Neutral endopeptidase 24.11, a membrane-bound metallopeptidase, cleaves, and degrades vasoactive peptides such as atrial natriuretic peptide, endothelin, angiotensin I, substance P, and bradykinin. Therefore, the presence of this metallopeptidase may contribute to the regulation of vascular tone and local inflammatory responses in the vascular endothelium and elsewhere. We determined neutral endopeptidase in cultured human endothelial cells from different vascular beds and studied its regulation by protein kinase C. Neutral endopeptidase was detected in all cultured endothelial cell types. Lowest concentrations were measured in human endothelial cells from umbilical veins (360 +/- 14 pg/mg protein), followed by pulmonary and coronary arteries; higher concentrations were found in endothelial cells from the cardiac microcirculation (1099 +/- 73 pg/mg protein). Neutral endopeptidase content increased during cell growth but was not affected by endothelial cell growth factor or modifications of the growth medium. Stimulation of protein kinase C with 1-oleoyl-2-acetyl-rac-glycerol (0.1 to 1 mumol/L) and phorbol 12-myristate 13-acetate (0.01 to 0.1 mumol/L) induced a time- and concentration-dependent increase of endothelial cells that was inhibited by cycloheximide (5 mumol/L), an inhibitor of protein synthesis. Incubation with phospholipase C (1 mumol/L) and thrombin (10 IU/mL) induced upregulation of neutral endopeptidase, resulting in 158 +/- 26% and 150 +/- 22% increases, respectively, compared with controls. The thrombin effect was inhibited by calphostin C (1 mumol/L), an inhibitor of protein kinase C. Endothelial neutral endopeptidase is constitutively expressed in endothelial cells from different origins and is inducible by thrombin via activation of the protein kinase C pathway.

There is evidence that asthma and other allergic diseases are increasing and air pollution has been considered an important contributing factor to this observation. Using a specially designed organ culture system, we examined the influence of ozone (0.06 to 0. 2 ppm) and nitrogen dioxide (NO2, 200 and 800 micrograms/m3) on nasal mucosa exposed for 24 h. Tissue was obtained from 105 patients undergoing surgical therapy (septoplasty and reduction of the inferior turbinates) for chronic nasal obstruction. The histamine content in the culture medium of ozone- and NO2-exposed samples was significantly elevated compared with the control cultures. This elevation was correlated with the number of degranulated mast cells in the tissue determined by histomorphometry (P < 0.001). Moreover, the cytokines interleukin (IL)-1beta (P < 0.05), IL-6 (P < 0.01), IL-8 (P < 0.001), and tumor necrosis factor-alpha (TNF-alpha, P < 0. 001) were significantly increased (ozone 0.1 ppm). Furthermore, we found significant increases in the release of IL-4, IL-6, IL-8, and TNF-alpha of ozone-exposed (0.1 ppm) samples of atopic versus nonatopic patients and to a lesser extent for histamine following exposure to 0.15 ppm ozone. These results indicate that low ozone concentrations and NO2 lead to an inflammation of human nasal mucosa in vitro and that priming factors such as atopy or preexisting inflammation do increase the sensitivity to ozone and NO2. This organ culture system proved to be a good experimental design for studying pathophysiologic alterations of human nasal mucosa under different experimental conditions (e.g., air pollutants).

Adjuvant steroid treatment following KPE may improve short-term (≤1 year) clearance rate of jaundice, but no significant effects on long-term (≥2 years) clearance rate of jaundice and native liver survival rate. Studies on doses and duration of steroids, and long-term follow-up studies are warranted.

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