Regulation Of Arginine In Rice Protein On Protective Mechanism Against DNA Oxidative Damage

DNA damage can lead to aging,cancer and other diseases.Activating endogenous antioxidant mechanism and p53 pathway can effectively prevent DNA damage.Rice protein,rich in arginine,is a plant dietary protein with antioxidant,anti-inflammatory,blood lipid regulation and other functions.However,up to now,a clear link between protection against DNA oxidative damage and the intake of rice protein is far from clear.In addition,whether and how rice protein can activate the protective mechanism against DNA damage,whether arginine can regulate the protective mechanism against DNA damage exerted by rice protein,and whether the age of experimental animals and dietary oil affect the protective mechanism against DNA damage exerted by rice protein need to be analyzed.Therefore,this thesis took rice protein as the subject,selected Wistar rats with different ages（growth and mature）as experimental animals,adopted the feeding mode of free intake and oral gavage under normal diets and oil-enriched diets,and combined the research method of dietary protein and amino acids.The thesis studied the protective role and mechanism against DNA damage exerted by rice protein,the regulation of arginine on p53/Nrf2/NF-κB signaling pathway,and the protective mechanism of rice protein against DNA oxidative damage regulated by arginine at the tissue and molecular levels.The main findings are as follows.Under normal diets and oil-enriched diets,after 2 weeks of free feeding,the results showed that rice protein could effectively reduce hepatic ROS and 8-OHd G levels,increase hepatic p53 contents of growing and adult rats,which suggesting rice protein could prevent DNA oxidative damage.Rice protein could increase the expression levels of ATM,Chk2,Chk1 and p53 in liver,reduce the expression of MDM2,which suggesting that the ATM-p53 signal pathway was activated.Rice protein could improve the activities of CAT and T-SOD in liver,effectively improve hepatic T-AOC.In addition,rice protein could reduce the protein expression and m RNA level of Keap1,activate Nrf2,increase the protein expression and m RNA levels of CAT,SOD and GPx,suggesting Nrf2 antioxidant signal pathway was activated and the level of oxidative stress was effectively reduced by rice protein.Studies showed that the activation of p53/Nrf2 signaling pathway is the main protective mechanism against DNA oxidative damage exerted by rice protein.Furthermore,the protective effect and mechanism against DNA damage exerted by rice protein were not significantly affected by animal’s age and dietary oil.After oral gavage with different doses of arginine for 14 days,the results showed that arginine could effectively reduce the hepatic content of 8-OHd G,increase hepatic content of p53 and activate the ATM-p53 signal pathway in growing rats.Arginine can significantly improve the hepatic ability to inhibit·OH and O2^·-,reduce H2O2level in liver,enhance the hepatic activity of CAT and T-SOD,increase hepatic and plasma T-AOC,inhibit the molecule expressions of Keap1 and Cul3,activate the endogenous Nrf2 pathway,and promote the protein expression and m RNA levels of CAT,SOD,HO-1 and NQO1,initiating the endogenous antioxidant mechanism.Arginine can effectively reduce the plasma activities of AST and ALT,promote expressions of IL-10 and IκBα,inhibit expressions of PI3K/Akt,prevent the activation of NF-κB signaling pathway and reduce the gene and protein expressions of COX-2 TNF-α,IL-1βand IL-6.In addition,supplementary arginine can promote arginine metabolism,improve the activities and molecular expressions of ARG1 and NOS,improve protein expression and m RNA levels of GCLC,GCLM,GS,GR,GST and GPx,promote the synthesis of endogenous antioxidant GSH.Meanwhile,under oil-enrich diets,after oral gavage of arginine for 14 days,the results showed that arginine could significantly reduce the hepatic contents of ROS,HNE and 8-OHd G in growing rats,increase hepatic p53 contents,activate ATM-p53 pathway and Nrf2antioxidant signal pathway.Results showed that activating ATM-p53 signaling pathway,initating Nrf2 endogenous antioxidant pathway,inhibiting the inflammatory response regulated by NF-κB,promoting arginine catabolism,enhancing GSH synthesis and metabolism,improving anti-oxidative activity are the protective mechanism against DNA damage exerted by arginine.Results indicated that oil-enriched diets did not affect the defense mechanism of arginine against DNA oxidative damage.Under normal diets and oil-enrich diets,oral gavage（arginine）and free intake（rice protein and rice protein added with arginine）were adopted.After feeding for 2weeks,through the comparative analysis of the regulatory effects of arginine,rice protein and rice protein added with arginine on hepatic ROS,HNE,8-OHd G and p53,the protein and gene expressions of ATM-Chk2-p53 signaling pathway and antioxidant enzymes,the experimental results showed that arginine played an important role on the regulation of the protective mechanism against DNA oxidative damage exerted by rice protein through activating p53/Nrf2 signaling pathway.Results indicated that oil-enriched diets did not affect the defense mechanism against DNA oxidative damage.From the molecular levels,this thesis clarified that activating ATM-Chk2-p53signaling pathway and endogenous Nrf2 antioxidant pathway were the main protective mechanisms against DNA oxidative damage exerted by rice protein,and this thesis also revealed the important regulatory role of arginine on regulating the protective mechanism of rice protein against DNA oxidative damage.This thesis provides a theoretical basis and new research ideas for understanding the protective effect of dietary protein against DNA damage and developing functional rice protein food with disease prevention and health care.