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Biomedical subjects

E M Salonen

Publications and source records attributed to E M Salonen.

At least 37 records · Page 2Linked to original sources
PubMed1989

Lipoprotein(a) binds to fibronectin and has serine proteinase activity capable of cleaving it.

The plasma concentration of human lipoprotein(a) [Lp(a)] is correlated with the risk of heart disease. A distinct feature of the Lp(a) particle is the apolipoprotein (a) [apo(a)], which is associated with apoB-100, the main protein component of low-density lipoprotein. We now report that apo(a), which has extensive homology to plasminogen, binds to immobilized fibronectin. The binding of Lp(a) was localized to the C-terminal heparin-binding domain of fibronectin. Incubation of Lp(a) with fibronectin resulted in fragmentation of fibronectin. The cleavage pattern, as visualized by gel electrophoresis and immunoblotting, was reproducibly obtained with Lp(a) purified from five different individuals and was distinct from that obtained upon proteolysis of fibronectin by plasmin or kallikrein. The use of synthetic peptide substrates demonstrated that the amino acid specificity for Lp(a) was arginine rather than lysine. The proteolytic activity of Lp(a) was localized to apo(a) and experiments with inhibitors indicated that the proteolytic activity was of serine proteinase-type.

Fibronectins↗
PubMed1989

Interaction of plasminogen activator inhibitor (PAI-1) with vitronectin.

Immobilized vitronectin was found to bind both purified plasminogen activator inhibitor type 1 (PAI-1) and the PAI-1 in conditioned culture medium of human sarcoma cells. Similarly, immobilized PAI-1 bound both purified vitronectin and vitronectin from normal human serum. These interactions were demonstrated using both enzyme immunoassay and radioiodinated proteins. Solid-phase vitronectin bound PAI-1 with Kd 1.9 x 10(-7) M, and the reverse interaction gave a Kd 5.5 x 10(-8) M. Evidence was also found for a second type of binding with a Kd below 10(-10) M. The molar ratios of the two proteins in the complex at the saturation levels were approximately one molecule of soluble PAI-1 bound per three molecules of immobilized vitronectin and approximately one molecule of soluble vitronectin being bound per one molecule of immobilized PAI-1. Binding of PAI-1 to vitronectin did not lead to an irreversible loss of the ability of PAI-1 to inhibit urokinase (u-PA) and tissue-type plasminogen activator (t-PA). Active u-PA released vitronectin-bound 125I-labeled PAI-1 radioactivity, suggesting that u-PA interacts with the complex. The Mr 50,000 urokinase cleavage product of PAI-1 also bound to vitronectin, but this bound fragment did not inhibit u-PA. Binding of PAI-1 to vitronectin did not interfere with the ability of vitronectin to promote the adhesion and spreading of cells. These results suggest that the interaction between vitronectin and PAI-1 may serve to confine pericellular u-PA activity to focal contact sites where cells use proteolysis in regional detachment.

Glycoproteins↗
PubMed1989

Elevated cerebrospinal fluid fibronectin concentration at diagnosis indicates poor prognosis in children with acute lymphoblastic leukemia.

We investigated whether the concentration of fibronectin (FN) in the cerebrospinal fluid (CSF) could be used for identifying patients with subclinical blast-cell infiltration in the central nervous system (CNS) and an increased risk of CNS relapse later in the course of their leukemia. Our series comprised 36 children with newly diagnosed acute lymphoblastic leukemia (ALL). The mean follow-up time was 54 months (range 5 to 96 months). The median concentration of CSF-FN at diagnosis was 2.24 mg/l (range 0.78 to 7.04 mg/l). The 3-year continuous complete remission rate for the 16 patients with CSF-FN concentrations less than or equal to 2 mg/l was 93% as compared with 37% for the 19 patients with CSF-FN greater than 2 mg/l (p = 0.001). When multivariate analysis was performed, the CSF-FN concentration retained its prognostic significance. When all relapses were considered as failures, the relative risks of relapse for patients with CSF-FN less than or equal to 2 mg/l and greater than 2 mg/l were I and 15.8 (95% confidence limits 1.8-135.6, p less than 0.02), respectively. If only CNS relapses (isolated and combined) were considered as failures, relative risks for the above-mentioned groups were I and 11.6 (1.4-99.5, p less than 0.05), respectively. We conclude that determination of the CSF-FN concentration may provide a new means of evaluating the CSF in children with ALL and may prove to be a sensitive indicator of leukemic CNS infiltration.

