Steroid hormones, particularly estrogens, modulate neuronal survival in the central nervous system and the retina; however, their specific cell-type-specific roles in the human retina remain incompletely characterized. We analyzed the single-cell RNA sequencing dataset E-MTAB-7316 to profile genes from the KEGG steroid hormone biosynthesis and oestrogen signalling pathways. Functional relevance of local oestrogen synthesis was tested in mouse retinal explants treated with the aromatase inhibitor letrozole (20 μM). Over 50% of steroid hormone metabolism genes were expressed in retinal cells, with cell-type specificity. COMT, HSD17B12, and HSD11B1L were broadly distributed, while LRTOMT, HSD17B7, and SRD5A1 were enriched in rod photoreceptors. Among oestrogen signalling genes, 114/139 were detected, with HSP90AA1 as the most abundant. When oestrogen synthesis was blocked with letrozole, retinal explants showed increased cell death, particularly in the outer nuclear layer, without inducing macrogliosis but with significant microglial activation (IBA1+). Our data indicate that the human retina expresses multiple components of steroid hormone metabolism and oestrogen signalling. The results are consistent with a potential role of locally synthesized oestrogens in photoreceptor maintenance and immune regulation, which may warrant further investigation as a possible avenue for retinal protection.

The rd2 mouse model, characterized by a mutation in the Prph2 gene, exhibits abnormal development of photoreceptor outer segments, resulting in progressive retinal degeneration. While the correlation between poly-ADP-ribose polymerase (PARP) activity and the degeneration of rod photoreceptors is established in the rd2 model, the specific mechanism driving cone degeneration in this model remains unclear. Furthermore, it is yet to be determined whether inhibiting PARP activity can effectively impede the degeneration of cone photoreceptors in this context. We demonstrated that PARP inhibitors Olaparib, BMN-673, and 3-aminobenzamide (3AB), effectively reduced photoreceptor cell loss in the rd2 retina. Notably, rd2 retinas exhibited decreased cone density, but treatment with PARP inhibitors significantly protected cone photoreceptors. The PARP inhibitors, particularly BMN-673, demonstrated a significant protective effect as evidenced by increased rhodopsin expression within the outer segment and a concurrent decrease in Müller cell activity indicated by GFAP expression. The treatment also resulted in significant changes for markers of oxidative stress, such as glutathione (GSH), and oxidized glutathione (GSSG). Notably, the administration of PARP inhibitors also reduced CD9 expression (extracellular vesicle marker), which were significantly increased within the outer nuclear layer (ONL) in the rd2 retinas. Among PARP inhibitors, BMN-673 demonstrated the highest efficacy in preserving photoreceptors, particularly benefiting cone cells. Graphical Abstract

Aims/Purpose: Retinitis Pigmentosa (RP) describes a group of hereditary retinopathies. Traditionally, therapeutic approaches have assumed that inner retinal neurons retain function, properties, and connectivity after photoreceptor degeneration. However, it is known that photoreceptor degeneration leads to dramatic changes in second‐ and third‐order neurons, such as amacrine cells and horizontal cells. In the present study, the main objective is to evaluate not only the protective capacity of lipoic acid against photoreceptor death but also its protective effect on these neurons and Müller cells.Methods: Rd1 mice were treated in accordance with the ARVO statement for the use of animals in ophthalmic and vision research. Mice were sacrificed at different postnatal days (11, 13, 17). Lipoic acid was administered orally (100 mg/kg). It was administered every two days, starting at PN7. The neuroprotective effect of this treatment was analyzed using the TUNEL assay. Müller cells, amacrine cells, and horizontal cells were studied by immunohistochemistry.Results: Lipoic acid treatment reduced photoreceptor death at PN11 and PN13, with no differences observed at PN17 in rd1 mice, demonstrating a partial treatment effect. The expression of GFAP was increased in the retinas at PN11, 13, and 17 rd1 mice, and lipoic acid treatment significantly reversed this effect.Regarding second‐ and third‐order neurons, there was an increase in amacrine cells at PN13 and PN17 in rd1 mice, but lipoic acid had no effect on this increase. As for horizontal cells, no changes were observed at PN13, but at PN17, there was a decrease in these cells that lipoic acid could not reverse.Conclusions: Lipoic acid partially protects photoreceptor death. However, no effect was seen on the studied amacrine and horizontal cells. Further research is necessary to deepen our understanding of RP, specifically examining the remaining neuronal populations.

