Photoreceptor cells are incessantly bombarded with photons of light, which, along with the cells' high rate of oxygen metabolism, continuously exposes them to elevated levels of toxic reactive oxygen intermediates (ROIs). Vacancy-engineered mixed-valence-state cerium oxide nanoparticles (nanoceria particles) scavenge ROIs. Our data show that nanoceria particles prevent increases in the intracellular concentrations of ROIs in primary cell cultures of rat retina and, in vivo, prevent loss of vision due to light-induced degeneration of photoreceptor cells. These data indicate that the nanoceria particles may be effective in inhibiting the progression of ROI-induced cell death, which is thought to be involved in macular degeneration, retinitis pigmentosa and other blinding diseases, as well as the ROI-induced death of other cell types in diabetes, Alzheimer's disease, atherosclerosis, stroke and so on. The use of nanoceria particles as a direct therapy for multiple diseases represents a novel strategy and suggests that they may represent a unique platform technology.

Promising results have been obtained using cerium (Ce) oxide nanoparticles (CNPs) as antioxidants in biological systems. CNPs have unique regenerative properties owing to their low reduction potential and the coexistence of both Ce(3+)/Ce(4+) on their surfaces. Defects in the crystal lattice due to the presence of Ce(3+) play an important role in tuning the redox activity of CNPs. The surface Ce(3+):Ce(4+) ratio is influenced by the microenvironment. Therefore, the microenvironment and synthesis method adopted also plays an important role in determining the biological activity and toxicity of CNPs. The presence of a mixed valance state plays an important role in scavenging reactive oxygen and nitrogen species. CNPs are found to be effective against pathologies associated with chronic oxidative stress and inflammation. CNPs are well tolerated in both in vitro and in vivo biological models, which makes CNPs well suited for applications in nanobiology and regenerative medicine.

The therapeutic application of nanomaterials has been a focus of numerous studies in the past decade. Due to its unique redox properties, cerium oxide (ceria) is finding widespread use in the treatment of medical disorders caused by the reactive oxygen intermediates (ROI). The radicalscavenging role of ceria nanoparticles (nanoceria) have been established, as well as the autocatalytic ability of nanoceria to regenerate under various environmental conditions. The synthesis of nanoceria in biocompatible media has also been reported along with cell viability in order to determine the potential use of nanoceria in biomedical applications.

Cerium oxide nanoparticles (Nanoceria) have shown promise as catalytic antioxidants in the test tube, cell culture models and animal models of disease. However given the reactivity that is well established at the surface of these nanoparticles, the biological utilization of Nanoceria as a therapeutic still poses many challenges. Moreover the form that these particles take in a biological environment, such as the changes that can occur due to a protein corona, are not well established. This review aims to summarize the existing literature on biological use of Nanoceria, and to raise questions about what further study is needed to apply this interesting catalytic material to biomedical applications. These questions include: 1) How does preparation, exposure dose, route and experimental model influence the reported effects of Nanoceria in animal studies? 2) What are the considerations to develop Nanoceria as a therapeutic agent in regards to these parameters? 3) What biological targets of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are relevant to this targeting, and how do these properties also influence the safety of these nanomaterials?

The intracellular localization of photoreceptor-specific proteins 33 kd, beta-transducin, and 48 kd, as determined by immunocytochemistry, is transient and dependent on the lighting environment to which the retina is exposed. Western analysis of the proteins in isolated rod outer segments from mouse retina demonstrates that beta-transducin actually moves from the outer segment to the inner segment in response to light and that 48 kd moves simultaneously in the opposite direction. The light-induced movements appear to be initiated by the absorption of light by rhodopsin because red light, which does not bleach rhodopsin, does not produce this redistribution of photoreceptor proteins. Time course analysis of these movements suggests that the light-induced shift is detectable at the earliest time examined (30 seconds). The bidirectional movement suggests that the photoreceptor cells have at least two distinct dynein-like or kinesin-like translocator molecules that act as microtubule-based motors. This movement appears to be a basic mechanism by which photoreceptor cells rapidly and radically alter the subcellular concentrations of photoreceptor-specific proteins, which in turn may affect the rapid changes in membrane potential that occur during phototransduction.

This compound was characterized by the expected spectroscopic features and gave satisfactory elemental analyses. It is possible that the actual phosphorylating agent is complexed with dioxane; at present we are unable to distinguish between such a complex and solvated metaphosphate.Visiting Fulbright Scholar on leave from the University of Valencia, Vaiencia. Spain.

Many neurodegenerative diseases are known to occur and progress because of oxidative stress, the presence of reactive oxygen species (ROS) in excess of the cellular defensive capabilities. Age related macular degeneration (AMD), diabetic retinopathy (DR) and inherited retinal degeneration share oxidative stress as a common node upstream of the blinding effects of these diseases. Knockout of the Vldlr gene results in a mouse that develops intraretinal and subretinal neovascular lesions within the first month of age and is an excellent model for a form of AMD called retinal angiomatous proliferation (RAP). Cerium oxide nanoparticles (nanoceria) catalytically scavenge ROS by mimicking the activities of superoxide dismutase and catalase. A single intravitreal injection of nanoceria into the Vldlr-/- eye was shown to inhibit: the rise in ROS in the Vldlr-/- retina, increases in vascular endothelial growth factor (VEGF) in the photoreceptor layer, and the formation of intraretinal and subretinal neovascular lesions. Of more therapeutic interest, injection of nanoceria into older mice (postnatal day 28) resulted in the regression of existing vascular lesions indicating that the pathologic neovessels require the continual production of excessive ROS. Our data demonstrate the unique ability of nanoceria to prevent downstream effects of oxidative stress in vivo and support their therapeutic potential for treatment of neurodegenerative diseases such as AMD and DR.

In the present study, we tested the hypothesis that 17␤-estradiol (␤E2) is a neuroprotectant in the retina, using two experimental approaches: 1) hydrogen peroxide (H 2 O 2 )-induced retinal neuron degeneration in vitro, and 2) light-induced photoreceptor degeneration in vivo. We demonstrated that both ␤E2 and 17␣-estradiol (␣E2) significantly protected against H 2 O 2 -induced retinal neuron degeneration; however, progesterone had no effect. ␤E2 transiently increased the phosphoinositide 3-kinase (PI3K) activity, when phosphoinositide 4,5-bisphosphate and [32 ␥ATP] were used as substrate. Phospho-Akt levels were also transiently increased by ␤E2 treatment. Addition of the estrogen receptor antagonist tamoxifen did not reverse the protective effect of ␤E2, whereas the PI3K inhibitor LY294002 inhibited the protective effect of ␤E2, suggesting that ␤E2 mediates its effect through some PI3K-dependent pathway, independent of the estrogen receptor. Pull-down experiments with glutathione S-transferase fused to the N-Src homology 2 domain of p85, the regulatory subunit of PI3K, indicated that ␤E2 and ␣E2, but not progesterone, identified phosphorylated insulin receptor ␤-subunit (IR␤) as a binding partner. Pretreatment with insulin receptor inhibitor, HNMPA, inhibited IR␤ activation of PI3K. Systemic administration of ␤E2 significantly protected the structure and function of rat retinas against light-induced photoreceptor cell degeneration and inhibited photoreceptor apoptosis. In addition, systemic administration of ␤E2 activated retinal IR␤, but not the insulin-like growth factor receptor-1, and produced a transient increase in PI3K activity and phosphorylation of Akt in rat retinas. The results show that estrogen has retinal neuroprotective properties in vivo and in vitro and suggest that the insulin receptor/PI3K/Akt signaling pathway is involved in estrogen-mediated retinal neuroprotection.