Astrocytic TIMP-1 regulates production of Anastellin, an inhibitor of oligodendrocyte differentiation and FTY720 responses

Astrocyte activation is associated with neuropathology and the production of tissue inhibitor of metalloproteinase-1 (TIMP1). TIMP1 is a pleiotropic extracellular protein that functions both as a protease inhibitor and as a growth factor. Astrocytes that lack expression of Timp1 do not support rat oligodendrocyte progenitor cell (rOPC) differentiation, and adult global Timp1 knockout (Timp1KO) mice do not efficiently remyelinate following a demyelinating injury. Here, we performed an unbiased proteomic analysis and identified a fibronectin-derived peptide called Anastellin (Ana) that was unique to the Timp1KO astrocyte secretome. Ana was found to block rOPC differentiation in vitro and enhanced the inhibitory influence of fibronectin on rOPC differentiation. Ana is known to act upon the sphingosine-1-phosphate receptor 1, and we determined that Ana also blocked the pro-myelinating effect of FTY720 (or fingolimod) on rOPC differentiation in vitro. Administration of FTY720 to wild-type C57BL/6 mice during MOG35-55-experimental autoimmune encephalomyelitis ameliorated clinical disability while FTY720 administered to mice lacking expression of Timp1 (Timp1KO) had no effect. Analysis of Timp1 and fibronectin (FN1) transcripts from primary human astrocytes from healthy and multiple sclerosis (MS) donors revealed lower TIMP1 expression was coincident with elevated FN1 in MS astrocytes. Last, analyses of proteomic databases of MS samples identified Ana peptides to be more abundant in the cerebrospinal fluid (CSF) of human MS patients with high disease activity. A role for Ana in MS as a consequence of a lack of astrocytic TIMP-1 production could influence both the efficacy of fingolimod responses and innate remyelination potential in the MS brain.

UBR5 promotes antiviral immunity by disengaging the transcriptional brake on RIG-I like receptors

The Retinoic acid-Inducible Gene I (RIG-I) like receptors (RLRs) are the major viral RNA sensors essential for the initiation of antiviral immune responses. RLRs are subjected to stringent transcriptional and posttranslational regulations, of which ubiquitination is one of the most important. However, the role of ubiquitination in RLR transcription is unknown. Here, we screen 375 definite ubiquitin ligase knockout cell lines and identify Ubiquitin Protein Ligase E3 Component N-Recognin 5 (UBR5) as a positive regulator of RLR transcription. UBR5 deficiency reduces antiviral immune responses to RNA viruses, while increases viral replication in primary cells and mice. Ubr5 knockout mice are more susceptible to lethal RNA virus infection than wild type littermates. Mechanistically, UBR5 mediates the Lysine 63-linked ubiquitination of Tripartite Motif Protein 28 (TRIM28), an epigenetic repressor of RLRs. This modification prevents intramolecular SUMOylation of TRIM28, thus disengages the TRIM28-imposed brake on RLR transcription. In sum, UBR5 enables rapid upregulation of RLR expression to boost antiviral immune responses by ubiquitinating and de-SUMOylating TRIM28.

CD8+ T cell depletion prevents neuropathology in a mouse model of globoid cell leukodystrophy

Globoid cell leukodystrophy (GLD) or Krabbe's disease is a fatal genetic demyelinating disease of the central nervous system caused by loss-of-function mutations in the galactosylceramidase (galc) gene. While the metabolic basis for disease is known, the understanding of how this results in neuropathology is not well understood. Herein, we report that the rapid and protracted elevation of CD8+ cytotoxic T lymphocytes occurs coincident with clinical disease in a mouse model of GLD. Administration of a function-blocking antibody against CD8α effectively prevented disease onset, reduced morbidity and mortality, and prevented CNS demyelination in mice. These data indicate that subsequent to the genetic cause of disease, neuropathology is driven by pathogenic CD8+ T cells, thus offering novel therapeutic potential for treatment of GLD.

Astrocytic TIMP-1 regulates production of Anastellin, a novel inhibitor of oligodendrocyte differentiation and FTY720 responses

Astrocyte activation is associated with neuropathology and the production of tissue inhibitor of metalloproteinase-1 (TIMP1). TIMP1 is a pleiotropic extracellular protein that functions both as a protease inhibitor and as a growth factor. We have previously demonstrated that murine astrocytes that lack expression of Timp1 do not support rat oligodendrocyte progenitor cell (rOPC) differentiation, and adult global Timp1 knockout ( Timp1 KO ) mice do not efficiently remyelinate following a demyelinating injury. To better understand the basis of this, we performed unbiased proteomic analyses and identified a fibronectin-derived peptide called anastellin that is unique to the murine Timp1 KO astrocyte secretome. Anastellin was found to block rOPC differentiation in vitro and enhanced the inhibitory influence of fibronectin on rOPC differentiation. Anastellin is known to act upon the sphingosine-1-phosphate receptor 1 (S1PR1), and we determined that anastellin also blocked the pro-myelinating effect of FTY720 (or fingolimod) on rOPC differentiation in vitro . Further, administration of FTY720 to wild-type C57BL/6 mice during MOG 35-55 -EAE ameliorated clinical disability while FTY720 administered to mice lacking expression of Timp1 in astrocytes ( Timp1 cKO ) had no effect. Analysis of human TIMP1 and fibronectin ( FN1 ) transcripts from healthy and multiple sclerosis (MS) patient brain samples revealed an inverse relationship where lower TIMP1 expression was coincident with elevated FN1 in MS astrocytes. Lastly, we analyzed proteomic databases of MS samples and identified anastellin peptides to be more abundant in the cerebrospinal fluid (CSF) of human MS patients with high versus low disease activity. The prospective role for anastellin generation in association with myelin lesions as a consequence of a lack of astrocytic TIMP-1 production could influence both the efficacy of fingolimod responses and the innate remyelination potential of the the MS brain.

Significance Statement

Astrocytic production of TIMP-1 prevents the protein catabolism of fibronectin. In the absence of TIMP-1, fibronectin is further digested leading to a higher abundance of anastellin peptides that can bind to sphingosine-1-phosphate receptor 1. The binding of anastellin with the sphingosine-1-phosphate receptor 1 impairs the differentiation of oligodendrocytes progenitor cells into myelinating oligodendrocytes in vitro , and negates the astrocyte-mediated therapeutic effects of FTY720 in the EAE model of chronic CNS inflammation. These data indicate that TIMP-1 production by astrocytes is important in coordinating astrocytic functions during inflammation. In the absence of astrocyte produced TIMP-1, elevated expression of anastellin may represent a prospective biomarker for FTY720 therapeutic responsiveness.

Capturing the multifaceted function of adipose tissue macrophages

Adipose tissue macrophages (ATMs) bolster obesity-induced metabolic dysfunction and represent a targetable population to lessen obesity-associated health risks. However, ATMs also facilitate adipose tissue function through multiple actions, including adipocyte clearance, lipid scavenging and metabolism, extracellular remodeling, and supporting angiogenesis and adipogenesis. Thus, high-resolution methods are needed to capture macrophages' dynamic and multifaceted functions in adipose tissue. Herein, we review current knowledge on regulatory networks critical to macrophage plasticity and their multifaceted response in the complex adipose tissue microenvironment.

Interleukin-17 Promotes the Infiltration of CD8+ T Cells into the Brain in a Mouse Model for Alzheimer's Disease

BACKGROUND

Interleukin-17 (IL-17) family cytokines play critical roles in inflammation and pathogen resistance. Inflammation in the central nervous system, denoted as neuroinflammation, promotes the onset and progression of Alzheimer's disease (AD). Previous studies showed that IL-17A neutralizing antibody treatment alleviated Amyloid β (Aβ) burden in rodent models of AD, while overexpression of IL-17A in mouse lateral ventricles rescued part of the AD pathology. However, the involvement of IL-17 in AD and its mechanism of action remain largely unknown.

METHODS

To investigate the role of IL-17 in AD, we crossed mice lacking the common receptor of IL-17 signaling (IL-17RA knockout mice) to the APP/PS1 mouse model of AD. We then analyzed the composition of immune cells and cytokines/chemokines during different phases of AD pathology, and interrogated the underlying mechanism by which IL-17 may regulate immune cell infiltration into AD brains.

