Oral Barrier Immunometabolism in Chronic Low-Grade Inflammation: Molecular Mechanisms and Systemic Implications

Chronic low-grade inflammation is a hallmark of aging and a major driver of metabolic and degenerative diseases. While systemic immune dysfunction has been widely investigated, the contribution of barrier tissues to persistent inflammatory signaling remains incompletely defined. The oral mucosa represents a uniquely exposed barrier, continuously challenged by microbial, mechanical, and metabolic stressors and characterized by a specialized immune architecture. Here, we synthesize current evidence supporting the oral barrier as an active immunometabolic interface linking local immune activation to systemic inflammatory tone. Spatially organized epithelial, neutrophil, and antigen-presenting cell (APC) compartments coordinate immune responses tightly coupled to metabolic reprogramming, including hypoxia-inducible factor-1α (HIF-1α)-dependent glycolysis and mitochondrial reactive oxygen species (mtROS) production. In parallel, the oral microbiota provides ligands and metabolites such as lipopolysaccharide (LPS), short-chain fatty acids (SCFAs), and succinate, which activate pattern-recognition receptors (PRRs), including toll-like receptors (TLRs) and the NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome, thereby sustaining nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB)-mediated inflammatory signaling. Barrier disruption and dysbiosis promote microbial translocation and persistent innate immune activation, while saliva and gingival crevicular fluid facilitate systemic dissemination of inflammatory mediators. Overall, sustained immunometabolic engagement at the oral barrier emerges as a key driver of chronic low-grade systemic inflammation and a potential therapeutic target in inflammaging.