Activin A levels are raised during human tuberculosis and blockade of the activin signaling axis influences murine responses to M. tuberculosis infection

Activin A strongly influences immune responses; yet, few studies have examined its role in infectious diseases. We measured serum activin A levels in two independent tuberculosis (TB) patient cohorts and in patients with pneumonia and sarcoidosis. Serum activin A levels were increased in TB patients compared to healthy controls, including those with positive tuberculin skin tests, and paralleled severity of disease, assessed by X-ray scores. In pneumonia patients, serum activin A levels were also raised, but in sarcoidosis patients, levels were lower. To determine whether blockade of the activin A signaling axis could play a functional role in TB, we harnessed a soluble activin type IIB receptor fused to human IgG1 Fc, ActRIIB-Fc, as a ligand trap in a murine TB model. The administration of ActRIIB-Fc to Mycobacterium tuberculosis-infected mice resulted in decreased bacterial loads and increased numbers of CD4 effector T cells and tissue-resident memory T cells in the lung. Increased frequencies of tissue-resident memory T cells corresponded with downregulated T-bet expression in lung CD4 and CD8 T cells. Altogether, the results suggest a disease-exacerbating role of ActRIIB signaling pathways. Serum activin A may be useful as a biomarker for diagnostic triage of active TB or monitoring of anti-tuberculosis therapy.

IMPORTANCE

Tuberculosis remains the leading cause of death by a bacterial pathogen. The etiologic agent of tuberculosis, Mycobacterium tuberculosis, can remain dormant in the infected host for years before causing disease. Significant effort has been made to identify biomarkers that can discriminate between latently infected and actively diseased individuals. We found that serum levels of the cytokine activin A were associated with increased lung pathology and could discriminate between active tuberculosis and tuberculin skin-test-positive healthy controls. Activin A signals through the ActRIIB receptor, which can be blocked by administration of the ligand trap ActRIIB-Fc, a soluble activin type IIB receptor fused to human IgG1 Fc. In a murine model of tuberculosis, we found that ActRIIB-Fc treatment reduced mycobacterial loads. Strikingly, ActRIIB-Fc treatment significantly increased the number of tissue-resident memory T cells. These results suggest a role for ActRIIB signaling pathways in host responses to Mycobacterium tuberculosis and activin A as a biomarker of ongoing disease.

Genetic and geographic influence on phenotypic variation in European sarcoidosis patients

Introduction

Sarcoidosis is a highly variable disease in terms of organ involvement, type of onset and course. Associations of genetic polymorphisms with sarcoidosis phenotypes have been observed and suggest genetic signatures.

Methods

After obtaining a positive vote of the competent ethics committee we genotyped 1909 patients of the deeply phenotyped Genetic-Phenotype Relationship in Sarcoidosis (GenPhenReSa) cohort of 31 European centers in 12 countries with 116 potentially disease-relevant single-nucleotide polymorphisms (SNPs). Using a meta-analysis, we investigated the association of relevant phenotypes (acute vs. sub-acute onset, phenotypes of organ involvement, specific organ involvements, and specific symptoms) with genetic markers. Subgroups were built on the basis of geographical, clinical and hospital provision considerations.

Results

In the meta-analysis of the full cohort, there was no significant genetic association with any considered phenotype after correcting for multiple testing. In the largest sub-cohort (Serbia), we confirmed the known association of acute onset with TNF and reported a new association of acute onset an HLA polymorphism. Multi-locus models with sets of three SNPs in different genes showed strong associations with the acute onset phenotype in Serbia and Lublin (Poland) demonstrating potential region-specific genetic links with clinical features, including recently described phenotypes of organ involvement.

Discussion

The observed associations between genetic variants and sarcoidosis phenotypes in subgroups suggest that gene-environment-interactions may influence the clinical phenotype. In addition, we show that two different sets of genetic variants are permissive for the same phenotype of acute disease only in two geographic subcohorts pointing to interactions of genetic signatures with different local environmental factors. Our results represent an important step towards understanding the genetic architecture of sarcoidosis.

