TGF-ß signaling in health and disease.

The TGF-ß regulatory system plays crucial roles in the preservation of organismal integrity. TGF-ß signaling controls metazoan embryo development, tissue homeostasis, and injury repair through coordinated effects on cell proliferation, phenotypic plasticity, migration, metabolic adaptation, and immune surveillance of multiple cell types in shared ecosystems. Defects of TGF-ß signaling, particularly in epithelial cells, tissue fibroblasts, and immune cells, disrupt immune tolerance, promote inflammation, underlie the pathogenesis of fibrosis and cancer, and contribute to the resistance of these diseases to treatment. Here, we review how TGF-ß coordinates multicellular response programs in health and disease and how this knowledge can be leveraged to develop treatments for diseases of the TGF-ß system.

TGF-ß activation and function in immunity.

The cytokine TGF-ß plays an integral role in regulating immune responses. TGF-ß has pleiotropic effects on adaptive immunity, especially in the regulation of effector and regulatory CD4(+) T cell responses. Many immune and nonimmune cells can produce TGF-ß, but it is always produced as an inactive complex that must be activated to exert functional effects. Thus, activation of latent TGF-ß provides a crucial layer of regulation that controls TGF-ß function. In this review, we highlight some of the important functional roles for TGF-ß in immunity, focusing on its context-specific roles in either dampening or promoting T cell responses. We also describe how activation of TGF-ß controls its function in the immune system, with a focus on the key roles for members of the integrin family in this process.

APOE4 impairs the microglial response in Alzheimer's disease by inducing TGFß-mediated checkpoints.

The APOE4 allele is the strongest genetic risk factor for late-onset Alzheimer's disease (AD). The contribution of microglial APOE4 to AD pathogenesis is unknown, although APOE has the most enriched gene expression in neurodegenerative microglia (MGnD). Here, we show in mice and humans a negative role of microglial APOE4 in the induction of the MGnD response to neurodegeneration. Deletion of microglial APOE4 restores the MGnD phenotype associated with neuroprotection in P301S tau transgenic mice and decreases pathology in APP/PS1 mice. MGnD-astrocyte cross-talk associated with ß-amyloid (Aß) plaque encapsulation and clearance are mediated via LGALS3 signaling following microglial APOE4 deletion. In the brains of AD donors carrying the APOE4 allele, we found a sex-dependent reciprocal induction of AD risk factors associated with suppression of MGnD genes in females, including LGALS3, compared to individuals homozygous for the APOE3 allele. Mechanistically, APOE4-mediated induction of ITGB8-transforming growth factor-ß (TGFß) signaling impairs the MGnD response via upregulation of microglial homeostatic checkpoints, including Inpp5d, in mice. Deletion of Inpp5d in microglia restores MGnD-astrocyte cross-talk and facilitates plaque clearance in APP/PS1 mice. We identify the microglial APOE4-ITGB8-TGFß pathway as a negative regulator of microglial response to AD pathology, and restoring the MGnD phenotype via blocking ITGB8-TGFß signaling provides a promising therapeutic intervention for AD.

Alveolar fibroblast lineage orchestrates lung inflammation and fibrosis.

Fibroblasts are present throughout the body and function to maintain tissue homeostasis. Recent studies have identified diverse fibroblast subsets in healthy and injured tissues1,2, but the origins and functional roles of injury-induced fibroblast lineages remain unclear. Here we show that lung-specialized alveolar fibroblasts take on multiple molecular states with distinct roles in facilitating responses to fibrotic lung injury. We generate a genetic tool that uniquely targets alveolar fibroblasts to demonstrate their role in providing niches for alveolar stem cells in homeostasis and show that loss of this niche leads to exaggerated responses to acute lung injury. Lineage tracing identifies alveolar fibroblasts as the dominant origin for multiple emergent fibroblast subsets sequentially driven by inflammatory and pro-fibrotic signals after injury. We identify similar, but not completely identical, fibroblast lineages in human pulmonary fibrosis. TGFß negatively regulates an inflammatory fibroblast subset that emerges early after injury and stimulates the differentiation into fibrotic fibroblasts to elicit intra-alveolar fibrosis. Blocking the induction of fibrotic fibroblasts in the alveolar fibroblast lineage abrogates fibrosis but exacerbates lung inflammation. These results demonstrate the multifaceted roles of the alveolar fibroblast lineage in maintaining normal alveolar homeostasis and orchestrating sequential responses to lung injury.

