The critical role of heme oxygenase in neutrophil migration impairment in polymicrobial sepsis

Background

Sepsis is a systemic inflammatory response resulting from the inability of the host to restrict local infection. During severe sepsis occurs a marked failure of neutrophil migration into the infectious focus, which is associated with dissemination of infection resulting in high mortality. Recently, we showed that heme oxygenase (HO) products, carbon monoxide and biliverdin, downregulate neutrophil recruitment by reducing the neutrophil/endothelium rolling and adhesion in a noninfectious inflammatory model. This study aimed to investigate a possible role of the HO-1 pathway on the failure of neutrophil recruitment in mice subjected to severe (S-CLP) polymicrobial sepsis induced by cecal ligation and puncture (CLP).

Materials and methods

To evaluate the role of HO-1 in S-CLP, the Balb/c mice were pretreated with a specific HO-1 inhibitor, zinc protoporphyirin IX (ZnPPIX 30 mg/kg, subcutaneously) 30 minutes before severe sepsis induction. Mice were killed 6 hours after CLP and HO-1 expression in mesenteric tissue and in blood neutrophils were determined. In another set of experiments, mice were killed 6 hours and 12 hours after CLP, and neutrophil migration to the peritoneal cavity, bacteremia, lung neutrophil sequestration assessed by myeloperoxidase activity and lung histology, cytokines, liver, kidney and cardiac function and mean arterial pressure were determined. The survival rate of animals was assessed every 12 hours up to 120 hours after surgery.

Results

A significant increase in HO-1 expression was observed in mesenteric tissue and in blood neutrophils after S-CLP. The ZnPPIX pretreatment prevents the failure of neutrophil endothelium rolling, adhesion and migration observed in vehicle-pretreated mice subjected to S-CLP. As consequence, these mice presented reduced bacteremia, low levels of seric TNFα and lung neutrophil sequestration, reduced liver, kidney and cardiac injury and improved mean arterial pressure, resulting in an increase of the survival rate.

Conclusion

These data suggest that during an infectious process HO-1 displays a crucial role on the failure of neutrophil migration to infectious focus and consequently on the susceptibility in severe sepsis.