Salivary Inflammatory Biomarkers in Chronic Non-Specific Low Back Pain Patients

Objectives To determine the expression level of inflammatory mediators in the saliva of Chronic Non-Specific Low Back Pain (CNSLBP) Patients compared to asymptomatic healthy individuals. Methods Twenty-eight patients with CNSLBP and Twenty-eight age and sex-matched asymptomatic participants were selected according to specific inclusion and exclusion criteria. Saliva samples were collected, and total RNA was isolated. Reverse transcription and qPCR were performed using the Quant Studio 3 Real-Time PCR system, ThermoFisher Scientific. Bioinformatics analysis was performed using the STRING database to explore cytokine protein-protein interaction (PPI) and miRNet for miRNA network analysis. Results The expression levels of IL-18, TNFα, IL-6, HMGB1, IFNG, IL-2, IL-8, and IL-1β were increased in the saliva of LBP patients compared to the control group. A STRING database analysis of IL-18 protein-protein interactions (PPI) reveals that the PPI enrichment is highly significant, with a p-value < 1.0e-16, and the gene ontology biological process revealed its role in regulating the inflammatory response and other cytokine production. miRNet analysis showed that multiple miRNAs can target more than 1 cytokine. Conclusion The expression levels of inflammatory mediators including IL-18, TNFα, IL-6, HMGB1, IFNG, IL-2, IL-8, and IL-1β were increased in the saliva of CNSLBP patients compared to the control group. A STRING database analysis of IL-18 protein-protein interactions (PPI) reveals that the PPI enrichment is highly significant, with a p-value < 1.0e-16. IL-18 interacts with other cytokines including IL-6, TNF, IL-1B, IFNG, and IL-8. Gene ontology (biological process) revealed its role in regulating the inflammatory response and the production of other cytokines and chemokines. miRNet analysis showed that multiple miRNAs can target both IL-1B and IL-6 including hsa-let-7a-5p, hsa-let-7c-5p, hsa-let-7d-5p, hsa-miR-21-5p, hsa-miR-23a-3p, hsa-miR-25-3p, hsa-miR-26a-5p, and hsa-miR-26b-5p.