Sequestration of extracellular hemoglobin within a haptoglobin complex decreases its hypertensive and oxidative effects in dogs and guinea pigs
Felicitas S. Boretti, … , Abdu I. Alayash, Dominik J. Schaer
Felicitas S. Boretti, … , Abdu I. Alayash, Dominik J. Schaer
Published July 20, 2009
Citation Information: J Clin Invest. 2009;119(8):2271-2280. https://doi.org/10.1172/JCI39115.
View: Text | PDF
Research Article

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

Felicitas S. Boretti, Paul W. Buehler, Felice D’Agnillo, Katharina Kluge, Tony Glaus, Omer I. Butt, Yiping Jia, Jeroen Goede, Claudia P. Pereira, Marco Maggiorini, Gabriele Schoedon, Abdu I. Alayash, Dominik J. Schaer

×

Figure 1

Increased plasma-binding capacity and intravascular retention of Hb, resulting from prednisone treatment in dogs.

Options: View larger image (or click on image) Download as PowerPoint
Increased plasma-binding capacity and intravascular retention of Hb, res...
(A) A 4-fold increase in Hp measured in plasma after 3 days of prednisone dosing (4 mg/kg twice daily) and immediately prior to Hb infusion is depicted (data are presented as mean ± SEM). (B) Hemoglobinuria in control animals (top left panel) and, conversely, absences of hemoglobinuria in prednisone-treated animals (top right panel). High-mass MALDI-MS spectra of urines are shown (bottom panel). The control animal sample is the top spectra; the prednisone-treated animal sample is the bottom spectra. Monoisotopic ion masses of α– and β–globin chains are observed at m/z ratios of 15 and 16 kDa, respectively (top). A third ion is evident at m/z of approximately 30 kDa, suggesting the presence of a cross-linked protein species. (C) Size exclusion chromatograms of plasma collected from control (left) and prednisone-treated dogs (right). The red dotted lines signify preinfusion Hb heterodimer eluting at 21 minutes. The Hb-Hp complex is evident in the plasma of control dogs eluting at 18 minutes, with an increasing fraction of non-complexed Hb heterodimer eluting at 21 minutes over the 8-hour period. Conversely, no free Hb is observed in the plasma of prednisone-treated dogs, and only the Hb-Hp complex eluting at 18 minutes is observed over the 8-hour time course.