Quantitative proteomics reveals ELP2 as a regulator to the inhibitory effect of TNF-α on osteoblast differentiation

ELP2-NLRP3-GSDMD/GSDME-mediated pyroptosis is induced by TNF-α in MC3T3-E1 cells during osteogenic differentiation

Tumour necrosis factor-α (TNF-α) is a cytokine involved in systemic inflammation. TNF-α slows down osteogenic differentiation, which may contribute to poor bone development in the inflammatory microenvironment. TNF-α inhibits osteogenic differentiation by activating the JAK-STAT3 pathway, of which Signal transducer and activator of transcription 3 (STAT3)-interacting protein 1 (StIP1, also known as elongator complex protein 2, ELP2) is a key protein in the JAK-STAT3 pathway. We investigated whether and how ELP2 activation mediates the TNF-α-induced pyroptosis during osteoblastic differentiation. Using in vitro cell cultures of preosteoblastic MC3T3-E1 cells, we found that TNF-α exposure causes cell pyroptosis in an inflammatory microenvironment during osteoblastic differentiation. Bioinformatics, protein docking model and co-immunoprecipitation analysis revealed an association between ELP2, STAT3 and NLRP3. Forced ELP2 expression promoted MC3T3-E1 cells pyroptosis, with an increase in the expression of STAT3, NLRP3 inflammasome, GSDMD/GSDME, osteoblast marker genes, and the activity of alkaline phosphatase. In contrast, ELP2 silencing ameliorated MC3T3-E1 cells pyroptosis, and osteogenic differentiation, especially after TNF-α stimulation. The TNF-α-induced cells pyroptosis during osteoblastic differentiation was therefore mediated by ELP2. These results suggest that ELP2 is upregulated at the pyroptosis of MC3T3-E1 cells and inhibits osteogenic differentiation in response to TNF-α through NLRP3-GSDMD/GSDME activation.

Smooth Muscle Cell Phenotypic Switch Induced by Traditional Cigarette Smoke Condensate: A Holistic Overview

Cigarette smoke (CS) is a risk factor for inflammatory diseases, such as atherosclerosis. CS condensate (CSC) contains lipophilic components that may represent a systemic cardiac risk factor. To better understand CSC effects, we incubated mouse and human aortic smooth muscle cells (SMCs) with CSC. We evaluated specific markers for contractile [i.e., actin, aortic smooth muscle (ACTA2), calponin-1 (CNN1), the Kruppel-like factor 4 (KLF4), and myocardin (MYOCD) genes] and inflammatory [i.e., IL-1β, and IL-6, IL-8, and galectin-3 (LGALS-3) genes] phenotypes. CSC increased the expression of inflammatory markers and reduced the contractile ones in both cell types, with KLF4 modulating the SMC phenotypic switch. Next, we performed a mass spectrometry-based differential proteomic approach on human SMCs and could show 11 proteins were significantly affected by exposition to CSC (FC ≥ 2.7, p ≤ 0.05). These proteins are active in signaling pathways related to expression of pro-inflammatory cytokines and IFN, inflammasome assembly and activation, cytoskeleton regulation and SMC contraction, mitochondrial integrity and cellular response to oxidative stress, proteostasis control via ubiquitination, and cell proliferation and epithelial-to-mesenchymal transition. Through specific bioinformatics resources, we showed their tight functional correlation in a close interaction niche mainly orchestrated by the interferon-induced double-stranded RNA-activated protein kinase (alternative name: protein kinase RNA-activated; PKR) (EIF2AK2/PKR). Finally, by combining gene expression and protein abundance data we obtained a hybrid network showing reciprocal integration of the CSC-deregulated factors and indicating KLF4 and PKR as the most relevant factors.

Novel Elongator Protein 2 Inhibitors Mitigating Tumor Necrosis Factor-α Induced Osteogenic Differentiation Inhibition

Tumor necrosis factor-α is a common cytokine that increases in inflammatory processes, slows the differentiation of bone formation, and induces osteodystrophy in the long-term inflammatory microenvironment. Our previous study confirmed that the Elongation protein 2 (ELP2) plays a significant role in osteogenesis and osteogenic differentiation, which is considered a drug discovery target in diseases related to bone formation and differentiation. In this study, we applied an in silico virtual screening method to select molecules that bind to the ELP2 protein from a chemical drug molecule library and obtained 95 candidates. Then, we included 11 candidates by observing the docking patterns and the noncovalent bonds. The binding affinity of the ELP2 protein with the candidate compounds was examined by SPR analysis, and 5 out of 11 compounds performed good binding affinity to the mouse ELP2 protein. After in vitro cell differentiation assay, candidates 2# and 5# were shown to reduce differentiation inhibition after tumor necrosis factor-α stimulation, allowing further optimization and development for potential clinical treatment of inflammation-mediated orthopedic diseases.

