Effect of bone morphogenic protein-7 on the expression of epithelial-mesenchymal transition markers in silicosis model

Dahuang Zhechong Pills Suppress Silicosis Fibrosis Progression via p38 MAPK/TGF-β1/Smad Pathway In Vitro

Background

Dahuang Zhechong pills (DHZCP) is a classic Chinese medicinal prescription in “Treatise on Cold Pathogenic and Miscellaneous Diseases (Shanghan Zabing Lun),” and it has the function of tonifying blood, nourishing Yin, and removing blood stasis. Previous studies have shown that DHZCP could alleviate SiO₂ induced pulmonary fibrosis in mice. This study aims to further explore the preventive and therapeutic effects of DHZCP against silicosis fibrosis and the underlying mechanisms in vitro.

Methods

We used the experimental model of SiO₂-induced MH-S cells to evaluate the therapeutic potential of DHZCP. MH-S cells induced by SiO₂ were intervened with the drug-containing serum of DHZCP, and the effects of drug-containing serum of DHZCP on the MH-S cells were detected by CCK8, ELISA, flow cytometry, western blot, and immunofluorescence.

Results

DHZCP improved cell viability by reducing apoptosis. It also decreased the levels of TNF-α, IL-1β, IL-6 in the supernatant of MH-S cells induced by SiO₂, inhibited the expression of p38 MAPK, blocked the activation of NF-κB, and controlled the upstream inflammatory response by multiple targeting. Concomitantly, we observed upregulation of Smad7 and a marked decline in TGF-β1, α-SMA, Smad2, Smad3 expression in MH-S cells treated with DHZCP.

Conclusion

To sum up, we conclude that DHZCP protects against SiO₂-induced silicosis by reducing the persistent irritation of inflammation, regulating the p38 MAPK/TGF-β1/Smad pathway.

Tanshinone IIA attenuates silica-induced pulmonary fibrosis via Nrf2-mediated inhibition of EMT and TGF-β1/Smad signaling

Silicosis is an occupational pulmonary fibrosis that is caused by inhalation of silica (SiO₂), and there are no effective drugs to treat this disease. Tanshinone IIA (Tan IIA), a natural product, has been reported to possess antioxidant and anti-fibrotic properties in various diseases. The purpose of the current study was to examine Tan IIA's protective effects against silica-induced pulmonary fibrosis and to explore the underlying mechanisms. We found that in vivo treatment with Tan IIA significantly relieved silica-induced lung fibrosis in a silicosis rat model by histological and immunohistochemical analyses. Further, in vitro mechanistic investigations, mainly using western blot and immunofluorescence analyses, revealed that Tan IIA administration markedly inhibited the silica-induced epithelial-mesenchymal transition (EMT) and transforming growth factor-β1 (TGF-β1)/Smad signaling pathway and also reduced silica-induced oxidative stress and activated the nuclear factor erythroid 2-related factor-2 (Nrf2) signaling pathway in A549 and human bronchial epithelial (HBE) cells. Furthermore, through transfection with siRNA, we demonstrate that Nrf2 activation partially mediates the suppression effects of Tan IIA on EMT and TGF-β1/Smad signaling pathway activation induced by silica exposure, thus mediating the anti-fibrotic effects of Tan IIA against silica-induced pulmonary fibrosis. In our study, Tan IIA has been identified as a possible anti-oxidative and anti-fibrotic drug for silicosis.

MicroRNA-29b Mediates Lung Mesenchymal-Epithelial Transition and Prevents Lung Fibrosis in the Silicosis Model

Lung epithelial-mesenchymal transition (EMT) plays an important role in silicosis fibrosis. The reverse process of EMT is mesenchymal-epithelial transition (MET), which is viewed as an anti-EMT therapy and is a good target toward fibrosis. MicroRNAs (miRNAs) have emerged as potent regulators of EMT and MET programs, and, hence, we tested the miRNA expression using microarray assay and investigated their roles in silica-induced EMT in lung epithelial cells. We found that miRNA-29b (miR-29b) was dynamically downregulated by silica and influenced the promotion of MET in RLE-6TN cells. Furthermore, delivery of miR-29b to mice significantly inhibited silica-induced EMT, prevented lung fibrosis, and improved lung function. Together, our results clearly demonstrated that miR-29b acted as a novel negative regulator of silicosis fibrosis-inhibited lung fibrosis, probably by promoting MET and by suppressing EMT in the lung. These findings may represent a new potential therapeutic target for treating silicosis fibrosis.

Dibutyryl-cAMP attenuates pulmonary fibrosis by blocking myofibroblast differentiation via PKA/CREB/CBP signaling in rats with silicosis

BACKGROUND

Myofibroblasts play a major role in the synthesis of extracellular matrix (ECM) and the stimulation of these cells is thought to play an important role in the development of silicosis. The present study was undertaken to investigate the anti-fibrotic effects of dibutyryl-cAMP (db-cAMP) on rats induced by silica.

METHODS

A HOPE MED 8050 exposure control apparatus was used to create the silicosis model. Rats were randomly divided into 4 groups: 1)controls for 16 w; 2)silicosis for 16 w; 3)db-cAMP pre-treatment; 4) db-cAMP post-treatment. Rat pulmonary fibroblasts were cultured in vitro and divided into 4 groups as follows: 1) controls; 2) 10^-7mol/L angiotensin II (Ang II); 3) Ang II +10^-4 mol/L db-cAMP; and 4) Ang II + db-cAMP+ 10^-6 mol/L H89. Hematoxylin-eosin (HE), Van Gieson staining and immunohistochemistry (IHC) were performed to observe the histomorphology of lung tissue. The levels of cAMP were detected by enzyme immunoassay. Double-labeling for α-SMA with Gαi3, protein kinase A (PKA), phosphorylated cAMP-response element-binding protein (p-CREB), and p-Smad2/3 was identified by immunofluorescence staining. Protein levels were detected by Western blot analysis. The interaction between CREB-binding protein (CBP) and Smad2/3 and p-CREB were measured by co-immunoprecipitation (Co-IP).

