Evaluation of the Effect of Caffeic Acid Phenethyl Ester (CAPE) on Pharmacological Responses of Isolated Rat Trachea in vitro

Caffeic acid phenethyl ester (CAPE) is one of the major components of honeybee propolis and its structure is similar to flavonoids. CAPE has been shown to possess anti-inflammatory, immunomodulatory, and antioxidant properties. Despite a wide range of biological activities of CAPE, detailed biochemical mechanisms of its action are poorly described. The aim of the present study was to investigate the in vitro effect of CAPE on isolated rat trachea.

A 20 mm long portion of rat tracheal spiral was submerged in 20 ml Krebs solution in an isolated organ bath at 37°C. Changes in tracheal contractility in response to the application of agonist agents were measured using an isometric transducer connected to a Harvard polygraph.

Acetylcholine (ACH), histamine (HIS), and CaCl2 caused the trachea to contract in a dose-dependent manner. Incubation of trachea with 10-7 M and 10-6M of CAPE induced a significant reduction in contraction induced by ACH and HIS. The degree of drug-induced tracheal contraction or relaxation was dose-dependent.

The CAPE potential to relax the trachea may antagonize cholinergic and histaminergic receptors of the trachea. The findings provide new insight into the effectiveness of CAPE in the control of asthma and the possible use of propolis for its treatment. The results highlight the anti-muscarinic, anti-histaminic, anti-inflammatory, and relaxant activities of CAPE and critically show its potential therapeutic effects.