Regulation of Nrf2/Keap1 signalling in human skeletal muscle during exercise to exhaustion in normoxia, severe acute hypoxia and post-exercise ischaemia: Influence of metabolite accumulation and oxygenation

Angel Gallego-Selles,Marcos Martin-Rincon,Miriam Martinez-Canton,Mario Perez-Valera,Saúl Martín-Rodríguez,Miriam Gelabert-Rebato,Alfredo Santana,David Morales-Alamo,Cecilia Dorado,Jose A.L Calbet

doi:10.1016/j.redox.2020.101627

Angel Gallego-Selles, Marcos Martin-Rincon + Show 8 more

Open Access

https://doi.org/10.1016/j.redox.2020.101627

Copy DOI

Abstract

The Nrf2 transcription factor is induced by reactive oxygen and nitrogen species and is necessary for the adaptive response to exercise in mice. It remains unknown whether Nrf2 signalling is activated by exercise in human skeletal muscle. Here we show that Nrf2 signalling is activated by exercise to exhaustion with similar responses in normoxia (PIO2: 143 mmHg) and severe acute hypoxia (PIO2: 73 mmHg). CaMKII and AMPKα phosphorylation were similarly induced in both conditions. Enhanced Nrf2 signalling was achieved by raising Nrf2 total protein and Ser40 Nrf2 phosphorylation, accompanied by a reduction of Keap1. Keap1 protein degradation is facilitated by the phosphorylation of p62/SQSTM1 at Ser349 by AMPK, which targets Keap1 for autophagic degradation. Consequently, the Nrf2-to-Keap1 ratio was markedly elevated and closely associated with a 2-3-fold increase in Catalase protein. No relationship was observed between Nrf2 signalling and SOD1 and SOD2 protein levels. Application of ischaemia immediately at the end of exercise maintained these changes, which were reverted within 1 min of recovery with free circulation. While SOD2 did not change significantly during either exercise or ischaemia, SOD1 protein expression was marginally downregulated and upregulated during exercise in normoxia and hypoxia, respectively. We conclude that Nrf2/Keap1/Catalase pathway is rapidly regulated during exercise and recovery in human skeletal muscle. Catalase emerges as an essential antioxidant enzyme acutely upregulated during exercise and ischaemia. Post-exercise ischaemia maintains Nrf2 signalling at the level reached at exhaustion and can be used to avoid early post-exercise recovery, which is O2-dependent.

Highlights

During exercise reactive oxygen (ROS) and nitrogen species (RNS) are produced depending on the fitness level, the energy substrates oxidized and the characteristics of exercise [1,2,3,4]
In the leg recovering with free circulation, pThr287 calmodulin-dependent protein kinase II (CaMKII) levels returned to pre-exercise values 1 min after the end of the IE
This study shows that nuclear factor erythroid-derived 2-like 2 (Nrf2) signalling is activated by exercise to exhaustion in human skeletal muscle

Summary

Introduction

During exercise reactive oxygen (ROS) and nitrogen species (RNS) (collectively called RONS) are produced depending on the fitness level, the energy substrates oxidized and the characteristics of exercise [1,2,3,4]. Total Nrf protein expression has been reported to increase after 90 min of continuous running [9] and nuclear Nrf protein content after 6 h of continuous running [10]. In humans, increased, unchanged and reduced Nrf mRNA levels have been reported in skeletal muscle biopsied 3–4 h after exercise [11,12,13,14]. The changes in Nrf protein levels and associated signalling events in response to acute exercise and recovery have not been deter mined in human skeletal muscle. This is relevant because reduced Nrf expression has been associated with lower exercise performance in an imal models of chronic disease [15]

Objectives

Methods

Results

Conclusion