Integrin-linked kinase acts as a pro-survival factor against high glucose-associated osmotic stress in human mesangial cells.
BACKGROUND
Integrin-linked kinase (ILK) is a protein that plays an important role in extracellular matrix-mediated signalling. Recent studies implicated ILK dysregulation in the development of diabetic nephropathy. However, little is known about the significance of ILK up-regulation in response to high glucose in mesangial cells.


METHODS
The ILK messenger (m)RNA and protein expression in human mesangial cells were analysed with quantitative real-time polymerase chain reaction (PCR) and western blotting after exposure to either 100, 200, or 500 mg/dl glucose, or 100 mg/dl glucose + 400 mg/dl mannitol. Activation of protein Kinase B (PKB)/Akt was also determined by western blot analysis. Cells were transfected with ILK siRNA to determine the effects of ILK knockdown on PKB/Akt activation and cell death following treatment with high glucose or mannitol.


RESULTS
High concentrations of glucose or mannitol for three days significantly up-regulated ILK mRNA and protein expression (P < 0.05 vs 100 mg/dl glucose). In contrast, ILK expression in cells exposed to the same conditions for seven days was unaffected. The time course of PKB/Akt phosphorylation was similar to that of ILK protein expression. The siRNA-mediated down-regulation of ILK expression inhibited the elevation of PKB/Akt phosphorylation induced by high glucose treatment. Furthermore, the inhibition of ILK expression promoted high glucose- or mannitol-induced apoptosis.


CONCLUSIONS
The ILK may act as a pro-survival factor and play a role in protecting mesangial cells from hyperglycaemic osmotic stress.
Ohnishi
Masayoshi
M
Department of Endocrinology and Metabolism, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, 465 Kajii-cho, Hirokoji, Kawaramachi-dori, Kamikyo-ku, Kyoto 602-8566, Japan.
Hasegawa
Goji
G
Yamasaki
Masahiro
M
Obayashi
Hiroshi
H
Fukui
Michiaki
M
Nakajima
Toshiki
T
Ichida
Yukiko
Y
Ohse
Hiroyuki
H
Mogami
Shin-ichi
S
Yoshikawa
Toshikazu
T
Nakamura
Naoto
N
D017209:Apoptosis; D016923:Cell Death; D002470:Cell Survival; D002478:Cells, Cultured; D003928:Diabetic Nephropathies / Q000378:metabolism / Q000473:pathology*; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D008353:Mannitol / Q000378:metabolism; D050527:Mesangial Cells / Q000166:cytology* / Q000378:metabolism*; D009995:Osmosis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D015854:Up-Regulation; D000099200:Scaffold Protein ILK
D005947:Glucose; D008353:Mannitol; D017346:Protein Serine-Threonine Kinases; D012313:RNA; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000099200:Scaffold Protein ILK