PKA signaling-mediated inhibition of the AIM2 inflammasome is involved in the radioprotective effect of Eleutheroside E

Abstract

Objective: To investigate the protective effect and underlying mechanism of Eleutheroside E (EE), derived from Acanthopanax senticosus, against γ-ray radiation-induced splenic injury.

Methods: The Cell Counting Kit-8 assay was used to determine the toxicity of the drug. Hematoxylin and eosin, terminal deoxynucleotidyl transferase dUTP nick end-labeling, and live/dead cell double staining assays were used to evaluate the protective effects of EE on the spleen. Immunofluorescence, immunohistochemical, and enzyme-linked immunosorbent assays (ELISA) were used to investigate the underlying mechanisms of EE. Cross-talk between the absent in melanoma 2 (AIM2) inflammasome and the protein kinase A (PKA) signaling pathway was clarified using selective inhibitors.

Results: EE reduced IR-induced splenic injury—the increased apoptosis rates and the levels of γ-H2AX and inflammatory factors in splenic cells were significantly alleviated. ELISA showed that EE reduced the level of interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-18 (IL-18), and tumor necrosis factor-α (TNF-α) in irradiated tissues. The radioprotective effects of EE were mediated by inhibition of the AIM2 inflammasome and stimulation of PKA signaling, in which EE inhibited the increased levels of AIM2, apoptosis-associated speck-like protein containing a CARD (ASC), and cleaved caspase-1 proteins upon ionizing radiation damage but rescued the decreased protein levels in PKA signaling. Suppression of AIM2 signaling was dependent on the activation of PKA signaling by EE treatment.

Conclusions: EE exerts a significant radioprotective effect on the spleen in vitro and in vivo. Activation of the PKA signaling pathway leads to AIM2 inflammasome inhibition, thereby attenuating radiation-induced DNA damage. This was demonstrated to be the mechanism involved in the radioprotective effects of EE. Thus, EE can be used as a potential radioprotective drug in clinical practice.

Keywords

AIM2 inflammasome / DNA damage / Eleutheroside E / PKA signaling pathway / Radiation damage

Conflict of interest statement

Yue Gao is the editorial board member of this journal and other authors declare no conflict of interest.

Funding

This work was financially supported by the National Natural Science Foundation of China (82103776, Zebin Liao; 82192911, Yue Gao), and innovation Team and Talents Cultivation Program of National Administration of Traditional Chinese Medicine (ZYYCXTD-D-202207, Yue Gao).

Author contributions

Yue Gao and Zebin Liao designed the project. Liangliang Zhang, Changkun Hu, and Zekun Wu performed most of the experiments and analyzed data. Liangliang Zhang and Changkun Hu performed molecular biology and cell biology experiments and conducted data curation and formal analysis. Liangliang Zhang and Zekun Wu performed the animal experiments. Liangliang Zhang and Zebin Liao wrote the manuscript. Yue Gao and Xianglin Tang contributed to the manuscript editing.

Ethical approval of studies and informed consent

Not applicable.

Acknowledgments

None.

Data availability

Data and materials are available upon request to the coresponding author.

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