ABSTRACT
Quercetin (Que) as an abundant flavonol element possesses potent antioxidative properties and has protective effect in lipopolysaccharide (LPS)-induced acute lung injury (ALI), but the specific mechanism is still unclear, so we investigated the effect of Que from in vivo and in vitro studies and the related mechanism of cAMP-PKA/Epac pathway. The results in mice suggested that Que can inhibit the release of inflammatory cytokine, block neutrophil recruitment, and decrease the albumin leakage in dose-dependent manners. At the same time, Que can increase the cAMP content of lung tissue, and Epac content, except PKA. The results in epithelial cell (MLE-12) suggested that Que also can inhibit the inflammatory mediators keratinocyte-derived chemokines release after LPS stimulation; Epac inhibitor ESI-09 functionally antagonizes the inhibitory effect of Que; meanwhile, PKA inhibitor H89 functionally enhances the inhibitory effect of Que. Overexpression of Epac1 in MLE-12 suggested that Epac1 enhance the effect of Que. All those results suggested that the protective effect of quercetin in ALI is involved in cAMP-Epac pathway.
Subject(s)
Acetylcysteine/analogs & derivatives , Acute Lung Injury/chemically induced , Cyclic AMP/metabolism , Erythromycin/analogs & derivatives , Quercetin/pharmacology , Acetylcysteine/metabolism , Animals , Cell Line , Erythromycin/metabolism , Inflammation/drug therapy , Inflammation/metabolism , Inflammation Mediators/antagonists & inhibitors , Lipopolysaccharides , Lung/drug effects , Lung/metabolism , Mice , Protective Agents/pharmacologyABSTRACT
Exchange protein directly activated by cAMP (Epac) is an important molecule in cAMP signal transduction, but the effect of Epac on lipopolysaccharide (LPS)-induced acute lung injury (ALI) is unclear. In this study, we treated in vitro and in vivo models with the Epac activator 8CPT to determine the effect and related mechanisms of Epac. The in vitro results indicate that 8CPT inhibits lipopolysaccharide (LPS)-induced tumor necrosis factor-α (TNF-α) release from mouse macrophages (MH-S), whereas the protein kinase A (PKA) activator 6BnZ has no effect. Furthermore, Epac over-expression can significantly suppress TNF-α release from LPS induced MH-S cell, while Epac siRNA can slightly increase TNF-α release. Moreover, 8CPT reduces LPS-induced microvascular permeability in human pulmonary microvascular endothelial cells (HPMVECs), whereas the PKA activator 6BnZ has no effect. In mice with LPS-induced ALI, 8CPT significantly reduces LPS-induced inflammatory cytokine release, neutrophil recruitment, and albumin leakage. LPS simultaneously decreases the Epac but not the PKA levels. However, 8CPT reverses the decreased Epac levels. Furthermore, the mechanism involves the small GTPase Rac1/2 but not the mitogen-activated protein kinase (MAPK) pathway. Thus, Epac activation reduces inflammation and microvascular permeability in LPS-induced lung injury and an Epac activator represents a novel choice for the early therapy of ALI.
Subject(s)
Acute Lung Injury/metabolism , Capillary Permeability/physiology , Endothelium, Vascular/metabolism , Guanine Nucleotide Exchange Factors/metabolism , Lipopolysaccharides/toxicity , Acute Lung Injury/chemically induced , Acute Lung Injury/pathology , Animals , Capillary Permeability/drug effects , Cell Line , Endothelium, Vascular/drug effects , Endothelium, Vascular/pathology , Humans , Inflammation/chemically induced , Inflammation/metabolism , Inflammation/pathology , Male , Mice , Mice, Inbred C57BLABSTRACT
This paper indicated that inactivated Bordetella pertussis (iBp) can enhance the lung airway hyperreactivity of the rats sensitized and challenged with OVA. The mechanisms were involved in the upregulation of cAMP-PDE activity and PDE4A, PDE4D, and PDE3 gene expression in the lungs. But only PDE4 activity was different between the OVA and OVA+iBp groups, and PDE4D expression was significantly increased in iBp rats alone. So, our data suggested that cosensitization with OVA and iBp affects lung airway reactivity by modulating the lung cAMP-PDE activity and PDE4D gene expression.
Subject(s)
Lung/enzymology , Pertussis Vaccine/pharmacology , Phosphoric Diester Hydrolases/metabolism , 3',5'-Cyclic-AMP Phosphodiesterases/metabolism , Animals , Bordetella pertussis/immunology , Cyclic Nucleotide Phosphodiesterases, Type 3/metabolism , Cyclic Nucleotide Phosphodiesterases, Type 4/metabolism , Gene Expression Regulation/drug effects , Lung/immunology , Male , Ovalbumin/immunology , Pertussis Vaccine/immunology , Rats , Rats, Sprague-Dawley , Up-Regulation/drug effects , Up-Regulation/immunology , Vaccines, InactivatedABSTRACT
cAMP-specific phosphodiesterase type 4 (PDE4) is one of the hot targets for treatment of inflammatory diseases. PDE4 inhibitors can suppress inflammation by increasing the concentration of cAMP in inflammatory cells. The efficacy and safety evaluations of several PDE4 inhibitors are currently carried on in clinical trials, for example GSK256066 in asthma, roflumilast and GSK256066 in chronic obstructive pulmonary disease, tetomilast in inflammatory bowel disease, and apremilast in dermatitis and arthritis etc. This article reviews the recent progress on PDE4-targeted therapy for inflammatory diseases.
