缺鐵誘導十二指腸腺窩絨毛底部細胞Epas1 及鐵轉運蛋白基因的表現

Abstract

目前已知十二指腸上皮細胞能適應膳食中鐵質的改變，但是有關基因以及腸道適應位置之資訊目前並不瞭解。為了探討這些問題，我們從正常、飲食缺乏鐵質及重新攝取鐵質等三組實驗大鼠中，將腸道腺窩-絨毛底部（C-pole）及絨毛頂部（V-pole）組織內的RNA 分離出來，進行基因微矩陣分析，再分別利用RT-PCR 及西方墨點法確認與缺氧及鐵質吸收相關表現的RNA 及蛋白質。在鐵質缺乏的大鼠組別中，其十二指腸中轉錄因子Arnt 及Epas1（Hlf2α）的表現有顯著上升的情況；而與鐵轉運相關的基因，如二價金屬運輸體（DMT1）、cytochrome b reductase（Cybrd 1）、ferroportin（FPN1）、hephaestin（Heph）、heme oxygenase（Hmox1）、Slc39a14（ZIP14）及Slc31a1（Ctr1）等，表現量也有顯著上升的情況，這些基因在絨毛底部（C-pole）都會提早表現；相較之下，細胞內的運輸體Slc31a7（Znt7）表現量不變，而Slc25a37（mitoferrin）的表現量卻下降。重新攝取鐵質之大鼠經血液檢查確認鐵質濃度復原後，發現除了Heph、ZIP14 及Ctr1 的表現量會回復至正常值外，Arnt、Hlf2α及大部分和鐵運輸相關的基因，其表現量依然比正常值高。這些結果可以證明膳食鐵質之攝取會刺激C-pole 到V-pole 漸次增加其細胞核內轉錄因子及鐵轉運蛋白的表現量，我們現有的結果支持C-pole 細胞是負責鐵質吸收適應的假說。

The duodenal epithelium adapting to changes in dietary iron is well appreciated, but the genes and the location of adaptation remain unclear. To examine these issues, RNAs from the crypt-villus bottom (C-pole) and the villus top (V-pole) are isolated form normal, iron deficient and iron-refed rats by gene microarrays.The expression of hypoxia inducible and iron absorptive transcripts and proteins were confirmed by RT-PCR and by Western blot respectively. In iron deficient rats, the duodenum expressed significantly higher transcription factor Arnt and Epas1 (HIf2α), and iron transport related genes such as divalent metal transporter 1 (DMT1), cytochrome b reductase (Cybrd1), ferroportin 1 (FPN1), hephaestin (Heph), heme oxygenase 1 (Hmox1), Slc39a14 (ZIP14) and Slc31a1 (Ctr1) than normal rats. Importantly, all of these genes were precociously expressed in the C-pole. In contrast, the expression of intracellular transporter Slc31a7 (Znt7) was unchanged and Slc25a37 (mitoferrin) was decreased. In iron-refed rats, when hematologicalcriteria were recovering, the Arnt and HIf2α and most iron transport genes retained higher than normal levels,except that Heph, ZIP14 and Ctr1 returned to normal levels. The data demonstrate that dietary iron stimulatesthe cells at the C-pole to increase nuclear transcription factor and iron transport protein expression that isprogresses to cells at the V-poles. The present data support the hypothesis that C-pole cells are responsible fordietary iron adaptation.