Free cholesterol accumulation impairs antioxidant activities and aggravates apoptotic cell death in menadione-induced oxidative injury

The Effect of Maternal Exposure to a Diet High in Fats and Cholesterol on the Placental Function and Phenotype of the Offspring in a Rabbit Model: A Summary Review of About 15 Years of Research

The rates of obesity and being overweight are increasing all around the world, especially among women of childbearing age, in part due to overconsumption of lipids. The aim of this summary review was to present the cellular and molecular effects of a hyperlipidic high-cholesterol (H) diet on the maternal and offspring phenotype at the early embryonic, neonatal, weaning and adult stages while considering the effects of sex and to identify the window(s) of vulnerability linked to this exposure in a rabbit model. Before breeding, the H diet induced dyslipidemia and aortic atherosclerosis lesions and increased the number of atretic follicles. In the offspring, the H diet disrupted the embryonic phenotype and induced fetal hypotrophy associated with sex-specific disturbances of the feto-placental unit. In adulthood, the offspring of the H dams were heavier and hyperphagic and had increased blood pressure associated with disturbed gonadal development in both sexes. Vulnerability windows were explored via embryo transfers. The maternal gestational diet was shown to play a key role in the feto-placental phenotype, and preconception programming was unquestionably also observed. These two periods could represent windows of intervention in the context of obesity or being overweight to limit fetal and placental consequences.

Long-term changes in the diurnal temporal regulation and set points of metabolic parameters associated with chronic maternal overnutrition in rabbits

Metabolic syndrome (MS) and obesity have become a worldwide epidemic with an alarming prevalence in women of reproductive age. Maternal metabolic condition is considered a risk factor for adverse birth outcomes and long-term MS. In this study, we developed a rabbit model of maternal overnutrition via the chronic intake of a high-fat and carbohydrate diet (HFCD), and we determined the effects of this diet on maternal metabolism and offspring metabolic set points and temporal metabolic regulation in adult life. Before and during pregnancy, the female rabbits that consumed the HFCD exhibited significant changes in body weight, serum levels of analytes associated with carbohydrate and lipid metabolism, levels of liver and kidney damage markers, and liver histology. Our data suggest that rabbits are a valuable model for studying the development of MS associated with the chronic intake of unbalanced diets and fetal metabolic programming. Furthermore, the offspring of overnourished dams exhibited considerable changes in 24-h serum metabolite profiles in adulthood, with notable sexual dimorphism. These data suggest that maternal nutritional conditions due to the chronic intake of an HFCD adversely impact key elements related to the development of circadian rhythmicity in offspring.NEW & NOTEWORTHY Maternal overnutrition previous and during pregnancy leads to long-term changes in the 24-h regulation and setpoint of metabolic profiles of the offspring.

ABCG1 Attenuates Oxidative Stress Induced by H2O2 through the Inhibition of NADPH Oxidase and the Upregulation of Nrf2-Mediated Antioxidant Defense in Endothelial Cells

Summary. Oxidative stress is an important factor that is related to endothelial dysfunction. ATP-binding cassette transporter G1 (ABCG1), a regulator of intracellular cholesterol efflux, has been found to prevent endothelial activation in vessel walls. To explore the role of ABCG1 in oxidative stress production in endothelial cells, HUAECs were exposed to H₂O₂ and transfected with the specific ABCG1 siRNA or ABCG1 overexpression plasmid. The results showed that overexpression of ABCG1 by ABCG1 plasmid or liver X receptor (LXR) agonist T0901317 treatment inhibited ROS production and MDA content induced by H₂O₂ in HUAECs. Furthermore, ABCG1 upregulation blunted the activity of prooxidant NADPH oxidase and the expression of Nox4, one of the NADPH oxidase subunits. Moreover, the increased migration of Nrf2 from the cytoplasm to the nucleus and antioxidant HO-1 expression were detected in HUAECs with upregulation of ABCG1. Conversely, ABCG1 downregulation by ABCG1 siRNA increased NADPH oxidase activity and Nox4 expression and abrogated the increase at Nrf2 nuclear protein levels. In addition, intracellular cholesterol load interfered with the balance between NADPH oxidase activity and HO-1 expression. It was suggested that ABCG1 attenuated oxidative stress induced by H₂O₂ in endothelial cells, which might be involved in the balance between decreased NADPH oxidase activity and increased Nrf2/OH-1 antioxidant defense signaling via its regulation for intracellular cholesterol accumulation.

