Biomarkers of lupus nephritis determined by serial urine proteomics

• Published in: Kidney international Vol. 74; no. 6; pp. 799 - 807
• Main Authors: Zhang, Xiaolan, Jin, Ming, Wu, Haifeng, Nadasdy, Tibor, Nadasdy, Gyongyi, Harris, Nathan, Green-Church, Kari, Nagaraja, Haikady, Birmingham, Daniel J., Yu, Chack-Yung, Hebert, Lee A., Rovin, Brad H.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.09.2008; Nature Publishing; Elsevier Limited
• Subjects: Albuminuria - diagnosis; alpha 1-Antitrypsin - urine; Amino Acid Sequence; Antimicrobial Cationic Peptides - urine; Biological and medical sciences; biomarker; Biomarkers - urine; Hepcidins; Humans; Kidneys; Lupus Erythematosus, Systemic - complications; Lupus Erythematosus, Systemic - diagnosis; lupus nephritis; Lupus Nephritis - diagnosis; Medical sciences; Molecular Weight; Nephrology. Urinary tract diseases; Predictive Value of Tests; Protein Array Analysis; Protein Isoforms; Proteinuria - diagnosis; Proteomics - methods; Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis; SELDI; Tandem Mass Spectrometry; Urinary system involvement in other diseases. Miscellaneous; biomarker; lupus nephritis; SELDI; Kidney disease; Urine; Immunopathology; Connective tissue disease; Skin disease; Nephrology; Urinary system disease; Biological marker; Autoimmune disease; Biological indicator; Lupus nephritis; Urology; Systemic lupus erythematosus; Systemic disease; Proteomics
• ISSN: 0085-2538; 1523-1755
• DOI: 10.1038/ki.2008.316

Lupus nephritis is a frequent and serious complication of systemic lupus erythematosus (SLE), the treatment of which often requires the use of immunosuppressives that can have severe side effects. Here we determined the low-molecular weight proteome of serial lupus urine samples to uncover novel and predictive biomarkers of SLE renal flare. Urine from 25 flare cycles of 19 patients with WHO Class III, IV, and V SLE nephritis were obtained at baseline, pre-flare, flare and post-flare. Each sample was first fractionated to remove proteins larger than 30kDa, then applied onto weak cation exchanger protein chips for analysis by SELDI-TOF mass spectrometry. We found 176 protein ions of which 27 were differentially expressed between specific flare intervals. On-chip peptide sequencing by integrated tandem mass spectrometry positively identified the 20 and 25 amino-acid isoforms of hepcidin, as well as fragments of α1-antitrypsin and albumin among the selected differentially expressed protein ions. Hepcidin 20 increased 4 months before renal flare and returned to baseline at renal flare, whereas hepcidin 25 decreased at renal flare and returned to baseline 4 months after the flare. These studies provide a beginning proteomic analysis aimed at predicting impending renal relapse, relapse severity, and the potential for recovery after SLE nephritis flare.