Maresin1 Promotes M2 Macrophage Polarization Through Peroxisome Proliferator-Activated Receptor-γ Activation to Expedite Resolution of Acute Lung Injury

Intratracheal administration of cross-linked water-soluble acrylic acid polymer is associated with inducible bronchi-related lymphoid tissue formation and allergic inflammation

In a Japanese chemical factory, lung diseases such as pneumoconiosis have been reported among workers handling cross-linked water-soluble acrylic acid polymers (CWAAP). Our previous study reported that a single intratracheal administration of CWAAP induces acute inflammation and fibrosis. In this study, we investigated the effects of multiple intratracheal administrations of CWAAP on inflammatory responses and pulmonary fibrosis along with inducible bronchus-associated lymphoid tissues (iBALT) formation, which is involved in allergic inflammation. Male F344 rats (190-200 g) received single or multiple intratracheal administrations of phosphate-buffered saline (PBS) or CWAAP. To assess inflammatory responses and pulmonary fibrosis, immunohistochemical and histological staining was performed. CD68, CD163, CD169, TGF-β, and collagen I positive cells/areas in the lungs of the CWAAP-group rats were significantly increased than those in the PBS group. Furthermore, the number of iBALT structures, CD4 + T cells, along with CD19, PAX5, IL-4, GATA-3, T-bet, and IgE-positive cells in the terminal bronchioles and blood vessels of the lungs were significantly increased in the CWAAP group. Moreover, pulmonary fibrosis, iBALT formation, and levels of specific IgG were significantly increased in rats who received multiple intratracheal administrations of CWAAP compared to those with single intratracheal administration. Multiple intratracheal administrations of CWAAP potentiated the classical fibrotic pathway (M2 macrophage-TGF-β-collagen I) more potently than single intratracheal administration. Furthermore, it was possible that iBALT was formed around terminal bronchioles and blood vessels and the number of immune cells was increased, resulting in enhanced allergic inflammation and pulmonary fibrosis.

Maresin1: A multifunctional regulator in inflammatory bone diseases

Inflammation plays a crucial role in the physical response to danger signals, the elimination of toxic stimuli, and the restoration of homeostasis. However, dysregulated inflammatory responses lead to tissue damage, and chronic inflammation can disrupt osteogenic-osteoclastic homeostasis, ultimately leading to bone loss. Maresin1 (MaR1), a member of the specialized pro-resolving mediators (SPMs) family, has been found to possess significant anti-inflammatory, anti-allergic, pro-hemolytic, pro-healing, and pain-relieving properties. MaR1 is synthesized by macrophages (Mφs) and omega-3 fatty acids, and it may have the potential to promote bone homeostasis and treat inflammatory bone diseases. MaR1 has been found to stimulate osteoblast proliferation through leucine-rich repeat G protein-coupled receptor 6 (LGR6). It also activates Mφ phagocytosis and M2-type polarization, which helps to control the immune system. MaR1 can regulate T cells to exert anti-inflammatory effects and inhibit neutrophil infiltration and recruitment. In addition, MaR1 is involved in antioxidant signaling, including nuclear factor erythroid 2-related factor 2 (NRF2). It has also been found to promote the autophagic behavior of periodontal ligament stem cells, stimulate Mφs against pathogenic bacteria, and regulate tissue regeneration and repair. In summary, this review provides new information and a comprehensive overview of the critical roles of MaR1 in inflammatory bone diseases, indicating its potential as a therapeutic approach for managing skeletal metabolism and inflammatory bone diseases.

Neuroprotective effects of different doses of Maresin1 pretreatment in aged rats after anesthesia/surgery

OBJECTIVE

The study is to investigate the neuroprotective effect of different doses of Maresin1 pretreatment in aged rats after anesthesia/surgery and the related mechanisms.

METHODS

Aged male rats were randomly divided into a control group, an anesthesia/surgery group, and low, medium, and high-dose Maresin1 pretreatment groups, and the hippocampus was taken for study. The Morris water maze was performed to detect the cognitive ability of rats. Western blot and immunofluorescence were used to detect the expression of glial fibrillary acidic protein (GFAP) and central nervous system-specific protein (S100β). The ultrastructure of astrocytes was observed by a transmission electron microscope. Quantitative real-time PCR was used to detect the relative expression of IL-1β, IL-6, and TNF-α mRNA.

