Baicalein significantly protects human retinal pigment epithelium cells against H2O2-induced oxidative stress by scavenging reactive oxygen species and downregulating the expression of matrix metalloproteinase-9 and vascular endothelial growth factor.

PURPOSE: Age-related macular degeneration is a leading cause of blindness in the elderly. At a later stage, neovascular or exudative age-related macular degeneration can lead to severe central vision loss that is related to aging-associated cumulative oxidative stress of the human retinal pigment epithelium (hRPE) cells. Early prevention with antioxidants is mandatory. The aim of this study was to determine whether and how baicalein can act as an antioxidant. METHODS: The methods used included lactate dehydrogenase, 2',7'-dichloro-fluorescein diacetate, or enzyme-linked immunosorbent assay to measure cell viability, oxygen free radical levels, or the levels of vascular endothelial growth factor (VEGF)/matrix metalloproteinase-9 (MMP-9), respectively. RESULTS: H2O2 dose-dependently reduced the cell viability of hRPE cells. This negative effect was dose-dependently (with a lower effect at 20µM) and significantly counteracted by pretreatment with baicalein (50µM). Treatment with H2O2 significantly stimulated the formation of oxygen free radicals. This increase was dose-dependently and significantly blunted by baicalein. Further, treatment with a sublethal dose of H2O2 was associated with an upregulation in the levels of VEGF and MMP-9. The increases in these proteins were also dose-dependently (with a lower effect at 20µM) and significantly (50µM) blunted by pretreatment with baicalein. CONCLUSION: This study supports an antioxidative role for baicalein whereby it protects hRPE cells against H2O2-induced oxidative stress by downregulating the levels of VEGF and MMP-9, which are increased by H2O2.

Therapeutic effects and mechanisms of action of mannitol during H2O2-induced oxidative stress in human retinal pigment epithelium cells.

BACKGROUND: Age-related macular degeneration (AMD) is a leading cause of blindness in the elderly. At a later stage, neovascular or exudative AMD can lead to severe central vision loss that is related to aging-associated cumulative oxidative stress of the human retinal pigment epithelium (hRPE) and choroid capillary. Early prevention with antioxidants is mandatory. The aim of this study was to determine whether and how mannitol can act as an antioxidant. METHODS: The methods used included measurements of cell viability, oxygen free radical (OFR) levels, lipid peroxide (LP) levels, and OFR-related enzyme protein levels. RESULTS: H(2)O(2) dose-dependently reduced the cell viability of hRPE cells. This negative effect was significantly counteracted by pretreatment with mannitol (1 mM). H(2)O(2) significantly stimulated the formation of OFR and LP. These increases were dose-dependently and significantly blunted by mannitol. Furthermore, treatment with H(2)O(2) was associated with a reduction in the level of catalase, but not of manganese superoxide dismutase (MnSOD). In contrast, it was shown that mannitol protected hRPE cells against the H(2)O(2)-induced oxidative stress by increasing the level of catalase, but not the level of MnSOD. CONCLUSION: This study supports an antioxidative role for mannitol that acts through up-regulating the level of catalase, which is decreased by H(2)O(2).