Plasminogen activator in psoriatic scales is of the tissue-type PA as identified by monoclonal antibodies

Serum is a potent stimulator of keratinocyte tissue plasminogen activator expression

The plasminogen activator (PA) proteolytic cascade comprises two enzymes known as urokinase PA (uPA) and tissue PA (tPA), both of which activate plasminogen to plasmin. In normal human epidermis uPA is the predominant PA. In lesional epidermis from patients with a variety of cutaneous diseases, including psoriasis, pemphigus foliaceous, pemphigus, vulgaris, bullous pemphigoid, and benign chronic pemphigus, however, tPA is selectively elevated and becomes the predominant PA activity. The enhanced tPA is likely to be a reaction to the disease challenge rather than an initiating event in these clinically and etiologically diverse lesions. In the present study, cultured human keratinocytes, propagated under serum-free conditions, have been shown to respond to the addition of bovine or human serum with an increase in tPA activity and antigen. Furthermore, tPA is found predominantly in the suprabasal keratinocytes both in lesional epidermis and in stratified cultures that have been incubated for approximately 8 d in the presence of serum. These results suggest a possible mechanism by which epidermal tPA may be increased in diverse cutaneous lesions: The plasma infiltrated into lesional epidermis may stimulate the suprabasal keratinocytes in vivo to express tPA.

Expression of plasminogen activator enzymes in psoriatic epidermis

The plasminogen activators, tissue type and urokinase type (tPA and uPA, respectively) have been identified in human skin under normal conditions and in various inflammatory dermatoses, including psoriasis. By Northern blot analyses, mRNA for uPA, but not for tPA, has been previously identified in epidermal extracts from normal skin, whereas in psoriasis, mRNA for tPA is readily detected. To further characterize uPA and tPA expression in psoriasis, the localization of uPA and tPA mRNAs was evaluated by in situ hybridization. Studies were conducted using lesional and nonlesional skin of patients with psoriasis as well as normal skin. Additionally, in situ zymography using casein gel overlays was utilized to assess enzymatic activity. In psoriatic lesional skin, both uPA and tPA mRNAs were demonstrated by in situ hybridization. Message for tPA was observed throughout the epidermis with areas of accentuation in the superficial stratum spinosum. Message for uPA was more focal and was localized primarily in the basal layer. Zymography showed tPA activity was coordinately increased in psoriatic lesions. Uninvolved skin of psoriatic patients was similar to that of normal skin with respect to expression of plasminogen activators. In normal epidermis, neither tPA nor uPA mRNA could be detected by in situ hybridization. Activity for uPA, but not tPA, was observed by zymography. These studies suggest that alterations in plasminogen activators expression may contribute to the pathogenesis of psoriasis.

Expression of plasminogen activator inhibitor type 2 in normal and psoriatic epidermis

The plasminogen activator (PA) proteolytic cascade has been implicated in the regulation of cell activities, including proliferation and differentiation, both of which occur continuously in normal human epidermis and are aberrant in psoriatic epidermis. To elucidate further the mechanisms by which PA is regulated in epidermis, we evaluated the levels of PA inhibitors type 1 (PAI-1) and type 2 (PAI-2) in normal and psoriatic epidermis. PAI-2, but not PAI-1, was detectable by mRNA, antigen, and activity assays, indicating that PAI-2 is the predominant epidermal PA inhibitor. In situ hybridization revealed that PAI-2 mRNA occurred throughout normal epidermis, although the signal was most intense in the granular layers. Similarly, PAI-2 antigen was most prominent in the granular layers; its distribution in these differential layers was along the cell periphery. Diffuse, fainter staining for PAI-2 was also detected in the basal cells and in some spinous layers of normal epidermis. Extracts of normal epidermis contained PA inhibitory activity identified as PAI-2 by immunoprecipitation with specific antibody. In psoriatic epidermis, PAI-2 mRNA and antigen were most prominent in the more superficial layers beneath the cornified cells. As with normal epidermis, PAI-2 assumed a pericellular distribution in the psoriatic cells. These data demonstrate that PAI-2 is constitutively expressed in vivo by keratinocytes in human epidermis and indicate that this protein is the predominant inhibitor of PA activity in normal and psoriatic human epidermis.

