Lipid-filled vesicles modulate macrophages

Lipid droplets in pathogen infection and host immunity

As the hub of cellular lipid metabolism, lipid droplets (LDs) have been linked to a variety of biological processes. During pathogen infection, the biogenesis, composition, and functions of LDs are tightly regulated. The accumulation of LDs has been described as a hallmark of pathogen infection and is thought to be driven by pathogens for their own benefit. Recent studies have revealed that LDs and their subsequent lipid mediators contribute to effective immunological responses to pathogen infection by promoting host stress tolerance and reducing toxicity. In this comprehensive review, we delve into the intricate roles of LDs in governing the replication and assembly of a wide spectrum of pathogens within host cells. We also discuss the regulatory function of LDs in host immunity and highlight the potential for targeting LDs for the diagnosis and treatment of infectious diseases.

Lipidomic landscape of lipokines in adipose tissue derived extracellular vesicles

Introduction: Adipose tissue-derived extracellular vesicles (EVs-AT) are recognized as critical mediators of metabolic alterations in obesity-related diseases. However, few studies have focused on the role of lipids within EVs-AT in the development of obesity-related diseases. Methods: In this study, we performed a targeted lipidomic analysis to compare the lipidome of EVs secreted by inguinal white adipose tissue (EVs-iWAT), epididymal white adipose tissue (EVs-eWAT), and interscapular brown adipose tissue (EVs-BAT) in lean and obese mice. Results: We uncovered a comprehensive lipidomic map, revealing the diversity and specific lipid sorting in EVs-iWAT, EVs-eWAT, and EVs-BAT in obesity. Biological function analyses suggested that lipids encapsulated within EVs-AT of obese individuals might correlate with metabolism, pro-inflammatory response, and insulin resistance. These effects were particularly pronounced in EVs-eWAT and EVs-BAT. Conclusion: Our findings indicated that EVs-AT serves as novel carriers for lipokines, thereby mediating the biological functions of EVs-AT. This study holds promise for the identification of new biomarkers for obesity-related diseases and the development of new strategies to combat metabolic diseases.

Therapeutics of Extracellular Vesicles in Cardiocerebrovascular and Metabolic Diseases

Extracellular vesicles (EVs) are nanoscale membranous vesicles containing DNA, RNA, lipids, and proteins, which play versatile roles in intercellular communications. EVs are increasingly being recognized as the promising therapeutic agents for many diseases, including cardiocerebrovascular and metabolic diseases, due to their ability to deliver functional and therapeutical molecules. In this chapter, the biological characteristics and functions of EVs are briefly summarized. Importantly, the current state of applying EVs in the prevention and treatment of cardiocerebrovascular and metabolic diseases, including myocardial infarction, atrial fibrillation, myocardial hypertrophy, stroke, diabetes, Alzheimer's disease, fatty liver, obesity, thyroid diseases, and osteoporosis, is discussed. Lastly, the challenges and prospects related to the preclinical and clinical application of EVs receive a particular focus.

Adipose tissue macrophages in remote modulation of hepatic glucose production

Hepatic glucose production (HGP) is fine-regulated via glycogenolysis or gluconeogenesis to maintain physiological concentration of blood glucose during fasting-feeding cycle. Aberrant HGP leads to hyperglycemia in obesity-associated diabetes. Adipose tissue cooperates with the liver to regulate glycolipid metabolism. During these processes, adipose tissue macrophages (ATMs) change their profiles with various physio-pathological settings, producing diverse effects on HGP. Here, we briefly review the distinct phenotypes of ATMs under different nutrition states including feeding, fasting or overnutrition, and detail their effects on HGP. We discuss several pathways by which ATMs regulate hepatic gluconeogenesis or glycogenolysis, leading to favorable or unfavorable metabolic consequences. Furthermore, we summarize emerging therapeutic targets to correct metabolic disorders in morbid obesity or diabetes based on ATM-HGP axis. This review puts forward the importance and flexibility of ATMs in regulating HGP, proposing ATM-based HGP modulation as a potential therapeutic approach for obesity-associated metabolic dysfunction.

