Abstract: SA-PO601
Macrophage Interactions with Collecting Ducts May Contribute to the Interstitial Fibrosis Observed in IgA Nephropathy Progression
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
- Pawluczyk, Izabella Z a, University of Leicester, Leicester, United Kingdom
- Soares, Maria F., Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom
- Barratt, William A., University of Leicester, Leicester, United Kingdom
- Brown, Jeremy Richard, University of Leicester, Leicester, United Kingdom
- Selvaskandan, Haresh, University Hospitals of Leicester, Leicester, United Kingdom
- Bhachu, Jasraj Singh, University Of Leicester, Leicester, United Kingdom
- Zeng, Yiqing, University of Leicester, Leicester, United Kingdom
- Sarania, Rishi, University of Leicester, Leicester, United Kingdom
- Molyneux, Karen, Leicester University, Leicester, United Kingdom
- Barratt, Jonathan, University of Leicester, Leicester, United Kingdom
Background
Tubulo-interstitial fibrosis is a powerful predictor of future progression in IgA nephropathy (IgAN). Proximal tubules, in concert with infiltrating macrophages, are regarded as the agents provocateurs for driving this process. However, evidence is now emerging for a contributory role of the distal nephron. The aim of this study was to examine the potential influence of macrophages on renal collecting ducts (CDEC) in the progression of IgAN.
Methods
Macrophage-conditioned media (MCM) were generated from U937 and THP-1 cells, cultured in the presence or absence of 100µg/ml IgA1. Collecting duct epithelial cells (CDEC) exposed to the MCMs were analysed for evidence of inflammation and fibrosis.
Results
Staining of IgAN biopsies for the macrophage marker CD68 demonstrated that macrophages were principally observed in and around proximal tubules. However, CD68+ macrophages were also observed in areas of medullary collecting ducts and within their lumens. CDEC exposure to THP-1-IgA-MCM exhibited markedly increased expression of the tubular injury marker neutrophil-associated gelatinase (NGAL) and raised levels of IL1β, TNFα, IL6 and IL8; effects that were replicated by 5ng/ml IL1ß alone. U937-IgA-MCM, on the other hand, significantly increased MCP-1 and fibronectin levels and reduced E-cadherin mRNA expression. Exosomes extracted from THP-1-IgA-MCMs stimulated similar increases in NGAL and cytokine expression to the source MCM, while in cross over experiments exosomes extracted from CDECs induced IL1β and IL6 mRNA expression in macrophages. MiRnome analysis using nanostring technology revealed that miR-146a was expressed more than 2 fold in CDECs treated with THP-1-IgA-MCM compared to THP-1-MCM. Enforced miR-146a suppression with a specific inhibitor further enhanced NGAL expression in CDECs in the presence of MCM while ectopic miR-146a over expression down-regulated it. Both NGAL mRNA and miR-146a were found, by RT-PCR, to be upregulated in the biopsies of progressive forms of IgAN compared to CKD controls.
Conclusion
Taken together these data suggest that macrophages and collecting ducts could interact to contribute to the tubulo-interstitial fibrosis and inflammation found in progressive forms of IgAN.
Funding
- Private Foundation Support