Abstract 15623: A Novel Protective Role of Nicotinamide Phosphoribosyltransferase Against Mouse Myocardial Ischemia/ Reperfusion Injury
Rationale: Our previous study identified a SNP (-1535C to T) in the promoter of human nicotinamide phophoribosyltranssferase (NAMPT) gene which alters the transcriptional activity. Subsequent epidemiological surveys found that this SNP is associated with higher HDL cholesterol, lower triglyceride level and lower risk to CAD. This study aims to elucidate the underlying mechanism by investigating the role of NAMPT in mouse myocardial ischemia/ reperfusion injury (IRI) of either wild type (Nampt+/+) or Nampt deficient type (Nampt+/-) mice prepared in our previous study to validate NAMPT as a new risk factor and a potential therapeutic target in CAD.
Methods: Male C57BL/6J Nampt+/+ and Nampt+/- mice, 10 week-old, were subjected to either sham operation or myocardial ischemia by a 40 min occlusion of the left anterior descending coronary artery followed by 3 h reperfusion. After which mice were sacrificed and their hearts were harvested for further analyses including assessing infarct size and area at risk, assaying apoptosis and profiling their transcriptomes by RNA-seq using Illumina's HiSeq1000 next generation DNA sequencing instrument. One of upregulated genes in IRI Nampt+/- mice, small nucleolar RNA 33 (snoRA33), was further investigated for its role in NAMPT mediated protection against myocardial IRI.
Results: The size of myocardial infarction/area at risk was significantly smaller in wild type (Nampt+/+) mice than in Nampt +/- mice (24.51 ± 3.22 % vs. 52.29 ± 8.76 %, n=6 animals/group, p<0.01). TUNEL assay detected less severe apoptosis in IRI Nampt+/+ mouse hearts than those of Nampt+/- mice. RNA-seq revealed that one of upregulated genes, snoRA33, was not detected in either sham-operated mouse hearts nor IRI Nampt+/+ mouse hearts but highly expressed in IRI Nampt+/- mouse hearts. In vitro "gain of function" experiments demonstrated that overexpression of snoRA33 significantly increased cell apoptosis.
Conclusion: NAMPT protects against mouse heart IRI by attenuating myocardial apoptosis, in part by inhibiting snoRA33 expression, which is a newly identified novel mechanism.
Funded By: NHLBI/NIH Grant (5RO1HL080042-04 & 3RO1 HL080042-04S1, Ye, SQ) and start-up fund of Children's Mercy Hospitals and Clinics, UMKC(Ye, SQ).
- © 2012 by American Heart Association, Inc.