Function of erythropoietin on glucose-induced neuronal damage in Ceanorhabditis elegans

Aims/hypothesis: Ceanorhabditis elegans (C. elegans) lacks a vascular system and is therefore a good model to discriminate mechanisms of glucose-mediated tissue damage involving the diabetic retina. Erythropoietin has been identified as prosurvival, angiogenic and neuroprotective factor in the diabetic retina via its ability to inhibit apoptosis through anti-apoptotic pathways such as PI3K-Akt pathway which negatively regulates FOXO transcription factors. We determined the function of erythropoietin in glucose-induced nerve cell dysfunction in C. elegans with respect to lifespan, neuronal function and ROS formation under high glucose conditions and evaluated the potential molecular mechanisms underlying these effects with relation to the diabetic retina.

Methods: Strains used in this study included wild-type (N2) and knock-out FOXO transcription factors (daf-16). Each strain of C. elegans was separated into 4 subgroups and each subgroup was supplemented with either 150µl of 5 IU/ml erythropoietin, 150µl 400mmol/l glucose solution or 150µl of 5 IU/ml erythropoietin + 400mmol/l glucose solution, alongside controls that were handled in the same manner but not exposed to erythropoietin or glucose solution. Function of erythropoietin on C. elegans was evaluated by using lifespan analysis, neuronal motility analysis and staining of ROS.

Results: Erythropoietin improved three neuronal parameters: relative head motility, body bending frequency and body angular velocity, both, under standard and high glucose conditions in wild-type (N2) nematodes. However, these changes were not affected in FOXO transcription factors (daf-16) knock-out worms. Interestingly, erythropoietin significantly decreased the ROS formation in both wild-type (N2) and FOXO transcription factors (daf-16) knock-out nematodes under high glucose conditions.

Conclusions/interpretation: Erythropoietin has antioxidative properties in a FOXO transcription factors (daf-16) independent manner. In contrast, its neuroprotective effect at least acts through the erythropoietin-mediated FOXO transcription factors (daf-16) pathway. Therefore, exogenous erythropoietin administration may help to prevent neuronal cell death in the early course of diabetic retinopathy (DR) via the erythropoietin-mediated PI3K-Akt pathway which negatively regulates FOXO transcription factors (daf-16).