Endothelial dysfunction inhibits the ability of haptoglobin to prevent hemoglobin-induced hypertension.
Intravascular hemolysis produces injury in a variety of human diseases including hemoglobinopathies, malaria, and sepsis. The adverse effects of increased plasma hemoglobin are partly mediated by depletion of nitric oxide (NO) and result in vasoconstriction. Circulating plasma proteins haptoglobin and hemopexin scavenge extracellular hemoglobin and cell-free heme, respectively. The ability of human haptoglobin or hemopexin to inhibit the adverse effects of NO scavenging by circulating murine hemoglobin was tested in C57Bl/6 mice. In healthy awake mice, the systemic hemodynamic effects of intravenous coinfusion of cell-free hemoglobin and exogenous haptoglobin or of cell-free hemoglobin and hemopexin were compared with the hemodynamic effects of infusion of cell-free hemoglobin or control protein (albumin) alone. We also studied the hemodynamic effects of infusing hemoglobin and haptoglobin as well as injecting either hemoglobin or albumin alone in mice fed a high-fat diet (HFD) and in diabetic (db/db) mice. Coinfusion of a 1:1 weight ratio of haptoglobin but not hemopexin with cell-free hemoglobin prevented hemoglobin-induced systemic hypertension in healthy awake mice. In mice fed a HFD and in diabetic mice, coinfusion of haptoglobin mixed with an equal mass of cell-free hemoglobin did not reverse hemoglobin-induced hypertension. Haptoglobin retained cell-free hemoglobin in plasma, but neither haptoglobin nor hemopexin affected the ability of hemoglobin to scavenge NO ex vivo. In conclusion, in healthy C57Bl/6 mice with normal endothelium, coadministration of haptoglobin but not hemopexin with cell-free hemoglobin prevents acute hemoglobin-induced systemic hypertension by compartmentalizing cell-free hemoglobin in plasma. In murine diseases associated with endothelial dysfunction, haptoglobin therapy appears to be insufficient to prevent hemoglobin-induced vasoconstriction.NEW & NOTEWORTHYCoadministraton of haptoglobin but not hemopexin with cell-free hemoglobin prevents hemoglobin-induced systemic hypertension in mice with a normal endothelium. In contrast, treatment with the same amount of haptoglobin is unable to prevent hemoglobin-induced vasoconstriction in mice with hyperlipidemia or diabetes mellitus, disorders that are associated with endothelial dysfunction.
Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Jan A
JA
Graw
Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Binglan
B
Yu
Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Emanuele
E
Rezoagli
Infectious Disease Unit, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; and.
H Shaw
HS
Warren
Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Emmanuel S
ES
Buys
Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.|Division of Rheumatology, Allergy and Immunology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Donald B
DB
Bloch
Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; wzapol@mgh.harvard.edu.
Warren M
WM
Zapol
D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000494:pharmacology*; D003920:Diabetes Mellitus / Q000503:physiopathology; D059305:Diet, High-Fat; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D006242:Haptoglobins / Q000008:administration & dosage / Q000494:pharmacology*; D006454:Hemoglobins; D006466:Hemopexin / Q000008:administration & dosage / Q000494:pharmacology*; D006973:Hypertension / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D007262:Infusions, Intravenous; D007668:Kidney / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000378:metabolism; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects*
D000959:Antihypertensive Agents; D006242:Haptoglobins; D006454:Hemoglobins; D009569:Nitric Oxide; D006466:Hemopexin
cell-free hemoglobin; endothelial dysfunction; haptoglobin; hemopexin; nitric oxide