Suppression of inflammation and histidine decarboxylase by protein synthesis inhibitors

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Abstract
Histidine decarboxylase (HD) can be activated in many tissues of animals; stimuli may be either systemic stressors or local irritants. Inhibitors of protein synthesis (puromycin, Actidione, and tenuazonic acid) blocked activation of HD by several stimuli. In contrast, actinomycin D, an inhibitor of RNA synthesis, did not block HD activation; in some experiments it caused a significant enhancement of activation. Thus, new synthesis of protein, but not of RNA, seems to be required for HD activation. Injection of turpentine into footpads of rats or mice causes a parallel activation of HD and development of an intense inflammatory reaction. Actidione and tenuazonic acid, in doses which block HD activation, showed extraordinary and anti-inflammatory potency; actinomycin D failed to suppress either HD activation or inflammation. These findings support the hypothesis that newly formed histamine may be a primary mediator in the slowly developing phase of the inflammatory response.