title: Sequestration of extracellular hemoglobin within a haptoglobin complex decreases its hypertensive and oxidative effects in dogs and guinea pigs.
abstract: Release of hemoglobin (Hb) into the circulation is a central pathophysiologic event that contributes to morbidity and mortality in chronic hemolytic anemias and severe malaria. These toxicities arise from Hb-mediated vasoactivity, possibly due to NO scavenging and localized tissue oxidative processes. Currently, there is no established treatment that targets circulating extracellular Hb. Here, we assessed the role of haptoglobin (Hp), the primary scavenger of Hb in the circulation, in limiting the toxicity of cell-free Hb infusion. Using a canine model, we found that glucocorticoid stimulation of endogenous Hp synthesis prevented Hb-induced hemodynamic responses. Furthermore, guinea pigs administered exogenous Hp displayed decreased Hb-induced hypertension and oxidative toxicity to extravascular environments, such as the proximal tubules of the kidney. The ability of Hp to both attenuate hypertensive responses during Hb exposure and prevent peroxidative toxicity in extravascular compartments was dependent on Hb-Hp complex formation, which likely acts through sequestration of Hb rather than modulation of its NO- and O2-binding characteristics. Our data therefore suggest that therapies involving supplementation of endogenous Hb scavengers may be able to treat complications of acute and chronic hemolysis, as well as counter the adverse effects associated with Hb-based oxygen therapeutics.
authors.affiliation: Clinic for Small Animals, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: Felicitas S
authors.initials: FS
authors.lastname: Boretti
authors.forename: Paul W
authors.initials: PW
authors.lastname: Buehler
authors.forename: Felice
authors.initials: F
authors.lastname: D'Agnillo
authors.forename: Katharina
authors.initials: K
authors.lastname: Kluge
authors.forename: Tony
authors.initials: T
authors.lastname: Glaus
authors.forename: Omer I
authors.initials: OI
authors.lastname: Butt
authors.forename: Yiping
authors.initials: Y
authors.lastname: Jia
authors.forename: Jeroen
authors.initials: J
authors.lastname: Goede
authors.forename: Claudia P
authors.initials: CP
authors.lastname: Pereira
authors.forename: Marco
authors.initials: M
authors.lastname: Maggiorini
authors.forename: Gabriele
authors.initials: G
authors.lastname: Schoedon
authors.forename: Abdu I
authors.initials: AI
authors.lastname: Alayash
authors.forename: Dominik J
authors.initials: DJ
authors.lastname: Schaer
mesh_terms: D000818:Animals; D004285:Dogs; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology; D006168:Guinea Pigs; D006242:Haptoglobins / Q000378:metabolism / Q000494:pharmacology*; D006454:Hemoglobins / Q000378:metabolism* / Q000633:toxicity; D006973:Hypertension / Q000517:prevention & control*; D007501:Iron / Q000378:metabolism; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D018384:Oxidative Stress
chemical_list: D005938:Glucocorticoids; D006242:Haptoglobins; D006454:Hemoglobins; D009569:Nitric Oxide; D007501:Iron