Exposure To Polystyrene Microplastics Induces Reproductive Toxicity Through Oxidative Stress And Activation Of The P38 MAPK Signaling Pathway

Internationally,plastic particles with a diameter of less than 2 millimeters are collectively referred to as microplastics(MP).As MPs increase their exposure to humans and the environment,their health impact is receiving increasing attention.At present,most reports on the effects of MP exposure have focused on the marine environment and marine life.Animal toxicology studies have found that MP have certain effects on the neurotoxicity,immunotoxicity,genetic toxicity,and reproductive toxicity of marine animals.However,there are few studies on the effects of MP on terrestrial animals.In particular,there is a lack of research on MP reproductive health in humans.This study investigated the effects of MP exposure on reproductive toxicity and related mechanisms by exposing polystyrene microplastics(PS)to male Balb/c mice.In this study,80 healthy male Balb/c mice were divided into 8 groups:(1)saline group;(2)100 mg/kg/dNAC;(3)5 mg/kg SB203580;(4)0.01 mg/d PS;(5)0.1 mg/d PS;(6)1 mg/d PS;(7)1 mg/d PS+NAC;(8)1 mg/d PS+SB203580.At a fixed time every day,mice were given 0.25 mL of different concentrations of PS(4,5,6,7,8)or saline control(group 1)by gastric administration for six weeks of exposure.In addition,we used the antioxidant N-acetylcysteine(NAC)and p38 MAPK-specific inhibitor SB203580 to block oxidative damage and p38 MAPK signaling pathways,respectively,to explore possible molecular mechanisms affecting the effects.In this experiment,we examined the changes in sperm count and sperm deformity rate in mouse testes,and changes in mouse weight;The effects of PS exposure on sperm quality were evaluated by analyzing the activities of sperm energy metabolism-related enzymes:succinate dehydrogenase(SDH)and lactate dehydrogenase(LDH)activities and changes in serum testosterone(T);The pathological changes of mouse testis tissue were detected by HE staining analysis;Test the oxygen free radical(ROS),glutathione(GSH),and malondialdehyde(MDA)levels in the testis to evaluate the oxidative damage of the testicles by PS exposure;The effect of PS exposure on activation of p38 MAPK and JNKMAPK signaling pathways was analyzed by immunohistochemical detection of p38 and JNK phosphorylation levels;and The effect of PS exposure on inflammatory factors Interleukin-6(IL-6),interleukin-1?(Interleukin-1 ?,IL-1?),tumor necrosis factor ?(TNF-?),apoptotic protein(Casp-3),and other cytokines.The experimental results showed that the exposure of three concentrations of PS caused different degrees of damage to the testicular tissue of mice and a significant decrease in body weight of the mice(p<0.05);And with the increase of PS exposure dose,the testicular tissue of mice became more loose,and the cavitation phenomenon became worse,especially in the 1 mg/d PS-exposed group,obvious cavitation appeared in the mouse testis,and the number of various spermatogenic cells decreased significantly.At the same time,the exposure of three concentrations of PS led to a significant decrease in sperm counts in mice(p<0.05),a significant increase in sperm deformity rate(p<0.05),and a dose effect.Analysis of sperm metabolism-related enzymes:The activities of SDH and LDH showed that PS exposure resulted in a decrease in SDH and LDH activities,of which high-dose(1 mg/d PS)exposure resulted in a significant reduction in the activity of both enzymes(p<0.01);Analysis of serum testosterone levels showed that PS exposure also caused a significant reduction in testosterone(p<0.05).Examination of the level of oxidative damage in the testis found that PS exposure caused an increase in ROS levels in the testis tissue,accompanied by an increase in MDA levels and a decrease in GSH content;The injection of NAC can effectively antagonize the oxidative stress caused by PS exposure,thereby slowing the damage of the above PS exposure to the testis group and inhibiting the effect on sperm quantity and quality.Analysis of the phosphorylation levels of p38 and JNK showed that PS exposure increased the activation level of JNK and p38 MAPK;while injection of p38 MAPK specific inhibitor SB203580 effectively blocked p38 MAPK activation,causing PS-induced testicular tissue damage and the effects of sperm quality and quantity are alleviated and testosterone secretion is improved.Conclusion:PS exposure caused damage to testicular tissues,decreased sperm quality and quantity in mice,and its pathogenic mechanisms involved oxidative stress and activation of p38 MAPK signaling pathway.