RESULTS

Ablation of IL-17RA in APP/PS1 mice decreased infiltration of CD8+ T cells and myeloid cells to mouse brain. IL-17 was able to promote the production of myeloid- and T cell-attracting chemokines CXCL1 and CXCL9/10 in primary glial cells. We also observed that IL-17 is upregulated in the late stage of AD development, and ectopic expression of IL-17 via adenoviral infection to the cortex trended towards worsened cognition in APP/PS1 mice, suggesting a pathogenic role of excessive IL-17 in AD.

CONCLUSION

Our data show that IL-17 signaling promotes neuroinflammation in AD by accelerating the infiltration of CD8+ T lymphocytes and Gr1+ CD11b+ myeloid cells.

Antigen-specific downregulation of miR-150 in CD4 T cells promotes cell survival

MicroRNA-150 (miR-150) has been shown to play a general role in the immune system, but very little is known about its role on CD4+ T cell responses. During T cell responses against superantigen Staphylococcal Enterotoxin A, miR-150 expression was down-regulated in antigen-specific CD4+ T cells but up-regulated in CD8+ T cells. CD4+ and CD8+ T cell clonal expansion was greater in miR-150-KO mice than in WT mice, but miR-150 selectively repressed IL-2 production in CD4+ T cells. Transcriptome analysis of CD4+ T cells demonstrated that apoptosis and mTOR pathways were highly enriched in the absence of miR-150. Mechanistic studies confirmed that miR-150 promoted apoptosis specifically in antigen-specific CD4+ T cells, but not in bystander CD4+ nor in CD8+ T cells. Furthermore, inhibition of mTOR-linked mitochondrial superoxidedismutase-2 increased apoptosis in miR-150-/- antigen-specific CD4+ T. Thus, miR-150 impacts CD4+ T cell helper activity by attenuating IL-2 production along with clonal expansion, and suppresses superoxidedismutase to promote apoptosis.

Macrophages at the Crossroad of Meta-Inflammation and Inflammaging

Macrophages are central players in systemic inflammation associated with obesity and aging, termed meta-inflammation and inflammaging. Activities of macrophages elicited by the two chronic conditions display shared and distinct patterns mechanistically, resulting in multifaceted actions for their pathogenic roles. Drastically expanded tissue macrophage populations under obesity and aging stress attribute to both enhanced recruitment and local expansion. Importantly, molecular networks governing the multifaceted actions of macrophages are directly altered by environmental cues and subsequently contribute to metabolic reprogramming, resulting in meta-inflammation in obesity or inflammaging in aging. In this review, we will summarize how meta-inflammation and inflammaging affect macrophages and the molecular mechanisms involved in these processes.

Nexinhib20 Inhibits Neutrophil Adhesion and β2 Integrin Activation by Antagonizing Rac-1-Guanosine 5'-Triphosphate Interaction

Neutrophils are critical for mediating inflammatory responses. Inhibiting neutrophil recruitment is an attractive approach for preventing inflammatory injuries, including myocardial ischemia-reperfusion (I/R) injury, which exacerbates cardiomyocyte death after primary percutaneous coronary intervention in acute myocardial infarction. In this study, we found out that a neutrophil exocytosis inhibitor Nexinhib20 inhibits not only exocytosis but also neutrophil adhesion by limiting β2 integrin activation. Using a microfluidic chamber, we found that Nexinhib20 inhibited IL-8-induced β2 integrin-dependent human neutrophil adhesion under flow. Using a dynamic flow cytometry assay, we discovered that Nexinhib20 suppresses intracellular calcium flux and β2 integrin activation after IL-8 stimulation. Western blots of Ras-related C3 botulinum toxin substrate 1 (Rac-1)-GTP pull-down assays confirmed that Nexinhib20 inhibited Rac-1 activation in leukocytes. An in vitro competition assay showed that Nexinhib20 antagonized the binding of Rac-1 and GTP. Using a mouse model of myocardial I/R injury, Nexinhib20 administration after ischemia and before reperfusion significantly decreased neutrophil recruitment and infarct size. Our results highlight the translational potential of Nexinhib20 as a dual-functional neutrophil inhibitory drug to prevent myocardial I/R injury.

Optimal CD8+ T cell effector function requires costimulation-induced RNA-binding proteins that reprogram the transcript isoform landscape

Boosting T cell activation through costimulation directs defense against cancer and viral infections. Despite multiple studies targeting costimulation in clinical trials, the increased potency and reprogramming of T cells endowed by costimulation is poorly understood. Canonical dogma states that transcription mediates T cell activation. Here, we show that the spliceosome, controlling post-transcriptional alternative splicing and alternative polyadenylation, is the most enriched pathway in T cells after CD134/CD137 costimulation. Costimulation of CD8+ T cells significantly increases expression of 29 RNA-binding proteins while RNA-seq uncovers over 1000 differential alternative splicing and polyadenylation events. Using in vivo mouse and in vitro human models, we demonstrate that RNA-binding protein Tardbp is required for effector cytokine production, CD8+ T cell clonal expansion, and isoform regulation after costimulation. The prospect of immune response optimization through reprogramming of mRNA isoform production offered herein opens new avenues for experimentally and therapeutically tuning the activities of T cells.

Evaluating the glycolytic potential of mouse costimulated effector CD8+ T cells ex vivo

Studying the metabolic fitness of T cells is fundamental to understand how immune responses are regulated. Here, we describe a step-by-step protocol optimized to efficiently generate and isolate effector antigen-specific CD8+ T cells ex vivo using costimulation. We also detail steps to evaluate their metabolic activity using Seahorse technology. This protocol can be used to measure the glycolytic potential of effector murine T cells in response to different manipulations, such as infections, adjuvant studies, gene editing, or metabolite supplementation. For complete details on the use and execution of this protocol, please refer to Agliano et al. (2022).

Nexinhib20 inhibits neutrophil adhesion and β2 integrin activation to prevent myocardial ischemia-reperfusion injury

Primary percutaneous coronary intervention (PPCI)—a therapy intended to restore blood flow after acute myocardial infarction—can also induce myocardial ischemia-reperfusion (I/R) injury, exacerbating cardiomyocyte death. Neutrophil-mediated cardiac tissue damage contributes prominently to the process of myocardial I/R injury. Therefore, limiting neutrophil recruitment and exocytosis may prevent myocardial I/R injury after PPCI. Here, we found out that a neutrophil exocytosis inhibitor Nexinhib20 inhibits both neutrophil adhesion and exocytosis and prevents myocardial I/R injury in a mouse model. Using a microfluidic chamber, we found that Nexinhib20 inhibited interleukin 8 (IL-8)-induced β2 integrin-dependent human neutrophil adhesion under flow. Using dynamic flow cytometry assay, we discovered that Nexinhib20 suppresses intracellular calcium flux and β2 integrin activation after IL-8 stimulation. Western blots of Rac-1-GTP pull-down assay confirmed that Nexinhib20 inhibited Rac-1 activation in leukocytes. In vitro competing assay showed that Nexinhib20 antagonized the binding of Rac-1 and GTP. Using a mouse model of myocardial I/R injury, Nexinhib20 administration after ischemia and before reperfusion significantly decreased neutrophil recruitment and infarct size. Our results highlight the translational potential of Nexinhib20 as a dual-functional neutrophil inhibitory drug to prevent myocardial I/R injury.

This research was supported by grants from the National Institutes of Health, National Heart, Lung, and Blood Institute, USA (R01HL145454, R41HL156322, R44HL152710, and K99HL153678), a Career Development Award from American Heart Association (18CDA34110426), and a startup fund from UConn Health.

