Prenatal Exposure to Curcumin Protects Rod Photoreceptors in a Transgenic Pro23His Swine Model of Retinitis Pigmentosa

Neuroprotection provided by polyphenols and flavonoids in photoreceptor degenerative diseases

The intricate landscape of neurodegenerative diseases complicates the search for effective therapeutic approaches. Photoreceptor degeneration, the common endpoint in various retinal diseases, including retinitis pigmentosa and age-related macular degeneration, leads to vision loss or blindness. While primary cell death is driven by genetic mutations, oxidative stress, and neuroinflammation, additional mechanisms contribute to disease progression. In retinitis pigmentosa, a multitude of genetic alterations can trigger the degeneration of photoreceptors, while other retinopathies, such as age-related macular degeneration, are initiated by combinations of environmental factors, such as diet, smoking, and hypertension, with genetic predispositions. Nutraceutical therapies, which blend the principles of nutrition and pharmaceuticals, aim to harness the health benefits of bioactive compounds for therapeutic applications. These compounds generally possess multi-target effects. Polyphenols and flavonoids, secondary plant metabolites abundant in plant-based foods, are known for their antioxidant, neuroprotective, and anti-inflammatory properties. This review focuses on the potential of polyphenols and flavonoids as nutraceuticals to treat neurodegenerative diseases such as retinitis pigmentosa. Furthermore, the importance of developing reliable delivery methods to enhance the bioavailability and therapeutic efficacy of these compounds will be discussed. By combining nutraceuticals with other emerging therapies, such as genetic and cell-based treatments, it is possible to offer a more comprehensive approach to treating retinal degenerative diseases. These advancements could lead to a viable and accessible option, improving the quality of life for patients with retinal diseases.

Perspectives of traditional herbal medicines in treating retinitis pigmentosa

Medicinal plants, also known as herbs, have been discovered and utilized in traditional medical practice since prehistoric times. Medicinal plants have been proven rich in thousands of natural products that hold great potential for the development of new drugs. Previously, we reviewed the types of Chinese traditional medicines that a Tang Dynasty monk Jianzhen (Japanese: Ganjin) brought to Japan from China in 742. This article aims to review the origin of Kampo (Japanese traditional medicine), and to present the overview of neurodegenerative diseases and retinitis pigmentosa as well as medicinal plants in some depth. Through the study of medical history of the origin of Kampo, we found that herbs medicines contain many neuroprotective ingredients. It provides us a new perspective on extracting neuroprotective components from herbs medicines to treat neurodegenerative diseases. Retinitis pigmentosa (one of the ophthalmic neurodegenerative diseases) is an incurable blinding disease and has become a popular research direction in global ophthalmology. To date, treatments for retinitis pigmentosa are very limited worldwide. Therefore, we intend to integrate the knowledge and skills from different disciplines, such as medical science, pharmaceutical science and plant science, to take a new therapeutic approach to treat neurodegenerative diseases. In the future, we will use specific active ingredients extracted from medicinal plants to treat retinitis pigmentosa. By exploring the potent bioactive ingredients present in medicinal plants, a valuable opportunity will be offered to uncover novel approaches for the development of drugs which target for retinitis pigmentosa.

Pig Models in Retinal Research and Retinal Disease

The pig has been used as a large animal model in biomedical research for many years and its use continues to increase because induced mutations phenocopy several inherited human diseases. In addition, they are continuous breeders, can be propagated by artificial insemination, have large litter sizes (on the order of mice), and can be genetically manipulated using all of the techniques that are currently available in mice. The pioneering work of Petters and colleagues set the stage for the use of the pig as a model of inherited retinal disease. In the last 10 years, the pig has become a model of choice where specific disease-causing mutations that are not phenocopied in rodents need to be studied and therapeutic approaches explored. The pig is not only used for retinal eye disease but also for the study of the cornea and lens. This review attempts to show how broad the use of the pig has become and how it has contributed to the assessment of treatments for eye disease. In the last 10 years, there have been several reviews that included the use of the pig in biomedical research (see body of the review) that included information about retinal disease. None directly discuss the use of the pig as an animal model for retinal diseases, including inherited diseases, where a single genetic mutation has been identified or for multifactorial diseases such as glaucoma and diabetic retinopathy. Although the pig is used to explore diseases of the cornea and lens, this review focuses on how and why the pig, as a large animal model, is useful for research in neural retinal disease and its treatment.

