Evidence for regulation of endothelial plasminogen-activating system by polymorphonuclear leukocyte elastase

Effects of inhibition of urokinase-type plasminogen activator (u-PA) by amiloride in the cornea and tear fluid of eyes irradiated with UVB

The purpose of the present study was to test our hypothesis that amiloride, a specific u-PA inhibitor, effectively decreases u-PA activity in cornea as well as in tear fluid and favourably affects corneal healing. Therefore, comparative histochemical and biochemical studies of u-PA and the effects of amiloride were performed on rabbit corneas and tear fluid using the sensitive fluorogenic substrate Z-Gly-Gly-Arg-7-amino-4-trifluoromethylcoumarin. Rabbit eyes were repeatedly irradiated with UVB for 9 days and during the irradiation topically treated with amiloride (1 mg/ml saline) or placebo (saline) (dropwise, 5 times daily). Results show that in placebo-treated eyes, UVB evoked the appearance of u-PA activity in cornea and tear fluid in early stages of irradiation, and u-PA levels increased during irradiation. Corneal epithelium was gradually lost and remnants of the epithelium as well as keratocytes in the upper part of corneal stroma showed high u-PA activity. Finally, corneas lost their epithelium completely. In corneal stroma, numerous u-PA-containing inflammatory cells were present. Corneas were vascularized. When amiloride was dropped on the eye surface on the first day of irradiation and subsequently daily until the end of the experiment, u-PA activity in both cornea and tear fluid was strongly inhibited. Corneas were covered with a continuous epithelium until the end of the experiment. The number of inflammatory cells was significantly decreased. Corneal vascularization was reduced by 50%. In conclusion, early application of amiloride inhibited u-PA activity in UVB-irradiated corneas as well as in tear fluid and diminished the development of corneal pathology.

The appearance and possible role of plasminogen activator of urokinase type (u-PA) activity in the cornea related to soft contact lens wear in rabbits

This is the first study in which u-PA activity is detected in situ during SCL wear. The histochemical localization of u-PA activity is done by the methods of Lojda using unfixed cryostat sections on semipermeable membranes and a gel incubation medium containing sensitive substrates with the 7-amino-4-trifluoromethylcoumarin (AFC) (Enzyme Systems Products, Sierra Lane, Dublin, CA, USA) leaving groups. Z-Gly-Gly-Arg-AFC and Glut-Gly-Arg-AFC were employed as the substrates. The results show that in the normal,cornea u-PA activity is absent. Also the wearing of SCL does not evoke the appearance of u-PA activity in the cornea within the first three days. On day 4 the first u-PA activity appears; it is located in the superficial layers of the corneal epithelium. On day 7 of SCL wear, u-PA activity is present in all layers of the corneal epithelium and (to a lesser extent) also in the comeal endothelium; keratocytes of the corneal stroma are only slightly active for u-PA. Extended SCL wear (for two weeks) leads to an increase of u-PA activity in keratocytes beneath the epithelium. Also, some inflammatory cells (mainly polymorphonuclear leukocytes, PMNs) present in the corneal stroma are enzymatically active. After three weeks of SCL wear the number of PMNs in the corneal stroma increases; some PMNs are highly active for u-PA. In the corneal endothelium the u-PA activity is also highly pronounced. It can be concluded that extended SCL wear leads to the gradual increase of u-PA activity in the rabbit cornea. It is suggested that active u-PA is involved in the corneal damage related to SCL wear.

The appearance of active plasminogen activator of urokinase type (u-PA) in the rabbit anterior eye segment irradiated by UVB rays. A histochemical and biochemical study

Repeated irradiation of the rabbit eye with UV rays of 312 nm wavelength (UVB) evoked the appearance of active plasminogen activator of urokinase type (u-PA) in the anterior eye segment. Using histochemistry, active u-PA appeared first in the corneal epithelium followed by the corneal endothelium, inflammatory cells in the corneal stroma and the lens epithelium. With a semiquantitative fluorescent method active u-PA was also found in the tear fluid and aqueous humour. UV rays of 365 nm wavelength (UVA) under the same conditions did not cause the appearance of active u-PA in the anterior eye segment.

Increased elastase-alpha 1-antitrypsin complex in fulminant hepatic failure: relationship to bacterial infection and activation of coagulation

To study the effect of infection, a frequent complication of fulminant hepatic failure (FHF), on the release of elastase from polymorphonuclear leucocytes and its inhibition in circulation we have measured the concentrations of alpha 1-antitrypsin, which binds and inhibits elastase in the circulation, and of elastase-alpha 1-antitrypsin complex, in 30 patients with FHF. Elastase-alpha 1-antitrypsin complex was significantly increased in FHF as compared to controls (303 +/- 51 micrograms/l compared to 37 +/- 5 micrograms/l; n = 10; P less than 0.001) demonstrating activation of leucocytes in FHF. Infection caused greater release of leucocyte elastase, complex levels were significantly greater in patients who were infected when compared to those who were not (463 +/- 84 micrograms/l; n = 13 compared to 180 +/- 46 micrograms/l; n = 17; P less than 0.01). Also patients who survived had significantly lower complex levels than those who did not (212 +/- 49 micrograms/l; n = 18 compared to 440 +/- 94 micrograms/l; n = 12; P less than 0.02). alpha 1-Antitrypsin activity was not significantly different from control subjects (0.99 +/- 0.06 U/ml compared to 0.97 +/- 0.05 U/ml). However alpha 1-antitrypsin activity was significantly higher in patients who survived (1.17 +/- 0.05 U/ml; n = 18) compared to those who did not (0.71 +/- 0.03 U/ml; n = 12; P less than 0.001) and patients who died had significantly lower levels than control subjects (P less than 0.01) indicating the importance of maintenance of normal inhibitor levels in patients with FHF. The leucocyte activation and release of elastase in FHF was linked to activation of the coagulation system; elastase--alpha 1-antitrypsin complex levels correlated significantly with thrombin-antithrombin III complex levels (r = 0.68; P less than 0.001) and inversely with fibrinogen (r = -0.71; P less than 0.001).

