OC-STAMP Overexpression Drives Lung Alveolar Epithelial Cell Type II Senescence in Silicosis.

Cellular senescence has been considered an important driver of many chronic lung diseases. However, the specific mechanism of cellular senescence in silicosis is still unknown. In the present study, silicotic rats and osteoclast stimulatory transmembrane protein (Ocstamp) overexpression of MLE-12 cells were used to explore the mechanism of OC-STAMP in cellular senescence in alveolar epithelial cell type II (AEC2). We found an increasing level of OC-STAMP in AEC2 of silicotic rats. Overexpression of Ocstamp in MLE-12 cells promoted epithelial-mesenchymal transition (EMT), endoplasmic reticulum (ER) stress, and cellular senescence. Myosin heavy chain 9 (MYH9) was a potential interacting protein of OC-STAMP. Knockdown of Ocstamp or Myh9 inhibited cellular senescence in MLE-12 cells transfected with pcmv6-Ocstamp. Treatment with 4-phenylbutyrate (4-PBA) to inhibit ER stress also attenuated cellular senescence in vitro or in vivo. In conclusion, OC-STAMP promotes cellular senescence in AEC2 in silicosis.

[Effect of N-acetyl-seryl-aspartyl-lysyl-proline on differentiation from pulmonary fibroblast to myofibroblast mediated by Rho-associated coiled-coil forming protein kinase pathway].

OBJECTIVE: To investigate whether N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) can inhibit the differentiation of pulmonary fibroblasts into myofibroblasts by regulating Rho-associated coiled-coil forming protein kinase (ROCK) pathway mediated by transforming growth factor-ß1 (TGF-ß1). METHODS: Primary culture of pulmonary fibroblasts was performed by trypsinization method. Four generations of pulmonary fibroblasts were divided into control group, TGF-ß-induced differentiation group, Y-27632 treatment group, and Ac-SDKP treatment group. The intracellular distributions of ROCK, serum response factor (SRF), and α-smooth muscle actin (α-SMA) were observed by confocal laser scanning microscopy. The protein expression of ROCK, SFR, α-SMA, and type I and type III collagen in pulmonary fibroblasts was measured by Western blot. The mRNA expression of ROCK, SFR, and α-SMA was measured by real-time quantitative PCR. RESULTS: Compared with the control group, the pulmonary fibroblasts stimulated by TGF-ß1 had a lot of α-SMA antibody-labeled myofilaments in parallel or cross arrangement, as observed by confocal laser scanning microscopy, and the mRNA and protein expression of ROCK, SRF, and α-SMA and protein expression of type I and type III collagen increased significantly after 6, 12, and 24 h of stimulation (P < 0.05). Compared with the TGF-ß1-induced differentiation group, the Y-27632 treatment group and Ac-SDKP treatment group had significantly decreased mRNA and protein expression of ROCK, SRF, and α-SMA and protein expression of type I and type III collagen at the same time point (P < 0.05). CONCLUSION: Ac-SDKP can inhibit the differentiation of pulmonary fibroblasts into myofibroblasts and the synthesis of collagen in rats by regulating the ROCK pathway mediated by TGF-ß1. That may be one of the mechanisms by which Ac-SDKP acts against (silicotic) pulmonary fibrosis.

[Regulating effect of N-acetyl-seryl-aspartyl-lysyl-proline on activation of c-jun N-terminal kinase pathway in rats with silicosis].

