Proresolving lipid mediators resolvin D1, resolvin D2, and maresin 1 are critical in modulating T cell responses

Positive and negative roles of lipids in mast cells and allergic responses

Mast cells are a central immune cell population that are crucial in allergic responses. They secrete granule contents and cytokines and produce a panel of lipid mediators in response to FcεRI-dependent or independent stimuli. Leukotrienes and prostaglandins derived from ω6 arachidonic acid, or specialized pro-resolving lipid mediators derived from ω3 eicosapentaenoic and docosahexaenoic acids, exert pleiotropic effects on various cells in the tissue microenvironment, thereby positively or negatively regulating allergic responses. Mast cells also express the inhibitory receptors CD300a and CD300f, which recognize structural lipids. CD300a or CD300f binding to externalized phosphatidylserine or extracellular ceramides, respectively, inhibits FcεRI-mediated mast cell activation. The inhibitory CD300-lipid axis downregulates IgE-driven, mast cell-dependent type I hypersensitivity through different mechanisms. Herein, we provide an overview of our current understanding of the biological roles of lipids in mast cell-dependent allergic responses.

Protectin D1 reduces imiquimod-induced psoriasiform skin inflammation

Specialized proresolving mediators are enzymatically oxygenated natural molecules derived from polyunsaturated fatty acids and are considered novel. These novel mediators include lipoxins from arachidonic acid, resolvins and protectins from omega-3 essential fatty acids, and new maresins. These mediators harbor potent dual proresolving and anti-inflammatory properties. Resolvins and protectins are known to be potent when administered to various inflammation-associated animal models of human diseases. Although psoriasis' etiology remains unknown, there is accumulating evidence indicating that cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-23, and IL-17, play pivotal roles in its development. Experimentally, resolvins, maresins, and lipoxins downregulate the cytokine expression of the IL-23/IL-17 axis and inhibition of mitogen-activated protein kinases and nuclear factor kappa-light-chain-enhancer of activated B (NF-κB) cell signaling transduction pathways. Here, we assessed the effects of protectin D1 (PD1) on imiquimod (IMQ)-induced psoriasiform skin inflammation and keratinocytes. PD1 showed clinical improvement in skin thickness, redness, and scaling in psoriasis mouse models. Moreover, PD1 decreased IL-1β, IL-6, IL-17, and CXCL1 mRNA expressions and reduced STAT1 and NF-κB signaling pathway activation in lesions. Serum myeloperoxidase, IgG2a, IL-1β, IL-6, IL-17, and TNF-α and spleen CD4⁺IFN-γ⁺IL-17⁺ T lymphocytes were reduced after PD1 treatment in IMQ-induced psoriasiform mouse models. In addition, IL-1β, IL-6, IL-8, and IL-18BP gene expressions were decreased in PD1-treated keratinocytes. Moreover, a decrease in the expression levels of CCL17 and IL-6 and an inhibition of the STAT1 and NF-κB signaling transduction pathways was observed in keratinocytes. These PD1 anti-inflammatory effects suggest that it is a good therapeutic candidate for psoriasis.

G-Protein Coupled Receptors Involved in the Resolution of Inflammation: Ligands and Therapeutic Perspectives

Dysregulated inflammation is a central pathological process in diverse disease states, including neurodegenerative disorders. The recent concept of "resolution of inflammation" is offering a conceptual change for the diagnosis and the development of new therapeutic approaches for chronic inflammatory diseases. Resolution of inflammation terminates the inflammatory response promoting the return to tissue homeostasis through the action of several classes of mediators, termed specialized pro-resolving lipid mediators (SPMs), that include lipoxins, resolvins, protectins, and maresins. SPMs provide "stop signals" that reduce the number of immune cells at the site of insult and increase the clearance of apoptotic cells through phagocytosis. SPMs elicit their effects through the interaction with specific G-protein coupled receptors (GPCRs). The elucidation of the pathways downstream of the GPCRs involved in the resolution of chronic inflammation is opening novel opportunities to generate novel anti-inflammatory agents. This review focuses on the SPMs and the receptors through which their effects are mediated. The medicinal chemistry of the modulators of the GPCRs involved in the resolution of inflammation will be illustrated, by highlighting the potential for developing new antiinflammatory drugs.

Differential Tissue Metabolic Signatures in IgG4-Related Ophthalmic Disease and Orbital Mucosa-Associated Lymphoid Tissue Lymphoma

Purpose

To identify tissue metabolomic profiles in biopsy specimens with IgG4-related ophthalmic disease (IgG4-ROD) and mucosa-associated lymphoid tissue (MALT) lymphoma and investigate their potential implication in the disease pathogenesis and biomarkers.

Methods

We conducted a comprehensive analysis of the metabolomes and lipidomes of biopsy-proven IgG4-ROD (n = 22) and orbital MALT lymphoma (n = 21) specimens and matched adjacent microscopically normal adipose tissues using liquid chromatography time-of-flight mass spectrometry. The altered metabolomic profiles were visualized by heat map and principal component analysis. Metabolic pathway analysis was performed by Metabo Analyst 4.0 using differentially expressed metabolites. The diagnostic performance of the metabolic markers was evaluated using receiver operating characteristic curves. Machine learning algorithms were implemented by random forest using the R environment. Finally, an independent set of 18 IgG4-ROD and 17 orbital MALT lymphoma specimens were used to validate the identified biomarkers.

Results

The principal component analysis showed a significant difference of both IgG4-ROD and orbital MALT lymphoma for biopsy specimens and controls. Interestingly, lesions in IgG4-ROD were uniquely enriched in arachidonic metabolism, whereas those in orbital MALT lymphoma were enriched in tricarboxylic acid cycle metabolism. We identified spermine as the best discriminator between IgG4-ROD and orbital MALT lymphoma, and the area under the receiver operating characteristic curve of the spermine to discriminate between the two diseases was 0.89 (95% confidence interval, 0.803–0.984). A random forest model incorporating a panel of five metabolites showed a high area under the receiver operating characteristic curve value of 0.983 (95% confidence interval, 0.981–0.984). The results of validation revealed that four tissue metabolites: N¹,N¹²-diacetylspermine, spermine, malate, and glycolate, had statistically significant differences between IgG4-ROD and orbital MALT lymphoma with receiver operating characteristic values from 0.708 to 0.863.

Conclusions

These data revealed the characteristic differences in metabolomic profiles between IgG4-ROD and orbital MALT lymphoma, which may be useful for developing new diagnostic biomarkers and elucidating the pathogenic mechanisms of these common orbital lymphoproliferative disorders.

Specialized Pro-Resolving Lipid Mediators in Neonatal Cardiovascular Physiology and Diseases

Cardiovascular disease remains a leading cause of mortality worldwide. Unresolved inflammation plays a critical role in cardiovascular diseases development. Specialized Pro-Resolving Mediators (SPMs), derived from long chain polyunsaturated fatty acids (LCPUFAs), enhances the host defense, by resolving the inflammation and tissue repair. In addition, SPMs also have anti-inflammatory properties. These physiological effects depend on the availability of LCPUFAs precursors and cellular metabolic balance. Most of the studies have focused on the impact of SPMs in adult cardiovascular health and diseases. In this review, we discuss LCPUFAs metabolism, SPMs, and their potential effect on cardiovascular health and diseases primarily focusing in neonates. A better understanding of the role of these SPMs in cardiovascular health and diseases in neonates could lead to the development of novel therapeutic approaches in cardiovascular dysfunction.

Pro-resolving lipid mediator lipoxin A4 attenuates neuro-inflammation by modulating T cell responses and modifies the spinal cord lipidome

The chronic neuro-inflammatory character of multiple sclerosis (MS) suggests that the natural process to resolve inflammation is impaired. This protective process is orchestrated by specialized pro-resolving lipid mediators (SPMs), but to date, the role of SPMs in MS remains largely unknown. Here, we provide in vivo evidence that treatment with the SPM lipoxin A4 (LXA4) ameliorates clinical symptoms of experimental autoimmune encephalomyelitis (EAE) and inhibits CD4+ and CD8+ T cell infiltration into the central nervous system (CNS). Moreover, we show that LXA4 potently reduces encephalitogenic Th1 and Th17 effector functions, both in vivo and in isolated human T cells from healthy donors and patients with relapsing-remitting MS. Finally, we demonstrate that LXA4 affects the spinal cord lipidome by significantly reducing the levels of pro-inflammatory lipid mediators during EAE. Collectively, our findings provide mechanistic insight into LXA4-mediated amelioration of neuro-inflammation and highlight the potential clinical application of LXA4 for MS.

