Expression patterns of RelA and c-mip are associated with different glomerular diseases following anti-VEGF therapy.

Renal toxicity constitutes a dose-limiting side effect of anticancer therapies targeting vascular endothelial growth factor (VEGF). In order to study this further, we followed up 29 patients receiving this treatment, who experienced proteinuria, hypertension, and/or renal insufficiency. Eight developed minimal change nephropathy/focal segmental glomerulopathy (MCN/FSG)-like lesions and 13 developed thrombotic microangiopathy (TMA). Patients receiving receptor tyrosine kinase inhibitors (RTKIs) mainly developed MCN/FSG-like lesions, whereas TMA complicated anti-VEGF therapy. There were no mutations in factor H, factor I, or membrane cofactor protein of the complement alternative pathway, while plasma ADAMTS13 activity persisted and anti-ADAMTS13 antibodies were undetectable in patients with TMA. Glomerular VEGF expression was undetectable in TMA and decreased in MCN/FSG. Glomeruli from patients with TMA displayed a high abundance of RelA in endothelial cells and in the podocyte nuclei, but c-mip was not detected. Conversely, MCN/FSG-like lesions exhibited a high abundance of c-mip, whereas RelA was scarcely detected. RelA binds in vivo to the c-mip promoter and prevents its transcriptional activation, whereas RelA knockdown releases c-mip activation. The RTKI sorafenib inhibited RelA activity, which then promoted c-mip expression. Thus, our results suggest that c-mip and RelA define two distinct types of renal damage associated with VEGF-targeted therapies.

Role of ADAMTS13 in the management of thrombotic microangiopathies including thrombotic thrombocytopenic purpura (TTP).

The clinical presentation of thrombotic thrombocytopenia purpura (TTP) and other thrombotic microangiopathies (TMAs) can often be similar. The role of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) in diagnosing TTP is accepted by most researchers but continues to be debated in a few studies. We report the experience of our single-centre academic institution, where ADAMTS13 is used to diagnose TTP and guide plasma exchange (PLEX). Patients presenting to our institution with thrombotic microangiopathy (60 patients) between January 2006 and December 2012 were divided into two groups based on ADAMTS13 activity and clinical history. Patients with ADAMTS13 activity <10% were included in the TTP (n = 30) cohort while patients with activity >11% were classified as 'other microangiopathies' (TMA, n = 30). PLEX was only initiated in patients with a high likelihood of TTP and discontinued when the baseline ADAMTS13 activity was >11%. Patients with severe ADAMTS13 deficiency (TTP group) showed significant presenting differences: lower platelet counts, less renal dysfunction, higher presence of neurological abnormalities, and greater haemolysis markers as compared to non-deficient patients (TMA group). Most importantly, patients without severe ADAMTS13 deficiency were safely managed without increased mortality despite receiving no PLEX or discontinuing PLEX after a short course (upon availability of ADAMTS13 results). In conclusion, ADAMTS13 can be used to diagnose TTP and guide appropriate PLEX therapy.

Thrombotic microangiopathies, thrombotic thrombocytopenic purpura, and ADAMTS-13.

Thrombotic microangiopathy (TMA) is a term used to describe a group of disorders characterized by hemolytic anemia (with prominent red blood cell fragmentation), thrombocytopenia, and thrombosis in the microvasculature. It may be used when describing patients with thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome, atypical hemolytic uremic syndrome, as well as a myriad of other disorders in which the TMA may be secondary to another disease or disorder. While limited information exists as to the exact cause of microthrombosis in many TMA, recent advances have been made in the understanding of TTP and its pathophysiology. This progress can be attributed to discovery of the von Willebrand factor cleaving protease ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), whose absence in TTP has given the disorder a distinct molecular identity. The discovery of this metalloprotease has prompted a significant amount of research relating to its role in TTP as well as its general function in hemostasis. The exact mechanisms by which this metalloprotease achieves its role are slowly being understood and these now provide other avenues by which TMA may occur.

Cancer awareness in atypical thrombotic microangiopathies.