Natural human monocyte gelatinase and its inhibitor

Gelatinases produced by stimulated peripheral blood monocytes were detected by substrate zymography and were compared with those derived from tumor cells. Stimulated monocytes were found to produce an 85 kDa gelatinase which co-migrated upon electrophoretic separation and cross-reacted in immunoprecipitation experiments with a phorbol ester inducible metalloprotease from human tumor cells. The intact natural gelatinase (85 kDa), a high molecular weight and complexed gelatinase as well as a proteolytic fragment (25 kDa) were purified by substrate- and antibody-affinity chromatography techniques. Aminoterminal sequence analysis showed that natural monocyte gelatinase occurs as a truncated form of tumor cell gelatinase/type IV collagenase. Furthermore, peripheral blood monocytes were found to also produce a tissue inhibitor of metalloproteases (TIMP). TIMP was co-purified with gelatinase on gelatin sepharose and identified by microsequencing. The balanced and regulated production of gelatinase and TIMP might be important in monocyte migration and tissue remodeling.

Tumor necrosis factor enhances the neutrophil-dependent increase in endothelial permeability

We examined the effect of tumor necrosis factor alpha (TNF alpha) on the increase in pulmonary microvascular endothelial monolayer permeability induced by activated neutrophils (PMN). Layering of PMN onto endothelial monolayers followed by activation of PMN with phorbol 12-myristate 13-acetate (PMA) increased 125I-albumin clearance rate across the monolayers. Pretreatment of endothelial monolayers for 6 hr with TNF alpha (200 U/ml) potentiated the PMN-dependent increase in endothelial permeability, whereas 1 hr or 6 hr pretreatment of endothelial monolayers with 200 U/ml and 100 U/ml, respectively, TNF alpha did not enhance the response. Adherence of PMN to the endothelial cells was increased at 1 and 6 hr after TNF alpha (200 U/ml) treatment, but the adherence response was markedly greater following 6 hr of TNF alpha. The TNF alpha treatment of endothelial cells did not enhance neutrophil activation responses to PMA. Pretreatment of PMN with IB4, a MAb to the CD18 integrin, the common beta subunit of the adhesion proteins LFA-1, Mac-1, and p150,95 of PMN, reduced the increases in PMN adherence and the endothelial monolayer permeability induced by the 6 hr TNF alpha treatment. In contrast, pretreatment of PMN with OKM-1, a MAb to the CD11b epitope (alpha-subunit), had no effect on the adherence and the potentiation of the increase in permeability. The potentiation of the PMN-dependent permeability increase and enhanced endothelial adhesivity at 6 hr after TNF alpha priming of endothelial cells was dependent on protein synthesis. The results indicate that protein synthesis-dependent expression of an endothelial ligand for CD18 and resultant endothelial hyperadhesiveness potentiates the PMN-mediated increase in endothelial permeability after TNF alpha activation of endothelial cells. The priming of endothelial cells by TNF alpha may be a critical step in the mediation of endothelial injury.

Pulmonary edema induced by phagocytosing neutrophils. Protective effect of monoclonal antibody against phagocyte CD18 integrin

We studied the changes in pulmonary hemodynamics and lung wet weight induced with opsonized zymosan (OZ) in isolated guinea pig lungs perfused with Ringer-albumin solution containing neutrophils (PMNs). Addition of OZ to the PMN-perfused lungs caused pulmonary vasoconstriction and weight gain; neither OZ nor PMNs added individually to the perfusate altered pulmonary vasomotor tone or wet weight. The steady gain in lung weight by 1,588 +/- 464 mg over the 45-minute study period was associated with pulmonary capillary hypertension and an increase in the capillary filtration coefficient, indicative of increased lung vascular permeability. These responses may not be due to generation of oxygen radicals, because the alterations in pulmonary hemodynamics and lung weight were not reduced by addition of superoxide dismutase, catalase, or superoxide dismutase plus catalase. We examined the basis of the PMN-mediated effects by layering PMNs on bovine pulmonary artery endothelial monolayers. Challenge with OZ resulted in increased endothelial permeability to 125I-albumin. The monoclonal antibody IB4 (directed against CD18, the common beta-subunit of structurally related adhesion receptors on phagocytes, LFA-1, Mac-1, and P150,95) prevented the OZ-mediated increase in PMN adherence to endothelial cells and the increase in endothelial permeability to 125I-albumin. IB4 also inhibited the lung weight gain mediated by the OZ-stimulated PMNs in intact lungs. The protective effect of IB4 could be ascribed neither to inhibition of uptake of OZ by PMNs nor to inhibition of release of oxygen radicals, myeloperoxidase, and elastase.(ABSTRACT TRUNCATED AT 250 WORDS)