title: Modulation of the NO/cGMP pathway reduces the vasoconstriction induced by acellular and PEGylated haemoglobin.
abstract: Activation of the NO/cGMP pathway modulates smooth muscle cells relaxation and hence vasoconstriction, a major hindrance for the use of cell-free haemoglobin (Hb) as blood substitute, despite conjugation with 5-kDa maleimide poly(ethylene)-glycol (PEG) reduces vasoconstriction in vivo. We aimed at assessing how a recently developed PEGylated-Hb (Deoxy-PEGHb) and manipulation of the NO/cGMP pathway enable modulation of vasoconstriction in isolated rat hearts. Hearts were Langendorff-perfused with oxygenated Krebs-Henseleit (15 ml/min) while monitoring the coronary pressure (CPP) after injection (1 min) of 50 nM norepinephrine followed by a 1 microM Hb or Deoxy-PEGHb bolus, without altering the flow. Deoxy-PEGHb induced less vasoconstriction than Hb. Although the presence of PEG could contribute to vasoconstriction, Deoxy-PEGHb did not contain appreciable amounts of free PEG. Whereas reducing endothelial NO release by 0.2 mM L-NAME increased vasoconstriction, abolishing NO scavenging by Hb using its cyanomet derivative almost completely blunted it. Furthermore, maintaining intracellular cyclic GMP by inhibiting phosphodiesterase-5 with 0.02 mM sildenafil enabled control of Hb-induced vasoconstriction. We conclude that, although PEG-Hb represents a possible approach to limit Hb-induced vasoconstriction, manipulating the NO/cGMP pathway may provide a powerful way to circumvent this problem.
authors.affiliation: Dipartimento di Medicina, Chirurgia e Odontoiatria, University of Milan, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Caretti
authors.forename: Monica
authors.initials: M
authors.lastname: Fantacci
authors.forename: Dario
authors.initials: D
authors.lastname: Caccia
authors.forename: Michele
authors.initials: M
authors.lastname: Perrella
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Lowe
authors.forename: Michele
authors.initials: M
authors.lastname: Samaja
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D006152:Cyclic GMP / Q000502:physiology*; D004731:Endotoxins / Q000633:toxicity; D006321:Heart / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology*; D006454:Hemoglobins / Q000009:adverse effects / Q000627:therapeutic use*; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000502:physiology; D009130:Muscle, Smooth / Q000098:blood supply / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology*; D010477:Perfusion / Q000379:methods; D011092:Polyethylene Glycols / Q000009:adverse effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
chemical_list: D004731:Endotoxins; D006454:Hemoglobins; D009569:Nitric Oxide; D011092:Polyethylene Glycols; D006152:Cyclic GMP