Introduction
Chronic Kidney Disease (CKD), is a syndrome characterized by the progressive and irreversible loss of nephrons due to various diseases [1,2]. CKD has not only significantly increased morbidity and mortality, but also decreases quality of life. The risk of mortality in hemodialysis (HD) patients is about 10 to 20 times higher than in the general population [3]. In these patients, many molecules (e.g. uremic toxins) accumulate in the body which contributes to uremic symptoms and increases mortality [4]. High level of uremic toxins lead to increased oxidative stress in several tissues. Furthermore, increased oxidative stress has negative effects on macromolecules such as lipids, proteins, and nucleic acids [5].
It is well known that oxidative balance is disrupted due to overproduction of free radicals and insufficient antioxidant system in HD patients. Therefore, there are many studies analyzing oxidative stress levels in HD patients [6-8]. Enzymatic and non-enzymatic defense mechanisms against the harmful effects of free radicals are known to exist. One of these antioxidant mechanisms is the presence of thiol-containing compounds. Thiols, also called mercaptans, are sulfhydryl group-containing (-SH) compounds. The main target of free radicals is thiol groups in the sulfur-containing amino acids of proteins. Thiol groups interact with free radicals to form reversible disulfide bonds it then reduced back to thiol groups by several antioxidants. Thus, dynamic thiol-disulfide balance is achieved [9].
Dynamic thiol-disulfide balance has a vital role in the organism and is important to maintain this balance. Thiol-disulfide balance has been measured in only one direction since 1979, but henceforth with novel automated method developed by Erel et al., the level of both variables can be measured distinctly and collectively [10]. In the literature, there are studies related to analysis of thiol levels in CKD patients, but yet there is no study showing the effect of dynamic thiol-disulfide balance and hemodialysis on thioredoxin reductase enzyme levels.
Thioredoxin reductase (TrxR) is a homodimeric flavoenzyme responsible for the catalysis of thioredoxins. TrxR is also of vital importance in controlling intracellular redox medium, cell growth, and apoptosis [11]. Thus, TrxR plays a pivotal role in the pathophysiology of chronic diseases. The sulfhydryl groups of thioredoxins are involved in cellular regulation of various biochemical mechanisms with different functions and the regeneration of inactive proteins as a result of oxidative stress [12]. In this study, we addressed to indicate the relationship between the dynamic thiol-disulfide balance, systemic oxidative stress parameters and TrxR enzyme levels in CKD (stage 3-5) and HD patients.