Gonadal steroid hormones are critical regulatory substances involved in various developmental and physiological processes from fetal development through adulthood. These hormones, derived from cholesterol, are synthesized primarily by the gonads, adrenal cortex, and placenta. The synthesis of these hormones involves a series of enzymatic steps starting in the mitochondria and includes enzymes such as cytochrome P450 and aromatase. Beyond their genomic actions, which involve altering gene transcription over hours, gonadal steroids also exhibit rapid, nongenomic effects through receptors located on the cell membrane. Additionally, recent research has highlighted the role of these hormones in the central nervous system (CNS). However, the interactions between gonadal steroid hormones and the retina have received limited attention, though it has been suggested that they may play a protective role in retinal diseases. This review explores the synthesis of gonadal hormones, their mechanisms of action, and their potential implications in various retinal and optic nerve diseases, such as glaucoma, age-related macular degeneration (AMD), diabetic retinopathy (DR), or retinitis pigmentosa (RP), discussing both protective and risk factors associated with hormone levels and their therapeutic potential.

Aims/Purpose: Nitric oxide (NO) is an essential signalling molecule, with gaseous nature. NO is synthesized by the conversion of L‐arginine to L‐citrulline. This reaction is catalysed by the enzyme nitric oxide synthase (NOS). There are three NOS isoforms, but nNOS reflects most of the production of NO in the retina. Although NO is employed in the retina to maintain ocular function, it has also been related to different visual diseases. Increased levels of NO have been associated with ocular diseases involving increased glutamate concentrations, ischaemia, oxidative stress and inflammation (such as retinitis pigmentosa (RP)). The main purpose of this work was to determine glutamate retinal concentrations at different stages of the retinal degeneration that occurs in the rds mice and to study possible NO metabolism alterations. Methods: Rds mice were treated in accordance with the ARVO statement for the use of animals in ophthalmic and vision research. Mice were sacrificed at different postnatal days (11, 17, 21 and 28). Retinal glutamate concentrations were determined by high pressure liquid chromatography (HPLC). The expression of different enzymes related with NO metabolism (nNOS, guanylate cyclase (GC) and arginase) was determined by histochemistry. Results: Glutamate as well as nNOS was observed to be increased in the retina of rds mice mainly between the peak of rods and cones death. GC was observed to be decreased in the rds mice compared to control ones and no significant changes were observed in arginase expression when we compared rds and control mice. Conclusions: There are alterations in the expression of glutamate, nNOS and GC in rds mice retina compared to control mice. RP is a disease with no effective treatment to date and NO metabolism may be a new target in RP treatment.

(1) Background: the aim of this work was to study microglia and autophagy alterations in a one retinitis pigmentosa (RP) model at different stages of the disease (when rods are dying and later, when there are almost no rods, and cones are the cells that die. (2) Methods: rd1 mice were used and retinas obtained at postnatal days (PN) 11, 17, 28, 35, and 42. Iba1 (ionized calcium-binding adapter molecule 1) was the protein selected to study microglial changes. The macroautophagy markers Beclin-1, Atg5, Atg7, microtubule-associated protein light chain 3 (LC3), and lysosomal-associated membrane protein 2 (LAMP2) (involved in chaperone-mediated autophagy (CMA)) were determined. (3) Results: the expression of Iba1 was increased in rd1 retinas compared to the control group at PN17 (after the period of maximum rod death), PN28 (at the beginning of the period of cone death), and PN42. The number of activated (ameboid) microglial cells increased in the early ages of the retinal degeneration and the deactivated forms (branched cells) in more advanced ages. The macroautophagy markers Atg5 at PN11, Atg7 and LC3II at PN17, and Atg7 again at PN28 were decreased in rd1 retinas. At PN35 and PN42, the results reveal alterations in LAMP2A, a marker of CMA in the retina of rd1 mice. (4) Conclusions: we can conclude that during the early phases of retinal degeneration in the rd1 mouse, there is an alteration in microglia and a decrease in the macroautophagy cycle. Subsequently, the CMA is decreased and later on appears activated as a compensatory mechanism.

