Prostaglandin E2 stimulates adaptive IL-22 production and promotes allergic contact dermatitis.

BACKGROUND: Atopic dermatitis (AD) and allergic contact dermatitis (ACD) are both forms of eczema and are common inflammatory skin diseases with a central role of T cell-derived IL-22 in their pathogenesis. Although prostaglandin (PG) E2 is known to promote inflammation, little is known about its role in processes related to AD and ACD development, including IL-22 upregulation. OBJECTIVES: We sought to investigate whether PGE2 has a role in IL-22 induction and development of ACD, which has increased prevalence in patients with AD. METHODS: T-cell cultures and in vivo sensitization of mice with haptens were used to assess the role of PGE2 in IL-22 production. The involvement of PGE2 receptors and their downstream signals was also examined. The effects of PGE2 were evaluated by using the oxazolone-induced ACD mouse model. The relationship of PGE2 and IL-22 signaling pathways in skin inflammation were also investigated by using genomic profiling in human lesional AD skin. RESULTS: PGE2 induces IL-22 from T cells through its receptors, E prostanoid receptor (EP) 2 and EP4, and involves cyclic AMP signaling. Selective deletion of EP4 in T cells prevents hapten-induced IL-22 production in vivo, and limits atopic-like skin inflammation in the oxazolone-induced ACD model. Moreover, both PGE2 and IL-22 pathway genes were coordinately upregulated in human AD lesional skin but were at less than significant detection levels after corticosteroid or UVB treatments. CONCLUSIONS: Our results define a crucial role for PGE2 in promoting ACD by facilitating IL-22 production from T cells.

Facilitation of IL-22 production from innate lymphoid cells by prostaglandin E2 prevents experimental lung neutrophilic inflammation.

Acute lung injury is a neutrophil-dominant, life-threatening disease without effective therapies and better understanding of the pathophysiological mechanisms involved is an urgent need. Here we show that interleukin (IL)-22 is produced from innate lymphoid cells (ILC) and is responsible for suppression of experimental lung neutrophilic inflammation. Blocking prostaglandin E2 (PGE2) synthesis reduces lung ILCs and IL-22 production, resulting in exacerbation of lung neutrophilic inflammation. In contrast, activation of the PGE2 receptor EP4 prevents acute lung inflammation. We thus demonstrate a mechanism for production of innate IL-22 in the lung during acute injury, highlighting potential therapeutic strategies for control of lung neutrophilic inflammation by targeting the PGE2/ILC/IL-22 axis.

Purine metabolism controls innate lymphoid cell function and protects against intestinal injury.

Inflammatory bowel disease (IBD) is a condition of chronic inflammatory intestinal disorder with increasing prevalence but limited effective therapies. The purine metabolic pathway is involved in various inflammatory processes including IBD. However, the mechanisms through which purine metabolism modulates IBD remain to be established. Here, we found that mucosal expression of genes involved in the purine metabolic pathway is altered in patients with active ulcerative colitis (UC), which is associated with elevated gene expression signatures of the group 3 innate lymphoid cell (ILC3)-interleukin (IL)-22 pathway. In mice, blockade of ectonucleotidases (NTPDases), critical enzymes for purine metabolism by hydrolysis of extracellular adenosine 5'-triphosphate (eATP) into adenosine, exacerbates dextran-sulfate sodium-induced intestinal injury. This exacerbation of colitis is associated with reduction of colonic IL-22-producing ILC3s, which afford essential protection against intestinal inflammation, and is rescued by exogenous IL-22. Mechanistically, activation of ILC3s for IL-22 production is reciprocally mediated by eATP and adenosine. These findings reveal that the NTPDase-mediated balance between eATP and adenosine regulates ILC3 cell function to provide protection against intestinal injury and suggest potential therapeutic strategies for treating IBD by targeting the purine-ILC3 axis.

Effector and central memory T helper 2 cells respond differently to peptide immunotherapy.