Sarcoidosis and obsessive-compulsive symptoms

INTRODUCTION

Autoimmune obsessive-compulsive disorder (OCD) in the context of pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections (PANDAS) has been observed for decades. The first cases of autoimmune OCD in adulthood were recently described. An association between obsessive-compulsive symptoms (OCS) and systemic autoimmune diseases in the form of connective tissue disease has also been reported. However, whether an association exists between OCD and sarcoidosis is unknown.

CASE STUDY

Here, the authors present an end 20-year-old female patient with symptoms of OCD in whom an advanced diagnostic work-up revealed inflammatory cerebrospinal fluid (CSF) changes (elevated IgG index, CSF-specific oligoclonal bands, intrathecal IgG synthesis, and a positive MRZ reaction). In tissue-based assays using unfixed mouse brain sections, both serum and CSF showed a distinct antinuclear antibody pattern with perinuclear staining. Electroencephalography identified frontocentral theta spindles. Upon endobronchial-guided lymph node biopsy demonstrating non-caseating lymph nodes in further work-up, sarcoidosis was diagnosed. Levels of the sarcoidosis parameters IL-2-R and neopterin were increased. Under immunotherapy for sarcoidosis, the OCS seemed to improve.

DISCUSSION

This case study is paradigmatic, as an association between sarcoidosis and OCD has not been previously reported. After exclusion of alternative causes, the inflammatory CSF changes would be compatible with an inflammatory brain involvement of sarcoidosis. Autoimmune OCD may occur more frequently than is thought, probably also in the context of neurosarcoidosis. This could open up new opportunities through immunotherapies in rare cases with OCD.

Inhaled aviptadil for the possible treatment of COVID-19 in patients at high risk for ARDS: study protocol for a randomized, placebo-controlled, and multicenter trial

Background

Despite the fast establishment of new therapeutic agents in the management of COVID-19 and large-scale vaccination campaigns since the beginning of the SARS-CoV-2 pandemic in early 2020, severe disease courses still represent a threat, especially to patients with risk factors. This indicates the need for alternative strategies to prevent respiratory complications like acute respiratory distress syndrome (ARDS) associated with COVID-19. Aviptadil, a synthetic form of human vasoactive intestinal peptide, might be beneficial for COVID-19 patients at high risk of developing ARDS because of its ability to influence the regulation of exaggerated pro-inflammatory proteins and orchestrate the lung homeostasis. Aviptadil has recently been shown to considerably improve the prognosis of ARDS in COVID-19 when applied intravenously. An inhaled application of aviptadil has the advantages of achieving a higher concentration in the lung tissue, fast onset of activity, avoiding the hepatic first-pass metabolism, and the reduction of adverse effects. The overall objective of this project is to assess the efficacy and safety of inhaled aviptadil in patients hospitalized for COVID-19 at high risk of developing ARDS.

Methods

This multicenter, placebo-controlled, double-blinded, randomized trial with 132 adult patients hospitalized for COVID-19 and at high risk for ARDS (adapted early acute lung injury score ≥ 2 points) is conducted in five public hospitals in Europe. Key exclusion criteria are mechanical ventilation at baseline, need for intensive care at baseline, and severe hemodynamic instability. Patients are randomly allocated to either inhale 67 μg aviptadil or normal saline (three times a day for 10 days), in addition to standard care, stratified by center. The primary endpoint is time from hospitalization to clinical improvement, defined as either hospital discharge, or improvement of at least two levels on the nine-level scale for clinical status suggested by the World Health Organization.

Discussion

Treatment strategies for COVID-19 are still limited. In the context of upcoming new variants of SARS-CoV-2 and possible inefficacy of the available vaccines and antibody therapies, the investigation of alternative therapy options plays a crucial role in decreasing associated mortality and improving prognosis. Due to its unique immunomodulating properties also targeting the SARS-CoV-2 pathways, inhaled aviptadil may have the potential to prevent ARDS in COVID-19.

Trial registration

ClinicalTrials.gov, NCT04536350. Registered 02 September 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06723-w.

