Targeting regulatory T cells for cardiovascular diseases

The immune system in cardiovascular diseases: from basic mechanisms to therapeutic implications

Immune system plays a crucial role in the physiological and pathological regulation of the cardiovascular system. The exploration history and milestones of immune system in cardiovascular diseases (CVDs) have evolved from the initial discovery of chronic inflammation in atherosclerosis to large-scale clinical studies confirming the importance of anti-inflammatory therapy in treating CVDs. This progress has been facilitated by advancements in various technological approaches, including multi-omics analysis (single-cell sequencing, spatial transcriptome et al.) and significant improvements in immunotherapy techniques such as chimeric antigen receptor (CAR)-T cell therapy. Both innate and adaptive immunity holds a pivotal role in CVDs, involving Toll-like receptor (TLR) signaling pathway, nucleotide-binding oligomerization domain-containing proteins 1 and 2 (NOD1/2) signaling pathway, inflammasome signaling pathway, RNA and DNA sensing signaling pathway, as well as antibody-mediated and complement-dependent systems. Meanwhile, immune responses are simultaneously regulated by multi-level regulations in CVDs, including epigenetics (DNA, RNA, protein) and other key signaling pathways in CVDs, interactions among immune cells, and interactions between immune and cardiac or vascular cells. Remarkably, based on the progress in basic research on immune responses in the cardiovascular system, significant advancements have also been made in pre-clinical and clinical studies of immunotherapy. This review provides an overview of the role of immune system in the cardiovascular system, providing in-depth insights into the physiological and pathological regulation of immune responses in various CVDs, highlighting the impact of multi-level regulation of immune responses in CVDs. Finally, we also discuss pre-clinical and clinical strategies targeting the immune system and translational implications in CVDs.

Baicalin Relieves Glaesserella parasuis-Triggered Immunosuppression Through Polarization via MIF/CD74 Signaling Pathway in Piglets

Glaesserella parasuis (G. parasuis) infection is responsible for Glässer's disease in pigs. G. parasuis could trigger piglet immunosuppression, but the mechanism of inducing immunosuppression by G. parasuis remains unknown. Macrophage migration inhibitory factor (MIF)/CD74 axis has been shown to participate in inflammation response and immunosuppression, but the function of MIF/CD74 during immunosuppression elicited by G. parasuis has not been fully explored. This experiment explored the efficacy of baicalin on immunosuppression elicited by G. parasuis alleviation through regulating polarization via the MIF/CD74 signaling pathway. Our data indicated that baicalin reduced IL-1β, IL-6, IL-8, IL-18, TNF-α, and COX-2 expression, and regulated MIF/CD74 axis expression in the spleen. Immunohistochemistry analysis showed that baicalin enhanced CD74 protein levels in the spleen of piglets induced by G. parasuis. Baicalin regulated the PI3K/Akt/mTOR signaling pathway and RAF/MEK/ERK signaling activation, modified the expression of the autophagy-related proteins Beclin-1, P62, and LC3B, promoted M2 polarization to M1 polarization, and enhanced CD3, CD4, CD8, and TIM3 levels in the spleen of piglets elicited by G. parasuis. Our study reveals the important functions of the MIF/CD74 axis in G. parasuis-induced immunosuppression and may offer a new therapeutic method to control G. parasuis infection.

Role of Peripheral Blood Regulatory T Cells and IL-2 in the Collateral Circulation of Acute Ischemic Stroke

Background

Inflammation is recognized as a pivotal factor in the pathophysiology of acute ischemic stroke (AIS) and has the potential to influence the collateral circulation of patients. The objective of this investigation was to explore the link between peripheral regulatory T cells (Tregs), interleukin-2 (IL-2), and the status of collateral circulation.

Methods

Between September 2023 and May 2024, the study incorporated 117 AIS patients from the neurology department, with 60 identified as having good collateral status (GCS) and 57 with poor collateral status (PCS). Additionally, a control group of 46 healthy individuals was included. Collateral circulation in AIS patients was assessed via computed tomography angiography. The levels of peripheral blood Tregs were quantified through flow cytometry, while IL-2 was measured by ELISA.

Results

In this investigation, patients diagnosed with PCS demonstrated reduced Tregs (5.77 ± 1.55%) and IL-2 levels (7.37 ± 2.61 pg/mL) compared to individuals with GCS (7.09 ± 1.32%, 9.95 ± 3.58 pg/mL) and healthy controls (7.17 ± 1.40%,10.33 ± 4.01 pg/mL). Logistic regression analysis identified significant associations between Tregs and IL-2 levels and collateral circulation status (p<0.05), with diminished levels of both being independent predictors of PCS when compared to GCS. A nomogram was developed to forecast risk factors for collateral circulation, further highlighting the potential of plasma Tregs and IL-2 levels as biomarkers in predicting collateral circulation among AIS patients. The diagnostic performance of Tregs and IL-2 was assessed utilizing receiver operating characteristic (ROC) analysis. The area under the ROC curve (AUC) for Tregs in differentiating GCS from PCS patients was ascertained to be 0.741 (95% confidence interval [CI]: 0.652-0.830), while for IL-2, it was 0.710 (95% CI: 0.618-0.803). Moreover, the combined measurement of Tregs and IL-2 resulted in an AUC of 0.779 (95% CI: 0.695-0.863).

