Developmental toxicity induced by PM2.5 through endoplasmic reticulum stress and autophagy pathway in zebrafish embryos

The aims of this study were to investigate the mechanism underlying the developmental toxicity of fine particulate matter (PM2.5) and provide a more thorough understanding of the toxicity of PM2.5 in an ecological environment. Zebrafish embryos at 4 h post-fertilization were exposed to PM2.5 at doses of 200, 300, 400, 500, 600 and 800 μg/mL for 120 h. The mortality, hatching rate, morphology score, body length, locomotor capacity, histological changes, antioxidant defense system, leukocyte migration, inflammation-related gene mRNA expression, endoplasmic reticulum stress (ERS) and autophagy were evaluated to study PM2.5-induced developmental toxicity and its underlying mechanisms. PM2.5 exposure significantly increased the mortality and malformations and reduced the hatching rate and body length of the zebrafish. PM2.5 significantly reduced the locomotor capacity of zebrafish larvae, increased the levels of ROS and disturbed the antioxidant defense system in zebrafish larvae. In addition, a histological examination showed that the heart, liver, intestines and muscle of the PM2.5-treated zebrafish exhibited abnormal changes and a significant increase in cellular autophagic accumulation. RT-PCR showed that the expression of genes related to inflammation (tgfβ and cox2), ERS (hspa5, chop, ire1, xbp1s, and atf6) and autophagy (lc3, beclin1 and atg3) pathways was significantly increased in the PM2.5-treated zebrafish, indicating that PM2.5 induced inflammation and promoted ERS and autophagy responses via the activation of the IRE1-XBP1 and ATF6 pathways. Together, our data indicate that PM2.5 induced a dose- and time-dependent increase in developmental toxicity to zebrafish embryos. Additionally, ERS and autophagy may play important roles in PM2.5-induced developmental toxicity.