1. Investigación

(1) Background: Retinitis pigmentosa (RP) is characterized by progressive photoreceptor death. A Prph2Rd2 or an rds mouse is an RP model that closely reflects human RP. The objective of this study was to investigate the relationship of rod and cone death with oxidative stress and inflammation in rds mice. (2) Methods: The retinas of control and rds mice on postnatal days (PN) 11, 17, 21, 28, 35, and 42 were used. Oxidative damage to macromolecules, glutathione (GSH and GSSG), GSH synthesis enzymes, glial fibrillar acidic protein (GFAP), ionized calcium-binding adapter molecule 1 (Iba1), and cluster of differentiation 68 (CD68) was studied. (3) Results: The time sequence of oxidative stress and inflammation changes in rds mice occurs as follows: (i) At PN11, there is a small increase in photoreceptor death and in the microglial cells; (ii) at PN17, damage to the macromolecules is observed; (iii) at PN21, the maximum photoreceptor death rate is detected and there is an increase in GSH-GSSG and GFAP; (iv) at PN21, the microglial cells are activated; and(v) at PN28, there is a decrease in GSH synthesis enzymes. (4) Conclusions: These findings contribute to the understanding of RP physiopathology and help us to understand whether oxidative stress and inflammation are therapeutic targets. These findings contribute to our understanding that, in RP, oxidative stress and inflammation evolution and their relationship are time-dependent. In this sense, it is important to highlight that both processes are potential therapeutic targets in this disease.

Retinitis pigmentosa (RP) is an inherited eye disorder which triggers a cascade of retinal disorders leading to photoreceptor cell death and for which there is currently no effective treatment. The purpose of this research was to study whether ocular administration of a solution of progesterone (PG) in -cyclodextrins (CD) could delay photoreceptor cell death and counteract the gliosis process in an animal model of RP (rds mice). The possible effect of PG reaching the contralateral eye through the circulatory system was also evaluated. Finally, this research discusses and evaluates the diffusion of the drug from possible topical formulations for ocular administration of PG. A group of rds mice received one drop of a solution of PG in CD every 12 h for 10 days to the left eye, while the right eye was left untreated. Another group of rds mice (control) received the drug vehicle (PBS) on the left eye and, again, the right eye was left untreated. Once the treatment was finished on postnatal day 21, the animals were euthanized and histological immunofluorescence studies (TUNEL, GFAP, and DAPI staining) were carried out. Our results showed that the administration of a solution of PG in CD (CD-PG) as drops significantly decreased cell death and inflammation in the retina of the PG-treated eyes of rds mice. No effect was seen in the contralateral eye from PG that may have entered systemic circulation. In conclusion, CD-PG applied topically as drops to the eye decreases photoreceptor cell death in the early stages of RP, delaying vision loss and decreasing gliosis.

The term retinitis pigmentosa (RP) describes a large group of hereditary retinopathies. From a cellular view, retinal degeneration is prompted by an initial death of rods, followed later by cone degeneration. This cellular progressive degeneration is translated clinically in tunnel vision, which evolves to complete blindness. The mechanism underlying the photoreceptor degeneration is unknown, but several mechanisms have been pointed out as main co-stars, inflammation being one of the most relevant. Retinal inflammation is characterized by proliferation, migration, and morphological changes in glial cells, in both microglia and Müller cells, as well as the increase in the expression of inflammatory mediators. Retinal inflammation has been reported in several animal models and clinical cases of RP, but the specific role that inflammation plays in the pathology evolution remains uncertain. Sulforaphane (SFN) is an antioxidant natural compound that has shown antiinflammatory properties, including the modulation of glial cells activation. The present work explores the effects of SFN on retinal degeneration and inflammation, analyzing the modulation of glial cells in the RP rd10 mice model. A daily dose of 20 mg/kg of sulforaphane was administered intraperitoneally to control (C57BL/6J wild type) and rd10 (Pde6brd10) mice, from postnatal day 14 to day 20. On postnatal day 21, euthanasia was performed. Histological retina samples were used to assess cellular degeneration, Müller cells, and microglia activation. SFN administration delayed the loss of photoreceptors. It also ameliorated the characteristic reactive gliosis, assessed by retinal GFAP expression. Moreover, sulforaphane treatment regulated the microglia activation state, inducing changes in the microglia morphology, migration, and expression through the retina. In addition, SFN modulated the expression of the interleukins 1β, 4, Ym1, and arginase inflammatory mediators. Surprisingly, M2 polarization marker expression was increased at P21 and was reduced by SFN treatment. To summarize, SFN administration reduced retinal neurodegeneration and modified the inflammatory profile of RP, which may contribute to the SFN neuroprotective effect.

Retinitis pigmentosa (RP) is an inherited ocular disorder with no effective treatment. RP onset and progression trigger a cascade of retinal disorders that lead to the death of photoreceptors. After photoreceptors death, neuronal, glial and vascular remodeling can be observed in the retina. The purpose of this study was to study if thioredoxin (TRX) administration is able to decrease photoreceptor death in an animal model of RP (rd1 mouse), but also if it is able to modulate the retinal oxidative stress, glial and vascular changes that can be observed as the disease progresses. Wild type and rd1 mice received several doses of TRX. After treatment, animals were euthanized at postnatals days 11, 17, or 28. Glutathione (GSH) and other thiol compounds were determined by high performance liquid chromatography (HPLC). Glial fibrilary acidic protein (GFAP) and anti-ionized calcium binding adaptor molecule 1 (Iba1) were studied by immunohistochemistry. Vascular endothelial growth factor (VEGF) and hepatic growth factor (HGF) expression were determined by western blot. TRX administration significantly diminished cell death in rd1 mouse retinas and increased GSH retinal concentrations at postnatal day 11 (PN11). TRX was also able to reverse glial alterations at PN11 and PN17. No alterations were observed in retinal VEGF and HGF expression in rd1 mice. In conclusion, TRX treatment decreases photoreceptor death in the first stages of RP and this protective effect may be due in part to the GSH system activation and to a partially decrease in inflammation.

The interactions between steroid gonadal hormones and the retina (a part of the visual system and the central nervous system (CNS)) have received limited attention and beneficial effects of these hormones in retinal diseases is controversial. Retinitis pigmentosa (RP) is the most common cause of retinal hereditary blindness and to date no treatment is available. However, results regarding the effects of progesterone on the progression of RP are promising. With the idea of demonstrating if the progesterone retinal protection in RP is related to its possible anti-inflammatory properties, we have administered orally progesterone to rd10 mice, an animal model of RP. We observed that progesterone decreased photoreceptors cell death, reactive gliosis and the increase in microglial cells caused by RP. We also examined the expression of neuronal and inducible nitric oxide synthase (nNOS and iNOS), the enzyme responsible for NO production. The results demonstrated a decrease in nNOS expression only in control mice treated with progesterone. Inflammation has been related with an increase in lipid peroxidation. Noticeably progesterone administration was able to diminish retinal malondialdehyde (MDA, a lipid peroxidation product) concentrations in rd10 mice. Altogether, we can conclude that progesterone could be a good therapeutic option not only in RP but also for other retinal diseases that have been associated with inflammation and lipid peroxidation.