Effects of human serum albumin glycation on the interaction with the tyrosine kinase inhibitor pazopanib unveiled by multi-spectroscopic and bioinformatic tools

Abstract

Human Serum Albumin (HSA) is the most abundant plasma transport protein in the human body. However, hyperglycemic conditions (as in diabetic patients) lead to glycated HSA (gHSA) formation, affecting many protein functionalities. Besides, diabetes is a well-known risk factor for various types of cancers, which turns the interactions of antitumoral drugs with gHSA into paramount relevance. In this view, this work focuses on the impact of the protein glycation in the binding of the drug Pazopanib (PAZO, a tyrosine kinase inhibitor used in antitumoral treatments) by applying multi-spectroscopical and theoretical techniques. Spectroscopic results reveal that PAZO quenches the HSA and gHSA intrinsic fluorescence following a static mechanism. On one side, PAZO presents a high and similar affinities for HSA (Ka = 6.76 × 105 M−1) and gHSA (Ka = 7.76 × 105 M−1) under low temperatures (296 K, pH 7.4). On another side, gHSA displayed less affinity to PAZO than HSA under physiological conditions (310 K, pH 7.4), indicating that gHSA presence can negatively affect drug distribution. Thermodynamic results indicate that HSA-PAZO interactions are governed by hydrophobic/Van der Waals forces and hydrogen bonds (ΔH° < 0 and ΔS° > 0). In contrast, only Van der Waals forces and hydrogen bonds (ΔH° < 0 and ΔS° < 0) predominate in the gHSA-PAZO interactions. FRET investigations attest to non-radioactive energy transfer between the drug and considered proteins. UV–Vis confirm the formation of the PAZO-HSA/-gHSA complexes. Synchronous Fluorescence measurements show microenvironmental changes in HSA Tyr residues upon association with PAZO, while the gHSA microenvironment remains unchanged in the drug presence. Molecular docking studies suggest HSA glycosylation may have a relevant effect on PAZO binding modes. In summary, the evidence presented here puts HSA glycation as a crucial factor to be considered when evaluating pharmacokinetics and pharmacodynamics of antitumoral drugs.