title: Dietary antioxidants at supranutritional doses modulate skeletal muscle heat shock protein and inflammatory gene expression in sheep exposed to heat stress.
abstract: The objective of this study was to investigate the effects of chronic heat (thermal) stress and dietary antioxidant supplementation on the expression of heat shock proteins and inflammatory genes in the skeletal muscle of sheep. Twenty-four Merino × Poll Dorset crossbred ewes were allocated to either a control (10 IU vitamin E and 0.24 mg Se/kg DM) or high-antioxidant (VitE+Se; 100 IU vitamin E and 1.20 mg Se/kg DM) diet and were exposed to 2 thermal (temperature) treatments (thermoneutral [TN]: 18°C-21°C and 26%-30% relative humidity; heat stress [HS]: 28°C-40°C and 40%-50% relative humidity) for 1 wk. Physiological parameters were recorded daily, and muscle biopsies were conducted at the end of thermal treatments. Total RNA was extracted from muscle samples and reverse transcribed to cDNA for real-time PCR analysis. Respiration rates and rectal temperature were increased in response to HS (84.2 vs. 161 breaths per minute and 39.52°C vs. 40.06°C for TN and HS conditions, respectively; P < 0.001). There were interactions between dietary and thermal treatments, indicating that dietary antioxidant supplementation reduced respiration rate (P = 0.097) and rectal temperature (P = 0.086) of sheep during HS but not TN conditions. Skeletal muscle heat shock transcription factor 1 (HSF1) mRNA abundance was increased by HS (1.3-fold; P < 0.050) but was not changed (P = 0.77) by dietary antioxidant supplementation. The expression of skeletal muscle heat shock protein 70 (HSP70) mRNA was increased (P < 0.001) 3.5-fold by HS and tended (P = 0.08) to be increased by dietary antioxidant supplementation. Although there were no main effects of diet (P = 0.42) or HS (P = 0.47) on skeletal muscle HSP90 mRNA expression, there was an interaction (P = 0.040) such that HSP90 mRNA expression was increased (P = 0.010) in antioxidant-supplemented sheep under HS compared to TN conditions. Skeletal muscle nuclear factor kappa B (NF-κB) and tissue necrosis factor α (TNF-α) mRNA abundances were increased by exposure to heat (5.2-fold, P = 0.005 for NF-κB; 5.7-fold, P = 0.013 for TNF-α) ,but there was no main effect (P > 0.05) of dietary antioxidant supplementation. There was, however, an interaction between thermal and dietary treatments such that dietary antioxidant supplementation ameliorated the effect of HS on NF-κB and TNF-α mRNA expression. Taken together, these results indicate that high dietary antioxidants modulate skeletal muscle expression of heat shock proteins, proinflammatory cytokine, and NF-κB transcription, which may protect against HS in sheep.
authors.affiliation: Department of Animal Husbandry, Government of Himachal Pradesh, Shimla 171005, India Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Vic 3010, Australia.
authors.forename: S S
authors.initials: SS
authors.lastname: Chauhan
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Vic 3010, Australia Faculty of Veterinary Science, University of Sydney, Sydney, NSW 2570, Australia.
authors.forename: P
authors.initials: P
authors.lastname: Celi
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Vic 3010, Australia Australian Meat Processors Corporation, 110 Walker Street, North Sydney, NSW 2060, Australia.
authors.forename: F T
authors.initials: FT
authors.lastname: Fahri
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Vic 3010, Australia.
authors.forename: B J
authors.initials: BJ
authors.lastname: Leury
authors.affiliation: Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Vic 3010, Australia fdunshea@unimelb.edu.au.
authors.forename: F R
authors.initials: FR
authors.lastname: Dunshea
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000494:pharmacology*; D001831:Body Temperature / Q000187:drug effects; D019587:Dietary Supplements; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature / Q000009:adverse effects*; D007249:Inflammation / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D056152:Respiratory Rate / Q000187:drug effects; D012643:Selenium / Q000008:administration & dosage / Q000494:pharmacology; D034561:Sheep, Domestic / Q000378:metabolism*; D013312:Stress, Physiological / Q000502:physiology*; D014810:Vitamin E / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D006360:Heat-Shock Proteins; D014810:Vitamin E; D012643:Selenium
keywords: HSP; antioxidants; gene expression; heat stress; sheep; skeletal muscle