Cysteinyl-specialized proresolving mediators link resolution of infectious inflammation and tissue regeneration via TRAF3 activation

Single-cell RNA sequencing reveals epithelial cells driving brain metastasis in lung adenocarcinoma

Brain metastases (BM) of lung adenocarcinoma (LUAD) are the most common intracranial malignancy leading to death. However, the cellular origins and drivers of BM from LUAD have not been clarified. Cellular composition was characterized by single-cell sequencing analysis of primary lung adenocarcinoma (pLUAD), BM and lymph node metastasis (LNM) samples in GSE131907. Our study briefly analyzed the tumor microenvironment (TME), focusing on the role of epithelial cells (ECs) in BM. We have discovered a population of brain metastasis-associated epithelial cells (BMAECs) expressing SPP1, SAA1, and CDKN2A, and it has been observed that this population is mainly composed of aneuploid cells from pLUAD, playing a crucial role in brain metastasis. Our study concluded that both LNM and BM in LUAD originated from pLUAD lesions, but there is currently insufficient evidence to prove a direct association between BM lesions and LNM lesions, which provides inspiration for further investigation of the TME in BM.

Specialized pro-resolving lipid mediators and resolution of viral diseases

The COVID-19 pandemics has made sparkly evident the importance of acute inflammation and its timely resolution to protect humans from pathogenic viruses while sparing them from collateral damages due to an uncontrolled immune response. It is clear now that resolution of inflammation is an active process regulated by endogenous specialized proresolving lipid mediators (SPM) biosynthesized from essential polyunsaturated fatty acids. Accruing evidence indicates that SPM are produced during viral infections and play key roles in controlling the magnitude and duration of the inflammatory response and in regulating adaptive immunity. Here, we reviewed biosynthesis and bioactions of SPM in virus-mediated human diseases. Harnessing SPM and their proresolutive actions can help in providing new therapeutic approaches to current and future human viral diseases by controlling infection, stimulating host immunity, and protecting from organ damage.

TRAF3/STAT6 axis regulates macrophage polarization and tumor progression

Converting tumor-associated macrophages (TAMs) from the M2 to the M1 phenotype is considered an effective strategy for cancer therapy. TRAF3 is known to regulate NF-κB signaling. However, the role of TRAF3 in TAM polarization has not yet been completely elucidated. Here, we found that ablation of TRAF3 increased M1 markers, iNOS, FGR and SLC4A7, while down-regulated M2 markers, CD206, CD36 and ABCC3, expression levels in macrophages. Moreover, TRAF3 deficiency enhanced LPS-induced M1 and abolished IL-4-induced macrophage polarization. Next, quantitative ubiquitomics assays demonstrated that among the quantitative 7618 ubiquitination modification sites on 2598 proteins, ubiquitination modification of IL-4 responding proteins was the most prominently reduced according to enrichment analysis. STAT6, a key factor of IL-4 responding protein, K450 and K129 residue ubiquitination levels were dramatically decreased in TRAF3-deficient macrophages. Ubiquitination assay and luciferase assay demonstrated that TRAF3 promotes STAT6 ubiquitination and transcriptional activity. Site mutation analysis revealed STAT6 K450 site ubiquitination played a vital role in TRAF3-mediated STAT6 activation. Finally, B16 melanoma mouse model demonstrated that myeloid TRAF3 deficiency suppressed tumor growth and lung metastasis in vivo. Taken together, TRAF3 plays a vital role in M2 polarization via regulating STAT6 K450 ubiquitination in macrophages.

Maresin: Macrophage Mediator for Resolving Inflammation and Bridging Tissue Regeneration-A System-Based Preclinical Systematic Review

