Characterization of lymphocyte subpopulations and cardiovascular markers in pericardial fluid of cardiac surgery patients

Accumulation of Inflammatory Mediators in the Normal Pericardial Fluid

There is paucity of studies that focus on the composition of pericardial fluid under resting conditions. The purpose of this study is to determine the levels of inflammatory mediators in pericardial fluid and their correlation with plasma levels in patients undergoing elective cardiac surgery. We conducted a prospective cohort study on candidates for elective aortic valve replacement surgery. Pericardial fluid and peripheral venous blood samples were collected after opening the pericardium. Levels of interleukin 1α (IL-1α); interleukin 1β (IL-1β); interleukin 2 (IL-2) interleukin 4 (IL-4); interleukin 6 (IL-6); interleukin 8 (IL8); interleukin 10 (IL10); tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), vascular endothelial growth factor (VEGF), monocyte chemotactic protein-1 (MCP-1) epidermal growth factor (EGF), soluble E-selectin, L-selectin, P-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) were determined in both pericardial fluid and serum samples. A total of 45 patients with a mean age of 74 years were included of which 66% were males. Serum levels of all study mediators were within normal limits. Serum and pericardial levels of IL-1 α, IL-1 β, IL-2, IL-4, and IL-10 were similar. Levels of VEGF, EGF, VCAM-2, ICAM 1, E-selectin, P-selectin, and L-selectin were significantly lower in pericardial fluid than in serum. However, levels of IL-6, IL-8, TNF-α, IFN-γ, MCP-1, and MCP-1 were significantly higher in the pericardial fluid than in serum. Under normal conditions, the pattern of distribution of different inflammatory mediators in the pericardial fluid does not reflect serum levels. This may either reflect the condition of the underlying myocardium and epicardial fat or the activity of the mesothelial and mononuclear cells present in pericardial fluid.

Regulatory T Cells in Pathological Cardiac Hypertrophy: Mechanisms and Therapeutic Potential

BACKGROUND

Pathological cardiac hypertrophy is linked to immune-inflammatory injury, and regulatory T cells (Tregs) play a crucial role in suppressing immune-inflammatory responses. However, the precise role of Tregs in pathological cardiac hypertrophy remains unclear.

OBJECTIVE

To summarize the current knowledge on the role and mechanisms of Tregs in pathological cardiac hypertrophy and explore their perspectives and challenges as a new therapeutic approach.

RESULTS

Treg cells may play an important protective role in pressure overload (hypertension, aortic stenosis), myocardial infarction, metabolic disorders (diabetes, obesity), acute myocarditis, cardiomyopathy (hypertrophic cardiomyopathy, storage diseases), and chronic obstructive pulmonary disease-related pathological cardiac hypertrophy. Although some challenges remain, the safety and efficacy of Treg-based therapies have been confirmed in some clinical trials, and engineered antigen-specific Treg cells may have better clinical application prospects due to stronger immunosuppressive function and stability.

CONCLUSION

Targeting the immune-inflammatory response via Treg-based therapies might provide a promising and novel future approach to the prevention and treatment of pathological cardiac hypertrophy.

Mechanism of IL-6-related spontaneous atrial fibrillation after coronary artery grafting surgery: IL-6 knockout mouse study and human observation

Clinical observation and ex vivo studies have established a strong association between inflammation and postoperative atrial fibrillation (POAF). However, it is unclear whether the inflammatory phenotype is causally linked to this event or is an epiphenomenon, and it is not known which inflammatory meditators may increase susceptibility to POAF. The limitations of available animal models of spontaneous POAF (sPOAF) makes it difficult to select an experimental system. Here, we provide experimental and clinical evidence for mechanistic involvement of interleukin-6 (IL-6) in sPOAF.

PHASE I

We established a mouse model of cardiac surgery with nonpaced sPOAF. IL-6 knockout mice were protected from sPOAF compared with wild-type mice.

PHASE II

At 48 hours after surgery, the heart was separated into 6 regions and cultured. IL-6 was expressed in all regions, with highest abundance in the left atrium (LA). In PHASE III, we demonstrated that IL-6 in the LA elicited early profibrotic properties in atria via the pSTAT3/STAT3 signaling pathway and contributed to sPOAF.

PHASE IV

In a translational prospective clinical study, we demonstrated that humans with POAF had a higher IL-6 concentration in pericardial drainage (PD). This study provides preliminary evidence of a causal relationship between IL-6 and POAF in a novel nonpaced sPOAF mouse model. IL-6 is a crucial prerequisite for eliciting profibrotic properties in cardiac myocytes via the pSTAT3 pathway during the early postoperative period, leading to an increased susceptibility to POAF. Measuring IL-6 in PD could be a new noninvasive biomarker for the clinical prediction of POAF.

An overview of human pericardial space and pericardial fluid

The pericardium is a double-layered fibro-serous sac that envelops the majority of the surface of the heart as well as the great vessels. Pericardial fluid is also contained within the pericardial space. Together, the pericardium and pericardial fluid contribute to a homeostatic environment that facilitates normal cardiac function. Different diseases and procedural interventions may disrupt this homeostatic space causing an imbalance in the composition of immune mediators or by mechanical stress. Inflammatory cells, cytokines, and chemokines are present in the pericardial space. How these specific mediators contribute to different diseases is the subject of debate and research. With the advent of highly specialized assays that can identify and quantify various mediators we can potentially establish specific and sensitive biomarkers that can be used to differentiate pathologies, and aid clinicians in improving clinical outcomes for patients.