Platelet desialylation is a novel mechanism and a therapeutic target in thrombocytopenia during sepsis: an open-label, multicenter, randomized controlled trial.

BACKGROUND: Studies in murine models suggested that platelet desialylation was an important mechanism of thrombocytopenia during sepsis. METHODS: First, we performed a prospective, multicenter, observational study that enrolled septic patients with or without thrombocytopenia to determine the association between platelet desialylation and thrombocytopenia in patients with sepsis, severe sepsis, and septic shock. Gender- and age-matched healthy adults were selected as normal controls in analysis of the platelet desialylation levels (study I). Next, we conducted an open-label randomized controlled trial (RCT) in which the patients who had severe sepsis with thrombocytopenia (platelet counts ≤50 × 109/L) were randomly assigned to receive antimicrobial therapy alone (control group) or antimicrobial therapy plus oseltamivir (oseltamivir group) in a 1:1 ratio (study II). The primary outcomes were platelet desialylation level at study entry, overall platelet response rate within 14 days post-randomization, and all-cause mortality within 28 days post-randomization. Secondary outcomes included platelet recovery time, the occurrence of bleeding events, and the amount of platelets transfused within 14 days post-randomization. RESULTS: The platelet desialylation levels increased significantly in the 127 septic patients with thrombocytopenia compared to the 134 patients without thrombocytopenia. A platelet response was achieved in 45 of the 54 patients in the oseltamivir group (83.3%) compared with 34 of the 52 patients in the control group (65.4%; P = 0.045). The median platelet recovery time was 5 days (interquartile range 4-6) in the oseltamivir group compared with 7 days (interquartile range 5-10) in the control group (P = 0.003). The amount of platelets transfused decreased significantly in the oseltamivir group compared to the control group (P = 0.044). There was no difference in the overall 28-day mortality regardless of whether oseltamivir was used. The Sequential Organ Failure Assessment score and platelet recovery time were independent indicators of oseltamivir therapy. The main reason for all of the mortalities was multiple-organ failure. CONCLUSIONS: Thrombocytopenia was associated with increased platelet desialylation in septic patients. The addition of oseltamivir could significantly increase the platelet response rate, shorten platelet recovery time, and reduce platelet transfusion. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR-IPR-16008542 .

High-dose dexamethasone corrects impaired myeloid-derived suppressor cell function via Ets1 in immune thrombocytopenia.

Myeloid-derived suppressor cells (MDSCs) are heterogeneous immature cells and natural inhibitors of adaptive immunity. In this study, the MDSC population was evaluated in adult patients with primary immune thrombocytopenia (ITP), where cell-mediated immune mechanisms are involved in platelet destruction. Our data demonstrated that both the numbers and suppressive functions of MDSCs were impaired in the peripheral blood and spleens of patients with ITP compared with healthy control patients. High-dose dexamethasone (HD-DXM) treatment rescued MDSC numbers in patients with ITP. And DXM modulation promoted the suppressive function of MDSCs induced in vitro. Moreover, the expression of interleukin 10 and transforming growth factor ß was significantly upregulated in DXM-modulated MDSCs compared with the unmodulated cultures. DXM-modulated MDSCs inhibited autologous CD4(+)T-cell proliferation and significantly attenuated cytotoxic T lymphocyte-mediated platelet lysis, further indicating enhanced control over T-cell responses. Elevated expression of the transcription factor Ets1 was identified in DXM-modulated MDSCs. Transfection of Ets-1 small interfering RNA efficiently blocked regulatory effects of MDSCs, which almost offset the augmentation of MDSC function by DXM. Meanwhile, splenocytes from CD61 knockout mice immunized with CD61(+)platelets were transferred into severe combined immunodeficient (SCID) mouse recipients (C57/B6 background) to induce a murine model of severe ITP. We passively transferred the DXM-modulated MDSCs induced from bone marrow of wild-type C57/B6 mice into the SCID mouse recipients, which significantly increased platelet counts in vivo compared with those receiving splenocyte engraftment alone. These findings suggested that impaired MDSCs are involved in the pathogenesis of ITP, and that HD-DXM corrected MDSC functions via a mechanism underlying glucocorticoid action and Ets1.

Interleukin 27 inhibits cytotoxic T-lymphocyte-mediated platelet destruction in primary immune thrombocytopenia.

Cytotoxic T-lymphocyte (CTL)-mediated platelet destruction and aberrant cytokine profiles play important roles in the pathogenesis of primary immune thrombocytopenia (ITP). Interleukin-27 (IL-27) has pleiotropic immunomodulatory effects. However, the effect of IL-27 on CTL activity in ITP has not been reported. In the present study, platelets from ITP patients were cultured with autologous CTLs in the presence of IL-27. We found that IL-27 could inhibit CTL-mediated platelet destruction. In these IL-27-treated CTLs, granzyme B and T-bet expression decreased significantly, whereas granzyme A, perforin, and eomesodermin were not affected. To further investigate the role of granzyme B in CTL-mediated platelet destruction, granzyme B inhibitor was added and platelet apoptosis was significantly inhibited. These results suggest that IL-27 negatively regulates CTL cytotoxicity toward platelets in ITP by decreasing granzyme B expression, which is associated with reduced T-bet expression. IL-27 may have a therapeutic role in treating ITP patients.