Maresins are lipid mediators derived from omega-3 fatty acids with anti-inflammatory and pro-resolving properties, capable of promoting tissue regeneration and potentially serving as a therapeutic agent for chronic inflammatory diseases. The aim of this review was to systematically investigate preclinical and clinical studies on maresin to inform translational research. Two independent reviewers performed comprehensive searches with the term "Maresin (NOT) Review" on PubMed. A total of 137 studies were included and categorized into 11 human organ systems. Data pertinent to clinical translation were specifically extracted, including delivery methods, optimal dose response, and specific functional efficacy. Maresins generally exhibit efficacy in treating inflammatory diseases, attenuating inflammation, protecting organs, and promoting tissue regeneration, mostly in rodent preclinical models. The nervous system has the highest number of original studies (n = 25), followed by the cardiovascular system, digestive system, and respiratory system, each having the second highest number of studies (n = 18) in the field. Most studies considered systemic delivery with an optimal dose response for mouse animal models ranging from 4 to 25 μg/kg or 2 to 200 ng via intraperitoneal or intravenous injection respectively, whereas human in vitro studies ranged between 1 and 10 nM. Although there has been no human interventional clinical trial yet, the levels of MaR1 in human tissue fluid can potentially serve as biomarkers, including salivary samples for predicting the occurrence of cardiovascular diseases and periodontal diseases; plasma and synovial fluid levels of MaR1 can be associated with treatment response and defining pathotypes of rheumatoid arthritis. Maresins exhibit great potency in resolving disease inflammation and bridging tissue regeneration in preclinical models, and future translational development is warranted.

Resolvins and cysteinyl-containing pro-resolving mediators activate resolution of infectious inflammation and tissue regeneration

This review is a synopsis of the main points from the opening presentation by the authors in the Resolution of Inflammation session at the 8th European Workshop on Lipid Mediators held at the Karolinska Institute, Stockholm, Sweden, June 29th, 2022. Specialized pro-resolving mediators (SPM) promote tissue regeneration, control infections and resolution of inflammation. These include resolvins, protectins, maresins and the newly identified conjugates in tissue regeneration (CTRs). We reported mechanisms of CTRs in activating primordial regeneration pathways in planaria using RNA-sequencing. Also, the 4S,5S-epoxy-resolvin intermediate in the biosynthesis of resolvin D3 and resolvin D4 was prepared by total organic synthesis. Human neutrophils convert this to resolvin D3 and resolvin D4, while human M2 macrophages transformed this labile epoxide intermediate to resolvin D4 and a novel cysteinyl-resolvin that is a potent isomer of RCTR1. The novel cysteinyl-resolvin significantly accelerates tissue regeneration with planaria and inhibits human granuloma formation.

Resolution of inflammation in oral diseases

The resolution of inflammation is an essential endogenous process that protects host tissues from an exaggerated chronic inflammatory response. Multiple interactions between host cells and resident oral microbiome regulate the protective functions that lead to inflammation in the oral cavity. Failure of appropriate regulation of inflammation can lead to chronic inflammatory diseases that result from an imbalance between pro-inflammatory and pro-resolution mediators. Thus, failure of the host to resolve inflammation can be considered an essential pathological mechanism for progression from the late stages of acute inflammation to a chronic inflammatory response. Specialized pro-resolving mediators (SPMs), which are essential polyunsaturated fatty acid (PUFA)-derived autacoid mediators, aid in regulating the endogenous inflammation resolving process by stimulating immune cell-mediated clearance of apoptotic polymorphonuclear neutrophils, cellular debris, and microbes, restricting further neutrophil tissue infiltration, and counter-regulating pro-inflammatory cytokine production. The SPM superfamily contains four specialized lipid mediator families: lipoxins, resolvins, protectins, and maresins that can activate resolution pathways. Understanding the crosstalk between resolution signals in the tissue response to injury has therapeutic application potential for preventing, maintaining, and regenerating chronically damaged tissues. Here, we discuss the fundamental concepts of resolution as an active biochemical process, novel concepts demonstrating the role of resolution mediators in tissue regeneration in periodontal and pulpal diseases, and future directions for therapeutic applications with particular emphasis on periodontal therapy.

Recent progress in the development of fluorescent probes for imaging pathological oxidative stress

Oxidative stress is closely related to the physiopathology of numerous diseases. Reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) are direct participants and important biomarkers of oxidative stress. A comprehensive understanding of their changes can help us evaluate disease pathogenesis and progression and facilitate early diagnosis and drug development. In recent years, fluorescent probes have been developed for real-time monitoring of ROS, RNS and RSS levels in vitro and in vivo. In this review, conventional design strategies of fluorescent probes for ROS, RNS, and RSS detection are discussed from three aspects: fluorophores, linkers, and recognition groups. We introduce representative fluorescent probes for ROS, RNS, and RSS detection in cells, physiological/pathological processes (e.g., Inflammation, Drug Induced Organ Injury and Ischemia/Reperfusion Injury etc.), and specific diseases (e.g., neurodegenerative diseases, epilepsy, depression, diabetes and cancer, etc.). We then highlight the achievements, current challenges, and prospects for fluorescent probes in the pathophysiology of oxidative stress-related diseases.

