Background: Coronary heart disease (CHD) is a leading cause of death worldwide. Myocardial ischemia/reperfusion (I/R) injury is a clinical manifestation of CHD. Timely reperfusion of coronary vessels in an ischemic injury is essential to limit the infarct size. However, reperfusion itself can induce cardiac cell death, and lead to increased adverse remodeling after an I/R injury. Previously, our lab has shown that pretreatment with ubiquitin (UB; a highly evolutionarily conserved protein) decreases inflammatory response and preserves heart function 3 days post-I/R. The objective of this study is to investigate the long-term cardioprotective potential of UB post-I/R. To enhance the clinical relevance, UB treatment was started at the time of reperfusion. It is hypothesized that UB treatment has long-term cardioprotective potential, improves cardiac function, and attenuates cardiac remodeling post injury.
Methods: C57BL/6 male mice underwent ligation of the left anterior descending coronary artery (LCA) for 45 min. Mice were then treated with UB (1 µg/g body weight, i.p. injection) or saline at time of reperfusion of LCA. Sham animals underwent the same surgery without the ligation of LCA. Mice were treated with UB or saline twice/day (i.p. injections) for 3 days followed by treatment with UB (1 μg/g/h) or saline using micro-osmotic pumps for 28 days. Heart function was measured at 3, 7, 14 and 28 days post-I/R using echocardiography. Mice were sacrificed at 28 days post-I/R. Left ventricular (LV) tissue was used to measure remodeling parameters and serum samples were used to measure a panel of 23 cytokines/chemokines using multiplex assay.
Results: I/R+saline group exhibited a significant reduction in heart function as observed by decreased percent fractional shortening (%FS) and percent ejection fraction (%EF) vs sham (plt;0.05) at 3, 7, 14 and 28 days post-I/R. However, I/R+UB group showed significantly higher %FS and %EF vs I/R+saline (plt;0.05) throughout the observation period. Increases in fibrosis (measured by trichrome staining), myocyte apoptosis (measured using TUNEL assay), and hypertrophy (measured using WGA staining) were significantly lower in I/R+UB vs I/R+saline (plt;0.05). Expression of MMP-2 and TIMP-4 was lower, while expression of MMP-9 (active) was significantly higher in I/R+UB vs I/R+saline (plt;0.05). Serum levels of IL-6, IL-2 and G-CSF were significantly lower in I/R+UB vs I/R+saline (plt;0.05).
Conclusion: Post-ischemic UB treatment improves heart function, and associates with decreased myocardial remodeling parameters (fibrosis, apoptosis, and hypertrophy) as well as decreased serum cytokines/chemokines levels.
This work is supported by National Institutes of Health (Grant numbers HL141947and HL156214) and a Merit Review award (number BX004045) from the Biomedical Laboratory Research and Development Service of the VA Office of Research and Development.
