Cigarette smoke-induced pulmonary inflammatory responses are mediated by EGR-1/GGPPS/MAPK signaling

Protective effect of the total alkaloid extract from Bulbus Fritillariae Pallidiflorae on cigarette smoke-induced Beas-2B cell injury model and transcriptomic analysis

Background

Bulbus Fritillariae Pallidiflorae (BFP) is a traditional Chinese medicine that has long been used to treat lung diseases, but the active components and mechanism are still unclear.

Objective

This study aimed to investigate the effect and mechanism of the total alkaloid extract from BFP (BFP-TA) on cigarette smoke extract (CSE)-induced Beas-2B cells injury.

Design

The Beas-2B cells injury model was induced by 2% CSE, then the effect of BFP-TA on the levels of total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and malondialdehyde (MDA) was detected according to the instructions of the T-AOC assay kit, the SOD detection kit and the MDA detection kit, and the production of ROS was detected by fluorescence microscopy. The effect of BFP-TA on Beas-2B cells apoptosis was detected by flow cytometry, and the effect of BFP-TA on related protein expression was detected by western blot. Subsequently, the effect of BFP-TA on differentially expressed genes (DEGs) in CSE-induced Beas-2B cells was studied by transcriptomic sequencing, and the expression of DEGs was verified by quantitative real-time polymerase chain reaction (qPCR).

Results

The results showed that BFP-TA could attenuate CSE-induced oxidative damage in Beas-2B cells by elevating T-AOC and SOD levels while inhibiting ROS and MDA levels, and the mechanism was potentially related to the SIRT1/Nrf2/Keap1 signaling pathway. Furthermore, BFP-TA could inhibit CSE-induced apoptosis by inhibiting the protein expression of Bax, MST1 and FOXO3a, and exert anti-inflammatory effect by inhibiting the activation of MAPK signaling pathway. Subsequently, transcriptome analysis and qPCR validation showed that BFP-TA could alleviate inflammation, oxidative stress, apoptosis and lipid metabolism disorders by regulating the expression of DEGs in PPAR and PI3K-Akt signaling pathways, thereby exerting a protective effect against CSE-induced Beas-2B cell injury.

Conclusion

This study is the first to demonstrate that BFP-TA could exert a protective effect on CSE-induced Beas-2B cell injury by exerting anti-inflammatory, antioxidant, anti-apoptotic and regulate lipid metabolism disorders.

Combining a lung microfluidic chip exposure model with transcriptomic analysis to evaluate the inflammation in BEAS-2B cells exposed to cigarette smoke

BACKGROUND

Typically, in vitro studies on the exposure of complex gaseous substances are performed in multi-well plate experiments by trapping and redissolving them, which could introduce potential bias into the results due to the use of inadequate trapping methods. Therefore, a more effective method is to expose complex gaseous substances in gaseous form online, such as using microfluidic chips in experiments. To address these challenges, we introduce a methodology that integrates a self-designed bionic-lung chip with transcriptome analysis to assess the impact of cigarette smoke (CS) exposure on changes in BEAS-2B cells cultured on-chip.

RESULTS

After the microfluidic chip underwent online gas exposure, total RNA was extracted via in situ cell lysis, and RNA-Seq transcriptome analysis was conducted. And the RNA-Seq findings revealed the significant involvement of the MAPK signaling pathway associated with the inflammatory response in the cellular effects induced by CS exposure. Moreover, the validation of inflammatory response-related biomarkers through in situ fluorescence corroborated the outcomes of the transcriptome analysis. Besides, the experiment involving the inhibition of inflammation by DEX on the microfluidic chip provided additional confirmation of the previous experimental findings.

SIGNIFICANT

In this study, we present an analytical strategy that combines microfluidic-based CS in situ exposure method with RNA-Seq technology. This strategy offers an experimental scheme for in situ exposure to complex gases, transcriptome analysis, and in situ fluorescence detection. Through the integration of the comprehensiveness of transcriptome analysis with the chip's direct and intuitive in situ fluorescence detection with the stability and reliability of RT-PCR and Western blot experiments, we have successfully addressed the challenges associated with in vitro risk assessment for online exposure to complex gaseous substances.

Role of early growth response 1 in inflammation-associated lung diseases

Early growth response 1 (EGR1), which is involved in cell proliferation, differentiation, apoptosis, adhesion, migration, and immune and inflammatory responses, is a zinc finger transcription factor. EGR1 is a member of the EGR family of early response genes and can be activated by external stimuli such as neurotransmitters, cytokines, hormones, endotoxins, hypoxia, and oxidative stress. EGR1 expression is upregulated during several common respiratory diseases, such as acute lung injury/acute respiratory distress syndrome, chronic obstructive pulmonary disease, asthma, pneumonia, and novel coronavirus disease 2019. Inflammatory response is the common pathophysiological basis of these common respiratory diseases. EGR1 is highly expressed early in the disease, amplifying pathological signals from the extracellular environment and driving disease progression. Thus, EGR1 may be a target for early and effective intervention in these inflammation-associated lung diseases.

Multi-omic association study identifies DNA methylation-mediated genotype and smoking exposure effects on lung function in children living in urban settings

Impaired lung function in early life is associated with the subsequent development of chronic respiratory disease. Most genetic associations with lung function have been identified in adults of European descent and therefore may not represent those most relevant to pediatric populations and populations of different ancestries. In this study, we performed genome-wide association analyses of lung function in a multiethnic cohort of children (n = 1,035) living in low-income urban neighborhoods. We identified one novel locus at the TDRD9 gene in chromosome 14q32.33 associated with percent predicted forced expiratory volume in one second (FEV1) (p = 2.4x10-9; βz = -0.31, 95% CI = -0.41- -0.21). Mendelian randomization and mediation analyses revealed that this genetic effect on FEV1 was partially mediated by DNA methylation levels at this locus in airway epithelial cells, which were also associated with environmental tobacco smoke exposure (p = 0.015). Promoter-enhancer interactions in airway epithelial cells revealed chromatin interaction loops between FEV1-associated variants in TDRD9 and the promoter region of the PPP1R13B gene, a stimulator of p53-mediated apoptosis. Expression of PPP1R13B in airway epithelial cells was significantly associated the FEV1 risk alleles (p = 1.3x10-5; β = 0.12, 95% CI = 0.06-0.17). These combined results highlight a potential novel mechanism for reduced lung function in urban youth resulting from both genetics and smoking exposure.

