Biomechanical stress in myocardial infarctions: can endothelin-1 and growth differentiation factor 15 serve as immunohistochemical markers?

Myocardial infarctions go along with biomechanical stress, i.e. stretching of muscle fibres, and the expression of certain marker molecules. We tested if two of those markers, endothelin-1 (ET-1) and growth differentiation factor 15 (GDF-15), can be used as immunohistochemical markers for myocardial ischaemia/infarctions. The study included experiments with an animal model, the isolated perfused Langendorff heart, as well as the investigation of human tissue samples drawn during autopsies. The overall picture of our results showed that GDF-15 is very sensitive and expressed very fast, not only as a consequence of ischaemia/infarctions, but also under other circumstances. Even an expression only caused by agony had to be discussed. ET-1, on the other hand, was less sensitive but only positive in those human cases with ischaemia/infarction that also showed typical alterations in conventional histology. Therefore, both markers did not proof to be a suitable diagnostic tool for myocardial infarctions. However, positive staining for ET-1 was also seen in rats' hearts that suffered from arrhythmias after electric shock and in the myocardium of the right ventricle in human control cases in which a right heart failure has to be discussed. Thus, especially ET-1 should be subject of further studies that focus on these pathologies.

Dityrosine as a marker of acute myocardial infarction? Experiments with the isolated Langendorff heart.

The isolated Langendorff heart was used to evaluate dityrosine as a marker of acute myocardial infarctions. The animal model allowed the generation of local infarctions with defined survival times, as well as infarctions with and without reperfusion. The results showed that dityrosine, at least under the conditions of the animal model, occurs very shortly after early ischemia and infarctions, since positive staining results were already obtained after a survival time of only 5 min. Furthermore, it could be proved that the occurrence of dityrosine does not depend on a reperfusion of the ischemic muscle area and that there are no differences in the staining patterns of infarctions with and without reperfusion. Positive staining results for dityrosine in control hearts without infarctions had to be considered when evaluating the tissue samples of the study hearts. In part, the positive staining results of the control hearts seemed to be an artefact of the Langendorff system, easily identifiable by a distinctive staining pattern. Positive staining results in tissue samples of hearts that suffered from arrhythmia on the other hand implied that the occurrence of dityrosine is not specific for myocardial infarctions. Taking into account the results of previous works on human tissue samples, however, these findings did not question the use of dityrosine as a diagnostic tool; they simply showed that myocardial damage due to oxidative stress might occur under various pathologic conditions.

Impact of shed blood products on stimulated cytokine release in an in vitro model of transfusion.

BACKGROUND: Blood transfusion is reported to suppress the recipient's immune system. To avoid allogenic transfusion, post-operative shed blood retransfusion is a commonly used method. The aim of this study was to investigate the dose-related impact of post-operatively collected shed blood products on the stimulated cytokine release in an in vitro model of transfusion. METHODS: Venous blood samples obtained from 20 patients undergoing hip arthroplasty were mixed with post-operatively collected unprocessed, processed, and irradiated shed blood as well as normal saline as a control. Shed blood was processed by centrifugation and separating the cellular fraction from the soluble fraction and washing the cellular fraction with phosphate buffered saline to eliminate any cell fragments and other substances. Mixing ratios were 1:3, 1:1, and 3:1. Endotoxin-stimulated release of Tumor Necrosis Factor-alpha (TNF-α) was measured after 24 h of culture by enzyme-linked immunosorbent assay. RESULTS: Unprocessed, irradiated shed blood and the soluble fraction caused a significant suppression of stimulated TNF-α release compared to control. The addition of the cellular shed blood fraction had no significant influence on the TNF-α release compared to control. CONCLUSION: Shed blood and its components caused a dose-independent immunomodulation as indicated by a suppressed stimulated TNF-α release. Leukocytes seem to play a minor role, as we observed a sustained suppression after transfusion of γ-irradiated shed blood. Only the elimination of soluble factors by centrifugation and followed by an additional washing step prevented the observed suppression of TNF-α. Thus, we assume that washing of shed blood can prevent potential detrimental effects.