Adolescent↗
PubMed1989

Plasminogen activator and its enhancement in differentiating mouse Friend erythroleukemia cells.

Urokinase-type plasminogen activator (u-PA) activity was found in the medium as well as in the lysates of cultured uninduced Friend leukemia (FL) cells. PA activity progressively increased during the cell differentiation induced by dimethyl sulphoxide (DMSO), 4-hydroxy-3-methoxybenzaldehyde or hypoxanthine. Both the differentiation and the enhancement of PA activity in cultures of DMSO-induced cells were blocked by treating the cells with 1 microM dexamethasone. A highly significant correlation (rs = 0.93) was found between the number of hemoglobinized cells and the rate of PA secretion, indicating that the increase in PA activity coincides with late events of the differentiation process. FL cells specifically adhere to fibronectin-coated surfaces but tend to lose this property during the differentiation process. Anti-u-PA IgG antibodies promoted the attachment of differentiating cells to fibronectin-coated surfaces, suggesting that u-PA plays a role in the detachment of FL cells from fibronectin immobilized on the growth substratum.

Animals↗
PubMed1989

Plasmin and fibronectin degradation in chronic secretory otitis media.

Mucoid effusions from 39 children with secretory otitis media, altogether 42 specimens, were analyzed for proteolytic activity using radial caseinolysis procedures, for fibronectin using a solid-phase enzyme immunoassay, and for fibronectin fragmentation using immunoblotting. All samples contained proteolytic activity, tentatively identified as plasmin on the basis of comigration with purified human plasmin in zymographic analysis. In 19 specimens the plasmin level exceeded 1 microgram/mg of protein; the highest value recorded was 18.7 micrograms/mg. Low levels of net plasminogen activator activity were found in 12 specimens and identified as urokinase according to comigration with the urokinase standard in zymography. Fibronectin was detected in all but one of the 42 specimens; in seven specimens the levels exceeded those in normal plasma, calculated per milligram of total protein. Extensive fragmentation of fibronectin was found in 19 specimens, correlating with high plasmin levels. The results are indicative of an ongoing proteolytic process in secretory otitis media and suggest that plasmin-caused degradation of the fibronectin-containing basement membrane and subsequent formation of granulation tissue may be involved in the development of adhesive middle ears.

Child↗
PubMed1989

Induction of morphological differentiation of human neuroblastoma cells is accompanied by induction of tissue-type plasminogen activator.

Human SH-SY5Y neuroblastoma cells treated with retinoic acid, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or nerve growth factor differentiated morphologically to neuronlike cells with increased amounts of neurofilament protein and mRNA. All three effectors induced an increase in the amount of relative molecular weight (Mr) 70,000 tissue-type plasminogen activator (t-PA) and its mRNA, as determined by immunocapture, enzyme activity, and Northern blotting analyses. About 90% of the t-PA activity was secreted to the culture medium. In contrast, of the three effectors studied, only TPA induced transcription of the proto-oncogene c-fos, studied as a control gene responsive to various stimuli, and induced a rapid increase in urokinase-type PA (u-PA). Most of the u-PA activity induced by TPA remained cell-associated. Because induction of differentiation correlated closely with induction of t-PA, and not u-PA, the authors propose that t-PA may have a functional role in the morphological differentiation of neuronal cells.

Cell Differentiation↗
PubMed1989

Histochemical study of alkali-burned rabbit anterior eye segment in which severe lesions were prevented by aprotinin treatment.

