TGF-β1/SMAD3-driven GLI2 isoform expression contributes to aggressive phenotypes of hepatocellular carcinoma

Hedgehog signaling is activated in response to liver injury, and modulates organogenesis. However, the role of non-canonical hedgehog activation via TGF-β1/SMAD3 in hepatic carcinogenesis is poorly understood. TGF-β1/SMAD3-mediated non-canonical activation was found in approximately half of GLI2-positive hepatocellular carcinoma (HCC), and two new GLI2 isoforms with transactivating activity were identified. Phospho-SMAD3 interacted with active GLI2 isoforms to transactivate downstream genes in modulation of stemness, epithelial-mesenchymal transition, chemo-resistance and metastasis in poorly-differentiated hepatoma cells. Non-canonical activation of hedgehog signaling was confirmed in a transgenic HBV-associated HCC mouse model. Inhibition of TGF-β/SMAD3 signaling reduced lung metastasis in a mouse in situ hepatic xenograft model. In another cohort of 55 HCC patients, subjects with high GLI2 expression had a shorter disease-free survival than those with low expression. Moreover, co-positivity of GLI2 with SMAD3 was observed in 87.5% of relapsed HCC patients with high GLI2 expression, indicating an increased risk of post-resection recurrence of HCC. The findings underscore that suppressing the non-canonical hedgehog signaling pathway may confer a potential strategy in the treatment of HCC.

Investigating dysregulation of TGF-β1/SMAD3 signaling in atopic dermatitis: a molecular and immunohistochemical analysis

Atopic dermatitis (AD) is a persistent and recurring inflammatory condition affecting the skin. An expanding corpus of evidence indicates the potential participation of transforming growth factor-β1 (TGF-β1) in the modulation of inflammation and tissue remodeling in AD. The primary objective of this study was to examine the aberrant modulation of TGF-β1/small mothers against decapentaplegic homolog 3 (SMAD3) signaling through a comprehensive analysis of their molecular and protein expression profiles. The study encompassed an aggregate of 37 participants, which included 25 AD patients and 12 controls. The assessment of mRNA and protein levels of TGF-β1 and SMAD3 was conducted utilizing quantitative real-time PCR and immunohistochemistry (IHC), whereas serum IgE and vitamin D levels were estimated by ELISA and chemiluminescence, respectively. Quantitative analysis demonstrated a 2.5-fold upregulation of TGF-β1 mRNA expression in the lesional AD skin (P < 0.0001). IHC also exhibited a comparable augmented pattern, characterized by moderate to strong staining intensities. In addition, TGF-β1 mRNA showed an association with vitamin D deficiency in serum (P < 0.02), and its protein expression was linked with the disease severity (P < 0.01) Furthermore, a significant decrease in the expression of the SMAD3 gene was observed in the affected skin (P = 0.0004). This finding was further confirmed by evaluating the protein expression and phosphorylation of SMAD3, both of which exhibited a decrease. These findings suggest that there is a dysregulation in the TGF-β1/SMAD3 signaling pathway in AD. Furthermore, the observed augmentation in mRNA and protein expression of TGF-β1, along with its correlation with the disease severity, holds considerable clinical significance and emphasizes its potential role in AD pathogenesis.

Adipose-derived stem cells promote glycolysis and peritoneal metastasis via TGF-β1/SMAD3/ANGPTL4 axis in colorectal cancer

Peritoneal metastasis, the third most common metastasis in colorectal cancer (CRC), has a poor prognosis for the rapid progression and limited therapeutic strategy. However, the molecular characteristics and pathogenesis of CRC peritoneal metastasis are poorly understood. Here, we aimed to elucidate the action and mechanism of adipose-derived stem cells (ADSCs), a prominent component of the peritoneal microenvironment, in CRC peritoneal metastasis formation. Database analysis indicated that ADSCs infiltration was increased in CRC peritoneal metastases, and high expression levels of ADSCs marker genes predicted a poor prognosis. Then we investigated the effect of ADSCs on CRC cells in vitro and in vivo. The results revealed that CRC cells co-cultured with ADSCs exhibited stronger metastatic property and anoikis resistance, and ADSCs boosted the intraperitoneal seeding of CRC cells. Furthermore, RNA sequencing was carried out to identify the key target gene, angiopoietin like 4 (ANGPTL4), which was upregulated in CRC specimens, especially in peritoneal metastases. Mechanistically, TGF-β1 secreted by ADSCs activated SMAD3 in CRC cells, and chromatin immunoprecipitation assay showed that SMAD3 facilitated ANGPTL4 transcription by directly binding to ANGPTL4 promoter. The ANGPTL4 upregulation was essential for ADSCs to promote glycolysis and anoikis resistance in CRC. Importantly, simultaneously targeting TGF-β signaling and ANGPTL4 efficiently reduced intraperitoneal seeding in vivo. In conclusion, this study indicates that tumor-infiltrating ADSCs promote glycolysis and anoikis resistance in CRC cells and ultimately facilitate peritoneal metastasis via the TGF-β1/SMAD3/ANGPTL4 axis. The dual-targeting of TGF-β signaling and ANGPTL4 may be a feasible therapeutic strategy for CRC peritoneal metastasis.

The effect of saraglitazar on TGF-β-induced smad3 phosphorylation and expression of genes related to liver fibrosis in LX2 cell line

BACKGROUND AND PURPOSE

Liver fibrosis is a reversible liver injury that occurs as a result of many chronic inflammatory diseases and can lead to cirrhosis, which is irreversible and fatal. So, we studied the anti-fibrotic effects of saroglitazar on LX-2 cell lines, as a dual PPARα/γ agonist.

METHODS

Cells, after 80% confluence, were treated with TGF-β (2 ng/mL) for 24 h. Then cells were treated with saroglitazar at different doses (2.5, 5, 10 µM) for 24 h. After same incubation, the cells of control group, TGF-β group, and TGF-β + saroglitazar group were harvested for RNA and protein extraction to determine the effects of saroglitazar. RT-PCR and western blot methods were used to express genes related to fibrosis.

RESULTS

Our results show that the relative expression of α-SMA, collagen1α, N-cadherin, NOX (1, 2, and 4), and phosphorylated Smad3 protein was significantly higher in TGF-β-treated cells compared with the normal group, and E-cadherin expression was decreased in TGF-β-treated cells. After TGF-β-treated cells were exposed to saroglitazar, the expression of these genes was significantly reversed (P < 0.05).

CONCLUSIONS

Our results clearly show the short-term inhibitory role of saroglitazar in the expression of fibrotic factors using the TGF-β/Smad signaling pathway. These results suggest that saroglitazar can be considered as a suitable therapeutic strategy for fibrotic patients. Although more studies are needed.

The possible correlation between miR-762, Hippo signaling pathway, TWIST1, and SMAD3 in lung cancer and chronic inflammatory diseases

MicroRNAs are small RNA molecules that have a significant role in translational repression and gene silencing through binding to downstream target mRNAs. MiR-762 can stimulate the proliferation and metastasis of various types of cancer. Hippo pathway is one of the pathways that regulate tissue development and carcinogenesis. Dysregulation of this pathway plays a vital role in the progression of cancer. This study aimed to evaluate the possible correlation between miR-762, the Hippo signaling pathway, TWIST1, and SMAD3 in patients with lung cancer, as well as patients with chronic inflammatory diseases. The relative expression of miR-762, MST1, LATS2, YAP, TWIST1, and SMAD3 was determined in 50 lung cancer patients, 30 patients with chronic inflammatory diseases, and 20 healthy volunteers by real-time PCR. The levels of YAP protein and neuron-specific enolase were estimated by ELISA and electrochemiluminescence immunoassay, respectively. Compared to the control group, miR-762, YAP, TWIST1, and SMAD3 expression were significantly upregulated in lung cancer patients and chronic inflammatory patients, except SMAD3 was significantly downregulated in chronic inflammatory patients. MST1, LATS2, and YAP protein were significantly downregulated in all patients. MiR-762 has a significant negative correlation with MST1, LATS2, and YAP protein in lung cancer patients and with MST1 and LATS2 in chronic inflammatory patients. MiR-762 may be involved in the induction of malignant behaviors in lung cancer through suppression of the Hippo pathway. MiR-762, MST1, LATS2, YAP mRNA and protein, TWIST1, and SMAD3 may be effective diagnostic biomarkers in both lung cancer patients and chronic inflammatory patients. High YAP, TWIST1, SMA3 expression, and NSE level are associated with a favorable prognosis for lung cancer.

Gulp1 regulates chondrocyte growth arrest and differentiation via the TGF-β/SMAD2/3 pathway

Chondrocyte differentiation is crucial for cartilage formation. However, the complex processes and mechanisms coordinating chondrocyte proliferation and differentiation remain incompletely understood. Here, we report a novel function of the adaptor protein Gulp1 in chondrocyte differentiation. Gulp1 expression is upregulated during chondrogenic differentiation. Gulp1 knockdown in chondrogenic ATDC5 cells reduces the expression of chondrogenic and hypertrophic marker genes during differentiation. Furthermore, Gulp1 knockdown impairs cell growth arrest during chondrocyte differentiation and reduces the expression of the cyclin-dependent kinase inhibitor p21. The activation of the TGF-β/SMAD2/3 pathway, which is associated with p21 expression in chondrocytes, is impaired in Gulp1 knockdown cells. Collectively, these results demonstrate that Gulp1 contributes to cell growth arrest and chondrocyte differentiation by modulating the TGF-β/SMAD2/3 pathway.