RESULTS

Db-cAMP treatment reduced the number and size of silicosis nodules, inhibited myofibroblast differentiation, and extracellular matrix deposition in vitro and in vivo. In addition, db-cAMP regulated Gαs protein and inhibited expression of Gαi protein, which increased endogenous cAMP. Db-cAMP increased phosphorylated cAMP-response element-binding protein (p-CREB) via protein kinase A (PKA) signaling, and decreased nuclear p-Smad2/3 binding with CREB binding protein (CBP), which reduced activation of p-Smads in fibroblasts induced by Ang II.

CONCLUSIONS

This study showed an anti-silicotic effect of db-cAMP that was mediated via PKA/p-CREB/CBP signaling. Furthermore, the findings offer novel insight into the potential use of cAMP signaling for therapeutic strategies to treat silicosis.

Earthworm extract attenuates silica-induced pulmonary fibrosis through Nrf2-dependent mechanisms

Silicosis is an occupational pulmonary fibrosis caused by inhalation of silica (SiO₂) and there are no ideal drugs to treat this disease. Earthworm extract (EE), a natural nutrient, has been reported to have anti-inflammatory, antioxidant, and anti-apoptosis effects. The purpose of the current study was to test the protective effects of EE against SiO₂-induced pulmonary fibrosis and to explore the underlying mechanisms using both in vivo and in vitro models. We found that treatment with EE significantly reduced lung inflammation and fibrosis and improved lung structure and function in SiO₂-instilled mice. Further mechanistic investigations revealed that EE administration markedly inhibited SiO₂-induced oxidative stress, mitochondrial apoptotic pathway, and epithelial-mesenchymal transition in HBE and A549 cells. Furthermore, we demonstrate that Nrf2 activation partly mediates the interventional effects of EE against SiO₂-induced pulmonary fibrosis. Our study has identified EE to be a potential anti-oxidative, anti-inflammatory, and anti-fibrotic drug for silicosis.

The protective effects of bone morphogenetic protein-7 against epithelial injury and matrix metalloproteases upregulation induced by silica in vitro

OBJECTIVE

We investigate the effects of bone morphogenetic protein-7 (BMP-7) on models with silica-induced and macrophage-mediated fibrosis and its possible mechanisms in vitro.

METHODS

Rat alveolar II epithelial (RLE-6TN) cells were incubated with the supernatant of mouse macrophage-like cells (RAW264.7) and treated with 0, 25, 50, and 100 μg/mL silica. Using Western blotting, the epithelial markers (surfactant proteins-C and E-cadherin) and the mesenchymal markers (fibronectin (FN) and viminten (Vim)) were detected. After neutralizing the BMP-7, the progress of fibrosis was assessed by the content of hydroxyproline (Hyp) and collagen I, III protein levels as well as the Smad signaling pathway proteins, including phosphorylated Smad1/5(P-Smad1/5) and phosphorylated Smad2/3(P-Smad2/3). Collagen I was also identified by immunofluorescence and pretreated with SB-431542, LDN-193189, or anti-BMP-7-neutralizing antibody. In addition, the levels of matrix metalloproteinase-2 (MMP-2) and MMP-9 were detected using Western blotting.

RESULTS

The model of RLE-6TN cells was established successfully, the expressions of Vim, FN, MMP-2, and MMP-9 were upregulated, while the concentration of silica is increased. Neutralizing BMP-7 stimulated the decrease of P-Smad1/5 and the increase of P-Smad2/3, as well as the collagen I, collagen III, FN, and Hyp via Smad signaling pathway. Furthermore, pretreated with LDN-193189 or anti-BMP-7-neutralizing antibody, the expression of collagen I was increased, yet it was decreased with SB-431542 intervention.

CONCLUSION

The activated BMP/Smad and suppressed transforming growth factor-β/Smad pathways could suppress silica-induced fibrosis via a MMP-dependent mechanism. BMP-7 is expected to be the optimized strategy of delaying the interstitial changes.

Bone morphogenetic protein-7 prevented epithelial-mesenchymal transition in RLE-6TN cells

Bone morphogenetic protein-7 (BMP-7) plays an important role in the epithelial-mesenchymal transition (EMT) process, and has been identified as the most potent factor that can promote mesenchymal-epithelial transition (MET) and reduce organ fibrosis. Here we examined the important role of BMP-7 in silica-induced EMT and investigated the relationship between BMP-7 and the balance of EMT/MET. We found that silica induced EMT and decreased the expression of BMP-7 in vivo and in vitro, while silica activated the p38 MAPK/transcription factor signaling pathway in RLE-6TN cells. Lentivirus mediated transfection was used to stably upregulate the expression of BMP-7. Exogenous BMP-7 brought on MET exceeded silica-induced EMT and restrained the p38 MAPK/transcription factor signaling pathway in RLE-6TN cells. Our results revealed that BMP-7 promoted MET above EMT induced by silica associated with inhibition of the p38 MAPK/transcription factor signaling pathway, and BMP-7 was a potential target for treatment of silicosis fibrosis.

Increased expression of bone morphogenetic protein-7 and its related pathway provides an anti-fibrotic effect on silica induced fibrosis in vitro

BMP-7 exerts an inhibitory effect on silica induced fibrosis in RLE-6TN cells via suppressing TGF-β signaling and activating BMP signaling.