Peroxisome-derived lipids are self antigens that stimulate invariant natural killer T cells in the thymus

Mitochondria regulate MR1 protein expression and produce self-metabolites that activate MR1-restricted T cells

Mitochondria coordinate several metabolic pathways, producing metabolites that influence the immune response in various ways. It remains unclear whether mitochondria impact antigen presentation by the MHC-class-I-related antigen-presenting molecule, MR1, which presents small molecules to MR1-restricted T-lymphocytes. Here, we demonstrate that mitochondrial complex III and the enzyme dihydroorotate dehydrogenase are essential for the cell-surface expression of MR1 and for generating uridine- and thymidine-related compounds that bind to MR1 and are produced upon oxidation by reactive oxygen species. One mitochondria-derived immunogenic formylated metabolite we identified is 5-formyl-deoxyuridine (5-FdU). Structural studies indicate that 5-FdU binds in the A'-antigen-binding pocket of MR1, positioning the deoxyribose toward the surface of MR1 for TCR interaction. 5-FdU stimulates specific T cells and detects circulating T cells when loaded onto MR1-tetramers. 5-FdU-reactive cells resemble adaptive T cells and express the phenotypes of naïve, memory, and effector cells, indicating prior in vivo stimulation. These findings suggest that mitochondria may play a role in MR1-mediated immune surveillance.

Modulation of endogenous plasmalogens by genetic ablation of lysoplasmalogenase (Tmem86b) in mice

Plasmalogens are a distinct subclass of glycerophospholipids that exhibit unique structural features, notably possessing a vinyl ether linkage at the sn1 position of the glycerol backbone. These specialized lipids play crucial roles in various biological functions. Although the biosynthetic pathway of plasmalogens has been well-characterized, their catabolism remains less studied. In this study, we investigated the impact of global and tissue-specific loss-of-function of a plasmalogen catabolizing enzyme, lysoplasmalogenase (TMEM86B), on circulatory and tissue lipidomes. We generated both global and hepatocyte-specific Tmem86b knockout mice using cre-loxP technology. Mice with homozygous global inactivation of Tmem86b (Tmem86b KO mice) were viable and did not display any marked phenotypic abnormalities. Tmem86b KO mice demonstrated significantly elevated levels of the plasmalogens, alkenylphosphatidylethanolamine (PE(P)), and alkenylphosphatidylcholine (PC(P)), as well as lysoplasmalogens, in the plasma, liver, and natural killer cells compared to their wild-type counterparts. The endogenous alkenyl chain composition of plasmalogens remained unaltered in Tmem86b KO mice. Consistent with the global knockout findings, hepatocyte-specific Tmem86b knockout mice also exhibited increased plasmalogen levels in the plasma and liver compared to their floxed control counterparts. Overall, our findings shed light on the role of Tmem86b in plasmalogen catabolism, demonstrating how its ablation leads to elevated plasmalogen levels in select tissues and cells. This study enhances our understanding of the regulatory mechanisms governing plasmalogen metabolism and highlights the potential of targeting Tmem86b to therapeutically raise plasmalogen levels.

Identification of α-galactosylceramide as an endogenous mammalian antigen for iNKT cells

Invariant natural killer T (iNKT) cells are unconventional T cells recognizing lipid antigens in a CD1d-restricted manner. Among these lipid antigens, α-galactosylceramide (α-GalCer), which was originally identified in marine sponges, is the most potent antigen. Although the presence of α-anomeric hexosylceramide and microbiota-derived branched α-GalCer is reported, antigenic α-GalCer has not been identified in mammals. Here, we developed a high-resolution separation and detection system, supercritical fluid chromatography tandem mass spectrometry (SFC/MS/MS), that can discriminate hexosylceramide diastereomers (α-GalCer, α-GlcCer, β-GalCer, or β-GlcCer). The B16 melanoma tumor cell line does not activate iNKT cells; however, ectopic expression of CD1d was sufficient to activate iNKT cells without adding antigens. B16 melanoma was unlikely to generate iNKT cell antigens; instead, antigen activity was detected in cell culture serum. Activity-based purification and SFC/MS/MS identified dihydrosphingosine-based saturated α-GalCer as an antigenic component in serum, bile, and lymphoid tissues. These results show the first evidence for the presence of potent antigenic α-GalCer in mammals.

Role and Function of Peroxisomes in Neuroinflammation

Peroxisomes are organelles involved in many cellular metabolic functions, including the degradation of very-long-chain fatty acids (VLCFAs; C ≥ 22), the initiation of ether-phospholipid synthesis, and the metabolism of reactive oxygen species. All of these processes are essential for the maintenance of cellular lipid and redox homeostasis, and their perturbation can trigger inflammatory response in immune cells, including in the central nervous system (CNS) resident microglia and astrocytes. Consistently, peroxisomal disorders, a group of congenital diseases caused by a block in peroxisomal biogenesis or the impairment of one of the peroxisomal enzymes, are associated with neuroinflammation. Peroxisomal function is also dysregulated in many neurodegenerative diseases and during brain aging, both of which are associated with neuroinflammation. This suggests that deciphering the role of peroxisomes in neuroinflammation may be important for understanding both congenital and age-related brain dysfunction. In this review, we discuss the current advances in understanding the role and function of peroxisomes in neuroinflammation.

Lipidomic scanning of self-lipids identifies headless antigens for natural killer T cells

To broadly measure the spectrum of cellular self-antigens for natural killer T cells (NKT), we developed a sensitive lipidomics system to analyze lipids trapped between CD1d and NKT T cell receptors (TCRs). We captured diverse antigen complexes formed in cells from natural endogenous lipids, with or without inducing endoplasmic reticulum (ER) stress. After separating protein complexes with no, low, or high CD1d-TCR interaction, we eluted lipids to establish the spectrum of self-lipids that facilitate this interaction. Although this unbiased approach identified fifteen molecules, they clustered into only two related groups: previously known phospholipid antigens and unexpected neutral lipid antigens. Mass spectrometry studies identified the neutral lipids as ceramides, deoxyceramides, and diacylglycerols, which can be considered headless lipids because they lack polar headgroups that usually form the TCR epitope. The crystal structure of the TCR-ceramide-CD1d complex showed how the missing headgroup allowed the TCR to predominantly contact CD1d, supporting a model of CD1d autoreactivity. Ceramide and related headless antigens mediated physiological TCR binding affinity, weak NKT cell responses, and tetramer binding to polyclonal human and mouse NKT cells. Ceramide and sphingomyelin are oppositely regulated components of the "sphingomyelin cycle" that are altered during apoptosis, transformation, and ER stress. Thus, the unique molecular link of ceramide to NKT cell response, along with the recent identification of sphingomyelin blockers of NKT cell activation, provide two mutually reinforcing links for NKT cell response to sterile cellular stress conditions.

Identification and validation of a blood- based diagnostic lipidomic signature of pediatric inflammatory bowel disease

Improved biomarkers are needed for pediatric inflammatory bowel disease. Here we identify a diagnostic lipidomic signature for pediatric inflammatory bowel disease by analyzing blood samples from a discovery cohort of incident treatment-naïve pediatric patients and validating findings in an independent inception cohort. The lipidomic signature comprising of only lactosyl ceramide (d18:1/16:0) and phosphatidylcholine (18:0p/22:6) improves the diagnostic prediction compared with high-sensitivity C-reactive protein. Adding high-sensitivity C-reactive protein to the signature does not improve its performance. In patients providing a stool sample, the diagnostic performance of the lipidomic signature and fecal calprotectin, a marker of gastrointestinal inflammation, does not substantially differ. Upon investigation in a third pediatric cohort, the findings of increased lactosyl ceramide (d18:1/16:0) and decreased phosphatidylcholine (18:0p/22:6) absolute concentrations are confirmed. Translation of the lipidomic signature into a scalable diagnostic blood test for pediatric inflammatory bowel disease has the potential to support clinical decision making.