Potential biomarkers for inflammatory response in acute lung injury

Acute lung injury (ALI) is a severe respiratory disorder occurring in critical care medicine, with high rates of mortality and morbidity. This study aims to screen the potential biomarkers for ALI. Microarray data of lung tissues from lung-specific geranylgeranyl pyrophosphate synthase large subunit 1 knockout and wild-type mice treated with lipopolysaccharide were downloaded. Differentially expressed genes (DEGs) between ALI and wild-type mice were screened. Functional analysis and the protein-protein interaction (PPI) modules were analyzed. Finally, a miRNA-transcription factor (TF)-target regulation network was constructed. Totally, 421 DEGs between ALI and wild-type mice were identified. The upregulated DEGs were mainly enriched in the peroxisome proliferator-activated receptor signaling pathway, and fatty acid metabolic process, while downregulated DEGs were related to cytokine-cytokine receptor interaction and regulation of cytokine production. Cxcl5, Cxcl9, Ccr5, and Cxcr4 were key nodes in the PPI network. In addition, three miRNAs (miR505, miR23A, and miR23B) and three TFs (PU1, CEBPA, and CEBPB) were key molecules in the miRNA-TF-target network. Nine genes including ADRA2A, P2RY12, ADORA1, CXCR1, and CXCR4 were predicted as potential druggable genes. As a conclusion, ADRA2A, P2RY12, ADORA1, CXCL5, CXCL9, CXCR1, and CXCR4 might be novel markers and potential druggable genes in ALI by regulating inflammatory response.

A Journey into the Clinical Relevance of Heme Oxygenase 1 for Human Inflammatory Disease and Viral Clearance: Why Does It Matter on the COVID-19 Scene?

Heme oxygenase 1 (HO-1), the rate-limiting enzyme in heme degradation, is involved in the maintenance of cellular homeostasis, exerting a cytoprotective role by its antioxidative and anti-inflammatory functions. HO-1 and its end products, biliverdin, carbon monoxide and free iron (Fe²⁺), confer cytoprotection against inflammatory and oxidative injury. Additionally, HO-1 exerts antiviral properties against a diverse range of viral infections by interfering with replication or activating the interferon (IFN) pathway. Severe cases of coronavirus disease 2019 (COVID-19), an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are characterized by systemic hyperinflammation, which, in some cases, leads to severe or fatal symptoms as a consequence of respiratory failure, lung and heart damage, kidney failure, and nervous system complications. This review summarizes the current research on the protective role of HO-1 in inflammatory diseases and against a wide range of viral infections, positioning HO-1 as an attractive target to ameliorate clinical manifestations during COVID-19.

Catechin regulates miR-182/GGPPS1 signaling pathway and inhibits LPS-induced acute lung injury in mice

AIM

Acute lung injury (ALI) and resultant acute respiratory distress syndrome (ARDS) are detrimental inflammatory disease associated with high rates of morbidity and mortality due to a lack of effective treatment options. Previous study has demonstrated that an inhibition of geranylgeranyl pyrophosphate synthase large subunit 1 (GGPPS1) show a protective effect against ALI.

METHOD

In this study, by using connective map (CMAP), we identified catechin as a potential drug to exhibit similar effects to inhibit GGPPS1. Furthermore, we detected the protective effect of catechin on lipopolysaccharide (LPS)-induced ALI and delineated the underlying mechanism.

RESULTS

We found that catechin effectively ameliorated LPS-induced lung inflammation and alleviated the release of cytokines into alveolar space. Notably, miR-182/GGPPS1 signaling pathway was reactivated upon catechin administration, which was essential for the catechin-induced protective effect against ALI.

CONCLUSION

catechin regulates miR-182/GGPPS1 signaling pathway and efficaciously ameliorates LPS-induced acute lung injury in mice model, which provided a promising therapeutic strategy in ALI and ARDS.

Geranylgeranyl diphosphate synthase deficiency aggravates lung fibrosis in mice by modulating TGF-β1/BMP-4 signaling

Geranylgeranyl diphosphate synthase (GGPPS) is an enzyme that catalyzes the synthesis of geranylgeranyl pyrophosphate (GGPP). GGPPS is implicated in many disorders, but its role in idiopathic pulmonary fibrosis (IPF) remains unclear. This study aimed to investigate the role of GGPPS in IPF. We established bleomycin-induced lung injury in a lung-specific GGPPS-deficient mouse (GGPPS-/-) and detected GGPPS expression in lung tissues by Western blot and immunohistochemistry analysis. We found that GGPPS expression increased during lung injury and fibrosis in mice induced by bleomycin, and GGPPS deficiency augmented lung fibrosis. GGPPS deficiency activated lung fibroblast by facilitating transforming growth factor β1 while antagonizing bone morphogenetic protein 4 signaling. Notably, the supplementation of exogenous GGPP mitigated lung fibrosis in GGPPS-/- mice induced by bleomycin. In conclusion, our findings suggest that GGPPS provides protection against pulmonary fibrosis and that the restoration of protein geranylgeranylation may benefit statin-induced lung injury.

Geranylgeranyl diphosphate synthase 1 knockout ameliorates ventilator-induced lung injury via regulation of TLR2/4-AP-1 signaling

OBJECTIVE

To investigate the role of geranylgeranyl diphosphate synthase 1 (GGPPS1) in ventilator-induced lung injury along with the underlying mechanism.

METHODS

A murine VILI model was induced by high-tidal volume ventilation in both wild-type and GGPPS1 knockout mice. GGPPS1 expression was detected in the bronchoalveolar lavage fluid (BALF) supernatants of acute respiratory distress syndrome (ARDS) patients and healthy volunteers, as well as in lung tissues and BALF supernatants of the VILI mice using enzyme-linked immunosorbent assay (ELISA), quantitative reverse transcription polymerase chain reaction (qRT-PCR), western bolt and immunohistochemical (IHC). The wet/dry ratio, total BALF proteins, and lung injury score were analyzed. The percentage of neutrophils was detected by flow cytometry and IHC. Inflammatory cytokine levels were measured by ELISA and qRT-PCR. The related expression of Toll-like receptor (TLR)2/4 and its downstream proteins was evaluated by western blot.

RESULTS

GGPPS1 in BALF supernatants was upregulated in ARDS patients and the VILI mice. Depletion of GGPPS1 significantly alleviated the severity of ventilator induced lung injury in mice. Total cell count, neutrophils and inflammatory cytokines (interleukin [IL]-6, IL-1β, IL-18 and tumor necrosis factor-α) levels in BALF were reduced after GGPPS1 depletion. Moreover, addition of exogenous GGPP in GGPPS-deficient mice significantly exacerbated the severity of ventilator induced lung injury as compared to the PBS treated controls. Mechanistically, the expression of TLR2/4, as well as downstream proteins including activator protein-1 (AP-1) was suppressed in lung tissues of GGPPS1-deficient mice.

CONCLUSION

GGPPS1 promoted the pathogenesis of VILI by modulating the TLR2/4-AP-1 signaling pathway, and GGPPS1 knockout significantly alleviated the lung injury and inflammation in the VILI mice.

