Isopanepoxydone inhibits oxidative damage in murine alveolar macrophages via NRF2 and NLRP3 inflammasome

Abstract

Background

Respiratory diseases due to particulate matter are a serious health issue. We sought to investigate the efficacy of isopanepoxydone (ISO) isolated from the Panus rudis as a therapeutic against particulate matter-induced respiratory complications.

Materials and Methods

ISO was isolated from a culture broth of Panus rudis using solvent partition, silica gel, and column chromatography, and high-performance liquid chromatography. Its chemical structure was determined spectroscopically. Murine alveolar macrophages (MH-S) were treated with ISO to investigate the inhibition of nitric oxide (NO) while cytotoxicity was investigated via a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. The expression of pro-inflammatory mediators, cytokines, and protein expression levels in the oxidative protective and inflammasome pathway were also investigated. Reactive oxygen species in MH-S cells were investigated using 2′,7′-dichlorofluorescein diacetate while immunofluorescence was performed to investigate the expression of activated apoptosis-associated speck-like proteins (ASC) containing a caspase recruitment domain in MH-S cells.

Results

ISO effectively inhibited CFA-induced NO production with no cytotoxicity on MH-S cells and pro-inflammatory mediators and cytokines were also inhibited (except tumor necrosis factor α and interleukin-6). ISO enhanced the protein expression of nuclear factor erythroid 2–related factor 2, while suppressing proteins in the inflammasome pathway, but did not suppress the expression of nuclear factor-kappa B. ISO also reduced detectable ROS other than preventing the activation of ASC.

Conclusion

Pathways of action of ISO in MH-S cells that prevent oxidative damage and suppress the expression of proteins in the inflammasome pathway were investigated. ISO may be developed as a treatment for respiratory inflammation.

Keywords:

• Isopanepoxydone
• reactive oxygen species
• NF-κB
• lung inflammation
• MH-S

Acknowledgments

The authors would like to thank Ms. Ji-Young Oh, Center for University-wide Research Facilities (CURF) at Jeonbuk National University, for performing NMR measurements.

Disclosure statement

The authors declare no conflict of interest.

Data availability statement

All data were presented in this manuscript.

Additional information

Funding

This research was supported and funded by the National Research Foundation of Korea [2018R1D1A1A09083797].