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 8

ABCA1 overexpression or treatment with HPBCD can partially prevent NFAT-mediated albuminuria.

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ABCA1 overexpression or treatment with HPBCD can partially prevent NFAT-...
(A) Electron microscopy analysis of double-transgenic (DT) mice fed doxycycline chow for 4 days resulted in segmental foot process effacement (arrowhead) compared with single-transgenic controls (ST). Scale bars: 0.5 μm. (B) Total cholesterol content in kidney cortexes of DT and ST mice (n = 6 per group) treated with HPBCD or vehicle control. One-way ANOVA; *P < 0.05, **P < 0.01. (C) Urinary albumin-to-creatinine ratio in DT mice treated with HPBCD or vehicle before doxycycline chow feeding (n = 6 per group). Two-tailed Student’s t test; *P < 0.05. (D) Urinary albumin-to-creatinine ratio in triple transgenic (TT), inducible podocyte-specific constitutively active NFAT mice overexpressing ABCA1, compared with DT controls after 4 months of doxycycline chow feeding (n = 3 per group). Two-tailed Student’s t test; *P < 0.05. (E) Analysis of WT1 podocytes per glomerular profile in DT and TT mice fed control or doxycycline diet for 4 months (n = 3). One-way ANOVA; #P < 0.05 compared with all columns. (F) Representative periodic acid–Schiff (PAS) staining (original magnification, ×20) of kidney sections from DT and TT mice fed doxycycline or control diet for 4 months. (G) Mesangial expansion scores on PAS-stained kidney sections from DT and TT mice fed doxycycline or control diet for 4 months (n = 3 per group) as assessed by 2 blinded, independent investigators. One-way ANOVA; #P < 0.05 compared with all columns. (H) Bar graph analysis of serum creatinine levels from DT and TT mice fed doxycycline or control diet for 4 months (n = 3 per group). One-way ANOVA; #P < 0.05 compared with all columns. (I) Bar graph analysis of picrosirius red–stained kidney sections from DT and TT mice fed doxycycline or normal diet (n = 3 per group). One-way ANOVA; #P < 0.05 compared with all columns. (J) Model of proposed mechanism of local TNF–induced podocyte injury in FSGS and DKD.