Circulating levels of platelet α-granule cytokines in trauma patients

To elucidate whether platelets differentiate cytokine release following trauma, we prospectively measured three major platelet-derived cytokines in 213 trauma patients on hospital arrival. We measured plasma levels of the anti-inflammatory beta-thromboglobulins (beta TGs), transforming growth factor-beta 1 (TGF beta 1) and the pro-inflammatory platelet factor 4 (PF4) cytokines. We also measured soluble glycoprotein VI (sGPVI), procoagulant platelet microparticles (PMPs) and white blood cell (WBC) counts, and evaluated in vitro platelet function in primary and secondary haemostasis by aggregometry and thromboelastometry, respectively. We evaluated associations of each cytokine by multivariate regression including injury severity score (ISS), WBC counts, sGPVI and platelet counts as explanatory variables. Severely injured patients (ISS > 15) had higher levels of beta TGs and TGF beta 1 (both p < 0.01) but lower levels of PF4 (p = 0.02). GPVI and PMPs levels correlated with TGF beta 1 and PF4 whereas we found no significant association between cytokine levels and measures of haemostasis. By multivariate regression, a high WBC count was associated with high levels of TGF beta 1 (p = 0.01) and beta TGs (p < 0.01) but with low levels of PF4 (p = 0.03). Severely injured patients had higher levels of beta TGs and TGF beta 1 but lower levels of the PF4; a high WBC count predicted this anti-inflammatory profile of platelet cytokines.