title: Exercise induces interleukin-8 expression in human skeletal muscle.
abstract: Skeletal muscle has been recognized as an endocrine organ, and muscle cell cultures express several cytokines with potential hormonal effects. Interleukin-8 (IL-8), a chemokine, which induces angiogenesis, is expressed in working muscles; however, the cell source of origin has not been identified. We aimed to elucidate if IL-8 protein is: (1) expressed in contracting muscle fibres and (2) whether there is a release of IL-8 from exercising muscle. Seventeen healthy male volunteers were included in two independent protocols: 3 h of ergometer bicycle exercise at 60% of VO2,max (n = 6) or rest (n = 5), and 3 h of two-legged knee-extensor exercise at 60% of maximal workload (n = 6). Repetitive muscle biopsy samples were obtained from the vastus lateralis in all experiments. A marked increase in IL-8 mRNA was found in muscle biopsy samples obtained after exercise. A marked IL-8 protein expression was demonstrated within the cytoplasm of muscle fibres in biopsy samples obtained in the recovery phase following 3 h of bicycle exercise, and the peak occurred 3-6 h postexercise. A small transient net release of IL-8 from working muscle was found at 1.5 h of knee-extensor exercise. However, the small release of IL-8 from muscle did not result in an increase in the systemic plasma concentration of IL-8, suggesting that muscle-derived IL-8 may play a local role, e.g. in angiogenesis.
authors.affiliation: The Copenhagen Muscle Research Centre, Rigshospitalet, Faculty of Health, University of Copenhagen, Denmark .
authors.forename: Thorbjorn
authors.initials: T
authors.lastname: Akerstrom
authors.forename: Adam
authors.initials: A
authors.lastname: Steensberg
authors.forename: Pernille
authors.initials: P
authors.lastname: Keller
authors.forename: Charlotte
authors.initials: C
authors.lastname: Keller
authors.forename: Milena
authors.initials: M
authors.lastname: Penkowa
authors.forename: Bente Klarlund
authors.initials: BK
authors.lastname: Pedersen
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D016209:Interleukin-8; D012333:RNA, Messenger