Effect of Eucommia ulmoides leaves extract on heat stress resistance of fish

Fish is a variable temperature animal, its growth and reproduction are closely related to temperature, light, air pressure and other climate factors, among which environmental temperature is the most important climate factor for fish growth and development In a certain temperature range, higher temperature makes fish grow faster, and lower temperature makes fish grow slower In cultured fish, when the water temperature is 15-32 ℃, most Cyprinids are suitable for survival, while the four big fish only enter the obvious growth period at 15-20 ℃, 25-30 ℃ into the most suitable long-term life, and beyond this temperature, heat stress will occur 1 the effect of heat stress on fish 1.1 the effect of heat stress on the nervous and endocrine system of fish The changes of catecholamine and cortisol will affect the immune function of fish In the process of stress, catecholamine mainly accelerates the decomposition of glycogen, increases blood sugar to meet the energy demand of the body during stress, in addition, it can promote the secretion of adrenocorticotropic hormone, auxin, triiodothyronine and thyroxine, so as to coordinate more defense mechanisms to combat stress response However, excessive catecholamine can also lead to the decrease of food intake, energy consumption, oxygen consumption and tissue ischemia Cortisol can promote fat mobilization, reduce fat synthesis, reduce body weight and cause growth stagnation 1.2 the effect of heat stress on the antioxidant capacity of fish spleen is one of the important immune organs of fish, which contains a large number of macrophages When macrophages are in a state of stress when stimulated by the outside world, they will produce a lot of free radicals, complete the physiological functions of phagocytosis and sterilization, and induce inflammation When the body is stimulated abnormally, the balance of production and elimination of free radicals in the body is broken, and the concentration of free radicals will increase abnormally High concentration of free radicals can attack DNA and RNA, break its main chain, destroy and degrade bases, cause base mutation, change its thermal stability, cause protein denaturation and produce autoimmune diseases Free radicals with strong oxidability will destroy the plasma membrane, cause lipid peroxidation and produce lipid peroxides Among them, malondialdehyde is a kind of substance which is produced after the decomposition of lipid peroxides and has a strong toxic effect on organisms 1.3 heat stress induced up regulation of HSP gene expression HSP is a non-specific product produced by fish under stress, which can enhance the adaptability of the body to high and low temperature, trauma, bacterial and viral infection The main physiological function of HSP is to promote and maintain the correct folding of new polypeptide chain, regulate the growth, division, differentiation and death of cells, participate in the process of anti injury, repair and heat tolerance of cells, contribute to the recovery of normal structure and function of cells, and play an important role in the treatment of various diseases At the same time, HSP has antioxidant effect Its antioxidative effects are as follows: HSP can inhibit the production of key enzymes of oxygen free radicals, reduce the production of oxygen free radicals through feedback; HSP can up regulate the level of endogenous antioxidant enzymes to maintain the function and survival of cells; HSP can influence the release and metabolism of glucocorticoids 2 The function of Eucommia leaves extract in anti heat stress Eucommia leaves extract is made from Eucommia leaves by using modern advanced extraction technology It has the advantages of anti-oxidation, scavenging free radicals, anti heat stress, bacteriostasis and improving immunity It is a green feed additive with high efficiency, environmental protection, safety and non-toxic side effects The anti heat stress effect of Eucommia ulmoides Oliv Leaves extract is mainly shown in the following aspects 2.1 The study of the effects of Eucommia ulmoides leaves extract on the blood hormone substances showed that chlorogenic acid in Eucommia ulmoides leaves extract could inhibit the contraction of fibroblast collagen network caused by fibroblasts and the increase of ACTH caused by stress response 2.2 the effect of Eucommia ulmoides leaves extract on the antioxidative function of fish Eucommia ulmoides leaves extract can clear the free radicals produced by heat stress in the body and protect the fish tissues from oxidative damage Chlorogenic acid and its derivatives in Eucommia ulmoides leaves extract have stronger free radical scavenging effect than ascorbic acid, caffeic acid and tocopherol, and can effectively scavenge DPPH free radical, hydroxyl free radical and superoxide anion free radical Chlorogenic acid has antioxidant effect because it contains a quantitative R-OH radical, which can form hydrogen free radical with antioxidant effect, so as to eliminate hydroxyl free radical and superoxide The activity of free radicals such as anions can protect tissues from oxidation Polysaccharides and flavonoids in Eucommia ulmoides leaves also have significant scavenging ability of free radicals The mechanism of action includes: 1 Scavenging free radicals by transferring electrons to free radicals; 2 Blocking the generation of free radicals by chelating with metal ions; 3 Activating antioxidant enzyme activity; 4 Inhibiting enzyme oxidation 2.3 the effect of Eucommia ulmoides leaves extract on HSP70 has been studied It has been shown that the heat tolerance and immune function of aquatic animals are closely related to the expression of HSP70 gene The results show that Hsp70 can maintain the homeostasis in cells, and its increase or high expression in cells can significantly improve cell viability and the tolerance of cells to heat stress Many Chinese herbal medicines or plant extracts with immune enhancing effects can not only significantly improve the non-specific immune function of cultured fish, but also induce HSP70 expression in various immune tissues It is reported that the traditional Chinese Medicine Anti stress granules can increase the level of HSP70 in pig liver to improve the cell heat tolerance Heat clearing compound Chinese herbal medicine can induce the increase of HSP70 expression in liver tissue of heat stressed rats and improve the tolerance of tissue cells Lei Aiying et al Reported that the expression of HSP70 gene mRNA in liver tissue of Penaeus vannamei was significantly higher than that of the control group after 10 days of feeding with 1% Chinese herbal feed Ellen et al Injected 1 ml (2 mg / ml tail) of yeast polysaccharide into the abdominal cavity of carp 24 hours after injection, HSP70 gene expression was significantly increased in the head and kidney, and then decreased rapidly Tang Jufen et al Studied the effect of plant polysaccharides on the expression of heat stress protein gene in tilapia The results showed that the injection of plant polysaccharides at a certain dose could significantly increase the expression of HSP70 gene in gill, head kidney, liver and spleen It can be seen that plant polysaccharides can make tilapia reach the state of heat adaptation in advance by inducing HSP70 gene expression in gill, head kidney, liver and spleen It has been reported that plant extracts can improve the immunity of aquatic animals, promote their blood circulation, maintain the stability of the endocrine system, make the metabolism of the body go on normally, provide material basis for the body to resist high temperature, and alleviate the adverse effects of high temperature on aquatic animals due to their dual functions of nutrition and medicine, especially heat clearing, heat relieving and detoxification Influence The extract of Eucommia ulmoides leaves can also effectively promote the high level expression of HSP70 in the liver of cultured fish under the condition of heat stimulation It is an effective additive that can be used to alleviate the heat stress of fish It can be seen that Eucommia ulmoides Oliv Leaves extract can improve the expression of HSP70 gene in the liver by eliminating the increase of free radicals caused by heat stress, so as to alleviate various problems caused by heat stress.