Energetic Stress-Induced Metabolic Regulation by Extracellular Vesicles

Mapping Organism-wide Single Cell mRNA Expression Linked to Extracellular Vesicle Biogenesis, Secretion, and Cargo

Extracellular vesicles (EVs) are functional lipid-bound nanoparticles trafficked between cells and found in every biofluid. It is widely claimed that EVs can be secreted by every cell, but the quantity and composition of these EVs can differ greatly among cell types and tissues. Defining this heterogeneity has broad implications for EV-based communication in health and disease. Recent discoveries have linked single-cell EV secretion to the expression of genes encoding EV machinery and cargo. To gain insight at single-cell resolution across an entire organism, we compared the abundance, variance, and co-expression of 67 genes involved in EV biogenesis and secretion, or carried as cargo, across >44 000 cells obtained from 117 cell populations in the Tabula Muris. Our analysis provides both novel holistic and cell population-specific insight into EV biology. The highest overall expression of EV genes occurs in secretory cells of the pancreas and perhaps more surprisingly, multiple non-neuronal cell populations of the brain. We find that the most abundant EV genes encode the most abundant EV cargo proteins (tetraspanins and syndecans), but these genes are highly differentially expressed across functionally distinct cell populations. Expression variance identifies dynamic and constitutively expressed EV genes while co-expression analysis reveals novel insights into cell population-specific coordination of expression. Results of our analysis illustrate the diverse transcriptional regulation of EV genes which could be useful for predicting how individual cell populations might communicate via EVs to influence health and disease.

Exploring the mechanism and crosstalk between IL-6 and IL- 1β on M2 macrophages under metabolic stress conditions

Macrophages are highly variable immune cells that are important in controlling inflammation and maintaining tissue balance. The ability to polarize into two major types-M1, promoting inflammation, and M2, resolving inflammation and contributing to tissue repair-determines their specific roles in health and disease. M2 macrophages are particularly important for reducing inflammation and promoting tissue regeneration, but their function is shaped mainly by surrounding cells. This is evident in obesity, diabetes, and chronic inflammation. Although many cytokines regulate macrophage polarization, interleukin-6 (IL-6) and interleukin-1β (IL-1β) are major players, but their effects on M2 macrophage behavior under metabolic stress remain unclear. This study describes the intricacies within M2 macrophages concerning IL-6 and IL-1β signaling when under metabolic stress. Though, more frequently than not, IL-6 is labelled as pro-inflammatory, it can also behave as an anti-inflammatory mediator. On the other hand, IL-1β is the main pro-inflammatory agent, particularly in metabolic disorders. The relationship between these cytokines and the macrophages is mediated through important pathways such as JAK/STAT and NFκB, which get perturbed by metabolic stress. Therefore, metabolic stress also alters the functional parameters of macrophages, including alterations in mitochondrial metabolism, glycolytic and oxidative metabolism. Phosphorylation alters the kinetics involved in energy consumption and affects their polarization and their function. However, it has been suggested that IL-6 and IL-1β may work in concert or competition when inducing M2 polarization and, importantly, implicate cytokine release, phagocytic activity, and tissue repair processes. In this review, we discuss the recent literature on the participation of IL-6 and IL-1β cytokines in macrophage polarization and how metabolic stress changes cytokine functions and synergistic relations. A better understanding of these cytokines would serve as an important step toward exploring alternative antiviral strategies directed against metabolic disturbance and, hence, approve further endeavors.

Brain penetration of peripheral extracellular vesicles from Alzheimer's patients and induction of microglia activation

Alzheimer's disease (AD) is an age-related neurodegenerative pathology. Brain-derived extracellular vesicles (EVs) have been demonstrated to be implicated in AD pathogenesis by facilitating the propagation of Tau, amyloid-β and inflammatory cytokines. However, the impact of peripheral EVs (pEVs) in AD pathogenesis remains poorly investigated. The objective of our study was to compare the passage of pEVs from adults, cognitively healthy elderly, and AD patients through the blood-brain barrier (BBB), to evaluate their uptake in the brain and to assess their impact on the microglia activity using in vitro and in vivo models. To this end, pEVs were enriched, characterized, and fluorescently labelled. The passage of pEVs through the endothelial bEnd.3 cells was studied in a Transwell device with either neuronal or microglia cells seeded at the bottom of the well. Following the internalization of pEVs from AD patients, microglia adopted an amoeboid morphology and released a heightened level of pro-inflammatory cytokine IL-6. To further assess their in vivo transport across the BBB, pEVs were injected into the blood circulation of 2-days post-fertilization Tg(flk1:EGFP) zebrafish. The biodistribution of pEVs was monitored at 1 and 24 h post-injection using confocal microscopy. We demonstrated that pEVs traverse the BBB by transcytosis and subsequently diffuse progressively into the brain. pEVs were then internalized by neuronal and radial glial cells as seen in Tg(huc:EGFP) and Tg(gfap:EGFP) zebrafish, respectively. Additional experiments were performed with the intrahippocampal injection of pEVs in the mouse, indicating their spreading throughout the brain and their uptake by neuronal and glial cells. These findings contribute to novel insights into the fate of pEVs following their passage through the BBB in vitro and in vivo, and demonstrate for the first time that pEVs from AD patients affect microglia activity. This suggests a potential mechanism through which peripheral tissue cues may contribute to AD pathogenesis.