The Influence of Nutritional Factors on Immunological Outcomes

Through food intake, humans obtain a variety of nutrients that are essential for growth, cellular function, tissue development, energy, and immune defense. A special interaction between nutrients and gut-associated lymphoid tissue occurs in the intestinal tract. Enterocytes of the intestinal barrier act as sensors for antigens from nutrients and the intestinal microbiota, which they deliver to the underlying immune system of the lamina propria, triggering an immune response. Studies investigating the mechanism of influence of nutrition on immunological outcomes have highlighted an important role of macronutrients (proteins, carbohydrates, fatty acids) and micronutrients (vitamins, minerals, phytochemicals, antioxidants, probiotics) in modulating immune homeostasis. Nutrients exert their role in innate immunity and inflammation by regulating the expression of TLRs, pro- and anti-inflammatory cytokines, thus interfering with immune cell crosstalk and signaling. Chemical substrates derived from nutrient metabolism may act as cofactors or blockers of enzymatic activity, influencing molecular pathways and chemical reactions associated with microbial killing, inflammation, and oxidative stress. Immune cell function appears to be influenced by certain nutrients that form parts of the cell membrane structure and are involved in energy production and prevention of cytotoxicity. Nutrients also contribute to the initiation and regulation of adaptive immune responses by modulating B and T lymphocyte differentiation, proliferation and activation, and antibody production. The purpose of this review is to present the available data from the field of nutritional immunology to elucidate the complex and dynamic relationship between nutrients and the immune system, the delineation of which will lead to optimized nutritional regimens for disease prevention and patient care.

μSPE followed by HPLC-MS/MS for the determination of series D and E resolvins in biological matrices

The critical role of acute inflammatory processes is recognized in many chronic diseases; a key point in molecular mechanisms of acute inflammation resolution is represented by a new group of pro-resolving lipid mediators that include distinct families of molecules: lipoxins, resolvins, protectins and maresins, collectively termed "specialized pro-resolving mediators" (SPMs). In particular, resolvins are active in the picogram to nanogram dose range, whereby they can directly modulate a plethora of anti-inflammatory responses. The presented method proposes an analytical protocol able to extract and to quantify 6 different resolvins from 3 different matrices (plasma, cells and exudates). The method, validated according to the EMA guideline for bioanalysis, exhibited good precision (1%-20%) and accuracy (2%-20%). In particular, the combination of two different sample preparation techniques, Liquid-Liquid Extraction (LLE) and micro-Solid Phase Extraction (μSPE), applied for the first on this class of molecules, used for the extraction and clean-up respectively, led to high enrichment factor (20 fold) and consequently a high sensitivity (LOQ between 1 and 38 pg mL^-1); moreover the validation data proved the versatility of μSPE as clean-up tool as it was capable to manage huge enrichment factor without negatively affect accuracy and precision of analysis.

Peritraumatic plasma Omega-3 fatty acid concentration predicts chronic pain severity following thermal burn injury

Chronic pain is a significant co-morbidity of burn injury affecting up to 60% of survivors. Currently, no treatments are available to prevent chronic pain after burn injury. Accumulating evidence suggests that omega-3 fatty acids (O3FA) improve symptoms across a range of painful conditions. In this study, we evaluated whether low peritraumatic levels of O3FA predicts greater pain severity during the year after burn injury. Burn survivors undergoing skin autograft were recruited from three participating burn centers. Plasma O3FA (n=77) levels were assessed in the early aftermath of burn injury using liquid chromatography/mass spectrometry and pain severity was assessed via the 0-10 numeric rating scale for 1 year following burn injury. Repeated-measures linear regression analyses were used to evaluate the association between peritraumatic O3FA concentrations and pain severity during the year following burn injury. Peritraumatic O3FA concentration and chronic pain severity were inversely related; lower levels of peritraumatic O3FA predicted worse pain outcomes (β=-.002, p=.020). Future studies are needed to evaluate biological mechanisms mediating this association and to assess the ability of O3FA to prevent chronic pain following burn injury.

Omega-3 Polyunsaturated Fatty Acid Intervention Against Established Autoimmunity in a Murine Model of Toxicant-Triggered Lupus

Workplace exposure to respirable crystalline silica dust (cSiO2) has been etiologically linked to the development of lupus and other human autoimmune diseases. Lupus triggering can be recapitulated in female NZBWF1 mice by four weekly intranasal instillations with 1 mg cSiO2. This elicits inflammatory/autoimmune gene expression and ectopic lymphoid structure (ELS) development in the lung within 1 week, ultimately driving early onset of systemic autoimmunity and glomerulonephritis. Intriguingly, dietary supplementation with docosahexaenoic acid (DHA), an ω-3 polyunsaturated fatty acid (PUFA) found in fish oil, beginning 2 week prior to cSiO2 challenge, prevented inflammation and autoimmune flaring in this novel model. However, it is not yet known how ω-3 PUFA intervention influences established autoimmunity in this murine model of toxicant-triggered lupus. Here we tested the hypothesis that DHA intervention after cSiO2-initiated intrapulmonary autoimmunity will suppress lupus progression in the NZBWF1 mouse. Six-week old NZWBF1 female mice were fed purified isocaloric diet for 2 weeks and then intranasally instilled with 1 mg cSiO2 or saline vehicle weekly for 4 consecutive weeks. One week after the final instillation, which marks onset of ELS formation, mice were fed diets supplemented with 0, 4, or 10 g/kg DHA. One cohort of mice (n = 8/group) was terminated 13 weeks after the last cSiO2 instillation and assessed for autoimmune hallmarks. A second cohort of mice (n = 8/group) remained on experimental diets and was monitored for proteinuria and moribund criteria to ascertain progression of glomerulonephritis and survival, respectively. DHA consumption dose-dependently increased ω-3 PUFA content in the plasma, lung, and kidney at the expense of the ω-6 PUFA arachidonic acid. Dietary intervention with high but not low DHA after cSiO2 treatment suppressed or delayed: (i) recruitment of T cells and B cells to the lung, (ii) development of pulmonary ELS, (iii) elevation of a wide spectrum of plasma autoantibodies associated with lupus and other autoimmune diseases, (iv) initiation and progression of glomerulonephritis, and (v) onset of the moribund state. Taken together, these preclinical findings suggest that DHA supplementation at a human caloric equivalent of 5 g/d was an effective therapeutic regimen for slowing progression of established autoimmunity triggered by the environmental toxicant cSiO2.

Cells of the Immune System in Cardiac Remodeling: Main Players in Resolution of Inflammation and Repair After Myocardial Infarction

The burden of heart failure (HF), developing after myocardial infarction MI, still represents a major issue in clinical practice. Failure of appropriate resolution of inflammation during post-myocardial injury is associated with unsuccessful left ventricular remodeling and underlies HF pathogenesis. Cells of the immune system have been shown to mediate both protective and damaging effects in heart remodeling. This ambiguity of the role of the immune system and inconsistent results of the recent clinical trials question the benefits of anti-inflammatory therapies during acute MI. The present review will summarize knowledge of the roles that different cells of the immune system play in the process of post-infarct cardiac healing. Data on the phenotype, active molecules and functions of the immune cells, based on the results of both experimental and clinical studies, will be provided. For some cellular subsets, such as macrophages, neutrophils, dendritic cells and lymphocytes, an anti-inflammatory activity has been attributed to the specific subpopulations. Activity of other cells, such as eosinophils, mast cells, natural killer (NK) cells and NKT cells has been shown to be highly dependent of the signals created by micro-environment. Also, new approaches for classification of cellular phenotypes based on the single-cell RNA sequencing allow better understanding of the phenotype of the cells involved in resolution of inflammation. Possible perspectives of immune-mediated therapy for AMI patients are discussed in the conclusion. We also outline unresolved questions that need to be solved in order to implement the current knowledge on the role of the immune cells in post-MI tissue repair into practice.

