Activation of LXRs Reduces Oxysterol Lipotoxicity in RPE Cells by Promoting Mitochondrial Function

Ginsenoside Rg3 Improved Age-Related Macular Degeneration Through Inhibiting ROS-Mediated Mitochondrion-Dependent Apoptosis In Vivo and In Vitro

Age-related macular degeneration (AMD) is marked by a progressive loss of central vision and is the third leading cause of irreversible blindness worldwide. The exact mechanisms driving the progression of this macular degenerative condition remain elusive, and as of now, there are no available preventative measures for dry AMD. According to ancient records, ginseng affects the eyes by brightening them and enhancing wisdom. Modern pharmacological research shows that the active ingredients in ginseng, ginsenosides, may be used to prevent or improve eye diseases that threaten vision. Some articles have reported that ginsenoside Rg3 can treat diabetic retinopathy in mice, but no reports exist on its effects and mechanisms in AMD. Therefore, the role and mechanism of ginsenoside Rg3 in AMD warrant further study. This study aims to investigate the effects of Rg3 on AMD and its underlying molecular mechanisms. We established a mouse model of AMD to examine the impact of ginsenoside Rg3 on NaIO3-induced apoptosis in the retina and to explore the related intrinsic mechanisms. The in vivo results indicated that ginsenoside Rg3 prevents NaIO3-induced apoptosis in retinal pigment epithelial cells by inhibiting reactive oxygen species production and preventing the reduction in mitochondrial membrane potential. Additionally, we assessed the levels of protein expression within the apoptosis pathway. Ginsenoside Rg3 decreased the expression of Bax, cleaved caspase-3, and cleaved caspase-9 proteins. Additionally, it increased the expression of Bcl-2 by decreasing P-JNK levels. Moreover, our in vivo results showed that ginsenoside Rg3 enhanced retinal structure, increased the relative thickness of the retina, and decreased the extent of disorganization in both the inner and outer nuclear layers. Ginsenoside Rg3 may safeguard the retina against NaIO3-induced cell apoptosis by attenuating reactive-oxygen-species-mediated mitochondrial dysfunction, in which the JNK signaling pathway is also involved. These findings suggest that ginsenoside Rg3 has the potential to prevent or attenuate the progression of AMD and other retinal pathologies associated with NaIO3-mediated apoptosis.

Aberrant Lipid Metabolism and Complement Activation in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) stands as a leading cause of severe visual impairment and blindness among the elderly globally. As a multifactorial disease, AMD's pathogenesis is influenced by genetic, environmental, and age-related factors, with lipid metabolism abnormalities and complement system dysregulation playing critical roles. This review delves into recent advancements in understanding the intricate interaction between these two crucial pathways, highlighting their contribution to the disease's progression through chronic inflammation, drusen formation, and retinal pigment epithelium dysfunction. Importantly, emerging evidence points to dysregulated lipid profiles, particularly alterations in high-density lipoprotein levels, oxidized lipid deposits, and intracellular lipofuscin accumulation, as exacerbating factors that enhance complement activation and subsequently amplify tissue damage in AMD. Furthermore, genetic studies have revealed significant associations between AMD and specific genes involved in lipid transport and complement regulation, shedding light on disease susceptibility and underlying mechanisms. The review further explores the clinical implications of these findings, advocating for a novel therapeutic approach that integrates lipid metabolism modulators with complement inhibitors. By concurrently targeting these pathways, the dual-targeted approach holds promise in significantly improving outcomes for AMD patients, heralding a new horizon in AMD management and treatment.

Liver X receptor activation mitigates oxysterol-induced dysfunction in fetoplacental endothelial cells