BET inhibitors drive Natural Killer activation in non-small cell lung cancer via BRD4 and SMAD3

Non-small-cell lung carcinoma (NSCLC) is the most common lung cancer and one of the pioneer tumors in which immunotherapy has radically changed patients' outcomes. However, several issues are emerging and their implementation is required to optimize immunotherapy-based protocols. In this work, we investigate the ability of the Bromodomain and Extra-Terminal protein inhibitors (BETi) to stimulate a proficient anti-tumor immune response toward NSCLC. By using in vitro, ex-vivo, and in vivo models, we demonstrate that these epigenetic drugs specifically enhance Natural Killer (NK) cell cytotoxicity. BETi down-regulate a large set of NK inhibitory receptors, including several immune checkpoints (ICs), that are direct targets of the transcriptional cooperation between the BET protein BRD4 and the transcription factor SMAD3. Overall, BETi orchestrate an epigenetic reprogramming that leads to increased recognition of tumor cells and the killing ability of NK cells. Our results unveil the opportunity to exploit and repurpose these drugs in combination with immunotherapy.

The immune regulation and therapeutic potential of the SMAD gene family in breast cancer

Breast cancer is a serious threat to human health. The transforming growth factor-β signaling pathway is an important pathway involved in the occurrence and development of cancer. The SMAD family genes are responsible for the TGF-β signaling pathway. However, the mechanism by which genes of the SMAD family are involved in breast cancer is still unclear. Therefore, it is necessary to investigate the biological roles of the SMAD family genes in breast cancer. We downloaded the gene expression data, gene mutation data, and clinical pathological data of breast cancer patients from the UCSC Xena database. We used the Wilcox test to estimate the expression of genes of the SMAD family in cancers. And the biological functions of SMAD family genes using the DAVID website. The Pearson correlation method was used to explore the immune cell infiltration and drug response of SMAD family genes. We conducted in biological experiments vitro and vivo. In this study, we integrated the multi-omics data from TCGA breast cancer patients for analysis. The expression of genes of SMAD family was significantly dysregulated in patients with breast cancer. Except for SMAD6, the expression of other SMAD family genes was positively correlated. We also found that genes of the SMAD family were significantly enriched in the TGF-β signaling pathway, Hippo signaling pathway, cell cycle, and cancer-related pathways. In addition, SMAD3, SMAD6, and SMAD7 were lowly expressed in stage II breast cancer, while SMAD4 and SMAD2 were lowly expressed in stage III cancer. Furthermore, the expression of genes of the SMAD family was significantly correlated with immune cell infiltration scores. Constructing a xenograft tumor mouse model, we found that SMAD3 knockdown significantly inhibited tumorigenesis. Finally, we analyzed the association between these genes and the IC50 value of drugs. Interestingly, patients with high expression of SMAD3 exhibited significant resistance to dasatinib and staurosporine, while high sensitivity to tamoxifen and auranofin. In addition, SMAD3 knockdown promoted the apoptosis of BT-549 cells and decreased cell activity, and BAY-1161909 and XK-469 increased drug efficacy. In conclusion, genes of the SMAD family play a crucial role in the development of breast cancer.

Single-cell transcriptomic sequencing data reveal aberrant DNA methylation in SMAD3 promoter region in tumor-associated fibroblasts affecting molecular mechanism of radiosensitivity in non-small cell lung cancer

OBJECTIVE

Non-small cell lung cancer (NSCLC) often exhibits resistance to radiotherapy, posing significant treatment challenges. This study investigates the role of SMAD3 in NSCLC, focusing on its potential in influencing radiosensitivity via the ITGA6/PI3K/Akt pathway.

METHODS

The study utilized gene expression data from the GEO database to identify differentially expressed genes related to radiotherapy resistance in NSCLC. Using the GSE37745 dataset, prognostic genes were identified through Cox regression and survival analysis. Functional roles of target genes were explored using Gene Set Enrichment Analysis (GSEA) and co-expression analyses. Gene promoter methylation levels were assessed using databases like UALCAN, DNMIVD, and UCSC Xena, while the TISCH database provided insights into the correlation between target genes and CAFs. Experiments included RT-qPCR, Western blot, and immunohistochemistry on NSCLC patient samples, in vitro studies on isolated CAFs cells, and in vivo nude mouse tumor models.

RESULTS

Fifteen key genes associated with radiotherapy resistance in NSCLC cells were identified. SMAD3 was recognized as an independent prognostic factor for NSCLC, linked to poor patient outcomes. High expression of SMAD3 was correlated with low DNA methylation in its promoter region and was enriched in CAFs. In vitro and in vivo experiments confirmed that SMAD3 promotes radiotherapy resistance by activating the ITGA6/PI3K/Akt signaling pathway.

CONCLUSION

High expression of SMAD3 in NSCLC tissues, cells, and CAFs is closely associated with poor prognosis and increased radiotherapy resistance. SMAD3 is likely to enhance radiotherapy resistance in NSCLC cells by activating the ITGA6/PI3K/Akt signaling pathway.

YTHDF2 governs muscle size through a targeted modulation of proteostasis

The regulation of proteostasis is fundamental for maintenance of muscle mass and function. Activation of the TGF-β pathway drives wasting and premature aging by favoring the proteasomal degradation of structural muscle proteins. Yet, how this critical post-translational mechanism is kept in check to preserve muscle health remains unclear. Here, we reveal the molecular link between the post-transcriptional regulation of m6A-modified mRNA and the modulation of SMAD-dependent TGF-β signaling. We show that the m6A-binding protein YTHDF2 is essential to determining postnatal muscle size. Indeed, muscle-specific genetic deletion of YTHDF2 impairs skeletal muscle growth and abrogates the response to hypertrophic stimuli. We report that YTHDF2 controls the mRNA stability of the ubiquitin ligase ASB2 with consequences on anti-growth gene program activation through SMAD3. Our study identifies a post-transcriptional to post-translational mechanism for the coordination of gene expression in muscle.

Thrombospondin-1 promotes mechanical stress-mediated ligamentum flavum hypertrophy through the TGFβ1/Smad3 signaling pathway

Lumbar spinal canal stenosis is primarily caused by ligamentum flavum hypertrophy (LFH), which is a significant pathological factor. Nevertheless, the precise molecular basis for the development of LFH remains uncertain. The current investigation observed a notable increase in thrombospondin-1 (THBS1) expression in LFH through proteomics analysis and single-cell RNA-sequencing analysis of clinical ligamentum flavum specimens. In laboratory experiments, it was demonstrated that THBS1 triggered the activation of Smad3 signaling induced by transforming growth factor β1 (TGFβ1), leading to the subsequent enhancement of COL1A2 and α-SMA, which are fibrosis markers. Furthermore, experiments conducted on a bipedal standing mouse model revealed that THBS1 played a crucial role in the development of LFH. Sestrin2 (SESN2) acted as a stress-responsive protein that suppressed the expression of THBS1, thus averting the progression of fibrosis in ligamentum flavum (LF) cells. To summarize, these results indicate that mechanical overloading causes an increase in THBS1 production, which triggers the TGFβ1/Smad3 signaling pathway and ultimately results in the development of LFH. Targeting the suppression of THBS1 expression may present a novel approach for the treatment of LFH.

Loeys-Dietz syndrome with a novel in-frame SMAD3 deletion diagnosed as a result of postpartum aortic dissection: A case report

OBJECTIVE

Loeys-Dietz syndrome (LDS) is a rare, autosomal dominant connective tissue disorder which can aggressively affect the aortic vasculature. Limited information is available regarding its impact on pregnancy and postpartum outcomes.

CASE REPORT

A pregnant 38-year-old nulliparous woman with mild aortic regurgitation and family history of aortic aneurysms presented with an aortic root measuring 49 mm. Despite concerns of an underlying connective tissue disorder, a definitive diagnosis was not reached. She delivered under strict blood pressure control, developed intractable uterine atony, and underwent uterine artery embolization. On the second postpartum day, aortic dissection was incidentally diagnosed, and aortic root replacement surgery was performed. Genetic testing revealed a novel in-frame SMAD3 deletion [NM_005902.4: c.703_708del, (p.Ile235_Ser236del)], leading to a diagnosis of LDS type 3.

CONCLUSION

This case highlights the high postpartum aortic dissection risk in women with LDS, emphasizing the importance of early diagnosis in pregnant women with few clinical symptoms.

Therapeutic potential for renal fibrosis by targeting Smad3-dependent noncoding RNAs

Renal fibrosis is a characteristic hallmark of chronic kidney disease (CKD) that ultimately results in renal failure, leaving patients with few therapeutic options. TGF-β is a master regulator of renal fibrosis and mediates progressive renal fibrosis via both canonical and noncanonical signaling pathways. In the canonical Smad signaling, Smad3 is a key mediator in tissue fibrosis and mediates renal fibrosis via a number of noncoding RNAs (ncRNAs). In this regard, targeting Smad3-dependent ncRNAs may offer a specific therapy for renal fibrosis. This review highlights the significance and innovation of TGF-β/Smad3-associated ncRNAs as biomarkers and therapeutic targets in renal fibrogenesis. In addition, the underlying mechanisms of these ncRNAs and their future perspectives in the treatment of renal fibrosis are discussed.