Transcriptome Analysis of Egg Yolk Sialoglycoprotein on Osteogenic Activity in MC3T3-E1 Cells

In this study, the effects of egg yolk sialoglycoprotein (EYG) on osteogenesis in MC3T3-E1 cells were investigated and the DEGs (differentially expressed genes) were explored by transcriptome analysis. The results found that EYG effectively increased cell proliferation, enhanced ALP activity, promoted the secretion of extracellular matrix protein COL-I and OCN, enhanced bone mineralization activity, exhibiting good osteogenic activity. Further study of the mechanism was explored through transcriptome analysis. Transcriptome analysis showed that 123 DEGs were triggered by EYG, of which 78 genes were downregulated and 45 genes were upregulated. GO (gene ontology) analysis showed that EYG mainly caused differences in gene expression of biological processes and cell composition categories in the top 30 most enriched items. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis showed that EYG inhibited inflammatory factors and downregulated inflammation-related pathways. The results also showed EYG regulated such genes as COL2A1, COL4A1 and COL4A2 to up-regulate pathways including ECM–receptor interaction, focal adhesion and protein digestion and absorption, enhancing the proliferation and differentiation of osteoblasts. Gene expression of COL-I, Runx2, BMP2 and β-catenin was determined by qRT-PCR for verification, which found that EYG significantly increased COL-I, Runx2, BMP2 and β-catenin gene expression, suggesting that BMP-2 mediated osteogenesis pathway was activated.

Targeted inhibition of GRK2 kinase domain by CP-25 to reverse fibroblast-like synoviocytes dysfunction and improve collagen-induced arthritis in rats

Rheumatoid arthritis (RA) is an autoimmune disease and is mainly characterized by abnormal proliferation of fibroblast-like synoviocytes (FLS). The up-regulated cellular membrane expression of G protein coupled receptor kinase 2 (GRK2) of FLS plays a critical role in RA progression, the increase of GRK2 translocation activity promotes dysfunctional prostaglandin E4 receptor (EP4) signaling and FLS abnormal proliferation. Recently, although our group found that paeoniflorin-6ʹ-O-benzene sulfonate (CP-25), a novel compound, could reverse FLS dysfunction via GRK2, little is known as to how GRK2 translocation activity is suppressed. Our findings revealed that GRK2 expression up-regulated and EP4 expression down-regulated in synovial tissues of RA patients and collagen-induced arthritis (CIA) rats, and prostaglandin E2 (PGE2) level increased in arthritis. CP-25 could down-regulate GRK2 expression, up-regulate EP4 expression, and improve synovitis of CIA rats. CP-25 and GRK2 inhibitors (paroxetine or GSK180736A) inhibited the abnormal proliferation of FLS in RA patients and CIA rats by down-regulating GRK2 translocation to EP4 receptor. The results of microscale thermophoresis (MST), cellular thermal shift assay, and inhibition of kinase activity assay indicated that CP-25 could directly target GRK2, increase the protein stability of GRK2 in cells, and inhibit GRK2 kinase activity. The docking of CP-25 and GRK2 suggested that the kinase domain of GRK2 might be an important active pocket for CP-25. G201, K220, K230, A321, and D335 in kinase domain of GRK2 might form hydrogen bonds with CP-25. Site-directed mutagenesis and co-immunoprecipitation assay further revealed that CP-25 down-regulated the interaction of GRK2 and EP4 via controlling the key amino acid residue of Ala321 of GRK2. Our data demonstrate that FLS proliferation is regulated by GRK2 translocation to EP4. Targeted inhibition of GRK2 kinase domain by CP-25 improves FLS function and represents an innovative drug for the treatment of RA by targeting GRK2.

Serum STIP1, a Novel Indicator for Microvascular Invasion, Predicts Outcomes and Treatment Response in Hepatocellular Carcinoma

Background: Previous studies reported that stress-induced phosphoprotein 1 (STIP1) can be secreted by hepatocellular carcinoma (HCC) cells and is increased in the serum of HCC patients. However, the therapy-monitoring and prognostic value of serum STIP1 in HCC remains unclear. Here, we aimed to systemically explore the prognostic significance of serum STIP1 in HCC.