Identification and Validation of a PEX5-Dependent Signature for Prognostic Prediction in Glioma

Gliomas, the most prevalent and lethal form of brain cancer, are known to exhibit metabolic alterations that facilitate tumor growth, invasion, and resistance to therapies. Peroxisomes, essential organelles responsible for fatty acid oxidation and reactive oxygen species (ROS) homeostasis, rely on the receptor PEX5 for the import of metabolic enzymes into their matrix. However, the prognostic significance of peroxisomal enzymes for glioma patients remains unclear. In this study, we elucidate that PEX5 is indispensable for the cell growth, migration, and invasion of glioma cells. We establish a robust prognosis model based on the expression of peroxisomal enzymes, whose localization relies on PEX5. This PEX5-dependent signature not only serves as a robust prognosis model capable of accurately predicting outcomes for glioma patients, but also effectively distinguishes several clinicopathological features, including the grade, isocitrate dehydrogenase (IDH) mutation, and 1p19q codeletion status. Furthermore, we developed a nomogram that integrates the prognostic model with other clinicopathological factors, demonstrating highly accurate performance in estimating patient survival. Patients classified into the high-risk group based on our prognostic model exhibited an immunosuppressive microenvironment. Finally, our validation reveals that the elevated expression of GSTK1, an antioxidant enzyme within the signature, promotes the cell growth and migration of glioma cells, with this effect dependent on the peroxisomal targeting signal recognized by PEX5. These findings identify the PEX5-dependent signature as a promising prognostic tool for gliomas.

Peroxisome deficiency underlies failures in hepatic immune cell development and antigen presentation in a severe Zellweger disease model

Peroxisome biogenesis disorders (PBDs) represent a group of metabolic conditions that cause severe developmental defects. Peroxisomes are essential metabolic organelles, present in virtually every eukaryotic cell and mediating key processes in immunometabolism. To date, the full spectrum of PBDs remains to be identified, and the impact PBDs have on immune function is unexplored. This study presents a characterization of the hepatic immune compartment of a neonatal PBD mouse model at single-cell resolution to establish the importance and function of peroxisomes in developmental hematopoiesis. We report that hematopoietic defects are a feature in a severe PBD murine model. Finally, we identify a role for peroxisomes in the regulation of the major histocompatibility class II expression and antigen presentation to CD4+ T cells in dendritic cells. This study adds to our understanding of the mechanisms of PBDs and expands our knowledge of the role of peroxisomes in immunometabolism.

CD1 lipidomes reveal lipid-binding motifs and size-based antigen-display mechanisms

The CD1 system binds lipid antigens for display to T cells. Here, we solved lipidomes for the four human CD1 antigen-presenting molecules, providing a map of self-lipid display. Answering a basic question, the detection of >2,000 CD1-lipid complexes demonstrates broad presentation of self-sphingolipids and phospholipids. Whereas peptide antigens are chemically processed, many lipids are presented in an unaltered form. However, each type of CD1 protein differentially edits the self-lipidome to show distinct capture motifs based on lipid length and chemical composition, suggesting general antigen display mechanisms. For CD1a and CD1d, lipid size matches the CD1 cleft volume. CD1c cleft size is more variable, and CD1b is the outlier, where ligands and clefts show an extreme size mismatch that is explained by uniformly seating two small lipids in one cleft. Furthermore, the list of compounds that comprise the integrated CD1 lipidome supports the ongoing discovery of lipid blockers and antigens for T cells.

Chronic inflammation, neuroglial dysfunction, and plasmalogen deficiency as a new pathobiological hypothesis addressing the overlap between post-COVID-19 symptoms and myalgic encephalomyelitis/chronic fatigue syndrome

After five waves of coronavirus disease 2019 (COVID-19) outbreaks, it has been recognized that a significant portion of the affected individuals developed long-term debilitating symptoms marked by chronic fatigue, cognitive difficulties ("brain fog"), post-exertional malaise, and autonomic dysfunction. The onset, progression, and clinical presentation of this condition, generically named post-COVID-19 syndrome, overlap significantly with another enigmatic condition, referred to as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Several pathobiological mechanisms have been proposed for ME/CFS, including redox imbalance, systemic and central nervous system inflammation, and mitochondrial dysfunction. Chronic inflammation and glial pathological reactivity are common hallmarks of several neurodegenerative and neuropsychiatric disorders and have been consistently associated with reduced central and peripheral levels of plasmalogens, one of the major phospholipid components of cell membranes with several homeostatic functions. Of great interest, recent evidence revealed a significant reduction of plasmalogen contents, biosynthesis, and metabolism in ME/CFS and acute COVID-19, with a strong association to symptom severity and other relevant clinical outcomes. These bioactive lipids have increasingly attracted attention due to their reduced levels representing a common pathophysiological manifestation between several disorders associated with aging and chronic inflammation. However, alterations in plasmalogen levels or their lipidic metabolism have not yet been examined in individuals suffering from post-COVID-19 symptoms. Here, we proposed a pathobiological model for post-COVID-19 and ME/CFS based on their common inflammation and dysfunctional glial reactivity, and highlighted the emerging implications of plasmalogen deficiency in the underlying mechanisms. Along with the promising outcomes of plasmalogen replacement therapy (PRT) for various neurodegenerative/neuropsychiatric disorders, we sought to propose PRT as a simple, effective, and safe strategy for the potential relief of the debilitating symptoms associated with ME/CFS and post-COVID-19 syndrome.

Ether lipid biosynthesis promotes lifespan extension and enables diverse pro-longevity paradigms in Caenorhabditis elegans

Biguanides, including the world's most prescribed drug for type 2 diabetes, metformin, not only lower blood sugar, but also promote longevity in preclinical models. Epidemiologic studies in humans parallel these findings, indicating favorable effects of metformin on longevity and on reducing the incidence and morbidity associated with aging-related diseases. Despite this promise, the full spectrum of molecular effectors responsible for these health benefits remains elusive. Through unbiased screening in Caenorhabditis elegans, we uncovered a role for genes necessary for ether lipid biosynthesis in the favorable effects of biguanides. We demonstrate that biguanides prompt lifespan extension by stimulating ether lipid biogenesis. Loss of the ether lipid biosynthetic machinery also mitigates lifespan extension attributable to dietary restriction, target of rapamycin (TOR) inhibition, and mitochondrial electron transport chain inhibition. A possible mechanistic explanation for this finding is that ether lipids are required for activation of longevity-promoting, metabolic stress defenses downstream of the conserved transcription factor skn-1/Nrf. In alignment with these findings, overexpression of a single, key, ether lipid biosynthetic enzyme, fard-1/FAR1, is sufficient to promote lifespan extension. These findings illuminate the ether lipid biosynthetic machinery as a novel therapeutic target to promote healthy aging.