Optimal CD8+ T cell effector function requires costimulation-induced RNA-binding proteins that reprogram the transcript isoform landscape

Boosting T cell activation through costimulation directs defense against cancer and viral infections. Despite many studies targeting costimulation in clinical trials, the increased potency and reprogramming of T cells endowed by costimulation is poorly understood. Canonical dogma states that transcription mediates T cell activation. Here, we show that the spliceosome, controlling post-transcriptional alternative splicing and alternative polyadenylation, is the most significantly enriched pathway in T cells after CD134/CD137 costimulation. Costimulation of CD8+ T cells significantly increased expression of 29 RNA-binding proteins (RBPs) while RNA-seq uncovered over 1000 differential alternative splicing and polyadenylation events. Using in vivo mouse and in vitro human CRISPR models, we demonstrate that RBP Tardbp, among multiple other RBPs, is required for effector cytokine production, CD8+ T cell clonal expansion, and isoform regulation after costimulation. The prospect of immune response optimization through reprogramming of mRNA isoform production offered herein opens new avenues for experimentally and therapeutically tuning the activities of T cells.

Supported by NIH grants AI136955 and R21AI139891.

AtheroSpectrum Reveals Novel Macrophage Foam Cell Gene Signatures Associated With Atherosclerotic Cardiovascular Disease Risk

BACKGROUND

Whereas several interventions can effectively lower lipid levels in people at risk for atherosclerotic cardiovascular disease (ASCVD), cardiovascular event risks remain, suggesting an unmet medical need to identify factors contributing to cardiovascular event risk. Monocytes and macrophages play central roles in atherosclerosis, but studies have yet to provide a detailed view of macrophage populations involved in increased ASCVD risk.

METHODS

A novel macrophage foaming analytics tool, AtheroSpectrum, was developed using 2 quantitative indices depicting lipid metabolism and the inflammatory status of macrophages. A machine learning algorithm was developed to analyze gene expression patterns in the peripheral monocyte transcriptome of MESA participants (Multi-Ethnic Study of Atherosclerosis; set 1; n=911). A list of 30 genes was generated and integrated with traditional risk factors to create an ASCVD risk prediction model (30-gene cardiovascular disease risk score [CR-30]), which was subsequently validated in the remaining MESA participants (set 2; n=228); performance of CR-30 was also tested in 2 independent human atherosclerotic tissue transcriptome data sets (GTEx [Genotype-Tissue Expression] and GSE43292).

RESULTS

Using single-cell transcriptomic profiles (GSE97310, GSE116240, GSE97941, and FR-FCM-Z23S), AtheroSpectrum detected 2 distinct programs in plaque macrophages-homeostatic foaming and inflammatory pathogenic foaming-the latter of which was positively associated with severity of atherosclerosis in multiple studies. A pool of 2209 pathogenic foaming genes was extracted and screened to select a subset of 30 genes correlated with cardiovascular event in MESA set 1. A cardiovascular disease risk score model (CR-30) was then developed by incorporating this gene set with traditional variables sensitive to cardiovascular event in MESA set 1 after cross-validation generalizability analysis. The performance of CR-30 was then tested in MESA set 2 (P=2.60×10-4; area under the receiver operating characteristic curve, 0.742) and 2 independent data sets (GTEx: P=7.32×10-17; area under the receiver operating characteristic curve, 0.664; GSE43292: P=7.04×10-2; area under the receiver operating characteristic curve, 0.633). Model sensitivity tests confirmed the contribution of the 30-gene panel to the prediction model (likelihood ratio test; df=31, P=0.03).

CONCLUSIONS

Our novel computational program (AtheroSpectrum) identified a specific gene expression profile associated with inflammatory macrophage foam cells. A subset of 30 genes expressed in circulating monocytes jointly contributed to prediction of symptomatic atherosclerotic vascular disease. Incorporating a pathogenic foaming gene set with known risk factors can significantly strengthen the power to predict ASCVD risk. Our programs may facilitate both mechanistic investigations and development of therapeutic and prognostic strategies for ASCVD risk.

Concentration of vaginal and systemic cytokines obtained early in pregnancy and their impact on preterm birth

OBJECTIVE

A number of factors can lead to a maternal pro-inflammatory response resulting in a spontaneous preterm birth. However, it remains unknown if an upregulation in the maternal immune system early in pregnancy leads to an increase in pro-inflammatory cytokines and ultimately preterm birth. Therefore, we hypothesize an increase in vaginal and systemic pro-inflammatory cytokines early pregnancy is associated with an increased risk of preterm birth.

STUDY DESIGN

Patients initiating prenatal care prior to 14 weeks gestation were recruited for eligibility. A vaginal swab and serum sample was obtained at the first prenatal visit and these were then stored at -80 C. Patients were then followed for their gestational age at delivery. Five patients delivering preterm (cases) were matched with ten patients delivering at term (controls) based on age, BMI, smoking status and ethnicity. The serum and vaginal swabs from the cases and controls were then analyzed for the following cytokines using a multiplex cytokine assay: GM-CSF, IL-1b, IL-6, TNFα, and Rantes.

RESULTS

A total of 116 patients were screened for eligibility and 96 of these patients had samples obtained prior to 14 weeks gestation. Of these 96, 5 had a spontaneous preterm birth and these were matched to 10 controls. There was no difference detected in the cytokine concentrations of GM-CSF, IL-1b, IL-6, TNFα, and Rantes in the serum or cervicovaginal fluid between cases and controls.

CONCLUSION

This study demonstrates there is no difference in cytokine concentrations of several pro-inflammatory cytokines in the vagina or in the serum prior to 14 weeks gestation in patients delivering preterm. Therefore, the concentration of the cytokines analyzed in this study from the vagina and serum have little predictive value on the risk of preterm birth. Further research is needed to deepen our understanding of the mechanisms leading to preterm birth.

An Essential Role of UBXN3B in B Lymphopoiesis

Hematopoiesis is finely regulated to enable timely production of the right numbers and types of mature immune cells to maintain tissue homeostasis. Dysregulated hematopoiesis may compromise antiviral immunity and/or exacerbate immunopathogenesis. Herein, we report an essential role of UBXN3B in maintenance of hematopoietic homeostasis and restriction of immunopathogenesis during respiratory viral infection. Ubxn3b deficient ( Ubxn3b ^-/- ) mice are highly vulnerable to SARS-CoV-2 and influenza A infection, characterized by more severe lung immunopathology, lower virus-specific IgG, significantly fewer B cells, but more myeloid cells than Ubxn3b ^+/+ littermates. This aberrant immune compartmentalization is recapitulated in uninfected Ubxn3b ^-/- mice. Mechanistically, UBXN3B controls precursor B-I (pre-BI) transition to pre-BII and subsequent proliferation in a cell-intrinsic manner, by maintaining BLNK protein stability and pre-BCR signaling. These results reveal an essential role of UBXN3B for the early stage of B cell development.

UBX Domain Protein 6 Positively Regulates JAK-STAT1/2 Signaling

Type I/III IFNs induce expression of hundreds of IFN-stimulated genes through the JAK/STAT pathway to combat viral infections. Although JAK/STAT signaling is seemingly straightforward, it is nevertheless subjected to complex cellular regulation. In this study, we show that an ubiquitination regulatory X (UBX) domain-containing protein, UBXN6, positively regulates JAK-STAT1/2 signaling. Overexpression of UBXN6 enhanced type I/III IFNs-induced expression of IFN-stimulated genes, whereas deletion of UBXN6 inhibited their expression. RNA viral replication was increased in human UBXN6-deficient cells, accompanied by a reduction in both type I/III IFN expression, when compared with UBXN6-sufficient cells. Mechanistically, UBXN6 interacted with tyrosine kinase 2 (TYK2) and inhibited IFN-β-induced degradation of both TYK2 and type I IFNR. These results suggest that UBXN6 maintains normal JAK-STAT1/2 signaling by stabilizing key signaling components during viral infection.

Granulocyte-macrophage colony-stimulating factor initiates amniotic membrane rupture and preterm birth in a mouse model

OBJECTIVE

Preterm premature rupture of membranes is associated with 30% of all preterm births. The weakening of amniotic membranes is associated with an increase in matrix metallopeptidases (MMPs) along with a decrease in their inhibitors, tissue inhibitor metallopeptidases (TIMPs). Additionally, granulocyte-macrophage colony-stimulating factor (GM-CSF) has been shown to weaken fetal membranes in-vitro. We hypothesize pregnant mice treated with GM-CSF lead to increased MMPs:TIMPs resulting in membrane rupture and preterm birth.