Methods: A total of 340 HCC patients were recruited to this study; 161 underwent curative resection and 179 underwent transcatheter arterial chemoembolization (TACE). Serum STIP1 was detected by enzyme-linked immunosorbent assay (ELISA). Optimal cutoff values for serum STIP1 in resection and TACE groups were determined by receiver operating characteristic (ROC) analysis. Prognostic value was assessed by Kaplan-Meier, log-rank, and Cox regression analyses. Predictive values of STIP1 for objective response (OR) to TACE and MVI were evaluated by ROC curves and logistic regression.

Results: Serum STIP1 was significantly increased in HCC patients when compared with chronic hepatitis B patients or health donors (both P < 0.05). Optimal cutoff values for STIP1 in resection and TACE groups were 83.43 and 112.06 ng/ml, respectively. High pretreatment STIP1 was identified as an independent prognosticator. Dynamic changes in high STIP1 status were significantly associated with long-term prognosis, regardless of treatment approaches. Moreover, post-TACE STIP1 was identified as an independent predictor for OR, with a higher area under ROC curve (AUC-ROC) than other clinicopathological features. Specifically, pretreatment STIP1 was significantly increased in patients with microvascular invasion (MVI), and was confirmed as a novel, powerful predictor for MVI.

Conclusions: Serum STIP1 is a promising biomarker for outcome evaluation, therapeutic response assessment, and MVI prediction in HCC. Integration serum STIP1 detection into HCC management might facilitate early clinical decision making to improve the prognosis of HCC.

Comparative iTRAQ proteomics revealed proteins associated with lobed fin regeneration in Bichirs

Background

Polypterus senegalus can fully regenerate its pectoral lobed fins, including a complex endoskeleton, with remarkable precision. However, despite the enormous potential of this species for use in medical research, its regeneration mechanisms remain largely unknown.

Methods

To identify the differentially expressed proteins (DEPs) during the early stages of lobed fin regeneration in P. senegalus, we performed a differential proteomic analysis using isobaric tag for relative and absolute quantitation (iTRAQ) approach based quantitative proteome from the pectoral lobed fins at 3 time points. Furthermore, we validated the changes in protein expression with multiple-reaction monitoring (MRM) analysis.

Results

The experiment yielded a total of 3177 proteins and 15,091 unique peptides including 1006 non-redundant (nr) DEPs. Of these, 592 were upregulated while 349 were downregulated after lobed fin amputation when compared to the original tissue. Bioinformatics analyses showed that the DEPs were mainly associated with Ribosome and RNA transport, metabolic, ECM-receptor interaction, Golgi and endoplasmic reticulum, DNA replication, and Regulation of actin cytoskeleton.

Conclusions

To our knowledge, this is the first proteomic research to investigate alterations in protein levels and affected pathways in bichirs’ lobe-fin/limb regeneration. In addition, our study demonstrated a highly dynamic regulation during lobed fin regeneration in P. senegalus. These results not only provide a comprehensive dataset on differentially expressed proteins during the early stages of lobe-fin/limb regeneration but also advance our understanding of the molecular mechanisms underlying lobe-fin/limb regeneration.

ELP2 negatively regulates osteoblastic differentiation impaired by tumor necrosis factor α in MC3T3-E1 cells through STAT3 activation

Tumor necrosis factor‐α (TNF‐α) is a pluripotent signaling molecule. The biological effect of TNF‐α includes slowing down osteogenic differentiation, which can lead to bone dysplasia in long‐term inflammatory microenvironments. Signal transducer and activator of transcription 3 (STAT3)‐interacting protein 1 (StIP1, also known as elongator complex protein 2, ELP2) play a role in inhibiting TNF‐α‐induced osteoblast differentiation. In the present study, we investigated whether and how ELP2 activation mediates the effects of TNF‐α on osteoblastic differentiation. Using in vitro cell cultures of preosteoblastic MC3T3‐E1 cells, we found that TNF‐α inhibited osteoblastic differentiation accompanied by an increase in ELP2 expression and STAT3 activation. Forced ELP2 expression inhibited osteogenic differentiation of MC3T3‐E1 cells, with a decrease in the expression of osteoblast marker genes, alkaline phosphatase activity, and matrix mineralization capacity. In contrast, ELP2 silencing ameliorated osteogenic differentiation in MC3T3‐E1 cells, even after TNF‐α stimulation. The TNF‐α‐induced inhibitory effect on osteoblastic differentiation was therefore mediated by ELP2, which was associated with Janus kinase 2 (JAK2)/STAT3 activation. These results suggest that ELP2 is upregulated at the differentiation of MC3T3‐E1 cells into osteoblasts and inhibits osteogenic differentiation in response to TNF‐α through STAT3 activation.