POH1 induces Smad3 deubiquitination and promotes lung cancer metastasis

Smad3 is the key mediator of TGF-β1-triggered signal transduction and the related biological responses, promoting cell invasion and metastasis in various cancers, including lung cancer. However, the deubiquitinase stabilizing Smad3 remains unknown. In this study, we present a paradigm in which POH1 is identified as a novel deubiquitinase of Smad3 that plays a tumor-promoting role in lung adenocarcinoma (LUAD) by regulating Smad3 stability. POH1 markedly increased Smad3 protein levels and prolonged its half-life. POH1 directly interacted and colocalized with Smad3, leading to the removal of poly-deubiquitination of Smad3. Functionally, POH1 facilitated cell proliferation, migration, and invasion by stabilizing Smad3. Importantly, POH1 also promoted liver metastasis of lung cancer cells. The protein levels of both POH1 and Smad3 were raised in the tumor tissues of patients with LUAD, which predicts poor prognosis. Collectively, we demonstrate that POH1 acts as an oncoprotein by enhancing TGF-β1/Smad3 signaling and TGF-β1-mediated metastasis of lung cancer.

Treatment for type 2 diabetes and diabetic nephropathy by targeting Smad3 signaling

TGF-β/Smad3 signaling plays a critical role in type 2 diabetes (T2D) and type 2 diabetic nephropathy (T2DN), but treatment by specifically targeting Smad3 remains unexplored. To develop a new Smad3-targeted therapy for T2D and T2DN, we treated db/db mice at the pre-diabetic or established diabetic stage with a pharmacological Smad3 inhibitor SIS3. The therapeutic effect and mechanisms of anti-Smad3 treatment on T2D and T2DN were investigated. We found that anti-Smad3 treatment on pre-diabetic db/db mice largely attenuated both T2D and T2DN by markedly reducing blood glucose levels, and inhibiting the elevated serum creatinine, microalbuminuria, and renal fibrosis and inflammation. Unexpectedly, although SIS3 treatment on the established diabetic db/db mice inhibited T2DN but did not significantly improve T2D. Mechanistically, we uncovered that inhibition of T2DN in SIS3-treated db/db mice was associated with effectively restoring the balance of TGF-β/Smad signaling by inhibiting Smad3 while increasing Smad7, thereby suppressing Smad3-mediated renal fibrosis and NF-κB-driven renal inflammation via lncRNA Erbb4-IR and LRN9884-dependent mechanisms. We also revealed that inhibition of islet β cell injury by preventing the loss of islet Pax 6 could be the mechanism through which the pre-diabetic treatment, rather than the late SIS3 treatment on db/db mice significantly improved the T2D phenotype.

The Snail signaling branch downstream of the TGF-β/Smad3 pathway mediates Rho activation and subsequent stress fiber formation

Cancer cells acquire malignant phenotypes through an epithelial-mesenchymal transition, which is induced by environmental factors or extracellular signaling molecules, including transforming growth factor-β (TGF-β). Among epithelial-mesenchymal transition-associated cell responses, cell morphological changes and cell motility are closely associated with remodeling of the actin stress fibers. Here, we examined the TGF-β signaling pathways leading to these cell responses. Through knockdown experiments in A549 lung adenocarcinoma cells, we found that Smad3-mediated induction of Snail, but not that of Slug, is indispensable for morphological changes, stress fiber formation, and enhanced motility in cells stimulated with TGF-β. Ectopic expression of Snail in SMAD3-knockout cells rescued the defect in morphological changes and stress fiber formation by TGF-β, indicating that the role of Smad3 in these responses is to upregulate Snail expression. Mechanistically, Snail is required for TGF-β-induced upregulation of Wnt5b, which in turn activates RhoA and subsequent stress fiber formation in cooperation with phosphoinositide 3-kinase. However, ectopic expression of Snail in SMAD3-knockout cells failed to rescue the defect in cell motility enhancement by TGF-β, indicating that activation of the Smad3/Snail/Wnt5b axis is indispensable but not sufficient for enhancing cell motility; a Smad3-dependent but Snail-independent pathway to activate Rac1 is additionally required. Therefore, the Smad3-dependent pathway leading to enhanced cell motility has two branches: a Snail-dependent branch to activate RhoA and a Snail-independent branch to activate Rac1. Coordinated activation of these branches, together with activation of non-Smad signaling pathways, mediates enhanced cell motility induced by TGF-β.

Knockdown of LINC00511 enhances radiosensitivity of lung adenocarcinoma via regulating miR-497-5p/SMAD3

As the most common histological subtype of primary lung cancer, lung adenocarcinoma (LUAD) causes enormous cancer deaths worldwide. Radiotherapy has been frequently used in LUAD cases, and radiosensitivity is vital for LUAD therapy. This research sought to explore the genetic factors affecting radiosensitivity in LUAD and inner mechanisms. LINC00511, miR-497-5p, and SMAD3 expression in LUAD cells were detected via qRT-PCR and western blot. CCK-8 assays, colony formation, and flow cytometry assays were employed to explore the cell viability, apoptosis, and radiosensitivity in PC-9 and A549 cells. The targeting relationship between LINC00511, miR-497-5p, and SMAD3 was verified by dual luciferase reporter assay. Furthermore, xenograft experiments were performed for the in vivo verification. In conclusion, LINC00511 was overexpressed in LUAD cells, which downregulated downstream miR-497-5p expression and mediately led to SMAD3 activation. LINC00511 downregulation suppressed cell viability while enhanced apoptosis rate in LUAD cells. Also, LINC00511 and SMAD3 were overexpressed, while miR-497-5p was downregulated in LUAD cells exposed to 4Gy irradiation treatment. Moreover, LINC00511 inhibition could block SMAD3 expression and promoted the radiosensitivity both in vitro and in vivo. These findings uncover LINC00511 knockdown promoted miR-497-5p expression and subsequently led to lower SMAD3 level, which enhanced radiosensitivity in LUAD cells. LINC00511/miR-497-5p/SMAD3 axis could be of considerable potential to enhance radiosensitivity in LUAD.

Circular RNA MTCL1 targets SMAD3 by sponging miR-145-5p for regulation of cell proliferation and migration in Hirschsprung's disease

BACKGROUND

Hirschsprung's disease (HSCR) is a congenital disorder resulting from abnormal development of the enteric nervous system (ENS). Given the complexity of its pathogenesis, it is important to investigate the role of epigenetic inheritance in its development. As Circ-MTCL1 is abundant in brain tissue and colon tissue, whether it has a significant part in the development of ENS is worth exploring. This study clarifies its role in HSCR and identifies the specific molecular mechanisms involved.

METHODS

Diseased and dilated segment colon tissues diagnosed as HSCR were collected for the assessment of gene expression levels using RT-PCR. EdU and CCK-8 assays were adopted to evaluate cell proliferation, and Transwell assay was adopted to assess cell migration. The interaction between Circ-MTCL1, miR-145-5p and SMAD3 was confirmed by dual luciferase reporter gene analysis, RT-PCR and Western blotting.

RESULTS

Circ-MTCL1 was down-regulated in the aganglionic colon tissues. The decreased expression of Circ-MTCL1 associated with a reduction in cell migration and proliferation. Bioinformatics analysis and cellular experiments confirmed its role might have been associated with the inhibition of miR-145-5p. MiR-145-5p was up-regulated in HSCR diseased segment colon tissues, exhibiting a negative correlation with Circ-MTCL1. Overexpression of miR-145-5p reversed the inhibition of cell migration and proliferation associated with Circ-MTCL1 down-regulation. The expression of SMAD3 was inhibited by miR-145-5p. The overexpression of SMAD3 eliminated the miR-145-5p-associated inhibition of cell migration and proliferation. Overexpression of miR-145-5p reversed the inhibitory effects of Circ-MTCL1 down-regulation-associated inhibition of cell migration and proliferation, while suppressing SMAD3 expression. Conversely, overexpression of SMAD3 counteracted the miR-145-5p-associated inhibition of cell migration and proliferation.

CONCLUSIONS

Circ-MTCL1 may function as a miR-145-5p sponge, regulating the expression of SMAD3 and influencing cell migration and proliferation, thus participating in the development of HSCR.

Jagged1 intracellular domain/SMAD3 complex transcriptionally regulates TWIST1 to drive glioma invasion

Jagged1 (JAG1) is a Notch ligand that correlates with tumor progression. Not limited to its function as a ligand, JAG1 can be cleaved, and its intracellular domain translocates to the nucleus, where it functions as a transcriptional cofactor. Previously, we showed that JAG1 intracellular domain (JICD1) forms a protein complex with DDX17/SMAD3/TGIF2. However, the molecular mechanisms underlying JICD1-mediated tumor aggressiveness remains unclear. Here, we demonstrate that JICD1 enhances the invasive phenotypes of glioblastoma cells by transcriptionally activating epithelial-to-mesenchymal transition (EMT)-related genes, especially TWIST1. The inhibition of TWIST1 reduced JICD1-driven tumor aggressiveness. Although SMAD3 is an important component of transforming growth factor (TGF)-β signaling, the JICD1/SMAD3 transcriptional complex was shown to govern brain tumor invasion independent of TGF-β signaling. Moreover, JICD1-TWIST1-MMP2 and MMP9 axes were significantly correlated with clinical outcome of glioblastoma patients. Collectively, we identified the JICD1/SMAD3-TWIST1 axis as a novel inducer of invasive phenotypes in cancer cells.

A novel pathogenic variant located just upstream of the C-terminal Ser423-X-Ser425 phosphorylation motif in SMAD3 causing Loeys-Dietz syndrome

OBJECTIVE

Loeys-Dietz syndrome (LDS) is a heritable disorder of connective tissue closely related to Marfan syndrome (MFS). LDS is caused by loss-of-function variants of genes that encode components of transforming growth factor-β (TGF-β) signaling; nevertheless, LDS type 1/2 caused by TGFBR1/2 pathogenic variants is frequently found to have paradoxical increases in TGF-β signaling in the aneurysmal aortic wall. Here, we present a Japanese LDS family having a novel SMAD3 variant.

