LPS-induced Pulmonary Fibrosis Research Articles

MiR-23b-3p Ameliorates LPS-Induced Pulmonary Fibrosis by Inhibiting EndMT via DPP4 Inhibition.

Acute respiratory distress syndrome is a disease triggered by severe pulmonary and systemic inflammation that may lead to fibrosis and the decline of lung function. Lung capillary endothelial-to-mesenchymal transition (EndMT) is one of the primary sources of fibroblasts in pulmonary fibrosis. The role of miRNAs as molecular markers of pulmonary fibrosis, and miRNAs as nucleic acid drugs has attracted increasing attention. To mock EndMT process, Human pulmonary microvascular endothelial cells (HPMECs) were induced with lipopolysaccharide (LPS). Similarly, LPS treatment was used to generate a mouse model of LPS-induced EndMT and pulmonary fibrosis. LPS-induced EndMT in HPMECs resulted in a significant reduction of miR-23b-3p. miR-23b-3p inhibited the interstitial transition of HPMECs, and miR-23b-3p could mediate this process via inhibiting dipeptidyl peptidase-4 (DPP4). Dual-luciferase assays confirmed the regulatory mechanism of miR-23b-3p. In our mouse model of LPS-induced pulmonary fibrosis, miR-23b-3p and a DPP4 inhibitor (sitagliptin) individually alleviated LPS-induced EndMT progression and pulmonary fibrosis, and their combined use achieved the strongest remission effect. To sum up, miR-23b-3p alleviates EndMT in pulmonary fibrosis by inhibiting the expression of DPP4.

α 2 -ADRENORECEPTOR ANTAGONIST AMELIORATES SEPSIS-ASSOCIATED PULMONARY FIBROSIS BY SUPPRESSING NOREPINEPHRINE-MEDIATED FIBROBLAST DIFFERENTIATION VIA INHIBITING PKC ACTIVATION.

Pulmonary fibrosis is an important factor affecting the prognosis of severe septic patients with acute lung injury. The objective of this study was to explore the effect of norepinephrine (NE) and α 2 -adrenoreceptor (AR) on sepsis-associated pulmonary fibrosis and the mechanism underlying these effects. We found pulmonary fibrotic changes, and increased NE production and α 2A -AR expression in the pulmonary tissue of mice subjected to cecal ligation and puncture surgery. Reserpine and yohimbine alleviated pulmonary fibrosis in mice with sepsis by exhausting NE derived from the lung's adrenergic nerve and blocking α 2 -AR, respectively. There was no significant difference in the expression of the three α 1 -AR subtypes. The effect of NE on promoting pulmonary fibroblast differentiation in vitro was suppressed by yohimbine. Both the protein and mRNA expression levels of α 2A -AR were increased in pulmonary fibroblasts treated with LPS. Clonidine, a selective α 2 -AR agonist, enhanced LPS-induced differentiation in pulmonary fibroblasts, as indicated by the increase in α-smooth muscle actin and collagen I/III, which was mitigated by inhibiting PKC and p38. Further in vivo results indicated that yohimbine alleviated pulmonary fibrosis and inhibited the phosphorylation of PKC, p38, and Smad2/3 in lung tissue of mice exposed to LPS for 4 weeks. Clonidine showed the opposite effect to yohimbine, which aggravated LPS-induced pulmonary fibrosis. These findings demonstrated that the sepsis-induced increase in NE promoted fibroblast differentiation via activating α 2 -AR. Blockage of α 2 -AR effectively ameliorated sepsis-associated pulmonary fibrosis by abolishing NE-induced lung fibroblast differentiation and inhibiting the PKC-p38-Smad2/3 pathway.

Citrus alkaline extracts improve LPS-induced pulmonary fibrosis via epithelial mesenchymal transition signals

