Single cell regulatory architecture of human pancreatic islets suggests sex differences in β cell function and the pathogenesis of type 2 diabetes

Biological sex affects the pathogenesis of type 2 and type 1 diabetes (T2D, T1D) including the development of β cell failure observed more often in males. The mechanisms that drive sex differences in β cell failure is unknown. Studying sex differences in islet regulation and function represent a unique avenue to understand the sex-specific heterogeneity in β cell failure in diabetes. Here, we examined sex and race differences in human pancreatic islets from up to 52 donors with and without T2D (including 37 donors from the Human Pancreas Analysis Program [HPAP] dataset) using an orthogonal series of experiments including single cell RNA-seq (scRNA-seq), single nucleus assay for transposase-accessible chromatin sequencing (snATAC-seq), dynamic hormone secretion, and bioenergetics. In cultured islets from nondiabetic (ND) donors, in the absence of the in vivo hormonal environment, sex differences in islet cell type gene accessibility and expression predominantly involved sex chromosomes. Of particular interest were sex differences in the X-linked KDM6A and Y-linked KDM5D chromatin remodelers in female and male islet cells respectively. Islets from T2D donors exhibited similar sex differences in differentially expressed genes (DEGs) from sex chromosomes. However, in contrast to islets from ND donors, islets from T2D donors exhibited major sex differences in DEGs from autosomes. Comparing β cells from T2D and ND donors revealed that females had more DEGs from autosomes compared to male β cells. Gene set enrichment analysis of female β cell DEGs showed a suppression of oxidative phosphorylation and electron transport chain pathways, while male β cell had suppressed insulin secretion pathways. Thus, although sex-specific differences in gene accessibility and expression of cultured ND human islets predominantly affect sex chromosome genes, major differences in autosomal gene expression between sexes appear during the transition to T2D and which highlight mitochondrial failure in female β cells.

Dimethyl Sulfoxide as a Novel Therapy in a Murine Model of Acute Lung Injury

INTRODUCTION

The endothelial glycocalyx (EGX) on the luminal surface of endothelial cells contributes to the permeability barrier of the pulmonary vasculature. Dimethyl sulfoxide (DMSO) has a disordering effect on plasma membranes, which prevents the formation of ordered membrane domains important in the shedding of the EGX. We hypothesized that DMSO would protect against protein leak by preserving the EGX in a murine model of acute respiratory distress syndrome (ARDS).

METHODS

C57BL/6 mice were given ARDS via intra-tracheally administered lipopolysaccharide (LPS). DMSO (220 mg/kg) was administered intravenously for 4 days. Animals were sacrificed post-injury day 4 after bronchoalveolar lavage (BAL). BAL cell counts and protein content was quantified. Lung sections were stained with FITC-labelled wheat germ agglutinin (FITC-WGA) to quantify the EGX. Cultured endothelial cells (HUVECs) were exposed to LPS. EGX was measured using FITC-WGA, and co-immunoprecipitation was performed to measure interaction between sheddases and syndecan-1.

RESULTS

DMSO treatment resulted in greater EGX staining intensity in the lung when compared to sham (9,641 vs. 36,659 A.U. p < 0.001). Total BAL cell counts were less for animals receiving DMSO (6.93 x 106 vs. 2.49 x 106 cells, p = 0.04). The treated group had less BAL macrophages (189.2 vs. 76.9 cells, p = 0.02) and lymphocytes (527.7 vs. 200.0 cells, p = 0.02). Interleukin-6 levels were lower in DMSO treated. Animals that received DMSO had less protein leak in BAL (1.48 vs. 1.08 ug/ul, p = 0.02). DMSO prevented LPS-induced EGX loss in HUVECs, and reduced the interaction between Matrix Metalloproteinase (MMP) 16 and syndecan-1.

CONCLUSIONS

Systemically administered DMSO protects the EGX in the pulmonary vasculature, mitigating pulmonary capillary leak after acute lung injury. DMSO also results in decreased inflammatory response. DMSO reduced the interaction between MMP16 and Syndecan-1 and prevented LPS-induced glycocalyx damage in cultured endothelial cells. DMSO may be a novel therapeutic for ARDS.

LEVEL OF EVIDENCE

Not applicable (animal studies).

Dimethyl malonate protects the lung in a murine model of acute respiratory distress syndrome

BACKGROUND

Succinate is a proinflammatory citric acid cycle metabolite that accumulates in tissues during pathophysiological states. Oxidation of succinate after ischemia-reperfusion leads to reversal of the electron transport chain and generation of reactive oxygen species. Dimethyl malonate (DMM) is a competitive inhibitor of succinate dehydrogenase, which has been shown to reduce succinate accumulation. We hypothesized that DMM would protect against inflammation in a murine model of ARDS.

METHODS

C57BL/6 mice were given ARDS via 67.7 μg of intratracheally administered lipopolysaccharide. Dimethyl malonate (50 mg/kg) was administered via tail vein injection 30 minutes after injury, then daily for 3 days. The animals were sacrificed on day 4 after bronchoalveolar lavage (BAL). Bronchoalveolar lavage cell counts were performed to examine cellular influx. Supernatant protein was quantified via Bradford protein assay. Animals receiving DMM (n = 8) were compared with those receiving sham injection (n = 8). Cells were fixed and stained with FITC-labeled wheat germ agglutinin to quantify the endothelial glycocalyx (EGX).

RESULTS

Total cell counts in BAL was less for animals receiving DMM (6.93 × 10 6 vs. 2.46 × 10 6 , p = 0.04). The DMM group had less BAL macrophages (168.6 vs. 85.1, p = 0.04) and lymphocytes (527.7 vs. 248.3; p = 0.04). Dimethyl malonate-treated animals had less protein leak in BAL than sham treated (1.48 vs. 1.15 μg/μl, p = 0.03). Treatment with DMM resulted in greater staining intensity of the EGX in the lung when compared with sham (12,016 vs. 15,186 arbitrary units, p = 0.03). Untreated animals had a greater degree of weight loss than treated animals (3.7% vs. 1.1%, p = 0.04). Dimethyl malonate prevented the upregulation of monocyte chemoattractant protein-1 (1.66 vs. 0.92 RE, p = 0.02) and ICAM-1 (1.40 vs. 1.01 RE, p = 0.05).

CONCLUSION

Dimethyl malonate reduces lung inflammation and capillary leak in ARDS. This may be mediated by protection of the EGX and inhibition of monocyte chemoattractant protein-1 and ICAM-1. Dimethyl malonate may be a novel therapeutic for ARDS.

