Thioredoxin plays a key role in retinal neuropathy prior to endothelial damage in diabetic mice

Abstract

Diabetes is a chronic metabolic syndrome that results in changes in carbohydrate, lipid and protein metabolism. With diabetes for a long time, it increases the risk of diabetic retinopathy (DR) and long-term morbidity and mortality. Moreover, emerging evidence suggests that neuron damage occurs earlier than microvascular complications in DR patients, but the underlying mechanism is unclear. We investigated diabetes-induced retinal neuropathy and elucidated key molecular events to identify new therapeutic targets for the clinical treatment and prevention of DR. For in vivo studies, a high-fat diet and streptozotocin (STZ) injection were used to generate the diabetes model. Hematoxylin-eosin staining was used for morphological observations and measurements of the outer nuclear layer thickness. Electroretinography (ERG) was used to assess retinal function. For in vitro studies, Neuro2a cells were incubated in normal (5.5 mM) and high-glucose (30 mM) conditions. Flow cytometry assays were performed to analyze apoptosis. Additionally, real-time PCR and Western blotting analyses were carried out to determine gene and protein expression in vitro and in vivo. Taken together, the results indicated that retinal neuropathy occurred prior to endothelial damage induced by diabetes, and thioredoxin (Trx) plays a key role in this process. This underlying mechanism may be related to activation of the Trx/ASK1/p-p38/Trx-interacting protein pathway.

Up-Regulation Thioredoxin Inhibits Advanced Glycation End Products-Induced Neurodegeneration

“…Several studies have shown that the decline of Trx expression was found in the development of many diseases including Parkinson's disease (PD), sepsis [13], age-related cataract [14] and DR. In our previous study, we also found that decreased Trx expression plays a key role in retinal neurodegeneration prior to endothelial damage in diabetic mice [15].…”

“…We also found that it can delay retina degeneration occurrence after Sulforaphane (SF), Lycium barbarum polysaccharides and grape seed proanthocyanidin extract treatment through up-regulating the expression of Trx in vitro and in vivo [15][16][17]. Moreover, Previous studies have shown that SF can up-regulate Trx [18] and that SF treatment inhibits retinal degeneration in Tubby mice [19].…”

“…Mice were dark adapted overnight and ERG was utilized to assess the function of the retina [15]. Mice were deeply anesthetized with single intraperitoneal injection of ketamine (40 mg/kg) and xylazine (7 mg/ kg).…”

“…Neuro 2A cells were treated with various treatments. Cells were then collected and re-suspended in 500μl 1xbinding buffer and then incubated for 15 Immunofluorescence Cells were seeded on coverslips 24 hours prior to treatment. After treatment with AGEs for 6 hours, the cells were fixed in 4% formaldehyde solution.…”

TRPV4 inhibition prevents increased water diffusion and blood-retina barrier breakdown in the retina of streptozotocin-induced diabetic mice

“…Because retinal fluid handling is not conserved in diabetic retinas (Berkowitz et al, 2012; Pannicke et al, 2006), the discrepancy between our MRI and histological values may also be attributed to differences in the dehydration process between eyes that were dissected prior PFA fixation in histology procedures, but not in MRI. Furthermore, histological examination has produced inconsistent results with thicknesses that are unchanged (Ganapathy et al, 2009; Martin et al, 2004) or reduced (Ren et al, 2017) at 4-5 weeks after onset of diabetes. At longer periods of diabetes, retinal thinning (Li et al, 2010; Martin et al, 2004; Ozaki et al, 2018; Qian et al, 2018; Sachdeva et al, 2018; Yang et al, 2018; Zheng et al, 2007) or thickening (Berkowitz et al, 2009; Li et al, 2013) has been observed.…”