BackgroundAcute respiratory distress syndrome (ARDS) is a serious life threatening clinical critical illness. ARDS-related pulmonary fibrosis is a common complication of ARDS. The occurrence of early pulmonary fibrosis indicates a higher incidence and mortality of multiple organ failure. LPS-induced ARDS-related pulmonary fibrosis model in mice was established in this study. And we have explored the anti-pulmonary fibrosis effects and molecular mechanisms of the Citrus Alkaline Extracts (CAE) in vivo and in vitro.MethodsPulmonary fibrosis mouse model and lung epithelial cell injury model were established in this study. H&E, Masson and Sirius Red staining were used to estimate lung tissue damage. Immunohistochemistry and western blotting were used to analyze proteins expression. Protein-protein interaction was observed by Co-Immunoprecipitation. Systemic impact of CAE on signaling pathway was examined by RNA-seq.ResultsThrough H&E, Masson and Sirius Red staining, it was convincingly indicated that therapeutic administration of CAE alleviated lung injury and fibrosis, while pretreated administration of CAE showed weak improvement. In vitro experiments showed that CAE had dual regulation to E-cadherin and N-cadherin, the important indicators of epithelial-mesenchymal transition (EMT). And it was further demonstrated that CAE reversed TGF-β1-induced EMT mainly through Wnt/β-catenin, Stat3/6 and COX2/PGE2 signals. Through RNA-Seq, we discovered important mechanisms by which CAE exerts its therapeutic effect. And network pharmacology analysis demonstrated core potential targets of CAE in EMT.ConclusionThus, this study provides new therapeutic effects of CAE in anti-fibrosis, and offers potential mechanisms for CAE in LPS-induced pulmonary fibrosis.Graphical

APELIN-13 AMELIORATES LPS-INDUCED ENDOTHELIAL-TO-MESENCHYMAL TRANSITION AND POST-ACUTE LUNG INJURY PULMONARY FIBROSIS BY SUPPRESSING TRANSFORMING GROWTH FACTOR-Β1 SIGNALING.

The pathophysiology of acute respiratory distress syndrome (ARDS) involves cytokine storms, alveolar-capillary barrier destruction, and fibrotic progression. Pulmonary interstitial fibrosis is an important factor affecting the prognosis of ARDS patients. Endothelial-to-mesenchymal transition (EndMT) plays an important role in the development of fibrotic diseases, and the occurrence of EndMT has been observed in experimental models of LPS-induced acute lung injury (ALI). Apelin is an endogenous active polypeptide that plays an important role in maintaining endothelial cell homeostasis and inhibiting fibrotic progression in various diseases. However, whether apelin attenuates EndMT in ALI and post-ALI pulmonary fibrosis remains unclear. We analyzed the serum levels of apelin-13 in patients with sepsis-associated ARDS to examine its possible clinical value. A murine model of LPS-induced pulmonary fibrosis and an LPS-challenged endothelial cell injury model were used to analyze the protective effect and underlying mechanism of apelin-13. Mice were treated with apelin-13 by i.p. injection, and human pulmonary microvascular endothelial cells were incubated with apelin-13 in vitro . We found that the circulating apelin-13 levels were significantly elevated in sepsis-associated ARDS patients compared with healthy controls. Our study also confirmed that LPS induced EndMT progression and pulmonary fibrosis, which were characterized by decreased CD31 expression and increased α-smooth muscle actin expression and collagen deposition. LPS also stimulated the production of transforming growth factor β1 and activated the Smad signaling pathway. However, apelin-13 treatment significantly attenuated these changes. Our findings suggest that apelin-13 may be a novel biomarker in patients with sepsis-associated ARDS. These results demonstrate that apelin-13 ameliorates LPS-induced EndMT and post-ALI pulmonary fibrosis by suppressing transforming growth factor β1 signaling.

The Apelin-APJ axis alleviates LPS-induced pulmonary fibrosis and endothelial mesenchymal transformation in mice by promoting Angiotensin-Converting Enzyme 2

Fibrotic alterations resulting from abnormal tissue repair after lung injury are responsible for the high mortality observed after acute respiratory distress syndrome. Therefore, the prevention and treatment of pulmonary fibrosis has been widely concerned. The Apelin-APJ axis plays an important role in the prevention and treatment of respiratory diseases and organ fibrosis. However, its underlying mechanism remains to be further studied. The aim of this study was to investigate whether the anti-pulmonary fibrosis effect of apelin-APJ axis is related to the activation of angiotensin-converting Enzyme 2 (ACE2). Here, we found that exogenous activation of the Apelin-APJ axis alleviates lipopolysaccharide (LPS)-induced pulmonary fibrosis in mice. In vitro studies revealed that Apelin-13 inhibited LPS-induced endothelial mesenchymal transition in lung microvascular endothelial cells, whereas [Ala13]-Apelin-13 (Apelin-APJ axis inhibitor) accelerated LPS-induced endothelial interstitial transformation in lung microvascular endothelial cells. Notably, angiotensin-converting enzyme 2 (ACE2) inhibitor blocks the beneficial effect of the Apelin-APJ axis activation on LPS-induced pulmonary fibrosis. This finding suggests that the Apelin-APJ axis inhibits pulmonary fibrosis by activating ACE2. Simultaneously, accumulating evidence suggests that ubiquitination may contribute to pulmonary fibrosis. Our study found that LPS increased the ubiquitination of ACE2 protein, whereas Apelin-13 inhibited it. In conclusion, exogenous activation of the Apelin-APJ axis improves LPS-induced pulmonary fibrosis in mice and may be a viable therapeutic target for pulmonary fibrosis.

