Elsevier

Kidney International

Volume 99, Issue 2, February 2021, Pages 443-455
Kidney International

Clinical Investigation
Fumarate modulates phospholipase A2 receptor autoimmunity-induced podocyte injury in membranous nephropathy

https://doi.org/10.1016/j.kint.2020.06.031Get rights and content

Downstream mechanisms that lead to podocyte injury following phospholipase A2 receptor (PLA2R) autoimmunity remain elusive. To help define this we compared urinary metabolomic profiles of patients with PLA2R-associated membranous nephropathy (MN) at the time of kidney biopsy with those of patients with minimal change disease (MCD) and to healthy individuals. Among the metabolites differentially expressed in patients with PLA2R-associated MN compared to healthy individuals, fumarate was the only significant differentially expressed metabolite in PLA2R-associated MN compared to MCD [fold-difference vs. healthy controls and vs. MCD: 1.76 and 1.60, respectively]. High urinary fumarate levels could predict the composite outcome of PLA2R-associated MN. Fumarate hydratase, which hydrolyzes fumarate, colocalized with podocalyxin, and its expression was lower in glomerular sections from patients with PLA2R-associated MN than in those from healthy individuals, patients with non-PLA2R-associated MN or MCD. Podocytes stimulated with IgG purified from serum with a high anti-PLA2R titer (MN-IgG) decreased expression of fumarate hydratase and increased fumarate levels. These changes were coupled to alterations in the expression of molecules involved in the phenotypic profile of podocytes (WT1, ZO-1, Snail, and fibronectin), an increase in albumin flux across the podocyte layer and the production of reactive oxygen species in podocytes. However, overexpression of fumarate hydratase ameliorated these alterations. Furthermore, knockdown of fumarate hydratase exhibited synergistic effects with MN-IgG treatment. Thus, fumarate may promote changes in the phenotypic profiles of podocytes after the development of PLA2R autoimmunity. These findings suggest that fumarate could serve as a potential target for the treatment of PLA2R-associated MN.

Section snippets

Baseline characteristics

The baseline characteristics of the study subjects at the time of kidney biopsy are presented in Table 1. No subjects received immunosuppressants at baseline. The median age of the PLA2R-associated MN group was 57 years, and 66.1% of the patients were male. The median anti-PLA2R titer was 126 RU/ml (interquartile range [IQR]: 21–221), and the median follow-up duration was 1067 days (IQR: 522–1659 days) in the PLA2R-associated MN group.

Differentially expressed metabolites in urine samples at the time of kidney biopsy

Each nuclear magnetic resonance (NMR) peak of 71 metabolites

Discussion

The pathologic mechanism that leads to podocyte injury downstream of PLA2R autoimmunity is clinically important because it may be a potential therapeutic target for MN, given that a significant proportion of patients do not respond to immunosuppressive treatment.17,18 We demonstrated that urinary, but not serum, levels of fumarate were differentially expressed in PLA2R-associated MN. This finding remained consistent even after exclusion of the diabetes patients, which was shown to be associated

Study subjects and specimens

This study was conducted according to the Declaration of Helsinki and was approved by the institutional review board of Seoul National University Hospital, Seoul, Korea (H-1601-076-734). The human biospecimens of the study subjects were provided by the National Biobank of Korea.34

The diagnostic algorithm of MN is described in Supplementary Figure S10. PLA2R-associated MN was defined as having positive serum anti-PLA2R antibodies or glomerular PLA2R antigens.35 The serum anti-PLA2R level was

Disclosure

All the authors declared no competing interests.

Acknowledgments

This work was supported by the Industrial Strategic Technology Development Program - Development of bio-core technology (10077474, Development of early diagnosis technology for acute/chronic renal failure) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea) and the Korea Basic Science Institute (C060200).

Author Contributions

DKK and GSH designed the study. DKK, GSH, HAJ, JSH, and SHY participated in the conception of the study. HAJ, SHY, CWJ, CK, YK, HL, JPL, KWJ, YSK, and DKK participated in the

References (45)

  • S.H. Yang et al.

    Roles of fluid shear stress and retinoic acid in the differentiation of primary cultured human podocytes

    Exp Cell Res

    (2017)
  • L.H. Beck et al.

    M-type phospholipase A2 receptor as target antigen in idiopathic membranous nephropathy

    N Engl J Med

    (2009)
  • H.C. Stanescu et al.

    Risk HLA-DQA1 and PLA2R1 alleles in idiopathic membranous nephropathy

    N Engl J Med

    (2011)
  • S. Gupta et al.

    Genetics of membranous nephropathy

    Nephrol Dial Transplant

    (2017)
  • A. Marson et al.

    Genetic basis of autoimmunity

    J Clin Invest

    (2015)
  • P. Ruggenenti et al.

    Anti-phospholipase A2 receptor antibody titer predicts post-rituximab outcome of membranous nephropathy

    J Am Soc Nephrol

    (2015)
  • E. Hoxha et al.

    M-type phospholipase A2 receptor autoantibodies and renal function in patients with primary membranous nephropathy

    Clin J Am Soc Nephrol

    (2014)
  • E.J. Song et al.

    Anti-phospholipase A2 receptor antibody as a prognostic marker in patients with primary membranous nephropathy

    Kidney Res Clin Pract

    (2018)
  • D.S. Wishart

    Emerging applications of metabolomics in drug discovery and precision medicine

    Nat Rev Drug Discov

    (2016)
  • R.H. Weiss et al.

    Metabolomics in the study of kidney diseases

    Nat Rev Nephrol

    (2012)
  • M. Guma et al.

    Metabolomics in rheumatic diseases: desperately seeking biomarkers

    Nat Rev Rheumatol

    (2016)
  • P.D. Burbelo et al.

    Detection of PLA2R autoantibodies before the diagnosis of membranous nephropathy

    J Am Soc Nephrol

    (2020)
  • Cited by (18)

    View all citing articles on Scopus
    11

    HAJ, JSH, and SHY contributed equally to this work.

    View full text