Imaging Inflammation Past, Present, and Future: Focus on Cardioimmunology

SPECT Imaging of Cardiac Inflammation by Targeting IL4 Receptor-α on Macrophages

The inflammation response is a prominent sign of myocardial infarction (MI), mediating the process of cardiac fibrosis and ventricular remodeling. Inflammation visualization holds new promise for guiding cardiac anti-inflammatory therapy. Interleukin-4 receptor α (IL4Rα) interacts with IL4, closely related to macrophage polarization. This study aimed to evaluate the feasibility of a technetium-99m (99mTc) labeled IL4Rα antibody probe ([99mTc]Tc-HYNIC-CM310) for targeting postinfarction macrophage SPECT imaging. [99mTc]Tc-HYNIC-CM310 was prepared by radiolabeling an IL4Rα-specific monoclonal antibody (CM310) with 99mTc. Images were acquired at 0.5, 6, 12, 24, and 36 h postinjection on the next day after MI and the sham model preparation, and a biodistribution study was performed at 36 h. The mean percentage of injected dose per gram (%ID/g) of various tissues was obtained by drawing the regions of interest. [18F]FDG myocardial metabolism and inflammation imaging were performed for comparison and verification. Immunofluorescence costaining and flow cytometry were conducted to validate the coexpression of IL4Rα and macrophages. The radiolabeling yield of [99mTc]Tc-HYNIC-CM310 was approximately 88.31% ± 1.70%, and the radiochemical purity was 93.70% ± 0.38%. The accumulation of [99mTc]Tc-HYNIC-CM310 in infarcted myocardium was increased starting at 12 h postinjection. The tracer uptake was significantly higher in the infarcted myocardium than the same site in sham-operated rats (P < 0.05). The tracer uptake region was consistent with the cardiac metabolic defect and inflammatory region seen by [18F]FDG PET. Immunofluorescence staining and flow cytometry confirmed the colocalization of IL4Rα+ cells and macrophage markers in the infarcted myocardium. We successfully prepared and validated the SPECT probe [99mTc]Tc-HYNIC-CM310 for precise visualization of macrophages, offering a new opportunity for guiding the treatment of cardiac inflammation.

Mechanisms of diabetic cardiomyopathy: Focus on inflammation

PURPOSE OF REVIEW

Type 2 diabetes (T2D) significantly increases the risk of heart failure (HF), either through the progression of coronary artery disease (CAD) or through direct myocardial alterations, termed diabetic cardiomyopathy. This review examines key pathophysiological mechanisms underlying diabetic cardiomyopathy, focusing on the role of inflammation. It also addresses diagnostic and therapeutic approaches to mitigate myocardial damage in T2D.

RECENT FINDINGS

Chronic low-grade inflammation is considered as a major contributor to diabetic cardiomyopathy. T2D-related factors, including hyperglycemia and insulin resistance, activate inflammatory pathways that worsen myocardial dysfunction. Despite advances in understanding these mechanisms, no therapies specifically targeting the cardiac changes in T2D have been identified.

SUMMARY

While significant advances have been made in elucidating the inflammatory mechanisms contributing to diabetic cardiomyopathy, therapeutic advancements remain limited, potentially due to an incomplete understanding of regulatory pathways. A comprehensive investigation into the specific roles of immune cells and inflammatory mediators in diabetic cardiomyopathy is essential for identifying novel therapeutic targets. Expanding our knowledge of these molecular mechanisms has the potential to facilitate the development of innovative therapeutic strategies, thereby improving clinical outcomes in patients with T2D.

Positron Emission Tomography Imaging of the Adaptive Immune System in Cardiovascular Diseases

Cardiovascular diseases are the leading cause of death around the globe. In recent years, a crucial role of the immune system has been acknowledged in cardiac disease progression, opening the door for immunomodulatory therapies. To this ongoing change of paradigm, positron emission tomography (PET) imaging of the immune system has become a remarkable tool to reveal immune cell trafficking and monitor disease progression and treatment response. Currently, PET imaging of the immune system in cardiovascular disease mainly focuses on the innate immune system such as macrophages, while the immune cells of the adaptive immune system including B and T cells are less studied. This can be ascribed to the lack of radiotracers specifically binding to B and T cell biomarkers compatible with PET imaging within the cardiovascular system. In this review, we summarize current knowledge about the role of the adaptive immune system (e.g., B and T cells) in major cardiovascular diseases and introduce key biomarkers for specific targeting of these immune cells and their subpopulations. Finally, we present available radiotracers for these biomarkers and propose a pathway for developing probes or optimizing those already used in other fields (e.g., oncology) to make them compatible with the cardiovascular system.

Non-invasive Assessment of Coronary Artery Disease: The Role of AI in the Current Status and Future Directions

Coronary artery disease (CAD) remains a significant public health concern due to its high morbidity and mortality rates. Early detection and timely evaluation are crucial for improving patient outcomes. While both invasive and non-invasive methods are available for assessing CAD risk, non-invasive approaches minimize the complications associated with invasive procedures. Over the past two decades, advancements in artificial intelligence (AI), particularly machine learning techniques such as deep learning and natural language processing, have revolutionized cardiology. These technologies enhance diagnostic accuracy and clinical efficiency in non-invasive CAD evaluation. However, the broader adoption of AI faces critical challenges, including ethical concerns such as data privacy, high computational costs, and resource allocation disparities. This article explores the current landscape of non-invasive CAD assessment, highlighting the transformative potential and associated challenges of AI integration.

Human and gut microbiota synergy in a metabolically active superorganism: a cardiovascular perspective

Despite significant advances in diagnosis and treatment over recent decades, cardiovascular disease (CVD) remains one of the leading causes of morbidity and mortality in Western countries. This persistent burden is partly due to the incomplete understanding of fundamental pathogenic mechanisms, which limits the effectiveness of current therapeutic interventions. In this context, recent evidence highlights the pivotal role of immuno-inflammatory activation by the gut microbiome in influencing cardiovascular disorders, potentially opening new therapeutic avenues. Indeed, while atherosclerosis has been established as a chronic inflammatory disease of the arterial wall, accumulating data suggest that immune system regulation and anti-inflammatory pathways mediated by gut microbiota metabolites play a crucial role in a range of CVDs, including heart failure, pericardial disease, arrhythmias, and cardiomyopathies. Of particular interest is the emerging understanding of how tryptophan metabolism-by both host and microbiota-converges on the Aryl hydrocarbon Receptor (AhR), a key regulator of immune homeostasis. This review seeks to enhance our understanding of the role of the immune system and inflammation in CVD, with a focus on how gut microbiome-derived tryptophan metabolites, such as indoles and their derivatives, contribute to cardioimmunopathology. By exploring these mechanisms, we aim to facilitate the development of novel, microbiome-centered strategies for combating CVD.

Difluoromethoxide Is a Strong Leaving Group in the Photoredox Deoxyradiofluorination of 2-Phenylpyridines

A 2-phenyl-3-difluoromethoxy-pyridinyl moiety features in potent phosphodiesterase 4D inhibitors that are considered to be candidate radiotracers for positron emission tomography if they are labeled with fluorine-18. Fluorine-18 could be installed as desired at the 3'-phenyl position with acridinium-mediated photoredox radiodeoxyfluorination in homologues bearing variously substituted 3'-aryloxy groups. However, a distal 3-difluoromethoxide (-OCHF2) group strongly competes as a leaving group, especially when an electron-deficient aryloxy group is present at position 3'. A yield of up to 50% may occur without observable 19F for 18F exchange.