Abstract
Inhibitors of adenosylmethionine (AdoMet)-dependent methyltransferases reduce histamine release from enzymatically dispersed human lung mast cells activated with either anti-human IgE or calcium ionophore A23187. The ic 25 values for adenosine and 3-deazaadenosine (DZA) inhibiting anti-IgE-induced histamine release were 395 μM and 301 μM respectively. The addition of homocysteine thiolactone (Hcy) potentiated the effects of adenosine and DZA, reducing their ic 25 values to 32 μM and 10.5 μM respectively. The adenosine deaminase (adenosine aminohydrolase EC 3.5.4.4) inhibitors erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) inhibited anti-IgE-induced histamine release with an ic 50 of 162 μM. This inhibition was not potentiated by Hcy. The combination of DZA and Hcy effectively inhibited histamine release induced by concentrations of A23187 which released a similar amount of histamine to anti-IgE. However the combination was 17 times less potent against A23187- compared with anti-IgE-induced release. These observations suggest that AdoMet-dependent methyltransferases play an important role in IgE-dependent histamine release from human lung mast cells but their role in A23187-induced release is less clear.
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