Maintaining the homeostasis of the placental vasculature is of paramount importance for ensuring normal fetal growth and development. Any disruption in this balance can lead to perinatal morbidity. Several studies have uncovered an association between high levels of oxidized cholesterol (oxysterols), and complications during pregnancy, including gestational diabetes mellitus (GDM) and preeclampsia (PE). These complications often coincide with disturbances in placental vascular function. Here, we investigate the role of two oxysterols (7-ketocholesterol, 7β-hydroxycholesterol) in (dys)function of primary fetoplacental endothelial cells (fpEC). Our findings reveal that oxysterols exert a disruptive influence on fpEC function by elevating the production of reactive oxygen species (ROS) and interfering with mitochondrial transmembrane potential, leading to its depolarization. Moreover, oxysterol-treated fpEC exhibited alterations in intracellular calcium (Ca2+) levels, resulting in the reorganization of cell junctions and a corresponding increase in membrane stiffness and vascular permeability. Additionally, we observed an enhanced adhesion of THP-1 monocytes to fpEC following oxysterol treatment. We explored the influence of activating the Liver X Receptor (LXR) with the synthetic agonist T0901317 (TO) on oxysterol-induced endothelial dysfunction in fpEC. Our results demonstrate that LXR activation effectively reversed oxysterol-induced ROS generation, monocyte adhesion, and cell junction permeability in fpEC. Although the effects on mitochondrial depolarization and calcium mobilization did not reach statistical significance, a strong trend towards stabilization of calcium mobilization was evident in LXR-activated cells. Taken together, our results suggest that high levels of systemic oxysterols link to placental vascular dysfunction and LXR agonists may alleviate their impact on fetoplacental vasculature.

Cholesterol metabolism: physiological regulation and diseases

Cholesterol homeostasis is crucial for cellular and systemic function. The disorder of cholesterol metabolism not only accelerates the onset of cardiovascular disease (CVD) but is also the fundamental cause of other ailments. The regulation of cholesterol metabolism in the human is an extremely complex process. Due to the dynamic balance between cholesterol synthesis, intake, efflux and storage, cholesterol metabolism generally remains secure. Disruption of any of these links is likely to have adverse effects on the body. At present, increasing evidence suggests that abnormal cholesterol metabolism is closely related to various systemic diseases. However, the exact mechanism by which cholesterol metabolism contributes to disease pathogenesis remains unclear, and there are still unknown factors. In this review, we outline the metabolic process of cholesterol in the human body, especially reverse cholesterol transport (RCT). Then, we discuss separately the impact of abnormal cholesterol metabolism on common diseases and potential therapeutic targets for each disease, including CVD, tumors, neurological diseases, and immune system diseases. At the end of this review, we focus on the effect of cholesterol metabolism on eye diseases. In short, we hope to provide more new ideas for the pathogenesis and treatment of diseases from the perspective of cholesterol.

Role of Oxysterols in Ocular Degeneration Mechanisms and Involvement of P2X7 Receptor

Ocular degeneration, including cataracts, glaucoma, macular degeneration, and diabetic retinopathy, is a major public health challenge, as it affects the quality of life of millions of people worldwide and, in its advanced stages, leads to blindness. Ocular degeneration, although it can affect different parts of the eye, shares common characteristics such as oxysterols and the P2X7 receptor. Indeed, oxysterols, which are cholesterol derivatives, are associated with ocular degeneration pathogenesis and trigger inflammation and cell death pathways. Activation of the P2X7 receptor is also linked to ocular degeneration and triggers the same pathways. In age-related macular degeneration, these two key players have been associated, but further studies are needed to extrapolate this interrelationship to other ocular degenerations.

Identification of 7-Ketocholesterol-Modulated Pathways and Sterculic Acid Protective Effect in Retinal Pigmented Epithelium Cells by Using Genome-Wide Transcriptomic Analysis

Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries. AMD is characterized by the formation of lipidic deposits between the retinal pigment epithelium (RPE) and the choroid called drusen. 7-Ketocholesterol (7KCh), an oxidized-cholesterol derivative, is closely related to AMD as it is one of the main molecules accumulated in drusen. 7KCh induces inflammatory and cytotoxic responses in different cell types, and a better knowledge of the signaling pathways involved in its response would provide a new perspective on the molecular mechanisms that lead to the development of AMD. Furthermore, currently used therapies for AMD are not efficient enough. Sterculic acid (SA) attenuates the 7KCh response in RPE cells and is presented as an alternative to improve these therapies. By using genome-wide transcriptomic analysis in monkey RPE cells, we have provided new insight into 7KCh-induced signaling in RPE cells, as well as the protective capacity of SA. 7KCh modulates the expression of several genes associated with lipid metabolism, endoplasmic reticulum stress, inflammation and cell death and induces a complex response in RPE cells. The addition of SA successfully attenuates the deleterious effect of 7KCh and highlights its potential for the treatment of AMD.