The role of macrophage–fibroblast interaction in lipopolysaccharide-induced pulmonary fibrosis: an acceleration in lung fibroblast aerobic glycolysis

AbstractRecent evidence has shown that lipopolysaccharide (LPS)-induced aerobic glycolysis of lung fibroblasts is closely associated with the pathogenesis of septic pulmonary fibrosis. Nevertheless, the underlying mechanism remains poorly defined. In this study, we demonstrate that LPS promotes c-Jun N-terminal kinase (JNK) signaling pathway activation and endogenous tumor necrosis factor-α (TNF-α) secretion in pulmonary macrophages. This, in turn, could significantly promote aerobic glycolysis and increase lactate production in lung fibroblasts through 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3) activation. Culturing human lung fibroblast MRC-5 cell line with TNF-α or endogenous TNF-α (cell supernatants of macrophages after LPS stimulation) both enhanced the aerobic glycolysis and increased lactate production. These effects could be prevented by treating macrophages with JNK pathway inhibitor, by administering TNF-α receptor 1 (TNFR1) siRNA, PFKFB3 inhibitor, or by silencing PFKFB3 with fibroblasts-specific shRNA. In addition, the inhibition of TNF-α secretion and PFKFB3 expression prevented LPS-induced pulmonary fibrosis in vivo. In conclusion, this study revealed that LPS-induced macrophage secretion of TNF-α could initiate fibroblast aerobic glycolysis and lactate production, implying that inflammation-metabolism interactions between lung macrophages and fibroblasts might play an essential role in LPS-induced pulmonary fibrosis.This study demonstrates that lipopolysaccharide promotes activation of the JNK signaling pathway and endogenous TNF-α secretion in pulmonary macrophages, which facilitates lung fibroblast aerobic glycolysis and lactate production through PFKFB3 activation. These findings suggests that inflammation-metabolism interactions between lung macrophages and fibroblasts might play an essential role in lipopolysaccharide-induced pulmonary fibrosis.

GANE can Improve Lung Fibrosis by Reducing Inflammation via Promoting p38MAPK/TGF-β1/NF-κB Signaling Pathway Downregulation.

There is a trend to use nanoparticles as distinct treatments for cancer treatment because they have overcome many of the limitations of traditional drug delivery systems. Gallic acid (GA) is an effective polyphenol in the treatment of tissue injuries. In this study, GA was loaded onto niosomes to produce gallic acid nanoemulsion (GANE) using a green synthesis technique. GANE’s efficiency, morphology, UV absorption, release, and Fourier-transform infrared spectroscopy (FTIR) analysis were evaluated. An in vitro study was conducted on the A549 lung carcinoma cell line to determine the GANE cytotoxicity. Also, our study was extended to evaluate the protective effect of GANE against lipopolysaccharide (LPS)-induced pulmonary fibrosis in rats. GANE showed higher encapsulation efficiency and strong absorption at 280 nm. Transmission electron microscopy presented a spherical shape of the prepared nanoparticles, and FTIR demonstrated different spectra for the free gallic acid sample compared to GANE. GANE showed cytotoxicity for the A549 carcinoma lung cell line with a low IC50 value. It was found that oral administration of GANE at 32.8 and 82 mg/kg.b.w. and dexamethasone (0.5 mg/kg) provided significant protection against LPS-induced pulmonary fibrosis. GANE enhanced production of superoxide dismutase, GPx, and GSH. It simultaneously reduced the MDA level. The GANE and dexamethasone, induced the production of IL-4, but suppressed TNF-α and IL-6. On the other hand, the lung p38MAPK, TGF-β1, and NF-κB gene expression was downregulated in rats administrated with GANE when compared with the LPS-treated rats. Histological studies confirmed the effective effect of GANE as it had a lung-protective effect against LPS-induced lung fibrosis. It was noticed that GANE can inhibit oxidative stress, lipid peroxidation, and cytokines and downregulate p38MAPK, TGF-β1, and NF-κB gene expression to suppress the proliferation and migration of lung fibrotic cells.

