NOD2 mediates cardiac remodeling after myocardial infarction by regulating the activity of extracellular matrix and inflammation

Abstract

Objective To investigate whether nucleotide-binding oligomerization domain containing 2 (NOD2) protein participate in the process of cardiac remodeling after myocardial infarction (MI) and the related mechanism of NOD2 regulating cardiac remodeling. Methods Mouse MI model was established by ligation of the left anterior descending coronary artery in mice. Sham operated ones underwent the same procedure but without ligation. Both infarct and remote myocardium from sham and post-MI 3, 7, 14 and 28 d were homogenized to evaluate mRNA expression of NOD2 by quantitative real-time polymerase chain reaction (qPCR), and its protein level was detected by Western blot and immunohistochemistry 28 days post-MI. To further investigate the role of NOD2 in post-MI cardiac remodeling process, NOD2 gene knockout mouse were used to establish myocardial infarction model. The experiment was divided into 4 groups: wild sham operation group, NOD2-/- knocking mouse sham operation group, wild model group and NOD2-/-knocking mouse model group. Left ventricular internal diameter and cardiac function 28 days post-MI were acquired by small animal echocardiography; Masson staining and Tunel staining were used to observe the degree of myocardial fibrosis and apoptosis after MI; the tissue proinflammatory factor levels were measured by enzyme-linked immunosorbent assay (ELISA); the protein level and activity changes of matrix metalloproteinase 9(MMP-9) of cardiac tissue lysates were detected by Western blot and gelatin zymography. The inflammatory cells infiltration after myocardial infarction and cardiac fibroblasts (cardiac fibroblast) trans-differentiation into cardiomyocytes fibroblasts were observed by immunohistochemical method. Results Compared with sham operation group, the expression of NOD2 mRNA in the non-infarct area and infarct area were all increased in MI group (P<0.05), both mRNA expression and protein expression of NOD2 in infarction area were increased most significantly. NOD2 deficiency exhibited improvements in cardiac dysfunction and remodeling after MI. Furthermore, TUNEL staining and Masson trichrome staining indicated that NOD2 deficiency protected against ischemia-induced cell death and cardiac fibrosis (both P<0.05). Also deletion of NOD2 reduced the levels of inflammatory mediators, inflammatory cell infiltration and MMP-9 activity after MI (all P<0.05). Conclusions NOD2 mediates cardiac remodeling after myocardial infarction by regulating the levels of MMP-9 protein and activity, inflammatory mediators production and inflammatory cell infiltration. Key words: Coronary artery disease; Ventricular remodeling; Nucleotide-binding oligomerization domain containing 2; Matrix metalloproteinase 9; Inflammation