Insights on the role of L-lactate as a signaling molecule in skin aging

Astrocyte-derived lactate in stress disorders

Stress disorders are psychiatric disorders arising following stressful or traumatic events. They could deleteriously affect an individual's health because they often co-occur with mental illnesses. Considerable attention has been focused on neurons when considering the neurobiology of stress disorders. However, like other mental health conditions, recent studies have highlighted the importance of astrocytes in the pathophysiology of stress-related disorders. In addition to their structural and homeostatic support role, astrocytes actively serve several functions in regulating synaptic transmission and plasticity, protecting neurons from toxic compounds, and providing metabolic support for neurons. The astrocyte-neuron lactate shuttle model sets forth the importance of astrocytes in providing lactate for the metabolic supply of neurons under intense activity. Lactate also plays a role as a signaling molecule and has been recently studied regarding its antidepressant activity. This review discusses the involvement of astrocytes and brain energy metabolism in stress and further reflects on the importance of lactate as an energy supply in the brain and its emerging antidepressant role in stress-related disorders.

Fisetin, a potential skin rejuvenation drug that eliminates senescent cells in the dermis

Accumulation of senescent fibroblasts, chronic inflammation, and collagen remodeling due to aging-related secretory phenotypes have been hypothesized to cause age-related skin aging, which results in wrinkles and loss of skin elasticity, thus compromising appearance attractiveness. However, the rejuvenating effects of removing senescent cells from the human skin and the efficacy of related therapeutic agents remain unclear. Here, we investigated the effects of fisetin, a potential anti-aging component found in various edible fruits and vegetables, on senescent human dermal fibroblasts (HDFs) and aging human skin. Senescence was induced in primary HDFs using long-term passaging and treatment with ionizing radiation, and cell viability was assessed after treatment with fisetin and a control component. A mouse/human chimeric model was established by subcutaneously transplanting whole skin grafts from aged individuals into nude mice, which were treated intraperitoneally with fisetin or control a component for 30 d. Skin samples were obtained and subjected to senescence-associated-beta-galactosidase staining; the extent of aging was evaluated using western blotting, reverse transcription-quantitative PCR, and histological analysis. Fisetin selectively eliminated senescent dermal fibroblasts in both senescence-induced cellular models; this effect is attributable to cell death induction by caspases 3, 8, and 9-mediated endogenous and exogenous apoptosis. Fisetin-treated senescent human skin grafts showed increased collagen density and decreased senescence-associated secretory phenotypes (SASP), including matrix metalloproteinases and interleukins. No apparent adverse events were observed. Thus, fisetin could improve skin aging through selective removal of senescent dermal fibroblasts and SASP inhibition, indicating its potential as an effective novel therapeutic agent for combating skin aging.

Associations between genetically predicted sex and growth hormones and facial aging in the UK Biobank: a two-sample Mendelian randomization study

Background

Aging is an inescapable process, but it can be slowed down, particularly facial aging. Sex and growth hormones have been shown to play an important role in the process of facial aging. We investigated this association further, using a two-sample Mendelian randomization study.

Methods

We analyzed genome-wide association study (GWAS) data from the UK Biobank database comprising facial aging data from 432,999 samples, using two-sample Mendelian randomization. In addition, single-nucleotide polymorphism (SNP) data on sex hormone-binding globulin (SHBG) and sex steroid hormones were obtained from a GWAS in the UK Biobank [SHBG, N = 189,473; total testosterone (TT), N = 230,454; bioavailable testosterone (BT), N = 188,507; and estradiol (E2), N = 2,607)]. The inverse-variance weighted (IVW) method was the major algorithm used in this study, and random-effects models were used in cases of heterogeneity. To avoid errors caused by a single algorithm, we selected MR-Egger, weighted median, and weighted mode as supplementary algorithms. Horizontal pleiotropy was detected based on the intercept in the MR-Egger regression. The leave-one-out method was used for sensitivity analysis.

Results

SHBG plays a promoting role, whereas sex steroid hormones (TT, BT, and E2) play an inhibitory role in facial aging. Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels had no significant effect on facial aging, which is inconsistent with previous findings in vitro.

Conclusion

Regulating the levels of SHBG, BT, TT, and E2 may be an important means to delay facial aging.

Redox signaling and modulation in ageing

In spite of considerable progress that has been reached in understanding how reactive oxygen species (ROS) interact with its cellular targets, several important challenges regarding regulatory effects of redox signaling mechanisms remain to be addressed enough in aging and age-related disorders. Redox signaling is precisely regulated in different tissues and subcellular locations. It modulates the homeostatic balance of many regulatory facilities such as cell cycle, circadian rhythms, adapting the external environments, etc. The newly proposed term "adaptive redox homeostasis" describes the transient increase in ROS buffering capacity in response to amplified ROS formation rate within a physiological range. Redox-dependent second messengers are generated in subcellular locations according to a specific set of rules and regulations. Their appearance depends on cellular needs in response to variations in external and internal stimulus. The intensity and magnitude of ROS signaling determines its downstream effects. This issue includes review and research papers in the context of redox signaling mechanisms and related redox-regulatory interventions, aiming to guide for understanding the degenerative processes of biological ageing and alleviating possible prevention approaches for age-related complications.

A new hydrocyanine probe for imaging reactive oxygen species in the mitochondria of live cells

A new hydrocyanine probe containing a ROS-responsive element and a mitochondrial-targeting moiety, as well as a thiol-reactive chloromethyl group, has been designed for imaging reactive oxygen species (ROS) in the mitochondria of live cells. This hydrocyanine probe is cell-permeable, selectively targets mitochondria and responds to superoxide and hydroxyl radical, and can be used for detection of ROS production in the mitochondria of live cells caused by an oxidative stress.

Ozone in the adjunct medical treatment. The round personality of a molecule with hormetic properties

Ozone, an allotrope of oxygen, is enjoying an increasing interest in the setting and management of the medical adjunct treatment, which is called, maybe too simplistically, "ozone therapy". Ozone is not a medicine, so the word therapy does not properly fit this gaseous molecule. Like many natural compounds, for example plant flavonoids, even ozone interacts with aryl hydrocarbon receptors (AhRs) and, at low doses, it works according to the paradoxical mechanism of hormesis, involving mitochondria (mitohormesis). Ozone, in the hormetic range, exerts cell protective functions via the Nrf2-mediated activation of the anti-oxidant system, then leading to anti-inflammatory effects, also via the triggering of low doses of 4-HNE. Moreover, its interaction with plasma and lipids forms reactive oxygen species (ROS) and lipoperoxides (LPOs), generally called ozonides, which are enabled to rule the major molecular actions of ozone in the cell. Ozone behaves as a bioregulator, by activating a wide population of reactive intermediates, which usually target mitochondria and their turnover/biogenesis, often leading to a pleiotropic spectrum of actions and behaving as a tuner of the fundamental mechanisms of survival in the cell. In this sense, ozone can be considered a novelty in the medical sciences and in the clinical approach to pharmacology and medical therapy, due to its ability to target complex regulatory systems and not simple receptors.