OBJECTIVE: To investigate the regulatory effect of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) on the activation of c-jun N-terminal kinase (JNK) signal transduction pathway and its role in silicotic fibrosis. METHODS: A rat model of silicosis was developed by intratracheal instillation. Sixty rats were randomly divided into 4-week control group (n = 10), 8-week control group (n = 10), 4-week silicosis model group (n = 10), 8-week silicosis model group (n = 10), AcSDKP treatment group (n = 10), and AcSDKP prevention group (n = 10). The content of hydroxyproline in lung tissue was measured using a p-dimethylaminoben-zaldehyde reagent; the expression levels of transforming growth factor (TGF)-beta 1 (TGF-ß1), phospho-JNK, JNK, and c-jun in lung tissue were measured by Western blot. The lung fibroblasts from neonatal rats were cultured, and the 4th generation of cells were used in the experiment; these cells were divided into control group, TGF-ß1 stimulation group, SP600125 intervention group, and AcSDKP intervention group. The distributions of phospho-JNK and c-jun in lung fibroblasts were observed by immunocytochemistry; the expression levels of type I collagen and type III collagen in lung fibroblasts were measured by Western blot. RESULTS: The expression levels of TGF-ß1, phospho-JNK, and c-jun and the content of hydroxyproline in the AcSDKP treatment group were 70.60%, 78.03%, 79.85%, and 71.28%, respectively, of those in the 4-week silicosis model group (P < 0.05) and 77.99%, 66.73%, 69.94%, and 64.82%, respectively, of those in the 8-week silicosis model group (P < 0.05); the expression levels of TGF-ß1, phospho-JNK, and c-jun and the content of hydroxyproline in the AcSDKP prevention group were 84.56%, 61.18%, 64.73%, and 74.96%, respectively, of those in the 8-week silicosis model group (P < 0.05). The expression levels of phospho-JNK and c-jun in the AcSDKP intervention group were 54.59% and 55.56%, respectively, of those in the TGF-ß1 stimulation group; the expression levels of type I collagen and type III collagen in the AcSDKP intervention group were 79.9% and 84.4%, respectively, of those in the TGF-ß1 stimulation group (P < 0.05). CONCLUSION: AcSDKP exerts anti-silicotic fibrosis effect probably by inhibiting the activation of JNK signal transduction pathway mediated by TGF-ß1 and the deposition of interstitial collagen.

[Effect of N-acetyl-seryl-aspartyl-lysyl-proline on regulation of expression of ras-raf-ERK1/2 signal transduction pathway in lung of rats with silicosis].

OBJECTIVE: to investigate the effect of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) on the expressions of c-Raf, ERK1/2 and TGF-ß1 in the lung of rats with silicosis, thus to investigate the regulating of AcSDKP on the Ras-Raf-ERK1/2 signal transduction pathway. METHODS: rats were instilled with silica through trachea as silicotic models and administered AcSDKP in the experiment. Rats were divided into 6 groups randomly, 10 rats in each group: Control 1 and 2 of silicotic model: each rat was intratracheally instilled with 1.0 ml normal sodium and was killed after 4 or 8 weeks; Silicotic model 1 and Silicotic model 2: each rat was intratracheally instilled with 1ml silica suspension and was killed after 4 or 8 weeks; Anti-fibrosis treatment of AcSDKP: after each rat was intratracheally instilled with 1ml silica suspension for 4 weeks, AcSDKP 800 microg × kg(-1) × d(-1) was administered into every rat and rats were killed at the eighth week; Preventing fibrosis treatment of AcSDKP: after AcSDKP 800 microg × kg(-1) × d(-1) was administered into every rat for 48 hours, each rat was intratracheally instilled with 1.0 ml silica suspension and rats were killed at the eighth week. The expression of c-Raf, phospho-c-Raf, ERK1/2, phospho-ERK1/2 and TGF-ß1 was measured by immunohistochemistry and western blot assay. RESULTS: compared with the corresponding control groups, the expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-ß1 increased in the lung tissue of the silicotic models. Compared with the corresponding model groups, after administration AcSDKP, the expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-ß1 in the lung tissue reduced obviously. In anti-fibrosis treatment of AcSDKP group, expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-ß1 decreased to 52.25%, 51.72% and 67.74% compared with those of the silicotic model 1, and expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-ß1 decreased to 49.37%, 55.76%, 65.63% compared with those of the silicotic model 2; In preventing fibrosis treatment of AcSDKP group, expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-ß1 decreased to 54.64%, 55.76% and 78.91% compared with those of the silicotic model 2 (P < 0.05) while the expressions of c-Raf and ERK1/2 were not different significantly among each groups. CONCLUSION: AcSDKP possibly plays an important role in anti-silicotic fibrosis by blocking the TGF-ß-induced Ras-Raf-ERK1/2 signal transduction pathway.