T. J. H. Clark

Identification and characterization of a monocyte-derived neutrophil-activating factor in corticosteroid-resistant bronchial asthma.

Peripheral blood mononuclear cells (PBMC) were isolated from seven normal subjects, eight asthmatic subjects clinically sensitive to corticosteroids (CS), and eight asthmatic subjects clinically resistant to corticosteroids (CR). PBMC were cultured at 37 degrees C for 24 h in the absence or presence of 10(-16) to 10(-4) M hydrocortisone. Calcium ionophore (A23187)-activated neutrophils (PMN) primed by supernatants of PBMC from asthmatic subjects cultured in the absence of hydrocortisone generated approximately threefold more leukotriene B4 than PMN primed by supernatants of PBMC from normal subjects (P less than 0.05). Incubation of PBMC derived from CS subjects with 10(-8) M hydrocortisone completely inhibited the production of the enhancing activity (P less than 0.01), whereas in CR subjects hydrocortisone at concentrations up to 10(-4) M did not suppress the release of enhancing activity. The enhancing activity was produced by monocytes. Enhancing activity eluted with an Mr of 3,000 D and a pI of 7.1. It eluted at 10% acetonitrile after reverse-phase HPLC. The activity was destroyed by heating to 60 degrees C for 60 min and was sensitive to pronase treatment. The purified factor also enhanced superoxide generation by PMN which had been stimulated submaximally by phorbol myristate acetate.

Circulating concentrations of histamine, neutrophil chemotactic activity, and catecholamines during the refractory period in exercise-induced asthma

Circulating mediators and catecholamine concentrations have been measured in eight subjects with asthma who were subjected to two bouts of cycle ergometer exercise separated by 1 hour. The maximum falls in FEV1 were 21.9 +/- 2.3% (mean +/- SEM; n = 8) and 5.5 +/- 1.3% (mean +/- SEM; n = 8) after the first and second exercises, respectively. Serum neutrophil chemotactic activity (NCA) and plasma histamine and catecholamine levels in venous blood were measured with a microchemotaxis and two radioenzymatic techniques, respectively. There was a significant increase in NCA and plasma histamine concentrations after both exercise challenges, and there was no significant difference in the release of these mediators between the two exercise tests. Gel filtration chromatography demonstrated that the NCA detected after the first and second exercise tests had molecular sizes of approximately 600,000 daltons. There was no significant time-dependent increase in plasma norepinephrine and epinephrine concentrations after either exercise task, even though the patients were refractory to exercise-induced asthma after the second exercise. These results suggest that the refractory period in exercise-induced asthma is not caused by mediator depletion, as indicated by NCA and histamine measurements, or by protection of the airways through catecholamine release.

Inhaled corticosteroid therapy: A substitute for theophylline as well as prednisolone?

Topical corticosteroid treatment can be successfully achieved by inhaled therapy and can effectively provide a safe substitute for oral steroids. More than 8 million patient years of experience gained over a decade of use of inhaled steroids has shown them to be acceptable to patients and clinicians, with side effects confined to the upper airway. At daily doses of 200 to 1600 micrograms BDP or the equivalent, minor systemic activity may occasionally be demonstrated but no adverse systemic side effects have been reported. The topical anti-inflammatory treatment provided by inhaled steroids thus compares favorably with prednisolone and with other asthma therapy with respect to morbidity and mortality, suggesting that inhaled steroids combined with an inhaled beta-agonist is a safe and comprehensive treatment for chronic asthma. This parallel attack on inflammation and bronchoconstriction can be achieved with a morbidity that is much less than that of asthma and also likely to be less than that of the frequently used combination of theophylline and inhaled beta-agonist. Twice-daily regimens of inhaled steroids over a dose range of 200 to 1600 micrograms BDP or the equivalent should enable most patients with chronic asthma to receive effective therapy without recourse to potentially more toxic oral bronchodilator or steroid therapy.

