Cytokines in Skeletal Muscle Growth and Decay

By definition, cytokines are the first messengers of intercellular communications observed among leukocytes. Numerous cytokines control immune system and biological reactions thereof, but are functionally grouped into pro- and anti-inflammatory varieties

  • PDF / 526,321 Bytes
  • 27 Pages / 439.36 x 666.15 pts Page_size
  • 1 Downloads / 212 Views

DOWNLOAD

REPORT


Cytokines in Skeletal Muscle Growth and Decay Arkadiusz Orzechowski

Abstract By definition, cytokines are the first messengers of intercellular communications observed among leukocytes. Numerous cytokines control immune system and biological reactions thereof, but are functionally grouped into proand anti-inflammatory varieties (the latter are also involved in allergic reactions). The bulk of evidence points to substantial role played by cytokines in skeletal muscle growth and wasting. Cytokines and growth factors of immune origin affect skeletal muscle growth and organ formation, regeneration, and wasting but are also produced and secreted by muscle fibers as myokines. To orchestrate skeletal muscle growth, hepatocyte growth factor/scatter factor (HGF/SF) and insulinlike growth factors (IGF-I and IGF-II) play the primary physiological role being mediated through PI3-K/Akt signaling pathway. Skeletal muscle mass is in turn controlled negatively by myostatin, a member of transforming growth factor beta (TGF-“) superfamily. Following muscle injury, the immune-derived cytokines are most important in activation of muscle satellite cells: tumor necrosis factor alpha (TNF-’) and interleukin 6 (IL-6); with IL-8 to arrange growth/regeneration; and IL-15 to control muscle hypertrophy. Some life-threatening diseases are associated with muscle wasting featured by accelerated muscle protein breakdown. In these catabolic states, cytokines such as TNF-’ was often reported as causal factor. Moreover, cross talk between myokines (IL-6, IL-15) and adipokines (leptin) is vital for correct metabolic interorgan relations. Thus, cytokines and growth factors exist as basic chemical signals that orchestrate skeletal muscle fate in normal and diseased states. Keywords Cytokines • Growth factors • Skeletal muscle • Growth • Regeneration • Cachexia

A. Orzechowski () Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw University of Life Sciences – SGGW, Warsaw, Poland e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2017 K. Sakuma (ed.), The Plasticity of Skeletal Muscle, DOI 10.1007/978-981-10-3292-9_5

113

114

A. Orzechowski

5.1 Cytokines in Skeletal Muscle Myogenesis and Somatic Growth In vertebrates skeletal muscles develop during embryonic life from paraxial mesoderm (dermomyotome, myotome) specified to the myogenic lineage by paracrine signals from surrounding tissues. Wingless-related integration sites (Wnts), sonic hedgehog (SHH), and Noggin (NOG) stimulate, whereas bone morphogenetic protein 4 (BMP4) inhibits the commitment to the myogenic lineage. Pax-3 and Pax-7 are paired box genes targeted and co-expressed in the myotomal cells (epithelial spheres of paraxial mesoderm) [166]. Next, sequential activation of basic helix-loop-helix transcription regulators known as myogenic regulatory factors (MRFs) determines muscle progenitors termed myoblasts. Initially, MyoD and/or Myf5 gene expressions are upregulated followed by Myogenin and/or MRF4 gene activation. The latter are essent