Role of Endoplasmic Reticulum Stress in Nano-Selenium Alleviating Prehierarchical Follicular Atresia Induced by Mercury in Laying Hens

This study investigated that the effect of nano-selenium (nano-Se) addition preventing prehierarchical follicular atresia induced by mercury (Hg) exposure in laying hens. Furthermore, endoplasmic reticulum (ER) stress pathway was explored to reveal the protective mechanism of nano-Se in vitro. The results revealed that Hg could significantly reduce laying performance ( P < 0.05) and egg quality ( P < 0.05), whereas nano-Se addition partially reversed the reductions. Besides, Hg significantly induced the deposition of Hg in prehierarchical follicles ( P < 0.05) and prehierarchical follicular atresia ( P < 0.05), whereas nano-Se addition could alleviate these toxicities in vitro. In addition, Hg exposure could significantly reduce cell viability ( P < 0.05) and induce pyknotic nucleus in prehierarchical granulosa cells, while nano-Se addition reversed these effects. The levels of follicle-stimulating hormone ( P < 0.05), luteinizing hormone ( P < 0.05), progesterone ( P < 0.05), and estradiol ( P < 0.05) were significantly decreased after Hg exposure in vitro. However, nano-Se addition reversed the decreases of sex hormone levels. Furthermore, Hg exposure significantly increased the gene expressions of CHOP ( P < 0.05), PERK ( P < 0.05), ATF4 ( P < 0.05), ATF6 ( P < 0.05), ASK1 ( P < 0.05), IRE1α ( P < 0.05), TRAF2 ( P < 0.05), caspase-9 ( P < 0.05), caspase-3 ( P < 0.05), and Bax/Bcl-2 ( P < 0.05), whereas nano-Se addition reversed these increases of gene expressions in vitro. In summary, this study provides that Hg can induce prehierarchical follicular atresia, whereas nano-Se addition can ameliorate it, and elucidates an important role of ER stress in nano-Se alleviating prehierarchical follicular atresia induced by Hg in laying hens.