STUDY DESIGN

Pregnant CD-1 mice on gestational day 17 received either an intrauterine injection of GM-CSF or vehicle control. A second series of mice were administered an intrauterine injection of Lipopolysaccharide along with either anti-mouse GM-CSF or control antibody. Mice were evaluated for rupture of membranes and/or preterm birth and the uterus, amniotic fluid, and serum were collected for analysis.

RESULTS

87.5% of GM-CSF mice exhibited evidence of membrane rupture or preterm birth, compared with 0% in control mice (p < .001). Treatment with GM-CSF decreased the expression of TNFα (p < .05) while increasing the ratio of MMP2:TIMP1 (p < .05), MMP2:TIMP2 (p < .05), MMP2:TIMP3 (p < .001), MMP9:TIMP1 (p < .01), MMP9:TIMP2 (p < .05), MMP9:TIMP3 (p < .001), and MMP10:TIMP1 (p < .05). Mice treated with LPS and the GM-CSF antibody resulted in a decrease in the ratio of MMP2:TIMP1 (p < .0001) compared with controls.

CONCLUSION

These studies demonstrate GM-CSF will result in membrane rupture and preterm birth by increasing the ratio MMPs:TIMPs in our animal model. By increasing our understanding of the molecular pathways associated with GM-CSF, we may be able to develop future therapies to prevent preterm birth and reduce neonatal morbidity.

Intracellular immune sensing promotes inflammation via gasdermin D-driven release of a lectin alarmin

Inflammatory caspase sensing of cytosolic lipopolysaccharide (LPS) triggers pyroptosis and the concurrent release of damage-associated molecular patterns (DAMPs). Collectively, DAMPs are key determinants that shape the aftermath of inflammatory cell death. However, the identity and function of the individual DAMPs released are poorly defined. Our proteomics study revealed that cytosolic LPS sensing triggered the release of galectin-1, a β-galactoside-binding lectin. Galectin-1 release is a common feature of inflammatory cell death, including necroptosis. In vivo studies using galectin-1-deficient mice, recombinant galectin-1 and galectin-1-neutralizing antibody showed that galectin-1 promotes inflammation and plays a detrimental role in LPS-induced lethality. Mechanistically, galectin-1 inhibition of CD45 (Ptprc) underlies its unfavorable role in endotoxin shock. Finally, we found increased galectin-1 in sera from human patients with sepsis. Overall, we uncovered galectin-1 as a bona fide DAMP released as a consequence of cytosolic LPS sensing, identifying a new outcome of inflammatory cell death.

Mechanically superior matrices promote osteointegration and regeneration of anterior cruciate ligament tissue in rabbits

The gold standard treatment for anterior cruciate ligament (ACL) reconstruction is the use of tendon autografts and allografts. Limiting factors for this treatment include donor site morbidity, potential disease transmission, and variable graft quality. To address these limitations, we previously developed an off-the-shelf alternative, a poly(l-lactic) acid (PLLA) bioengineered ACL matrix, and demonstrated its feasibility to regenerate ACL tissue. This study aims to 1) accelerate the rate of regeneration using the bioengineered ACL matrix by supplementation with bone marrow aspirate concentrate (BMAC) and growth factors (BMP-2, FGF-2, and FGF-8) and 2) increase matrix strength retention. Histological evaluation showed robust tissue regeneration in all groups. The presence of cuboidal cells reminiscent of ACL fibroblasts and chondrocytes surrounded by an extracellular matrix rich in anionic macromolecules was up-regulated in the BMAC group. This was not observed in previous studies and is indicative of enhanced regeneration. Additionally, intraarticular treatment with FGF-2 and FGF-8 was found to suppress joint inflammation. To increase matrix strength retention, we incorporated nondegradable fibers, polyethylene terephthalate (PET), into the PLLA bioengineered ACL matrix to fabricate a "tiger graft." The tiger graft demonstrated the greatest peak loads among the experimental groups and the highest to date in a rabbit model. Moreover, the tiger graft showed superior osteointegration, making it an ideal bioengineered ACL matrix. The results of this study illustrate the beneficial effect bioactive factors and PET incorporation have on ACL regeneration and signal a promising step toward the clinical translation of a functional bioengineered ACL matrix.

A Critical Role for STING Signaling in Limiting Pathogenesis of Chikungunya Virus

The stimulator of interferon gene (STING) pathway controls both DNA and RNA virus infection. STING is essential for induction of innate immune responses during DNA virus infection, while its mechanism against RNA virus remains largely elusive. We show that STING signaling is crucial for restricting chikungunya virus infection and arthritis pathogenesis. Sting-deficient mice (Stinggt/gt) had elevated viremia throughout the viremic stage and viral burden in feet transiently, with a normal type I IFN response. Stinggt/gt mice presented much greater foot swelling, joint damage, and immune cell infiltration than wild-type mice. Intriguingly, expression of interferon-γ and Cxcl10 was continuously upregulated by approximately 7 to 10-fold and further elevated in Stinggt/gt mice synchronously with arthritis progression. However, expression of chemoattractants for and activators of neutrophils, Cxcl5, Cxcl7, and Cxcr2 was suppressed in Stinggt/gt joints. These results demonstrate that STING deficiency leads to an aberrant chemokine response that promotes pathogenesis of CHIKV arthritis.

Macrophage scavenger receptor 1 controls Chikungunya virus infection through autophagy in mice

Macrophage scavenger receptor 1 (MSR1) mediates the endocytosis of modified low-density lipoproteins and plays an important antiviral role. However, the molecular mechanism underlying MSR1 antiviral actions remains elusive. We report that MSR1 activates autophagy to restrict infection of Chikungunya virus (CHIKV), an arthritogenic alphavirus that causes acute and chronic crippling arthralgia. Msr1 expression was rapidly upregulated after CHIKV infection in mice. Msr1 knockout mice had elevated viral loads and increased susceptibility to CHIKV arthritis along with a normal type I IFN response. Induction of LC3 lipidation by CHIKV, a marker of autophagy, was reduced in Msr1^-/- cells. Mechanistically, MSR1 interacted with ATG12 through its cytoplasmic tail and this interaction was enhanced by CHIKV nsP1 protein. MSR1 repressed CHIKV replication through ATG5-ATG12-ATG16L1 and this was dependent on the FIP200-and-WIPI2-binding domain, but not the WD40 domain of ATG16L1. Our results elucidate an antiviral role for MSR1 involving the autophagic function of ATG5-ATG12-ATG16L1.

Bioactive polymeric materials and electrical stimulation strategies for musculoskeletal tissue repair and regeneration

Electrical stimulation (ES) is predominantly used as a physical therapy modality to promote tissue healing and functional recovery. Research efforts in both laboratory and clinical settings have shown the beneficial effects of this technique for the repair and regeneration of damaged tissues, which include muscle, bone, skin, nerve, tendons, and ligaments. The collective findings of these studies suggest ES enhances cell proliferation, extracellular matrix (ECM) production, secretion of several cytokines, and vasculature development leading to better tissue regeneration in multiple tissues. However, there is still a gap in the clinical relevance for ES to better repair tissue interfaces, as ES applied clinically is ineffective on deeper tissue. The use of a conducting material can transmit the stimulation applied from skin electrodes to the desired tissue and lead to an increased function on the repair of that tissue. Ionically conductive (IC) polymeric scaffolds in conjunction with ES may provide solutions to utilize this approach effectively. Injectable IC formulations and their scaffolds may provide solutions for applying ES into difficult to reach tissue types to enable tissue repair and regeneration. A better understanding of ES-mediated cell differentiation and associated molecular mechanisms including the immune response will allow standardization of procedures applicable for the next generation of regenerative medicine. ES, along with the use of IC scaffolds is more than sufficient for use as a treatment option for single tissue healing and may fulfill a role in interfacing multiple tissue types during the repair process.