iNKT cell-neutrophil crosstalk promotes colorectal cancer pathogenesis

iNKT cells account for a relevant fraction of effector T-cells in the intestine and are considered an attractive platform for cancer immunotherapy. Although iNKT cells are cytotoxic lymphocytes, their functional role in colorectal cancer (CRC) is still controversial, limiting their therapeutic use. Thus, we examined the immune cell composition and iNKT cell phenotype of CRC lesions in patients (n = 118) and different murine models. High-dimensional single-cell flow-cytometry, metagenomics, and RNA sequencing experiments revealed that iNKT cells are enriched in tumor lesions. The tumor-associated pathobiont Fusobacterium nucleatum induces IL-17 and Granulocyte-macrophage colony-stimulating factor (GM-CSF) expression in iNKT cells without affecting their cytotoxic capability but promoting iNKT-mediated recruitment of neutrophils with polymorphonuclear myeloid-derived suppressor cells-like phenotype and functions. The lack of iNKT cells reduced the tumor burden and recruitment of immune suppressive neutrophils. iNKT cells in-vivo activation with α-galactosylceramide restored their anti-tumor function, suggesting that iNKT cells can be modulated to overcome CRC-associated immune evasion. Tumor co-infiltration by iNKT cells and neutrophils correlates with negative clinical outcomes, highlighting the importance of iNKT cells in the pathophysiology of CRC. Our results reveal a functional plasticity of iNKT cells in CRC, suggesting a pivotal role of iNKT cells in shaping the tumor microenvironment, with relevant implications for treatment.

Protective Properties of Marine Alkyl Glycerol Ethers in Chronic Stress

In this paper we discuss the effect of alkyl glycerol ethers (AGs) from the squid Berryteuthis magister on a chronic stress model in rats. The study was performed on 32 male Wistar rats. Animals received AGs at a dose of 200 mg/kg through a gavage for six weeks (1.5 months), and were divided into four groups: group 1 (control), group 2 (animals received AGs), group 3 (stress control), group 4 (animals received AGs and were subjected to stress). Chronic immobilization stress was induced by placing each rat into an individual plexiglass cages for 2 h daily for 15 days. The serum lipid spectrum was evaluated by the content of total cholesterol, triglycerides, high-density lipoprotein cholesterol, low lipoprotein cholesterol and very low-density lipoprotein cholesterol. The atherogenic coefficient was calculated. The hematological parameters of peripheral blood were evaluated. The neutrophil-lymphocyte ratio was counted. The levels of cortisol and testosterone in blood plasma were determined. AGs at the selected dose did not have a significant effect on the body weight of rats in the preliminary period of the experiment. Under stress, the body weight gain, the concentrations of very low-density lipoprotein cholesterol and blood triglycerides decreased significantly. The neutrophil-lymphocyte ratio in animals treated with AGs shifted towards lymphocytes. A favorable increase in the percentage of lymphocytes was found in the stressed group of animals treated with AGs. So, for the first time, it was found that AGs prevent stress-induced suppression of the immune system. This confirms the benefit of AGs for the immune system under chronic stress. Our results prove the efficiency of the use of AGs for treating chronic stress, a serious social problem in modern society.

CD8+ T-cell immunity orchestrated by iNKT cells

CD8⁺ T cells belonging to the adaptive immune system play key roles in defending against viral infections and cancers. The current CD8⁺ T cell-based immunotherapy has emerged as a superior therapeutic avenue for the eradication of tumor cells and long-term prevention of their recurrence in hematologic malignancies. It is believed that an effective adaptive immune response critically relies on the help of the innate compartment. Invariant natural killer T (iNKT) cells are innate-like T lymphocytes that have been considered some of the first cells to respond to infections and can secrete a large amount of diverse cytokines and chemokines to widely modulate the innate and adaptive immune responders. Like CD8⁺ T cells, iNKT cells also play an important role in defense against intracellular pathogenic infections and cancers. In this review, we will discuss the CD8⁺ T-cell immunity contributed by iNKT cells, including iNKT cell-mediated cross-priming and memory formation, and discuss recent advances in our understanding of the mechanisms underlying memory CD8⁺ T-cell differentiation, as well as aging-induced impairment of T-cell immunity.

Chemical Synthesis and Molecular Interaction Analysis of α-Galactosyl Ceramide Derivatives as CD1d Ligands

CD1d is a non-classical major histocompatibility complex (MHC) protein, responsible for lipid antigen presentation, which presents lipids to natural killer T (NKT) cells. Various CD1d lipid ligands have been reported, including microbial and endogenous glycolipids/phospholipids. Among them, an α-galactosylceramide (α-GalCer), a representative CD1d ligand, is one of the most potent ligands and its derivatives have been developed. In this chapter, the chemistry of α-GalCer and its derivatives are described with an emphasis on their chemical syntheses and molecular interaction analysis with CD1d are described.

Mouse Models to Study Peroxisomal Functions and Disorders: Overview, Caveats, and Recommendations

During the last three decades many mouse lines were created or identified that are deficient in one or more peroxisomal functions. Different methodologies were applied to obtain global, hypomorph, cell type selective, inducible, and knockin mice. Whereas some models closely mimic pathologies in patients, others strongly deviate or no human counterpart has been reported. Often, mice, apparently endowed with a stronger transcriptional adaptation, have to be challenged with dietary additions or restrictions in order to trigger phenotypic changes. Depending on the inactivated peroxisomal protein, several approaches can be taken to validate the loss-of-function. Here, an overview is given of the available mouse models and their most important characteristics.

The peroxisome: an up-and-coming organelle in immunometabolism

Peroxisomes are essential metabolic organelles, well known for their roles in the metabolism of complex lipids and reactive ionic species. In the past 10 years, peroxisomes have also been cast as central regulators of immunity. Lipid metabolites of peroxisomes, such as polyunsaturated fatty acids (PUFAs), are precursors for important immune mediators, including leukotrienes (LTs) and resolvins. Peroxisomal redox metabolism modulates cellular immune signaling such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation. Additionally, peroxisomal β-oxidation and ether lipid synthesis control the development and aspects of the activation of both innate and adaptive immune cells. Finally, peroxisome number and metabolic activity have been linked to inflammatory diseases. These discoveries have opened avenues of investigation aimed at targeting peroxisomes for therapeutic intervention in immune disorders, inflammation, and cancer.

The physiological functions of human peroxisomes

Peroxisomes are subcellular organelles that play a central role in human physiology by catalyzing a range of unique metabolic functions. The importance of peroxisomes for human health is exemplified by the existence of a group of usually severe diseases caused by an impairment in one or more peroxisomal functions. Among others these include the Zellweger spectrum disorders, X-linked adrenoleukodystrophy, and Refsum disease. To fulfill their role in metabolism, peroxisomes require continued interaction with other subcellular organelles including lipid droplets, lysosomes, the endoplasmic reticulum, and mitochondria. In recent years it has become clear that the metabolic alliance between peroxisomes and other organelles requires the active participation of tethering proteins to bring the organelles physically closer together, thereby achieving efficient transfer of metabolites. This review intends to describe the current state of knowledge about the metabolic role of peroxisomes in humans, with particular emphasis on the metabolic partnership between peroxisomes and other organelles and the consequences of genetic defects in these processes. We also describe the biogenesis of peroxisomes and the consequences of the multiple genetic defects therein. In addition, we discuss the functional role of peroxisomes in different organs and tissues and include relevant information derived from model systems, notably peroxisomal mouse models. Finally, we pay particular attention to a hitherto underrated role of peroxisomes in viral infections.

