The Effects of Retinoic Acid and MAPK Inhibitors on Phosphorylation of Smad2/3 Induced by Transforming Growth Factor β1

Retinoid X receptor agonists alleviate fibroblast activation and post-infarction cardiac remodeling via inhibition of TGF-β1/Smad pathway

Retinoid X receptor (RXR), particularly RXRα, has been implicated in cardiovascular diseases. However, the functional role of RXR activation in myocardial infarction (MI) remains unclear. This study aimed to determine the effects of RXR agonists on MI and to dissect the underlying mechanisms. Sprague-Dawley (SD) rats were subjected to MI and then treated (once daily for 4 weeks) with either RXR agonist bexarotene (10 or 30 mg/kg body weight) or vehicle. Heart function was determined using echocardiography and cardiac hemodynamic measurements. Four weeks post MI, myocardial tissues were collected to evaluate cardiac remodeling. Primary cardiac fibroblasts (CFs) were treated with or without RXR ligand 9-cis-RA followed by stimulation with TGF-β1. Immunoblot, immunofluorescence, and co-immunoprecipitation were performed to elucidate the regulatory role of RXR agonists in TGF-β1/Smad signaling. In vivo treatment with Bexarotene moderately affects systemic inflammation and apoptosis and ameliorated left ventricular dysfunction after MI in rat model. In contrast, bexarotene significantly inhibited post-MI myocardial fibrosis. Immunoblot analysis of heart tissue homogenates from MI rats revealed that bexarotene regulated the activation of the TGF-β1/Smad signaling pathway. In vitro, 9-cis-RA inhibited the TGF-β1-induced proliferation and collagen production of CFs. Importantly, upon activation by 9-cis-RA, RXRα interacted with p-Smad2 in cytoplasm, inhibiting the TGF-β1-induced nuclear translocation of p-Smad2, thereby negatively regulating TGF-β1/Smad signaling and attenuating the fibrotic response of CFs. These findings suggest that RXR agonists ameliorate post-infarction myocardial fibrosis, maladaptive remodeling, and heart dysfunction via attenuation of fibrotic response in CFs through inhibition of the TGF-β1/Smad pathway activation.

A New Potential Therapeutic Target for Cancer in Ubiquitin-Like Proteins-UBL3

Ubiquitin-like proteins (Ubls) are involved in a variety of biological processes through the modification of proteins. Dysregulation of Ubl modifications is associated with various diseases, especially cancer. Ubiquitin-like protein 3 (UBL3), a type of Ubl, was revealed to be a key factor in the process of small extracellular vesicle (sEV) protein sorting and major histocompatibility complex class II ubiquitination. A variety of sEV proteins that affects cancer properties has been found to interact with UBL3. An increasing number of studies has implied that UBL3 expression affects cancer cell growth and cancer prognosis. In this review, we provide an overview of the relationship between various Ubls and cancers. We mainly introduce UBL3 and its functions and summarize the current findings of UBL3 and examine its potential as a therapeutic target in cancers.

Scorpion Venom Polypeptide Inhibits Pulmonary Epithelial-Mesenchymal Transition in Systemic Sclerosis-Interstitial Lung Disease Model Mice by Intervening TGF-β1/Smad Signaling Pathway

Objective

Interstitial lung disease (ILD) is an important complication of systemic sclerosis (SSc). The aim of this study was to investigate the effect and possible mechanism of polypeptide extract of scorpion venom (PESV) on SSc-ILD.

Methods

C57/BL6 mice were injected with bleomycin to establish a SSc-ILD model. Different concentrations of PESV solution were administered to SSc-ILD mice, and dexamethasone was used as a positive control. H&E staining and Masson staining were used to observe the pathological changes. The TGF-β1 expression level was detected by immunohistochemistry. The expression of epithelial-mesenchymal transition (EMT)-related proteins was detected by Western blot, and the expression of TGF-β1/Smad pathway-related proteins was also detected. The content of inflammatory cytokines in serum and BALF was determined by ELISA.

Results

Pathological analysis showed that PESV could alleviate SSc-ILD-induced pulmonary inflammation and fibrosis. Compared with the model group, the content of inflammatory cytokines IL-6 and TNF-α significantly decreased after PESV treatment. PESV could increase the expression of epithelial marker (E-cadherin) and reduce the expression of interstitial markers (collagen I, vimentin, N-cadherin, and a-SMA). In addition, PESV could reduce the expression level of TGF-β1/Smad pathway-related protein.