A benzimidazole inhibitor attenuates sterile inflammation induced in a model of systemic autoinflammation in female mice

Sterile stimuli can trigger inflammatory responses, and in some cases can lead to a variety of acute or chronic diseases. In this study, we hypothesize that a benzimidazole inhibitor may be used as a therapeutic in the treatment of sterile inflammation. In vitro, this inhibitor blocks TLR signalling and inflammatory responses. The benzimidazole inhibitor does not prevent mouse macrophage activation after stimulation with 2,6,10,14-tetramethylpentadecane (TMPD, also known as pristane), a hydrocarbon oil that mimics features of sterile inflammation when injected in vivo. However, C57BL/6J female mice treated with the benzimidazole inhibitor exhibited a significant reduction of pristane-dependent induction of splenocyte number and weight. Conversely, no significant difference was observed in males. Using mass spectrometry, we found that the urine of pristane-injected mice contained increased levels of putative markers for several inflammatory diseases, which were reduced by the benzimidazole inhibitor. To study the mechanism, we showed that pristane-injected mice had increased cell free DNA in serum, which was not impacted by inhibitor treatment. However, chemokine release (e.g. MCP-1, RANTES and TARC) was significantly reduced in inhibitor-treated mice. Thus, the benzimidazole inhibitor might be used as a new drug to block the recruitment of immune cells during sterile inflammatory diseases in humans.

Costimulation Induces CD4 T Cell Antitumor Immunity via an Innate-like Mechanism

Chronic exposure to tumor-associated antigens inactivates cognate T cells, restricting the repertoire of tumor-specific effector T cells. This problem was studied here by transferring TCR transgenic CD4 T cells into recipient mice that constitutively express a cognate self-antigen linked to MHC II on CD11c-bearing cells. Immunotherapeutic agonists to CD134 plus CD137, "dual costimulation," induces specific CD4 T cell expansion and expression of the receptor for the Th2-associated IL-1 family cytokine IL-33. Rather than producing IL-4, however, they express the tumoricidal Th1 cytokine IFNγ when stimulated with IL-33 or IL-36 (a related IL-1 family member) plus IL-12 or IL-2. IL-36, which is induced within B16-F10 melanomas by dual costimulation, reduces tumor growth when injected intratumorally as a monotherapy and boosts the efficacy of tumor-nonspecific dual costimulated CD4 T cells. Dual costimulation thus enables chronic antigen-exposed CD4 T cells, regardless of tumor specificity, to elaborate tumoricidal function in response to tumor-associated cytokines.

The kinase activity of IRAK4 controls sterile autoinflammation and manifestations of Murine Lupus

Interleukin-1 receptor-associated kinase (IRAK) 4 is a serine/threonine kinase involved in TLR/IL-1R responses. Upon TLR/IL-1R activation, autophosphorylation of IRAK4 induces proinflammatory gene transcription. In this study we hypothesize that the kinase activity of IRAK4 may be a druggable target in the treatment of sterile autoinflammation and Lupus. C57BL/6 female mice injected with the hydrocarbon oil Pristane, exhibited a significant Pristane-dependent induction of splenomegaly; whereas treatment with the IRAK4 kinase inhibitor reduced this inflammatory symptom. Conversely, no significant difference was observed in males. Using mass spectrometry, we found that the urine of Pristane-injected mice contained increased levels of putative markers for several inflammatory diseases, which were reduced by IRAK4 kinase inhibition. We showed that Pristane-injected mice had increased cell free DNA in serum, which was not impacted by kinase inhibitor treatment. However, chemokine release was significantly reduced in IRAK4 kinase inhibitor-treated mice. We further analyzed the kinase activity of IRAK4 in MRL-lpr mice, which were compared with MRL-lpr/IRAK4 kinase-inactive (KDKI) mice (where IRAK4 is expressed but its kinase activity is lost). Although MRL-lpr/IRAK4KDKI and MRL-lpr mice did not show differences in CD4+ and CD8+ cells activation, we found a significantly reduced splenomegaly in MRL-lpr/IRAK4KDKI mice compared to controls, also exhibiting a gender bias. Thus, IRAK4 kinase activity might represent a new therapeutic and druggable target in the recruitment of immune cells during sterile inflammatory diseases in humans, including Systemic Lupus Erythematous (SLE).

Long Non-coding RNA LincRNA-EPS Inhibits Host Defense Against Listeria monocytogenes Infection

Long non-coding RNAs (lncRNAs) have emerged as key regulators of gene expression in several biological systems. The long intergenic RNA-erythroid pro-survival (lincRNA-EPS) has been shown to play a critical role in restraining inflammatory gene expression. However, the function of lincRNA-EPS during bacterial infections remains unknown. Here, we demonstrate that following infection with the intracellular bacterium Listeria monocytogenes, both mouse macrophages and dendritic cells lacking lincRNA-EPS exhibit an enhanced expression of proinflammatory cytokine genes, as well as an increased expression of the inducible nitric oxide synthase (iNos) and nitric oxide (NO) production. Importantly, we found that lincRNA-EPS^−/− mice intraperitoneally infected with L. monocytogenes exhibit lower bacterial burdens in spleen and liver and produce more NO than control mice. Furthermore, lincRNA-EPS^−/− mice are less susceptible to a lethal dose of L. monocytogenes than wild type (WT) mice. Collectively these findings show that lincRNA-EPS suppresses host protective NO expression and impairs the host defense against L. monocytogenes infection.

Evaluation of a bioengineered ACL matrix's osteointegration with BMP-2 supplementation

A poly (l-lactic) acid bioengineered anterior cruciate ligament (ACL) matrix has previously demonstrated the ability to support tissue regeneration in a rabbit ACL reconstruction model. The matrix was designed for optimal bone and ligament regeneration by developing a matrix with differential pore sizes in its bone and ligament compartments. Building upon past success, we designed a new bioengineered ACL matrix that is easier to install and can be used with endobutton fixation during ACL reconstruction. To achieve this, a new braiding procedure was developed to allow the matrix to be folded in half, making two-limbs, while maintaining its bone and ligament compartments. The osteointegration of the matrix with and without bone morphogenetic protein 2 (BMP-2) supplementation was evaluated in a rabbit ACL reconstruction model. Two doses of BMP-2 were evaluated, 1 and 10 μg, and delivered by saline injection into the bone tunnel at the end of surgery. A fibrous matrix-to-bone interface with occasional Sharpey’s fibers was the primary mode of osteointegration observed. The matrix was also found to support a fibrocartilage matrix-to-bone interface. In some cases, the presence of chondrocyte-like cells was observed at the aperture of the bone tunnel and the center of the matrix within the bone tunnel. Treatment with BMP-2 was associated with a trend towards smaller bone tunnel cross-sectional areas, and 1 μg of BMP-2 was found to significantly enhance osteoid seam width in comparison with no BMP-2 or 10 μg of BMP-2 treatment. Regenerated tissue was well organized within the bioengineered ACL matrix and aligned with the poly (l-lactic) acid fibers. Disorganized tissue was found between the two-limbs of the bioengineered ACL matrix and hypothesized to be due to a lack of structural scaffolding. This study suggests that the bioengineered ACL matrix can undergo similar modes of osteointegration as current autografts and allografts, and that BMP-2 treatment may enhance osteoblastic activity within the bone tunnels.

IL-17 inhibits CXCL9/10-mediated recruitment of CD8+ cytotoxic T cells and regulatory T cells to colorectal tumors

BACKGROUND

The IL-17 family cytokines are potent drivers of colorectal cancer (CRC) development. We and others have shown that IL-17 mainly signals to tumor cells to promote CRC, but the underlying mechanism remains unclear. IL-17 also dampens Th1-armed anti-tumor immunity, in part by attracting myeloid cells to tumor. Whether IL-17 controls the activity of adaptive immune cells in a more direct manner, however, is unknown.

METHODS

Using mouse models of sporadic or inducible colorectal cancers, we ablated IL-17RA in the whole body or specifically in colorectal tumor cells. We also performed adoptive bone marrow reconstitution to knockout CXCR3 in hematopoietic cells. Histological and immunological experimental methods were used to reveal the link among IL-17, chemokine production, and CRC development.