METHODS

The proband was tested via clinical, genetic, and histological analyses. In vitro analysis was performed for pathogenic evaluation.

RESULTS

The novel heterozygous missense variant of SMAD3 [c.1262G>A, p.(Cys421Tyr)], located just upstream of the C-terminal Ser423-X-Ser425 phosphorylation motif, was found in this instance of LDS type 3. This variant led to reduced phospho-SMAD3 (Ser423/Ser425) levels and transcription activity in vitro; however, a paradoxical upregulation of TGF-β signaling was evident in the aortic wall.

CONCLUSIONS

Our results revealed the presence of TGF-β paradox in this case with the novel loss-of-function SMAD3 variant. The precise mechanism underlying the paradox is unknown, but further research is warranted to clarify the influence of the SMAD3 variant type and location on the LDS3 phenotype as well as the molecular mechanism leading to LDS3 aortopathy.

LINC02253 promote the malignant phenotype of Colon adenocarcinoma cells by up-regulating WWP1-mediated SMAD3 ubiquitination

OBJECTIVES

Colon adenocarcinoma (COAD) represents a type of common malignant tumor originating in the digestive tract. Long non-coding RNAs (lncRNAs) have been identified to engage in regulating the initiation and development of COAD. LncRNA LINC02253 has been reported abnormal expressed in COAD, but the underlying mechanism has not been discussed so far. This study aimed to determine the role and the molecular biology mechanism of LINC02253 in COAD progression and unearthed its specific molecular mechanism.

MATERIALS AND RESULTS

RT-qPCR and Western blot assays were conducted to detect gene expression. Function assays were performed to evaluate the effect of gene expression on COAD cell phenotype. Mechanism analyses were done to verify the association among genes after bioinformatics analysis. The obtained data revealed that LINC02253 demonstrated a high expression in COAD tissues and cells. This gene served as an oncogene, permitting to stimulate proliferation and suppress apoptosis of COAD cells. Mechanically, it was found that LINC02253 recruited FUS to stabilize WWP1 mRNA and WWP1 could mediate SMAD3 ubiquitination, thereby promoting the malignant phenotype formation of COAD cells.

CONCLUSIONS

LINC02253 was uncovered to exert an oncogenic role, enhancing the proliferation of COAD cells and repressing the cell apoptosis by recruiting FUS and encouraging WWP1-mediated SMAD3 ubiquitination.

[Silencing of SMAD family member 3 promotes M2 polarization of macrophages and the expression of SMAD7 in rheumatoid arthritis]

Objective To investigate the effect of SMAD family member 3(SMAD3) silenced by small interfering RNA (siRNA) on macrophage polarization and transforming growth factor β1 (TGF-β1)/ SMAD family signaling pathway in rheumatoid arthritis (RA). Methods RA macrophages co-cultured with rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) were used as a cell model. TGF-β1 was used to stimulate macrophages, and SMAD3-specific siRNA (si-SMAD3) and negative control siRNA (si-NC) were transfected into human RA macrophages co-cultured in TranswellTM chamber. The expression of SMAD3 mRNA was detected by real-time fluorescence quantitative PCR, and the expression of TGF-β1, SMAD3 and SMAD7 protein was detected by Western blot analysis. The contents of TGF-β1 and IL-23 in cell culture supernatant were determined by ELISA. Cell proliferation was detected by CCK-8 assay. TranswellTM chamber was used to measure cell migration. Results Compared with the model group and the si-NC group, the expression of TGF-β1, SMAD3 mRNA and protein in RA macrophages decreased significantly after silencing SMAD3. In addition, the secretion of IL-23 decreased significantly, and the cell proliferation activity and cell migration were inhibited, with high expression of SMAD7. Conclusion Knockdown of SMAD3 can promote M2 polarization and SMAD7 expression in RA macrophages.

SIRT2 alleviated renal fibrosis by deacetylating SMAD2 and SMAD3 in renal tubular epithelial cells

Transforming growth factor-β (TGF-β) is the primary factor that drives fibrosis in most, if not all, forms of chronic kidney disease. In kidneys that are obstructed, specific deletion of Sirt2 in renal tubule epithelial cells (TEC) has been shown to aggravate renal fibrosis, while renal tubule specific overexpression of Sirt2 has been shown to ameliorate renal fibrosis. Similarly, specific deletion of Sirt2 in hepatocyte aggravated CCl4-induced hepatic fibrosis. In addition, we have demonstrated that SIRT2 overexpression and knockdown restrain and enhance TGF-β-induced fibrotic gene expression, respectively, in TEC. Mechanistically, SIRT2 reduced the phosphorylation, acetylation, and nuclear localization levels of SMAD2 and SMAD3, leading to inhibition of the TGF-β signaling pathway. Further studies have revealed that that SIRT2 was able to directly interact with and deacetylate SMAD2 at lysine 451, promoting its ubiquitination and degradation. Notably, loss of SMAD specific E3 ubiquitin protein ligase 2 abolishes the ubiquitination and degradation of SMAD2 induced by SIRT2 in SMAD2. Regarding SMAD3, we have found that SIRT2 interact with and deacetylates SMAD3 at lysine 341 and 378 only in the presence of TGF-β, thereby reducing its activation. This study provides initial indication of the anti-fibrotic role of SIRT2 in renal tubules and hepatocytes, suggesting its therapeutic potential for fibrosis.

circEIF3I facilitates the recruitment of SMAD3 to early endosomes to promote TGF-β signalling pathway-mediated activation of MMPs in pancreatic cancer

BACKGROUND

Among digestive tract tumours, pancreatic ductal adenocarcinoma (PDAC) shows the highest mortality trend. Moreover, although PDAC metastasis remains a leading cause of cancer-related deaths, the biological mechanism is poorly understood. Recent evidence demonstrates that circular RNAs (circRNAs) play important roles in PDAC progression.

METHODS

Differentially expressed circRNAs in normal and PDAC tissues were screened via bioinformatics analysis. Sanger sequencing, RNase R and actinomycin D assays were performed to confirm the loop structure of circEIF3I. In vitro and in vivo functional experiments were conducted to assess the role of circEIF3I in PDAC. MS2-tagged RNA affinity purification, mass spectrometry, RNA immunoprecipitation, RNA pull-down assay, fluorescence in situ hybridization, immunofluorescence and RNA-protein interaction simulation and analysis were performed to identify circEIF3I-interacting proteins. The effects of circEIF3I on the interactions of SMAD3 with TGFβRI or AP2A1 were measured through co-immunoprecipitation and western blotting.

RESULTS

A microarray data analysis showed that circEIF3I was highly expressed in PDAC cells and correlated with TNM stage and poor prognosis. Functional experiments in vitro and in vivo revealed that circEIF3I accelerated PDAC cells migration, invasion and metastasis by increasing MMPs expression and activity. Mechanistic research indicated that circEIF3I binds to the MH2 domain of SMAD3 and increases SMAD3 phosphorylation by strengthening the interactions between SMAD3 and TGFβRI on early endosomes. Moreover, AP2A1 binds with circEIF3I directly and promotes circEIF3I-bound SMAD3 recruitment to TGFβRI on early endosomes. Finally, we found that circEif3i exerts biological functions in mice similar to those of circEIF3I in humans PDAC.

CONCLUSIONS

Our study reveals that circEIF3I promotes pancreatic cancer progression. circEIF3I is a molecular scaffold that interacts with SMAD3 and AP2A1 to form a ternary complex, that facilitates the recruitment of SMAD3 to early endosomes and then activates the TGF-β signalling pathway. Hence, circEIF3I is a potential prognostic biomarker and therapeutic target in PDAC.

Epigenetic and molecular coordination between HDAC2 and SMAD3-SKI regulates essential brain tumour stem cell characteristics

Histone deacetylases are important epigenetic regulators that have been reported to play essential roles in cancer stem cell functions and are promising therapeutic targets in many cancers including glioblastoma. However, the functionally relevant roles of specific histone deacetylases, in the maintenance of key self-renewal and growth characteristics of brain tumour stem cell (BTSC) sub-populations of glioblastoma, remain to be fully resolved. Here, using pharmacological inhibition and genetic loss and gain of function approaches, we identify HDAC2 as the most relevant histone deacetylase for re-organization of chromatin accessibility resulting in maintenance of BTSC growth and self-renewal properties. Furthermore, its specific interaction with the transforming growth factor-β pathway related proteins, SMAD3 and SKI, is crucial for the maintenance of tumorigenic potential in BTSCs in vitro and in orthotopic xenograft models. Inhibition of HDAC2 activity and disruption of the coordinated mechanisms regulated by the HDAC2-SMAD3-SKI axis are thus promising therapeutic approaches for targeting BTSCs.

SMAD3 promotes expression and activity of the androgen receptor in prostate cancer

Overexpression of androgen receptor (AR) is the primary cause of castration-resistant prostate cancer, although mechanisms upregulating AR transcription in this context are not well understood. Our RNA-seq studies revealed that SMAD3 knockdown decreased levels of AR and AR target genes, whereas SMAD4 or SMAD2 knockdown had little or no effect. ChIP-seq analysis showed that SMAD3 knockdown decreased global binding of AR to chromatin. Mechanistically, we show that SMAD3 binds to intron 3 of the AR gene to promote AR expression. Targeting these binding sites by CRISPRi reduced transcript levels of AR and AR targets. In addition, ∼50% of AR and SMAD3 ChIP-seq peaks overlapped, and SMAD3 may also cooperate with or co-activate AR for AR target expression. Functionally, AR re-expression in SMAD3-knockdown cells partially rescued AR target expression and cell growth defects. The SMAD3 peak in AR intron 3 overlapped with H3K27ac ChIP-seq and ATAC-seq peaks in datasets of prostate cancer. AR and SMAD3 mRNAs were upregulated in datasets of metastatic prostate cancer and CRPC compared with primary prostate cancer. A SMAD3 PROTAC inhibitor reduced levels of AR, AR-V7 and AR targets in prostate cancer cells. This study suggests that SMAD3 could be targeted to inhibit AR in prostate cancer.

