Kano Ryotaro, Tabuchi Ayaka, Tanaka Yoshinori, Shirakawa Hideki, Hoshino Daisuke, Poole David C, Kano Yutaka
Department of Engineering Science, Bioscience and Technology Program, University of Electro-Communications, Chofu, Japan.
Research Fellowship for Young Scientists, Japan Society for the Promotion of Science, Tokyo, Japan.
Am J Physiol Regul Integr Comp Physiol. 2024 Jan 1;326(1):R43-R52. doi: 10.1152/ajpregu.00152.2023. Epub 2023 Oct 30.
Hydrogen peroxide (HO) and calcium ions (Ca) are functional regulators of skeletal muscle contraction and metabolism. Although HO is one of the activators of the type-1 ryanodine receptor (RyR1) in the Ca release channel, the interdependence between HO and Ca dynamics remains unclear. This study tested the following hypotheses using an in vivo model of mouse tibialis anterior (TA) skeletal muscle. ) Under resting conditions, elevated cytosolic HO concentration ([HO]) leads to a concentration-dependent increase in cytosolic Ca concentration ([Ca]) through its effect on RyR1; and ) in hypoxia (cardiac arrest) and muscle contractions (electrical stimulation), increased [HO] induces Ca accumulation. Cytosolic HO (HyPer7) and Ca (Fura-2) dynamics were resolved by TA bioimaging in young C57BL/6J male mice under four conditions: ) elevated exogenous HO; ) cardiac arrest; ) twitch (1 Hz, 60 s) contractions; and ) tetanic (30 s) contractions. Exogenous HO (0.1-100 mM) induced a concentration-dependent increase in [HO] (+55% at 0.1 mM; +280% at 100 mM) and an increase in [Ca] (+3% at 1.0 mM; +8% at 10 mM). This increase in [Ca] was inhibited by pharmacological inhibition of RyR1 by dantrolene. Cardiac arrest-induced hypoxia increased [HO] (+33%) and [Ca] (+20%) 50 min postcardiac arrest. Compared with the exogenous 1.0 mM HO condition, [HO] after tetanic muscle contractions rose less than one-tenth as much, whereas [Ca] was 4.7-fold higher. In conclusion, substantial increases in [HO] levels evoke only modest Ca accumulation via their effect on the sarcoplasmic reticulum RyR1. On the other hand, contrary to hypoxia secondary to cardiac arrest, increases in [HO] from muscle contractions are small, indicating that HO generation is unlikely to be a primary factor driving the significant Ca accumulation after, especially tetanic, muscle contractions. We developed an in vivo mouse myocyte HO imaging model during exogenous HO loading, ischemic hypoxia induced by cardiac arrest, and muscle contractions. In this study, the interrelationship between cytosolic HO levels and Ca homeostasis during muscle contraction and hypoxic conditions was revealed. These results contribute to the elucidation of the mechanisms of muscle fatigue and exercise adaptation.
过氧化氢（HO）和钙离子（Ca）是骨骼肌收缩和代谢的功能调节因子。尽管HO是钙释放通道中1型兰尼碱受体（RyR1）的激活剂之一，但HO与钙动力学之间的相互依存关系仍不清楚。本研究使用小鼠胫前肌（TA）骨骼肌的体内模型检验了以下假设：）在静息条件下，胞质HO浓度（[HO]）升高通过其对RyR1的作用导致胞质钙浓度（[Ca]）呈浓度依赖性增加；以及）在缺氧（心脏骤停）和肌肉收缩（电刺激）时，[HO]升高诱导钙积累。通过对年轻C57BL/6J雄性小鼠的TA进行生物成像，在四种条件下解析了胞质HO（HyPer7）和钙（Fura-2）的动力学：）外源性HO升高；）心脏骤停；）单次抽搐（1 Hz，60秒）收缩；以及）强直（30秒）收缩。外源性HO（0.1 - 100 mM）诱导[HO]呈浓度依赖性增加（0.1 mM时增加55%；100 mM时增加280%）以及[Ca]增加（1.0 mM时增加3%；10 mM时增加8%）。丹曲林对RyR1的药理抑制作用可抑制这种[Ca]的增加。心脏骤停诱导的缺氧在心脏骤停后50分钟使[HO]增加33%，[Ca]增加20%。与外源性1.0 mM HO条件相比，强直肌肉收缩后的[HO]升高不到十分之一，而[Ca]则高出4.7倍。总之，[HO]水平的大幅升高仅通过其对肌浆网RyR1的作用引起适度的钙积累。另一方面，与心脏骤停继发的缺氧相反，肌肉收缩引起的[HO]升高较小，这表明HO的产生不太可能是驱动肌肉收缩尤其是强直收缩后显著钙积累的主要因素。我们建立了一个体内小鼠心肌细胞HO成像模型，用于研究外源性HO加载、心脏骤停诱导的缺血缺氧和肌肉收缩过程。在本研究中，揭示了肌肉收缩和缺氧条件下胞质HO水平与钙稳态之间的相互关系。这些结果有助于阐明肌肉疲劳和运动适应的机制。