Abnormal FeV1 and body mass index are associated with impaired cough-related quality of life in sarcoidosis patients

Sarcoidosis is a granulomatous disease that mainly manifests within the lungs and may thereby impair lung function. Beyond and independently from organ impairment, sarcoidosis may affect quality of life which can be quantified by questionnaires. The Leicester Cough Questionnaire (LCQ) has been developed to assess cough-related quality of life. We analysed data from a prospectively collected cohort of sarcoidosis patients for validation of the German LCQ version. Our analyses demonstrated that LCQ values add additional information beyond routinely monitored parameters (e.g. lung function). Only FeV1 and BMI slightly influence LCQ scores, where all other parameters tested did not correlate with LCQ scores. In summary, LCQ is a valuable tool providing information on the patient' quality of life beyond routine follow-up parameters. FeV1 and BMI may represent treatable traits to reduce cough-related disease burden.

Analysis of single nucleotide polymorphisms in chronic beryllium disease

Sarcoidosis and chronic beryllium disease (CBD) are phenocopies, however the latter one has a clear trigger factor that is beryllium exposure. This study analyses single nucleotide polymorphisms (SNPs) in a large cohort for beryllium-exposed persons. SNPs were chosen for their relevance in sarcoidosis. Even though one of largest cohorts of beryllium-exposed persons was analysed, no statistically relevant association between any SNP and CBD could be verified. Notably, some SNPs exhibit inverse OR for beryllium sensitization and CBD with nominally statistical significance, which allows hypothesizing about pathophysiological role of genes for the disease triggering and development.

Bronchoalveolar Lavage Fluid Reflects a TH1-CD21low B-Cell Interaction in CVID-Related Interstitial Lung Disease

Background

About 20% of patients with common variable immunodeficiency (CVID) suffer from interstitial lung disease (ILD) as part of a systemic immune dysregulation. Current understanding suggests a role of B cells in the pathogenesis based on histology and increased levels of BAFF and IgM associated with active disease corroborated by several reports which demonstrate the successful use of rituximab in CVID-ILD. It is debated whether histological confirmation by biopsy or even video-assisted thoracoscopy is required and currently not investigated whether less invasive methods like a bronchoalveolar lavage (BAL) might provide an informative diagnostic tool.

Objective

To gain insight into potential immune mechanisms underlying granulomatous and lymphocytic interstitial lung disease (GLILD) and to define biomarkers for progressive ILD by characterizing the phenotype of B- and T-cell populations and cytokine profiles in BAL fluid (BALF) of CVID-ILD compared to sarcoidosis patients and healthy donors (HD).

Methods

Sixty-four CVID, six sarcoidosis, and 25 HD BALF samples were analyzed by flow cytometric profiling of B- and T-cells and for cytokines by ELISA and Multiplexing LASER Bead technology.

Results

Both sarcoidosis and CVID-ILD are characterized by a predominantly T-cell mediated lymphocytosis in the BALF. There is an increase in T follicular helper (TFH)-like memory and decrease of regulatory T cells in CVID-ILD BALF. This TFH-like cell subset is clearly skewed toward TH1 cells in CVID-ILD. In contrast to sarcoidosis, CVID-ILD BALF contains a higher percentage of B cells comprising mostly CD21low B cells, but less class-switched memory B cells. BALF analysis showed increased levels of APRIL, CXCL10, and IL-17.

Conclusion

Unlike in sarcoidosis, B cells are expanded in BALF of CVID-ILD patients. This is associated with an expansion of TFH- and TPH-like cells and an increase in APRIL potentially supporting B-cell survival and differentiation and proinflammatory cytokines reflecting not only the previously described TH1 profile seen in CVID patients with secondary immune dysregulation. Thus, the analysis of BALF might be of diagnostic value not only in the diagnosis of CVID-ILD, but also in the evaluation of the activity of the disease and in determining potential treatment targets confirming the prominent role of B-cell targeted strategies.