M6A RNA methylation-mediated RMRP stability renders proliferation and progression of non-small cell lung cancer through regulating TGFBR1/SMAD2/SMAD3 pathway

Non-small cell lung cancer (NSCLC) has the highest mortality rate among all malignancies worldwide. The role of long noncoding RNAs (lncRNAs) in the progression of cancers is a contemporary research hotspot. Based on an integrative analysis of The Cancer Genome Atlas database, we identified lncRNA-RNA Component of Mitochondrial RNA Processing Endoribonuclease (RMRP) as one of the most highly upregulated lncRNAs that are associated with poor survival in NSCLC. Furthermore, N(6)-methyladenosine (m6A) was highly enriched within RMRP and enhanced its RNA stability. In vitro and in vivo experiments showed that RMRP promoted NSCLC cell proliferation, invasion, and migration. In terms of mechanism, RMRP recruited YBX1 to the TGFBR1 promotor region, leading to upregulation of the transcription of TGFBR1. The TGFBR1/SMAD2/SMAD3 pathway was also regulated by RMRP. In addition, RMRP promoted the cancer stem cells properties and epithelial mesenchymal transition, which promote the resistance to radiation therapy and cisplatin. Clinical data further confirmed a positive correlation between RMRP and TGFBR1. In short, our work reveals that m6A RNA methylation-mediated RMRP stability renders proliferation and progression of NSCLC through regulating TGFBR1/SMAD2/SMAD3 pathway.

SMAD3, Cell proliferation and lymph nodes metastasis in breast cancer hormone-dependent

INTRODUCTION

Tumor Growth Factor-β (TGF-β) is a multifunctional cytokine that plays a crucial role in various biological processes. TGF-β is also involved in various pathologies including breast cancer (BC). BC is strongly dependent on hormone receptors such as Estrogen receptors (ERa, ERb) and Progesterone Receptor (PR).

AIM

To audit the potential cross-talk between TGF-β and the molecular distribution of hormone receptors (ERs and PR).

METHODS

The current study analyzes the expression patterns of SMAD3, ERα, ERβ and PR in 40 breast tumor tissues using qRT-PCR. Furthermore, the Ki-67 and HER2/neu status have been detected by Immunohistochemistry.

RESULTS

Our results show a decrease in the SMAD3 expression in 27 of the 40 cases while its expression is increased in the remaining 13 cases (p=0.003). The over-expression of SMAD3 is associated with high tumor grades. Moreover, there is a significant positive correlation between SMAD3+ with a high proliferative index and metastases (p=0.001 and p=0.01respectevely). The SMAD3 expression relative to (ERα, ERβ) subgroups shows a significant association of SMAD3+ with the (ERα+, ERβ+) subgroups (p=0.009). The same is true for PR, our results show a significant association of SMAD3+ with PR+ (p=0.02). Moreover, analysis of the expression of molecular subgroups (SMAD3+, ERα+, ERβ+) and (SMAD3+, PR+) compared to clinical and pathological information shows a significant association with high grade tumors, a high proliferation index (p=0.02, p= 0.01 respectively) and lymph node infiltration.

CONCLUSION

It is concluded that SMAD3 can promote cell proliferation and metastases in (ERα+, ERβ+) and PR+ breast cancer.

The Expression of TGF-β1, SMAD3, ILK and miRNA-21 in the Ectopic and Eutopic Endometrium of Women with Endometriosis

The molecular pathogenesis of endometriosis has been associated with pathological alterations of protein expression via disturbances in homeostatic genes, miRNA expression profiles, and signaling pathways that play an essential role in the epithelial-mesenchymal transition (EMT) process. TGF-β1 has been hypothesized to play a key role in the development and progression of endometriosis, but the activation of a specific mechanism via the TGF-β-SMAD-ILK axis in the formation of endometriotic lesions is poorly understood. The aim of this study was to assess the expression of EMT markers (TGF-β1, SMAD3, ILK) and miR-21 in ectopic endometrium (ECE), in its eutopic (EUE) counterpart, and in the endometrium of healthy women. The expression level of the tested genes and miRNA was also evaluated in peripheral blood mononuclear cells (PBMC) in women with and without endometriosis. Fifty-four patients (n = 54; with endometriosis, n = 29, and without endometriosis, n = 25) were enrolled in the study. The expression levels (RQ) of the studied genes and miRNA were evaluated using qPCR. Endometriosis patients manifested higher TGF-β1, SMAD3, and ILK expression levels in the eutopic endometrium and a decreased expression level in the ectopic lesions in relation to control tissue. Compared to the endometrium of healthy participants, miR-21 expression levels did not change in the eutopic endometrium of women with endometriosis, but the RQ was higher in their endometrial implants. In PBMC, negative correlations were found between the expression level of miR-21 and the studied genes, with the strongest statistically significant correlation observed between miR-21 and TGF-β1. Our results suggest the loss of the endometrial epithelial phenotype defined by the differential expression of the TGF-β1, SMAD3 and ILK genes in the eutopic and ectopic endometrium. We concluded that the TGF-β1-SMAD3-ILK signaling pathway, probably via a mechanism related to the EMT, may be important in the pathogenesis of endometriosis. We also identified miR-21 as a possible inhibitor of this TGF-β1-SMAD3-ILK axis.

LOC554202 contributes to chordoma progression by sponging miR-377-3p and up-regulating SMAD3

Chordoma is a rare malignant bone tumor originating from the remnants of the notochord. Here, the role of long noncoding LOC554202 in chordoma progression and its associated mechanism were explored. Cell proliferation was analyzed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5 diphenyltetrazolium bromide and colony formation assays. Flow cytometry was conducted to analyze cell apoptosis rate. The migration and invasion of chordoma cells were analyzed by transwell migration and invasion assays and wound healing assays. A xenograft tumor model was established in nude mice to explore the role of LOC554202 in regulating tumor growth in vivo . The interaction between microRNA-377-3p (miR-377-3p) and LOC554202 or sekelsky mothers against d PP (SMAD) family member 3 (SMAD3) was verified by dual-luciferase reporter and RNA immunoprecipitation assays. The glycolytic rate of chordoma cells was analyzed using glucose assay kit, lactic acid kit and ApoSENSOR ADP/ATP ratio assay kit. LOC554202 expression was upregulated in chordoma tissues and cell lines. LOC554202 silencing suppressed the proliferation, migration and invasion and induced the apoptosis of chordoma cells. LOC554202 knockdown restrained xenograft tumor growth in vivo . miR-377-3p was confirmed as a target of LOC554202, and miR-377-3p silencing largely overturned LOC554202 knockdown-mediated anti-tumor effects in chordoma cells. miR-377-3p interacted with the 3' untranslated region (3'UTR) of SMAD3 and miR-377-3p overexpression-mediated antitumor effects in chordoma cells were largely attenuated by SMAD3 overexpression. LOC554202 could positively regulate SMAD3 expression by sponging miR-377-3p in chordoma cells. LOC554202 contributed to the glycolysis of chordoma cells by targeting binding to miR-377-3p/SMAD3 axis. LOC554202 facilitated the proliferation, migration, invasion and glycolysis and inhibited the apoptosis of chordoma cells by mediating miR-377-3p/SMAD3 axis.

Indole-derived compound SIS3 targets a subset of activated Smad complexes

Smad2 and Smad3 are receptor-regulated Smad proteins that transmit signals from cytokines belonging to the transforming growth factor (TGF)-β family, which are vital for adult tissue homeostasis. The overactivation of such proteins often engenders the development of pathological conditions. Smad3 reportedly mediates TGF-β–induced fibrosis. Although various potential Smad3-specific inhibitors are being developed, their specificity and action mechanisms remain largely unknown. This study aimed to establish a biochemical platform to monitor Smad2- or Smad3-dependent TGF-β signaling using SMAD2, SMAD3 and SMAD2/3 knockout cell lines alongside TGF-β–dependent luciferase reporters and Smad mutant proteins. Using this platform, SIS3, an indole-derived compound widely used as a specific Smad3 inhibitor, was observed to preferentially suppress a subset of activated Smad complexes. However, its inhibition did not favor Smad3 signaling over Smad2 signaling. These findings indicate that SIS3 can be employed as a probe to examine the heterogeneous nature of Smad signaling that induces gene expression. However, its use as a Smad3-specific inhibitor should be avoided.

Alteration of miR-21, miR-433 and miR-590 tissue expression related to the TGF-β signaling pathway in ulcerative colitis patients

Ulcerative colitis (UC) is an inflammatory disease, and studies have suggested a role for TGF-β signalling pathway in the pathogenesis of UC. In the present study, we evaluated expression of TGF-β signalling genes and their regulatory microRNAs in patients with UC and control subjects. The expression of TGF-β1, SMAD2, SMAD3, miR-21, miR-101, miR-433, and miR-590 were evaluated using real-time PCR in biopsy samples of the patients and controls. Results showed increased expression of TGF-β1 and SMAD3 in the patients compared to controls. In addition, miR-21 and miR-433 were found to be higher in the patients compared to controls; however, miR-590 was found to be lower. Moreover, miR-433 was demonstrated to have positive correlation with SMAD3 and TGF-β while miR-21 was positively correlated with TGF-β1. MiR-590 was negatively correlated with SMAD2 and SMAD3. Results of the present study suggested a role for TGF-β signalling pathway related microRNAs in pathogenesis of UC.

