An Ovine Model Yields Histology and Gene Expression Changes Consistent with Laryngotracheal Stenosis.

OBJECTIVES: Animal models for laryngotracheal stenosis (LTS) are critical to understand underlying mechanisms and study new therapies. Current animal models for LTS are limited by small airway sizes compared to human. The objective of this study was to develop and validate a novel, large animal ovine model for LTS. METHODS: Sheep underwent either bleomycin-coated polypropylene brush injury to the subglottis (n = 6) or airway stent placement (n = 2) via suspension microlaryngoscopy. Laryngotracheal complexes were harvested 4 weeks following injury or stent placement. For the airway injury group, biopsies (n = 3 at each site) were collected of tracheal scar and distal normal regions, and analyzed for fibrotic gene expression. Lamina propria (LP) thickness was compared between injured and normal areas of trachea. RESULTS: No mortality occurred in sheep undergoing airway injury or stent placement. There was no migration of tracheal stents. After protocol optimization, LP thickness was significantly increased in injured trachea (Sheep #3: 529.0 vs. 850.8 um; Sheep #4: 933.0 vs. 1693.2 um; Sheep #5: 743.7 vs. 1378.4 um; Sheep #6: 305.7 vs. 2257.6 um). A significant 62-fold, 20-fold, 16-fold, 16-fold, and 9-fold change of COL1, COL3, COL5, FN1, and TGFB1 was observed in injured scar specimen relative to unaffected airway, respectively. CONCLUSION: An ovine LTS model produces histologic and transcriptional changes consistent with fibrosis seen in human LTS. Airway stent placement in this model is safe and feasible. This large airway model is a reliable and reproducible method to assess the efficacy of novel LTS therapies prior to clinical translation. LEVEL OF EVIDENCE: N/A Laryngoscope, 2024.

A Comprehensive Flow Cytometry Panel for Analysis of Idiopathic Subglottic Stenosis.

OBJECTIVE: To present a comprehensive flow cytometry panel for idiopathic subglottic stenosis (iSGS). STUDY DESIGN: Controlled ex vivo cohort study. SETTING: Tertiary care academic hospital in a metropolitan area. METHODS: Flow cytometry and single-cell RNA sequencing were performed on 9 paired normal and scar tissue samples from iSGS patients. Flow cytometry was used to assess the presence of myeloid (CD11b, CD14, CD15, Siglec8), lymphoid (CD3, CD4, CD8, gamma delta [γδ], FOXP3), endothelial (CD31), fibroblast (CD90, SMA), and epithelial (CD326, CK5) markers. RESULTS: On flow cytometry, iSGS scar is characterized by an increased presence of myeloid, lymphoid, endothelial, and fibroblast cell types, but a decreased presence of epithelial cells. In the myeloid lineage, iSGS scar samples demonstrated increased CD11b+ monocytes (P < .001), Siglec8+ eosinophils (P = .03), and CD14+ monocytes (P = .02). In the lymphoid lineage, iSGS scar demonstrated increased CD3+ T-cells (P < .001), CD4+ helper T-cells (P < .001), γδ+ T-cells (P < .001), and FOXP3+ regulatory T-cells (P = .002). iSGS scar exhibited specific increases in CD90+ (P = .04) and SMA+ (P < .001) fibroblasts but decreased CD326+ (E-cadherin) epithelial cells (P = .01) relative to normal samples. CONCLUSION: We present a comprehensive flow cytometry panel for iSGS. This flow panel may serve as a common platform among airway scientists to elucidate the cellular mechanisms underpinning iSGS and other upper airway pathologies. Scar iSGS samples demonstrate a distinct cellular profile relative to normal iSGS specimens, exhibiting increased fibroblast, endothelial, and inflammatory cell types but decreased epithelium.

Adoptive transfer of CD49a+ Tissue resident memory cells reverses pulmonary fibrosis in mice.