Peptide immunotherapy (PIT) offers realistic prospects for the treatment of allergic diseases, including allergic asthma. Much is understood of the behavior of naive T cells in response to PIT. However, treatment of patients with ongoing allergic disease requires detailed understanding of the responses of allergen-experienced T cells. CD62L expression by allergen-experienced T cells corresponds to effector/effector memory (CD62L(lo)) and central memory (CD62L(hi)) subsets, which vary with allergen exposure (e.g., during, or out with, pollen season). The efficacy of PIT on different T helper 2 (Th2) cell memory populations is unknown. We developed a murine model of PIT in allergic airway inflammation (AAI) driven by adoptively transferred, traceable ovalbumin-experienced Th2 cells. PIT effectively suppressed AAI driven by unfractionated Th2 cells. Selective transfer of CD62L(hi) and CD62L(lo) Th2 cells revealed that these two populations behaved differently from one another and from previously characterized (early deletional) responses of naive CD4(+) T cells to PIT. Most notably, allergen-reactive CD62L(lo) Th2 cells were long-lived within the lung after PIT, before allergen challenge, in contrast to CD62L(hi) Th2 cells. Despite this, PIT was most potent against CD62L(lo) Th2 cells in protecting from AAI, impairing their ability to produce Th2 cytokines, whereas this capacity was heightened in PIT-treated CD62L(hi) Th2 cells. We conclude that Th2 cells do not undergo an early deletional form of tolerance after PIT. Moreover, memory Th2 subsets respond differently to PIT. These findings have implications for the clinical translation of PIT in different allergic scenarios.

Filaggrin-null mutations are associated with increased maturation markers on Langerhans cells.

BACKGROUND: Mutations in the gene encoding filaggrin (FLG), an epidermal structural protein, are the strongest risk factor identified for the development of atopic dermatitis (AD). Up to 50% of patients with moderate-to-severe AD in European populations have FLG-null alleles compared with a general population frequency of 7% to 10%. OBJECTIVE: This study aimed to investigate the relationship between FLG-null mutations and epidermal antigen-presenting cell (APC) maturation in subjects with and without AD. Additionally, we investigated whether the cis isomer of urocanic acid (UCA), a filaggrin breakdown product, exerts immunomodulatory effects on dendritic cells. METHODS: Epidermal APCs from nonlesional skin were assessed by using flow cytometry (n = 27) and confocal microscopy (n = 16). Monocyte-derived dendritic cells from healthy volunteers were used to assess the effects of cis- and trans-UCA on dendritic cell phenotype by using flow cytometry (n = 11). RESULTS: Epidermal APCs from FLG-null subjects had increased CD11c expression. Confocal microscopy confirmed this and additionally revealed an increased number of epidermal CD83(+) Langerhans cells in FLG-null subjects. In vitro differentiation in the presence of cis-UCA significantly reduced costimulatory molecule expression on monocyte-derived dendritic cells from healthy volunteers and increased their ability to induce a regulatory T-cell phenotype in mixed lymphocyte reactions. CONCLUSIONS: We show that subjects with FLG-null mutations have more mature Langerhans cells in nonlesional skin irrespective of whether they have AD. We also demonstrate that cis-UCA reduces maturation of dendritic cells and increases their capacity to induce regulatory T cells, suggesting a novel link between filaggrin deficiency and immune dysregulation.

The long-term time course of septic arthritis.

