Role of the Janus kinase (JAK)/signal transducters and activators of transcription (STAT) cascade in advanced glycation end-product-induced cellular mitogenesis in NRK-49F cells

Advanced glycation end product (AGE) is important in the pathogenesis of di abetic nephropathy, which is characterized by cellular hypertrophy/hyperpla sia leading to renal fibrosis. However, the signal transduction pathways of AGE remain poorly understood. The Janus kinase (JAK)/signal transducers an d activators of transcription (STAT) pathway has been associated with cellu lar proliferation in some extra-renal cells. Because interstitial fibroblas t proliferation might be important in renal fibrosis, we studied the role o f the JAK/STAT pathway in NRK-49F (normal rat kidney fibroblast) cells cult ured in AGE/BSA and non-glycated BSA. We showed that AGE dose-dependently ( 10-200 mu g/ml) increased cellular mitogenesis in NRK-49F cells at 5 and 7 days. However, cellular mitogenesis was unaffected by the simultaneous pres ence of BSA. Regarding the JAK/STAT pathway AGE (100 mu g/ml) induced tyros ine phosphorylation of JAK2 (but not JAK1, JAK3 or TYK2) at 15-60 min; it a lso induced the tyrosine phosphorylation of STAT1 and STAT3 at 1-2 h and 0. 5-4 h respectively. Being a transcription factor, AGE also increased the DN A-binding activities of STAT1 and STAT3 AG-490 (a specific JAK2 inhibitor) (5 mu M) inhibited tyrosine phosphorylation of JAK2 and the DNA-binding act ivities of STAT1 and STAT3. The same results were obtained by using specifi c 'decoy' oligodeoxynucleotides (ODNs) that prevented STAT1 and STAT3 from binding to DNA. Meanwhile, the STAT1 or STAT3 decoy ODN and AG-490 were eff ective in reversing AGE-induced cellular mitogenesis. We concluded that the JAK2-STAT1/STAT3 signal transduction pathway is necessary for AGE-induced cellular mitogenesis in NRK-49F cells.