Immunohistochemical characterization of the plasminogen activator system in psoriatic epidermis

The relative topographical distribution of urokinase-type plasminogen activator (uPA), tissue-type PA (tPA), PA-inhibitor-1 (PAI-1), PA-inhibitor-2 (PAI-2), plasmin(ogen), alpha 2-antiplasmin, and alpha 2-macroglobulin was studied in lesional epidermis of psoriasis vulgaris, and in normal epidermis, by immunohistochemistry. In psoriatic epidermis, tPA predominated, although uPA was found in some biopsies. PAs were not detected in normal epidermis. PAI-1 was not detected in normal epidermis and was only present in a proportion of biopsies of psoriatic lesions. PAI-2 was found in normal and psoriatic epidermis. Plasmin(ogen) was confined to the basal cell layer of normal epidermis, whereas in lesional psoriatic skin it was scattered throughout the epidermis. Alpha 2-antiplasmin and alpha 2-macroglobulin were not found in the epidermis of normal skin. In psoriatic epidermis alpha 2-antiplasmin was confined to the subcorneal layer, whereas staining for alpha 2-macroglobulin was found only in a proportion of biopsies, in the upper epidermis. Our immunohistological findings indicate that colocalization of tPA and its substrate plasminogen may allow efficient generation of plasmin, and that the focal absence of plasmin inhibitors may then favour the persistence of plasmin activity.

Urokinase-type plasminogen activator in human eccrine sweat

The presence of urokinase-type plasminogen activator (uPA) in human eccrine sweat has not been reported previously. Clean sweat was obtained from the upper trunk and arms of subjects which had been painted with white petrolatum to minimize epidermal contamination. Sweat was concentrated x 50 by ultrafiltration, and its PA activity determined by the two-step assay method (conversion of plasminogen to plasmin with the subsequent assay of plasmin activity using the substrate S-2251). PA activity was detectable in nine of 17 subjects by this method, which probably represents an underestimate of the true activity because of possible loss of the enzyme during concentration. Scraped (crude) sweat samples contained less PA activity. Sephacryl S-200 gel chromatography of the PA-positive pooled sweat showed a major peak of PA activity at M(r) 55,000. Gelatin-polyacrylamide enzymography revealed a major PA band at M(r) 55,000 and a minor band at 33,000. Sweat PA activity was 94% inhibited by epidermal PA inhibitor and anti-uPA IgG, but not by anti-tPA IgG. We conclude that the PA activity in sweat is derived from the sweat gland and is most likely of the urokinase type. The physiological significance of sweat uPA remains to be determined.

Urokinase plasminogen activator is immunocytochemically detectable in squamous cell but not basal cell carcinomas

The presence of plasminogen activators (PA) in a variety of solid tumors appears to correlate, in a number of instances, with enhanced invasive or metastatic capabilities. In the present study, we have immunocytochemically examined basal cell (BCC) and squamous cell carcinomas (SCC) comprising a spectrum of histologic subtypes for the presence of urokinase-type (uPA) and tissue-type (tPA) PA. Neither uPA nor tPA was noted in any BCC, whether of the nodular, infiltrative, morpheaform, or basosquamous variety. uPA but not tPA was seen in 12 of 16 SCC examined; the tumors lacking uPA were all histologically well differentiated. No relationship between uPA expression and depth of invasion was noted, and uPA was not preferentially expressed at tumor borders. We conclude that uPA presence in SCC may relate to the degree of differentiation.

mRNA for tissue-type plasminogen activator is present in lesional epidermis from patients with psoriasis, pemphigus, or bullous pemphigoid, but is not detected in normal epidermis

