Ang-(1-7) offers cytoprotection against ischemia-reperfusion injury by restoring intracellular calcium homeostasis

Accumulating evidence indicates that angiotensin-(1-7) [Ang-(1-7)] offers protective effects against ischemia-reperfusion (I/R) induced arrhythmias and contractile dysfunction, which are related to disturbances of intracellular calcium homeostasis. However, whether or not Ang-(1-7) regulates intracellular calcium in I/R is not clear. To shed light on this issue, we carried out studies with a cellular model of simulated I/R in isolated rat ventricular myocytes and measured calcium transients using laser scanning confocal microscopy. Our results showed that Ang-(1-7) had no effects on the calcium transient in myocytes superfused with normal solution; however, in myocytes of simulated I/R, Ang-(1-7) significantly attenuated the increased diastolic intracellular Ca during reperfusion, restored the decreased peak Ca of calcium transient during ischemia, and reversed the decreased amplitude of calcium transient throughout the I/R periods. Additionally, Ang-(1-7) significantly suppressed the reactive oxygen species production in I/R, especially during the ischemic phase. These data indicated that Ang-(1-7) affords significant cytoprotective effects through directly improving calcium homeostasis independent of its anti-oxidative action. Most notably, the effects of Ang-(1-7) on intracellular Ca dynamics manifests only in the diseased states, that is, I/R. This unique property suggests that upregulation of Ang-(1-7) expression and/or activation of the Ang-(1-7)/Mas signaling cascade is a highly desirable strategy for the treatment of myocardial impairment induced by I/R.