No abstract

Circulating levels of C-reactive protein (CRP) constitute a cardiovascular risk marker. Immunohistochemical studies have revealed co-localization of CRP and activated complement in human infarcted myocardium suggesting CRP to enhance inflammation in ischemic myocardium by inducing local complement activation. The aim was to establish whether CRP activates complement in infarcted human myocardium and to assess the relationship between this activation and the duration of infarction. Myocardial tissue samples from 56 patients that had died from acute myocardial infarction were evaluated. Specimens were taken from infarcted as well as noninfarcted sites of the heart. CRP-mediated complement activation was assessed by immunohistochemistry and by measuring levels of complement, CRP, and CRP-complement complexes, specific markers for CRP-mediated activation, in homogenates of the heart. Infarctions of 12 hours to 5 days had significantly more extensive depositions of complement and CRP and contained significantly more CRP, activated complement, and CRPcomplement complexes than infarctions that were less than 12 hours old. Levels of CRP complexes correlated significantly with CRP and complement con- Circulating levels of the acute phase reactant C-reactive protein (CRP) constitute a cardiovascular risk factor: levels in healthy persons or patients with stable or unstable angina pectoris are associated with an increased incidence of cardiovascular events. [1][2][3] In addition, the course of CRP after acute myocardial infarction (AMI) is associated with the development of complications and with outcome. 4,5 These associations between CRP and cardiovascular events are considered to reflect that CRP, by virtue of its acute phase behavior, is an indirect parameter for the degree of inflammation ensuing in atherosclerotic lesions or in the infarcted myocardium. However, we have shown that CRP localizes in infarcted human myocardium, similarly as has been reported in a rabbit model for AMI. 6,7 This raises the possibility that CRP participates in the inflammatory changes locally ensuing in the infarcted myocardium. As a matter of fact CRP is able to activate complement via the classical pathway, implying that CRP may enhance inflammation by activating complement. 8 -10 Indeed, Griselli and coworkers 11 have demonstrated in a rat model that human CRP enhances myocardial infarct size by activating complement. Immunohistochemical co-localization of CRP and activated complement in myocardial tissue of patients with AMI suggests a similar proinflammatory role for CRP in human myocardial infarction.7 However, co-localization of CRP and activated complement does not definitely prove that CRP indeed activates complement locally in infarcted myocardium.In the present study we sought for evidence that CRP activates complement in human myocardial infarction, and determined the relationship between such activation and the duration of infarction. Myocardial tissue specimens were obtained from patients who had died from AMI. These specime...

Objective-Advanced glycation end products (AGEs), such as N -(carboxymethyl)lysine (CML), are implicated in vascular disease. We previously reported increased CML accumulation in small intramyocardial blood vessels in diabetes patients. Diabetes patients have an increased risk for acute myocardial infarction (AMI). Here, we examined a putative relationship between CML and AMI. Methods and Results-Heart tissue was stained for CML, myeloperoxidase, and E-selectin in AMI patients (nϭ26), myocarditis patients (nϭ17), and control patients (nϭ15). In AMI patients, CML depositions were 3-fold increased compared with controls in the small intramyocardial blood vessels and predominantly colocalized with activated endothelium (E-selectin-positive) both in infarction and noninfarction areas. A trend of increased CML positivity of the intima of epicardial coronary arteries did not reach significance in AMI patients. In the rat heart AMI model, CML depositions were undetectable after 24 hours of reperfusion, but became clearly visible after 5 days of reperfusion. In line with an inflammatory contribution, human myocarditis was also accompanied by accumulation of CML on the endothelium of intramyocardial blood vessels. Conclusions-CML, present predominantly on activated endothelium in small intramyocardial blood vessels in patients with AMI, might reflect an increased risk for AMI rather than being a result of AMI.

Type II secretory phospholipase A2 (sPLA2) is a cardiovascular risk factor. We recently found depositions of sPLA2 in the necrotic center of infarcted human myocardium and normally appearing cardiomyocytes adjacent to the border zone. The consequences of binding of sPLA2 to ischemic cardiomyocytes are not known. To explore a potential effect of sPLA2 on ischemic cardiomyocytes at a cellular level we used an in vitro model. The cardiomyocyte cell line H9c2 or adult cardiomyocytes were isolated from rabbits that were incubated with sPLA2 in the presence of metabolic inhibitors to mimic ischemia-reperfusion conditions. Cell viability was established with the use of annexin V and propidium iodide or 7-aminoactinomycin D. Metabolic inhibition induced an increase of the number of flip-flopped cells, including a population that did not stain with propidium iodide and that was caspase-3 negative. sPLA2 bound to the flip-flopped cells, including those negative for caspase-3. sPLA2 binding induced cell death in these latter cells. In addition, sPLA2 potentiated the binding of C-reactive protein (CRP) to these cells. We conclude that by binding to flip-flopped cardiomyocytes, including those that are caspase-3 negative and presumably reversibly injured, sPLA2 may induce cell death and tag these cells with CRP.