Direct aldosterone action as a profibrotic factor via ROS-mediated SGK1 in peritoneal fibroblasts.
OBJECTIVE
Peritoneal fibrosis leads to discontinuation of peritoneal dialysis. Although aldosterone promotes tissue fibrosis in many organs, its contribution to peritoneal fibrosis and the underlying mechanism are poorly understood. The present study investigated the direct effect of aldosterone on cultured rat peritoneal fibroblasts (RPFs).


METHODS
The expression of aldosterone synthase (CYP11B2), mineralocorticoid receptors (MRs), 11beta-hydroxysteroid dehydrogenase 2 (11beta-HSD2), serum- and glucocorticoid-inducible protein kinase 1 (SGK1), and connective tissue growth factor (CTGF) mRNA was evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR). To determine the role of reactive oxygen species (ROS) induced by aldosterone, an active oxygen assay with several inhibitors was used. The ability of RPFs to produce aldosterone was examined by enzyme immunoassay. Small interfering RNA (siRNA) of SGK1 was transfected into cultured cells using lipofectamine.


RESULTS
CYP11B2, MRs, and 11beta-HSD2 were expressed in RPFs. The release of aldosterone from RPFs into the culture medium was confirmed. Aldosterone increased the expression of SGK1 mRNA via ROS generation. Spironolactone, apocynin, and tempol significantly reduced SGK1 expression. Aldosterone upregulated CTGF transcripts significantly. SGK1 gene silencing suppressed aldosterone-induced CTGF expression.


CONCLUSIONS
The local aldosterone system acts directly as a profibrotic factor via ROS-mediated SGK1 in RPFs.
Yamahara
Hideki
H
Department of Medicine II, Kansai Medical University, Osaka, Japan.
Kishimoto
Noriko
N
Nakata
Midori
M
Okazaki
Akiko
A
Kimura
Taikou
T
Sonomura
Kazuhiro
K
Matsuoka
Eiko
E
Shiotsu
Yayoi
Y
Adachi
Takaomi
T
Matsubara
Hiroaki
H
Iwasaka
Toshiji
T
Mori
Yasukiyo
Y
D000450:Aldosterone / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D055513:Connective Tissue Growth Factor / Q000096:biosynthesis; D005786:Gene Expression Regulation; D017874:Immediate-Early Proteins / Q000235:genetics*; D056627:Peritoneal Fibrosis / Q000209:etiology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D000099184:Serum-Glucocorticoid Regulated Kinases
D000450:Aldosterone; D055513:Connective Tissue Growth Factor; D017874:Immediate-Early Proteins; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D000099184:Serum-Glucocorticoid Regulated Kinases