Function of NKCC1 in the Aortic Fibrosis of Rats with Chronic Kidney Disease

This work explored the role of NKCC1 (Na-K-2Cl cotransporter 1) in aortic fibrosis in CKD (chronic kidney disease) rats. The CKD rat model was established by 5/6 nephrectomy. Blood pressure was measured by tail cuff method. BUN (blood urea nitrogen) was measured by urease method. Scr (serum creatine) was measured by sarcosine oxidase method. Tissue morphology was observed by HE (hematoxylin and eosin) staining, and fibrosis was observed by Masson-trichrome staining. The expression of NKCC1 in rat kidney and aorta was detected by Real-time PCR, Western blot and immunohistochemical staining. Rat aortic EC (endothelial cell) was cultured in vitro. Immunofluorescence experiments were performed to observe the expression of Col-I (collagenI) and Col-III (collagen-III) in the cells. Western blot was used to detect the expression of α-SMA (α-smooth muscle actin), CD31 (platelet-endothelial cell adhesion molecule), E-cadherin and vimentin. The results showed that the mean SBP (systolic blood pressure) of CKD rats was significantly higher than that of the preoperative and sham groups (P<0.05). The expression levels of BUN and Scr were significantly higher than those of the sham group (P<0.05). Kidney and aorta of CKD rats were severely damaged and showed obvious fibrosis. The expression of NKCC1 was significantly increased compared with that in the sham group. When NKCC1 in EC were activeted by aldosterone, the expression leves of Col-I, Col-III and the interstitial cell markers α SMA, vimentin were up-regulated, while the endothelial cell markers CD31 and E-cadherin were down-regulated. On this basis, when NKCC1 activity were inhibited by bumetanide, the expression of Col-I, Col-III, α-SMA and vimentin was down-regulated, while CD31 and E-cadherin were up-regulated. This study shows that NKCC1 may promote CKD aortic fibrosis by enhancing EndoMT (endothelial-to-mesenchymal transition).