RESULTS

Compared with the control group, the cognition of rats in the anesthesia/surgery group was significantly reduced. The expression of astrocyte markers (GFAP and S100β) in the hippocampus of rats in the anesthesia/surgery group was increased. The levels of hippocampal inflammatory cytokines (TNF-α, IL-1β, and IL-6) were also higher in the anesthesia/surgery group than in the control group. After pretreatment with different doses of Maresin1, the cognitive impairment of rats was alleviated to varying degrees. Maresin1 pretreatment decreased the expression of astrocyte markers and inflammatory factors in the hippocampus of rats after anesthesia/surgery, and improve the microstructures of activated astrocytes, especially in the medium-dose group.

CONCLUSION

Pretreatment with Maresin1 (especially at medium-dose) showed neuroprotective effects in aged rats after anesthesia/surgery, which may be related to the inhibition of astrocyte activation.

Regulatory T cell and macrophage crosstalk in acute lung injury: future perspectives

Acute lung injury (ALI) describes the injury to endothelial cells in the lungs and associated vessels due to various factors. Furthermore, ALI accompanied by inflammation and thrombosis has been reported as a common complication of SARS-COV-2 infection. It is widely accepted that inflammation and the cytokine storm are main causes of ALI. Two classical anti-inflammatory cell types, regulatory T cells (Tregs) and M2 macrophages, are theoretically capable of resisting uncontrolled inflammation. Recent studies have indicated possible crosstalk between Tregs and macrophages involving their mutual activation. In this review, we discuss the current findings related to ALI pathogenesis and the role of Tregs and macrophages. In particular, we review the molecular mechanisms underlying the crosstalk between Tregs and macrophages in ALI pathogenesis. Understanding the role of Tregs and macrophages will provide the potential targets for treating ALI.

Single-Cell Sequencing Reveals the Regulatory Role of Maresin1 on Neutrophils during Septic Lung Injury

Acute lung injury (ALI) is the most common type of organ injury in sepsis, with high morbidity and mortality. Sepsis is characterized by an inappropriate inflammatory response while neutrophils exert an important role in the excessive inflammatory response. The discovery of specialized pro-resolving mediators (SPMs) provides a new direction for the treatment of a series of inflammatory-related diseases including sepsis. Among them, the regulation of Maresin1 on immune cells was widely demonstrated. However, current research on the regulatory effects of Maresin1 on immune cells has remained at the level of certain cell types. Under inflammatory conditions, the immune environment is complex and immune cells exhibit obvious heterogeneity. Neutrophils play a key role in the occurrence and development of septic lung injury. Whether there is a subpopulation bias in the regulation of neutrophils by Maresin1 has not been elucidated. Therefore, with the well-established cecal ligation and puncture (CLP) model and single-cell sequencing technology, our study reveals for the first time the regulatory mechanism of Maresin1 on neutrophils at the single-cell level. Our study suggested that Maresin1 can significantly reduce neutrophil infiltration in septic lung injury and that this regulatory effect is more concentrated in the Neutrophil-Cxcl3 subpopulation. Maresin1 can significantly reduce the infiltration of the Neutrophil-Cxcl3 subpopulation and inhibit the expression of related inflammatory genes and key transcription factors in the Neutrophil-Cxcl3 subpopulation. Our study provided new possibilities for specific modulation of neutrophil function in septic lung injury.

