Analysis of thioredoxin 1 levels in a mouse model of unilateral renal ischemia-reperfusion injury

Abstract

Kidney disease, acute and chronic, is associated with high morbidity and mortality. Currently, a major obstacle in the field of nephrology is the lack of novel and more sensitive biomarkers that would allow an early diagnose and a proper monitoring of disease progression. Oxidative stress and the increased production of reactive oxygen species (ROS) have been implicated in the pathophysiology of a variety of renal diseases. Proteins of the thioredoxin (Trx) family, among others thioredoxins (Trxs) and glutaredoxins (Grxs), represent one of the most important protective systems in the defense against ROS as well as in the repair of their intracellular effects. Thioredoxin 1 (Trx1) is a cytosolic redox protein that catalyzes the reduction of protein disulfides using the thiol groups of two cysteine residues on its CGPC active site. Trx1 is abundantly expressed in different segments of the nephron and has been shown to be released from cells under conditions of oxidative stress in vitro and in vivo. We hypothesized that renal IRI induces the release of Trx1 from cells into extracellular fluids such as serum and tubular fluid/urine and that Trx1 increase may correlate with the degree of damage in the kidney. We established an effective mouse model of unilateral renal ischemia-reperfusion injury (IRI) and studied Trx1 levels in the serum, urine, as well as in various nephron segments of mice following IRI or sham surgery. We compared different reperfusion times (4h, 8h, 16h, 24h, 48h, 96h, and 168h) to track Trx1 levels fluctuation over time. Serum levels of Trx1 increased 4h after renal IRI, while other markers such as blood urea nitrogen and creatinine remained low. Serum Trx1 showed a positive correlation with tubular injury score helping predict intrarenal damage over time. Additionally, immunohistochemistry studies revealed an increase in Trx1 signals in the proximal tubules and collecting ducts as well as a strong nuclear localization in the same nephron segments that became more intense by 96h, a time point characterized by an intense mitotic activity in the tubules. Between 16 and 24h, Trx1 appeared in the lumen of proximal tubules, however urinary levels of Trx1 did not significantly increase. Based on these findings we conclude that serum Trx1 may represent a novel biomarker for assessing renal damage. In addition to this, we hypothesize that intrarenal changes in Trx1 expression and localization might be related to the activation of regeneration mechanisms in the renal tubular epithelium. Further studies are needed to understand the role of Trx1 in the regeneration process after renal IRI. This work was funded by the Center of Integrative Mammalian Research of Ross University School of Veterinary Medicine and by a Startup funding from Long Island University. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.