Resolution therapy: Harnessing efferocytic macrophages to trigger the resolution of inflammation

Therapeutic implication of targeting mitochondrial drugs designed for efferocytosis dysfunction

Efferocytosis refers to the process by which phagocytes remove apoptotic cells and related apoptotic products. It is essential for the growth and development of the body, the repair of damaged or inflamed tissues, and the balance of the immune system. Damaged efferocytosis will cause a variety of chronic inflammation and immune system diseases. Many studies show that efferocytosis is a process mediated by mitochondria. Mitochondrial metabolism, mitochondrial dynamics, and communication between mitochondria and other organelles can all affect phagocytes' clearance of apoptotic cells. Therefore, targeting mitochondria to modulate phagocyte efferocytosis is an anticipated strategy to prevent and treat chronic inflammatory diseases and autoimmune diseases. In this review, we introduced the mechanism of efferocytosis and the pivoted role of mitochondria in efferocytosis. In addition, we focused on the therapeutic implication of drugs targeting mitochondria in diseases related to efferocytosis dysfunction.

Friend or foe? Inflammation and the foreign body response to orthopedic biomaterials

The use of biomaterials and implants for joint replacement, fracture fixation, spinal stabilization and other orthopedic indications has revolutionized patient care by reliably decreasing pain and improving function. These surgical procedures always invoke an acute inflammatory reaction initially, that in most cases, readily subsides. Occasionally, chronic inflammation around the implant develops and persists; this results in unremitting pain and compromises function. The etiology of chronic inflammation may be specific, such as with infection, or be unknown. The histological hallmarks of chronic inflammation include activated macrophages, fibroblasts, T cell subsets, and other cells of the innate immune system. The presence of cells of the adaptive immune system usually indicates allergic reactions to metallic haptens. A foreign body reaction is composed of activated macrophages, giant cells, fibroblasts, and other cells often distributed in a characteristic histological arrangement; this reaction is usually due to particulate debris and other byproducts from the biomaterials used in the implant. Both chronic inflammation and the foreign body response have adverse biological effects on the integration of the implant with the surrounding tissues. Strategies to mitigate chronic inflammation and the foreign body response will enhance the initial incorporation and longevity of the implant, and thereby, improve long-term pain relief and overall function for the patient. The seminal research performed in the laboratory of Dr. James Anderson and co-workers has provided an inspirational and driving force for our laboratory's work on the interactions and crosstalk among cells of the mesenchymal, immune, and vascular lineages, and orthopedic biomaterials. Dr. Anderson's delineation of the fundamental biologic processes and mechanisms underlying acute and chronic inflammation, the foreign body response, resolution, and eventual functional integration of implants in different organ systems has provided researchers with a strategic approach to the use of biomaterials to improve health in numerous clinical scenarios.

The role and therapeutic potential of macrophages in the pathogenesis of diabetic cardiomyopathy

This review provides a comprehensive analysis of the critical role played by macrophages and their underlying mechanisms in the progression of diabetic cardiomyopathy (DCM). It begins by discussing the origins and diverse subtypes of macrophages, elucidating their spatial distribution and modes of intercellular communication, thereby emphasizing their significance in the pathogenesis of DCM. The review then delves into the intricate relationship between macrophages and the onset of DCM, particularly focusing on the epigenetic regulatory mechanisms employed by macrophages in the context of DCM condition. Additionally, the review discusses various therapeutic strategies aimed at targeting macrophages to manage DCM. It specifically highlights the potential of natural food components in alleviating diabetic microvascular complications and examines the modulatory effects of existing hypoglycemic drugs on macrophage activity. These findings, summarized in this review, not only provide fresh insights into the role of macrophages in diabetic microvascular complications but also offer valuable guidance for future therapeutic research and interventions in this field.

[Strong as death or how efferocytotic macrophages promote the resolution of inflammation]

The resolution of inflammation is an active process leading to the restoration of tissue homeostasis. A critical step in the initiation of this process is the elimination of apoptotic immune cells by macrophages. This well-organized process, called efferocytosis, involves four different steps, namely the attraction of macrophages to the site where the cells die, the recognition of apoptotic cells, their internalization and their digestion leading to the activation of different metabolic pathways. All these steps are responsible for the reprogramming of macrophages towards a pro-resolving profile. Efferocytic macrophages produce several factors involved in the resolution of inflammation. These factors include lipids (i.e., specialized pro-resolving mediators such as lipoxins), and proteins (e.g., IL-10 or TGF-β). Here, we describe the different steps of efferocytosis and the mechanisms responsible for both macrophage reprogramming and the release of pro-resolving factors. These factors may represent a new therapeutic approach, called resolution therapy.