Discovery of novel elongator protein 2 inhibitors by compound library screening using surface plasmon resonance

Tumour necrosis factor-α (TNF-α) is a pleiotropic cytokine that becomes elevated in chronic inflammatory states, including slowing down osteogenic differentiation, which leads to bone dysplasia in long-term inflammatory microenvironments. The elongator complex plays a role in gene regulation and association with various cellular activities, including the downstream signal transduction of TNF-α in osteogenic cells. To find an inhibitor of Elongator Protein 2 (Elp2), we performed a compound library screen and verified the pharmaceutical effects of candidate compounds on the mouse myoblast cell (C2C12) and mouse osteoblastic cells (MC3T3-E1). The commercial FDA-approved drug (FD) library and the bioactive compound (BC) library were used as candidate libraries. After a label-free, high-throughput affinity measurement with surface plasmon resonance (SPRi), seven kinds of compounds showed binding affinity with mouse Elp2 protein. The seven candidates were then used to perform an inhibition test with TNF-α-induced C2C12 and MC3T3-E1 cell lines. One candidate compound reduced the differentiation suppression caused by TNF-α with resuscitated alkaline phosphatase (ALP) activity, mineralization intensity and expression of osteogenic differentiation marker genes. The results of our study provide a competitive candidate to mitigate the TNF-α-induced osteogenic differentia.

Identification of potential target genes and related regulatory transcription factors in spontaneous hairline fracture induced by hypervitaminosis A

BACKGROUND

The aim was to research the molecular changes of bone cells induced by excessive dose of vitamin A, and analyze molecular mechanism underlying spontaneous fracture.

METHODS

The gene expression profile of GSE29859, including 4 cortical bone marrow samples with excessive doses of Vitamin A and 4 control cortical bone marrow samples, was obtained from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DGEs) between cortical bone marrow samples and control samples were screened out and pathway enrichment analysis was undertaken. Based on the MSigDB database, the potential regulatory transcription factors (TFs) were identified.

RESULTS

A total of 373 DEGs including 342 up- and 31 down-regulated genes were identified. These DEGs were significantly enriched in pathways of protein processing in endoplasmic reticulum, ubiquitin mediated proteolysis and glycerophospholipid metabolism. Finally, the most significant regulatory TFs were obtained, including E2F Transcription Factor 1 (E2F1), GA Binding Protein Transcription Factor (GABP), Nuclear Factor, Erythroid 2-Like 2 (NRF2) and ELK1, Member of ETS Oncogene Family (ELK1).

CONCLUSION

Key TFs including E2F1, GABP, NRF2 and ELK1 and their targets genes such as Ube2d3, Uba1, Phb2 and Tomm22 may play potential key roles in spontaneous fracture induced by hypervitaminosis A. The pathways of protein processing in endoplasmic reticulum, ubiquitin mediated proteolysis and glycerophospholipid metabolism may be key mechanisms involved in spontaneous fracture induced by hypervitaminosis A. Our findings will provide new insights for the target selection in clinical application to prevent spontaneous fracture induced by hypervitaminosis A.

Defining the proteomic landscape of rheumatoid arthritis: progress and prospective clinical applications

INTRODUCTION

The heterogeneity of Rheumatoid Arthritis (RA) and the absence of clinical tests accurate enough to identify the early stages of this disease have hampered its management. Therefore, proteomics research is increasingly focused on the discovery of novel biological markers, which would not only be able make an early diagnosis, but also to gain insight into the different pathological mechanisms underlying the heterogeneity of RA and also to stratify patients, which is critical to enabling effective treatments. Areas covered: The proteomic approaches that have been utilised to provide knowledge about RA pathogenesis, and to identify biomarkers for RA diagnosis, prognosis, disease monitoring and prediction of response to therapy, are summarized. Expert commentary: Although each proteomic study is unique in its design, all of them have contributed to the understanding of RA pathogenesis and the discovery of promising biomarkers for patient stratification, which would improve clinical care of RA patients. Still, efforts need to be made to validate these findings and translate them into clinical practice.

