Platelet storage lesion and apoptosis: are they related?

The relationship between the platelet storage lesion (PSL) and programmed cell death (apoptosis) is poorly understood. Nevertheless, there is some experimental evidence that platelets contain most of the components of the apoptosis machinery and both the apoptotic process and the PSL lead to platelet activation and microvesiculation with expression of phosphatidyl serine (PS) on the outer layer of cell membrane, a hallmark of all nucleated cells. The PS exposure is believed to contribute to the development of inflammatory or immunomodulation process, to the regulation of haemostatic balance and the ultimate clearance of dead or fragmented cells from the circulation. While there is no doubt that apoptosis, as a form of genetically encoded programmed cell death in nucleated cells, is triggered by several signalling stimuli at the nuclear level, there is some doubt as to whether platelets, as enucleated cells have retained the memory of the "parental" megakaryocytes for apoptosis or whether platelet mitochondrial DNA has a major role in both the apoptotic process and the PSL. The storage lesion occurs during processing and storage subsequent to mechanical trauma, hypoxic conditions or exposure to cold. In this brief report some observational evidence is provided in support of the notion that the PSL and apoptosis may be related to each other, despite the fact that, in contrast to the 'parental' megakarocyte, the platelets appear to survive upon stimulation with a high concentration of protein kinase inhibitors such as staurosporine (STS), in the presence of cycloheximide (CHX) which inhibit protein synthesis. This is a model which is often used to regulate the level of survival signals. The possible relevance of platelet microvesiculation to transfusion practice is briefly discussed.