MiR-221-5p/Smad3 axis in osteoclastogenesis and its function: Potential therapeutic target for osteoporosis

OBJECTIVE

To probe the role of miR-221-5p in osteoclastogenesis and the underlying mechanism.

METHODS

Serum from patients with postmenopausal osteoporosis and healthy controls was collected for determination of miR-221-5p expression. For in vitro experiment, RAW264.7 macrophages, in which the expression of miR-221-5p and/or Smad3 was altered, were induced by RANKL to differentiate into osteoclasts. For in vivo experiment, ovariectomy was performed to construct osteoporosis mouse models, followed by tail vein injection of miR-221-5p agomir. qRT-PCR and/or western blot were applied to measure the expression of miR-221-5p, Smad3, and osteoclastogenesis-related genes (NFATc1 and TRAF6). TRAP staining was utilized for assessment of osteoclast formation, MTT assay for assessment of osteoclast viability, and H&E staining for observation of histomorphological changes. The targeting relationship between miR-221-5p and Smad3 was verified by dual-luciferase reporter gene assay.

RESULTS

Compared with healthy controls, patients with postmenopausal osteoporosis had decreased miR-221-5p expression and lower lumbar vertebra bone mineral density. MiR-221-5p expression was decreased and Smad3 level was increased during osteoclastogenesis. The osteoclastogenesis was suppressed by miR-221-5p and promoted by Smad3, as evidenced by diminished number and viability of osteoclasts following overexpression of miR-221-5p or knockdown of Smad3. MiR-221-5p negatively mediated Smad3 expression. Smad3 suppression nullified the pro-osteoclastogenesis effect of miR-221-5p inhibition. Consistent results were observed in osteoporosis mouse models.

CONCLUSION

MiR-221-5p may alleviate postmenopausal osteoporosis through suppressing osteoclastogenesis via Smad3, which provides new ideas for molecule-targeted therapy of osteoporosis.

Study on the mechanism of let-7a-5p in regulating the proliferation in cervical cancer cells

PURPOSE

To explore the regulatory effect of let-7a-5p/TGFBR1/Smad3 on the proliferation activity of cervical cancer cells.

METHODS

The difference in let-7a-5p expression between normal people and patients with cervical cancer was detected by miREIA assay. The differences of let-7a-5p expression between cervical cancer cell line C33a and adjacent normal epithelial cell line HUCEC were determined by qRT-PCR.

RESULTS

miREIA result showed that let-7a-5p concentrations were 178.5 ± 24.3 μg/L in healthy individuals and 106.1 ± 14.8 μg/L in cervical cancer patients (P = 0.0002). qRT-PCR showed that let-7a-5p in cervical cancer tissue (0.57 ± 0.03) was lower than that in adjacent normal tissue (0.84 ± 0.04, P = 0.0107). Compared with normal cervical epithelial cells (HUCEC), the expression of let-7a-5p was lower in cervical cancer cells (C33a, Hela, P = 0.0001). The results of CCK-8 and EDU detection showed that activation of let-7a-5p inhibited the proliferation of C33a (P = 0.00130, P << 0.0001) and Hela (P = 0.00254, P = 0.0066) cells. According to the analysis using Starbase V2.0 online database, let-7a-5p could target TGFβR1 in cervical cancer cell lines, and the let-7a-5p mimic reduces the mRNA expression level of TGFβR1 in cervical cancer cell C33a (P = 0.0067). Western blot results showed that TGFBR1 expression significantly decreased in cervical cancer cells after let-7a-5p mimic treatment (P = 0.0048) and significantly increased after let-7a-5p mimic inhibitor treatment (P = 0.0003).

CONCLUSIONS

let-7a-5p represents the independent novel anti-oncogenes in cervical cancer, which can regulate TGF-β1/TGFBR1/pSmad3 cell pathway and interfere with the proliferation of cervical cancer cells. Therefore, let-7a-5p can serve as a novel potential therapeutic target for the treatment of cervical cancer.

Mechanisms involved in suppression of osteoclast supportive activity by transforming growth factor-β1 via the ubiquitin-proteasome system

Orthodontic treatment requires the regulation of bone remodeling in both compression and tension sides. Transforming growth factor-β1 (TGF-β1) is an important coupling factor for bone remodeling. However, the mechanism underlying the TGF-β1-mediated regulation of the osteoclast-supporting activity of osteoblasts and stromal cells remain unclear. The current study investigated the effect of TGF-β1 on receptor activator of nuclear factor kappa-B ligand (RANKL) expression in stromal cells induced by 1α,25(OH)2D3 (D3) and dexamethasone (Dex). TGF-β1 downregulated the expression of RANKL induced by D3 and Dex in mouse bone marrow stromal lineage, ST2 cells. Co-culture system revealed that TGF-β1 suppressed osteoclast differentiation from bone marrow cell induced by D3 and Dex-activated ST2 cells. The inhibitory effect of TGF-β1 on RANKL expression was recovered by inhibiting the interaction between TGF-β1 and the TGF-β type I/activin receptor or by downregulating of smad2/3 expression. Interestingly, TGF-β1 degraded the retinoid X receptor (RXR)-α protein which forms a complex with vitamin D receptor (VDR) and regulates transcriptional activity of RANKL without affecting nuclear translocation of VDR and phosphorylation of signal transducer and activator of transcription3 (STAT3). The degradation of RXR-α protein by TGF-β1 was recovered by a ubiquitin-proteasome inhibitor. We also observed that poly-ubiquitination of RXR-α protein was induced by TGF-β1 treatment. These results indicated that TGF-β1 downregulates RANKL expression and the osteoclast-supporting activity of osteoblasts/stromal cells induced by D3 and Dex through the degradation of the RXR-α protein mediated by ubiquitin-proteasome system.

Smad3 Promotes Cancer-Associated Fibroblasts Generation via Macrophage-Myofibroblast Transition

Cancer-associated fibroblasts (CAFs) are important in tumor microenvironment (TME) driven cancer progression. However, CAFs are heterogeneous and still largely underdefined, better understanding their origins will identify new therapeutic strategies for cancer. Here, the authors discovered a new role of macrophage-myofibroblast transition (MMT) in cancer for de novo generating protumoral CAFs by resolving the transcriptome dynamics of tumor-associated macrophages (TAM) with single-cell resolution. MMT cells (MMTs) are observed in non-small-cell lung carcinoma (NSCLC) associated with CAF abundance and patient mortality. By fate-mapping study, RNA velocity, and pseudotime analysis, existence of novel macrophage-lineage-derived CAF subset in the TME of Lewis lung carcinoma (LLC) model is confirmed, which is directly transited via MMT from M2-TAM in vivo and bone-marrow-derived macrophages (BMDM) in vitro. Adoptive transfer of BMDM-derived MMTs markedly promote CAF formation in LLC-bearing mice. Mechanistically, a Smad3-centric regulatory network is upregulated in the MMTs of NSCLC, where chromatin immunoprecipitation sequencing(ChIP-seq) detects a significant enrichment of Smad3 binding on fibroblast differentiation genes in the macrophage-lineage cells in LLC-tumor. More importantly, macrophage-specific deletion and pharmaceutical inhibition of Smad3 effectively block MMT, therefore, suppressing the CAF formation and cancer progression in vivo. Thus, MMT may represent a novel therapeutic target of CAF for cancer immunotherapy.

SARS-CoV-2 N Protein Induces Acute Kidney Injury via Smad3-Dependent G1 Cell Cycle Arrest Mechanism

COVID-19 is infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and can cause severe multiple organ injury and death. Kidney is one of major target organs of COVID-19 and acute kidney injury (AKI) is common in critically ill COVID-19 patients. However, mechanisms through which COVID-19 causes AKI remain largely unknown and treatment remains unspecific and ineffective. Here, the authors report that normal kidney-specifically overexpressing SARS-CoV-2 N develops AKI, which worsens in mice under ischemic condition. Mechanistically, it is uncovered that SARS-CoV-2 N-induced AKI is Smad3-dependent as SARS-CoV-2 N protein can interact with Smad3 and enhance TGF-β/Smad3 signaling to cause tubular epithelial cell death and AKI via the G1 cell cycle arrest mechanism. This is further confirmed in Smad3 knockout mice and cells in which deletion of Smad3 protects against SARS-CoV-2 N protein-induced cell death and AKI in vivo and in vitro. Most significantly, it is also found that targeting Smad3 with a Smad3 pharmacological inhibitor is able to inhibit SARS-CoV-2 N-induced AKI. In conclusion, the authors identify that SARS-CoV-2 N protein is a key mediator for AKI and induces AKI via the Smad3-dependent G1 cell cycle arrest mechanism. Targeting Smad3 may represent as a novel therapy for COVID-19-asscoaited AKI.

Smad2 and Smad3 expressed in skeletal muscle promote immobilization-induced bone atrophy in mice

Skeletal muscle is known to regulate bone homeostasis through muscle-bone interaction, although factors that control this activity remain unclear. Here, we newly established Smad3-flox mice, and then generated skeletal muscle-specific Smad2/Smad3 double conditional knockout mice (DcKO) by crossing Smad3-flox with skeletal muscle-specific Ckmm Cre and Smad2-flox mice. We show that immobilization-induced gastrocnemius muscle atrophy occurring due to sciatic nerve denervation was partially but significantly inhibited in DcKO mice, suggesting that skeletal muscle cell-intrinsic Smad2/3 is required for immobilization-induced muscle atrophy. Also, tibial bone atrophy seen after sciatic nerve denervation was partially but significantly inhibited in DcKO mice. Bone formation rate in wild-type mouse tibia was significantly inhibited by immobilization, but inhibition was abrogated in DcKO mice. We propose that skeletal muscle regulates immobilization-induced bone atrophy via Smad2/3, and Smad2/3 represent potential therapeutic targets to prevent both immobilization-induced bone and muscle atrophy.