In situ neutrophil apoptosis and macrophage efferocytosis mediated by Glycyrrhiza protein nanoparticles for acute inflammation therapy

In the progression of acute inflammation, the activation and recruitment of macrophages and neutrophils are mutually reinforcing, leading to amplified inflammatory response and severe tissue damage. Therefore, to regulate the axis of neutrophils and macrophages is essential to avoid tissue damage induced from acute inflammatory. Apoptotic neutrophils can regulate the anti-inflammatory activity of macrophages through the efferocytosis. The strategy of in situ targeting and inducing neutrophil apoptosis has the potential to modulate macrophage activity and transfer anti-inflammatory drugs. Herein, a natural glycyrrhiza protein nanoparticle loaded with dexamethasone (Dex@GNPs) was constructed, which could simultaneously regulate neutrophil and macrophage function during acute inflammation treatment by combining in situ neutrophil apoptosis and macrophage efferocytosis. Dex@GNPs can be rapidly and selectively internalized by neutrophils and subsequently induce neutrophils apoptosis through a ROS-dependent mechanism. The efferocytosis of apoptotic neutrophils not only promoted the polarization of macrophages into anti-inflammatory state, but also facilitated the transfer of Dex@GNPs to macrophages. This enabled dexamethasone to further modulate macrophage function. In mouse models of acute respiratory distress syndrome and sepsis, Dex@GNPs significantly ameliorated the disordered immune microenvironment and alleviated tissue injury. This study presents a novel strategy for drug delivery and inflammation regulation to effectively treat acute inflammatory diseases.

Harnessing anti-inflammatory pathways and macrophage nano delivery to treat inflammatory and fibrotic disorders

Targeting specific organs and cell types using nanotechnology and sophisticated delivery methods has been at the forefront of applicative biomedical sciences lately. Macrophages are an appealing target for immunomodulation by nanodelivery as they are heavily involved in various aspects of many diseases and are highly plastic in their nature. Their continuum of functional "polarization" states has been a research focus for many years yielding a profound understanding of various aspects of these cells. The ability of monocyte-derived macrophages to metamorphose from pro-inflammatory to reparative and consequently to pro-resolving effectors has raised significant interest in its therapeutic potential. Here, we briefly survey macrophages' ontogeny and various polarization phenotypes, highlighting their function in the inflammation-resolution shift. We review their inducing mediators, signaling pathways, and biological programs with emphasis on the nucleic acid sensing-IFN-I axis. We also portray the polarization spectrum of macrophages and the characteristics of their transition between different subtypes. Finally, we highlighted different current drug delivery methods for targeting macrophages with emphasis on nanotargeting that might lead to breakthroughs in the treatment of wound healing, bone regeneration, autoimmune, and fibrotic diseases.

Osteopathic manipulative treatment for chronic inflammatory diseases

Chronic inflammatory diseases (CIDs) are debilitating and potentially lethal illnesses that affect a large proportion of the global population. Osteopathic manipulative treatment (OMT) is a manual therapy technique developed and performed by osteopathic physicians that facilitates the body's innate healing processes. Therefore, OMT may prove a beneficial anti-inflammatory modality useful in the management and treatment of CIDs. This work aims to objectively evaluate the therapeutic benefits of OMT in patients with various CIDs. In this review, a structured literature search was performed. The included studies involving asthma, chronic obstructive pulmonary disease, irritable bowel syndrome, ankylosing spondylitis, and peripheral arterial disease were selected for this work. Various OMT modalities, including lymphatic, still, counterstain, and muscle energy techniques, were utilized. Control treatments included sham techniques, routine care, or no treatment. OMT utilization led to variable patient outcomes in individuals with pathologies linked to CID.

Efferocytosis in liver disease

The process of dead cell clearance by phagocytic cells, called efferocytosis, prevents inflammatory cell necrosis and promotes resolution and repair. Defective efferocytosis contributes to the progression of numerous diseases in which cell death is prominent, including liver disease. Many gaps remain in our understanding of how hepatic macrophages carry out efferocytosis and how this process goes awry in various types of liver diseases. Thus far, studies have suggested that, upon liver injury, liver-resident Kupffer cells and infiltrating monocyte-derived macrophages clear dead cells, limit inflammation, and, through macrophage reprogramming, repair liver damage. However, in unusual settings, efferocytosis can promote liver disease. In this review, we will focus on efferocytosis in various types of acute and chronic liver diseases, including metabolic dysfunction-associated steatohepatitis. Understanding the mechanisms and consequences of efferocytosis by hepatic macrophages has the potential to shed new light on liver disease pathophysiology and to guide new treatment strategies to prevent disease progression.

