Eugenol inhibits neutrophil myeloperoxidase in vitro and attenuates LPS-induced lung inflammation in mice

Abstract Eugenol (Eug) is a polyphenol extracted from the essential oil of Syzygium aromaticum (L.) Merr. & Perry (Myrtaceae). Health benefits of eugenol in human diseases were proved in several studies. This work aims to evaluate the anti-inflammatory effect of eugenol in chronic lung pathologies. For this purpose, using human neutrophils, the antioxidant activity of eugenol was investigated in vitro. Animal model of LPS-induced lung injury was used to study the anti-inflammatory effect, in vivo. Results showed that eugenol inhibits luminol-amplified chemiluminescence of resting neutrophils and after stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLF) peptide or phorbol myristate acetate (PMA). This effect was dose dependent and was significant from a low concentration of 0.1 µg/mL. Furthermore, eugenol inhibited myeloperoxidase (MPO) activity without affecting its dégranulation. Eugenol has no scavenging effect on hydrogen peroxide (H2O2) and superoxide anion (O2.-). Pretreatment of mice with eugenol prior to the administration of intratracheal LPS significantly reduced neutrophil accumulation in the bronchoalveloar lavage fluid (BALF) and decreased protein concentration. Moreover, eugenol clearly inhibited the activity of matrix metalloproteinases 2 and 9, stimulated by LPS administration. These results suggest that the anti-inflammatory effect of eugenol against the LPS-induced lung inflammation could be exerted via inhibiting myeloperoxidase and metalloproteinases activity. Thus, eugenol could be a promising molecule for the treatment of lung diseases.