Figure 3.

EPO Administration Impairs Pathogen Clearance in Salmonella Infection In Vivo

(A and C) C57BL/6 mice were infected i.p. with 500 CFU of S. typhimurium and treated with PBS or EPO on days 3 and 4 after infection. Livers (A) and spleens (C) were removed and formalin-fixed samples were further processed for HE staining. Whereas PBS-treated Salmonella-infected (S. Tm.) animals had microabscesses in livers (indicated by arrowheads) and preserved splenic organ architecture, EPO-treated Salmonella-infected mice presented with macroabscesses in livers (indicated by an arrow) and scattered inflammatory foci in the spleens due to multiple microabscesses. No signs of thrombo-embolic events were observed in either group. Scale bars represent 200 μm.

(B and D) Bacterial loads were determined in livers (B) and spleens (D) on day 5 after infection. Data were combined from three independent experiments with similar results. Values from 11 or 12 mice per group were log-transformed and compared by means of Student's t test. Individual values and means are depicted and statistical significances between PBS- and EPO-treatment are indicated.

(E) C57BL/6 mice were infected i.p. with 500 CFU of S. typhimurium and treated with PBS or EPO every second day starting on day 1 (24 hr) after infection (n = 14–16 per group). Time points of EPO (or PBS) applications are indicated by arrows. Survival was monitored during an observation period of 7 days. The cumulative survival was analyzed by the log-rank test: p < 0.001 for the comparison of the two groups.

(F) Spleen samples were subjected to RNA preparation and quantitative determination of immune gene expression by RT-PCR. Data from 8–12 samples per group are shown as relative abundance of target gene expression in relation to the house-keeping gene hypoxanthin phospho-ribosyl transferase (Hprt).

(G) Spleen samples (n = 8–12 per group) were used for the preparation of nuclear extracts and NF-κB p65 binding activity was measured.