Nucleotides and Mucin Release from Cultured Airway Epithelial Cells

Mucociliary clearance is a major function of the airway epithelium. This important function depends both on the physicochemical properties of the airway mucus and on the activity of the cilia. The former, in turn, is dependent mainly on the quality and quantity of mucous glycoproteins or mucins, which are produced by two different cell types, namely, goblet cells of the epithelium and mucous cells of the submucosal gland. Neither the structural nor the functional differences of mucins produced by these two cell types are yet known. The availability of primary airway epithelial cell culture systems, however, has made it possible to study the structure and regulation of airway goblet cells to some extent.The epithelial mucins are extremely hydrophobic and are associated with various macromolecules, the quality and quantity of which may also affect the physicochemical properties of the mucus. Secretion of epithelial mucins is stimulated by various factors, including a number of inflammatory agents. The recent progress in mucin molecular biological research will allow us to identify different mucin core proteins produced by those different cell types, and, hopefully, the differential functions of these mucins in health and disease.

Section: Tumour Necrosis Factor-alpha (Tnf-α) Tnf-α Has Beenmentioning

confidence: 99%

Airway goblet cell mucin: its structure and regulation of secretion

Kim¹,

McCracken²,

Lee³

et al. 1997

“…These airway mucins are secreted by two types of cell; goblet cells of the surface epithelium and mucous cells of the submucosal gland. It has been shown that secretion of airway goblet cell mucin is stimulated by extracellular nucleotides [1] by binding to a P 2 purinoceptor located on the cell membrane [2][3][4], which is coupled to phospholipase C (PLC) through, at least in part, pertussis toxin-sensitive G proteins [5]. Recently, LETHEM et al [4] demonstrated that uridine triphosphate (UTP) is almost equipotent with adenosine triphosphate (ATP) in its ability to stimulate mucin release from human airway epithelial explants [4], suggesting the presence of a receptor type specific both for ATP and UTP in airway epithelial cells, which may regulate the mucin release.…”

mentioning

confidence: 99%

Nucleotide-induced mucin release from primary hamster tracheal surface epithelial cells involves the P2u purinoceptor

Park²,

Shin³

et al. 1996

Mucin release by airway surface epithelial cells is regulated by extracellular adenosine triphosphate (ATP) via a P 2 purinoceptor-mediated mechanism. The objective of the present experiment was to examine the possible involvement of uridine triphosphate (UTP) in this purinergic signal transduction pathway.Using primary hamster tracheal surface epithelial cells, ATP and UTP were compared in their abilities: 1) to displace ATPγS 35 -binding to intact cells; 2) to accumulate inositol phosphates; and 3) to stimulate mucin release. Finally, the presence of a P 2u receptor message was examined.Our results showed that: 1) UTP was much less effective than ATP in displacing ATPγS 35 -binding (median inhibitory concentrations (IC50s) 240 vs 2.9 µM); 2) UTP was more potent than ATP in accumulating inositol phosphates (100 vs 43% increase at 2 mM); 3) UTP was equipotent with ATP in stimulating mucin release; 4) Northern blot analysis of messenger ribonucleic acids (mRNAs) with a mouse P 2u receptor complementary deoxyribonucleic acid (cDNA) probe revealed a single specific band (2.8 kb), partial sequencing of which showed a great homology with those of human or mouse P 2u receptors.We conclude that, although both ATP and UTP are equipotent in stimulating mucin release, their binding kinetics to the cell surface are quite different, suggesting the presence of a common binding domain which may be responsible for the mucin release by these nucleotides. We suggest that the P 2u purinoceptor is likely to be responsible for mucin release by these nucleotides, probably via activation of phospholipase C. Eur Respir J., 1996, 9, 542-548 P 2u receptors purely based on agonist potency orders in which UTP = ATP > ATPγS > 2-methylthio ATP > α,β-methylene ATP [6]. However, our recent binding study indicated that, whilst there appears to be a good correlation between the mucin-releasing potency and the ATPγ S 35 displacement potency among various nucleotides, the ATPγS 35 displacement potency of UTP was, surprisingly, lower than ATP [10].Despite a plethora of information regarding the P 2u receptor in various systems, great variations among these systems make it difficult to conclude whether or not these nucleotides indeed act through the same mechanism, especially in the regulation of airway mucin secretion. Therefore, in the present experiment, this problem was approached by directly comparing these two nucleotides using a primary airway epithelial cell culture system, which has been well characterized for secretion of mucin both biochemically and morphologically [11,12]. This is the first report which attempts to elucidate the biochemical mechanism of the nucleotide-induced mucin release at various levels, from receptor-binding to actual secretion.In the airway, mucus plays an important role in the host's defence, and its proper function is believed to be attributed mainly to the quality and quantity of mucus glycoproteins or mucins which are present in the mucus. These airway mucins are secreted by two types of cell; goblet...

“…KIM and co-workers [23,24] have reported that hamster tracheal epithelial cells in culture are morphologically and biochemically similar to goblet cells. Using this system, it has been reported that the secretion of high molecular weight glycoconjugates (HMWG), a marker of mucus, is not influenced by pharmacological agents such as acetylcholine or histamine, but is influenced by alteration of the pH and osmolarity of the medium, cationic proteases, mechanical strain of cells and adenosine triphosphate (ATP) [25][26][27][28][29]. We found that protein kinase C was involved in HMWG secretion in hamster tracheal epithelial cells in culture [30].…”

Section: In Vitro Screening Systems For Airway Secretion In Inflammationmentioning

confidence: 99%

Current opinion of muco-active drug research: strategies and problems

Miyata

Kai²,

Isohama³

et al. 1998

In general, mucoactive drugs are classified into several groups. However, since many drugs have overlapping effects, it is difficult to classify the drugs into groups based on their major actions. It has been reported that many mucoactive drugs have antioxidant effects. It is reasonable to suggest that an anti-inflammatory property is crucial to demonstrate effectiveness in a clinical context. From this point of view, we have evaluated several mucoactive drugs over two decades. Of these, we will consider the following drugs with anti-inflammatory properties: sodium aceneuramate; glucocorticoids; traditional Chinese medicines; and new cysteine derivatives. On the basis of these findings, we believe that the efforts to seek for compatible actions between glucocorticoids and oriental medicines may provide new opportunities for development of ideal mucoactive drugs with specified actions, i.e. suppression of gene expression.