Proinflammatory cytokines IL-6, IL-1β, TNF-α in infective endocarditis

Abstract

Aim. To study the features of macrophages in the tissues of resected valves in operated patients with infective endocarditis (IE), their significance and interaction with inflammatory markers to improve the effectiveness of IE diagnosis. Materials and methods. Prospectively the research included 25 adult patients with active IE (Duke criteria 2015) and 24 patients with heart defects without IE, hospitalized in a cardiosurgical hospital in Moscow (2021–2022). A standard laboratory and instrumental examination was carried out for the diagnosis of IE, including etiological diagnosis with microbiological and molecular biological methods, and echocardiographic examination of heart. Additionally, the neutrophil-to-lymphocyte ratio (NLR) was calculated. The study of macrophages was carried out in the tissues of resected valves with the determination of the expression of pro- and anti-inflammatory cytokine genes, macrophage markers (CD 68+) using real-time PCR. Results. Increased expression of proinflammatory cytokines IL-1β, TNF-α and IL-6 was revealed in the group of operated patients with IE with significant differences in IL-1β (CI [IQR] 0.00367 [0.00047–0.01553] vs 0.00018 [0.00012–0.00262]; p0.05) and IL-6 (CI [IQR] 0.00367 [0.00047–0.01553] vs 0.00018 [0.00012–0.00262]; p0.05) and IL-6 (CI [IQR] 0.00338 [0.00066–0.01674] vs 0.00054 [0.00044–0.00378]; p0.05). The expression of anti-inflammatory cytokines in valve tissues prevailed in the control group without significant differences from patients with IE. The macrophage marker CD 68+ was revealed in all examined patients with a significant quantitative predominance in the group of patients with IE. There were no differences in the expression of pro- and anti-inflammatory cytokines depending on the presence of embolic events, intracardiac complications, etiological affiliation to S. aureus, as well as hospital mortality and combined endpoint (death from all causes or recurrence of IE 6 months after surgery) in patients with IE with or without events. Cytokines IL-1β and IL-6 positively correlated with each other, with leukocytes and NLR. ROC analysis determined that IL-1β and NLR had the most favorable features for the diagnosis of IE [IL-1β AUC 0.816 (p=0.02), NLR AUC 0.807 (p=0.03)]. IL-6 did not show a diagnostic value in IE. The threshold value for IL-1β was 0.00029 (sensitivity 86.4%, specificity 60.0%, prognostic value of negative result 75.0% and positive 76.0%, AUC 0.761; p=0.008). Conclusion. The valve macrophages of patients with IE express elevated levels of proinflammatory cytokines IL-1β and IL-6, regardless of etiological affiliation or complicated course of IE. IL-1β has a high diagnostic value for determining the inflammatory activity in IE.

Keywords

• infective endocarditis
• cytokines
• macrophages
• diagnosis
• prognosis