YB-1 Interferes with TNFα-TNFR Binding and Modulates Progranulin-Mediated Inhibition of TNFα Signaling

Inflammation and an influx of macrophages are common elements in many diseases. Among pro-inflammatory cytokines, tumor necrosis factor α (TNFα) plays a central role by amplifying the cytokine network. Progranulin (PGRN) is a growth factor that binds to TNF receptors and interferes with TNFα-mediated signaling. Extracellular PGRN is processed into granulins by proteases released from immune cells. PGRN exerts anti-inflammatory effects, whereas granulins are pro-inflammatory. The factors coordinating these ambivalent functions remain unclear. In our study, we identify Y-box binding protein-1 (YB-1) as a candidate for this immune-modulating activity. Using a yeast-2-hybrid assay with YB-1 protein as bait, clones encoding for progranulin were selected using stringent criteria for strong interaction. We demonstrate that at physiological concentrations, YB-1 interferes with the binding of TNFα to its receptors in a dose-dependent manner using a flow cytometry-based binding assay. We show that YB-1 in combination with progranulin interferes with TNFα-mediated signaling, supporting the functionality with an NF-κB luciferase reporter assay. Together, we show that YB-1 displays immunomodulating functions by affecting the binding of TNFα to its receptors and influencing TNFα-mediated signaling via its interaction with progranulin.

A Cluster of Beryllium Sensitization Traced to the Presence of Beryllium in Concrete Dust

BACKGROUND

Chronic beryllium disease (CBD), a granulomatous disease with similarities to sarcoidosis, arises only in individuals exposed to beryllium. Inhaled beryllium can elicit a T-cell-dominated alveolitis leading nonnecrotizing granulomata. CBD can be distinguished from sarcoidosis by demonstrating beryllium sensitization in a lymphocyte proliferation test.

RESEARCH QUESTION

Beryllium exposure usually occurs in an occupational setting. Because of the diagnosis of CBD in a patient without evident beryllium exposure, we performed a beryllium-lymphocyte proliferation test (BeLPT) among his work colleagues.

STUDY DESIGN AND METHODS

This field study investigated a cohort of work colleagues without obvious beryllium exposure. Twenty-one of 30 individuals were assessed in our outpatient clinic for beryllium sensitization. Therefore, BeLPT was performed with freshly collected peripheral blood mononuclear cells. Data were extracted from clinical charts, including geographical data. Beryllium content in dust samples collected at the workplace was measured by graphite-furnace atomic absorption spectroscopy and was compared with samples from different areas of Germany.

RESULTS

For the initial patient, the diagnosis of sarcoidosis was reclassified as CBD based on two positive BeLPT results. Assessment of his workplace did not identify a source of beryllium. However, BeLPTs performed on his workmates demonstrated beryllium sensitization in 5 of 21 individuals, suggesting a local beryllium source. Concrete dust obtained from the building yard, the workplace of the index patient, contained high amounts of beryllium (1138 ± 162 μg/kg), whereas dust from other localities (control samples) showed much lower beryllium content (range, 147 ± 18-452 ± 206 μg/kg). Notably, the control dust collected from different places all over Germany exhibit different beryllium concentrations.

INTERPRETATION

We describe a cluster of beryllium-sensitized workers from an industry not related to beryllium caused by environmental exposure to beryllium-containing concrete dust, which exhibited markedly elevated beryllium content. Importantly, analyses of dust samples collected from different localities showed that they contain markedly different amounts of beryllium. Thus, besides workplace-related exposure, environmental factors also are capable of eliciting a beryllium sensitization.

Immunohistochemistry and Radiomic Features for Survival Prediction in Small Cell Lung Cancer

Background: The aim of the study was to evaluate the role of different immunohistochemical and radiomics features in patients with small cell lung cancer (SCLC).

Methods: Consecutive patients with histologically proven SCLC with limited (n = 47, 48%) or extensive disease (n = 51, 52%) treated with radiotherapy and chemotherapy at our department were included in the analysis. The expression of different immunohistochemical markers from the initial tissue biopsy, such as CD56, CD44, chromogranin A, synaptophysin, TTF-1, GLUT-1, Hif-1 a, PD-1, and PD-L1, and MIB-1/KI-67 as well as LDH und NSE from the initial blood sample were evaluated. H-scores were additionally generated for CD44, Hif-1a, and GLUT-1. A total of 72 computer tomography (CT) radiomics texture features from a homogenous subgroup (n = 31) of patients were correlated with the immunohistochemistry, the survival (OS), and the progression-free survival (PFS).

