Mercuric Chloride Induced Ovarian Oxidative Stress by Suppressing Nrf2-Keap1 Signal Pathway and its Downstream Genes in Laying Hens
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The present study evaluated the effects of mercury chloride (HgCl2) on follicular atresia rate, sex hormone secretion, and ovarian oxidative stress in laying hens. Antioxidant enzyme genes and the nuclear factor erythroid 2-related factor 2 (Nrf2)-Kelch-like ECH-associated protein 1 (Keap1) signal pathway were further studied to uncover the molecular mechanism. A total of 768 40-week-old Hy-Line Brown laying hens were randomly allocated to four treatments with eight pens per treatment and 24 hens of each pen. The birds were fed with four experimental diets containing graded levels of mercury (Hg) at 0.280, 3.325, 9.415, and 27.240 mg/kg, respectively. Results revealed that a positive relationship occurred between the accumulation of Hg in ovary and follicular atresia rate. Progesterone (P4) level significantly decreased in all Hg-treatment groups (P < 0.05), and follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were the lowest in the 27.240-mg/kg Hg group. Besides, the activities of catalase (CAT), superoxidative dismutase (SOD), glutathione reductase (GR), and glutathione (GSH) content were significantly decreased in all Hg-treatment groups (P < 0.05). Glutathione peroxidase (GSH-Px) activity significantly decreased, while malondialdehyde (MDA) content sharply increased in the 27.240-mg/kg Hg group (P < 0.05). In addition, there were positive relationships between antioxidant enzyme activities and antioxidant gene expressions or between antioxidant gene expressions and Nrf2 mRNA expression, while negative correlations occurred between Nrf2 and Keap1 at transcription and protein levels. It could be concluded that Hg induced ovarian function disorders and ovarian oxidative stress by means of impairing the Nrf2-Keap1 signal pathway in laying hens.
KeywordsLaying hens Mercury Nrf2-Keap1 Ovary Oxidative stress
This research was supported by the Modern Argo-industry Technology Research System of China (CARS-40-K10) and the National Key Technology R&D Program (204BAD13B04).
Compliance with Ethical Standards
The experiment was carried out according to the Guiding Principles in the Use of Animals in Toxicology, adopted by the Chinese Society of Toxicology. The animal procedures were approved by the Animal Ethics Committee of Zhejiang University (Hangzhou, China).
Conflict of Interest
The authors declare that they have no conflict of interest.
- 7.Grotto D, de Castro MM, Barcelos GR, Garcia SC, Barbosa JF (2009) Low level and sub-chronic exposure to methylmercury induces hypertension in rats: nitric oxide depletion and oxidative damage as possible mechanisms. Arch Toxicol 83(7):653–662. https://doi.org/10.1007/s00204-009-0437-8 CrossRefPubMedGoogle Scholar
- 9.Reiter RJ, Tan DX, Acuna-Castroviejo D (2000) Melatonin: mechanisms and actions as an antioxidant. Curr Top Biophys 24:171–183Google Scholar
- 23.Hassanpour H, Khalaji-Pirbalouty V, Nasiri L, Mohebbi A, Bahadoran S (2015) Oxidant and enzymatic antioxidant status (gene expression and activity) in the brain of chickens with cold-induced pulmonary hypertension. Int J Biometeorol 59(11):1615–1621. https://doi.org/10.1007/s00484-015-0968-z CrossRefPubMedGoogle Scholar
- 35.Zhang QF, Li YW, Liu ZH, Chen QL (2016) Reproductive toxicity of inorganic mercury exposure in adult zebrafish: histological damage, oxidative stress, and alterations of sex hormone and gene expression in the hypothalamic-pituitary-gonadal axis. Aquat Toxicol 177:417–424. https://doi.org/10.1016/j.aquatox.2016.06.018 CrossRefPubMedGoogle Scholar
- 37.Zeng L, Zheng JL, Wang YH, Xu MY, Zhu AY, Wu CW (2016) The role of Nrf2/Keap1 signaling in inorganic mercury induced oxidative stress in the liver of large yellow croaker Pseudosciaena crocea. Ecotoxicol Environ Saf 132:345–352. https://doi.org/10.1016/j.ecoenv.2016.05.002 CrossRefPubMedGoogle Scholar
- 38.Wu P, Jiang WD, Liu Y, Chen GF, Jiang J, Li SH, Feng L, Zhou XQ (2014) Effect of choline on antioxidant defenses and gene expressions of Nrf2 signaling molecule in the spleen and head kidney of juvenile Jian carp (Cyprinus carpio var. Jian). Fish Shellfish Immunol 38(2):374–382. https://doi.org/10.1016/j.fsi.2014.03.032 CrossRefPubMedGoogle Scholar
- 40.Itoh K, Tong KI, Yamamoto M (2004) Molecular mechanism activating Nrf2-Keap1 pathway in regulation of adaptive response to electrophiles. Free Radic Biol Med 36(10):1208–1213. https://doi.org/10.1016/j.freeradbiomed.2004.02.075 CrossRefPubMedGoogle Scholar
- 41.Toyama T, Shinkai Y, Yasutake A, Uchida K, Yamamoto M, Kumagai Y (2011) Isothiocyanates reduce mercury accumulation via an Nrf2-dependent mechanism during exposure of mice to methylmercury. Environ Health Perspect 119(8):1117–1122. https://doi.org/10.1289/ehp.1003123 CrossRefPubMedPubMedCentralGoogle Scholar
- 43.Shanmugam T, Selvaraj M, Poomalai S (2016) Epigallocatechin gallate potentially abrogates fluoride induced lung oxidative stress, inflammation via Nrf2/Keap1 signaling pathway in rats: an in-vivo and in-silico study. Int Immunopharmacol 39:128–139. https://doi.org/10.1016/j.intimp.2016.07.022 CrossRefPubMedGoogle Scholar
- 44.Kensler TW, Wakabayashi N, Biswal S (2007) Cell survival responses to environmental stress via the Keap1-Nrf2-ARE pathway. Annu Rev Pharmacol Toxicol 47(1):89–116. https://doi.org/10.1146/annurev.pharmtox.46.120604.141046 CrossRefPubMedGoogle Scholar