Screening of Cellular Stress Responses Induced by Ambient Aerosol Ultrafine Particle Fraction PM0.5 in A549 Cells

Effects of airborne particles on the expression status of markers of cellular toxic stress and on the release of eicosanoids, linked with inflammation and oxidative damage, remain poorly characterized. Therefore, we proposed a set of various methodological approaches in order to address complexity of PM0.5-induced toxicity. For this purpose, we used a well-characterized model of A549 pulmonary epithelial cells exposed to a non-cytotoxic concentration of ambient aerosol particle fraction PM0.5 for 24 h. Electron microscopy confirmed accumulation of PM0.5 within A549 cells, yet, autophagy was not induced. Expression profiles of various cellular stress response genes that have been previously shown to be involved in early stress responses, namely unfolded protein response, DNA damage response, and in aryl hydrocarbon receptor (AhR) and p53 signaling, were analyzed. This analysis revealed induction of GREM1, EGR1, CYP1A1, CDK1A, PUMA, NOXA and GDF15 and suppression of SOX9 in response to PM0.5 exposure. Analysis of eicosanoids showed no oxidative damage and only a weak anti-inflammatory response. In conclusion, this study helps to identify novel gene markers, GREM1, EGR1, GDF15 and SOX9, that may represent a valuable tool for routine testing of PM0.5-induced in vitro toxicity in lung epithelial cells.

Modificated Mahuang-Tang, a traditional herbal medicine suppresses inflammatory responses induced by cigarette smoke in human airway epithelial cell and mice

BACKGROUND

Cigarette smoke (CS) is a major contributor to the high incidence of chronic obstructive pulmonary disease (COPD) featured as chronic inflammation and airway obstruction. Mahuang-Tang is a traditional polyherbal mixture composed of four different herbs. It is widely used in Asia as a remedy for allergic reaction and inflammation.

PURPOSE

We investigated the effects of a modificated Mahuang-Tang water extract (MTWE) against airway inflammation caused by CS and lipopolysaccharide (LPS) in mice and cigarette smoke condensate (CSC)-stimulated NCI-H292 cells.

METHODS

CS exposed to animals for 1 h per day from day 1 to day 7 and treated with LPS intranasally on day 4. One hour before CS exposure, animals were received MTWE (50 or 100 mg/kg) by oral gavage. Inflammatory cell count and cytokines levels were measured in the bronchoalveolar lavage fluid. Expression levels of matrix metalloprotease-9 (MMP-9) and extracellular signal-regulated kinase (Erk) were analyzed by western blotting.

RESULTS

MTWE markedly decreased the neutrophil and other inflammatory cell counts in the bronchoalveolar lavage fluid and reduced proinflammatory mediators as evidenced by the decreases in inflammatory cell recruitment in lung tissue. Furthermore, MTWE meaningfully declined MMP-9 expression and reduced the Erk phosphorylation, caused by the CS and LPS exposure. In in vitro experiments, MTWE suppressed the elevated expression of proinflammatory cytokines induced by CSC treatment. MTWE reduced Erk phosphorylation and MMP-9 expression in CSC-stimulated H292 cells.

CONCLUSION

Overall, MTWE effectively inhibited the pulmonary inflammation and MMP-9 expression caused by the CS and LPS exposure, which was closely involved in suppression of Erk phosphorylation. These results suggest that MTWE possesses a potential for the treatment of COPD.

Inhibition of GGPPS1 attenuated LPS-induced acute lung injury and was associated with NLRP3 inflammasome suppression

Inhibition of the mevalonate pathway using statins has been shown to be beneficial in the treatment of acute lung injury (ALI). Here, we investigated whether partial inhibition of this pathway by targeting geranylgeranyl pyrophosphate synthase large subunit 1 (GGPPS1), a catalase downstream of the mevalonate pathway, was effective at treating lung inflammation in ALI. Lipopolysaccharide (LPS) was intratracheally instilled to induce ALI in lung-specific GGPPS1-knockout and wild-type mice. Expression of GGPPS1 in lung tissues and alveolar epithelial cells was examined. The severity of lung injury and inflammation was determined in lung-specific GGPPS1 knockout and wild-type mice by measuring alveolar exudate, neutrophil infiltration, lung injury, and cell death. Change in global gene expression in response to GGPPS1 depletion was measured using mRNA microarray and verified in vivo and in vitro. We found that GGPPS1 levels increased significantly in lung tissues and alveolar epithelial cells in LPS-induced ALI mice. Compared with wild-type and simvastatin treated mice, the specific deletion of pulmonary GGPPS1 attenuated the severity of lung injury by inhibiting apoptosis of AECs. Furthermore, deletion of GGPPS1 inhibited LPS-induced inflammasome activation, in terms of IL-1β release and pyroptosis, by downregulating NLRP3 expression. Finally, downregulation of GGPPS1 reduced the membrane expression of Ras-related protein Rab10 and Toll-like receptor 4 (TLR4) and inhibited the phosphonation of IκB. This effect might be attributed to the downregulation of GGPP levels. Our results suggested that inhibition of pulmonary GGPPS1 attenuated LPS-induced ALI predominantly by suppressing the NLRP3 inflammasome through Rab10-mediated TLR4 replenishment.

Notch promotes DNMT-mediated hypermethylation of Klotho leads to COPD-related inflammation

AIM

Klotho expression significantly declines in alveolar macrophages and airway epithelial cells in chronic obstructive pulmonary disease (COPD) patients, and cigarette smoke extract dramatically inhibits the expression and secretion of α-Klotho. This suggests that the silencing of Klotho is the major factor promoting COPD related inflammatory responses. This study aims to investigate the mechanism of Klotho downregulation and its effect on the inflammatory cytokines secretion and cell apoptosis.

METHODS

Expression of DNA methyltransferases (DNMTs) and Notch signaling activation were quantified in MH-S and 16HBE cells stimulated with cigarette smoke extract (CSE) solution. Specific inhibitors of DNMTs or Notch pathway were added together with CSE into treated and control cells. Inflammatory cytokines, cell viability and cell death were determined to explore the effect of Klotho on COPD related inflammation.

RESULTS

CSE treatment statistically increased the level of DNMTs expression, Klotho promoter methylation, and activated the Notch signaling pathway. Notch signal activation played a critical role in the process of modification of Klotho promoter methylation. The inhibition of DNMTs and Notch pathway rescued Klotho levels and inhibited inflammation and cell apoptosis after CSE treatment.

CONCLUSION

Notch-mediated Klotho hypermethylation inhibited Klotho expression, which promoted inflammatory response and cell apoptosis that were associated with the development of COPD.

Cigarette Smoke Extract Promotes TIM4 Expression in Murine Dendritic Cells Leading to Th2 Polarization through ERK-Dependent Pathways

Smoking is considered to be the main source of indoor pollution, and it has been identified as an important environmental factor contributing to asthma onset. We know that T helper 2 (Th2) response plays a crucial role in the process of asthma disease. We have investigated the reaction of cigarette smoke extract (CSE) on Th polarization which is controlled by dendritic cells (DCs). Stimulated by CSE, immature DCs from murine bone marrow showed upregulated levels of TIM4. Cocultured with CD4+ T cells, stimulated DCs increased the ratio of IL-4+ versus IFN-γ+ of CD4+ T cells. This suggests a differentiation towards Th2 response. Moreover, antibodies against TIM4 reversed the upexpression of the IL-4+/IFN-γ+ ratio provoked by CSE, indicating that the Th2 polarization which was induced by CSE is via TIM4 mechanisms. CSE could activate mitogen-activated protein kinase pathways like ERK and p38. Upregulation of TIM4 expression by CSE stimulation was found to be inhibited by an ERK inhibitor but not p38 and JNK. In conclusion, DC-induced Th2 polarization is a hallmark of CSE allergy, and this aspect can be explained by CSE-induced TIM4 expression.

