Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study

Introduction Methods Resuts Discussion Conclusions Acknowledgments Authors' contributions Competing interests Ethical approval References Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study Inaam N. Ali1, Muthana M. Awad2, Alaa S. Mahmood2,* 1 Water and Environment Directorate, Ministry of Sciences and Technology, Baghdad, Iraq 2 Department of Biology, College of Science, University of Anbar, Anbar, Iraq * Corresponding author: A. S. Mahmood (alaashm91@gmail.com) Abstract: Objective: To assess the effect of methotrexate and omega-3 combination on cytogenetic changes of bone marrow and activities of some enzymatic antioxidants. Methods: Fifty-six mature male Wistar rats were divided into two experimental groups and a control group. The first experimental group was sub-divided into three sub-groups depending on the concentration of methotrexate (MTX): X1 (0.05 mg/kg MTX), X2 (0.125 mg/kg MTX) and X3 (0.250 mg/kg MTX), which were given intraperitoneally on a weekly basis for eight weeks. The second experimental group (MTX and omega-3 group) was also sub-divided into three sub-groups (Y1, Y2 and Y3), which were injected intraperitoneally with 0.05, 0.125 and 0.25 mg/kg MTX, respectively, weekly for eight weeks accompanied by the oral administration of 300 mg/kg omega-3. The rats of the control group were given distilled water. The enzymatic activity of catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR) were measured in the sera of rats. In addition, the mitotic index (MI) and chromosomal aberrations of bone marrow were also studied. Results: MTX resulted in a significant decrease in the activities of CAT, SOD and GR compared to the controls. It also increased the MI and chromosomal aberrations of rat bone marrows. On the other hand, omega-3 significantly increased the activities of the investigated enzymatic antioxidants and reduced the MI and chromosomal aberrations in treated mice when given in combination with MTX. Conclusions: MTX has a genotoxic effect on the bone marrow by increasing the MI and all types of chromosomal aberrations and decreasing the enzymatic activity of CAT, SOD and GR. The addition of omega-3 can lead to a protective effect by reducing the toxic and mutagenic effects of MTX. Keywords: Methotrexate, Omega-3, Antioxidant, Wistar rat, Chromosomal aberration, Mitotic index 1. Introduction Methotrexate (MTX) is a folic acid antagonist because of their chemical similarity [1]. Vezmar et al. [2] showed that MTX affects the synthesis of nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) by interfering with the biosynthesis of thymine and purines. It also directly affects the rapidly dividing and intact cells, especially those in the mucous membranes of the mouth, intestine and bone marrow [3]. Omega-3 is a type of unsaturated fats, which are classified as essential fatty acids that cannot be manufactured by the body and should be taken with food [4]. Sources of omega-3 include fish oils, such as salmon, sardines and tuna, as well as soybeans, walnuts, raisins and linseed, almonds and olive oils [5]. Omega-3 is used in the prevention of a number of diseases such as rheumatoid arthritis, ulcerative colitis, asthma, atherosclerosis, cancer, and cardiovascular diseases [6]. A large amount of evidence indicates that omega-3 fatty acids have significant health benefits, including anti-inflammatory and antioxidant properties besides their effect on blood cholesterol levels [7]. Antioxidants retard the oxidation process by different mechanisms such as the removal of free radicals [8]. Enzymatic antioxidants include catalase (CAT), which is the first line of defense in the cell that removes hydrogen peroxide formed during biological processes by converting it into an aldehyde, and superoxide dismutase (SOD). There are three major families of SOD enzymes: manganese SOD (Mn-SOD) in the mitochondria and peroxisomes, iron SOD (Fe-SOD) in prokaryote cells and copper/zinc SOD (Cu-Zn SOD) in the cytoplasm of eukaryote cells [9]. Therefore, changes in the metal co-factors (manganese, iron, copper and zinc) can alter the effectiveness of SOD and may lead to diseases as a result of oxidative stress [10]. Glutathione reductase (GR) is also an enzymatic antioxidant that converts the oxidized glutathione to the reduced glutathione in the presence of NADPH, which is oxidized to NADP [11]. Therefore, the aim of the present study was to assess the effects of MTX and omega-3 on the cytogenetic changes of bone marrow as well as the activities of CAT, SOD and GR enzymatic antioxidants in male rats. 2. Method 2.1. Laboratory animals and experimental design Fifty-six mature male Wistar rats (Rattus norvegicus), aged 10–12 weeks old and weighing 250–300 gm, were used in the present study. The rats were kept in separate cages, with natural 13- hour light and 11-hour dark periods in a contamination-free