Possibility of the regression of atherosclerosis through the prevention of endothelial senescence by the regulation of nitric oxide and free radical scavengers

Biological Potential and Mechanisms of Tea's Bioactive Compounds in Tea: An Updated Review

BACKGROUND

Tea (Camellia sinensis) has a rich history and is widely consumed across many countries, and is categorized into green tea, white tea, oolong tea, yellow tea, black tea, and dark tea based on the level of fermentation. Based on a review of previous literature, the commonly recognized bioactive substances in tea include tea polyphenols, amino acids, polysaccharides, alkaloids, terpenoids, macro minerals, trace elements, and vitamins, which have been known to have various potential health benefits, such as anticancer, antioxidant, anti-inflammatory, anti-diabetes, and anti-obesity properties, cardiovascular protection, immune regulation, and control of the intestinal microbiota. Most studies have only pointed out the characteristics of tea's bioactivities, so a comprehensive summary of the pharmacological characteristics and mechanisms of tea's bioactivities and their use risks are vital.

AIM

of Review The aim of this paper is to summarize the bioactive substances of tea and their pharmacological characteristics and mechanisms, providing a scientific basis for the application of bioactive substances in tea and outlining future research directions for the study of bioactive substances in tea. Key Scientific Concepts of Review This review summarizes the main biologically active substances, pharmacological effects, and mechanisms and discusses the potential risks. It may help researchers to grasp more comprehensive progress in the study of tea bioactive substances to further promote the application of tea as a natural bioactive substance in the medical field.

Retrospecting the Antioxidant Activity of Japanese Matcha Green Tea–Lack of Enthusiasm?

Matcha tea is a traditional Japanese tea that is said to possess ten times higher bioactive components and polyphenols than that of conventional green teas. Matcha is remotely popular among the global community and meagerly researched and infamous among the scientific population. It is the powdered form of green tea leaves that are directly suspended in hot water and drunk without filtration. Matcha is said to be one of the richest antioxidant sources naturally available. This review summarizes the available research publications related to matcha and compares the research accomplishments of green tea and matcha researchers. The fact that green tea is backed up by 35,000 publications while matcha has merely 54 publications to its credit is highlighted in this review for the first time. The future of matcha for tapping its enormous antioxidant activity and health potentials remains connected to the volume of scientific awareness and enhanced research attention in this area. If green tea has so much to offer towards human health and welfare, there is certainly room for more benefits from matcha, which is yet to be disclosed. As public awareness cannot be won without scientific approval, this review seeks that this gap may be bridged using essential knowledge gained from matcha applications and allied research.

Antioxidant mechanism of tea polyphenols and its impact on health benefits

Tea trees have a long history of cultivation and utilization. People in many countries have the habit of drinking tea and choosing green tea, oolong tea, or black tea according to different regions and personal tastes. Tea polyphenols are a general term for polyphenol compounds in tea, and has been shown to have good effects on antioxidant, anti-inflammatory, cancer prevention and regulation of lipid metabolism. Tea polyphenols have been widely used as antioxidants in disease treatment and animal husbandry, but their specific mechanism of action needs to be further clarified and revealed. This review focuses on the definition, classification, antioxidant activity and the regulation of signaling pathways of tea polyphenols. This paper also aims to examine the application of tea polyphenols in human and animal health, providing a scientific basis for this application in addition to proposing future directions for the development of this resource.

Senescent Microvesicles: A Novel Advance in Molecular Mechanisms of Atherosclerotic Calcification

Atherosclerosis, a chronic inflammatory disease that causes the most heart attacks and strokes in humans, is the leading cause of death in the developing world; its principal clinical manifestation is coronary artery disease. The development of atherosclerosis is attributed to the aging process itself (biological aging) and is also associated with the development of chronic diseases (premature aging). Both aging processes produce an increase in risk factors such as oxidative stress, endothelial dysfunction and proinflammatory cytokines (oxi-inflamm-aging) that might generate endothelial senescence associated with damage in the vascular system. Cellular senescence increases microvesicle release as carriers of molecular information, which contributes to the development and calcification of atherosclerotic plaque, as a final step in advanced atherosclerotic plaque formation. Consequently, this review aims to summarize the information gleaned to date from studies investigating how the senescent extracellular vesicles, by delivering biological signalling, contribute to atherosclerotic calcification.

