(P-CB-26) Soluble GPIbα and Ristocetin Response: Redox Imbalance and Neuraminidase as Drivers of Platelet Dysfunction During Room Storage and Riboflavin-UV Treatment

Background/Case Studies: Ristocetin-induced platelet aggregation (RIPA) is a functional marker of platelet adhesion and activation that depends on the GPIb receptor complex. GPIb also regulates the clearance of senescent and transfused platelets via hepatic recognition, thereby influencing thrombopoietin production. Soluble GPIbα (glycocalicin) is a shed fragment of the receptor and is a surrogate marker of platelet senescence. This study evaluated the behavior and determinants of RIPA response and soluble GPIbα levels during platelet storage at room temperature and after the riboflavin and UV treatment.

Study

Design/Methods: An experimental study was performed with ten double-dose platelet concentrates stored at 22°C during nine days, and treated with saline (control), riboflavin (R), UV, or riboflavin+UV (RUV). Multiple linear regression and moderation models (IBM SPSS v27) were applied to examine the relationship between soluble GPIbα (ELISA) and RIPA (light aggregometry), concerning extracellular neuraminidase activity (colorimetry), malondialdehyde adduct (MDA; ELISA), GSH/GSSG ratio (colorimetry), and ferric reducing antioxidant power (FRAP; colorimetry). The regression coefficients are presented as standardized (β).

Results/Findings: The RIPA decreased to 50% on day 9 in the control group; on day 5, both in the UV and R group; and immediately after the RUV-treatment; and the above was observed with GPIbα concentrations of 98.8, 65.6, 47.6, and 39.3 ng/mL, respectively. In the saline group, ristocetin response was significantly associated with GPIbα levels (β=–0.526). In the UV group, the strongest predictors were neuraminidase activity (β= –0.144) and GSH/GSSG ratio (β=0.545). MDA (β= –0.296) and GSH/GSSG (β=0.569) predicted a reduced response in riboflavin-treated samples. The RUV group showed similar patterns, associated with neuraminidase (β= –0.245) and GSH/GSSG (β=0.545). Regarding GPIbα shedding, MDA was consistently associated with higher levels across all treatments, with the most substantial effect in the RUV group (β=0.674). GSH/GSSG was inversely associated with GPIbα, particularly under UV (β= –0.540) and riboflavin (β= –0.439). MDA (β=0.257) and FRAP (β=–0.528) were relevant predictors in saline. All models had R2 between 0.378 and 0.891 (p< 0.05)(Figure A).

Conclusions: Oxidative stress and desialylation markers differentially contribute to platelet dysfunction during room storage and after UV and riboflavin treatments. The impaired ristocetin response might depend not only on the GPIbα shedding but also on the oxidation and desialylation of the remaining GPIb membrane complex. RIPA and glycocalicin might be functional markers during platelet storage and after pathogen-reduction treatment.