Th17/Treg balance and indoleamine 2,3 dioxygenase activity in periodontitis-associated atherosclerotic patients

OBJECTIVE: This study investigated the peripheral Th17/Treg balance and its potential controlling factor indoleamine 2,3 dioxygenase (IDO) in patients with periodontitis and atherosclerosis (AS), as well as its correlation with Porphyromonas gingivalis infection. METHODS: In this retrospective study, P. gingivalis-infected atherosclerotic patients (Pg-AS), atherosclerotic patients (AS), P. gingivalis-infected periodontitis patients (Pg), and healthy controls (HCs) were selected after clinical examination, subgingival plaque examination, and plasma anti-P. gingivalis antibody analysis. Treg and Th17 cell percentages, related transcription factors, and functional cytokines in peripheral blood were analysed. Plasma tryptophan (Trp) and kynurenine (Kyn) were measured to determine IDO activity. RESULTS: Atherosclerotic patients (Pg-AS and AS groups) had significantly lower IDO activity and higher Th17/Treg ratio than those in the Pg and HC groups. The Th17/Treg ratio was higher and IDO activity was lower in the Pg-AS group compared with the AS group. Transcription factors and cytokines exhibited the same trend as the Th17 and Treg cells. Additionally, IDO activity was negatively correlated with the plasma anti-P. gingivalis antibody titre and the Th17/Treg ratio in the atherosclerotic group. CONCLUSIONS: P. gingivalis may reduce IDO activity and further promote Th17/Treg imbalance to facilitate AS development. IDO may be a novel molecular marker to predict periodontitis-associated AS.