Reduced antioxidant capacities in platelets from patients with autoimmune thrombocytopenia purpura (ITP)

Variations of Redox Balance in Different Stages of Childhood Immune Thrombocytopenic Purpura

BACKGROUND

 Few previous studies indicated the role of oxidative stress in the pathogenesis of childhood idiopathic thrombocytopenic purpura (ITP), but there are little data regarding changes in redox balance in different forms of the disease, and changes after therapeutic procedures. We aimed to investigate the values of pro-oxidants and antioxidative capacity in various forms of ITP before and after the applying therapy.

MATERIALS AND METHODS

 The research included 102 children, classified into the following groups: (1) newly diagnosed ITP (ndITP), (2) persistent ITP, (3) chronic ITP (chITP), and (4) control groups: (A) healthy control and (B) previously experienced ITP-healthy children who had been suffering from ITP earlier. During the clinical assessment, a blood sample was taken from the patients, from which the value of pro-oxidants (index of lipid peroxidation measured as TBARS, nitrites [NO2 -], as measurement of nitric oxide [NO] production, superoxide anion radical [O2 -], and hydrogen peroxide [H2O2]) and the capacity of antioxidant protection (activity of superoxide dismutase and catalase, and quantity of reduced glutathione) were determined spectrophotometrically.

RESULTS

 Our results demonstrated that values of pro-oxidants, especially reflected through the TBARS and O2 -, were the highest in the ndITP and exacerbated chITP groups. Also, the activity of the endogenous antioxidative defense system was the lowest in these groups. Intravenous immunoglobulin therapy in the ndITP group exerted the most prominent effect on the redox balance.

CONCLUSION

 It can be concluded that severity and exacerbation of the ITP are closely related to the redox status.

Novel Biomarkers for Diagnosis and Monitoring of Immune Thrombocytopenia

Lower-than-normal platelet counts are a hallmark of the acquired autoimmune illness known as immune thrombocytopenia, which can affect both adults and children. Immune thrombocytopenia patients' care has evolved significantly in recent years, but the disease's diagnosis has not, and it is still only clinically achievable with the elimination of other causes of thrombocytopenia. The lack of a valid biomarker or gold-standard diagnostic test, despite ongoing efforts to find one, adds to the high rate of disease misdiagnosis. However, in recent years, several studies have helped to elucidate a number of features of the disease's etiology, highlighting how the platelet loss is not only caused by an increase in peripheral platelet destruction but also involves a number of humoral and cellular immune system effectors. This made it possible to identify the role of immune-activating substances such cytokines and chemokines, complement, non-coding genetic material, the microbiome, and gene mutations. Furthermore, platelet and megakaryocyte immaturity indices have been emphasized as new disease markers, and prognostic signs and responses to particular types of therapy have been suggested. Our review's goal was to compile information from the literature on novel immune thrombocytopenia biomarkers, markers that will help us improve the management of these patients.

Reduced intracellular antioxidant capacity in platelets contributes to primary immune thrombocytopenia via ROS-NLRP3-caspase-1 pathway

Primary immune thrombocytopenia (ITP) is a common acquired autoimmune hemorrhagic disease characterized by a low platelet count and increased risk of bleeding. However, some patients do not respond well to current therapeutic approaches. Further studies on pathogenesis and pathophysiology of ITP are needed to discover new therapeutic targets. We explored the role of enhanced intracellular oxidative stress and NLRP3 inflammasome activation of platelets in ITP. The expression of NLRP3 inflammasome was assessed in platelets from active ITP patients and healthy donors. Both the mRNA and protein expression level of platelet NLRP3 inflammasome was upregulated in ITP patients compared with healthy donors. Besides, the elevated caspase-1 activity and increased co-localization of NLRP3 and its adaptor molecule ASC indicated activation of NLRP3 inflammasome in ITP platelets. Significantly decreased intracellular antioxidant capacity was observed in ITP platelets. H₂O₂ supplementation elevated the expression of NLRP3 inflammasome and increased IL-1β secretion in ITP platelets. Preincubating ITP platelets with NAC down-regulated the expression of NLRP3 inflammasome. Pretreating ITP platelets with NLRP3 inhibitor MCC950 or caspase-1 inhibitor Z-YVAD-FMK significantly reduced the proportion of pyroptotic cells in H₂O₂-treated ITP platelets and suppressed IL-1β secretion in supernatants. Hence, platelet NLRP3 inflammasome activation resulted from reduced intracellular antioxidant capacity plays a critical role in ITP and might have potential diagnostic or therapeutic implications.

