(096) Chronic Oral Exposure to Short Chain - Chlorinated Paraffins Induced Testicular Toxicity by Promoting NRF2-mediated Oxidative Stress

Abstract Introduction Chlorinated paraffins (CPs) are important additives in a variety of chemical processing. Based on the lengths of the carbon chains, CPs are classified into short-chain CPs (SCCPs, C10-13), medium-chain CPs (MCCPs, C14-17) and long-chain CPs (LCCPs, C18-30) with the chlorine content ranging from 30%-70%. SCCPs were listed in the persistent organic pollutants (POPs) by Stockholm Convention due to its toxicity, bioaccumulation potential, long range transport potential and environmental persistence. Numerous studies have analyzed the toxicities of SCCPs in various organisms, with the toxic effects including lethality and carcinogenicity, developmental toxicity, endocrine disrupting effect and immunomodulatory effect. Objectives As a widespread environmental contaminant, short chain chlorinated paraffins (SCCPs) has attracted great attention. However, the toxicity of SCCPs on male reproductive system remains ambiguous. In this study, we investigated the toxic effects of SCCPs on testis. Methods We treated mice with 1,10 or 100 mg/kg bm/d SCCPs by gavage once a day for 35 days. The tissues and blood samples were collected after treatment. The weight of mice and testes were measured. The organ index is the body weight divided by the weight of the testis. The left testes were used for protein extraction, RNA extraction and measurement of SOD, CAT, GST and MDA. The left epididymis was used for analysis of sperm parameters. The right testis and epididymis were fixed in Bouin’s solution for H&E and TUNEL staining. GC2 cell (mouse spermatocyte) treated with SCCPs was used to examined the cell viability by CCK8 kits. Cellular ROS generation was evaluated by 2',7'Dichlorodihydrofluorescein diacetate (DCFH-DA). We used Apoptosis Detection Kit to detect the cell apoptosis by dual staining cells with Annexin V-fluorescein isothiocyanate (FITC) and propidium iodide (PI). Results SCCPs resulted in disorderly arranged seminiferous epithelium and increased apoptotic cells in testes. Both in vivo and in vitro experiments indicated that the oxidative stress was induced after SCCPs exposure, and dysfunction of nuclear factor erythroid-related factor (NRF2) signaling pathway played a role in this process. Moreover, resveratrol, an NRF2 activator, could alleviate the damage of SCCPs on spermatogenetic cells in vitro. Our study indicated that oxidative stress is the key point for explaining the testicular toxicity caused by SCCPs, and NRF2 could be used as a potential target for clinical treatment to alleviate the reproductive toxicity induced by SCCPs. Conclusions Our study is the first to evaluate the toxic effects of SCCPs on male reproductive system, which is associated with overproduction of ROS. This study also indicates that NRF2/ARE pathway plays the vital role in the toxic effects of SCCPs in spermatogenesis, thus providing a target for the prophylaxis and treatment. Disclosure No