Stromal cells control the epithelial residence of DCs and memory T cells by regulated activation of TGF-ß.

Cells of the immune system that reside in barrier epithelia provide a first line of defense against pathogens. Langerhans cells (LCs) and CD8(+) tissue-resident memory T cells (TRM cells) require active transforming growth factor-ß1 (TGF-ß) for epidermal residence. Here we found that integrins αvß6 and αvß8 were expressed in non-overlapping patterns by keratinocytes (KCs) and maintained the epidermal residence of LCs and TRM cells by activating latent TGF-ß. Similarly, the residence of dendritic cells and TRM cells in the small intestine epithelium also required αvß6. Treatment of the skin with ultraviolet irradiation decreased integrin expression on KCs and reduced the availability of active TGF-ß, which resulted in LC migration. Our data demonstrated that regulated activation of TGF-ß by stromal cells was able to directly control epithelial residence of cells of the immune system through a novel mechanism of intercellular communication.

Obesity alters pathology and treatment response in inflammatory disease.

Decades of work have elucidated cytokine signalling and transcriptional pathways that control T cell differentiation and have led the way to targeted biologic therapies that are effective in a range of autoimmune, allergic and inflammatory diseases. Recent evidence indicates that obesity and metabolic disease can also influence the immune system1-7, although the mechanisms and effects on immunotherapy outcomes remain largely unknown. Here, using two models of atopic dermatitis, we show that lean and obese mice mount markedly different immune responses. Obesity converted the classical type 2 T helper (TH2)-predominant disease associated with atopic dermatitis to a more severe disease with prominent TH17 inflammation. We also observed divergent responses to biologic therapies targeting TH2 cytokines, which robustly protected lean mice but exacerbated disease in obese mice. Single-cell RNA sequencing coupled with genome-wide binding analyses revealed decreased activity of nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) in TH2 cells from obese mice relative to lean mice. Conditional ablation of PPARγ in T cells revealed that PPARγ is required to focus the in vivo TH response towards a TH2-predominant state and prevent aberrant non-TH2 inflammation. Treatment of obese mice with a small-molecule PPARγ agonist limited development of TH17 pathology and unlocked therapeutic responsiveness to targeted anti-TH2 biologic therapies. These studies reveal the effects of obesity on immunological disease and suggest a precision medicine approach to target the immune dysregulation caused by obesity.

Anti-Integrin αvß6 Autoantibodies Are a Novel Biomarker That Antedate Ulcerative Colitis.

