Ultrastructural changes in the melanocytes of aging human choroid

Autophagy and vesicular trafficking in human uveal melanoma: A histopathological study

Uveal melanoma is an ocular tumor with a high risk of developing metastases. The endo-lysosomal system can affect the melanoma progression by accelerating and facilitating invasion or metastasis. This study aims to conduct comparative analysis of normal choroidal melanocytes and uveal melanoma cells ultrastructure with a focus on intracellular transport system, and to examine the patterns of autophagy- and vesicular trafficking-related proteins expression in a case series of uveal melanomas. Transmission electron microscopy was used to assess the ultrastructure of normal choroidal melanocytes and uveal melanoma cells. The expression levels of autophagy- and vesicular trafficking-related proteins in three histological types of uveal melanoma were analyzed by immunofluorescence staining. Electron microscopy results showed that the autophagic vacuoles were more abundant in normal choroidal melanocytes, than in uveal melanoma cells. The normal choroidal melanocytes were characterized by active intracellular vesicular trafficking; however, the proportion of caveolae was higher in uveal melanoma cells. The spindle type of tumor was characterized by a high expression levels of LC3 beta, while Rab7 and Rab11 proteins expression was significantly up-regulated in the mixed-type tumor cells. The results indicate that uveal melanoma cells probably have lower basal levels of autophagy and higher receptor-mediated endocytic trafficking-associated with caveolae than normal choroidal melanocytes. RESEARCH HIGHLIGHTS: The autophagic vacuoles are abundant in normal choroidal melanocytes. Uveal melanoma cells are characterized by a high proportion of caveolae. The high expression levels of LC3 beta were revealed in a spindle type of tumor, while Rab7 and Rab11 proteins expression was up-regulated in the mixed-type tumor cells.

The Role of Oxidative Stress in the Aging Eye

Given the expanding elderly population in the United States and the world, it is important to understand the processes underlying both natural and pathological age-related changes in the eye. Both the anterior and posterior segment of the eye undergo changes in biological, chemical, and physical properties driven by oxidative stress. With advancing age, changes in the anterior segment include dermatochalasis, blepharoptosis, thickening of the sclera, loss of corneal endothelial cells, and stiffening of the lens. Changes in the posterior segment include lowered viscoelasticity of the vitreous body, photoreceptor cell loss, and drusen deposition at the macula and fovea. Age-related ocular pathologies including glaucoma, cataracts, and age-related macular degeneration are largely mediated by oxidative stress. The prevalence of these diseases is expected to increase in the coming years, highlighting the need to develop new therapies that address oxidative stress and slow the progression of age-related pathologies.

Recognition of Melanocytes in Immuno-Neuroendocrinology and Circadian Rhythms: Beyond the Conventional Melanin Synthesis

Melanocytes produce melanin to protect the skin from UV-B radiation. Notwithstanding, the spectrum of their functions extends far beyond their well-known role as melanin production factories. Melanocytes have been considered as sensory and computational cells. The neurotransmitters, neuropeptides, and other hormones produced by melanocytes make them part of the skin’s well-orchestrated and complex neuroendocrine network, counteracting environmental stressors. Melanocytes can also actively mediate the epidermal immune response. Melanocytes are equipped with ectopic sensory systems similar to the eye and nose and can sense light and odor. The ubiquitous inner circadian rhythm controls the body’s basic physiological processes. Light not only affects skin photoaging, but also regulates inner circadian rhythms and communicates with the local neuroendocrine system. Do melanocytes “see” light and play a unique role in photoentrainment of the local circadian clock system? Why, then, are melanocytes responsible for so many mysterious functions? Do these complex functional devices work to maintain homeostasis locally and throughout the body? In addition, melanocytes have also been shown to be localized in internal sites such as the inner ear, brain, and heart, locations not stimulated by sunlight. Thus, what can the observation of extracutaneous melanocytes tell us about the “secret identity” of melanocytes? While the answers to some of these intriguing questions remain to be discovered, here we summarize and weave a thread around available data to explore the established and potential roles of melanocytes in the biological communication of skin and systemic homeostasis, and elaborate on important open issues and propose ways forward.

