Shortwave UV-Induced Damage as Part of the Solar Damage Spectrum Is Not a Major Contributor to Mitochondrial Dysfunction

Modeling of the Senescence-Associated Phenotype in Human Skin Fibroblasts

Modern understanding of aging is based on the accumulation of cellular damage during one’s life span due to the gradual deterioration of regenerative mechanisms in response to the continuous effect of stress, lifestyle, and environmental factors, followed by increased morbidity and mortality. Simultaneously, the number of senescent cells accumulate exponentially as organisms age. Cell culture models are valuable tools to investigate the mechanisms of aging by inducing cellular senescence in stress-induced premature senescence (SIPS) models. Here, we explain the three-step and one-step H₂O₂-induced senescence models of SIPS designed and reproduced on different human dermal fibroblast cell lines (CCD-1064Sk, CCD-1135Sk, and BJ-5ta). In both SIPS models, it was evident that the fibroblasts developed similar aging characteristics as cells with replicative senescence. Among the most noticeable senescent biomarkers were increased β-Gal expression, high levels of the p21 protein, altered levels of cell-cycle regulators (i.e., CDK2 and c-Jun), compromised extracellular matrix (ECM) composition, reduced cellular viability, and delayed wound healing properties. Based on the significant increase in senescence biomarkers in fibroblast cultures, reduced functional activity, and metabolic dysfunction, the one-step senescence model was chosen as a feasible and reliable method for future testing of anti-aging compounds.

The Role of microRNAs in Organismal and Skin Aging

The aging process starts directly after birth and lasts for the entire lifespan; it manifests itself with a decline in an organism’s ability to adapt and is linked to the development of age-related diseases that eventually lead to premature death. This review aims to explore how microRNAs (miRNAs) are involved in skin functioning and aging. Recent evidence has suggested that miRNAs regulate all aspects of cutaneous biogenesis, functionality, and aging. It has been noted that some miRNAs were down-regulated in long-lived individuals, such as let-7, miR-17, and miR-34 (known as longevity-related miRNAs). They are conserved in humans and presumably promote lifespan prolongation; conversely, they are up-regulated in age-related diseases, like cancers. The analysis of the age-associated cutaneous miRNAs revealed the increased expression of miR-130, miR-138, and miR-181a/b in keratinocytes during replicative senescence. These miRNAs affected cell proliferation pathways via targeting the p63 and Sirtuin 1 mRNAs. Notably, miR-181a was also implicated in skin immunosenescence, represented by the Langerhans cells. Dermal fibroblasts also expressed increased the levels of the biomarkers of aging that affect telomere maintenance and all phases of the cellular life cycle, such as let-7, miR-23a-3p, 34a-5p, miR-125a, miR-181a-5p, and miR-221/222-3p. Among them, the miR-34 family, stimulated by ultraviolet B irradiation, deteriorates collagen in the extracellular matrix due to the activation of the matrix metalloproteinases and thereby potentiates wrinkle formation. In addition to the pro-aging effects of miRNAs, the plausible antiaging activity of miR-146a that antagonized the UVA-induced inhibition of proliferation and suppressed aging-related genes (e.g., p21WAF-1, p16, and p53) through targeting Smad4 has also been noticed. Nevertheless, the role of miRNAs in skin aging is still not fully elucidated and needs to be further discovered and explained.

mRNA expression of ageing-associated genes in calorie reduction is subject to donor variability and can be induced by calorie restriction mimetics

BACKGROUND

Finding ways to a healthier ageing are increasingly becoming the focus of geriatric research. One way to accomplish this could be calorie restriction, as this is known to positively influence the ageing of model organisms.

AIM

The aim of this study was to investigate the influence of calorie reduction (F. X. Mayr therapy) and of the calorie restriction mimetics resveratrol and spermidine on the expression of ageing-associated genes.

METHODS

mRNA expression in peripheral blood mononuclear cells (PBMCs) of 18 participants taking part in an F. X. Mayr therapy was analysed. The PBMCs of one additional participant were treated ex vivo with spermidine or resveratrol. mRNA expression of SIRT1, SIRT3, FOXO3 and SOD2 was determined for these two calorie restriction mimetics. For the F. X. Mayr therapy samples, mRNA of XPA was analysed additionally.

