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

Key Points Glutathione accumulated in tertiary lymphoid structures (TLS), where dendritic cells and fibroblasts specifically expressed cystine/glutamate transporter. Pharmacologic inhibition of the cystine/glutamate transporter prevented the formation of TLS. Urinary glutathione concentrations efficiently detected the presence of TLS in the kidney in mice and humans. Background Tertiary lymphoid structure (TLS), 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 TLS. However, it remains unclear whether metabolic remodeling occurs during this formation and its underlying mechanism. Methods In a murine model of TLS in the kidney, we used imaging mass spectrometry and metabolome analysis to investigate the metabolic pathway that characterizes TLS. We also performed in situ hybridization with immunofluorescence and pharmacologic 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 TLS in the kidney. Results Significant glutathione accumulation and depletion of cysteine, which is essential for glutathione synthesis, was observed specifically within TLS. The kidneys with TLS exhibited higher glutathione concentrations than healthy kidneys. TLS also showed significant accumulation of 4-hydroxynonenal and 8-hydroxy-2′ -deoxyguanosine, markers of oxidative stress. Dendritic cells and fibroblasts within TLS expressed the cystine/glutamate transporter, which regulates glutathione synthesis, and supplied synthesized glutathione to lymphocytes, which lacked its expression. Pharmacologic inhibition of the cystine/glutamate transporter prevented the formation of TLS in the kidney. Furthermore, enhanced glutathione synthesis within TLS was reflected in elevated urinary glutathione concentrations in both mice and humans, which effectively detected the presence of TLS in the kidney in IgA nephropathy patients. Conclusions Glutathione significantly accumulated within TLS in the kidney. Inhibition of the cystine/glutamate transporter prevented the formation of TLS. Urinary glutathione served as a biomarker to detect TLS in the kidney.