Evaluation of choroidal melanin-containing tissue in healthy Japanese subjects by polarization-sensitive optical coherence tomography

In this study, the choroidal melanin content in healthy eyes was evaluated with polarization-sensitive optical coherence tomography (PS-OCT). We evaluated 105 healthy eyes of 105 Japanese subjects. The mean thickness of melanin-containing tissue in the choroid (thickness of MeCh) and the choroidal melanin occupancy rate within a 5-mm circular region from the foveal center were calculated using the degree of polarization uniformity obtained by PS-OCT and compared with the choroidal thickness, patient age, and axial length. To evaluate regional variations, the 5-mm circular region was divided into a center area and an outer ring area, and the outer ring area was further divided into four areas (nasal, temporal, superior, and inferior). The mean thickness of MeCh showed a significant positive correlation with the choroidal thickness. The mean choroidal melanin occupancy rate showed a significant positive correlation with age. The mean choroidal melanin occupancy rate of the center area was significantly larger than that of the outer ring area. The mean thickness of MeCh and choroidal melanin occupancy rate of the nasal area were significantly lower than those of other areas. The distribution of melanin-containing tissue in the choroid varies significantly with age and location.

Aging of the human choriocapillaris: Evidence that early pericyte damage can trigger endothelial changes

The choriocapillaris (CC), the capillary bed in the choroid, essentially nourishes the photoreceptor cells. Its damage in aging and age-related diseases significantly influences the survival of the photoreceptor cells. Earlier reports implicated endothelial loss in aged and diseased CC; however, age-related pericyte changes and their contribution in CC death remain unknown. We examined human donor eyes (age: 56-94 years; N = 24), and found that CC pericyte damage preceded endothelial changes. With aging (>70 years), the sub-macular choroid accumulated debris in Bruch's membrane (BM). Of the debris content, the long-spaced collagens had a tendency to settle over the capillary basal lamina (BL), and this often resulted in endothelial projection into capillary lumen. Between 75 and 83 years, pericytes contained dark mitochondria, and their processes facing the BM debris showed partial loss of BL and intermediate filaments (IFs), when the endothelium remained unaltered. The endothelial changes appeared beyond 83 years, the abundance of IFs and autophagy reinforced their survival until late aging. TUNEL⁺ pericytes, and immunoreactivity to carboxymethyl lysine and 4-hydroxy 2-nonenal, but no nitro-tyrosine, was detected in aged CC walls. Iba-1⁺ dystrophic microglia were present in the vicinity of the CC. Our data indicate that (1) BM debris exerts pressure on the CC, leading to the damage of the capillary BL and pericyte processes (2) loss of IFs results in early pericyte destabilization (3) capillary wall undergoes lipid peroxidative and glycative damage, and (4) pericyte damage leads to late endothelial changes and ultimately CC loss. Future research should explore the normal ways of pericyte maintenance in the aging nervous system.

Exploring the choroidal vascular labyrinth and its molecular and structural roles in health and disease

The choroid is a key player in maintaining ocular homeostasis and plays a role in a variety of chorioretinal diseases, many of which are poorly understood. Recent advances in the field of single-cell RNA sequencing have yielded valuable insights into the properties of choroidal endothelial cells (CECs). Here, we review the role of the choroid in various physiological and pathophysiological mechanisms, focusing on the role of CECs. We also discuss new insights regarding the phenotypic properties of CECs, CEC subpopulations, and the value of measuring transcriptomics in primary CEC cultures derived from post-mortem eyes. In addition, we discuss key phenotypic, structural, and functional differences that distinguish CECs from other endothelial cells such as retinal vascular endothelial cells. Understanding the specific clinical and molecular properties of the choroid will shed new light on the pathogenesis of the broad clinical range of chorioretinal diseases such as age-related macular degeneration, central serous chorioretinopathy and other diseases within the pachychoroid spectrum, uveitis, and diabetic choroidopathy. Although our knowledge is still relatively limited with respect to the clinical features and molecular pathways that underlie these chorioretinal diseases, we summarise new approaches and discuss future directions for gaining new insights into these sight-threatening diseases and highlight new therapeutic strategies such as pluripotent stem cell‒based technologies and gene therapy.