Neuroinflammation in retinitis pigmentosa: Therapies targeting the innate immune system

Retinitis pigmentosa (RP) is an important cause of irreversible blindness worldwide and lacks effective treatment strategies. Although mutations are the primary cause of RP, research over the past decades has shown that neuroinflammation is an important cause of RP progression. Due to the abnormal activation of immunity, continuous sterile inflammation results in neuron loss and structural destruction. Therapies targeting inflammation have shown their potential to attenuate photoreceptor degeneration in preclinical models. Regardless of variations in genetic background, inflammatory modulation is emerging as an important role in the treatment of RP. We summarize the evidence for the role of inflammation in RP and mention therapeutic strategies where available, focusing on the modulation of innate immune signals, including TNFα signaling, TLR signaling, NLRP3 inflammasome activation, chemokine signaling and JAK/STAT signaling. In addition, we describe epigenetic regulation, the gut microbiome and herbal agents as prospective treatment strategies for RP in recent advances.

Plant-derived polyphenols in sow nutrition: An update

Oxidative stress is a potentially critical factor that affects productive performance in gestating and lactating sows. Polyphenols are a large class of plant secondary metabolites that possess robust antioxidant capacity. All polyphenols are structurally characterized by aromatic rings with multiple hydrogen hydroxyl groups; those make polyphenols perfect hydrogen atoms and electron donors to neutralize free radicals and other reactive oxygen species. In the past decade, increasing attention has been paid to polyphenols as functional feed additives for sows. Polyphenols have been found to alleviate inflammation and oxidative stress in sows, boost their reproductivity, and promote offspring growth and development. In this review, we provided a systematical summary of the latest research advances in plant-derived polyphenols in sow nutrition, and mainly focused on the effects of polyphenols on the (1) antioxidant and immune functions of sows, (2) placental functions and the growth and development of fetal piglets, (3) mammary gland functions and the growth and development of suckling piglets, and (4) the long-term growth and development of progeny pigs. The output of this review provides an important foundation, from more than 8,000 identified plant phenols, to screen potential polyphenols (or polyphenol-enriched plants) as functional feed additives suitable for gestating and lactating sows.

Inherited Retinal Dystrophies: Role of Oxidative Stress and Inflammation in Their Physiopathology and Therapeutic Implications

Inherited retinal dystrophies (IRDs) are a large group of genetically and clinically heterogeneous diseases characterized by the progressive degeneration of the retina, ultimately leading to loss of visual function. Oxidative stress and inflammation play fundamental roles in the physiopathology of these diseases. Photoreceptor cell death induces an inflammatory state in the retina. The activation of several molecular pathways triggers different cellular responses to injury, including the activation of microglia to eliminate debris and recruit inflammatory cells from circulation. Therapeutical options for IRDs are currently limited, although a small number of patients have been successfully treated by gene therapy. Many other therapeutic strategies are being pursued to mitigate the deleterious effects of IRDs associated with oxidative metabolism and/or inflammation, including inhibiting reactive oxygen species’ accumulation and inflammatory responses, and blocking autophagy. Several compounds are being tested in clinical trials, generating great expectations for their implementation. The present review discusses the main death mechanisms that occur in IRDs and the latest therapies that are under investigation.

Role of Curcumin in Retinal Diseases-A review

PURPOSE

To review the role of curcumin in retinal diseases, COVID era, modification of the molecule to improve bioavailability and its future scope.

METHODS

PubMed and MEDLINE searches were pertaining to curcumin, properties of curcumin, curcumin in retinal diseases, curcumin in diabetic retinopathy, curcumin in age-related macular degeneration, curcumin in retinal and choroidal diseases, curcumin in retinitis pigmentosa, curcumin in retinal ischemia reperfusion injury, curcumin in proliferative vitreoretinopathy and curcumin in current COVID era.

RESULTS

In experimental models, curcumin showed its pleiotropic effects in retinal diseases like diabetic retinopathy by increasing anti-oxidant enzymes, upregulating HO-1, nrf2 and reducing or inhibiting inflammatory mediators, growth factors and by inhibiting proliferation and migration of retinal endothelial cells in a dose-dependent manner in HRPC, HREC and ARPE-19 cells. In age-related macular degeneration, curcumin acts by reducing ROS and inhibiting apoptosis inducing proteins and cellular inflammatory genes and upregulating HO-1, thioredoxin and NQO1. In retinitis pigmentosa, curcumin has been shown to delay structural defects of P23H gene in P23H-rhodopsin transgenic rats. In proliferative vitreoretinopathy, curcumin inhibited the action of EGF in a dose- and time-dependent manner. In retinal ischemia reperfusion injury, curcumin downregulates IL-17, IL-23, NF_KB, STAT-3, MCP-1 and JNK. In retinoblastoma, curcumin inhibits proliferation, migration and apoptosis of RBY79 and SO-RB50. Curcumin has already proven its efficacy in inhibiting viral replication, coagulation and cytokine storm in COVID era.

