A Piezo1/KLF15/IL-6 axis mediates immobilization-induced muscle atrophy
Yu Hirata, Kazuhiro Nomura, Daisuke Kato, Yoshihisa Tachibana, Takahiro Niikura, Kana Uchiyama, Tetsuya Hosooka, Tomoaki Fukui, Keisuke Oe, Ryosuke Kuroda, Yuji Hara, Takahiro Adachi, Koji Shibasaki, Hiroaki Wake, Wataru Ogawa
Yu Hirata, Kazuhiro Nomura, Daisuke Kato, Yoshihisa Tachibana, Takahiro Niikura, Kana Uchiyama, Tetsuya Hosooka, Tomoaki Fukui, Keisuke Oe, Ryosuke Kuroda, Yuji Hara, Takahiro Adachi, Koji Shibasaki, Hiroaki Wake, Wataru Ogawa
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Research Article Metabolism Muscle biology

A Piezo1/KLF15/IL-6 axis mediates immobilization-induced muscle atrophy

Abstract

Although immobility is a common cause of muscle atrophy, the mechanism underlying this causality is unclear. We here show that Krüppel-like factor 15 (KLF15) and IL-6 are upregulated in skeletal muscle of limb-immobilized mice and that mice with KLF15 deficiency in skeletal muscle or with systemic IL-6 deficiency are protected from immobility-induced muscle atrophy. A newly developed Ca2+ bioimaging revealed that the cytosolic Ca2+ concentration ([Ca2+]i) of skeletal muscle is reduced to below the basal level by immobilization, which is associated with the downregulation of Piezo1. Acute disruption of Piezo1 in skeletal muscle induced Klf15 and Il6 expression as well as muscle atrophy, which was prevented by antibodies against IL-6. A role for the Piezo1/KLF15/IL-6 axis in immobility-induced muscle atrophy was validated in human samples. Our results thus uncover a paradigm for Ca2+ signaling in that a decrease in [Ca2+]i from the basal level triggers a defined biological event.

Authors

Yu Hirata, Kazuhiro Nomura, Daisuke Kato, Yoshihisa Tachibana, Takahiro Niikura, Kana Uchiyama, Tetsuya Hosooka, Tomoaki Fukui, Keisuke Oe, Ryosuke Kuroda, Yuji Hara, Takahiro Adachi, Koji Shibasaki, Hiroaki Wake, Wataru Ogawa

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Figure 2

IL-6 is a downstream effector of KLF15 in immobilization-induced muscle atrophy.

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IL-6 is a downstream effector of KLF15 in immobilization-induced muscle ...
(A) DNA microarray analysis of gene expression in gastrocnemius of WT or M-KLF15KO mice after cast immobilization (IM) of the hind limbs for 3 days. The heatmap shows genes for humoral factors whose expression was upregulated in immobilized WT mice compared with control WT mice. (B) Quantitative RT-PCR analysis of inflammation-related gene expression in gastrocnemius of mice as in A (n = 6 mice). (C) Quantitative RT-PCR analysis of Il6 mRNA (n = 6 independent experiments) in C2C12 myotubes infected with an adenovirus encoding LacZ (control) or mouse KLF15 (Ad-KLF15). (D and E) ChIP assay of KLF15 binding to the mouse Il6 promoter region in C2C12 myotubes. Immunoprecipitation (IP) was performed with antibodies against KLF15 or with control immunoglobulin G (IgG). A schematic representation of the promoter region indicating the positions of putative KLF binding sites and PCR primers as well as representative gel electrophoresis of PCR products are shown in D. Quantitative data for the ChIP analysis of KLF15 binding to the Il6 promoter region or to Gapdh (negative control) are shown in E (n = 4 independent experiments). (F–J) Ratio of muscle mass to body mass (n = 8 mice) (F), histological determination of muscle fiber area in soleus (G and H), atrophy-related gene expression in gastrocnemius (n = 8 mice) (I), and immunoblot analysis of total and phosphorylated (p-) forms of STAT3 in gastrocnemius (n = 4 mice) (J) are shown for control or cast-immobilized mice subjected to intraperitoneal injection of neutralizing antibodies against IL-6 (0.1 mg/mouse) or control IgG at the onset of limb immobilization. Scale bar: 50 μm (G). The area of 800 fibers pooled from 4 mice was measured for each condition in H. Quantitative data are mean ± SEM (B, C, E, F, I, and J) or medians (H). *P < 0.05, **P < 0.01 by unpaired Student’s t test (C and E) or 2-way ANOVA with Bonferroni’s post hoc test (B, F, and H–J). NS, not significant.