IL-8 released constitutively by primary bronchial epithelial cells in culture forms an inactive complex with secretory component.

The bronchial epithelium is a source of both alpha and beta chemokines and, uniquely, of secretory component (SC), the extracellular ligand-binding domain of the polymeric IgA receptor. Ig superfamily relatives of SC, such as IgG and alpha(2)-macroglobulin, bind IL-8. Therefore, we tested the hypothesis that SC binds IL-8, modifying its activity as a neutrophil chemoattractant. Primary bronchial epithelial cells were cultured under conditions to optimize SC synthesis. The chemokines IL-8, epithelial neutrophil-activating peptide-78, growth-related oncogene alpha, and RANTES were released constitutively by epithelial cells from both normal and asthmatic donors and detected in high m.w. complexes with SC. There were no qualitative differences in the production of SC-chemokine complexes by epithelial cells from normal or asthmatic donors, and in all cases this was the only form of chemokine detected. SC contains 15% N-linked carbohydrate, and complete deglycosylation with peptide N-glycosidase F abolished IL-8 binding. In micro-Boyden chamber assays, no IL-8-dependent neutrophil chemotactic responses to epithelial culture supernatants could be demonstrated. SC dose-dependently (IC(50) approximately 0.3 nM) inhibited the neutrophil chemotactic response to rIL-8 (10 nM) in micro-Boyden chamber assays and also inhibited IL-8-mediated neutrophil transendothelial migration. SC inhibited the binding of IL-8 to nonspecific binding sites on polycarbonate filters and endothelial cell monolayers, and therefore the formation of haptotactic gradients, without effects on IL-8 binding to specific receptors on neutrophils. The data indicate that in the airways IL-8 may be solubilized and inactivated by binding to SC.

DNA and actin bind and inhibit interleukin-8 function in cystic fibrosis sputa: in vitro effects of mucolytics.

Infection of the cystic fibrosis (CF) airways elicits an exaggerated, interleukin-8 (IL-8) mediated, neutrophil inflammatory response. Necrosing neutrophils release DNA and actin into the airways, increasing the viscoelasticity of airway secretions. Mucolytics aim to improve airway clearance by reducing this viscoelasticity. DNase I reduces the viscoelasticity of CF sputum, and a human recombinant form of this enzyme is widely administered to patients with CF. Gelsolin, which cleaves actin polymers, is also known to reduce CF sputum viscosity in vitro, and it has been proposed as a future mucolytic agent. We have shown that the anionic polymers DNA and actin bind and mask immunologic recognition of the basic peptide IL-8 and prevent this chemokine from binding to neutrophil receptors. Reduction of CF sputum viscosity by DNase I or gelsolin in vitro was demonstrated to increase the proportion of free IL-8 and the IL-8-dependent neutrophil chemotactic activity of sputum supernatants. We hypothesize that an electrostatic interaction between polymer and chemokine may limit the inflammatory potential of the latter, but that this interaction may be weakened by polymer cleavage. The potential risk of increased inflammation via this mechanism suggests a caveat should be attendant on treatment of patients with CF with these mucolytic agents.

The effect of processing on inflammatory markers in induced sputum.

The effects of the mucolytic agent, dithioerythritol (DTE), and the temperature at which sputum processing is conducted on cellular and biochemical markers in induced sputum was assessed. Samples from healthy and atopic asthmatic subjects were treated with either DTE or phosphate-buffered saline (PBS) at 22 or 37 degrees C and compared for cell counts and concentrations of histamine, tryptase, eosinophil cationic protein (ECP), free interleukin (IL)-8, immunoglobulin (Ig)A, IL-8/IgA complexes and secretory component (SC). In addition, the influence of DTE on in vitro mediator release from blood eosinophils, basophils and bronchoalveolar lavage (BAL) mast cells was studied. Processing with DTE improved cytospin quality and increased the cell yield and measurable ECP, tryptase, IgA and SC, but reduced levels of histamine in PBS-treated samples and had no effect on IL-8. Cell counts or mediator levels were similar when sputum was processed at 22 or 37 degrees C, even though DTE induced blood basophils and BAL mast cells to release histamine at 37 degrees C. In spiking experiments, recovery of added ECP, tryptase, total IL-8 and histamine from sputum was similar in DTE- and PBS-processed sputum, but reduced for free IL-8 in PBS-treated samples. In conclusion, dithioerythritol improves cell and mediator recovery without causing cell activation when sputum processing is conducted at room temperature. The extent of recovery depends on the mediator studied.

Regulation of interleukin-8 binding and function by heparin and alpha2-macroglobulin.

BACKGROUND: Increased expression of interleukin-8 (IL-8), a potent neutrophil chemoattractant, is associated with a number of inflammatory diseases. Interleukin-8 binds to the glycosaminoglycan (GAG) heparin and the protease inhibitor alpha2-macroglobulin, molecules which regulate the function of a number of cytokines. Heparan sulphate was previously shown to enhance neutrophil chemotactic responses to IL-8. OBJECTIVE: The purpose of this study was to investigate the effect of heparin, heparan sulphate and alpha2-macroglobulin on IL-8 binding to neutrophils and subsequent functional effects in vitro. METHODS: The binding of 125I-IL-8 to normal neutrophils at 4 degrees C was studied and the IL-8 induced neutrophil chemotactic response was investigated using micro-Boyden chambers. Complexation of IL-8 with alpha2-macroglobulin was confirmed using gel filtration chromatography. RESULTS: Heparin, but not heparan sulphate, inhibited the binding of 125I-IL-8 to neutrophils (IC50=26 microg/mL) and IL-8 induced neutrophil chemotactic responses (IC50=4 microg/mL). The specific inhibitory effect of heparin was apparently due to an interaction with IL-8 which was charge-dependent, since dextran sulphate had a greater inhibitory effect on chemotactic responses (IC50=2 microg/mL) and FITC-heparin did not bind to neutrophils. The heparin-induced inhibition of IL-8 binding and chemotactic responses was reversed in a dose-dependent manner in the presence of alpha2-macroglobulin. The binding of 125I-IL-8 to neutrophils in the presence of alpha2-macroglobulin appears to be, in part, through the specific IL-8 receptor. CONCLUSION: These results point to an anti-inflammatory role for heparin and a novel, potentially, pro-inflammatory role for alpha2-macroglobulin which together indicate the importance of cytokine-binding macromolecules in determining net cytokine function.

A survey of marginal wheelchair users.

Significant numbers of wheelchair users experience difficulties with propulsion due to impaired upper limb function (termed marginal users for this study). A survey of wheelchair users in Tayside, Scotland, was carried out to identify and describe the marginal user population and their propulsion difficulties. Subjects for the survey were identified from the records of National Health Service wheelchair users at Dundee Limb Fitting Centre. Subjects were interviewed at home about their wheelchair-propelling experiences. Survey results indicated that marginal users represent approximately 15% of the occupant-propelled wheelchair population. The average age of the marginal users surveyed was 48 years and the modal diagnosis was multiple sclerosis. Fifty-nine percent of the marginal users questioned felt that their wheelchairs were not adequate for their requirements.

Intelligence and early academic underachievement.

This investigation examined the early incidence of underachievement among a sample of intellectually average, bright and superior grade one students (ranging in age from 6:3 to 7:3 years) in order to assess the relative incidence of underachievement among children of differing intellectual levels. Overall, 20 per cent of the students were identified as underachievers. However, underachievers were found to be equally represented among these three groups.