Advanced glycation end-product-inhibited cell proliferation and protein expression of beta-catenin and cyclin D1 are dependent on glycogen synthase kinase 3beta in LLC-PK1 cells.

Glycogen synthase kinase 3beta (GSK3beta) is increased by high glucose in mesangial cells. Thus, we studied the role of GSK3beta in advanced glycation end-product (AGE)-induced effects in the proximal tubule-like LLC-PK1 cells. We found that AGE (100 microg/ml) time-dependently (8-48 h) increased phospho-GSK3beta-Tyr216 (active GSK3beta) and time-dependently (4-24 h) decreased phospho-GSK3beta-Ser21/9 (inactive GSK3beta) protein expression. Meanwhile, AGE (100 microg/ml) activated GSK3beta kinase at 8-48 h. AGE (100 microg/ml) dose-dependently (75-100 microg/ml) decreased beta-catenin protein expression but AGE did not decrease beta-catenin protein expression until 48 h. SB216763 (a GSK3beta inhibitor) and GSK3beta shRNA attenuated AGE (100 microg/ml)-inhibited cell proliferation and protein expression of beta-catenin and cyclin D1 at 48 h. SB216763 also attenuated AGE-induced type IV collagen. We conclude that AGE activates GSK3beta in LLC-PK1 cells. AGE-inhibited beta-catenin and cyclin D1 protein expression are dependent on GSK3beta. Moreover, AGE-inhibited cell proliferation and AGE-induced type IV collagen protein expression are dependent on GSK3beta.