Succinate metabolism and membrane reorganization drives the endotheliopathy and coagulopathy of traumatic hemorrhage

Acute hemorrhage commonly leads to coagulopathy and organ dysfunction or failure. Recent evidence suggests that damage to the endothelial glycocalyx contributes to these adverse outcomes. The physiological events mediating acute glycocalyx shedding are undefined, however. Here, we show that succinate accumulation within endothelial cells drives glycocalyx degradation through a membrane reorganization-mediated mechanism. We investigated this mechanism in a cultured endothelial cell hypoxia-reoxygenation model, in a rat model of hemorrhage, and in trauma patient plasma samples. We found that succinate metabolism by succinate dehydrogenase mediates glycocalyx damage through lipid oxidation and phospholipase A2-mediated membrane reorganization, promoting the interaction of matrix metalloproteinase 24 (MMP24) and MMP25 with glycocalyx constituents. In a rat hemorrhage model, inhibiting succinate metabolism or membrane reorganization prevented glycocalyx damage and coagulopathy. In patients with trauma, succinate levels were associated with glycocalyx damage and the development of coagulopathy, and the interaction of MMP24 and syndecan-1 was elevated compared to healthy controls.

Architecture of androgen receptor pathways amplifying glucagon-like peptide-1 insulinotropic action in male pancreatic β cells

Male mice lacking the androgen receptor (AR) in pancreatic β cells exhibit blunted glucose-stimulated insulin secretion (GSIS), leading to hyperglycemia. Testosterone activates an extranuclear AR in β cells to amplify glucagon-like peptide-1 (GLP-1) insulinotropic action. Here, we examined the architecture of AR targets that regulate GLP-1 insulinotropic action in male β cells. Testosterone cooperates with GLP-1 to enhance cAMP production at the plasma membrane and endosomes via: (1) increased mitochondrial production of CO2, activating the HCO3--sensitive soluble adenylate cyclase; and (2) increased Gαs recruitment to GLP-1 receptor and AR complexes, activating transmembrane adenylate cyclase. Additionally, testosterone enhances GSIS in human islets via a focal adhesion kinase/SRC/phosphatidylinositol 3-kinase/mammalian target of rapamycin complex 2 actin remodeling cascade. We describe the testosterone-stimulated AR interactome, transcriptome, proteome, and metabolome that contribute to these effects. This study identifies AR genomic and non-genomic actions that enhance GLP-1-stimulated insulin exocytosis in male β cells.

Exosomes and Microvesicles From Adipose-derived Mesenchymal Stem Cells Protects the Endothelial Glycocalyx From LPS Injury

INTRODUCTION

Endothelial glycocalyx damage occurs in numerous pathological conditions and results in endotheliopathy. Extracellular vesicles, including exosomes and microvesicles, isolated from adipose-derived mesenchymal stem cells (ASC) have therapeutic potential in multiple disease states, however, their role in preventing glycocalyx shedding has not been defined. We hypothesized that ASC-derived exosomes and microvesicles would protect the endothelial glycocalyx from damage by LPS injury in cultured endothelial cells.

METHODS

Exosomes and microvesicles were collected from ASC conditioned media by centrifugation (10,000 g for microvesicles, 100,000 g for exosomes). Human umbilical vein endothelial cells (HUVECs) were exposed to 1 μg/mL lipopolysaccharide (LPS). LPS injured cells (n = 578) were compared to HUVECS with concomitant LPS injury plus 1.0 μg/mL of exosomes (n = 540) or microvesicles (n = 510) for 24 hours. These two cohorts were compared to control HUVECs that received phosphate-buffered saline only (n = 786) and HUVECs exposed to exosomes (n = 505) or microvesicles (n = 500) alone. Cells were fixed and stained with FITC-labelled wheat germ agglutinin (WGA) to quantify EGX. Real-time quantitative reverse-transcription polymerase chain reaction were used on HUVECs cell lystate to quantify Hyaluron Synthase-1 (HAS1) expression.

RESULTS

Exosomes alone decreased endothelial glycocalyx staining intensity when compared to control (4.94 vs. 6.41 AU, p < 0.001), while microvesicles did not cause a change glycocalyx staining intensity (6.39 vs. 6.41, p = 0.99). LPS injury resulted in decreased glycocalyx intensity as compared to control (5.60 vs. 6.41, p < 0.001). Exosomes (6.85 vs. 5.60, p < 0.001) and microvesicles (6.35 vs. 5.60, p < 0.001) preserved endothelial glycocalyx staining intensity after LPS injury. HAS1 levels were found to be higher in the exosome (1.14 vs. 3.67 RE, p = 0.02) and microvesicle groups (1.14 vs. 3.59 RE, p = 0.02) when compared to LPS injury. Hyaluron Synthase-2 and -3 expression were not different in the various experimental groups.

CONCLUSIONS

Exosomes alone can damage the endothelial glycocalyx. However, in the presence of LPS injury, both exosomes and microvesicles protect the glycocalyx layer. This effect appears to be mediated by HAS1.

LEVEL OF EVIDENCE

Basic Science study.

Glycocalyx degradation and the endotheliopathy of viral infection

The endothelial glycocalyx (EGX) contributes to the permeability barrier of vessels and regulates the coagulation cascade. EGX damage, which occurs in numerous disease states, including sepsis and trauma, results in endotheliopathy. While influenza and other viral infections are known to cause endothelial dysfunction, their effect on the EGX has not been described. We hypothesized that the H1N1 influenza virus would cause EGX degradation. Human umbilical vein endothelial cells (HUVECs) were exposed to varying multiplicities of infection (MOI) of the H1N1 strain of influenza virus for 24 hours. A dose-dependent effect was examined by using an MOI of 5 (n = 541), 15 (n = 714), 30 (n = 596), and 60 (n = 653) and compared to a control (n = 607). Cells were fixed and stained with FITC-labelled wheat germ agglutinin to quantify EGX. There was no difference in EGX intensity after exposure to H1N1 at an MOI of 5 compared to control (6.20 vs. 6.56 Arbitrary Units (AU), p = 0.50). EGX intensity was decreased at an MOI of 15 compared to control (5.36 vs. 6.56 AU, p<0.001). The degree of EGX degradation was worse at higher doses of the H1N1 virus; however, the decrease in EGX intensity was maximized at an MOI of 30. Injury at MOI of 60 was not worse than MOI of 30. (4.17 vs. 4.47 AU, p = 0.13). The H1N1 virus induces endothelial dysfunction by causing EGX degradation in a dose-dependent fashion. Further studies are needed to characterize the role of this EGX damage in causing clinically significant lung injury during acute viral infection.

Abstract 3530: Microbial-Interleukin 17 receptor A (IL-17RA) signaling axis modulates tumor growth and microenvironment

Microbiota, both within the gut and the tumors, has emerged as a significant player influencing tumor growth and responses to therapies. Recent evidence links microbiota and pancreatic ductal adenocarcinoma (PDAC), an aggressive cancer surrounded by a highly immuno-suppressive tumor microenvironment which limits efficacy of most available therapies. The immunosuppressive tumor microenvironment of PDAC is partially facilitated by a proinflammatory cytokine Interleukin 17 (IL-17). IL-17 can be stimulated by intestinal commensal bacteria under normal physiological conditions. It is critical for microbial defense as well as immunopathology. Both IL-17 neutralization and antibiotics reduce murine PDAC growth. While the vital role of microbiota in affecting tumor immunity has been identified, there is still a gap of knowledge as to how microbes may regulate pro-tumorigenic IL-17 signaling. We wanted to investigate the systemic and local role of IL-17 in regulating the microbial-tumor immune axis. For this purpose, we genetically deleted the IL-17 receptor A (IL-17RA) in different compartments and evaluated tumor growth. We found that IL-17RA signaling was important for maintaining microbial homeostasis and its disruption resulted in differential tumor growth. Absence of IL-17RA signaling in the gut lead to local inflammation as well as systemic immune effects. Our data suggests that modulation of IL-17 signaling could serve as a therapeutic intervention to alter microbial mediated tumor effects. The significance of these findings may extend to other cancers as well.

