Attenuation of acute lung injury by Lonicerae Japonicae Flos extracts is associated with the rebalancing of Th1/Th2/Th17/Treg cells in lungs and colons

Ethnopharmacological relevance: Lonicerae Japonicae Flos (LF), a traditional Chinese medicine sourced from the dried flower buds or the newly-unfurled blossoms of Lonicera japonica Thunb., is widely used to manage diverse respiratory conditions. Current pharmacological studies have revealed its anti-inflammatory actions in cases of acute lung injury (ALI). However, the underlying mechanisms accountable for this action are yet to be exhaustively explicated in the view of gut-lung axis.

Aim of the study: To delve into the potential mechanism of LF in treating ALI through the regulation of CD4⁺ T cells (Th1/Th2/Th17/Treg) in the lungs and colons.

Materials and methods: Male ICR mice were utilized to establish an ALI model via intraperitoneal instillation of 10 mg/kg lipopolysaccharide (LPS). The LF extracts at low-, medium-, and high-doses (LLF, MLF and HLF) were administered for treatment, with dexamethasone (DEX) serving as the positive control. Lung weight and lung index were calculated after 24 h of LPS induction. Histopathologic analysis of the lungs and colons was conducted based on their hematoxylin and eosin (HE)-stained tissue sections. T cell proportions were measured using flow cytometry. qRT-PCR analysis was used to assess the relative mRNA expression of genes. Protein expression was detected using western blot, immunohistochemistry, and immunofluorescence.

Results: LF extracts and DEX reduced the lung weight/index, the lung tissue damage and inflammation scores, as well as the expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in the ALI mice. Additionally, LF extracts and DEX inhibited the colon tissue damage and the expression of pro-inflammatory cytokines, while increasing the expression of epithelial tight-junctional proteins (ZO-1 and occludin). Importantly, LF extracts effectively regulated the typical cytokines expression of Th1/Th2/Th17/Treg cells, and restored the balance of Th1/Th2 and Th17/Treg cells, thereby alleviating tissue inflammation in both the lungs and colons of the ALI mice. The therapeutic effects of LF extracts were associated with the regulation of gene and protein expression of Th1/Th2/Th17/Treg-type transcription factors. Specifically, at the protein level, LF extracts significantly suppressed the expression of T-bet and RORγT (Th1-/Th17-related transcription factors), while increased the expression of GATA3 and Foxp3 (Th2-/Treg-related transcription factors) in the lungs and colons. Furthermore, LF extracts inhibited the activation of CCR6/CCL20 signaling pathway in the lungs and colons.

Conclusions: The attenuating effect of LF extracts on LPS-induced ALI is associated with the rebalancing of Th1/Th2/Th17/Treg cells in both the lungs and colons.