Objective To explore the role and underlying mechanism of type Ⅲ secretion system(T3SS)in regulating the internalization of Pseudomonas aeruginosa(PA)into pulmonary epithelial cells.Methods The human non-small cell lung cancer A549 cells were infected with or without PA strains,including wild-type PAO1(a standard experimental PA strain),△exsA(knockout of the critical activator for T3SS genes),△pscJ(T3SS secretion-defective strain)and PAO1-E(EGTA-induced high expression of T3SS genes).The A549 cells pretreated with ERK inhibitor U0126 or reactive oxygen species(ROS)inhibitor apocynin(APO)/N-acetyl-L-cysteine(NAC)were infected with PAO1 or PAO1-E strain.Thus,the experiment was grouped as follows:the mock-treated group,PAO1-or PAO1-E-infected group,inhibitor-treated group,and PAO1/PAO1-E plus inhibitor-treated group.Extracellular bacteria were killed by gentamicin,and the cell lysates were diluted and then plated on PA screening plates.Bacterial amounts were detected by counting colony-forming units(CFUs).The production of ROS was analyzed using fluorescent probe labeling and flow cytometry.The activation of the ERK pathway was detected by Western blotting.Results Compared with the PAO1-infected group,the intracellular bacteria and ROS level in △exsA-or△pscJ-infected cells were lower(P＜0.05,P＜0.01),so was the generation of ROS(P＜0.01);In contrast,those of the PAO1-E strain-infected cells displayed an opposite trend(P＜0.01).Compared with the PAO1-or PAO1-E-infected group,the cells pretreated with APO/NAC followed by PAO1 or PAO1-E infection showed reduced intracellular bacterial amounts(P＜0.01).Compared to the PAO1-infected A549 cells,the phosphorylation level of ERK was increased in the △exsA-or △pscJ-infected cells(P＜0.01),while that level was suppressed in the PAO1-E-treated cells(P＜0.01).Compared with the PAO1-infected group,the PAO1-infected cells pretreated with U0126 displayed reduced ERK activation,elevated ROS production,and increased intracellular counts of PAO1(P＜0.01).Conclusion T3SS-mediated inhibition of the ERK pathway promotes the production of ROS and the internalization of PA in lung epithelial cells.

Traditional Chinese herbs (TCH) are currently gaining attention in disease prevention and health care plans. However, their general bitter taste hinders their use. Despite the development of a variety of taste evaluation methods, it is still a major challenge to establish a quantitative detection technique that is objective, authentic and sensitive. Based on the two-bottle preference test (TBP), we proposed a novel quantitative strategy using a standardized animal test and a unified quantitative benchmark. To reduce the difference of results, the methodology of TBP was optimized. The relationship between the concentration of quinine and animal preference index (PI) was obtained. Then the PI of TCH was measured through TBP, and bitterness results were converted into a unified numerical system using the relationship of concentration and PI. To verify the authenticity and sensitivity of quantified results, human sensory testing and electronic tongue testing were applied. The quantified results showed a good discrimination ability. For example, the bitterness of Coptidis Rhizoma was equal to 0.0579 mg/mL quinine, and Nelumbinis Folium was equal to 0.0001 mg/mL. The validation results proved that the new assessment method for TCH was objective and reliable. In conclusion, this study provides an option for the quantification of bitterness and the evaluation of taste masking effects.