title: Myocardial ischemic tolerance in rats subjected to endurance exercise training during adaptation to chronic hypoxia.
abstract: Chronic hypoxia and exercise are natural stimuli that confer sustainable cardioprotection against ischemia-reperfusion (I/R) injury, but it is unknown whether they can act in synergy to enhance ischemic resistance. Inflammatory response mediated by tumor necrosis factor-α (TNF-α) plays a role in the infarct size limitation by continuous normobaric hypoxia (CNH), whereas exercise is associated with anti-inflammatory effects. This study was conducted to determine if exercise training performed under conditions of CNH (12% O2) affects myocardial ischemic resistance with respect to inflammatory and redox status. Adult male Wistar rats were assigned to one of the following groups: normoxic sedentary, normoxic trained, hypoxic sedentary, and hypoxic trained. ELISA and Western blot analysis, respectively, were used to quantify myocardial cytokines and the expression of TNF-α receptors, nuclear factor-κB (NF-κB), and selected components of related signaling pathways. Infarct size and arrhythmias were assessed in open-chest rats subjected to I/R. CNH increased TNF-α and interleukin-6 levels and the expression of TNF-α type 2 receptor, NF-κB, inducible nitric oxide synthase (iNOS), cytosolic phospholipase A2α, cyclooxygenase-2, manganese superoxide dismutase (MnSOD), and catalase. None of these effects occurred in the normoxic trained group, whereas exercise in hypoxia abolished or significantly attenuated CNH-induced responses, except for NF-κB, iNOS, and MnSOD. Both CNH and exercise reduced infarct size, but their combination provided the same degree of protection as CNH alone. In conclusion, exercise training does not amplify the cardioprotection conferred by CNH. High ischemic tolerance of the CNH hearts persists after exercise, possibly by maintaining the increased antioxidant capacity despite attenuating TNF-α-dependent protective signaling.NEW & NOTEWORTHYChronic hypoxia and regular exercise are natural stimuli that confer sustainable myocardial protection against acute ischemia-reperfusion injury. Signaling mediated by TNF-α via its type 2 receptor plays a role in the cardioprotective mechanism of chronic hypoxia. In the present study, we found that exercise training of rats during adaptation to hypoxia does not amplify the infarct size-limiting effect. Ischemia-resistant phenotype is maintained in the combined hypoxia-exercise setting despite exercise-induced attenuation of TNF-α-dependent protective signaling.
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.
authors.forename: Petra
authors.initials: P
authors.lastname: Alánová
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.
authors.forename: Anna
authors.initials: A
authors.lastname: Chytilová
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.
authors.forename: Jan
authors.initials: J
authors.lastname: Neckář
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Hrdlička
authors.affiliation: Department of Physiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
authors.forename: Petra
authors.initials: P
authors.lastname: Míčová
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.
authors.forename: Kristýna
authors.initials: K
authors.lastname: Holzerová
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.|Department of Physiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
authors.forename: Markéta
authors.initials: M
authors.lastname: Hlaváčková
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.
authors.forename: Kristýna
authors.initials: K
authors.lastname: Macháčková
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.
authors.forename: František
authors.initials: F
authors.lastname: Papoušek
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.
authors.forename: Jana
authors.initials: J
authors.lastname: Vašinová
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Benák
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and.|Department of Physiology, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
authors.forename: Olga
authors.initials: O
authors.lastname: Nováková
authors.affiliation: Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic; and kolar@biomed.cas.cz.
authors.forename: František
authors.initials: F
authors.lastname: Kolář
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D051546:Cyclooxygenase 2 / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology*; D015850:Interleukin-6 / Q000378:metabolism; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology*; D016328:NF-kappa B / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000099156:Superoxide Dismutase 2
chemical_list: D051546:Cyclooxygenase 2; D015850:Interleukin-6; D016328:NF-kappa B; D052247:Nitric Oxide Synthase Type II; D047889:Receptors, Tumor Necrosis Factor, Type II; D013482:Superoxide Dismutase; D014409:Tumor Necrosis Factor-alpha; D000099156:Superoxide Dismutase 2
keywords: antioxidants; cardioprotection; chronic hypoxia; cytokines; exercise training