Our studies tried to demonstrate Eha (Et haemolysin activator) could regulate the resistance of the bacterium against acidification to survive in the macrophage and explain its underlying molecular mechanism.When the bacteria infected the macrophages at time intervals,intracellular survival rate in bafilomycin-treated macrophages was higher than that with untreated cells,and the rate of wild type ET 13 was higher than that of its eha mutant,respectively (P＜0.05).The survival rate of the wild type was higher than that of the mutant under acid treatment (P＜0.05).To determine the conditions that induced the highest eha expression,we constructed a pMP220-Peha LacZ plasmid and determined the lacZ expression under different conditions.After exposure of pH6.3 medium for 2 h time,we performed the whole transcriptomic profiles of the wild type and mutant by RNA-sequencing.We identified 147 differentially-expressed genes ([log2 ratio| ≥1),113 and 34 of which were significantly up-and down-regulated,respectively in the mutant,comparing with the wild type.These findings were validated by qRT-PCR.GO functional analysis revealed that these genes were divided into 25 categories,including the bacterial catalysis,cellular composition,combination,localization,metabolism,processing,and transportation.Based on the KEGG database,these genes were distributed in 55 pathways,such as two-component system,ABC transporters,and microbial metabolism in diverse environments.Overall,Eha is an important regulator to affect all kinds of target genes and pathways for E.tarda to adapt to an acid environment.These results could be helpful for further investigations of the mechanisms by which E.tarda survives in macrophages.

Objective To study the effect of caffeine on hyperoxic lung injury of premature rats and its relationship with p38 motigen-activated protein kinase( MAPK) signal pathway. Methods Sixty Wistar premature rats were divided into 4 groups(n＝15) according to the random number table:air + normal sa-line group(A+N group),air + caffeine group( A+C group),hyperoxia + normal saline group( H+N group),and hyperoxia + caffeine group(H+C group). Among them,H+N group and H+C group were continually exposed to hyperoxia ( oxygen concentration was 60% ~70%). For A + C group and H + C group,the premature rats were injected with caffeine of 29 mg/(kg·d) into their peritoneal cavities every day after birth. For A+N group and H+N group,the premature rats were injected with normal saline of the same volume into their peritoneal cavities. In each group,the lung tissues of 5 premature rats were randomly select-ed on the third, seventh and fourteenth day respectively. The pathological changes of lung tissue, radiated alveolar count(RAC) and collagen content in lung tissue were observed under a light microscope. The wet/dry ratio ( W/D) was measured. Two-step immunohistochemistry was used to detect the distribution of p38MAPK in lung tissue. The content of phosphorylated p38MAPK( p-p38MAPK) protein was detected by western blot. Results Compared with the air groups,the lung tissues of premature rats in high oxygen expo-sure groups showed different degree of inflammatory changes on the third,seventh,and fourteenth day. The changes were more obvious with the prolonged exposure to hyperoxia. Pulmonary fibrosis was visible on the fourteenth day,which was improved after caffeine intervention. The RAC value of premature rats in hyperoxia exposure groups was significantly lower than that in air-exposure groups(P<0. 05),and the W/D ratio and collagen content in lung tissue increased significantly (P<0. 05),which were improved after caffeine inter-vention(P<0. 05). The results of two-step immunohistochemistry showed that the number of p-p38MAPK positive cells in the lung tissue of premature rats in hyperoxia exposure groups increased and widely distribu-ted, but decreased after caffeine intervention. The results of western blot showed that the content of p-p38MAPK protein in lung tissue of premature rats in hyperoxia exposure groups was significantly higher than that of air groups(P<0. 05),but it decreased after caffeine intervention(P<0. 05). Conclusion Hy-peroxia can promote the formation of pulmonary fibrosis by activating p38MAPK signal pathway. Caffeine can interdict the expression of p38MAPK to alleviate the fibrosis of lung tissue exposed to hyperoxia and thus protects the lung tissue.