Conclusion

PESV can attenuate SSc-ILD by regulating EMT, and the effect was linked to the TGF-β1/Smad signaling pathway, which indicated that PESV may serve as a candidate drug for SSc-ILD.

GRK2 promotes activation of lung fibroblast cells and contributes to pathogenesis of pulmonary fibrosis through increasing Smad3 expression

Pulmonary fibrosis is a chronic, progressive, and irreversible interstitial lung disease. Transforming growth factor beta1 (TGF-β1) plays a major role in lung fibroblast cell differentiation to myofibroblast cells and production of extracellular matrix, which are hallmarks of pulmonary fibrosis. G protein-coupled receptor kinase-2 (GRK2) has been shown to play controversial roles in TGF-β1-induced signal transduction in different cell types; however, the roles of GRK2 in TGF-β1-induced activation of lung fibroblast cells and development of pulmonary fibrosis have not been revealed. In this study, we found that GRK2 levels were induced in lungs and isolated fibroblast cells in a murine model of pulmonary fibrosis, as well as TGF-β1-treated lung fibroblasts. GRK2 levels were not changed in lungs in the injury phase of pulmonary fibrosis. Post-treatment with GRK2 inhibitor reduced ECM accumulation in lungs in bleomycin-challenged mice, suggesting that GRK2 activation contributes to the progressive phase of pulmonary fibrosis. Inhibition or downregulation of GRK2 attenuates fibronectin, collagen, and α-smooth muscle actin expression in TGF-β1-induced lung fibroblast cells or myofibroblast cells isolated from pulmonary fibrosis patients. Further, we showed that GRK2 regulates Smad3 expression, indicating that inhibition of GRK2 attenuates ECM accumulation through downregulation of Smad3 expression. This study reveals that GRK2 is a therapeutic target in treating pulmonary fibrosis and inhibition of GRK2 dampens pulmonary fibrosis by suppression of Smad3 expression, eventually attenuating TGF-β1 signal pathway and ECM accumulation.

Inhibition of epithelial-mesenchymal transition in retinal pigment epithelial cells by a retinoic acid receptor-α agonist

Epithelial-mesenchymal transition (EMT) in retinal pigment epithelial (RPE) cells plays a key role in proliferative retinal diseases such as age-related macular degeneration by contributing to subretinal fibrosis. To investigate the potential role of retinoic acid receptor-α (RAR-α) signaling in this process, we have now examined the effects of the RAR-α agonist Am580 on EMT induced by transforming growth factor-β2 (TGF-β2) in primary mouse RPE cells cultured in a three-dimensional type I collagen gel as well as on subretinal fibrosis in a mouse model. We found that Am580 inhibited TGF-β2-induced collagen gel contraction mediated by RPE cells. It also attenuated the TGF-β2-induced expression of the mesenchymal markers α-smooth muscle actin, fibronectin, and collagen type I; production of pro-matrix metalloproteinase 2 and interleukin-6; expression of the focal adhesion protein paxillin; and phosphorylation of SMAD2 in the cultured RPE cells. Finally, immunofluorescence analysis showed that Am580 suppressed both the TGF-β2-induced translocation of myocardin-related transcription factor-A (MRTF-A) from the cytoplasm to the nucleus of cultured RPE cells as well as subretinal fibrosis triggered by laser-induced photocoagulation in a mouse model. Our observations thus suggest that RAR-α signaling inhibits EMT in RPE cells and might attenuate the development of fibrosis associated with proliferative retinal diseases.

