PB1288 - Impact of periodontal inflammation on the cardiac tissues in a murine model

Background: Periodontitis is a highly prevalent, oral inflammatory disease of infectious origin associated with cardiovascular worsened outcome, Porphyromonas gingivalis being the main causative pathogen.

Aims: To compare the effects of mechanical and/or P.gingivalis gum injury on the heart tissue in a murine experimental model of periondontitis.

Methods: In C57BL-6 mice, a 2 or 4-weeks gum injury was performed by ligatures with silk thread (LIG) soaked or not with P.gingivalis (LP and LP4w, thrice/week). Data were compared to 2-weeks P.gingivalis oral gavage (gvg), intraperitoneal injection (IP). Other IP-treated mice were simultaneously injected with Cl-amidin (4mg/ml), a PAD4 inhibitor (IP+Inh). After sacrifice, cardiac proteins were extracted from the left heart, pro-atherothrombotic and pro-inflammatory markers assessed by western blot.

Results: Compared to untreated mice (CTL) or P.gingivalis gavage, IP induced elevation of all inflammatory markers in heart tissue: VCAM (IP:0.8±0.1,CTL:0.2±0.05,p < 0.0001), Gasdermin (IP:1.2±0.2,CTL0.2±0.06 p=0.0009),TNF-alpha (IP:1.6± 0.2,CTL:2±0.03 p< 0.0001), IL-6 (IP:1.1±0.6,CTL 0.2±0.05 p< 0.001), IL-10 (IP: 1.2±0.2 CTL 0.3±0.09, p=0.04). PAD-4 only down-regulated IL-10 (IP+INH:0.3 ±0.06, IP:1.2±0.2), suggesting the impact of netosis on anti-inflammatory responses. After 2 weeks-ligature, P.gingivalis-soaked threads significantly upregulated VCAM and Gasdermin (LP:0.5±0.1,p < 0.0001;LP:0.6±0.1, p< 0.001 respectively; CTL:0.2±0.055), while LIG had no effect. A 4-weeks sustained treatment raised the expression of VCAM(LP4W: 0.4±0.03 , CTL 0.2±0.03 p< 0.0001), TNF-alpha (LP4W: 0.7±0.1 ,CTL 0.2±0.03 p< 0.0001) and IL-6 (LP4w: 0.8±0.1, CTL 0.2±0.05 p< 0.001). Strikingly, only the IL-10 expression reached the peak values induced by IP (LP4w: 1.1±0.2,IP: 1.2±0.2 vs CTL0,3±0,09, p=0.04), strongly suggesting an anti-inflammatory effect prompted by P.gingivalis. Indeed, gavage led to elevated IL-10 already after 2 weeks (0.9±0.03).

Conclusion(s): Data confirm the model as suitable for the study of remote cardiac effects by P.gingivalis local infection. Moreover, low but sustained pathogen-induced periodontitis alter the balance of heart inflammatory mediators. The control of netosis appears valuable to preserve or delay heart tissue inflammation.