Exploring the anti-inflammatory effects of Radix Curcumae essential oil in pulmonary sarcoidosis via the TLR4/MyD88/NF-κB pathway

Abstract

Background

Pulmonary sarcoidosis (PS) is an immune-mediated disorder characterised by a significant association with various immune cell types including macrophages, T-helper 1 (TH1) cells, and TH17 cells. Dysregulation of immune cell differentiation leads to pronounced inflammatory responses in the pulmonary system, resulting in granuloma formation. Currently, the therapeutic approach for PS predominantly involves the use of immunosuppressive agents. However, the considerable adverse effects associated with these treatments underscore the urgent need to develop novel anti-PS pharmacological interventions.

Purpose

To investigate whether essential oil from Radix Curcumae (RCEO) improves pulmonary function in PS mice by inhibiting inflammation mediated by the Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear factor kappa-B (NF-κB) (TLR4/MyD88/NF-κB) pathway.

Methods

Bioinformatics and network pharmacology methodologies were used to predict potential therapeutic targets of RCEO in the context of PS. The primary components of RCEO were analysed using gas chromatography-mass spectrometry. A murine model of PS was established by induction with Propionibacterium acnes, and alterations in pulmonary function were evaluated using whole-body plethysmography. An enzyme-linked immunosorbent assay was used to measure changes in inflammatory mediators in the blood and bronchoalveolar lavage fluid. Additionally, flow cytometry was performed to determine the differentiation of CD4+ T cells into TH1 and TH17 subsets in the lung tissues of mice in the model group. Immunofluorescence analysis was used to quantify the differentiation of macrophages into M1 and M2 phenotypes in the lung tissues. Polymerase chain reaction (PCR) and western blotting (WB) were used to assess alterations in the mRNAs expression levels and proteins associated with the TLR4/MyD88/NF-κB signalling pathway in pulmonary tissues.

Results

Bioinformatics and network pharmacology predictions suggested that the therapeutic effects of RCEO on PS are linked to the modulation of inflammation via the TLR4/MyD88/NF-κB pathway. In a murine model of PS, RCEO significantly reduced pathological alterations in lung tissue and enhanced pulmonary function. Subsequent experimental analyses revealed that RCEO inhibited the differentiation of macrophages into M1-type macrophages and reduced the differentiation of CD4+ T cells into TH1 and TH17 cells, thereby preventing granuloma formation in the mouse pulmonary tissue. Further PCR and WB analyses indicated that RCEO modulated immune cell differentiation by inhibiting inflammation mediated through the TLR4/MyD88/NF-κB signalling pathway. Immunofluorescence experiments demonstrated that RCEO conferred a protective effect against PS by attenuating inflammation in macrophages.

Conclusion

RCEO inhibited the differentiation of macrophages into M1-type macrophages and suppressed the differentiation of CD4+T cells into TH1 and TH17 cells by blocking the inflammatory response mediated by the TLR4/MyD88/NF-κB pathway. This further reduced the formation of granulomas in lung tissue and improved lung function in PS mice.