GDF1 ameliorates cognitive impairment induced by hearing loss.

Hearing loss is associated with an increased risk of Alzheimer disease (AD). However, the mechanisms of hearing loss promoting the onset of AD are poorly understood. Here we show that hearing loss aggravates cognitive impairment in both wild-type mice and mouse models of AD. Embryonic growth/differentiation factor 1 (GDF1) is downregulated in the hippocampus of deaf mice. Knockdown of GDF1 mimics the detrimental effect of hearing loss on cognition, while overexpression of GDF1 in the hippocampus attenuates the cognitive impairment induced by deafness. Strikingly, overexpression of GDF1 also attenuates cognitive impairment in APP/PS1 transgenic mice. GDF1 activates Akt, which phosphorylates asparagine endopeptidase and inhibits asparagine endopeptidase-induced synaptic degeneration and amyloid-ß production. The expression of GDF1 is downregulated by the transcription factor CCAAT-enhancer binding protein-ß. These findings indicate that hearing loss could promote AD pathological changes by inhibiting the GDF1 signaling pathway; thus, GDF1 may represent a therapeutic target for AD.

Low plasma growth/differentiation factor 1 levels are associated with liver fibrosis in patients with stable angina.

BACKGROUND: Growth differentiation factor 1 (GDF1) is a member of the transforming growth factor-ß (TGF-ß) superfamily and a protective mediator against the development of post-infarction cardiac remodeling by negatively regulating MEK-ERK1/2 and Smad signaling pathways in the heart. The TGF-ß/SMAD pathway has been shown to play a key role in the development of hepatic fibrosis. In addition, fatty liver disease has been associated with reduced MEK/ERK1/2 signaling. However, no previous study has investigated the association between GDF1 and liver fibrosis. Therefore, the aim of this study was to investigate the association between plasma GDF1 and liver fibrosis in patients with stable angina. METHODS: We included 327 consecutive patients with stable angina. ELISA was used to measure circulating levels of GDF1, and the fibrosis-4 index was used to assess liver fibrosis. RESULTS: The advanced liver fibrosis group had lower median plasma GDF1 levels than those with minimal liver fibrosis. There was a significant negative association between GDF1 plasma level and fibrosis-4 index (r = -0.135, p = 0.019). A lower concentration of GDF1 was significantly and independently associated with an increased risk of liver fibrosis when concentration was analyzed as a continuous variable and by tertile. In addition, fibrosis-4 index, aspartate aminotransferase (AST)-to-platelet ratio index, and AST/alanine aminotransferase ratio were significantly associated with GDF1 concentration. CONCLUSIONS: Our results indicated an association between low plasma GDF1 and liver fibrosis in the enrolled patients. Further investigations into the role of plasma GDF1 in the pathogenesis of liver fibrosis are warranted.

Homozygous variants in the GDF1 gene related to recurrent right isomerism and complex CHD in two Indian families.

Disorders of laterality are often associated with complex CHD. There is considerable debate about the appropriate terminology to describe these conditions. As our understanding of the genetic basis of these disorders improves, it is likely that terminology will be dictated by the genetic aetiology. The genetic basis of laterality disorders in the Indian population has not been studied. We report two families with autosomal recessive inheritance of isomerism and homozygous variants in the GDF1 gene in affected family members.

Growth differentiation factor 1-induced tumour plasticity provides a therapeutic window for immunotherapy in hepatocellular carcinoma.

