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Biomedical subjects

M C Boffa

Publications and source records attributed to M C Boffa.

At least 37 records · Page 2Linked to original sources
PubMed1997

Thrombomodulin, a functional surface protein on human keratinocytes, is regulated by retinoic acid.

Thrombomodulin, a major anticoagulant proteoglycan of the endothelial cell membrane, is a thrombin receptor that acts as a cofactor for protein C activation. It has previously been shown that thrombomodulin, present in human epidermis and in lysates of cultured keratinocytes, is implicated in cellular differentiation during mouse fetal development. The role of retinoic acid in keratinocyte differentiation prompted us to study retinoic acid regulation of thrombomodulin expression in primary cultures of keratinocytes isolated from adult human skin, grown at low (undifferentiated keratinocytes) and normal calcium levels (differentiated keratinocytes). Thrombomodulin antigen levels and total and surface activities were measured in cultures without and with retinoic acid. Thrombomodulin mRNA visualized by in situ hybridization was quantified by computer-based image analysis. Functional thrombomodulin was expressed on the surface and in the cytoplasm of cultured human keratinocytes regardless of the calcium concentration. In contrast, retinoic acid induced significant increases in the total antigen level and in surface and intracellular thrombomodulin activities only in keratinocytes grown in a low-calcium medium. In these undifferentiated keratinocytes, quantification of mRNA transcripts showed a threefold increase after retinoic acid stimulation. Thus, functional thrombomodulin is a human keratinocyte surface protein whose expression is controlled through the keratinocyte differentiation program and is modulated in vitro by retinoic acid.

Adult↗
PubMed1997

[Thrombomodulin: physiology and clinical applications (excluding systemic diseases)].

Thrombomodulin (TM) is a proteoglycan present on the surface of endothelial and mesothelial cells where it acts as a strong anticoagulant. TM is also located in other cells (keratinocytes, osteoblasts, mononuclear phagocytes...) where it might be involved in cell differentiation or inflammatory processes. The damage of endothelial cells releases cleavage fragments. Plasma TM appears to be a marker of endothelium damage. Plasma TM has been investigated in several disorders: it is usually increased in the case of diffuse endothelial damage.

Cardiovascular Diseases↗
PubMed1997

Thrombomodulin is synthesized by human mesangial cells.

Thrombomodulin (TM), an endothelial receptor for thrombin, endowed with a powerful anticoagulant activity, plays an important role in the antithrombogenicity of the vascular endothelium. Its presence within the human renal glomerulus is already known but was thought to be only endothelial. We looked for TM expression in human mesangial cells (MC), both in situ, in freshly prepared glomeruli, and in primary culture. Both fresh and cultured MC were strongly reactive for TM by immunocytochemical methods. Total TM antigen measured on MC lysates and surface TM activity on MC were 0.292 +/- 0.075 ng/mg of cellular proteins and 1.20 +/- 0.02 pmole of activated protein C/min/mg of cellular proteins, respectively. As shown by the presence of numerous transcripts detected by in situ hybridization, TM was shown to be synthesized by MC in vivo and in culture. The synthesis of active TM by both endothelial and mesangial cells within the renal glomerulus stresses the importance of its role in maintaining renal hemostatic equilibrium, and sheds some light on the conflicting reports of TM over- and underexpression in glomerulopathies to open a new field for investigation.

Antigens↗
PubMed1996

Plasma levels of thrombomodulin in pulmonary hypertension.

BACKGROUND: Long-standing pulmonary hypertension (PH) leads to structural alterations of the pulmonary vasculature and its endothelium, and occlusion of small vessels by microthrombi. In patients with PH, the search for factors inducing or worsening endothelium damage and in situ thrombi is still ongoing. Thrombomodulin (TM), an endothelial cell membrane protein, is a receptor for thrombin and a major anticoagulant proteoglycan. PURPOSE: To analyze plasma TM levels in patients with different forms of severe PH. PATIENTS: We prospectively studied 32 consecutive patients with PH referred for heart, lung, or heart-lung transplantation: 11 patients with primary PH (group 1), 11 patients with secondary precapillary PH (Eisenmenger's syndrome, group 2) and 10 patients with secondary postcapillary PH due to congestive heart failure (group 3). Thirty-eight healthy subjects were also studied as a control group. METHODS: Plasma concentrations of TM were measured by an immunoenzymatic technique that uses two anti-TM monoclonal antibodies that have a strong avidity and react with different epitopes of the molecule. RESULTS: Thrombomodulin plasma levels decreased in all patients with precapillary PH, and this decrease was highly significant compared with controls (26 +/- 2 versus 44 +/- 2 ng/mL, P = 0.0001). In primary PH, the TM decrease was only significant in males whereas in the Eisenmenger's syndrome TM values were the lowest of all the patients studied, with mean values twice as low as controls (22 +/- 2 versus 44 +/- 2 ng/mL, P = 0.0001). In contrast, in postcapillary PH, studied only in males, TM levels were increased (85 +/- 17 versus 54 +/- 3 ng/mL, P = 0.02). Patients with precapillary PH had more severe disease than patients with postcapillary PH, with higher pulmonary artery pressure and pulmonary vascular resistance (P < 0.001). There was no correlation between TM plasma levels and all hemodynamic variables. CONCLUSION: We found low levels of plasma TM in patients with precapillary PH but not in postcapillary PH compared with healthy controls. This may be related to the severity of PH and may contribute to the initiation or worsening of in situ thromboses frequently found in pulmonary hypertension. Further studies should analyze whether other markers of endothelial cell damage are correlated with plasma TM levels in patients with precapillary pulmonary hypertension.