Resolvin E1 Regulates Th17 Function and T Cell Activation

Resolvin E1 (RvE1) is a specialized pro-resolving lipid mediator derived from eicosapentaenoic acid and plays a critical role in resolving inflammation and tissue homeostasis. T_h17 cells are a distinct group of T helper (T_h) cells with tissue-destructive functions in autoimmune and chronic inflammatory diseases via the secretion of IL-17. Dendritic cell (DC)-mediated antigen presentation regulates the T_h17-induced progression of inflammation and tissue destruction. In this study, we hypothesized that the RvE1 would restore homeostatic balance and inflammation by targeting the T_h17 function. We designed three experiments to investigate the impact of RvE1 on different phases of T_h17 response and the potential role of DCs: First CD4⁺ T cells were induced by IL-6/TGF_β to measure the effect of RvE1 on T_h17 differentiation in an inflammatory milieu. Second, we measured the impact of RvE1 on DC-stimulated T_h17 differentiation in a co-culture model. Third, we measured the effect of RvE1 on DC maturation. RvE1 blocked the CD25, CCR6 and IL-17 expression; IL-17, IL-21, IL-10, and IL-2 production, suggesting inhibition of T cell activation, T_h17 stimulation and chemoattraction. RvE1 also suppressed the activation of DCs by limiting their pro-inflammatory cytokine production. Our findings collectively demonstrated that the RvE1 targeted the T_h17 activation and the DC function as a potential mechanism for inflammatory resolution and acquired immune response.

Maresin 1 protects the liver against ischemia/reperfusion injury via the ALXR/Akt signaling pathway

BACKGROUND

Hepatic ischemia/reperfusion (I/R) injury can be a major complication following liver surgery contributing to post-operative liver dysfunction. Maresin 1 (MaR1), a pro-resolving lipid mediator, has been shown to suppress I/R injury. However, the mechanisms that account for the protective effects of MaR1 in I/R injury remain unknown.

METHODS

WT (C57BL/6J) mice were subjected to partial hepatic warm ischemia for 60mins followed by reperfusion. Mice were treated with MaR1 (5-20 ng/mouse), Boc2 (Lipoxin A4 receptor antagonist), LY294002 (Akt inhibitor) or corresponding controls just prior to liver I/R or at the beginning of reperfusion. Blood and liver samples were collected at 6 h post-reperfusion. Serum aminotransferase, histopathologic changes, inflammatory cytokines, and oxidative stress were analyzed to evaluate liver injury. Signaling pathways were also investigated in vitro using primary mouse hepatocyte (HC) cultures to identify underlying mechanisms for MaR1 in liver I/R injury.

RESULTS

MaR1 treatment significantly reduced ALT and AST levels, diminished necrotic areas, suppressed inflammatory responses, attenuated oxidative stress and decreased hepatocyte apoptosis in liver after I/R. Akt signaling was significantly increased in the MaR1-treated liver I/R group compared with controls. The protective effect of MaR1 was abrogated by pretreatment with Boc2, which together with MaR1-induced Akt activation. MaR1-mediated liver protection was reversed by inhibition of Akt.

CONCLUSIONS

MaR1 protects the liver against hepatic I/R injury via an ALXR/Akt signaling pathway. MaR1 may represent a novel therapeutic agent to mitigate the detrimental effects of I/R-induced liver injury.

Comparing the efficacy of γ- and electron-irradiation of PBMCs to promote secretion of paracrine, regenerative factors

Cell-free secretomes represent a promising new therapeutic avenue in regenerative medicine, and γ-irradiation of human peripheral blood mononuclear cells (PBMCs) has been shown to promote the release of paracrine factors with high regenerative potential. Recently, the use of alternative irradiation sources, such as artificially generated β- or electron-irradiation, is encouraged by authorities. Since the effect of the less hazardous electron-radiation on the production and functions of paracrine factors has not been tested so far, we compared the effects of γ- and electron-irradiation on PBMCs and determined the efficacy of both radiation sources for producing regenerative secretomes. Exposure to 60 Gy γ-rays from a radioactive nuclide and 60 Gy electron-irradiation provided by a linear accelerator comparably induced cell death and DNA damage. The transcriptional landscapes of PBMCs exposed to either radiation source shared a high degree of similarity. Secretion patterns of proteins, lipids, and extracellular vesicles displayed similar profiles after γ- and electron-irradiation. Lastly, we detected comparable biological activities in functional assays reflecting the regenerative potential of the secretomes. Taken together, we were able to demonstrate that electron-irradiation is an effective, alternative radiation source for producing therapeutic, cell-free secretomes. Our study paves the way for future clinical trials employing secretomes generated with electron-irradiation in tissue-regenerative medicine.

Untangling Local Pro-Inflammatory, Reparative, and Regulatory Damage-Associated Molecular-Patterns (DAMPs) Pathways to Improve Transplant Outcomes

Detrimental inflammatory responses after solid organ transplantation are initiated when immune cells sense pathogen-associated molecular patterns (PAMPs) and certain damage-associated molecular patterns (DAMPs) released or exposed during transplant-associated processes, such as ischemia/reperfusion injury (IRI), surgical trauma, and recipient conditioning. These inflammatory responses initiate and propagate anti-alloantigen (AlloAg) responses and targeting DAMPs and PAMPs, or the signaling cascades they activate, reduce alloimmunity, and contribute to improved outcomes after allogeneic solid organ transplantation in experimental studies. However, DAMPs have also been implicated in initiating essential anti-inflammatory and reparative functions of specific immune cells, particularly Treg and macrophages. Interestingly, DAMP signaling is also involved in local and systemic homeostasis. Herein, we describe the emerging literature defining how poor outcomes after transplantation may result, not from just an over-abundance of DAMP-driven inflammation, but instead an inadequate presence of a subset of DAMPs or related molecules needed to repair tissue successfully or re-establish tissue homeostasis. Adverse outcomes may also arise when these homeostatic or reparative signals become dysregulated or hijacked by alloreactive immune cells in transplant niches. A complete understanding of the critical pathways controlling tissue repair and homeostasis, and how alloimmune responses or transplant-related processes disrupt these will lead to new immunotherapeutics that can prevent or reverse the tissue pathology leading to lost grafts due to chronic rejection.

Omega 3 Fatty Acid and Skin Diseases

Humans are exposed to various external environmental factors. Food intake is one of the most influential factors impacting daily lifestyle. Among nutrients obtained from foods, omega-3 polyunsaturated fatty acids (PUFAs) have various beneficial effects on inflammatory diseases. Furthermore, omega-3 PUFA metabolites, including resolvins, are known to demonstrate strong anti-inflammatory effects during allergic and inflammatory diseases; however, little is known regarding the actual impact of these metabolites on skin diseases. In this review, we focused on metabolites that have strong anti-inflammatory actions in various inflammatory diseases, as well as those that present antitumor actions in malignancies, in addition to the actual effect of omega-3 PUFA metabolites on various cells.

Bioactive Lipids in MSCs Biology: State of the Art and Role in Inflammation

Lipidomics is a lipid-targeted metabolomics approach that aims to the comprehensive analysis of lipids in biological systems in order to highlight the specific functions of lipid species in health and disease. Lipids play pivotal roles as they are major structural components of the cellular membranes and energy storage molecules but also, as most recently shown, they act as functional and regulatory components of intra- and intercellular signaling. Herein, emphasis is given to the recently highlighted roles of specific bioactive lipids species, as polyunsaturated fatty acids (PUFA)-derived mediators (generally known as eicosanoids), endocannabinoids (eCBs), and lysophospholipids (LPLs), and their involvement in the mesenchymal stem cells (MSCs)-related inflammatory scenario. Indeed, MSCs are a heterogenous population of multipotent cells that have attracted much attention for their potential in regulating inflammation, immunomodulatory capabilities, and reparative roles. The lipidomics of the inflammatory disease osteoarthritis (OA) and the influence of MSCs-derived lipids have also been addressed.

