Hypercapnic hypoxia as a potential means to extend life expectancy and improve physiological activity in mice

The potential longevity-promoting hypoxic-hypercapnic environment as a measure for radioprotection

Many biological mechanisms of aging well converge with radiation's biological effects. We used scientific insights from the field of aging to establish a novel hypoxic-hypercapnic environment (HHE) concept for radioprotection. According to this concept, HHE which possesses an anti-aging and longevity-promoting potential, should also act as a radiomitigator and radioprotector. As such, it might contribute greatly to the safety and wellbeing of individuals exposed to high levels of radiation, whether in planned events (e.g. astronauts) or in unplanned events (e.g. first responders in nuclear accidents).

Healthy Aging at Moderate Altitudes: Hypoxia and Hormesis

BACKGROUND

Aging is associated with cellular and tissue responses that collectively lead to functional and structural deterioration of tissues. Poor tissue oxygenation, or hypoxia, is involved in such responses and contributes to aging. Consequently, it could be speculated that living at higher altitude, and therefore in hypoxic conditions, accelerates aging. This assumption is indeed supported by evidence from populations residing at very high altitudes (>3,500 m). In contrast, accumulating evidence suggests that living at moderate altitudes (1,500-2,500 m) is protective rather than injurious, at least for some body systems.

SUMMARY

In this review, we critically evaluate the hypothesis that the physiological responses to mild hypoxic stress associated to life at moderate altitudes provide protection from many hypoxia-related diseases through hormesis. Hormesis means that a low dose of a stressor (here hypoxia) elicits beneficial outcomes, while a higher dose can be toxic and might explain at least in part the dose-dependent contrasting effects of hypoxia on the aging processes. The lack of well-designed longitudinal studies focusing on the role of the altitude of residence, and difficulties in accounting for potentially confounding factors such as migration, ethnicity/genetics, and socioeconomic and geoclimatic conditions, currently hampers translation of related research into uncontroversial paradigms.

KEY MESSAGES

Deeper investigations are required to understand the impact of altitude-related hypoxia on age-related diseases and to develop molecular markers of ageing/senescence in humans that are linked to hypoxia. However, the presented emerging evidence supports the view that hypoxia conditioning has the potential to improve life quality and expectancy.

Sport and longevity: an observational study of international athletes

The human lifespan is influenced by various factors, with physical activity being a significant contributor. Despite the clear benefit of exercise on health and longevity, the association between different types of sports and lifespan is yet to be considered. Accordingly, we aimed to study this association in a large international cohort of former athletes using a robust linear regression model. We collected data on athletes from public sources, accumulating a total of 95,210 observations, 95.5% of which were accounted for by males. The dataset represented athletes born between 1862 and 2002 from 183 countries across 44 sports disciplines. We calculated the change in lifespan by measuring the difference in age between athletes and the corresponding reference populations, while accounting for variations caused by sex, year of death, and country. The results revealed that various sports impacted lifespan differently, with male athletes being more likely to experience benefits from sports than female athletes. Among male athletes, pole vaulting and gymnastics were linked to the highest extension in lifespan (8.4 years, 95% CI [6.8, 9.9] and 8.2 years, 95% CI [7.4, 9], respectively), while volleyball and sumo wrestling were the most negatively associated with lifespan (- 5.4 years, 95% CI [- 7, - 3.8]; - 9.8 years, 95% CI [- 11, - 8.6], respectively). The association between lifespan and popular team sports in males was positive for cricket, rowing, baseball, water polo, Australian rules, hurling, lacrosse, field hockey, minimal for rugby, canoeing and kayaking, basketball, gridiron football, and football (soccer), and negative for handball and volleyball. Racquet sports (i.e., tennis and badminton) exhibited a consistent and positive association in both male and female athletes, as shown by an extended lifespan of up to 5.7 years in males (95% CI [5, 6.5]) and 2.8 years in females (95% CI [1.8, 3.9]). Although lacking conclusive evidence, we theorize that the observed results may be attributed to the aerobic and anaerobic characteristics of each sport, with mixed sports yielding the maximum benefits for the lifespan. While results from female athletes should be cautiously interpreted, our study highlights the complex interplay between sports and lifespan and contributes to the growing body of knowledge on the multifaceted relationship between physical activity and human longevity.

