Retinal heat shock protein 25 in early experimental diabetes

Diabetic retinopathy is the leading cause of blindness in adults, and oxidative stress has been pathogenically associated with retinal neurodegeneration. Cellular stresses induce expression of heat shock proteins (HSPs) and this results in cytoprotection. Our aim was to assess retinal expression of HSP25 in early experimental diabetes. Mice were rendered diabetic by streptozotocin injection. Ten weeks after diabetes onset retinal HSP25 expression were studied by real-time PCR, immunoblotting and immunohistochemistry (IHC). Expression of nitrotyrosine and Cu/Zn superoxide dismutase (SOD), was assessed by IHC and apoptosis by TUNEL. Retinal HSP25 mRNA and protein expression was significantly increased in diabetic as compared to non-diabetic animals and localised predominantly within the retinal ganglion cells (RGC) layer. This was paralleled overexpression of nitrotyrosine and SOD and enhanced apoptosis. In early experimental diabetes, HSP25 is overexpressed in the RGC layer in parallel with markers of oxidative stress and apoptosis.