Conclusion

Plasma levels of peripheral blood Tregs and IL-2 may function as promising biomarkers for the prediction of collateral circulation status, suggesting potential new therapeutic approaches aimed at enhancing cerebral collateral circulation, and providing new therapeutic targets for acute ischemic stroke.

Immunometabolism in the Aging Heart

Structural, functional, and molecular-level changes in the aging heart are influenced by a dynamic interplay between immune signaling and cellular metabolism that is referred to as immunometabolism. This review explores the crosstalk between cellular metabolic pathways including glycolysis, oxidative phosphorylation, fatty acid metabolism, and the immune processes that govern cardiac aging. With a rapidly aging population that coincides with increased cardiovascular risk and cancer incidence rates, understanding the immunometabolic underpinnings of cardiac aging provides a foundation for identifying therapeutic targets to mitigate cardiac dysfunction. Aging alters the immune environment of the heart by concomitantly driving the changes in immune cell metabolism, mitochondrial dysfunction, and redox signaling. Shifts in these metabolic pathways exacerbate inflammation and impair tissue repair, creating a vicious cycle that accelerates cardiac functional decline. Treatment with cancer therapy further complicates this landscape, as aging-associated immunometabolic disruptions augment the susceptibility to cardiotoxicity. The current review highlights therapeutic strategies that target the immunometabolic axis to alleviate cardiac aging pathologies. Interventions include modulating metabolic intermediates, improving mitochondrial function, and leveraging immune signaling pathways to restore cardiac health. Advances in immunometabolism thus hold significant potential for translating preclinical findings into therapies that improve the quality of life for the aging population and underscore the need for approaches that address the immunometabolic mechanisms of cardiac aging, providing a framework for future research.

Regulatory T-cells: The Face-off of the Immune Balance

Regulatory T-cells (Tregs) play a crucial role in maintaining immune homeostasis, ensuring a balanced immune response. Tregs primarily operate in an antigen-specific fashion, facilitated by their distinct distribution within discrete niches. Tregs have been studied extensively, from their point of origin in the thymus origin to their fate in the periphery or organs. Signals received from antigen-presenting cells (APCs) stimulate Tregs to dampen inflammation. Almost all tumors are characterized by a pathological abundance of immune suppression in their microenvironment. Conversely, the lack thereof proves detrimental to immunological disorders. Achieving a balanced expression of Tregs in relation to other immune compartments is important in establishing an effective and adaptable immune tolerance towards cancer cells and autoantigens. In the context of cancer, it is essential to decrease the frequency of Tregs to overcome tumor suppression. A lower survival rate is associated with the presence of excessive exhausted effector immune cells and an increased frequency of regulatory cells. However, when it comes to treating graft rejection and autoimmune diseases, the focus lies on immune tolerance and the transfer of Tregs. Here, we explore the complex mechanisms that Tregs use in human disease to balance effector immune cells.

Peripheral inflammation as a potential mechanism and preventive strategy for perioperative neurocognitive disorder under general anesthesia and surgery

General anesthesia, as a commonly used medical intervention, has been widely applied during surgical procedures to ensure rapid loss of consciousness and pain relief for patients. However, recent research suggests that general anesthesia may be associated with the occurrence of perioperative neurocognitive disorder (PND). PND is characterized by a decline in cognitive function after surgery, including impairments in attention, memory, learning, and executive functions. With the increasing trend of population aging, the burden of PND on patients and society's health and economy is becoming more evident. Currently, the clinical consensus tends to believe that peripheral inflammation is involved in the pathogenesis of PND, providing strong support for further investigating the mechanisms and prevention of PND.

Beyond the Granuloma: New Insights into Cardiac Sarcoidosis Using Spatial Proteomics

Cardiac sarcoidosis is poorly understood, challenging to diagnose, and portends a poor prognosis. A lack of animal models necessitates the use of residual human samples to study sarcoidosis, which in turn necessitates the use of analytical tools compatible with archival, fixed tissue. We employed high-plex spatial protein analysis within a large cohort of archival human cardiac sarcoidosis and control tissue samples, studying the immunologic, fibrotic, and metabolic landscape of sarcoidosis at different stages of disease, in different cardiac tissue compartments, and in tissue regions with and without overt inflammation. Utilizing a small set of differentially expressed protein biomarkers, we also report the development of a predictive model capable of accurately discriminating between control cardiac tissue and sarcoidosis tissue, even when no histologic evidence of sarcoidosis is present. This finding has major translational implications, with the potential to markedly improve the diagnostic yield of clinical biopsies obtained from suspected sarcoidosis patients.

