Thermal injury increases the number of eosinophil progenitors in rat spleen and bone marrow

Insulin attenuates the cytokine response in a burn wound infection model

A massive burn is one of the most serious injuries resulting in major imbalances of the immune system. The aftermath of a burn is frequently complicated by infections and septic events that additionally increase mortality and morbidity. The aim of the present study was to investigate if insulin attenuates the cytokine response of burned mice challenged with Pseudomonas. Male mice (C57/BL/6) received a full thickness burn of 35% of their total body surface area. Mice received 5 IU/kg insulin i.p. or an equal volume of saline for 5 days after burn. Mice were challenged with 5x10 colony forming units Pseudomonas aeruginosa intraperitoneally. Serum was harvested 6 h after the bacterial challenge, and 18 serum cytokines were measured using the Bio-Plex suspension array system (Bio-Rad, Hercules, Calif). All 18 cytokines were elevated after the Pseudomonas challenge. However, mice treated with insulin showed significantly lower proinflammatory cytokine concentrations of interleukin 5, interleukin 6, and keratinocyte-derived chemokine after the Pseudomonas infection when compared with placebo-treated mice (P<0.05). In contrast, serum concentrations of G-CSF were significantly higher in insulin-treated animals when compared with placebo (P<0.05). We conclude, that insulin treatment selectively modulates specific cytokines in a burn wound infection model.

EFFECT OF THERMAL INJURY ON SPLENIC MYELOPOIESIS

Thermal injury increases the number of macrophage progenitors in the bone marrow but leads to a decrease in the number of granulocyte progenitors. In the spleen, thermal injury increases the numbers of myeloid progenitors, but the lineage commitment of these cells is unknown. In this study mice were given a scald burn, and the number of splenic myeloid progenitors as well as their progeny was determined. BrdU uptake was used to monitor the de novo production of splenocytes for 8 days after the burn. Burn injury increased the numbers of splenic granulocyte-macrophage (GM), granulocyte (G), and macrophage (M) progenitors at postburn day 8 by 12-, 11-, and 18-fold, respectively. Scald injury increased the number of mature PMN (CD11b GR1(bright)) in the spleen and increased the number of white pulp monocyte/macrophages. Increased numbers of BrdU-positive PMN and monocyte/macrophages were seen after injury. Burn macrophages produced increased levels of the anti-inflammatory hematopoietic cytokine G-CSF. Our work clearly shows that the increased myelopoiesis observed postinjury leads to the production of mature myeloid cells. However, the effects of thermal injury on progenitors in the spleen and marrow are not equivalent.