BACKGROUND & AIMS: Better biomarkers for prediction of ulcerative colitis (UC) development and prognostication are needed. Anti-integrin αvß6 (anti-αvß6) autoantibodies have been described in patients with UC. We tested for the presence of anti-αvß6 antibodies in the preclinical phase of UC and studied their association with disease-related outcomes after diagnosis. METHODS: Anti-αvß6 autoantibodies were measured in 4 longitudinal serum samples collected from 82 subjects who later developed UC and 82 matched controls from a Department of Defense preclinical cohort (PREDICTS [Proteomic Evaluation and Discovery in an IBD Cohort of Tri-service Subjects]). In a distinct, external validation cohort (Crohn's and Colitis Canada Genetic Environmental Microbial project cohort), we tested 12 pre-UC subjects and 49 matched controls. Furthermore, anti-αvß6 autoantibodies were measured in 2 incident UC cohorts (COMPASS [Comprehensive Care for the Recently Diagnosed IBD Patients], n = 55 and OSCCAR [Ocean State Crohn's and Colitis Area Registry], n = 104) and associations between anti-αvß6 autoantibodies and UC-related outcomes were defined using Cox proportional hazards model. RESULTS: Anti-αvß6 autoantibodies were significantly higher among individuals who developed UC compared with controls up to 10 years before diagnosis in PREDICTS. The anti-αvß6 autoantibody seropositivity was 12.2% 10 years before diagnosis and increased to 52.4% at the time of diagnosis in subjects who developed UC compared with 2.7% in controls across the 4 time points. Anti-αvß6 autoantibodies predicted UC development with an area under the curve of at least 0.8 up to 10 years before diagnosis. The presence of anti-αvß6 autoantibodies in preclinical UC samples was validated in the GEM cohort. Finally, high anti-αvß6 autoantibodies was associated with a composite of adverse UC outcomes, including hospitalization, disease extension, colectomy, systemic steroid use, and/or escalation to biologic therapy in recently diagnosed UC. CONCLUSIONS: Anti-integrin αvß6 autoantibodies precede the clinical diagnosis of UC by up to 10 years and are associated with adverse UC-related outcomes.

IRE1α drives lung epithelial progenitor dysfunction to establish a niche for pulmonary fibrosis.

After lung injury, damage-associated transient progenitors (DATPs) emerge, representing a transitional state between injured epithelial cells and newly regenerated alveoli. DATPs express profibrotic genes, suggesting that they might promote idiopathic pulmonary fibrosis (IPF). However, the molecular pathways that induce and/or maintain DATPs are incompletely understood. Here we show that the bifunctional kinase/RNase-IRE1α-a central mediator of the unfolded protein response (UPR) to endoplasmic reticulum (ER) stress is a critical promoter of DATP abundance and function. Administration of a nanomolar-potent, monoselective kinase inhibitor of IRE1α (KIRA8)-or conditional epithelial IRE1α gene knockout-both reduce DATP cell number and fibrosis in the bleomycin model, indicating that IRE1α cell-autonomously promotes transition into the DATP state. IRE1α enhances the profibrotic phenotype of DATPs since KIRA8 decreases expression of integrin αvß6, a key activator of transforming growth factor ß (TGF-ß) in pulmonary fibrosis, corresponding to decreased TGF-ß-induced gene expression in the epithelium and decreased collagen accumulation around DATPs. Furthermore, IRE1α regulates DNA damage response (DDR) signaling, previously shown to promote the DATP phenotype, as IRE1α loss-of-function decreases H2AX phosphorylation, Cdkn1a (p21) expression, and DDR-associated secretory gene expression. Finally, KIRA8 treatment increases the differentiation of Krt19CreERT2-lineage-traced DATPs into type 1 alveolar epithelial cells after bleomycin injury, indicating that relief from IRE1α signaling enables DATPs to exit the transitional state. Thus, IRE1α coordinates a network of stress pathways that conspire to entrap injured cells in the DATP state. Pharmacological blockade of IRE1α signaling helps resolve the DATP state, thereby ameliorating fibrosis and promoting salutary lung regeneration.

Induced hepatic stellate cell integrin, α8ß1, enhances cellular contractility and TGFß activity in liver fibrosis.

