Browsing by Author "Santos, Daniela F."
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- Aliskiren decreases oxidative stress and angiogenic markers in retinal pigment epithelium cellsPublication . S, Simão; Santos, Daniela F.; Silva, Gabriela A.There is growing evidence on the role of ocular renin-angiotensin system (RAS) in the development of diabetic retinopathy (DR), particularly due to the trigger of oxidative stress and angiogenesis. Despite this there is no effective RAS-based therapy in DR capable of preventing retinal damage induced by RAS activation. We recently described that retinal pigment epithelium (RPE) cells express the main components of the RAS. We here propose to investigate the role of glucose upon the retinal RAS and whether aliskiren, a direct renin inhibitor, protects RPE cells from angiogenesis and oxidative stress. RPE cells were chosen as target since one of the first events in DR is the dysfunction of the RPE retinal layer, which as a key function in maintaining the integrity of the retina. We found that the RAS present in the RPE cells was deregulated by hyperglycemic glucose concentrations. Exposure of RPE cells to angiotensin II increased the levels of the main pro-angiogenic factor, vascular endothelial growth factor (VEGF) in a concentration-dependent manner. Additionally, angiotensin II also stimulated the production of reactive oxygen species in RPE cells. Treatment of RPE cells with aliskiren decreased the levels of oxidative stress and promoted the expression of anti-angiogenic factors such as the pigment epithelium-derived factor and the VEGF(165)b isoform. Our findings demonstrate that the RAS is deregulated in hyperglycemic conditions and that aliskiren successfully protected RPE cells from RAS over activation. These anti-angiogenic and antioxidant properties described for aliskiren over RPE cells suggest that this drug has potential to be used in the treatment of diabetic retinopathy.
- Aliskiren inhibits the renin-angiotensin system in retinal pigment epithelium cellsPublication . S, Simão; Santos, Daniela F.; Silva, GabrielaObservations of increased angiotensin II levels and activation of the (pro)renin receptor in retinopathies support the role of ocular renin-angiotensin system (RAS) in the development of retinal diseases. While targeting RAS presents significant therapeutic potential, current RAS-based therapies are ineffective halting the progression of these diseases. A new class of drugs, the direct renin inhibitors such as aliskiren, is a potential therapeutic alternative. However, it is unclear how aliskiren acts in the retina, in particular in the retinal pigment epithelium (RPE), the structure responsible for the maintenance of retinal homeostasis whose role is deeply compromised in retinal diseases. We firstly analyzed the expression and activity of the main RAS components in RPE cells. Time- and concentration-dependent treatments with aliskiren were performed to modulate different pathways of the RAE in RPE cells. Our data demonstrate that RPE cells express the main RAS constituents. Exposure of RPE cells to aliskiren inhibited the activity of renin and consequently decreased the levels of angiotensin II. Additionally, aliskiren reduced the translocation of the (pro)renin receptor to the cellular membrane of RPE cells preventing the activation of ERK1/2.Our findings of the RPE well-defined RAS, together with the demonstration that aliskiren effectively blocks this system at different steps of the cascade, suggest that aliskiren might be an alternative and successful drug in preventing the deleterious effects derived from the overactivation of the RAS, known to contribute to the pathogenesis of different retinal diseases. (C) 2016 Elsevier B.V. All rights reserved.
- Identification of new targets of S-nitrosylation in neural stem cells by thiol redox proteomicsPublication . Santos, Ana Isabel; Lourenco, Ana S.; Simão, Sónia; Marques-da-Silva, Dorinda; Santos, Daniela F.; Carvalho, Ana Paula Onofre de; Pereira, Ana Catarina; Izquierdo-Álvarez, Alicia; Ramos, Elena; Morato, Esperanza; Marina, Anabel; Martínez-Ruiz, Antonio; Araújo, InêsNitric oxide (NO) is well established as a regulator of neurogenesis. NO increases the proliferation of neural stem cells (NSC), and is essential for hippocampal injury-induced neurogenesis following an excitotoxic lesion. One of the mechanisms underlying non-classical NO cell signaling is protein S-nitrosylation. This post-translational modification consists in the formation of a nitrosothiol group (R-SNO) in cysteine residues, which can promote formation of other oxidative modifications in those cysteine residues. S-nitrosylation can regulate many physiological processes, including neuronal plasticity and neurogenesis. In this work, we aimed to identify S-nitrosylation targets of NO that could participate in neurogenesis. In NSC, we identified a group of proteins oxidatively modified using complementary techniques of thiol redox proteomics. S-nitrosylation of some of these proteins was confirmed and validated in a seizure mouse model of hippocampal injury and in cultured hippocampal stem cells. The identified S-nitrosylated proteins are involved in the ERK/MAPK pathway and may be important targets of NO to enhance the proliferation of NSC.
- Nitric Oxide Regulates Neurogenesis in the Hippocampus following SeizuresPublication . Carreira, Bruno P.; Santos, Daniela F.; Santos, Ana Isabel; Carvalho, Caetana M.; Araújo, InêsHippocampal neurogenesis is changed by brain injury. When neuroinflammation accompanies injury, activation of resident microglial cells promotes the release of inflammatory cytokines and reactive oxygen/nitrogen species like nitric oxide (NO). In these conditions, NO promotes proliferation of neural stem cells (NSC) in the hippocampus. However, little is known about the role of NO in the survival and differentiation of newborn cells in the injured dentate gyrus. Here we investigated the role of NO following seizures in the regulation of proliferation, migration, differentiation, and survival of NSC in the hippocampus using the kainic acid (KA) induced seizuremouse model. We show that NO increased the proliferation of NSC and the number of neuroblasts following seizures but was detrimental to the survival of newborn neurons. NO was also required for the maintenance of long-term neuroinflammation. Taken together, our data show that NO positively contributes to the initial stages of neurogenesis following seizures but compromises survival of newborn neurons.