Relationship between Hypoxia and Hypercapnia Tolerance and Life Expectancy

The review discusses the potential relationship between hypoxia resistance and longevity, the influence of carbon dioxide on the mechanisms of aging of the mammalian organism, and intermittent hypercapnic-hypoxic effects on the signaling pathways of aging mechanisms. In the article, we focused on the potential mechanisms of the gero-protective efficacy of carbon dioxide when combined with hypoxia. The review summarizes the possible influence of intermittent hypoxia and hypercapnia on aging processes in the nervous system. We considered the perspective variants of the application of hypercapnic-hypoxic influences for achieving active longevity and the prospects for the possibilities of developing hypercapnic-hypoxic training methods.

The skin of the naked mole-rat and its resilience against aging and cancer

The naked mole-rat (NMR) Heterocephalus glaber (from the Greek/latin words ἕτερος, heteros = divergent, κεφαλή, kephalē = head and glabra = hairless) was first described by Rüppell (Fig. 1) and belongs to the Hystricognath (from the Greek words ὕστριξ, hystrix = porcupine and γνάθος, gnathos = jaw) as a suborder of rodents. NMR are characterized by the highest longevity among rodents and reveal a profound cancer resistance. Details of its skin-specific protective and resistance mechanisms against aging and carcinogenesis have so far not been adequately characterized. Recently, our knowledge of NMR skin biology was complemented and expanded by published data using state-of-the art histological and molecular techniques. Here we review and integrate novel published data regarding skin morphology and histology of the aging NMR and the underlying mechanisms at the cellular and molecular level. We relate this data to the longevity of the NMR and its resistance to neoplastic transformation and discuss further open questions to understand its extraordinary longevity. In addition, we will address the exposome, defined as "the total of all non-genetic, endogenous and exogenous environmental influences" on the skin, respiratory tract, stomach, and intestine. Finally, we will discuss in perspective further intriguing possibilities arising from the interaction of skin with other organs.

The Naked Mole-Rat as a Model for Healthy Aging

Naked mole-rats (NMRs, Heterocephalus glaber) are the longest-lived rodents with a maximum life span exceeding 37 years. They exhibit a delayed aging phenotype and resistance to age-related functional decline/diseases. Specifically, they do not display increased mortality with age, maintain several physiological functions until nearly the end of their lifetime, and rarely develop cancer and Alzheimer's disease. NMRs live in a hypoxic environment in underground colonies in East Africa and are highly tolerant of hypoxia. These unique characteristics of NMRs have attracted considerable interest from zoological and biomedical researchers. This review summarizes previous studies of the ecology, hypoxia tolerance, longevity/delayed aging, and cancer resistance of NMRs and discusses possible mechanisms contributing to their healthy aging. In addition, we discuss current issues and future perspectives to fully elucidate the mechanisms underlying delayed aging and resistance to age-related diseases in NMRs.

Hypercapnic hypoxia improves cognitive and motor functions of children with cerebral palsy