Aims: The aims of this study were to: 1) report on a cohort of skeletally mature patients with native hip and knee septic arthritis over a 14-year period; 2) to determine the rate of joint failure in patients who had experienced an episode of hip or knee septic arthritis; and 3) to assess the outcome following septic arthritis relative to the infecting organism, whether those patients infected by Staphylococcus aureus would be more likely to have adverse outcomes than those infected by other organisms. Methods: All microbiological samples from joint aspirations between March 2000 and December 2014 at our institution were reviewed in order to identify cases of culture-proven septic arthritis. Cases in children (aged < 16 years) and prosthetic joints were excluded. Data were abstracted on age at diagnosis, sex, joint affected (hip or knee), type of organisms isolated, cause of septic arthritis, comorbidities within the Charlson Comorbidity Index (CCI), details of treatment, and outcome. Results: A total of 142 patients were confirmed to have had an episode of septic arthritis in a native hip (n = 17) or knee joint (n = 125). S. aureus accounted for 57.7% of all hip and knee joint infections. There were 13 inpatient deaths attributed to septic arthritis. The median age of the patients who died was 77.5 (46.9 to 92.2) and their median age-adjusted CCI was 8 (6 to 12). A failure of the joint occurred in 26 knees (21%) and nine hips (53%). Of the knee joints infected by S. aureus (n = 71), 23 knees (32%) went into failure of joint, whereas of those infected by other organisms (n = 54), only three knees (6%) failed. Conclusion: Based on our study findings, hip and knee septic arthritis long-term outcomes were substantially worse than their immediate outcome suggested. Failure of knee joint is 6.1 times more likely to occur in those infected with S. aureus.

Combination peptide immunotherapy based on T-cell epitope mapping reduces allergen-specific IgE and eosinophilia in allergic airway inflammation.

Peptide immunotherapy using soluble peptides containing allergen-derived immunodominant T-cell epitopes holds therapeutic promise for allergic asthma. Previous studies in BALB/c mice using the immunodominant peptide epitope of chicken ovalbumin (p323-339) have been unable to demonstrate therapeutic effects in ovalbumin-induced allergic airway inflammation. We have previously shown that intravenous application of p323-339 can effectively tolerise p323-339-reactive T cells in a non-allergic model in C57BL/6 mice. This study aimed to assess the effects of using p323-339 immunotherapy in a C57BL/6 model of ovalbumin-induced allergic airway inflammation, identify any additional epitopes recognized by the ovalbumin-responsive T-cell repertoire in C57BL/6 mice and assess the effects of combination peptide immunotherapy in this model. Ovalbumin-reactive T-cell lines were generated from ovalbumin-immunized C57BL/6 mice and proliferative responses to a panel of overlapping peptides covering the ovalbumin sequence were assessed. Soluble peptides (singly or combined) were administered intravenously to C57BL/6 mice before the induction of ovalbumin-induced allergic airway inflammation. Peptide immunotherapy using the 323-339 peptide alone did not reduce the severity of allergic airway inflammation. An additional immunodominant T-cell epitope in ovalbumin was identified within the 263-278 sequence. Combination peptide immunotherapy, using the 323-339 and 263-278 peptides together, reduced eosinophilia in the bronchoalveolar lavage and ovalbumin-specific IgE, with apparent reductions in interleukin-5 and interleukin-13. Characterization of the T-cell response to a model allergen has allowed the development of combination peptide immunotherapy with improved efficacy in allergic airway inflammation. This model holds important potential for future mechanistic studies using peptide immunotherapy in allergy.

Kynurenine monooxygenase regulates inflammation during critical illness and recovery in experimental acute pancreatitis.

Kynurenine monooxygenase (KMO) blockade protects against multiple organ failure caused by acute pancreatitis (AP), but the link between KMO and systemic inflammation has eluded discovery until now. Here, we show that the KMO product 3-hydroxykynurenine primes innate immune signaling to exacerbate systemic inflammation during experimental AP. We find a tissue-specific role for KMO, where mice lacking Kmo solely in hepatocytes have elevated plasma 3-hydroxykynurenine levels that prime inflammatory gene transcription. 3-Hydroxykynurenine synergizes with interleukin-1ß to cause cellular apoptosis. Critically, mice with elevated 3-hydroxykynurenine succumb fatally earlier and more readily to experimental AP. Therapeutically, blockade with the highly selective KMO inhibitor GSK898 rescues the phenotype, reducing 3-hydroxykynurenine and protecting against critical illness and death. Together, our findings establish KMO and 3-hydroxykynurenine as regulators of inflammation and the innate immune response to sterile inflammation. During critical illness, excess morbidity and death from multiple organ failure can be rescued by systemic KMO blockade.

