Evaluation of the salivary level of glutathione reductase, catalase and free thiol in patients with oral lichen planus

Oral Lichen planus (OLP) has been described as a chronic mucocutaneous inflammatory illness, in which oral mucosa is usually involved [1]. It is more predominant in middle-aged women and white patients [1, 2]. The occurrence of OLP is 1–2% in the overall population, while its dominance in the Asian population is 2.6% [3].

Clinical manifestations of OLP include erythema and white lines on the oral mucosa, described as Wickham striae, with various appearances, such as papular, reticular, atrophic, plaque, erosive, and bullous [4, 5]. Erosive or atrophic types of OLP can trigger symptoms varying from a burning sensation to severe pain that influence the patients’ condition of life [4]. The particular etiology of OLP stays uncertain. Collected data verify the participation of cell-mediated immune dysfunction in the progress of OLP [4, 6]. Keratinocyte apoptosis and lymphocytic infiltration have been surveyed to likely stimulate the creation of a cell-mediated immune reaction [7]. Lichen planus is assumed to result from an atypical T-cell-mediated immune reaction in which basal epithelial cells are distinguished as exotic due to alterations in the antigenicity of their cell surface. The reason for this immune-mediated basal cell injury is undiscovered. Also, it is yet undiscovered whether lichen planus characterizes a solitary disease procedure or numerous intently associated entities with related clinical demonstrations [8, 9].

Catalase is an ordinary enzyme discovered in almost all living creatures exposed to oxygen (such as plants, bacteria and animals). It catalyzes the breakdown of hydrogen peroxide into water and oxygen [10]. Hydrogen peroxide is a destructive product of many routine metabolic processes; to avoid damage to cells and tissues, it should be quickly transformed into other, less dangerous materials [11].

Glutathione (GSH) is important in preserving suitable tasks and avoiding oxidative stress in human cells. Furthermore, it acts as the main character in the metabolism and clearance of xenobiotics, performs as a cofactor in confident detoxifying enzymes, contributes to transportation, and regenerates antioxidants such as Vitamins C and E into their reactive forms [12]. The GSR gene in humans encodes the enzyme glutathione reductase (GR), also referred to as glutathione-disulfide reductase (GSR). The conversion of glutathione disulfide (GSSG) to glutathione sulfhydryl form (GSH) is catalyzed by glutathione reductase. The ratio of GSSG/GSH present in the cell is an essential feature in correctly preserving the oxidative equilibrium of the cell; it is substantial that the cell maintains high levels of reduced glutathione and a low level of oxidized glutathione disulfide. This narrow balance is kept by glutathione reductase, which catalyzes the reduction of GSSG to GSH [12].

Apart from the character that disulfides act in protein construction, alterations of reactive cysteine thiols can change the role of proteins and can be included in the modulation of enzymatic activity. Thiols thus function not only in normal cell signaling via S-nitrosation, S-glutathionylation, or S-sulfonation but can also be permanently oxidized by aging and illness and disturb protein tasks [13, 14]. In the existence of oxidants (thiol oxidase), protein thiols can also develop mixed disulfides with glutathione (GSH) [15]. Thiol clusters are essential supporters of the antioxidant team and have been shown to terminate ROS and other free radicals through enzymatic and non-enzymatic methods [16]. Total thiol groups of proteins are primarily responsible for their antioxidant response and may behave as a sensitive marker of oxidative stress [17].

Total thiol groups are highly vulnerable to oxidation and known as one of the most significant plasma sacrificial antioxidants. Once the cells are exposed to oxidative stress, thiol groups are the first antioxidants that are affected. Thiol oxidase is an enzyme that catalyzes the chemical reaction between the reduced type of thiol (free thiol) to the oxidized type of thiol (disulfide form) [17].

The use of saliva as a diagnostic fluid is a moderately topical development. Saliva is a mottled oral fluid arising from major and minor salivary glands. Oral fluid, frequently described as the reflection of the body’s condition, is a precise method to be surveyed for disease and health observation. Saliva is the first line of defense against oxidative stress (OS), the primary source of several systemic and oral illnesses. Significant causes of oral free radicals and reactive oxygen species (ROS) are periodontitis, tobacco smoke and other oral diseases. Saliva contains antioxidants: albumin, ascorbate, uric acid and enzymes that establish the antioxidant capacity of saliva [18].

The inequity in antioxidants is considered crucial in this illness [19, 20]. Increased lipid peroxidation levels, oxidative stress, and serum or salivary oxygen free radicals precede inflammatory procedures and harm the cellular membranes [21]. Reduced antioxidant protection and elevated oxidative stress can play a significant part in the etiology of several diseases, including diabetes [22], Periodontitis [23], Psoriasis [24], Vitiligo [25], and digestive system complaints [20].

Regarding previous studies and since no similar studies evaluated these biological markers, we aimed to determine the salivary levels of catalase, glutathione reductase and thiol oxidate in patients with OLP and the association between these values and the types of disease.