Pulmonary fibrosis is a devastating disease with no effective treatments to cure, stop or reverse the unremitting, fatal fibrosis. A critical barrier to treating this disease is the lack of understanding of the pathways leading to fibrosis as well as those regulating the resolution of fibrosis. Fibrosis is the pathologic side of normal tissue repair that results when the normal wound healing programs go awry. Successful resolution of tissue injury requires several highly coordinated pathways, and this research focuses on the interplay between these overlapping pathways: immune effectors, inflammatory mediators and fibroproliferation in the resolution of fibrosis. Previously we have successfully prevented, mitigated, and even reversed established fibrosis using vaccinia vaccination immunotherapy in two models of murine lung fibrosis. The mechanism by which vaccinia reverses fibrosis is by vaccine induced lung specific Th1 skewed tissue resident memory (TRMs) in the lung. In this study, we isolated a population of vaccine induced TRMs - CD49a+ CD4+ T cells - that are both necessary and sufficient to reverse established pulmonary fibrosis. Using adoptive cellular therapy, we demonstrate that intratracheal administration of CD49a+ CD4+ TRMs into established fibrosis, reverses the fibrosis histologically, by promoting a decrease in collagen, and functionally, by improving lung function, without the need for vaccination. Furthermore, co-culture of in vitro derived CD49+ CD4+ human TRMs with human fibroblasts from individuals with idiopathic pulmonary fibrosis (IPF) results in the down regulation of IPF fibroblast collagen production. Lastly, we demonstrate in human IPF lung histologic samples that CD49a+ CD4+ TRMs, which can down regulate human IPF fibroblast function, fail to increase in the IPF lungs, thus potentially failing to promote resolution. Thus, we define a novel unappreciated role for tissue resident memory T cells in regulating established lung fibrosis to promote resolution of fibrosis and re-establish lung homeostasis. We demonstrate that immunotherapy, in the form of adoptive transfer of CD49a+ CD4+ TRMs into the lungs of mice with established fibrosis, not only stops progression of the fibrosis but more importantly reverses the fibrosis. These studies provide the insight and preclinical rationale for a novel paradigm shifting approach of using cellular immunotherapy to treat lung fibrosis.

Similarity Network Analysis of the Adaptive Immune Response in the Proximal Airway.

OBJECTIVES: Recent immunologic study of the adaptive immune repertoire in the subglottic airway demonstrated high-frequency T cell clones that do not overlap between individuals. However, the anatomic distribution and antigenic target of the T cell repertoire in the proximal airway mucosa remain unresolved. METHODS: Single-cell RNA sequencing of matched scar and unaffected mucosa from idiopathic subglottic stenosis patients (iSGS, n = 32) was performed and compared with airway mucosa from healthy controls (n = 10). T cell receptor (TCR) sequences were interrogated via similarity network analysis to explore antigenic targets using the published algorithm: Grouping of Lymphocyte Interactions by Paratope Hotspots (GLIPH2). RESULTS: The mucosal T cell repertoire in healthy control airways consisted of highly expressed T cell clones conserved across anatomic subsites (trachea, bronchi, bronchioles, and lung). In iSGS, high-frequency clones were equally represented in both scar and adjacent non-scar tissue. Significant differences in repertoire structure between iSGS scar and unaffected mucosa was observed, driven by unique low-frequency clones. GLIPH2 results suggest low-frequency clones share targets between multiple iSGS patients. CONCLUSION: Healthy airway mucosa has a highly conserved T cell repertoire across multiple anatomic subsites. Similarly, iSGS patients have highly expressed T cell clones present in both scar and unaffected mucosa. iSGS airway scar possesses an abundance of less highly expanded clones with predicted antigen targets shared between patients. Interrogation of these shared motifs suggests abundant adaptive immunity to viral targets in iSGS airway scar. These results provide insight into disease pathogenesis and illuminate new treatment strategies in iSGS. LEVEL OF EVIDENCE: Level NA Laryngoscope, 2024.

Murine Model of Airway Fibrosis has Anatomic, Physiologic, and Molecular Congruency to Human iSGS.