A randomized, triple-blind, placebo-controlled trial involving 42 patients between 3 and 7 years of age with spastic cerebral palsy was performed. For the treatment test group (n=22), daily respiratory exercises with hypercapnic hypoxia were performed using a Carbonic training apparatus for 20 minutes per day; a total of 14 to 16 sessions were performed. Before the start of the study and the day after training was completed, the patients underwent neurological and neurophysiological examinations (electroencephalography, magnetic stimulation of the pyramidal tract, and cognitive potentials Р300).The evoked potentials showed a decrease in the peak latency of the P3 component of the test group after treatment (302 ms) that was more pronounced than that of the placebo group (305 ms; p<0.05). Magnetic stimulation showed that hypercapnic hypoxic training resulted in reductions in central motor conduction time by 2.2 to 2.5 ms (p<0.05) and in the excitation threshold of the motor cortex by 12% to 16% (р<0.01) depending on the lateralization; The strategy of adjusting to hypercapnic hypoxia, either unfavorable (hyperventilation and avoidance) or favorable (homeostatic with the achievement of preset values for hypercapnia and hypoxia), did not change during the process of training in the placebo group; however, it shifted considerably toward favorable (from 33% to 57%; р<0.05) in the test group.Respiratory training with hypercapnic hypoxia can have a positive impact on the functional state of the nervous system of children with cerebral palsy and can be considered a method of improving the efficiency of standard therapy.

Deciphering the whale's secrets to have a long life

Whales are marine creatures known for their enormous size and that live in all the oceans on earth. One of the oldest known organisms is bowhead whales, which can survive up to 200 years, and similarly, other species of whales have shown a remarkable long lifespan. In addition to this, whales are highly resistant to cancer, a disease that is strongly related to aging and the accumulation of damage over time. These two characteristics make whales an interesting model to study and that can provide us with a track both to delay aging and to avoid pathologies associated with it, such as cancer. In the present work, we try to analyze different aspects of whales such as metabolism, hematological and biochemical characteristics, and properties of their genome and transcriptome in order to elucidate possible molecular mechanisms that evolution has provided to these aquatic mammals.

To breathe or not to breathe: Understanding how oxygen sensing contributes to age-related phenotypes

Aging is characterized by a progressive loss of tissue integrity and functionality due to disrupted homeostasis. Molecular oxygen is pivotal to maintain tissue functions, and aerobic species have evolved a sophisticated sensing system to ensure proper oxygen supply and demand. It is not surprising that aberrations in oxygen and oxygen-associated pathways subvert health and promote different aspects of aging. In this review, we discuss emerging findings on how oxygen-sensing mechanisms regulate different cellular and molecular processes during normal physiology, and how dysregulation of oxygen availability lead to disease and aging. We describe various clinical manifestations associated with deregulation of oxygen balance, and how oxygen-modulating therapies and natural oxygen oscillations influence longevity. We conclude by discussing how a better understanding of oxygen-related mechanisms that orchestrate aging processes may lead to the development of new therapeutic strategies to extend healthy aging.

Rejuvenation Through Oxygen, More or Less

Modest modulation of oxygen intake, either by inducing mild intermittent hypoxia or hyperoxia appears to induce modest rejuvenative changes in mammals, in part, by activating key regulator hypoxia-induced factor 1a (HIF-1a). Interestingly both lower oxygen and transient higher oxygen levels induce this hypoxia regulator. Hyperbaric oxygen induces HIF-1a by the hyperoxic-hypoxic paradox that results from an overinduction of protective factors under intermittent hyperoxic conditions, leading to a state somewhat similar to that induced by hypoxia. A key difference being that SIRT1 is induced by hyperoxia, whereas it is reduced during hypoxia by the activity of HIF-1a. In a recent report, a small clinical trial employing 60 sessions of intermittent hyperbaric oxygen therapy (HBOT) studying old humans resulted in increased mean telomere length of immune cells including B cells, natural killer cells, T helper, and cytotoxic T lymphocytes. Moreover, there was a reduction in CD28^null senescent T helper and cytotoxic T cells. In a parallel report, HBOT has been reported to enhance cognition in older adults, especially attention and information processing speed through increased cerebral blood flow (CBF) in brain regions where CBF tends to decline with age. The durability of these beneficial changes is yet to be determined. These preliminary results require follow-up, including more extensive characterization of changes in aging-associated biomarkers. An interesting avenue of potential work is to elucidate potential connections between hypoxia and epigenetics, especially the induction of the master pluripotent regulatory factors, which when expressed transiently have been reported to ameliorate some aging biomarkers and pathologies.