Citation Format: Vidhi Chandra, Yu Zhang, Olivereen Le Roux, Joseph Petrosino, Jay Kolls, Florencia McAllister. Microbial-Interleukin 17 receptor A (IL-17RA) signaling axis modulates tumor growth and microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3530.

Interferon-γ promotes monocyte-mediated lung injury during influenza infection

Influenza A virus (IAV) infection triggers an exuberant host response that promotes acute lung injury. However, the host response factors that promote the development of a pathologic inflammatory response to IAV remain incompletely understood. In this study, we identify an interferon-γ (IFN-γ)-regulated subset of monocytes, CCR2⁺ monocytes, as a driver of lung damage during IAV infection. IFN-γ regulates the recruitment and inflammatory phenotype of CCR2⁺ monocytes, and mice deficient in CCR2 (CCR2^-/-) or IFN-γ (IFN-γ^-/-) exhibit reduced lung inflammation, pathology, and disease severity. Adoptive transfer of wild-type (WT) (IFN-γR1^+/+) but not IFN-γR1^-/- CCR2⁺ monocytes restore the WT-like pathological phenotype of lung damage in IAV-infected CCR2^-/- mice. CD8⁺ T cells are the main source of IFN-γ in IAV-infected lungs. Collectively, our data highlight the requirement of IFN-γ signaling in the regulation of CCR2⁺ monocyte-mediated lung pathology during IAV infection.

Interleukin-22 mitigates acute respiratory distress syndrome (ARDS)

BACKGROUND

The goal of this study was to determine if IL-22:Fc would Acute Respiratory Distress Syndrome (ARDS).

SUMMARY BACKGROUND DATA

No therapies exist for ARDS and treatment is purely supportive. Interleukin-22 (IL-22) plays an integral component in recovery of the lung from infection. IL-22:Fc is a recombinant protein with a human FC immunoglobulin that increases the half-life of IL-22.

STUDY DESIGN

ARDS was induced in C57BL/6 mice with intra-tracheal lipopolysaccharide (LPS) at a dose of 33.3 or 100 ug. In the low-dose LPS group (LDG), IL-22:FC was administered via tail vein injection at 30 minutes (n = 9) and compared to sham (n = 9). In the high-dose LPS group (HDG), IL-22:FC was administered (n = 11) then compared to sham (n = 8). Euthanasia occurred after bronchioalveolar lavage (BAL) on post-injury day 4.

RESULTS

In the LDG, IL-22:FC resulted in decreased protein leak (0.15 vs. 0.25 ug/uL, p = 0.02). BAL protein in animals receiving IL-22:Fc in the HDG was not different. For the HDG, animals receiving IL-22:Fc had lower BAL cell counts (539,636 vs 3,147,556 cells/uL, p = 0.02). For the HDG, IL-6 (110.6 vs. 527.1 pg/mL, p = 0.04), TNF-α (5.87 vs. 25.41 pg/mL, p = 0.04), and G-CSF (95.14 vs. 659.6, p = 0.01) levels were lower in the BAL fluid of IL-22:Fc treated animals compared to sham.

CONCLUSIONS

IL-22:Fc decreases lung inflammation and lung capillary leak in ARDS. IL-22:Fc may be a novel therapy for ARDS.

Surgical stabilization of traumatic rib fractures is associated with reduced readmissions and increased survival

BACKGROUND

Surgical stabilization for rib fractures (SSRF) in trauma patients remains controversial, with guidelines currently suggesting the procedure for only select patient groups. How surgical stabilization for rib fractures affect hospital readmission in patients with traumatic rib fractures is unknown. We hypothesized that surgical stabilization for rib fractures would not decrease the risk of readmission.

METHODS

The National Readmission Database was examined for adults with any rib fractures from 2010 to 2017. Readmission up to 90 days was examined. Patients receiving surgical stabilization for rib fractures were compared with those receiving nonoperative treatment.

RESULTS

In total, 864,485 patients met criteria, with 13,701 (1.6%) receiving SSRF. For patients receiving SSRF, 338 (1.5%) were readmitted. Readmitted patients had higher Charlson Comorbidity Index and were more likely to have flail chest. On multivariate propensity score-matched analysis, SSRF (Hazard Ratio [HR]: 0.55, 95% confidence interval [CI] 0.33-0.92, P = .022) was associated with reduced readmission. Addition of surgical stabilization for rib fractures to video-assisted thoracoscopic surgery (VATS) (Odds Ratio [OR]: 0.95, 95% CI 0.52-1.73, P = .86) or thoracotomy (OR: 1.97, 95% CI 0.83-4.70, P = .13) was not associated with increased readmission. On further propensity matched analysis, VATS + SSRF when compared with SSRF alone (HR: 0.75, 95% CI 0.18-3.20, P = .696), and VATS + SSRF when compared with VATS alone (HR: 0.49, 95% CI 0.11-2.22, P = .355) was also not associated with increased readmission. SSRF on primary admission was associated with increased in-hospital survival (HR: 0.27, 95% CI 0.22-0.32, P < .001). For patients with retained hemothorax who underwent VATS, addition of SSRF did not improve survival (HR = 0.92, 95% CI 0.58-1.46, P = .72). However, for patients requiring thoracotomy for retained hemothorax, concomitant SSRF was associated with improved survival (HR = 0.14, 95% CI 0.06-0.32, P < .001).

CONCLUSION

Surgical stabilization for rib fractures is associated with reduced readmission risk while also being associated with improved survival. Patients who had a thoracotomy for retained hemothorax appear to especially benefit from concomitant surgical stabilization for rib fractures.

Systemic overexpression of interleukin-22 induces the negative immune-regulator SOCS3 and potently reduces experimental arthritis in mice

OBJECTIVE

High levels of IL-22 are present in serum and synovial fluid of patients with RA. As both pro- and anti-inflammatory roles for IL-22 have been described in studies using animal models of RA, its exact function in arthritis remains poorly defined. With this study we aimed to further unravel the mechanism by which IL-22 exerts its effects and to decipher its therapeutic potential by overexpression of IL-22 either locally or systemically during experimental arthritis.