OBJECTIVE: To narrow knowledge gaps in the pathophysiology of idiopathic subglottic stenosis (iSGS) through comparison of a murine subglottic stenosis model with iSGS. STUDY DESIGN: In vivo animal study. SETTING: Academic institution. METHODS: Murine samples/measurements were obtained from mice that underwent chemomechanical injury with a wire brush and bleomycin. Human samples/measurements were obtained from iSGS patients. Anatomic, physiologic, and epithelial molecular data were collected using histology, human peak expiratory flow (PEF) and murine airway conductance, gene expression analysis with quantitative polymerase chain reaction, and protein analysis with quantitative immunohistochemistry. RESULTS: Anatomic patterns of scars at the subglottis and proximal trachea seen in the murine model are similar to iSGS patients. Subglottic stenosis (SGS) mice had a decrease (P = .0194) in airway conductance compared to healthy controls, similar to a decrease (P = .0001) in predilation PEF versus postdilation in iSGS patients. There was decreased epithelial gene expression of E-cadherin (ECAD) (P < 0.01), occludin (OCLN) (P < .01), and cytokeratin-5 (CK5) (P < .05) and protein expression of ECAD (H/M: P < .001), OCLN (H: P < 0.05, M: P < .001), and CK5 (H: P < .001, M: P < .01) in murine SGS and iSGS versus controls. CONCLUSION: The murine SGS model shows anatomic, physiologic, and molecular congruency with human iSGS, making it a reasonable model to investigate iSGS. The molecular similarities in epithelial barrier dysfunction suggest it may best be suited to explore epithelial mechanisms of iSGS and therapies directed at epithelial reconstitution. This model provides a foundation to collect data that will improve understanding of iSGS, and, ultimately, translate into more accurate animal models for future use.

Characterizing the T Cell Repertoire in the Proximal Airway in Health and Disease.

OBJECTIVES: Recent translational scientific efforts in subglottic stenosis (SGS) support a disease model where epithelial alterations facilitate microbiome displacement, dysregulated immune activation, and localized fibrosis. Given the observed immune cell infiltrate in SGS, we sought to test the hypothesis that SGS cases possessed a low diversity (highly clonal) adaptive immune response when compared with healthy controls. METHODS: Single cell RNA sequencing (scRNA-seq) of subglottic mucosal scar in iSGS (n = 24), iLTS (n = 8), and healthy controls (n = 7) was performed. T cell receptor (TCR) sequences were extracted, analyzed, and used to construct repertoire structure, compare diversity, interrogate overlap, and define antigenic targets using the Immunarch bioinformatics pipeline. RESULTS: The proximal airway mucosa in health and disease are equally diverse via Hill framework quantitation (iSGS vs. iLTS vs. Control, p > 0.05). Repertoires do not significantly overlap between individuals (Morisita <0.02). Among iSGS patients, clonality of the TCR repertoire is driven by CD8+ T cells, and iSGS patients possess numerous TCRs targeting viral and intercellular pathogens. High frequency clonotypes do not map to known targets in public datasets. CONCLUSION: SGS cases do not possess a lower diversity adaptive immune infiltrate when compared with healthy controls. Interestingly, the TCR repertoire in both health and disease contains a restricted number of high frequency clonotypes that do not significantly overlap between individuals. The target of the high frequency clonotypes in health and disease remain unresolved. LEVEL OF EVIDENCE: NA Laryngoscope, 134:1757-1764, 2024.

Localizing Hormone Receptor Expression to Cellular Compartments in Idiopathic Subglottic Stenosis.

OBJECTIVES: Idiopathic subglottic stenosis (iSGS) is an unexplained progressive fibrosis of the upper airway. iSGS almost exclusively affects women; as a result, female hormones (estrogen and progesterone) have been proposed to participate in the pathogenesis of iSGS. Our aim was to localize cell-specific gene expression of estrogen receptors (ESR1 and ESR2) and progesterone receptor (PGR) using an established iSGS single-cell RNA sequencing (scRNAseq) cell atlas. STUDY DESIGN: Ex vivo molecular study of airway scar and healthy mucosa from iSGS patients. METHODS: An established scRNAseq atlas consisting of 25,974 individually sequenced cells from subglottic scar (n = 7) or matched unaffected mucosa (n = 3) in iSGS patients was interrogated for RNA expression of ESR1, ESR2, and PGR. Results were quantified and compared across cell subsets, then visualized using Uniform Manifold Approximation and Projection (UMAP). Confirmatory protein assessment of endocrine receptors in fibroblasts from iSGS patients (n = 5) was performed via flow cytometry. RESULTS: The proximal airway mucosa in iSGS patients demonstrates differential expression of endocrine receptors (ESR1, ESR2, PGR). Within airway scar, endocrine receptors are primarily expressed by fibroblasts, immune cells, and endothelial cells. Fibroblasts show strong ESR1 and PGR expression, while immune cells possess RNA for both ESR1 and ESR2. Endothelial cells predominantly express ESR2. Epithelial cells in unaffected mucosa express all three receptors, which are all reduced in airway scar. CONCLUSIONS: scRNAseq data localized endocrine receptor expression to specific cell subsets. These results provide the foundation for future work interrogating how hormone-dependent mechanisms promote, sustain, or participate in iSGS disease pathogenesis. LEVEL OF EVIDENCE: NA; Basic science Laryngoscope, 133:3506-3511, 2023.

