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 3

Glomerular TNF expression correlates to eGFR and is sufficient to cause podocyte apoptosis.

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Glomerular TNF expression correlates to eGFR and is sufficient to cause ...
(A) Serum TNF levels from patients with FSGS from the NEPTUNE cohort do not correlate with glomerular TNF expression in kidney biopsies as determined by microarray analysis. (B–F) Microarray analysis of glomeruli from patients enrolled in the NEPTUNE cohort reveals that glomerular TNF expression does not correlate with TNFR1 expression (B), positively correlates with TNFR2 expression (C), and inversely correlates with eGFR (D). Neither TNFR1 expression (E) nor TNFR2 expression (F) correlates with eGFR. (G) Caspase 3 activity was measured in cultured human podocytes that were exposed to recombinant human TNF, TNFR1, or TNFR2. TNF but not TNFR1 or TNFR2 increased caspase 3 activity compared with untreated controls (C). One-way ANOVA; *P < 0.05. (H) TNF overexpression (TNFOE) in human podocytes causes increased cleaved caspase 3 activity compared with empty vector controls (C), which was prevented by the TNF inhibitor infliximab (I) (n = 4). One-way ANOVA; *P < 0.05. (I) Treatment of human podocytes with infliximab prevents DKD+ sera–induced cleaved caspase 3 activity (n = 4). One-way ANOVA; #P < 0.01 DKD+ without I vs. C, C with I, DKD–, DKD– with I, DKD+ with I. (J) Treatment of human podocytes with infliximab prevents FSGS sera–induced (n = 6) caspase 3 activity (n = 3). One-way ANOVA; **P < 0.01. (K) Knockdown of TNF (siTNF) prevents cleaved caspase 3 activity in podocytes exposed to serum from patients with FSGS (n = 7) compared with siCO-treated podocytes (n = 3). One-way ANOVA; ***P < 0.001.