The role of macrophages in healing the wounded lung.

Acute tissue injury is often considered in the context of a wound. The host response to wounding is an orchestrated series of events, the fundamentals of which are preserved across all multicellular organisms. In the human lung, there are a myriad of causes of injury, but only a limited number of consequences: complete resolution, persistent and/or overwhelming inflammation, a combination of resolution/remodelling with fibrosis or progressive fibrosis. In all cases where complete resolution does not occur, there is the potential for significant ongoing morbidity and ultimately death through respiratory failure. In this review, we consider the elements of injury, resolution and repair as they occur in the lung. We specifically focus on the role of the macrophage, long considered to have a pivotal role in regulating the host response to injury and tissue repair.

Ly6Chi monocytes direct alternatively activated profibrotic macrophage regulation of lung fibrosis.

RATIONALE: Idiopathic pulmonary fibrosis (IPF) is a devastating disease. Antiinflammatory therapies, including corticosteroids, are of no benefit. The role of monocytes and macrophages is therefore controversial. OBJECTIVES: To define the role of monocytes and macrophages during lung fibrogenesis and resolution, and explore the phenotype of the cells involved. METHODS: We used multiple in vivo depletional strategies, backed up by adoptive transfer techniques. Further studies were performed on samples from patients with IPF. MEASUREMENTS AND MAIN RESULTS: Depletion of lung macrophages during fibrogenesis reduced pulmonary fibrosis as measured by lung collagen (P = 0.0079); fibrosis score (P = 0.0051); and quantitative polymerase chain reaction for surrogate markers of fibrosis Col1 (P = 0.0083) and a-smooth muscle actin (P = 0.0349). There was an associated reduction in markers of the profibrotic alternative macrophage activation phenotype, Ym1 (P = 0.0179), and Arginase 1. The alternative macrophage marker CD163 was expressed on lung macrophages from patients with IPF. Depletion of Ly6Chi circulating monocytes reduced pulmonary fibrosis (P = 0.0052) and the number of Ym1- positive alternatively activated lung macrophages (P = 0.0310). Their adoptive transfer during fibrogenesis exacerbated fibrosis (P = 0.0304); however, adoptively transferred CD45.1 Ly6Chi cells were not found in the lungs of recipient CD45.2 mice. CONCLUSIONS: We demonstrate the importance of circulating monocytes and lung macrophages during pulmonary fibrosis, and emphasize the importance of the alternatively activated macrophage phenotype. We show that Ly6Chi monocytes facilitate the progression of pulmonary fibrosis, but are not obviously engrafted into lungs thereafter. Finally, we provide empirical data to suggest that macrophages may have a resolution-promoting role during the reversible phase of bleomycin-induced pulmonary fibrosis.

Septic arthritis in an in vivo murine model induced by Staphylococcus aureus : a comparison between actions of the haemolysin toxin and the effects of the host immune response.

AIMS: Staphylococcus aureus is a major cause of septic arthritis, and in vitro studies suggest α haemolysin (Hla) is responsible for chondrocyte death. We used an in vivo murine joint model to compare inoculation with wild type S. aureus 8325-4 with a Hla-deficient strain DU1090 on chondrocyte viability, tissue histology, and joint biomechanics. The aim was to compare the actions of S. aureus Hla alone with those of the animal's immune response to infection. METHODS: Adult male C57Bl/6 mice (n = 75) were randomized into three groups to receive 1.0 to 1.4 × 107 colony-forming units (CFUs)/ml of 8325-4, DU1090, or saline into the right stifle joint. Chondrocyte death was assessed by confocal microscopy. Histological changes to inoculated joints were graded for inflammatory responses along with gait, weight changes, and limb swelling. RESULTS: Chondrocyte death was greater with 8325-4 (96.2% (SD 5.5%); p < 0.001) than DU1090 (28.9% (SD 16.0%); p = 0.009) and both were higher than controls (3.8% (SD 1.2%)). Histology revealed cartilage/bone damage with 8325-4 or DU1090 compared to controls (p = 0.010). Both infected groups lost weight (p = 0.006 for both) and experienced limb swelling (p = 0.043 and p = 0.018, respectively). Joints inoculated with bacteria showed significant alterations in gait cycle with a decreased stance phase, increased swing phase, and a corresponding decrease in swing speed. CONCLUSION: Murine joints inoculated with Hla-producing 8325-4 experienced significantly more chondrocyte death than those with DU1090, which lack the toxin. This was despite similar immune responses, indicating that Hla was the major cause of chondrocyte death. Hla-deficient DU1090 also elevated chondrocyte death compared to controls, suggesting a smaller additional deleterious role of the immune system on cartilage.Cite this article: Bone Joint Res 2022;11(9):669-678.