PI3K-Akt-mTOR/PFKFB3 pathway mediated lung fibroblast aerobic glycolysis and collagen synthesis in lipopolysaccharide-induced pulmonary fibrosis

Metabolic reprogramming plays a critical role in many diseases. A recent study revealed that aerobic glycolysis in lung tissue is closely related to pulmonary fibrosis, and also occurs during lipopolysaccharide (LPS)-induced sepsis. However, whether LPS induces aerobic glycolysis in lung fibroblasts remains unknown. The present study demonstrated that LPS promotes collagen synthesis in the lung fibroblasts through aerobic glycolysis via the activation of the PI3K-Akt-mTOR/PFKFB3 pathway. Challenging the human lung fibroblast MRC-5 cell line with LPS activated the PI3K-Akt-mTOR pathway, significantly upregulated the expression of 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3), enhanced the aerobic glycolysis, and promoted collagen synthesis. These phenomena could be reversed by the PI3K-Akt inhibitor LY294002, mTOR inhibitor rapamycin, PFKFB3 inhibitor 3PO, or PFKFB3 silencing by specific shRNA, or aerobic glycolysis inhibitor 2-DG. In addition, PFKFB3 expression and aerobic glycolysis were also detected in the mouse model of LPS-induced pulmonary fibrosis, which could be reversed by the intraperitoneal injection of PFKFB3 inhibitor 3PO. Taken together, this study revealed that in LPS-induced pulmonary fibrosis, LPS might mediate lung fibroblast aerobic glycolysis through the activation of the PI3K-Akt-mTOR/PFKFB3 pathway.

An observational study on the involvement of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 in aerobic glycolysis in lung fibroblasts and lung tissue induced by lipopolysaccharide

Objective To observe the effects of lipopolysaccharide (LPS) on the expression of a key enzyme during aerobic glycolysis, 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3), and its relationship with aerobic glycolysis, so as to explore the potential mechanism of aerobic glycolysis in lung fibroblasts and lung tissue during LPS-induced pulmonary fibrosis. Methods Human embryonic lung fibroblasts (MRC-5 cell line) were divided into two groups according to the random number table method (n=3): a PBS control (PBS) group and an LPS group. After LPS stimulation for 6 h, the expression of PFKFB3 was detected by Western blot, while the intracellular localization of PFKFB3 was determined by immunofluorescence. The oxygen consumption rate (OCR) and the extracellular acidification rate (ECAR) were mea-sured by the Seahorse Extracellular Flux Analyzer, and the colorimetric method was used to detect the production of lactic acid, a product of aer-obic glycolysis. Meanwhile, the synthesis of collagenⅠwas detected by Western blot after LPS stimulation for 48 h. Twenty-four C57BL/6 mice were divided into two groups according to the random number table method (n=12): a normal saline control group (group C), and an LPS group(group L). Groups L and C were intraperitoneally injected with 5 mg/kg LPS or an equal volume of normal saline for five consecutive days. Six mice of each group were sacrificed on Day 7 after modeling to obtain the plasma and lung tissue. The expression of PFKFB3 in lung tissue of each group was detected by Western blot and immunofluorescence, and the colorimetric method was used to detect the content of lactic acid in the plasma of mice in each group. Lung tissues were collected from the remaining mice on Day 28 after modeling, where a lung was collected to detect collagen Ⅰ synthesis by Western blot, while the other lung were taken to prepare paraffin sections for pathological examination. Results Compared with the PBS group, the expression of PFKFB3 in lung fibroblasts significantly increased after LPS stimulation for 6 h (P< 0.05). After LPS stimulation for 48 h, compared with the PBS group, the LPS group presented a decreased OCR, an increased ECAR, and a re-markably increased amount of lactic acid (P<0.05), with significantly increased synthesis of collagen Ⅰin the cells (P<0.05). Compared with group C, the expression of PFKFB3 in lung tissue significantly increased after intraperitoneal injection of LPS into the mice of group L for seven days (P<0.05), with a significantly increased content of lactic acid in the plasma (P<0.05). After LPS injection for 28 days, the mice in group L presented significantly increased expression of collagenⅠ (P<0.05), with obvious fibrosis in lung tissue. Conclusions LPS can induce the ex-pression of PFKFB3 in lung fibroblasts and lung tissue during LPS-induced pulmonary fibrosis, which is related to aerobic glycolysis. The upreg-ulated expression of PFKFB3 may be a key step of LPS-induced aerobic glycolysis and pulmonary fibrosis in lung fibroblasts and lung tissue. Key words: Lung; Lipopolysaccharide; Fibroblasts; 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3; Aerobic glycolysis; Pulmonary fibrosis