Results: The median OS, calculated from diagnosis, was 21 months for patients with limited disease and 13 months for patients with extensive disease. The expression of synaptophysin correlated with a better OS (HR 0.546 95% CI 0.308–0.966, p = 0.03). The expression of TTF-1 (HR 0.286, 95% CI: 0.117–0.698, p = 0.006) and a lower GLUT-1 H-score (median = 50, HR: 0.511, 95% CI: 0.260–1.003, p = 0.05) correlated with a better PFS. Patients without chromogranin A expression had a higher risk for developing cerebral metastases (p = 0.02) and patients with PD 1 expression were at risk for developing metastases (p = 0.02). Our radiomics analysis did not reveal a single texture feature that correlated highly with OS or PFS. Correlation coefficients ranged between −0.48 and 0.39 for OS and between −0.46 and 0.38 for PFS.

Conclusions: The role of synaptophysin should be further evaluated as synaptophysin-negative patients might profit from treatment intensification. We report an, at most, moderate correlation of radiomics features with overall and progression free survival and no correlation with the expression of different immunohistochemical markers.

Safety and efficacy of abatacept in patients with treatment-resistant SARCoidosis (ABASARC) - protocol for a multi-center, single-arm phase IIa trial

Introduction

Sarcoidosis is a granulomatous systemic disease that becomes chronic in approximately one third of affected patients resulting in quality of life and functional impairment. Immunosuppressive drugs other than steroids represent alternative therapeutic options, but side effects like liver and bone marrow toxicity or increased susceptibility to infections limit their use. Pathophysiological studies in sarcoidosis patients demonstrate altered regulatory T-cell functions with a reduced expression of CTLA-4 (CD152) and prolonged inflammation. Therefore, interfering with CTLA-4 using abatacept might be a therapeutic option in sarcoidosis similar to rheumatoid arthritis therapy.

Methods/design

This is a multicenter prospective open-labeled single arm phase II study addressing the safety of abatacept in sarcoidosis patients. 30 patients with chronic sarcoidosis requiring immunosuppressive therapy beyond 5 mg prednisolone equivalent will be treated with abatacept in combination with corticosteroids for one year in two centers.

The primary endpoint is the number and characterization of severe infectious complications under treatment with abatacept.

Secondary endpoints are the rate of all infections, patient-related outcomes (assessed by questionnaires), lung function and immunological parameters including alveolar inflammation assessed by bronchoaveolar lavage.

Discussion

This is the first trial of abatacept in patients with sarcoidosis. It is hypothesized that administration of abatacept is safe in patients with chronic sarcoidosis and can limit ongoing inflammation. Patients’ wellbeing is assessed by established questionnaires. Immunological work-up will highlight the effect of abatacept on inflammatory pathways in sarcoidosis.

Trial registration

The trial has been registered at the German Clinical Trial Registry (Deutsches Register Klinischer Studien, DRKS) with the identity number DRKS00011660.

The value of bronchoalveolar lavage for discrimination between healthy and diseased individuals

BACKGROUND

Bronchoalveolar lavage (BAL) is standard diagnostic procedure. Procedural recommendations have been made by pneumological societies including normal values for interpretation of BAL cytology. These normal values derive from small studies in healthy volunteers and have never been analysed for their sensitivity and specificity.

OBJECTIVES

This study aims to analyse sensitivity and specificity of these normal values by assessing lavage cell composition in healthy and diseased individuals.

METHODS

More than 6000 BAL were retrospectively analysed for their cellular distribution including BALs of 250 healthy individuals. All BALs were obtained under similar conditions.

RESULTS

Bronchoalveolar lavage cytology of healthy individuals mirrors data from previous studies with smoking being the most important manipulator of BAL cytology. Analyses of proposed normal values demonstrate specificity between 80% and 95%, whereas sensitivity ranges between 35% and 65%. Using different mathematical models, a value summing up the differences to ATS-proposed normal values of the cytological pattern was found to best discriminate between healthy and diseased individuals with a sensitivity of nearly 60% with a predefined specificity of 95%.

CONCLUSION

In summary, our analysis confirmed prior results for healthy volunteers and enlarged these findings by analysing sensitivity and specificity of lavage results in an independent validation cohort of diseased individuals. Thereby, the study may influence the acceptance of BAL in the diagnostic workup of individuals with pulmonary diseases. Additionally, the study proposes a novel value that facilitates lavage interpretation and may therefore be useful in further studies.