Calpeptin attenuates cigarette smoke-induced pulmonary inflammation via suppressing calpain/IκBα signaling in mice and BEAS-2B cells

Exposure to cigarette smoke including secondhand smoking is the most important risk factor in the development of chronic obstructive pulmonary disease where incidence has substantially increased in recent decades. The mechanisms responsible for cigarette smoke-induced pulmonary inflammation remain unclear, and thus lack of effective treatment. The present study investigated the effect of calpeptin on attenuating cigarette smoke induced pulmonary inflammation and its potential mechanism and function. When BALB/c mice were exposed to cigarette smoke and received calpeptin intraperitoneally injection after 90 days, calpeptin histologically attenuated the accumulation of neutrophils (P < 0.001), eosinophils (P < 0.001), macrophages (P < 0.01), fibrinous exudation and proliferation within the interstitial and alveolar spaces. BEAS-2B cells were added with cigarette smoke extract in vitro and treated with calpeptin for 24 h in the treatment group. The markedly upregulation of μ-calpain (P < 0.01), m-calpain (P < 0.001) and IκBα (P < 0.01) in cigarette smoke-induced lungs were simultaneously decreased by calpeptin treatment (P < 0.05). The increased expression of μ-calpain, m-calpain and IκBα (P < 0.05) in cigarette smoke extract-stimulated BEAS-2B cells were also decreased by calpeptin treatment (P < 0.05). These data indicated that calpeptin attenuated cigarette smoke-induced pulmonary inflammation by suppressing the pathway of μ-calpain, m-calpain and IκBα in vivo and in vitro. Calpeptin might have a potential for prevention of the development of inflammatory pulmonary diseases and warrant further pharmaceutical investigation.

Early growth response-1 negative feedback regulates skeletal muscle postprandial insulin sensitivity via activating Ptp1b transcription

Postprandial insulin desensitization plays a critical role in maintaining whole-body glucose homeostasis by avoiding the excessive absorption of blood glucose; however, the detailed mechanisms that underlie how the major player, skeletal muscle, desensitizes insulin action remain to be elucidated. Herein, we report that early growth response gene-1 ( Egr-1) is activated by insulin in skeletal muscle and provides feedback inhibition that regulates insulin sensitivity after a meal. The inhibition of the transcriptional activity of Egr-1 enhanced the phosphorylation of the insulin receptor (InsR) and Akt, thus increasing glucose uptake in L6 myotubes after insulin stimulation, whereas overexpression of Egr-1 decreased insulin sensitivity. Furthermore, deletion of Egr-1 in the skeletal muscle improved systemic insulin sensitivity and glucose tolerance, which resulted in lower blood glucose levels after refeeding. Mechanistic analysis demonstrated that EGR-1 inhibited InsR phosphorylation and glucose uptake in skeletal muscle by binding to the proximal promoter region of protein tyrosine phosphatase-1B (PTP1B) and directly activating transcription. PTP1B knockdown largely restored insulin sensitivity and enhanced glucose uptake, even under conditions of EGR-1 overexpression. Our results indicate that EGR-1/PTP1B signaling negatively regulates postprandial insulin sensitivity and suggest a potential therapeutic target for the prevention and treatment of excessive glucose absorption.-Wu, J., Tao, W.-W., Chong, D.-Y., Lai, S.-S., Wang, C., Liu, Q., Zhang, T.-Y., Xue, B., Li, C.-J. Early growth response-1 negative feedback regulates skeletal muscle postprandial insulin sensitivity via activating Ptp1b transcription.

Overexpression of geranylgeranyl diphosphate synthase contributes to tumour metastasis and correlates with poor prognosis of lung adenocarcinoma

This study aimed to evaluate the biological role of geranylgeranyl diphosphate synthase (GGPPS) in the progression of lung adenocarcinoma. GGPPS expression was detected in lung adenocarcinoma tissues by qRT‐PCR, tissue microarray (TMA) and western blotting. The relationships between GGPPS expression and the clinicopathological characteristics and prognosis of lung adenocarcinoma patients were assessed. GGPPS was down‐regulated in SPCA‐1, PC9 and A549 cells using siRNA and up‐regulated in A549 cells using an adenoviral vector. The biological roles of GGPPS in cell proliferation, apoptosis, migration and invasion were determined by MTT and colony formation assays, flow cytometry, and transwell and wound‐healing assays, respectively. In addition, the regulatory roles of GGPPS on the expression of several epithelial‐mesenchymal transition (EMT) markers were determined. Furthermore, the Rac1/Cdc42 prenylation was detected after knockdown of GGPPS in SPCA‐1 and PC9 cells. GGPPS expression was significantly increased in lung adenocarcinoma tissues compared to that in adjacent normal tissues. Overexpression of GGPPS was correlated with large tumours, high TNM stage, lymph node metastasis and poor prognosis in patients. Knockdown of GGPPS inhibited the migration and invasion of lung adenocarcinoma cells, but did not affect cell proliferation and apoptosis. Meanwhile, GGPPS inhibition significantly increased the expression of E‐cadherin and reduced the expression of N‐cadherin and vimentin in lung adenocarcinoma cells. In addition, the Rac1/Cdc42 geranylgeranylation was reduced by GGPPS knockdown. Overexpression of GGPPS correlates with poor prognosis of lung adenocarcinoma and contributes to metastasis through regulating EMT.

MAPK/FoxA2-mediated cigarette smoke-induced squamous metaplasia of bronchial epithelial cells

Objective

To explore the effect of cigarette smoke (CS) on the development of squamous metaplasia in human airway epithelial cells and the role of MAPK- and FoxA2-signaling pathways in the process.

Materials and methods

In an in vitro study, we treated the bronchial epithelial cell line BEAS2B with CS extract, followed by treatment with the ERK inhibitor U0126, the JNK inhibitor SP600125, or the p38 inhibitor SB203580. In vivo, we used a CS-induced rat model. After treatment with CS with or without MAPK inhibitors for 90 days, lung tissues were harvested. p-ERK, p-p38 and p-JNK protein levels in cells and lung tissue were measured using enzyme-linked immunosorbent assays, mRNA- and protein-expression profiles of FoxA2, E-cadherin, CD44, and ZO1 were measured using quantitative real-time polymerase chain reaction and Western blotting, respectively, and morphological changes in bronchial epithelial cells were observed using lung-tissue staining.