Thy-1 depletion and integrin β3 upregulation-mediated PI3K-Akt-mTOR pathway activation inhibits lung fibroblast autophagy in lipopolysaccharide-induced pulmonary fibrosis

Lipopolysaccharide (LPS)-induced autophagy inhibition in lung fibroblasts is closely associated with the activation of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K-Akt-mTOR) pathway. However, the underlying mechanism remains unknown. In this study, we demonstrated that LPS activated the PI3K-Akt-mTOR pathway and inhibited lung fibroblast autophagy by depleting thymocyte differentiation antigen-1 (Thy-1) and upregulating integrin β3 (Itgb3). Challenge of the human lung fibroblast MRC-5 cell line with LPS resulted in significant upregulation of integrin β3, activation of the PI3K-Akt-mTOR pathway and inhibition of autophagy, which could be abolished by integrin β3 silencing by specific shRNA or treatment with the integrin β3 inhibitor cilengitide. Meanwhile, LPS could inhibit Thy-1 expression accompanied with PI3K-Akt-mTOR pathway activation and lung fibroblast autophagy inhibition; these effects could be prevented by Thy-1 overexpression. Meanwhile, Thy-1 downregulation with Thy-1 shRNA could mimic the effects of LPS, inducing the activation of PI3K-Akt-mTOR pathway and inhibiting lung fibroblast autophagy. Furthermore, protein immunoprecipitation analysis demonstrated that LPS reduced the binding of Thy-1 to integrin β3. Thy-1 downregulation, integrin β3 upregulation and autophagy inhibition were also detected in a mouse model of LPS-induced pulmonary fibrosis, which could be prohibited by intratracheal injection of Thy-1 overexpressing adeno-associated virus (AAV) or intraperitoneal injection of the integrin β3 inhibitor cilengitide. In conclusion, this study demonstrated that Thy-1 depletion and integrin β3 upregulation are involved in LPS-induced pulmonary fibrosis, and may serve as potential therapeutic targets for pulmonary fibrosis.

Lipopolysaccharide induced the proliferation of mouse lung fibroblasts by suppressing FoxO3a/p27 pathway.

Aberrant aggregation and activation of lung fibroblasts is a key process in pulmonary fibrosis, but the underlying mechanism remains enigmatic. Forkhead Box O3a (FoxO3a) is considered to be an important transcription factor that could regulate both cell cycle and cell viability. To investigate the role of FoxO3a on LPS-induced lung fibroblast proliferation, we transfected FoxO3a-SiRNA or FoxO3a-OE lentivirus into cultured mouse lung fibroblasts to knockdown or overexpress FoxO3a and pretreated mouse lung fibroblasts with gefitinib to enhance FoxO3a activity. The proliferation of lung fibroblasts was evaluated by CCK8 assay, the expression of FoxO3a, phosphorylated FoxO3a (p-FoxO3a) and p27 were measured by Western blot. We found that the proliferation of mouse lung fibroblasts mediated by LPS is accompanied by the inactivation of FoxO3a. The knockdown of FoxO3a could further decreased the expression of p27 mediated by LPS, while the overexpression of FoxO3a significantly increased the expression of p27 and suppressed LPS-induced lung fibroblast proliferation. Upon treating fibroblasts with gefitinib, the phosphorylation of FoxO3a was reduced and FoxO3a translocated into the nucleus, the expression of p27 was significantly increased and the proliferation of lung fibroblasts mediated by LPS could also be inhibited effectively. The results indicate that overexpression and reduced phosphatase activity of FoxO3a inhibit LPS-induced lung fibroblast proliferation through the activation of FoxO3a/p27 signaling pathways. Thus, to enhance FoxO3a activity could be a potential therapeutic target for LPS-induced pulmonary fibrosis.

