Hydrocortisone regulates the dynamics of plasminogen activator and plasminogen activator inhibitor expression in cultured murine keratinocytes

Gender affects skin wound healing in plasminogen deficient mice

The fibrinolytic activity of plasmin plays a fundamental role in resolution of blood clots and clearance of extravascular deposited fibrin in damaged tissues. These vital functions of plasmin are exploited by malignant cells to accelerate tumor growth and facilitate metastases. Mice lacking functional plasmin thus display decreased tumor growth in a variety of cancer models. Interestingly, this role of plasmin has, in regard to skin cancer, been shown to be restricted to male mice. It remains to be clarified whether gender also affects other phenotypic characteristics of plasmin deficiency or if this gender effect is restricted to skin cancer. To investigate this, we tested the effect of gender on plasmin dependent immune cell migration, accumulation of hepatic fibrin depositions, skin composition, and skin wound healing. Gender did not affect immune cell migration or hepatic fibrin accumulation in neither wildtype nor plasmin deficient mice, and the existing differences in skin composition between males and females were unaffected by plasmin deficiency. In contrast, gender had a marked effect on the ability of plasmin deficient mice to heal skin wounds, which was seen as an accelerated wound closure in female versus male plasmin deficient mice. Further studies showed that this gender effect could not be reversed by ovariectomy, suggesting that female sex-hormones did not mediate the accelerated skin wound healing in plasmin deficient female mice. Histological examination of healed wounds revealed larger amounts of fibrotic scars in the provisional matrix of plasmin deficient male mice compared to female mice. These fibrotic scars correlated to an obstruction of cell infiltration of the granulation tissue, which is a prerequisite for wound healing. In conclusion, the presented data show that the gender dependent effect of plasmin deficiency is tissue specific and may be secondary to already established differences between genders, such as skin thickness and composition.

Comparative ultrastructural analyses of platelets and fibrin networks using the murine model of asthma

The murine Balb/c asthma model has been used successfully for a number of in vivo immunological applications and for testing novel therapeutics, and it is a reliable, clinically relevant facsimile of the human disease. Here we investigate whether this model can be used to study other components of the human body, e.g. ultrastructure. In particular, we investigate the effect of the phytomedicine Euphorbia hirta (used to treat asthma), on the ultrastructure of fibrin as well as platelets, cellular structures that both play an important role in the coagulation process. Hydrocortisone is used as positive control. Ultrastructure of the fibrin networks and platelets of control mice were compared to mice that were asthmatic, treated with two concentrations of hydrocortisone and one concentration of the plant material. Results indicate control mice possess major, thick fibers and minor thin fibers as well as tight round platelet aggregates with typical pseudopodia formation. Minor fibers of asthmatic mice have a netlike appearance covering the major fibers, while the platelets seem to form loosely connected, granular aggregates. Both concentrations of hydrocortisone make the fibrin more fragile and that platelet morphology changes form a tight platelet aggregate to a more granular aggregate not closely fused to each other. We conclude that E. hirta does not impact on the fragility of the fibrin and that it prevents the minor fibers to form the dense netlike layer over the major fibers, as is seen in untreated asthmatic mice. This ultrastructural morphology might give us better insight into asthma and the possible new treatment regimes.

Activation of gelatinases by fibrin is PA/plasmin system-dependent in human glomerular endothelial cells

Evidence suggests that fibrin deposit is related to severity of glomerulonephropathy. Fibrin is considered to play an active role beyond a haemostatic plug or temporary matrix in response to injury. We have reported that fibrin induced specific morphological changes and up-regulated intercellular adhesion molecule-1 expression of glomerular endothelial cells (GECs). Changes of gelatinases activity have been implicated playing a prominent role in glomerular diseases involving matrix turnover. This study examined whether overlying fibrin influences the expression of gelatinase A and B in cultured human GECs and mechanism underlying the activation. No gelatinase activity was detectable in supernatant of cultured GECs; however, physiological concentration of fibrin (0.5-2.0 mg/ml) induced a dramatic expression of activated MMP-2 and MMP-9 at both mRNA and protein level in a dose and time dependent manner. Increased mRNA level of membrane-type 1 matrix metalloproteinases (MT1-MMPs) was also found. Interestingly, we observed that fibrin also induced the expression of tissue type plasminogen activator (tPA), urokinase type plasminogen activator (uPA) and plasminogen activator inhibitor-1 by casein zymographic and reverse zymographic analysis. Fibrin plate assay revealed the net activity was PA predominant. Serine protease inhibitor aprotinin blocked the conversion of pro-gelatinase A and B to their active forms. The results demonstrate that overlying fibrin increased the secretion of gelatinase A and B from GECs. PA/plasmin proteolytic pathways contributed to the activation of gelatinases.

