Laboratory Investigation of Lipid Metabolic Reprogramming in Pulpitis: The Linolenic Acid-FASN-NR4A1 Axis in Modulating Dental Pulp Inflammation.

Aim: This study explores how lipid metabolic reprogramming contributes to the pathogenesis of pulpitis and identifies key molecular targets involved in regulating inflammation, with the goal of developing metabolic interventions to preserve dental pulp vitality.

Methodology: Primary human dental pulp cells (HDPCs) were stimulated with lipopolysaccharide (LPS) and subjected to integrated transcriptomic and metabolomic profiling to map inflammation-associated metabolic shifts. Functional validation included linolenic acid (LA) supplementation (alone or combined with a Fatty Acid Synthase (FASN) inhibitor, TVB-2640), Nuclear receptor subfamily 4 group A member 1 (NR4A1) knockdown, cytokine/NF-κB assessment (ELISA, Western blot), and lipid droplet/FASN visualisation (immunofluorescence). FASN expression was confirmed in vivo (rat pulpitis model). Key findings were verified in clinical pulpitis samples (histology, immunofluorescence, targeted fatty acid profiling).

Results: LPS stimulation significantly upregulated FASN expression and induced lipid accumulation in HDPCs and rat pulpitis models (p < 0.001). Transcriptomic analysis revealed marked downregulation of NR4A1, while metabolomic profiling showed depletion of key anti-inflammatory/pro-resolving PUFA precursors, including LA and γ-linolenic acid (GLA). Integrated transcriptomic-metabolomic analysis identified LA as a metabolite with high centrality in the lipid metabolic network, and NR4A1 as a significantly downregulated transcription factor linked to multiple lipid-related pathways. LA supplementation suppressed pro-inflammatory cytokines (IL-1β, TNF-α, phosphorylated NF-κB p65) and restored NR4A1 expression (p < 0.05). Combining LA with the FASN inhibitor TVB-2640 synergistically enhanced NR4A1 restoration and anti-inflammatory effects (p < 0.001). siRNA-mediated NR4A1 knockdown abolished the benefits of LA. In human pulpitis tissues, FASN upregulation, NR4A1 downregulation, and elevated palmitic acid were observed (p < 0.001), along with increased levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Conclusions: This study reveals a pathological FASN-LA-NR4A1 regulatory axis linking lipid metabolism to inflammatory amplification in pulpitis. Dual targeting of fatty acid synthesis and lipid depletion-through FASN inhibition and LA supplementation-attenuates inflammation via NR4A1-dependent mechanisms. These findings lay the groundwork for metabolic approaches to modulate inflammation in endodontics.