Alkyl Glycerol Ethers as Adaptogens

Τhis mini-review summarizes the hematopoietic and immunostimulating properties of alkyl glycerol ethers (AGs) reported earlier in the literature available to us. The role of AGs in the nervous system and aging of the body are also briefly described. We made an attempt to consider the data in terms of adaptation. The hematopoietic, immunostimulating and antioxidant properties of AGs in a variety of experimental situations, including stress, as well as the protective action of AGs against some adaptation diseases, allow us to consider them as substances that prevent some negative effects of stress and promote adaptation. The new approach to AGs as adaptogens seems promising and opens good opportunities for their new application.

Plasmalogens and platelet-activating factor roles in chronic inflammatory diseases

Fatty acids and phospholipid molecules are essential for determining the structure and function of cell membranes, and they hence participate in many biological processes. Platelet activating factor (PAF) and its precursor plasmalogen, which represent two subclasses of ether phospholipids, have attracted increasing research attention recently due to their association with multiple chronic inflammatory, neurodegenerative, and metabolic disorders. These pathophysiological conditions commonly involve inflammatory processes linked to an excess presence of PAF and/or decreased levels of plasmalogens. However, the molecular mechanisms underlying the roles of plasmalogens in inflammation have remained largely elusive. While anti-inflammatory responses most likely involve the plasmalogen signal pathway; pro-inflammatory responses recruit arachidonic acid, a precursor of pro-inflammatory lipid mediators which is released from membrane phospholipids, notably derived from the hydrolysis of plasmalogens. Plasmalogens per se are vital membrane phospholipids in humans. Changes in their homeostatic levels may alter cell membrane properties, thus affecting key signaling pathways that mediate inflammatory cascades and immune responses. The plasmalogen analogs of PAF are also potentially important, considering that anti-PAF activity has strong anti-inflammatory effects. Plasmalogen replacement therapy was further identified as a promising anti-inflammatory strategy allowing for the relief of pathological hallmarks in patients affected by chronic diseases with an inflammatory component. The aim of this Short Review is to highlight the emerging roles and implications of plasmalogens in chronic inflammatory disorders, along with the promising outcomes of plasmalogen replacement therapy for the treatment of various PAF-related chronic inflammatory pathologies.

Gut Microbiota-Derived Unconventional T Cell Ligands: Contribution to Host Immune Modulation

Besides the prototypic innate and adaptive pathways, immune responses by innate-like lymphocytes have gained significant attention due to their unique roles. Among innate-like lymphocytes, unconventional T cells such as NKT cells and mucosal-associated invariant T (MAIT) cells recognize small nonpeptide molecules of specific chemical classes. Endogenous or microbial ligands are loaded to MHC class I-like molecule CD1d or MR1, and inducing immediate effector T cell and ligand structure is one of the key determinants of NKT/MAIT cell functions. Unconventional T cells are in close, constant contact with symbiotic microbes at the mucosal layer, and CD1d/MR1 can accommodate diverse metabolites produced by gut microbiota. There is a strong interest to identify novel immunoactive molecules of endobiotic (symbiont-produced) origin as new NKT/MAIT cell ligands, as well as new cognate Ags for previously uncharacterized unconventional T cell subsets. Further studies will open an possibility to explore basic biology as well as therapeutic potential.

Plasmalogen-Mediated Activation of GPCR21 Regulates Cytolytic Activity of NK Cells against the Target Cells

It is widely known that the immune system becomes slower to respond among elderly people, making them more susceptible to viral infection and cancer. The mechanism of aging-related immune deficiency remained mostly elusive. In this article, we report that plasmalogens (Pls), special phospholipids found to be reduced among the elderly population, critically control cytolytic activity of human NK cells, which is associated with activation of a cell surface receptor, G protein-coupled receptor 21 (GPCR21). We found the extracellular glycosylation site of GPCR21, which is conserved among the mammalian species, to be critically important for the activation of NK cells by Pls. The Pls-GPCR21 signaling cascade induces the expression of Perforin-1, a cytolytic pore-forming protein, via activation of STAT5 transcription factor. Inhibition of STAT5 abrogates GPCR21-mediated cytolytic activation of NK cells against the target cancer cells. In addition, oral ingestion of Pls inhibited cancer growth in SCID mice and inhibited the systemic spread of murine CMV in adult C57BL/6J mice. These findings advocate that Pls-GPCR21 signaling could be critical in maintaining NK cell function, and that the age-related reduction of this signaling cascade could be one of the factors behind immune deficiency in mammals, including humans.

Brain and testicular metabonomics revealed the protective effects of Guilingji on senile sexual dysfunction rats

ETHNOPHARMACOLOGICAL RELEVANCE

Guilingji (GLJ), which has been used to treat male diseases in China for centuries, contains 28 Chinese herbs and was previously established as an effective treatment for male sexual dysfunction. However, its mechanism of action remains unclear.

AIM OF THE STUDY

To explore the efficacy and mechanism of action of GLJ in improving senile sexual dysfunction (SSD) in aging rats.

MATERIALS AND METHODS

An aging rat model of SSD was induced by the subcutaneous injection of d-galactose (300 mg⋅kg^-1) and used to analyse the effects of GLJ (different concentrations of 37.5, 75, and 150 mg⋅kg^-1) on the mating of aging rats. At the end of the 8th week, histopathological analysis of testicular tissues, assessment of the hypothalamic-pituitary-gonadal (HPG) axis hormone levels in serum or brain, and metabonomics analysis of the brain and testicular tissue with liquid chromatography-mass spectrometry was performed to explore the mechanism of action of GLJ.

RESULT

After treatment with GLJ, the mount and ejaculation latency levels were increased in the treatment group than those in model group (P < 0.05), moreover, the testicular morphology was improved. Gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) levels in rats were also improved significant (P < 0.05) compared with those in the model group. Furthermore, the metabonomics results in the testicular and brain tissue showed that GLJ improved SSD by adjusting amino acid and lipid metabolism.

CONCLUSION

This study integrated the complementary metabolic profiles of the target tissues. GLJ might affect SSD rats by regulating amino acid and lipid metabolism and may modulate sensitivity to the signaling pathway in the HPG axis. This study provides an essential basis for the broad clinical application of GLJ.

Peroxisomes Regulate Cellular Free Fatty Acids to Modulate Mast Cell TLR2, TLR4, and IgE-Mediated Activation

Mast cells are specialized, tissue resident, immune effector cells able to respond to a wide range of stimuli. MCs are involved in the regulation of a variety of physiological functions, including vasodilation, angiogenesis and pathogen elimination. In addition, MCs recruit and regulate the functions of many immune cells such as dendritic cells, macrophages, T cells, B cells and eosinophils through their selective production of multiple cytokines and chemokines. MCs generate and release multi-potent molecules, such as histamine, proteases, prostanoids, leukotrienes, heparin, and many cytokines, chemokines, and growth factors through both degranulation dependent and independent pathways. Recent studies suggested that metabolic shifts dictate the activation and granule content secretion by MCs, however the metabolic signaling promoting these events is at its infancy. Lipid metabolism is recognized as a pivotal immunometabolic regulator during immune cell activation. Peroxisomes are organelles found across all eukaryotes, with a pivotal role in lipid metabolism and the detoxification of reactive oxygen species. Peroxisomes are one of the emerging axes in immunometabolism. Here we identified the peroxisome as an essential player in MCs activation. We determined that lack of functional peroxisomes in murine MCs causes a significant reduction of interleukin-6, Tumor necrosis factor and InterleukinL-13 following immunoglobulin IgE-mediated and Toll like receptor 2 and 4 activation compared to the Wild type (WT) BMMCs. We linked these defects in cytokine release to defects in free fatty acids homeostasis. In conclusion, our study identified the importance of peroxisomal fatty acids homeostasis in regulating mast cell-mediated immune functions.