The Role of Sphingolipids and Specialized Pro-Resolving Mediators in Alzheimer's Disease

Alzheimer’s disease (AD) is the leading cause of dementia worldwide giving rise to devastating forms of cognitive decline, which impacts patients’ lives and that of their proxies. Pathologically, AD is characterized by extracellular amyloid deposition, neurofibrillary tangles and chronic neuroinflammation. To date, there is no cure that prevents progression of AD. In this review, we elaborate on how bioactive lipids, including sphingolipids (SL) and specialized pro-resolving lipid mediators (SPM), affect ongoing neuroinflammatory processes during AD and how we may exploit them for the development of new biomarker panels and/or therapies. In particular, we here describe how SPM and SL metabolism, ranging from ω-3/6 polyunsaturated fatty acids and their metabolites to ceramides and sphingosine-1-phosphate, initiates pro- and anti-inflammatory signaling cascades in the central nervous system (CNS) and what changes occur therein during AD pathology. Finally, we discuss novel therapeutic approaches to resolve chronic neuroinflammation in AD by modulating the SPM and SL pathways.

Role of the Specialized Pro-resolving Mediator Resolvin D1 in Hashimoto's Thyroiditis

OBJECTIVE

Resolvins are produced by the catabolism of polyunsaturated fatty acids (PUFAs) and play vital roles in inflammation resolution. Resolvins have been associated with autoimmune disorders. This study aimed to measure the level of Resolvin D1 (RVD1) in the serum of Hashimoto's thyroiditis (HT) patients and healthy controls (HCs) and to further analyse its correlation with thyroid autoantibodies and inflammatory factors.

METHODS

Sixty-three participants were recruited, namely, 30 untreated HT patients and 33 sex- and age-matched HCs. Serum RVD1 and inflammatory chemokine (MCP-1 and IP-10) levels were measured by ELISA according to the manufacturer's protocol. Serum total T3 (TT3), TT4, free T3 (FT3), FT4, thyroglobulin antibody (TgAb), thyroid peroxidase antibody (TPOAb) and thyroid-stimulating hormone (TSH) levels were measured using an electrochemiluminescence immunoassay. Thyroid homeostasis parameters, including the thyroid secretory capacity (SPINA-GT), the total deiodinase activity (SPINA-GD), Jostel's TSH index (TSHI) and the thyrotroph thyroid hormone sensitivity index (TTSI), were calculated.

RESULTS

Serum RVD1 levels in HT patients (134.76, 85.35-201.36 pg/mL) were significantly lower than those in HCs (187.64, 131.01-326.85 pg/mL) (P=0.004). As the TPOAb level increased, the RVD1 level showed a decreasing trend (P for trend=0.002). Both multinomial and ordinal logistics analyses revealed that serum RVD1 levels were negatively correlated with TPOAb levels in the adjusted models. Moreover, RVD1 showed a negative correlation with the inflammatory chemokine IP-1 0 (r=-0.276, P=0.034), TSHI (r=-0.269, P=0.036) and TTSI (r=-0.277, P=0.031).

CONCLUSIONS

Thyroid autoimmunity may be associated with low levels of RVD1. Decreased RVD1 levels indicate impaired resolution of inflammation in HT patients.

Dietary Fish, Fish Nutrients, and Immune Function: A Review

Dietary habits have a major impact on the development and function of the immune system. This impact is mediated both by the intrinsic nutritional and biochemical qualities of the diet, and by its influence on the intestinal microbiota. Fish as a food is rich in compounds with immunoregulatory properties, among them omega-3 fatty acids, melatonin, tryptophan, taurine and polyamines. In addition, regular fish consumption favors the proliferation of beneficial members of the intestinal microbiota, like short-chain fatty acid-producing bacteria. By substituting arachidonic acid in the eicosanoid biosynthesis pathway, long-chain omega-3 fatty acids from fish change the type of prostaglandins, leukotrienes and thromboxanes being produced, resulting in anti-inflammatory properties. Further, they also are substrates for the production of specialized pro-resolving mediators (SPMs) (resolvins, protectins, and maresins), lipid compounds that constitute the physiological feedback signal to stop inflammation and give way to tissue reparation. Evidence from human observational and interventional studies shows that regular fish consumption is associated with reduced incidence of chronic inflammatory conditions like rheumatoid arthritis, and that continuous infusion of fish oil to tube-fed, critically ill patients may improve important outcomes in the ICU. There is also evidence from animal models showing that larger systemic concentrations of omega-3 fatty acids may counter the pathophysiological cascade that leads to psoriasis. The knowledge gained over the last few decades merits future exploration of the potential role of fish and its components in other conditions characterized by deregulated activation of immune cells and a cytokine storm like viral sepsis or COVID-19.

A simple model of immune and muscle cell crosstalk during muscle regeneration

Muscle injury during aging predisposes skeletal muscles to increased damage due to reduced regenerative capacity. Some of the common causes of muscle injury are strains, while other causes are more complex muscle myopathies and other illnesses, and even excessive exercise can lead to muscle damage. We develop a new mathematical model based on ordinary differential equations of muscle regeneration. It includes the interactions between the immune system, healthy and damaged myonuclei as well as satellite cells. Our new mathematical model expands beyond previous ones by accounting for 21 specific parameters, including those parameters that deal with the interactions between the damaged and dead myonuclei, the immune system, and the satellite cells. An important assumption of our model is the replacement of only damaged parts of the muscle fibers and the dead myonuclei. We conduce systematic sensitivity analysis to determine which parameters have larger effects on the model and therefore are more influential for the muscle regeneration process. We propose additional validation for these parameters. We further demonstrate that these simulations are species-, muscle-, and age-dependent. In addition, the knowledge of these parameters and their interactions, may suggest targeting or selecting these interactions for treatments that accelerate the muscle regeneration process.

Specialized proresolving mediators in infection and lung injury

Specialized proresolving mediators (SPMs) are endogenous lipid metabolites of long-chain polyunsaturated fatty acids that are involved in promoting the resolution of inflammation. Many disease conditions characterized by excessive inflammation have impaired or altered SPM biosynthesis, which may lead to chronic, unresolved inflammation. Exogenous administration of SPMs in infectious conditions has been shown to be effective at improving infection clearance and survival in preclinical models. SPMs have also shown tremendous promise in the context of inflammatory lung conditions, such as acute respiratory distress syndrome and chronic obstructive pulmonary disease, mostly in preclinical settings. To date, SPMs have not been studied in the context of the novel Coronavirus, severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2), however their preclinical efficacy in combatting infections and improving acute respiratory distress suggest they may be a valuable resource in the fight against Coronavirus disease-19 (COVID-19). Overall, while the research on SPMs is still evolving, they may offer a novel therapeutic option for inflammatory conditions.

Bioactive Lipids in COVID-19-Further Evidence

Previously, I suggested that arachidonic acid (AA, 20:4 n-6) and similar bioactive lipids (BALs) inactivate SARS-CoV-2 and thus, may be of benefit in the prevention and treatment of COVID-19. This proposal is supported by the observation that (i) macrophages and T cells (including NK cells, cytotoxic killer cells and other immunocytes) release AA and other BALs especially in the lungs to inactivate various microbes; (ii) pro-inflammatory metabolites prostaglandin E2 (PGE2) and leukotrienes (LTs) and anti-inflammatory lipoxin A4 (LXA4) derived from AA (similarly, resolvins, protectins and maresins derived from eicosapentaenoic acid: EPA and docosahexaenoic acid: DHA) facilitate the generation of M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages respectively; (iii) AA, PGE2, LXA4 and other BALs inhibit interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) synthesis; (iv) mesenchymal stem cells (MSCs) that are of benefit in COVID-19 elaborate LXA4 to bring about their beneficial actions and (v) subjects with insulin resistance, obesity, type 2 diabetes mellitus, hypertension, coronary heart disease and the elderly have significantly low plasma concentrations of AA and LXA4 that may render them more susceptible to SARS-CoV-2 infection and cytokine storm that is associated with increased mortality seen in COVID-19. Statins, colchicine, and corticosteroids that appear to be of benefit in COVID-19 can influence BALs metabolism. AA, and other BALs influence cell membrane fluidity and thus, regulate ACE-2 (angiotensin converting enzyme-2) receptors (the ligand through which SARS-CoV2 enters the cell) receptors. These observations lend support to the contention that administration of BALs especially, AA could be of significant benefit in prevention and management of COVI-19 and other enveloped viruses.