Results

In both the in vitro and in vivo studies, phosphorylation of the ERK1/2, JNK, and p38 proteins was significantly increased (P<0.05) and mRNA and protein expression of E-cadherin and FoxA2 significantly decreased (P<0.05) compared with the control group. ERK, JNK, and p38 inhibitors reversed the CS-extract-induced changes in E-cadherin, CD44, and ZO1 mRNA and protein expression (P<0.05), decreased p-ERK, p-p38, and p-JNK protein levels in cells and lung tissue, suppressed bronchial epithelial hyperplasia and local squamous metaplasia, and decreased FoxA2 expression.

Conclusion

MAPK and FoxA2 mediate CS-induced squamous metaplasia. MAPK inhibitors upregulate FoxA2, resulting in a reduction in the degree of squamous metaplasia.

Role of early growth response 1 in liver metabolism and liver cancer

The liver is an essential organ for nutrient and drug metabolism - possessing the remarkable ability to sense environmental and metabolic stimuli and provide an optimally adaptive response. Early growth response 1 (Egr1), an immediate early transcriptional factor which acts as a coordinator of the complex response to stress, is induced during liver injury and controls the expression of a wide range of genes involved in metabolism, cell proliferation, and role of Egr1 in liver injury and repair, deficiency of Egr1 delays liver regeneration process. The known upstream regulators of Egr1 include, but are not limited to, growth factors (e.g. transforming growth factor β1, platelet-derived growth factor, epidermal growth factor, hepatocyte growth factor), nuclear receptors (e.g. hepatocyte nuclear factor 4α, small heterodimer partner, peroxisome proliferator-activated receptor-γ), and other transcription factors (e.g. Sp1, E2F transcription factor 1). Research efforts using various animal models such as fatty liver, liver injury, and liver fibrosis contribute greatly to the elucidation of Egr1 function in the liver. Hepatocellular carcinoma (HCC) represents the second leading cause of cancer mortality worldwide due to the heterogeneity and the late stage at which cancer is generally diagnosed. Recent studies highlight the involvement of Egr1 in HCC development. The purpose of this review is to summarize current studies pertaining to the role of Egr1 in liver metabolism and liver diseases including liver cancer.

Protective effects of neem (Azadirachta indica A. Juss.) leaf extract against cigarette smoke- and lipopolysaccharide-induced pulmonary inflammation

Neem (Azadirachta indica A. Juss.) leaf has been reported to exert anti-inflammatory, antibacterial and antioxidant effects. The purpose of this study was to investigate the protective effects of neem leaf extract (NLE) against cigarette smoke (CS)- and lipopolysaccharide (LPS)-induced pulmonary inflammation. Treatment with NLE significantly attenuated the infiltration of inflammatory cells, such as neutrophils and macrophages in bronchoalveolar lavage fluid (BALF). NLE also reduced the production of reactive oxygen species and the activity of neutrophil elastase in BALF. Moreover, NLE attenuated the release of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 in BALF. NLE inhibited the recruitment of inflammatory cells and the expression of monocyte chemoattractant protein-1 (MCP-1) in the lungs of mice with CS- and LPS-induced pulmonary inflammation. NLE also decreased the expression of inducible nitric oxide synthase (iNOS) in the lungs of the mice CS- and LPS-induced pulmonary inflammation. Furthermore, treatment with NLE significantly attenuated the activation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) in the lungs mice exposed to CS and LPS. NLE also inhibited the phosphorylation of nuclear factor (NF)-κB and inhibitor of NF-κB (IκB) in the lungs of mice expose to CS and LPS. These findings thus suggest that NLE has potential for use in the treatment of chronic obstructive pulmonary disease.

Recent Advances in the Development of Mammalian Geranylgeranyl Diphosphate Synthase Inhibitors

The enzyme geranylgeranyl diphosphate synthase (GGDPS) catalyzes the synthesis of the 20-carbon isoprenoid geranylgeranyl diphosphate (GGPP). GGPP is the isoprenoid donor for protein geranylgeranylation reactions catalyzed by the enzymes geranylgeranyl transferase (GGTase) I and II. Inhibitors of GGDPS result in diminution of protein geranylgeranylation through depletion of cellular GGPP levels, and there has been interest in GGDPS inhibitors as potential anti-cancer agents. Here we discuss recent advances in the development of GGDPS inhibitors, including insights gained by structure-function relationships, and review the preclinical data that support the continued development of this novel class of drugs.

Asiatic acid inhibits pulmonary inflammation induced by cigarette smoke

Asiatic acid (AA) is one of the major components of Titrated extract of Centella asiatica (TECA), which has been reported to possess antioxidant and anti-inflammatory activities. The purpose of this study was to investigate the protective effect of AA on pulmonary inflammation induced by cigarette smoke (CS). AA significantly attenuated the infiltration of inflammatory cells in bronchoalveolar lavage fluid (BALF) of CS exposure mice. AA also decreased ROS production and NE activity, and inhibited the release of proinflammatory cytokines in BALF. AA reduced the recruitment of inflammatory cells and MCP-1 expression in lung tissue of CS exposure mice. AA also attenuated mucus overproduction, and decreased the activation of MAPKs and NF-kB in lung tissue. Furthermore, AA increased HO-1 expression and inhibited the reduced expression of SOD3 in lung tissue. These findings indicate that AA effectively inhibits pulmonary inflammatory response, which is an important process in the development of chronic obstructive pulmonary disease (COPD) via suppression of inflammatory mediators and induction of HO-1. Therefore, we suggest that AA has the potential to treat inflammatory disease such as COPD.

Geranylgeranyl Diphosphate Synthase Modulates Fetal Lung Branching Morphogenesis Possibly through Controlling K-Ras Prenylation

G proteins play essential roles in regulating fetal lung development, and any defects in their expression or function (eg, activation or posttranslational modification) can lead to lung developmental malformation. Geranylgeranyl diphosphate synthase (GGPPS) can modulate protein prenylation that is required for protein membrane-anchoring and activation. Here, we report that GGPPS regulates fetal lung branching morphogenesis possibly through controlling K-Ras prenylation during fetal lung development. GGPPS was continuously expressed in lung epithelium throughout whole fetal lung development. Specific deletion of geranylgeranyl diphosphate synthase 1 (Ggps1) in lung epithelium during fetal lung development resulted in neonatal respiratory distress syndrome-like disease. The knockout mice died at postnatal day 1 of respiratory failure, and the lungs showed compensatory pneumonectasis, pulmonary atelectasis, and hyaline membranes. Subsequently, we proved that lung malformations in Ggps1-deficient mice resulted from the failure of fetal lung branching morphogenesis. Further investigation revealed Ggps1 deletion blocked K-Ras geranylgeranylation and extracellular signal-related kinase 1 or 2/mitogen-activated protein kinase signaling, which in turn disturbed fibroblast growth factor 10 regulation on fetal lung branching morphogenesis. Collectively, our data suggest that GGPPS is essential for maintaining fetal lung branching morphogenesis, which is possibly through regulating K-Ras prenylation.

