Lability of the Nrf2/Keap/ARE Cell Defense System in Different Models of Cell Aging and Age-Related Pathologies

Evolution of Longevity in Tetrapods: Safety Is More Important than Metabolism Level

Various environmental morphological and behavioral factors can determine the longevity of representatives of various taxa. Long-lived species develop systems aimed at increasing organism stability, defense, and, ultimately, lifespan. Long-lived species to a different extent manifest the factors favoring longevity (gerontological success), such as body size, slow metabolism, activity of body's repair and antioxidant defense systems, resistance to toxic substances and tumorigenesis, and presence of neotenic features. In continuation of our studies of mammals, we investigated the characteristics that distinguish long-lived ectotherms (crocodiles and turtles) and compared them with those of other ectotherms (squamates and amphibians) and endotherms (birds and mammals). We also discussed mathematical indicators used to assess the predisposition to longevity in different species, including standard indicators (mortality rate, maximum lifespan, coefficient of variation of lifespan) and their derivatives. Evolutionary patterns of aging are further explained by the protective phenotypes and life history strategies. We assessed the relationship between the lifespan and various studied factors, such as body size and temperature, encephalization, protection of occupied ecological niches, presence of protective structures (for example, shells and osteoderms), and environmental temperature, and the influence of these factors on the variation of the lifespan as a statistical parameter. Our studies did not confirm the hypothesis on the metabolism level and temperature as the most decisive factors of longevity. It was found that animals protected by shells (e.g., turtles with their exceptional longevity) live longer than species that have poison or lack such protective adaptations. The improvement of defense against external threats in long-lived ectotherms is consistent with the characteristics of long-lived endotherms (for example, naked mole-rats that live in underground tunnels, or bats and birds, whose ability to fly is one of the best defense mechanisms).

Recent progress and applications of small molecule inhibitors of Keap1-Nrf2 axis for neurodegenerative diseases

The Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) pathway serves as a crucial regulator against oxidative stress (OS) damage in various cells and organs. It has garnered significant attention as a potential therapeutic target for neurodegenerative diseases (NDD). Although progress has been achieved in strategies to regulate the Keap1-Nrf2 pathway, the availability of Nrf2 activators applicable to NDD is currently limited. Currently, the FDA has approved the Nrf2 activators dimethyl fumarate (DMF) and Omaveloxolone (Omav) as novel first-line oral drugs for the treatment of patients with relapsing forms of multiple sclerosis and Friedreich's ataxia. A promising alternative approach involves the direct inhibition of Keap1-Nrf2 protein-protein interactions (PPI), which offers numerous advantages over the use of electrophilic Nrf2 activators, primarily in avoiding off-target effects. This review examines the compelling evidence supporting the beneficial role of Nrf2 in NDD and explores the potential of Keap1 inhibitors and Keap1-Nrf2 PPI inhibitors as therapeutic agents, with the aim to provide further insights into the development of inhibitors targeting this pathway for the treatment of NDD.

Evolution of Longevity as a Species-Specific Trait in Mammals

From the evolutionary point of view, the priority problem for an individual is not longevity, but adaptation to the environment associated with the need for survival, food supply, and reproduction. We see two main vectors in the evolution of mammals. One is a short lifespan and numerous offspring ensuring reproductive success (r-strategy). The other one is development of valuable skills in order compete successfully (K-strategy). Species with the K-strategy should develop and enhance specific systems (anti-aging programs) aimed at increasing the reliability and adaptability, including lifespan. These systems are signaling cascades that provide cell repair and antioxidant defense. Hence, any arbitrarily selected long-living species should be characterized by manifestation to a different extent of the longevity-favoring traits (e.g., body size, brain development, sociality, activity of body repair and antioxidant defense systems, resistance to xenobiotics and tumor formation, presence of neotenic traits). Hereafter, we will call a set of such traits as the gerontological success of a species. Longevity is not equivalent to the evolutionary or reproductive success. This difference between these phenomena reaches its peak in mammals due to the development of endothermy and cephalization associated with the cerebral cortex expansion, which leads to the upregulated production of oxidative radicals by the mitochondria (and, consequently, accelerated aging), increase in the number of non-dividing differentiated cells, accumulation of the age-related damage in these cells, and development of neurodegenerative diseases. The article presents mathematical indicators used to assess the predisposition to longevity in different species (including the standard mortality rate and basal metabolic rate, as well as their derivatives). The properties of the evolution of mammals (including the differences between modern mammals and their ancestral forms) are also discussed.

Transcription Factor Nrf2 and Mitochondria - Friends or Foes in the Regulation of Aging Rate

