Endothelial-derived microparticles: Biological conveyors at the crossroad of inflammation, thrombosis and angiogenesis

Endothelial microparticles (EMP) are complex vesicular structures that can be shed by activated or apoptotic endothelial cells. EMP are composed of a phospholipid bilayer that exposes transmembrane proteins and receptors and encloses cytosolic components such as enzymes, transcription factors and mRNA derived from their parent cells. Thus, EMP behave as biological conveyors playing a key role in the tuning of vascular homeostasis. This review focuses on the multifaceted roles of EMP, notably in coagulation, inflammation and angiogenesis and also on the mechanisms that trigger their formation. In this context, EMP could compromise vascular homeostasis and then represent key players in the pathogenesis of several inflammatory and thrombotic diseases. Consequently, elucidating their role and their mechanisms of formation will bring new insights into the understanding of endothelial-associated diseases. Moreover, in the future, it can open novel therapeutic perspectives based on the inhibition of EMP release.

Leukocyte- and endothelial-derived microparticles: a circulating source for fibrinolysis

BACKGROUND

We recently assigned a new fibrinolytic function to cell-derived microparticles in vitro. In this study we explored the relevance of this novel property of microparticles to the in vivo situation.

DESIGN AND METHODS

Circulating microparticles were isolated from the plasma of patients with thrombotic thrombocytopenic purpura or cardiovascular disease and from healthy subjects. Microparticles were also obtained from purified human blood cell subpopulations. The plasminogen activators on microparticles were identified by flow cytometry and enzyme-linked immunosorbent assays; their capacity to generate plasmin was quantified with a chromogenic assay and their fibrinolytic activity was determined by zymography.

RESULTS

Circulating microparticles isolated from patients generate a range of plasmin activity at their surface. This property was related to a variable content of urokinase-type plasminogen activator and/or tissue plasminogen activator. Using distinct microparticle subpopulations, we demonstrated that plasmin is generated on endothelial and leukocyte microparticles, but not on microparticles of platelet or erythrocyte origin. Leukocyte-derived microparticles bear urokinase-type plasminogen activator and its receptor whereas endothelial microparticles carry tissue plasminogen activator and tissue plasminogen activator/inhibitor complexes.

CONCLUSIONS

Endothelial and leukocyte microparticles, bearing respectively tissue plasminogen activator or urokinase-type plasminogen activator, support a part of the fibrinolytic activity in the circulation which is modulated in pathological settings. Awareness of this blood-borne fibrinolytic activity conveyed by microparticles provides a more comprehensive view of the role of microparticles in the hemostatic equilibrium.

Comparative safety and efficiency of five percutaneous kidney biopsy approaches of native kidneys: a multicenter study

BACKGROUND

Renal biopsy (RB) is necessary for the diagnosis, prognosis, and therapy guidance of native kidney diseases. Few studies have compared outcomes of RB procedures. We retrospectively compared the safety and efficiency of five biopsy procedures.

METHODS

The number of glomeruli on light microscopy (LM) and on immunofluorescence (IF) and serious adverse events following RB performed in five nephrology units (C1-C5) were collected. C1 performed ultrasound (US) assessment before RB and used a 14-gauge core-cutting needle biopsy gun, C2 US guidance and a 14-gauge needle, C3 tomodensitometry guidance and a 14-gauge needle, C4 US guidance and a 16-gauge needle, and C5 tomodensitometry guidance and a 16-gauge needle.

RESULTS

RB was performed in 943 adults between January 2006 and July 2010. Serious adverse events occurred in 1.5% of biopsies. The complication rate was not different between nephrology units. The mean number of glomeruli on biopsy was 14.2 ± 8.6 with LM and 4.4 ± 3.3 on IF. It was different according to the nephrology unit for LM (p = 0.01) and for IF (p < 0.001). The number of failed biopsies was influenced by the nephrology unit and radiological guidance technique, favoring real-time US guidance. Failed biopsies using US or tomodensitometry assessment before RB was certainly due to kidney imprecise localization since it was often non-renal tissue sampling. At least 10 glomeruli were found in 69% of biopsies on LM. This rate varied according to the nephrology unit (p = 0.004) and was higher when 14-gauge needles were used in comparison with 16-gauge needles.

CONCLUSION

RB is safe regardless of the technical procedure, but radiological guidance and needle size influence the efficiency of biopsies.

