Low-grade systemic inflammation in patients with long COVID: The role of imbalance of endotoxin-releasing systems and vasoconstrictor markers

Background. Currently, the pathophysiological mechanisms of acute damage to organs and systems caused by coronavirus infection have been studied quite fully, but the mechanisms underlying the clinical manifestations of long COVID have not yet been accurately described. The mechanisms of persistence of a number of symptoms in patients who have had COVID-19 and the role of systemic inflammation and endotoxemia markers in it remain a understudied aspect and a promising direction for further studying. The aim of the study. To assess the markers of systemic inflammation, endotoxin-releasing systems, intestinal permeability and endothelial dysfunction in patients with long COVID at the stage of health resort treatment. Methods. The study included 32 patients who had recovered from coronavirus infection and were undergoing health resort treatment in the pulmonology department of the I.M. Sechenov Academic Research Institute for Physical Therapy, Medical Climatology and Rehabilitation. We also selected a control group (n = 20). All patients underwent peripheral blood analysis to detect the levels of markers of systemic inflammation, endotoxin-releasing systems, intestinal permeability, endothelial dysfunction and vasoconstrictor agents: C-reactive protein (CRP), lipopolysaccharide-binding protein (LPB), tissue-type plasminogen activator (tPA), zonulin, bactericidal/ permeability-increasing protein (BPI), vasopressors of angiotensin 2 and endothelin (EDN1). Results. Patients who had recovered from coronavirus infection had a statistically significant increase in the levels of CRP (3.4 [2.56; 4.0] mg/l), LBP (18.46 [14.0; 25.5] ng/ml), tPA (0.07 [0.02; 0.32] ng/ml), angiotensin 2 (133.3 [63.0; 503.7] pg/ml) and a decrease in the level of BPI (1576 [276; 3588] pg/ml) (p < 0.05). Conclusion. A statistically significant increase in markers of systemic inflammation, endotoxinemia, and vasoconstrictor agents in patients with long COVID indicates an imbalance in endotoxin-binding and endotoxin-releasing systems in patients who have had coronavirus infection. Further study of the described markers is necessary to improve approaches to long-term personalized therapy for this category of patients.