Tumour lineage plasticity is an emerging hallmark of aggressive tumours. Tumour cells usually hijack developmental signalling pathways to gain cellular plasticity and evade therapeutic targeting. In the present study, the secreted protein growth and differentiation factor 1 (GDF1) is found to be closely associated with poor tumour differentiation. Overexpression of GDF1 suppresses cell proliferation but strongly enhances tumour dissemination and metastasis. Ectopic expression of GDF1 can induce the dedifferentiation of hepatocellular carcinoma (HCC) cells into their ancestral lineages and reactivate a broad panel of cancer testis antigens (CTAs), which further stimulate the immunogenicity of HCC cells to immune-based therapies. Mechanistic studies reveal that GDF1 functions through the Activin receptor-like kinase 7 (ALK7)-Mothers against decapentaplegic homolog 2/3 (SMAD2/3) signalling cascade and suppresses the epigenetic regulator Lysine specific demethylase 1 (LSD1) to boost CTA expression. GDF1-induced tumour lineage plasticity might be an Achilles heel for HCC immunotherapy. Inhibition of LSD1 based on GDF1 biomarker prescreening might widen the therapeutic window for immune checkpoint inhibitors in the clinic.

Arsenic suppresses GDF1 expression via ROS-dependent downregulation of specificity protein 1.

Inorganic arsenic, an environmental contaminant, has adverse health outcomes. Our previous studies showed that arsenic causes abnormal cardiac development in zebrafish embryos by downregulating Dvr1/GDF1 expression and that folic acid protects against these effects. However, the mechanism by which arsenic represses Dvr1/GDF1 expression remains unknown. Herein, we demonstrate that specificity protein 1 (Sp1) acts as a transcriptional activator of GDF1. Arsenic treatment downregulated Sp1 at both the mRNA and protein level and its downstream targets GDF1 and SIRT1. Chromatin immunoprecipitation analysis showed that the occupancy of Sp1 on the GDF1 or SIRT1 promoter was significantly reduced in response to arsenite. Further investigation showed that Sp1 overexpression inhibited the arsenic-mediated decrease in GDF1 and SIRT1, while Sp1 knockdown had the opposite effect. We found that expression of the oxidative adaptor p66shc was inversely related to that of SIRT1 and that the binding of SIRT1 to the p66shc promoter was sharply attenuated by arsenite treatment. SIRT1 overexpression attenuated p66shc expression but enhanced GDF1 protein expression, while SIRT1 depletion exerted the opposite effect. Both the antioxidants N-acetylcysteine and folic acid reversed the arsenic-mediated repression of Sp1, GDF1 and SIRT1. Moreover, wild-type p66shc overexpression enhanced the arsenic-mediated repression of Sp1, GDF1 and SIRT1, which was accompanied by an increase in intracellular reactive oxygen species (ROS) levels, while both overexpression of a dominant negative p66shcSer36Ala mutant and deficiency in p66shc reversed these effects. Taken together, our results revealed that arsenic suppresses GDF1 expression via the ROS-dependent downregulation of the Sp1/SIRT1 axis, which forms a negative feedback loop with p66shc to regulate oxidative stress. Our findings reveal a novel molecular mechanism underlying arsenic toxicity and provide new insight into the protective effect of folic acid in arsenic-mediated toxicity.

A founder truncating variant in GDF1 causes autosomal-recessive right isomerism and associated congenital heart defects in multiplex Arab kindreds.

The genetic basis of congenital heart malformations associated with disruption of left-right (L-R) asymmetry is broad and heterogenous, with variants in over 25 genes implicated thus far. Of these, deleterious variants in the Growth/Differentiation Factor 1 (GDF1) gene have been shown to cause heterotaxy with varied complex heart malformations of left-right patterning, in 23 individuals reported to date, either in monoallelic or biallelic state. We report three unrelated individuals exhibiting right isomerism with congenital heart defects, each originating from a consanguineous kindred of Arab-Muslim descent. Using whole exome sequencing, a shared novel homozygous truncating c.608G > A (p.W203*) variant in the GDF1 gene was revealed as the molecular basis of their disease. Subsequently, targeted sequencing of this variant showed full segregation with the disease in these families, with a total of over 15 reportedly affected individuals, enabling genetic counseling, prenatal diagnosis, and planning of future pregnancies. Our findings further confirm the association of biallelic GDF1 variants, heterotaxy and congenital heart defects of left-right patterning, and expand the previously described phenotypic spectrum and mutational profile. Moreover, we suggest targeted screening for the p.W203* variant in relevant clinical circumstances.

