Differential effects of the estrogen receptor agonist estradiol on toxicity induced by enzymatically-derived or autoxidation-derived oxysterols in human ARPE-19 cells

Coronary Microvascular Dysfunction Is Associated With Augmented Lysosomal Signaling in Hypercholesterolemic Mice

BACKGROUND

Accumulating evidence indicates that coronary microvascular dysfunction (CMD) caused by hypercholesterolemia can lead to myocardial ischemia, with or without obstructive atherosclerotic coronary artery disease. However, the molecular pathways associated with compromised coronary microvascular function before the development of myocardial ischemic injury remain poorly defined. In this study, we investigated the effects of hypercholesterolemia on the function and integrity of the coronary microcirculation in mice and the underlying mechanisms.

METHODS AND RESULTS

Mice were fed a hypercholesterolemic Paigen's diet for 8 weeks. Echocardiography data showed that Paigen's diet caused CMD, characterized by significant reductions in coronary blood flow and coronary flow reserve, but did not affect cardiac remodeling or dysfunction. Immunofluorescence studies revealed that Paigen's diet-induced CMD was associated with activation of coronary arterioles inflammation and increased myocardial inflammatory cell infiltration. These pathological changes occurred in parallel with the upregulation of lysosomal signaling pathways in endothelial cells (ECs). Treating hypercholesterolemic mice with the cholesterol-lowering drug ezetimibe significantly ameliorated Paigen's diet-induced adverse effects, including hypercholesterolemia, steatohepatitis, reduced coronary flow reserve, coronary endothelial cell inflammation, and myocardial inflammatory cell infiltration. In cultured mouse cardiac ECs, 7-ketocholesterol increased mitochondrial reactive oxygen species and inflammatory responses. Meanwhile, 7-ketocholesterol induced the activation of transcriptional factor EB and lysosomal signaling in mouse cardiac ECs, whereas the lysosome inhibitor bafilomycin A1 blocked 7-ketocholesterol-induced transcriptional factor EB activation and exacerbated 7-ketocholesterol-induced inflammation and cell death. Interestingly, ezetimibe synergistically enhanced 7-ketocholesterol-induced transcriptional factor EB activation and attenuated 7-ketocholesterol-induced mitochondrial reactive oxygen species and inflammatory responses in mouse cardiac ECs.

CONCLUSIONS

These results suggest that CMD can develop and precede detectable cardiac functional or structural changes in the setting of hypercholesterolemia and that upregulation of transcriptional factor EB-mediated lysosomal signaling in endothelial cells plays a protective role against CMD.

Coronary Microvascular Dysfunction is Associated with Augmented Lysosomal Signaling in Hypercholesterolemic Mice

Accumulating evidence indicates that coronary microvascular dysfunction (CMD) caused by hypercholesterolemia can lead to myocardial ischemia, with or without obstructive atherosclerotic coronary artery disease (CAD). However, the molecular pathways associated with compromised coronary microvascular function prior to the development of myocardial ischemic injury remain poorly defined. In this study, we investigated the effects of hypercholesterolemia on the function and integrity of the coronary microcirculation in mice and the underlying mechanisms. Mice were fed with a hypercholesterolemic Paigen's diet (PD) for 8 weeks. Echocardiography data showed that PD caused CMD, characterized by significant reductions in coronary blood flow and coronary flow reserve (CFR), but did not affect cardiac remodeling or dysfunction. Immunofluorescence studies revealed that PD-induced CMD was associated with activation of coronary arterioles inflammation and increased myocardial inflammatory cell infiltration. These pathological changes occurred in parallel with the upregulation of lysosomal signaling pathways in endothelial cells (ECs). Treating hypercholesterolemic mice with the cholesterol-lowering drug ezetimibe significantly ameliorated PD-induced adverse effects, including hypercholesterolemia, steatohepatitis, reduced CFR, coronary EC inflammation, and myocardial inflammatory cell infiltration. In cultured mouse cardiac endothelial cells (MCECs), 7-ketocholesterol (7K) increased mitochondrial reactive oxygen species (ROS) and inflammatory responses. Meanwhile, 7K induced the activation of TFEB and lysosomal signaling in MCECs, whereas the lysosome inhibitor bafilomycin A1 blocked 7K-induced TFEB activation and exacerbated 7K-induced inflammation and cell death. Interestingly, ezetimibe synergistically enhanced 7K-induced TFEB activation and attenuated 7K-induced mitochondrial ROS and inflammatory responses in MCECs. These results suggest that CMD can develop and precede detectable cardiac functional or structural changes in the setting of hypercholesterolemia, and that upregulation of TFEB-mediated lysosomal signaling in ECs plays a protective role against CMD.