Possibility of averting cytokine storm in SARS-COV 2 patients using specialized pro-resolving lipid mediators

Fatal "cytokine storms (CS)" observed in critically ill COVID-19 patients are consequences of dysregulated host immune system and over-exuberant inflammatory response. Acute respiratory distress syndrome (ARDS), multi-system organ failure, and eventual death are distinctive symptoms, attributed to higher morbidity and mortality rates among these patients. Consequent efforts to save critical COVID-19 patients via the usage of several novel therapeutic options are put in force. Strategically, drugs being used in such patients are dexamethasone, remdesivir, hydroxychloroquine, etc. along with the approved vaccines. Moreover, it is certain that activation of the resolution process is important for the prevention of chronic diseases. Until recently Inflammation resolution was considered a passive process, rather it's an active biochemical process that can be achieved by the use of specialized pro-resolving mediators (SPMs). These endogenous mediators are an array of atypical lipid metabolites that include Resolvins, lipoxins, maresins, protectins, considered as immunoresolvents, but their role in COVID-19 is ambiguous. Recent evidence from studies such as the randomized clinical trial, in which omega 3 fatty acid was used as supplement to resolve inflammation in COVID-19, suggests that direct supplementation of SPMs or the use of synthetic SPM mimetics (which are still being explored) could enhance the process of resolution by regulating the aberrant inflammatory process and can be useful in pain relief and tissue remodeling. Here we discussed the biosynthesis of SPMs, & their mechanistic pathways contributing to inflammation resolution along with sequence of events leading to CS in COVID-19, with a focus on therapeutic potential of SPMs.

Periodontal Stem Cells Synthesize Maresin Conjugate in Tissue Regeneration 3

Periodontal disease is a significant public health problem worldwide. Excess unresolved chronic inflammation destroys the periodontal tissues that surround and support the teeth, and efforts to control inflammation by removal of bacterial deposits on the teeth have limited long-term impact. Likewise, procedures aimed at regeneration of the periodontal tissues have shown limited success. Recent advances in stem cell research have shown promising novel prospects for the use of periodontal ligament stem cells (PDLSCs) in tissue regeneration; however, control of inflammation remains a barrier. Human PDLSCs have been shown to release specialized proresolving lipid mediators (SPMs) that modulate the immune response and promote resolution of inflammation, tissue repair, and regeneration. Studies on stem cell biology in periodontology have also been limited by the lack of a good large animal model. Herein, we describe PDLSC biology of the Yorkshire pig (pPDLSCs). pPDLSCs were isolated and characterized. Using lipid mediator profiling, we demonstrate for the first time that pPDLSCs biosynthesize cysteinyl-containing SPMs (cys-SPMs), specifically, maresin conjugates in tissue regeneration 3 (MCTR3) and its authentication using liquid chromatography/tandem mass spectrometry. The exogenous addition of the n-3 precursor docosahexaenoic acid enhances MCTR3 biosynthesis. Using immunocytochemistry, we show that pPDLSCs express 4 of the SPM biosynthetic pathway enzymes necessary for SPM biosynthesis, including 5-lipoxygenase, 12-lipoxygenase, and 15-lipoxygenase-1. In addition, we identified and quantified the cytokine/chemokine profile of pPDLSCs using a 13-plex immunology multiplex assay and found that the pretreatment of pPDLSCs with MCTR3 in an inflammatory environment reduced the production of acute and chronic proinflammatory cytokines/chemokines. Together, these results suggest that enhancing resolution of inflammation pathways and mediators may be a possible key early event in predictable periodontal regeneration.

Obesity Dysregulates the Immune Response to Influenza Infection and Vaccination Through Metabolic and Inflammatory Mechanisms

The COVID-19 pandemic demonstrates that obesity alone, independent of comorbidities, is a significant risk factor for severe outcomes from infection. This susceptibility mirrors a similar pattern with influenza infection; that is, obesity is a unique risk factor for increased morbidity and mortality. Therefore, it is critical to understand how obesity contributes to a reduced ability to respond to respiratory viral infections. Herein, we discuss human and animal studies with influenza infection and vaccination that show obesity impairs immunity. We cover several key mechanisms for the dysfunction. These mechanisms include systemic and cellular level changes that dysregulate immune cell metabolism and function in addition to how obesity promotes deficiencies in metabolites that control the resolution of inflammation and infection. Finally, we discuss major gaps in knowledge, particularly as they pertain to diet and mechanisms, which will drive future efforts to improve outcomes in response to respiratory viral infections in an increasingly obese population.