[New Pathogenetic Concepts and Early Pharmacological Studies in Sarcoidosis]

The etiology of sarcoidosis is still elusive, yet there has been considerable progress in various areas of basic and clinical research. This review focuses on mechanisms of granuloma formation and on new findings in autoimmunity and genetics of sarcoidosis. A new promising concept arose, where serum amyloid A and/or mycobacterial antigens serve as nidus for granuloma formation. Furthermore, autoimmunity in sarcoidosis was neglected for a long time, yet new studies found autoantigens and abnormalities in antigen presentation in sarcoidosis. Last but not least, large genome-wide association studies discovered several new predisposing genes, leading to new hypotheses on pathomechanisms of sarcoidosis.In the second part, we focus on ongoing or recently completed clinical-pharmacological studies in patients with sarcoidosis: Positive studies were published in well characterized and homogenous subcohorts of sarcoid patients. Several drugs have shown a positive effect on sarcoidosis-associated fatigue, on sarcoidosis of the skin and on pulmonary hypertension in sarcoid patients. It seems that the generation of clinically closely defined subcohorts is necessary to achieve positive outcomes in studies on sarcoidosis.

[Diagnosis and treatment of sarcoidosis. Current standards]

Sarcoidosis is a granulomatous disease that mainly affects the lungs and intrathoracic lymph nodes; however, virtually any organ can be affected. As an orphan disease, recommendations are mainly based on observational or small randomized studies as well as experts' opinion. Diagnosing sarcoidosis requires proof of non-necrotizing granulomas in patients with a compatible symptomatic pattern and the exclusion of other granulomatous diseases. Granulomas can be detected best in the lungs or intrathoracic lymph nodes. Therefore, bronchoscopy and endobronchial ultrasound with biopsies of lymph nodes are the major tools to diagnose sarcoidosis. Frequently, close follow-up and symptomatic therapy are sufficient to allow for spontaneous resolution. In case of functional organ impairment, cardial or CNS involvement, or other complications, steroid therapy is necessary with a starting dose of 0.5 mg/kg body weight that should be tapered-off over 6-12 months. Steroid-refractory disease can be treated by adding methotrexate or azathioprine, two drugs long known in sarcoidosis treatment. Monoclonal antibodies against TNF and lung transplantation are further therapeutic options.

YB-1 is an early and central mediator of bacterial and sterile inflammation in vivo

In vitro studies identified Y-box-binding protein (YB)-1 as a key regulator of inflammatory mediators. In this study, we observed increased levels of secreted YB-1 in sera from sepsis patients. This led us to investigate the in vivo role of YB-1 in murine models of acute peritonitis following LPS injection, in sterile renal inflammation following unilateral ureteral obstruction, and in experimental pyelonephritis. LPS injection enhanced de novo secretion of YB-1 into the urine and the peritoneal fluid of LPS-treated mice. Furthermore, we could demonstrate a significant, transient upregulation and posttranslational modification (phosphorylation at serine 102) of YB-1 in renal and inflammatory cells. Increased renal cytoplasmic YB-1 amounts conferred enhanced expression of proinflammatory chemokines CCL2 and CCL5. Along these lines, heterozygous YB-1 knockout mice (YB-1(+/d)) that display 50% reduced YB-1 levels developed significantly lower responses to both LPS and sterile inflammation induced by unilateral ureteral obstruction. This included diminished immune cell numbers due to impaired migration propensities and reduced chemokine expression. YB-1(+/d) mice were protected from LPS-associated mortality (20% mortality on day 3 versus 80% in wild-type controls); however, immunosuppression in YB-1(+/d) animals resulted in 50% mortality. In conclusion, our findings identify YB-1 as a major, nonredundant mediator in both systemic and local inflammatory responses.

Rat Mrp2 gene expression is regulated by an interleukin-1β-stimulated biphasic response with enhanced transcription and subcellular shuttling of YB-1

INTRODUCTION

Expression of hepatobiliary transporters is decreased during endotoxemia. Reduction of Mrp2 is mediated by IL-1β-dependent signals but underlying mechanisms are still unclear. YB-1 is a predominantly cytoplasmic protein that translocates to the nucleus in response to various stimuli. Previously we have shown that YB-1 down-regulates Mrp2 expression in vitro. Therefore we investigated the potential role of YB-1 as regulator of hepatic acute phase genes.

