Tomomi Matsuyama

Novel monoclonal antibody-based enzyme immunoassay for determining plasma levels of ADAMTS13 activity

BACKGROUND: ADAMTS13 specifically cleaves unusually large von Willebrand factor (VWF) multimers, which induce platelet thrombi formation under high shear stress. ADAMTS13 activity is deficient in patients with thrombotic thrombocytopenic purpura (TTP). The determination of plasma levels of ADAMTS13 activity is a prerequisite for a differential diagnosis of thrombotic microangiopathies. Here, a unique and highly sensitive enzyme immunoassay (EIA) of ADAMTS13 activity is described.

Comprehensive analysis of ADAMTS13 in patients with liver cirrhosis.

Decreased plasma ADAMTS13 activity (ADAMTS13:AC) results in the accumulation of unusually large von Willebrand factor multimer (UL-VWFM) and the formation of platelet thrombi. It remains controversial whether or not plasma ADAMTS13:AC decreases in patients with liver cirrhosis (LC), and its relationship to clinical features has not been fully investigated. We measured ADAMTS13:AC and its related parameters in plasma in 33 patients with chronic hepatitis (CH) and in 109 patients with LC. ADAMTS13:AC decreased with increasing severity of liver disease (controls means 100%, CH 87%, Child A-LC 79%, Child B-LC 63%, and Child C-LC 31%), and showed severe deficiency (<3% of controls) in five end-stage LC. Activities measured by act-ELISA strongly correlated with those determined by the VWFM assay and ADAMTS13 antigen. Multivariate analysis showed Child-Pugh score and spleen volume independent factors contributing to ADAMTS13:AC. VWFM patterns were normal in 53% of cases, degraded in 31%, and unusually large in 16%. Patients with unusually large VWFM had the lowest ADAMTS13:AC as well as the highest Child-Pugh score, serum creatinine and blood ammonia levels. Plasma inhibitor against ADAMTS13 detected in 83% of patients with severe to moderate ADAMTS13:AC deficiency mostly showed marginal zone between 0.5 and 1.0 BU/ml. The IgG-type autoantibodies specific to plasma derived-ADAMTS13 was detected by Western blot in only five end-stage LC with severe ADAMTS13:AC deficiency. In conclusion, both plasma ADAMTS13 activity and antigen levels decreased with increasing severity of cirrhosis. An imbalance between the decreased ADAMTS13:AC and its increased substrate may reflect the predisposing state for platelet thrombi formation in patients with advanced LC.

Heterogeneous pathogenic processes of thrombotic microangiopathies in patients with connective tissue diseases

To clarify the pathogenic processes of thrombotic microangiopathies (TMAs) in patients with connective tissue disease (CTD), we analysed clinical characteristics and plasma ADAMTS13 levels in 127 patients with CTD-TMAs, including patients with systemic lupus erythematosus (SLE), systemic sclerosis, polymyositis/dermatomyositis, and rheumatoid arthritis (RA), and 64 patients with acquired idiopathic thrombotic thrombocytopenic purpura (ai-TTP). Plasma levels of ADAMTS13 activity, antigen, and inhibitors were determined by enzyme immunoassays. IgG type anti-ADAMTS13 antibodies were also detected by immunoblots using purified ADAMTS13. ADAMTS13 activity was significantly decreased in CTD-TMAs, regardless of the underlying disease, but the frequency of severe deficiency (defined as <0.5% of normal) was lower in CTD-TMA patients than in ai-TTP patients (16.5% vs. 70.3%, p < 0.01). Severe deficiency of ADAMTS13 activity was predominantly detected in patients with RA- and SLE-TMAs, and was closely associated with the presence of anti-ADAMTS13 IgG antibodies. CTD-TMA patients with severe deficiency of ADAMTS13 activity appeared to have lower platelet counts and better therapeutic outcomes. At least two phenotypic TMAs occur in patients with CTDs: a minor population with deficient ADAMTS13 activity caused by neutralising autoantibodies, and a major population with normal or moderately reduced activity. Classifying CTD-TMAs by ADAMTS13 activity may be useful in predicting the clinical course and therapeutic outcomes, as patients with moderately reduced activity are likely to have more prominent renal impairment and poor prognoses.

ADAMTS13 activity may predict the cumulative survival of patients with liver cirrhosis in comparison with the Child-Turcotte-Pugh score and the Model for End-Stage Liver Disease score.