The lens proteome undergoes dramatic composition changes during development and maturation. A defective developmental process leads to congenital cataracts that account for about 30% of cases of childhood blindness. Gene mutations are associated with approximately 50% of early-onset forms of lens opacity, with the remainder being of unknown etiology. To gain a better understanding of cataractogenesis, we utilized a transgenic mouse model expressing a mutant ubiquitin protein in the lens (K6W-Ub) that recapitulates most of the early pathological changes seen in human congenital cataracts. We performed mass spectrometry-based tandem-mass-tag quantitative proteomics in E15, P1, and P30 control or K6W-Ub lenses. Our analysis identified targets that are required for early normal differentiation steps and altered in cataractous lenses, particularly metabolic pathways involving glutathione and amino acids. Computational molecular phenotyping revealed that glutathione and taurine were spatially altered in the K6W-Ub cataractous lens. High-performance liquid chromatography revealed that both taurine and the ratio of reduced glutathione to oxidized glutathione, two indicators of redox status, were differentially compromised in lens biology. In sum, our research documents that dynamic proteome changes in a mouse model of congenital cataracts impact redox biology in lens. Our findings shed light on the molecular mechanisms associated with congenital cataracts and point out that unbalanced redox status due to reduced levels of taurine and glutathione, metabolites already linked to age-related cataract, could be a major underlying mechanism behind lens opacities that appear early in life.

(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.

Purpose: The term retinitis pigmentosa (RP) describes a group of hereditary retinopathies. The first clinical signs of RP are night blindness and loss of peripheral vision. Central vision remains preserved until advanced stages of the disease. At a cellular level, the rods are the first to degenerate. Subsequently, there is degeneration of the cones. Inflammation plays a fundamental role in RP. The microglia respond quickly to alterations, acquiring amoeboid morphology; migrating to damage focus; acquiring macrophages functions; phagocytosing cellular debris; secreting molecules that initiate tissue repair; and favouring neuroprotection. However, if the activation is excessive, the constant secretion of nitric oxide and proinflammatory cytokines lead to pathological side effects. The purpose of this work was to review published studies in order to know if the inhibition of micloglial activation may be a good option to increase photoreceptor protection. Methods: A systematic literature review was conducted, in accordance with PRISMA criteria, in different bibliographic databases: Medline, Embase, SCOPUS and Web of Science. We searched human and animal reviews, published in English in the past 10 years. Initial search terms were ‘retina’, ‘retinitis pigmentosa’, ‘retinal degeneration’ and ‘therapeutics. Duplicate studies were removed, and the remaining articles were assessed for eligibility by full-text review. Results: Understanding the mechanisms leading to photoreceptor death is essential for the development of new treatments in RP. It has been shown increased retinal infiltration of activated microglia in many animal models of RP. Different works have studied the clinical efficacy of antioxidants, minocycline, transforming growth factor beta or tamoxifen. However, the complete efficacy in RP has not been fully established. Conclusions: Pharmacological inhibition of microglial activation may be a good therapeutic target to reduce photoreceptor cell death in RP.

Purpose: Retinitis pigmentosa (RP) describes a large group of hereditary retinopathies. It mainly affects the rods. However, once the rods have degenerated, the cones, also die, leading to complete blindness. Although, the mutations that cause RP have been identified in different genes, the mechanisms that cause the death of photoreceptor cells are still unknown. Gonadal hormones may play a protective role in RP. Our research group has shown that oral administration of progesterone to RP mice significantly conserves the number of photoreceptors. 5α-reductase inhibitors (such as dutasteride (DUT)) are approved treatments for androgenic alopecia. Modulation or inhibition of 5α-reductase activity increases the levels of the neuroprotective steroid progesterone and 17β-estradiol. The purpose of this study was to administer DUT to RP mice. This may be another form of increasing progesterone levels in the retina and therefore, may be neuroprotective. Methods: Animals were treated in accordance with the ARVO statement for the use of animals. rds mice were treated intraperitoneally with DUT and euthanized on day 21. Haematoxylin–eosin, cell death, and rod and cone immunohistochemistry were performed to determine if DUT was able to delay photoreceptor death. Immunohistochemical techniques were used to study changes in retinal microglia (Iba-1) and macroglial cells. Neuronal nitric oxide synthase (nNOS) was also quantified. Results: DUT increased photoreceptor survival in rds mice. An increase in iba-1 positive cells was found in rds retinas and DUT normalized the number, migration and the length and number of branches in these cells. DUT decreased GFAP (glial fibrillar acid protein) expression. We have also observed a slightly increase in nNOS expression in rds mice. DUT administration was also able to decrease nNOS expression. Conclusions: DUT may be used to improve cell survival, to ameliorate retinal micro and macroglial activation as well as alterations in nNOS in RP.

