01) and HLHK9∆ureA/arcA1/arcA2 (p < 0.01) (Figure 3C), and the reduction trend became more pronounced after 3 and 5 h incubation (Figure 3D). At pH 2 and 3, the survival counts of HLHK9∆ureA started to decrease (P <0.05), whereas there were dramatic decreases in the survival counts of HLHK9∆arcA1/arcA2 (p < 0.001) and triple knockout
mutant HLHK9∆ureA/arcA1/arcA2 strains, which were almost completely killed (p < 0.001) (Figure 3C). These showed that the ADI pathway of L. hongkongensis played a more important role than the urease in resisting acidic environments. Intracellular survival in J774 macrophages and mRNA expression level analyses Survival Ferroptosis inhibitor drugs of wild type L. hongkongensis HLHK9, HLHK9∆ureA, HLHK9∆arcA1/arcA2 and HLHK9∆ureA/arcA1/arcA2 in J774 macrophages were shown in Figure 4A. Survival of HLHK9∆ureA/arcA1/arcA2 and HLHK9∆arcA1/arcA2 in macrophages were markedly decreased (p < 0.001 and p < 0.01 respectively) but that of HLHK9∆ureA was slightly decreased (p < 0.05), Temsirolimus nmr compared to wild type L. hongkongensis HLHK9. The decrease of survival was more prominent in HLHK9∆ureA/arcA1/arcA2, compared to HLHK9∆arcA1/arcA2 (p < 0.05) and HLHK9∆ureA (p < 0.01); and in HLHK9∆arcA1/arcA2,
compared to HLHK9∆ureA (p < 0.05). Given the above results, we further investigated the expression level of ADI genes (arcA1 and arcA2) and ureA gene of wild type L. hongkongensis HLHK9 survived in macrophages using real-time quantitative RT-PCR assay. At 8 h post infection, the mRNA levels of arcA1, arcA2 and ureA genes were markedly increased Nutlin-3a in vitro compared to those at 2 h post infection (p < 0.05, p < 0.01 STK38 and p < 0.05 respectively) (Figure 4B). Figure 4 Intracellular survival assays in J774 macrophages. A, Recovery rates of wild type L. hongkongensis HLHK9, HLHK9∆ureA,
HLHK9∆arcA1/arcA2 and HLHK9∆ureA/arcA1/arcA2 in J774 macrophages. B, Expression level of ADI genes (arcA1 and arcA2) and ureA gene of HLHK9 in macrophages. Error bars represent means ± SEM of three independent experiments. An asterisk indicates a significant difference (*, p < 0.05; **, p < 0.01; ***, p < 0.001). Survival of L. hongkongensis strains in BALB/c mice To further investigate the role of urease and ADI pathway in acid tolerance of L. hongkongensis, we compared the survival ability of HLHK9, mutant strains HLHK9∆ureA, HLHK9∆arcA1/arcA2 and HLHK9∆ureA/arcA1/arcA2 after transit through the stomach of mice. Using this mouse model, HLHK9∆ureA exhibited similar survival abilities as HLHK9 (Figure 5). In contrast, the viable counts of HLHK9∆arcA1/arcA2 and HLHK9∆ureA/arcA1/arcA2 were reduced by 1.2-log and 1.3-log respectively, compared to that of HLHK9 (p < 0.01) (Figure 5). This also indicated that the ADI pathway played a more significant role than urease in the survival of L.