METHODS

CIA was induced in DBA-1 mice by immunization and booster injection with type II collagen (col II). Before arthritis onset, IL-22 was overexpressed either locally by intra-articular injection or systemically by i.v. injection using an adenoviral vector and clinical arthritis was scored for a period of 10 days. Subsequently, joints were isolated for histological analysis of arthritis severity and mRNA and protein expression of various inflammatory mediators was determined in the synovium, spleen and serum.

RESULTS

Local IL-22 overexpression did not alter arthritis pathology, whereas systemic overexpression of IL-22 potently reduced disease incidence, severity and pathology during CIA. Mice systemically overexpressing IL-22 showed strongly reduced serum cytokine levels of TNF-α and macrophage inflammatory protein 1α that correlated significantly with the enhanced expression of the negative immune regulator SOCS3 in the spleen.

CONCLUSION

With this study, we revealed clear anti-inflammatory effects of systemic IL-22 overexpression during CIA. Additionally, we are the first to show that the protective effect of systemic IL-22 during experimental arthritis is likely orchestrated via upregulation of the negative regulator SOCS3.

A Comparison of Growth Factors and Cytokines in Fresh Frozen Plasma and Never Frozen Plasma

BACKGROUND

Fresh frozen plasma (FFP) contains proinflammatory mediators released from cellular debris during frozen storage. In addition, recent studies have shown that transfusion of never-frozen plasma (NFP), instead of FFP, may be superior in trauma patients. We hypothesized that FFP would have higher levels of inflammatory mediators when compared to NFP.

MATERIALS AND METHODS

FFP (n = 8) and NFP (n = 8) samples were obtained from an urban, level 1 trauma center blood bank. The cytokines in these samples were compared using a Milliplex (Milliplex Sigma) human cytokine magnetic bead panel multiplex assay for 41 different biomarkers.

RESULTS

Growth factors that were higher in NFP included platelet-derived growth factor-AA (PDGF-AA; 8.09 versus 108.00 pg/mL, P < 0.001) and PDGF-AB (0.00 versus 215.20, P= 0.004). Soluble CD40-ligand (sCD40L), a platelet activator and pro-coagulant, was higher in NFP (31.81 versus 80.45 pg/mL, P< 0.001). RANTES, a leukocyte chemotactic cytokine was higher in NFP (26.19 versus 1418.00 pg/mL, P< 0.001). Interleukin-4 (5.70 versus 0.00 pg/mL, P= 0.03) and IL-8 (2.20 versus 0.52 pg/ml, P= 0.03) levels were higher in were higher in FFP.

CONCLUSIONS

Frozen storage of plasma may result in decrease of several growth factors and/or pro-coagulants found in NFP. In addition, the freezing and thawing process may induce release of pro-inflammatory chemokines. Further studies are needed to determine if these cytokines result in improved outcomes with NFP over FFP in transfusion of trauma patients.

Interleukin 22 mitigates endothelial glycocalyx shedding after lipopolysaccharide injury

BACKGROUND

The endothelial glycocalyx (EG) on the luminal surface of endothelial cells contributes to the permeability barrier of vessels and prevents activation of the coagulation cascade. Endothelial glycocalyx damage, which occurs in the shock state, results in endotheliopathy. Interleukin (IL)-22 is a cytokine with both proinflammatory and anti-inflammatory properties, and how IL-22 affects the EG has not been studied. We hypothesized that IL-22:Fc, a recombinant fusion protein with human IL-22 and the Fc portion of human immunoglobulin G1 (which extends the protein half-life), would not affect EG shedding in endothelium after injury.

METHODS

Human umbilical vein endothelial cells (HUVECs) were exposed to 1 μg/mL lipopolysaccharide (LPS). Lipopolysaccharide-injured cells (n = 284) were compared with HUVECs with LPS injury plus 0.375 μg/mL of IL-22:Fc treatment (n = 293) for 12 hours. These two cohorts were compared with control HUVECs (n = 286) and HUVECs exposed to IL-22:Fc alone (n = 269). Cells were fixed and stained with fluorescein isothiocyanate-labeled wheat germ agglutinin to quantify EG. Total RNA was collected, and select messenger RNAs were quantified by real time - quantitative polymerase chain reaction (RT-qPCR) using SYBR green fluorescence.

RESULTS

Exposure of HUVECs to LPS resulted in degradation of the EG compared with control (5.86 vs. 6.09 arbitrary unit [AU], p = 0.01). Interleukin-22:Fc alone also resulted in degradation of EG (5.08 vs. 6.09 AU, p = 0.01). Treatment with IL-22:Fc after LPS injury resulted in less degradation of EG compared with LPS injury alone (5.86 vs. 5.08 AU, p = 0.002). Expression of the IL-22Ra1 receptor was not different for IL-22:Fc treated compared with LPS injury only (0.69 vs. 0.86 relative expression, p = 0.10). Treatment with IL-22:Fc after LPS injury resulted in less matrix metalloproteinase 2 (0.79 vs. 1.70 relative expression, p = 0.005) and matrix metalloproteinase 14 (0.94 vs. 2.04 relative expression, p = 0.02).

CONCLUSIONS

Interleukin-22:Fc alone induces EG degradation. However, IL-22:Fc treatment after LPS injury appears to mitigate EG degradation. This protective effect appears to be mediated via reduced expression of metalloproteinases.

Surgical stabilization of rib fractures is associated with improved survival but increased acute respiratory distress syndrome

Background

How the surgical stabilization of rib fractures after trauma affects the development of acute respiratory distress syndrome and impacts survival has yet to be determined in a large database. We hypothesized that surgical stabilization of rib fractures would not decrease the incidence of acute respiratory distress syndrome.

Methods

The National Trauma Data Bank was queried for all traumatic rib fractures in 2016. Patients were divided into groups with single rib fractures, multiple rib fractures, and flail chest. Nonoperative therapy was compared with stabilization of rib fractures of 1 to 2 ribs or 3+ ribs.

Results

There were 114,972 total patients with rib fractures meeting inclusion criteria, with 5,106 (4.4%) having flail chest, 24,726 (21.5%) having single rib fractures, and 85,140 (74.1%) having multiple rib fractures. Those with flail chest (15.9%) were most likely to get rib plating in comparison to multiple rib fractures (0.9%) and single rib fractures (0.2%); P < .001. On logistic regression, surgical stabilization of rib fractures 1 to 2 ribs (odds ratio: 0.17, 95% confidence interval: 0.10–0.28) or 3+ ribs (odds ratio: 0.17, 95% confidence interval: 0.11–0.28), with nonoperative therapy as the reference was associated with survival. Variables associated with mortality included increasing age, male sex, increasing injury severity score, decreased Glasgow coma scale, requirement of transfusions, and hypotension on admission. Surgical stabilization of rib fractures 3+ ribs (odds ratio: 2.30, 95% confidence interval: 1.58–3.37) was associated with acute respiratory distress syndrome but not 1 to 2 ribs (odd ratio: 1.55, 95% confidence interval: 0.97–2.48). On logistic regression of only patients with flail chest, stabilization of rib fractures was associated with decreased mortality but not increased risk of acute respiratory distress syndrome.

