PURPOSE: Shear-mediated platelet activation (SMPA) is a main driver of MCS thrombosis. A target of MCS shear, driving activation, is the platelet membrane - leading to potential alteration of biophysical properties. Here, we examined the effect of shear stress-accumulation on platelet membrane fluidity and on platelet lipid species profile - both retained (membrane) and free (ejected) post-activation. METHODS: Human gel-filtered platelets (20,000 plts/uL) were exposed to shear in a hemodynamic shearing device (70 dynes/cm2 x 10'); or to thrombin (1U/mL x 10') as a chemical agonist comparator. Membrane fluidity was determined by fluorescence anisotropy of the probe TMA-DPH (1uM, 5' @ 37C). Platelet lipids - both retained (cellular) and free (ejected) following activation - were extracted and analyzed via high resolution liquid-chromatography tandem mass spectrometry (LC-MS/MS). RESULTS: Shear stress accumulation increases platelet membrane fluidity - with a 6% increase noted even for the brief shear exposure examined. Shear stress exposure results in significant alteration of overall platelet lipid composition, with increase in supernatant lipid species relative to the non-activated samples such that 72% of identified lipid species have >2-fold increase. Lipid species altered in the supernatant of sheared platelets were unaltered under thrombin treatment. Interestingly, within the limits of our analysis, a gender-based difference in retained lipid species was seen with shear but not with thrombin activation. Male donors showed at least a 2-fold decrease in 53% of lipids identified in the pellet of the sheared platelets using negative mode MS. In contrast, female donors had only 6% of lipids decrease >2-fold relative to non-activated platelets, while 77% of lipids showed a less than 2-fold change in either direction. CONCLUSION: Shear stress has a specific impact on platelet membranes - leading to an increase in fluidity, and alteration of platelet lipidomic profile, which differs from biochemical activation, with evident gender-based differences. Specifically, shear leads to an increase in the number of lipids ejected across all donors, and a male-preferred decrease in retained lipid species. This sex-based difference in platelet composition resulting from shear exposure raises the issue of altered responsiveness that may impart gender differences in in MCS outcomes.
|Original language||English (US)|
|Journal||The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation|
|State||Published - Apr 1 2020|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Cardiology and Cardiovascular Medicine