Heme oxygenase-1 is a modulator of inflammation and vaso-occlusion in transgenic sickle mice
John D. Belcher, Hemachandra Mahaseth, Thomas E. Welch, Leo E. Otterbein, Robert P. Hebbel,, Gregory M. Vercellotti
John D. Belcher, Hemachandra Mahaseth, Thomas E. Welch, Leo E. Otterbein, Robert P. Hebbel,, Gregory M. Vercellotti
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Research Article Hematology

Heme oxygenase-1 is a modulator of inflammation and vaso-occlusion in transgenic sickle mice

Abstract

Transgenic sickle mice expressing βS hemoglobin have activated vascular endothelium that exhibits enhanced expression of NF-κB and adhesion molecules that promote vascular stasis in sickle, but not in normal, mice in response to hypoxia/reoxygenation. Sickle mice hemolyze rbcs in vivo as demonstrated by increased reticulocyte counts, plasma hemoglobin and bilirubin, and reduced plasma haptoglobin. The heme content is elevated in sickle organs, which promotes vascular inflammation and heme oxygenase-1 expression. Treatment of sickle mice with hemin further increases heme oxygenase-1 expression and inhibits hypoxia/reoxygenation–induced stasis, leukocyte-endothelium interactions, and NF-κB, VCAM-1, and ICAM-1 expression. Heme oxygenase inhibition by tin protoporphyrin exacerbates stasis in sickle mice. Furthermore, treatment of sickle mice with the heme oxygenase enzymatic product carbon monoxide or biliverdin inhibits stasis and NF-κB, VCAM-1, and ICAM-1 expression. Local administration of heme oxygenase-1 adenovirus to subcutaneous skin increases heme oxygenase-1 and inhibits hypoxia/reoxygenation–induced stasis in the skin of sickle mice. Heme oxygenase-1 plays a vital role in the inhibition of vaso-occlusion in transgenic sickle mice.

Authors

John D. Belcher, Hemachandra Mahaseth, Thomas E. Welch, Leo E. Otterbein, Robert P. Hebbel,, Gregory M. Vercellotti

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Figure 2

Hemin increases HO-1 expression.

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Hemin increases HO-1 expression. (A) HO-1 expression can be further upre...
(A) HO-1 expression can be further upregulated in the organs of sickle mice with hemin treatment. S+S-Antilles mice were either untreated or injected with hemin (40 μmol/kg/d, i.p.) for 3 days. Twenty-four hours after the third injection, the organs were harvested, and Western blots for HO-1 were performed on lung, liver, and spleen homogenates (1 μg of organ homogenate DNA per lane). The mean HO-1 band intensities (n = 3) ± SD are expressed as a percentage of those in untreated S+S-Antilles mice (100%), which represent the same untreated S+S-Antilles organs shown in Figure 1. Below each bar is a representative HO-1 band from the Western blot. *P < 0.05, untreated versus hemin. (B) HO-1 activity in normal and S+S-Antilles livers. HO-1 activity was measured in microsomes isolated from another group of normal and S+S-Antilles sickle mice as previously described (36). Mice were untreated, injected with hemin (40 μmol/kg/d, i.p.) for 3 days, or injected with hemin plus SnPP (40 μmol/kg/d of each porphyrin, i.p.) for 3 days. Twenty-four hours after the third injection, the livers were harvested, microsomes were isolated at 105,000 g, and HO-1 enzymatic activity was measured. The results in triplicate are expressed as mean ± SEM picomoles of bilirubin generated per milligram microsomal protein per hour. *P < 0.05, normal versus sickle.