PB0683 - Elevated calcium and Depolarized mitochondrial membrane potential of ITP platelets

Background: Immune Thrombocytopenia Purpura (ITP) is an autoimmune disorder characterized by the presence of a decreased platelet count. Platelets of ITP tend to have a reduced half-life and undergo immune-mediated clearance from the circulation. Since ITP platelets do not follow a programmed cell death mechanism for the clearance but do follow macrophage-mediated abrupt clearance, we aimed to understand the cellular changes of ITP platelets by studying their membrane and cellular contents.

Aims: To investigate the cellular changes of platelets in Immune Thrombocytopenia Purpura.

Methods: A total of 12 chronic ITP patients and 22 healthy individuals were included in this study. Blood samples were collected into 3.2% sodium-citrated tubes for the flow cytometry studies. The Phosphatidyl Serine (PS), P-Selectin, αIIbβ3, changes of mitochondrial membrane potential (⧍Ψm) and the intracellular level of calcium in the platelets were measured by flow cytometry using FACS Canto (BD Bioscience). Antibodies and assays followed for these measurements are listed in table 1. A statistical analysis of Welch's t-test was applied with 95% confidence interval; P values less than 0.05 were considered significant.

Results: Flow cytometry analysis suggested a significantly higher expression of PS on the surface of the ITP platelets (p = 0.01). In addition, increased level of calcium (p = 0.032) and significant loss of mitochondrial membrane potential (⧍Ψm) (p = 0.038) were observed in ITP platelets. No significant alterations were observed for the P-Selectin and αIIbβ3 expressions on the ITP platelets. (Table 1 and Figure 1).

Conclusion(s): Platelets of ITP undergo cellular changes (as observed by mitochondrial membrane potential loss, increased intracellular calcium level, and PS exposure) without undergoing full activation (as observed by no significant alterations for P-Selectin and αIIbβ3 expressions). The current study suggests that ITP platelets undergo clearance following a distinct pathway of cell death, possibly programmed cell necrosis.

Funding: DST-SERB (ID: EMR-000955).