ATP-binding cassette A1 deficiency causes cardiolipin-driven mitochondrial dysfunction in podocytes
G. Michelle Ducasa, … , Flavia Fontanesi, Alessia Fornoni
G. Michelle Ducasa, … , Flavia Fontanesi, Alessia Fornoni
Published July 22, 2019
Citation Information: J Clin Invest. 2019;129(8):3387-3400. https://doi.org/10.1172/JCI125316.
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Research Article Metabolism Nephrology

ATP-binding cassette A1 deficiency causes cardiolipin-driven mitochondrial dysfunction in podocytes

Abstract

Fibroblasts from patients with Tangier disease carrying ATP-binding cassette A1 (ABCA1) loss-of-function mutations are characterized by cardiolipin accumulation, a mitochondrial-specific phospholipid. Suppression of ABCA1 expression occurs in glomeruli from patients with diabetic kidney disease (DKD) and in human podocytes exposed to DKD sera collected prior to the development of DKD. We demonstrated that siRNA ABCA1 knockdown in podocytes led to reduced oxygen consumption capabilities associated with alterations in the oxidative phosphorylation (OXPHOS) complexes and with cardiolipin accumulation. Podocyte-specific deletion of Abca1 (Abca1fl/fl) rendered mice susceptible to DKD, and pharmacological induction of ABCA1 improved established DKD. This was not mediated by free cholesterol, as genetic deletion of sterol-o-acyltransferase-1 (SOAT1) in Abca1fl/fl mice was sufficient to cause free cholesterol accumulation but did not cause glomerular injury. Instead, cardiolipin mediates ABCA1-dependent susceptibility to podocyte injury, as inhibition of cardiolipin peroxidation with elamipretide improved DKD in vivo and prevented ABCA1-dependent podocyte injury in vitro and in vivo. Collectively, we describe a pathway definitively linking ABCA1 deficiency to cardiolipin-driven mitochondrial dysfunction. We demonstrated that this pathway is relevant to DKD and that ABCA1 inducers or inhibitors of cardiolipin peroxidation may each represent therapeutic strategies for the treatment of established DKD.

Authors

G. Michelle Ducasa, Alla Mitrofanova, Shamroop K. Mallela, Xiaochen Liu, Judith Molina, Alexis Sloan, Christopher E. Pedigo, Mengyuan Ge, Javier Varona Santos, Yanio Hernandez, Jin-Ju Kim, Cyrille Maugeais, Armando J. Mendez, Viji Nair, Matthias Kretzler, George W. Burke, Robert G. Nelson, Yu Ishimoto, Reiko Inagi, Santanu Banerjee, Shaoyi Liu, Hazel H. Szeto, Sandra Merscher, Flavia Fontanesi, Alessia Fornoni

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Figure 1

P sera–treated podocytes show reduced ABCA1 expression and function associated with increased cytotoxicity.

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P sera–treated podocytes show reduced ABCA1 expression and function asso...
(A) Expression of several genes important in lipid metabolism was assessed by real-time PCR in NP (n = 13–16) and P (n = 14–15) sera–treated podocytes, at baseline and at time of biopsy. (B) Quantification of the percentage of radiolabeled cholesterol effluxed via the ABCA1 transporter after treatment with sera from patients obtained at baseline and at time of biopsy. Sera from NP and P patients were used in the analysis (n = 4 pooled sera for all groups). (C) Quantification of the lipid droplet content in human podocytes treated with NP and P patient sera via bodipy fluorescent intensity per cell (n = 14–15). (D) Representative images (original magnification ×20) showing bodipy staining of normal human podocytes treated with the sera from patients with NP and P DKD. (E and F) Bar graph analysis showing CellRox cytoplasmatic intensity (n = 3 for NP, n = 5 for P; pooled sera) (E) and cytotoxicity normalized to viability (n = 13 for NP, n = 14 for P) (F) in human podocytes treated with baseline P sera– compared with NP sera–treated podocytes. (G) Glomerular Abca1 expression of ob/ob mice (n = 7) compared with their heterozygous controls, ob/+ (n = 4) quantified via qRT-PCR. (H) Glomerular Abca1 expression of db/db mice (n = 5) compared with their heterozygous controls, db/+ (n = 6) quantified via qRT-PCR. (I) Correlation analysis between albumin-to-creatinine ratios (μg/mg) and glomerular Abca1 expression in db/db and ob/ob mice. Two-tailed t test (all panels except I) and linear regression used for correlation analyses (I) with r2 and P values shown. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.