Macrophage monocarboxylate transporter 1 promotes peripheral nerve regeneration after injury in mice.

Peripheral nerves have the capacity for regeneration, but the rate of regeneration is so slow that many nerve injuries lead to incomplete recovery and permanent disability for patients. Macrophages play a critical role in the peripheral nerve response to injury, contributing to both Wallerian degeneration and nerve regeneration, and their function has recently been shown to be dependent on intracellular metabolism. To date, the impact of their intracellular metabolism on peripheral nerve regeneration has not been studied. We examined conditional transgenic mice with selective ablation in macrophages of solute carrier family 16, member 1 (Slc16a1), which encodes monocarboxylate transporter 1 (MCT1), and found that MCT1 contributed to macrophage metabolism, phenotype, and function, specifically in regard to phagocytosis and peripheral nerve regeneration. Adoptive cell transfer of wild-type macrophages ameliorated the impaired nerve regeneration in macrophage-selective MCT1-null mice. We also developed a mouse model that overexpressed MCT1 in macrophages and found that peripheral nerves in these mice regenerated more rapidly than in control mice. Our study provides further evidence that MCT1 has an important biological role in macrophages and that manipulations of macrophage metabolism can enhance recovery from peripheral nerve injuries, for which there are currently no approved medical therapies.

mTORC1 Signaling Regulates Proinflammatory Macrophage Function and Metabolism.

Metabolic programming is integrally linked to immune cell function. Nowhere is this clearer than in the differentiation of macrophages. Proinflammatory M1 macrophages primarily use glycolysis as a rapid energy source but also to generate antimicrobial compounds, whereas alternatively activated M2 macrophages primarily rely on oxidative phosphorylation for the longevity required for proper wound healing. mTOR signaling has been demonstrated to be a key regulator of immune cell metabolism and function. mTORC2 signaling is required for the generation of M2 macrophages, whereas the role of mTORC1 signaling, a key regulator of glycolysis, has been controversial. By using genetic deletion of mTORC1 signaling in C57BL/6 mouse macrophages, we observed enhanced M1 macrophage function in vitro and in vivo. Surprisingly, this enhancement occurred despite a significant defect in M1 macrophage glycolytic metabolism. Mechanistically, enhanced M1 function occurred because of inhibition of the class III histone deacetylases the sirtuins, resulting in enhanced histone acetylation. Our findings provide a counterpoint to the paradigm that enhanced immune cell function must occur in the presence of increased cellular metabolism and identifies a potential, pharmacologic target for the regulation of inflammatory responses.

Airway compliance measurements in mouse models of respiratory diseases.

The quantification of airway compliance (Caw) is essential to the study of airway alterations in disease models. However, the required measurements of airway pressure and volume are difficult to acquire in mice. We hypothesized that the inflation limb of full-range pressure-volume (PV) curves could be used to quantify Caw, as it contains a segment where only the airway tree is distended. The study objective was to assess the feasibility of the approach by analysis of full-range PV curves previously collected in three mouse models: an elastase model of emphysema, a genetic model spontaneously developing emphysema (leukotriene C4 synthase knockout; LTC4S-KO), and a bleomycin model of lung fibrosis. Attempts to validate results included Caw change relative to respiratory system compliance (ΔCaw/ΔC), the minute work of breathing (mWOB), and the elastance at 20.5 Hz (Ers_20.5) from prior respiratory mechanics measurements in the same subjects. Caw was estimated at 3% of total compliance in healthy mice or 2.3 ± 1 µL/cmH2O (n = 17). The technique detected changes in models of respiratory obstructive and restrictive diseases relative to control mice as well as differences in the two emphysema models studied. The changes in Caw were consistent with those seen in ΔCaw/ΔC, mWOB, or Ers_20.5, with some variations according to the model, as well as with results reported in the literature in humans and mice. Direct Caw measurements in subjects as small as mice could prove useful to further characterize other respiratory disease models associated with airway remodeling or to assess treatment effects.

