Journal of Life Science (생명과학회지)

Korean Society of Life Science (한국생명과학회)
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Ethanol Extract of Mori Folium Inhibits AICAR-induced Muscle Atrophy Through Inactivation of AMPK in C2C12 Myotubes

C2C12 근관세포에서 상엽에 의한 AMPK의 불활성화와 AICAR로 유도된 근위축 억제의 연관성에 관한 연구

  • Lee, Yu Sung (Department of Horticultural Biotechnology, College of Life Sciences, Kyunghee University) ;
  • Kim, Hong Jae (Open Laboratory for Muscular & Skeletal Disease Control and Department of Biochemistry, Dongeui University College of Korean Medicine) ;
  • Jeong, Jin-Woo (Freshwater Bioresources Utilization Bureau, Nakdonggang National Institute of Biological Resources) ;
  • Han, Min-Ho (Team of Marine Bio-Resources, National Marine Biodiversity Institute of Korea) ;
  • Hong, Su Hyun (Open Laboratory for Muscular & Skeletal Disease Control and Department of Biochemistry, Dongeui University College of Korean Medicine) ;
  • Choi, Yung Hyun (Open Laboratory for Muscular & Skeletal Disease Control and Department of Biochemistry, Dongeui University College of Korean Medicine) ;
  • Park, Cheol (Department of Molecular Biology, College of Natural Sciences, Dongeui University)
  • 이유성 (경희대학교 생명과학대학 원예생명공학과) ;
  • 김홍재 (동의대학교 한의과대학 생화학교실 및 근.골격계 질환제어 융합연구실) ;
  • 정진우 (낙동강생물자원관 담수생물특성연구실) ;
  • 한민호 (국립해양생물자원관 해양생명자원관리부) ;
  • 홍수현 (동의대학교 한의과대학 생화학교실 및 근.골격계 질환제어 융합연구실) ;
  • 최영현 (동의대학교 한의과대학 생화학교실 및 근.골격계 질환제어 융합연구실) ;
  • 박철 (동의대학교 자연과학대학 분자생물학과)
  • Received : 2018.02.19
  • Accepted : 2018.04.27
  • Published : 2018.04.30
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Abstract

AMP-activated protein kinase (AMPK) functions as a metabolic master through regulating and restoring cellular energy balance. In skeletal muscle, AMPK increases myofibril protein degradation through the expression of muscle-specific ubiquitin ligases. Mori Folium, the leaf of Morus alba, is a traditional medicinal herb with various pharmacological functions; however, the effects associated with muscle atrophy have not been fully identified. In this study, we confirmed the effects of AMPK activation by examining the effects of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), an activator of AMPK, on the induction of atrophy and expression of atrophy-related genes in C2C12 myotubes. We also investigated the effects of the ethanol extract of Mori Folium (EEMF) on the recovery of AICAR-induced muscle atrophy in C2C12 myotubes. It was found that exposure to AICAR resulted in the stimulation of Forkhead box O3a (FOXO3a); an up-regulation of muscle-specific ubiquitin ligases such as Muscle Atrophy F-box (MAFbx)/atrogin-1 and muscle RING finger-1 (MuRF1), and a down-regulation of muscle-specific transcription factors, such as MyoD and myogenin; with the activation of AMPK. In addition, AICAR without cytotoxicity indicated a decrease in diameter of C2C12 myotubes. However, treatment with EEMF significantly suppressed AICAR-induced muscle atrophy of C2C12 myotubes in a dose-dependent manner as confirmed by a decrease in myotube diameter, which is associated with a reversed stimulation of FOXO3a by the inhibition of AMPK activation. These results indicate that the activation of AMPK by AICAR induces muscle atrophy, and EEMF has preeminent effects on the inhibition of AICAR-induced muscle atrophy through the AMPK signaling pathway.

AMPK는 세포 내 에너지 균형을 조절하는 조절자 및 에너지 센서이며, 특히 골격근에서는 muscle-specific ubiquitin ligases의 조절을 통한 근육 단백질 분해를 증가시키는 것으로 알려져 있다. 한편 상엽은 다양한 약리학적 효능을 가지는 전통약재 중 하나이지만 근위축과 관련된 효능에 대해서는 거의 알려져 있지 않다. 본 연구에서는 C2C12 myotubes에서 AMPK 활성제인 AICAR가 유발하는 근위축 및 관련 유전자의 발현과 함께 상엽 에탄올 추출물(ethanol extracts of Mori Folium, EEMF)이 유발하는 근위축 억제 효능에 대해서 조사하였다. 먼저 C2C12 myoblasts에 AICAR를 처리하였을 경우 AMPK 활성화가 유발되었으며, 하위 단계에 있는 FoxO3a의 발현 증가와 함께 muscle-specific ubiquitin ligases인 MAFbx/atrogin-1 및 MuRF1의 발현 증가와 muscle-specific transcription factors인 MyoD 및 myogenin의 발현 감소가 유발되었다. 또한 분화가 유발된 C2C12 myotubes에 세포독성이 없는 조건의 AICAR를 처리하였을 경우 근위축이 유발되었으며, EEMF는 AMPK 불활성화 및 FoxO3a 발현 억제를 유발함으로서 AICAR 처리에 의한 근위축을 억제하는 것으로 나타났다. 본 연구 결과에서 AICAR에 의한 AMPK 활성화가 근위축을 유발한다는 것을 알 수 있었으며, EEMF는 AMPK signaling pathway를 통하여 AICAR에 의한 근위축을 억제한다는 것을 알 수 있었다.

Keywords

References

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