Restoration of the type I IFN-IL-1 balance through targeted blockade of PTGER4 inhibits autoimmunity in NOD mice

Gαz-independent and -dependent Improvements With EPA Supplementation on the Early Type 1 Diabetes Phenotype of NOD Mice

Prostaglandin E2 (PGE2) is a key mediator of inflammation and is derived from the omega-6 polyunsaturated fatty acid, arachidonic acid (AA). In the β-cell, the PGE2 receptor, Prostaglandin EP3 receptor (EP3), is coupled to the unique heterotrimeric G protein alpha subunit, Gɑz to reduce the production of cyclic adenosine monophosphate (cAMP), a key signaling molecule that activates β-cell function, proliferation, and survival pathways. Nonobese diabetic (NOD) mice are a strong model of type 1 diabetes (T1D), and NOD mice lacking Gɑz are protected from hyperglycemia. Therefore, limiting systemic PGE2 production could potentially improve both the inflammatory and β-cell dysfunction phenotype of T1D. Here, we sought to evaluate the effect of eicosapentaenoic acid (EPA) feeding, which limits PGE2 production, on the early T1D phenotype of NOD mice in the presence and absence of Gαz. Wild-type and Gαz knockout NOD mice were fed a control or EPA-enriched diet for 12 weeks, beginning at age 4 to 5 weeks. Oral glucose tolerance, splenic T-cell populations, islet cytokine/chemokine gene expression, islet insulitis, measurements of β-cell mass, and measurements of β-cell function were quantified. EPA diet feeding and Gɑz loss independently improved different aspects of the early NOD T1D phenotype and coordinated to alter the expression of certain cytokine/chemokine genes and enhance incretin-potentiated insulin secretion. Our results shed critical light on the Gαz-dependent and -independent effects of dietary EPA enrichment and provide a rationale for future research into novel pharmacological and dietary adjuvant therapies for T1D.

Fatty acid-mediated signaling as a target for developing type 1 diabetes therapies

INTRODUCTION

Type 1 diabetes (T1D) is an autoimmune disease in which pro-inflammatory and cytotoxic signaling drive the death of the insulin-producing β cells. This complex signaling is regulated in part by fatty acids and their bioproducts, making them excellent therapeutic targets.

AREAS COVERED

We provide an overview of the fatty acid actions on β cells by discussing how they can cause lipotoxicity or regulate inflammatory response during insulitis. We also discuss how diet can affect the availability of fatty acids and disease development. Finally, we discuss development avenues that need further exploration.

EXPERT OPINION

Fatty acids, such as hydroxyl fatty acids, ω-3 fatty acids, and their downstream products, are druggable candidates that promote protective signaling. Inhibitors and antagonists of enzymes and receptors of arachidonic acid and free fatty acids, along with their derived metabolites, which cause pro-inflammatory and cytotoxic responses, have the potential to be developed as therapeutic targets also. Further, because diet is the main source of fatty acid intake in humans, balancing protective and pro-inflammatory/cytotoxic fatty acid levels through dietary therapy may have beneficial effects, delaying T1D progression. Therefore, therapeutic interventions targeting fatty acid signaling hold potential as avenues to treat T1D.

Blockade of prostaglandin E2 receptor 4 ameliorates peritoneal dialysis-associated peritoneal fibrosis

Inflammatory responses in the peritoneum contribute to peritoneal dialysis (PD)-associated peritoneal fibrosis. Results of our previous study showed that increased microsomal prostaglandin E synthase-1-mediated production of prostaglandin E2 (PGE2) contributed to peritoneal fibrosis. However, the role of its downstream receptor in the progression of peritoneal fibrosis has not been established. Here, we examined the role of PGE2 receptor 4 (EP4) in the development of peritoneal fibrosis. EP4 was significantly upregulated in peritoneal tissues of PD patients with ultrafiltration failure, along with the presence of an enhanced inflammatory response. In vitro experiments showed that exposure to high glucose concentrations enhanced EP4 expression in rat peritoneal mesothelial cells (RPMCs). High-glucose–induced expression of inflammatory cytokines (monocyte chemoattractant protein-1, tumour necrosis factor α, and interleukin 1β) was significantly reduced in RPMCs treated with ONO-AE3-208, an EP4 receptor antagonist. ONO-AE3-208 also significantly decreased the expression of extracellular matrix proteins induced by high glucose concentrations. Furthermore, ONO-AE3-208 blunted activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome and phosphorylation of nuclear factor kappa B (NF-κB) (p-p65). To further investigate the functional role of EP4, ONO-AE3-208 was administrated for 4 weeks in a rat model of PD, the results of which showed that ONO-AE3-208 inhibited peritoneal fibrosis and improved peritoneal dysfunction. Additionally, inflammatory cytokines in the peritoneum of PD rats treated with ONO-AE3-208 were downregulated, in line with inhibition of the NLRP3 inflammasome and NF-κB phosphorylation. In conclusion, an EP4 antagonist reduced the development of peritoneal fibrosis, possibly by suppressing NLRP3 inflammasome- and p-p65–mediated inflammatory responses. Our findings suggest that an EP4 antagonist may be therapeutically beneficial for PD-associated peritoneal fibrosis.

