Essential Oil from Cinnamomum Cassia  Presl Bark Regulates Macrophage Polarization and Ameliorates Lipopolysaccharide-Induced Acute Lung Injury Through Tlr4/Myd88/Nf-Κb Pathway

Abstract

Background: Cinnamomum cassia Presl, a traditional Chinese medicine recorded in "Shennong's Herbal Classic," has been historically used to treat respiratory diseases and is employed to address inflammation. The essential oil derived from Cinnamomum cassia bark is a primary anti-inflammatory agent. However, there remains ambiguity regarding the chemical composition of cinnamon bark essential oil (BCEO), its principal anti-inflammatory components, and their potential efficacy in typical inflammatory respiratory conditions, such as acute lung injury (ALI).Purpose: This study aimed to unveil the chemical composition of BCEO. In addition, the mechanism of action of BCEO in ameliorating ALI and regulating macrophage polarization through the TLR4/MyD88/NF-κB pathway was elucidated.

Methods: BCEO was extracted using supercritical fluid extraction (SFE) and characterized through gas chromatography-mass spectrometry (GC-MS) analysis. The pharmacological effects and underlying mechanisms of BCEO were evaluated in a mouse model of ALI, which was induced by administering 5 mg/kg of lipopolysaccharide (LPS) through intratracheal instillation.

Results: GC-MS analysis revealed 99.08% of the constituents of BCEO. The primary components of BCEO were trans-cinnamaldehyde, o-methoxycinnamaldehyde, (+)-α-muurolene, δ-cadinene, and copaene. BCEO treatment significantly reduced lung W/D ratio, total protein concentration in BALF, levels of TNF-α, IL-6, and IL-1β in BALF, WBC count and NEU% in peripheral blood, and lung histological damage. Pulmonary function, IL-10 levels, and LYM% in peripheral blood also showed imporvement. BCEO effectively decreased the proportion of M1 phenotype macrophages in BALF, M1/M2 ratio, and apoptotic cells in the lung tissue while increasing the proportion of M2 phenotype macrophages in BALF. These findings indicate BCEO's ability to hinder the polarization of M1 phenotype macrophages in BALF, enhance the polarization of M2 phenotype macrophages, and control apoptosis of lung tissue cells. Furthermore, BCEO treatment led to reduced protein and mRNA levels of TLR4, MyD88, and p-p65, alongside increased p65 expression, suggesting its potential to impede the TLR4/MyD88/NF-κB signaling pathway.

Conclusion: SFE-extracted BCEO or its major constituents could serve as a viable treatment for ALI by reducing lung inflammation, improving pulmonary function, and protecting against LPS-induced ALI in mice. This therapeutic effect is achieved by inhibiting M1 macrophage polarization, promoting M2 macrophage polarization, and suppressing the TLR4/MyD88/NF-κB signaling pathway.

Note:
Funding declaration: This research was supported by the Key Research Projects of Henan Higher Education Institutions (23A360015) and the National Natural Science Foundationof China (No. 82204736)

Conflict of Interests: The authors declare that they have no conflict of interest.

Ethical Approval: All animal care and experimental procedures were approved by the Henan University of Chinese Medicine Animal Ethical Committee. The Animal Care and Use Committee of Henan University of Chinese Medicine granted approval for the experimental design outlined in this study (approval ID:193 DWLLGZR202202204).

Keywords: essential oil extracted from the bark of Cinnamomum cassia Presl, gas chromatography-mass spectrometry, Acute lung injury, Toll-Like Receptor 4, M1 macrophage polarization, M2 macrophage polarization