PPM1A as a key target of the application of Jiawei‑Maxing‑Shigan decoction for the attenuation of radiation‑induced epithelial‑mesenchymal transition in type II alveolar epithelial cells

Jiawei Maxing Shigan Tang alleviates radiation-induced lung injury via TGF-β1/Smad signaling pathway mediated by regulatory T cells

ETHNOPHARMACOLOGICAL RELEVANCE

Radiation-induced lung injury (RILI) is a common complication during thoracic radiotherapy which impairs the quality of life in patients and limits radiation doses. Jiawei Maxing Shigan Tang (JMST), which is a modified decoction made of Ephedra, Apricot Kernel, Gypsum, and Licorice, can alleviate the symptoms of RILI in patients. Previous studies and preliminary findings suggested a potential molecular mechanism of JMST in the treatment of RILI. Further studies are needed.

AIM OF THE STUDY

To elucidate the mechanisms of how regulatory T cells (Tregs) promote RILI and the effect of JMST on Tregs, as well as the corresponding pathway.

MATERIALS AND METHODS

CD4+CD25+ Tregs were isolated from rats, and the supernatant's TGF-β1 level was examined by using enzyme-linked immunosorbent assay (ELISA). Type II alveolar epithelial cells (AECs) were co-cultured with the supernatant of Tregs, and the expression levels of epithelial-to-mesenchymal transition (EMT)-related and TGF-β1/Smad signaling pathway-related proteins were analyzed by using western blotting (WB). Afterward, the Tregs were incubated with different concentrations of JMST. The cell viability and TGF-β1 concentration were confirmed by cell counting kit-8 (CCK-8) assay and ELISA, respectively. The optimized concentration of JMST was applied in vitro and vivo experiments. The specific mechanism was investigated through the combination of using flow cytometry, lung histopathology analysis, ELISA, and WB.

RESULTS

Radiation could promote Tregs to secrete TGF-β1. After radiation, the expression levels of Smad2/3, phosphorylated Smad2/3 (p-Smad2/3), Smad4 and mesenchymal markers Vimentin and α-SMA were all increased, while the expression level of epithelial markers E-cadherin was decreased. The expression levels of these proteins were reversed after interventions involving Treg cell activation inhibition or TGF-β1 receptor inhibitor. JMST reduced the number of Tregs in lung tissue and alleviated the degree of pulmonary fibrosis. The expression of Smad2/3, p-Smad2/3, Smad4, TGF-β1, Vimentin, and α-SMA were significantly downregulated, while the E-cadherin was upregulated, through the intervention of JMST.

CONCLUSION

Tregs could mediate EMT through TGF-β1/Smad pathway. JMST inhibits EMT via TGF-β1/Smad pathway by regulating Tregs, therefore alleviating RILI.

3,3'-Diindolylmethane attenuates inflammation and fibrosis in radiation-induced lung injury by regulating NF-κB/TGF-β/Smad signaling pathways

OBJECTIVE

This study aims to investigate the protective effect of 3,3'-diindolylmethane (DIM) on the radiation-induced lung injury (RILI) model and to explore its possible mechanism. Methods: A mouse model of RILI was established by thoracic irradiation, and dexamethasone was used as a positive drug to investigate the effect of DIM on RILI mice. Lung histopathology was analyzed by HE staining and Masson staining. Then the levels of inflammatory cytokines (TGF-β, TNF-α, IL-1β, and IL-6), inflammatory cell counts, and activity of MPO were detected. The expression of TGFβ1/Smad signaling pathway-related proteins was determined by immunohistochemistry. qPCR was used to analyze the mRNA expression levels of inflammatory factors, α‑SMA and COL1A1. The expression of COX-2, NF-κB, IκBα, PI3K, and Akt proteins was assessed by Western blot. Results: Histopathological staining of lung tissues showed that DIM administration alleviated the pulmonary inflammation and fibrosis caused by RILI. Moreover, the content of inflammatory factors such as IL-1β and IL-6, the expression of NF-κB pathway-related proteins, and the counts of inflammatory cells were inhibited in lung tissue, indicating that DIM can inhibit the NF-κB pathway to reduce inflammation. In addition, DIM could down-regulate the mRNA levels of α-SMA, COL1A1, and downregulate TGFβ1, Smad3, and p-Smad2/3 in lung tissues. Conclusion: Our study confirms that DIM has the potential to treat RILI in vivo by inhibiting fibrotic and inflammatory responses in lung tissue through the TGFβ/Smad and NF-κB dual pathways, respectively.