No effective therapy exists for fatal fibrosis. New therapeutic targets are needed for hepatic fibrosis because the incidence keeps increasing. The activation and differentiation of fibroblasts into myofibroblasts that causes excessive matrix deposition is central to fibrosis. Here, we investigated whether (and which) integrin receptors for matrix proteins activate hepatic stellate cells (HSCs). First, integrin α-subunits were investigated systematically for their expression over the course of HSC activation and their distribution on fibroblasts and other systemic primary cells. The most upregulated in plate culture-activated HSCs and specifically expressed across fibroblast linages was the α8 subunit. An anti-α8 neutralizing mAb was evaluated in three different murine fibrosis models: for cytotoxic (CCl4 treatment), non-alcoholic steatohepatitis-associated and cholestatic fibrosis. In all models, pathology and fibrosis markers (hydroxyproline and α-smooth muscle actin) were improved following the mAb injection. We also CCl4 -treated mice with inducible Itga8-/-; these mice were protected from increased hydroxyproline levels. Furthermore, ITGA8 was upregulated in specimens from 90 patients with liver fibrosis, indicating the relevance of our findings to liver fibrosis in people. Mechanistically, inhibition or ligand engagement of HSC α8 suppressed and enhanced myofibroblast differentiation, respectively, and HSC/fibroblast α8 activated latent TGFß. Finally, integrin α8ß1 potentially fulfils the growing need for anti-fibrotic drugs and is an integrin not to be ignored. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Innate antiviral host defense attenuates TGF-ß function through IRF3-mediated suppression of Smad signaling.

TGF-ß signaling is essential in many processes, including immune surveillance, and its dysregulation controls various diseases, including cancer, fibrosis, and inflammation. Studying the innate host defense, which functions in most cell types, we found that RLR signaling represses TGF-ß responses. This regulation is mediated by activated IRF3, using a dual mechanism of IRF3-directed suppression. Activated IRF3 interacts with Smad3, thus inhibiting TGF-ß-induced Smad3 activation and, in the nucleus, disrupts functional Smad3 transcription complexes by competing with coregulators. Consequently, IRF3 activation by innate antiviral signaling represses TGF-ß-induced growth inhibition, gene regulation and epithelial-mesenchymal transition, and the generation of Treg effector lymphocytes from naive CD4(+) lymphocytes. Conversely, silencing IRF3 expression enhances epithelial-mesenchymal transition, TGF-ß-induced Treg cell differentiation upon virus infection, and Treg cell generation in vivo. We present a mechanism of regulation of TGF-ß signaling by the antiviral defense, with evidence for its role in immune tolerance and cancer cell behavior.

IL-17A Recruits Rab35 to IL-17R to Mediate PKCα-Dependent Stress Fiber Formation and Airway Smooth Muscle Contractility.

IL-17A is a critical proinflammatory cytokine for the pathogenesis of asthma including neutrophilic pulmonary inflammation and airway hyperresponsiveness. In this study, by cell type-specific deletion of IL-17R and adaptor Act1, we demonstrated that IL-17R/Act1 exerts a direct impact on the contraction of airway smooth muscle cells (ASMCs). Mechanistically, IL-17A induced the recruitment of Rab35 (a small monomeric GTPase) and DennD1C (guanine nucleotide exchange factor [GEF]) to the IL-17R/Act1 complex in ASMCs, resulting in activation of Rab35. Rab35 knockdown showed that IL-17A-induced Rab35 activation was essential for protein kinase Cα (PKCα) activation and phosphorylation of fascin at Ser39 in ASMCs, allowing F-actin to interact with myosin to form stress fibers and enhance the contraction induced by methacholine. PKCα inhibitor or Rab35 knockdown indeed substantially reduced IL-17A-induced stress fiber formation in ASMCs and attenuated IL-17A-enhanced, methacholine-induced contraction of airway smooth muscle. Taken together, these data indicate that IL-17A promotes airway smooth muscle contraction via direct recruitment of Rab35 to IL-17R, followed by PKCα activation and stress fiber formation.

A disease-associated mutation in fibrillin-1 differentially regulates integrin-mediated cell adhesion.