RESULTS

Loss of IL-17 signaling in mouse CRC resulted in marked increase in the recruitment of CD8+ cytotoxic T lymphocytes (CTLs) and regulatory T cells (Tregs), starting from early stage CRC lesions. This is accompanied by the increased expression of anti-inflammatory cytokines IL-10 and TGF-β. IL-17 signaling also inhibits the production of T cell attracting chemokines CXCL9 and CXCL10 by tumor cells. Conversely, the inability of hematopoietic cells to respond to CXCL9/10 resulted in decreased tumor infiltration by CTLs and Tregs, decreased levels of IL-10 and TGF-β, and increased numbers of tumor lesions. Blockade of IL-17 signaling resulted in increased expression of immune checkpoint markers. On the other hand, treatment of mouse CRC with anti-CTLA-4 antibody led to increased expression of pro-tumor IL-17.

CONCLUSION

IL-17 signals to colorectal tumor cells and inhibits their production of CXCL9/10 chemokines. By doing so, IL-17 inhibits the infiltration of CD8+ CTLs and Tregs to CRC, thus promoting CRC development. Cancer immunotherapy may be benefited by the use of anti-IL-17 agents as adjuvant therapies, which serve to block both IL-17-mediated tumor promotion and T cell exclusion.

Functional polymeric nerve guidance conduits and drug delivery strategies for peripheral nerve repair and regeneration

Peripheral nerve injuries can be extremely debilitating, resulting in sensory and motor loss-of-function. Endogenous repair is limited to non-severe injuries in which transection of nerves necessitates surgical intervention. Traditional treatment approaches include the use of biological grafts and alternative engineering approaches have made progress. The current article serves as a comprehensive, in-depth perspective on peripheral nerve regeneration, particularly nerve guidance conduits and drug delivery strategies. A detailed background of peripheral nerve injury and repair pathology, and an in-depth look into augmented nerve regeneration, nerve guidance conduits, and drug delivery strategies provide a state-of-the-art perspective on the field.

A mathematical model of combined CD8 T cell costimulation by 4-1BB (CD137) and OX40 (CD134) receptors

Combined agonist stimulation of the TNFR costimulatory receptors 4-1BB (CD137) and OX40(CD134) has been shown to generate supereffector CD8 T cells that clonally expand to greater levels, survive longer, and produce a greater quantity of cytokines compared to T cells stimulated with an agonist of either costimulatory receptor individually. In order to understand the mechanisms for this effect, we have created a mathematical model for the activation of the CD8 T cell intracellular signaling network by mono- or dual-costimulation. We show that supereffector status is generated via downstream interacting pathways that are activated upon engagement of both receptors, and in silico simulations of the model are supported by published experimental results. The model can thus be used to identify critical molecular targets of T cell dual-costimulation in the context of cancer immunotherapy.

Activated T-effector seeds: cultivating atherosclerotic plaque through alternative activation

Atherosclerosis is a chronic inflammatory pathology that precipitates substantial morbidity and mortality. Although initiated by physiological patterns of low and disturbed flow that differentially prime endothelial cells at sites of vessel branch points and curvature, the chronic, smoldering inflammation of atherosclerosis is accelerated by comorbidities involving inappropriate activation of the adaptive immune system, such as autoimmunity. The innate contributions to atherosclerosis, especially in the transition of monocyte to lipid-laden macrophage, are well established, but the mechanisms underpinning the infiltration, persistence, and effector dynamics of CD8 T cells in particular are not well understood. Adaptive immunity is centered on a classical cascade of antigen recognition and activation, costimulation, and effector cytokine secretion upon recall of antigen. However, chronic inflammation can generate alternative cues that supplant this behavior pattern and promote the retention and activation of peripherally activated T cells. Furthermore, the atherogenic foci that activated immune cell infiltrate are unique lipid-laden environments that offer a diverse array of stimuli, including those of survival, antigen hyporesponsiveness, and inflammatory cytokine expression. This review will focus on how known cardiovascular comorbidities may be influencing CD8 T-cell activation and how, once infiltrated within atherogenic foci, these T cells face a multitude of cues that skew the classical cascade of T-cell behavior, highlighting alternative modes of activation that may help contextualize associations of autoimmunity, viral infection, and immunotherapy with cardiovascular morbidity.

Alarmin(g) outcomes of intracellular LPS sensing

Intracellular sensing of LPS by inflammatory caspases such as caspase-11 has emerged as a key mechanism of innate immune activation during Gram-negative bacterial infections. Cytosolic recognition of LPS by caspase-11 leads to inflammatory cell death or pyroptosis and maturation of IL-1 cytokines. Remarkably, the activation of inflammatory caspases also results in the extracellular release of alarmins and damage associated molecular patterns (DAMPs). These alarmins and DAMPs lack leader signals for classical secretion and are therefore released via a caspase-11 mediated unconventional secretory mechanism. Alarmins and DAMPs—structurally diverse molecules participating in various cellular processes under steady state conditions—are released rapidly upon infections and tissue damage. In the extracellular milieu, these proteins elicit inflammatory reactions by regulating pattern recognition receptor signaling and recruiting innate cells. Despite their potential roles in sepsis, the identity of alarmins and DAMPs released as a result of cytosolic LPS sensing and their contribution to sepsis are poorly understood. Addressing this knowledge gap, we employed an unbiased proteomic approach involving two-dimensional liquid phase fractionation system and mass spectrometry and identified alarmins released in response to caspase-11 activation by cytosolic LPS. In this presentation, the molecular basis of secretion of a candidate alarmin in vitro and in vivo as well as its function in murine models of host defense will be discussed.

Noncanonical Inflammasome-Induced release of Alarmins during Sepsis

Sepsis is a life-threatening disease caused by the immune system’s response to infection that results in excessive inflammation, organ damage and often death. In fact, sepsis is the leading cause of death in intensive care units and is responsible for more than 250,000 deaths every year in the USA. Activation of inflammatory caspases, such as caspase-11 by lipopolysaccharide (LPS) from Gram-negative bacteria, is a key mechanism of innate immune defense against infection. Intracellular sensing of LPS by caspase-11 results in pyroptosis, maturation of caspase-1, IL-1β and IL-18 and unconventional secretion of intracellular proteins that lack a leader sequence for conventional secretion via endoplasmic reticulum-Golgi route. These proteins can act as alarmins or damage associated molecular patterns (DAMPs) to regulate the inflammatory response and therefore play an important role during infectious diseases. However, caspase-11-dependent release of alarmins and DAMPs following noncanonical inflammasome activation is poorly characterized. Using a proteomics approach involving ProteomeLab’s PF2D fractionation system followed by mass spectrometry, we have profiled several new alarmins released in a caspase-11 dependent manner following Gram-negative bacterial infection. By employing various mutant mice and cells, we have defined the molecular and cellular mechanisms underlying the release of a candidate alarmin as a consequence of noncanonical inflammasome activation in vitro and in vivo. Importantly, our in vivo studies demonstrate a critical role for this alarmin in LPS shock. Overall, these findings provide new insights into potential biomarkers and therapeutic targets for blocking the lethal inflammation in sepsis.

Long Noncoding RNAs in Host-Pathogen Interactions

Long noncoding RNAs (lncRNAs) are key molecules that regulate gene expression in a variety of organisms. LncRNAs can drive different transcriptional and post-transcriptional events that impact cellular functions. Recent studies have identified many lncRNAs associated with immune cell development and activation; however, an understanding of their functional role in host immunity to infection is just emerging. Here, we provide a detailed and updated review of the functional roles of lncRNAs in regulating mammalian immune responses during host-pathogen interactions, because these functions may be either beneficial or detrimental to the host. With increased mechanistic insight into the roles of lncRNAs, it may be possible to design and/or improve lncRNA-based therapies to treat a variety of infectious and inflammatory diseases.