Activities of different enzymes (acid glycosidases, phosphatases, Na+ - K+ -dependent ATPase, proteases, dehydrogenases) and acid glycosaminoglycans were studied by histochemical methods in sections of rabbit anterior eye segments after experimental alkali burn and treatment with aprotinin, an inhibitor of plasmin and other serine proteinases. Solutions of sodium hydroxide (0.25-1.0 M) were applied on corneas using 12-mm-diameter plastic tube for 15-60 s. After wiping with cotton and rinsing with tap water aprotinin solutions were applied in saline (in experimental animals) and saline (in control animals) dropwise in 12-h intervals for a month. Within the first two weeks aprotinin was used at a concentration of 5000 IU/ml. During the subsequent two weeks the aprotinin concentration was reduced to 2500 IU/ml. Striking differences in enzyme activities and in the healing between treated and untreated eyes were found. Without aprotinin, ulcers developed in most corneas within 3 weeks and plasmin was regularly demonstrated in tears and in the aqueous. When aprotinin treatment was started within 24 h after the burn, the number of enzymatically active inflammatory cells was significantly lower, not only in the cornea itself but also in the whole anterior eye segment. With aprotinin treatment no ulcerations and no plasmin in tears and the aqueous were observed and the corneas healed within a month. The healing process started from the zone of enzymatically activated corneal cells in the unburned zone at the corneal periphery. In the regenerating epithelium and endothelium high activities of Na+ -K+ -dependent ATPase, gamma-glutamyltransferase, lactate and succinate dehydrogenases appeared very soon.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Phosphatase↗
PubMed1989

Contact lens wear is associated with the appearance of plasmin in the tear fluid--preliminary results.

We determined biochemically the plasmin concentration in tear fluid from 50 externally healthy eyes and from 49 eyes during contact lens (CL) wear. After cessation of CL wear, samples were collected again from 41 of the 49 eyes. Plasmin was detected more frequently (P less than 0.0001) in the CL-wearing group (75.5%) than in the control group (20%). After the cessation of CL wear (3-21 days), the frequency of plasmin detection in tear fluid decreased significantly (P less than 0.0006) but was still higher (39%) than in the control group. We conclude that the occurrence of plasmin in tear fluid is correlated with CL wear. The proteolytic activity of plasmin may contribute to the development of corneal epithelial pathology associated with CL wear.

Contact Lenses↗
PubMed1989

Activation of pro-urokinase and plasminogen on human sarcoma cells: a proteolytic system with surface-bound reactants.

Human HT-1080 fibrosarcoma cells produce urokinase-type plasminogen activator (u-PA) and type 1 plasminogen activator inhibitor (PAI-1). We found that after incubation of monolayer cultures with purified native human plasminogen in serum-containing medium, bound plasmin activity could be eluted from the cells with tranexamic acid, an analogue of lysine. The bound plasmin was the result of plasminogen activation on the cell surface; plasmin activity was not taken up onto cells after deliberate addition of plasmin to the serum-containing medium. The cell surface plasmin formation was inhibited by an anticatalytic monoclonal antibody to u-PA, indicating that this enzyme was responsible for the activation. Preincubation of the cells with diisopropyl fluorophosphate-inhibited u-PA led to a decrease in surface-bound plasmin, indicating that a large part, if not all, of the cell surface plasminogen activation was catalyzed by surface-bound u-PA. In the absence of plasminogen, most of the cell surface u-PA was present in its single-chain proenzyme form, while addition of plasminogen led to formation of cell-bound two-chain u-PA. The latter reaction was catalyzed by cell-bound plasmin. Cell-bound u-PA was accessible to inhibition by endogenous PAI-1 and by added PAI-2, while the cell-bound plasmin was inaccessible to serum inhibitors, but accessible to added aprotinin and an anticatalytic monoclonal antibody. A model for cell surface plasminogen activation is proposed in which plasminogen binding to cells from serum medium is followed by plasminogen activation by trace amounts of bound active u-PA, to form bound plasmin, which in turn serves to produce more active u-PA from bound pro-u-PA. This exponential process is subject to regulation by endogenous PAI-1 and limited to the pericellular space.

Cell Line↗
PubMed1989

Tissue-type plasminogen activator in subretinal fluid.

The plasminogen activation system is quantitatively the major mechanism of extracellular proteolysis. To evaluate its role in retinal detachment, plasmin and plasminogen activators were measured in subretinal fluid (SRF) from 12 eyes of twelve patients. Plasmin was detected in 5 eyes (mean 6.26 micrograms/ml, SD = 3.7 micrograms/ml). Tissue-type plasminogen activator was present in 5 eyes (mean activity 0.33 IU/ml, SD = 0.24 IU/ml) but the activity did not associate with the plasmin activity in all of the SRF samples. Urokinase-type plasminogen activator was not detected in SRF. We conclude that the plasmin system has been activated in SRF in some eyes with retinal detachment with tissue-type plasminogen activator as the predominant activator. Plasmin in SRF may enhance dispersion of pigment epithelial cells into the subretinal space and the vitreous, a phenomenon seen frequently in eyes with retinal detachment.

