title: The tight junction protein transcript abundance changes and oxidative damage by tryptophan deficiency or excess are related to the modulation of the signalling molecules, NF-κB p65, TOR, caspase-(3,8,9) and Nrf2 mRNA levels, in the gill of young grass carp (Ctenopharyngodon idellus).
abstract: This study is for the first time to explore the possible effects of dietary tryptophan (Trp) on structural integrity and the related signalling factor gene expression in the gill of young grass carp (Ctenopharyngodon idella). Fish were fed with six different experimental diets containing graded levels of Trp at 0.7 (control), 1.7, 3.1, 4.0, 5.2 and 6.1 g kg(-1) diet for 8 weeks. The results firstly demonstrated that Trp deficiency or excess caused increases in reactive oxygen species (ROS) contents, and severe oxidative damage (lipid peroxidation and protein oxidation) in the gill of fish, and those negative effects could be reversed by optimal Trp levels. Secondly, compared with the optimal Trp levels, Trp deficiency could cause decreases in the mRNA levels of the barrier functional proteins (occludin, zonula occludens-1, claudin-c, and -3) and increases in the mRNA levels of the pore-formation proteins (claudin-12 and -15) mRNA levels in the gill of fish, and those were reversed by the optimal levels of Trp. The negative effects of Trp deficiency on those tight junction protein gene expression might be partly related to the increases in the mRNA levels of pro-inflammatory cytokines and related signalling factors (tumor necrosis factor α, interleukin 8, interleukin 1β and transcription factor-κB) and decreases in the mRNA levels of anti-inflammatory cytokines and related signalling factors [interleukin 10, transforming growth factor-β1, nuclear inhibitor factor κBα (iκBα), target of rapamyc and ribosome protein S6 kinase 1 (S6K1)] in the gill of fish. In addition, optimal dietary Trp protected the gill of fish against its deficiency-caused increases in the mRNA levels of the apoptosis signalling (caspase-3, caspase-8, caspase-9) and decreases in anti-superoxide radicals capacity, anti-hydroxyl radical capacity, glutathione contents and the activities of Cu/Zn superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST) in the gill of fish. Additionally, compared with the Trp deficiency, optimal Trp up-regulated the mRNA levels of SOD, CAT, GPx, GR and GST, which might be partly ascribed to the up-regulation of the NF-E2-related factor 2 (Nrf2) mRNA levels and the down-regulation of Kelch-like-ECH-associated protein 1 (Keap1) mRNA levels in the gill of fish. Interestingly, excessive Trp caused similar results with its deficiency. Collectively, Trp deficiency or excess could cause antioxidant system disruption and change tight junction protein transcription abundances, which were partly related to the signalling factors, NF-κB p65, TOR, caspase-(3,8,9) and Nrf2, in fish gill, those could be blocked by the optimal Trp levels.
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Fish Nutrition and Safety in Production Sichuan University Key Laboratory, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China.
authors.forename: Wei-Dan
authors.initials: WD
authors.lastname: Jiang
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China.
authors.forename: Hai-Lang
authors.initials: HL
authors.lastname: Wen
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Fish Nutrition and Safety in Production Sichuan University Key Laboratory, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Animal Nutrition Institute, Sichuan Academy of Animal Science, Chengdu, 610066, China.
authors.forename: Sheng-Yao
authors.initials: SY
authors.lastname: Kuang
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Fish Nutrition and Safety in Production Sichuan University Key Laboratory, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Wu
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Animal Nutrition Institute, Sichuan Academy of Animal Science, Chengdu, 610066, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Tang
authors.affiliation: Animal Nutrition Institute, Sichuan Academy of Animal Science, Chengdu, 610066, China.
authors.forename: Wu-Neng
authors.initials: WN
authors.lastname: Tang
authors.affiliation: Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
authors.forename: Yong-An
authors.initials: YA
authors.lastname: Zhang
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Fish Nutrition and Safety in Production Sichuan University Key Laboratory, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China. Electronic address: zhouxq@sicau.edu.cn.
authors.forename: Xiao-Qiu
authors.initials: XQ
authors.lastname: Zhou
authors.affiliation: Animal Nutrition Institute, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Fish Nutrition and Safety in Production Sichuan University Key Laboratory, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Sichuan, Chengdu, 611130, China. Electronic address: fenglin@sicau.edu.cn.
authors.forename: Lin
authors.initials: L
authors.lastname: Feng
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002347:Carps / Q000235:genetics* / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism; D004032:Diet / Q000662:veterinary; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D005880:Gills / Q000187:drug effects; D017422:Sequence Analysis, DNA / Q000662:veterinary; D062725:Tight Junction Proteins / Q000235:genetics* / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism* / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D016207:Cytokines; D029941:Fish Proteins; D062725:Tight Junction Proteins; D014364:Tryptophan
keywords: Antioxidant defense; Apoptosis; Cytokine; Gene expression; Tight junction protein; Tryptophan