Aim:  Decreased plasma ADAMTS13 activity (ADAMTS13:AC) results in accumulation of unusually large von Willebrand factor multimers and platelet thrombi formation. Our aim was to evaluate whether ADAMTS13:AC is a prognostic marker in patients with liver cirrhosis.

Plasma ADAMTS13 activity parallels the APACHE II score, reflecting an early prognostic indicator for patients with severe acute pancreatitis.

Objective. Severe acute pancreatitis (SAP) frequently progresses to pancreatitis-associated multiorgan failure (MOF) with high mortality. Decreased plasma ADAMTS13 activity (ADAMTS13:AC) results in the accumulation of unusually large von Willebrand factor multimers (UL-VWFM) and the formation of platelet thrombi, ultimately leading to MOF. The purpose of the study was to investigate the potential role of ADAMTS13:AC in the severity of SAP. Material and methods. Plasma ADAMTS13:AC and its related parameters were sequentially determined in 13 SAP patients. ADAMTS13:AC was determined by the chromogenic act-ELISA. Results. Within 1 or 2 days after admission, ADAMTS13:AC was lower in SAP patients (mean 28%) than in healthy controls (99%), and gradually recovered in the 11 survivors but further decreased in the 2 non-survivors. Patients with higher sepsis-related organ failure assessment (SOFA) scores showed lower ADAMTS13:AC than those without these scores. The inhibitor against ADAMTS13 was undetectable. On day 1, von Willebrand factor antigen (VWF:Ag) was higher (402%, p<0.001) in SAP patients than in controls (100%). VWF:Ag gradually decreased in the survivors, except in the 3 patients needing a necrosectomy, but remained high in the non-survivors. ADAMTS13:AC was inversely correlated with the APACHE II score (r=−0.750, p<0.005), and increased plasma concentrations of interleukin 6 (IL-6) and IL-8 at admission. UL-VWFM-positive patients had lower ADAMTS13:AC and decreased serum calcium concentrations, but higher VWF:Ag and IL-8 concentrations than UL-VWFM-negative patients. Conclusions. Plasma ADAMTS13:AC was closely related to the APACHE II score. This intimate relationship may serve as an early prognostic indicator for SAP patients. The imbalance between decreased ADAMTS13:AC and increased UL-VWFM could contribute to SAP pathogenesis through enhanced thrombogenesis.

Potential Role of Enhanced Cytokinemia and Plasma Inhibitor on the Decreased Activity of Plasma ADAMTS13 in Patients With Alcoholic Hepatitis: Relationship to Endotoxemia

BACKGROUND Deficiency of ADAMTS13 (adisintegrin-like and metalloproteinase with thrombospondin type-1 motifs 13) results in an increase in unusually large von Willebrand factor multimer (UL-VWFM) of the plasma and finally causes microcirculatory disturbance. Our previous study demonstrated that the imbalance of increased UL-VWFM over decreased ADAMTS13 activity may contribute to the development of multiorgan failure in patients with alcoholic hepatitis (AH). The aim of this study was to explore the potential mechanism to reduce the activity of plasma ADAMTS13. METHODS Plasma cytokine levels including interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha (TNF-alpha), plasma endotoxin concentration, and the plasma inhibitor against ADAMTS13 were determined together with ADAMTS13 activity, VWF antigen (VWF:Ag), and UL-VWFM in 24 patients with AH and 5 patients with severe alcoholic hepatitis (SAH). RESULTS The concentrations of IL-6, IL-8, and TNF-alpha on admission were significantly higher in patients with SAH than in those with AH and controls. The ADAMTS13 activity concomitantly decreased, and the VWF:Ag progressively elevated with increasing concentrations of these cytokines from normal range to over 100 pg/ml. Plasma endotoxin concentration was markedly higher in patients with SAH (mean 52.3 pg/ml) and AH (21.7 pg/ml) than in controls (7.9 pg/ml). The endotoxin concentration inversely correlated with ADAMTS13 activity and was higher in patients with UL-VWFM than those without. The inhibitor was detected in 4 patients with SAH (0.9 to 2.1 BU/ml) and 6 patients with AH (0.5 to 1.6 BU/ml). Patients with the inhibitor showed lower functional liver capacity, higher endotoxin concentration, and marked inflammatory signs than those without. At the recovery stage, the ADAMTS13 activity increased to normal range, the VWF:Ag decreased, and the UL-VWFM disappeared with the decrease in the concentrations of cytokines and endotoxin, and the disappearance of the inhibitor. CONCLUSION Decreased ADAMTS13 activity and increased VWF:Ag could be induced not only by pro-inflammatory cytokinemia, but also by its inhibitor, both of which may be closely related to enhanced endotoxemia in patients with AH and SAH.