Adult↗
PubMed1989

Plasmin and plasminogen activator activities in tear fluid during corneal wound healing after anterior keratectomy.

Plasmin can degrade fibronectin and laminin, two important components of the extracellular matrix facilitating cell sliding and healing following a wound. In this study we investigated the relationship between the tear fluid level of plasmin and plasminogen activator and the healing of a corneal wound. Anterior keratectomy (AKE) was performed for seven rabbits (11 eyes). Eight eyes were rewounded after re-epithelialization. Tear fluid samples were collected with capillaries before wounding and during wound healing. Plasmin and plasminogen activator (PA) activities were determined using radial caseinolysis procedures. After AKE the plasmin concentrations increased rapidly, from a mean (+/- SEM) of 3.9 +/- 0.9 micrograms/ml to a mean of 37.9 +/- 7.8 micrograms/ml (p less than 0.01), and decreased during wound healing. Rewounding also resulted in an increase in plasmin concentration in the tear fluid (from a mean of 2.9 +/- 0.6 micrograms/ml to a mean of 5.0 +/- 1.1 micrograms/ml; p greater than 0.05). The PA activity showed an inverse trend as it decreased after AKE from a mean of 2.0 +/- 0.6 IU/ml to a mean of 0.3 +/- 0.1 IU/ml (p less than 0.001). During wound healing and re-epithelialization, the PA activity increased again, to 2.1 +/- 0.3 IU/ml (p less than 0.001). Abrasion of the newly grown epithelium in eight eyes caused a second elevation of PA activity which was not significant. This study demonstrates a close association between the healing of corneal wounds and changes in the plasmin and PA activities in tear fluid. Determination of the activity of these enzymes may therefore be useful for monitoring corneal wound healing.

Animals↗
PubMed1989

Plasmin-like proteinase associated with high molecular weight complexes in blister fluid of bullous pemphigoid.

Blister fluid from tense bullae of 10 patients with bullous pemphigoid was investigated using a radial caseinolysis assay and zymography. Proteolytic activity, varying from 4.7 to 10 micrograms/ml, was found in 3 out of 10 patients, by using the caseinolysis assay. Zymography revealed that a major part of this caseinolytic activity co-migrated with plasmin standard. In addition, in the zymography, proteolytically active high molecular weight complexes were seen. This characteristic pattern was seen in the zymography of both positive and negative samples in the caseinolysis assay. These high molecular weight complexes were not seen in the zymography of the blister fluid of 2 patients with epidermolysis bullosa or in the suction blister fluid of 3 healthy control patients. These findings suggest that plasmin is generated at some phase of the blister formation, being possibly involved in the pathomechanism of bullous pemphigoid.

Blister↗
PubMed1988

Elevation of tear fluid plasmin in corneal disease.

Plasmin concentration was determined in tear fluid from 76 eyes showing corneal epithelial disorders, such as corneal ulcers and erosions due to trauma or contact lens wear. Nearly 70% of the eyes with corneal disease had plasmin in their tear fluid, whereas plasmin was present in only 20% of the eyes in a control group of 50 eyes. Re-examination of the plasmin positive control eyes revealed conjunctival bacterial growth or mild subclinical viral infection in most cases. We conclude that plasmin is released into the tear fluid in the presence of corneal or conjunctival lesions or infections, suggesting a pathogenic role of plasmin in these disorders. The significance of the occurrence of plasmin in tear fluid during corneal wound healing is discussed.

Adult↗
PubMed1988

Plasmin in subretinal fluid.

Proteolytic activity was studied in subretinal fluid from 56 eyes with rhegmatogenous retinal detachment without vitreous or subretinal hemorrhage. Active plasmin (1.0-15.2 micrograms/ml) was found in 33 eyes and plasmin-inhibitor complexes in 3 eyes. Plasmin was detected more often in large detachments, but there was no clear correlation with the duration of the detachment or characteristics of the holes in the retina. It seems possible that plasmin in subretinal fluid may enhance release of cells from the pigment epithelium by degrading the extracellular matrix and contribute to the development of proliferative vitreoretinopathy.

Electrophoresis, Polyacrylamide Gel↗