Inflammation and resolution signaling in cardiac repair and heart failure

Unresolved inflammation is a key mediator of advanced heart failure. Especially, damage, pathogen, and lifestyle-associated molecular patterns are the major factors in initiating baseline inflammatory diseases, particularly in cardiac pathology. After a significant cardiac injury like a heart attack, splenic and circulating leukocytes begin a highly optimized sequence of immune cell recruitment (neutrophils and monocytes) to coordinate effective tissue repair. An injured cardiac tissue repair and homeostasis are dependent on clearance of cellular debris where the recruited leukocytes transition from a pro-inflammatory to a reparative program through resolution process. After a cardiac injury, macrophages play a decisive role in cardiac repair through the biosynthesis of endogenous lipid mediators that ensure a timely tissue repair while avoiding chronic inflammation and impaired cardiac repair. However, dysregulation of resolution of inflammation processes due to cardiometabolic defects (obesity, hypertension, and diabetes), aging, or co-medication(s) lead to impaired cardiac repair. Hence, the presented review demonstrates the fundamental role of leukocytes, in particular macrophages orchestrate the inflammation and resolution biology, focusing on the biosynthesis of specialized lipid mediators in cardiac repair and heart failure. This work was supported by research funds from National Institutes of Health (AT006704, HL132989, and HL144788) to G.V.H. The authors acknowledges the use of Servier Medical Art image bank and Biorender that is used to create schematic Figures 1–3.

Polyunsaturated fatty acids and fatty acid-derived lipid mediators: Recent advances in the understanding of their biosynthesis, structures, and functions

Polyunsaturated fatty acids (PUFAs) are structural components of membrane phospholipids, and influence cellular function via effects on membrane properties, and also by acting as a precursor pool for lipid mediators. These lipid mediators are formed via activation of pathways involving at least one step of dioxygen-dependent oxidation, and are consequently called oxylipins. Their biosynthesis can be either enzymatically-dependent, utilising the promiscuous cyclooxygenase, lipoxygenase, or cytochrome P450 mixed function oxidase pathways, or nonenzymatic via free radical-catalyzed pathways. The oxylipins include the classical eicosanoids, comprising prostaglandins, thromboxanes, and leukotrienes, and also more recently identified lipid mediators. With the advent of new technologies there is growing interest in identifying these different lipid mediators and characterising their roles in health and disease. This review brings together contributions from some of those at the forefront of research into lipid mediators, who provide brief introductions and summaries of current understanding of the structure and functions of the main classes of nonclassical oxylipins. The topics covered include omega-3 and omega-6 PUFA biosynthesis pathways, focusing on the roles of the different fatty acid desaturase enzymes, oxidized linoleic acid metabolites, omega-3 PUFA-derived specialized pro-resolving mediators, elovanoids, nonenzymatically oxidized PUFAs, and fatty acid esters of hydroxy fatty acids.

Role of Specialized Pro-Resolving Mediators in Modifying Host Defense and Decreasing Bacterial Virulence

Bacterial infection activates the innate immune system as part of the host’s defense against invading pathogens. Host response to bacterial pathogens includes leukocyte activation, inflammatory mediator release, phagocytosis, and killing of bacteria. An appropriate host response requires resolution. The resolution phase involves attenuation of neutrophil migration, neutrophil apoptosis, macrophage recruitment, increased phagocytosis, efferocytosis of apoptotic neutrophils, and tissue repair. Specialized Pro-resolving Mediators (SPMs) are bioactive fatty acids that were shown to be highly effective in promoting resolution of infectious inflammation and survival in several models of infection. In this review, we provide insight into the role of SPMs in active host defense mechanisms for bacterial clearance including a new mechanism of action in which an SPM acts directly to reduce bacterial virulence.

