Neutrophil cytosolic factor 4 may serve as a potential biomarker for ankylosing spondylitis

In recent years, biomarkers have gained prominence in the pursuit of early diagnosis for ankylosing spondylitis (AS) and in the selection of appropriate treatment for patients. A recent article published in the Journal of Musculoskeletal and Neuronal Interactions suggests that Neutrophil Cytosolic Factor 4 (NCF4) could serve as a diagnostic and prognostic biomarker for AS. 

The study included ten patients from The First Hospital of Qiqihar, divided into AS (n=5) and control (n=5) groups. Researchers employed GEO2R and weighted gene co-expression network analysis (WGCNA) to identify differentially expressed genes (DEGs) and key modules, and analyzed Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein-protein interactions (PPI) to identify core genes. The analysis revealed 1,100 DEGs and a brown module, with 444 core genes associated with specific pathways. PPI analysis showed a key module comprising six genes linked to the phagosome pathway. Upon KEGG pathway analysis of DEGs, NCF4 was identified as a biomarker gene related to the phagocytic pathway. 

The level of NCF4 expression in patients with AS was found to be closely associated with erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels. Additionally, there was a significant decrease in NCF4 expression after anti-TNF medication, suggesting its potential as a target gene for AS treatment. The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) demonstrated a positive linear correlation with NCF4 expression, with higher scores indicating increased expression. Quantitative real-time reverse-transcription PCR (qRT-PCR) results indicated significantly higher mRNA expression of NCF4 in the AS clinical samples group (AS group) compared to the normal control group (NC group). Similarly, Western blot analysis revealed elevated protein levels of NCF4 in the AS group. Both qRT-PCR and Western blot analyses were performed on peripheral blood samples collected before and after anti-TNF therapy. Results indicated that mRNA and protein expression of NCF4 were significantly higher in the before group than in the after group, suggesting that anti-TNF therapy regulates the phagosome pathway in the treatment of AS by inhibiting NCF4 expression. 

NCF4 plays a crucial role in the phagocytic pathway and the gene product acts as a cytosolic regulator of phagocyte NADPH-oxidase, which is a vital enzyme system for host defense. Chronic granulomatous disease (CGD) is a primary phagocytic immunodeficiency caused by a lack of NADPH oxidase (PHOX), resulting from genetic variations in NCF4 and subsequent deficiency of Nox2 oxidase in phagocytic cells. 

The present findings suggest that anti-TNF therapy in AS may act by inhibiting NCF4 expression and regulating the phagocytosis process. Therefore, NCF4 has the potential to serve as a biomarker for the diagnosis and prognosis of AS. However, further verification of the role and function of NCF4 through clinical trials or cytological experiments is necessary. 

 Reference 

  1. Liu S, Zhu H. Anti-TNF Therapy Regulates Phagosome Pathway by Inhibiting NCF4 Expression to Treat Ankylosing Spondylitis. J Musculoskelet Neuronal Interact. 2023 Sep 1;23(3):355–64. 
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