The Effects And Regulated Mechanism Of Esculentoside A On Experimentally Induced Respiratory Inflammation

[Objective] Respiratory diseases are very common in Veterinary Clinic which hashigh morbidity and mortality. Respiratory inflammation is the main reason causingrespiratory diseases. Respirable microbial pathogens, allergens and pollutantsstimulate inflammation through different mechanisms. Recent studies found that thesestimulus also initiate airway inflammation by causing oxidative stress.Oxidants and inflammatory stimulus inhaled into respiratory tracts, induced a largenumber of reactive oxygen species (ROS) accumulation through NADPH oxidationenzyme. On one hand, ROS caused tissue DNA, protein and lipid injury. On the otherhand, ROS induced inflammatory mediators to recruit inflammatory cells, promotingmore cytokine release by activation of MAPKs and NF-κB signaling pathways,followed by enhancing airway inflammation, and caused allergy asthma, acute lunginjury (ALI) and chronic obstructive pulmonary disease (COPD), accompanied withsmall airway obstruction and pulmonary parenchymal damage, eventually leading torespiratory dysfunction or failure. Therefore, target-based screening drugs are greatlymeaningful for clinical respiratory disease drug development.In pre-experiments, several natural molecules were found existing anti-inflammatory and antioxidant activities, including esculentoside A which is one ofactivated compounds of the root of Phytolacca esculenta. EsA has the ability to inhibitproduction of pro-inflammatory cytokines such as TNF-, IL-1β, IL-6in several celltypes. Its effect on airway inflammation still remains unknown. The object of ourpresent study is attempt to explain the effects and regulated mechanism of EsA onLPS-induced ALI, OVA-induced asthma, and CS-induced airway inflammatorymodel, and on recover the anti-inflammatory activity of glucocorticoids onCSE-induced inflammation.[Methods] In the present study, LPS or CSE was used to induce inflammation andoxidative stress in BEAS-2B cells, and pro-inflammatory cytokine concentrations,levels of ROS and GSH were measured to evaluate anti-inflammatory and anti-oxidative activities of EsA in vitro. Furthermore, ALI, allergic asthma, andCS-induced airway inflammation models were established to assess the effects of EsAon experimental airway inflammation and oxidative injury. MAPKs、NF-κB, and Nrf2relevant proteins were tested. To investigate the regulated mechanism of EsA, nuclearNrf2in BEAS-2B cells that treated by EsA was measured. More than that, RNAinterference technology was used to investigate the potential target of EsA. In addition,pro-inflammatory cytokines and HDAC2level were measured to evaluate thesynergistic effect of EsA on anti-inflammatory activity of glucocorticoids andregulated mechanism.[Results] The results showed that:1The elevation of TNF-, IL-1β, and IL-6levels and iNOS and COX2mRNAexpression induced by LPS or CSE were significantly decreased by EsA.2EsA pretreatment down-regulated the ROS production and increased the GSH levelin BEAS-2B cells induced by LPS or CSE.3EsA alleviated the airway inflammation in mice induced by LPS or CS exposurereflected by inhibition of TNF-, IL-1β, and IL-6concentrations and neutrophil andmacrophage amounts in BALF of ALI and COPD models, lessened the severity oflung edema induced by LPS, suppression the mRNA expression of MMP-12andTIMP-1induced by CS. In additional, EsA inhibited OVA induced airway Th2cytokine production and eosinophils infiltration. The level of IgE in serum, andmRNA level of VCAM-1, ICAM-1, and eotaxin in lung tissues elevated by OVA alsodescended by EsA pretreatment.4EsA inhibited ROS production in lung tissues and descended levels of oxidativebiomarkers8-isoprostane,8-OHdG and3-nitrotyrosine in BALF in LPS-induced ALI,OVA-induced asthma and CS-induced COPD models. EsA also promoted inductionsof relevant antioxidant enzymes and glutathione activities in lungs from ALI, asthmaand COPD models.5EsA decreased the phosphorylated levels of MAPKs and NF-κB pathways relativeproteins in lung tissues in LPS or OVA-challenged mice. EsA up-regulated the Nrf2and HO-1levels in lung tissues in CS-challenged mice.6EsA promoted the HO-1and nuclear Nrf2protein levels. Nrf2SiRNA diminishedthe anti-inflammatory effects of EsA on LPS or CSE-induced BEAS-2B.7The low dosage of EsA enhanced the inhibitory effect of Dex on IL-1β and IL-6 secretion from BEAS-2B cells stimulated by CSE. EsA increased HDAC2proteinlevel. Nrf2SiRNA diminished the effects of EsA HDAC2protein andanti-inflammatory effect of Dex.[Conclusions] In conclusion, our present study reveals the effects of EsA on differentexperimentally induced airway inflammation. In addition, EsA promoted theanti-inflammatory activity of dexamethasone against CSE-induced inflammation inThp-1cells. We also uncovered the mechanism of EsA. EsA acted on LPS-, OVA-orCSE-induced airway inflammation by enhance the expression of endogenousantioxidants to inhibit the production of ROS and oxidant through promoting Nrf2nuclear translocation, and finally reducing inflammation and oxidative damage. Ourstudy provide theoretical basis for clinical screening new drugs against differentairway inflammation, and also provide the platform for drugs screening.