Research Paper Volume 10, Issue 11 pp 3089—3103

Glucose negatively affects Nrf2/SKN-1-mediated innate immunity in C. elegans

Figure 4. Activation of SKN-1 pathway mitigates the negative effect of glucose on immune response to S. typhimurium. (A) Knocking down wdr-23 bypasses glucose to activate gst-4::gfp. Animals expressing the SKN-1 reporter gst-4::gfp were fed bacteria expressing double-stranded RNA of wdr-23 from L1 stage to L4/young adult stage on medium with and without glucose, then infected with S. typhimurium for 2 days before imaging. Two independent trials gave similar results and data from one of them were shown. Scale bars are 600 µm. (B) Quantifications of gst-4::gfp intensity of 10 animals in images shown in A by ImageJ software. Ctrl, control; gluc, 0.5% glucose; S, S. typhimurium. P values were obtained by student’s t-test. **, P<0.001. ns, not significant. (C) Knocking down wdr-23 alleviates glucose’s negative effect on infection. Animals fed bacteria expressing double-stranded RNA of wdr-23 from L1 stage to L4/young adult stage on medium with and without glucose were infected with S. typhimurium for 2 days. The numbers of infected pathogen were determined colony forming assay of live S. typhimurium inside the worms. Colony forming unit (CFU) was plotted using Log2. P values were obtained by student’s t-test. **, P<0.001. (D) Knocking down wdr-23 prevents glucose from shortening lifespan of infected C. elegans. Lifespan and infection were carried out at 20 ºC. Animals fed bacteria expressing double-stranded RNA of wdr-23 from L1 stage to L4/young adult stage on medium with and without glucose were infected with S. typhimurium for 2 days. Worms were then transferred to non-infected RNAi bacterial plates. Survival was recorded every other day until all worms died. Data were collected from two independent experiments with number of worms >100. See Table S3 for details.