title: Polyethylene Glycol Camouflaged Earthworm Hemoglobin.
abstract: Nearly 21 million components of blood and whole blood and transfused annually in the United States, while on average only 13.6 million units of blood are donated. As the demand for Red Blood Cells (RBCs) continues to increase due to the aging population, this deficit will be more significant. Despite decades of research to develop hemoglobin (Hb) based oxygen (O2) carriers (HBOCs) as RBC substitutes, there are no products approved for clinical use. Lumbricus terrestris erythrocruorin (LtEc) is the large acellular O2 carrying protein complex found in the earthworm Lumbricus terrestris. LtEc is an extremely stable protein complex, resistant to autoxidation, and capable of transporting O2 to tissue when transfused into mammals. These characteristics render LtEc a promising candidate for the development of the next generation HBOCs. LtEc has a short half-life in circulation, limiting its application as a bridge over days, until blood became available. Conjugation with polyethylene glycol (PEG-LtEc) can extend LtEc circulation time. This study explores PEG-LtEc pharmacokinetics and pharmacodynamics. To study PEG-LtEc pharmacokinetics, hamsters instrumented with the dorsal window chamber were subjected to a 40% exchange transfusion with 10 g/dL PEG-LtEc or LtEc and followed for 48 hours. To study the vascular response of PEG-LtEc, hamsters instrumented with the dorsal window chamber received multiple infusions of 10 g/dL PEG-LtEc or LtEc solution to increase plasma LtEc concentration to 0.5, then 1.0, and 1.5 g/dL, while monitoring the animals' systemic and microcirculatory parameters. Results confirm that PEGylation of LtEc increases its circulation time, extending the half-life to 70 hours, 4 times longer than that of unPEGylated LtEc. However, PEGylation increased the rate of LtEc oxidation in vivo. Vascular analysis verified that PEG-LtEc showed the absence of microvascular vasoconstriction or systemic hypertension. The molecular size of PEG-LtEc did not change the colloid osmotic pressure or blood volume expansion capacity compared to LtEc, due to LtEc's already large molecular size. Taken together, these results further encourage the development of PEG-LtEc as an O2 carrying therapeutic.
authors.affiliation: Bioengineering, University of California San Diego, La Jolla, California, United States of America.
authors.forename: Vivek P
authors.initials: VP
authors.lastname: Jani
authors.affiliation: Bioengineering, University of California San Diego, La Jolla, California, United States of America.
authors.forename: Alborz
authors.initials: A
authors.lastname: Jelvani
authors.affiliation: Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America.
authors.forename: Selamawit
authors.initials: S
authors.lastname: Moges
authors.affiliation: Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America.
authors.forename: Parimala
authors.initials: P
authors.lastname: Nacharaju
authors.affiliation: Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America.
authors.forename: Camille
authors.initials: C
authors.lastname: Roche
authors.affiliation: Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Dantsker
authors.affiliation: William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, Ohio, United States of America.
authors.forename: Andre
authors.initials: A
authors.lastname: Palmer
authors.affiliation: Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America.
authors.forename: Joel M
authors.initials: JM
authors.lastname: Friedman
authors.affiliation: Bioengineering, University of California San Diego, La Jolla, California, United States of America.
authors.forename: Pedro
authors.identifier: http://orcid.org/0000-0002-8794-2839
authors.initials: P
authors.lastname: Cabrales
mesh_terms: D000818:Animals; D001160:Arterioles / Q000187:drug effects; D001783:Blood Flow Velocity / Q000187:drug effects; D001802:Blood Substitutes; D002196:Capillaries / Q000187:drug effects; D006207:Half-Life; D006454:Hemoglobins / Q000737:chemistry* / Q000493:pharmacokinetics*; D007262:Infusions, Intravenous; D008297:Male; D008647:Mesocricetus; D009572:Nitrite Reductases / Q000737:chemistry; D009835:Oligochaeta / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011092:Polyethylene Glycols / Q000737:chemistry*; D014699:Venules / Q000187:drug effects
chemical_list: D001802:Blood Substitutes; D006454:Hemoglobins; C064665:erythrocruorin; D011092:Polyethylene Glycols; D009572:Nitrite Reductases; D010100:Oxygen