Seasonal variations of systemic lupus erythematosus flares in southern France

OBJECTIVE

Exposure to sunlight is one of the environmental factors involved in the pathogenesis of systemic lupus erythematosus. We investigated whether there is seasonal variation in the incidence of cutaneous and noncutaneous severe lupus flares in southern France.

METHODS

We retrospectively reviewed clinical and biological data from all SLE patients hospitalized for a flare of the disease during a two year period in our centre and collected corresponding meteorological data from the official website of MeteoFrance.

RESULTS

Forty one patients, mean age 36.7 ± 13.8 years, were included. Twenty-six patients (63.4%) had kidney biopsy performed, showing in all cases proliferative nephritis, associated with membranous nephritis in 9 (22%). We found a clear seasonal pattern for overall lupus flares with 39% of flares occurred in Spring. Among patients without any cutaneous involvement, this seasonal pattern was still observed (p=0.024). Patients under antimalarials presented flares significantly later in the sunny season than those without (respectively median in July versus May, p=0.044). There were strong positive correlations between occurrence of lupus flares and maximum temperature increase (ρ=0.87, p<0.001), minimum temperature increase (ρ=0.87, p<0.001), and duration of sunshine increase (ρ=0.78, p=0.003). These correlations were also observed in patients with renal flares.

CONCLUSION

We confirmed a seasonal pattern for lupus flares among patients living in Southern France, with most flares in spring, in correlation with an increase in temperature and duration of sunshine. A similar seasonal pattern was observed in patients with no cutaneous involvement and with visceral involvement.

New treatment options for lupus - a focus on belimumab

Belimumab is the first biologic approved for patients with systemic lupus erythematosus (SLE). Belimumab is the first of a new class of drug targeting B cell-stimulating factors or their receptors to reach the market. Its target, BLyS, also known as BAFF (B cell-activating factor from the tumor necrosis factor family), is a type II transmembrane protein that exists in both membrane-bound and soluble forms. Additionally to a robust rational from murine experiments conducted in lupus prone mice, BLyS circulating levels are increased in SLE patients. After the negative results of a Phase II trial, two Phase III trials met their primary endpoints. Some SLE patients are still refractory to the standard options of care or necessitate prolonged high-dose corticotherapy and/or long-term immunosuppressive regimens. However, some experts still feel that the effect of this biologic might not be clinically relevant and blame the use of the new systemic lupus response index as well as the discrepancies between both trials and the noninclusion of the severe form of the disease as nephritis. In this review, we aim to discuss the characteristics of belimumab, critically evaluate the different steps of its development, and consider its future place in the arsenal against SLE, taking into account the patients’ perspectives.

IgG4-related systemic disease: features and treatment response in a French cohort: results of a multicenter registry

IgG4-related systemic disease is now recognized as a systemic disease that may affect various organs. The diagnosis is usually made in patients who present with elevated IgG4 in serum and tissue infiltration of diseased organs by numerous IgG4+ plasma cells, in the absence of validated diagnosis criteria. We report the clinical, laboratory, and histologic characteristics of 25 patients from a French nationwide cohort. We also report the treatment outcome and show that despite the efficacy of corticosteroids, a second-line treatment is frequently necessary. The clinical findings in our patients are not different from the results of previous reports from Eastern countries. Our laboratory and histologic findings, however, suggest, at least in some patients, a more broad polyclonal B cell activation than the skewed IgG4 switch previously reported. These observations strongly suggest the implication of a T-cell dependent B-cell polyclonal activation in IgG4-related systemic disease, probably at least in part under the control of T helper follicular cells.

[Posterior reversible encephalopathy syndrome induced by a cough and cold drug containing pseudoephedrine]

INTRODUCTION

Posterior reversible encephalopathy syndrome is a clinico-radiological entity characterized by neurologic symptoms in association with usually reversible bilateral posterior hemispheric oedema on neuroimaging. Many pathological conditions and treatments have been associated with this syndrome.

CASE REPORT

We report a 19-year-old woman, followed-up for hypocomplementemic urticarial vasculitis, who presented with a posterior reversible encephalopathy syndrome induced by the intake of an over-the-counter cold remedy containing pseudoephedrine. Clinical manifestations and radiological abnormalities resolved after anti-hypertensive therapy and withdrawal of sympathomimetic drug.

CONCLUSION

The diagnosis of posterior reversible encephalopathy syndrome should be considered in patients with compatible clinical and radiological presentation because of its potential reversibility with an appropriate management. Intake of drugs, including over-the-counter cough and cold drugs, should be looked for in the history as well as autoimmune disorders.