Simulated microgravity hampers Notch signaling in the fight against myocardial ischemia-reperfusion injury

The gravitational field is an important determinant of cardiovascular function. Exposure to microgravity during spaceflight may lead to a series of maladaptive alterations in the cardiovascular system. The authors have previously demonstrated that microgravity can increase the susceptibility to myocardial ischemia-reperfusion (IR) injury under simulated microgravity. Although Notch1 signaling protects against myocardial IR injury, whether Notch1 protects against myocardial IR injury under simulated weightlessness remains unknown. The present study is designed to investigate the role of the Notch1 receptor in myocardial IR injury under simulated weightlessness. The differences in Notch signaling expression and myocardial infarct size following myocardial IR were compared between normal rats and tail-suspended rats that were kept in 30° head-down tilt and hindlimb unloading position. The data revealed low expression levels of Notch1 receptor and its endogenous ligand Jagged1 in normal adult rat hearts. However, significantly higher expression of Notch1 was observed in the border zone compared with the infarcted area and the remote zone following myocardial IR. Notch1 expression was notably reduced in the infarcted hearts of tail-suspended rats compared with the control group. Conversely, the myocardial infarct size was significantly increased in tail-suspended rats compared with the control rats. In conclusion, these data suggested that the proper function of Notch signaling may be hampered under simulated microgravity.