Single cell transcriptomics based-MacSpectrum reveals novel macrophage activation signatures in diseases

Adipose tissue macrophages (ATM) are crucial for maintaining adipose tissue homeostasis and mediating obesity-induced metabolic abnormalities, including prediabetic conditions and type 2 diabetes mellitus. Despite their key functions in regulating adipose tissue metabolic and immunologic homeostasis under normal and obese conditions, a high-resolution transcriptome annotation system that can capture ATM multifaceted activation profiles has not yet been developed. This is primarily attributed to the complexity of their differentiation/activation process in adipose tissue and their diverse activation profiles in response to microenvironmental cues. Although the concept of multifaceted macrophage action is well-accepted, no current model precisely depicts their dynamically regulated in vivo features. To address this knowledge gap, we generated single-cell transcriptome data from primary bone marrow-derived macrophages under polarizing and non-polarizing conditions to develop new high-resolution algorithms. The outcome was creation of a two-index platform, MacSpectrum (https://macspectrum.uconn.edu), that enables comprehensive high-resolution mapping of macrophage activation states from diverse mixed cell populations. MacSpectrum captured dynamic transitions of macrophage subpopulations under both in vitro and in vivo conditions. Importantly, MacSpectrum revealed unique "signature" gene sets in ATMs and circulating monocytes that displayed significant correlation with BMI and homeostasis model assessment of insulin resistance (HOMA-IR) in obese human patients. Thus, MacSpectrum provides unprecedented resolution to decode macrophage heterogeneity and will open new areas of clinical translation.

Direct CD137 costimulation of CD8 T cells promotes retention and innate-like function within nascent atherogenic foci

Effector CD8 T cells infiltrate atherosclerotic lesions and are correlated with cardiovascular events, but the mechanisms regulating their recruitment and retention are not well understood. CD137 (4-1BB) is a costimulatory receptor induced on immune cells and expressed at sites of human atherosclerotic plaque. Genetic variants associated with decreased CD137 expression correlate with carotid-intimal thickness and its deficiency in animal models attenuates atherosclerosis. These effects have been attributed in part to endothelial responses to low and disturbed flow (LDF), but CD137 also generates robust effector CD8 T cells as a costimulatory signal. Thus, we asked whether CD8 T cell-specific CD137 stimulation contributes to their infiltration, retention, and IFNγ production in early atherogenesis. We tested this through adoptive transfer of CD8 T cells into recipient C57BL/6J mice that were then antigen primed and CD137 costimulated. We analyzed atherogenic LDF vessels in normolipidemic and PCSK9-mediated hyperlipidemic models and utilized a digestion protocol that allowed for lesional T-cell characterization via flow cytometry and in vitro stimulation. We found that CD137 activation, specifically of effector CD8 T cells, triggers their intimal infiltration into LDF vessels and promotes a persistent innate-like proinflammatory program. Residence of CD137⁺ effector CD8 T cells further promoted infiltration of endogenous CD8 T cells with IFNγ-producing potential, whereas CD137-deficient CD8 T cells exhibited impaired vessel infiltration, minimal IFNγ production, and reduced infiltration of endogenous CD8 T cells. Our studies thus provide novel insight into how CD137 costimulation of effector T cells, independent of plaque-antigen recognition, instigates their retention and promotes innate-like responses from immune infiltrates within atherogenic foci. NEW & NOTEWORTHY Our studies identify CD137 costimulation as a stimulus for effector CD8 T-cell infiltration and persistence within atherogenic foci, regardless of atherosclerotic-antigen recognition. These costimulated effector cells, which are generated in pathological states such as viral infection and autoimmunity, have innate-like proinflammatory programs in circulation and within the atherosclerotic microenvironment, providing mechanistic context for clinical correlations of cardiovascular morbidity with increased CD8 T-cell infiltration and markers of activation in the absence of established antigen specificity.

Block of Granulocyte-Macrophage Colony-Stimulating Factor Prevents Inflammation-Induced Preterm Birth in a Mouse Model for Parturition

OBJECTIVE

A multitude of factors promotes inflammation in the reproductive tract leading to preterm birth. Macrophages peak in the cervix prior to birth and their numbers are increased by the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF). We hypothesize GM-CSF is produced from multiple sites in the genital tract and is a key mediator in preterm birth.

STUDY DESIGN

Ectocervical, endocervical, and amniotic fluid mesenchymal stem cells were treated with lipopolysaccharide (LPS), and the concentration and expression of GM-CSF was measured. Pregnant CD-1 mice on gestational day 17 received LPS and an intravenous injection of either anti-mouse GM-CSF or control antibody. After 6 hours, the preterm birth rate was recorded.

RESULTS

Treatment with LPS increased the GM-CSF concentration and messenger RNA expression after 24 hours in all 3 cell lines ( P < .01). Mice treated with LPS and the GM-CSF antibody had a preterm birth rate of 25%, compared to a 66.7% preterm birth rate in controls, within 6 hours ( P < .05, χ²). Treatment with the anti-mouse GM-CSF antibody decreased the concentration of GM-CSF in the mouse serum ( P < .01) but did not alter the number of macrophages or collagen content in the cervix.

CONCLUSION

These studies demonstrate that GM-CSF is produced from multiple sites in the genital tract and that treatment with an antibody to GM-CSF prevents preterm birth. Curiously, the anti-mouse GM-CSF antibody did not decrease the number of macrophages in the cervix. Further research is needed to determine whether antibodies to GM-CSF can be utilized as a therapeutic agent to prevent preterm birth.

Understanding how combinatorial targeting of TLRs and TNFR family costimulatory members promote enhanced T cell responses

INTRODUCTION

Due to the ability of pathogen-associated molecular patters and tumor necrosis factor receptor (TNFR) family costimulatory agonists to boost T cell responses, studies have combined Toll-like receptor (TLR) ligands with TNFR family costimulatory receptor agonists to induce impressive and long-lasting T cell responses. Although some studies have determined how these combinatorial vaccines promote enhanced T cell responses, much remains unknown about the mechanism used by these combinations to promote synergistic T cell responses - especially in settings of infectious diseases or cancer.

AREAS COVERED

In this review, we look in detail at the signaling pathways induced by combinatorial targeting of TLR and TNFR family costimulatory members that help them promote synergistic T cell responses. Understanding this can greatly aid the development of novel vaccine regimens that promote cellular immune responses, which is essential for treating certain infectious diseases and cancer.

EXPERT OPINION

Vaccines against some infectious diseases as well as therapeutic cancer vaccines require cellular immunity. Therefore, we evaluate here how signaling pathways induced by TLR ligand and costimulatory agonist combinations promote enhanced T cell responses during immunization with model antigens, viral pathogens, or tumor antigens. Once pathways that drive these combinatorial vaccines to boost T cell activation are identified, they can be incorporated in vaccines designed to target pathogens or cancer.

T cell-directed IL-17 production by lung granular γδ T cells is coordinated by a novel IL-2 and IL-1β circuit

Immune-mediated lung is considered the result of an exacerbated innate injury immune response, although a role for adaptive lymphocytes is emerging. αβ T cells specific for S. aureus enterotoxin A orchestrate a Tγδ17 response during lung injury. However, the mechanism driving IL-17 production is unclear. Here, we show a role for IL-2 triggering IL-17 production by lung granular γδ T cells as IL-17 synthesis and neutrophil recruitment was reduced by IL-2 blocking mAbs in vitro and in vivo. Mass cytometry analysis revealed that lung γδ T cells responded directly to IL-2 as evident from STAT5 phosphorylation and RoRγt expression. IL-2 receptor blocking mAbs and JAK inhibition impaired STAT5 phosphorylation and IL-17 release. Moreover, inhalation of S. aureus enterotoxin A induced IL-2 secretion and caspase-1-dependent IL-1β activation to drive IL-17 production. This T-cell-mediated inflammasome-dependent IL-17 response is maximum when lung Tγδ17 cells were sequentially stimulated first with IL-2 then IL-1β. Interestingly, when IL-2 is given therapeutically to cancer patients it carries a known risk of lung injury that is largely indistinguishable from that seen in sepsis. Hence, this novel mechanism reveals therapeutic targets treating both acute lung injury and high-dose IL-2 toxicity in cancer.