Association of functional variant in GDF1 promoter with risk of congenital heart disease and its regulation by Nkx2.5.

GDF1 plays an important role in left-right patterning and genetic mutations in the coding region of GDF1 are associated with congenital heart disease (CHD). However, the genetic variation in the promoter of GDF1 with sporadic CHD and its expression regulation is little known. The association of the genetic variation in GDF1 promoter with CHD was examined in two case-control studies, including 1084 cases and 1198 controls in the first study and 582 cases and 615 controls in the second study. We identified one single nucleotide polymorphism (SNP) rs181317402 and two novel genetic mutations located in the promoter region of GDF1. Analysis of combined samples revealed a significant association in genotype and allele frequencies of rs181317402 T/G polymorphism between CHD cases in overall or ventricular septal defects or Tetralogy of Fallot and the control group. rs181317402 allele G polymorphism was significantly associated with a decreased risk of CHD. Furthermore, luciferase assay, chromatin immunoprecipitation and DNA pulldown assay indicated that Nkx2.5 transactivated the expression of GDF1 by binding to the promoter of GDF1. Luciferase activity assay showed that rs181317402 allele G significantly increased the basal and Nkx2.5-mediated activity of GDF1 promoter, while the two genetic mutations had the opposite effect. rs181317402 TG genotype was associated with significantly increased mRNA level of GDF1 compared with TT genotype in 18 CHD individuals. Our results demonstrate for the first time that Nkx2.5 acts upstream of GDF1 and the genetic variants in GDF1 promoter may confer genetic susceptibility to sporadic CHD potentially by altering its expression.

Phylogenetic evidence for independent origins of GDF1 and GDF3 genes in anurans and mammals.

Growth differentiation factors 1 (GDF1) and 3 (GDF3) are members of the transforming growth factor superfamily (TGF-ß) that is involved in fundamental early-developmental processes that are conserved across vertebrates. The evolutionary history of these genes is still under debate due to ambiguous definitions of homologous relationships among vertebrates. Thus, the goal of this study was to unravel the evolution of the GDF1 and GDF3 genes of vertebrates, emphasizing the understanding of homologous relationships and their evolutionary origin. Our results revealed that the GDF1 and GDF3 genes found in anurans and mammals are the products of independent duplication events of an ancestral gene in the ancestor of each of these lineages. The main implication of this result is that the GDF1 and GDF3 genes of anurans and mammals are not 1:1 orthologs. In other words, genes that participate in fundamental processes during early development have been reinvented two independent times during the evolutionary history of tetrapods.

Growth Differentiation Factor-15 Is a Predictor of Mortality in Critically Ill Patients with Sepsis.

Growth differentiation factor-15 (GDF-15) is a member of the transforming growth factor-ß superfamily related to inflammation and macrophage activation. Serum concentrations of GDF-15 can predict poor survival in chronic diseases, but its role in sepsis is obscure. Therefore, we investigated GDF-15 as a prognostic biomarker in critically ill patients. We measured GDF-15 levels in 219 critically ill patients (146 with sepsis, 73 without sepsis) upon admission to the intensive care unit (ICU), in comparison to 66 healthy controls. GDF-15 levels were significantly increased in ICU patients compared to controls. GDF-15 was further increased in sepsis and showed a strong association with organ dysfunction (kidney, liver and lactate) and disease severity (APACHE II and SOFA score). High GDF-15 concentrations at admission independently predicted ICU (HR 3.42; 95% CI 1.33-8.78) and overall mortality (HR 2.02, 95% CI 1.02-3.88) in all ICU critically ill patients as well as in a large subgroup of sepsis patients (ICU mortality: HR 3.16; 95% CI 1.10-9.07; overall mortality: HR 2.62; 95% CI 1.14-6.02). Collectively, serum GDF-15 levels are significantly increased in critically ill patients, associated with sepsis, organ failure, and disease severity. High GDF-15 levels at ICU admission predict short- and long-term mortality risk.