Maresin 1 enhances osteogenic potential of mesenchymal stem cells by modulating macrophage peroxisome proliferator-activated receptor-γ-mediated inflammation resolution

Inflammation resolution plays a significant role in attenuating bone injury aggravated by acute inflammation and maintaining bone homeostasis. Maresin 1 (MaR1), a specialized pro-resolving mediators (SPMs), is biosynthesised in macrophages (Mφs) that regulates acute inflammation. Strategies to accelerate the resolution of inflammation in bone repair include not only promoting vanish of acute inflammation, also improving osteogenic microenvironment. Here, previously prepared difunctional demineralized bone matrix (DBM) scaffold was used to study thoroughly the "cross-talk" between Mφs lipid metabolism and mesenchymal stem cells (MSCs) behaviors in vitro. The pro-resolving mechanism in Mφs treated with MaR1 was elaborated. Furthermore, the biological behaviors of MSCs in co-culture system were evaluated. The results indicated that MaR1 had an enhanced capability and performance in peroxisome proliferator-activated receptor-γ (PPAR-γ) activation, M2-type Mφs polarization, and lipid droplets (LDs) biogenesis in Mφs in vitro. The nuclear receptor PPAR-γ enhanced the anti-inflammatory proteins expression and the polarization of Mφs toward M2 subtype, thereby favoring the proliferation, migration, and osteogenesis of MSCs. Overall, the results verified that MaR1 facilitated MSCs behaviors by regulating PPAR-γ-mediated inflammatory response, which implied that PPAR-γ exhibited a significant role in the dialogue between MSCs behaviors and Mφs lipid metabolism.

Can PPAR γ Keep Cadmium in Check?

Cd, a naturally occurring endocrine toxin found in tobacco leaves, originates in the environment and enters the body through inhalation, targeting the lungs and kidneys. A study published by Larsen-Carey et al. revealed that cadmium mediates the persistence of classically activated lung macrophages to exacerbate lung injury. The research discovered a novel role for PPAR γ as an effective regulator for the alternative activation of macrophages in response to Cd and Cd-induced lung injury.

A cell-free difunctional demineralized bone matrix scaffold enhances the recruitment and osteogenesis of mesenchymal stem cells by promoting inflammation resolution

The dialogue between host macrophages (Mφs) and endogenous mesenchymal stem cells (MSCs) promotes M2 Mφs polarization to resolve early-stage inflammation, thereby effectively guiding in situ bone regeneration. Once inflammation is unresolved/incontrollable, it will induce the impediment of MSCs homing at bone defect site, implying the seasonable resolution of inflammation in balancing bone homeostasis. Repeatedly, evidence elucidated that specialized pro-resolving mediators (SPMs) could conduce to proper resolve inflammation and promote the repairing of bone defect. A difunctional demineralized bone matrix (DBM) scaffold co-modified by maresin 1 (MaR1) and aptamer 19S (Apt19S) was fabricated to facilitate the osteogenesis of MSCs. To confirm the osteogenesis and immunomodulatory role of the difunctional DBM scaffold, the proliferation, recruitment, and osteogenic differentiation of MSCs and the Mφs M2 subtype polarization were evaluated in vitro. Then, the DBM scaffolds were implanted into mice model with critical size calvarial defect to evaluate bone repair efficiency. Finally, the specific resolution mechanism in Mφs cultured on the difunctional DBM scaffold was further in-depth investigated. This difunctional DBM scaffold exhibited an enhanced function on the recruitment, proliferation, migration, osteogenesis of MSCs and the resolution of inflammation, finally improved bone-scaffold integration. At the same time, MaR1 modified on the difunctional DBM scaffold increased the biosynthesis of 12-lipoxygenase (12-LOX) and 12S-hydroxy-eicosatetraenoic acid (12S-HETE), and also directly stimulated lipid droplets (LDs) biogenesis in Mφs, which suggested that MaR1 regulated Mφ lipid metabolism at bone repair site. Findings based on this synergy strategy demonstrated that Mφ lipid metabolism was essential in bone homeostasis, which might provide a theoretical direction for the treatment-associated application of MaR1 in inflammatory bone disease.

Maresin-1 and Inflammatory Disease

Inflammation is an essential action to protect the host human body from external, harmful antigens and microorganisms. However, an excessive inflammation reaction sometimes exceeds tissue damage and can disrupt organ functions. Therefore, anti-inflammatory action and resolution mechanisms need to be clarified. Dietary foods are an essential daily lifestyle that influences various human physiological processes and pathological conditions. Especially, omega-3 fatty acids in the diet ameliorate chronic inflammatory skin diseases. Recent studies have identified that omega-3 fatty acid derivatives, such as the resolvin series, showed strong anti-inflammatory actions in various inflammatory diseases. Maresin-1 is a derivative of one of the representative omega-3 fatty acids, i.e., docosahexaenoic acid (DHA), and has shown beneficial action in inflammatory disease models. In this review, we summarize the detailed actions of maresin-1 in immune cells and inflammatory diseases.

