Salt intake induces epithelial-to-mesenchymal transition of the peritoneal membrane in rats.
BACKGROUND
Dietary salt intake has been linked to hypertension and cardiovascular disease through volume-mediated effects. Accumulating evidence points to direct negative influence of salt intake independent of volume overload, such as cardiac and renal fibrosis, mediated through transforming growth factor beta (TGF-beta). Epithelial-to-mesenchymal transition (EMT) has been implicated as a key process in chronic fibrotic diseases, such as chronic kidney disease or heart failure. The potential role of dietary salt intake on cell transdifferentiation has never been investigated. This study analysed the effect of dietary salt intake on EMT and fibrosis in the peritoneal membrane (PM) in a rat model.


METHODS
Twenty-eight Wistar rats were randomized to a normal salt (NS) or a high salt (HS) intake. NS and HS rats had free access to tap water or NaCl 2% as drinking water, respectively. After 2 weeks, samples of peritoneum were taken, and TGF-beta(1), Interleukin 6 (IL-6) and vascular endothelial growth factor (VEGF) mRNA expression were quantified with qRT-PCR. Fibrosis and submesothelial PM thickness were scored. EMT was evaluated using fluorescence staining with cytokeratin and alpha smooth muscle actin (alpha-SMA).


RESULTS
Dietary salt intake caused peritoneal fibrosis and thickening of the submesothelial layer and induced EMT as identified by colocalization of cytokeratin and alpha-SMA in cells present in the submesothelial layer. Peritoneal TGF-beta(1) and IL-6 mRNA expression were upregulated in the HS group.


CONCLUSIONS
High dietary salt intake induces EMT and peritoneal fibrosis, a process coinciding with upregulation of TGF-beta1.
Renal Division, Department of Internal Medicine, Gent University Hospital, Gent, Belgium.
Anneleen
A
Pletinck
Claudia
C
Consoli
Maria
M
Van Landschoot
Sonja
S
Steppan
Nick
N
Topley
Jutta
J
Passlick-Deetjen
Raymond
R
Vanholder
Wim
W
Van Biesen
D000199:Actins / Q000032:analysis; D000818:Animals; D004847:Epithelial Cells / Q000473:pathology*; D005260:Female; D005355:Fibrosis; D015850:Interleukin-6 / Q000235:genetics; D007633:Keratins / Q000032:analysis; D008648:Mesoderm / Q000473:pathology*; D010537:Peritoneum / Q000473:pathology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D017673:Sodium Chloride, Dietary / Q000633:toxicity*; D053773:Transforming Growth Factor beta1 / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
D000199:Actins; D015850:Interleukin-6; D007633:Keratins; D012333:RNA, Messenger; D017673:Sodium Chloride, Dietary; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A; C498862:Acta2 protein, rat