Identification of the vascular endothelial growth factor signalling pathway by quantitative proteomic analysis of rat condylar cartilage

Angiogenesis mediated by vascular endothelial growth factor (VEGF) is known to play an important role in regulating cartilage remodelling and endochondral ossification. However, the details of how VEGF signalling mechanisms affect condyle remodelling in response to alterations in functional loading remains unclear. To explore this, eighty 16‐day‐old male SD rats were divided into two equal groups which were fed either a soft/powdery diet or a hard diet for 4 weeks; the stiffness of the diet results in alteration of mastication force and hence temporomandibular joint (TMJ) development. We performed a proteomic analysis of rat condylar cartilage using isobaric tags for relative and absolute quantification (iTRAQ) labelling, followed by 2D nano‐high performance liquid chromatography and MALDI‐TOF/time‐of‐flight technology. After protein identification, we used biological information analysis to identify the differentially expressed proteins associated with the VEGF signalling pathway. Among the identified differentially expressed proteins, we found VEGF signalling mainly via the p44/42 MAPK and p38 mitogen‐activated protein kinase (MAPK) pathways in condylar cartilage, including VEGFD, VGFR2, KPCB, KPCT, KPCZ, ARAF, RASN, PLCG2, PLCG1, JUN and M3K12. Furthermore, four representative protein candidates, VEGF, p38 MAPK and p44/42 MAPK/phospho‐p44/42 MAPK, were confirmed by immunohistochemical staining and western blot. Our data suggest that VEGF might play an important role in TMJ development and remodelling in response to alterations in functional loading through the p44/42 MAPK and p38 MAPK signalling pathway. This study provides new clues to the understanding of the signalling mechanism responsible for VEGF production in response to different masticatory functions at the protein level.

Contribution of Mass Spectrometry-Based Proteomics to the Understanding of TNF-α Signaling

NF-κB is a family of ubiquitous dimeric transcription factors that play a role in a myriad of cellular processes, ranging from differentiation to stress response and immunity. In inflammation, activation of NF-κB is mediated by pro-inflammatory cytokines, in particular the prototypic cytokines IL-1β and TNF-α, which trigger the activation of complex signaling cascades. In spite of decades of research, the system level understanding of TNF-α signaling is still incomplete. This is partially due to the limited knowledge at the proteome level. The objective of this review is to summarize and critically evaluate the current status of the proteomic research on TNF-α signaling. We will discuss the merits and flaws of the existing studies as well as the insights that they have generated into the proteomic landscape and architecture connected to this signaling pathway. Besides delineating past and current trends in TNF-α proteomic research, we will identify research directions and new methodologies that can further contribute to characterize the TNF-α associated proteome in space and time.

Phytochemical study and biological evaluation of chemical constituents of Platanus orientalis and Platanus × acerifolia buds

One flavonol glycoside, two O-isoprenylated flavonols, one α,α-dimethylallyl flavonol, one dihydrochalcone, two furanocoumarins and one terpenoid previously undescribed, along with 42 known compounds were isolated from the buds of two European Platanaceae, Platanus orientalis and Platanus × acerifolia. Their chemical structures were elucidated on the basis of spectroscopic analysis, including homonuclear and heteronuclear correlation NMR (COSY, NOESY, HSQC, and HMBC) experiments, as well as HRMS data. The estrogen-like and antiestrogen-like activity of dichloromethane and methanol extracts of P. orientalis and P. × acerifolia buds and isolated compounds was evaluated using estrogen-responsive cell lines. The potency of selected estrogen agonists to regulate gene expression through ERα and/or ERβ was compared with their in vitro osteoblastogenic activity. Kaempferol and 8-C-(1,1-dimethyl-2-propen-1-yl)-5,7-dihydroxyflavonol displayed osteoblastogenic as well as ERα-mediated estrogenic activity similar to estradiol.

