Investigating the effect of a course of swimming exercise training and silymarin supplementation on metallothionein in the lungs of rats exposed to cadmium poisoning during pregnancy and lactation.

Dissertation for Master's Degree in

Physical Education and Sports Sciences - Sports Physiology

Abstract:

Background and Objective: During metabolic changes during pregnancy, the mother's contact with heavy metals is considered very important for placental function and fetal health. However, it has been assumed that endurance training with an effect on the activity of metalloproteins such as MT can be a solution to deal with the harmful effects of heavy metals. Hence, the aim of the present study was to investigate the reaction of MT in the lungs of mother rats exposed to cadmium poisoning after a period of endurance training program of swimming and consumption of silymarin.

Research method: 72 female Wistar rats with an average weight of 190 grams in 9 separate groups (control, Halal, exercise, silymarin, cadmium, exercise-cadmium, silymarin-cadmium, exercise-silysmarin, exercise-silymarin-cadmium). The exercise program during pregnancy was swimming 60 minutes a day, 5 days a week, for 3 weeks in a swimming pool with dimensions of 50x50x100, which continued until the end of pregnancy. Cadmium chloride at the rate of 400 mg/kg of body weight per day as a solution in drinking water was given to the subjects and silymarin at the rate of 100 mg/kg of body weight was injected subcutaneously 3 times a week. The ELISA method was used to measure MT levels in the lungs of infants of mothers exposed to cadmium metal poisoning during pregnancy and breastfeeding. To analyze the findings of this research, the Kolmogorov-Smirnov test, one-way analysis of variance and LED were used at the error level (? ? 0.05). Findings: The research results indicate a significant increase in MT protein levels in the lung tissue of maternal rats in the cadmium group compared to all groups. Also, despite the change in MT levels in the silymarin, swimming, swimming-silymarin, cadmium-silymarin, cadmium-swimming, cadmium-swimming-silymarin groups compared to the control group, no significant difference was observed. The only significant difference compared to the control group was related to the cadmium group with an increase of 127.78 percent (P?0.001). Conclusion: swimming and silymarin or even the interactive effect of the two on the subjects who were exposed to pollution such as cadmium caused a decrease in MT levels in the lung tissue. It is possible that it is due to the increase in the antioxidant properties of swimming and silyman that it can be said that this solution can play an effective vital role during pregnancy.

Key words: endurance training and swimming and cadmium, silymarin, metallothionein, pregnancy, lung

1- Introduction

Today, the growth of industry and the expansion of technology, in addition to creating prosperity and comfort for mankind, cause pollution. has also provided them in their living environment. All these environmental pollutions eventually lead to infectious diseases, endangering people's health and destroying the environment. Laboratory, human and animal studies suggest that heavy metals such as chromium, cadmium[1], nickel, lead and arsenic cause poisoning and damage to many organs by increasing the production of reactive oxygen species (ROS)[2]. Cadmium is one of the most important industrial and environmental pollutants and one of the most toxic heavy metals that is found everywhere and imposes its most negative effects on organs such as lungs, bones and kidneys. [2; 3] Cadmium can enter the human body both through inhalation in factories manufacturing batteries containing cadmium, as well as cigarette smoke, and through food items contaminated with industrial wastewater, such as rice, river oysters, and mushrooms.[1] Cadmium from industrial waste or mineral waste is one of the main water pollutants and is also used in metal plating. [1] Therefore, discovering practical solutions to deal with the impact of this pollutant on human health is one of the goals of biological science researchers. Cadmium has an acute or chronic effect on the respiratory system and diseases such as chronic inflammation of the nose, throat and larynx. It will lead to olfactory disorders as well as chronic structural lung disease[1]. On the other hand, during metabolic changes during pregnancy, the mother's contact with heavy metals is considered very important for the function of the placenta and the health of the fetus, and it has been said that cadmium has toxic effects on the embryo and fetus.[4] The transfer of this element through the mother to the fetus and the resulting effects on the baby [5] have prompted researchers to search for ways to prevent its negative effects.Duston et al. (1979) showed the effect of cadmium on the development of lung hyperplasia, respiratory distress syndrome and the effect on pulmonary surfactant in infants. [6]

Chronic contamination with cadmium involves a variety of defense and detoxification processes such as antioxidants, metallothionein (MT) [3], glutathione (GSH) [4] and heat shock protein (HSP) [5] [7]. Metallothioneins are a group of cysteine-rich metal-binding proteins that scavenge ROS[8]. The very long half-life of cadmium in living organisms is partly attributed to MT formation [9].  Also, the expression and induction of MT has been associated with protection against DNA damage, oxidative stress, and apoptosis [10]. In fact, this protein is considered one of the main antioxidant agents and plays a key role in the anti-apoptotic activities of cells in various pathological conditions, such as clearing and inhibiting reactive oxygen species (ROS) [12, 11]. On the other hand, epidemiologic reports show that physical fitness is related to reducing the occurrence of various diseases related to oxidative stress, including heart diseases, diabetes, neurological disorders, and various cancers. It has also been reported that regular exercise induces MT and has beneficial effects on antioxidant defense[13]. In addition, in order to deal with oxidative stress caused by cadmium and exercise, it seems that the use of antioxidant supplements can be fruitful. The milk thistle plant [6] is considered one of the most important medicinal plants that can play an effective role [14]. The milk thistle plant has tannin, a kind of bitter substance, a resin, and its seeds are also an oily substance, starch, and albuminoid substances. New researches show the existence of a substance called silymarin, which itself contains three main isomers called silybin[7], silydianin[8] and silychristin[9]. It has been extracted and identified that the most effects of the plant have been attributed to this category of materials [15; 16] In the same direction, the current research seeks to study the interaction of the above variables on the activity level of metallothionein levels in the lungs of infants after birth and during infancy.

Cadmium is a toxic metal with a special biological function that enters the human body through water and food, first accumulates in the liver and kidney and causes harmful effects on these two tissues and other body tissues. This toxic substance effectively causes an imbalance in the oxidant and antioxidant status of the body, and this imbalance creates through the production of ROS [17] Cadmium accumulation in the placenta of smoking mothers begins during the first trimester of pregnancy. A study on laboratory animals has also shown that the protective capacity of the fetus against cadmium is stronger during the last trimester of pregnancy than at other stages. During pregnancy, cadmium is called up by the liver and is transferred to the kidney and placenta through the blood plasma, and it probably increases the concentration of cadmium in the blood [4].   Some researchers believe that the consumption of cadmium during pregnancy may cause a decrease in birth weight, placenta, and necrosis [18]. Pringle [10] and colleagues showed that in the first trimester of human pregnancy, extravillous cytotrophoblast cells [11] create a hypoxic environment and cause obstruction of the cochlear arteries [12] of the uterus, which in turn is very necessary for the success of pregnancy [19]. The extremely long half-life of cadmium in living organisms is attributed to the formation of MT, a metal-containing protein[13] that is induced at the transcriptional level by cadmium. The accumulation of cadmium in the liver and kidney may be due to their ability to produce large amounts of MT [9]. Normally, the formation of MT in cells significantly reduces cadmium poisoning. However, it has been reported [9]. that the long residence time of cadmium in the body due to binding to MT may contribute to tumor formation MT induction in the living organism by a variety of physical and chemical stresses related to oxidative damage is consistent with the function of MT as an antioxidant [20]. Thornley and Vasak [14] (1985) have shown that MT acts more strongly than GSH in scavenging free radicals [20].