Calpain activation mediates microgravity-induced myocardial abnormalities in mice via p38 and ERK1/2 MAPK pathways

Liwen Liang,Huili Li,Ting Cao,Lina Qu,Lulu Zhang,Guo-Chang Fan,Peter A Greer,Jianmin Li,Douglas L Jones,Tianqing Peng

doi:10.1074/jbc.ra119.011890

Abstract

The human cardiovascular system has adapted to function optimally in Earth's 1G gravity, and microgravity conditions cause myocardial abnormalities, including atrophy and dysfunction. However, the underlying mechanisms linking microgravity and cardiac anomalies are incompletely understood. In this study, we investigated whether and how calpain activation promotes myocardial abnormalities under simulated microgravity conditions. Simulated microgravity was induced by tail suspension in mice with cardiomyocyte-specific deletion of Capns1, which disrupts activity and stability of calpain-1 and calpain-2, and their WT littermates. Tail suspension time-dependently reduced cardiomyocyte size, heart weight, and myocardial function in WT mice, and these changes were accompanied by calpain activation, NADPH oxidase activation, and oxidative stress in heart tissues. The effects of tail suspension were attenuated by deletion of Capns1. Notably, the protective effects of Capns1 deletion were associated with the prevention of phosphorylation of Ser-345 on p47phox and attenuation of ERK1/2 and p38 activation in hearts of tail-suspended mice. Using a rotary cell culture system, we simulated microgravity in cultured neonatal mouse cardiomyocytes and observed decreased total protein/DNA ratio and induced calpain activation, phosphorylation of Ser-345 on p47phox, and activation of ERK1/2 and p38, all of which were prevented by calpain inhibitor-III. Furthermore, inhibition of ERK1/2 or p38 attenuated phosphorylation of Ser-345 on p47phox in cardiomyocytes under simulated microgravity. This study demonstrates for the first time that calpain promotes NADPH oxidase activation and myocardial abnormalities under microgravity by facilitating p47phox phosphorylation via ERK1/2 and p38 pathways. Thus, calpain inhibition may be an effective therapeutic approach to reduce microgravity-induced myocardial abnormalities.

Highlights

The human cardiovascular system has adapted to function optimally in Earth’s 1G gravity, and microgravity conditions cause myocardial abnormalities, including atrophy and dysfunction
Inhibition of ERK1/2 with PD98059 did not affect the phosphorylated levels of p38 in cardiomyocytes following simulated microgravity (Fig. 7C), suggesting that ERK1/2 and p38 independently facilitate p47phox phosphorylation in microgravity, whereas ERK1/2 and p38 exert their roles at early and relatively late phases of microgravity, respectively. In support of this conclusion, co-incubation of PD98059 and SB20358 did not further inhibit p47phox phosphorylation in microgravity compared with PD98059 or SB203580 alone (Fig. S5). These results suggest that calpain activation mediates microgravityinduced phosphorylation of Ser-345 on p47phox through p38 and ERK1/2 signaling in cardiomyocytes
The major findings of this study are that disruption of calpain preserves cardiomyocyte size, heart mass, and myocardial function in tail-suspended mice, indicating an important role of calpain in myocardial atrophy under microgravity

Summary

Introduction

The human cardiovascular system has adapted to function optimally in Earth’s 1G gravity, and microgravity conditions cause myocardial abnormalities, including atrophy and dysfunction. Tail suspension time-dependently induces calpain activation, reduces cardiomyocyte size and heart weight, and promotes myocardial dysfunction in mice Our recent study reported that simulated microgravity induced NADPH oxidase activation in tail-suspended mouse hearts [30].

Results

Conclusion