Diesel Particulate Extract Accelerates Premature Skin Aging in Human Fibroblasts via Ceramide-1-Phosphate-Mediated Signaling Pathway

Bioactive sphingolipids as emerging targets for signal transduction in cancer development

Sphingolipids, crucial components of cellular membranes, play a vital role in maintaining cellular structure and signaling integrity. Disruptions in sphingolipid metabolism are increasingly implicated in cancer development. Key bioactive sphingolipids, such as ceramides, sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), and glycosphingolipids, profoundly impact tumor biology. They influence the behavior of tumor cells, stromal cells, and immune cells, affecting tumor aggressiveness, angiogenesis, immune modulation, and extracellular matrix remodeling. Furthermore, abnormal expression of sphingolipids and their metabolizing enzymes modulates the secretion of tumor-derived extracellular vesicles (TDEs), which are key players in creating an immunosuppressive tumor microenvironment, remodeling the extracellular matrix, and facilitating oncogenic signaling within in situ tumors and distant pre-metastatic niches (PMNs). Understanding the role of sphingolipids in the biogenesis of tumor-derived extracellular vesicles (TDEs) and their bioactive contents can pave the way for new biomarkers in cancer diagnosis and prognosis, ultimately enhancing comprehensive tumor treatment strategies.

Mechanisms of Senescence and Anti-Senescence Strategies in the Skin

The skin is the layer of tissue that covers the largest part of the body in vertebrates, and its main function is to act as a protective barrier against external environmental factors, such as microorganisms, ultraviolet light and mechanical damage. Due to its important function, investigating the factors that lead to skin aging and age-related diseases, as well as understanding the biology of this process, is of high importance. Indeed, it has been reported that several external and internal stressors contribute to skin aging, similar to the aging of other tissues. Moreover, during aging, senescent cells accumulate in the skin and express senescence-associated factors, which act in a paracrine manner on neighboring healthy cells and tissues. In this review, we will present the factors that lead to skin aging and cellular senescence, as well as ways to study senescence in vitro and in vivo. We will further discuss the adverse effects of the accumulation of chronic senescent cells and therapeutic agents and tools to selectively target and eliminate them.

Barrier Abnormalities in Type 1 Diabetes Mellitus: The Roles of Inflammation and Ceramide Metabolism

Xerosis is a common sign of both type 1 and type 2 diabetes mellitus (DM), and patients with DM and mouse models for DM show a compromised epidermal permeability barrier. Barrier defects then allow the entry of foreign substances into the skin, triggering inflammation, infection, and worsening skin symptoms. Characterizing how barrier abnormalities develop in DM could suggest treatments for xerosis and other skin disease traits. Because the proper ratio, as well as proper bulk amounts, of heterogeneous ceramide species are keys to forming a competent barrier, we investigated how ceramide metabolism is affected in type 1 DM using a mouse model (induced by streptozotocin). Chronic inflammation, evident in the skin of mice with DM, leads to (i) decreased de novo ceramide production through serine racemase activation-mediated attenuation of serine palmitoyl transferase activity by D-serine; (ii) changes in ceramide synthase activities and expression that modify the ratio of ceramide molecular species; and (iii) increased ceramide-1-phosphate, a proinflammatory lipid mediator, that stimulates inflammatory cytokine expression (TNFα and IFN-γ). Together, chronic inflammation affects ceramide metabolism, which attenuates epidermal permeability barrier formation, and ceramide-1-phosphate could amplify this inflammation. Alleviation of chronic inflammation is a credible approach for normalizing barrier function and ameliorating diverse skin abnormalities in DM.

