Relationship between bronchoalveolar lavage neutrophil numbers and lavage fluid elastase and antielastase activities

Polymeric stent materials dysregulate macrophage and endothelial cell functions: implications for coronary artery stent

BACKGROUND

Biodegradable polymers have been applied as bulk or coating materials for coronary artery stents. The degradation of polymers, however, could induce endothelial dysfunction and aggravate neointimal formation. Here we use polymeric microparticles to simulate and demonstrate the effects of degraded stent materials on phagocytic activity, cell death and dysfunction of macrophages and endothelial cells.

METHODS

Microparticles made of low molecular weight polyesters were incubated with human macrophages and coronary artery endothelial cells (ECs). Microparticle-induced phagocytosis, cytotoxicity, apoptosis, cytokine release and surface marker expression were determined by immunostaining or ELISA. Elastase expression was analyzed by ELISA and the elastase-mediated polymer degradation was assessed by mass spectrometry.

RESULTS

We demonstrated that poly(D,L-lactic acid) (PLLA) and polycaprolactone (PCL) microparticles induced cytotoxicity in macrophages and ECs, partially through cell apoptosis. The particle treatment alleviated EC phagocytosis, as opposed to macrophages, but enhanced the expression of vascular cell adhesion molecule (VCAM)-1 along with decreased nitric oxide production, indicating that ECs were activated and lost their capacity to maintain homeostasis. The activation of both cell types induced the release of elastase or elastase-like protease, which further accelerated polymer degradation.

CONCLUSIONS

This study revealed that low molecule weight PLLA and PCL microparticles increased cytotoxicity and dysregulated endothelial cell function, which in turn enhanced elastase release and polymer degradation. These indicate that polymer or polymer-coated stents impose a risk of endothelial dysfunction after deployment which can potentially lead to delayed endothelialization, neointimal hyperplasia and late thrombosis.

Intra-alveolar urinary trypsin inhibitor cannot inhibit polymorphonuclear elastase activity in the lung in postsurgical patients with acute respiratory distress syndrome

The aim of this study was to evaluate the concentrative relationship between polymorphonuclear elastase (PMNE) and urinary trypsin inhibitor (UTI) in the bronchoalveolar lavage fluid (BALF) of patients with acute respiratory distress syndrome (ARDS). A total of eight patients who developed ARDS after gastroenterological surgery and eight patients with normal respiratory function during general anesthesia using tracheal intubation were the subjects of this study. BALF was collected from the right middle lobe using saline, and the PMNE and UTI concentrations were measured. The PMNE concentrations were 1277 +/- 1589 ng/ml and 38 +/- 26 ng/ml in the patients with ARDS and those with normal lung function, respectively, and the UTI concentrations were 225 +/- 175 mU/ml and 81 +/- 40 mU/ml, respectively, expressed as mean +/- SD. Based on the UTI concentration which can inhibit PMNE activity, the PMNE concentration in the ARDS patients was not entirely inhibited by UTI. Since only UTI can inhibit PMNE activity in the inflammatory tissues, PMNE in the BALF may induce and aggravate lung injury in ARDS. Thus, we conclude that PMNE released from activated neutrophils in the lung is associated with the development of ARDS.

Interaction with Secretory Component Stimulates Effector Functions of Human Eosinophils But Not of Neutrophils

Eosinophils and their products are important in the pathophysiology of allergic inflammation in mucosal tissues. Secretory component bound to IgA mediates transepithelial transport of IgA and confers increased stability on the resultant secretory IgA; however, the effect of secretory component on the biologic activity of IgA is unknown. Here, we report that secretory IgA and secretory component preferentially activate human eosinophils. When eosinophils were stimulated with immobilized secretory IgA, degranulation and superoxide production were two- to threefold greater than when stimulated with serum IgA. In contrast, neutrophils responded similarly to secretory IgA and serum IgA. Flow cytometric analysis showed that eosinophils bound to purified secretory component. The binding of 125I-labeled secretory component was inhibited by unlabeled secretory component or secretory IgA but not by serum IgA. Superoxide production by eosinophils stimulated with cytokines or IgG was enhanced synergistically by immobilized secretory component; secretory component showed no effect on neutrophil activation. Finally, anti-CD18 mAb abolished eosinophil superoxide production stimulated with secretory IgA or secretory component but not with serum IgA, suggesting a crucial role for β2 integrins in eosinophil interactions with secretory IgA or secretory component. Thus, secretory component plays important roles in activating eosinophil functions but not neutrophil functions. This preferential interaction between secretory component and eosinophils may provide a novel mechanism to regulate mucosal tissue inflammation.