Abstract 14052: miR-223 Attenuates Cardiac Dysfunction in Polymicrobial Sepsis Through Inhibition of Sema3a Expression
Background: The occurrence of cardiovascular dysfunction in sepsis is associated with a significantly increased mortality rate of 70% to 90% compared with 20% in septic patients without cardiovascular impairment. Recent work has implicated microRNAs (miRs) in sepsis-associated inflammatory response, however, whether miRs are dys-regulated in septic hearts and their potential role remain elusive.
Methods and Results: Male C57BL/6 mice (10-wk old) underwent cecal ligation and puncture (CLP) to induce sepsis. Six hours later, CLP-hearts and sham-operated mouse hearts were collected for isolation of total RNA to perform miR array analysis. Among 13 miRs dys-regulated in CLP-hearts, miR-223 was most significantly downregulated, which was further validated by stem-loop RT-PCR (n=6, p<0.001). To test whether a drop of miR-223 plays a role in sepsis-induced cardiac dysfunction, we first knocked down of miR-223 in cultured adult rat cardiomyocytes by adenoviral vector containing shRNA, followed by endotoxin (LPS, 1 μg/ml) treatment overnight. Myocyte contraction was measured by a video edge motion detector, and revealed that knockdown of miR-223 greatly decreased the fractional shortening (FS%: by 28%), the maximal rates of contraction (+dL/dt: by 21%) and relaxation (–dL/dt: by 19%), compared with control cells. Conversely, adenovirus-mediated overexpression of miR-223 remarkably attenuated LPS-induced detrimental effects on myocyte contractility. Using a transgenic (TG) mouse model with cardiac-specific overexpression of miR-223 (11-fold), we observed that CLP-triggered depression in left ventricle ejection fraction (LVEF) was markedly reduced in miR-223-TG hearts (decreased by 17%, n=10), compared to non-TG controls (decreased by 42%, n=11), assessed by echocardiography. Using target prediction software, Western-blotting and luciferase reporter assay, we identified Sema3a, a protein known to regulate myocardial contraction, as a bona fide target of miR-223 in the heart.
Conclusions: These results indicate that elevation of miR-223 protects hearts against myocardial depression in sepsis via antithetical regulation of Sema3a.
- © 2013 by American Heart Association, Inc.