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L M Mauro

Publications and source records attributed to L M Mauro.

6 recordsLinked to original sources
PubMed2005

Endothelial microparticles induce formation of platelet aggregates via a von Willebrand factor/ristocetin dependent pathway, rendering them resistant to dissociation.

Endothelial microparticles (EMP) released from activated or apoptotic endothelial cells (EC) are emerging as useful markers for detection of EC dysfunction. Our recent observation that EMP carry von Willebrand factor (vWf) led us to investigate their interaction with platelets. EMP were incubated with normal washed platelets in the presence or absence of ristocetin, then platelet aggregates were measured by flow cytometry. In the absence of ristocetin, negligible EMP conjugated with platelets (< 5%) but in the presence of ristocetin (1 mg mL(-1)), EMP induced up to 95% of platelets to aggregate. EMP-platelet interaction was 80% blocked by anti-CD42b, or by 0.1 microm filtration to remove EMP. Platelet aggregates induced by normal plasma or high molecular weight vWf (Humate-P) dissociated 50% within 15-25 min following 1:20 dilution. In contrast, aggregates formed with EMP persisted two- to threefold longer with the same treatment, indicating greater stability. A similar degree of prolongation of dissociation was observed using plasma from thrombotic thrombocytopenic purpura (TTP) patients compared with normal plasma. Addition of EMP to plasma from severe von Willebrand disease restored his ristocetin-induced platelet aggregation. Multimer analysis of vWf on EMP showed unusually large vWf (ULvWf). In summary, EMP carries ULvWf multimers, promote platelet aggregates, and increase the stability of the aggregates thus formed.

Cells, Cultured↗
PubMed2001

Elevated plasma endothelial microparticles in multiple sclerosis.

OBJECTIVE: To assess endothelial dysfunction in patients with MS and to investigate whether plasma from patients with MS induces endothelial cell dysfunction in vitro. BACKGROUND: Endothelial cell dysfunction may contribute to the pathogenesis of MS. Elevations of soluble adhesion molecules intracellular adhesion molecule, vascular cell adhesion molecule, and platelet-endothelial cell adhesion molecule-1 (CD31) have been reported as markers of blood-brain barrier (BBB) damage in MS, but direct assay of endothelium has been difficult. Endothelial cells release microparticles < approximately 1.5 microm (EMP) during activation or apoptosis. The authors developed a flow cytometric assay of EMP and studied EMP as markers of endothelial damage in MS. METHODS: Platelet-poor plasma (PPP) from 50 patients with MS (30 in exacerbation and 20 in remission) and 48 controls were labeled with fluorescein isothiocyanate (FITC)-conjugated anti-CD31 and anti-CD51 (vitronectin receptor) antibodies, and two classes of EMP (CD31+ and CD51+) were assayed by flow cytometry. For in vitro studies, patients' plasma was added to the microvascular endothelial cell (MVEC) culture and release of CD31+ and CD51+ EMP were measured in the supernatant. RESULTS: Plasma from patients in exacerbation had 2.85-fold elevation of CD31+ EMP as compared with healthy controls, returning to near control value during remission. The CD31+ EMP concentration showed a positive association with gadolinium enhancement in patients with MS. In contrast, CD51+ EMP remained elevated in both exacerbation and remission. This suggests that CD31+ EMP is a marker of acute injury, whereas CD51+ EMP reflects chronic injury of endothelium. MS plasma induced release of both CD31+ and CD51+ EMP from MVEC culture in vitro. CONCLUSION: Endothelial dysfunction is evident during exacerbation of MS, evidenced by shedding of EMP expressing PECAM-1 (CD31). The in vitro data indicate contribution of one or more plasma factors in endothelial dysfunction of MS.

Adult↗
PubMed2001

Elevated endothelial microparticles in thrombotic thrombocytopenic purpura: findings from brain and renal microvascular cell culture and patients with active disease.

Endothelial injury is believed to be a key initiating event in the pathogenesis of thrombotic thrombocytopenic purpura (TTP), leading to platelet activation and formation of platelet-rich thrombi in microvasculature. However, the nature of endothelial injury in TTP is poorly defined and clinical assays to rapidly and reliably monitor endothelial damage are not readily available. Using flow cytometry, we measured endothelial microparticles (EMPs) generated from cultured renal and brain microvascular endothelial cells (MVECs) during activation and apoptosis, and evaluated the effect of TTP plasma on them. EMPs were measured using positivity for monoclonal antibodies (mAbs) CD31 and CD51, and their procoagulant activity was assessed using a Russell viper venom assay. Both cell lines generated procoagulant EMPs when cultured with inducers of activation (tumour necrosis factor alpha; TNF-alpha) or apoptosis (mitomycin C). TTP plasma induced a five- to sixfold increase of EMP generation and a two- to threefold increase of procoagulant activity in cultured brain and renal MVECs. TTP plasma induced a threefold and 13-fold increase of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression, respectively, on renal MVECs. Procoagulant activity tended to parallel EMP numbers. The effect of TTP plasma on cell viability was similar to that of TNF-alpha, implying that it induced activation rather than apoptosis. Control plasma and idiopathic thrombocytopenic purpura (ITP) plasma had little effect. In the clinical study, EMP assay of blood from acute TTP patients showed levels markedly elevated compared with normal controls, but values returned to normal in remission. In conclusion, TTP plasma activated and induced injury to MVECs in culture, judged by production of EMP and expression of activation markers. Released procoagulant EMP may play a role in the pathogenesis of TTP. Assay of EMP may be a useful marker of disease activity and endothelial injury in TTP and possibly other thrombotic disorders.

Adult↗