CONCLUSION

Curcumin is an easily available spice used traditionally in Indian cooking. The benefits of curcumin are manifold, and large randomized controlled trials are required to study its effects not only in treating retinal diseases in humans but in their prevention too.

In depth understanding of retinitis pigmentosa pathogenesis through optical coherence tomography angiography analysis: a narrative review

Retinitis pigmentosa (RP) is the most recognized inherited retinal disorder involving progressive photoreceptors degeneration which eventually causes blindness. However, the pathogenesis of RP is still unclear, making it difficult to establish satisfying treatments. Evidence have been found to support the theory that vascular dysfunction is associated with the progression of RP. Optical coherence tomography angiography (OCTA) is a newly developed technology that enables visualization as well as quantitative assessment of retinal and choroidal vasculature non-invasively. Advances in OCTA have opened a window for in-depth understanding of RP pathogenesis. Here, we propose a hypothesis of RP pathogenesis based on the current OCTA findings in RP, which includes four stages and two important key factors, vascular dysfunction and microglia activation. Further, we discuss the future animal experiments needed and how advanced OCTA technology can help to further verity the hypothesis. The final goal is to explore potential treatment options with enhanced understanding of RP pathogenesis.

Recent Advances and Disputes About Curcumin in Retinal Diseases

Curcumin belongs to the group of so-called phytocompounds, biologically active molecules produced by plants exerting a beneficial effect on health. Curcumin shows a wide spectrum of different properties, being an anti-inflammatory, antioxidant, antimicrobial and antimutagenic molecule. The purpose of the review is to examine what literature reported on the characteristics of curcumin, particularly, on the beneficial and controversial aspects of this molecule, aiming for a better therapeutic management of retinal diseases. The retina is a constant target of oxidative stress, this tissue being characterized by cells rich in mitochondria and by vessels and being, obviously, continuously reached from photons affecting its layers. Particularly, the retinal ganglion cells and the photoreceptors are extremely sensitive to oxidative stress damage and it is well known that an imbalance in reactive oxygen species is often involved in several retinal diseases, such as uveitis, age-related macular degeneration, diabetic retinopathy, central serous chorioretinopathy, macular edema, retinal ischemia-reperfusion injury, proliferative vitreoretinopathy, hereditary tapeto-retinal degenerations, and retinal and choroidal tumors. To date, several studies suggest that oral treatment with curcumin is generally well tolerated in humans and, in addition, it seems to have no negative effects: therefore, curcumin is a promising candidate as a retinal disease therapy. Unfortunately, the primary limitation of curcumin is represented by its poor bioavailability, in fact only a minimal fraction of this substance can reach the blood stream in the form of a biologically active compound. However, many steps have been made in several fields. In the future, it is expected that the strategies developed until now to allow curcumin to reach the target tissues in adequate concentrations could be ameliorated and, above all, large in vivo studies on humans are needed to demonstrate the total safety of these compounds and their effectiveness in different eye diseases.

Retinal Inflammation, Cell Death and Inherited Retinal Dystrophies

Inherited retinal dystrophies (IRDs) are a group of retinal disorders that cause progressive and severe loss of vision because of retinal cell death, mainly photoreceptor cells. IRDs include retinitis pigmentosa (RP), the most common IRD. IRDs present a genetic and clinical heterogeneity that makes it difficult to achieve proper treatment. The progression of IRDs is influenced, among other factors, by the activation of the immune cells (microglia, macrophages, etc.) and the release of inflammatory molecules such as chemokines and cytokines. Upregulation of tumor necrosis factor alpha (TNFα), a pro-inflammatory cytokine, is found in IRDs. This cytokine may influence photoreceptor cell death. Different cell death mechanisms are proposed, including apoptosis, necroptosis, pyroptosis, autophagy, excessive activation of calpains, or parthanatos for photoreceptor cell death. Some of these cell death mechanisms are linked to TNFα upregulation and inflammation. Therapeutic approaches that reduce retinal inflammation have emerged as useful therapies for slowing down the progression of IRDs. We focused this review on the relationship between retinal inflammation and the different cell death mechanisms involved in RP. We also reviewed the main anti-inflammatory therapies for the treatment of IRDs.