IL10 Secretion Endows Intestinal Human iNKT Cells with Regulatory Functions Towards Pathogenic T Lymphocytes

BACKGROUND AND AIMS

Invariant natural killer T [iNKT] cells perform pleiotropic functions in different tissues by secreting a vast array of pro-inflammatory and cytotoxic molecules. However, the presence and function of human intestinal iNKT cells capable of secreting immunomodulatory molecules such as IL-10 has never been reported so far. Here we describe for the first time the presence of IL10-producing iNKT cells [NKT10 cells] in the intestinal lamina propria of healthy individuals and of Crohn's disease [CD] patients.

METHODS

Frequency and phenotype of NKT10 cells were analysed ex vivo from intestinal specimens of Crohn's disease [n = 17] and controls [n = 7]. Stable CD-derived intestinal NKT10 cell lines were used to perform in vitro suppression assays and co-cultures with patient-derived mucosa-associated microbiota. Experimental colitis models were performed by adoptive cell transfer of splenic naïve CD4+ T cells in the presence or absence of IL10-sufficient or -deficient iNKT cells. In vivo induction of NKT10 cells was performed by administration of short chain fatty acids [SCFA] by oral gavage.

RESULTS

Patient-derived intestinal NKT10 cells demonstrated suppressive capabilities towards pathogenic CD4+ T cells. The presence of increased proportions of mucosal NKT10 cells associated with better clinical outcomes in CD patients. Moreover, an intestinal microbial community enriched in SCFA-producing bacteria sustained the production of IL10 by iNKT cells. Finally, IL10-deficient iNKT cells failed to control the pathogenic activity of adoptively transferred CD4+ T cells in an experimental colitis model.

CONCLUSIONS

These results describe an unprecedentd IL10-mediated immunoregulatory role of intestinal iNKT cells in controlling the pathogenic functions of mucosal T helper subsets and in maintaining the intestinal immune homeostasis.

Modulation of the cell membrane lipid milieu by peroxisomal β-oxidation induces Rho1 signaling to trigger inflammatory responses

Phagocytosis, signal transduction, and inflammatory responses require changes in lipid metabolism. Peroxisomes have key roles in fatty acid homeostasis and in regulating immune function. We find that Drosophila macrophages lacking peroxisomes have perturbed lipid profiles, which reduce host survival after infection. Using lipidomic, transcriptomic, and genetic screens, we determine that peroxisomes contribute to the cell membrane glycerophospholipid composition necessary to induce Rho1-dependent signals, which drive cytoskeletal remodeling during macrophage activation. Loss of peroxisome function increases membrane phosphatidic acid (PA) and recruits RhoGAPp190 during infection, inhibiting Rho1-mediated responses. Peroxisome-glycerophospholipid-Rho1 signaling also controls cytoskeleton remodeling in mouse immune cells. While high levels of PA in cells without peroxisomes inhibit inflammatory phenotypes, large numbers of peroxisomes and low amounts of cell membrane PA are features of immune cells from patients with inflammatory Kawasaki disease and juvenile idiopathic arthritis. Our findings reveal potential metabolic markers and therapeutic targets for immune diseases and metabolic disorders.

Mice with a deficiency in Peroxisomal Membrane Protein 4 (PXMP4) display mild changes in hepatic lipid metabolism

Peroxisomes play an important role in the metabolism of a variety of biomolecules, including lipids and bile acids. Peroxisomal Membrane Protein 4 (PXMP4) is a ubiquitously expressed peroxisomal membrane protein that is transcriptionally regulated by peroxisome proliferator-activated receptor α (PPARα), but its function is still unknown. To investigate the physiological function of PXMP4, we generated a Pxmp4 knockout (Pxmp4^-/-) mouse model using CRISPR/Cas9-mediated gene editing. Peroxisome function was studied under standard chow-fed conditions and after stimulation of peroxisomal activity using the PPARα ligand fenofibrate or by using phytol, a metabolite of chlorophyll that undergoes peroxisomal oxidation. Pxmp4^-/- mice were viable, fertile, and displayed no changes in peroxisome numbers or morphology under standard conditions. Also, no differences were observed in the plasma levels of products from major peroxisomal pathways, including very long-chain fatty acids (VLCFAs), bile acids (BAs), and BA intermediates di- and trihydroxycholestanoic acid. Although elevated levels of the phytol metabolites phytanic and pristanic acid in Pxmp4^-/- mice pointed towards an impairment in peroxisomal α-oxidation capacity, treatment of Pxmp4^-/- mice with a phytol-enriched diet did not further increase phytanic/pristanic acid levels. Finally, lipidomic analysis revealed that loss of Pxmp4 decreased hepatic levels of the alkyldiacylglycerol class of neutral ether lipids, particularly those containing polyunsaturated fatty acids. Together, our data show that while PXMP4 is not critical for overall peroxisome function under the conditions tested, it may have a role in the metabolism of (ether)lipids.

Identification of an at-risk subpopulation with high immune infiltration based on the peroxisome pathway and TIM3 in colorectal cancer

Background

Peroxisomes are pivotal metabolic organelles that exist in almost all eukaryote cells. A reduction in numbers and enzymatic activities of peroxisomes was found in colon adenocarcinomas. However, the role of peroxisomes or the peroxisome pathway in colorectal cancer (CRC) is not defined.

Methods

In the current study, a peroxisome score was calculated to indicate the activity of the peroxisome pathway using gene set variant analysis based on transcriptomic datasets. CIBERSORTx was chosen to infer enriched immune cells for tumors among subgroups. The SubMap algorithm was applied to predict its sensitivity to immunotherapy.

Results

The patients with a relatively low peroxisome score and high level of T-cell immunoglobulin and mucin domain 3 (TIM-3) presented the worse overall survival than others. Moreover, low peroxisome scores were associated with high infiltration of lymphocytes and poor prognosis in those CRC patients. Thus, a PER^LowTIM3^High CRC risk subpopulation was identified and characterized by high immune infiltration. The results also showed that CD8 T cells and macrophages highly infiltrated tumors of the PER^LowTIM3^High group, regardless of consortium molecular subtype and microsatellite instability status. This subgroup had the highest tumor mutational burden and overexpression of immune checkpoint genes. Further, the PER^LowTIM3^High group showed a higher probability of responding to programmed cell death protein-1-based immunotherapy. In addition, genes involved in peroxisomal metabolic processes in CRC were also investigated since peroxisome is a rather pleiotropic and highly metabolic organelle in cell. The results indicated that only those genes involved in fatty acid alpha oxidation could be used to stratify CRC patients as similar as peroxisome pathway genes.

Conclusions

We revealed the favorable prognostic value of the peroxisome pathway in CRC and provided a new CRC stratification based on peroxisomes and TIM3, which might be helpful for CRC diagnostics and personalized treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-09085-9.