Plasminogen activator (PA), which catalyzes the conversion of plasminogen to the proteinase plasmin, has been implicated in a variety of cutaneous disorders. Lesional epidermis from patients with psoriasis, pemphigus, bullous pemphigoid, and Hailey-Hailey disease contains elevated levels of tissue-type PA (tPA) activity compared to non-lesional epidermis or to epidermis from normal individuals. In the present study, we have used Northern blot analysis to demonstrate that mRNA for tPA is detectable in lesions from patients with psoriasis, pemphigus, and bullous pemphigoid, but is not detectable in normal epidermis. These data strongly suggest that the tPA enzymatic activity present in lesional epidermis results from enhanced synthesis of the enzyme in situ, secondary to elevated steady-state levels of tPA mRNA. Cultured keratinocytes likewise are shown to contain tPA mRNA. Previous investigators have suggested that the phenotypes of keratinocytes in culture, psoriatic epidermis, and epidermis in the process of wound reepithelialization are comparable. Our findings, combined with those of other investigators, suggest that elevated tPA expression may be another common feature of epidermis under these circumstances.

Role of specific membrane receptors in urokinase-dependent migration of human keratinocytes

On the basis of both 125I-labeled plasminogen activator binding analysis and transmission electron microscopy studies of the interaction of a plasminogen activator/gold complex with cell membranes, we have found that human keratinocytes have specific receptors for human urokinase-type plasminogen activator distributed on the cell surface as singlets, or as small or large clusters. The use in binding experiments of the purified A chain of urokinase-plasminogen activator and of anti-A chain monoclonal antibodies has indicated that cell receptors are specific for a sequence present on the A chain, as previously reported for other cells. The interaction of both the native molecule and the purified A chain with such receptors stimulates mobilization of keratinocytes in an in vitro cell model system (Boyden chamber), when present in the lower compartment of the migration apparatus in nanomolar concentrations. Preincubation of chemoattractants with a monoclonal antibody which prevents receptor/ligand interaction also prevents plasminogen activator-induced cell migration. These data suggest that, under the conditions used in this in vitro model system, the plasminogen activator-dependent mobilization of keratinocytes depends on the interaction of the ligand with free receptors on the cell surface, and is independent of plasmin generation.

Influence of culturing temperature and proteinase inhibitors on the spontaneously occurring changes in the organ culture of psoriatic skin

Skin explants from involved psoriatic lesions showed dissociation of keratinocytes, dermal-epidermal separation and degenerative changes such as cytoplasmic swelling of subcorneal prickled cells within 24 h after culture initiation at 37 degrees C in the absence of fetal bovine serum (FBS). These histological changes developed time dependently, while normal skin explants did not exhibit such phenomena. Some of the uninvolved psoriatic skin explants showed only degenerative change 48 to 72 h after culture initiation at 37 degrees C. To determine the nature of these spontaneously occurring changes in psoriatic skin explants and then to approach the pathogenesis of psoriasis, the effects of FBS, various proteinase inhibitors (PIs) and culturing temperature (37, 31, 24 degrees C) were examined in skin organ culture of normal and involved psoriatic skin. At 37 degrees C, only serine PIs (5 or 10 mg/ml of soybean trypsin inhibitor (SBTI), 1000 KIU/ml of aprotinin, or 2 mg/ml of camostat mesilate in the medium) or FBS (20% in the medium) could suppress the occurrence of dissociation of keratinocytes and dermal-epidermal separation but not the degenerative change in involved psoriatic skin explants, while other types of PIs did not exhibit any such inhibition. When the culturing temperature was reduced from 37 degrees C to 31 or 24 degrees C, the formation of dissociation of keratinocytes and dermal-epidermal separation was almost non-existent and only moderate degenerative change was observed. The addition of FBS or serine PIs to the culture at 31 degrees C revealed the formation of very weak degenerative change.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue-type plasminogen activator in plasma from breast cancer patients determined by enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) using monoclonal and polyclonal antibodies against t-PA was used to measure the concentration of tissue-type plasminogen activator (t-PA) in plasma from 34 healthy donors and 92 breast cancer patients with a varying extent of disease. The mean value of t-PA in plasma for the healthy donors was 2.4 +/- 2.1 ng ml-1 (s.d.). The mean value for the breast cancer patients was 5.3 +/- 4.3 ng ml-1. This increase was statistically significant at the 1% level. There was a positive correlation between the mean t-PA plasma concentration and the extent of disease in different groups of patients. Taking 5.0 ng ml-1 as cut-off point, about 40% of the patients were positive, and 6% of the normal controls were false positive. Twenty-five per cent of the patients in complete remission, 28% of the patients with minimal tumour burden, 60% of the patients with moderate tumour burden, and 90% of the patients with massive tumour burden were positive. It is possible that the patients with an elevated plasma t-PA represent a group with a particularly bad prognosis.