Polarized Macrophages in Periodontitis: Characteristics, Function, and Molecular Signaling

Periodontitis (PD) is a common chronic infectious disease. The local inflammatory response in the host may cause the destruction of supporting periodontal tissue. Macrophages play a variety of roles in PD, including regulatory and phagocytosis. Moreover, under the induction of different factors, macrophages polarize and form different functional phenotypes. Among them, M1-type macrophages with proinflammatory functions and M2-type macrophages with anti-inflammatory functions are the most representative, and both of them can regulate the tendency of the immune system to exert proinflammatory or anti-inflammatory functions. M1 and M2 macrophages are involved in the destructive and reparative stages of PD. Due to the complex microenvironment of PD, the dynamic development of PD, and various local mediators, increasing attention has been given to the study of macrophage polarization in PD. This review summarizes the role of macrophage polarization in the development of PD and its research progress.

Maresin 1 protects against lipopolysaccharide/d-galactosamine-induced acute liver injury by inhibiting macrophage pyroptosis and inflammatory response

BACKGROUND

Acute liver injury (ALI) caused by sepsis is a fearful disease with high mortality and poor prognosis. This study aimed to explore the roles and mechanism of Maresin 1 (MaR1) in lipopolysaccharide/d-galactosamine (LPS/D-GalN)-induced ALI.

METHODS

We established an ALI mouse model induced by LPS/D-GalN. Each group was treated with or without LPS/D-GalN or MaR1. For the vitro experiments, RAW264.7, NCTC1469 cells, and bone marrow-derived macrophages (BMDMs) were stimulated with LPS. The effects of MaR1 on the reactive oxygen species (ROS), pyroptosis and inflammatory response in macrophages were investigated.

RESULTS

MaR1 significantly inhibited an excessive inflammatory response and proinflammatory markers during LPS/D-GalN-induced ALI. MaR1 markedly decreased the levels of ROS, tumor necrosis factor-α, and interleukin-1β (IL-1β) in macrophages, and limited hepatocyte apoptosis in vitro. Upon exploring the mechanisms underlying the protective role of MaR1, we found MaR1 markedly upregulated the nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), and considerably reduced the phosphorylation of p38, ERK, and nuclear factor-kappa B (NF-κB)-p65. Knocking down Nrf2 decreased the effect of MaR1. Furthermore, we observed that MaR1 reduced inflammatory injury by inhibiting M1 macrophages and promoting M2 macrophage polarization. Finally, we observed that MaR1 could inhibit the production of gasdermin D N-terminus (GSDMD-N) in vivo. In vitro, MaR1 could significantly suppressed the expression of NLR family pyrin domain containing 3 (NLRP3) inflammasome, GSDMD-N, and IL-1β caused by LPS and nigericin stimulation in BMDMs.

CONCLUSION

MaR1 could ameliorate inflammation during LPS/D-GalN induced ALI by suppressing mitogen-activated protein kinase /NF-κB signaling and NLRP3 inflammasome-induced pyroptosis, activating macrophage M1/M2 polarization and Nrf2/HO-1 signaling. This provides new evidence for the potential of developing MaR1 for ALI treatment.