A Brief Overview of the Toxic Sphingomyelinase Ds of Brown Recluse Spider Venom and Other Organisms and Simple Methods To Detect Production of Its Signature Cyclic Ceramide Phosphate

A special category of phospholipase D (PLD) in the venom of the brown recluse spider (Loxosceles reclusa) and several other sicariid spiders accounts for the dermonecrosis and many of the other clinical symptoms of envenomation. Related proteins are produced by other organisms, including fungi and bacteria. These PLDs are often referred to as sphingomyelinase Ds (SMase Ds) because they cleave sphingomyelin (SM) to choline and "ceramide phosphate." The lipid product has actually been found to be a novel sphingolipid: ceramide 1,3-cyclic phosphate (Cer1,3P). Since there are no effective treatments for the injury induced by the bites of these spiders, SMase D/PLDs are attractive targets for therapeutic intervention, and some of their features will be described in this minireview. In addition, two simple methods are described for detecting the characteristic SMase D activity using a fluorescent SM analog, (N-[12-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]dodecanoyl]-SM (C12-NBD-SM), that is cleaved to C12-NBD-Cer1,3P, which is easily separated from other potential metabolites by thin-layer chromatography and visualized under UV light. Besides confirming that C12-NBD-Cer1,3P is the only product detected upon incubation of C12-NBD-SM with brown recluse spider venom, the method was also able to detect for the first time very low levels of activity in venom from another spider, Kukulcania hibernalis The simplicity of the methods makes it relatively easy to determine this signature activity of SMase D/PLD. SIGNIFICANCE STATEMENT: The sphingomyelinase D/phospholipase D that are present in the venom of the brown recluse spider and other sources cause considerable human injury, but detection of the novel sphingolipid product, ceramide 1,3-cyclic phosphate, is not easy by previously published methods. This minireview describes simple methods for detection of this activity that will be useful for studies of its occurrence in spider venoms and other biological samples, perhaps including lesions from suspected spider bites and infections.

Lipid Peroxidation as the Mechanism Underlying Polycyclic Aromatic Hydrocarbons and Sunlight Synergistic Toxicity in Dermal Fibroblasts

Light and atmospheric pollution are both independently implicated in cancer induction and premature aging. Evidence has been growing more recently on the toxic synergy between light and pollutants. Polycyclic aromatic hydrocarbons (PAHs) originate from the incomplete combustion of organic matter. Some PAHs, such as the Benzo[a]pyrene (BaP), absorb ultraviolet A (UVA) wavelengths and can act as exogenous chromophores, leading to synergistic toxicity through DNA damage and cytotoxicity concomitant to ROS formation. In this study, we shed light on the mechanism underlying the toxic synergy between PAHs and UVA. Using dermal fibroblasts co-exposed to UVA and BaP, we have demonstrated that the photosensitization reaction causes mortality, which is most likely caused by ROS accumulation. We have shown that these ROS are concentrated in the lipids, which causes an important induction of lipid peroxidation and malondialdehyde, by-products of lipid peroxidation. We have also shown the accumulation of bulky DNA damage, most likely generated by these by-products of lipid peroxidation. To our knowledge, this study represents the first one depicting the molecular effects of photo-pollution on dermal skin.

Ethosomes for Curcumin and Piperine Cutaneous Delivery to Prevent Environmental-Stressor-Induced Skin Damage

Diesel particulate matter is one of the most dangerous environmental stressors affecting human health. Many plant-derived compounds with antioxidant and anti-inflammatory properties have been proposed to protect the skin from pollution damage. Curcumin (CUR) has a plethora of pharmacological activities, including anticancer, antimicrobial, anti-inflammatory and antioxidant. However, it has low bioavailability due to its difficult absorption and rapid metabolism and elimination. CUR encapsulation in nanotechnological systems and its combination with biopotentiators such as piperine (PIP) can improve its pharmacokinetics, stability and activity. In this study, ethosomes (ETs) were investigated for CUR and PIP delivery to protect the skin from damage induced by diesel particulate matter. ETs were produced by different strategies and characterized for their size distribution by photon correlation spectroscopy, for their morphology by transmission electron microscopy, and for their drug encapsulation efficiency by high-performance liquid chromatography. Franz cells enabled us to evaluate in vitro the drug diffusion from ETs. The results highlighted that ETs can promote the skin permeation of curcumin. The studies carried out on their antioxidant activity demonstrated an increase in the antioxidant power of CUR using a combination of CUR and PIP separately loaded in ETs, suggesting their possible application for the prevention of skin damage due to exogenous stressors. Ex vivo studies on human skin explants have shown the suitability of drug-loaded ETs to prevent the structural damage to the skin induced by diesel engine exhaust exposure.