Retinitis Pigmentosa and Retinal Degenerations: Deciphering Pathways and Targets for Drug Discovery and Development

Inherited retinal diseases (IRDs) are a group of retinopathies generally caused by genetic mutations. Retinitis pigmentosa (RP) represents one of the most studied IRDs. RP leads to intense vision loss or blindness resulting from the degeneration of photoreceptor cells. To date, RP is mainly treated with palliative supplementation of vitamin A and retinoids, gene therapies, or surgical interventions. Therefore, a pharmacologically based therapy is an urgent need requiring a medicinal chemistry approach, to validate molecular targets able to deal with retinal degeneration. This Review aims at outlining the recent research efforts in identifying new drug targets for RP, especially focusing on the neuroprotective role of the Wnt/β-catenin/GSK3β pathway and apoptosis modulators (in particular PARP-1) but also on growth factors such as VEGF and BDNF. Furthermore, the role of spatiotemporally expressed G protein-coupled receptors (GPR124) in the retina and the emerging function of histone deacetylase inhibitors in promoting retinal neuroprotection will be discussed.

Gross anatomy, histological, and histochemical analysis of the eyelids and orbital glands of the neonate pygmy hippopotamus (Suina: Choeropsis liberiensis or Hexaprotodon liberiensis, Morton 1849) with reference to its habitat

The pygmy hippopotamus is phylogenetically related to members of both the Suidae and Cetacea. However, differences in their habitats may have resulted in variation in the anatomy and physiology of the ocular adnexa between these species. Therefore, this study focuses on the identification of accessory organs of the eye, which are typical for the pygmy hippopotamus and are comparable to organs present in mammals related to it. Moreover, the secretions produced by the superficial gland of the third eyelid, the deep gland of the third eyelid and the lacrimal gland were examined, as they ensure eyeball protection. In the upper and lower eyelids, numerous serous glands where identified, which were typical for the pygmy hippopotamus and similar as in the Cetacea. This study enabled to identify additional folds in the eyelids of the pygmy hippopotamus. Lymphoid follicles and diffuse lymphocytes were not found in the lymphoid region in the upper or lower eyelids and the third eyelid, which was most likely caused by the age of the studied hippopotamuses. An accurate histochemical analysis revealed that the secretions of the pygmy hippopotamus are very similar to the Sus scrofa. The structural differences between the pygmy hippopotamus and representatives of Cetacea are most likely caused by the fact that most of Cetacea live in saltwater and are exposed to more frequent fluctuations in water temperature compared to the pygmy hippopotamus, which lives in fresh water and does not lead a migratory lifestyle like the Cetacea.

Curcumin as a Therapeutic Option in Retinal Diseases

The retina is subjected to oxidative stress due to its high vascularization, long time light exposition and a high density of mitochondria. Oxidative stress can lead to pathological processes, like cell apoptosis, angiogenesis and inflammation ending in retinal pathologies. Curcumin, a major bioactive component obtained from the spice turmeric (Curcuma longa) rhizome has been used for centuries in Asian countries for cooking and for curing all kinds of diseases like dysentery, chest congestion and pain in general, due to its antioxidant effects. Curcumin prevents the formation of reactive oxygen species and so it is a good protective agent. Curcumin has shown also anti-inflammatory, and antitumor properties. Curcumin is a natural product, which can be a therapeutic option in a variety of retinal diseases due to its pleiotropic properties. Some drawbacks are its poor solubility, bioavailability and lack of stability at physiological conditions; which have been shown in curcumin skeptical publications. In this review, we provide some lights and shadows on curcumin administration on the major retinal pathologies.

Anatomic Studies of the Miniature Swine Cornea

The domestic swine eye resembles the human eye both anatomically and physiologically. Xenotransplantation of the swine cornea to humans in need of full keratoplasty shows promise as a potential therapeutic strategy to restore vision in individuals with advanced corneal disease, especially those residing in developing nations. That said, we characterized the morphology of corneas from miniature swine, which are smaller in size, easier to handle, and more cost-effective compared to domestic swine. Eyes (N = 15) were harvested from miniature swine from different age groups: 1 month (N = 3), 2 month (N = 3), 4 month (N = 3), 8 month (N = 3), as well as 24 month old adult domestic swine (N = 3). They were immediately submerged in fixative and processed for histological examination at the light and transmission electron microscopic level. Gross anatomic measurements of the cornea were significantly less (P value ≤ 0.05) in miniature swine versus domestic swine. Corneal strata exhibited morphological characteristics similar to the domestic swine cornea. Adult miniature swine corneas show similar overall corneal thickness at 8 months of age versus domestic swine. Miniature swine exhibit similar corneal morphology with the domestic pig and humans, with the exception of Bowman's layer, which is absent in pigs. Therefore, miniature pigs may be a useful resource of corneal tissue for humans in need of full keratoplasty, as well as serve as a large eye model for ophthalmology residents to develop surgical skills and for development and testing of ocular therapeutic strategies that translate to humans. Anat Rec, 301:1955-1967, 2018. © 2018 Wiley Periodicals, Inc.