Protective Effects of Hydrogen-Rich Saline Against Lipopolysaccharide-Induced Alveolar Epithelial-to-Mesenchymal Transition and Pulmonary Fibrosis.

BackgroundFibrotic change is one of the important reasons for the poor prognosis of patients with acute respiratory distress syndrome (ARDS). The present study investigated the effects of hydrogen-rich saline, a selective hydroxyl radical scavenger, on lipopolysaccharide (LPS)-induced pulmonary fibrosis.Material/MethodsMale ICR mice were divided randomly into 5 groups: Control, LPS-treated plus vehicle treatment, and LPS-treated plus hydrogen-rich saline (2.5, 5, or 10 ml/kg) treatment. Twenty-eight days later, fibrosis was assessed by determination of collagen deposition, hydroxyproline, and type I collagen levels. Development of epithelial-to-mesenchymal transition (EMT) was identified by examining protein expressions of E-cadherin and α-smooth muscle actin (α-SMA). Transforming growth factor (TGF)-β1 content, total antioxidant capacity (T-AOC), malondialdehyde (MDA) content, catalase (CAT), and superoxide dismutase (SOD) activity were determined.ResultsMice exhibited increases in collagen deposition, hydroxyproline, type I collagen contents, and TGF-β1 production in lung tissues after LPS treatment. LPS-induced lung fibrosis was associated with increased expression of α-SMA, as well as decreased expression of E-cadherin. In addition, LPS treatment increased MDA levels but decreased T-AOC, CAT, and SOD activities in lung tissues, indicating that LPS induced pulmonary oxidative stress. Hydrogen-rich saline treatment at doses of 2.5, 5, or 10 ml/kg significantly attenuated LPS-induced pulmonary fibrosis. LPS-induced loss of E-cadherin in lung tissues was largely reversed, whereas the acquisition of α-SMA was dramatically decreased by hydrogen-rich saline treatment. In addition, hydrogen-rich saline treatment significantly attenuated LPS-induced oxidative stress.ConclusionsHydrogen-rich saline may protect against LPS-induced EMT and pulmonary fibrosis through suppressing oxidative stress.

Effect and mechanism of inhibition of lipopolysaccharide-induced pulmonary fibrosis by butyric acid