Fibrillins serve as scaffolds for the assembly of elastic fibers that contribute to the maintenance of tissue homeostasis and regulate growth factor signaling in the extracellular space. Fibrillin-1 is a modular glycoprotein that includes 7 latent transforming growth factor ß (TGFß)-binding protein-like (TB) domains and mediates cell adhesion through integrin binding to the RGD motif in its 4th TB domain. A subset of missense mutations within TB4 cause stiff skin syndrome (SSS), a rare autosomal dominant form of scleroderma. The fibrotic phenotype is thought to be regulated by changes in the ability of fibrillin-1 to mediate integrin binding. We characterized the ability of each RGD-binding integrin to mediate cell adhesion to fibrillin-1 or a disease-causing variant. Our data show that 7 of the 8 RGD-binding integrins can mediate adhesion to fibrillin-1. A single amino acid substitution responsible for SSS (W1570C) markedly inhibited adhesion mediated by integrins α5ß1, αvß5, and αvß6, partially inhibited adhesion mediated by αvß1, and did not inhibit adhesion mediated by α8ß1 or αIIbß3. Adhesion mediated by integrin αvß3 depended on the cell surface expression level. In the SSS mutant background, the presence of a cysteine residue in place of highly conserved tryptophan 1570 alters the conformation of the region containing the exposed RGD sequence within the same domain to differentially affect fibrillin's interactions with distinct RGD-binding integrins.

Loss of Integrin αvß8 in Murine Hepatocytes Accelerates Liver Regeneration.

Recent fate-mapping studies in mice have provided substantial evidence that mature adult hepatocytes are a major source of new hepatocytes after liver injury. In other systems, integrin αvß8 has a major role in activating transforming growth factor (TGF)-ß, a potent inhibitor of hepatocyte proliferation. We hypothesized that depletion of hepatocyte integrin αvß8 would increase hepatocyte proliferation and accelerate liver regeneration after injury. Using Itgb8flox/flox;Alb-Cre mice to deplete hepatocyte αvß8, after partial hepatectomy, hepatocyte proliferation and liver-to-body weight ratio were significantly increased in Itgb8flox/flox;Alb-Cre mice compared with control mice. Antibody-mediated blockade of hepatocyte αvß8 in vitro, with assessment of TGF-ß signaling pathways by real-time quantitative PCR array, supported the hypothesis that integrin αvß8 inhibition alters hepatocyte TGF-ß signaling toward a pro-regenerative phenotype. A diethylnitrosamine-induced model of hepatocellular carcinoma, used to examine the possibility that this pro-proliferative phenotype might be oncogenic, revealed no difference in either tumor number or size between Itgb8flox/flox;Alb-Cre and control mice. Immunohistochemistry for integrin αvß8 in healthy and injured human liver demonstrated that human hepatocytes express integrin αvß8. Depletion of hepatocyte integrin αvß8 results in increased hepatocyte proliferation and accelerated liver regeneration after partial hepatectomy in mice. These data demonstrate that targeting integrin αvß8 may represent a promising therapeutic strategy to drive liver regeneration in patients with a broad range of liver diseases.

Dual antagonists of α5ß1/αvß1 integrin for airway hyperresponsiveness.

Inhibition of integrin α5ß1 emerges as a novel therapeutic option to block transmission of contractile forces during asthma attack. We designed and synthesized novel inhibitors of integrin α5ß1 by backbone replacement of known αvß1 integrin inhibitors. These integrin α5ß1 inhibitors also retain the nanomolar potency against αvß1 integrin, which shows promise for developing dual integrin α5ß1/αvß1 inhibitor. Introduction of hydrophobic adamantane group significantly boosted the potency as well as selectivity over integrin αvß3. We also demonstrated one of the inhibitors (11) reduced airway hyperresponsiveness in ex vivo mouse tracheal ring assay. Results from this study will help guide further development of integrin α5ß1 inhibitors as potential novel asthma therapeutics.

Blocking immunosuppression by human Tregs in vivo with antibodies targeting integrin αVß8.