Mmp12 Is Translationally Regulated in Macrophages during the Course of Inflammation

Despite the importance of rapid adaptive responses in the course of inflammation and the notion that post-transcriptional regulation plays an important role herein, relevant translational alterations, especially during the resolution phase, remain largely elusive. In the present study, we analyzed translational changes in inflammatory bone marrow-derived macrophages upon resolution-promoting efferocytosis. Total RNA-sequencing confirmed that apoptotic cell phagocytosis induced a pro-resolution signature in LPS/IFNγ-stimulated macrophages (Mϕ). While inflammation-dependent transcriptional changes were relatively small between efferocytic and non-efferocytic Mϕ; considerable differences were observed at the level of de novo synthesized proteins. Interestingly, translationally regulated targets in response to inflammatory stimuli were mostly downregulated, with only minimal impact of efferocytosis. Amongst these targets, pro-resolving matrix metallopeptidase 12 (Mmp12) was identified as a translationally repressed candidate during early inflammation that recovered during the resolution phase. Functionally, reduced MMP12 production enhanced matrix-dependent migration of Mϕ. Conclusively, translational control of MMP12 emerged as an efficient strategy to alter the migratory properties of Mϕ throughout the inflammatory response, enabling Mϕ migration within the early inflammatory phase while restricting migration during the resolution phase.

Efferocytosis and Respiratory Disease

Cells are the smallest units that make up living organisms, which constantly undergo the processes of proliferation, differentiation, senescence and death. Dead cells need to be removed in time to maintain the homeostasis of the organism and keep it healthy. This process is called efferocytosis. If the process fails, this may cause different types of diseases. More and more evidence suggests that a faulty efferocytosis process is closely related to the pathological processes of respiratory diseases. In this review, we will first introduce the process and the related mechanisms of efferocytosis of the macrophage. Secondly, we will propose some methods that can regulate the function of efferocytosis at different stages of the process. Next, we will discuss the role of efferocytosis in different lung diseases and the related treatment approaches. Finally, we will summarize the drugs that have been applied in clinical practice that can act upon efferocytosis, in order to provide new ideas for the treatment of lung diseases.

Efferocytes release extracellular vesicles to resolve inflammation and tissue injury via prosaposin-GPR37 signaling

Macrophages release soluble mediators following efferocytic clearance of apoptotic cells to facilitate intercellular communication and promote the resolution of inflammation. However, whether inflammation resolution is modulated by extracellular vesicles (EVs) and vesicular mediators released by efferocytes is not known. We report that efferocyte-derived EVs express prosaposin, which binds to macrophage GPR37 to increase expression of the efferocytosis receptor Tim4 via an ERK-AP1-dependent signaling axis, leading to increased macrophage efferocytosis efficiency and accelerated resolution of inflammation. Neutralization and knockdown of prosaposin or blocking GRP37 abrogates the pro-resolution effects of efferocyte-derived EVs in vivo. Administration of efferocyte-derived EVs in a murine model of atherosclerosis is associated with an increase in lesional macrophage efferocytosis efficiency and a decrease in plaque necrosis and lesional inflammation. Thus, we establish a critical role for efferocyte-derived vesicular mediators in increasing macrophage efferocytosis efficiency and accelerating the resolution of inflammation and tissue injury.

Cellular mechanisms underlying the impairment of macrophage efferocytosis

The phagocytosis and clearance of dying cells by macrophages, a process termed efferocytosis, is essential for both maintaining homeostasis and promoting tissue repair after infection or sterile injury. If not removed in a timely manner, uncleared cells can undergo secondary necrosis, and necrotic cells lose membrane integrity, release toxic intracellular components, and potentially induce inflammation or autoimmune diseases. Efferocytosis also initiates the repair process by producing a wide range of pro-reparative factors. Accumulating evidence has revealed that macrophage efferocytosis defects are involved in the development and progression of a variety of inflammatory and autoimmune diseases. The underlying mechanisms of efferocytosis impairment are complex, disease-dependent, and incompletely understood. In this review, we will first summarize the current knowledge about the normal signaling and metabolic processes of macrophage efferocytosis and its importance in maintaining tissue homeostasis and repair. We then will focus on analyzing the molecular and cellular mechanisms underlying efferocytotic abnormality (impairment) in disease or injury conditions. Next, we will discuss the potential molecular targets for enhanced efferocytosis in animal models of disease. To provide a balanced view, we will also discuss some deleterious effects of efferocytosis.