Urokinase- and tissue-type plasminogen activators in keratinocytes during wound reepithelialization in vivo

Urokinase- and tissue-type plasminogen activators (u-PA and t-PA) were identified immunohistochemically during reepithelialization of mouse and human skin wounds, by means of polyclonal and monoclonal antibodies. In incised mouse skin wounds u-PA immunoreactivity was found in keratinocytes at the edge of the wound after 12 h, and at days 2 to 10 after wounding it was found in virtually all keratinocytes of the epithelial outgrowth that gradually covered the wound. At day 14, the epidermis appeared normal and no u-PA immunoreactivity was detected. t-PA immunoreactivity was found from day 5 to day 10 in some keratinocytes located superficially in the epidermal outgrowths near the edge of the mouse wounds. In 3- and 5-day old human skin wounds, u-PA immunoreactivity was found in keratinocytes in the epithelial outgrowths, whereas no t-PA immunoreactivity was detected. No u-PA and no t-PA immunoreactivity was found in normal mouse and human epidermis. The specificity of the staining was supported by a variety of controls, including absorption of the polyclonal antibodies with highly purified u-PA and t-PA preparations and zymographic analysis of extracts of wound tissue. The function of the plasminogen activators during reepithelialization is discussed and it is suggested that the keratinocytes use plasmin activated by u-PA for dissecting their way through the provisional matrix in the upper part of the granulation tissue.

Epidermal plasminogen activator is abnormal in cutaneous lesions

To investigate the role of plasminogen activator (PA) in cutaneous disease, we have used biochemical and immunocytochemical techniques to examine PA in normal and lesional skin. In normal human dermis, tissue PA is the predominant PA activity; however, in normal epidermis, urokinase type PA is the predominant PA activity. In contrast, PA activity in epidermis from lesions of patients with a variety of cutaneous diseases was predominantly tissue type enzyme with a much smaller contribution from urokinase. Our patient population included individuals with benign chronic pemphigus, pemphigus vulgaris, pemphigus foliaceous, bullous pemphigoid, or psoriasis. Using rabbit antibody specific for tissue type PA, we have immunocytochemically localized this enzyme in lesions from individuals with the above disorders. Our results indicate that tissue PA is consistently elevated in cutaneous lesions with diverse etiology, pathology, and clinical presentation.

A monoclonal antibody recognizing plasminogen and plasmin--altered reactivity in psoriatic lesions

To study the organization of the plasminogen activator/plasminogen-plasmin (PA/PG-P) system in human epidermis we raised monoclonal antibodies with specificity for human plasminogen and plasmin (PG-P). Monoclonal antibody P2, which appeared most suitable for immunohistology, is a mouse monoclonal antibody of IgG1 subtype, specific for the precursor enzyme plasminogen and for the high molecular weight chain of the active enzyme, plasmin. Immunofluorescence analysis of normal human epidermis revealed that reactivity with P2 was confined to the basal cell layer. In psoriatic lesions, however, this regional organization was not found. Immunoreactivity in this case was scattered throughout all the hyperproliferating cell layers, which is taken as evidence for an altered distribution of PG-P in psoriatic lesions. In psoriasis other components of the PA/PG-P system have previously been found to be altered. In this context our findings add to the hypothesis that this system may be involved in the pathology or the pathogenesis of psoriatic lesions.

