Role of S100b protein and BDNF in immunopathogenesis of neuroinflammation in the patients with induced immunocompromised state

Post-operation cognitive dysfunctions, related to mild manifestations of neurological pathology occuring after surgery, represent an important challenge for both fundamental and clinical medicine. The underlying phenomena of neuroinflammation are still poorly understood and discutable. The studies in immunopathogenesis of neuroinflammation may help in understanding the development of pathology and suggest ways to solve this problem. A special role for implementation of this process belongs to neuropeptides. Objective: to characterize immunopathogenesis of neuroinflammation in the individuals with immunocompromised state induced during aorto-coronary bypass surgery. A total of 110 patients with ischemic heart disease who underwent myocardial revascularization under extracorporeal circulation conditions were examined. Pathological neuroinflammation was recognized by development of postoperative cognitive dysfunction based on changing results of the cognitive examination (Montreal scale, MoCa test). The patients were tested before intervention, and on day 7 after surgery. According to the test results, all the patients were divided into 2 groups: (1) without signs of postoperative cognitive dysfunction and (2) with the mentioned signs. Venous blood was collected four times, on the day of surgery before the intervention, immediately after the surgery, 24 hours later, and on the 7^th day after surgery. S100b and BDNF contents were determined in the venous blood serum. The baseline level of the S100b protein in the study groups did not differ from the reference values. After surgery, an increase in S100b was observed in both groups, but in patients with emerging postoperative cognitive dysfunction, these indexes were significantly higher. Despite a tendency for stabilization, the increased level of neuropeptides persisted 24 hours after the surgery; on the 7^th day, the index was within the reference values, but in the 1^st group it was lower than in the 2^nd group. Prior to the operation, the BDNF level was significantly higher in the patients from group 1, compared with group 2. In the second group, the index was lower than the values obtained from the control group volunteers. After surgery, the values of BDNF in blood serum showed some differences: immediately after surgery, the level of neuropeptide was higher in patients without cognitive dysfunction. On day 7, the level of BDNF was within reference values, but in patients from group 2, the values were higher than in group 1.