Extracellular Vesicles: Advanced Tools for Disease Diagnosis, Monitoring, and Therapies

Extracellular vesicles (EVs) are a heterogeneous group of membrane-encapsulated vesicles released by cells into the extracellular space. They play a crucial role in intercellular communication by transporting bioactive molecules such as proteins, lipids, and nucleic acids. EVs can be detected in body fluids, including blood plasma, urine, saliva, amniotic fluid, breast milk, and pleural ascites. The complexity and diversity of EVs require a robust and standardized approach. By adhering to standardized protocols and guidelines, researchers can ensure the consistency, purity, and reproducibility of isolated EVs, facilitating their use in diagnostics, therapies, and research. Exosomes and microvesicles represent an exciting frontier in modern medicine, with significant potential to transform the diagnosis and treatment of various diseases with an important role in personalized medicine and precision therapy. The primary objective of this review is to provide an updated analysis of the significance of EVs by highlighting their mechanisms of action and exploring their applications in the diagnosis and treatment of various diseases. Additionally, the review addresses the existing limitations and future potential of EVs, offering practical recommendations to resolve current challenges and enhance their viability for clinical use. This comprehensive approach aims to bridge the gap between EV research and its practical application in healthcare.

Exercise mediates myocardial infarction via non-coding RNAs

Myocardial infarction (MI), a widespread cardiovascular issue, mainly occurs due to blood clot formation in the coronary arteries, which reduces blood flow to the heart muscle and leads to cell death. Incorporating exercise into a lifestyle can significantly benefit recovery and reduce the risk of future cardiac events for MI patients. Non-coding RNAs (ncRNAs) play various roles in the effects of exercise on myocardial infarction (MI). ncRNAs regulate gene expression, influence cardiac remodeling, angiogenesis, inflammation, oxidative stress, apoptosis, cardioprotection, and cardiac electrophysiology. The expression of specific ncRNAs is altered by exercise, leading to beneficial changes in heart structure, function, and recovery after MI. These ncRNAs modulate molecular pathways that contribute to improved cardiac health, including reducing inflammation, enhancing angiogenesis, promoting cell survival, and mitigating oxidative stress. Furthermore, they are involved in regulating changes in cardiac remodeling, such as hypertrophy and fibrosis, and can influence the electrical properties of the heart, thereby decreasing the risk of arrhythmias. Knowledge on MI has entered a new phase, with investigations of ncRNAs in physical exercise yielding invaluable insights into the impact of this therapeutic modality. This review compiled research on ncRNAs in MI, with an emphasis on their applicability to physical activity.

Mitochondrial Extracellular Vesicles (mitoEVs): Emerging mediators of cell-to-cell communication in health, aging and age-related diseases

Mitochondria are metabolic and signalling hubs that integrate a plethora of interconnected processes to maintain cell homeostasis. They are also dormant mediators of inflammation and cell death, and with aging damages affecting mitochondria gradually accumulate, resulting in the manifestation of age-associated disorders. In addition to coordinate multiple intracellular functions, mitochondria mediate intercellular and inter-organ cross talk in different physiological and stress conditions. To fulfil this task, mitochondrial signalling has evolved distinct and complex conventional and unconventional routes of horizontal/vertical mitochondrial transfer. In this regard, great interest has been focused on the ability of extracellular vesicles (EVs), such as exosomes and microvesicles, to carry selected mitochondrial cargoes to target cells, in response to internal and external cues. Over the past years, the field of mitochondrial EVs (mitoEVs) has grown exponentially, revealing unexpected heterogeneity of these structures associated with an ever-expanding mitochondrial function, though the full extent of the underlying mechanisms is far from being elucidated. Therefore, emerging subsets of EVs encompass exophers, migrasomes, mitophers, mitovesicles, and mitolysosomes that can act locally or over long-distances to restore mitochondrial homeostasis and cell functionality, or to amplify disease. This review provides a comprehensive overview of our current understanding of the biology and trafficking of MitoEVs in different physiological and pathological conditions. Additionally, a specific focus on the role of mitoEVs in aging and the onset and progression of different age-related diseases is discussed.