Premature senescence of endothelial cells upon chronic exposure to TNFα can be prevented by N-acetyl cysteine and plumericin

Cellular senescence is characterized by a permanent cell-cycle arrest and a pro-inflammatory secretory phenotype, and can be induced by a variety of stimuli, including ionizing radiation, oxidative stress, and inflammation. In endothelial cells, this phenomenon might contribute to vascular disease. Plasma levels of the inflammatory cytokine tumor necrosis factor alpha (TNFα) are increased in age-related and chronic conditions such as atherosclerosis, rheumatoid arthritis, psoriasis, and Crohn's disease. Although TNFα is a known activator of the central inflammatory mediator NF-κB, and can induce the intracellular generation of reactive oxygen species (ROS), the question whether TNFα can induce senescence has not been answered conclusively. Here, we investigated the effect of prolonged TNFα exposure on the fate of endothelial cells and found that such treatment induced premature senescence. Induction of endothelial senescence was prevented by the anti-oxidant N-acetyl cysteine, as well as by plumericin and PHA-408, inhibitors of the NF-κB pathway. Our results indicated that prolonged TNFα exposure could have detrimental consequences to endothelial cells by causing senescence and, therefore, chronically increased TNFα levels might possibly contribute to the pathology of chronic inflammatory diseases by driving premature endothelial senescence.

Leucine supplementation via drinking water reduces atherosclerotic lesions in apoE null mice

AIM

Recent evidence suggests that the essential amino acid leucine may be involved in systemic cholesterol metabolism. In this study, we investigated the effects of leucine supplementation on the development of atherosclerosis in apoE null mice.

METHODS

ApoE null mice were fed with chow supplemented with leucine (1.5% w/v) in drinking water for 8 week. Aortic atherosclerotic lesions were examined using Oil Red O staining. Plasma lipoprotein-cholesterol levels were measured with fast protein liquid chromatography. Hepatic gene expression was detected using real-time PCR and Western blot analyses.

RESULTS

Leucine supplementation resulted in 57.6% reduction of aortic atherosclerotic lesion area in apoE null mice, accompanied by 41.2% decrease of serum LDL-C levels and 40.2% increase of serum HDL-C levels. The body weight, food intake and blood glucose level were not affected by leucine supplementation. Furthermore, leucine supplementation increased the expression of Abcg5 and Abcg8 (that were involved in hepatic cholesterol efflux) by 1.28- and 0.86-fold, respectively, and significantly increased their protein levels. Leucine supplementation also increased the expression of Srebf1, Scd1 and Pgc1b (that were involved in hepatic triglyceride metabolism) by 3.73-, 1.35- and 1.71-fold, respectively. Consequently, leucine supplementation resulted in 51.77% reduction of liver cholesterol content and 2.2-fold increase of liver triglyceride content. Additionally, leucine supplementation did not affect the serum levels of IL-6, IFN-γ, TNF-α, IL-10 and IL-12, but markedly decreased the serum level of MCP-1.

CONCLUSION

Leucine supplementation effectively attenuates atherosclerosis in apoE null mice by improving the plasma lipid profile and reducing systemic inflammation.

Efficacy of female rat models in translational cardiovascular aging research

Cardiovascular disease is the leading cause of death in women in the United States. Aging is a primary risk factor for the development of cardiovascular disease as well as cardiovascular-related morbidity and mortality. Aging is a universal process that all humans undergo; however, research in aging is limited by cost and time constraints. Therefore, most research in aging has been done in primates and rodents; however it is unknown how well the effects of aging in rat models translate into humans. To compound the complication of aging gender has also been indicated as a risk factor for various cardiovascular diseases. This review addresses the systemic pathophysiology of the cardiovascular system associated with aging and gender for aging research with regard to the applicability of rat derived data for translational application to human aging.

Adult Stem Cells and Diseases of Aging

Preservation of adult stem cells pools is critical for maintaining tissue homeostasis into old age. Exhaustion of adult stem cell pools as a result of deranged metabolic signaling, premature senescence as a response to oncogenic insults to the somatic genome, and other causes contribute to tissue degeneration with age. Both progeria, an extreme example of early-onset aging, and heritable longevity have provided avenues to study regulation of the aging program and its impact on adult stem cell compartments. In this review, we discuss recent findings concerning the effects of aging on stem cells, contributions of stem cells to age-related pathologies, examples of signaling pathways at work in these processes, and lessons about cellular aging gleaned from the development and refinement of cellular reprogramming technologies. We highlight emerging therapeutic approaches to manipulation of key signaling pathways corrupting or exhausting adult stem cells, as well as other approaches targeted at maintaining robust stem cell pools to extend not only lifespan but healthspan.

