Advances in immunopathogenesis of adult immune thrombocytopenia

Primary immune thrombocytopenia(ITP)is an autoimmune disorder characterized by immune-mediated accelerated platelet destruction and/or suppressed platelet production.Although the development of autoantibodies against platelet glycoproteins remains central in the pathophysiology of ITP,several abnormalities involving the cellular mechanisms of immune modulation have been identified,and the pathways behind the immune-mediated destruction of platelets have opened new avenues for the design of specific immunotherapies in an attempt to reduce the platelet destruction.This review is primarily focused on the recent literature with respect to immunopathological mechanisms in patients with ITP.

MST4 kinase regulates immune thrombocytopenia by phosphorylating STAT1-mediated M1 polarization of macrophages

Primary immune thrombocytopenia(ITP)is an autoimmune hemorrhagic disorder in which macrophages play a critical role.Mammalian sterile-20-like kinase 4(MST4),a member of the germinal-center kinase STE20 family,has been demonstrated to be a regulator of inflammation.Whether MST4 participates in the macrophage-dependent inflammation of ITP remains elusive.The expression and function of MST4 in macrophages of ITP patients and THP-1 cells,and of a macrophage-specific Mst4−/−(Mst4ΔM/ΔM)ITP mouse model were determined.Macrophage phagocytic assays,RNA sequencing(RNA-seq)analysis,immunofluorescence analysis,coimmunoprecipitation(co-IP),mass spectrometry(MS),bioinformatics analysis,and phosphoproteomics analysis were performed to reveal the underlying mechanisms.The expression levels of the MST4 gene were elevated in the expanded M1-like macrophages of ITP patients,and this elevated expression of MST4 was restored to basal levels in patients with remission after high-dose dexamethasone treatment.The expression of the MST4 gene was significantly elevated in THP-1-derived M1 macrophages.Silencing of MST4 decreased the expression of M1 macrophage markers and cytokines,and impaired phagocytosis,which could be increased by overexpression of MST4.In a passive ITP mouse model,macrophage-specific depletion of Mst4 reduced the numbers of M1 macrophages in the spleen and peritoneal lavage fluid,attenuated the expression of M1 cytokines,and promoted the predominance of FcγRIIb in splenic macrophages,which resulted in amelioration of thrombocytopenia.Downregulation of MST4 directly inhibited STAT1 phosphorylation,which is essential for M1 polarization of macrophages.Our study elucidates a critical role for MST4 kinase in the pathology of ITP and identifies MST4 kinase as a potential therapeutic target for refractory ITP.

Modified Sijunzi Granules Exhibit Hemostatic Effect by Activating Akt and Erk Signal Pathways via Regulating 5-HT and Its Receptors Levels

Objective:To investigate the hemostatic effect of modified Sijunzi Granules(MSG)in primary immune thrombocytopenia(ITP)zebrafish model and explore the potential mechanism.Methods:AB strain wild type zebrafish were treated with simvastatin(6μmol/L)for 24 h to establish the hemorrhage model(model control group).The zebrafish were treated with MSG at different doses(55.6,167,and 500μg/mL),respectively.The hemostatic effect was assessed by examining the intestinal bleeding and hemostatic rate.5-hydroxytryptamine(5-HT)content was determined using enzyme-linked immunosorbent assay(ELISA)assay.The expressions of5-HT2aR,5-HT2bR,and SERT genes were detected by quantitative real-time polymerase chain reaction(PCR).The protein expressions of protein kinase B(Akt),p-Akt,extracellular regulated protein kinases(Erk),and p-Erk were examined using Western blot analysis.Results:The intestinal bleeding rate was 37%,40%,and 80%in the55.6,167,and 500μg/mL dose of MSG,respectively,in which 55.6 and 167μg/mL MSG dose groups were associated with significantly decreased intestinal bleeding rate when compared with the model control group(70%,P<0.05).Significantly higher hemostatic rates were also observed in the 55.6μg/mL(54%)and 167μg/mL(52%)MSG dose groups(P<0.05).MSG increased the 5-HT content and mRNA expression levels of 5-HT2aR,5-HT2bR,and SERT(P<0.05).In addition,caspase3/7 activity was inhibited(P<0.05).Significant increase in p-Akt and p-Erk was also detected after treatment with MSG(P<0.05).Conclusions:MSG could reduce the incidence and severity of intestinal bleeding in zebrafish by activating MAPK/Erk and PI3K/Akt signal pathways through regulating the levels of 5-HT and its receptors,which may provide evidence for the treatment of ITP.