Lutein enhances survival and reduces neuronal damage in cerebral and retinal ischemia/reperfusion injury

Abstract

Purpose Stroke is one of the leading causes of death worldwide. Protective agents that could diminish the injuries induced by cerebral ischemia/reperfusion (I/R) are crucial to alleviate the detrimental outcome of stroke. Retinal I/R also occurs in many ocular diseases and leads to neuronal death and therefore blindness. Lutein, a safe and potent antioxidant, is known to protect the retina in age-related macular degeneration. The aim of this study is to investigate the protective roles of lutein in cerebral and retinal I/R injury. Methods Two-hour cerebral ischemia was induced by unilateral middle cerebral artery occlusion (MCAo) in mice. Either lutein (0.2mg/kg) or vehicle was given to mice intraperitoneally 1hr after MCAo and 1hr after reperfusion. Neurological deficits were evaluated at 22hr after reperfusion while survival rate was assessed daily until 7 days after reperfusion. Flash electroretinogram (flash ERG) was taken to assess retinal function. After sacrifice, mouse brains were cut into 2mm-thick coronal slices and stained with 2% 2,3,5-triphenyltetrazolium chloride to determine the infarct size after MCAo. Eyes were also enucleated. Paraffin-embedded brain and retinal sections were prepared for TUNEL assay and immunohistochemistry. Protein lysate was collected for Western blotting experiments. Lutein's effect on Müller cells was further evaluated using a model of cobalt chloride-induced hypoxia in immortalized rat Müller cells (rMC-1). Results Higher survival rate, better neurological scores, smaller infarct area and smaller infarct volume were noted in the lutein-treated group. Immunohistochemistry data showed a decrease of immunoreactivity of nitrotyrosine, poly(ADP-ribose) and NFkB in the lutein-treated brains. Western blotting data showed decreased levels of Cox-2, pERK, and pIkB, but increased levels of Bcl-2, heat shock protein 70 and pAkt in the lutein-treated brains. In the retina, severe cell loss in retinal ganglion cell (RGC) layer was noted after I/R injury. Increased oxidative stress was observed in the injured retina. Lutein treatment protected RGC as well as decreased oxidative stress in I/R retina. Lutein treatment also minimized the deterioration of b-wave/a-wave ratio and oscillatory potentials in flash ERG as well as inhibited the up-regulation of GFAP in retinal I/R injury. In the cultured Müller cells, lutein treatment reduced level of nuclear NF-kB together with decreased levels of IL-1b and Cox- 2. Conclusions Post-treatment of lutein protected both the brain and retina from I/R injury. The neuroprotective effect of lutein was associated with reduced oxidative stress. Less production of pro-inflammatory factors from Müller cells suggested an anti-inflammatory role of lutein in retinal ischemic/hypoxic injury. Our results suggest that lutein could diminish the deleterious outcomes of cerebral and retinal I/R probably by its antiapoptotic, anti-oxidative and anti-inflammatory properties. Lutein may have a therapeutic role in protecting the brain in stroke and inner retina in eye diseases with acute ischemia.