cells using HSA model and Chou-Talalay method. These approaches discovered ERK1/2 inhibitor U0126 potently antagonized ouabain-mediated growth inhibition, and subsequent ELISA and Western blot analysis revealed U0126 reduced FGF2 release and FGFR1 phosphorylation mediated by ouabain. Both EGFR activation and MKP1 reduction were found to contribute to ERK1/2 phosphorylation as evidenced by pharmacological approaches using EGFR inhibitor Gefitinib and MKP1 inhibitor NSC95397. Therefore, we concluded that cardiac glycoside ouabain activated ERK1/2 via both upstream EGFR phosphorylation and MKP1 diminishment to promote FGF2 release and susequent FGF2/FGFR1 signaling in A549 cells.