Deflazacort modulates the fibrinolytic pattern and reduces uPA-dependent chemioinvasion and proliferation in rheumatoid arthritis synoviocytes

OBJECTIVE

Extracellular fibrinolysis, controlled by the cell-associated fibrinolytic system (urokinase plasminogen activator, uPA; uPA receptor, uPAR; plasminogen activator inhibitor type-1, PAI-1), is involved in cartilage damage generation and in rheumatoid arthritis (RA) synovitis. Since steroids reduce the rate of radiological progression of RA, we planned to evaluate in healthy and RA synoviocytes the effects of the steroid deflazacort on uPA, uPAR and PAI-1 expression, and subsequent phenotypic modifications in terms of uPA/uPAR-dependent invasion and proliferation.

METHODS

uPA, uPAR and PAI-1 levels were studied by ELISA, RT-PCR (uPAR) and zymography (uPA) in synoviocytes from four RA patients and four healthy controls. Chemoinvasion was assessed by the Boyden chamber invasion assay, using Matrigel as the invasion substrate. Proliferation was evaluated by cell counting. Both invasion and proliferation were measured upon treatment with deflazacort 5 muM with or without parallel stimulation with uPA 500 ng/ml or in the presence of monoclonal anti-uPA and anti-uPAR antibodies.

RESULTS

Invasion and proliferation of RA synoviocytes require a proper functional balance of the fibrinolytic system. Both deflazacort and monoclonal antibodies against uPA and uPAR reduced expression and activity of the system, thus inhibiting invasion and proliferation. In RA synoviocytes, deflazacort induced higher PAI-1 and lower uPA and uPAR levels, as well as a decrease in uPA enzymatic activity. The levels of uPAR mRNA were concomitantly reduced, as was uPA-induced chemoinvasion. All these effects were also shown in controls, though to a lesser extent.

CONCLUSIONS

Deflazacort might control RA synovial proliferation and invasion by differential modulation of single members of the fibrinolytic system.

Non-invasive visualization of epidermal responses to injury using a fluorescent transgenic reporter

We describe transgenic mice in which expression of a reporter, the yellow fluorescent protein (YFP), is locally activated in epidermal cells at sites of injury. YFP is detectable a day after injury; its levels peak within 3 d, and then decline over the subsequent week. Expression is also activated by a chemical irritant, and is suppressed by topical administration of hydrocortisone. These mice permit non-invasive time-lapse monitoring of responses to injury in vivo. They can be used to detect epidermal activation and to test agents that may provoke or attenuate epidermal responses.

Changes of uPA and uPA-R expression in the cornea after alkali burn

PURPOSE

To investigate the expression levels of uPA and uPA-R in corneal repair after alkali burn.

METHODS

The corneal alkali burn models were established in vitro and in vivo, then immunocytochemistry (ICC) of uPA/uPA-R and image analysis and statistical evaluation were performed to determine their expression levels both in vitro and in vivo.

RESULTS

Compared with control group, the expressions of uPA and uPA-R after alkali burn had no significant increases till 6h, then increased rapidly from 12h to 24h and reached their maxima at 24h. From 24h, their expression levels decreased rapidly. In vivo, they rebounded again after 48h and attained their second peaks at 96h, respectively. After that, their expressions decreased again. The uPA-positive reaction mainly distributed in the cytoplasm while that of uPA-R mostly distributed on the cellular membrane. Their expression changes were similar to each other, both in vivo and in vitro. In vivo, uPA and uPA-R expressed and gathered in the basal layer of corneal epithelium.

CONCLUSIONS

These results suggest that the time phase of 24h after wound is the typical stage associating with the expressional maximum of uPA and uPA-R both in vivo and in vitro. Furthermore, the results also imply that the expression changes of uPA and uPA-R correlate to the wound healing after the corneal alkali burn, uPA and uPA-R coordinate with each other to stimulate the wound healing.

Elevated expression and release of tissue-type, but not urokinase-type, plasminogen activator after binding of autoantibodies to bullous pemphigoid antigen 180 in cultured human keratinocytes

In bullous pemphigoid (BP), the binding of BP180-specific antibodies to their hemidesmosomal target antigen is not sufficient for blister formation, but must be accompanied by the release of proteases. Using plasminogen activator (PA) knock-out mice, the PA system has previously been shown to be a prerequisite for blister formation in experimental murine BP. Here, we found elevated levels of plasmin and tPA, but not of uPA, in blister fluid from BP patients (n = 7) compared to blisters from patients with toxic epidermal necrolysis (n = 4) and suction blisters in healthy controls (n = 7). Subsequently, we addressed the question whether keratinocytes release PA in response to the binding of anti-BP180 antibodies. Treatment of cultured normal human keratinocytes with BP IgG, but not with control IgG, led to both increased protein and mRNA levels of tPA, but not of uPA, as determined by ELISA and RT-PCR, respectively. The specificity of this finding was confirmed using BP180-deficient keratinocytes from a patient with generalized atrophic benign epidermolysis bullosa, where no tPA release was observed after stimulation with BP IgG. Our results show the elevated expression and release of tPA from normal human keratinocytes upon stimulation with antibodies to human BP180. Keratinocytes, by secreting tPA, may thus play an active role in blister formation of BP.

