Glutathione Synthesis via the Cystine/Glutamate Transporter Promotes the Formation of Tertiary Lymphoid Structures in the Kidney.

Background: Tertiary lymphoid structure, an ectopic lymphoid tissue induced under chronic inflammation, develops in various kidney diseases and is associated with poor prognosis. The immune system requires metabolic resources to support immune function and lymphocyte proliferation. Hence, dramatic metabolic alterations presumably occur during the formation of tertiary lymphoid structure. However, it remains unclear whether metabolic remodeling occurs during this formation and its underlying mechanism.

Methods: In a murine model of renal tertiary lymphoid structures, we used imaging mass spectrometry and metabolome analysis to investigate the metabolic pathway that characterizes tertiary lymphoid structures. We also performed in situ hybridization with immunofluorescence and pharmacological inhibition to explore the expression and function of the key molecules governing the pivotal metabolic pathway. We analyzed urine samples from mice and humans to explore the metabolites estimating the presence of renal tertiary lymphoid structures.

Results: Significant glutathione accumulation and depletion of cysteine, which is essential for glutathione synthesis, was observed specifically within tertiary lymphoid structures. The kidneys with tertiary lymphoid structures exhibited higher glutathione concentrations than healthy kidneys. Tertiary lymphoid structures also showed significant accumulation of 4-HNE and 8-OHdG, markers of oxidative stress. Dendritic cells and fibroblasts within tertiary lymphoid structures expressed the cystine/glutamate transporter, that regulates glutathione synthesis, and supplied synthesized glutathione to lymphocytes, which lacked its expression. Pharmacological inhibition of the cystine/glutamate transporter prevented tertiary lymphoid structure formation in the kidney. Furthermore, enhanced glutathione synthesis within tertiary lymphoid structures was reflected in elevated urinary glutathione concentrations both in mice and humans, which effectively detected the presence of tertiary lymphoid structures in the kidney in IgA nephropathy patients.

Conclusions: Glutathione significantly accumulated within tertiary lymphoid structures in the kidney. Inhibition of the cystine/glutamate transporter prevented the formation of tertiary lymphoid structures. Urinary glutathione served as a biomarker to detect tertiary lymphoid structures in the kidney.