Antifibrotic effects of eupatilin on TGF-β1-treated human vocal fold fibroblasts

Vocal fold scarring is a major cause of dysphonia. Vocal fold fibroblasts (VFFs) and the TGF-β signaling pathway play important roles in scar formation. Eupatilin, a chromone derivative of the Artemisia species, is a traditional folk remedy for wound healing. However, until recently, few studies investigated the therapeutic effects of eupatilin. We investigated the antifibrogenic effects of eupatilin on TGF-β1-treated human vocal fold fibroblasts (hVFFs). The optimal concentration of eupatilin was determined by a cell viability assay. Western blotting was used to measure the expression of alpha-smooth muscle actin during myofibroblast differentiation, fibronectin (FN), collagen type I (Col I), and collagen type III (Col III) extracellular matrix proteins, and Smad2, Smad3, and p38 in the fibrotic pathway. Measurements were made before and after eupatilin treatment. Eupatilin at 100 nM was shown to be safe for use in hVFFs. TGF-β1 induced hVFFs to proliferate and differentiate into myofibroblasts and increased Col III and FN synthesis in a time- and dose-dependent manner. Eupatilin suppressed TGF-β1-induced hVFF proliferation and differentiation into myofibroblasts through the Smad and p38 signaling pathways. Furthermore, eupatilin inhibited TGF-β1-induced FN, Col I, and Col III synthesis in hVFFs. Our in vitro findings show that eupatilin effectively suppressed TGF-β1-induced fibrotic changes in hVFFs via the Smad and p38 signaling pathways. Thus, eupatilin may be considered a novel therapeutic agent for the treatment of vocal fold fibrosis.

All-trans-retinoic acid inhibits mink hair follicle growth via inhibiting proliferation and inducing apoptosis of dermal papilla cells through TGF-β2/Smad2/3 pathway

Dermal papilla cells (DPCs), an important component of hair follicles, its proliferation and apoptosis directly regulate and maintain the growth of hair follicles. All-trans-retinoic acid (ATRA) plays a critical role in hair growth. In this study, the effects of ATRA on cultured mink hair follicle growth were studied by administration of different concentrations of ATRA for 12 days in vitro. In addition, the proliferation and apoptosis of DPCs were measured after treating with ATRA. The mRNA and protein levels of hair follicle growth associated factor transforming growth factor-β2 (TGF-β2) and the phosphorylation levels of Smad2/3 were determined. Moreover, TGF-β type I and type II receptor inhibitor LY2109761 and specific inhibitor of Smad3 (SIS3) were administered to investigate the underlying molecular mechanism. The results showed that ATRA inhibited hair follicle growth, promoted TGF-β2 expression and activated phosphorylation of Smad2/3. In addition, ATRA inhibited cell proliferation by arresting the cell cycle at G1 phase and induced apoptosis of DPCs by enhancing the ratio of Bax/Bcl-2 and promoted the cleavage of caspase-3. Furthermore, LY2109761 or SIS3 partially reversed the decreased cell viability, increased apoptosis that were induced by ATRA. In conclusion, ATRA could inhibit hair follicle growth via inhibiting proliferation and inducing apoptosis of DPCs partially through the TGF-β2/Smad2/3 pathway.

TGF-β induced EMT and stemness characteristics are associated with epigenetic regulation in lung cancer

Transforming growth factor-β (TGF-β) promotes tumor invasion and metastasis by inducing epithelial-mesenchymal transition (EMT). EMT is often related with acquisition of stemness characteristics. The objective of this study was to determine whether EMT and stemness characteristics induced by TGF-β might be associated with epigenetic regulation in lung cancer. A human normal lung epithelial cell line and four lung cancer cell lines were treated with TGF-β. Transcriptome analysis of BEAS-2B and A549 cells incubated with TGF-β were analyzed through next-generation sequencing (NGS). Western blotting was carried out to investigate expression levels of epithelial and mesenchymal markers. Wound healing and Matrigel invasion assay, sphere formation assay, and in vivo mice tumor model were performed to evaluate functional characteristics of EMT and stemness acquisition. To investigate whether activation of EMT and stem cell markers might be involved in epigenetic regulation of lung cancer, experiment using a DNA methyltransferase inhibitor (5-azacytidine, AZA), methylation-specific PCR (MSP) and bisulfite sequencing were performed. NGS revealed changes in expression levels of EMT markers (E-cadherin, N-cadherin, fibronectin, vimentin, slug and snail) and stem cell markers (CD44 and CD87) in both BEAS-2B and A549 cells. Functional analysis revealed increased migration, invasion, sphere formation, and tumor development in mice after TGF-β treatment. Expression of slug and CD87 genes was activated following treatment with AZA and TGF-β. MSP and bisulfite sequencing indicated DNA demethylation of slug and CD87 genes. These results suggest that TGF-β induced EMT and cancer stemness acquisition could be associated with activation of slug and CD87 gene by their promoter demethylation.