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.