Adolescent↗
PubMed1996

Advantage of using both anionic and zwitterionic phospholipid antigens for the detection of antiphospholipid antibodies.

To investigate the benefit of assaying for antiphospholipid antibodies (aPA) with different antigenic specificities, sera from 141 patients suspected of having aPA were tested by ELISA for IgG and IgM antibodies directed against the following phospholipids (PL) coated individually or together: cardiolipin, phosphatidylinositol, phosphatidylserine and phosphatidylethanolamine. Nonspecific background optical density (OD) was systematically subtracted from the test OD value. Positive reactions were defined as having an OD greater than the 97th percentile OD distribution obtained with sera from 100 healthy individuals. Although the majority of the 79 detected aPA (89% IgG and 77% IgM) were polyspecific, 11 reacted with a single PL and, moreover, belonged to only one isotype. Seven of these 11 patients presented recurrent fetal losses or thrombotic events. These results suggest that routine use of a mixture of both anionic and zwitterionic PL antigens to coat ELISA plates would better detect aPA involved in suggestive pathologies and enhance the ability to identify patients with these mono- or polyspecific antibodies directed or not against cardiolipin, the current standard.

Antibodies, Antiphospholipid↗
PubMed1996

Antiphosphatidylethanolamine antibodies as the only antiphospholipid antibodies. I. Association with thrombosis and vascular cutaneous diseases.

OBJECTIVE: To detect antiphosphatidylethanolamine antibodies (aPE) as the only antiphospholipid antibodies (aPL) in 122 patients we investigated for aPL and to correlate the presence of aPL with clinical manifestations. METHODS: Patients with autoimmune diseases (n = 41), thromboembolic episodes (TEE) (n = 34), livedo reticularis (LR) without (n = 17) or with (n = 14) thrombosis or recurrent fetal losses (RFL), systemic vasculitides (n = 10), and miscellaneous disorders (n = 6) were investigated for antibodies directed against 4 anionic phospholipids (PL) (cardiolipin, phosphatidylserine, inositol, phosphatidic acid) and lupus anticoagulant (LAC) and then for aPE by modified ELISA. RESULTS: 15 patients had aPE and no antibodies to anionic PL including LAC. 7 had IgM, 4 had IgG plus IgM, and 4 had IgG. These aPE were significantly more often associated with TEE alone, with TEE and LR, or with LR alone (p = 0.004) than with autoimmune diseases. CONCLUSION: The detection of aPE as the sole aPL in one patient with mesenteric infarcts and RFL led to the diagnosis of primary antiphospholipid syndrome. Followup of 3 patients showed that aPE cannot be considered as transient autoantibodies. Therefore, patients whose clinical symptoms suggest antiphospholipid syndrome but whose sera are negative for antibodies to cardiolipin or another anionic PL should be screened for aPE, particularly patients with thrombosis, RFL, and/or LR.

Adolescent↗
PubMed1996

Antiphosphatidylethanolamine antibodies as the only antiphospholipid antibodies detected by ELISA. II. Kininogen reactivity.

