Insulin attenuates apoptosis induced by high glucose via the PI3-kinase/Akt pathway in rat peritoneal mesothelial cells.
BACKGROUND
Peritoneal mesothelial cells play an important role in peritoneal dialysis and are often exposed to dialysis fluid containing high glucose levels. Loss of peritoneal function is a major complication associated with long-term peritoneal dialysis. In this study, we hypothesized that high glucose levels induce apoptosis, and that insulin attenuates this apoptosis in peritoneal mesothelial cells. To clarify this hypothesis, we examined the effects of insulin on the phosphatidylinositol 3-kinase/Akt signaling pathway and apoptosis in rat peritoneal mesothelial cells.


METHODS
Phosphorylated insulin receptor and Akt were detected by western blot analysis. Apoptosis was evaluated by measuring caspase 3 activity and by TUNNEL staining.


RESULTS
Insulin (100 nmol/L) increased tyrosine phosphorylation of insulin receptor in peritoneal mesothelial cells. Furthermore, insulin (1-100 nmol/L) dose-dependently stimulated Akt phosphorylation. Treatment with the phosphatidylinositol 3-kinase inhibitors wortmannin (100 nmol/L) and LY294002 (10 micromol/L) attenuated insulin-induced Akt phosphorylation, indicating that insulin phosphorylates Akt via a phosphatidylinositol 3-kinase-dependent pathway. Insulin attenuated caspase 3 activity and decreased the number of TUNNEL-positive cells. The phosphatidylinositol 3-kinase inhibitors and overexpression of a dominant-negative mutant of Akt inhibited the effect of insulin on apoptosis.


CONCLUSIONS
The present data indicate that insulin attenuates high glucose-induced apoptosis via the phosphatidylinositol 3-kinase/Akt signaling pathway in peritoneal mesothelial cells. Therefore, the insulin signaling pathway may play a protective role in peritoneal function.
Kaifu
Kumiko
K
Department of Cardiorenal and Cerebrovasular Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan.
Kiyomoto
Hideyasu
H
Hitomi
Hirofumi
H
Matsubara
Keisuke
K
Hara
Taiga
T
Moriwaki
Kumiko
K
Ihara
Genei
G
Fujita
Yoshiko
Y
Sugasawa
Noriko
N
Nagata
Daisuke
D
Nishiyama
Akira
A
Kohno
Masakazu
M
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D018929:Cell Culture Techniques; D002867:Chromones / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects* / Q000473:pathology; D005947:Glucose / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D010537:Peritoneum / Q000187:drug effects* / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D005947:Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one