Mechanisms of dexamethasone-mediated inhibition of cAMP-induced tPA expression in rat mesangial cells

BACKGROUND

Glucocorticoids are efficiently used as antiinflammatory and immunosuppressive therapies of renal diseases. However, long-term treatment often is associated with net changes in the turnover of extracellular matrix (ECM) components.

METHODS

We examined the impact of glucocorticoids on cAMP-triggered expression of tissue plasminogen activator (tPA), a protease prominently involved in glomerular ECM turnover.

RESULTS

By ELISA, the db-cAMP-mediated increase in extracellular tPA activity secreted by mesangial cells (MC) was markedly reduced in the presence of 100 nmol/L dexamethasone. The decrease of enzymatic activity was accompanied by an attenuation of tPA expression, as shown by Northern blot analysis. Furthermore, dexamethasone increased the steady-state mRNA level of the tPA-inhibitor 1 (PAI-1), thereby providing an additional mode of regulation of tPA activity. Mutational analysis revealed that the inhibition of tPA expression was localized within the proximal 2.3 kb of the 5'-flanking region of the rat tPA gene and critically depended on a cAMP response element (CRE) at position -185. EMSA demonstrated that binding to this CRE was affected by dexamethasone, since the db-cAMP-caused DNA binding of CREB and C/EBPbeta-immunopositive complexes was substantially reduced by dexamethasone. In parallel, dexamethasone decreased the nuclear abundance of db-cAMP-induced C/EBPbeta and phosphorylated CREB protein without affecting the total level of either transcription factor.

CONCLUSIONS

Suppression of cAMP-stimulated tPA expression by glucocorticoids occurs by interference with CREB and C/EBPbeta, the major transcription factors mediating cAMP responses. These observations may provide the molecular basis for the sclerotic processes within the glomerulus often complicating chronic glucocorticoid treatment.

Production of plasminogen activator inhibitor-1 by human mast cells and its possible role in asthma

The plasminogen activator inhibitor type 1 (PAI-1) has an essential role in tissue remodeling. The PAI-1 gene was induced by a combination of phorbol ester and calcium ionophore at the highest level among the inducible human mast cell genes that we have analyzed on a DNA microarray. PAI-1 was secreted by both a human mast cell line (HMC)-1 and primary cultured human mast cells upon stimulation, whereas PAI-1 was undetectable in either group of unstimulated cells. The secretion of PAI-1 was due to de novo synthesis of PAI-1 rather than secretion of preformed PAI-1. The functional significance of PAI-1 secretion was demonstrated by complete inhibition of tissue-type plasminogen activator activity with supernatants of stimulated HMC-1 cells. Furthermore, we were able to regulate PAI-1 gene expression in HMC-1 cells by known therapeutic agents. High-dose (1 microM) dexamethasone induced PAI-1 mRNA expression. Cyclosporin down-regulated the expression of the PAI-1 gene. Cycloheximide abrogated PAI-1 mRNA expression, suggesting that transcription of the PAI-1 gene requires de novo synthesis of early gene products, including transcription factors. Finally, we demonstrated PAI-1 in lung mast cells from a patient with asthmatic attack by double-immunofluorescence study. This is the first report demonstrating that activated human mast cells release a striking amount of functionally active PAI-1. These results suggest that PAI-1 could play an important role in airway remodeling of asthma, and inhibition of PAI-1 activity could represent a novel therapeutic approach in the management of airway remodeling.

Stimulatory effects of dibutyryl cyclic adenosine monophosphate on cytokine production by keratinocytes and fibroblasts

BACKGROUND

Clinical studies have shown that ointment containing dibutyryl cyclic adenosine monophosphate (DBcAMP) promotes wound healing.

OBJECTIVES

We aimed to elucidate the mechanisms of the beneficial effect of DBcAMP in wound healing.

METHODS

An investigation was made of the effects of DBcAMP on in vitro cytokine release from cultured keratinocytes and fibroblasts derived from normal human skin.

RESULTS

DBcAMP stimulated keratinocyte proliferation through increased interleukin (IL)-6 production by fibroblasts, and transiently enhanced production of transforming growth factor (TGF)-beta1 by fibroblasts at an early stage of incubation. DBcAMP also stimulated fibroblast proliferation, resulting in further increases in IL-6 and TGF-beta1.

CONCLUSIONS

We conclude that this series of stimulative actions on cytokine secretion, together with the facilitation of cell proliferation, contribute to the effects of DBcAMP on the healing of skin ulcers.