Immune dysregulation as a driver of idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) affects hundreds of thousands of people worldwide, reducing their quality of life and leading to death from respiratory failure within years of diagnosis. Treatment options remain limited, with only two FDA-approved drugs available in the United States, neither of which reverse the lung damage caused by the disease or prolong the life of individuals with IPF. The only cure for IPF is lung transplantation. In this review, we discuss recent major advances in our understanding of the role of the immune system in IPF that have revealed immune dysregulation as a critical driver of disease pathophysiology. We also highlight ways in which an improved understanding of the immune system's role in IPF may enable the development of targeted immunomodulatory therapies that successfully halt or potentially even reverse lung fibrosis.

Targeting glutamine metabolism enhances tumor-specific immunity by modulating suppressive myeloid cells.

Myeloid cells comprise a major component of the tumor microenvironment (TME) that promotes tumor growth and immune evasion. By employing a small-molecule inhibitor of glutamine metabolism, not only were we able to inhibit tumor growth, but we markedly inhibited the generation and recruitment of myeloid-derived suppressor cells (MDSCs). Targeting tumor glutamine metabolism led to a decrease in CSF3 and hence recruitment of MDSCs as well as immunogenic cell death, leading to an increase in inflammatory tumor-associated macrophages (TAMs). Alternatively, inhibiting glutamine metabolism of the MDSCs themselves led to activation-induced cell death and conversion of MDSCs to inflammatory macrophages. Surprisingly, blocking glutamine metabolism also inhibited IDO expression of both the tumor and myeloid-derived cells, leading to a marked decrease in kynurenine levels. This in turn inhibited the development of metastasis and further enhanced antitumor immunity. Indeed, targeting glutamine metabolism rendered checkpoint blockade-resistant tumors susceptible to immunotherapy. Overall, our studies define an intimate interplay between the unique metabolism of tumors and the metabolism of suppressive immune cells.

Inhibition of glutamine metabolism accelerates resolution of acute lung injury.

Despite recent advances, acute respiratory distress syndrome (ARDS) remains a severe and often fatal disease for which there is no therapy able to reduce the underlying excessive lung inflammation or enhance resolution of injury. Metabolic programming plays a critical role in regulating inflammatory responses. Due to their high metabolic needs, neutrophils, macrophages, and lymphocytes rely upon glutamine metabolism to support activation and function. Additionally, during times of physiologic stress, nearly all cells, including fibroblasts and epithelial cells, require glutamine metabolism. We hypothesized that inhibiting glutamine metabolism reduces lung inflammation and promotes resolution of acute lung injury. Lung injury was induced by instilling lipopolysaccharide (LPS) intratracheally. To inhibit glutamine metabolism, we administered a glutamine analogue, 6-diazo-5-oxo-L-norleucine (DON) that binds to glutamine-utilizing enzymes and transporters, after injury was well established. Treatment with DON led to less lung injury, fewer lung neutrophils, lung inflammatory and interstitial macrophages, and lower levels of proinflammatory cytokines and chemokines at 5 and/or 7 days after injury. Additionally, DON led to earlier expression of the growth factor amphiregulin and more rapid recovery of LPS-induced weight loss. Thus, DON reduced lung inflammation and promoted resolution of injury. These data contribute to our understanding of how glutamine metabolism regulates lung inflammation and repair, and identifies a novel target for future therapies for ARDS and other inflammatory lung diseases.

mTORC2 Signaling Selectively Regulates the Generation and Function of Tissue-Resident Peritoneal Macrophages.

