Involvement of mineralocorticoid receptor in high glucose-induced big mitogen-activated protein kinase 1 activation and mesangial cell proliferation.
We previously demonstrated that high glucose-induced cell proliferation in cultured rat mesangial cells (RMCs) is mediated through activation of big mitogen-activated protein kinase 1 (BMK1). We also found that, in aldosterone-treated rats, mesangial proliferation is associated with BMK1 activation and that these effects were prevented by treatment with a selective mineralocorticoid receptor antagonist, eplerenone. In this study, we investigated the contribution of mineralocorticoid receptors to high glucose-induced BMK1 activation and cell proliferation in RMCs. BMK1 phosphorylation was measured by western blot analysis. Cell proliferation was evaluated by [3H]-thymidine incorporation. High glucose treatment (15.5 mmol/l) increased BMK1 phosphorylation in both the nucleus and cytosol of RMCs. High glucose-induced BMK1 phosphorylation was attenuated by pretreatment with eplerenone (10 micromol/l), mineralocorticoid receptor small interfering RNA or PD98059 (100 micromol/l), a specific inhibitor of extracellular signal-regulated kinase kinase (MEK). Likewise, high glucose-induced increases in [H]-thymidine incorporation were prevented by eplerenone or PD98059 and transfection of dominant-negative MEK5, which is the upstream regulator of BMK1. These results suggest that mineralocorticoid receptors are involved in high glucose-induced BMK1 phosphorylation and cell proliferation. The inhibitory actions of mineralocorticoid receptor antagonists may contribute to their preventive effects on diabetic nephropathy, which have been reported in recent clinical studies.
Liu
Gang
G
Department of Pharmacology, Kagawa University Medical School, Kagawa, Japan.
Miyata
Kayoko
K
Hitomi
Hirofumi
H
Yao
Li
L
Sun
Guang-Ping
GP
Suzaki
Yuki
Y
Hosomi
Naohisa
N
Kiyomoto
Hideyasu
H
Nakano
Daisuke
D
Tamaki
Toshiaki
T
Yoshizumi
Masanori
M
Nishiyama
Akira
A
D000818:Animals; D001483:Base Sequence; D049109:Cell Proliferation; D002478:Cells, Cultured; D004789:Enzyme Activation; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D005947:Glucose / Q000494:pharmacology*; D008297:Male; D048054:Mitogen-Activated Protein Kinase 7 / Q000378:metabolism*; D010766:Phosphorylation; D034741:RNA, Small Interfering; D051381:Rats; D017207:Rats, Sprague-Dawley; D018161:Receptors, Mineralocorticoid / Q000502:physiology*
D034741:RNA, Small Interfering; D018161:Receptors, Mineralocorticoid; D048054:Mitogen-Activated Protein Kinase 7; D005947:Glucose