Plasminogen activator release from cultured murine mast cells

Matrix metalloproteinases and their tissue inhibitors in endometrial remodelling and menstruation

The architecture of the human endometrium is extensively remodelled during the course of each normal menstrual cycle, unlike most other tissues and organs which undergo very little change during adult life. During menstruation, when loss of most of the functionalis layer occurs, there is concomitant epithelial regrowth; repair of the luminal surface is complete almost as bleeding ceases. During the proliferative phase of the cycle and under the influence of rising oestrogen levels, the stromal cells, glands and blood vessels undergo rapid proliferation which results in tissue thickening. Following ovulation (around day 14 of the idealized 28-day cycle), the secretory phase of the cycle is characterized by increasing tortuosity of the spiral arterioles and glands and increased glandular secretory activity. After about day 22, decidualization of many of the stromal fibroblasts also occurs, the resultant decidual cells having many characteristics typical of epithelial cells. Periods of tissue oedema are apparent both in mid-proliferative (days 8–11) and mid-secretory (days 20–23) endometrium. Late in the cycle, there is regression of the tissue as menstruation is initiated.

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.

Molecular and functional characterization of the urokinase receptor on human mast cells

The urokinase receptor system is involved in several biological processes including extracellular proteolysis, cell invasion, and chemotaxis. Mast cells are multifunctional perivascular cells that play an important role in the regulation of microenvironmental events. We report that primary human mast cells and the human mast cell line HMC-1 express the receptor for urokinase. As assessed by Northern blotting and reverse transcription polymerase chain reaction technique, purified human lung mast cells and HMC-1 cells expressed urokinase receptor mRNA in a constitutive manner. Using a toluidine blue/immunofluorescence double staining technique and monoclonal antibodies, surface expression of urokinase receptor was demonstrable in lung, skin, uterus, heart, and tonsil mast cells, whereas the low density lipoprotein receptor-related protein was not detectable. Binding of monoclonal antibody VIM5 (recognizing the urokinase binding domain of urokinase receptor) to HMC-1 could be blocked by high molecular weight but not low molecular weight urokinase. Binding analyses performed with 123I-urokinase revealed expression of 271,000 +/- 55,000 high affinity urokinase binding sites per HMC-1 cell, with a calculated dissociation constant of 1. 29 +/- 0.3 nM. Purified urokinase induced dose-dependent migration of primary mast cells and HMC-1 in a chemotaxis assay without inducing release of histamine. The mast cell agonist stem cell factor also induced migration of HMC-1 and caused up-regulation of expression of urokinase receptor mRNA. Together, our data show that human mast cells express functional receptors for urokinase. Expression of urokinase receptors on mast cells may have implications for mast cell-dependent microvascular processes associated with fibrinolysis, migration, or local tissue repair.

An electrophysiological and histological study of trypsin induced demyelination

Ten-microliters quantities of trypsin or saline were injected into rat tibial nerve and the physiological and histological changes evaluated and compared to the focal demyelinating lesions induced by intraneural injection of rabbit EAN serum and proteinase K. The injection of trypsin produced progressive conduction block that was maximal on day 4, and a slowing of motor nerve conduction. Early retraction of myelin at paranodes, vesicular change, and macrophage stripping of myelin from nerve axons were seen on histological examination. At day 4, the first groups of completely demyelinated axons were seen, typically in a perivascular distribution. These changes were similar to those seen in the positive controls and thus support the postulate that proteolytic enzymes from macrophages--the dominant cellular species within the demyelinating lesion, play a central role in degradation of the myelin sheath in demyelinating diseases.

Partial inhibition of bone resorption by disodium cromoglycate in a synchronized model of bone remodeling

In a previous study we observed that mast cell degranulation might be associated to bone resorption. To verify this assumption, the efficiency of cromoglycate was assessed on a synchronized sequence of bone remodeling induced in male Wistar rats along the mandibular cortex. After 4 days (time of osteoclastic peak in this model), cromoglycate (15/mg/kg and 30 mg/kg/d per os) decreased the number of degranulating mast cells, especially in the population adjacent to the bone surface. Concomitantly the extent of resorption surface was decreased vs untreated animals. Active osteoclasts were lower whereas the total number of osteoclasts (both active and inactive) was not statistically modified. The mean osteoclast-bone interface was not modified. No dose effect was found. These data indicate that mast cell degranulation is involved in the events leading to osteoclast resorption, presumably in the mechanisms providing osteoclast access to bone surface.

Changes in mast cell number during the activation phase of an induced synchronized remodeling sequence in the rat

Increase in mast cell (MC) number has been reported in some pathological conditions with increased remodeling. However, it is not known whether MCs are involved in the physiological remodeling of bone. In the present study the possible variations in MCs were investigated during the activation phase in a rat model of synchronized remodeling. Seven groups of 10 rats were used. As early as the first day of induction, MCs increased by 50% and then decreased on day 2. The same pattern of changes recurred on days 3 and 4. Intact non-degranulating MCs increased mainly at some distance from the bone surface. Degranulating MCs conversely decreased near the cambium layer of the periosteum. Prostaglandins were not involved in these changes. These results suggest an association between the events leading to the onset of bone resorption and MCs. Degranulation might induce the release of agents active on these events.