Redox Mechanism of Azathioprine and Its Interaction with DNA.

Mihaela-Cristina Bunea,Monica Enculescu,Horia Iovu,Victor-Constantin Diculescu,Teodor Adrian Enache

doi:10.3390/ijms22136805

Abstract

The electrochemical behavior and the interaction of the immunosuppressive drug azathioprine (AZA) with deoxyribonucleic acid (DNA) were investigated using voltammetric techniques, mass spectrometry (MS), and scanning electron microscopy (SEM). The redox mechanism of AZA on glassy carbon (GC) was investigated using cyclic and differential pulse (DP) voltammetry. It was proven that the electroactive center of AZA is the nitro group and its reduction mechanism is a diffusion-controlled process, which occurs in consecutive steps with formation of electroactive products and involves the transfer of electrons and protons. A redox mechanism was proposed and the interaction of AZA with DNA was also investigated. Morphological characterization of the DNA film on the electrode surface before and after interaction with AZA was performed using scanning electron microscopy. An electrochemical DNA biosensor was employed to study the interactions between AZA and DNA with different concentrations, incubation times, and applied potential values. It was shown that the reduction of AZA molecules bound to the DNA layer induces structural changes of the DNA double strands and oxidative damage, which were recognized through the occurrence of the 8-oxo-deoxyguanosine oxidation peak. Mass spectrometry investigation of the DNA film before and after interaction with AZA also demonstrated the formation of AZA adducts with purine bases.

Highlights

The medical use of azathioprine (6-([1-methyl-4-nitro-1Himidazol-5-yl]-sulphonyl)7H-purine, AZA), which metabolically breaks down to 6-mercaptopurine in the human body, dates back to 1963 [1,2]
In the second part of the study, the deoxyribonucleic acid (DNA) electrochemical biosensors were used in order to observe changes of the conformation of the DNA immobilized at the glassy carbon (GC) electrode surface
The electrochemical results were correlated with morphological characterization using Field-Emission Scanning Electron Microscopy (FESEM) and mass spectrometry investigations

Summary

Introduction

The medical use of azathioprine (6-([1-methyl-4-nitro-1Himidazol-5-yl]-sulphonyl)7H-purine, AZA), which metabolically breaks down to 6-mercaptopurine in the human body, dates back to 1963 [1,2]. AZA blocks purine metabolism and DNA synthesis, and in recent times has been administrated as an immunosuppressive (mainly to prevent renal transplant rejection) and antileukemic drug to treat autoimmune diseases such as ulcerative colitis, rheumatoid arthritis, dermatitis, lupus erythematosus, and Crohn’s disease [3,4,5]; there have been many reports about the high risk of skin cancer for patients exposed to solar radiation under AZA treatment, a fact that limits the administration of AZA [6,7,8,9,10]. In order to sustain the pharmacokinetics studies, one of the aims of this study was to investigate the electrochemical behavior and electron transfer mechanism of AZA, using cyclic and differential pulse voltammetry on a glassy carbon electrode. Electrochemical studies have been performed investigating the voltammetric behavior of AZA, but a complete redox mechanism has not been proposed to date [11,12,13]

Objectives

Methods

Results

Conclusion