Altered tissue specialized pro-resolving mediators in chronic rhinosinusitis

Current literature implicates arachidonic acid-derived leukotrienes and prostaglandins in the pathogenesis of chronic rhinosinusitis. However, other omega-3 and omega-6 derived lipid mediators, such as specialized pro-resolving mediators (SPMs), may also be important in chronic inflammatory disorders of the upper airway. We hypothesize that SPMs differ among CRS subtypes compared to controls and in relation to sinonasal microbiota. Ethmoid sinus tissue and middle meatal swabs were collected from a convenience sample of 66 subjects, including non-CRS controls, CRS with polyps (CRSwNP), and CRS without polyps (CRSsNP). Lipid mediator pathways were analyzed by liquid chromatography/tandem mass spectrometry. Bacterial taxa were profiled in parallel by 16S rRNA gene sequencing. Resolvin D2 was elevated in both CRSwNP (p = 0.00076) and CRSsNP (p = 0.030) compared with non-CRS controls. Lipoxin A4 was significantly increased in CRSwNP compared with CRSsNP (p = 0.000033) and controls (p = 0.044). Cigarette smoking was associated with significantly lower concentrations of several 15-lipoxygenase metabolites including resolvin D1 (p = 0.0091) and resolvin D2 (p = 0.0097), compared with never-smokers. Several of the lipid compounds also correlated with components of the sinonasal mucosal microbiota, including bacterial pathogens such as Pseudomonas aeruginosa. These data suggest that dysfunctional lipid mediator pathways in CRS extend beyond the traditional descriptions of leukotrienes and prostaglandins and include SPMs. Furthermore, dysregulated SPM signaling may contribute to persistent inflammation and bacterial colonization in CRS.

Role of DAMPs in respiratory virus-induced acute respiratory distress syndrome-with a preliminary reference to SARS-CoV-2 pneumonia

When surveying the current literature on COVID-19, the "cytokine storm" is considered to be pathogenetically involved in its severe outcomes such as acute respiratory distress syndrome, systemic inflammatory response syndrome, and eventually multiple organ failure. In this review, the similar role of DAMPs is addressed, that is, of those molecules, which operate upstream of the inflammatory pathway by activating those cells, which ultimately release the cytokines. Given the still limited reports on their role in COVID-19, the emerging topic is extended to respiratory viral infections with focus on influenza. At first, a brief introduction is given on the function of various classes of activating DAMPs and counterbalancing suppressing DAMPs (SAMPs) in initiating controlled inflammation-promoting and inflammation-resolving defense responses upon infectious and sterile insults. It is stressed that the excessive emission of DAMPs upon severe injury uncovers their fateful property in triggering dysregulated life-threatening hyperinflammatory responses. Such a scenario may happen when the viral load is too high, for example, in the respiratory tract, "forcing" many virus-infected host cells to decide to commit "suicidal" regulated cell death (e.g., necroptosis, pyroptosis) associated with release of large amounts of DAMPs: an important topic of this review. Ironically, although the aim of this "suicidal" cell death is to save and restore organismal homeostasis, the intrinsic release of excessive amounts of DAMPs leads to those dysregulated hyperinflammatory responses-as typically involved in the pathogenesis of acute respiratory distress syndrome and systemic inflammatory response syndrome in respiratory viral infections. Consequently, as briefly outlined in this review, these molecules can be considered valuable diagnostic and prognostic biomarkers to monitor and evaluate the course of the viral disorder, in particular, to grasp the eventual transition precociously from a controlled defense response as observed in mild/moderate cases to a dysregulated life-threatening hyperinflammatory response as seen, for example, in severe/fatal COVID-19. Moreover, the pathogenetic involvement of these molecules qualifies them as relevant future therapeutic targets to prevent severe/ fatal outcomes. Finally, a theory is presented proposing that the superimposition of coronavirus-induced DAMPs with non-virus-induced DAMPs from other origins such as air pollution or high age may contribute to severe and fatal courses of coronavirus pneumonia.

Chronic Inflammation in PCOS: The Potential Benefits of Specialized Pro-Resolving Lipid Mediators (SPMs) in the Improvement of the Resolutive Response

PCOS as the most common endocrine disorder of women in their reproductive age affects between 5–15% of the female population. Apart from its cardinal symptoms, like irregular and anovulatory cycles, hyperandrogenemia and a typical ultrasound feature of the ovary, obesity, and insulin resistance are often associated with the disease. Furthermore, PCOS represents a status of chronic inflammation with permanently elevated levels of inflammatory markers including IL-6 and IL-18, TNF-α, and CRP. Inflammation, as discovered only recently, consists of two processes occurring concomitantly: active initiation, involving “classical” mediators including prostaglandins and leukotrienes, and active resolution processes based on the action of so-called specialized pro-resolving mediators (SPMs). These novel lipid mediator molecules derive from the essential ω3-poly-unsaturated fatty acids (PUFAs) DHA and EPA and are synthesized via specific intermediates. The role and benefits of SPMs in chronic inflammatory diseases like obesity, atherosclerosis, and Diabetes mellitus has become a subject of intense research during the last years and since PCOS features several of these pathologies, this review aims at summarizing potential roles of SPMs in this disease and their putative use as novel therapeutics.

HIF1α activation in dendritic cells under sterile conditions promotes an anti-inflammatory phenotype through accumulation of intracellular lipids

Obesity is among the leading causes of elevated cardiovascular disease mortality and morbidity. Adipose tissue dysfunction, insulin resistance and inflammation are recognized as important risk factors for the development of cardiovascular disorders in obesity. Hypoxia appears to be a key factor in adipose tissue dysfunction affecting not only adipocytes but also immune cell function. Here we examined the effect of hypoxia-induced transcription factor HIF1α activation on classical dendritic cell (cDCs) function during obesity. We found that deletion of Hif1α on cDCs results in enhanced adipose-tissue inflammation and atherosclerotic plaque formation in a mouse model of obesity. This effect is mediated by HIF1α-mediated increased lipid synthesis, accumulation of lipid droplets and alter synthesis of lipid mediators. Our findings demonstrate that HIF1α activation in cDCs is necessary to control vessel wall inflammation.

Specialized Proresolving Mediators Overcome Immune Suppression Induced by Exposure to Secondhand Smoke

Tobacco smoke exposure is associated with multiple diseases including, respiratory diseases like asthma and chronic obstructive pulmonary disease. Tobacco smoke is a potent inflammatory trigger and is immunosuppressive, contributing to increased susceptibility to pulmonary infections in smokers, ex-smokers, and vulnerable populations exposed to secondhand smoke. Tobacco smoke exposure also reduces vaccine efficacy. Therefore, mitigating the immunosuppressive effects of chronic smoke exposure and improving the efficacy of vaccinations in individuals exposed to tobacco smoke, is a critical unmet clinical problem. We hypothesized that specialized proresolving mediators (SPMs), a class of immune regulators promoting resolution of inflammation, without being immunosuppressive, and enhancing B cell Ab responses, could reverse the immunosuppressive effects resulting from tobacco smoke exposure. We exposed mice to secondhand smoke for 8 wk, followed by a period of smoke exposure cessation, and the mice were immunized with the P6 lipoprotein from nontypeable Haemophilus influenzae, using 17-HDHA and aspirin-triggered-resolvin D1 (AT-RvD1) as adjuvants. 17-HDHA and AT-RvD1 used as adjuvants resulted in elevated serum and bronchoalveolar lavage levels of anti-P6-specific IgG and IgA that were protective, with immunized mice exhibiting more rapid bacterial clearance upon challenge, reduced pulmonary immune cell infiltrates, reduced production of proinflammatory cytokines, and less lung-epithelial cell damage. Furthermore, the treatment of mice with AT-RvD1 during a period of smoke-cessation further enhanced the efficacy of SPM-adjuvanted P6 vaccination. Overall, SPMs show promise as novel vaccine adjuvants with the ability to overcome the tobacco smoke-induced immunosuppressive effects.