OBJECTIVE: To study the requirement for serum and for low (LMWK) and high molecular weight kininogen (HMWK) and/or HMWK binding proteins to detect antiphosphatidylethanolamine antibodies (aPE) in ELISA. METHODS: Eighteen patients with aPE (9 IgG and 13 IgM) as the only antiphospholipid antibody (aPL) detected by ELISA were assigned to 4 groups: thromboembolic episodes (TEE) (Group I, n = 6); livedo reticularis (LR) without TEE, (Group II, n = 4); both LR and thrombosis (Group III, n = 4); and systemic lupus erythematosus (SLE) or primary antiphospholipid syndrome (APS) (Group IV, n = 4). All sera were analyzed in ELISA with and without bovine serum and with a purified chromatographic fraction containing LMWK, HMWK, and HMWK binding proteins. RESULTS: Eleven aPE were serum dependent: mostly IgG (7/9) and some IgM (4/13). Among the 11 serum dependent aPE, all the 7 IgG and 2 IgM were kininogen reactive. Some serum independent IgM were better detected in the absence than in the presence of serum in the ELISA. CONCLUSION: In the 18 patients, kininogens and/or HMWK binding proteins served as a "cofactor" significantly more often for aPE IgG than for aPE IgM (p = 0.007). Kininogen dependent aPE Ig were observed more often in patients with LR with or without TEE (6/8) than in those with SLE or primary APS (0/4) but this difference merely tended to significance (p = 0.06). In 2 patients, one with TEE, the other with primary APS, the IgM aPE was dependent on a serum "cofactor" that was not kininogen.

Antibodies, Antiphospholipid↗
PubMed1996

High prevalence of antiphospholipid antibodies in precapillary pulmonary hypertension.

OBJECTIVE: To assess prevalence and clinical associations of various antiphospholipid antibodies (aPL) in patients with primary and secondary pulmonary hypertension. METHODS: A prospective trial of aPL in 38 consecutive patients with pulmonary hypertension. Nine patients had primary pulmonary hypertension. Twenty-nine patients had pulmonary hypertension secondary to different etiologies: left heart failure, 8; congenital heart defect, 11; various lung diseases, 10. The search for aPL directed against 4 phospholipids (cardiolipin, phosphatidylserine, inositol, ethanolamine) was by ELISA. RESULTS: Eleven patients (29%) had aPL, with various phospholipid specificities. Mean pulmonary artery pressure and mean pulmonary vascular resistance of aPL positive patients were not different from those of aPL negative patients. Mean pulmonary wedge pressure was significantly lower in aPL positive patients than those without aPL. Positive aPL were detected only in patients with precapillary pulmonary hypertension (11/30; 36.6%). The prevalence of aPL in primary (4/9; 44%) was not significantly different from aPL in secondary (7/29; 24%) pulmonary hypertension. There was no association between the presence of aPL and prior thrombosis or recurrent fetal losses. CONCLUSION: The frequent positivity of aPL in precapillary pulmonary hypertension, irrespective of its cause and severity, suggests the existence of an associated endothelial disease. These antibodies might play a role in the initiation and/or progression of in situ thromboses frequently observed in precapillary pulmonary hypertension. Our results reinforce the necessity of longterm anticoagulant treatment in these patients.

Adolescent↗
PubMed1996

[Antiphospholipid antibody/cofactors. What are they? Why, when and how to search for them? Is treatment justified?].

Antiphospholipid antibodies are a wide family of antibodies, dominated by lupus anticoagulant (LA) and anti-cardiolipin antibodies (aCL), encountered in various circumstances. Unnecessary laboratory tests can be avoided by carefully weighing the indications, especially regarding patient age. Three steps are required to demonstrate LA: screening, mixing studies, then confirmation by neutralization tests. Two coagulation tests at least should be performed aCL are detected with ELISA kits using plates coated with cardiolipin. Due to the large number of kits available and to the lack of agreement on cut-off values, all laboratories must indicate their own standards. Other kits use plates coated with a mixture of phospholipids. Recent data suggest that pathogenic aPL are more specifically directed against phospholipid-associated proteins rather than towards phospholipids. In the future, tests for aCL might be replaced by tests for beta 2-glycoprotein I. The presence of aPL requires a specific treatment only in patients presenting clinical manifestations thought to be aPL-induced (thromboses, fetal losses). Long term warfarin aimed at an INR of 3-3.5 is effective for the secondary prevention of thrombosis. In primary APS, prevention of recurrent miscarriages is frequently achieved by a combination of subcutaneous heparin plus aspirin.

Antibodies, Antiphospholipid↗
PubMed1995

[Antiphospholipid antibodies: cause of thrombosis or an epiphenomenon?].

Antiphospholipid antibodies (aPL) present in systemic lupus erythematosus and the primary antiphospholipid syndrome are a well-known risk factor for thrombosis. Most of them require the presence of a cofactor, beta 2-glycoprotein I for anticardiolipin antibodies, prothrombin for lupus anticoagulant. These aPL are of the "immune" type. APL are also found in various non-immunological conditions, in which repeated endothelial or membranous damages appear to be frequent, but thromboses are rare. Most of these aPL are cofactor-independent, except those induced by chlorpromazine, and might belong to "natural" antibodies.

Animals↗