OBJECTIVE: To specify the clinical and biological characteristics of thrombotic microangiopathies (TMAs) associated with a recent diagnosis of cancer. PATIENTS AND Methods. Multicenter study involving 14 national centers. Cross-sectional analysis of 20 patients with cancer-associated TMAs included in our national registry from October 2000 to July 2007. Patients were also compared with 134 adult patients with an acquired idiopathic TMA by univariate analysis. RESULTS: Patients with a cancer-associated TMA typically displayed severe weight loss, dyspnea, bone pain, as well as disseminated intravascular coagulopathy and massive erythromyelemia (75%, 55%, 50%, 41%, and 85% of cases, respectively). By contrast, these features were observed with a much lower incidence in patients with an idiopathic TMA (8.9%, 19.7%, 0.8%, 7.1%, and 17.5%, respectively). Moreover, median platelet count was higher (48 x 10(9)/l; range, 21-73 x 10(9)/l versus 19 x 10(9)/l; range, 10-38 x 10(9)/l, respectively) and median serum creatinine level was lower (74 microM [range, 68-102] versus 113 microM [range, 80-225], respectively). The activity of the specific von Willebrand factor-cleaving proteinase ADAMTS13 was detectable in 14/17 studied patients. Platelet count improvement was observed in only seven patients and paralleled the response to chemotherapy. Prognosis of patients with cancer-associated TMAs was very poor, with a 30-day and 2-year mortality rate of 50% and 95%, respectively. CONCLUSION: Cancer-associated TMAs display specific features at onset that should prompt investigation of an underlying disseminated malignancy. In this context, chemotherapy rather than plasma is mandatory since TMA prognosis parallels that of cancer.

The role of ADAMTS-13 in the coagulopathy of sepsis.

The interaction between platelets and the vessel wall is mediated by various receptors and adhesive proteins, of which von Willebrand factor (VWF) is the most prominent. The multimeric size of VWF is an important determinant of a more intense platelet-vessel wall interaction, and is regulated by the VWF-cleaving protease ADAMTS-13. A deficiency in ADAMTS-13 leads to higher concentrations of ultralarge VWF multimers and pathological platelet-vessel wall interactions, in its most typical and extreme form leading to thrombocytopenic thrombotic purpura, a thrombotic microangiopathy characterized by thrombocytopenia, non-immune hemolysis, and organ dysfunction. Thrombotic microangiopathy associated with low levels of ADAMTS-13 may be a component of the coagulopathy observed in patients with sepsis. Here, we review the potential role of ADAMTS-13 deficiency and ultralarge VWF multimers in sepsis, and their relationship with sepsis severity and prognosis. In addition, we discuss the possible benefit of restoring ADAMTS-13 levels or reducing the effect of ultralarge VWF as an adjunctive treatment in patients with sepsis.

Derivation and external validation of the PLASMIC score for rapid assessment of adults with thrombotic microangiopathies: a cohort study.

BACKGROUND: Among the syndromes characterised by thrombotic microangiopathy, thrombotic thrombocytopenic purpura is distinguished by a severe deficiency in the ADAMTS13 enzyme. Patients with this disorder need urgent treatment with plasma exchange. Because ADAMTS13 activity testing typically requires prolonged turnaround times and might be unavailable in resource-poor settings, a method to rapidly assess the likelihood of severe ADAMTS13 deficiency is needed. METHODS: All consecutive adult patients presenting to three large academic medical centres in Boston, MA, USA, with thrombotic microangiopathy and a possible diagnosis of thrombotic thrombocytopenic purpura between Jan 8, 2004, and Dec 6, 2015, were included in an ongoing multi-institutional registry (the Harvard TMA Research Collaborative). Univariate analysis was used to identify covariates for a logistic regression model predictive of severe ADAMTS13 deficiency (≤10% activity). A clinical point score was generated, and its diagnostic performance was assessed using internal and external validation cohorts and compared to clinical assessment alone. FINDINGS: 214 patients with thrombotic microangiopathy were included in the derivation cohort. A seven-component clinical prediction tool, termed the PLASMIC score, was developed and found to reliably assess the pretest probability of severe ADAMTS13 deficiency (C statistic 0·96, 95% CI 0·92-0·98). Our diagnostic model was reproducibly accurate in both the internal (0·95, 0·91-0·98) and external (0·91, 0·85-0·95) validation cohorts. The scoring system also more consistently diagnosed thrombotic microangiopathy due to severe ADAMTS13 deficiency than did standard clinical assessment, as measured by C statistic (0·96, 95% CI 0·92-0·98 for PLASMIC vs 0·83, 0·77-0·88 for clinical assessment; p<0·0001) and mean Brier score (0·065 for PLASMIC vs 0·111 for clinical assessment; mean paired difference 0·05, 95% CI 0·01-0·08; p<0·0001). When utilised in addition to clinical assessment, the PLASMIC score contributed significant discriminatory power (integrated discrimination improvement 0·24, 95% CI 0·11-0·37). INTERPRETATION: We have developed and validated a clinical prediction tool-the PLASMIC score-to stratify patients with thrombotic microangiopathy according to their risk of having severe ADAMTS13 deficiency. We have shown that this scoring system is superior to standard clinical assessment in addressing the diagnostic challenge presented by thrombotic microangiopathy. Its use, together with clinical judgment, may facilitate treatment decisions in patients for whom timely results of ADAMTS13 activity testing are unavailable. FUNDING: The Luick Family Fund of Massachusetts General Hospital.