Effects of Arachidonic Acid and Its Metabolites on Functional Beta-Cell Mass

Arachidonic acid (AA) is a polyunsaturated 20-carbon fatty acid present in phospholipids in the plasma membrane. The three primary pathways by which AA is metabolized are mediated by cyclooxygenase (COX) enzymes, lipoxygenase (LOX) enzymes, and cytochrome P450 (CYP) enzymes. These three pathways produce eicosanoids, lipid signaling molecules that play roles in biological processes such as inflammation, pain, and immune function. Eicosanoids have been demonstrated to play a role in inflammatory, renal, and cardiovascular diseases as well type 1 and type 2 diabetes. Alterations in AA release or AA concentrations have been shown to affect insulin secretion from the pancreatic beta cell, leading to interest in the role of AA and its metabolites in the regulation of beta-cell function and maintenance of beta-cell mass. In this review, we discuss the metabolism of AA by COX, LOX, and CYP, the roles of these enzymes and their metabolites in beta-cell mass and function, and the possibility of targeting these pathways as novel therapies for treating diabetes.

Personalized Immunotherapies for Type 1 Diabetes: Who, What, When, and How?

Our understanding of the immunopathological features of type 1 diabetes (T1D) has greatly improved over the past two decades and has shed light on disease heterogeneity dictated by multiple immune, metabolic, and clinical parameters. This may explain the limited effects of immunotherapies tested so far to durably revert or prevent T1D, for which life-long insulin replacement remains the only therapeutic option. In the era of omics and precision medicine, offering personalized treatment could contribute to turning this tide. Here, we discuss how to structure the selection of the right patient at the right time for the right treatment. This individualized therapeutic approach involves enrolling patients at a defined disease stage depending on the target and mode of action of the selected drug, and better stratifying patients based on their T1D endotype, reflecting intrinsic disease aggressiveness and immune context. To this end, biomarker screening will be critical, not only to help stratify patients and disease stage, but also to select the best predicted responders ahead of treatment and at early time points during clinical trials. This strategy could contribute to increase therapeutic efficacy, notably through the selection of drugs with complementary effects, and to further develop precision multi-hit medicine.

Innate immune stimulation of whole blood reveals IFN-1 hyper-responsiveness in type 1 diabetes

AIMS/HYPOTHESIS

Self-antigen-specific T cell responses drive type 1 diabetes pathogenesis, but alterations in innate immune responses are also critical and not as well understood. Innate immunity in human type 1 diabetes has primarily been assessed via gene-expression analysis of unstimulated peripheral blood mononuclear cells, without the immune activation that could amplify disease-associated signals. Increased responsiveness in each of the two main innate immune pathways, driven by either type 1 IFN (IFN-1) or IL-1, have been detected in type 1 diabetes, but the dominant innate pathway is still unclear. This study aimed to determine the key innate pathway in type 1 diabetes and assess the whole blood immune stimulation assay as a tool to investigate this.

METHODS

The TruCulture whole blood ex vivo stimulation assay, paired with gene expression and cytokine measurements, was used to characterise changes in the stimulated innate immune response in type 1 diabetes. We applied specific cytokine-induced signatures to our data, pre-defined from the same assays measured in a separate cohort of healthy individuals. In addition, NOD mice were stimulated with CpG and monocyte gene expression was measured.

RESULTS

Monocytes from NOD mice showed lower baseline vs diabetes-resistant B6.g7 mice, but higher induced IFN-1-associated gene expression. In human participants, ex vivo whole blood stimulation revealed higher induced IFN-1 responses in type 1 diabetes, as compared with healthy control participants. In contrast, neither the IL-1-induced gene signature nor response to the adaptive immune stimulant Staphylococcal enterotoxin B were significantly altered in type 1 diabetes samples vs healthy control participants. Targeted gene-expression analysis showed that this enhanced IFN response was specific to IFN-1, as IFN-γ-driven responses were not significantly different.