Fluorescein-Containing Superoxide Probes with a Modular Copper-Based Trigger

Fluorescein-derived superoxide probes featuring a copper(II) complex that can be activated by superoxide to initiate ether bond cleavage and uncage a fluorescein reporter for imaging in live cells are described. Compared to other superoxide sensing moieties, this bond cleavage strategy can be modularly adapted to fluorescent reporters with different properties without compromising the superoxide reactivity and selectivity. A green-emitting probe and its lysosome-targeting analogue have been successfully developed. Both probes are sensitive with more than 30-fold fluorescence enhancement towards superoxide and are highly selective with no significant response towards other reactive oxygen species. A structure-activity relationship study of the copper-based superoxide trigger showed that the secondary coordination environment of the copper(II) center is important for the superoxide reactivity and selectivity. The probes have been applied in imaging changes in intracellular superoxide level in live HeLa and HEK293T cells upon menadione stimulation and also in a cellular inflammation model in RAW 264.7 cells.

A modular trigger for the development of selective superoxide probes

We report here a new bioinspired copper-based strategy of superoxide sensing and the development of sensitive (>90-fold fluorescence turn-on) and selective superoxide probes for imaging variations in the endogenous superoxide level in various live mammalian cells (HEK293T, HeLa and A431).

Momordica charantia polysaccharides could protect against cerebral ischemia/reperfusion injury through inhibiting oxidative stress mediated c-Jun N-terminal kinase 3 signaling pathway

Momordica charantia (MC) is a medicinal plant for stroke treatment in Traditional Chinese Medicine, but its active compounds and molecular targets are unknown yet. M. charantia polysaccharide (MCP) is one of the important bioactive components in MC. In the present study, we tested the hypothesis that MCP has neuroprotective effects against cerebral ischemia/reperfusion injury through scavenging superoxide (O2(-)), nitric oxide (NO) and peroxynitrite (ONOO(-)) and inhibiting c-Jun N-terminal protein kinase (JNK3) signaling cascades. We conducted experiments with in vivo global and focal cerebral ischemia/reperfusion rat models and in vitro oxygen glucose deprivation (OGD) neural cells. The effects of MCP on apoptotic cell death and infarction volume, the bioactivities of scavenging O2(-), NO and ONOO(-), inhibiting lipid peroxidation and modulating JNK3 signaling pathway were investigated. Major results are summarized as below: (1) MCP dose-dependently attenuated apoptotic cell death in neural cells under OGD condition in vitro and reduced infarction volume in ischemic brains in vivo; (2) MCP had directing scavenging effects on NO, O2(-) and ONOO(-) and inhibited lipid peroxidation; (3) MCP inhibited the activations of JNK3/c-Jun/Fas-L and JNK3/cytochrome C/caspases-3 signaling cascades in ischemic brains in vivo. Taken together, we conclude that MCP could be a promising neuroprotective ingredient of M. charantia and its mechanisms could be at least in part attributed to its antioxidant activities and inhibiting JNK3 signaling cascades during cerebral ischemia/reperfusion injury.

Site-2 protease responds to oxidative stress and regulates oxidative injury in mammalian cells

Site-2 protease (S2P) is a membrane-embedded protease that site-specifically cleaves intramembrane transcription factors, a necessary step for their maturation. S2P is well known to regulate cholesterol biosynthesis and endoplasmic reticulum stress in mammalian cells. In this study, we hypothesized that S2P could be responsible for the regulation of cellular oxidative injury under oxidative stress. Wild type Chinese hamster ovary (WT CHO) cells and their mutant M19 cells with defective S2P gene were exposed to different oxidative stress conditions. Results showed that oxidative stress significantly up-regulated S2P expression in WT CHO cells. Notably, M19 cells had remarkably higher level of superoxide and elevated rates of cell death than WT CHO cells. The vulnerability to oxidative stress was reversed by the transfection of S2P gene but not rescued by exogenous supplement of cholesterol, oleate, and mevalonate, indicating that lack of S2P gene leads cells to be more vulnerable to oxidative stress. Furthermore, compared with WT CHO cells, M19 cells had higher nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and lower paraoxonase-2 expression. Taken together, these results suggest that S2P can be a protease responding to oxidative stress and has the function of regulating cellular oxidative injury.

