BackgroundAge-related macular degeneration (AMD) is a leading cause of vision loss in elderly people, and dry AMD is the most common type of AMD. Oxidative stress and alternative complement pathway activation may play essential roles in the pathogenesis of dry AMD. There are no available drugs for dry AMD. Qihuang Granule (QHG) is an herbal formula for the treatment of dry AMD, and it achieves a good clinical effect in our hospital. However, its potential mechanism is unclear. Our study investigated the effects of QHG on oxidative stress-associated retinal damage to reveal its underlying mechanism.MethodsOxidative stress models were established using H2O2 and NaIO3 in ARPE-19 cells and C57BL/6 mice. Cell apoptosis and viability were assessed using phase contrast microscopy and flow cytometry, respectively. Alterations in the mouse retinal structure were evaluated using Masson staining and transmission electron microscopy (TEM). The expression of complement factor H (CFH), complement component 3a (C3a) and complement component 5a (C5a) in retinal pigment epithelium (RPE) cells and mice was measured using RT-PCR, Western blot analysis and ELISA.ResultsPretreatment with QHG significantly prevented cell apoptosis and disorder of the RPE and inner segment/outer segment (IS/OS) in H2O2-treated RPE cells and NaIO3-injected mice. QHG alleviated mitochondrial damage in mouse RPE cells, as shown by TEM. QHG also promoted CFH expression and inhibited the expression of C3a and C5a.ConclusionsThe results suggest that QHG protects the retinal pigment epithelium from oxidative stress, likely by regulating the alternative complement pathway.