Harnessing invariant natural killer T cells to control pathological inflammation

Invariant natural killer T (iNKT) cells are innate T cells that are recognized for their potent immune modulatory functions. Over the last three decades, research in murine models and human observational studies have revealed that iNKT cells can act to limit inflammatory pathology in a variety of settings. Since iNKT cells are multi-functional and can promote inflammation in some contexts, understanding the mechanistic basis for their anti-inflammatory effects is critical for effectively harnessing them for clinical use. Two contrasting mechanisms have emerged to explain the anti-inflammatory activity of iNKT cells: that they drive suppressive pathways mediated by other regulatory cells, and that they may cytolytically eliminate antigen presenting cells that promote excessive inflammatory responses. How these activities are controlled and separated from their pro-inflammatory functions remains a central question. Murine iNKT cells can be divided into four functional lineages that have either pro-inflammatory (NKT1, NKT17) or anti-inflammatory (NKT2, NKT10) cytokine profiles. However, in humans these subsets are not clearly evident, and instead most iNKT cells that are CD4⁺ appear oriented towards polyfunctional (T_H0) cytokine production, while CD4^- iNKT cells appear more predisposed towards cytolytic activity. Additionally, structurally distinct antigens have been shown to induce T_H1- or T_H2-biased responses by iNKT cells in murine models, but human iNKT cells may respond to differing levels of TCR stimulation in a way that does not neatly separate T_H1 and T_H2 cytokine production. We discuss the implications of these differences for translational efforts focused on the anti-inflammatory activity of iNKT cells.

Human intestinal and circulating invariant natural killer T cells are cytotoxic against colorectal cancer cells via the perforin-granzyme pathway

Invariant natural killer T (iNKT) cells are lipid-specific T lymphocytes endowed with cytotoxic activities and are thus considered important in antitumor immunity. While several studies have demonstrated iNKT cell cytotoxicity against different tumors, very little is known about their cell-killing activities in human colorectal cancer (CRC). Our aim was to assess whether human iNKT cells are cytotoxic against colon cancer cells and the mechanisms underlying this activity. For this purpose, we generated stable iNKT cell lines from peripheral blood and colon specimens and used NK-92 and peripheral blood natural killer cells as cell-mediated cytotoxicity controls. In vitro cytotoxicity was assessed using a panel of well-characterized human CRC cell lines, and the cellular requirements for iNKT cell cytotoxic functions were evaluated. We demonstrated that both intestinal and circulating iNKT cells were cytotoxic against the entire panel of CRC lines, as well as against freshly isolated patient-derived colonic epithelial cancer cells. Perforin and/or granzyme inhibition impaired iNKT cell cytotoxicity, whereas T-cell receptor (TCR) signaling was a less stringent requirement for efficient killing. This study is the first evidence of tissue-derived iNKT cell cytotoxic activity in humans, as it shows that iNKT cells depend on the perforin-granzyme pathway and both adaptive and innate signal recognition for proper elimination of colon cancer cells.

Changes in sow milk lipidome across lactation occur in fatty acyl residues of triacylglycerol and phosphatidylglycerol lipids, but not in plasma membrane phospholipids

Milk fats are vital to neonate survival and development, but vary highly by diet, maternal metabolic state and stage of lactation. To gain a better understanding of changes in lipid composition of sow milk across lactation, milk was collected from nine multiparous sows on days 0, 3, 7, and 14, relative to birth and lipids were profiled using multiple reaction monitoring (MRM) profiling. Percent fat was determined by creamatocrit, and found to be different (P < 0.05) between day 0 (12.36 ± 5.90%) and day 3 (16.22 ± 3.65%) but not between day 7 (13.13 ± 2.19%) and day 14 (12.13 ± 2.45%). Fat was extracted from milk (n = 6/day) using the Bligh-Dyer method and profiled using tandem mass spectrometry MRM to determine the abundance of lipids defined by class and fatty acyl residue composition. Lipid species relative concentration was calculated from internal standards, and data analysis was performed using Metaboanalyst 4.0. Concentration of phosphatidyl-choline, -serine, -ethanolamine, -inositol, cholesteryl ester and sphingomyelin did not vary across lactation days, nor did the distribution of associated fatty acyl residues. The total abundance of triacylglycerides (TGs) and phosphatidylglycerols (PGs) increased (P < 0.05) from colostrum (day 0) to transitional (days 3 and 7) and mature milk (day 14). As lactation days increased from day 0 to day 14, the number of carbons and unsaturation within fatty acyl residues decreased (P < 0.05) in both TGs and PGs. The proportion of TGs and PGs increased (P < 0.05) relative to other lipid classes. Changes in composition of milk triglycerides and phosphatidylglycerols likely reflect the metabolic activity of the mammary gland and developmental needs of neonates.

Shark liver oil supplementation enriches endogenous plasmalogens and reduces markers of dyslipidemia and inflammation

Plasmalogens are membrane glycerophospholipids with diverse biological functions. Reduced plasmalogen levels have been observed in metabolic diseases; hence, increasing their levels might be beneficial in ameliorating these conditions. Shark liver oil (SLO) is a rich source of alkylglycerols that can be metabolized into plasmalogens. This study was designed to evaluate the impact of SLO supplementation on endogenous plasmalogen levels in individuals with features of metabolic disease. In this randomized, double-blind, placebo-controlled cross-over study, the participants (10 overweight or obese males) received 4-g Alkyrol® (purified SLO) or placebo (methylcellulose) per day for 3 weeks followed by a 3-week washout phase and were then crossed over to 3 weeks of the alternate placebo/Alkyrol® treatment. SLO supplementation led to significant changes in plasma and circulatory white blood cell lipidomes, notably increased levels of plasmalogens and other ether lipids. In addition, SLO supplementation significantly decreased the plasma levels of total free cholesterol, triglycerides, and C-reactive protein. These findings suggest that SLO supplementation can enrich plasma and cellular plasmalogens and this enrichment may provide protection against obesity-related dyslipidemia and inflammation.

Dengue and metabolomics in humans

BACKGROUND

Dengue virus causes dengue fever (DF)disease, transmitted by the mosquito Aedes aegypti. The symptoms could be severe and disable the affected individuals for weeks. The severe form, dengue hemorrhagic fever (DHF), can lead to death if not adequately attended to. Due to global warming, the vector mosquito will advance over new areas and expose more people to this disease over the next decades. Despite the severity, there are no treatments nor efficient vaccines available. Metabolomic studies have shown a new perspective to understand this disease better at a new molecular level.

AIM OF REVIEW

Many published works rely on samples obtained from animal studies. This review will mainly focus on human samples and cell culture experiments to view how the dengue virus affects the metabolomic profile.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The review compiles the sample sources, metabolomic techniques used, the detected compounds, and how they behave in different DF stages. This disease causes a significant change in many metabolites, but some results are still conflicting between studies. The results gathered here show that metabolomic approaches prove to be an excellent and viable way to expand knowledge about DF.

Coronavirus-Induced Host Cubic Membranes and Lipid-Related Antiviral Therapies: A Focus on Bioactive Plasmalogens

Coronaviruses have lipid envelopes required for their activity. The fact that coronavirus infection provokes the formation of cubic membranes (CM) (denoted also as convoluted membranes) in host cells has not been rationalized in the development of antiviral therapies yet. In this context, the role of bioactive plasmalogens (vinyl ether glycerophospholipids) is not completely understood. These lipid species display a propensity for non-lamellar phase formation, facilitating membrane fusion, and modulate the activity of membrane-bound proteins such as enzymes and receptors. At the organism level, plasmalogen deficiency is associated with cardiometabolic disorders including obesity and type 2 diabetes in humans. A straight link is perceived with the susceptibility of such patients to SARS-CoV-2 (severe acute respiratory syndrome-coronavirus-2) infection, the severity of illness, and the related difficulty in treatment. Based on correlations between the coronavirus-induced modifications of lipid metabolism in host cells, plasmalogen deficiency in the lung surfactant of COVID-19 patients, and the alterations of lipid membrane structural organization and composition including the induction of CM, we emphasize the key role of plasmalogens in the coronavirus (SARS-CoV-2, SARS-CoV, or MERS-CoV) entry and replication in host cells. Considering that plasmalogen-enriched lung surfactant formulations may improve the respiratory process in severe infected individuals, plasmalogens can be suggested as an anti-viral prophylactic, a lipid biomarker in SARS-CoV and SARS-CoV-2 infections, and a potential anti-viral therapeutic component of lung surfactant development for COVID-19 patients.

