A comparative analysis of HMGB1 and pCTS-L immunomodulatory properties in human peripheral blood mononuclear cells

High Mobility Group Box 1 (HMGB1) and Procathepsin L (pCTS-L) are crucial inflammatory mediators, yet their immunomodulating properties in human immune cells have not been systematically compared. This study employed RNA-sequencing to comparatively analyze their transcriptional effects on primary human peripheral blood mononuclear cells (PBMCs). Our findings demonstrate that while both mediators elicited significant transcriptional changes indicative of robust inflammatory responses, HMGB1 consistently induced a more extensive and diversified inflammatory program. Specifically, at a lower concentration of 0.5 µg/ml, HMGB1 triggered nearly four times more differentially expressed genes (DEGs) than pCTS-L (2.0 µg/ml). Despite this quantitative difference, an overlap of 412 DEGs (272 upregulated, 140 downregulated) revealed shared core inflammatory pathways, including the extensive upregulation of pro-inflammatory cytokines (e.g., IL1A, IL1B, and IL6), chemokines (e.g., CCL2 and CXCL1), and S100 proteins (e.g., S100A8, S100A9, and S100A12). Both mediators also converged on activating the non-canonical NF-κB pathway, evidenced by NFKB2 and RELB upregulation, suggesting a common underlying regulatory mechanism. Notably, HMGB1 uniquely upregulated CASP4 and CASP5—key components of the non-canonical inflammasome pathway—and a broader spectrum of cytokines and chemokines (e.g., IL23A, CXCL5). These findings delineate the distinct yet overlapping roles of HMGB1 and pCTS-L in orchestrating immune responses, offering a foundation for targeted therapeutic development for inflammatory diseases.