GGPPS-mediated Rab27A geranylgeranylation regulates β cell dysfunction during type 2 diabetes development by affecting insulin granule docked pool formation

Loss of first-phase insulin secretion associated with β cell dysfunction is an independent predictor of type 2 diabetes mellitus (T2DM) onset. Here we found that a critical enzyme involved in protein prenylation, geranylgeranyl pyrophosphate synthase (GGPPS), is required to maintain first-phase insulin secretion. GGPPS shows a biphasic expression pattern in islets of db/db mice during the progression of T2DM: GGPPS is increased during the insulin compensatory period, followed by a decrease during β cell dysfunction. Ggpps deletion in β cells results in typical T2DM β cell dysfunction, with blunted glucose-stimulated insulin secretion and consequent insulin secretion insufficiency. However, the number and size of islets and insulin biosynthesis are unaltered. Transmission electron microscopy shows a reduced number of insulin granules adjacent to the cellular membrane, suggesting a defect in docked granule pool formation, while the reserve pool is unaffected. Ggpps ablation depletes GGPP and impairs Rab27A geranylgeranylation, which is responsible for the docked pool deficiency in Ggpps-null mice. Moreover, GGPPS re-expression or GGPP administration restore glucose-stimulated insulin secretion in Ggpps-null islets. These results suggest that GGPPS-controlled protein geranylgeranylation, which regulates formation of the insulin granule docked pool, is critical for β cell function and insulin release during the development of T2DM.

EGR1 regulates hepatic clock gene amplitude by activating Per1 transcription

The mammalian clock system is composed of a master clock and peripheral clocks. At the molecular level, the rhythm-generating mechanism is controlled by a molecular clock composed of positive and negative feedback loops. However, the underlying mechanisms for molecular clock regulation that affect circadian clock function remain unclear. Here, we show that Egr1 (early growth response 1), an early growth response gene, is expressed in mouse liver in a circadian manner. Consistently, Egr1 is transactivated by the CLOCK/BMAL1 heterodimer through a conserved E-box response element. In hepatocytes, EGR1 regulates the transcription of several core clock genes, including Bmal1, Per1, Per2, Rev-erbα and Rev-erbβ, and the rhythm amplitude of their expression is dependent on EGR1's transcriptional function. Further mechanistic studies indicated that EGR1 binds to the proximal region of the Per1 promoter to activate its transcription directly. When the peripheral clock is altered by light or feeding behavior transposition in Egr1-deficient mice, the expression phase of hepatic clock genes shifts normally, but the amplitude is also altered. Our data reveal a critical role for EGR1 in the regulation of hepatic clock circuitry, which may contribute to the rhythm stability of peripheral clock oscillators.

Lipid-induced Muscle Insulin Resistance Is Mediated by GGPPS via Modulation of the RhoA/Rho Kinase Signaling Pathway

Elevated circulating free fatty acid levels are important contributors to insulin resistance in the muscle and liver, but the underlying mechanisms require further elucidation. Here, we show that geranylgeranyl diphosphate synthase 1 (GGPPS), which is a branch point enzyme in the mevalonic acid pathway, promotes lipid-induced muscle insulin resistance through activation of the RhoA/Rho kinase signaling pathway. We have found that metabolic perturbation would increase GGPPS expression in the skeletal muscles of db/db mice and high fat diet-fed mice. To address the metabolic effects of GGPPS activity in skeletal muscle, we generated mice with specific GGPPS deletions in their skeletal muscle tissue. Heterozygous knock-out of GGPPS in the skeletal muscle improved systemic insulin sensitivity and glucose homeostasis in mice fed both normal chow and high fat diets. These metabolic alterations were accompanied by activated PI3K/Akt signaling and enhanced glucose uptake in the skeletal muscle. Further investigation showed that the free fatty acid-stimulated GGPPS expression in the skeletal muscle was able to enhance the geranylgeranylation of RhoA, which further induced the inhibitory phosphorylation of IRS-1 (Ser-307) by increasing Rho kinase activity. These results implicate a crucial role of the GGPPS/RhoA/Rho kinase/IRS-1 pathway in skeletal muscle, in which it mediates lipid-induced systemic insulin resistance in obese mice. Therefore, skeletal muscle GGPPS may represent a potential pharmacological target for the prevention and treatment of obesity-related type 2 diabetes.

Single nucleotide polymorphisms of the NF-κB and STAT3 signaling pathway genes predict lung cancer prognosis in a Chinese Han population

Inflammation contributes to human carcinogenesis and cancer progression. This study selected and analyzed single nucleotide polymorphisms (SNPs) of the NF-κB and STAT3 signaling pathway genes for associations with prognosis in 1,165 lung cancer patients from a Chinese Han population. The data showed that eight SNPs (i.e., rs10836, rs3732131, rs3732133, rs4072391, rs2273650, rs1053023, rs3744483, and rs28372683) can be grouped into low-, medium-, and high-risk genotypes based on survival data. The median overall survival time (MST) of this cohort of patients was 24.6 months, whereas the MST of patients with low-risk genotypes reached 79.7 months; MST of patients with the medium-risk genotypes was 25.5 months, and those with high-risk genotypes was 22.7 months. Overall survival was statistically different for sex (P = 0.004), age (P = 0.010), histological types (P = 0.035), tumor stage (P < 0.001), tumor size (P < 0.001), surgery (P < 0.001), chemoradiotherapy (P = 0.007), and Karnofsky score (P < 0.001). Multivariate analysis and the data from the current study demonstrated that sex, tumor stage and size, surgery, chemoradiotherapy, and the aforementioned eight SNPs were all independent predictors for overall survival of lung cancer patients.

Regulation of mice liver regeneration by early growth response-1 through the GGPPS/RAS/MAPK pathway

BACKGROUND & AIMS

Liver regeneration (LR) consists of a series of complicated processes in which several transcription factors play important roles. Among them, the early growth response 1 gene (EGR-1) is rapidly induced in response to liver resection. Previous studies have shown that EGR-1-/- mice exhibit delayed hepatocellular mitotic progression after partial hepatectomy (PH). The mechanism underlying the EGR-1 regulated LR is still unknown. Our aim is to elucidate the underlying mechanism.

METHODS

Mice infected with adenoviral vectors expressing GFP, EGR-1 or dominant negative EGR-1 (dnEGR-1) were subjected to 2/3 PH. The serum starvation recovery cell model was chosen to mimic the regeneration process for the in vitro studies. Cell proliferation and signaling pathways downstream of geranylgeranyl diphosphate synthase (GGPPS) were examined in the regenerating liver and serum starvation recovery cell model.

RESULTS

Loss of function of EGR-1 significantly inhibited liver recovery and the expression of cyclin D1, cyclin E, and proliferating cell nuclear antigen (PCNA). The expression of GGPPS and the activity of the downstream RAS/MAPK pathway were inhibited in dnEGR-1-infected liver, which was consistent with the serum-induced cell model. In addition, loss of function of EGR-1 aggravated liver damage with increased serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels.