Cocaine can induce severe neurobehavioral changes, among others, the ones involved in learning and memory processes. It is known that during drug consumption, cocaine-associated memory and learning processes take place. However, much less is known about the effects of this drug upon the mechanisms involved in forgetting.The present report focuses on the mechanisms by which cocaine affects memory consolidation of experiences acquired prior to drug administration. We also study the involvement of hippocampus in these processes, with special interest on the role of Nuclear factor kappa B (NF-κB), N-methyl-D-aspartate glutamate receptor 2B (GluN2B), and their relationship with other proteins, such as cyclic AMP response element binding protein (CREB). For this purpose, we developed a rat experimental model of chronic cocaine administration in which spatial memory and the expression or activity of several proteins in the hippocampus were assessed after 36 days of drug administration. We report an impairment in memory acquisition of experiences gathered prior to cocaine administration, associated to an increase in GluN2B expression in the hippocampus. We also demonstrate a decrease in NF-κB activity, as well as in the expression of the active form of CREB, confirming the role of these transcription factors in the cocaine-induced memory impairment.

En Journal of Steroid Biochemistry and Molecular Biology. Oxford (Reino Unido): Elsevier. Vol. 189 (may. 2019), pp. 291-301. ISSN 0960-0760.

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.

Oxidative stress has been documented to be a key factor in the cause and progression of different retinal diseases. Oxidative cellular unbalance triggers a sequence of reactions which prompt cell degeneration and retinal dysfunction, both hallmarks of several retinal pathologies. There is no effective treatment, yet, for many retinal diseases. Antioxidant treatment have been pointed out to be an encouraging palliative treatment; the beneficial effects documented involve slowing the progression of the disease, a reduction of cell degeneration, and improvement of retinal functions. There is a vast information corpus on antioxidant candidates. In this review, we expose three of the main antioxidant treatments, selected for their promising results that has been reported to date. Recently, the sulforaphane, an isothiocyanate molecule, has been unveiled as a neuroprotective candidate, by its antioxidant properties. Progesterone, a neurosteroid has been proposed to be a solid and effective neuroprotective agent. Finally, the lipoic acid, an organosulfur compound, is a well-recognized antioxidant. All of them, have been tested and studied on different retinal disease models. In this review, we summarized the published results of these works, to offer a general view of the current antioxidant treatment advances, including the main effects and mechanisms described.

We have previously observed that in vivo lipoic acid (LA) treatment induced a protective effect onto primary cortical neurons after brain injury. In an effort to better understand LA action mechanism in the brain, in the present study, we stressed brain cells in vitro and ex vivo and then analyzed by inmmunocytochemistry and biochemical assays, the changes induced by LA on cell survival and on the concentration of oxidative stress markers, such as glutathione (GSH), oxidized glutathione (GSSG), and malondialdehyde (MDA). The stressors used were lipopolysaccharide (LPS), dopamine, and l-buthionine-S,R-sulfoximine (BSO). Our results showed that LA decreased cell death and increased GSH/GSSG ratio in cells stressed by LPS + dopamine, suggesting that the mechanism underlying LA action is regeneration of GSSG to GSH. When cells were stressed by BSO, LA diminished cell death and decreased GSH/GSSG ratio. In this case, it could be concluded that, due to the low GSH basal levels, GSSG reduction is not possible and therefore it might be thought that cell death prevention might be mediated through other mechanisms. Finally, we induced chemical oxidative damage in brain homogenate. After LA treatment, GSH and GSH/GSSG ratio increased and MDA concentration decreased, demonstrating again that LA was not able to increase de novo GSH synthesis but is able to increase GSSG conversion to GSH.