RESULTS

mRNA expression of the ageing-associated genes showed a distinct donor variation during F. X. Mayr therapy, with a significant increase in mRNA expression of SIRT1. Expression of XPA was similar to SIRT1, with a significant correlation at the last time point tested. Spermidine treatment of PBMCs resulted in a significantly increased expression of all genes tested, whereas resveratrol treatment caused a significant increase of SIRT3, FOXO3 and SOD2 mRNA expression.

CONCLUSIONS

By increasing SIRT1 and XPA mRNA expression, calorie reduction in the form of F. X. Mayr therapy could contribute to a healthier ageing; however, the donor variability observed showed that not everyone benefited from this. Calorie restriction mimetics may be an option for promote healthier ageing for those who do not benefit from calorie reduction.

12 days of in vivo caloric reduction can improve important parameters of aging in humans

Caloric reduction (CR) is considered as the most reasonable intervention to delay aging and age-related diseases. Numerous studies in various model organisms provide the main basis for this hypothesis. Human studies exist, but they differ widely in study design, characteristics of test persons and study outcome. In this study we investigated CR in humans on a molecular level to gain a better understanding in these processes. For that purpose, we analyzed human peripheral blood mononuclear cells of healthy people fasting according to F.X. Mayr. In a previous study our group could show a significantly improved DNA repair capacity after fasting. Here we were able to confirm these findings despite a slightly modified fasting therapy. Furthermore, the function of the mitochondrial respiratory chain and the mRNA levels of the mitochondria-associated genes SIRT3 and NDUFS1 were significantly affected by CR. However, these changes were only detectable in people who exhibited no improvement in DNA repair capacity. In contrast to that we could not observe any changes in ROS levels, mitochondrial DNA copy number and non-mitochondrial respiration. Altogether our results reveal that CR in form of F. X. Mayr therapy is able to positively influence several cellular parameters and especially mitochondrial function.

A New Efficient Method for Measuring Oxygen Consumption Rate Directly ex vivo in Human Epidermal Biopsies

Skin cells are constantly exposed to environmental influences such as air pollution, chemicals, pathogens and UV radiation. UV radiation can damage different biological structures, but most importantly cellular DNA. Mitochondria contain their own genome and accumulate UV-induced DNA mutations to a large extent. This can result, e.g., in accelerated skin aging. Understanding the impact of harmful external influences on mitochondrial function is therefore essential for a better view on the development of age-related diseases. Previous studies have been carried out on cell cultures derived from primary cells, which does not fully represent the real situation in the skin, while the mitochondrial parameters were considered barely or not at all. Here we describe a method to measure mitochondrial respiratory parameters in epithelial tissue derived from human skin biopsies using an Agilent Seahorse XF24 Flux Analyzer. Before the assay, epidermis and dermis are separated enzymatically, we then used the XF24 Islet capture microplates to position the epidermis samples to measure oxygen consumption rates (OCR) and extracellular acidification rates (ECAR). In these plates, small nets can be fixed to the plate bottom. The epidermis was placed with the vital-basal-side on the net. Active ingredients in the three ports were injected consecutively to determine the effect of each compound. This allows determining the efficiency of the individual complexes within the respiratory chain. This protocol enables the testing of toxic substances and their influence on the mitochondrial respiration parameters in human epithelial tissue.

Accelerated Regeneration of ATP Level after Irradiation in Human Skin Fibroblasts by Coenzyme Q10

Human skin is exposed to a number of harmful agents of which the ultraviolet (UV) component of solar radiation is most important. UV-induced damages include direct DNA lesions as well as oxidative damage in DNA, proteins and lipids caused by reactive oxygen species (ROS). Being the main site of ROS generation in the cell, mitochondria are particularly affected by photostress. The resulting mitochondrial dysfunction may have negative effects on many essential cellular processes. To counteract these effects, coenzyme Q10 (CoQ10 ) is used as a potent therapeutic in a number of diseases. We analyzed the mitochondrial respiration profile, the mitochondrial membrane potential and cellular ATP level in skin fibroblasts after irradiation. We observed an accelerated regeneration of cellular ATP level, a decrease in mitochondrial dysfunction as well as a preservation of the mitochondrial membrane potential after irradiation in human skin fibroblasts by treatment with CoQ10 . We conclude that the faster regeneration of the ATP level was achieved by a preservation of mitochondrial function by the addition of CoQ10 and that the protective effect of CoQ10 is primarily mediated via its antioxidative function. We suggest also that it might be further dependent on a stimulation of DNA repair enzymes by CoQ10 .