Abstract: SA-PO623
APOL1 and JAK1/2 Are Required for Interferon Gamma-Stimulated Inflammatory Responses in Human Kidney Cells
Session Information
- Glomerular Diseases: Immunology, Inflammation - II
November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1202 Glomerular Diseases: Immunology and Inflammation
Authors
- Zhang, Hongyu, University of Michigan, Ann Arbor, Michigan, United States
- Sampson, Matt G., University of Michigan, Ann Arbor, Michigan, United States
- Vega-Warner, V., University of Michigan, Ann Arbor, Michigan, United States
- Ju, Wenjun, 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 glomerular diseases including diabetic kidney disease (DKD). Recent data suggest that APOL1 and JAK1/2 signaling contribute to the pro-inflammatory milieu in FSGS and DKD, respectively. 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 in FSGS and by JAK2 overexpression in diabetic podocytes. We therefore determined whether and how APOL1 and JAK signaling interact to stimulate CXCL9 in a human kidney cell.
Methods
Human kidney 2 (HK-2) cell monolayers were grown to confluence and treated with interferon gamma (IFNg) (30ng/ml), interleukin-6 (10ng/ml), or tumor necrosis factor-alpha (10ng/ml) from 30 min to 48 hr. Levels of JAK2, APOL1 and CXCL9 mRNAs were determined in response to agonists. Inhibition of JAK1 and JAK2, with baricitinib (500nM) or siRNA knockdown of APOL1 expression was performed in some experiments befpre IFNg exposure. Effects of APOL1 knockdown on IFNg-stimulated gene expression were examined. These genes were identified by transcriptomic analysis of IFNg-treated podocytes.
Results
HK-2 cells express APOL1, JAK2 and CXCL9. Stimulation of HK-2 cell monolayers with IFNg, but not IL-6 or TNF, resulted in a rapid and sustained 4-50-fold increase in mRNA expression of JAK2, APOL1 and CXCL9. These increases were largely abrogated by pretreatment with the JAK1/2 inhibitor as were IFNg-induced increases in STAT3 phosphorylation and APOL1 protein levels. APOL1 knockdown resulted in an 80% reduction in CXCL9 expression and a 40-50% reduction in interferon-induced guanylate-binding protein 2, HLA class II histocompatibility antigen, DR alpha chain and ubiquitin D. Expression of other IFNg-stimulated genes was not consistently affected by APOL1 knockdown.
Conclusion
In cultured human kidney cells, IFNg triggered responses in kidney cells resulting in increased expression of pro-inflammatory mediators and APOL1. This cascade was largely abrogated by specific inhibition of JAK1/2 signaling and selectively inhibited by knockdown of APOL1. These findings suggest that APOL1 plays an important role in the IFNg-mediated inflammatory response in kidney cells.
Funding
- NIDDK Support