Diosmetin attenuates the ubiquitination of epidermal hypoxia-inducible factor 1 alpha by diminishing the formation of RhoBTB3/PHD2 complex in ultraviolet radiation-induced sunburn in mice.

BACKGROUND

The accumulation of excessive reactive oxygen species (ROS) in keratinocytes is a pivotal mechanism underlying ultraviolet radiation (UVR)-induced skin damage and carcinogenesis. Disruption of redox homeostasis exacerbates ROS levels and instigates inflammation. Hypoxia-inducible factor 1 alpha (HIF-1α), essential for maintaining redox balance, is expressed in keratinocytes and plays a protective role in preserving the skin barrier. Stabilization of HIF-1α presents a potential therapeutic approach for UVR-induced sunburn. Our observations indicate that diosmetin inhibits the hydroxylation and ubiquitination of HIF-1α in UVR-induced sunburn. However, the precise mechanisms remain unclear.

PURPOSE: This study aims to elucidate the role and underlying mechanisms of diosmetin in the context of UVR-induced skin sunburn.

METHODS

In vivo UVR-induced sunburn mice models and in vitro UVR-exposed HaCaT cell models were established. We employed histopathological grade, oxidative stress assessment, ROS production measurement, and immunofluorescence staining of inflammatory markers to evaluate the activity of diosmetin. Additionally, RNA sequencing assay and co-immunoprecipitation assays were conducted to elucidate the underlying mechanisms. To verify the role of Rho Binding BTB Protein 3 (RhoBTB3), we performed intradermal injection rAAV-RhoBTB3-GFP to overexpress of RhoBTB3in mice.

RESULTS

Diosmetin effectively inhibits the hydroxylation and ubiquitination of HIF-1α, resulting in significant antioxidative and anti-inflammatory effects in UVR-induced sunburn. RNA sequencing analysis and co-immunoprecipitation experiments demonstrated that diosmetin reduces the formation of the RhoBTB3/PHD2 complex, thereby modulating the ubiquitination of HIF-1α and mitigating oxidative stress. Immunohistochemical analysis conducted on the wild-type and RhoBTB3-overexpressing mice revealed an enrichment of RhoBTB3, Prolyl Hydroxylase Domain protein 2 (PHD2), and HIF-1α in the epidermis. Notably, diosmetin stabilizes the HIF-1α protein and reduces oxidative stress by limiting the formation of the RhoBTB3/PHD2 complex in the epidermis of mice.

CONCLUSIONS

Our study suggests that diosmetin acts as a regulator of the RhoBTB3/PHD2/HIF-1α axis to alleviate oxidative stress in sunburn, providing novel insights into potential treatments and mechanisms for sunburn.