Conclusion

The increased risk of acute respiratory distress syndrome should be considered in the preoperative assessment for stabilization of rib fractures.

The Integrin Binding Peptide, ATN-161, as a Novel Therapy for SARS-CoV-2 Infection

Many efforts to design and screen therapeutics for severe acute respiratory syndrome coronavirus (SARS-CoV-2) have focused on inhibiting viral cell entry by disrupting ACE2 binding with the SARS-CoV-2 spike protein. This work focuses on inhibiting SARS-CoV-2 entry through a hypothesized α5β1 integrin-based mechanism, and indicates that inhibiting the spike protein interaction with α5β1 integrin (+/- ACE2), and the interaction between α5β1 integrin and ACE2 using a molecule ATN-161 represents a promising approach to treat COVID-19.

Biomarkers that differentiate false positive urinalyses from true urinary tract infection

BACKGROUND

The specificity of the leukocyte esterase test (87%) is suboptimal. The objective of this study was to identify more specific screening tests that could reduce the number of children who unnecessarily receive antimicrobials to treat a presumed urinary tract infection (UTI).

METHODS

Prospective cross-sectional study to compare inflammatory proteins in blood and urine samples collected at the time of a presumptive diagnosis of UTI. We also evaluated serum RNA expression in a subset.

RESULTS

We enrolled 200 children; of these, 89 were later demonstrated not to have a UTI based on the results of the urine culture obtained. Urinary proteins that best discriminated between children with UTI and no UTI were involved in T cell response proliferation (IL-9, IL-2), chemoattractants (CXCL12, CXCL1, CXCL8), the cytokine/interferon pathway (IL-13, IL-2, INFγ), or involved in innate immunity (NGAL). The predictive power (as measured by the area under the curve) of a combination of four urinary markers (IL-2, IL-9, IL-8, and NGAL) was 0.94. Genes in the pathways related to inflammation were also upregulated in serum of children with UTI.

CONCLUSIONS

Urinary proteins involved in the inflammatory response may be useful in identifying children with false positive results with current screening tests for UTI; this may reduce unnecessary treatment.

Host and Bacterial Markers that Differ in Children with Cystitis and Pyelonephritis

OBJECTIVE

To determine whether treatment for urinary tract infections in children could be individualized using biomarkers for acute pyelonephritis.

STUDY DESIGN

We enrolled 61 children with febrile urinary tract infections, collected blood and urine samples, and performed a renal scan within 2 weeks of diagnosis to identify those with pyelonephritis. Renal scans were interpreted centrally by 2 experts. We measured inflammatory proteins in blood and urine using LUMINEX or an enzyme-linked immunosorbent assay. We evaluated serum RNA expression using RNA sequencing in a subset of children. Finally, for children with Escherichia coli isolated from urine cultures, we performed a polymerase chain reaction for 4 previously identified virulence genes.

RESULTS

Urinary markers that best differentiated pyelonephritis from cystitis included chemokine (C-X-C motif) ligand (CXCL)1, CXCL9, CXCL12, C-C motif chemokine ligand 2, INF γ, and IL-15. Serum procalcitonin was the best serum marker for pyelonephritis. Genes in the interferon-γ pathway were upregulated in serum of children with pyelonephritis. The presence of E coli virulence genes did not correlate with pyelonephritis.

CONCLUSIONS

Immune response to pyelonephritis and cystitis differs quantitatively and qualitatively; this may be useful in differentiating these 2 conditions.

Defining the dynamic chromatin landscape of mouse nephron progenitors

Six2⁺ cap mesenchyme cells, also called nephron progenitor cells (NPC), are precursors of all epithelial cell types of the nephron, the filtering unit of the kidney. Current evidence indicates that perinatal ‘old’ NPC have a greater tendency to exit the progenitor niche and differentiate into nascent nephrons than their embryonic ‘young’ counterpart. Understanding the underpinnings of NPC development may offer insights to rejuvenate old NPC and expand the progenitor pool. Here, we compared the chromatin landscape of young and old NPC and found common features reflecting their shared lineage but also intrinsic differences in chromatin accessibility and enhancer landscape supporting the view that old NPC are epigenetically poised for differentiation. Annotation of open chromatin regions and active enhancers uncovered the transcription factor Bach2 as a potential link between the pro-renewal MAPK/AP1 and pro-differentiation Six2/b-catenin pathways that might be of critical importance in regulation of NPC fate. Our data provide the first glimpse of the dynamic chromatin landscape of NPC and serve as a platform for future studies of the impact of genetic or environmental perturbations on the epigenome of NPC.

Summary: An investigation of the chromatin landscape of mouse nephron progenitors across their life span supports the view that old nephron progenitors are epigenetically poised for differentiation.

Nrf2 selectively regulates IL-22 and IL-17A production in Th17 cells

Th17 cell-derived IL-17A and IL-22 are critical for mounting both inflammatory and tissue protective responses. It remains unclear whether cytokine responses can be modified differently to achieve targeted functional outcome. A therapeutic strategy which inhibits CD4+ T cell-derived inflammatory IL-17A responses but concomitantly promotes IL-22-dependent tissue protective or regenerative response is of great clinical significance.

Here, we showed that nuclear factor (erythroid-derived 2)-like 2 (Nrf2) selectively regulated IL-17A and IL-22 responses in CD4+ T cells. We found that Nrf2−/− mice had reduced IL-22 responses in Ovaalbumin (Ova) + LPS and separately concanavalin A (Con A) administered mice. Furthermore, CDDO-Im, a selective Nrf2 activator, induced IL-22 but suppressed IL-17A response in CD4+ T cells polarized under Th17 cell condition. Our qPCR data revealed that CDDO-Im-activated CD4+ T cells had lower Rorc, but increased Cybb, Sod1 and Sod3 transcript. The expression pattern of Il23r and Sod2 was unaltered. CDDO-Im-dependent IL-17A but not IL-22 response was regulated by Sod3. Interestingly, we found that CDDO-Im induced aryl hydrocarbon receptor (Ahr) and its downstream Cyp1a1 and Cyp1b1 gene expression. The luciferase reporter assay data showed that CDDO-Im regulated Ahr promoter activity in a dose-dependent manner. Additionally, CDDO-Im induced Nqo1 expression, a Nrf2-activated gene, in WT mice but not in Ahr−/− mice. Finally, we confirmed that the CDDO-Immediated induction of IL-22 production in CD4+ T cells was abrogated in Ahr−/− mice.

Collectively, our data show that Nrf2 promotes IL-22 production while it inhibits IL-17A expression in Th17 cells.

