Hemolysis can saturate the hemoglobin/heme scavenging system resulting in increased circulating cell-free hemoglobin (CF-Hb) in hereditary and acquired hemolytic disease. While recent studies suggest a central role for intravascular hemolysis and CF-Hb in the development of vascular dysfunction, this concept has stimulated considerable debate. This highlights the importance of determining the contribution of CF-Hb to vascular complications associated with hemolysis. Therefore, a novel Hb-binding peptide was synthesized and linked to a small fragment of apolipoprotein-E (amino acids 141-150) to facilitate endocytic clearance. Plasma clearance of hE-Hb-b10 displayed a rapid phase t1/2 of 16 minutes and slow phase t1/2 of 10 hours, trafficking primarily through the liver. Peptide hE-Hb-B10 decreased CF-Hb in mice treated with phenylhydrazine, a model of acute hemolysis. Administration of hE-Hb-B10 also attenuated CF-Hb in two models of chronic hemolysis: Berkley sickle cell disease (SS) mice and mice with severe hereditary spherocytosis (HS). Hemolytic rate was unaltered in either chronic hemolysis model supporting the conclusion that hE-Hb-B10 promotes CF-Hb clearance without affecting erythrocyte lysis. Interestingly, hE-Hb-B10 also decreased plasma ALT activity in SS and HS mice. Although acetylcholine-mediated facialis artery vasodilation was not improved by hE-Hb-B10 treatment, the peptide shifted vascular response in favor of NO-dependent vasodilation in SS mice. Taken together, these data demonstrate that hE-Hb-B10 decreases CF-Hb with a concomitant reduction in liver injury and changes in vascular response. Therefore, hE-Hb-B10 can be used to investigate the different roles of CF-Hb in hemolytic pathology and may have therapeutic benefit in the treatment of CF-Hb-mediated tissue damage.
- sickle cell disease
- hereditary spherocytosis
- mouse models
- Copyright © 2012, American Journal of Physiology - Heart and Circulatory Physiology