The anatomy, physiology, pharmacology and pathology of tracheobronchial mucus secretion and the use of expectorant drugs in human disease

A reappraisal of the mucoactive activity and clinical efficacy of bromhexine

Since its introduction to the market in 1963, bromhexine, an over-the-counter drug, has been investigated for its activity in animal models and in humans with diverse respiratory conditions. Bromhexine is a derivate of the Adhatoda vasica plant used in some countries for the treatment of various respiratory diseases. Bromhexine has been found to enhance the secretion of various mucus components by modifying the physicochemical characteristics of mucus. These changes, in turn, increase mucociliary clearance and reduce cough. Principal clinical research studies were primarily developed in an era when stringent methodological approaches and good clinical practices were not developed yet. Clinical studies were conducted mainly in patients with chronic bronchitis and in patients with various respiratory diseases, and demonstrated the efficacy of bromhexine in improving respiratory symptoms. Furthermore, the co-administration of antibiotics with bromhexine amplified the actions of the antibiotic. Although the clinical evidence shows only modest but positive results, bromhexine is indicated for its mucoactive activity. Larger trials with adequate methodology are required to identify when treatment with bromhexine can improve clinical outcomes.

Surface tension in human pathophysiology and its application as a medical diagnostic tool

Introduction: Pathological features of disease appear to be quite different. Despite this diversity, the common feature of various disorders underlies physicochemical and biochemical factors such as surface tension. Human biological fluids comprise various proteins and phospholipids which are capable of adsorption at fluid interfaces and play a vital role in the physiological function of human organs. Surface tension of body fluids correlates directly to the development of pathological states.

Methods: In this review, the variety of human diseases mediated by the surface tension changes of biological phenomena and the failure of biological fluids to remain in their native state are discussed.

Results: Dynamic surface tension measurements of human biological fluids depend on various parameters such as sex, age and changes during pregnancy or certain disease. It is expected that studies of surface tension behavior of human biological fluids will provide additional information and might become useful in medical practice. Theoretical background on surface tension measurement and surface tension values of reference fluids obtained from healthy and sick patients are depicted.

Conclusion: It is well accepted that no single biomarker will be effective in clinical diagnosis. The surface tension measurement combined with routine lab tests may be a novel non-invasive method which can not only facilitate the discovery of diagnostic models for various diseases and its severity, but also be a useful tool for monitoring treatment efficacy. We therefore expect that studies of surface tension behavior of human biological fluids will provide additional useful information in medical practice.

N-acetylcysteine (NAC) and glutathione (GSH): antioxidant and chemopreventive properties, with special reference to lung cancer

Lung cancer arises as a focal transformation of chronically injured epithelium with cigarette smoke as one of its well-recognized causes. Apart from oxidants (free radicals), cigarette smoke contains such a multitude of (pre)carcinogens that it is astonishing that not every heavy smoker becomes a victim of malignancy. This points to the interindividual variability in susceptibility to carcinogens; several lines of evidence suggest that metabolic factors are involved in such variability. Metabolism of carcinogens as well as the subsequent (multi)steps of carcinogenesis are affected by host factors and governed by the balance between opposing forces, such as metabolic activation and detoxification, formation and scavenging of radicals, and DNA damage and repair, which seem to imply that carcinogenic compounds can initiate tumor growth only in amounts saturating detoxification mechanisms. In this context it is well known that glutathione (GSH) plays a crucial role in the detoxification of xenobiotics. N-Acetylcysteine (NAC), an aminothiol and synthetic precursor of intracellular cysteine and GSH, has been used for many years in Europe as a mucolytic drug. Clinically, it is a safe agent without major side effects and has been considered to have a place in cancer prevention, too. The antimutagenic and anticarcinogenic properties of NAC could be ascribed to multiple protective mechanisms, such as NAC nucleophilicity, antioxidant activity, its ability to act as a precursor of intracellular reduced GSH, modulation of detoxification, and DNA repair processes. On these grounds, NAC has emerged as a most promising cancer chemopreventive agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of "mucoregulatory" agents in Young's syndrome

Eight patients with Young's syndrome were treated with four "mucoregulatory" agents for eight weeks in a randomised, open crossover study. There was no improvement in tracheobronchial clearance, pulmonary function, or sperm count.

The effect of leukotriene C4 on mucin release into the cat trachea in vivo and in vitro

We have tested the effect of leukotriene C4 (LTC4, 6 X 10(-8) to 6 X 10(-5) M) on the output of radiolabelled mucins from the trachea of the anaesthetized cat. Doses between 6 X 10(-7) M and 6 X 10(-5) M stimulated mucin release. FPL 55712 (9.5 X 10(-6) M) partially antagonized the effect of the highest dose of LTC4. Tests of LTC4 (6 X 10(-8) to 6 X 10(-6) M) on cat trachea in vitro failed to show any effect on mucin secretion. We conclude that leukotrienes may be one of the mediators of mucus secretion into the inflamed airway.

Bronchial hypersecretion in preterm neonates

During an 18-month period, 11 preterm infants with birthweights between 700 and 1560 g (mean 1.2 kg) developed excessive tracheobronchial secretions during intensive care. No single obstetric factor was incriminated. Copious, viscous, tracheobronchial secretions were noted at about 5 days during mechanical ventilation via endotracheal tube causing recurrent segmental collapse, hypoxia, and hypercapnia (median peak PCO2 13.5 kPa). All infants were treated with frequent bronchial lavages and continued intermittent positive pressure ventilation, together with high concentrations of oxygen. No infant died, but morbidity was high. Tracheostomy was performed on 2 infants (one at age 3 months, because of severe croup) and 2 others had clinical or physiological evidence of upper airways narrowing. Follow-up studies showed that this group had more problems of airways obstruction throughout the first year of life as well as increased lung stiffness. The hypersecretion group showed a higher incidence of chronic lung disease. Likely aetiological factors were sought. Contamination of the mechanical ventilation equipment by detergent and activated glutaraldehyde was found; this could have been a contributory factor.

The distribution and structure of cells in the tracheal epithelium of the mouse

The tracheal epithelium of the mouse is a single layer of columnar cells resting on a basement membrane. Many of the cell types resemble those of other species. However, goblet cells are rare and ciliated cells occur only in scattered patches. Submucosal glands are absent from all but the highest reaches of the airway. The major proportion of the epithelial cells are non-ciliated. These usually project into the lumen of the trachea. Large amounts of smooth endoplasmic reticulum and many secretory vesicles occur within the cytoplasm. Secretory activity of these cells may be either apocrine or merocrine and these cells may transform into other cell types. It is suggested that these non-ciliated cells are Clara cells and that the mouse tracheal epithelium may make a useful model for the study of this type of cell.