New Insights on the Effects of Dietary Omega-3 Fatty Acids on Impaired Skin Healing in Diabetes and Chronic Venous Leg Ulcers

Long-chain Omega-3 polyunsaturated fatty acids (Omega-3 PUFAs) are widely recognized as powerful negative regulators of acute inflammation. However, the precise role exerted by these dietary compounds during the healing process is still largely unknown, and there is increasing interest in understanding their specific effects on the implicated cells/molecular factors. Particular attention is being focused also on their potential clinical application in chronic pathologies characterized by delayed and impaired healing, such as diabetes and vascular diseases in lower limbs. On these bases, we firstly summarized the current knowledge on wound healing (WH) in skin, both in normal conditions and in the setting of these two pathologies, with particular attention to the cellular and molecular mechanisms involved. Then, we critically reviewed the outcomes of recent research papers investigating the activity exerted by Omega-3 PUFAs and their bioactive metabolites in the regulation of WH in patients with diabetes or venous insufficiency and showing chronic recalcitrant ulcers. We especially focused on recent studies investigating the mechanisms through which these compounds may act. Considerations on the optimal dietary doses are also reported, and, finally, possible future perspectives in this area are suggested.

Lipid-Derived Mediators are Pivotal to Leukocyte and Lung Cell Responses in Sepsis and ARDS

Acute inflammation in the lung is essential for host defense against pathogens and other injuries but chronic or excessive inflammation can contribute to several common respiratory diseases. In health, the inflammatory response is controlled by several cellular and molecular mechanisms. In addition to anti-inflammatory processes, there are non-phlogistic pro-resolving mechanisms that are engaged to promote the resolution of inflammation and a return to homeostasis. Defects in the production or actions of specialized pro-resolving mediators are associated with diseases characterized by excess or chronic inflammation. In this article, we review cellular and biochemical mechanisms for specialized pro-resolving mediators in health and in sepsis and the acute respiratory distress syndrome as examples of unrestrained inflammatory responses that result in life-threatening pathology. We are honored to contribute to this special edition of the Journal to help celebrate Professor Viswanathan Natarajan's contributions to our understanding of lipid-derived mediators and metabolism in lung cell responses to inflammatory, infectious, or mechanical insults; his foundational discoveries in cell biochemistry and biophysics are continuing to catalyze further advances by the field to uncover the mechanistic underpinnings of important human diseases.

Development of mode of action networks related to the potential role of PPARγ in respiratory diseases

The peroxisome proliferator-activated receptor γ (PPARγ) is a key transcription factor, operating at the intercept of metabolic control and immunomodulation. It is ubiquitously expressed in multiple tissues and organs, including lungs. There is a growing body of information supporting the role of PPARγ signalling in respiratory diseases. The aim of the present study was to develop mode of action (MoA) networks reflecting the relationships between PPARγ signalling and the progression/alleviation of a spectrum of lung pathologies. Data mining was performed using the resources of the NIH PubMed and PubChem information systems. By linking available data on pathological/therapeutic effects of PPARγ modulation, knowledge-based MoA networking at different levels of biological organization (molecular, cellular, tissue, organ, and system) was performed. Multiple MoA networks were developed to relate PPARγ modulation to the progress or the alleviation of pulmonary disorders, triggered by diverse pathogenic, genetic, chemical, or mechanical factors. Pharmacological targeting of PPARγ signalling was discussed with regard to ligand- and cell type-specific effects in the context of distinct disease inductor- and disease stage-dependent patterns. The proposed MoA networking analysis allows for a better understanding of the potential role of PPARγ modulation in lung pathologies. It presents a mechanistically justified basis for further computational, experimental, and clinical monitoring studies on the dynamic control of PPARγ signalling in respiratory diseases.

Quantitative profiling of inflammatory and pro-resolving lipid mediators in human adolescents and mouse plasma using UHPLC-MS/MS

OBJECTIVES

Lipid mediators are bioactive lipids which help regulate inflammation. We aimed to develop an ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method to quantify 58 pro-inflammatory and pro-resolving lipid mediators in plasma, determine preliminary reference ranges for adolescents, and investigate how total parenteral nutrition (TPN) containing omega-3 polyunsaturated fatty acid (n-3 PUFA) or n-6 PUFA based lipid emulsions influence lipid mediator concentrations in plasma.

METHODS

Lipid mediators were extracted from plasma using SPE and measured using UHPLC-MS/MS. EDTA plasma was collected from healthy adolescents between 13 and 17 years of age to determine preliminary reference ranges and from mice given intravenous TPN for seven days containing either an n-3 PUFA or n-6 PUFA based lipid emulsion.

