Temporal expression of CXCR2 ligands in a rat model of LPS-induced pulpitis.

Neutrophils play a central yet dual role in pulpitis, the inflammatory response to dental caries. Because CXCR2 ligands regulate neutrophil recruitment and function, this study focused on the temporal expression of two major CXCR2 ligands (CXCL1 and CXCL2) during the progression of LPS induced pulpitis. A controlled rat model of progressive pulpitis (n = 102) was developed using LPS from Escherichia coli or PBS applied to mechanically exposed pulp, followed by sealing of the pulp–dentin wound to allow inflammation to progress over defined time points. Extracted teeth underwent histological, immunohistochemical (myeloperoxidase, CXCL1, CXCL2) and genomic analyses (IL-6, MMP-9, CXCL1).The model reproduced the temporal dynamics of pulp–dentin inflammation, with a progressive increase in IL-6 expression and tissue alterations. IL-6 and MMP-9 transcription suggested a pivotal shift in the inflammatory process around 48 h. Neutrophil recruitment and activation, reflected by myeloperoxidase expression, closely paralleled tissue damage. Interestingly, CXCL1 correlated with neutrophil activity and lesion severity, whereas CXCL2 showed delayed and localized expression, indicating a potential role in fine-tuning the response. As this study focused specifically on ligand dynamics, it characterizes the temporal pattern of CXCL1 and CXCL2 expression and provides new insight into chemokine‑driven inflammatory processes during pulpitis in rat.