Mechanism of Hip Arthropathy in Ankylosing Spondylitis: Abnormal Myeloperoxidase

Abstract

Ankylosing spondylitis (AS) is a chronic inflammation of the joints and spine. Its pathogenesis has not been elucidated, especially involving hip joint disease. The purpose of this study was to analyze the proteome of diseased hip in AS and to identify key protein biomarkers. We used label-free quantification combined with liquid chromatography mass spectrometry (LC–MS/MS) to screen for differentially expressed proteins in hip ligament samples between AS and No-AS groups. Key protein was screened by Bioinformatics methods and verified by in vitro experiments. There were 3755 identified proteins, of which 92.916% were quantified. 193 DEPs (49 up-regulated proteins and 144 down-regulated proteins) were identified according to P < 0.01 and Log|FC| > 1. DEPs were mainly involved in cell compartment, including the vacuolar lumen, azurophil granule,primary lysosome, etc. The main KEGG pathway included Phagosome, Glycerophospholipid metabolism, Lysine degradation, Pentose phosphate pathway. Myeloperoxidase (MPO) was identified as a key protein participated in Phagosome pathway, which induces hip lesions in ankylosing spondylitis. Further experiments confirmed that MPO promoted the inflammatory response of fibroblasts in AS-affected hip joint.