The Regulation of NFE2L2 (NRF2) Signalling and Epithelial-to-Mesenchymal Transition in Age-Related Macular Degeneration Pathology

Age-related macular degeneration (AMD) is a mounting cause of loss of sight in the elderly in the developed countries, a trend enhanced by the continual ageing of the population. AMD is a multifactorial and only partly understood, malady. Unfortunately, there is no effective treatment for most AMD patients. It is known that oxidative stress (OS) damages the retinal pigment epithelium (RPE) and contributes to the progression of AMD. We review here the potential importance of two OS-related cellular systems in relation to AMD. First, the nuclear factor erythroid 2-related factor 2 (NFE2L2; NRF2)-mediated OS response signalling pathway is important in the prevention of oxidative damage and a failure of this system could be critical in the development of AMD. Second, epithelial-to-mesenchymal transition (EMT) represents a change in the cellular phenotype, which ultimately leads to the fibrosis encountered in RPE, a characteristic of AMD. Many of the pathways triggering EMT are promoted by OS. The possible interconnections between these two signalling routes are discussed here. From a broader perspective, the control of NFE2L2 and EMT as ways of preventing OS-derived cellular damage could be potentially valuable in the therapy of AMD.

Establishment of an In Vitro-In Vivo Correlation for Melanin Binding and the Extension of the Ocular Half-Life of Small-Molecule Drugs

A large variety of drugs bind effectively to melanin, and this binding influences their ocular pharmacokinetic and distribution profiles. We aimed to establish a correlation between in vitro melanin binding and in vivo ocular pharmacokinetics (PK). The extent of melanin binding in vitro was determined for a set of model drugs; binding kinetics and binding isotherms were generated and fitted to a mechanistic model to derive the drug-melanin binding parameters (B_max, K_D, k_on, and k_off). In addition, in vitro ADME properties such as cellular permeability, P-glycoprotein-mediated efflux, plasma protein binding, and octanol partition coefficients were determined. Moreover, cellular uptake was measured in the nonpigmented ARPE-19 cells and in lightly pigmented human epidermal melanocytes. Finally, in vivo ocular PK studies were performed in albino and pigmented rats using intravenous injections. Substantial drug enrichment accompanied by a very long residence time was observed in pigmented ocular tissues, which could be linked to the melanin binding determined in vitro and to the intracellular drug uptake into the pigmented cells. The resulting ocular PK profile is shown to be a consequence of the interplay of melanin binding with concurrent processes such as systemic clearance, plasma protein binding, cellular permeation, P-glycoprotein efflux, pH partitioning, and tissue binding. Understanding this interplay at a mechanistic level could help in the rational design and development of new small-molecule drug candidates with the desired PK/pharmacodynamic profile to target the back of the eye.

The promise of marine molecules as cosmetic active ingredients

The marine environment represents an underexploited resource for the discovery of novel products, despite its high level of biological and chemical diversity. With increasing awareness of the harmful effects of chronic ultraviolet exposure, and a universal desire to improve cosmetic appearance, the market for new cosmetic ingredients is growing, and current trends have generated a greater demand for products sourced from the environment. A growing number of novel molecules from marine flora and fauna exhibit potent and effective dermatological activities. Secondary metabolites isolated from macroalgae, including carotenoids and polyphenols, have demonstrated antioxidant, anti-ageing and anti-inflammatory activities. In addition, marine extremophilic bacteria have recently been shown to produce bioactive exopolymeric molecules, some of which have been commercialized. Available data on their activities show significant antioxidant, moisturizing and anti-ageing activities, but a more focussed investigation into their mechanisms and applications is required. This review surveys the reported biological activities of an emerging and growing portfolio of marine molecules that show promise in the treatment of cosmetic skin problems including ultraviolet damage, ageing and cutaneous dryness.

Emerging preclinical interest concerning the role of circadian function in Parkinson's disease

The importance of circadian function in the aetiology, progression and treatment of Parkinson's disease is a topic of increasing interest to the scientific and clinical community. While clinical studies on this theme are relatively new and limited in number there are many preclinical studies which explore possible circadian involvement in Parkinson's disease and speculate as to the mechanism by which clinical benefit can be derived by manipulating the circadian system. The present review explores the sequelae of circadian related studies from a historical perspective and reveals mechanisms that may be involved in the aetiology and progression of the disease. A systematic review of these studies also sets the stage for understanding the basic neuroscientific approaches which have been applied and provides new direction from which circadian function can be explored.