Tissue-resident macrophages play critical roles in sentinel and homeostatic functions as well as in promoting inflammation and immunity. It has become clear that the generation of these cells is highly dependent upon tissue-specific cues derived from the microenvironment that, in turn, regulate unique differentiation programs. Recently, a role for GATA6 has emerged in the differentiation programming of resident peritoneal macrophages. We identify a critical role for mTOR in integrating cues from the tissue microenvironment in regulating differentiation and metabolic reprogramming. Specifically, inhibition of mTORC2 leads to enhanced GATA6 expression in a FOXO1 dependent fashion. Functionally, inhibition of mTORC2 promotes peritoneal resident macrophage generation in the resolution phase during zymosan-induced peritonitis. Also, mTORC2-deficient peritoneal resident macrophages displayed increased functionality and metabolic reprogramming. Notably, mTORC2 activation distinguishes tissue-resident macrophage proliferation and differentiation from that of M2 macrophages. Overall, our data implicate a selective role for mTORC2 in the differentiation of tissue-resident macrophages.

Loss of macrophage fatty acid oxidation does not potentiate systemic metabolic dysfunction.

Fatty acid oxidation in macrophages has been suggested to play a causative role in high-fat diet-induced metabolic dysfunction, particularly in the etiology of adipose-driven insulin resistance. To understand the contribution of macrophage fatty acid oxidation directly to metabolic dysfunction in high-fat diet-induced obesity, we generated mice with a myeloid-specific knockout of carnitine palmitoyltransferase II (CPT2 Mϕ-KO), an obligate step in mitochondrial long-chain fatty acid oxidation. While fatty acid oxidation was clearly induced upon IL-4 stimulation, fatty acid oxidation-deficient CPT2 Mϕ-KO bone marrow-derived macrophages displayed canonical markers of M2 polarization following IL-4 stimulation in vitro. In addition, loss of macrophage fatty acid oxidation in vivo did not alter the progression of high-fat diet-induced obesity, inflammation, macrophage polarization, oxidative stress, or glucose intolerance. These data suggest that although IL-4-stimulated alternatively activated macrophages upregulate fatty acid oxidation, fatty acid oxidation is dispensable for macrophage polarization and high-fat diet-induced metabolic dysfunction. Macrophage fatty acid oxidation likely plays a correlative, rather than causative, role in systemic metabolic dysfunction.

Deletion of mTORC1 Activity in CD4+ T Cells Is Associated with Lung Fibrosis and Increased γδ T Cells.

Pulmonary fibrosis is a devastating, incurable disease in which chronic inflammation and dysregulated, excessive wound healing lead to progressive fibrosis, lung dysfunction, and ultimately death. Prior studies have implicated the cytokine IL-17A and Th17 cells in promoting the development of fibrosis. We hypothesized that loss of Th17 cells via CD4-specific deletion of mTORC1 activity would abrogate the development of bleomycin-induced pulmonary fibrosis. However, in actuality loss of Th17 cells led to increased mortality and fibrosis in response to bleomycin. We found that in the absence of Th17 cells, there was continued production of IL-17A by γδ T cells. These IL-17A+ γδ T cells were associated with increased lung neutrophils and M2 macrophages, accelerated development of fibrosis, and increased mortality. These data elucidate the critical role of IL-17A+ γδ T cells in promoting chronic inflammation and fibrosis, and reveal a novel therapeutic target for treatment of pulmonary fibrosis.

Vaccinia vaccine-based immunotherapy arrests and reverses established pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a fatal disease without any cure. Both human disease and animal models demonstrate dysregulated wound healing and unregulated fibrogenesis in a background of low-grade chronic T lymphocyte infiltration. Tissue-resident memory T cells (Trm) are emerging as important regulators of the immune microenvironment in response to pathogens, and we hypothesized that they might play a role in regulating the unremitting inflammation that promotes lung fibrosis. Herein, we demonstrate that lung-directed immunotherapy, in the form of i.n. vaccination, induces an antifibrotic T cell response capable of arresting and reversing lung fibrosis. In mice with established lung fibrosis, lung-specific T cell responses were able to reverse established pathology - as measured by decreased lung collagen, fibrocytes, and histologic injury - and improve physiologic function. Mechanistically, we demonstrate that this effect is mediated by vaccine-induced lung Trm. These data not only have implications for the development of immunotherapeutic regimens to treat IPF, but also suggest a role for targeting tissue-resident memory T cells to treat other tissue-specific inflammatory/autoimmune disorders.