Transcription factor specificity protein 1-mediated Serine/threonine kinase 39 upregulation promotes the proliferation, migration, invasion and epithelial-mesenchymal transition of hepatocellular carcinoma cells by activating the transforming growth factor-β1 /Smad2/3 pathway

Bioinformatics analysis showed that Serine/threonine kinase 39 (STK39), which was testified to play an important role in human cancers, may be a hub gene in diagnosing hepatocellular carcinoma (HCC). This study aimed to explore whether STK39 could be regulated by specificity protein 1 (SP1) to affect HCC cells malignant processes. Firstly, STK39 expression in tissues of HCC patients and several cell lines was analyzed. After STK39 silencing, cell proliferation was evaluated by methyl thiazolyl tetrazolium and colony formation assay. Tunel staining was used to detect cell apoptosis. Then, the abilities of cell migration and invasion were determined with wound healing and transwell assays. The expression of epithelial-mesenchymal transition (EMT)-related proteins and transforming growth factor-β1 (TGF-β1)/Smad2/3 pathway proteins was tested by western blot analysis. Thereafter, cells were overexpressed with SP1 under the circumstance of STK39 knockdown, and then the above cellular processes were under observation. Results revealed that the increased expression of STK39, which was found in both HHC patients and HCC cell lines, exhibited poor HCC prognosis. STK39 silencing inhibited Hep3b cell proliferation, migration, invasion, EMT and TGF-β1/Smad2/3 expression but promoted cell apoptosis. Additionally, SP1 could bind to the STK39 promoter and facilitate STK39 expression. Further studies revealed that the effects of STK39 silencing on Hep3b cells were blocked by SP1 overexpression. In conclusion, SP1-mediated STK39 up-regulation leads to the increased proliferation, migration, invasion and EMT of HCC cells via activating TGF-β1/Smad2/3 pathway. Therapies that target SP1 to knockdown STK39 expression may contribute to the inhibition of HCC progression.

Dexmedetomidine Promotes Lipopolysaccharide-Induced Differentiation of Cardiac Fibroblasts and Collagen I/III Synthesis through α2A Adrenoreceptor-Mediated Activation of the PKC-p38-Smad2/3 Signaling Pathway in Mice

Dexmedetomidine (DEX), a selective α₂ adrenergic receptor (AR) agonist, is commonly used as a sedative drug during critical illness. In the present study, we explored a novel accelerative effect of DEX on cardiac fibroblast (CF) differentiation mediated by LPS and clarified its potential mechanism. LPS apparently increased the expression of α-SMA and collagen I/III and the phosphorylation of p38 and Smad-3 in the CFs of mice. These effects were significantly enhanced by DEX through increasing α_2A-AR expression in CFs after LPS stimulation. The CFs from α_2A-AR knockout mice were markedly less sensitive to DEX treatment than those of wild-type mice. Inhibition of protein kinase C (PKC) abolished the enhanced effects of DEX on LPS-induced differentiation of CFs. We also found that the α-SMA level in the second-passage CFs was much higher than that in the nonpassage and first-passage CFs. However, after LPS stimulation, the TNF-α released from the nonpassage CFs was much higher than that in the first- and second-passage CFs. DEX had no effect on LPS-induced release of TNF-α and IL-6 from CFs. Further investigation indicated that DEX promoted cardiac fibrosis and collagen I/III synthesis in mice exposed to LPS for four weeks. Our results demonstrated that DEX effectively accelerated LPS-induced differentiation of CFs to myofibroblasts through the PKC-p38-Smad2/3 signaling pathway by activating α_2A-AR.

SESN3 Inhibited SMAD3 to Relieve Its Suppression for MiR-124, Thus Regulating Pre-Adipocyte Adipogenesis

Sestrin-3, together with the other two members Sestrin-1 and Sestrin-2, belongs to the Sestrin family. The Sestrin protein family has been demonstrated to be involved in antioxidative, metabolic homeostasis, and even the development of nonalcoholic steatohepatitis (NASH). However, the adipogenic regulatory role of SESN3 in adipogenesis still needs to be further explored. In this study, we demonstrated SESN3 inhibited porcine pre-adipocyte proliferation, thus suppressing its adipogenesis. Meanwhile, SESN3 has been demonstrated to inhibit Smad3 thus protecting against NASH. Further, for our previous study, we found mmu-miR-124 involved in 3T3-L1 cell adipogenesis regulation. In this study, we also identified that ssc-miR-124 inhibited porcine pre-adipocyte proliferation, thus suppressing its adipogenesis, and the SMAD3 was an inhibitor of ssc-miR-124 by binding to its promoter. Furthermore, the ssc-miR-124 targeted porcine C/EBPα and GR and thus inhibited pre-adipocyte adipogenesis. In conclusion, SESN3 inhibited SMAD3, thus improving ssc-miR124, and then suppressed C/EBPα and GR to regulate pre-adipocytes adipogenesis.

Drug-containing serum of rhubarb-astragalus capsule inhibits the epithelial-mesenchymal transformation of HK-2 by downregulating TGF-β1/p38MAPK/Smad2/3 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Rheum palmatum L; Astragalus membranaceus (Fisch.), is referred to as 'Dahuang, Huangqi' in China. As an important medicinal plant, the rhizome of rhubarb and astragalus is traditionally used in the treatment of kidney diseases associated with renal failure, inflammation and tumors.

AIM OF THE STUDY

This study aimed to investigate the effect of a drug-containing serum of rhubarb-astragalus capsules (composed of rhubarb and astragalus) and to elucidate its mechanism in the epithelial-mesenchymal transformation of renal tubular epithelial cells.

MATERIALS AND METHODS

Epithelial-mesenchymal transformation (EMT) of HK-2 cells was induced by TGF-β1, and rhubarb-astragalus and losartan drug-containing serum from rats, as well as SB203580 (a specific inhibitor of p38 MAPK), were used. High-performance liquid chromatography analysis was performed to determine the main components of the drug-containing serum of rhubarb-astragalus from rats. Western blotting and immunofluorescence analysis were used to determine the levels of protein expression, and real-time quantitative PCR analysis was used to detect the levels of gene expression.

RESULTS

The drug-containing serum of rhubarb-astragalus contained emodin (0.36 μg/ml) and danthraquinone (0.96 μg/ml). Rhubarb-astragalus significantly decreased the protein expression levels of α-SMA, FN, vimentin and N-cadherin in HK-2 cells that were increased by TGF-β1, while it significantly increased the E-cadherin protein expression level that was decreased by TGF-β1. Rhubarb-astragalus also significantly decreased the protein expression levels of TGF-β1 and p38 MAPK and the mRNA expression levels of α-SMA, vimentin, TGF-β1, p38 MAPK, Smad2 and Smad3 in HK-2 cells that were increased by TGF-β1. It is worth noting that SB203580 (a p38 MAPK inhibitor) had similar effects as rhubarb-astragalus in this study.

CONCLUSION

The drug-containing serum of rhubarb-astragalus can inhibit EMT in HK-2 cells by downregulating the TGF-β1/p38 MAPK/Smad2/3 pathway.

KAT6A Acetylation of SMAD3 Regulates Myeloid-Derived Suppressor Cell Recruitment, Metastasis, and Immunotherapy in Triple-Negative Breast Cancer

Aberrant SMAD3 activation has been implicated as a driving event in cancer metastasis, yet the underlying mechanisms are still elusive. Here, SMAD3 is identified as a nonhistone substrate of lysine acetyltransferase 6A (KAT6A). The acetylation of SMAD3 at K20 and K117 by KAT6A promotes SMAD3 association with oncogenic chromatin modifier tripartite motif-containing 24 (TRIM24) and disrupts SMAD3 interaction with tumor suppressor TRIM33. This event in turn promotes KAT6A-acetylated H3K23-mediated recruitment of TRIM24-SMAD3 complex to chromatin and thereby increases SMAD3 activation and immune response-related cytokine expression, leading to enhanced breast cancer stem-like cell stemness, myeloid-derived suppressor cell (MDSC) recruitment, and triple-negative breast cancer (TNBC) metastasis. Inhibiting KAT6A in combination with anti-PD-L1 therapy in treating TNBC xenograft-bearing animals markedly attenuates metastasis and provides a significant survival benefit. Thus, the work presents a KAT6A acetylation-dependent regulatory mechanism governing SMAD3 oncogenic function and provides insight into how targeting an epigenetic factor with immunotherapies enhances the antimetastasis efficacy.