Peroxisomal Metabolite and Cofactor Transport in Humans

Peroxisomes are membrane-bound organelles involved in many metabolic pathways and essential for human health. They harbor a large number of enzymes involved in the different pathways, thus requiring transport of substrates, products and cofactors involved across the peroxisomal membrane. Although much progress has been made in understanding the permeability properties of peroxisomes, there are still important gaps in our knowledge about the peroxisomal transport of metabolites and cofactors. In this review, we discuss the different modes of transport of metabolites and essential cofactors, including CoA, NAD⁺, NADP⁺, FAD, FMN, ATP, heme, pyridoxal phosphate, and thiamine pyrophosphate across the peroxisomal membrane. This transport can be mediated by non-selective pore-forming proteins, selective transport proteins, membrane contact sites between organelles, and co-import of cofactors with proteins. We also discuss modes of transport mediated by shuttle systems described for NAD⁺/NADH and NADP⁺/NADPH. We mainly focus on current knowledge on human peroxisomal metabolite and cofactor transport, but also include knowledge from studies in plants, yeast, fruit fly, zebrafish, and mice, which has been exemplary in understanding peroxisomal transport mechanisms in general.

Bioactive Ether Lipids: Primordial Modulators of Cellular Signaling

The primacy of lipids as essential components of cellular membranes is conserved across taxonomic domains. In addition to this crucial role as a semi-permeable barrier, lipids are also increasingly recognized as important signaling molecules with diverse functional mechanisms ranging from cell surface receptor binding to the intracellular regulation of enzymatic cascades. In this review, we focus on ether lipids, an ancient family of lipids having ether-linked structures that chemically differ from their more prevalent acyl relatives. In particular, we examine ether lipid biosynthesis in the peroxisome of mammalian cells, the roles of selected glycerolipids and glycerophospholipids in signal transduction in both prokaryotes and eukaryotes, and finally, the potential therapeutic contributions of synthetic ether lipids to the treatment of cancer.

Intravital imaging of interactions between iNKT and kupffer cells to clear free lipids during steatohepatitis

Rationale: Invariant natural killer T (iNKT) cells and Kupffer cells represent major hepatic populations of innate immune cells. However, their roles in steatohepatitis remain poorly understood. To elucidate their functions in steatohepatitis development, real-time, in vivo analysis is necessary to understand the pathophysiological events in the dynamic interactions between them during diet-induced steatohepatitis.

Methods: We used a steatohepatitis animal model induced by a methionine-choline-deficient (MCD) diet. Multi-photon confocal live imaging and conventional experimental techniques were employed to investigate the hepatic pathological microenvironment of iNKT and Kupffer cells, interactions between them, and the biological effects of these interactions in steatohepatitis.

Results: We found that iNKT cells were recruited and aggregated into small clusters and interacted dynamically with Kupffer cells in the early stage of steatohepatitis. Most significantly, the iNKT cells in the cluster cleared free lipids released by necrotic hepatocytes and presented a non-classical activation state with high IFN-γ expression. Furthermore, the Kupffer cells in the cell cluster were polarized to type M1. The transcriptome sequencing of iNKT cells showed upregulation of genes related to phagocytosis and lipid processing. Adoptive transfer of iNKT cells to Jα18^-/- mice showed that iNKT and Kupffer cell clusters were essential for balancing the liver and peripheral lipid levels and inhibiting liver fibrosis development.

Conclusions: Our study identified an essential role for dynamic interactions between iNKT cells and Kupffer cells in promoting lipid phagocytosis and clearance by iNKT cells during early liver steatohepatitis. Therefore, modulating iNKT cells is a potential therapeutic strategy for early steatohepatitis.

Plasmalogens, platelet-activating factor and beyond - Ether lipids in signaling and neurodegeneration

Glycerol-based ether lipids including ether phospholipids form a specialized branch of lipids that in mammals require peroxisomes for their biosynthesis. They are major components of biological membranes and one particular subgroup, the plasmalogens, is widely regarded as a cellular antioxidant. Their vast potential to influence signal transduction pathways is less well known. Here, we summarize the literature showing associations with essential signaling cascades for a wide variety of ether lipids, including platelet-activating factor, alkylglycerols, ether-linked lysophosphatidic acid and plasmalogen-derived polyunsaturated fatty acids. The available experimental evidence demonstrates links to several common players like protein kinase C, peroxisome proliferator-activated receptors or mitogen-activated protein kinases. Furthermore, ether lipid levels have repeatedly been connected to some of the most abundant neurological diseases, particularly Alzheimer's disease and more recently also neurodevelopmental disorders like autism. Thus, we critically discuss the potential role of these compounds in the etiology and pathophysiology of these diseases with an emphasis on signaling processes. Finally, we review the emerging interest in plasmalogens as treatment target in neurological diseases, assessing available data and highlighting future perspectives. Although many aspects of ether lipid involvement in cellular signaling identified in vitro still have to be confirmed in vivo, the compiled data show many intriguing properties and contributions of these lipids to health and disease that will trigger further research.

Early-life exposure to perfluorinated alkyl substances modulates lipid metabolism in progression to celiac disease

Celiac disease (CD) is a systemic immune-mediated disorder with increased frequency in the developed countries over the last decades implicating the potential causal role of various environmental triggers in addition to gluten. Herein, we apply determination of perfluorinated alkyl substances (PFAS) and combine the results with the determination of bile acids (BAs) and molecular lipids, with the aim to elucidate the impact of prenatal exposure on risk of progression to CD in a prospective series of children prior the first exposure to gluten (at birth and at 3 months of age). Here we analyzed PFAS, BAs and lipidomic profiles in 66 plasma samples at birth and at 3 months of age in the Type 1 Diabetes Prediction and Prevention (DIPP) study (n = 17 progressors to CD, n = 16 healthy controls, HCs). Plasma PFAS levels showed a significant inverse association with the age of CD diagnosis in infants who later progressed to the disease. Associations between BAs and triacylglycerols (TGs) showed different patterns already at birth in CD progressors, indicative of different absorption of lipids in these infants. In conclusion, PFAS exposure may modulate lipid and BA metabolism, and the impact is different in the infants who develop CD later in life, in comparison to HCs. The results indicate more efficient uptake of PFAS in such infants. Higher PFAS exposure during prenatal and early life may accelerate the progression to CD in the genetically predisposed children.

Integrated adrenal and testicular metabolomics revealed the protective effects of Guilingji on the Kidney-Yang deficiency syndrome rats

ETHNOPHARMACOLOGICAL RELEVANCE

Guilingji (GLJ) is a well-known traditional Chinese medicine (TCM) prescription for the treatment of Kidney-Yang deficiency syndrome (KYDS).

AIM OF THE STUDY

This study aimed to address the protective effects of GLJ against KYDS in rats with pharmacodynamic indicators and target tissues (adrenal gland and testis) metabolomics.