Identification of novel autoantigens via mass spectroscopy-based antibody-mediated identification of autoantigens (MS-AMIDA) using immune thrombocytopenic purpura (ITP) as a model disease

Immune thrombocytopenic purpura (ITP) is one of the best characterized autoimmune diseases. Autoantibodies (AABs) against platelet antigens are considered as the diagnostic hallmark of ITP, but are detectable in only 50% of patients. We designed and applied a novel proteomic approach termed Mass Spectroscopy-based Antibody-Mediated Identification of Autoantigens (MS-AMIDA) for platelet antigens. Patients were separated into patients with classical AABs [ITP(+)] and patients without AABs [ITP(-)]. Altogether, 181 potential AAGs were found in ITP(+) and 135 AAGs in ITP(-), with 34 and 23 AAGs reproducibly found in two runs of MS-AMIDA. After subtracting identifiers from the controls, 57 AAGs in ITP(+) and 29 AAGs in ITP(+) remained, with 16 AAGs commonly found in ITP(+) and ITP(-) patients. Label-free quantification (LFQ) revealed 15 potential AAGs that are quantitatively stronger in ITP. Dot blot validation was performed on hexokinase 1 (HK1), E1 pyruvate dehydrogenase (E1-PDH), coagulation factor XIII, filamin A (FLNA), non-muscle myosin 9. Eleven patients were found to have anti-HK1 AABs, one patient had anti-E1-PDH AABs, and two patients had anti-FLNA AABs. Most antigens were of intracellular origin with significant association with actin-cytoskeleton and regulation of programmed cell death. In conclusion, novel AAGs for ITP were identified using MS-AMIDA.

Effect of short-term, high-dose methylprednisolone on oxidative stress in children with acute immune thrombocytopenia

Background

Immune thrombocytopenia (ITP) is the most common cause of acquired childhood thrombocytopenia and is characterized by increased immune-mediated destruction of circulating thrombocytes. Oxidative damage may be involved in ITP pathogenesis; paraoxonase (PON) and arylesterase (ARE) enzymes are closely associated with the cellular antioxidant system. We investigated the effect of short-term high-dose methylprednisolone (HDMP) treatment on the total oxidant status (TOS), total antioxidant capacity (TAC), oxidative stress index (OSI), and PON and ARE enzymatic activity in children with acute ITP.

Methods

Thirty children with acute ITP constituted the study group and 30 healthy children constituted the control group. Children with acute ITP were treated with HDMP: 30 mg/kg for 3 days, then 20 mg/kg for 4 days. The TOS, TAC, OSI, PON, and ARE levels were determined before and after 7 days of HDMP treatment.

Results

The TAC level (P<0.001), and PON (P<0.001) and ARE (P=0.001) activities were lower and the TOS (P=0.003) and OSI (P<0.001) levels were higher in children with acute ITP than those in healthy children in the control group. We also observed statistically significant increases in the TAC (P<0.01), PON (P<0.001) and ARE levels (P=0.001) and decreases in the TOS (P<0.05) and OSI levels (P<0.05) with 7 days of HDMP treatment compared to their values before treatment.

Conclusion

Our study demonstrated increased oxidative stress (OSI and TOC) and decreased antioxidant capacity (TAC), PON, and ARE in ITP patients and that steroid treatment could be effective in reducing the oxidative stress.

Oxidant/antioxidant status in children and adolescents with immune thrombocytopenia (ITP) and the role of an adjuvant antioxidant therapy

BACKGROUND

Free oxygen radicals might have an adverse effect on platelets which might be reflected either on its count and/or degree of bleeding severity.

AIM

To assess oxidant-antioxidant systems and evaluate effect of antioxidant therapy on platelet count (PC) and bleeding score (BS) in children and adolescents with ITP.