Comparison of Biological Activities and Protective Effects on PAH-Induced Oxidative Damage of Different Coffee Cherry Pulp Extracts

Polycyclic aromatic hydrocarbons (PAHs) are the main toxic components of ambient air particulate matter (PM), causing oxidative damage to the skin and ultimately resulting in skin aging. This study was conducted to determine the anti-oxidant, anti-aging properties and protective effects of the extracts of coffee cherry pulp (Coffea arabica L.), which is a by-product of the coffee industry, against the oxidative damage induced by PAH exposure in human epidermal keratinocytes (HaCaT). Three different techniques were used to extract the coffee cherry pulp: maceration, Soxhlet and ultrasonication to obtain CCM, CCS and CCU extract, respectively, which were then compared to investigate the total phenolic content (TPC) and total flavonoid content (TFC). The chemical compositions were identified and quantified using high-performance liquid chromatography (HPLC). The results demonstrated that Soxhlet could extract the highest content of chlorogenic acid, caffeine and theophylline. CCS showed the significantly highest TPC (324.6 ± 1.2 mg GAE/g extract), TFC (296.8 ± 1.2 mg QE/g extract), anti-radical activity against DPPH free radicals (98.2 ± 0.8 µM Trolox/g extract) and lipid peroxidation inhibition (136.6 ± 6.2 µM Trolox/g extract). CCS also showed the strongest anti-aging effects based on collagenase, elastase, hyaluronidase and tyrosinase inhibitory enzymes. In addition, CCS can protect human keratinocyte cells from PAH toxicity by increasing the cellular anti-oxidant capacity. This study suggests that CCS has the potential to be used as a cosmetic material that helps alleviate skin damage caused by air pollution.

The role of cellular senescence in skin aging and age-related skin pathologies

Aging is the result of a gradual functional decline at the cellular, and ultimately, organismal level, resulting in an increased risk of developing a variety of chronic illnesses, such as cardiovascular disease, stroke, cancer and diabetes. The skin is the largest organ of the human body, and the site where signs of aging are most visible. These signs include thin and dry skin, sagging, loss of elasticity, wrinkles, as well as aberrant pigmentation. The appearance of these features is accelerated by exposure to extrinsic factors such as ultraviolet (UV) radiation or pollution, as well as intrinsic factors including time, genetics, and hormonal changes. At the cellular level, aging is associated with impaired proteostasis and an accumulation of macromolecular damage, genomic instability, chromatin reorganization, telomere shortening, remodelling of the nuclear lamina, proliferation defects and premature senescence. Cellular senescence is a state of permanent growth arrest and a key hallmark of aging in many tissues. Due to their inability to proliferate, senescent cells no longer contribute to tissue repair or regeneration. Moreover, senescent cells impair tissue homeostasis, promote inflammation and extracellular matrix (ECM) degradation by secreting molecules collectively known as the "senescence-associated secretory phenotype" (SASP). Senescence can be triggered by a number of different stimuli such as telomere shortening, oncogene expression, or persistent activation of DNA damage checkpoints. As a result, these cells accumulate in aging tissues, including human skin. In this review, we focus on the role of cellular senescence during skin aging and the development of age-related skin pathologies, and discuss potential strategies to rejuvenate aged skin.

Morus alba L. root decreases melanin synthesis via sphingosine-1-phosphate signaling in B16F10 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Morus alba L. has long been used for beauty in many Asian countries and regions, including anti-aging and hyperpigmentation.