LncRNA GAS5 protects against TGF-β-induced renal fibrosis via the Smad3/miRNA-142-5p axis

Increasing evidence shows that long noncoding RNAs (lncRNAs) play an important role in kidney disease. In this study, we investigated the role of the lncRNA growth arrest-specific 5 (GAS5) in the pathogenesis of renal fibrosis. We found that GAS5 was markedly decreased in the fibrotic kidney of a unilateral ureteral obstructive nephropathy mouse model. In addition, GAS5 was expressed in mouse tubular epithelial cells (mTECs) and interstitial fibroblasts in normal renal tissue and was especially highly expressed in the cytoplasm. In vitro experiments showed that GAS5 was downregulated by transforming growth factor-β1 (TGF-β1) in a dose- and time-dependent manner. Overexpression of GAS5 blocked TGF-β1-induced collagen type I and fibronectin expression and vice versa. Mechanistic experiments revealed that Smad3 but not Smad2 drove the regulation of GAS5. More importantly, GAS5 interacted with miR-142-5p and was involved in the renoprotective effect by participating in the competing endogenous RNA network. Finally, we also found that knockdown of GAS5 promoted TGF-β1-induced mouse tubular epithelial cell apoptosis via the Smad3 pathway. Taken together, our results uncovered a lncRNA/miRNA competing endogenous RNA network-based mechanism that modulates extracellular matrix formation and cell apoptosis via the Smad3 pathway.NEW & NOTEWORTHY In this work, we mainly discuss long noncoding RNA growth arrest-specific 5 (GAS5), acting in a renoprotective role via the Smad3/miRNA-142-5p axis, that modulates extracellular matrix formation and cell apoptosis. Overexpression of GAS5 effectively blocked renal fibrosis in vitro. This study reveals that GAS5 may represent as a novel and precision therapeutic target for alleviating renal fibrosis.

Activation of Smad2/3 signaling by low fluid shear stress mediates artery inward remodeling

Endothelial cell (EC) sensing of wall fluid shear stress (FSS) from blood flow governs vessel remodeling to maintain FSS at a specific magnitude or set point in healthy vessels. Low FSS triggers inward remodeling to restore normal FSS but the regulatory mechanisms are unknown. In this paper, we describe the signaling network that governs inward artery remodeling. FSS induces Smad2/3 phosphorylation through the type I transforming growth factor (TGF)-β family receptor Alk5 and the transmembrane protein Neuropilin-1, which together increase sensitivity to circulating bone morphogenetic protein (BMP)-9. Smad2/3 nuclear translocation and target gene expression but not phosphorylation are maximal at low FSS and suppressed at physiological high shear. Reducing flow by carotid ligation in rodents increases Smad2/3 nuclear localization, while the resultant inward remodeling is blocked by the EC-specific deletion of Alk5. The flow-activated MEKK3/Klf2 pathway mediates the suppression of Smad2/3 nuclear translocation at high FSS, mainly through the cyclin-dependent kinase (CDK)-2-dependent phosphosphorylation of the Smad linker region. Thus, low FSS activates Smad2/3, while higher FSS blocks nuclear translocation to induce inward artery remodeling, specifically at low FSS. These results are likely relevant to inward remodeling in atherosclerotic vessels, in which Smad2/3 is activated through TGF-β signaling.

Partial inhibition of activin receptor-like kinase 4 alleviates bladder fibrosis caused by bladder outlet obstruction

The bladder undergoes profound structural alterations after bladder outlet obstruction (BOO), characterized by hypertrophy of the bladder wall and accumulation of extracellular matrix (ECM). Transforming growth factor-β (TGF-β) has been found to promote fibrosis of the bladder induced by partial bladder outlet obstruction (pBOO). Activin receptor-like kinase 4 (ALK4) is a downstream receptor of the TGF-β superfamily. However, the role of the ALK4-Smad2/3 pathway in the pathogenesis of bladder fibrosis caused by pBOO remains unknown. This study focused on learning the role of ALK4 in the process of bladder fibrosis caused by pBOO. The pBOO mice models showed that ALK4 expression was found to upregulate in the wild-type bladder 6 weeks after pBOO compared to control group. Then, mice with heterozygous knockout of the ALK4 gene (ALK4+/-) were generated. Histological analysis and Western blot (WB) results showed significant suppression of collagen expression in the bladders of ALK4+/- mice after pBOO compared with WT mice. WB also showed that ALK4+/- mice demonstrated significant suppression of phosphorylated Smad2/3 (p-Smad2/3) expression in the bladder 6 weeks after pBOO but not of phosphorylated extracellular signal-regulated kinase, c-Jun N-terminal kinase or protein 38 (p-ERK, p-JNK, p-P38) expression. This effect might have occurred through partial inactivation of the Smad2/3 signaling pathway. In vitro, ALK4 overexpression promoted collagen production in cultured BSMCs and activated the Smad2/3 signaling pathway. Taken together, our results demonstrated that ALK4 insufficiency alleviated bladder fibrosis in a mouse model of pBOO partly by suppressing Smad2/3 activity.

TGFβ signalling is required to maintain pluripotency of human naïve pluripotent stem cells

The signalling pathways that maintain primed human pluripotent stem cells (hPSCs) have been well characterised, revealing a critical role for TGFβ/Activin/Nodal signalling. In contrast, the signalling requirements of naive human pluripotency have not been fully established. Here, we demonstrate that TGFβ signalling is required to maintain naive hPSCs. The downstream effector proteins - SMAD2/3 - bind common sites in naive and primed hPSCs, including shared pluripotency genes. In naive hPSCs, SMAD2/3 additionally bind to active regulatory regions near to naive pluripotency genes. Inhibiting TGFβ signalling in naive hPSCs causes the downregulation of SMAD2/3-target genes and pluripotency exit. Single-cell analyses reveal that naive and primed hPSCs follow different transcriptional trajectories after inhibition of TGFβ signalling. Primed hPSCs differentiate into neuroectoderm cells, whereas naive hPSCs transition into trophectoderm. These results establish that there is a continuum for TGFβ pathway function in human pluripotency spanning a developmental window from naive to primed states.

Rack1 is essential for corticogenesis by preventing p21-dependent senescence in neural stem cells

Normal neurodevelopment relies on intricate signaling pathways that balance neural stem cell (NSC) self-renewal, maturation, and survival. Disruptions lead to neurodevelopmental disorders, including microcephaly. Here, we implicate the inhibition of NSC senescence as a mechanism underlying neurogenesis and corticogenesis. We report that the receptor for activated C kinase (Rack1), a family member of WD40-repeat (WDR) proteins, is highly enriched in NSCs. Deletion of Rack1 in developing cortical progenitors leads to a microcephaly phenotype. Strikingly, the absence of Rack1 decreases neurogenesis and promotes a cellular senescence phenotype in NSCs. Mechanistically, the senescence-related p21 signaling pathway is dramatically activated in Rack1 null NSCs, and removal of p21 significantly rescues the Rack1-knockout phenotype in vivo. Finally, Rack1 directly interacts with Smad3 to suppress the activation of transforming growth factor (TGF)-β/Smad signaling pathway, which plays a critical role in p21-mediated senescence. Our data implicate Rack1-driven inhibition of p21-induced NSC senescence as a critical mechanism behind normal cortical development.

Human cytomegalovirus blocks canonical TGFβ signaling during lytic infection to limit induction of type I interferons

Human cytomegalovirus (HCMV) microRNAs (miRNAs) significantly rewire host signaling pathways to support the viral lifecycle and regulate host cell responses. Here we show that SMAD3 expression is regulated by HCMV miR-UL22A and contributes to the IRF7-mediated induction of type I IFNs and IFN-stimulated genes (ISGs) in human fibroblasts. Addition of exogenous TGFβ interferes with the replication of a miR-UL22A mutant virus in a SMAD3-dependent manner in wild type fibroblasts, but not in cells lacking IRF7, indicating that downregulation of SMAD3 expression to limit IFN induction is important for efficient lytic replication. These findings uncover a novel interplay between SMAD3 and innate immunity during HCMV infection and highlight the role of viral miRNAs in modulating these responses.

Cells trigger the interferon (IFN) response to induce the expression of cellular genes that limit virus replication. In turn, viruses have evolved numerous countermeasures to avoid the effects of IFN signaling. Using a microRNA (miRNA) mutant virus we have uncovered a novel means of regulating the IFN response during human cytomegalovirus (HCMV) infection. Lytic HCMV infection induces the production of TGFβ, which binds to the TGFβ receptor and activates the receptor-associated SMAD SMAD3. SMAD3, together with IRF7, induces the expression of IFNβ and downstream IFN-stimulated genes in human fibroblasts. To counteract this, HCMV miR-UL22A, along with other HCMV gene products, directly targets SMAD3 for downregulation. Infection of fibroblasts with a miR-UL22A mutant virus results in enhanced type I IFN production in a SMAD3- and IRF7-dependent manner and the virus is impaired for growth in the presence of TGFβ, but only when both SMAD3 and IRF7 are present, highlighting the unique interaction between TGFβ and innate immune signaling.

Osteoarthritis-Related Inflammation Blocks TGF-β's Protective Effect on Chondrocyte Hypertrophy via (de)Phosphorylation of the SMAD2/3 Linker Region

Osteoarthritis (OA) is a degenerative joint disease characterized by irreversible cartilage damage, inflammation and altered chondrocyte phenotype. Transforming growth factor-β (TGF-β) signaling via SMAD2/3 is crucial for blocking hypertrophy. The post-translational modifications of these SMAD proteins in the linker domain regulate their function and these can be triggered by inflammation through the activation of kinases or phosphatases. Therefore, we investigated if OA-related inflammation affects TGF-β signaling via SMAD2/3 linker-modifications in chondrocytes. We found that both Interleukin (IL)-1β and OA-synovium conditioned medium negated SMAD2/3 transcriptional activity in chondrocytes. This inhibition of TGF-β signaling was enhanced if SMAD3 could not be phosphorylated on Ser213 in the linker region and the inhibition by IL-1β was less if the SMAD3 linker could not be phosphorylated at Ser204. Our study shows evidence that inflammation inhibits SMAD2/3 signaling in chondrocytes via SMAD linker (de)-phosphorylation. The involvement of linker region modifications may represent a new therapeutic target for OA.