CONCLUSIONS/INTERPRETATION

Our study identifies increased responsiveness to IFN-1 as a feature of both the NOD mouse model of autoimmune diabetes and human established type 1 diabetes. A stimulated IFN-1 gene signature may be a potential biomarker for type 1 diabetes and used to evaluate the effects of therapies targeting this pathway.

DATA AVAILABILITY

Mouse gene expression data are found in the gene expression omnibus (GEO) repository, accession GSE146452 ( www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE146452 ). Nanostring count data from the human experiments were deposited in the GEO repository, accession GSE146338 ( www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE146338 ). Data files and R code for all analyses are available at https://github.com/rodriguesk/T1D_truculture_diabetologia . Graphical abstract.

Type I IFN ineffectively activates neonatal dendritic cells limiting respiratory antiviral T-cell responses

Insufficient T-cell responses contribute to the increased burden of viral respiratory disease in infancy. Neonatal dendritic cells (DCs) often provide defective activation of pathogen-specific T cells through mechanisms that are incompletely understood, which hinders vaccine design for this vulnerable age group. Enhancing our characterization of neonatal DC sub-specialization and function is therefore critical to developing their potential for immunomodulation of T-cell responses. In this study, we engineered respiratory syncytial virus (RSV) to express a model protein, ovalbumin, to track antigen-presenting DCs in vivo. We found that murine neonatal conventional DC1s (cDC1s) efficiently migrated and presented RSV-derived antigen, challenging the paradigm that neonatal DCs are globally immature. In a key observation, however, we discovered that during infection neonatal cDC1s presenting viral antigen were unable to upregulate costimulatory molecules in response to type I interferons (IFN-I), contributing to poor antiviral T-cell responses. Importantly, we showed that the deficient response to IFN-I was also exhibited by human neonatal cDC1s, independent of infection. These findings reveal a functionally distinct response to IFN-I by neonatal cDC1s that may leave young infants susceptible to viral infections, and provide a new target for exploration, in light of failed efforts to design neonatal RSV vaccines.

Innately Adaptive or Truly Autoimmune: Is There Something Unique About Systemic Juvenile Idiopathic Arthritis?

Systemic juvenile idiopathic arthritis (JIA) is a form of arthritis in childhood that is initially dominated by innate immunity-driven systemic inflammation and is thus considered a polygenic autoinflammatory disease. However, systemic JIA can progress toward an adaptive immunity-driven afebrile arthritis. Based on this observation of biphasic disease progression, a "window of opportunity" for optimal, individualized and target-directed treatment has been proposed. This hypothesis requires testing, and in this review we summarize current evidence regarding molecular factors that may contribute to the progression from an initially predominantly autoinflammatory disease phenotype to autoimmune arthritis. We consider the involvement of innately adaptive γδ T cells and natural killer T cells that express γδ or αβ T cell receptors but cannot be classified as either purely innate or adaptive cells, versus classic B and T lymphocytes in this continuum. Finally, we discuss our understanding of how and why some primarily autoinflammatory conditions can progress toward autoimmune-mediated disorders over the disease course while others do not and how this knowledge may be used to offer individualized treatment.

PDL1 is expressed in the islets of people with type 1 diabetes and is up-regulated by interferons-α and-γ via IRF1 induction

Background

Antibodies targeting PD-1 and its ligand PDL1 are used in cancer immunotherapy but may lead to autoimmune diseases, including type 1 diabetes (T1D). It remains unclear whether PDL1 is expressed in pancreatic islets of people with T1D and how is it regulated.

Methods

The expression of PDL1, IRF1, insulin and glucagon was evaluated in samples of T1D donors by immunofluorescence. Cytokine-induced PDL1 expression in the human beta cell line, EndoC-βH1, and in primary human pancreatic islets was determined by real-time RT-PCR, flow cytometry and Western blot. Specific and previously validated small interference RNAs were used to inhibit STAT1, STAT2, IRF1 and JAK1 signaling. Key results were validated using the JAK inhibitor Ruxolitinib.

Findings

PDL1 was present in insulin-positive cells from twelve T1D individuals (6 living and 6 deceased donors) but absent from insulin-deficient islets or from the islets of six non-diabetic controls. Interferons-α and -γ, but not interleukin-1β, induced PDL1 expression in vitro in human islet cells and EndoC-βH1 cells. Silencing of STAT1 or STAT2 individually did not prevent interferon-α-induced PDL1, while blocking of JAKs – a proposed therapeutic strategy for T1D – or IRF1 prevented PDL1 induction.

Interpretation

These findings indicate that PDL1 is expressed in beta cells from people with T1D, possibly to attenuate the autoimmune assault, and that it is induced by both type I and II interferons via IRF1.