Studies using lectins to determine mineral interactions with cellular membranes

Area of Science:

• Cell Biology
• Toxicology
• Biochemistry

Background:

• Chrysotile asbestos exposure stimulates mucin secretion in tracheal organ cultures.
• This response occurs without apparent damage to tracheal epithelial cells.
• The mechanism is hypothesized to involve fiber interaction with cell surface carbohydrate residues.

Purpose of the Study:

• To investigate the role of specific carbohydrate residues in asbestos-induced mucin hypersecretion.
• To determine if the positive surface charge of chrysotile is critical for this interaction.

Main Methods:

• Organ cultures were treated with chrysotile asbestos and various lectins targeting specific carbohydrate residues.
• Mucin secretion was measured using 3H-glucosamine incorporation.
• Enzyme treatments (carboxypeptidase A, phospholipase A2, neuraminidase) and polycation treatments were employed.

Main Results:

• Blocking alpha-D-mannose and alpha-D-glucose residues significantly inhibited chrysotile-induced mucin hypersecretion.
• Carboxypeptidase A and phospholipase A2 pre-treatment diminished the secretory response.
• Leached chrysotile, lacking Mg2+, failed to induce hypersecretion, while polycations showed a lesser effect.

Conclusions:

• Chrysotile-induced mucin hypersecretion is mediated by the interaction of a positively charged component (likely Mg2+) with alpha-D-mannose or alpha-D-glucose residues on cell surface glycoproteins and glycolipids.
• This interaction occurs independently of significant morphologic cell damage.