Effect Of Ferulic Acid On Alleviating Ionizing Radiation-Induced Lens Injury Through Activating Nrf2 Signal Pathway And Its Mechanism

Purpose:With the rapid development of nuclear technology,ionizing radiation(IR)is widely used in many fields of human life(such as industry,agriculture,military and medicine).The risk of human exposure to IR is increasing.Lens is one of the most radiosensitive tissues in the human body.The oxidative damage of lens caused by IR-induced reactive oxygen species(ROS)plays an important role in the pathogenesis of IR-induced cataract.Cataract is the leading cause of blindness throughout the world.At present,there is no effective agent for the prevention and treatment of cataract,except for surgery.Despite the sophisticated skill for cataract surgery,it may lead to some serious complications,especially for the patients with systematic diseases.Furthermore,the cost of the surgery brings burden to families and society.Therefore,it is necessary to identify some agents for the prevention and alleviation of IR-induced cataract.Nuclear factor erythroid 2-related factor 2(Nrf2)is the main antioxidant transcription factor in the body.Upon activation,it upregulates the expression of its downstream antioxidant enzymes and phase ? detoxification enzymes to protect cells against oxidative damage.Exploring an effective activator of Nrf2 can provide a new method for the prevention and treatment of IR-induced cataract.Recently,scholars from worldwide have found some radioprotective Nrf2 activators in traditional Chinses medicine,such as Si-Wu-Tang and Shengma.It has been found that the radioprotective effect of these Chinses medicine is related to an active constituent-ferulic acid(FA).FA can reduce IR-induced oxidative damage by activating Nrf2 antioxidant defense system.Therefore,we put forward the hypothesis that FA could alleviate IR-induced lens injury by activating Nrf2 antioxidative defense system to inhibit oxidative stress,so as to prevent and ameliorate IR-induced cataract.It is expected to provide a new target and strategy for the prevention and treatment of IR-induced cataract,and to provide a theoretical basis for the application of Nrf2 activators in the treatment of IR-induced cataract.Methods:Establish neutron radiation-induced rat lens injury with four doses(0 Sv,0.4 Sv,1.2 Sv,and 3.6 Sv).The rats were sacrificed 1 week after radiation and lenses were dissected for histological evaluation with HE,lens epithelial cell apoptosis evaluation with TUNEL,biochemical(malondialdehyde(MDA),glutathione(GSH)and superoxide dismutase(SOD))and western blot(Nrf2,glutamate-cysteine ligase catalytic subunit(GCLC)and heme oxygenase-1(HO-1))analyses.Establish IR-induced lens injury models of rats(10 Gy of y ray)and cells(4 Gy of x ray)and intervene with FA.The changes of lens microstructure and cell morphology were observed.The levels of MDA,GSH and ROS were detected,so as the activities of SOD and glutathione reductase(GR).The effects of FA on the expression of protein and gene of Nrf2 signal pathway related molecules(HO-1 and GCL)were detected by western blot and PCR.To observe the activation of Nrf2 by FA,the expression of nuclear and cytoplasmic protein levels of Nrf2 were detected by western blot.In addition,for cell experiment,to explore the effect of FA on IR-induced apoptosis in HLECs,the apoptotic cells were observed under fluorescence microscope with Calcein AM/PI staining,and the qualified apoptosis was detected by flow cytometry.The transcription and expression of Bax,Bcl-2,and caspase-3 were detected using PCR and western blot.Results:1.IR affects Nrf2 signal pathway in a two-stage process.Low-dose IR activates Nrf2 signal pathway and upregulates its downstream enzymes to combat oxidative damage in the lenses.However,as the IR dose increases further,the compromised activation of Nrf2 leads to its incapacity to inhibit excessive oxidative stress,which causes oxidative damage in the lens and eventually leads to cataract.2.FA can alleviate IR-induced microstructure damage of lens and morphology change of HLECs;3.FA can alleviate IR induced oxidative damage of lens and HLECs by promoting Nrf2 nuclear translocation and activating Nrf2 signal pathway to upregulate the transcription and expression of antioxidant enzymes(such as HO-1 and GCL),increase activity of SOD and GR,and reduce levels of ROS and MDA;4.FA can downregulate the transcription and expression of Bax,upregulated Bcl-2,and downregulate caspase-3 to inhibit the IR-induced apoptosis of HLECs.Conclusions:These results suggest that FA can alleviate IR-induced structure damage of lens,improve morphological changes and reduce apoptosis of HLECs by activating Nrf2 signal pathway to inhibit oxidative stress.This study will provide evidence for the development of FA as a clinical agent for the prevention and treatment of IR-induced cataract,provide a new target for the prevention and treatment of IR-induced and even various kinds of cataracts,and bring hope for patients who can't tolerate surgery.