Maternal high-fat diet induces follicular atresia but does not affect fertility in adult rabbit offspring

Alterations to the metabolic environment in utero can have an impact on subsequent female reproductive performance. Here, we used a model of rabbits receiving a high-fat diet (H diet; 7.7% fat and 0.2% cholesterol) or a control diet (C diet; 1.8% fat, no cholesterol) from 10 weeks of age up to mating at 27 weeks and throughout gestation and lactation. At weaning at 5 weeks of age, F1 female offspring were placed on either C or H diet, resulting in a total of four groups C/C, C/H, H/C and H/H diet. Female offspring were mated between 18 and 22 weeks of age and euthanized at 28 days of gestation. A few days before mating and/or just before euthanasia, F1 female rabbits were fasted overnight, weighed, and blood sampled for steroids and biochemistry. Organs were weighed at euthanasia and the ovaries were collected. C/H and H/H F1 offspring had higher cholesterol and high-density lipoprotein plasma concentrations, together with a higher fat mass compared with C/C does, reflecting the effect of the postnatal diet; however, no effect of the antenatal diet was observed on most parameters. The number of primordial, primary and secondary follicles were not different between the groups, but a significantly higher number of atretic follicles was observed in the C/H (P<0.001) and in the H/C (P<0.001) compared with control C/C ovaries, demonstrating both an effect of prenatal and postnatal maternal nutrition. These data indicated that both maternal and postnatal high-fat diet may induce follicular apoptosis; however, in this model, the reproduction was not affected.

Pulmonary abnormalities in animal models due to Niemann-Pick type C1 (NPC1) or C2 (NPC2) disease

Niemann-Pick C (NPC) disease is due to loss of NPC1 or NPC2 protein function that is required for unesterified cholesterol transport from the endosomal/lysosomal compartment. Though lung involvement is a recognized characteristic of Niemann-Pick type C disease, the pathological features are not well understood. We investigated components of the surfactant system in both NPC1 mutant mice and felines and in NPC2 mutant mice near the end of their expected life span. Histological analysis of the NPC mutant mice demonstrated thickened septae and foamy macrophages/leukocytes. At the level of electron microscopy, NPC1-mutant type II cells had uncharacteristically larger lamellar bodies (LB, mean area 2-fold larger), while NPC2-mutant cells had predominantly smaller lamellar bodies (mean area 50% of normal) than wild type. Bronchoalveolar lavage from NPC1 and NPC2 mutant mice had an approx. 4-fold and 2.5-fold enrichment in phospholipid, respectively, and an approx. 9-fold and 35-fold enrichment in cholesterol, consistent with alveolar lipidosis. Phospholipid and cholesterol also were elevated in type II cell LBs and lung tissue while phospholipid degradation was reduced. Enrichment of surfactant protein-A in the lung and surfactant of the mutant mice was found. Immunocytochemical results showed that cholesterol accumulated in the LBs of the type II cells isolated from the affected mice. Alveolar macrophages from the NPC1 and NPC2 mutant mice were enlarged compared to those from wild type mice and were enriched in phospholipid and cholesterol. Pulmonary features of NPC1 mutant felines reflected the disease described in NPC1 mutant mice. Thus, with the exception of lamellar body size, the lung phenotype seen in the NPC1 and NPC2 mutant mice were similar. The lack of NPC1 and NPC2 proteins resulted in a disruption of the type II cell surfactant system contributing to pulmonary abnormalities.

Genome-wide association for sensitivity to chronic oxidative stress in Drosophila melanogaster

Reactive oxygen species (ROS) are a common byproduct of mitochondrial energy metabolism, and can also be induced by exogenous sources, including UV light, radiation, and environmental toxins. ROS generation is essential for maintaining homeostasis by triggering cellular signaling pathways and host defense mechanisms. However, an imbalance of ROS induces oxidative stress and cellular death and is associated with human disease, including age-related locomotor impairment. To identify genes affecting sensitivity and resistance to ROS-induced locomotor decline, we assessed locomotion of aged flies of the sequenced, wild-derived lines from the Drosophila melanogaster Genetics Reference Panel on standard medium and following chronic exposure to medium supplemented with 3 mM menadione sodium bisulfite (MSB). We found substantial genetic variation in sensitivity to oxidative stress with respect to locomotor phenotypes. We performed genome-wide association analyses to identify candidate genes associated with variation in sensitivity to ROS-induced decline in locomotor performance, and confirmed the effects for 13 of 16 mutations tested in these candidate genes. Candidate genes associated with variation in sensitivity to MSB-induced oxidative stress form networks of genes involved in neural development, immunity, and signal transduction. Many of these genes have human orthologs, highlighting the utility of genome-wide association in Drosophila for studying complex human disease.