Dai-Shun Liu

Quercetin inhibits IL-1 beta-induced ICAM-1 expression in pulmonary epithelial cell line A549 through the MAPK pathways

Quercetin is a herbal flavonoid derived from various foods of plant origin and widely used as a major constituent of nutritional supplements. Quercetin has been shown to have anti-inflammatory properties and can play a role in anti-inflammatory procedure. Intercellular adhesion molecule-1 (ICAM-1) is one of the important pro-inflammatory factors, especially in early phage of inflammation. However, the mechanisms regulating ICAM-1 expression by quercetin in human A549 cells were still unclear. In this study, the inhibitory effect of quercetin on ICAM-1 expression by interleukin-1 beta (IL-1 beta)-stimulated A549 cells was investigated, and the roles of mitogen-activated protein kinases (MAPK) pathways were explored. Quercetin attenuated IL-1 beta-induced expression of ICAM-1 mRNA and protein in a dose-dependent manner. The experiment suggested that quercetin actively inhibited inhibitory protein of nuclear factor-kappa B (I kappa B) degradation, and nuclear factor-kappa B (NF-kappa B) activity. The c-fos and c-jun, components of activator protein-1 (AP-1), were mediated by MAPK pathways. ERK and p38 were involved in the c-fos mRNA expression, and JNK was involved in the c-jun mRNA expression. The inhibitory effect of quercetin on ICAM-1 expression was mediated by the sequential attenuation of the c-fos and c-jun mRNA expressions. These inhibitory effects were partially inhibited by SB203580, a specific inhibitor of p38 MAPK, but not by PD98059, a specific inhibitors of extracellular signal-regulated kinase (ERK), and SP600125, a specific inhibitor of c-Jun-N-terminal kinase (JNK). Taken together, these results suggest that quercetin negatively modulating ICAM-1 partly dependent on MAPK pathways.

Macrolides attenuate mucus hypersecretion in rat airways through inactivation of NF‐κB

Background and objective:  To examine the effect of a 14‐membered ring macrolide on airway mucus hypersecretion in rats treated with LPS.

Simvastatin attenuates experimental small airway remodelling in rats

Background and objective:  The aim of this study was to assess the beneficial effects of simvastatin on cigarette smoke‐induced small airway remodeling in rats.

VEGFR-2 antagonist SU5416 attenuates bleomycin-induced pulmonary fibrosis in mice

OBJECTIVE Abnormal angiogenesis is a central hallmark for the development and progression of idiopathic pulmonary fibrosis. It has been shown that vascular endothelial growth factor (VEGF) is one of the critical angiogenic factors in angiogenesis. The aim of the present study was to assess whether disruption of VEGF pathway would attenuate bleomycin-induced pulmonary fibrosis. METHODS Bleomycin-induced pulmonary fibrosis mice were treated intraperitoneally with VEGF receptor tyrosine kinase inhibitor SU5416 at different phases after bleomycin infusion. We measured angiogenesis and inflammatory response in both bleomycin-treated and control mice, and correlated these levels with pulmonary fibrosis. RESULTS The increased expressions of VEGF/VEGFR (Flk-1) were correlated to a larger number of microvessels and a higher score of pulmonary fibrosis. Early administration of SU5416 inhibited pulmonary collagen deposition, histopathologic fibroplasias and the activation of TGF-beta1/Smad3 signaling pathway in bleomycin-stimulated lung. These were also paralleled by a reduction of VEGF/VEGFR-2 (Flk-1) expression and microvessel numbers in lung. Furthermore, SU5416 inhibited inflammatory cell numbers and LDH activity in BALF and IL-13 expression in lung tissue at early inflammatory phase of bleomycin-induced pulmonary fibrosis. CONCLUSION These results suggest that the VEGFR-2 inhibitor, SU5416, attenuates histopathologic fibroplasias and collagen deposition by regulating angiogenesis and inflammation in the lung.

Ghrelin inhibit cell apoptosis in pancreatic β cell line HIT-T15 via mitogen-activated protein kinase/phosphoinositide 3-kinase pathways

Ghrelin stimulates growth hormone (GH) release and induces positive energy balances. Previous studies have reported that ghrelin inhibits apoptosis in several cell types but the precise underlying protective mechanisms in pancreatic beta cells are poorly understood. Therefore, we investigated which pathway was related with its anti-apoptotic effect in pancreatic beta cells. Exposure of HIT-T15 cells to ghrelin caused a rapid activation of MAPKs and Akt. Chemical inhibitors of MAPK and PI3K blocked the anti-apoptotic of ghrelin. Ghrelin also stimulated the mitochondrial pathways of apoptosis and it showed increased Bcl-2, decreased Bax, prevention cytochrome c release and inhibition of caspase-3 activation in pancreatic beta cell line HIT-T15. Our findings suggest that ghrelin may act as a survival factor that inhibits the apoptotics pathways, and the MAPKs, AKT pathways could be key roles in the apoptosis of pancreatic beta cells.

