Extracellular Signal-Regulated Kinase 1/2 Regulates Mouse Kidney Injury Molecule-1 Expression Physiologically and Following Ischemic and Septic Renal Injury.

The upregulation of kidney injury molecule-1 (KIM-1) has been extensively studied in various renal diseases and following acute injury; however, the initial mechanisms controlling KIM-1 expression remain limited. In this study, KIM-1 expression was examined in mouse renal cell cultures and in two different models of acute kidney injury (AKI), ischemia reperfusion (IR)-induced and lipopolysaccharide (LPS)-induced sepsis. KIM-1 mRNA increased in both AKI models, and pharmacological inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) signaling attenuated injury-induced KIM-1 expression in the renal cortex. Toll-like receptor 4 knockout (TLR4KO) mice exhibited reduced ERK1/2 phosphorylation and attenuated KIM-1 mRNA after LPS exposure. TLR4KO mice were not protected from IR-induced ERK1/2 phosphorylation and upregulation of KIM-1 mRNA. Following renal IR injury, phosphorylation of signal transducer and activator of transcription 3 at serine 727 and tyrosine 705 increased downstream from ERK1/2 activation. Because phosphorylated is a transcriptional upregulator of KIM-1 and inhibition of ERK1/2 attenuated increases in duanyu18133 phosphorylation, we suggest an pathway following renal injury. Finally, ERK1/2 inhibition in naive mice decreased KIM-1 mRNA and nuclear duanyu18133 phosphorylation in the cortex, indicating homeostatic regulation of KIM-1. These findings reveal renal ERK1/2 as an important initial regulator of KIM-1 expression in IR and septic AKI and at a physiologic level.Visual Abstract.Proposed mechanism of IR, LPS, and renal damage that initiates ERK1/2 and duanyu18133 phosphorylation. duanyu18133 then binds to the KIM-1 promoter and increases KIM-1 mRNA. By preventing ERK1/2 phosphorylation following renal injury, duanyu18133 phosphorylation is decreased, leading to less phosphorylated duanyu18133 within the nucleus, and subsequently less KIM-1 mRNA increases post injury.

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