Mitochondrial Function and Dysfunction in White Adipocytes and Therapeutic Implications

For a long time, white adipocytes were thought to function as lipid storages due to the sizeable unilocular lipid droplet that occupies most of their space. However, recent discoveries have highlighted the critical role of white adipocytes in maintaining energy homeostasis and contributing to obesity and related metabolic diseases. These physiological and pathological functions depend heavily on the mitochondria that reside in white adipocytes. This article aims to provide an up-to-date overview of the recent research on the function and dysfunction of white adipocyte mitochondria. After briefly summarizing the fundamental aspects of mitochondrial biology, the article describes the protective role of functional mitochondria in white adipocyte and white adipose tissue health and various roles of dysfunctional mitochondria in unhealthy white adipocytes and obesity. Finally, the article emphasizes the importance of enhancing mitochondrial quantity and quality as a therapeutic avenue to correct mitochondrial dysfunction, promote white adipocyte browning, and ultimately improve obesity and its associated metabolic diseases. © 2024 American Physiological Society. Compr Physiol 14:5581-5640, 2024.

The interplay of extracellular vesicles in the pathogenesis of metabolic impairment and type 2 diabetes

The pathogenesis of type 2 diabetes (T2D) involves dysfunction in multiple organs, including the liver, muscle, adipose tissue, and pancreas, leading to insulin resistance and β cell failure. Recent studies highlight the significant role of extracellular vesicles (EVs) in mediating inter-organ communication in T2D. This review investigates the role of EVs, focusing on their presence and biological significance in human plasma and tissues affected by T2D. We explore specific EV cargo, such as miRNAs and proteins, which affect insulin signaling and glucose metabolism, emphasizing their potential as biomarkers. By highlighting the diagnostic and therapeutic potential of EVs, we aim to provide new insights into their role in early detection, disease monitoring, and innovative treatment strategies for T2D.

Environmental pollutants and exosomes: A new paradigm in environmental health and disease

This study investigates the intricate interplay between environmental pollutants and exosomes, shedding light on a novel paradigm in environmental health and disease. Cellular stress, induced by environmental toxicants or disease, significantly impacts the production and composition of exosomes, crucial mediators of intercellular communication. The heat shock response (HSR) and unfolded protein response (UPR) pathways, activated during cellular stress, profoundly influence exosome generation, cargo sorting, and function, shaping intercellular communication and stress responses. Environmental pollutants, particularly lipophilic ones, directly interact with exosome lipid bilayers, potentially affecting membrane stability, release, and cellular uptake. The study reveals that exposure to environmental contaminants induces significant changes in exosomal proteins, miRNAs, and lipids, impacting cellular function and health. Understanding the impact of environmental pollutants on exosomal cargo holds promise for biomarkers of exposure, enabling non-invasive sample collection and real-time insights into ongoing cellular responses. This research explores the potential of exosomal biomarkers for early detection of health effects, assessing treatment efficacy, and population-wide screening. Overcoming challenges requires advanced isolation techniques, standardized protocols, and machine learning for data analysis. Integration with omics technologies enhances comprehensive molecular analysis, offering a holistic understanding of the complex regulatory network influenced by environmental pollutants. The study underscores the capability of exosomes in circulation as promising biomarkers for assessing environmental exposure and systemic health effects, contributing to advancements in environmental health research and disease prevention.

Small extracellular vesicles - A host for advanced bioengineering and "Trojan Horse" of non-coding RNAs

Small extracellular vesicles (sEVs) are a type of membranous vesicles that can be released by cells into the extracellular space. The relationship between sEVs and non-coding RNAs (ncRNAs) is highly intricate and interdependent. This symbiotic relationship plays a pivotal role in facilitating intercellular communication and holds profound implications for a myriad of biological processes. The concept of sEVs and their ncRNA cargo as a "Trojan Horse" highlights their remarkable capacity to traverse biological barriers and surreptitiously deliver their cargo to target cells, evading detection by the host-immune system. Accumulating evidence suggests that sEVs may be harnessed as carriers to ferry therapeutic ncRNAs capable of selectively silencing disease-driving genes, particularly in conditions such as cancer. This approach presents several advantages over conventional drug delivery methods, opening up new possibilities for targeted therapy and improved treatment outcomes. However, the utilization of sEVs and ncRNAs as therapeutic agents raises valid concerns regarding the possibility of unforeseen consequences and unintended impacts that may emerge from their application. It is important to consider the fundamental attributes of sEVs and ncRNAs, including by an in-depth analysis of the practical and clinical potentials of exosomes, serving as a representative model for sEVs encapsulating ncRNAs.