Proteomics Study on Nonallergic Hypersensitivity Induced by Compound 4880 and Ovalbumin

Nonallergic hypersensitivity reaction (NHR) accounts for more than 77% of all immune-mediated immediate hypersensitivity reactions and has become a serious threat to public health. Here, proteomics was used to study the NHR mechanism of two typical substances, the compound 4880 and ovalbumin. Twelve different proteins were suggested as potential biomarkers for examining the NHR mechanism, and our results revealed that the mechanism mainly encompassed 2 processes, i.e., generation and effect processes. The generation process could be classified as direct stimulation, complement (classical and alternative), coagulation, kallikrein-kinin, and integrated pathways. Thus glutathione peroxidase 1, terminal complement complex (complement factor 4d and Bb), coagulation 13, kininogen-1, and IgE could be used as candidate biomarkers for the indication of the corresponding pathways respectively, the proteins were further confirmed by ELISA. And the effect process was mainly composed of histamine as well as proteins such as DCD and MYLPF, which could be used as important indices for the symptoms of NHR. Our study differs from previous studies in that C4880 was found to not only be involved in the direct stimulation pathway, but also in the activated complement and kallikrein-kinin pathways through the coagulation pathway. We also report for the first time that ovalbumin-induced NHR could be a combination of the coagulation, classical complement, and integrated pathways.

Cordycepin protected against the TNF-α-induced inhibition of osteogenic differentiation of human adipose-derived mesenchymal stem cells

Cordycepin, 3'-deoxyadenosine, is an effective component isolated from the rare Chinese caterpillar fungus Cordyceps militaris. It exerts potent anti-inflammatory actions in different cell and animal models. However, its action remains unclear on the TNF-α-induced inhibition of osteogenic differentiation of adipose-derived mesenchymal stem cells (ADMSCs). In the present study, we demonstrated that cordycepin induced cell death at 20 and 40 μg/mL. Interestingly, 10 μg/mL cordycepin abrogated the cell death induced by 20 ng/mL TNF-α. Meanwhile, cordycepin exhibited a dose-dependent regulation of the osteogenesis of human ADMSCs: it promoted the differentiation at 10 μg/mL, whereas inhibited differentiation at 40 μg/mL. Furthermore, we discovered that 10 μg/mL cordycepin protected against the TNF-α (induced inhibition of osteogenic differentiation of human ADMSCs. It was also revealed that 10 μg/mL cordycepin restored Runx2 and Osx mRNA levels, which were significantly inhibited by TNF-αduring osteogenesis. At the same time, we found that 10 μg/mL cordycepin suppressed TNF-α-activated NF-κB signaling, by inhibiting IκBα phosphorylation and subsequent p65 release and translocation into the cell nucleus. Of clinical interest, the present study revealed mechanisms involved in inflammatory cytokine-inhibited osteogenesis, and it highlights the potential of cordycepin to promote the osteogenesis of human ADMSCs in cell-based therapy for inflammatory bone diseases.

STAT-3 contributes to pulmonary fibrosis through epithelial injury and fibroblast-myofibroblast differentiation

Lung fibrosis is the hallmark of the interstitial lung diseases. Alveolar epithelial cell (AEC) injury is a key step that contributes to a profibrotic microenvironment. Fibroblasts and myofibroblasts subsequently accumulate and deposit excessive extracellular matrix. In addition to TGF-β, the IL-6 family of cytokines, which signal through STAT-3, may also contribute to lung fibrosis. In the current manuscript, the extent to which STAT-3 inhibition decreases lung fibrosis is investigated. Phosphorylated STAT-3 was elevated in lung biopsies from patients with idiopathic pulmonary fibrosis and bleomycin (BLM)-induced fibrotic murine lungs. C-188-9, a small molecule STAT-3 inhibitor, decreased pulmonary fibrosis in the intraperitoneal BLM model as assessed by arterial oxygen saturation (control, 84.4 ± 1.3%; C-188-9, 94.4 ± 0.8%), histology (Ashcroft score: untreated, 5.4 ± 0.25; C-188-9, 3.3 ± 0.14), and attenuated fibrotic markers such as diminished α-smooth muscle actin, reduced collagen deposition. In addition, C-188-9 decreased the expression of epithelial injury markers, including hypoxia-inducible factor-1α (HIF-1α) and plasminogen activator inhibitor-1 (PAI-1). In vitro studies show that inhibition of STAT-3 decreased IL-6- and TGF-β-induced expression of multiple genes, including HIF-1α and PAI-1, in AECs. Furthermore, C-188-9 decreased fibroblast-to-myofibroblast differentiation. Finally, TGF-β stimulation of lung fibroblasts resulted in SMAD2/SMAD3-dependent phosphorylation of STAT-3. These findings demonstrate that STAT-3 contributes to the development of lung fibrosis and suggest that STAT-3 may be a therapeutic target in pulmonary fibrosis.