Contribution of rare inherited and de novo variants in 2,871 congenital heart disease probands.

Congenital heart disease (CHD) is the leading cause of mortality from birth defects. Here, exome sequencing of a single cohort of 2,871 CHD probands, including 2,645 parent-offspring trios, implicated rare inherited mutations in 1.8%, including a recessive founder mutation in GDF1 accounting for ∼5% of severe CHD in Ashkenazim, recessive genotypes in MYH6 accounting for ∼11% of Shone complex, and dominant FLT4 mutations accounting for 2.3% of Tetralogy of Fallot. De novo mutations (DNMs) accounted for 8% of cases, including ∼3% of isolated CHD patients and ∼28% with both neurodevelopmental and extra-cardiac congenital anomalies. Seven genes surpassed thresholds for genome-wide significance, and 12 genes not previously implicated in CHD had >70% probability of being disease related. DNMs in ∼440 genes were inferred to contribute to CHD. Striking overlap between genes with damaging DNMs in probands with CHD and autism was also found.

Analytically Sensitive Protein Detection in Microtiter Plates by Proximity Ligation with Rolling Circle Amplification.

BACKGROUND: Detecting proteins at low concentrations in plasma is crucial for early diagnosis. Current techniques in clinical routine, such as sandwich ELISA, provide sensitive protein detection because of a dependence on target recognition by pairs of antibodies, but detection of still lower protein concentrations is often called for. Proximity ligation assay with rolling circle amplification (PLARCA) is a modified proximity ligation assay (PLA) for analytically specific and sensitive protein detection via binding of target proteins by 3 antibodies, and signal amplification via rolling circle amplification (RCA) in microtiter wells, easily adapted to instrumentation in use in hospitals. METHODS: Proteins captured by immobilized antibodies were detected using a pair of oligonucleotide-conjugated antibodies. Upon target recognition these PLA probes guided oligonucleotide ligation, followed by amplification via RCA of circular DNA strands that formed in the reaction. The RCA products were detected by horseradish peroxidase-labeled oligonucleotides to generate colorimetric reaction products with readout in an absorbance microplate reader. RESULTS: We compared detection of interleukin (IL)-4, IL-6, IL-8, p53, and growth differentiation factor 15 (GDF-15) by PLARCA and conventional sandwich ELISA or immuno-RCA. PLARCA detected lower concentrations of proteins and exhibited a broader dynamic range compared to ELISA and iRCA using the same antibodies. IL-4 and IL-6 were detected in clinical samples at femtomolar concentrations, considerably lower than for ELISA. CONCLUSIONS: PLARCA offers detection of lower protein levels and increased dynamic ranges compared to ELISA. The PLARCA procedure may be adapted to routine instrumentation available in hospitals and research laboratories.

Epigenetic silencing of GDF1 disrupts SMAD signaling to reinforce gastric cancer development.

Accumulating evidence reveals the effectiveness of epigenetic therapy in gastric cancer. However, the molecular mechanisms and targets underlying such therapeutic responses remain elusive. Herein, we report an aberrant yet therapeutically rectifiable epigenetic signaling in gastric carcinogenesis. Administration of DNA-demethylating drug 5-aza-2'-deoxycytidine (5-aza-dC) reduced gastric cancer incidence by ~74% (P < 0.05) in N-nitroso-N-methylurea-treated mice. Through genome-wide methylation scanning, novel promoter hypermethylation-silenced and drug-targeted genes were identified in the resected murine stomach tumors and tissues. We uncovered that growth/differentiation factor 1 (Gdf1), a member of the transforming growth factor-ß superfamily, was silenced by promoter hypermethylation in control tumor-bearing mice, but became reactivated in 5-aza-dC-treated mice (P < 0.05). In parallel, the downregulated SMAD2/3 phosphorylation in gastric cancer was revived by 5-aza-dC in vivo. Such hypermethylation-dependent silencing and 5-aza-dC-mediated reactivation of GDF1-SMAD2/3 activity was conserved in human gastric cancer cells (P < 0.05). Subsequent functional characterization further revealed the antiproliferative activity of GDF1, which was exerted through activation of SMAD2/3/4-mediated signaling, transcriptional controls on p15, p21 and c-Myc cell-cycle regulators and phosphorylation of retinoblastoma protein. Clinically, hypermethylation and loss of GDF1 was significantly associated with reduced phosphorylated-SMAD2/3 and poor survival in stomach cancer patients (P < 0.05). Taken together, we demonstrated a causal relationship between DNA methylation and a tumor-suppressive pathway in gastric cancer. Epigenetic silencing of GDF1 abrogates the growth-inhibitory SMAD signaling and renders proliferation advantage to gastric epithelial cells during carcinogenesis. This study lends support to epigenetic therapy for gastric cancer chemoprevention and identifies a potential biomarker for prognosis.

