Abstract: FR-PO676

JAK1/2 Regulate APOL1, CXCL9 and JAK2 Expression in Human Kidney Cells

Session Information

Category: Glomerular

  • 1001 Glomerular: Basic/Experimental Immunology and Inflammation

Authors

  • Zhang, Hongyu, University of Michigan, Ann Arbor, Michigan, United States
  • Wu, Gordon S, Wayne State University School of Medicine, Ann Arbor, Michigan, United States
  • Vega-Warner, V, University of Michigan, Ann Arbor, Michigan, United States
  • Sampson, Matt G., University of Michigan, Ann Arbor, Michigan, United States
  • Brosius, Frank C., University of Arizona, Tucson, Arizona, United States
Background

Chronic inflammation contributes to progression of all glomerular diseases. Recent data suggest that both APOL1 and JAK1/2 signaling contribute to the pro-inflammatory milieu in a variety of kidney diseases including FSGS, diabetic kidney disease, and other causes of nephrotic syndrome. Based on systems genetic and transcriptomic analyses of humans and of murine models of glomerular diseases, the expression of CXCL9, a T-cell chemoattractant belonging to the CXC chemokine family, is increased by APOL1 high risk genotype expression and by JAK2 overexpression in podocytes.

Methods

Human kidney 2 (HK-2) cell monolayers were grown to confluence and treated with interferon-gamma (IFN) (30ng/ml), interleukin-6 (IL-6) (10ng/ml), or tumor necrosis factor-alpha (TNF) (10ng/ml) from 30 min to 48 hr. mRNA levels of JAK2, APOL1 and CXCL-9 were determined at multiple timepoints in response to these agonists. A commercially available inhibitor of JAK1 and JAK2, baricitinib (Bari; 500nM), was then applied 30 min prior to agonist incubation.

Results

HK-2 cells were found to express APOL1, JAK2 and CXCL9. Stimulation of HK-2 cell monolayers of with IFN, but not IL-6 or TNF, resulted in a large, rapid and sustained (maximal at 48 hr) increases in mRNA expression of JAK2, APOL1 and CXCL9 (Figure). All of these increases were abrogated by 30 minutes of pretreatment with the JAK1/2 inhibitor as was the IFN induced increase in STAT3 phosphorylation.

Conclusion

In cultured human kidney cells, IFN stimulation triggers a cascade of events resulting in large increases in expression of pro-inflammatory mediators and APOL1. This cascade is completely abrogated by specific inhibition of JAK1/2 signaling. These findings suggest that JAK1/2-STAT3 signaling regulates APOL1, CXCL9 chemokine and JAK2 expression by parenchymal cells in the kidney. Future studies will examine effects of APOL1 modulation and genotype on this process.

IFN-induced increases in APOL1, CXCL9 and JAK2 (-) were completely inhibited by preincubation with Bari (+). N = 3 separate experiments for each timepoint.