Human regulatory T cells (Tregs) suppress other T cells by converting the latent, inactive form of TGF-ß1 into active TGF-ß1. In Tregs, TGF-ß1 activation requires GARP, a transmembrane protein that binds and presents latent TGF-ß1 on the surface of Tregs stimulated through their T cell receptor. However, GARP is not sufficient because transduction of GARP in non-Treg T cells does not induce active TGF-ß1 production. RGD-binding integrins were shown to activate TGF-ß1 in several non-T cell types. Here we show that αVß8 dimers are present on stimulated human Tregs but not in other T cells, and that antibodies against αV or ß8 subunits block TGF-ß1 activation in vitro. We also show that αV and ß8 interact with GARP/latent TGF-ß1 complexes in human Tregs. Finally, a blocking antibody against ß8 inhibited immunosuppression by human Tregs in a model of xenogeneic graft-vs.-host disease induced by the transfer of human T cells in immunodeficient mice. These results show that TGF-ß1 activation on the surface of human Tregs implies an interaction between the integrin αVß8 and GARP/latent TGF-ß1 complexes. Immunosuppression by human Tregs can be inhibited by antibodies against GARP or against the integrin ß8 subunit. Such antibodies may prove beneficial against cancer or chronic infections.

ß6 -integrin serves as a novel serum tumor marker for colorectal carcinoma.

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths worldwide and the need for novel biomarkers and therapeutic strategies to improve diagnosis and surveillance is obvious. This study aims to identify ß6 -integrin (ITGB6) as a novel serum tumor marker for diagnosis, prognosis, and surveillance of CRC. ITGB6 serum levels were validated in retro- and prospective CRC patient cohorts. ITGB6 serum levels were analyzed by ELISA. Using an initial cohort of 60 CRC patients, we found that ITGB6 is present in the serum of CRC, but not in non-CRC control patients. A cut-off of ≥2 ng/mL ITGB6 reveals 100% specificity for the presence of metastatic CRC. In an enlarged study cohort of 269 CRC patients, ITGB6 predicted the onset of metastatic disease and was associated with poor prognosis. Those data were confirmed in an independent, prospective cohort consisting of 40 CRC patients. To investigate whether ITGB6 can also be used for tumor surveillance, serum ITGB6-levels were assessed in 26 CRC patients, pre- and post-surgery, as well as during follow-up visits. After complete tumor resection, ITGB6 serum levels declined completely. During follow-up, a new rise in ITGB6 serum levels indicated tumor recurrence or the onset of new metastasis as confirmed by CT scan. ITGB6 was more accurate for prognosis of advanced CRC and for tumor surveillance as the established marker carcinoembryonic antigen (CEA). Our findings identify ITGB6 as a novel serum marker for diagnosis, prognosis, and surveillance of advanced CRC. This might essentially contribute to an optimized patient care.

Cell division cycle 7 kinase is a negative regulator of cell-mediated collagen degradation.

Although extensive work has delineated many of the mechanisms of extracellular matrix (ECM) production, far less is known about pathways that regulate ECM degradation. This is particularly true of cellular internalization and degradation of matrix, which play an underappreciated role in ECM metabolism and lung fibrosis. For example, genetic perturbation of this pathway leads to exacerbated fibrosis in experimental animal models. In this work, we present the results of an unbiased screen of Drosophila phagocytes that yielded multiple genes that, when silenced, led to increased collagen uptake. We further describe the function of cell division cycle 7 kinase (CDC7) as a specific suppressor of collagen uptake. We show that the genetic or pharmacological inhibition of CDC7 results in increased expression of the collagen endocytic receptor Endo180. Chromobox 5 (CBX5) is a putative target of CDC7, and genetic silencing of CBX5 also results in increased Endo180 and collagen uptake. Finally, CRISPR-mediated activation of Endo180 expression results in increased collagen uptake, suggesting that CDC7 regulates collagen internalization through increased Endo180 expression. Targeting the regulatory elements of the collagen degradative machinery may be a useful therapeutic approach in diseases of fibrosis or malignancy.

An Epithelial Integrin Regulates the Amplitude of Protective Lung Interferon Responses against Multiple Respiratory Pathogens.