METHODS

Liver sections from LPS-injected rats (20 h) were stained with YB-1-specific antibodies. Real-time RT-PCR quantification was performed for Mrp2, MMP-2 and YB-1. YB-1 protein was quantified from IL-1β- or TNFα-stimulated rat hepatoma cells (FaO) and the localization of a YFP-YB-1-CFP fusion protein was visualized by confocal microscopy in HepG2 human hepatocellular carcinoma cells. ChIP-assays and EMSA were performed to analyze YB-1 binding to DNA promoter elements.

RESULTS

In endotoxemic livers Mrp2 mRNA was down-regulated by 80%, while YB-1 mRNA expression increased 2.5-fold. Immunohistochemical staining showed a marked up-regulation and predominant nuclear localization of YB-1 protein in LPS challenged rats. In FAO cells IL-1β incubation increased cytoplasmic YB-1 protein content up to 16h. IL-1β stimulation resulted in a 6-fold up-regulation of endogenous YB-1 in the nuclear compartment, which occurred within 90min. In accord with these findings nuclear fluorescence was detected with a YFP-YB-1-CFP fusion protein introduced in HepG2 cells. In addition to DNA binding studies with endotoxemic rat liver tissue, ChIP assays revealed an IL-1β-dependent increase of YB-1 binding to the Mrp2-promoter in FAO cells.

CONCLUSION

YB-1 is activated during the hepatic acute phase response. IL-1β promotes a rapid nuclear YB-1 protein shuttling in hepatoma cells within 90 min and a transcriptional induction thereafter. This biphasic response may explain the IL-1β-mediated suppression of Mrp2 expression in endotoxemic rats.

Y-box binding protein-1 mediates profibrotic effects of calcineurin inhibitors in the kidney

The immunosuppressive calcineurin inhibitors (CNIs) cyclosporine A (CsA) and tacrolimus are widely used in transplant organ recipients, but in the kidney allograft, they may cause tubulointerstitial as well as mesangial fibrosis, with TGF-β believed to be a central inductor. In this study, we report that the cold-shock protein Y-box binding protein-1 (YB-1) is a TGF-β independent downstream effector in CsA- as well as in tacrolimus- but not in rapamycin-mediated activation of rat mesangial cells (rMCs). Intracellular content of YB-1 is several-fold increased in MCs following CNI treatment in vitro and in vivo in mice. This effect ensues in a time-dependent manner, and the operative concentration range encompasses therapeutically relevant doses for CNIs. The effect of CNI on cellular YB-1 content is abrogated by specific blockade of translation, whereas retarding the transcription remains ineffective. The activation of rMCs by CNIs is accomplished by generation of reactive oxygen species. In contrast to TGF-β-triggered reactive oxygen species generation, hydrogen peroxide especially could be identified as a potent inductor of YB-1 accumulation. In line with this, hindering TGF-β did not influence CNI-induced YB-1 upregulation, whereas ERK/Akt pathways are involved in CNI-mediated YB-1 expression. CsA-induced YB-1 accumulation results in mRNA stabilization and subsequent generation of collagen. Our results provide strong evidence for a CNI-dependent induction of YB-1 in MCs that contributes to renal fibrosis via regulation of its own and collagen translation.

Extracellular YB-1 blockade in experimental nephritis upregulates Notch-3 receptor expression and signaling

BACKGROUND

Notch receptors are involved in kidney development and pathogenesis of inflammatory glomerular diseases. Given the secretion of Y-box (YB) protein-1 following cytokine stimulation and subsequent extracellular association with membrane receptor Notch-3 in vitro, we elucidated functional effects of YB-1 targeting on the Notch-3 signaling pathway.

METHODS

Rat mesangial cells were challenged with a monoclonal anti-YB-1 antibody (YB-1-mAb) and analyzed for YB-1 and Notch-3 expression. Notch-3 expression in mice with a targeted disruption of one YB-1 allele (YB-1(+/d)) was compared with their wild-type littermates. Furthermore, YB-1-mAb was applied during mesangioproliferative anti-Thy1.1 nephritis, and glomerular Notch-3, Notch target genes and YB-1 expression were analyzed by immunohistochemistry, quantitative real-time PCR and immunoblotting.

