Hemoglobin-based oxygen carrier induces hepatic heme oxygenase 1 expression in Kupffer cells.

Background: Kupffer cells (liver macrophages) are a key initiator of inflammation following hepatic insults such as infection, ischemia/reperfusion, and rejection. Heme oxygenase 1 (HO-1) is protective against inflammatory injury. A hemoglobin-based oxygen carrier (HBOC) has been shown to prevent organ inflammation from hemorrhagic shock as well as induce HO-1 at the cellular level. Therefore, we hypothesize that HBOC can induce Kupffer cell HO-1 production.

Methods: Mice administered 20% blood volume HBOC or saline intravenously were sacrificed at 0, 12, 24, 48 hours (n = 4-6/group). Hepatic protein underwent Western blotting for HO-1 and heat shock protein 72. Hepatic frozen sections underwent immunofluorescent staining for HO-1/CD68.

Results: Following HBOC injection, hepatic HO-1 fold change peaked at 12 hours (7.3 +/- 0.8) (p < .01), remained increased at 24 hours (4.7 +/- 0.4) (p < .01), and returned to baseline by 48 hours. HSP72 expression was unaffected in all groups. Twleve-hour liver section immunostaining confirmed significant induction of HO-1 by HBOC. Double staining for HO-1 and CD68 identified Kupffer cells as the majority of cells expressing HO-1.

Conclusion: HBOC induces hepatic HO-1 expression in Kupffer cells without heat shock protein response. These data provide the basis for further investigation into a clinical therapy to induce Kupffer cell HO-1 expression with the goal of attenuating the hepatic immunoresponse to various insults.