Topical application of emu oil and menthol alleviates inflammation via modulation of NF-κB pathway in mouse model

Abstract Objective The anti-inflammatory effects of emu oil and menthol as functional foods and topical medicinal formulations have been established both in vivo and through topical application. However, the mechanisms underlying their anti-inflammatory effects during in vitro transdermal application remain elusive. Thus, this study aimed to evaluate the anti-inflammatory effects of a composite cream enriched with emu oil and menthol in a mouse ear swelling model and investigate its mechanisms underlying the local anti-inflammatory actions. Methods The xylene-induced ear swelling model was utilized to evaluate the topical anti-inflammatory efficacy of the composite cream. Histopathological assessments of ear tissue were conducted using hematoxylin and eosin staining. Additionally, real-time quantitative PCR was performed to quantify the mRNA levels of NF-κB, IL-6, and IL-1β in ear tissues. Lastly, immunohistochemistry staining was performed to measure the protein expression levels of NF-κB p65 and IL-6. Results The application of the composite cream effectively alleviated ear swelling elicited by xylene exposure. Moreover, it relieved ear tissue edema and microvascular bleeding induced by xylene and reversed alterations in the mRNA and protein expression levels of NF-κB and IL-6 in the same tissues. Additionally, emu oil and menthol exerted anti-inflammatory effects in mice, mitigating xylene-induced ear inflammation and exhibiting a synergy between these two. Conclusions The composite cream may serve as a promising topical formulation for alleviating localized inflammation, which is associated with the modulation of NF-κB pathway. Additionally, emu oil and menthol can be used as active anti-inflammatory ingredients in cosmetic formulations.