PACAP-38 in Acute ST-Segment Elevation Myocardial Infarction in Humans and Pigs: A Translational Study

Abstract

Acute myocardial infarction (MI) is one of the most common causes of death worldwide. Pituitary adenylate cyclase activating polypeptide (PACAP) is a cardioprotective neuropeptide expressing its receptors in the cardiovascular system. The aim of our study was to examine tissue PACAP-38 in a translational porcine MI model and plasma PACAP-38 levels in patients with ST-segment elevation myocardial infarction (STEMI). Significantly lower PACAP-38 levels were detected in the non-ischemic region of the left ventricle (LV) in MI heart compared to the ischemic region of MI-LV and also to the Sham-operated LV in porcine MI model. In STEMI patients, plasma PACAP-38 level was significantly higher before percutaneous coronary intervention (PCI) compared to controls, and decreased after PCI. Significant negative correlation was found between plasma PACAP-38 and troponin levels. Furthermore, a significant effect was revealed between plasma PACAP-38, hypertension and HbA1c levels. This was the first study showing significant changes in cardiac tissue PACAP levels in a porcine MI model and plasma PACAP levels in STEMI patients. These results suggest that PACAP, due to its cardioprotective effects, may play a regulatory role in MI and could be a potential biomarker or drug target in MI.

Keywords: ELISA; STEMI; acute myocardial infarction; cardioprotection; closed-chest myocardial infarction model; pituitary adenylate cyclase activating polypeptide; prognostic factor.

Figure 1

PACAP-38 levels of the different heart chambers (LV: left ventricle, LA: left atrium, RA: right atrium). In healthy, Sham-operated animals PACAP-38 level of the left ventricle (LV) was significantly higher than in left (LA) or in right atrium (RA). Data are expressed in ratio of Sham-LV PACAP-38 levels. The boxes show the interquartile ranges, and the whiskers indicate the most extreme observations. The middle line within the boxes represents the median value. Individual values are presented as black dots and squares. One-way ANOVA with Tukey post-hoc, ** p < 0.001 vs. Sham-LV group. n = 7–8.

Figure 2

Differences between the tissue PACAP-38 levels in left ventricle in Sham-operated animals (Sham) and after myocardial infarction (MI) with time matched three-hour reperfusion. PACAP-38 level was significantly reduced in the non-ischemic left ventricular samples of MI hearts compared to the ischemic LV samples and also to the Sham hearts. Data are expressed in ratio of Sham-LV PACAP-38 level. The boxes show the interquartile ranges, and the whiskers indicate the most extreme observations. The middle line within the boxes represents the median values. Individual values are presented as black dots and squares. One-way ANOVA with Tukey’s post hoc test, * p < 0.05, ** p < 0.001 vs. Sham group. n = 7 (From each animal, two determinations were performed from 2 different region of the left ventricle (in case MI-LV: ischemic (MI-LV-I) and non-ischemic region (MI-LV-NI)/heart, in case Sham-LV: 2 regions equivalent to the MI-LV-I and MI-LV-NI regions/heart).

Figure 3

Comparison of the tissue PACAP-38 levels between different heart chambers and regions 3 h (A) or 72 h (B) after myocardial infarction (MI). PACAP-38 level was decreased in the non-ischemic region of the left ventricle (LV-NI) compared to the left ventricle ischemic region (LV-I) at 3 h after myocardial infarction (A). Significantly lower PACAP-38 levels were detected both in right atrium (RA) and left atrium (LA) compared to the ischemic LV region. Similar expression pattern was detected 72 h after myocardial infarction (B). The boxes show the interquartile ranges, and the whiskers indicate the most extreme observations. The middle line within the boxes represents the median values. Individual values are presented as black dots and squares. One-way ANOVA with Tukey post-hoc, * p < 0.05, ** p < 0.001 versus LV-I groups. n = 7–8.

Figure 4

Differences between the tissue PACAP-38 levels of the Sham-operated (Sham), myocardial infarction (MI) alone and combined with ischemic conditioning methods: ischemic preconditioning (IPreC); ischemic postconditioning (IPostC); remote ischemic conditioning (RIC). There was no significant difference in PACAP-38 level in the ischemic zone of left ventricle between groups. The boxes show the interquartile ranges, and the whiskers indicate the most extreme observations. The middle line within the boxes represents the median values. Individual values are presented as black dots and squares. One-way ANOVA with Bonferroni’s post-hoc test. n = 4–8.

Figure 5

Changes of plasma PACAP levels in STEMI patient after PCI and in healthy control group. The solid bars represent medians of 16 patients and 12 controls. The boxes show the interquartile ranges, and the whiskers indicate the 10th and 90th percentile, outliers are also plotted with dots, rhombus and triangles. The middle line within the boxes represents the mean values. Wilcoxon Rank-Sum Test was used, statistically significant differences with p-values of ** < 0.001 and * < 0.05 are indicated.

Figure 6

Correlation between PACAP and troponin levels in STEMI patients.

Figure 7

Connection between the additive impacting effect of hypertension and HbA1c and PACAP levels in MI patients.

Figure 8

Groups of our clinically relevant, closed-chest porcine model of reperfused acute myocardial infarction. Sham: Sham-operated group; MI-3 h: myocardial infarction group with 3-h reperfusion; MI-72 h: myocardial infarction group with 72-h reperfusion; IPreC: ischemic preconditioning group; IPostC: ischemic postconditioning group; RIC: remote ischemic conditioning group.

Figure 9

Human study protocol. STEMI: ST-elevation myocardial infarction, ECG: electrocardiography, lab.: laboratory examinations, hs-cTn: hypersensitive cardiac troponin.