Immunity and vaccines against sexually transmitted Chlamydia trachomatis infection.

PURPOSE OF REVIEW: The aim is to review recent findings on immunity and vaccine development to Chlamydia trachomatis. RECENT FINDINGS: There is increasing knowledge on the interactions between C. trachomatis and infected host cells. During genital infection the organism avoids generating protective immunity but immune responses to a number of chlamydial proteins have been associated with reproductive tract pathology. Various vaccine and adjuvant preparations have been tried experimentally. Information generated by proteomics and complex studies of serological and T-lymphocyte immune responses points to novel vaccine candidates. SUMMARY: C. trachomatis, an obligate intracellular bacterium, is the commonest sexually transmitted infection worldwide and is associated with reproductive pathology. To develop rational vaccines it is necessary to understand the complex lifecycle of the organism, the host immune response to infection and how these relate to disease. Infection does not prevent re-infection and antibiotic treatment prevents antibody production at a population level. It remains unclear what type of immune response would be sufficient to prevent infection and/or re-infection. Although the prevalence and demographics of infection and the severity of disease associations suggest that it would be desirable, there is no vaccine currently available. A number of studies have identified novel vaccine candidates.

Oxidative damage and TGF-ß differentially induce lung epithelial cell sonic hedgehog and tenascin-C expression: implications for the regulation of lung remodelling in idiopathic interstitial lung disease.

Idiopathic interstitial lung diseases (iILDs) are characterized by inflammation, hyperplasia of Type-II alveolar epithelial cells (AECs) and lung remodelling often with progressive fibrosis. It remains unclear which signals initiate iILD and/or maintain the disease processes. Using real-time RT-PCR and immunohistochemistry on archival biopsies of three patterns of iILD (usual interstitial pneumonitis/UIP, non-specific interstitial pneumonitis/NSIP and cryptogenic organizing pneumonia/COP) we investigated whether hedgehog signalling (previously associated with lung damage and repair) was functional and whether the damage associated extracellular matrix protein tenascin-C was present in activated Type-II AECs in all three iILDs. Using tissue culture, protein and mRNA detection we also determined how two signals (oxidative damage and TGF-ß) associated with iILD pathogenesis affected Sonic hedgehog (SHH) and tenascin-C production by a Type-II AEC cell line. We report that SHH pathway and tenascin-C mRNA and proteins were found in UIP, NSIP and COP. SHH signalling was most active at sites of immature organizing fibrous tissue (fibroblastic foci) in UIP. In vitro Type-II AECs constitutively secrete SHH but not tenascin-C. Oxidative injury stimulated SHH release whereas TGF-ß inhibited it. TGF-ß and oxidative damage both upregulated tenascin-C mRNA but only TGF-ß induced synthesis and release of a distinct protein isoform. SHH signalling is active in Type-II AECs from three types of ILD and all three express tenascin-C.

Human dendritic cells produce TGF-beta 1 under the influence of lung carcinoma cells and prime the differentiation of CD4+CD25+Foxp3+ regulatory T cells.

