Kidney Injury Molecule-1 is Elevated in Nephropathy and Mediates Macrophage Activation via the Mapk Signalling Pathway

Background/Aims: Kidney injury molecule-1 (KIM-1) is highly expressed in renal tubular cells after injury and is usually regarded as an early biomarker of acute kidney injury(AKI). The aim of this study was to determine the role of KIM-1 in the development of renal tubular injury Methods: Clinical samples, three different animal models and in vitro experiments were utilized to determine the possible mechanism underlying the involvement of KIM-1 in kidney injury. Results: Both plasma and urinary KIM-1 expression levels were significantly higher in AKI and chronic kidney disease (CKD) patients than in healthy volunteers, and urinary KIM-1 expression was significantly higher in CKD patients than in AKI patients. According to the results of our research involving three different mouse models, KIM-1 expression was significantly increased during the early stage of kidney injury and was persistently elevated in renal fibrosis. Our immunofluorescence staining results indicated that KIM-1-positive tubules were surrounded by macrophage infiltrates in regions of kidney injury. Moreover, our transwell, western blotting and real-time PCR data showed that macrophage migration and phenotype transitions were mediated by KIM-1 through the mitogen-activated protein kinase (MAPK) pathway. MAPK pathway inhibition could significantly reverse the effects of KIM-1 with respect to these macrophage phenotype changes and migration. Conclusions: KIM-1 expression was markedly elevated in both acute and chronic kidney injury and may play a pivotal role in macrophage activation via the MAPK pathway in kidney disease.