The influence of inhalative corticosteroids on circulating Nerve Growth Factor, Brain-Derived Neurotrophic Factor and Neurotrophin-3 in allergic asthmatics

BACKGROUND

The neurotrophins Nerve Growth Factor (NGF), Brain-Derived Neurotrophic Factor (BDNF) and Neurotrophin (NT)-3 are produced, stored and released by various immunological cells. The influence of NTs upon the function of these cells is described. Elevated plasma levels were found in inflammatory, autoimmune and allergic diseases with the highest levels in allergic asthma. A connection between bronchial hyper-responsiveness and serum levels has been reported.

OBJECTIVE

Little is known about the influence of treatment with inhaled corticosteroids (ICS) on serum NT levels and their influence on the asthmatic state.

METHODS

Eighty-seven volunteers were studied. Thirty-eight were stable allergic asthmatics with constant ICS doses, 29 were asthmatics not receiving anti-asthmatic treatment and 20 were age- and sex-matched healthy controls. Demographic and lung function data were evaluated. NT serum levels were determined by ELISA.

RESULTS

NGF and BDNF levels were significantly increased in untreated asthmatics compared to the control and the treated group, while NT-3 demonstrated significantly higher levels in treated asthmatics compared to healthy controls. After stabilization of untreated subjects with ICS, the NT levels decreased significantly.

CONCLUSIONS

These results suggest that NTs participate in allergic inflammation and asthma. Effective treatment leads to a decrease of circulating neurotrophic factors.

Heparin, derived from the mast cells of human lungs is responsible for the generation of kinins in allergic reactions due to the activation of the contact system

BACKGROUND

In a recent study mast cell heparin proteoglycan (HepPG) of a cell line derived from a mouse mastocytoma was isolated. Glycosaminoglycans proved to be an initiating surface for starting contact activation and could explain kinin generation present in allergic reactions. It is the aim of the present study to prove that HepPG or glycosaminoglycan derived from human mast cells is also capable of acting as a physiologic macromolecule and to induce contact activation.

METHODS

HepPG molecules were isolated by anionic column chromatography. Their ability to accelerate reciprocal activation of factor XII was investigated by spectrophotometry. The anticoagulant effect was demonstrated by an increase in partial thromboplastin time. HPLC was performed to correlate these effects with molecular weight (MW).

RESULTS

The isolated heparin showed high contact-activating and anticoagulant potency. Both actions were suppressed by incubation with heparinase I. The maximum contact activation peak appeared at a lower MW than the anticoagulant effect.

CONCLUSION

These in vitro results explain the results of in vivo allergen challenge studies where a high degree of kinin generation occurs. Heparin derived from human mast cells therefore seems to represent the physiological macromolecule capable of activating the contact system and could be a missing link between cellular and humoral responses in allergic reactions.

Glucocorticoids and protein kinase C regulate neutral endopeptidase 24.11 in human vascular smooth muscle cells

Neutral endopeptidase 24.11 (NEP) degrades vasoactive peptides, including natriuretic peptides, kinins, angiotensins, and endothelins. It contributes to the regulation of vascular tone and body fluid homeostasis. In the present study the expression of NEP was investigated in cultured human smooth muscle cells derived from umbilical veins (HSMC) and human coronary arteries (HCSMC). A constitutive NEP expression was found in growing and starved smooth muscle cells and was about 4 fold higher than in endothelial cells derived from umbilical veins. Treatment of smooth muscle cells with dexamethasone (0.01-0.1 microM Dex) and with the protein kinase C activator, phorbol myristate acetate (0.1 microM PMA), increased NEP mRNA by 3-4 fold and two fold, respectively. Dexamethasone (0.1 microM) and prednisolone (0.1 microM) increased protein concentrations of NEP and NEP-activity after 3 days and continued to increase at 5 days, whereas PMA induced maximal increase of NEP concentrations after 48 hours. The effect of dexamethasone was concentration-dependent and was completely abolished by cycloheximide (10 microM), a protein synthesis inhibitor. The effect of PMA on NEP protein was completely blocked by protein kinase C inhibitors, calphostin C and H7 (both 10 microM). NEP 24.11 is constitutively expressed in human smooth muscle cells from umbilical veins and coronary arteries and is upregulated by glucocorticoids and by protein kinase C activation in these cells.