Modulation of tryptase secretion from human colon mast cells by histamine

To investigate the ability of histamine to modulate tryptase release from human colon mast cells and the potential mechanisms.

Enzymatically dispersed cells from human colons were challenged with histamine, anti-IgE or calcium ionophore A23187 (CI), and the cell supernatants after challenge were collected. Tryptase release was determined with a sandwich ELISA procedure.

Histamine at concentrations from 1 ng/mL was able to induce a "bell" shape dose related release of tryptase from colon mast cells. The maximum release of tryptase was approximately 3.5 fold more than spontaneous release. As little as 10 ng/mL histamine showed a similar potency to 10 microg/mL anti-IgE in induction of tryptase release. Histamine induced release of tryptase initiated at 10 s when histamine (100 ng/mL) was added to cells, gradually increased thereafter, and completed at 5 min. Both pertussis toxin or metabolic inhibitors were able to inhibit histamine induced tryptase release. When histamine and anti-IgE were added to colon mast cells at the same time, the quantity of tryptase released was similar to that induced by anti-IgE alone. The similar results were observed with CI. However, when various concentrations of histamine were incubated with cells for 20 min before adding anti-IgE or CI, the quantity of tryptase released was similar to that was induced by histamine alone.

Histamine is a potent activator of human colon mast cells, which represents a novel and pivotal self-amplification mechanism of mast cell degranulation.