Simvastatin attenuates acrolein-induced mucin production in rats: involvement of the Ras/extracellular signal-regulated kinase pathway.

Airway mucus overproduction is a cardinal feature of airway inflammatory diseases, such as chronic obstructive pulmonary disease and cystic fibrosis. Since the small G-protein Ras is known to modulate cellular functions in the lung, we sought to investigate whether the Ras inhibitor simvastatin could attenuate acrolein-induced mucin production in rat airways. Rats were exposed to acrolein for 12 days, after first being pretreated intragastrically for 24 h with either simvastatin alone or simvastatin in combination with mevalonate, which prevents the isoprenylation needed for Ras activation. Lung tissue was analyzed for extracellular signal-regulated kinase (ERK) activity, goblet cell metaplasia and mucin production. To analyze the effect of simvastatin on mucin production in more detail, acrolein-exposed human airway epithelial NCI-H292 cells were pretreated with simvastatin alone or together with mevalonate. Culture medium was collected to detect mucin secretion, and cell lysates were examined for Ras-GTPase activity and epidermal growth factor receptor (EGFR)/ERK phosphorylation. In vivo, simvastatin treatment dose-dependently suppressed acrolein-induced goblet cell hyperplasia and metaplasia in bronchial epithelium and inhibited ERK phosphorylation in rat lung homogenates. Moreover, simvastatin inhibited Muc5AC mucin synthesis at both the mRNA and protein levels in the lung. In vitro, simvastatin pretreatment attenuated the acrolein-induced significant increase in MUC5AC mucin expression, Ras-GTPase activity and EGFR/ERK phosphorylation. These inhibitory effects of simvastatin were neutralized by mevalonate administration both in vitro and in vivo. Our results suggest that simvastatin may attenuate acrolein-induced mucin protein synthesis in the airway and airway inflammation, possibly by blocking ERK activation mediated by Ras protein isoprenylation. Thus, the evidence from the experiment suggests that human trials are warranted to determine the potential safety and efficacy of simvastatin for treatment of over production of airway mucus.

Blockade of advanced glycation end product formation attenuates bleomycin-induced pulmonary fibrosis in rats

BackgroundAdvanced glycation end products (AGEs) have been proposed to be involved in pulmonary fibrosis, but its role in this process has not been fully understood. To investigate the role of AGE formation in pulmonary fibrosis, we used a bleomycin (BLM)-stimulated rat model treated with aminoguanidine (AG), a crosslink inhibitor of AGE formation.MethodsRats were intratracheally instilled with BLM (5 mg/kg) and orally administered with AG (40, 80, 120 mg/kg) once daily for two weeks. AGEs level in lung tissue was determined by ELISA and pulmonary fibrosis was evaluated by Ashcroft score and hydroxyproline assay. The expression of heat shock protein 47 (HSP47), a collagen specific molecular chaperone, was measured with RT-PCR and Western blot. Moreover, TGFβ1 and its downstream Smad proteins were analyzed by Western blot.ResultsAGEs level in rat lungs, as well as lung hydroxyproline content and Ashcroft score, was significantly enhanced by BLM stimulation, which was abrogated by AG treatment. BLM significantly increased the expression of HSP47 mRNA and protein in lung tissues, and AG treatment markedly decreased BLM-induced HSP47 expression in a dose-dependent manner (p < 0.05). In addition, AG dose-dependently downregulated BLM-stimulated overexpressions of TGFβ1, phosphorylated (p)-Smad2 and p-Smad3 protein in lung tissues.ConclusionThese findings suggest AGE formation may participate in the process of BLM-induced pulmonary fibrosis, and blockade of AGE formation by AG treatment attenuates BLM-induced pulmonary fibrosis in rats, which is implicated in inhibition of HSP47 expression and TGFβ/Smads signaling.

