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Niki Mastrodimou, Silvia Lisa Ferrer, Ruth Ibán Arias, Despina Kokona, Ioannis Charalampopoulos, Achilleas Gravanis, Kyriaki Thermos; The novel microneurotrophin BNN27 protects retinal neurons in the in vivo STZ-model of Diabetic Retinopathy by activating NGF TrkA receptor. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):155.
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© ARVO (1962-2015); The Authors (2016-present)
Diabetic retinopathy (DR) is characterized by a neovascular and a neurodegenerative component. While available treatments target the neovascular aspects of the disease, no therapy exists for the neurodegenerative component. Dehydroepiandrosterone (DHEA) and its spiro-epoxy derivative BNN27 were shown to have antiapoptotic activity [Calogeropoulou et al., 2009]. In the retina, DHEA afforded neuroprotection against AMPA excitotoxicity in vivo [Kokona et al., 2012] and in the streptozotocin (STZ)-model of DR [Koulakis et al., unpublished data]. The aim of the present study was to investigate the mechanisms involved in the neuroprotection afforded to the diabetic retina by BNN27.
Adult Sprague-Dawley rats were administered with a single dose of STZ (70mg/kg, ip) and DR was observed four weeks after the injection. Subsequently, the diabetic rats were treated for one week with BNN27 (2,10,50mg/kg, ip) or DHEA (10mg/kg, ip) and the viability of amacrine [nitric oxide synthetase (bNOS)- and tyrosine hydroxylase (TH)-expressing] cells and ganglion cell axons (NFL) was examined. SAPK/JNK phosphorylation was employed to assess apoptotic cell death. Western blot analysis was performed using antibodies against the phosphorylated and total form of TrkA and ERK1/2 proteins to assess the involvement of the TrkA receptor in the neuroprotection.
BNN27 protected both the bNOS and TH expressing amacrine cells and ganglion axons in a dose-dependent manner. SAPK/JNK activation was increased in diabetic rats depicting apoptotic cell death. BNN27 (10mg/kg, ip) reversed this increase to control levels. The phosphorylation of TrkA receptor and ERK1/2 protein was also increased in a dose-dependent manner. DHEA (10mg/kg, ip) afforded the same profile as BNN27 (10, 50mg/kg,ip), increasing the phosphorylation of both TrkA and ERK1/2 proteins. The TrkA inhibitor, intravitreally administered, reversed the activation of both proteins as shown by immunochemical and immunoblotting data.
These results suggest that NGF TrkA receptor and its downstream signaling are involved in the neuroprotection of retinal neurons by BNN27, administered ip, in the STZ model of DR. Other routes of administration are also examined to assess further the possible value of BNN27 in DR and to promote its further investigation at the clinical level.
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