Potential Role of ADAMTS13 in the Progression of Alcoholic Hepatitis

Alcoholic hepatitis (AH) is a potentially life-threatening complication of alcohol abuse. The severe form of AH, severe alcoholic hepatitis (SAH), is characterized by multiorgan failure (MOF) with manifestations of acute hepatic failure and is associated with high morbidity and mortality. However, the pathogenesis of SAH in addition to AH remains to be elucidated. Recent advances showed that ADAMTS13 (a disintegrin-like and metalloproteinase with thrombospondin type-1 motifs 13) is closely related to thrombotic thrombocytopenic purpura, a multiorgan disorder. Decreased activity of plasma ADAMTS13 (ADAMTS13:AC) leads to the accumulation of unusually large von Willebrand factor multimers (UL-VWFM) and subsequent platelet clumping and/or thrombi under high shear stress, resulting in microcirculatory disturbances. Immunological studies and in situ hybridization have indicated that ADAMTS13 is produced exclusively in hepatic stellate cells (HSCs). Plasma ADAMTS13:AC was extremely low in fatal SAH cases, and enhanced UL-VWFM production with deficient ADAMTS13:AC may contribute to the progression of MOF through microcirculatory disturbances in SAH and AH. Considering that ADAMTS13 is synthesized in HSCs and its substrate, UL-VWFM, is produced in transformed vascular endothelial cells, the imbalance between ADAMTS13:AC and VWF:Ag in AH patients might also involve sinusoidal microcirculatory disturbances and subsequent liver injury. It will be necessary to clarify the mechanism of the decrease in plasma ADAMTS13:AC in association with pro-inflammatory cytokinemia, an ADAMTS13 inhibitor and the production of ADAMTS13 in HSCs. The determination of ADAMTS13:AC and its substrate will give us new insights into the pathophysiology of acute alcoholic liver injury and help to elucidate additional therapeutic strategies for this disease.

Crucial Role of ADAMTS13 Related to Endotoxemia and Subsequent Cytokinemia in the Progression of Alcoholic Hepatitis

Excessive alcohol consumption causes a variety of liver diseases including alcoholic steatosis, alcoholic hepatitis (AH), liver fibrosis, cirrhosis and hepatocellular carcinoma (Mandayam et al. 2004). Alcoholic steatosis is, generally, a benign lesion if the patient abstains from alcohol intake, whereas AH observed in the approximately 20% of heavy drinkers is much more serious and requires treatment with the development of hepatocellular necrosis and inflammation (Menon et al., 2001). The severe form of AH, severe alcoholic hepatitis (SAH), is characterized by multiorgan failure with manifestations of acute hepatic failure and is associated with high morbidity and mortality (Haber et al., 2003; Ishii et al., 1993; Maddrey et al., 1978; Mookerjee et al., 2003; Sougioultzis, 2005). Alcohol-induced liver injury (ALD) occurs through the multiple steps involving a range from innate immune cells to the liver parenchymal cells, and out of many factors contributing to the pathogenesis of ALD gut-derived endotoxin plays a central role in the induction of steatosis, inflammation, and fibrosis in the liver (Bode & Bode, 2005; Fukui et al., 1991; Mandrekar & Szabo, 2009; McClain et al, 2005; Nolan, 2010; Vidali et al., 2008). AH is a multifactorial process involving gut-derived endotoxin-induced Kupffer cell activation via hepatic reticuloendothelial dysfunction and increased intestinal permeability, and subsequent cytokine stimulation. Additional factors include ethanol metabolism to toxic products, oxidative stress, acetaldehyde adducts, nutritional impairment and impaired hepatic regeneration (Haber et al., 2003; Ishii et al., 1993, Mookerjee et al., 2003; Nath & Szabo, 2009; Nolan, 2010; Sakaguchi et al., 2011; Sougioultzis et al., 2005; Tsukamoto et al., 2009; Wu & Cederbaum, 2009). In SAH pathogenesis, endotoxemia may trigger enhanced pro-inflammatory cytokine production, potentially causing a systemic inflammatory response syndrome together with microcirculatory disturbances, systemic haemodynamic derangements, and subsequent multiorgan failure (Fukui, 2005; Haber et al., 2003; Ishii et al., 1993; Mookerjee et al., 2003; Sougioultzis et al., 2005).