Investigation on the Detoxification of Indoxyl Sulfate (IS) and Indole-3-Acetic Acid (IAA) Protein-Bound Uremic Toxins (PBUTs) Using Trametes versicolor Biocompatible Laccase: In Situ Synchrotron Imaging, Experimental and Computational Studies.

Abstract

The removal of protein-bound uremic toxins (PBUTs), such as indoxyl sulfate (IS) and indole-3-acetic acid (IAA), from hemodialysis (HD) patients remains a significant challenge due to their strong binding to serum proteins, such as albumin. This study aimed to evaluate the potential of using the enzyme laccase, derived from Trametes versicolor, for the decomposition and removal of IS and IAA during HD. Molecular docking was utilized to investigate the interactions between laccase and the toxins, identifying key functional groups involved. To assess the detoxification efficacy, liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) were employed, allowing for the identification of decomposition byproducts and their toxicity assessment. Additionally, in situ synchrotron radiation micro-computed tomography (SR-µCT) at the Canadian Light Source (CLS) was used to analyze the binding of human serum albumin (HSA) with IS and IAA before and after laccase treatment. Our findings revealed that laccase effectively decomposed IAA into five byproducts, including indole, as confirmed by GC-MS, while IS remained unaffected. The byproducts exhibited lower toxicity ratings than IAA and were more easily eliminated through HD. However, synchrotron-based μ-CT analysis showed reduced HSA-IAA adsorption on the HD membrane post-laccase treatment, with no impact on HSA-IS adsorption. Notably, the transformation of indole into IS in the liver suggests that laccase may not be suitable for IAA detoxification in HD. Despite the lack of expected outcomes, these results provide valuable insights into toxin-enzyme interactions and guide future research toward alternative strategies for PBUTs removal in HD.