Arginase in retinopathy

Ischemic retinopathies, such as diabetic retinopathy (DR), retinopathy of prematurity and retinal vein occlusion are a major cause of blindness in developed nations worldwide. Each of these conditions is associated with early neurovascular dysfunction. However, conventional therapies target clinically significant macula edema or neovascularization, which occur much later. Intra-ocular injections of anti-VEGF show promise in reducing retinal edema, but the effects are usually transient and the need for repeated injections increases the risk of intraocular infection. Laser photocoagulation can control pathological neovascularization, but may impair vision and in some patients the retinopathy continues to progress. Moreover, neither treatment targets early stage disease or promotes repair. This review examines the potential role of the ureahydrolase enzyme arginase as a therapeutic target for the treatment of ischemic retinopathy. Arginase metabolizes l-arginine to form proline, polyamines and glutamate. Excessive arginase activity reduces the l-arginine supply for nitric oxide synthase (NOS), causing it to become uncoupled and produce superoxide and less NO. Superoxide and NO react and form the toxic oxidant peroxynitrite. The catabolic products of polyamine oxidation and glutamate can induce more oxidative stress and DNA damage, both of which can cause cellular injury. Studies indicate that neurovascular injury during retinopathy is associated with increased arginase expression/activity, decreased NO, polyamine oxidation, formation of superoxide and peroxynitrite and dysfunction and injury of both vascular and neural cells. Furthermore, data indicate that the cytosolic isoform arginase I (AI) is involved in hyperglycemia-induced dysfunction and injury of vascular endothelial cells whereas the mitochondrial isoform arginase II (AII) is involved in neurovascular dysfunction and death following hyperoxia exposure. Thus, we postulate that activation of the arginase pathway causes neurovascular injury by uncoupling NOS and inducing polyamine oxidation and glutamate formation, thereby reducing NO and increasing oxidative stress, all of which contribute to the retinopathic process.

Quantifying the evolution of vascular barrier disruption in advanced atherosclerosis with semipermeant nanoparticle contrast agents

Rationale

Acute atherothrombotic occlusion in heart attack and stroke implies disruption of the vascular endothelial barrier that exposes a highly procoagulant intimal milieu. However, the evolution, severity, and pathophysiological consequences of vascular barrier damage in atherosclerotic plaque remain unknown, in part because quantifiable methods and experimental models are lacking for its in vivo assessment.

Objective

To develop quantitative nondestructive methodologies and models for detecting vascular barrier disruption in advanced plaques.

Methods and Results

Sustained hypercholesterolemia in New Zealand White (NZW) rabbits for >7–14 months engendered endothelial barrier disruption that was evident from massive and rapid passive penetration and intimal trapping of perfluorocarbon-core nanoparticles (PFC-NP: ∼250 nm diameter) after in vivo circulation for as little as 1 hour. Only older plaques (>7 mo), but not younger plaques (<3 mo) demonstrated the marked enhancement of endothelial permeability to these particles. Electron microscopy revealed a complex of subintimal spongiform channels associated with endothelial apoptosis, superficial erosions, and surface-penetrating cholesterol crystals. Fluorine (¹⁹F) magnetic resonance imaging and spectroscopy (MRI/MRS) enabled absolute quantification (in nanoMolar) of the passive permeation of PFC-NP into the disrupted vascular lesions by sensing the unique spectral signatures from the fluorine core of plaque-bound PFC-NP.

Conclusions

The application of semipermeant nanoparticles reveals the presence of profound barrier disruption in later stage plaques and focuses attention on the disrupted endothelium as a potential contributor to plaque vulnerability. The response to sustained high cholesterol levels yields a progressive deterioration of the vascular barrier that can be quantified with fluorine MRI/MRS of passively permeable nanostructures. The possibility of plaque classification based on the metric of endothelial permeability to nanoparticles is suggested.