The overall goal of this proposal is to understand how diabetes impairs the survival of retinalneurons. The specific objective is to investigate how diabetes-induced hyperglycemia and inflammatorymediators accelerate the death of retinal neurons by reducing neurotrophin-mediated signaling pathways.The rationale for this proposal is that understanding the mechanisms that compromise the survival ofretinal neurons will lead to improved means to prevent vision loss in diabetes and other retinaldegenerations. Diabetes damages the retina by multiple insults, including hyperglycemia, inflammation and alteredpro-survival signaling, but the mechanisms that cause neurons to die remain uncertain. Growth factorsignaling through Akt (protein kinase B) is central to the survival of neurons, and is impaired as a sharedfeature of diabetes, systemic infections, immune-mediated inflammation, and degenerative brain diseases.Numerous clinical and animal studies have now established diabetes-induced death of retinal neurons as acomponent of early diabetic retinopathy. The investigators have demonstrated that retinal pro-survivalsignaling via the insulin receptor and Akt is normally activated by insulin, insulin-like growth factors andlight, and diabetes reduces this basal pro-survival activity concomitant with the onset of retinal neuronsdeath. We have shown that hyperglycemia disrupts the survival of retinal neurons in culture and now findthat cytokines block the neurotrophic actions of growth factors. Reduction of hyperglycemia with phlorizintreatment reduces the death of retinal neurons and restores pro-survival signaling in diabetic rats.Moreover, ocular delivery of growth factors also augments pro-survival signaling and reduces retinal celldeath. We have also generated a novel mouse model with conditional retinal insulin receptor knockdownthat provides a powerful tool to examine the role of retinal pro-survival signaling. Together, these datademonstrate that insulin receptor/Akt signaling is a key survival pathway for retinal neurons. Thus, wepropose the general hypothesis that hyperglycemia and inflammation impair neurotrophin-mediatedsurvival of retinal neurons in diabetes.
Three specific aims using biochemical, molecular and geneticapproaches in retinal neuron cultures, diabetic rats, and mice with knockdown of the insulin receptor/Aktpathway will test the hypothesis. A strong interdisciplinary research team of will elucidate the mechanismsby which hyperglycemia and cytokines impair neurotrophin-mediated survival of retinal neurons in a culturesystem and in diabetic rats. We will also determine the impact of insulin receptor/Akt signaling on retinalneuron survival and vision in diabetes using novel genetically modified mice.
This proposal is intended to determine why the nerve cells in the retina that are most critical for vision die in diabetes. We will test the hypothesis that excess glucose and inflammatory molecules suppress the normal effects of hormones that keep nerve cells alive. The projected outcome is to have better means to maintain the health of retinal nerve cells in persons with diabetes to preserve vision and reduce the need for laser treatments.
Showing the most recent 10 out of 40 publications
