Advanced glycation end-product-induced mitogenesis is dependent on Janus kinase 2-induced heat shock protein 70 in normal rat kidney interstitial fibroblast cells

Kidney interstitial fibroblast proliferation is important in the pathogenesis of diabetic renal fibrosis. In this regard, advanced glycation end-product (AGE)-induced proliferation in normal rat kidney interstitial fibroblast (NRK-49F) cells is dependent on the Janus kinase 2 (JAK2) signal transducers and activators of transcription (STAT) pathway. Heat shock protein (Hsp) is a molecular target of JAK/STAT. Thus, the role of Hsp70 in AGE-induced mitogenesis in NRK-49F cells was studied. The AGE dose (1100-200 mu g/mL) and time (16-72 h) dependently increased Hsp70 protein expression. AGE-induced Hsp70 was attenuated by AG-490 (a JAK2 inhibitor) and N-acetylcysteine. AGE also increased tyrosine phosphorylation of Hsp70, cyclin E, and cyclin D1 (to a lesser extent) while increasing Hsp70 protein interactions with STAT1, STAT3, STAT5b, cyclin D1, and cyclin E. AGE-induced tyrosine phosphorylation of Hsp70 and cyclin E (but not cyclin D1) was attenuated by AG-490. AGE-induced mitogenesis, cyclin D1, and cyclin E were attenuated by Hsp70 antisense oligodeoxynucleotide and 2-aminopurine (an Hsp70 inhibitor). AGE-induced Hsp70 and mitogenesis were also attenuated by N-acetylcysteine. It was concluded that AGE-induced Hsp70 protein expression and tyrosine phosphorylation are dependent on JAK2 in NRK-49F cells. AGE increased protein-protein interactions among Hsp70, STAT1, STAT3, STAT5b, cyclin D1, and cyclin E. Moreover, AGE-induced mitogenesis is dependent on Hsp70 and oxidative stress.