Impact of Oxysterols in Age-Related Disorders and Strategies to Alleviate Adverse Effects

Oxysterols or cholesterol oxidation products are a class of molecules with the sterol moiety, derived from oxidative reaction of cholesterol through enzymatic and non-enzymatic processes. They are widely reported in animal-origin foods and prove significant involvement in the regulation of cholesterol homeostasis, lipid transport, cellular signaling, and other physiological processes. Reports of oxysterol-mediated cytotoxicity are in abundance and thus consequently implicated in several age-related and lifestyle disorders such as cardiovascular diseases, bone disorders, pancreatic disorders, age-related macular degeneration, cataract, neurodegenerative disorders such as Alzheimer's and Parkinson's disease, and some types of cancers. In this chapter, we attempt to review a selection of physiologically relevant oxysterols, with a focus on their formation, properties, and roles in health and disease, while also delving into the potential of natural and synthetic molecules along with bacterial enzymes for mitigating oxysterol-mediated cell damage.

Inhibition of Candida albicans biofilm by pure selenium nanoparticles synthesized by pulsed laser ablation in liquids

Selenoproteins play an important role in the human body by accomplishing essential biological functions like oxido-reductions, antioxidant defense, thyroid hormone metabolism and immune response; therefore, the possibility to synthesize selenium nanoparticles free of any contaminants is exciting for future nano-medical applications. This paper reports the first synthesis of selenium nanoparticles by femtosecond pulsed laser ablation in de-ionized water. Those pure nanoparticles have been successfully used to inhibit the formation of Candida albicans biofilms. Advanced electron microscopy images showed that selenium nanoparticles easily adhere on the biofilm, then penetrate into the pathogen, and consequently damage the cell structure by substituting with sulfur. 50% inhibition of Candida albicans biofilm was obtained at only 25 ppm. Finally, the two physical parameters proved to affect strongly the viability of Candida albicans are the crystallinity and particle size.

27-Hydroxycholesterol contributes to disruptive effects on learning and memory by modulating cholesterol metabolism in the rat brain

Cholesterol metabolism is important for neuronal function in the central nervous system (CNS). The oxysterol 27-hydroxycholesterol (27-OHC) is a cholesterol metabolite that crosses the blood-brain barrier (BBB) and may be a useful substitutive marker for neurodegenerative diseases. However, the effects of 27-OHC on learning and memory and the underlying mechanisms are unclear. To determine this mechanism, we investigated learning and memory and cholesterol metabolism in rat brain following the injection of various doses of 27-OHC into the caudal vein. We found that 27-OHC increased cholesterol levels and upregulated the expression of liver X receptor-α (LXR-α) and adenosine triphosphate (ATP)-binding cassette transporter protein family member A1 (ABCA1). In addition, 27-OHC decreased the expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CR) and low-density lipoprotein receptor (LDLR) in rat brain tissues. These findings suggest that 27-OHC may negatively modulate cognitive effects and cholesterol metabolism in the brain.

Estrogen signalling in the pathogenesis of age-related macular degeneration

Age-related macular degeneration (AMD) is a multifactorial eye disease that is associated with aging, family history, smoking, obesity, cataract surgery, arteriosclerosis, hypertension, hypercholesterolemia and unhealthy diet. Gender has commonly been classified as a weak or inconsistent risk factor for AMD. This disease is characterized by degeneration of retinal pigment epithelial (RPE) cells, Bruch's membrane, and choriocapillaris, which secondarily lead to damage and death of photoreceptor cells and central visual loss. Pathogenesis of AMD involves constant oxidative stress, chronic inflammation, and increased accumulation of lipofuscin and drusen. Estrogen has both anti-oxidative and anti-inflammatory capacity and it regulates signaling pathways that are involved in the pathogenesis of AMD. In this review, we discuss potential cellular signaling targets of estrogen in retinal cells and AMD pathology.