The generation and cellular distribution of leukotriene C4 in human eosinophils stimulated by unopsonized zymosan and glucan particles

Human eosinophils (EOSs) stimulated under optimal conditions with 5 X 10(8) unopsonized zymosan particles at 37 degrees C for 30 minutes produced an average total immunoreactive leukotriene (LT) C4 of 1.6 ng per 10(6) EOSs, and 30% to 60% of the generated product remained cell associated. The dose-response characteristics of zymosan-induced LTC4 generation were different from those of phagocytosis, suggesting that the two events were independent. Pretreatment of EOSs with 10(-8) mol/L of formyl-methionyl-leucyl-phenylalanine for 30 minutes led to a twofold to fivefold augmentation of LTC4 generation by cells subsequently activated by unopsonized zymosan. Optimal EOS activation with 1 mumol/L of the calcium ionophore A23187 at 37 degrees C for 15 minutes produced more than 100 times greater quantities of LTC4 than with zymosan. The amount of immunoreactive LTC4 that remained cell associated after calcium ionophore A23187 stimulation reached a maximum after 5 minutes and then declined. Of the relatively small amount generated in the first minute, 71% was cell associated, but this figure declined to 9% after 15 minutes, by which time there had been a redistribution of the LTC4 to the supernatant. Inflammatory leukocytes may respond to zymosan because the cells recognize either one or both of its major polysaccharide components, glucan and mannan. Glucan, but not mannan, stimulated EOSs to generate LTC4 in a dose- and time-dependent manner. Under optimal conditions, there was no significant difference in the total quantities of LTC4 elaborated by EOSs stimulated by glucan and by unopsonized zymosan. This suggests that zymosan may induce leukotriene generation in the human EOS through a glucan recognition mechanism.

Immediate response to cigarette smoke.

Using an automated method of calculating airways resistance in the body plethysmograph, we have investigated changes occurring immediately after inhalation of cigarette smoke. Decreases in specific conductance occurred by the time of the first measurement seven or eight seconds after exposure to single inhalations of cigarette smoke in 12 smokers and 12 non-smokers. Less than half of the initial change was present 40 seconds after the inhalation. Initial responses were greater in the non-smokers. Responses recurred with repeated inhalations in smokers and non-smokers. Prior administration of salbutamol and ipratropium bromide significantly inhibited the response and this inhibition appeared to be greater in non-smokers. Sodium cromoglycate inhaled as a dry powder had no effect on the response.

Protective effect of circulating epinephrine within the physiologic range on the airway response to inhaled histamine in nonasthmatic subjects

The specific airway conductance response of six normal subjects to increasing doses of inhaled histamine was studied on two occasions. On each occasion either epinephrine (0.025 micrograms/kg/min) or saline was infused intravenously during the histamine challenge. This dose of epinephrine, when it was administered to seated normal subjects, produces plasma levels similar to those found at the end of strenuous exercise. Epinephrine caused a significant elevation in the concentration of histamine required to cause a 35% fall in specific airway conductance (PC35), although this was in part caused by a small airway dilator effect. The mean (+/-SD) PC35 rose from 21 mg/ml (+/-6) during saline infusion to 58 mg/ml (+/-27) during epinephrine infusion, p less than 0.05. Levels of circulating epinephrine, similar to those found during exercise in normal subjects, appear to be capable of protecting against bronchoconstrictor stimuli.

Automated system for the measurement of airways resistance, lung volumes, and flow-volume loops.

Using a digital computer and body plethysmograph measurements of airways resistance, lung volumes, and flow-volume loops may be obtained from a single manoeuvre performed by the patient. All the measurements together with a display of the flow-volume loop are displayed within 10 seconds of the patient completing the manoeuvre. The system appears to offer considerable advantages in speed, objectivity, and reproducibility when compared with conventional methods.

Immediate Responses to Lung Irritants Detected by Automated Measurements of Airway Resistance and Partial Flow-Volume Curves

Automated measurements of specific conductance and partial flow-volume curves have allowed the detailed investigation of changes occurring in the first 30 seconds after inhalation of cigarette smoke. Smokers and non-smokers show transient airway narrowing which appears to be a nervously mediated reflex contraction of smooth muscle. The major part of the stimulus is produced by the particulate matter in the smoke.