Arginase 1 is upregulated at admission in patients with ST-elevation myocardial infarction.

BACKGROUND: The mechanisms underlying rupture of a coronary atherosclerotic plaque and development of myocardial ischemia-reperfusion injury in ST-elevation myocardial infarction (STEMI) remain unresolved. Increased arginase 1 activity leads to reduced nitric oxide (NO) production and increased formation of reactive oxygen species due to uncoupling of the NO-producing enzyme endothelial NO synthase (eNOS). This contributes to endothelial dysfunction, plaque instability and increased susceptibility to ischemia-reperfusion injury in acute myocardial infarction. OBJECTIVE: The purpose of this study was to test the hypothesis that arginase gene and protein expression are upregulated in patients with STEMI. METHODS: Two cohorts of patients with STEMI were included. In the first cohort (n = 51), expression of arginase and NO-synthases as well as arginase 1 protein levels were determined and compared to a healthy control group (n = 45). In a second cohort (n = 68), plasma arginase 1 levels and infarct size were determined using cardiac magnetic resonance imaging. RESULTS: Expression of the gene encoding arginase 1 was significantly elevated at admission and 24-48 h after STEMI but not 3 months post STEMI, in comparison with the control group. Expression of the genes encoding arginase 2 and endothelial NO synthase (NOS3) were unaltered. Arginase 1 protein levels were elevated at admission, 24 h post STEMI and remained elevated for up to 6 months. No significant correlation between plasma arginase 1 protein levels and infarct size was observed. CONCLUSION: The markedly increased gene and protein expression of arginase 1 already at admission indicates a role of arginase 1 in the development of STEMI.