Association of GDF1 rs4808863 with fetal congenital heart defects: a case-control study.

BACKGROUND: Congenital heart defects (CHDs) are the most common fetal defects and the most important cause of child mortality and morbidity. OBJECTIVE: To investigate the association between growth/differentiation factor 1 (GDF1) polymorphisms and fetal CHDs, by evaluating the association of GDF1 rs4808863 with fetal CHDs. DESIGN: A case-control study. SETTING: Beijing, China. PARTICIPANTS: We selected 124 fetuses with a CHD and a normal karyotype and normal array-based comparative genomic hybridisation analysis and compared them with 124 normal fetuses matched for gestational age and sex. Fetuses with a CHD, from 20 to 32 weeks of gestation were included. Fetuses with any chromosomal abnormalities, and fetuses from multiple pregnancies and those carried by pregnant women with chronic diseases, were excluded from this research. DNA extraction and genotyping were carried out for all cases to investigate the genotype distributions of GDF1 rs4808863. RESULTS: A significant difference was noted for the CT phenotype of GDF1 rs4808863 between the controls and the fetuses with CHDs using homozygote and heterozygote comparisons. The minor allele (T allele) of GDF1 rs4808863 was associated with an increased risk of CHD (p<0.05). A statistically significant difference between controls and fetuses with CHDs was noted in a comparison with the mutation genotype CT+TT and wild-type genotype CC (p<0.05) using dominant modal analysis. After stratification analysis, the CT phenotype, the minor allele (T allele) and the mutation genotype CT+TT of the rs4808863 polymorphism were associated with atrioventricular septal defect (AVSD), left ventricular outflow tract obstruction (LVOTO) and left-right laterality defects (p<0.05). CONCLUSIONS: Our results suggest that the GDF1 rs4808863 polymorphism contributes to an increased risk of fetal CHDs, especially the subtypes of AVSD, LVOTO and left-right laterality defects.

Cardioprotective role of growth/differentiation factor 1 in post-infarction left ventricular remodelling and dysfunction.

Growth/differentiation factor 1 (GDF1) is a secreted glycoprotein of the transforming growth factor-ß (TGF-ß) superfamily that mediates cell differentiation events during embryonic development. GDF1 is expressed in several tissues, including the heart. However, the functional role of GDF1 in myocardial infarction (MI)-induced cardiac remodelling and dysfunction is not known. Here, we performed gain-of-function and loss-of-function studies using cardiac-specific GDF1 transgenic (TG) and knockout (KO) mice to determine the role of GDF1 in the pathogenesis of functional and architectural cardiac remodelling after MI, which was induced by surgical left anterior descending coronary artery ligation. Our results demonstrate that overexpression of GDF1 in the heart causes a significant decrease in MI-derived mortality post-MI and leads to attenuated infarct size expansion, left ventricular (LV) dilatation, and cardiac dysfunction at 1 week and 4 weeks after MI injury. Compared with control animals, cardiomyocyte apoptosis, inflammation, hypertrophy, and interstitial fibrosis were all remarkably reduced in the GDF1-TG mice following MI. In contrast, GDF1 deficiency greatly exacerbated the pathological cardiac remodelling response after infarction. Further analysis of the in vitro and in vivo signalling events indicated that the beneficial role of GDF1 in MI-induced cardiac dysfunction and LV remodelling was associated with the inhibition of non-canonical (MEK-ERK1/2) and canonical (Smad) signalling cascades. Overall, our data reveal that GDF1 in the heart is a novel mediator that protects against the development of post-infarction cardiac remodelling via negative regulation of the MEK-ERK1/2 and Smad signalling pathways. Thus, GDF1 may serve as a valuable therapeutic target for the treatment of MI.