RESULTS

Upon challenge with YB-1-mAb, rat mesangial cells showed an increased expression of YB-1 and Notch-3 protein. Concordantly, we found a significant upregulation of Notch-3 expression in renal cells of YB-1(+/d) mice. YB-1-mAb treatment in anti-Thy1.1 nephritis resulted in enhanced mesangial Notch-3 expression and differential Notch target gene activation (HES2/Hey-2). Notably, YB-1 mRNA content did not differ between groups; however, glomerular YB-1 protein was significantly increased, suggesting a posttranslational mechanism.

CONCLUSION

Extracellular targeting of YB-1 potently induces glomerular Notch-3 receptor expression, Notch signaling and YB-1 stabilization, most likely via an autoregulatory feedback mechanism.

YB-1 acts as a ligand for Notch-3 receptors and modulates receptor activation

Y-box (YB) protein-1 is secreted by mesangial and immune cells after cytokine challenge, but extracellular functions are unknown. Here, we demonstrate that extracellular YB-1 associates with outer cell membrane components and interacts with extracellular Notch-3 receptor domains. The interaction appears to be specific for Notch-3, as YB-1-green fluorescent protein binds to the extracellular domains and full-length forms of Notch-3 but not to Notch-1. YB-1-green fluorescent protein and Notch-3 proteins co-localize at cell membranes, and extracellular YB-1 activates Notch-3 signaling, resulting in nuclear translocation of the Notch-3 intracellular domain and up-regulation of Notch target genes. The YB-1/Notch-3 interaction may be of particular relevance for inflammatory mesangioproliferative disease, as both proteins co-localize in an experimental nephritis model and receptor activation temporally and spatially correlates with YB-1 expression.

Y-box protein-1 is actively secreted through a non-classical pathway and acts as an extracellular mitogen

Y-box protein (YB)-1 of the cold-shock protein family functions in gene transcription and RNA processing. Extracellular functions have not been reported, but the YB-1 staining pattern in inflammatory glomerular diseases, without adherence to cell boundaries, suggests an extracellular occurrence. Here, we show the secretion of YB-1 by mesangial and monocytic cells after inflammatory challenges. It should be noted that YB-1 was secreted through a non-classical mode resembling that of the macrophage migration inhibitory factor. YB-1 release requires ATP-binding cassette transporters, and microvesicles protect YB-1 from protease degradation. Two lysine residues in the YB-1 carboxy-terminal domain are crucial for its release, probably because of post-translational modifications. The addition of purified recombinant YB-1 protein to different cell types results in increased DNA synthesis, cell proliferation and migration. Thus, the non-classically secreted YB-1 has extracellular functions and exerts mitogenic as well as promigratory effects in inflammation.

Differential regulation of chemokine CCL5 expression in monocytes/macrophages and renal cells by Y-box protein-1

The Y-box protein-1 (YB-1) belongs to the family of cold shock proteins that have pleiotropic functions such as gene transcription, RNA splicing, and mRNA translation. YB-1 has a critical role in atherogenesis due to its regulatory effects on chemokine CCL5 (RANTES) gene transcription in vascular smooth muscle cells. Since CCL5 is a key mediator of kidney transplant rejection, we determined whether YB-1 is involved in allograft rejection by manipulating its expression. In human kidney biopsies, YB-1 transcripts were amplified 17-fold in acute and 21-fold in chronic allograft rejection with a close correlation between CCL5 and YB-1 mRNA expression in both conditions. Among three possible YB-1 binding sites in the CCL5 promoter, a critical element was mapped at -28/-10 bps. This site allowed up-regulation of CCL5 transcription in monocytic THP-1 and HUT78 T-cells and in human primary monocytes; however, it repressed transcription in differentiated macrophages. Conversely, YB-1 knockdown led to decreased CCL5 transcription and secretion in monocytic cells. We show that YB-1 is a cell-type specific regulator of CCL5 expression in infiltrating T-cells and monocytes/macrophages and acts as an adaptive controller of inflammation during kidney allograft rejection.