Contractile responses to allergen and cholinergic stimulation in bronchus and trachea of cockroach allergen-sensitized guinea pigs

The effects of cannabidiol on the antigen-induced contraction of airways smooth muscle in the guinea-pig

(-)-Δ(9)-Tetrahydrocannabinol has been demonstrated to have beneficial effects in the airways, but its psychoactive effects preclude its therapeutic use for the treatment of airways diseases. In the present study we have investigated the effects of (-)-cannabidiol, a non-psychoactive component of cannabis for its actions on bronchial smooth muscle in vitro and in vivo. Guinea-pig bronchial smooth muscle contractions induced by exogenously applied spasmogens were measured isometrically. In addition, contractile responses of bronchial smooth muscle from ovalbumin-sensitized guinea-pigs were investigated in the absence or presence of (-)-cannabidiol. Furthermore, the effect of (-)-cannabidiol against ovalbumin-induced airway obstruction was investigated in vivo in ovalbumin-sensitized guinea-pigs. (-)-Cannabidiol did not influence the bronchial smooth muscle contraction induced by carbachol, histamine or neurokinin A. In contrast, (-)-cannabidiol inhibited anandamide- and virodhamine-induced responses of isolated bronchi. A fatty acid amide hydrolase inhibitor, phenylmethanesulfonyl fluoride reversed the inhibitory effect of (-)-cannabidiol on anandamide-induced contractions. In addition, (-)-cannabidiol inhibited the contractile response of bronchi obtained from allergic guinea-pigs induced by ovalbumin. In vivo, (-)-cannabidiol reduced ovalbumin-induced airway obstruction. In conclusion, our results suggest that cannabidiol can influence antigen-induced airway smooth muscle tone suggesting that this molecule may have beneficial effects in the treatment of obstructive airway disorders.

A comparative study on cockroach and ovalbumin sensitizations and challenge responses in Hartley guinea-pigs

The role of allergens in asthmatic inflammation is not clearly understood. To elucidate the mechanism of cockroach allergen (CRa)-induced airway disease, we studied three groups of Hartley guinea-pigs sensitized to control, ovalbumin (OA) or CRa. Parameters measured were anaphylactic antibodies by allergy skin test (AST), PCA assay and Western blot, changes in specific airway resistance (SRaw), analysis of bronchoalveolar lavage (BAL) and contracture responses of tracheal muscle (TSM) to non-specific and specific stimuli, in vitro. Both OA and CRa animals showed a similar allergic sensitization (AST and PCA), while Western blot identified several reaginic bands in CRa group compared to a single band in OA group. SRaw illustrated that CRa induce dual-asthmatic responses (4/6) in the CRa group, whereas OA induce only an early asthmatic response (3/6) in the OA group (P<0.01). The average total leukocytes in BALF of the CRa were 27.0x10(6), mostly neutrophils and eosinophils, while those of the OA showed 3.5x10(6), mostly eosinophils, respectively (P<0.0001). TSM responses to non-specific stimuli were similar in both groups (P>0.1), while the antigen-specific TSM contractions were more brisk in the OA group than those of CRa group (P<0.001). Thus, the study indicates that both CRa and OA sensitize guinea-pigs, yet CRa induces more severe and persistent late-phase inflammation than OA. This appears to be related to an influx of neutrophils rather than anaphylactic bronchospasm.