To evaluate the inhibitory effect of butyric acid (BA) as a histone deacetylase (HDAC) inhibitor on lipopolysaccharide (LPS)-induced pulmonary fibrosis and its mechanism. Thirty C57/BL6 mice were randomly divided into three groups according to the random number method, namely control group (physiological saline was given intraperitoneally and by gavage), LPS challenge group (LPS-induced murine model of pulmonary fibrosis was reproduced with intraperitoneal injection of 10 mg/kg LPS), and BA preconditioning + LPS challenge group (10 mg/kg BA was given followed by intraperitoneal injection of 10 mg/kg LPS), with 10 mice in each group. Mice were sacrificed painlessly, and lung tissue samples were harvested at 2 weeks and 4 weeks respectively (five samples every group each time). HDAC activity was evaluated with fluorescence analysis kit. Protein expression of acetylated-histone H3 (Ace-H3), acetylated-histone H4 (Ace-H4) and thymocyte differentiation antigen 1 (Thy-1) were determined by Western Blot. The mRNA expression of Thy-1 was assessed by real-time reverse transcription- polymerase chain reaction (real-time RT-PCR). The degree of lung inflammation and fibrosis were microscopic detected after hematoxylin-eosin (HE) staining and Masson collagen staining. The deposition of lung collagen was detected by hydroxyproline content measurement kit. Compared to control group, the degree of lung inflammation and fibrosis was aggravated after LPS challenge, as manifested by increased hydroxyproline content (μg/mg, 2 weeks: 8.384±0.632 vs. 4.388±0.334, 4 weeks: 8.308±0.244 vs. 4.370±0.342, both P < 0.01), increased HDAC activity (μmol/L, 2 weeks: 7.243±0.384 vs. 3.628±0.641, 4 weeks: 6.479±0.202 vs. 3.238±0.524, both P < 0.01), increased deacetylation degree of histone H3 and H4 [relative expression of Ace-H3 (gray value): 0.516±0.115 vs. 1.005±0.359 at 2 weeks, 0.633±0.143 vs. 1.092±0.193 at 4 weeks, both P < 0.05; relative expression of Ace-H4 (gray value): 0.402±0.164 vs. 0.759±0.187 at 2 weeks, P > 0.05; 0.426±0.098 vs. 0.858±0.177 at 4 weeks, P < 0.01], and lowered Thy-1 mRNA and protein expression [Thy-1 mRNA (2(-ΔΔCt)): 0.606±0.066 vs. 1.005±0.109 at 2 weeks, P < 0.01; 0.824±0.101 vs. 1.210±0.400 at 4 weeks, P > 0.05; relative expression of Thy-1 protein (gray value): 0.725±0.284 vs. 1.249±0.297 at 2 weeks, 0.589±0.139 vs. 1.372±0.343 at 4 weeks, both P < 0.05]. Compared with LPS group, BA precondition could inhibit above processes, as manifested by decreased hydroxyproline content (μg/mg: 5.943±0.726 vs. 8.384±0.632 at 2 weeks, 4.938±0.209 vs. 8.308±0.244 at 4 weeks, both P < 0.01), decreased HDAC activity (μmol/L: 4.386±0.117 vs. 7.243±0.384 at 2 weeks, 4.863±0.096 vs. 6.479±0.202 at 4 weeks, both P < 0.01), increased Thy-1 mRNA expression at 2 weeks (2(-ΔΔCt): 0.884±0.216 vs. 0.606±0.066, P < 0.05), increased acetylation degree of histone H4 and Thy-1 protein expression at 4 weeks [relative expression of Ace-H4 (gray value): 0.715±0.145 vs. 0.426±0.098, P < 0.05; relative protein expression of Thy-1 (gray value): 0.939±0.098 vs. 0.589±0.139, P < 0.01]. LPS-induced pulmonary fibrosis was related with activation of HDAC, deacetylation of histone H3 and H4 and Thy-1 gene silencing. HDAC inhibitor BA could inhibit LPS-induced pulmonary fibrosis and Thy-1 gene silencing through inhibiting activation of HDAC and deacetylation of histone H4.

Retraction Note to: Coexpression of HSP47 Gene and Type I and Type III Collagen Genes in LPS-Induced Pulmonary Fibrosis in Rats

Diffuse alveolar damage is the histopathologic hallmark of acute respiratory distress syndrome (ARDS). A significant proportion of ARDS survivors have residual pulmonary fibrosis and compromised pulmonary function. On the other hand, heat shock protein 47 (HSP47) is a collagen-binding stress protein that is assumed to act as a collagen-specific molecular chaperone during the biosynthesis and secretion of procollagen in living cells. The synthesis of HSP47 has been reported to correlate with that of collagen in several cell lines. We examined the expression of HSP47 mRNA and protein during the progression of lipopolysaccharide (LPS)-induced ARDS in rat lung. Male Wistar rats were randomly divided into two groups: a control group with instillation of 0.9% NaCl solution alone, and a LPS group with instillation of LPS dissolved in 0.9% NaCl solution (10 mg/kg). Histologic changes thereafter appeared in the LPS-treated rats. Northern blot analysis revealed the expression of HSP47 mRNA to be markedly induced during the progression of lung damage in parallel with type I and type III collagen mRNA. These results suggest that the upregulation of HSP47 and collagen may play an important role in the fibrotic process of LPS-induced ARDS lung.

Chitosan aerosol inhalation alleviates lipopolysaccharide- induced pulmonary fibrosis in rats

