Screening of Candidate Biomarkers for Primary Membranous Nephropathy Based on Proteomic Analysis of Peripheral Blood Mononuclear Cells

Abstract

Background: Primary membranous nephropathy (PMN) is the leading cause of nephrotic syndromes in adults. However, biopsy is a commonly used approach in diagnosing as well as assessing renal disease progression. This study aimed to screen potential PMN biomarkers using proteomic methods on peripheral blood mononuclear cells (PBMCs) and to provide an important reference value for the scientific diagnosis of PMN. Methods: Peripheral blood samples were obtained from both PMN patients and healthy controls. Total RNA was extracted and subsequently reverse-transcribed into cDNA. Meanwhile, by combining proteomics analysis with Liquid Chromatography with tandem mass spectrometry (LC-MS/MS) technique, candidate biomarkers for PMN were screened employing bioinformatics analysis of PBMCs. Furthermore, the expression levels of differentially expressed proteins in both PMN patients and normal controls were assessed using quantitative real-time polymerase chain reaction (qRT-PCR). Results: A total of 81 differential expressed proteins (DEPs), of which 29 were up-regulated and 52 were down-regulated, were isolated and screened. Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathway enrichment of DEPs was observed for fatty acid metabolism. Furthermore, four candidate PMN biomarkers were identified, including H2A clustered histone 20 (H2AC20), H2B clustered histone 21 (H2BC21), splicing factor 3a subunit 1 (SF3A1), and serine and arginine rich splicing factor 1 (SRSF1). The mRNA expression levels of these genes were assessed using the qRT-PCR analysis and were found consistent with LC-MS/MS data. Moreover, the mRNA expression levels of H2AC20, H2BC21, SF3A1, and SRSF1 were significantly reduced in PMN patients compared to the healthy controls. Conclusion: In summary, H2AC20, H2BC21, SF3A1, and SRSF1 are the candidate PMN biomarkers using proteomic methods based on PBMCs. More importantly, these findings suggest a potential link between fatty acid metabolic pathways and PMN. Finally, this study provides a scientific reference for the diagnosis of PMN.