Clusterin can mediate apoptosis-induced molecular mechanisms in immune thrombocytopenia

Abnormalities in the apoptosis pathway have been implicated into the pathogenesis of various autoimmune diseases, including immune thrombocytopenia (ITP). Our data suggest that mechanisms associated with impaired clusterin-mediated apoptosis might play a role in the pathophysiology of ITP platelets and their production by MKs. Platelet-rich plasma from 10 patients with ITP compared with healthy controls was used for the apoptosis proteomic profiling and clusterin (CLU) expression validation by reverse transcription polymerase chain reaction. We used the megakaryoblastic (MEG-01) cell line, treated for 2 hours with plasma from patients with newly diagnosed ND), chronic ITP or healthy controls and pan-caspase inhibitor (Z-VAD-FMK), apoptosis inducer ABT-737, rotenone (Rot), or rapamycin (Rap). Our apoptosis proteomic profiling revealed significantly increased expression levels of certain apoptotic genes such as CLU, phospho-p53 (S46), procaspase-3, and cleaved caspase 3 (CASP-3) in patients with ITP compared with healthy controls. Treatment with pan-caspase inhibitor or Rap had a significant downregulatory effect at messenger RNA (mRNA) level for CLU; CASP-3, -8, and -9; p53; and B-cell lymphoma-2-associated X protein (BAX) in ITP plasma-treated cells in comparison with control plasma-treated MEG-01 cells, whereas Rot or ABT-737 had opposite effects. We observed a significant downregulation of mRNA expression levels of these apoptotic markers in ITP plasma-treated and CLU or glucose-regulated protein 78 small interfering RNA-transfected MEG-01 cells. Our results indicate an upregulation of CLU and BAX in platelets and MKs which may contribute to deciphering the cause of platelet destruction in ITP disease.