CONCLUSIONS

EGR-1-induced GGPPS plays a vital role in the LR after PH through the RAS/MAPK signaling.

GGPPS deficiency aggravates CCl4-induced liver injury by inducing hepatocyte apoptosis

GGPPS catalyses the expression of GGPP, a key protein in the mevalonate metabolic pathway. HMG-CoA reductase inhibitor statins can induce liver injury by inhibiting GGPP. However, the function of GGPPS in liver injury has not yet been revealed. In this study, we found that GGPPS increased in liver injury and that GGPPS deletion augmented liver injury and fibrosis. GGPPS inhibition induced hepatocyte apoptosis, inflammation and TGF-β1 secretion, which activated hepatic stellate cells. Our findings imply that GGPPS deletion induces hepatocyte apoptosis, which makes the liver vulnerable to hepatotoxicity.

A systems biology approach reveals the dose- and time-dependent effect of primary human airway epithelium tissue culture after exposure to cigarette smoke in vitro

To establish a relevant in vitro model for systems toxicology-based mechanistic assessment of environmental stressors such as cigarette smoke (CS), we exposed human organotypic bronchial epithelial tissue cultures at the air liquid interface (ALI) to various CS doses. Previously, we compared in vitro gene expression changes with published human airway epithelia in vivo data to assess their similarities. Here, we present a follow-up evaluation of these in vitro transcriptomics data, using complementary computational approaches and an integrated mRNA-microRNA (miRNA) analysis. The main cellular pathways perturbed by CS exposure were related to stress responses (oxidative stress and xenobiotic metabolism), inflammation (inhibition of nuclear factor-κB and the interferon gamma-dependent pathway), and proliferation/differentiation. Within post-exposure periods up to 48 hours, a transient kinetic response was observed at lower CS doses, whereas higher doses resulted in more sustained responses. In conclusion, this systems toxicology approach has potential for product testing according to "21st Century Toxicology".

Hyaluronan fragments as mediators of inflammation in allergic pulmonary disease

Asthma is frequently caused and/or exacerbated by sensitization to allergens, which are ubiquitous in many indoor and outdoor environments. Severe asthma is characterized by airway hyperresponsiveness and bronchial constriction in response to an inhaled allergen, leading to a disease course that is often very difficult to treat with standard asthma therapies. As a result of interactions among inflammatory cells, structural cells, and the intercellular matrix of the allergic lung, patients with sensitization to allergens may experience a greater degree of tissue injury followed by airway wall remodeling and progressive, accumulated pulmonary dysfunction as part of the disease sequela. In addition, turnover of extracellular matrix (ECM) components is a hallmark of tissue injury and repair. This review focuses on the role of the glycosaminoglycan hyaluronan (HA), a component of the ECM, in pulmonary injury and repair with an emphasis on allergic asthma. Both the synthesis and degradation of the ECM are critical contributors to tissue repair and remodeling. Fragmented HA accumulates during tissue injury and functions in ways distinct from the larger native polymer. There is gathering evidence that HA degradation products are active participants in stimulating the expression of inflammatory genes in a variety of immune cells at the injury site. In this review, we will consider recent advances in the understanding of the mechanisms that are associated with HA accumulation and inflammatory cell recruitment in the asthmatic lung.

Anti-malarial drug artesunate protects against cigarette smoke-induced lung injury in mice

Cigarette smoking is the primary cause of chronic obstructive pulmonary disease (COPD), which is mediated by lung infiltration with inflammatory cells, enhanced oxidative stress, and tissue destruction. Anti-malarial drug artesunate has been shown to possess anti-inflammatory and anti-oxidative actions in mouse asthma models. We hypothesized that artesunate can protect against cigarette smoke-induced acute lung injury via its anti-inflammatory and anti-oxidative properties. Artesunate was given by oral gavage to BALB/c mice daily 2h before 4% cigarette smoke exposure for 1h over five consecutive days. Bronchoalveolar lavage (BAL) fluid and lungs were collected for analyses of cytokines, oxidative damage and antioxidant activities. Bronchial epithelial cell BEAS-2B was exposed to cigarette smoke extract (CSE) and used to study the mechanisms of action of artesunate. Artesunate suppressed cigarette smoke-induced increases in BAL fluid total and differential cell counts; levels of IL-1β, MCP-1, IP-10 and KC; and levels of oxidative biomarkers 8-isoprostane, 8-OHdG and 3-nitrotyrosine in a dose-dependent manner. Artesunate promoted anti-oxidant catalase activity and reduced NADPH oxidase 2 (NOX2) protein level in the lungs from cigarette smoke-exposed mice. In BEAS-2B cells, artesunate suppressed pro-inflammatory PI3K/Akt and p44/42 MAPK signaling pathways, and increased nuclear Nrf2 accumulation in response to CSE. Artesunate possesses anti-inflammatory and anti-oxidative properties against cigarette smoke-induced lung injury, probably via inhibition of PI3K and p42/22 MAPK signaling pathways, augmentation of Nrf2 and catalase activities, and reduction of NOX2 level. Our data suggest that artesunate may have therapeutic potential for treating COPD.

GGPPS1 predicts the biological character of hepatocellular carcinoma in patients with cirrhosis

Background

Hepatocellular carcinoma (HCC) has been associated with diabetes and obesity, but a possible connection with the metabolic syndrome (MetS) and its potential interaction with hepatitis and cirrhosis are open to discussion. Our previous investigations have shown that GGPPS1 plays a critical role during hyperinsulinism. In this report, the expression and distribution of GGPPS1 in liver cancer, and its clinical significance were investigated.

Methods

70 patients with hepatocellular carcinoma (HCC) were included in this study. Three different types of tissues from each HCC patient were assembled immediately after surgical resection: tumor-free tissue >5 cm far from tumor edge (TF), adjacent nonmalignant tissue within 2 cm (AT), and tissue from the tumor (TT). Normal liver tissues from 10 liver transplant donors served as healthy control (HC) while 10 patients with liver cirrhosis as cirrhosis control (CC). The expression and distribution of GGPPS1 were detected by immunohistochemistry, western blots, or real-time PCR. The relationship between the expression of GGPPS1 and clinic pathologic index were analyzed.

Results

We found that GGPPS1 was intensified mainly in the cytoplasm of liver tumor cells. Both the expression of GGPPS1 mRNA and protein were upregulated in TT comparing to AT or TF. Meanwhile, HCC patients with cirrhosis had relative higher expression of GGPPS1. In addition, many pathologic characters show close correlation with GGPPS1, such as tumor stage, vessel invasion, and early recurrence.

Conclusion

GGPPS1 may play a critical role during the development of HCC from cirrhosis and is of clinical significance for predicting biological character of HCC.