environment with a controlled temperature (28.0 ± 1.0°C). In addition, rats were maintained on a standard diet and tap water ad libitum. The rats were randomly allocated to two experimental groups and a control group. The first experimental group (MTX group) included 24 rats injected intraperitoneally with different MTX dilutions with distilled water [12]. It was sub-divided into three sub-groups (eight rats per sub-group) according to MTX concentration as follows: X1 (0.05 mg/kg MTX), X2 (0.125mg/kg MTX) and X3 (0.25 mg/kg MTX). All rats were given a single dose of the specified MTX concentration weekly for eight weeks. The second experimental group (MTX and omega-3 group) included 24 rats allocated to three sub-groups (Y1, Y2 and Y3), which were injected intraperitoneally with 0.05, 0.125 and 0.25 mg/kg MTX, respectively, weekly for eight weeks accompanied by the oral administration of 300 mg/kg omega-3. The control group included eight rats that were intraperitoneally injected with distilled water and given a single dose of distilled water orally weekly for eight weeks. 2.2. Blood collection and processing After the end of the dosing period, 5 ml of blood were withdrawn from the heart (by cardiac puncture) using a 5 cc disposable syringe. The collected blood was immediately poured into a clean sterile screw-capped tube (plain tube) and left for coagulation in a water bath at 37°C for 15 minutes. After coagulation of blood, the plain tube was centrifuged for 5 minutes at 1500 rpm. Then the samples were stored at -20°C for subsequent analysis. 2.3. Measurement of the activity of antioxidant enzymes The antioxidant activities of CAT, SOD and GR were measured using enzyme-linked immunosorbent assay kits purchased from Kamiya Biomedical Company (Seattle, WA, US), according to the manufacturer's instructions. 2.4. Cytogenetic study of bone marrow Rats were killed by cervical dislocation, and their hip bones were cleaned from surrounding muscles and then dissected by cutting both ends of the bone. Five milliliters of physiological buffered saline were injected inside the bone to withdraw bone marrow into a test tube. Tubes were centrifuged at 2000 rpm/10 minutes. The supernatant was then removed, and 10 ml of KCL solution (0.075 M) were added to the sediment. The mixture was then incubated at 37 °C in a water bath for 30 minutes, with shaking from time to time. The tubes were then centrifuged at 2000rpm/10 minutes to remove the supernatant. However, 5 ml of a freshly prepared fixative solution (methanol: glacial acetic acid 1:3) were added gradually in the form of droplets into the inner wall of the tube with constant mixing. After that, the tubes were placed at 4 °C for half an hour to fix the cells. This process was repeated for three times, and the cells were then suspended in 2 ml of the fixative solution. The tubes were centrifuged at 2000 rpm for 5 minutes, and the supernatant was then removed while the cells were re-suspended in 1-2 ml of cold fixative solution. After shaking the tubes, 4–5 drops were then taken from each tube onto a clean slide from a height of about three feet to provide an opportunity for the cells and nuclei to spread well. The slides were stained with acridine orange solution (0.01%) for 4–5 minutes, incubated in Sorensen’s buffer (0.06M, pH 6.5) for a minute. and then examined using a fluorescence microscope Olympus BX 51 America at a wavelength of 450–500 nm [13, 14]. A total of 1000 cells were examined, and both dividing and non-dividing cells were calculated [13]. Mitotic index (MI) was calculated according to the following formula [13]: MI= No. of dividing cells / 1000 × 100 2.5. Analysis of chromosomal aberrations of bone marrow cells A total of 1000 dividing cells were examined on the stained slides under a fluorescence microscope at a wavelength of 45–500 nm. The examined cells were at the first metaphase of the mitotic division, where chromosomal aberrations are clear and can be easily seen [13]. 2.6. Statistical analysis Data were analyzed using the Statistical Analysis System (SAS®) software, version 9.1 (Cary, NC, USA) [15]. Effects were expressed as mean ± standard error (SE) and statistically compared using a completely randomized design analysis of variance and least significant differences. Differences at P values <5 were considered statistically significant. 3. Results 3.1. Effects of MTX and MTX-omega-3 combination on antioxidant enzymatic activities Table (1) shows significantly lower SOD activities among rats treated with MTX or MTX-omega-3 compared to controls. Moreover, sera of rats receiving relatively high doses of MTX (sub-groups X2 and X3) showed the lowest enzymatic activities of 4.29 ± 0.01 IU and 3.93 ± 0.11 IU, respectively. On the other hand, CAT activity differed significantly between treated and control rats as well as among treated rats themselves, In this respect, the controls showed the highest activ