Cardiac fibrogenesis: an immuno-metabolic perspective

Cardiac fibrosis is a major and complex pathophysiological process that ultimately culminates in cardiac dysfunction and heart failure. This phenomenon includes not only the replacement of the damaged tissue by a fibrotic scar produced by activated fibroblasts/myofibroblasts but also a spatiotemporal alteration of the structural, biochemical, and biomechanical parameters in the ventricular wall, eliciting a reactive remodeling process. Though mechanical stress, post-infarct homeostatic imbalances, and neurohormonal activation are classically attributed to cardiac fibrosis, emerging evidence that supports the roles of immune system modulation, inflammation, and metabolic dysregulation in the initiation and progression of cardiac fibrogenesis has been reported. Adaptive changes, immune cell phenoconversions, and metabolic shifts in the cardiac nonmyocyte population provide initial protection, but persistent altered metabolic demand eventually contributes to adverse remodeling of the heart. Altered energy metabolism, mitochondrial dysfunction, various immune cells, immune mediators, and cross-talks between the immune cells and cardiomyocytes play crucial roles in orchestrating the transdifferentiation of fibroblasts and ensuing fibrotic remodeling of the heart. Manipulation of the metabolic plasticity, fibroblast-myofibroblast transition, and modulation of the immune response may hold promise for favorably modulating the fibrotic response following different cardiovascular pathological processes. Although the immunologic and metabolic perspectives of fibrosis in the heart are being reported in the literature, they lack a comprehensive sketch bridging these two arenas and illustrating the synchrony between them. This review aims to provide a comprehensive overview of the intricate relationship between different cardiac immune cells and metabolic pathways as well as summarizes the current understanding of the involvement of immune-metabolic pathways in cardiac fibrosis and attempts to identify some of the previously unaddressed questions that require further investigation. Moreover, the potential therapeutic strategies and emerging pharmacological interventions, including immune and metabolic modulators, that show promise in preventing or attenuating cardiac fibrosis and restoring cardiac function will be discussed.

Diagnostic criteria for myocarditis on cardiac magnetic resonance imaging: an educational review

Acute myocarditis represents one of the most mysterious acute cardiovascular diseases due to the great diversity of its clinical presentation, ranging from simple symptoms such as flu-like syndrome to lethal conditions such as cardiogenic shock or sudden cardiac death. The diagnosis will be suspicious in the presence of chest pain in a subject with risk factors, and guided mainly by the ECG, biological markers, trans-thoracic echocardiography, and the cardiac MRI. In this sense, and returning to the pathophysiological bases of this condition, the positive diagnosis will rely mainly on the detection of tissue abnormalities secondary to the myocardial inflammatory storm. Cardiac MRI represents a diagnostic pillar, given the information it can provide, both in analyzing the morphology, and the myocardial function but also tissue abnormalities that represent the main element of the diagnostic criteria of Lake Louisse.

Blood Immune Cell Alterations in Patients with Hypertensive Left Ventricular Hypertrophy and Heart Failure with Preserved Ejection Fraction

(1) Background: Chronic inflammation and fibrosis are key players in cardiac remodeling associated with left ventricular hypertrophy (LVH) and heart failure with a preserved ejection fraction (HFpEF). Monocytes and T-helpers (Th) are involved in both pro-inflammatory and fibrotic processes, while regulatory T-cells (Treg) could be considered to suppress chronic inflammation in the hypertrophied myocardium. We aimed to estimate the relationship between the frequencies of circulating CD4⁺ T-cell and monocyte subpopulations and the variables of left ventricular (LV) diastolic function in patients with LVH depending on the presence of HFpEF. (2) Methods: We enrolled 57 patients with asymptomatic hypertensive LVH (n = 21), or LVH associated with HFpEF (n = 36). A clinical assessment and echocardiographs were analyzed. CD4⁺ Treg, activated Th (Th-act), and monocyte (classical, intermediate, and non-classical) subpopulations were evaluated via direct immunofluorescence and flow cytometry. (3) Results: Patients with HFpEF had a lower Treg/Th-act ratio (p = 0.001). Though asymptomatic patients and patients with HFpEF were comparable in terms of both the total monocyte number and monocyte subsets, there were moderate correlations between intermediate monocyte count and conventional and novel echocardiographic variables of LV diastolic dysfunction in patients with HFpEF. (4) Conclusions: In patients with LVH, the clinical deterioration (transition to HFpEF) and progression of LV diastolic dysfunction are probably associated with T-cell disbalance and an increase in intermediate monocyte counts.