Abstract: TH-PO237

Extracellular Signal-Regulated Kinase 1/2 Regulates Kidney Injury Molecule-1 Following Renal Injury through STAT3 Phosphorylation

Session Information

Category: Acute Kidney Injury

  • 001 AKI: Basic

Authors

  • Collier, Justin B., Medical University of South Carolina, Charleston, South Carolina, United States
  • Schnellmann, Rick G., University of Arizona, Tucson, Arizona, United States
Background

Kidney injury molecule-1 (KIM-1) is a transmembrane glycoprotein that is highly upregulated during injury and is a renal injury biomarker. Because KIM-1 transcription is highly induced, we explored the role of extracellular signal-regulated kinase 1/2 (ERK1/2) in KIM-1 expression in cells and in different mouse models of acute kidney injury.

Methods

Mouse kidney proximal tubule cells (TK) were treated with varying concentrations of hydroxyurea, hydrogen peroxide, and tert-butyl-hydroperoxide with and without pretreatment with the MEK1/2 inhibitor trametinib (10nM). Trametinib (1mg/kg) was administered 1 h before renal I/R injury to mice. Trametinib was administered 1 h prior to I/R injury or LPS (10 mg/kg) exposure to TLR4 KO and WT mice and euthanized 18 h later, respectively. KIM-1 mRNA was measured by RT-qPCR.

Results

Trametinib blocked ERK1/2 phosphorylation in all experiments. Toxicant exposure to TK cells for 24 h upregulated KIM-1 mRNA and was blocked by trametinib. At 3 and 24 h post renal I/R cortical KIM-1 mRNA increased 4- and 600-fold, and pretreatment with trametinib resulted in a 50% and 66% decrease, respectively, in induced KIM-1 mRNA. Trametinib also decreased KIM-1 protein 24 h post I/R. ERK1/2 phosphorylated the transcription factor STAT3 at sites, Y705 and S727, following I/R and was prevented by trametinib. WT mice pretreated with trametinib before LPS had decreased KIM-1 mRNA and protein. In contrast to TLR4 KO mice subjected to I/R, TLR4 KO mice injected with LPS did not exhibit increased KIM-1 mRNA or protein, nor activated ERK1/2 after 18 h.

Conclusion

We have linked ERK1/2 to KIM-1 transcriptional upregulation in the kidney cortex through STAT3 Y705/S727 phosphorylation following renal injury. In I/R and LPS-induced kidney injury KIM-1 mRNA and protein increased and ERK1/2 inhibition attenuated this increase. However, ERK1/2 mediated KIM-1 upregulation was dependent on TLR4 in LPS treated mice but not mice subjected to I/R. These results demonstrate that ERK1/2 is a key initiator of renal KIM-1 expression and that KIM-1 expression is regulated by different ERK1/2 pathways following renal injury.

Funding

  • NIDDK Support