Molecular genetics and emerging therapies for retinitis pigmentosa: Basic research and clinical perspectives

Retinitis Pigmentosa (RP) is a hereditary retinopathy that affects about 2.5 million people worldwide. It is characterized with progressive loss of rods and cones and causes severe visual dysfunction and eventual blindness in bilateral eyes. In addition to more than 3000 genetic mutations from about 70 genes, a wide genetic overlap with other types of retinal dystrophies has been reported with RP. This diversity of genetic pathophysiology makes treatment extremely challenging. Although therapeutic attempts have been made using various pharmacologic agents (neurotrophic factors, antioxidants, and anti-apoptotic agents), most are not targeted to the fundamental cause of RP, and their clinical efficacy has not been clearly proven. Current therapies for RP in ongoing or completed clinical trials include gene therapy, cell therapy, and retinal prostheses. Gene therapy, a strategy to correct the genetic defects using viral or non-viral vectors, has the potential to achieve definitive treatment by replacing or silencing a causative gene. Among many clinical trials of gene therapy for hereditary retinal diseases, a phase 3 clinical trial of voretigene neparvovec (AAV2-hRPE65v2, Luxturna) recently showed significant efficacy for RPE65-mediated inherited retinal dystrophy including Leber congenital amaurosis and RP. It is about to be approved as the first ocular gene therapy biologic product. Despite current limitations such as limited target genes and indicated patients, modest efficacy, and the invasive administration method, development in gene editing technology and novel gene delivery carriers make gene therapy a promising therapeutic modality for RP and other hereditary retinal dystrophies in the future.

Swine models, genomic tools and services to enhance our understanding of human health and diseases

The pig is becoming increasingly important as a biomedical model. Given the similarities between pigs and humans, a greater understanding of the underlying biology of human health and diseases may come from the pig rather than from classical rodent models. With an increasing need for swine models, it is essential that the genomic tools, models and services be readily available to the scientific community. Many of these are available through the National Swine Resource and Research Center (NSRRC), a facility funded by the US National Institutes of Health at the University of Missouri. The goal of the NSRRC is to provide high-quality biomedical swine models to the scientific community.

Progression of Pro23His Retinopathy in a Miniature Swine Model of Retinitis Pigmentosa

Purpose

We characterize the progression of retinopathy in Filial 1 (F1) progeny of a transgenic (Tg) founder miniswine exhibiting severe Pro23His (P23H) retinopathy.

Methods

The F1 TgP23H miniswine progeny were created by crossing TgP23H founder miniswine 53-1 with wild type (WT) inbred miniature swine. Scotopic (rod-driven) and photopic (cone-driven) retinal functions were evaluated in F1 TgP23H and WT littermates using full field electroretinograms (ffERGs) at 1, 2, 3, 6, 9, 12, and 18 months of age, as well as the Tg founder miniswine at 6 years of age. Miniswine were euthanized and their retinas processed for morphologic evaluation at the light and electron microscopic level. Retinal morphology of a 36-month-old Tg miniswine also was examined.

Results

Wild type littermates reached mature scotopic and photopic retinal function by 3 months, while TgP23H miniswine showed abnormal scotopic ffERGs at the earliest time point, 1 month, and depressed photopic ffERGs after 2 months. Rod and cone photoreceptors (PR) exhibited morphologic abnormalities and dropout from the outer nuclear layer at 1 month, with only a monolayer of cone PR somata remaining after 2 months. The retinas showed progressive neural remodeling of the outer retina that included dendritic retraction of rod bipolar cells and glial seal formation by Müller cells. The TgP23H founder miniswine showed cone PR with relatively intact morphology exclusive to the area centralis.

Conclusions

The F1 Tg miniswine and the TgP23H founder miniswine exhibit similar retinopathy.

Translational Relevance

TgP23H miniswine are a useful large-eye model to study pathogenesis and preservation cone PRs in humans with retinitis pigmentosa.