IL-17 receptor and IL-22 receptor signaling in Citrrobacter rodentium infection

Th17 cells producing cytokines, IL-17A and IL-22 are important key player in host defense. We have reported that intestinal epithelial expression of IL-17 receptors in gut epithelial cells control the development of microbiota. To study the roles of these receptors in response to an attaching and effacing pathogen we challenged Citobacter rodenium (C. rodentium) to intestinal epithelial specific IL-17RA or IL-22RA1 KO mice. Conditional deletion of Il17ra or Il22ra1 resulted in increased bacterial growth in the colon as well as enhanced dissemination to the spleen. It suggested both cytokine receptors are required for control of this infection. In addition this was supported by unbiased RNAseq analysis of the colonic epithelium that showed diminished expression of Pigr, Duox2 and Duoxa2 in the absence of IL-17RA signaling and reduced Bcl3 expression in the absence of IL-22ra1 expression. To elucidate whether production from epithelial cells effect bacteria killing we cultured crypt and stimulated IL-17A. It resulted in increasing Pigr, Duoxa2 and Duox2 were associated with increasing bacteria killing. Pigr binds dimeric IgA and translocation into lumen from lamina propria, while Duox2 and Duoxa2 make complex and produce hydrogen peroxide into lumen from apical epithelial cell membrane. These result suggested mucosal immunity to C. rodentium requires both IL-17RA and IL-22ra1 signaling and that IL-17RA regulates transcytosis of C. rodentium specific IgA as well as luminal hydrogen peroxide concentrations to control bacterial growth. In contrast, Il-22Ra1 regulates epithelial Bcl3 expression, which restrains TNFα and NF-κB signaling in the colonic epithelium.

Ex vivo lung perfusion as a human platform for preclinical small molecule testing

The acute respiratory distress syndrome (ARDS) causes an estimated 70,000 US deaths annually. Multiple pharmacologic interventions for ARDS have been tested and failed. An unmet need is a suitable laboratory human model to predictively assess emerging therapeutics on organ function in ARDS. We previously demonstrated that the small molecule BC1215 blocks actions of a proinflammatory E3 ligase-associated protein, FBXO3, to suppress NF-κB signaling in animal models of lung injury. Ex vivo lung perfusion (EVLP) is a clinical technique that maintains lung function for possible transplant after organ donation. We used human lungs unacceptable for transplant to model endotoxemic injury with EVLP for 6 hours. LPS infusion induced inflammatory injury with impaired oxygenation of pulmonary venous circulation. BC1215 treatment after LPS rescued oxygenation and decreased inflammatory cytokines in bronchoalveolar lavage. RNA sequencing transcriptomics from biopsies taken during EVLP revealed robust inflammatory gene induction by LPS with a strong signal for NF-κB-associated transcripts. BC1215 treatment reduced the LPS induction of genes associated with inflammatory and host defense gene responses by Gene Ontology (GOterm) and pathways analysis. BC1215 also significantly antagonized LPS-mediated NF-κB activity. EVLP may provide a unique human platform for preclinical study of chemical entities such as FBXO3 inhibitors on tissue physiology.

Update on regulation and effector functions of Th17 cells

T-helper cells that produce IL-17 are recognized as a significant subset within cell-mediated adaptive immunity. These cells are implicated in both the pathology of inflammatory disorders as well as the clearance of extracellular infections and the maintenance of the microbiota. However, the dynamic nature of this cell type has created controversy in understanding Th17 induction as well as Th17 phenotyping, since these cells may switch from Th17 to Treg or Th17 to Th1 cytokine profiles under certain conditions. This review highlights recent advances in Th17 cells in understanding their role in commensal regulation, sex difference in immune outcomes and the immunology of pregnancy, as well as inventive experimental models that have allowed for an increased understanding of Th17 regulation and induction.

Murine models of Pneumocystis infection recapitulate human primary immune disorders

Despite the discovery of key pattern recognition receptors and CD4+ T-cell subsets in laboratory mice, there is ongoing discussion of the value of murine models to reflect human disease. We recognize a strong parallel between human and mouse CD4+ T-cell immunity using the hallmark example of CD4+ T-cell dependent immunity, Pneumocystis pneumonia. Pneumocystis jirovecii infection was the first AIDS-defining illness and most closely tied with peripheral CD4+ T-cell counts. Due to successful control of HIV, the epidemiology of Pneumocystis infection in children is now primarily due to primary human immunodeficiencies and immunosuppressive therapies. To this end, we found that every human genetic immunodeficiency associated with Pneumocystis infection, recapitulated susceptibility in Pneumocystis infection in mice bearing similar mutations. Similar to human IL-21R deficiency, we found that IL-21R and CD4+ T-cell STAT3 signaling were required for both protective anti-fungal class-switched antibody responses and CD4+ effector T-cell mediated protection. Furthermore, we discerned that CD4+ T-cell intrinsic IL-21R/STAT3 signaling was required for inducing a Pneumocystis-specific IL-22 response, and that IL-22 inhibited trophozoite binding to alveolar epithelial cells. Moreover, recombinant IL-22 administration to Il21r−/− mice induced the expression of a fungicidal peptide, cathelicidin anti-microbial peptide which showed in vitro fungicidal activity. In conclusion, SPF laboratory mice faithfully replicate many aspects of human primary immunodeficiency and provide useful tools to understand the generation and nature of effector CD4+ T-cell immunity.

The Kallikrein-kinin system: a novel player of IL-17-driven anti-Candida immune response in the Kidney

Disseminated candidiasis is the fourth most common hospital acquired infection and is associated with a 40–60% mortality rate. During disseminated candidiasis, Candida albicans form invasive hyphae that damage kidney, leading to renal failure. Treatment of candidiasis is hindered by drug toxicity, the development of antifungal drug resistance and lack of vaccines against fungal pathogens. Previous studies have identified a key role of interleukin-17 (IL-17) in controlling systemic infection. The mechanisms of IL-17-mediated renal immunity have so far been assumed to occur solely through the regulation of antimicrobial mechanisms. Here, we discovered an unanticipated role for IL-17 in inducing the Kallikrein (Klk)-Kinin System (KKS) in the infected kidney, and we show that the KKS provides significant renal protection in candidiasis. Consequently, overexpression of Klk1 or treatment with bradykinin rescued IL-17RA−/− mice from candidiasis. Therapeutic manipulation of IL-17-KKS pathways restored renal function and prolonged survival by preventing apoptosis of renal cells following disseminated infection. Moreover, combining a minimally effective dose of fluconazole with bradykinin strikingly improved survival compared to either drug alone. These findings have potential translational significance, as agonists of the KKS are in routine clinical use. Therefore, these results not only identify downstream mediators that could serve as novel drug targets, but could possibly be used to guide decisions on whether targeting these mediators could be a useful therapeutic option in conjunction with current antifungal drugs.

Mesenchymal stem cells use extracellular vesicles to outsource mitophagy and shuttle microRNAs

Mesenchymal stem cells (MSCs) and macrophages are fundamental components of the stem cell niche and function coordinately to regulate haematopoietic stem cell self-renewal and mobilization. Recent studies indicate that mitophagy and healthy mitochondrial function are critical to the survival of stem cells, but how these processes are regulated in MSCs is unknown. Here we show that MSCs manage intracellular oxidative stress by targeting depolarized mitochondria to the plasma membrane via arrestin domain-containing protein 1-mediated microvesicles. The vesicles are then engulfed and re-utilized via a process involving fusion by macrophages, resulting in enhanced bioenergetics. Furthermore, we show that MSCs simultaneously shed micro RNA-containing exosomes that inhibit macrophage activation by suppressing Toll-like receptor signalling, thereby de-sensitizing macrophages to the ingested mitochondria. Collectively, these studies mechanistically link mitophagy and MSC survival with macrophage function, thereby providing a physiologically relevant context for the innate immunomodulatory activity of MSCs.