Doxycycline attenuates acrolein-induced mucin production, in part by inhibiting MMP-9

Matrix metalloproteinases (MMPs), especially MMP-9, have been found to increase the expression of epidermal growth factor (EGF) receptor, a possible regulator of acrolein-induced mucin expression in the airway epithelium. The aim of this study was to investigate whether doxycycline, a tetracycline antibiotic that inhibits MMPs, attenuates mucus production and synthesis of mucin MUC5AC in acrolein-exposed rats. Sprague-Dawley rats were exposed to acrolein aerosol [3.0parts/million (ppm), 6h/day, 12days] and they received 20mg/kg doxycycline daily by gavage, beginning two days before exposure to acrolein until the end of the experiment. The production of mucin glycoproteins and expression of the MMP-9 and MUC5AC genes were measured in rat trachea. The increase in levels of MMP-9 mRNA and protein in airway epithelium after acrolein exposure was accompanied by an increase in MUC5AC mRNA expression. Doxycycline significantly prevented these increases in acrolein-induced expression of MMP-9 and MUC5AC and attenuated mucus production in tracheal epithelium. These results indicate that doxycycline attenuated acrolein-induced mucin synthesis, in part by inhibiting expression of MMP-9. Thus doxycycline may have a prophylactic effect in the treatment of smoking-induced mucus hypersecretion.

Rosiglitazone, a peroxisome proliferator-activated receptor-γ agonist, attenuates acrolein-induced airway mucus hypersecretion in rats

BACKGROUND Peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a member of the ligand-activated nuclear receptor superfamily, has been shown to be implicated in anti-inflammatory and immunomodulatory responses, but its role in airway mucus hypersecretion remains not clear. OBJECTIVE To investigate the role of PPAR-gamma in airway mucus hypersecretion, we used an acrolein-exposed rat model treated with rosiglitazone, a peroxisome proliferator-activated receptor-gamma agonist. METHODS Rats were exposed to acrolein (3.0 ppm, 6h/day, 7 days/week) and orally administered with rosiglitazone (2, 4, 8 mg/kg) once daily for up to 2 weeks. The expressions of Muc5ac protein and mRNA, and infiltration of inflammatory cells and levels of inflammatory cytokines (interleukin (IL)-1beta, IL-8 and tumor necrosis factor (TNF)-alpha) in bronchoalveolar lavage fluid (BALF) were detected with real-time PCR, Western blot, cell counting and ELISA. In addition, the role of nuclear factor (NF)-kappaB pathway in this process was also explored. RESULTS Acrolein exposure significantly induced goblet cell hyperplasia in bronchial epithelium and Muc5ac mRNA and protein expressions in rat lungs, as well as the associated airway inflammation evidenced by the increased numbers of inflammatory cells and levels of inflammatory cytokines in BALF, which were attenuated with rosiglitazone treatment in a dose-dependent manner (P<0.05). Simultaneously, the increased expression of NF-kappaB and decreased expression of cytoplasmic IkappaB in acrolein-exposed lungs were reversed by rosiglitazone treatment. CONCLUSIONS These findings suggest that PPAR-gamma activation by its ligands can attenuate acrolein-induced airway mucus hypersecretion in rats, which may be involved in inhibition of NF-kappaB pathway.

Toll-like Receptor 4 Relates to Lipopolysaccharide-induced Mucus Hypersecretion in Rat Airway

BACKGROUND Toll-like receptor 4 (TLR4) is a transmembrane protein that participates in the recognition of lipopolysaccharide (LPS), a potentially important source of inflammation. To investigate the role of TLR4 in LPS-induced airway mucus hypersecretion (AMH), we used a LPS-induced rat model treated with dexamethasone (DEX). METHODS Rats were randomly divided into four experimental groups: 1) saline (SA)-treated with distilled water (DW) (control group); 2) LPS-treated with DW (LPS group); 3) LPS-treated with DEX (LPS plus DEX group); 4) SA-treated with DEX (DEX group). DEX (5 mg/kg) was intraperitoneally injected 1 h before being administered intratracheally with LPS. Expressions of TLR4 and MUC5AC were evaluated with RT-PCR, in situ hybridization, immunohistochemistry and Alcian blue/Periodic acid-schiff (AB/PAS) staining. RESULTS Increased expressions of TLR4 protein and mRNA were found in rat airway treated with LPS and peaked on day 2 after LPS administration. Following this, LPS increased MUC5AC expression and AB/PAS-stained goblet cells in rat airway. Correlation analysis showed TLR4 correlated well with the expression of MUC5AC (r = 0.684, p <0.01) and AB/PAS-stained area (r = 0.781, p <0.01). In addition, DEX pretreatment significantly reduced LPS-induced overexpression of TLR4 (p <0.05) in rat airway. CONCLUSIONS These results suggest TLR4 relates to LPS-induced AMH and support a role of TLR4 in DEX inhibition of LPS-induced AMH.