METHODS

Six months prospective randomized single blind study registered as (NCT 01763658) including 39 patients with newly diagnosed (ND) ITP; group 1 (G1) and 39 patients with chronic ITP (G2), each group was randomly allocated (2:1) to one of two subgroups respectively; (G1A and G2A) interventional arm received daily antioxidant therapy, while G1B and G2B; received a placebo. Both groups were compared with healthy controls (n = 39). The primary efficacy endpoints were the difference in the change from baseline to 6 month in ITP specific bleeding assessment tool (ITP-BAT), PC, total antioxidant capacity (TAC), catalase (CAT), reduced glutathione (GSH) and serum malondialdehyde (MDA).

RESULTS

Baseline TAC was significantly lower in patients with (ND) ITP compared to patients with chronic ITP (P < 0.05), both showed significantly lower levels than healthy controls (P < 0.001). At end of study both BS and PC significantly improved in patients receiving antioxidant compared to placebo (P < 0.05). Patients with chronic ITP receiving antioxidant showed better improvement.

CONCLUSION

Reduced antioxidant mechanisms were reported in patients with ITP. Antioxidant therapy ameliorated the oxidative stress in both ND and chronic ITP groups which might explain the improvement in both BS and PC.

Redox control of platelet functions in physiology and pathophysiology

SIGNIFICANCE

An imbalance between the production and the detoxification of reactive oxygen species and reactive nitrogen species (ROS/RNS) can be implicated in many pathological processes. Platelets are best known as primary mediators of hemostasis and can be either targets of ROS/RNS or generate radicals during cell activation. These conditions can dramatically affect platelet physiology, leading even, as an ultimate event, to the cell number modification. In this case, pathological conditions such as thrombocytosis (promoted by increased cell number) or thrombocytopenia and myelodysplasia (promoted by cell decrease mediated by accelerated apoptosis) can occur.

RECENT ADVANCES

Usually, in peripheral blood, ROS/RNS production is balanced by the rate of oxidant elimination. Under this condition, platelets are in a nonadherent "resting" state. During endothelial dysfunction or under pathological conditions, ROS/RNS production increases and the platelets respond with specific biochemical and morphologic changes. Mitochondria are at the center of these processes, being able to both generate ROS/RNS, that drive redox-sensitive events, and respond to ROS/RNS-mediated changes of the cellular redox state. Irregular function of platelets and enhanced interaction with leukocytes and endothelial cells can contribute to pathogenesis of atherosclerotic and thrombotic events.

CRITICAL ISSUES

The relationship between oxidative stress, platelet death, and the activation-dependent pathways that drive platelet pro-coagulant activity is unclear and deserves to be explored.

FUTURE DIRECTIONS

Expanding knowledge about how platelets can mediate hemostasis and modulate inflammation may lead to novel and effective therapeutic strategies for the long and growing list of pathological conditions that involve both thrombosis and inflammation.

Oxidative stress is predominant in female but not in male patients with autoimmune thrombocytopenia

As the involvement of oxidative stress (OS) in autoimmune thrombocytopenia (AITP) has been reported, a fast and rapid test for the reliable measurement of OS and antioxidant capacities (AOCs) might be a useful tool in extending current diagnostic possibilities. The free oxygen radical test (FORT) and free oxygen radical defence (FORD) assay (Callegari, Italy) are easy to perform and reliable, with results available within 15 minutes. Thirty-seven AITP patients and 37 matched healthy individuals were included in this study. All participants responded to a standard questionnaire provided by these assays. Female patients with AITP were observed to demonstrate significantly higher OS in comparison to female controls (P = 0.0027) and male AITP patients (P = 0.0018). The AOCs were not reduced in patients with AITP (P = 0.7648). Correlation of OS with platelet count identified a weak positive correlation (P = 0.0327, Spearman R = 0.4672). The questionnaire revealed that ITP patients in comparison to healthy controls are more stressed, feel exhausted and fatigued, and eat a healthier diet. In conclusion, OS is predominant in female but not in male patients with AITP suggesting gender-specific differences in the pathomechanisms of AITP. Identification of patients with high levels of OS might be beneficial in the management of AITP.