Local TNF causes NFATc1-dependent cholesterol-mediated podocyte injury
Christopher E. Pedigo, … , Sandra Merscher, Alessia Fornoni
Christopher E. Pedigo, … , Sandra Merscher, Alessia Fornoni
Published August 2, 2016
Citation Information: J Clin Invest. 2016;126(9):3336-3350. https://doi.org/10.1172/JCI85939.
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Research Article Inflammation

Local TNF causes NFATc1-dependent cholesterol-mediated podocyte injury

Abstract

High levels of circulating TNF and its receptors, TNFR1 and TNFR2, predict the progression of diabetic kidney disease (DKD), but their contribution to organ damage in DKD remains largely unknown. Here, we investigated the function of local and systemic TNF in podocyte injury. We cultured human podocytes with sera collected from DKD patients, who displayed elevated TNF levels, and focal segmental glomerulosclerosis (FSGS) patients, whose TNF levels resembled those of healthy patients. Exogenous TNF administration or local TNF expression was equally sufficient to cause free cholesterol–dependent apoptosis in podocytes by acting through a dual mechanism that required a reduction in ATP-binding cassette transporter A1–mediated (ABCA1-mediated) cholesterol efflux and reduced cholesterol esterification by sterol-O-acyltransferase 1 (SOAT1). TNF-induced albuminuria was aggravated in mice with podocyte-specific ABCA1 deficiency and was partially prevented by cholesterol depletion with cyclodextrin. TNF-stimulated free cholesterol–dependent apoptosis in podocytes was mediated by nuclear factor of activated T cells 1 (NFATc1). ABCA1 overexpression or cholesterol depletion was sufficient to reduce albuminuria in mice with podocyte-specific NFATc1 activation. Our data implicate an NFATc1/ABCA1-dependent mechanism in which local TNF is sufficient to cause free cholesterol–dependent podocyte injury irrespective of TNF, TNFR1, or TNFR2 serum levels.

Authors

Christopher E. Pedigo, Gloria Michelle Ducasa, Farah Leclercq, Alexis Sloan, Alla Mitrofanova, Tahreem Hashmi, Judith Molina-David, Mengyuan Ge, Mariann I. Lassenius, Carol Forsblom, Markku Lehto, Per-Henrik Groop, Matthias Kretzler, Sean Eddy, Sebastian Martini, Heather Reich, Patricia Wahl, GianMarco Ghiggeri, Christian Faul, George W. Burke III, Oliver Kretz, Tobias B. Huber, Armando J. Mendez, Sandra Merscher, Alessia Fornoni

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Figure 2

Analysis of podocyte TNF, TNFR1, and TNFR2 expression after treatment with serum from patients with FSGS or DKD, after exposure to TNF or after TNF overexpression.

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Analysis of podocyte TNF, TNFR1, and TNFR2 expression after treatment wi...
(A–C) Quantitative real-time (RT) PCR analysis of TNF (A), TNFR1 (B), and TNFR2 (C) expression in podocytes exposed to pooled sera from patients with diabetic kidney disease (DKD+) or diabetes (DKD–) and healthy controls (C) (n = 3). One-way ANOVA; *P < 0.05 DKD–, DKD+ vs. C. (D–F) Quantitative RT-PCR analysis of TNF (D), TNFR1 (E), and TNFR2 (F) expression in podocytes exposed to sera from individual patients with FSGS (n = 6) and serum from healthy controls (C, n = 6). Two-tailed Student’s t test; *P < 0.05. **P < 0.01. (G–I) Quantitative RT-PCR analysis of TNF (G), TNFR1 (H), and TNFR2 (I) expression in podocytes exposed to recombinant human TNF (n = 3). Two-tailed Student’s t test; *P < 0.05. (J–L) Quantitative RT-PCR analysis of TNF (J), TNFR1 (K), and TNFR2 (L) expression in podocytes overexpressing TNF (TNFOE) compared with empty vector controls (C) (n = 3). Two-tailed Student’s t test; *P < 0.05, **P < 0.01.