Atherosclerosis is characterized by a chronic inflammation, involving autoimmune components, in the arterial wall. An increase in proinflammatory activity relative to anti-inflammatory activity is considered to cause a progression of the disease towards plaque instability and risk of atherothrombotic events, such as acute coronary syndrome (ACS). Cortisol, the end product of the hypothalamus-pituitary-adrenal (HPA) axis, is a powerful endogenous anti-inflammatory mediator. Disturbances in the HPA axis have been reported in chronic inflammatory/autoimmune diseases, like rheumatoid arthritis. The aim of this thesis was to study various markers of systemic inflammation in patients with acute and stable conditions of coronary artery disease (CAD) and relate these findings to the cortisol response.
Both patients with ACS and patients with stable CAD had high levels of C-reactive protein (CRP), interleukin (IL)-6 and IL-1 receptor antagonist, compared with healthy controls. In addition, patients with stable CAD had significantly more neutrophil-platelet aggregates than controls, as a possible indicator of neutrophil activation.
The cortisol response was determined in two different cohorts of CAD patients; one consisting of patients with a first-time myocardial infarction and one consisting of patients with long-term stable CAD. From the acute phase to 3 months, the patients with a myocardial infarction showed a higher 24-h cortisol secretion and a flattened diurnal slope caused by higher cortisol levels in the evening, as compared with healthy controls. The patients with long-term stable CAD showed similarly high levels of cortisol in the evening. The levels of evening cortisol were strongly correlated with CRP and IL-6. When exposed to acute physical or acute psychological stress at 3 months, the ACS patients showed a markedly blunted cortisol response compared with healthy controls. Following the stress tests, a significant increase in CRP was observed in the patients but not in the controls, indicating a failure of the HPA axis to compensate for stress-induced inflammation in CAD.
In the ACS patients, the time course of matrix metalloproteinases (MMPs) and their tissue inhibitor TIMP-1 was determined during the 3 months follow-up. A major finding was that the MMP-9 and TIMP-1 levels remained significantly higher in the patients at all time points compared to the controls. MMP-9 and TIMP-1, but not MMP-2, MMP-3 or MMP-7, were related to inflammatory activity, as assessed by CRP and IL-6. MMP-9 and TIMP-1 showed significant correlation with evening cortisol, even after adjustment for CRP and IL-6, lending further support for a link between ´high´ flat cortisol rhythm and systemic inflammatory activity.
The activation status of neutrophils in stable CAD was further examined by measuring the expression, affinity state and signalling capacity of b2-integrins and the innate production of reactive oxygen species (ROS). However, the neutrophils in patients were not more activated in vivo than were cells in healthy controls, neither were they more prone to activation ex vivo. The data rather indicated an impaired function of neutrophils in stable CAD.
The neutrophils in CAD patients showed a significantly lower number of total glucocorticoid receptors (GRs) and a lower GRa:GRb ratio compared to healthy controls, indicating a chronic over activation of the HPA axis and, possibly, a state of glucocorticoid resistance. Moreover, the evening cortisol levels in patients were associated with an overexpression of annexin-1, the ´second messenger´ of glucocorticoid action. In contrast to neutrophils in controls, the neutrophils in patients also showed a hyper responsiveness to exogenous annexin-1 resulting in impaired neutrophil function.
To conclude, clinically stable CAD was associated with a systemic inflammatory activity, involving a high MMP-9:TIMP-1 ratio and an increased inflammatory response to acute stress but not any activation of neutrophils. This inflammatory activity was associated with a dysregulated cortisol secretion, defined by a flat diurnal rhythm and a blunted cortisol response to stress. Although the clinical relevance remains to be verified, an intriguing hypothesis is that a hyporesponsive HPA axis favours the development towards plaque instability.
Linköping: Linköping University Electronic Press , 2008. , 92 p.
2008-02-01, Berzeliussalen, Campus US, Linköpings universitet, Linköping, 13:00 (Swedish)
On the day of the defence date the title of article III was: "A sustained elevation of serum matrix metalloproteinase-9 is associated with diurnal salivary cortisol in patients with acute myocardial infarction-a 3-month follow-up".