The atherosclerotic process and its consequences are considered driven by an imbalance between pro- and ant-inflammatory actions. One contributing factor in this scenario is an altered regulation of apoptosis, which affects both immune, vascular and myocardial cells. The general aim of this thesis was to measure soluble markers of apoptosis in peripheral venous blood, in various clinical stages of coronary artery disease (CAD) and to further identify possible sources with specific focus on natural killer (NK) cell apoptosis and myocardial ischemia-reperfusion (IR)-injury.

There was evidence of an increased apoptosis of NK cells, but not T cells, in the circulation of CAD patients. Spontaneous NK cell apoptosis and the cells´ sensitivity to oxidative stress in the form of oxidized lipids ex vivo, were increased. Findings were thus suggestive of an enhanced apoptosis contributing to the reduced NK cell activity seen in CAD. However, we could not verify that oxidative stress in the circulation was a driving force behind this loss.

Soluble forms of the cell surface bound receptors of apoptosis include soluble (s) Fas and sFas ligand (L). They are detected in plasma and used as surrogate markers of apoptosis. Here we investigated the relationship between these markers and NK cell apoptosis and NK cell levels, in a 12 month longitudinal study on CAD patients. Plasma levels of sFasL correlated with increased susceptibility to NK cell apoptosis ex vivo but also with the levels of NK cells in the circulation after a coronary event. NK cells undergoing apoptosis ex vivo were also found to be a major source of sFasL themselves, indicating potential usefulness of sFasL in monitoring changes in NK cell levels.

Apoptosis is suggested to be a key event in IR-injury, resulting in increased infarct size, left ventricular (LV) dysfunction, remodeling and heart failure. We investigated soluble markers of apoptosis in relation to these parameters in a ST-elevation myocardial infarction (STEMI) population. In addition to sFas and sFasL, we also measured tumor necrosis factor (TNF) receptor (R) I and II in this study. Acute phase levels of sTNFRI and sTNFRII, but not sFas or sFasL, correlated to cardiac MR (CMR) measures of infarct size and LV-dysfunction at 4 months after the ischemic event. Also, the soluble markers of apoptosis were correlated with matrix metalloproteinase (MMP)-2, a mechanistic trigger for cardiomyocyte apoptosis, further strengthening the role of apoptosis in IR-injury.

Finally we explored the temporal patterns of soluble markers of apoptosis after an MI and, furthermore, investigated possible differences between patients presenting with a non(N)-STEMI versus STEMI. The sTNFRI/II and the sFas/sFasL pathways of apoptosis showed different temporal changes indicating diverse roles of these two systems. NSTEMI and STEMI patients however, shared these temporal patterns pointing to apoptosis as equally involved in either infarct type. Furthermore sTNFRs, but not sFas/sFasL correlated to levels of cytokine interleukin (IL)-6 illustrating the overlapping role TNF signaling in inflammation and apoptosis, while again suggesting differences between the TNF and the Fas/FasL systems during myocardial IR--‐injury.