Transitional Vacuole Formation Following a Bolus Infusion of Peg-Hemoglobin in the Rat

Abstract

This study was designed to assess the morphological effects of a bolus infusion of PEG-hemoglobin on the heart, lung, liver, spleen and kidney of laboratory rats. Of particular interest was the determination of PEG-hemoglobin's potential to form vacuoles in the tissues and whether these were transitory and article specific. One hundred ten female Sprague-Dawley rats were used in this study. The first experiment determined whether vacuole formation was test article specific by infusing either stroma-free bovine hemoglobin, PEG-hemoglobin, bovine serum albumin, PEG-bovine serum albumin or free PEG. The second experiment assessed the transitory nature of vacuolization. In both experiments, unconscious rats received an intravenous top-loading (bolus) injection of test article via the tail vein. Rats were sacrificed at various time points following administration and had their tissues examined for the presence of vacuoles by light microscope morphological examination and iron staining. Formation of vacuoles appeared to be test article specific with only prolonged circulating, high solute test articles producing vacuoles. These vacuoles appeared dose responsive and transitory in nature. The vacuolization found was non-toxic and believed to be due to the known effect of lysosomal overloading following the phagocytosis of vascularly persistent high solute test articles.

Safety of PEGylated recombinant human full‐length coagulation factor VIII (BAX 855) in the overall context of PEG and PEG conjugates

“…Vacuole formation has also been reported for haemoglobin (Hb) and bovine serum albumin (BSA), both conjugated to a 5 kDa PEG . Rats treated with a single i.v.…”

The Pharmacology of PEGylation: Balancing PD with PK to Generate Novel Therapeutics

“…PEG itself has been approved by the FDA for use in food and cosmetics, and itself is considered essentially nontoxic 16, 17. Uptake of PEGylated drugs into Kuppfer cells in the liver has also been reported,12 and while some reports indicate that such intracellular uptake of PEGylated molecules can lead to vacuolization, no toxic consequences of this phenomenon have been observed 18–20. Researchers have attempted to capitalize on this postulated cellular uptake property of PEG by using it to enhance uptake of enzymes such as catalase and superoxide dismutase into cells and deliver to their site of action 21.…”

Protein–polymer conjugation — moving beyond PEGylation

“…Several studies have shown that PEGylated proteins induced vacuole formation in organs including liver, kidneys and spleen [7-11]. One should keep in mind however, that in the majority of these studies, the PEGylated protein is bovine hemoglobin (bHb), which is known to be absorbed by the liver and spleen [11]. In addition, the various studies investigating this issue have reported some contradictory findings.…”