Gasdermin D Restrains Type I Interferon Response to Cytosolic DNA by Disrupting Ionic Homeostasis

Inflammasome-activated caspase-1 cleaves gasdermin D to unmask its pore-forming activity, the predominant consequence of which is pyroptosis. Here, we report an additional biological role for gasdermin D in limiting cytosolic DNA surveillance. Cytosolic DNA is sensed by Aim2 and cyclic GMP-AMP synthase (cGAS) leading to inflammasome and type I interferon responses, respectively. We found that gasdermin D activated by the Aim2 inflammasome suppressed cGAS-driven type I interferon response to cytosolic DNA and Francisella novicida in macrophages. Similarly, interferon-β (IFN-β) response to F. novicida infection was elevated in gasdermin D-deficient mice. Gasdermin D-mediated negative regulation of IFN-β occurred in a pyroptosis-, interleukin-1 (IL-1)-, and IL-18-independent manner. Mechanistically, gasdermin D depleted intracellular potassium (K⁺) via membrane pores, and this K⁺ efflux was necessary and sufficient to inhibit cGAS-dependent IFN-β response. Thus, our findings have uncovered an additional interferon regulatory module involving gasdermin D and K⁺ efflux.

T Cell-Directed IL-17 production by Lung Granular γδ T cells is Coordinated by a Novel IL-2 and IL-1β Circuit

Immune-mediated lung injury is considered the result of an exacerbated innate immune response, although a role for adaptive lymphocytes is emerging. αβ T cells specific for S. aureus enterotoxin A orchestrates a typical innate-like Tγδ17 response during lung injury. However, the mechanism by which a specific T cell response drives an innate immune response in the lung is unclear. Here, we show a role for IL-2 triggering IL-17 production by lung granular γδ T cells as IL-17 synthesis was reduced by IL-2 blocking mAbs in vitro and in vivo. Granular γδ T cells in the lung constitute a rare population, hence Mass Cytometry (CyTOF) was utilized to characterize this population. CyTOF analysis revealed that lung γδ T cells responded directly to IL-2 as evident from STAT5 phosphorylation and RoRγt expression. IL-2 receptor blocking mAbs and JAK inhibition impaired STAT5 phosphorylation and IL-17 release. Moreover, inhalation of S. aureus enterotoxin A induced IL-2 secretion and caspase-1-dependent IL-1β activation to drive IL-17 production. This T cell-mediated inflammasome dependent IL-17 response is maximum when lung Tγδ17 cells were sequentially stimulated first with IL-2 then IL-1β. Further investigation is still needed to identify the cellular source of IL-1β. Interestingly, when IL-2 is given therapeutically to cancer patients it carries a known risk of lung injury that is largely indistinguishable from that seen in sepsis. Hence, this novel mechanism reveals therapeutic targets treating both acute lung injury and high dose IL-2 toxicity in cancer.

Altered flow triggers activated T cell accumulation and inflammation in early atherosclerosis

Atherosclerosis is linked to systemic inflammation. Yet, the inflamed plaques predicating cardiovascular morbidity and mortality preferentially develop in areas of low and disturbed flow (LDF). Partial carotid artery ligation (PCAL) of the left carotid exposes vascular endothelium to LDF without disturbing flow contralaterally and when combined with high fat diet, LDF regions develop plaques within 2 wks. We show that just 48 hr after PCAL, LDF triggers significant upregulation of IL-36, a new member of the proinflammatory IL-1 family, and Cathepsin S, its enzymatic activator. The IL-1 family and IFNγ are intimately tied to atherogenesis and our past work establishes IL-36 as a robust stimulator of IFNγ from effector T cells. Thus, we hypothesize that LDF triggers an IL-36-IFNγ loop, promoting early disease independent of plaque-specific antigen. To test this, we assessed the homing of adoptively transferred CD8 TCR transgenic T cells that were antigen-primed and CD137-costimulated within recipient mice. Comparison of physiologic LDF regions (aortic arch) with experimentally induced LDF (PCAL) reveals that effector CD8 T cells substantially and preferentially accumulate within LDF areas, even without TCR-specific stimuli in the vessel wall. Notably, cells isolated from these regions produce IFNγ in response to IL-36. Mass cytometry (CYTOF) and single cell RNA-seq analyses are underway to build mechanistic understandings of how LDF triggers immune cell recruitment and signaling cascades. Overall, our studies propose a novel role for IL-36 within the vascular system and provide insight into the early pathogenesis of atherosclerosis, especially in the context of autoimmunity and antigen-independent T cell activation.

Addressing current challenges in cancer immunotherapy with mathematical and computational modelling

The goal of cancer immunotherapy is to boost a patient's immune response to a tumour. Yet, the design of an effective immunotherapy is complicated by various factors, including a potentially immunosuppressive tumour microenvironment, immune-modulating effects of conventional treatments and therapy-related toxicities. These complexities can be incorporated into mathematical and computational models of cancer immunotherapy that can then be used to aid in rational therapy design. In this review, we survey modelling approaches under the umbrella of the major challenges facing immunotherapy development, which encompass tumour classification, optimal treatment scheduling and combination therapy design. Although overlapping, each challenge has presented unique opportunities for modellers to make contributions using analytical and numerical analysis of model outcomes, as well as optimization algorithms. We discuss several examples of models that have grown in complexity as more biological information has become available, showcasing how model development is a dynamic process interlinked with the rapid advances in tumour-immune biology. We conclude the review with recommendations for modellers both with respect to methodology and biological direction that might help keep modellers at the forefront of cancer immunotherapy development.

An Immunotherapeutic CD137 Agonist Releases Eomesodermin from ThPOK Repression in CD4 T Cells

Agonists to the TNF/TNFR costimulatory receptors CD134 (OX40) and CD137 (4-1BB) elicit antitumor immunity. Dual costimulation with anti-CD134 plus anti-CD137 is particularly potent because it programs cytotoxic potential in CD8⁺ and CD4⁺ T cells. Cytotoxicity in dual-costimulated CD4 T cells depends on the T-box transcription factor eomesodermin (Eomes), which we report is induced via a mechanism that does not rely on IL-2, in contrast to CD8⁺ CTL, but rather depends on the CD8 T cell lineage commitment transcription factor Runx3, which supports Eomes expression in mature CD8⁺ CTLs. Further, Eomes and Runx3 were indispensable for dual-costimulated CD4 T cells to mediate antitumor activity in an aggressive melanoma model. Runx3 is also known to be expressed in standard CD4 Th1 cells where it fosters IFN-γ expression; however, the CD4 T cell lineage commitment factor ThPOK represses transcription of Eomes and other CD8 lineage genes, such as Cd8a Hence, CD4 T cells can differentiate into Eomes⁺ cytotoxic CD4⁺CD8⁺ double-positive T cells by terminating ThPOK expression. In contrast, dual-costimulated CD4 T cells express Eomes, despite the continued expression of ThPOK and the absence of CD8α, indicating that Eomes is selectively released from ThPOK repression. Finally, although Eomes was induced by CD137 agonist, but not CD134 agonist, administered individually, CD137 agonist failed to induce CD134^-/- CD4 T cells to express Eomes or Runx3, indicating that both costimulatory pathways are required for cytotoxic Th1 programming, even when only CD137 is intentionally engaged with a therapeutic agonist.

Macrophage polarization and meta-inflammation

Chronic overnutrition and obesity induces low-grade inflammation throughout the body. Termed "meta-inflammation," this chronic state of inflammation is mediated by macrophages located within the colon, liver, muscle, and adipose tissue. A sentinel orchestrator of immune activity and homeostasis, macrophages adopt variable states of activation as a function of time and environmental cues. Meta-inflammation phenotypically skews these polarization states and has been linked to numerous metabolic disorders. The past decade has revealed several key regulators of macrophage polarization, including the signal transducer and activator of transcription family, the peroxisome proliferator-activated receptor gamma, the CCAAT-enhancer-binding proteins (C/EBP) family, and the interferon regulatory factors. Recent studies have also suggested that microRNAs and long noncoding RNA influence macrophage polarization. The pathogenic alteration of macrophage polarization in meta-inflammation is regulated by both extracellular and intracellular cues, resulting in distinct secretome profiles. Meta-inflammation-altered macrophage polarization has been linked to insulin insensitivity, atherosclerosis, inflammatory bowel disease, cancer, and autoimmunity. Thus, further mechanistic exploration into the skewing of macrophage polarization promises to have profound impacts on improving global health.