Non-inflammatory Physiology of "Inflammatory" Mediators - Unalamation, a New Paradigm

Many small molecules (mostly lipids derived from polyunsaturated fatty acids) and proteins (e. g., cytokines and chemokines) are labeled as inflammatory mediators for their role in eliciting physiological responses to injury. While acute inflammatory events are controlled by anti-inflammatory drugs, lasting damage to the tissues as a result of persistent inflammation is increasingly viewed as the root cause of many chronic diseases that include cardiovascular, neurological, and metabolic disorders, rheumatoid arthritis, and cancer. Interestingly, some of the “inflammatory” mediators also participate in normal developmental physiology without eliciting inflammation. Anti-inflammatory drugs that target the biosynthesis of these mediators are too indiscriminate to distinguish their two divergent physiological roles. A more precise definition of these two physiological processes partaken by the “inflammatory” mediators is warranted to identify their differences. The new paradigm is named “unalamation” ('ə‘n'əlAmāSH(ə)n) to distinguish from inflammation and to identify appropriate intervention strategies to mitigate inflammation associated pathophysiology without affecting the normal developmental physiology.

Clinical influence of calcium hydroxide and N-acetylcysteine on the levels of resolvins E1 and D2 in apical periodontitis

AIM

To investigate the presence of resolvins E1 (RvE1) and D2 (RvD2) in teeth with primary endodontic infections and apical periodontitis, and to assess the influence of calcium hydroxide medication [Ca(OH)₂ ], in association with 2% chlorhexidine gel (2% CHX gel), and N-acetylcysteine (NAC) on the levels of RvE1 and RvD2 in periapical tissues.

METHODOLOGY

Thirty-six single-rooted teeth with primary endodontic infections and apical periodontitis were selected and randomly divided into three groups according to the medication: [Ca(OH)₂ ] + saline solution (SSL) [Ca(OH)₂  + SSL group] (n = 12), Ca(OH)₂  + 2% chlorhexidine gel [Ca(OH)₂  + 2% CHX gel group] (n = 12) and NAC [NAC group] (n = 12). Samples were collected from the periapical interstitial fluid at two different sampling times: before (S1) and after 14 days of intracanal medications (S2). Resolvins were measured using the enzyme-linked immunosorbent assay. Data were analysed using paired t-test, Wilcoxon test and Kruskal-Wallis test, followed by Dunn's post hoc test; all statistical tests were performed at a significance level of 5%.

RESULTS

RvE1 and RvD2 were detected in 100% of the samples (36/36) at S1 and S2. Ca(OH)₂ medication did not increase the levels of RvE1 or RvD2 (both P > 0.05); however, NAC significantly increased the levels of RvE1 and RvD2 after 14 days of treatment (P < 0.05).

CONCLUSIONS

RvE1 and RvD2 were detected in periapical tissues from teeth with root canal infections. Moreover, calcium hydroxide medication did not increase the levels of resolvins in apical periodontitis. In contrast, the use of NAC intracanal medication significantly increased the levels of RvE1 and RvD2 after 14 days of treatment.

Resolvins: Emerging Players in Autoimmune and Inflammatory Diseases

Resolvins, belonging to the group of specialized proresolving mediators (SPMs), are metabolic products of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) and are synthesized during the initial phases of acute inflammatory responses to promote the resolution of inflammation. Resolvins are produced for termination of neutrophil infiltration, stimulation of the clearance of apoptotic cells by macrophages, and promotion of tissue remodeling and homeostasis. Metabolic dysregulation due to either uncontrolled activity of pro-inflammatory responses or to inefficient resolution of inflammation results in chronic inflammation and may also lead to atherosclerosis or other chronic autoimmune diseases such as rheumatoid arthritis, psoriasis, systemic lupus erythematosus, vasculitis, inflammatory bowel diseases, and type 1 diabetes mellitus. The pathogenesis of such diseases involves a complex interplay between the immune system and, environmental factors (non-infectious or infectious), and critically depends on individual susceptibility to such factors. In the present review, resolvins and their roles in the resolution of inflammation, as well as the role of these mediators as potential therapeutic agents to counteract specific chronic autoimmune and inflammatory diseases are discussed.

The Role of Specialized Pro-Resolving Mediators in Cystic Fibrosis Airways Disease

Cystic Fibrosis (CF) is a recessive genetic disease due to mutations of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene encoding the CFTR chloride channel. The ion transport abnormalities related to CFTR mutation generate a dehydrated airway surface liquid (ASL) layer, which is responsible for an altered mucociliary clearance, favors infections and persistent inflammation that lead to progressive lung destruction and respiratory failure. The inflammatory response is normally followed by an active resolution phase to return to tissue homeostasis, which involves specialized pro-resolving mediators (SPMs). SPMs promote resolution of inflammation, clearance of microbes, tissue regeneration and reduce pain, but do not evoke unwanted immunosuppression. The airways of CF patients showed a decreased production of SPMs even in the absence of pathogens. SPMs levels in the airway correlated with CF patients' lung function. The prognosis for CF has greatly improved but there remains a critical need for more effective treatments that prevent excessive inflammation, lung damage, and declining pulmonary function for all CF patients. This review aims to highlight the recent understanding of CF airway inflammation and the possible impact of SPMs on functions that are altered in CF airways.

Lipid mediators and biomarkers associated with type 1 diabetes development

Type 1 diabetes (T1D) is a consequence of autoimmune β cell destruction, but the role of lipids in this process is unknown. We previously reported that activation of Ca2+-independent phospholipase A2β (iPLA2β) modulates polarization of macrophages (MΦ). Hydrolysis of the sn-2 substituent of glycerophospholipids by iPLA2β can lead to the generation of oxidized lipids (eicosanoids), pro- and antiinflammatory, which can initiate and amplify immune responses triggering β cell death. As MΦ are early triggers of immune responses in islets, we examined the impact of iPLA2β-derived lipids (iDLs) in spontaneous-T1D prone nonobese diabetic mice (NOD), in the context of MΦ production and plasma abundances of eicosanoids and sphingolipids. We find that (a) MΦNOD exhibit a proinflammatory lipid landscape during the prediabetic phase; (b) early inhibition or genetic reduction of iPLA2β reduces production of select proinflammatory lipids, promotes antiinflammatory MΦ phenotype, and reduces T1D incidence; (c) such lipid changes are reflected in NOD plasma during the prediabetic phase and at T1D onset; and (d) importantly, similar lipid signatures are evidenced in plasma of human subjects at high risk for developing T1D. These findings suggest that iDLs contribute to T1D onset and identify select lipids that could be targeted for therapeutics and, in conjunction with autoantibodies, serve as early biomarkers of pre-T1D.

Low levels of pro-resolving lipid mediators lipoxin-A4, resolvin-D1 and resolvin-E1 in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a disease in which joint inflammation is at the forefront but the whole body is affected, and prevention of inflammation is the main treatment approach. Lipoxins (LXs) and resolvins (Rvs) are critical molecules in the resolution of inflammation. In this study, we aimed to investigate the role of LXs and Rvs in the RA pathogenesis. To this end, we measured the LXA 4, RvD 1, RvE 1 levels, and inflammatory cytokines and chemokines IL-6, IL-8, IL-10, IL-17a, IL-22 and MCP-1 in patients with RA and healthy individuals. We found that the LXA4, RvD1, RvE1 levels of the active RA cases were significantly lower than in remission RA and healthy individuals, but the levels of inflammatory cytokines and chemokines were significantly higher. The decreases in LXs and Rvs were independent of disease activity, suggesting that there might be an impairment of LX and Rvs synthesis or catabolism in patients with RA.

Alzheimer's Disease and Specialized Pro-Resolving Lipid Mediators: Do MaR1, RvD1, and NPD1 Show Promise for Prevention and Treatment?