RESULTS

We successfully quantified 43 lipid mediators in human plasma with good precision and recovery including several leukotrienes, prostaglandins, resolvins, protectins, maresins, and lipoxins. We found that the addition of methanol to human plasma after blood separation reduces post blood draw increases in 12-hydroxyeicosatetraenoic acid (12-HETE), 12-hydroxyeicosapentaenoic acid (12-HEPE), 12S-hydroxyeicosatrienoic acid (12S-HETrE), 14-hydroxydocosahexaenoic acid (14-HDHA) and thromboxane B2 (TXB2). Compared to the n-6 PUFA based TPN, the n-3 PUFA based TPN increased specialized pro-resolving mediators such as maresin 1 (MaR1), MaR2, protectin D1 (PD1), PDX, and resolvin D5 (RvD5), and decreased inflammatory lipid mediators such as leukotriene B4 (LTB4) and prostaglandin D2 (PGD2).

CONCLUSIONS

Our method provides an accurate and sensitive quantification of 58 lipid mediators from plasma samples, which we used to establish a preliminary reference range for lipid mediators in plasma samples of adolescents; and to show that n-3 PUFA, compared to n-6 PUFA rich TPN, leads to a less inflammatory lipid mediator profile in mice.

Macrophage-mediated tumor homing of hyaluronic acid nanogels loaded with polypyrrole and anticancer drug for targeted combinational photothermo-chemotherapy

Rationale: Development of nanosystems that can be integrated with macrophages (MAs), an emerging carrier system, for effective tumor therapy remains to be challenging. We report here the development of MAs specifically loaded with hyaluronic acid (HA) nanogels (NGs) encapsulated with a photothermal agent of polypyrrole (PPy) and anticancer drug doxorubicin (DOX) (HA/DOX@PPy NGs) for tumor homing and combination photothermo-chemotherapy. Methods: Cystamine dihydrochloride-crosslinked HA NGs were first prepared through a double emulsification method, then loaded with PPy via an in-situ oxidization polymerization and physically encapsulated with DOX. The created HA/DOX@PPy NGs were well characterized and subjected to be endocytosed by MAs (MAs-NGs). The MAs-mediated tumor-homing property, phenotype changes and photothermal performance of MAs-NGs were investigated in vitro, and a subcutaneous tumor model was also established to confirm their targeting capability and enhanced antitumor therapy effect in vivo. Results: The generated hybrid NGs possess a size around 77 nm and good colloidal stability, and can be specifically endocytosed by MAs without appreciably affecting their normal biofunctionalities. In particular, NG-loaded MAs display excellent in-vitro cancer cell and in-vivo tumor homing property. Systemic administration of the MAs-NGs leads to the significant inhibition of a subcutaneous tumor model through combination photothermo-chemotherapy under laser irradiation. Conclusions: The developed hybrid HA-based NG nanosystem incorporated with PPy and DOX fully integrates the coordination and heating property of PPy to regulate the optimized DOX release in the tumor region with the assistance of MA-mediated tumor homing, providing a promising cell therapy strategy for enhanced antitumor therapy.

Endurance Exercise Mitigates Immunometabolic Adipose Tissue Disturbances in Cancer and Obesity

Adipose tissue is considered an endocrine organ whose complex biology can be explained by the diversity of cell types that compose this tissue. The immune cells found in the stromal portion of adipose tissue play an important role on the modulation of inflammation by adipocytokines secretion. The interactions between metabolic active tissues and immune cells, called immunometabolism, is an important field for discovering new pathways and approaches to treat immunometabolic diseases, such as obesity and cancer. Moreover, physical exercise is widely known as a tool for prevention and adjuvant treatment on metabolic diseases. More specifically, aerobic exercise training is able to increase the energy expenditure, reduce the nutrition overload and modify the profile of adipocytokines and myokines with paracrine and endocrine effects. Therefore, our aim in this review was to cover the effects of aerobic exercise training on the immunometabolism of adipose tissue in obesity and cancer, focusing on the exercise-related modification on adipose tissue or immune cells isolated as well as their interaction.