Pulmonary delivery of docosahexaenoic acid mitigates bleomycin-induced pulmonary fibrosis.

BACKGROUND: Pulmonary fibrosis is an untreatable, fatal disease characterized by excess deposition of extracellular matrix and inflammation. Although the etiology of pulmonary fibrosis is unknown, recent studies have implicated dysregulated immune responses and wound healing. Since n-3 polyunsaturated fatty acids (n-3 PUFAs) may beneficially modulate immune responses in a variety of inflammatory disorders, we investigated the therapeutic role of docosahexaenoic acid (DHA), a single n-3 PUFA, in lung fibrosis. METHODS: Intratracheal DHA or PBS was administered to mouse lungs 4 days prior to intratracheal bleomycin treatment. Body weight and survival were monitored for 21 days. Bronchoalveolar fluid (BALF) and lung inflammatory cells, cytokines, eicosanoids, histology and lung function were determined on serial days (0, 3, 7, 14, 21) after bleomycin injury. RESULTS: Intratracheal administration of DHA mitigated bleomycin-induced lung injury. Mice pretreated with DHA had significantly less weight loss and mortality after bleomycin injury. The lungs from DHA-pretreated mice had markedly less fibrosis. DHA pretreatment also protected the mice from the functional changes associated with bleomycin injury. Bleomycin-induced cellular inflammation in BALF and lung tissue was blunted by DHA pretreatment. These advantageous effects of DHA pretreatment were associated with decreased IL-6, LTB4, PGE2 and increased IL-10. CONCLUSIONS: Our findings demonstrate that intratracheal administration of DHA, a single PUFA, protected mice from the development of bleomycin-induced pulmonary inflammation and fibrosis. These results suggest that further investigations regarding the role of n-3 polyunsaturated fatty acids in fibrotic lung injury and repair are needed.

An Fc domain protein-small molecule conjugate as an enhanced immunomodulator.

Proteins as well as small molecules have demonstrated success as therapeutic agents, but their pharmacologic properties sometimes fall short against particular drug targets. Although the adenosine 2a receptor (A(2A)R) has been identified as a promising target for immunotherapy, small molecule A(2A)R agonists have suffered from short pharmacokinetic half-lives and the potential for toxicity by modulating nonimmune pathways. To overcome these limitations, we have tethered the A(2A)R agonist CGS-21680 to the immunoglobulin Fc domain using expressed protein ligation with Sf9 cell secreted protein. The protein small molecule conjugate Fc-CGS retained potent Fc receptor and A(2A)R interactions and showed superior properties as a therapeutic for the treatment of a mouse model of autoimmune pneumonitis. This approach may provide a general strategy for optimizing small molecule therapeutics.

Egr3 induces a Th17 response by promoting the development of γδ T cells.

The transcription factor Early Growth Response 3 (Egr3) has been shown to play an important role in negatively regulating T cell activation and promoting T cell anergy in Th1 cells. However, its role in regulating other T helper subsets has yet to be described. We sought to determine the role of Egr3 in a Th17 response using transgenic mice that overexpress Egr3 in T cells (Egr3 TG). Splenocytes from Egr3 TG mice demonstrated more robust generation of Th17 cells even under non-Th17 skewing conditions. We found that while Egr3 TG T cells were not intrinsically more likely to become Th17 cells, the environment encountered by these cells was more conducive to Th17 development. Further analysis revealed a considerable increase in the number of γδ T cells in both the peripheral lymphoid organs and mucosal tissues of Egr3 TG mice, a cell type which normally accounts for only a small fraction of peripheral lymphocytes. Consistent with this marked increase in peripheral γδ T cells, thymocytes from Egr3 TG mice also appear biased toward γδ T cell development. Coculture of these Egr3-induced γδ T cells with wildtype CD4+ T cells increases Th17 differentiation, and Egr3 TG mice are more susceptible to bleomycin-induced lung inflammation. Overall our findings strengthen the role for Egr3 in promoting γδ T cell development and show that Egr3-induced γδ T cells are both functional and capable of altering the adaptive immune response in a Th17-biased manner. Our data also demonstrates that the role played by Egr3 in T cell activation and differentiation is more complex than previously thought.