At the first sight, the transcription factor Nrf2 as a master regulator of cellular antioxidant systems, and mitochondria as the main source of reactive oxygen species (ROS), should play the opposite roles in determining the pace of aging. However, since the causes of aging cannot be confined to the oxidative stress, the role of Nrf2 role cannot be limited to the regulation of antioxidant systems, and moreover, the role of mitochondria is not confined to the ROS production. In this review, we discussed only one aspect of this problem, namely, the molecular mechanisms of interaction between Nrf2 and mitochondria that influence the rate of aging and the lifespan. Experimental data accumulated so far show that the Nrf2 activity positively affects both the mitochondrial dynamics and mitochondrial quality control. Nrf2 influences the mitochondrial function through various mechanisms, e.g., regulation of nuclear genome-encoded mitochondrial proteins and changes in the balance of ROS or other metabolites that affect the functioning of mitochondria. In turn, multiple regulatory proteins functionally associated with the mitochondria affect the Nrf2 activity and even form mutual regulatory loops with Nrf2. We believe that these loops enable the fine-tuning of the cellular redox balance and, possibly, of the cellular metabolism as a whole. It has been commonly accepted for a long time that all mitochondrial regulatory signals are mediated by the nuclear genome-encoded proteins, whereas the mitochondrial genome encodes only a few respiratory chain proteins and two ribosomal RNAs. Relatively recently, mtDNA-encoded signal peptides have been discovered. In this review, we discuss the data on their interactions with the nuclear regulatory systems, first of all, Nrf2, and their possible involvement in the regulation of the aging rate. The interactions between regulatory cascades that link the programs ensuring the maintenance of cellular homeostasis and cellular responses to the oxidative stress are a significant part of both aging and anti-aging programs. Therefore, understanding these interactions will be of great help in searching for the molecular targets to counteract aging-associated diseases and aging itself.

Does Nrf2 Play a Role of a Master Regulator of Mammalian Aging?

For a long time Nrf2 transcription factor has been attracting attention of researchers investigating phenomenon of aging. Numerous studies have investigated effects of Nrf2 on aging and cell senescence. Nrf2 is often considered as a key player in aging processes, however this needs to be proven. It should be noted that most studies were carried out on invertebrate model organisms, such as nematodes and fruit flies, but not on mammals. This paper briefly presents main mechanisms of mammalian aging and role of inflammation and oxidative stress in this process. The mechanisms of Nrf2 activity regulation, its involvement in aging and development of the senescence-associated secretory phenotype (SASP) are also discussed. Main part of this review is devoted to critical analysis of available experimental data on the role of Nrf2 in mammalian aging.

In Vitro Study of the Therapeutic Potential of Brown Crude Fucoidans in Osteoarthritis Treatment

Osteoarthritis, one of the most common joint degenerative pathologies, still has no cure, and current treatments, such as nonsteroidal anti-inflammatory drugs, can cause serious adverse effects when taken for a long time. Brown seaweed crude fucoidans are used for the clinical treatment of several pathologies. In this study, the therapeutical potential of these biocompounds was analyzed in primary chondrocytes and the 260TT human chondrocyte cell line. Crude fucoidan from Undaria pinnatifida (Up) and Sargassum muticum (Sm) was obtained by different extraction techniques (microwave-assisted extraction, pressurized hot-water extraction, ultrasound-assisted extraction) and chemically and structurally characterized by Fourier transform infrared spectroscopy, high-performance size-exclusion chromatography, proton nuclear magnetic resonance, and scanning electron microscopy. Once cell viability was confirmed in chondrocytes treated with crude fucoidans, we evaluated their anti-inflammatory effects, observing a significant reduction in IL-6 production stimulated by IL-1β. Findings were confirmed by analysis of IL-6 and IL-8 gene expression, although only fucoidans from Up achieved a statistically significant reduction. Besides this, the antioxidant capacity of crude fucoidans was observed through the upregulation of Nrf-2 levels and the expression of its transcriptional target genes HO-1 and SOD-2, with compounds from Up again showing a more consistent effect. However, no evidence was found that crude fucoidans modulate senescence, as they failed to reduced β-galactosidase activity, cell proliferation, or IL-6 production in chondrocytes stimulated with etoposide. Thus, the findings of this research seem to indicate that the tested crude fucoidans are capable of partially alleviating OA-associated inflammation and oxidative stress, but fail to attenuate chondrocyte senescence.

Neuroprotective Capability of Narcissoside in 6-OHDA-Exposed Parkinson's Disease Models through Enhancing the MiR200a/Nrf-2/GSH Axis and Mediating MAPK/Akt Associated Signaling Pathway

We assessed the antioxidant potential of narcissoside from Sambucus nigra flowers (elderflowers) in Parkinson's disease models in vitro and in vivo. The results showed that narcissoside lessened the 6-hydroxydopamine (6-OHDA)-induced increase in reactive oxygen species (ROS) and apoptosis in SH-SY5Y cells. In the 6-OHDA-exposed Caenorhabditis elegans model, narcissoside reduced degeneration of dopaminergic neurons and ROS generation, and also improved dopamine-related food-sensitive behavior and shortened lifespan. Moreover, NCS increased total glutathione (GSH) by increasing the expression of the catalytic subunit and modifier subunit of γ-glutamylcysteine ligase in cells and nematodes. Treatment with a GSH inhibitor partially abolished the anti-apoptotic ability of narcissoside. Furthermore, narcissoside diminished the 6-OHDA-induced phosphorylation of JNK and p38, while rising activities of ERK and Akt in resisting apoptosis. The antioxidant response element (ARE)-luciferase reporter activity analysis and electromobility gel shift assay showed that narcissoside promotes the transcriptional activity mediated by Nrf2. Finally, we found that narcissoside augmented the expression of miR200a, a translational inhibitor of the Nrf2 repressor protein Keap1. Downregulation of Nrf2 and miR200a by RNAi and anti-miR200a, respectively, reversed the neuroprotective ability of narcissoside. In summary, narcissoside can enhance the miR200a/Nrf2/GSH antioxidant pathway, alleviate 6-OHDA-induced apoptosis, and has the neuroprotective potential.