Extracellular signal-regulated kinase mediates renal regeneration in rats with myoglobinuric acute renal injury

In vitro data support that extracellular signal-regulated kinase (ERR) and c-Jun N-terminal kinase (JNK), members of mitogen-activated protein (MAP) k inases, mediate the signal transduction pathways responsibly for the cell p roliferation. However, in vivo role of these MAP kinases is poorly understo od, Intramuscular injection of 50% glycerol solution induces acute renal fa ilure in rats. This injury is known as a model of rhabdomyolysis in human. To investigate the molecular mechanism of the signaling pathway in this inj ury, we examined the role of ERK and JNK After the glycerol injection JNK w as rapidly and transiently activated at about 4 h, while the activation of ERK was gradually increased and the levels were sustained at least to 24 h. Next; we examined the expression of cell-cycle related proteins after the glycerol injection using Western blot analysis. The levels of proliferating cell nuclear antigen (PCNA) protein as a marker for cell proliferation wer e induced at 2 h and significantly increased to 24 h after the injection. P n addition, cyclins D1, D2, and D3 as markers for G(1) phase also increased with similar time courses. To examine whether activation of ERK and/or JNK are involved in the renal regeneration after the glycerol injection, we ex amined the effect of genistein, which is an inhibitor of tyrosine kinase, o n the activation of ERK and JNK Administration of genistein to rats with th is injury decreased the activation of ERK but not JNK; The induction of PCN A and cyclin D1 was also prevented by this treatment. in this condition, re nal function was further worsened as compared to control rats. These result s provide the first evidence that ERK may be involved in the repair process of renal tubules damaged by this injury. (C) 1999 Academic Press.