Nature and extent of left/right axis defects in T(Wis) /T(Wis) mutant mouse embryos.

BACKGROUND: Mutations in the T-box gene Brachyury have well known effects on invagination of the endomesodermal layer during gastrulation, but the gene also plays a role in the determination of left/right axis determination that is less well studied. Previous work has implicated node morphology in this effect. We use the T(Wis) allele of Brachyury to investigate the molecular and morphological effects of the T locus on axis determination in the mouse. RESULTS: Similar to embryos mutant for the T allele, T(Wis) /T(Wis) embryos have a high incidence of ventral and/or reversed heart looping. In addition, heterotaxia between the direction of heart looping and the direction of embryo turning is common. Scanning electron microscopy reveals defects in node morphology including irregularity, smaller size, and a decreased number of cilia, although the cilia appear morphologically normal. Molecular analysis shows a loss of perinodal expression of genes involved in Nodal signaling, namely Cer2, Gdf1, and Nodal itself. There is also loss of Dll1 expression, a key component of the Notch signaling pathway, in the presomitic mesoderm. CONCLUSIONS: Morphological abnormalities of the node as well as disruptions of the molecular cascade of left/right axis determination characterize T(Wis) /T(Wis) mutants. Decreased Notch signaling may account for both the morphological defects and the absence of expression of genes in the Nodal signaling pathway.

Nodal·Gdf1 heterodimers with bound prodomains enable serum-independent nodal signaling and endoderm differentiation.

The TGFß family member Nodal is central to control pluripotent stem cell fate, but its use as a stem cell differentiation factor is limited by low specific activity. During development, Nodal depends on growth and differentiation factor (Gdf)-1 and on the shared co-receptor Cryptic to specify visceral left-right axis asymmetry. We therefore asked whether the functionality of Nodal can be augmented by Gdf1. Because Nodal and Gdf1 coimmunoprecipitate each other, they were predicted to form heterodimers, possibly to facilitate diffusion or to increase the affinity for signaling receptors. Here, we report that Gdf1 suppresses an unexpected dependence of Nodal on serum proteins and that it is critically required for non-autonomous signaling in cells expressing Cryptic. Nodal, Gdf1, and their cleaved propeptides copurified as a heterodimeric low molecular weight complex that stimulated Activin receptor (Acvr) signaling far more potently than Nodal alone. Although heterodimerization with Gdf1 did not increase binding of Nodal to Fc fusions of co-receptors or Acvr extracellular domains, it was essential for soluble Acvr2 to inhibit Nodal signaling. This implies that Gdf1 potentiates Nodal activity by stabilizing a low molecular weight fraction that is susceptible to neutralization by soluble Acvr2. Finally, in differentiating human ES cells, endodermal markers were more efficiently induced by Nodal·Gdf1 than by Nodal, suggesting that Nodal·Gdf1 is an attractive new reagent to direct stem cell differentiation.

Rab23 regulates Nodal signaling in vertebrate left-right patterning independently of the Hedgehog pathway.