Plasminogen activator inhibitors from placenta and fibrosarcoma cells are antigenically different as evaluated with monoclonal and polyclonal antibodies

Plasminogen activator inhibitor (PAI) purified from human placenta was compared to PAI purified from conditioned cell culture fluid of the human fibrosarcoma cell line HT-1080. The two inhibitors had a similar mobility (Mr approximately 50,000) in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Purified placental inhibitor revealed 2 major and 1 minor Coomassie blue stainable bands, while the fibrosarcoma inhibitor appeared as one band. By immunoblotting analysis both monoclonal and polyclonal antibodies against each of the inhibitors showed reaction with the inhibitor against which they were raised, but not cross reaction with the other inhibitor. Similar results were obtained, when antibody binding was tested by ELISA with the inhibitors coated on the solid phase. HPLC fingerprint patterns of cyanogen bromide fragments of the two inhibitors were different. The inhibitory activity of the placental PAI was decreased by a factor of 3 after incubation with SDS, while that of the fibrosarcoma PAI was increased by a factor of 30. It is concluded that the two inhibitors show no detectable common antigenic determinants and most likely are products of different genes.

Immunohistochemical localization of urokinase- and tissue-type plasminogen activators in psoriatic skin

Biopsies of involved and uninvolved skin from psoriatic patients and of normal skin were stained immunocytochemically with monoclonal antibodies against urokinase-type (u-PA) and tissue-type (t-PA) plasminogen activator using a multilayer peroxidase technique. Epidermis from psoriatic lesions showed focal staining for u-PA in and between the basal keratinocytes in the suprapapillary epidermal areas, while t-PA was found in the superficial keratinizing cells, including both stratum spinosum and the parakeratotic layer. No staining of keratinocytes was observed in uninvolved and normal skin. The specificity of the staining was supported by the finding that 3 different monoclonal antibodies and polyclonal antibodies against each of the plasminogen activators gave identical staining, while monoclonal antibodies of irrelevant specificity gave no staining. The present findings suggest abnormalities in the regulation of both types of plasminogen activators in psoriatic epidermis.

Hormonal regulation of extracellular plasminogen activators and Mr approximately 54,000 plasminogen activator inhibitor in human neoplastic cell lines, studied with monoclonal antibodies

We have studied the regulation by glucocorticoids and dibutyryl cAMP of the amounts of urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA) and a Mr approximately 54000 plasminogen activator inhibitor accumulated in serum-free conditioned culture fluid by a human fibrosarcoma, a human glioblastoma and a human melanoma cell line (HT-1080, UCT/gl-1 and Bowes). For the quantitation of u-PA and t-PA, we used sandwich-type ELISA with a combination of polyclonal and monoclonal antibodies. For an estimation of variations in the amount of the inhibitor, we used sodium dodecyl sulphate-polyacrylamide gel electrophoresis followed by Coomassie blue staining of conditioned culture fluid proteins, the inhibitor protein band being identified by its selective removal by passage of the conditioned culture fluids through a column with monoclonal antibodies against the inhibitor. The modulation of the 3 proteins by the hormonal agents varied greatly between the cell lines. The proteins were independently regulated, in the sense that the hormonal agents did not concomitantly change their levels in the direction expected either to increase or decrease total extracellular plasminogen activator activity. In conditioned culture fluids containing both t-PA and inhibitor, the two were present in the medium as a Mr approximately 120 000 complex. In contrast, no u-PA inhibitor complexes were found in conditioned culture fluid from any of the cell lines; this is likely to be due to the occurrence of u-PA in the culture fluid in the one-chain proenzyme form, which, unlike active u-PA, does not react with the inhibitor. These findings illustrate the complexity of the regulation of extracellular plasminogen activator activity, and imply that the presumed functional diversity of u-PA and t-PA may be related to their independent regulation.

Plasminogen activators catalyse conversion of inhibitor from fibrosarcoma cells to an inactive form with a lower apparent molecular mass

Purified approximately 54 kDa plasminogen activator inhibitor from human fibrosarcoma cells was converted to an inactive form with slightly higher electrophoretic mobility by incubation with catalytic amounts of urokinase-type or tissue-type plasminogen activator. Serine proteinase inhibitors and a monoclonal antibody against urokinase-type plasminogen activator inhibited the conversion, indicating that it was caused by plasminogen activator-catalyzed proteolysis. These findings represent the first demonstration of a well-defined protein apart from plasminogen, constituting a substrate for plasminogen activators.