Dendritic cells (DCs) have a central role in the development of adaptive immune responses, including antitumor immunity. Factors present in the tumor milieu can alter the maturation of DCs and inhibit their capacity to activate T cells. Using gene expression analysis, we found that human DCs increased the expression of TGF-beta1 transcripts following culture with human lung carcinoma cells (LCCs). These DCs produced increased amounts of TGF-beta1 protein compared with DCs not exposed to tumor cells. LCCs also decreased the expression of CD86 and HLA-DR by immature DCs. Furthermore, LCCs decreased CD86 expression and the production of TNF-alpha and IL-12 p70 by mature DCs. Moreover, LCCs also converted mature DCs into cells producing TGF-beta1. These TGF-beta1-producing DCs were poor at eliciting the activation of naive CD4(+) T cells and sustaining their proliferation and differentiation into Th1 (IFN-gamma(+)) effectors. Instead, TGF-beta1-producing DCs demonstrated an increased ability to generate CD4(+)CD25(+)Foxp3(+) regulatory T cells that suppress the proliferation of T lymphocytes. These results identify a novel mechanism by which the function of human DCs is altered by tumor cells and contributes to the evasion of the immune response.

Modified adenine (9-benzyl-2-butoxy-8-hydroxyadenine) redirects Th2-mediated murine lung inflammation by triggering TLR7.

Substitute adenine (SA)-2, a synthetic heterocycle chemically related to adenine with substitutions in positions 9-, 2-, and 8- (i.e., 9-benzyl-2-butoxy-8-hydroxyadenine), induces in vitro immunodeviation of Th2 cells to a Th0/Th1 phenotype. In this article, we evaluate the in vivo ability of SA-2 to affect Th2-mediated lung inflammation and its safety. TLR triggering and NF-kappaB activation by SA-2 were analyzed on TLR-transfected HEK293 cells and on purified bone marrow dendritic cells. The in vivo effect of SA-2 on experimental airway inflammation was evaluated in both prepriming and prechallenge protocols by analyzing lung inflammation, including tissue eosinophilia and goblet cell hyperplasia, bronchoalveolar lavage fluid cell types, and the functional profile of Ag-specific T cells from draining lymph nodes and spleens. SA-2 induced mRNA expression and production of proinflammatory (IL-6, IL-12, and IL-27) and regulatory (IL-10) cytokines and chemokines (CXCL10) in dendritic cells but down-regulated TGF-beta. Prepriming administration of SA-2 inhibited OVA-specific Abs and Th2-driven lung inflammation, including tissue eosinophilia and goblet cells, with a prevalent Foxp3-independent regulatory mechanism. Prechallenge treatment with SA-2 reduced the lung inflammation through the induction of a prevalent Th1-related mechanism. In this model the activity of SA-2 was route-independent, but adjuvant- and Ag dose-dependent. SA-2-treated mice did not develop any increase of serum antinuclear autoantibodies. In conclusion, critical substitutions in the adenine backbone creates a novel synthetic TLR7 ligand that shows the ability to ameliorate Th2-mediated airway inflammation by a complex mechanism, involving Th1 redirection and cytokine-mediated regulation, which prevents autoreactivity.

Progressive severe lung injury by zinc oxide nanoparticles; the role of Zn2+ dissolution inside lysosomes.