Alzheimer's disease (AD) is a common neurodegenerative disease and a major contributor to progressive cognitive impairment in an aging society. As the pathophysiology of AD involves chronic neuroinflammation, the resolution of inflammation and the group of lipid mediators that actively regulate it-i.e., specialized pro-resolving lipid mediators (SPMs)-attracted attention in recent years as therapeutic targets. This review focuses on the following three specific SPMs and summarizes their relationships to AD, as they were shown to effectively address and reduce the risk of AD-related neuroinflammation: maresin 1 (MaR1), resolvin D1 (RvD1), and neuroprotectin D1 (NPD1). These three SPMs are metabolites of docosahexaenoic acid (DHA), which is contained in fish oils and is thus easily available to the public. They are expected to become incorporated into promising avenues for preventing and treating AD in the future.

Obesity-Driven Deficiencies of Specialized Pro-resolving Mediators May Drive Adverse Outcomes During SARS-CoV-2 Infection

Obesity is a major independent risk factor for increased morbidity and mortality upon infection with Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2), which is responsible for the current coronavirus disease pandemic (COVID-19). Therefore, there is a critical need to identify underlying metabolic factors associated with obesity that could be contributing toward increased susceptibility to SARS-CoV-2 in this vulnerable population. Here, we focus on the critical role of potent endogenous lipid metabolites known as specialized pro-resolving mediators (SPMs) that are synthesized from polyunsaturated fatty acids. SPMs are generated during the transition of inflammation to resolution and have a vital role in directing damaged tissues to homeostasis; furthermore, SPMs display anti-viral activity in the context of influenza infection without being immunosuppressive. We cover evidence from rodent and human studies to show that obesity, and its co-morbidities, induce a signature of SPM deficiency across immunometabolic tissues. We further discuss how the effects of obesity upon SARS-CoV-2 infection are likely exacerbated with environmental exposures that promote chronic pulmonary inflammation and augment SPM deficits. Finally, we highlight potential approaches to overcome the loss of SPMs using dietary and pharmacological interventions. Collectively, this mini-review underscores the need for mechanistic studies on how SPM deficiencies driven by obesity and environmental exposures may exacerbate the response to SARS-CoV-2.

Dynamic transcriptome analysis unveils key proresolving factors of chronic inflammatory arthritis

Despite recent advances in understanding chronic inflammation remission, global analyses have not been explored to systematically discover genes or pathways underlying the resolution dynamics of chronic inflammatory diseases. Here, we performed time-course gene expression profiling of mouse synovial tissues along progression and resolution of collagen-induced arthritis (CIA) and identified genes associated with inflammation resolution. Through network analysis of these genes, we predicted 3 key secretory factors responsible for the resolution of CIA: Itgb1, Rps3, and Ywhaz. These factors were predominantly expressed by Tregs and antiinflammatory M2 macrophages, suppressing production of proinflammatory cytokines. In particular, Ywhaz was elevated in the sera of mice with arthritis resolution and in the urine of rheumatoid arthritis (RA) patients with good therapeutic responses. Moreover, adenovirus-mediated transfer of the Ywhaz gene to the affected joints substantially inhibited arthritis progression in mice with CIA and suppressed expression of proinflammatory cytokines in joint tissues, lymph nodes, and spleens, suggesting Ywhaz is an excellent target for RA therapy. Therefore, our comprehensive analysis of dynamic synovial transcriptomes provides previously unidentified antiarthritic genes, Itgb1, Rps3, and Ywhaz, which can serve as molecular markers to predict disease remission, as well as therapeutic targets for chronic inflammatory arthritis.

Specialized pro-resolving mediators: It's anti-oxidant stress role in multiple disease models

Oxidative stress-related injury is a negative state caused by the imbalance between oxidation and antioxidant effects in the internal environment of the body. Oxidative stress has been confirmed to be an important factor in aging and a variety of diseases and the inhibition of inappropriate oxidative stress responses are important for maintaining normal physiological functions. Recently, considerable attention has been focused on specialized pro-resolving mediators(SPMs). SPMs are endogenous mediators derived from polyunsaturated fatty acids, which have multiple protective effects such as anti-inflammation, pro-resolution, and promoting tissue damage repair, etc. Moreover, the role of SPMs on oxidative stress has been extensively researched and provides a possible treatment method. In the current study, we review the positive role of SPMs in oxidative stress-related disease and outline the possible involved mechanism, thus providing the theoretical support for a better understanding of the roles of SPMs in oxidative stress and the theoretical basis for finding targets for the oxidative stress-related diseases.

Alox12/15 Deficiency Exacerbates, While Lipoxin A4 Ameliorates Hepatic Inflammation in Murine Alcoholic Hepatitis

Alcoholism is one of the leading and increasingly prevalent reasons of liver associated morbidity and mortality worldwide. Alcoholic hepatitis (AH) constitutes a severe disease with currently no satisfying treatment options. Lipoxin A₄ (LXA₄), a 15-lipoxygenase (ALOX15)-dependent lipid mediator involved in resolution of inflammation, showed promising pre-clinical results in the therapy of several inflammatory diseases. Since inflammation is a main driver of disease progression in alcoholic hepatitis, we investigated the impact of endogenous ALOX15-dependent lipid mediators and exogenously applied LXA₄ on AH development. A mouse model for alcoholic steatohepatitis (NIAAA model) was tested in Alox12/15^+/+ and Alox12/15^-/- mice, with or without supplementation of LXA₄. Absence of Alox12/15 aggravated parameters of liver disease, increased hepatic immune cell infiltration in AH, and elevated systemic neutrophils as a marker for systemic inflammation. Interestingly, i.p. injections of LXA₄ significantly lowered transaminase levels only in Alox12/15^-/- mice and reduced hepatic immune cell infiltration as well as systemic inflammatory cytokine expression in both genotypes, even though steatosis progressed. Thus, while LXA₄ injection attenuated selected parameters of disease progression in Alox12/15^-/- mice, its beneficial impact on immunity was also apparent in Alox12/15^+/+ mice. In conclusion, pro-resolving lipid mediators may be beneficial to reduce inflammation in alcoholic hepatitis.

Human NK Cell Cytoskeletal Dynamics and Cytotoxicity Are Regulated by LIM Kinase

NK cells provide immune surveillance and host protection against viruses and tumors through their cytotoxic effector function. Cytoskeletal rearrangement is necessary for NK cell lytic granule trafficking and immune synapse formation to trigger apoptosis of targeted cells. LIM kinase (LIMK) regulates F-actin remodeling by phosphorylating cofilin to inhibit actin severing and depolymerization. In this study, in human NK cells, the glucocorticoid dexamethasone downregulated LIMK expression, F-actin accumulation at the immune synapse, lytic granule trafficking, and cytotoxicity. In contrast, the specialized proresolving mediator lipoxin A₄ promoted NK cell LIMK expression, lytic granule polarization to the immune synapse and cytotoxicity. Using a LIMK inhibitor, we show that LIMK activity is necessary for NK cell cytotoxicity, including lipoxin A₄'s proresolving actions. Together, our findings identify LIMK as an important control mechanism for NK cell cytoskeletal rearrangement that is differentially regulated by glucocorticoids and specialized proresolving mediators to influence NK cell cytotoxicity.

Fatty Acid Mediators in the Tumor Microenvironment

Patients with cancer frequently overexpress inflammatory cytokines with an associated neutrophilia both of which may be downregulated by diets with high omega-3 polyunsaturated fatty acids (ω-3 PUFA). The anti-inflammatory activity of dietary ω-3 PUFA has been suggested to have anticancer properties and to improve survival of cancer patients. Currently, the majority of dietary research efforts do not differentiate between obesity and dietary fatty acid consumption as mediators of inflammatory cell expansion and tumor microenvironmental infiltration, initiation, and progression. In this chapter, we discuss the relationships between dietary lipids, inflammation, neoplasia and strategies to regulate these relationships. We posit that dietary composition, notably the ratio of ω-3 vs. ω-6 PUFA, regulates tumor initiation and progression and the frequency and sites of metastasis that, together, impact overall survival (OS). We focus on three broad topics: first, the role of dietary lipids in chronic inflammation and tumor initiation, progression, and regression; second, lipid mediators linking inflammation and cancer; and third, dietary lipid regulation of murine and human tumor initiation, progression, and metastasis.