High IFN-γ and low SLPI mark severe asthma in mice and humans

Severe asthma (SA) is a challenge to control, as patients are not responsive to high doses of systemic corticosteroids (CS). In contrast, mild-moderate asthma (MMA) is responsive to low doses of inhaled CS, indicating that Th2 cells, which are dominant in MMA, do not solely orchestrate SA development. Here, we analyzed broncholalveolar lavage cells isolated from MMA and SA patients and determined that IFN-γ (Th1) immune responses are exacerbated in the airways of individuals with SA, with reduced Th2 and IL-17 responses. We developed a protocol that recapitulates the complex immune response of human SA, including the poor response to CS, in a murine model. Compared with WT animals, Ifng-/- mice subjected to this SA model failed to mount airway hyperresponsiveness (AHR) without appreciable effect on airway inflammation. Conversely, AHR was not reduced in Il17ra-/- mice, although airway inflammation was lower. Computer-assisted pathway analysis tools linked IFN-γ to secretory leukocyte protease inhibitor (SLPI), which is expressed by airway epithelial cells, and IFN-γ inversely correlated with SLPI expression in SA patients and the mouse model. In mice subjected to our SA model, forced SLPI expression decreased AHR in the absence of CS, and it was further reduced when SLPI was combined with CS. Our study identifies a distinct immune response in SA characterized by a dysregulated IFN-γ/SLPI axis that affects lung function.

IL-22 reduces the pulmonary injury and lethality of influenza infection (CCR4P.201)

Influenza A hospitalization and mortality are often due to fulminant inflammation/acute respiratory failure (ARDS) or the development of secondary bacterial infections. Epithelial injury is a critical component of ARDS, thus identifying ways to attenuate inflammation while promoting epithelial integrity are vital in improving recovery after infection. We have identified IL-22 as an epithelial specific cytokine that is integral in lung epithelial repair, leading us to hypothesize that IL-22 has therapeutic potential during Influenza infection. To test this, mice infected with an LD90 or LD50 dose of H1N1(PR8/8/34) were treated with IL-22:Fc. While IL-22 treatment did not reduce viral load, It caused a significant reduction in inflammartion, neutrophilia, and lung leak. Importantly, this led to improved health outcomes (reduced weight loss, greater activity scores) and decreased mortality. This effect was specific to the IL-22Ra1 signaling as EIIa-cre x IL-22Ra1fl/fl mice (a global receptor knockout) were non-responsive to IL-22 treatment. Further, we believe IL-22Ra1 signaling is critical in the lung, as albumin-cre X IL-22Ra1fl/fl mice (liver specific) did not have reduced lung pathology with IL-22:Fc treatment. Taken together these data lead us to believe IL-22 is an important cytokine for improving recovery after influenza infection. We are currently working to identify the mechanisms and key IL-22ra1+ cells required for the therapeutic efficacy of IL-22.

MCPIP1/Regnase is a negative feedback inhibitor of IL-17-mediated signaling and inflammation (CCR3P.200)

IL-17 came to prominence with the discovery of Th17 cells. IL-17 induces inflammatory pathology in autoimmunity and certain infections, and thus constraint of this pathway is an essential part of its regulation. However, to date our understanding of IL-17 signaling checkpoints remains quite limited. Here, we identify MCPIP1 (Regnase-1, Zc3h12a) as a novel negative feedback inhibitor of IL-17 signaling. IL-17 treatment of fibroblasts stimulated increased MCPIP1 expression, whereas MCPIP1 silencing enhanced IL-17-mediated signal transduction. Conversely, reconstitution of MCPIP1-/- cells restricted IL-17 signaling, which was dependent on the MCPIP1 endonuclease domain, not its deubiquitinase domain. In vivo, MCPIP1 deficiency enhanced IL-17-dependent autoimmunity and host resistance to infection. Namely, susceptibility to candidiasis was reduced in MCPIP1 haploinsufficient mice, whereas IL-17-dependent pathology in EAE and pulmonary inflammation was enhanced. In addition to its well-documented capacity to degrade cytokine mRNA transcripts such as Il6, we found that MCPIP1 regulates some, though not all, IL-17-dependent promoters. In addition, we identified a novel function for MCPIP1 in mediating decay of mRNA transcripts encoding inflammatory receptors, including IL-17R subunits, in a manner independent of their 3’ UTR elements. This is the first demonstration that MCPIP1 restricts IL-17R signal transduction, and that this enzyme regulates inflammatory receptor expression.

The iron sequestering protein Lipocalin 2 is critical to IL-33-exposed dendritic cell stimulation of Th2 responses and allergic airway disease (IRC7P.424)

IL-33 is an IL-1 cytokine with emerging pleotropic functions, but ascribed a prominent role in Type 2-mediated responses to pathogens due to its capacity to generate and support T helper type 2 (Th2) cells. Likewise, IL-33 and Th2 cell are viewed as dominant drivers of inflammatory lung disorders, including asthma. Previous studies have revealed that IL-33 stimulates the capacity of dendritic cells (DC) to initiate Th2 responses and, thus instigate allergic airway disease (AAD) in mice. However, the precise mechanisms by which IL-33 promotes DC-mediated Th2 polarization was not known. To answer this question, we preformed microarray analysis on DC after exposure to IL-33. This analysis identified multiple genes involved in iron homeostasis and metabolism upregulated by IL-33. The most dramatically increase gene in DC by IL-33 was Lipocalin 2 (Lcn2), an iron sequestering protein that facilitates DC iron uptake. After IL-33-exposure, DC deficient in Lcn2 displayed a significantly reduced capacity to generate Th2 responses, however, LPS-exposed DC lacking Lcn2 were fully capable of Th1 polarization. Identical finding were observed when DC iron uptake was blocked through chelation during their exposure to IL-33. In a DC-induced model of AAD, blocking DC iron uptake resulted in significantly decreased disease severity. These data define a novel role for IL-33-stimulated iron uptake by Lcn2 in the generation of Th2 responses.