Role of macrophages in age-related oxidative stress and lipofuscin accumulation in mice

The age-related changes in the immune functions (immunosenescence) may be mediated by an increase of oxidative stress and damage affecting leukocytes. Although the “oxidation-inflammation” theory of aging proposes that phagocytes are the main immune cells contributing to “oxi-inflamm-aging”, this idea has not been corroborated. The aim of this work was to characterize the age-related changes in several parameters of oxidative stress and immune function, as well as in lipofuscin accumulation (“a hallmark of aging”), in both total peritoneal leukocyte population and isolated peritoneal macrophages. Adult, mature, old and long-lived mice (7, 13, 18 and 30 months of age, respectively) were used. The xanthine oxidase (XO) activity-expression, basal levels of superoxide anion and ROS, catalase activity, oxidized (GSSG) and reduced (GSH) glutathione content and lipofuscin levels, as well as both phagocytosis and digestion capacity were evaluated. The results showed an age-related increase of oxidative stress and lipofuscin accumulation in murine peritoneal leukocytes, but especially in macrophages. Macrophages from old mice showed lower antioxidant defenses (catalase activity and GSH levels), higher oxidizing compounds (XO activity/expression and superoxide, ROS and GSSG levels) and lipofuscin levels, together with an impaired macrophage functions, in comparison to adults. In contrast, long-lived mice showed in their peritoneal leukocytes, and especially in macrophages, a well-preserved redox state and maintenance of their immune functions, all which could account for their high longevity. Interestingly, macrophages showed higher XO activity and lipofuscin accumulation than lymphocytes in all the ages analyzed. Our results support that macrophages play a central role in the chronic oxidative stress associated with aging, and the fact that phagocytes are key cells contributing to immunosenescence and “oxi-inflamm-aging”. Moreover, the determination of oxidative stress and immune function parameters, together with the lipofuscin quantification, in macrophages, can be used as useful markers of the rate of aging and longevity.

•

Peritoneal macrophages from old mice have higher oxidant levels than lymphocytes.

•

Long-lived mice have a well-preserved redox state in both macrophages and lymphocytes.

•

Peritoneal macrophages have higher lipofuscin levels than lymphocytes along aging.

Clinical and Genetic Features of Choroideremia in Childhood

PURPOSE

To review the functional and anatomic characteristics of choroideremia in the pediatric population, aiming to describe the earliest features of the disease and to identify biomarkers useful for monitoring disease progression.

DESIGN

Retrospective case series.

PARTICIPANTS

Children diagnosed with choroideremia at a single institution.

METHODS

Patients were identified using an electronic patient record system. Case notes and retinal imaging (color fundus photography [CFP], spectral-domain [SD] optical coherence tomography [OCT], and fundus autofluorescence [FAF]) then were reviewed. The results of genetic testing also were recorded.

MAIN OUTCOME MEASURES

Presenting symptoms, visual acuity, fundus changes (CFP, SD OCT, FAF), and CHM sequencing results.

RESULTS

Twenty-nine patients were identified with a mean age at referral of 9 years (range, 3-16 years). CHM mutations were identified in 15 of 19 patients tested. Nyctalopia was the predominant symptom (66%). Five of 29 patients were asymptomatic at presentation. At the final follow-up visit (mean age, 16 years; range, 7-26 years), most maintained excellent visual acuity (mean, 0.98±0.13 decimalized Snellen acuity). The first sign of retinopathy was widespread pigment clumping at the level of the retinal pigment epithelium (RPE). This later evolved to chorioretinal atrophy, most marked in the mid-peripheral retina. Peripapillary atrophy also was an early feature and was progressive in nature. Three different zones of FAF change were visible. Persistence of the inner retinal layers, detected by SD OCT, was visible at presentation in 15 of 27 patients. Subfoveal choroidal thickness decreased with age, whereas central retinal thickness increased over a similar interval. Four patients in whom visual acuity decreased over the follow-up period recorded a reduction in central retinal thickness.

CONCLUSIONS

Progressive structural changes occur at a time when central visual function is maintained. Pigmentary changes at the level of the RPE occur early in the disease course. Peripapillary chorioretinal atrophy, central retinal thickness, and subfoveal choroidal thickness are likely to be valuable in monitoring disease progression and should be considered as potential biomarkers in future therapeutic trials.