The healthy lung maintains a steady state of immune readiness to rapidly respond to injury from invaders. Integrins are important for setting the parameters of this resting state, particularly the epithelial-restricted αVß6 integrin, which is upregulated during injury. Once expressed, αVß6 moderates acute lung injury (ALI) through as yet undefined molecular mechanisms. We show that the upregulation of ß6 during influenza infection is involved in disease pathogenesis. ß6-deficient mice (ß6 KO) have increased survival during influenza infection likely due to the limited viral spread into the alveolar spaces leading to reduced ALI. Although the ß6 KO have morphologically normal lungs, they harbor constitutively activated lung CD11b+ alveolar macrophages (AM) and elevated type I IFN signaling activity, which we traced to the loss of ß6-activated transforming growth factor-ß (TGF-ß). Administration of exogenous TGF-ß to ß6 KO mice leads to reduced numbers of CD11b+ AMs, decreased type I IFN signaling activity and loss of the protective phenotype during influenza infection. Protection extended to other respiratory pathogens such as Sendai virus and bacterial pneumonia. Our studies demonstrate that the loss of one epithelial protein, αVß6 integrin, can alter the lung microenvironment during both homeostasis and respiratory infection leading to reduced lung injury and improved survival.

Pulmonary Th17 Antifungal Immunity Is Regulated by the Gut Microbiome.

Commensal microbiota are critical for the development of local immune responses. In this article, we show that gut microbiota can regulate CD4 T cell polarization during pulmonary fungal infections. Vancomycin drinking water significantly decreased lung Th17 cell numbers during acute infection, demonstrating that Gram-positive commensals contribute to systemic inflammation. We next tested a role for RegIIIγ, an IL-22-inducible antimicrobial protein with specificity for Gram-positive bacteria. Following infection, increased accumulation of Th17 cells in the lungs of RegIIIγ(-/-) and Il22(-/-) mice was associated with intestinal segmented filamentous bacteria (SFB) colonization. Although gastrointestinal delivery of rRegIIIγ decreased lung inflammatory gene expression and protected Il22(-/-) mice from weight loss during infection, it had no direct effect on SFB colonization, fungal clearance, or lung Th17 immunity. We further show that vancomycin only decreased lung IL-17 production in mice colonized with SFB. To determine the link between gut microbiota and lung immunity, serum-transfer experiments revealed that IL-1R ligands increase the accumulation of lung Th17 cells. These data suggest that intestinal microbiota, including SFB, can regulate pulmonary adaptive immune responses.

Pharmacologic Blockade of αvß1 Integrin Ameliorates Renal Failure and Fibrosis In Vivo.

Activated fibroblasts are deemed the main executors of organ fibrosis. However, regulation of the pathologic functions of these cells in vivo is poorly understood. PDGF receptor ß (PDGFRß) is highly expressed in activated pericytes, a main source of fibroblasts. Studies using a PDGFRß promoter-driven Cre system to delete αv integrins in activated fibroblasts identified these integrins as core regulators of fibroblast activity across solid organs, including the kidneys. Here, we used the same PDGFRß-Cre line to isolate and study renal fibroblasts ex vivo We found that renal fibroblasts express three αv integrins, namely αvß1, αvß3, and αvß5. Blockade of αvß1 prevented direct binding of fibroblasts to the latency-associated peptide of TGF-ß1 and prevented activation of the latent TGF-ß complex. Continuous administration of a recently described potent small molecule inhibitor of αvß1, compound 8, starting the day of unilateral ureteral obstruction operation, inhibited collagen deposition in the kidneys of mice 14 days later. Compound 8 also effectively attenuated renal failure, as measured by BUN levels in mice fed an adenine diet known to cause renal injury followed by fibrosis. Inhibition of αvß1 integrin could thus hold promise as a therapeutic intervention in CKD characterized by renal fibrosis.