Cavin-3 dictates the balance between ERK and Akt signaling

Cavin-3 is a tumor suppressor protein of unknown function. Using both in vivo and in vitro approaches, we show that cavin-3 dictates the balance between ERK and Akt signaling. Loss of cavin-3 increases Akt signaling at the expense of ERK, while gain of cavin-3 increases ERK signaling at the expense Akt. Cavin-3 facilitates signal transduction to ERK by anchoring caveolae to the membrane skeleton of the plasma membrane via myosin-1c. Caveolae are lipid raft specializations that contain an ERK activation module and loss of the cavin-3 linkage reduces the abundance of caveolae, thereby separating this ERK activation module from signaling receptors. Loss of cavin-3 promotes Akt signaling through suppression of EGR1 and PTEN. The in vitro consequences of the loss of cavin-3 include induction of Warburg metabolism (aerobic glycolysis), accelerated cell proliferation, and resistance to apoptosis. The in vivo consequences of cavin-3 knockout are increased lactate production and cachexia. DOI:http://dx.doi.org/10.7554/eLife.00905.001.

Activation of Egr-1 in human lung epithelial cells exposed to silica through MAPKs signaling pathways

The alveolar type II epithelial cell, regarded historically as a key target cell in initial injury by silica, now appears to be important in both defense from lung damage as well as elaboration of chemokines and cytokines. The molecular basis for silica-induced epithelial cell injury is poorly understood. In this study we explored the activation of nuclear factor Egr-1 and related signal pathway. Human II alveolar epithelial line A549 cells were exposed to silica for indicated time to assay the expression and activation of Egr-1 and upstream MAPKs. Immunofluorescence, western-blot techniques, RT-PCR, Electrophoretic mobility shift assay (EMSA), transient transfection assay, kinase inhibitor experiments were performed. It was found that the expression of Egr-1 at mRNA and protein level was significantly increased in A549 cells after administration with silica and the activity of Egr-1 peaked by silica treatment for 60 minutes. Furthermore, phosphorylated-ERK1/2, P38 MAPKs (the upstream kinase of Egr-1) ballooned during 15-30minutes, 30-60minutes respectively after silica exposure in A549 cells. By administration of ERK1/2, P38 inhibitor, the expression and transcription of Egr-1 were both markedly decreased. But PKC inhibitor did not prevent the increase of Egr-1. These results indicated Egr-1 played a critical role in silica-induced pulmonary fibrosis in an ERK1/2, P38 MAPKs-dependent manner, which suggests Egr-1 is an essential regulator in silicosis, and underlines a new molecular mechanism for fibrosis induced by silica.

Inhibition of vitamin d receptor translocation by cigarette smoking extracts

Background

Vitamin D can translocate a vitamin D receptor (VDR) from the nucleus to the cell membranes. The meaning of this translocation is not elucidated in terms of a role in pathogenesis of chronic obstructive pulmonary disease (COPD) till now. VDR deficient mice are prone to develop emphysema, suggesting that abnormal function of VDR might influence a generation of COPD. The blood levels of vitamin D have known to be well correlated with that of lung function in patients with COPD, and smoking is the most important risk factor in development of COPD. This study was performed to investigate whether cigarette smoke extracts (CSE) can inhibit the translocation of VDR and whether mitogen activated protein kinases (MAPKs) are involved in this inhibition.

Methods

Human alveolar basal epithelial cell line (A549) was used in this study. 1,25-(OH₂)D₃ and/or MAPKs inhibitors and antioxidants were pre-incubated before stimulation with 10% CSE, and then nucleus and microsomal proteins were extracted for a Western blot of VDR.

Results

Five minutes treatment of 1,25-(OH₂)D₃ induced translocation of VDR from nucleus to microsomes by a dose-dependent manner. CSE inhibited 1,25-(OH₂)D₃-induced translocation of VDR in both concentrations of 10% and 20%. All MAPKs inhibitors did not suppress the inhibitory effects of CSE on the 1,25-(OH₂)D₃-induced translocation of VDR. Quercetin suppressed the inhibitory effects of CSE on the 1,25-(OH₂)D₃-induced translocation of VDR, but not in n-acetylcysteine.

Conclusion

CSE has an ability to inhibit vitamin D-induced VDR translocation, but MAPKs are not involved in this inhibition.

GGPPS, a new EGR-1 target gene, reactivates ERK 1/2 signaling through increasing Ras prenylation

Cigarette smoke activates the extracellular signal-regulated kinase (ERK) 1/2 mitogen activated-protein kinase pathway, which, in turn, is responsible for early growth response gene-1 (EGR-1) activation. Here we provide evidence that EGR-1 activation can also reactivate ERK 1/2 mitogen activated-protein kinase through a positive feedback loop through its target gene (geranylgeranyl diphosphate synthase) GGPPS. For the first time, the GGPPS gene is identified as a target of EGR-1, as EGR-1 can directly bind to the predicted consensus-binding site in the GGPPS promoter and regulate its transcription. Long-term observations show that there are two ERK 1/2 phosphorylation peaks after cigarette smoke extract stimulation in human lung epithelial Beas-2B cells. The first peak (at 10 minutes) is responsible for EGR-1 accumulation, and the second (at 4 hours) is diminished after the disruption of EGR-1 transcriptional activity. EGR-1 overexpression enhances Ras prenylation and membrane association in a GGPPS-dependent manner, and it augments ERK 1/2 activation. Likewise, a great reduction of the second peak of ERK 1/2 phosphorylation is observed during long-term cigarette smoke extract stimulation in cells where GGPPS is disrupted. Thus, we have uncovered an intricate positive feedback loop in which ERK 1/2-activated EGR-1 promotes ERK 1/2 reactivation through promoting GGPPS transcription, which might affect cigarette smoke-related lung pathological processes.

Egr-1 decreases adipocyte insulin sensitivity by tilting PI3K/Akt and MAPK signal balance in mice

It is well known that insulin can activate both PI3K/Akt pathway, which is responsible for glucose uptake, and MAPK pathway, which is crucial for insulin resistance formation. But, it is unclear exactly how the two pathways coordinate to regulate insulin sensitivity upon hyperinsulinism stress of type 2 diabetes mellitus (T2DM). Here, we show that an early response transcription factor Egr-1 could tilt the signalling balance by blocking PI3K/Akt signalling through PTEN and augmenting Erk/MAPK signalling through GGPPS, resulting in insulin resistance in adipocytes. Egr-1, PTEN and GGPPS are upregulated in the fat tissue of T2DM patients and db/db mice. Egr-1 overexpression in epididymal fat induced systematic insulin resistance in wild-type mice, and loss of Egr-1 function improved whole-body insulin sensitivity in diabetic mice, which is mediated by Egr-1 controlled PI3K/Akt and Erk/MAPK signalling balance. Therefore, we have revealed, for the first time, the mechanism by which Egr-1 induces insulin resistance under hyperinsulinism stress, which provides an ideal pharmacological target since inhibiting Egr-1 can simultaneously block MAPK and augment PI3K/Akt activation during insulin stimulation.