The effect of theophylline on macrophage elastase secretion

Elastase activity in bronchoalveolar lavage fluid from oxygen-exposed, Pseudomonas-infected baboons

The adult respiratory distress syndrome is a major cause of morbidity and mortality in critical care patients. Lung injury in this syndrome is frequently associated with lung infection. The combined insults result in an influx of neutrophils and damage to the pulmonary epithelium. We investigated whether active neutrophil elastolytic activity was present in the bronchoalveolar fluid in baboons with mild or moderate hyperoxic lung injury and infection. Group A (N = 7) was exposed for 6 days to FIO2 = 0.8 and then inoculated by intratracheal bolus with Pseudomonas aeruginosa strain DGI-R130 (PA); the FIO2 was reduced to 0.5. Group B (N = 6) was exposed to similar concentrations of inspired oxygen but inoculated with buffered saline. Antibiotics included parenteral penicillin and topical gentamicin and polymyxin B. All 3 were given continuously in group B but stopped 24 h prior to PA inoculation in group A. Bronchoalveolar lavage fluid was collected 1 week before oxygen administration, when the FIO2 was reduced (day 6 or 7) and prior to necropsy (day 11). Hemodynamic, pulmonary function, microbiological, and biochemical variables were studied. Injured, infected animals (group A) had significant elevations of mean pulmonary artery pressure and decreases in total lung capacity and PaO2 compared both to baseline and to group B at day 11. At autopsy, group A had significant increases of bronchoalveolar lavage fluid (BALF) neutrophils and bacterial pathogens. Elastase levels in BALF (equal to 0 at baseline) rose to 136 +/- 98 ng/ml in group A vs. 6 +/- 14 ng/ml in group B. The elastase was inhibited by inhibitors of serine proteases including ones specific for neutrophil elastase. On Sephacryl S-300 chromatography the elastase activity eluted near human alpha 2-macroglobulin and separated from other proteolytic activity. These studies demonstrate a significant level of elastase in BALF from injured, infected baboons compared to injured, uninfected animals.

Fc-receptor-mediated phagocytosis: abnormalities associated with diabetes mellitus

The family of Fc receptors (FcR) for IgG play pivotal roles in affector, effector, and regulatory functions of cells of the immune system. Thus, changes in expression and activation of FcRs may contribute to a variety of disease manifestations that are the consequence of abnormalities in immune system function. Patients with diabetes mellitus are often plagued with recurrent bacterial and mycotic infections, as well as large and small vessel injury which may in part be immune mediated and which lead to organ dysfunction. Hormone-mediated changes in immune system function have been postulated to contribute to a variety of the complications experienced by patients with diabetes mellitus. It is the purpose of this review to summarize current knowledge regarding abnormalities in immune system function in diabetes mellitus with special emphasis on classical hormonal modulation of Fc receptor-mediated phagocytosis.

Studies on the elastolytic activity of chymotrypsin

Chymotrypsin can completely solubilize insoluble [3H]-labeled ligamentum nuchae elastin. At similar enzyme levels, trypsin solubilizes only 5% of the elastin substrate whereas pancreatic elastase completely solubilizes the elastin at one-tenth the concentration required for chymotrypsin solubilization. The elastolytic activity of chymotrypsin is dependent on Ca+2, is enhanced by SDS, and is inhibited by NaCl at concentrations above 10 mM. The elastolytic activity of chymotrypsin is also inhibited by TPCK, a chymotrypsin specific inhibitor, but not by TLCK, a trypsin specific inhibitor. Neither TPCK nor TLCK abolish the elastolytic activity of pancreatic elastase. The sizes of [3H]elastin fragments produced by the elastolytic activity of chymotrypsin are similar to those produced by pancreatic elastase, and larger than those produced by trypsin.

Elastolytic activity of peripheral blood monocytes

Human peripheral blood monocytes have been purified by Ficoll-Hypaque density gradient centrifugation and adherence to plastic dishes, and assayed for elastolytic activity using insoluble [3H]elastin. Approximately 5-10 micrograms of elastin are solubilized at pH 7.5 per mg protein per h. The specific activity in monocytes varies between 3 and 15% of that of neutrophils obtained at the same time from the same subjects. The enzymatic activity derives principally from monocytes. Lymphocytes purified by Sephadex G-10 gel filtration chromatography exhibit only trace elastolytic activity, while neutrophils comprise 1% or less of the cell population. Monocyte elastolytic activity is inhibited by alpha-1-antitrypsin and Succinyl-Ala-Ala-Pro-Val-chloromethylketone indicating that it is a serine-type protease. When extracts of monocytes are analyzed by gel filtration, the elastolytic activity appears in large molecular weight forms; however, these forms are not observed when extracts of monocyte lysosomes are analyzed. Such variation in forms is also seen with neutrophil extracts. Monocytes are a source of elastolytic activity for various physiologic and pathologic actions in the lung and other organs.