Angiotensin II receptor blocker reverses heart failure by attenuating local oxidative stress and preserving resident stem cells in rats with myocardial infarction

The present study aimed to test whether angiotensin receptor blockers (ARBs) are cardioprotective after myocardial infarction (MI) by preventing augmented local renin-angiotensin-system (RAS)-induced oxidative stress injury and senescence, preserving resident stem cells, and restoring the insulin-like growth factor (IGF-1)/IGF-1 receptor (IGF-R) pathway. Sprague-Dawley rats with ligated or unligated coronary arteries were treated with losartan (20 mg/kg/d) or vehicle for 3 or 9 weeks. Heart function and molecular and histological changes were assessed. It was found MI induced left ventricular dysfunction and remodeling, increased levels of the oxidative stress marker 8-hydroxy-2’-deoxyguanosine and cell senescence marker p16ink4a , and downregulated the IGF-1/IGF-1R/Akt path- way after both 3 and 9 weeks post-MI. MI induced an increase in stem cells identified by immunostaining for c-kit and Wilms’ tumor-1 predominantly after 3 weeks. Losartan significantly inhibited local cardiac RAS activation and improved left ventricular function and remodeling at both timepoints. Losartan also preserved c-kit- and Wilms’ tumor-1-positive cells (particularly at 3 weeks), attenuated 8-hydroxy-2’-deoxyguanosine- and p16ink4a -positive car- diomyocytes, and restored the IGF-1/IGF-1R/Akt pathway at both 3 and 9 weeks. In conclusion, ARBs aided cardiac repair post-MI through short-term preservation of stem cells and persistent anti-oxidative stress and anti-senes- cence effects, partially by attenuating activation of cardiac RAS and restoring the local IGF-1/IGF-1R/Akt pathway.