Intracellular lipid droplet accumulation occurs early following viral infection and is required for an efficient interferon response

Lipid droplets (LDs) are increasingly recognized as critical organelles in signalling events, transient protein sequestration and inter-organelle interactions. However, the role LDs play in antiviral innate immune pathways remains unknown. Here we demonstrate that induction of LDs occurs as early as 2 h post-viral infection, is transient and returns to basal levels by 72 h. This phenomenon occurs following viral infections, both in vitro and in vivo. Virally driven in vitro LD induction is type-I interferon (IFN) independent, and dependent on Epidermal Growth Factor Receptor (EGFR) engagement, offering an alternate mechanism of LD induction in comparison to our traditional understanding of their biogenesis. Additionally, LD induction corresponds with enhanced cellular type-I and -III IFN production in infected cells, with enhanced LD accumulation decreasing viral replication of both Herpes Simplex virus 1 (HSV-1) and Zika virus (ZIKV). Here, we demonstrate, that LDs play vital roles in facilitating the magnitude of the early antiviral immune response specifically through the enhanced modulation of IFN following viral infection, and control of viral replication. By identifying LDs as a critical signalling organelle, this data represents a paradigm shift in our understanding of the molecular mechanisms which coordinate an effective antiviral response.

Roles of Macrophages and Exosomes in Liver Diseases

Exosomes are small discoid extracellular vesicles (EVs) originating from endosomes that are 30-150 nm in diameter and have a double lipid layer. They participate in the immune response, cell migration, cell differentiation, and tumor invasion and mediate intercellular communication, regulating the biological activity of receptor cells through the proteins, nucleic acids, and lipids that they carry. Exosomes also play vital roles in the diagnosis and treatment of liver diseases. Macrophages, which show unique phenotypes and functions in complex microenvironments, can be divided into M1 and M2 subtypes. M1 macrophages function in immune surveillance, and M2 macrophages downregulate the immune response. Recent studies have shown that macrophages are involved in non-alcoholic fatty liver disease, liver fibrosis, and hepatocellular carcinoma. Moreover, several studies have demonstrated that liver diseases are associated with exosomes derived from or transferred to macrophages. This review focuses on the participation of macrophages and exosomes in liver diseases.

An Eclectic Cast of Cellular Actors Orchestrates Innate Immune Responses in the Mechanisms Driving Obesity and Metabolic Perturbation

The escalating problem of obesity and its multiple metabolic and cardiovascular complications threatens the health and longevity of humans throughout the world. The cause of obesity and one of its chief complications, insulin resistance, involves the participation of multiple distinct organs and cell types. From the brain to the periphery, cell-intrinsic and intercellular networks converge to stimulate and propagate increases in body mass and adiposity, as well as disturbances of insulin sensitivity. This review focuses on the roles of the cadre of innate immune cells, both those that are resident in metabolic organs and those that are recruited into these organs in response to cues elicited by stressors such as overnutrition and reduced physical activity. Beyond the typical cast of innate immune characters invoked in the mechanisms of metabolic perturbation in these settings, such as neutrophils and monocytes/macrophages, these actors are joined by bone marrow-derived cells, such as eosinophils and mast cells and the intriguing innate lymphoid cells, which are present in the circulation and in metabolic organ depots. Upon high-fat feeding or reduced physical activity, phenotypic modulation of the cast of plastic innate immune cells ensues, leading to the production of mediators that affect inflammation, lipid handling, and metabolic signaling. Furthermore, their consequent interactions with adaptive immune cells, including myriad T-cell and B-cell subsets, compound these complexities. Notably, many of these innate immune cell-elicited signals in overnutrition may be modulated by weight loss, such as that induced by bariatric surgery. Recently, exciting insights into the biology and pathobiology of these cell type-specific niches are being uncovered by state-of-the-art techniques such as single-cell RNA-sequencing. This review considers the evolution of this field of research on innate immunity in obesity and metabolic perturbation, as well as future directions.

The function and clinical application of extracellular vesicles in innate immune regulation

The innate immune system plays a crucial role in the host defense against viral and microbial infection. Exosomes constitute a subset of extracellular vesicles (EVs) that can be released by almost all cell types. Owing to their capacity to shield the payload from degradation and to evade recognition and subsequent removal by the immune system, exosomes efficiently transport functional components to recipient cells. Accumulating evidence has recently shown that exosomes derived from tumor cells, host cells and even bacteria and parasites mediate the communication between the invader and innate immune cells and thus play an irreplaceable function in the dissemination of pathogens and donor cell-derived molecules, modulating the innate immune responses of the host. In this review, we describe the current understanding of EVs (mainly focusing on exosomes) and summarize and discuss their crucial roles in determining innate immune responses. Additionally, we discuss the potential of using exosomes as biomarkers and cancer vaccines in diagnostic and therapeutic applications.