Apoptotic markers are increased in platelets stored at 37 degrees C.
BACKGROUND
PLTs for transfusion lose viability during storage in blood banking. This loss of viability is accelerated at 37 degrees C, as is the risk of bacterial contamination, and has led to the selection of 22 degrees C as the routine storage temperature. Because PLTs contain an intact apoptotic mechanism, we sought to determine whether PLTs undergo apoptosis during storage and whether storage at 37 degrees C accelerated this process.


METHODS
PLT-rich plasma from PLT concentrates was stored at 37 or 22 degrees C in small aliquots or whole bags, with and without cell-permeable caspase inhibitors. Number of PLTs, pH, LDH level, and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium activity were analyzed over time. PLT lysates were prepared and tested for the presence and activation of apoptotic proteins by enzyme assay and Western blotting.


RESULTS
PLT viability was greatly reduced after 1 to 2 days of storage at 37 degrees C; however, signs of apoptosis were evident by 3 hours after temperature shift. In temperature-stressed PLTs only, a gradual rise in caspase-3 activity was detected that correlated with the appearance of the 17- to 20-kDa cleavage products of caspase-3. Gelsolin, a caspase-3 substrate, underwent cleavage within the same time frame. Bcl-xL and caspase-2 also declined significantly; caspase-9 activity rose. Specific caspase inhibitors could prevent caspase activation but did not improve PLT cellular viability at 37 degrees C.


CONCLUSIONS
PLTs contain apoptotic proteins that are activated during PLT storage at 37 degrees C and may account for the rapid decline in PLT cellular viability. Although ineffective here, inhibition of PLT apoptosis may improve PLT cellular viability.
Bertino
A M
AM
Department of Medicine, Division of Hematology and Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Qi
X Q
XQ
Li
J
J
Xia
Y
Y
Kuter
D J
DJ
D017209:Apoptosis; D015415:Biomarkers / Q000097:blood*; D001792:Blood Platelets / Q000166:cytology*; D001793:Blood Preservation / Q000379:methods*; D053143:Caspase 2; D053148:Caspase 3; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000097:blood; D002470:Cell Survival; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018260:Gelsolin / Q000378:metabolism; D006801:Humans; D017713:Platelet Transfusion; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000097:blood; D013696:Temperature; D013997:Time Factors; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; D015415:Biomarkers; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D018260:Gelsolin; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053143:Caspase 2; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases