PPARα modulation of macrophage polarization and inflammatory signaling in mimic periodontitis

Abstract

Objective: This study investigates the role of peroxisome proliferator-activated receptor alpha (PPARα) in regulating macrophage polarization and inflammatory signaling under stimulation by periodontal pathogens. Methodology: THP-1-derived macrophages were stimulated with Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) in the presence or absence of PPARα agonists fenofibrate and WY14643, or the antagonist GW6471. Protein expression levels of TNF-α, IL-10, and phosphorylated NF-κB were assessed by Western blot. Immunofluorescence staining was used to evaluate IL-10, NF-κB, and CD36 expression. Flow cytometry quantified changes in macrophage polarization markers, including CD14+CD86+ (M1) and CD68+CD206+ / CD163+ (M2) populations. THP-1 cells transfected with a secreted embryonic alkaline phosphatase (SEAP) reporter plasmid were treated with Pg-LPS (1 μg/mL) ± fenofibrate (50 μM) to assess NF-κB/AP-1 activity. PPARα reporter cells were treated with increasing concentrations of GW590735 or WY14643 and exposed to TNF-α, LPS, or GW6471+LPS to evaluate PPARα transcriptional activity. Results: PPARα activation by fenofibrate reduced TNF-α expression in Pg-LPS-stimulated macrophages and attenuated NF-κB signaling via both TLR2 and TLR4 pathways. Fenofibrate significantly increased IL-10 and CD36 expression, inhibited Pg-LPS-induced NF-κB nuclear translocation, and promoted a phenotypic shift from pro-inflammatory M1 to anti-inflammatory M2 macrophages. Moreover, inflammatory stimuli such as TNF-α and LPS suppressed PPARα activity, which could be restored by potent PPARα agonists. Conclusion: These findings suggest that PPARα activation modulates macrophage polarization and suppresses inflammatory signaling in response to periodontal bacterial antigens.