Design And Synthesis Of Small Molecules Targeting Nrf2 And Their Mechanism Of Action

Neurodegenerative diseases are caused by the loss of function of certain specific nerve cells;these diseases include Alzheimer’s disease(AD),Parkinson’s disease(PD),Huntington’s chorea(HD),etc.,and a large body of research evidence now suggests that oxidative stress may be one of the most important factors contributing to nerve cell dysfunction.The key to the normal physiological function of cells is the maintenance of redox homeostasis;when redox homeostasis is disrupted,i.e.,the level of intracellular reactive oxygen species(ROS)production is much higher than the response capacity of the intracellular antioxidant system,it will cause a large accumulation of reactive oxygen species and eventually oxidative stress(Oxidative Stress,OS),and the normal physiological activities of the body will be affected.Currently,two ways to prevent or treat oxidative stress-related diseases are to supplement exogenous antioxidants(e.g.,vitamin C)or to activate the body’s endogenous antioxidant defense system,the latter of which has received more attention from researchers because it is regulated at the transcriptional level and can consistently produce antioxidant effects.Activation of the Nrf2(nuclear factor E2-associated factor 2)-ARE(antioxidant response element)signaling pathway is one of the most central antioxidant defense mechanisms in living organisms,which can enhance the antioxidant defense system and thus effectively protect against various types of damage caused by oxidative stress.Therefore,this signaling pathway may be an important target for the potential treatment of neurodegenerative diseases.Through our preliminary study,a small molecule compound,S-20,was found to exhibit good neuroprotective effects on PC12 cells,and we further explored its potential mechanism of action,which provides a reliable experimental basis and theoretical rationale for further development and utilization of more small molecule Nrf2 activators.In the first part,we first introduced neurodegenerative diseases and oxidative stress,followed by a detailed description of the components,functions and regulatory mechanisms of the Keap1-Nrf2-ARE signaling pathway,and finally a review of activators of the Keap1-Nrf2-ARE signaling pathway in recent years.In the second part,20 compounds were designed and synthesized through literature research,and their structures were characterized.The third part firstly screened the synthesized 20 compounds for preliminary biological activity,and the results showed that compound S-20 could effectively protect PC12 cells and effectively alleviate the oxidative damage induced by H2O2 or 6-OHDA.Further mechanistic studies revealed that compound S-20 could promote Nrf2 entry into the nucleus and bind to the ARE of various antioxidant genes,thus increasing the expression levels of its downstream antioxidant genes Txn1,Txnrd1,Homx1,Nqo1,Gclc and Gclm,as well as significantly enhancing the expression of antioxidant protein Trx R and antioxidant molecule GSH.These experimental evidences indicated that compound S-20 could enhance the antioxidant defense system in PC12 cells by activating the Nrf2/ARE signaling pathway,effectively alleviating the excessive production and accumulation of ROS in PC12 cells,which in turn alleviated the apoptosis caused by oxidative stress.The present work is an inspiration for the future development of Nrf2 activators with coumarin as the parent structure,and also provides some ideas for the rational development of more structurally diverse Nrf2 activators.