Thrombotic Microangiopathy Syndrome in a Basic Underwater Demolition/SEAL Student.

Thrombotic microangiopathy (TMA) syndromes represent a spectrum of illnesses that share common clinical and pathologic features of microangiopathic hemolytic anemia, thrombocytopenia, and organ injury from pathologic small-vessel thrombosis. At least nine primary TMA syndromes have been described and classified based on common probable etiologies, diagnostic criteria, and treatments. The most recognized of the TMA syndromes include thrombotic thrombocytopenic purpura (TTP) and hemolytic-uremic syndrome (HUS). Advanced laboratory techniques are required to distinguish between these syndromes; however, all patients should initially be treated with plasma exchange for presumed ADAMTS13 deficiency-mediated TMA. The authors present a case of a TMA syndrome in a Navy SEAL (Sea, Air, Land) candidate.

VWF excess and ADAMTS13 deficiency: a unifying pathomechanism linking inflammation to thrombosis in DIC, malaria, and TTP.

Absent or severely diminished activity of ADAMTS13 (A Disintegrin And Metalloprotease with a ThromboSpondin type 1 motif, member 13) resulting in the intravascular persistence and accumulation of highly thrombogenic ultra large von Willebrand factor (UL-VWF) multimers is the pathophysiological mechanism underlying thrombotic thrombocytopenic purpura. Reduced VWF-cleaving protease levels, however, are not uniquely restricted to primary thrombotic microangiopathy (TMA), e. g. thrombotic thrombocytopenic purpura, but also occur in other life-threatening thrombocytopenic conditions: severely decreased ADAMTS13 activity is seen in severe sepsis, disseminated intravascular coagulation (DIC) and complicated malarial infection. The clinical relevance of these secondary thrombotic microangiopathies is increasingly recognised, but its therapeutic implications have not yet been determined. The presence of a secondary TMA in certain diseases may define patient groups which possibly could benefit from ADAMTS13 replacement or a VWF-targeting therapy. This short-review focuses on the role of UL-VWF multimers in secondary TMA and discusses the potential of investigational therapies as candidates for the treatment of TTP. In conclusion, prospective clinical trials on the effectiveness of protease replacementin vivo seem reasonable. Carefully selected patients with secondary TMA may benefit from therapies primarily intended for the use in patients with TTP.

Structure and proteolytic properties of ADAMTS13, a metalloprotease involved in the pathogenesis of thrombotic microangiopathies.

ADAMTS13 is a 190-kDa zinc protease encoded by a gene located on chromosome 9q34. This protease specifically hydrolyzes von Willebrand factor (VWF) multimers, thus causing VWF size reduction. ADAMTS13 belongs to the A Disintegrin And Metalloprotease with ThromboSpondin type 1 repeats (ADAMTS) family, involved in proteolytic processing of many matrix proteins. ADAMTS13 consists of numerous domains, including a metalloprotease domain, a disintegrin domain, several thrombospondin type 1 (TSP1) repeats, a cysteine-rich domain, a spacer domain, and two CUB (Complement c1r/c1s, sea Urchin epidermal growth factor, and Bone morphogenetic protein) domains. ADAMTS13 cleaves a single peptide bond (Tyr(1605)-Met(1606)) in the central A2 domain of the VWF molecule. This proteolytic cleavage is essential to reduce the size of ultralarge VWF polymers, which, when exposed to high shear stress in the microcirculation, are prone to form platelets clumps, which cause severe syndromes called thrombotic microangiopathies (TMAs). In this chapter, we (a) discuss the current knowledge of structure-function aspects of ADAMTS13 and its involvement in the pathogenesis of TMAs, (b) address the ongoing controversies, and (c) indicate the direction of future investigations.

Thrombotic microangiopathies: multimers, metalloprotease, and beyond.

The pathophysiology of various types of thrombotic microangiopathies is coming progressively into focus. Therapeutic advances are likely to follow at a quickening pace. This discussion focuses on thrombotic thrombocytopenic purpura (TTP), the hemolytic-uremic syndrome (HUS), thrombotic microangiopathies associated with transplantation-immunosuppression or anti-angiogenesis therapy, and the preeclampsia/hemolysis-elevated liver enzymes and low platelets syndrome (HELLP).