Recombinant outer membrane protein: a potential candidate for Th17 based vaccine against Klebsiella pneumonia (VAC4P.1066)

Bacterial pneumonia is a leading cause of mortality and one major pathogen associated with this disease is Klebsiella pneumoniae (KP). Recently, the emergence of antibiotic resistant strains demands an effective vaccine against these bacteria. We have previously shown that intranasal immunization with heat-killed KP or crude outer membrane proteins (OMPs) isolated from KP induced antigen specific Th17 responses and these Th17 cells conferred serotype independent protection against various clinical isolates of K. pneumoniae including the recently described multidrug resistant New Delhi Metallo-beta-lactamase-1 strain. To develop a clinically relevant vaccine, we cloned individual OMPs from K. pneumoniae and successfully expressed OmpX in the BL21 E. coli. The purified recombinant OmpX was recognized by KP immune serum by direct ELISA and also recognized by Th17 cells from KP immunized mice. In vivo, intranasal immunization of the purified OmpX induced robust mucosal Th17 responses and left IL-17 producing gamma-delta T cells unaffected. In combination with a mucosal adjuvant, both intranasal and intramuscular immunization provided serotype independent protection against live bacterial challenge. Taken together, these data demonstrated that OMPs serves as an excellent candidate for the development of clinical relevant vaccines against K. penumoniae especially the newly emerged antibiotic-resistant strains that impose great threat to the public health.

CD4 signaling and Pneumocystis clearance: a critical role of IL-21R and STAT3 for effector function (MPF2P.745)

Pneumocystis jirovecii is an opportunist infection that is a significant cause of disease in immunocompromised patients. Patients whose blood CD4 counts drop below 200 cell/μl due to HIV infection or immunosuppressive therapies are at high risk of developing Pneumocystis jirovecii pneumonia (PJP). However, the exact role of CD4 cells and the specific effector subtype that is required for clearance has yet to be determined. We investigated this question with several cytokine and STAT knock out mice using both in vivo infection as well as the assessment of effector CD4+ T-cell function by adoptive transfer into Pneumocystis infected Rag1-/- mice. We observe that classical Th1, Th2, Th17, and Tfh cell effector functions are dispensable for organism clearance. However we found an essential role for both IL21 receptor signaling on CD4 cells as well as CD4+ T-cell intrinsic STAT3 activation are required for clearance. These data are consistent with the recent identification of human IL21R deficiency and susceptibility to PJP. We are currently examining potential novel downstream mechanisms that may mediate immunity against Pneumocystis pneumonia in this context.

The role of IL-22 signaling in the pathogenesis of necrotizing enterocolitis (HUM1P.314)

Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in premature infants and the specific molecular mechanisms responsible for NEC development remain unclear. NEC is characterized by intestinal epithelial barrier disruption and impaired mucosal healing. Recent evidence suggests a critical role for IL-22 in the regulation of intestinal epithelial barrier integrity and gut inflammation in inflammatory bowel disease. Thus, we hypothesized that IL-22 signaling plays an important role in NEC pathogenesis. To test this, we subjected wild type and IL-22Ra1 intestinal specific knock out mice (villin-cre X IL22ra1fl/fl) to an experimental model of NEC using gavage formula feeds and intermittent hypoxia. NEC severity was assessed by intestinal mucosal cytokines and a NEC severity score assigned by a blinded pathologist. We discovered the IL-22Ra1 intestinal specific knock out mice demonstrated earlier NEC-related mortality than WT mice. Further, histology on the IL-22Ra1 intestinal specific knock out mice demonstrated disruption in the intestinal mucosal architecture and upregulation of pro-inflammatory cytokines. Taken together, these data suggest that IL-22 signaling may play an important role in attenuating the immune response in NEC pathogenesis. These findings raise the possibility for novel therapeutic approaches in the management of this devastating disease by exploring the efficacy of IL-22 treatment for NEC and the mechanisms involved.

Liver is the major source of elevated serum lipocalin-2 levels after bacterial infection or partial hepatectomy: a critical role for IL-6/STAT3

Lipocalin-2 (LCN2) was originally isolated from human neutrophils and termed neutrophil gelatinase-associated lipocalin (NGAL). However, the functions of LCN2 and the cell types that are primarily responsible for LCN2 production remain unclear. To address these issues, hepatocyte-specific Lcn2 knockout (Lcn2(Hep-/-)) mice were generated and subjected to bacterial infection (with Klesbsiella pneumoniae or Escherichia coli) or partial hepatectomy (PHx). Studies of Lcn2(Hep-/-) mice revealed that hepatocytes contributed to 25% of the low basal serum level of LCN2 protein (∼ 62 ng/mL) but were responsible for more than 90% of the highly elevated serum LCN2 protein level (∼ 6,000 ng/mL) postinfection and more than 60% post-PHx (∼ 700 ng/mL). Interestingly, both Lcn2(Hep-/-) and global Lcn2 knockout (Lcn2(-/-)) mice demonstrated comparable increases in susceptibility to infection with K. pneumoniae or E. coli. These mice also had increased enteric bacterial translocation from the gut to the mesenteric lymph nodes and exhibited reduced liver regeneration after PHx. Treatment with interleukin (IL)-6 stimulated hepatocytes to produce LCN2 in vitro and in vivo. Hepatocyte-specific ablation of the IL-6 receptor or Stat3, a major downstream effector of IL-6, markedly abrogated LCN2 elevation in vivo. Furthermore, chromatin immunoprecipitation (ChIP) assay revealed that STAT3 was recruited to the promoter region of the Lcn2 gene upon STAT3 activation by IL-6.

CONCLUSION

Hepatocytes are the major cell type responsible for LCN2 production after bacterial infection or PHx, and this response is dependent on IL-6 activation of the STAT3 signaling pathway. Thus, hepatocyte-derived LCN2 plays an important role in inhibiting bacterial infection and promoting liver regeneration.

AIDS-related mycoses: the way forward

The contribution of fungal infections to the morbidity and mortality of HIV-infected individuals is largely unrecognized. A recent meeting highlighted several priorities that need to be urgently addressed, including improved epidemiological surveillance, increased availability of existing diagnostics and drugs, more training in the field of medical mycology, and better funding for research and provision of treatment, particularly in developing countries.

Recombinant outer membrane protein: a potential candidate for Th17 based vaccine against Klebsiella pneumoniae. (VAC7P.967)

Bacterial pneumonia is a leading cause of mortality and one major pathogen associated with this disease is Klebsiella pneumoniae. Recently, the emergence of antibiotic resistant strains demands an effective vaccine against these bacteria. We have previously shown that intranasal immunization with heat-killed K. pneumoniae or crude outer membrane proteins isolated from K. pneumoniae induced antigen specific Th17 responses and these Th17 cells conferred serotype independent protection against various clinical isolates of K. pneumoniae including the recently described multidrug resistant New Delhi Metallo-beta-lactamase-1 strain. To develop a clinically relevant Klebsiella vaccine, we cloned single OMP genes by PCR from K. pneumoniae and successfully expressed one recombinant outer membrane protein, OmpX, in the BL21 E. coli strain. The purified recombinant OmpX was recognized by Klebsiella immune serum by direct ELISA and also recognized by Th17 cells from Klebsiella immunized mice. In vivo, intranasal immunization of the purified OmpX induced robust mucosal Th17 responses and left IL-17 producing gamma-delta T cells unaffected. Ongoing work will determine whether these Th17 responses will result in serotype independent protection against live bacterial challenge including the multidrug resistant strains.