Effects of fixed oil of Caryocar coriaceum Wittm. Seeds on the respiratory system of rats in a short-term secondhand-smoke exposure model

Ethnopharmacological relevance: Pequi fruit are obtained from the pequi tree (Caryocar coriaceum), from which the pulp and nut are used in order to extract an oil that is commonly used in popular medicine as an antiinflammatory agent, particularly for the treatment of colds, bronchitis and bronchopulmonary infections. Making use of the fixed oil of Caryocar coriaceum (FOCC), an attractive alternative for the treatment of diseases caused by exposure to environmental tobacco smoke.

Aim of the study: To evaluate whether oral intake FOCC provides beneficial effects in the respiratory system of rats submitted to a short-term secondhand smoke (SHS) exposure model.

Materials and methods: The experiments were performed on Wistar rats divided into 4 groups; in the SHS + O and SHS + T groups, the animals were pretreated orally with 0.5 mL of FOCC (SHS + O) or vehicle (Tween-80 [1%] solution) (SHS + T). Immediately after pretreatment, the animals were submitted to the SHS exposure protocol, for a total period of 14 days. Exposures were performed 6 times per day, with a duration of 40 min per exposure (5 cigarettes per exposure), followed by a 1-h interval between subsequent exposures. In the AA + O and AA + T groups, animals were submitted to daily oral pretreatment with 0.5 mL of FOCC (AA + O) or vehicle (AA + T). These animals were then subjected to the aforementioned exposure protocol, but using ambient air. After the exposure period, we investigated the effects of FOCC in respiratory mechanics in vivo (Newtonian resistance -R_N, tissue elastance -H, tissue resistance -G, static compliance -C_ST, inspiratory capacity -IC, PV loop area) histopathology and lung parenchymal morphometry in vitro (polymorphonuclear cells -PMN, mean alveolar diameter -L_m, bronchoconstriction index -BCI), temporal evolution of subjects' masses, and percent composition of the FOCC.

Results: Regarding the body mass of the animals, the results demonstrated an average body mass gain of 10.5 g for the animals in the AA + T group, and 15.5 g for those in the AA + O group. On the other hand, the body mass of animals in the SHS + T and SHS + O suffered an average loss of 14.4 and 4.75 g, respectively. Regarding respiratory system analyzes, our results demonstrated significant changes in all respiratory mechanics variables and lung parenchyma morphometry analyzed for the SHS + T group when compared to the AA + T group (p < 0,05), confirming the establishment of pulmonary injury induced by SHS exposure. We also observed that rats pretreated orally with FOCC (SHS + O) showed improvement in all variables when compared to the SHS + T group (p < 0,05), thus demonstrating the effectiveness of FOCC in preventing lung damage induced by short-term SHS exposure.

Conclusion: In conclusion, our results demonstrate that FOCC was able to prevent lung injury in rats submitted to short-term SHS exposure.