Asymmetric fluid flow in the node and Nodal signaling in the left lateral plate mesoderm (LPM) drive left-right patterning of the mammalian body plan. However, the mechanisms linking fluid flow to asymmetric gene expression in the LPM remain unclear. Here we show that the small GTPase Rab23, known for its role in Hedgehog signaling, plays a separate role in Nodal signaling and left-right patterning in the mouse embryo. Rab23 is not required for initial symmetry breaking in the node, but it is required for expression of Nodal and Nodal target genes in the LPM. Microinjection of Nodal protein and transfection of Nodal cDNA in the embryo indicate that Rab23 is required for the production of functional Nodal signals, rather than the response to them. Using gain- and loss-of function approaches, we show that Rab23 plays a similar role in zebrafish, where it is required in the teleost equivalent of the mouse node, Kupffer׳s vesicle. Collectively, these data suggest that Rab23 is an essential component of the mechanism that transmits asymmetric patterning information from the node to the LPM.

Growth/differentiation factor 1 alleviates pressure overload-induced cardiac hypertrophy and dysfunction.

Pathological cardiac hypertrophy is a major risk factor for developing heart failure, the leading cause of death in the world. Growth/differentiation factor 1 (GDF1), a transforming growth factor-ß family member, is a regulator of cell growth and differentiation in both embryonic and adult tissues. Evidence from human and animal studies suggests that GDF1 may play an important role in cardiac physiology and pathology. However, a critical role for GDF1 in cardiac remodelling has not been investigated. Here, we performed gain-of-function and loss-of-function studies using cardiac-specific GDF1 knockout mice and transgenic mice to determine the role of GDF1 in pathological cardiac hypertrophy, which was induced by aortic banding (AB). The extent of cardiac hypertrophy was evaluated by echocardiographic, hemodynamic, pathological, and molecular analyses. Our results demonstrated that cardiac specific GDF1 overexpression in the heart markedly attenuated cardiac hypertrophy, fibrosis, and cardiac dysfunction, whereas loss of GDF1 in cardiomyocytes exaggerated the pathological cardiac hypertrophy and dysfunction in response to pressure overload. Mechanistically, we revealed that the cardioprotective effect of GDF1 on cardiac remodeling was associated with the inhibition of the MEK-ERK1/2 and Smad signaling cascades. Collectively, our data suggest that GDF1 plays a protective role in cardiac remodeling via the negative regulation of the MEK-ERK1/2 and Smad signaling pathways.

mTNF reverse signalling induced by TNFα antagonists involves a GDF-1 dependent pathway: implications for Crohn's disease.

OBJECTIVE: Mechanisms of action (MoA) of anti-tumour necrosis factor α (TNFα) therapies in Crohn's disease (CD) may critically involve induction of immune cell apoptosis via membrane-bound TNFα (mTNFα) binding. Certolizumab pegol (CZP), which is effective in induction and maintenance of remission in CD lacks the ability to induce apoptosis. The aim of this study was to analyse transcriptomal responses of reverse signalling induced by the TNFα binding agents infliximab (IFX) and CZP in myelomonocytic cells. DESIGN: Induction of transcriptional patterns upon anti-TNFα stimulation was assessed using oligonucleotide microarrays. mRNA expression of GDF-1/ LASS1, which was identified as a shared target, was studied in inflammatory bowel disease by real-time PCR, while signalling pathways induced by growth and differentiation factor 1 (GDF-1) were investigated using western blots and ELISA. RESULTS: IFX and CZP induced a common signature of 20 transcripts that could be categorised into control of cell cycle, transcription activation and pre-mRNA processing. We selected GDF-1/LASS1 for functional follow-up, which was found to be upregulated in inflamed CD tissues. We show that downregulation of GDF-1/LASS1 depends on autocrine release of transforming growth factor ß after mTNFα ligation. We demonstrate that GDF-1 itself acts as a novel proinflammatory factor via induction of interleukin 6 and signal transducer and activator of transcription 3 and is downregulated after IFX treatment. CONCLUSION: Commonalities in the MoA of IFX and CZP comprise modulation of non-apoptotic pathways through downregulation of proinflammatory GDF-1. Further characterisation of the molecular role of GDF-1 in complex inflammatory processes in vivo is warranted to decide whether this proinflammatory molecule is a promising therapeutic target in patients with CD.