Bioactive lipids, inflammation and chronic diseases

Endogenous bioactive lipids are part of a complex network that modulates a plethora of cellular and molecular processes involved in health and disease, of which inflammation represents one of the most prominent examples. Inflammation serves as a well-conserved defence mechanism, triggered in the event of chemical, mechanical or microbial damage, that is meant to eradicate the source of damage and restore tissue function. However, excessive inflammatory signals, or impairment of pro-resolving/anti-inflammatory pathways leads to chronic inflammation, which is a hallmark of chronic pathologies. All main classes of endogenous bioactive lipids - namely eicosanoids, specialized pro-resolving lipid mediators, lysoglycerophopsholipids and endocannabinoids - have been consistently involved in the chronic inflammation that characterises pathologies such as cancer, diabetes, atherosclerosis, asthma, as well as autoimmune and neurodegenerative disorders and inflammatory bowel diseases. This review gathers the current knowledge concerning the involvement of endogenous bioactive lipids in the pathogenic processes of chronic inflammatory pathologies.

Targeting of G-protein coupled receptors in sepsis

The Third International Consensus Definitions (Sepsis-3) define sepsis as life-threatening multi-organ dysfunction caused by a dysregulated host response to infection. Sepsis can progress to septic shock-an even more lethal condition associated with profound circulatory, cellular and metabolic abnormalities. Septic shock remains a leading cause of death in intensive care units and carries a mortality of almost 25%. Despite significant advances in our understanding of the pathobiology of sepsis, therapeutic interventions have not translated into tangible differences in the overall outcome for patients. Clinical trials of antagonists of various pro-inflammatory mediators in sepsis have been largely unsuccessful in the past. Given the diverse physiologic roles played by G-protein coupled receptors (GPCR), modulation of GPCR signaling for the treatment of sepsis has also been explored. Traditional pharmacologic approaches have mainly focused on ligands targeting the extracellular domains of GPCR. However, novel techniques aimed at modulating GPCR intracellularly through aptamers, pepducins and intrabodies have opened a fresh avenue of therapeutic possibilities. In this review, we summarize the diverse roles played by various subfamilies of GPCR in the pathogenesis of sepsis and identify potential targets for pharmacotherapy through these novel approaches.

Use of DAMPs and SAMPs as Therapeutic Targets or Therapeutics: A Note of Caution

This opinion article discusses the increasing attention paid to the role of activating damage-associated molecular patterns (DAMPs) in initiation of inflammatory diseases and suppressing/inhibiting DAMPs (SAMPs) in resolution of inflammatory diseases and, consequently, to the future roles of these novel biomarkers as therapeutic targets and therapeutics. Since controlled production of DAMPs and SAMPs is needed to achieve full homeostatic restoration and repair from tissue injury, only their pathological, not their homeostatic, concentrations should be therapeutically tackled. Therefore, distinct caveats are proposed regarding choosing DAMPs and SAMPs for therapeutic purposes. For example, we discuss the need to a priori identify and define a context-dependent “homeostatic DAMP:SAMP ratio” in each case and a “homeostatic window” of DAMP and SAMP concentrations to guarantee a safe treatment modality to patients. Finally, a few clinical examples of how DAMPs and SAMPs might be used as therapeutic targets or therapeutics in the future are discussed, including inhibition of DAMPs in hyperinflammatory processes (e.g., systemic inflammatory response syndrome, as currently observed in Covid-19), administration of SAMPs in chronic inflammatory diseases, inhibition of SAMPs in hyperresolving processes (e.g., compensatory anti-inflammatory response syndrome), and administration/induction of DAMPs in vaccination procedures and anti-cancer therapy.

The Role of Endogenous Eicosapentaenoic Acid and Docosahexaenoic Acid-Derived Resolvins in Systemic Sclerosis

Resolvins, the member of specialized pro-resolving mediators, are produced from omega-3 polyunsaturated fatty acids as a response to an acute inflammatory process in that termination and resolution of inflammation. In the acute inflammation, these lipid mediators limit polymorphonuclear cells infiltration, proinflammatory cytokine production; promote efferocytosis, and regulate several cell types being important roles in innate and adaptive immunity. Any dysregulation or defect of the resolution phase result in prolonged, persistent inflammation and eventually fibrosis. Resolvins are implicated in the development of various chronic autoimmune diseases. Systemic sclerosis (SSc) is a very complicated, chronic autoimmune disorder proceeding with vasculopathy, inflammation, and fibrosis. Dysregulation of innate and adaptive immunity is another important contributing factor in the pathogenesis of SSc. In this review, we will focus on the different roles of this new family of lipid mediators, characterized by the ability to prevent the spread of inflammation and its chronicity in various ways and how they can control the development of fibrotic diseases like SSc.

Specialized Pro-Resolving Lipid Mediators: Emerging Therapeutic Candidates for Multiple Sclerosis

Multiple sclerosis (MS) is a neuroinflammatory disease in which unresolved and uncontrolled inflammation disrupts normal cellular homeostasis and leads to a pathological disease state. It has long been recognized that endogenously derived metabolic by-products of omega fatty acids, known as specialized pro-resolving lipid mediators (SPMs), are instrumental in resolving the pathologic inflammation. However, there is minimal data available on the functional status of SPMs in MS, despite the fact that MS presents a classical model of chronic inflammation. Studies to date indicate that dysfunction of the SPM biosynthetic pathway is responsible for their altered levels in patient-derived biofluids, which contributes to heightened inflammation and disease severity. Collectively, current findings suggest the contentious role of SPMs in MS due to variable outcomes in biological matrices across studies conducted so far, which could, in part, also be attributed to differences in population characteristics. It seems that SPMs have neuroprotective action on MS by exerting proresolving effects on brain microglia in its preclinical model; however, there are no reports demonstrating the direct effect of SPMs on oligodendrocytes or neurons. This reveals that "one size does not fit all" notion holds significance for MS in terms of the status of SPMs in other inflammatory conditions. The lack of clarity served as the impetus for this review, which is the first of its kind to summarize the relevant data regarding the role of SPMs in MS and the potential to target them for biomarker development and future alternative therapies for this disease. Understanding the mechanisms behind biological actions of SPMs as resolution mediators may prevent or even cure MS and other neurodegenerative pathologies.

Resolvin D1 and D2 inhibit tumour growth and inflammation via modulating macrophage polarization

Plastic polarization of macrophage is involved in tumorigenesis. M1-polarized macrophage mediates rapid inflammation, entity clearance and may also cause inflammation-induced mutagenesis. M2-polarized macrophage inhibits rapid inflammation but can promote tumour aggravation. ω-3 long-chain polyunsaturated fatty acid (PUFA)-derived metabolites show a strong anti-inflammatory effect because they can skew macrophage polarization from M1 to M2. However, their role in tumour promotive M2 macrophage is still unknown. Resolvin D1 and D2 (RvD1 and RvD2) are docosahexaenoic acid (DHA)-derived docosanoids converted by 15-lipoxygenase then 5-lipoxygenase successively. We found that although dietary DHA can inhibit prostate cancer in vivo, neither DHA (10 μmol/L) nor RvD (100 nmol/L) can directly inhibit the proliferation of prostate cancer cells in vitro. Unexpectedly, in a cancer cell-macrophage co-culture system, both DHA and RvD significantly inhibited cancer cell proliferation. RvD1 and RvD2 inhibited tumour-associated macrophage (TAM or M2d) polarization. Meanwhile, RvD1 and RvD2 also exhibited anti-inflammatory effects by inhibiting LPS-interferon (IFN)-γ-induced M1 polarization as well as promoting interleukin-4 (IL-4)-mediated M2a polarization. These differential polarization processes were mediated, at least in part, by protein kinase A. These results suggest that regulation of macrophage polarization using RvDs may be a potential therapeutic approach in the management of prostate cancer.