AIM OF THE STUDY

This study aimed at the inhibitory effect of Morus alba L. root on melanogenesis in B16F10 melanoma cells and the mechanism involved.

MATERIALS AND METHODS

This study evaluated the anti-melanogenic effect of Morus alba L. root extract (MAR) on B16F10 melanoma cells by assessing cell viability, melanin accumulation, cellular tyrosinase activity, intra/inter-cellular S1P levels, cellular S1P-related metabolic enzyme activity, and western blot analysis. In addition, the potential S1P lyase (S1PL) inhibitory constituents in MAR were identified by LC-MS/MS.

RESULTS

Without affecting the viability of B16F10 melanoma cells, MAR inhibited intracellular tyrosinase activity in a dose-dependent manner, thereby reducing the accumulation of melanin. MAR also downregulated the expression level of MITF via activating the ERK signaling pathway. Furthermore, MAR increased the intra/inter-cellular S1P by inhibiting S1PL. Several compounds with inhibitory S1PL activity have been identified in MAR, such as mulberroside A and oxyresveratrol.

CONCLUSIONS

The anti-melanogenic effects of MAR mainly involve promoting MITF degradation mediated via S1P-S1PR3-ERK signaling through increasing cellular S1P levels by inhibiting S1PL activity.

Effects of Air Pollution on Cellular Senescence and Skin Aging

The human skin is exposed daily to different environmental factors such as air pollutants and ultraviolet (UV) light. Air pollution is considered a harmful environmental risk to human skin and is known to promote aging and inflammation of this tissue, leading to the onset of skin disorders and to the appearance of wrinkles and pigmentation issues. Besides this, components of air pollution can interact synergistically with ultraviolet light and increase the impact of damage to the skin. However, little is known about the modulation of air pollution on cellular senescence in skin cells and how this can contribute to skin aging. In this review, we are summarizing the current state of knowledge about air pollution components, their involvement in the processes of cellular senescence and skin aging, as well as the current therapeutic and cosmetic interventions proposed to prevent or mitigate the effects of air pollution in the skin.

Euphorbia supina Extracts Block NADPH Oxidase-Mediated, Ceramide-Induced Apoptosis Initiated by Diesel Particulate Matter

Air pollutants contribute to the development of diseases such as asthma, chronic obstructive pulmonary disease (COPD), pulmonary cancer, cardiovascular problems, and some skin diseases. We recently found that a major air pollutant, diesel particulate matter (DPM), induces apoptosis in human keratinocytes by increasing a proapoptotic lipid mediator, ceramide. DPM activates nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX), which stimulates sphingomyelinase, leading to an increased conversion of sphingomyelin to ceramide. Interestingly, we characterized that although NOX is a reactive oxygen species (ROS) generator, the activation of sphingomyelinases by NOX is an ROS-independent mechanism. A Korean weed, prostrate spurge Euphorbia supina Rafin (ESR), has been used for centuries as a folk medicine to treat bronchitis, hepatitis, hemorrhage, and skin inflammation. Flavonoids, terpenes and tannins are enriched in ESR, and although ESR has proven antioxidative activity, its biological activities are largely unknown. Here, we investigate whether and how ESR protects keratinocytes against DPM-mediated apoptosis. We found that ESR-extracts (ESR-Ex) protect keratinocytes from DPM-induced apoptosis by inhibiting NOX activation in keratinocytes in response to DPM. We also demonstrated that ESR-Ex suppresses NOX activation via a blockage of the aryl hydrocarbon receptor (AhR) activation-mediated transcription of neutrophil cytosolic factor 1 (NCF1)/p47phox, a subunit of NOX. Our study reveals previously uncharacterized biological activity of ESR-Ex; i.e., its inhibition of Ahr and NOX activation. Thus, because the inhibition of NOX has already been developed to treat NOX-mediated diseases, including various types of cardiovascular diseases and cancers, initiated by air pollutants and because AhR activation contributes to the development of chronic inflammatory diseases, our study provides further advantages for the medical use of ESR.