Short Communication: Renal Tubular Vacuolation in Animals Treated with Polyethylene-Glycol-Conjugated Proteins

Abstract

During toxicologic evaluation of a dimeric PEG-linked protein, tumor necrosis factor binding protein (TNF-bp), vacuolation of renal cortical tubular epithelium was seen in male and female Sprague-Dawley rats (200-300 g) given i.v. doses of 40, 20, or 10 mg/kg every other day for 3 months. Tubular lesions in rats treated with 20 or 40 mg/kg for 3 months were only partially reversible after a 2-month recovery period. Despite the presence of marked vacuolation, there were no changes in BUN, creatinine, urinalysis parameters, urinary NAG, urinary B2-microglobulin, or fractional sodium excretion. Single i.v. doses > or = 20 mg/kg TNF-bp caused similar but milder changes. However, equivalent doses of PEG alone or the non-PEG-linked TNF-bp did not cause light microscopic evidence of vacuolation. Treatment of rats with another PEG-linked protein of similar molecular weight resulted in similar changes. Immunostaining for TNF-bp revealed positivity in the apical cytoplasm of renal tubular epithelium within 1 h of i.v. dosing. Immunostaining of kidneys from chronically dosed rats indicated that protein was present in some vacuoles as long as dosing continued; however, kidneys from animals on a reversibility study had vacuoles but no immunostaining for TNF-bp. These results, along with a study that showed more severe lesions with PEG-linked proteins of lower molecular weight and minimal if any lesions with PEG-linked proteins > 70 kDa, suggest that TNF-bp is filtered through the glomerulus and that the protein with attached PEG is reabsorbed by the proximal tubules. Vacuolation may be a result of fluid distension of lysosomes due to the hygroscopic nature of PEG. These studies demonstrated that PEG-linked proteins have the capacity to induce renal tubular vacuolation at high doses. However, the change was not associated with alteration of clinical pathology or functional markers.

Highly glycosylated human alpha interferon: An insight into a new therapeutic candidate

“…After degradation of the therapeutic protein, PEG accumulates in the lysosomes, with the risk of creating a "lysosomal storage disease". This has been demonstrated after injection of pegylated tumor necrosis factor binding protein in rats, where significant vacuolation and renal cortical tubular epithelium due to accumulated PEG was detected (Bendele et al, 1998). Furthermore, pegylated proteins have been found to generate anti-PEG antibodies that could influence the residence time of the conjugate in the circulating blood.…”

TXNIP regulates AKT‐mediated cellular senescence by direct interaction under glucose‐mediated metabolic stress

“…In this study, scoring of renal tubular vacuolation was based on the following criteria: 0%—normal (0), <10%—minimal (1), 10%–30%—mild (2), 31%–50%—moderate (3), and >51%—severe (4). We considered the presence of clear vacuoles in renal tubule, and the distribution of tubular vacuolation was graded (Bendele, Seely, Richey, Sennello, & Shopp, 1998). …”

Effects of pharmaceutical PEGylation on drug metabolism and its clinical concerns

“…Experiment dealt with TNF binding protein has demonstrated the presence of vacuoles in lysosomes after administration of its PEGylated conjugate. However, after a 2-month convalescence, these vacuoles are no longer positive for TNF-binding protein but are associated with PEG alone, demonstrating the metabolism of PEGylated protein [38].…”