title: The effect of hyperthermia on liver histology, oxidative stress and disease resistance of the Wuchang bream, Megalobrama amblycephala.
abstract: This study aimed to investigate the effects of hyperthermia on serum hormones, hepatic oxidization indices, hepatic heat shock protein (HSP60, 70, and 90) mRNA expression levels and liver cell ultrastructure in Megalobrama amblycephala before and after high temperature stress. Fish were exposed to the optimal temperature (25 ± 1 °C) or high temperature (32 ± 1 °C) and then challenged with Aeromonas hydrophila. The results showed that hyperthermic stress significantly increased serum adrenocorticotropic hormone (ACTH) at 0.5 and 2 d, serum cortisol (COR) at 0.5, 14, and 21 d and serum 3,5,3'-triiodothyronine (T3) at 1, 14, and 21 d after stress. Additionally, hyperthermia led to oxidative stress, as evidenced by a significant decrease in the hepatic anti-superoxide anion free radical concentration (ASAFER) at 1, 2, 7, and 21 d and in hepatic superoxide dismutase (SOD) activity at 1, 2, 14 and 21 d after stress; however, hepatic malondialdehyde content (MDA) increased at 1, 2, and 7 d after stress. Moreover, the expression of HSP60 at 1 d, HSP70 at 1 and 2 d, and HSP90 at 0.25, 0.5, 1 and 2 d after stress was higher in the stress group compared with the control group. The histological results clearly showed that hyperthermia resulted in fat and glycogen accumulation and structural alterations of the hepatocytes, mitochondria, and nuclei. The cumulative mortality increased in the high temperature stress group at 1 d after acute stress and at 2 and 7 d after chronic stress compared with the control group. Overall, 1 d or 2 d after hyperthermia stress damaged the hepatic ultrastructure and impaired mitochondrial bioenergetics. Dysfunction of the mitochondria subsequently mediated oxidative stress and improved HSP expression modulated the cellular anti-stress response, which in turn led to reduced efficacy of the immune system and increased mortality from Aeromonas hydrophila infection in Megalobrama amblycephala.
authors.affiliation: Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi 214081, PR China. Electronic address: liub@ffrc.cn.
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.affiliation: Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi 214081, PR China.
authors.forename: Pao
authors.initials: P
authors.lastname: Xu
authors.affiliation: Department of Forestry and Natural Resources, Purdue University, West Lafayette, 47907, Indiana, USA.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Brown
authors.affiliation: Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi 214081, PR China. Electronic address: Xiej@ffrc.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Xie
authors.affiliation: Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi 214081, PR China. Electronic address: gexp@ffrc.cn.
authors.forename: Xianping
authors.initials: X
authors.lastname: Ge
authors.affiliation: Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi 214081, PR China.
authors.forename: Linghong
authors.initials: L
authors.lastname: Miao
authors.affiliation: Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi 214081, PR China.
authors.forename: Qunlan
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi 214081, PR China.
authors.forename: Mingchun
authors.initials: M
authors.lastname: Ren
authors.affiliation: Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi 214081, PR China.
authors.forename: Liangkun
authors.initials: L
authors.lastname: Pan
mesh_terms: D016980:Aeromonas hydrophila / Q000502:physiology*; D000818:Animals; D003530:Cyprinidae; D060467:Disease Resistance; D005393:Fish Diseases / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D016905:Gram-Negative Bacterial Infections / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006358:Hot Temperature / Q000009:adverse effects*; D008099:Liver / Q000382:microbiology / Q000502:physiology / Q000648:ultrastructure; D018384:Oxidative Stress
chemical_list: D029941:Fish Proteins; D006360:Heat-Shock Proteins
keywords: HSPs gene expression; High temperature; Liver histology; Megalobrama amblycephala; Oxidative stress