Effect of sensitization on spontaneous and phosphatidylserine-induced histamine release and on cyclic AMP and GMP levels in isolated rat mast cells

On the mechanism by which theophylline inhibits histamine release from rat mast cells

Theophylline (2.5 mM) did not influence the spontaneous release of histamine but inhibited histamine release induced by antigen, compound 48/80 or phosphatidylserine. The effect on 48/80-induced histamine release could not be reversed by increasing extracellular Ca2+. Exogenous adenosine (10(-8) to 10(-4) M) did not influence spontaneous histamine release or 48/80-induced release but potentiated antigen-induced release. The adenosine potentiation was competitively inhibited by theophylline in concentrations (10(-5) to 10(-4) M) lower than those required to inhibit antigen-induced histamine release in the absence of adenosine. In order to see if endogenous adenosine levels are high enough to potentiate an anaphylactic histamine release in vivo, adenosine was determined in mast cell incubates and in plasma from 4 different strains of rat. The levels were 0.18 to 0.99 microM in plasma, which is sufficient to cause significant potentiation of histamine release, but only 3 x 10(-8) M in mast cell incubates. Theophylline (2.5 mM) increased cAMP levels about 100%, whereas adenosine (10(-5) M) had little effect on cAMP and cGMP levels. However, when incubated together, adenosine could inhibit the theophylline-induced increase in cAMP levels but not the inhibition of histamine release. It is concluded that the effect of low concentrations of theophylline could be due partly to antagonism of adenosine effects. In addition, in higher doses, theophylline appears to exert an inhibitory action that is unrelated to cyclic nucleotides, extracellular calcium and adenosine.

Evidence against a role of cyclic nucleotides in the regulation of anaphylactic histamine release in isolated rat mast cells

The effect of different phosphodiesterase (PDE) inhibitors on the antigen or 48/80 induced histamine release from isolated Hooded Lister rat mast cells was tested. The unselective PDE inhibitors theophylline (2.5 mM) and IBMX (0.2 mM) and the selective cyclic GMP PDE inhibitor M & B 22948 (0.1 mM) inhibited the antigen induced histamine release by 50% while 48/80 induced release was inhibited by about 25%. The cyclic AMP selective PDE inhibitors ICI 63197 (0.5 mM) or Ro 20-1724 (0.2 mM) had no effect on 48/80 induced histamine release but tended to enhance antigen induced release. There was no correlation between the measured levels of cyclic AMP and the effect on histamine release by the investigated PDE inhibitors. Cyclic AMP or cyclic GMP up to 10(-3) M did not affect the anaphylactic histamine release. Dibutyryl-cAMP and dibutyryl-cGMP (10(-4) M) both inhibited the release about 20% but this effect could be explained by the effect of butyric acid as sodium butyrate (2 X 10(-4) M) also inhibited the release by 20%. The presence results suggest that cyclic nucleotides are not important regulators of histamine release from isolated mast cells.

Effect of sensitization and non-antibody IgE on 48/80 induced histamine release from isolated rat mast cells

Histamine release from isolated rat mast cells from non-immunized and immunized Hooded Lister rats was induced by compound 48/80. The histamine release was decreased with a lower maximum at the optimal concentration of 48/80 when using cells from immunized rats compared to non-immunized control rats. The stimulation of IgE antibody production, after immunization using B. pertussis as an adjuvant was also accompanied by an elevation of total serum IgW. The 48/80 induced histamine release from Sprague Dawley mast cells was not inhibited by immunization. Non-antibody IgE showed a non-competitive inhibition of 48/80 induced histamine release when myeloma IgE was incubated with mast cells from both Hooded Lister and Sprague Dawley rats. The results indicate the existence of different receptors for IgE and 48/80.

Total serum IgE influence on the anaphylactic and 48/80 induced histamine release from isolated rat mast cells

We have investigated the influence of non-specific IgE on histamine release induced by antigen or compound 48/80. Our results indicate that increased amounts of IgE influence antigen mediated histamine release as well as release induced by a non-immunological stimulus like compound 48/80.

Are the anti-allergic actions of theophylline due to antagonism at the adenosine receptor

Adenosine potentiated anaphylactic histamine release from isolated rat mast cells in a dose-dependent manner between 10(-8) and 10(-5) M. Adenosine was found to be present during a normal incubation of mast cells, but the concentration was low (2 x 10(-8) M). In rat plasma the concentration was 1.5 x 10(-7) M. The effect of 10(-5) M adenosine was dose-dependently inhibited by theophylline. 50% inhibition was found at 3 x 10(-5) M theophylline. Cyclic nucleotide phosphodiesterase inhibition required much higher concentrations (IC50 approximately 10(-3) M). It is suggested that some of the anti-allergic actions of theophylline (clinical concentration range: 10(-5) M) does not involve cyclic nucleotides but may be due to inhibition of the effects of endogenous adenosine.

Relationship between serum IgE levels and anaphylactic histamine release from isolated rat mast cells

Inbred Hooded Lister rats were immunized with egg albumin with B. pertussis vaccine used as an adjuvant. The serum levels of total IgE and IgE antibody (egg albumin specific) were determined by radioimmunoassay techniques before and after immunization. The basic level of total IgE in serum was 560 +/- 110 ng/ml. After immunization a maximal peak at day 11 of 1940 +/- 160 ng/ml was registered. Anti-egg albumin IgE antibody showed a maximum around day 13 of 75 +/- 11 units/ml. Pleural mast cells were isolated on Ficoll between day 14 and 20 after immunization. A significant negative correlation between the basic total IgE level and histamine release by antigen (egg albumin) was found and also a significant positive correlation of specific IgE antibody (determined at day 11) and histamine release. The correlation between IgE level and histamine release was slightly improved if instead the ratio of specific IgE antibody over total IgE was used.