ABSTRACTPurpose: Pulmonary fibrosis (PF) is an insidiously progressive scarring disorder of the alveoli and is associated with high mortality. Currently, therapies available are associated with restricted efficacy and side effects. This study aimed to investigate the effect of chitosan aerosol inhalation on lipopolysaccharide (LPS)-induced pulmonary remodeling and fibrosis in rats. Methods: A rat model of PF was established by intratracheal injection of LPS (5 mg/kg). Chitosan was nebulized to rats from day 4 to 28 after LPS injection. We analyzed the effect of chitosan on LPS-induced pulmonary remodeling and fibrosis by hematoxylin-eosin staining (HE), Masson staining, and the determination of the hydroxyproline content. The expression intensities of matrix metalloproteinase-3 (MMP-3) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were analyzed by western blots. Results: Histological assessments showed that chitosan aerosol inhalation attenuated the fibrotic changes in LPS-induced PF in rats. Compared with the LPS group, the fibrosis parameters were significantly improved in the LPS + chitosan group (LCh group), although not as good as those of the control group. The expressions of MMP-3 and TIMP-1 in the LCh group were markedly less than that of the LPS group on the 28th day. Conclusions: Our findings show that chitosan aerosol inhalation inhibits the expression of MMP-3 and TIMP-1, and ameliorates LPS-induced pulmonary remodeling and fibrosis in rats.

Overexpression of PTEN suppresses lipopolysaccharide-induced lung fibroblast proliferation, differentiation and collagen secretion through inhibition of the PI3-K-Akt-GSK3beta pathway

BackgroundAbnormal and uncontrolled proliferation of lung fibroblasts may contribute to pulmonary fibrosis. Lipopolysaccharide (LPS) can induce fibroblast proliferation and differentiation through activation of phosphoinositide3-Kinase (PI3-K) pathway. However, the detail mechanism by which LPS contributes to the development of lung fibrosis is not clearly understood. To investigate the role of phosphatase and tensin homolog (PTEN), a PI3-K pathway suppressor, on LPS-induced lung fibroblast proliferation, differentiation, collagen secretion and activation of PI3-K, we transfected PTEN overexpression lentivirus into cultured mouse lung fibroblasts with or without LPS treatment to evaluate proliferation by MTT and Flow cytometry assays. Expression of PTEN, alpha-smooth muscle actin (alpha-SMA), glycogen synthase kinase 3 beta (GSK3beta) and phosphorylation of Akt were determined by Western-blot or real-time RT-PCR assays. The PTEN phosphorylation activity was measured by a malachite green-based assay. The content of C-terminal propeptide of type I procollagen (PICP) in cell culture supernatants was examined by ELISA.ResultsWe found that overexpression of PTEN effectively increased expression and phosphatase activity of PTEN, and concomitantly inhibited LPS-induced fibroblast proliferation, differentiation and collagen secretion. Phosphorylation of Akt and GSK3beta protein expression levels in the LPS-induced PTEN overexpression transfected cells were significantly lower than those in the LPS-induced non-transfected cells, which can be reversed by the PTEN inhibitor, bpV(phen).ConclusionsCollectively, our results show that overexpression and induced phosphatase activity of PTEN inhibits LPS-induced lung fibroblast proliferation, differentiation and collagen secretion through inactivation of PI3-K-Akt-GSK3beta signaling pathways, which can be abrogated by a selective PTEN inhibitor. Thus, expression and phosphatase activity of PTEN could be a potential therapeutic target for LPS-induced pulmonary fibrosis. Compared with PTEN expression level, phosphatase activity of PTEN is more crucial in affecting lung fibroblast proliferation, differentiation and collagen secretion.

RETRACTED ARTICLE: Coexpression of HSP47 Gene and Type I and Type III Collagen Genes in LPS-Induced Pulmonary Fibrosis in Rats

Diffuse alveolar damage is the histopathologic hallmark of acute respiratory distress syndrome (ARDS). A significant proportion of ARDS survivors have residual pulmonary fibrosis and compromised pulmonary function. On the other hand, heat shock protein 47 (HSP47) is a collagen-binding stress protein that is assumed to act as a collagen-specific molecular chaperone during the biosynthesis and secretion of procollagen in living cells. The synthesis of HSP47 has been reported to correlate with that of collagen in several cell lines. We examined the expression of HSP47 mRNA and protein during the progression of lipopolysaccharide (LPS)-induced ARDS in rat lung. Male Wistar rats were randomly divided into two groups: a control group with instillation of 0.9% NaCl solution alone, and a LPS group with instillation of LPS dissolved in 0.9% NaCl solution (10 mg/kg). Histologic changes thereafter appeared in the LPS-treated rats. Northern blot analysis revealed the expression of HSP47 mRNA to be markedly induced during the progression of lung damage in parallel with type I and type III collagen mRNA. These results suggest that the upregulation of HSP47 and collagen may play an important role in the fibrotic process of LPS-induced ARDS lung.