Zeaxanthin, a retinal carotenoid, protects retinal cells against oxidative stress

To investigate whether zeaxanthin, the predominant carotenoid pigment of the macular pigments in human retina, provides neuroprotection against retinal cell damage.

We used in vitro cultured retinal ganglion cells (RGCs), specifically RGC-5, an E1A virus-transformed rat cell line. Cell damage was induced either by a 24-hr exposure to hydrogen peroxide (H2O2) or by serum deprivation. Cell viability was measured using the tetrazolium salt, WST-8. The scavenging capacity of zeaxanthin for H2O2, superoxide anion radical (O2.-), and hydroxyl radical (HO.) was measured using a radical scavenging capacity assay with CM-H2DCFDA, a reactive oxygen species (ROS)-sensitive probe.

When added to RGC-5 cell cultures, 0.1, 10, and 1 microM zeaxanthin scavenged the free radicals induced by H2O2, O2.-, and HO., respectively. In addition, pretreatment with 1 microM zeaxanthin permitted scavenging of staurosporine-induced intracellular radicals. Zeaxanthin also inhibited the neurotoxicity induced by H2O2 or serum deprivation and scavenged the intracellular radicals induced by H2O2 or serum deprivation.

Our results suggest that zeaxanthin provides effective protection against oxidative stress-induced retinal cell damage.