BACKGROUND: Large production volumes of zinc oxide nanoparticles (ZnONP) might be anticipated to pose risks, of accidental inhalation in occupational and even in consumer settings. Herein, we further investigated the pathological changes induced by ZnONP and their possible mechanism of action. METHODS: Two doses of ZnONP (50 and 150 cm2/rat) were intratracheally instilled into the lungs of rats with assessments made at 24 h, 1 wk, and 4 wks after instillation to evaluate dose- and time-course responses. Assessments included bronchoalveolar lavage (BAL) fluid analysis, histological analysis, transmission electron microscopy, and IgE and IgA measurement in the serum and BAL fluid. To evaluate the mechanism, alternative ZnONP, ZnONP-free bronchoalveolar lavage exudate, and dissolved Zn2+ (92.5 µg/rat) were also instilled to rats. Acridine orange staining was utilized in macrophages in culture to evaluate the lysosomal membrane destabilization by NP. RESULTS: ZnONP induced eosinophilia, proliferation of airway epithelial cells, goblet cell hyperplasia, and pulmonary fibrosis. Bronchocentric interstitial pulmonary fibrosis at the chronic phase was associated with increased myofibroblast accumulation and transforming growth factor-ß positivity. Serum IgE levels were up-regulated by ZnONP along with the eosinophilia whilst serum IgA levels were down-regulated by ZnONP. ZnONP are rapidly dissolved under acidic conditions (pH 4.5) whilst they remained intact around neutrality (pH 7.4). The instillation of dissolved Zn2+ into rat lungs showed similar pathologies (eg., eosinophilia, bronchocentric interstitial fibrosis) as were elicited by ZnONP. Lysosomal stability was decreased and cell death resulted following treatment of macrophages with ZnONP in vitro. CONCLUSIONS: We hypothesise that rapid, pH-dependent dissolution of ZnONP inside of phagosomes is the main cause of ZnONP-induced diverse progressive severe lung injuries.

Prostaglandin E2 promotes intestinal inflammation via inhibiting microbiota-dependent regulatory T cells.

The gut microbiota fundamentally regulates intestinal homeostasis and disease partially through mechanisms that involve modulation of regulatory T cells (Tregs), yet how the microbiota-Treg cross-talk is physiologically controlled is incompletely defined. Here, we report that prostaglandin E2 (PGE2), a well-known mediator of inflammation, inhibits mucosal Tregs in a manner depending on the gut microbiota. PGE2 through its receptor EP4 diminishes Treg-favorable commensal microbiota. Transfer of the gut microbiota that was modified by PGE2-EP4 signaling modulates mucosal Treg responses and exacerbates intestinal inflammation. Mechanistically, PGE2-modified microbiota regulates intestinal mononuclear phagocytes and type I interferon signaling. Depletion of mononuclear phagocytes or deficiency of type I interferon receptor diminishes PGE2-dependent Treg inhibition. Together, our findings provide emergent evidence that PGE2-mediated disruption of microbiota-Treg communication fosters intestinal inflammation.

Cervical epithelial damage promotes Ureaplasma parvum ascending infection, intrauterine inflammation and preterm birth induction in mice.

Around 40% of preterm births are attributed to ascending intrauterine infection, and Ureaplasma parvum (UP) is commonly isolated in these cases. Here we present a mouse model of ascending UP infection that resembles human disease, using vaginal inoculation combined with mild cervical injury induced by a common spermicide (Nonoxynol-9, as a surrogate for any mechanism of cervical epithelial damage). We measure bacterial load in a non-invasive manner using a luciferase-expressing UP strain, and post-mortem by qPCR and bacterial titration. Cervical exposure to Nonoxynol-9, 24 h pre-inoculation, facilitates intrauterine UP infection, upregulates pro-inflammatory cytokines, and increases preterm birth rates from 13 to 28%. Our results highlight the crucial role of the cervical epithelium as a barrier against ascending infection. In addition, we expect the mouse model will facilitate further research on the potential links between UP infection and preterm birth.

Kynurenine 3-monooxygenase is a critical regulator of renal ischemia-reperfusion injury.

Acute kidney injury (AKI) following ischemia-reperfusion injury (IRI) has a high mortality and lacks specific therapies. Here, we report that mice lacking kynurenine 3-monooxygenase (KMO) activity (Kmonull mice) are protected against AKI after renal IRI. We show that KMO is highly expressed in the kidney and exerts major metabolic control over the biologically active kynurenine metabolites 3-hydroxykynurenine, kynurenic acid, and downstream metabolites. In experimental AKI induced by kidney IRI, Kmonull mice had preserved renal function, reduced renal tubular cell injury, and fewer infiltrating neutrophils compared with wild-type (Kmowt) control mice. Together, these data confirm that flux through KMO contributes to AKI after IRI, and supports the rationale for KMO inhibition as a therapeutic strategy to protect against AKI during critical illness.