Lycii Fructus and Chrysanthemum Flos, a Chinese medicine herbal pair, ameliorates retinal degeneration of mice induced by sodium iodate and protects Müller cells from oxidative stress

Ethnopharmacological relevance: The combination of Lycii Fructus (LF) and Chrysanthemum Flos (CF) is a well-known herbal pair utilized in Chinese medicine for the treatment of retinal degeneration diseases commonly found in the elderly, such as age-related macular degeneration (AMD). However, the precise mechanisms of action mechanism and active constituents responsible for the therapeutic effects of the LF-CF herbal pair in improving AMD remain unknown.

Aim of the study: This study aims to evaluate the effect of the LF-CF herbal pair on alleviating retinal damage and Apoptosis in Müller cells of a dry AMD mouse model, especially its role in enhancing oxidative stress in the retina. Moreover, it endeavors to clarify the underlying action mechanisms and identify the bioactive ingredients in the LF - CF herbal pair that act on Müller cells to alleviate oxidative stress.

Materials and methods: A mice model of dry AMD was established through intraperitoneal administration of sodium iodate. Various Solvents were employed to prepare extracts of the LF-CF herbal pair. The impact of these solvent extracts on ameliorating oxidative damage and determination of oxidation index in the retina was assessed. The ability of LF-CF herbal pair on regulating Nrf2/HO-1 signaling pathway in model mice was also detected. The MIO-M1 cell cultures were employed to assess the impact of extracts on protecting cells from oxidative damage caused by sodium iodate. The cell cultures were also utilized to investigate the potential mechanism of action and identify the active components involved.

Results: The LF-CF herbal pair extracts showed evident protective effects on the mouse retina against sodium iodate-induced oxidative damage. They maintained retinal structural integrity and inhibited Apoptosis. Among the extracts, the aqueous and 70 % ethanol ones were more effective in preventing retina injury. These two extracts enhanced antioxidant enzyme activity, reduced oxidative products in the experimental mice's retina, reversing the down-regulation of glutamine synthetase (a Müller cell marker). In vitro, the aqueous and 70 % ethanol extracts of the LF-CF herbal pair also protected MIO-M1 cells from sodium iodate-induced oxidative stress via regulating caspase-dependent and Nrf2/HO-1 signaling pathways. Lycium barbarum Polysaccharides and luteolin are likely the active ingredients responsible for these effects.

Conclusions: The LF-CF herbal pair demonstrated the ability to mitigate oxidative stress in the retina and suppress Apoptosis in Müller cells through the regulation of caspase-dependent and Nrf2/HO-1 signaling pathways. These findings contribute to the growing body of scientific evidences supporting the potential of LF-CF herbal pair as a viable therapeutic option or preventive measure for dry AMD.