MATERIALS AND METHODS

The rats were injected intraperitoneally (i.p) hydrocortisone to simulate KYDS and administered orally of GLJ for 30 days. Traditional pharmacodynamic indicators (body weight, behavioral indicators, biochemical parameters and histological examination) were performed to evaluate the efficacy of GLJ. Furthermore, adrenal gland and testis metabolic profiles obtained by UHPLC-Q Exactive Orbitrap-MS coupled with multivariate analysis were conducted to explore the metabolic regulation mechanism of GLJ.

RESULTS

After administration of GLJ, the weight, levels of behavioral indicators and biochemical parameters of rats were increased compared with those of the model group, and the abnormalities of morphology in adrenal and testicular tissues were improved. Furthermore, GLJ had recovering effects via the adjustment of vitamins metabolism, which was accompanied by lipids metabolism, amino acid metabolism and nucleotides metabolism.

CONCLUSIONS

The study firstly integrated the target tissues metabolic profiles, which were complementary, and GLJ had protective effects on KYDS rats via the regulation of steroid hormone biosynthesis, oxidant-antioxidant balance and energy acquisition.

License to Kill: When iNKT Cells Are Granted the Use of Lethal Cytotoxicity

Invariant Natural Killer T (iNKT) cells are a non-conventional, innate-like, T cell population that recognize lipid antigens presented by the cluster of differentiation (CD)1d molecule. Although iNKT cells are mostly known for mediating several immune responses due to their massive and diverse cytokine release, these cells also work as effectors in various contexts thanks to their cytotoxic potential. In this Review, we focused on iNKT cell cytotoxicity; we provide an overview of iNKT cell subsets, their activation cues, the mechanisms of iNKT cell cytotoxicity, the specific roles and outcomes of this activity in various contexts, and how iNKT killing functions are currently activated in cancer immunotherapies. Finally, we discuss the future perspectives for the better understanding and potential uses of iNKT cell killing functions in tumor immunosurveillance.

NK and NKT Cell-Mediated Immune Surveillance against Hematological Malignancies

Recent cancer treatment modalities have been intensively focused on immunotherapy. The success of chimeric antigen receptor T cell therapy for treatment of refractory B cell acute lymphoblastic leukemia has pushed forward research on hematological malignancies. Among the effector types of innate lymphocytes, natural killer (NK) cells show great importance in immune surveillance against infectious and tumor diseases. Particularly, the role of NK cells has been argued in either elimination of target tumor cells or escape of tumor cells from immune surveillance. Therefore, an NK cell activation approach has been explored. Recent findings demonstrate that invariant natural killer T (iNKT) cells capable of producing IFN-γ when optimally activated can promptly trigger NK cells. Here, we review the role of NKT and/or NK cells and their interaction in anti-tumor responses by highlighting how innate immune cells recognize tumors, exert effector functions, and amplify adaptive immune responses. In addition, we discuss these innate lymphocytes in hematological disorders, particularly multiple myeloma and acute myeloid leukemia. The immune balance at different stages of both diseases is explored in light of disease progression. Various types of innate immunity-mediated therapeutic approaches, recent advances in clinical immunotherapies, and iNKT-mediated cancer immunotherapy as next-generation immunotherapy are then discussed.

Stabilization of FASN by ACAT1-mediated GNPAT acetylation promotes lipid metabolism and hepatocarcinogenesis

Metabolic alteration for adaptation of the local environment has been recognized as a hallmark of cancer. GNPAT dysregulation has been implicated in hepatocellular carcinoma (HCC). However, the precise posttranslational regulation of GNPAT is still undiscovered. Here we show that ACAT1 is upregulated in response to extra palmitic acid (PA). ACAT1 acetylates GNPAT at K128, which represses TRIM21-mediated GNPAT ubiquitination and degradation. Conversely, GNPAT deacetylation by SIRT4 antagonizes ACAT1's function. GNPAT represses TRIM21-mediated FASN degradation and promotes lipid metabolism. Furthermore, shRNA-mediated ACAT1 ablation and acetylation deficiency of GNPAT repress lipid metabolism and tumor progression in xenograft and DEN/CCl₄-induced HCC. Otherwise, ACAT1 inhibitor combination with sorafenib enormously retards tumor formation in mice. Collectively, we demonstrate that stabilization of FASN by ACAT1-mediated GNPAT acetylation plays a critical role in hepatocarcinogenesis.

DAMPs, PAMPs, and LAMPs in Immunity and Sterile Inflammation

Recognizing the importance of leukocyte trafficking in inflammation led to some therapeutic breakthroughs. However, many inflammatory pathologies remain without specific therapy. This review discusses leukocytes in the context of sterile inflammation, a process caused by sterile (non-microbial) molecules, comprising damage-associated molecular patterns (DAMPs). DAMPs bind specific receptors to activate inflammation and start a highly optimized sequence of immune cell recruitment of neutrophils and monocytes to initiate effective tissue repair. When DAMPs are cleared, the recruited leukocytes change from a proinflammatory to a reparative program, a switch that is locally supervised by invariant natural killer T cells. In addition, neutrophils exit the inflammatory site and reverse transmigrate back to the bloodstream. Inflammation persists when the program switch or reverse transmigration fails, or when the coordinated leukocyte effort cannot clear the immunostimulatory molecules. The latter causes inappropriate leukocyte activation, a driver of many pathologies associated with poor lifestyle choices. We discuss lifestyle-associated inflammatory diseases and their corresponding immunostimulatory lifestyle-associated molecular patterns (LAMPs) and distinguish them from DAMPs.

Invariant NKT cells facilitate cytotoxic T-cell activation via direct recognition of CD1d on T cells

Invariant natural killer T (iNKT) cells are a major subset of NKT cells that recognize foreign and endogenous lipid antigens presented by CD1d. Although iNKT cells are characteristically autoreactive to self-antigens, the role of iNKT cells in the regulation of cytotoxic T lymphocytes (CTL) has been elucidated using α-galactosylceramide (α-GalCer), a strong synthetic glycolipid that is presented by professional antigen presenting cells (APCs), such as dendritic cells. Despite the well-known effects of α-GalCer and dendritic cells on lipid antigen presentation, the physiological role of endogenous antigens presented by CTLs during crosstalk with iNKT cells has not yet been addressed. In this study, we found that antigen-primed CTLs with transient CD1d upregulation could present lipid self-antigens to activate the iNKT cell production of IFN-γ. CTL-mediated iNKT cell activation in turn enhanced IFN-γ production and the proliferation and cytotoxicity of CTLs. We also found that the direct interaction of iNKT cells and CTLs enhanced the antitumor immune responses of CTLs. This partially explains the functional role of iNKT cells in CTL-mediated antitumor immunity. Our findings suggest that in the absence of exogenous iNKT cell ligands, iNKT cells enhanced the CTL production of IFN-γ and CTL proliferation and cytotoxicity via direct interaction with CD1d expressed on T cells without interacting with APCs.

Cancer-killing T cells engage in a form of molecular crosstalk with other specialized immune cells to enhance anti-tumor immune responses in mice. Se-Ho Park and colleagues from Korea University in Seoul, South Korea, studied a specialized population of immune cells known as invariant natural killer T (iNKT) cells, which serve as important mediators of tumor surveillance. They showed that iNKT cells directly interact with cancer-killing cytotoxic T cells through surface molecules and not through other immune cells. The resulting activation of iNKT cells leads to the production of a pro-inflammatory signaling molecule, which in turn enhances the proliferation and killing potential of the cytotoxic T cells, ultimately producing more potent tumor control in a mouse model of lymphoma. The findings could aid in the development of iNKT-based cancer immunotherapies.