Specialized Proresolving Mediators Facilitate the Immunomodulation of the Periodontal Ligament Stem Cells

Recent investigations into the regulation of the inflammation in the periodontitis have revealed that chronic inflammatory diseases such as periodontitis are characterized by an imbalance in the proinflammatory and proresolution mediators and can be characterized by a failure of the resolution pathways in the late stages of the acute inflammatory response. The proresolution mediators, termed as specialized proresolving mediators (SPMs), comprise the lipoxins, resolvins, protectins, and maresins that are derived from the arachidonic acid or omega-3 polyunsaturated fatty acids. In the animal studies, treatment of the periodontitis with the topical SPMs return the inflammatory lesion to the homeostasis with the regeneration of all the components of the periodontal organ lost to the disease. In this article, the study investigates the immunomodulatory role of SPMs in the periodontal ligament stem cells (PDLSCs). Primary porcine PDLSCs (pPDLSCs) were stimulated with interleukin-1β (IL-1β) and interleukin-17 (IL-17) in vitro to simulate the periodontal inflammation in the presence or absence of SPMs. This study found that IL-1β and IL-17 synergistically activated the proinflammatory genes of pPDLSCs and altered the immune phenotype of pPDLSCs including the key signaling pathways. Addition of SPMs rescued the pPDLSCs phenotype and induced further production of the additional SPMs, which was reflected by upregulation of the requisite enzymes 12- and 15-lipoxygenase by pPDLSCs. This study interrogated the immunomodulatory actions of pPDLSCs on the monocytes/macrophages, focusing on the porcine CD14/CD16/CD163 markers by using flow cytometry. This study utilized the CD14+CD16+/CD14+CD16− ratio and CD163 on the monocytes/macrophages to differentiate between a proinflammation phenotype (lower ratio) and a resolution of the inflammation phenotype (higher ratio). This study also found that the conditioned medium from pPDLSCs treated with the cytokines and Maresin1 increased the CD14+CD16+/CD14+CD16− ratio and had the highest CD163 expression. This study concludes that in an inflammatory environment, pPDLSCs become proinflammatory and exert immunomodulatory functions. Maresin 1 resolves the inflammation by acting on pPDLSCs directly and by shifting the monocytes/macrophages phenotype to the proresolution dominance.

Protectins PCTR1 and PD1 Reduce Viral Load and Lung Inflammation During Respiratory Syncytial Virus Infection in Mice

Viral pneumonias are a major cause of morbidity and mortality, owing in part to dysregulated excessive lung inflammation, and therapies to modulate host responses to viral lung injury are urgently needed. Protectin conjugates in tissue regeneration 1 (PCTR1) and protectin D1 (PD1) are specialized pro-resolving mediators (SPMs) whose roles in viral pneumonia are of interest. In a mouse model of Respiratory Syncytial Virus (RSV) pneumonia, intranasal PCTR1 and PD1 each decreased RSV genomic viral load in lung tissue when given after RSV infection. Concurrent with enhanced viral clearance, PCTR1 administration post-infection, decreased eosinophils, neutrophils, and NK cells, including NKG2D⁺ activated NK cells, in the lung. Intranasal PD1 administration post-infection decreased lung eosinophils and Il-13 expression. PCTR1 increased lung expression of cathelicidin anti-microbial peptide and decreased interferon-gamma production by lung CD4⁺ T cells. PCTR1 and PD1 each increased interferon-lambda expression in human bronchial epithelial cells in vitro and attenuated RSV-induced suppression of interferon-lambda in mouse lung in vivo. Liquid chromatography coupled with tandem mass spectrometry of RSV-infected and untreated mouse lungs demonstrated endogenous PCTR1 and PD1 that decreased early in the time course while cysteinyl-leukotrienes (cys-LTs) increased during early infection. As RSV infection resolved, PCTR1 and PD1 increased and cys-LTs decreased to pre-infection levels. Together, these results indicate that PCTR1 and PD1 are each regulated during RSV pneumonia, with overlapping and distinct mechanisms for PCTR1 and PD1 during the resolution of viral infection and its associated inflammation.

Pro-Resolving Ligands Orchestrate Phagocytosis

The resolution of inflammation is a tissue protective program that is governed by several factors including specialized pro-resolving mediators (SPMs), proteins, gasses and nucleotides. Pro-resolving mediators activate counterregulatory programs to quell inflammation and promote tissue repair in a manner that does not compromise host defense. Phagocytes like neutrophils and macrophages play key roles in the resolution of inflammation because of their ability to remove debris, microbes and dead cells through processes including phagocytosis and efferocytosis. Emerging evidence suggests that failed resolution of inflammation and defective phagocytosis or efferocytosis underpins several prevalent human diseases. Therefore, understanding factors and mechanisms associated with enhancing these processes is a critical need. SPMs enhance phagocytosis and efferocytosis and this review will highlight mechanisms associated with their actions.