Combination of Bevacizumab and NGF Reduces the Risk of Diabetic Retinopathy

Spermine oxidase: A promising therapeutic target for neurodegeneration in diabetic retinopathy

Diabetic Retinopathy (DR), is a significant public health issue and the leading cause of blindness in working-aged adults worldwide. The vision loss associated with DR affects patients' quality of life and has negative social and psychological effects. In the past, diabetic retinopathy was considered as a vascular disease; however, it is now recognized to be a neuro-vascular disease of the retina. Current therapies for DR, such as laser photocoagulation and anti-VEGF therapy, treat advanced stages of the disease, particularly the vasculopathy and have adverse side effects. Unavailability of effective treatments to prevent the incidence or progression of DR is a major clinical problem. There is a great need for therapeutic interventions capable of preventing retinal damage in DR patients. A growing body of evidence shows that neurodegeneration is an early event in DR pathogenesis. Therefore, studies of the underlying mechanisms that lead to neurodegeneration are essential for identifying new therapeutic targets in the early stages of DR. Deregulation of the polyamine metabolism is implicated in various neurodegenerative diseases, cancer, renal failure, and diabetes. Spermine Oxidase (SMOX) is a highly inducible enzyme, and its dysregulation can alter polyamine homeostasis. The oxidative products of polyamine metabolism are capable of inducing cell damage and death. The current review provides insight into the SMOX-regulated molecular mechanisms of cellular damage and dysfunction, and its potential as a therapeutic target for diabetic retinopathy. Structural and functional changes in the diabetic retina and the mechanisms leading to neuronal damage (excitotoxicity, loss of neurotrophic factors, oxidative stress, mitochondrial dysfunction etc.) are also summarized in this review. Furthermore, existing therapies and new approaches to neuroprotection are discussed.

Intravitreal Bevacizumab Injection Attenuates Diabetic Retinopathy in Adult Rats with Experimentally Induced Diabetes in the Early Stage

Diabetic retinopathy is the leading cause of blindness, yet its treatment is very limited. Anti-VEGF drug has been widely applied in ocular disease, but its effects on diabetic retinopathy and the underlying mechanism have remained to be fully explored. To elucidate the role of anti-VEGF treatment, we sought to determine the effects of bevacizumab on diabetic neurovascular changes extending from the 3rd to 9th week with induced diabetes in adult rats. The retinal neurovascular changes included increased expression of VEGF, nNOS, iNOS, eNOS, and NO in the course of diabetes progression. In diabetic rats given bevacizumab injection, the ganglion cell loss and alterations of retinal thickness were ameliorated. In this connection, the immunofluorescence labeling of the above biomarkers was noticeably decreased. Along with this, Western blotting confirmed that bevacizumab treatment was associated with a decrease of VEGF, Flk-1, and cAMP response element binding and protein kinase C protein expression. The present results suggest that bevacizumab treatment in the early stage of the retinopathy may ameliorate the lesions of retinopathy, in which VEGF/Flk-1 signaling has been shown here to play an important role.

Nerve growth factor protects against palmitic acid-induced injury in retinal ganglion cells

Accumulating evidence supports an important role for nerve growth factor (NGF) in diabetic retinopathy. We hypothesized that NGF has a protective effect on rat retinal ganglion RGC-5 cells injured by palmitic acid (PA), a metabolic factor implicated in the development of diabetes and its complications. Our results show that PA exposure caused apoptosis of RGC-5 cells, while NGF protected against PA insult in a concentration-dependent manner. Additionally, NGF significantly attenuated the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) in RGC-5 cells. Pathway inhibitor tests showed that the protective effect of NGF was completely reversed by LY294002 (PI3K inhibitor), Akt VIII inhibitor, and PD98059 (ERK1/2 inhibitor). Western blot analysis revealed that NGF induced the phosphorylation of Akt/FoxO1 and ERK1/2 and reversed the PA-evoked reduction in the levels of these proteins. These results indicate that NGF protects RGC-5 cells against PA-induced injury through anti-oxidation and inhibition of apoptosis by modulation of the PI3K/Akt and ERK1/2 signaling pathways.