No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Nicotinamide mononucleotide reduces melanin production in aged melanocytes by inhibiting cAMP/Wnt signaling
Abstract
Nicotinamide mononucleotide (NMN) is a representative anti-aging drug that, after long-term administration in mice, causes an increase in energy and lipid metabolism, improves eye function, immune response, and increases insulin sensitivity. However, the effects of NMN on skin pigmentation are still unknown. In this study, we aimed to demonstrate the effects of NMN on melanogenesis.
NMN was applied to both young and aged melanocytes, and melanin production, protein expression, and mRNA levels were analyzed. A reconstituted human skin model was used to validate the effect of NMN on melanogenesis in vivo. NMN treatment showed no apparent effects on young melanocytes, however, in aged melanocytes, a marked reduction in melanin production was observed. NMN treatment also efficiently reduced melanin production in a reconstituted human skin with aged melanocytes. Genome-wide analysis showed the downregulation of melanogenesis-related cyclic adenosine monophosphate (cAMP)/Wnt signaling in aged melanocytes. Moreover, NMN treatment downregulated forskolin-induced expression of melanogenesis-related proteins, tyrosinase (TYR), tyrosinase-related protein (TRP)-1, and TRP-2. Nicotinamide adenine dinucleotide (NAD⁺), an NMN product within the cells, also reduced cAMP/Wnt signaling in aged melanocytes. SLC12A6 was the most highly expressed gene among the SLC12A family members in melanocytes and was significantly influenced by NMN or NAD⁺ treatment, indicating that SLC12A6 protein is an NMN transporter in melanocytes. In conclusion, NMN reduces melanogenesis in aged melanocytes by downregulating the signaling of melanogenesis-associated receptors. Therefore, NMN is a human-friendly anti-melanogenic agent with the potential to aid in aging-related hyperpigmentation therapy.
... The findings of this study shows that NMN may be useful in preventing and treating skin photoaging . NMN inhibits cAMP/Wnt signaling, which lowers melanin synthesis in elderly melanocytes and reduces skin pigmentation (Brito et al. 2022). An animal study also reported that NAM and its metabolite N-methylnicotinamide increase skin vascular permeability (Pietrzak, Mogielnicki, and Buczko 2009). ...
The study of nicotinamide adenine dinucleotide (NAD⁺) biology has gained popularity recently. Research discovered that two NAD⁺ biosynthesis intermediates, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), are biosynthetic precursors of NAD⁺, an essential chemical for metabolism. Many studies show that NAD⁺ levels fall considerably with aging, with NAD⁺ regeneration in aging animals increasing longevity and enhancing health. According to research on the two molecules, NMN and NR, supplementation with either raises NAD⁺ levels during aging. The objective of this review is to highlight current developments in the biology of NAD⁺ in relation to NR or NMN supplement. This review highlightings significant discoveries about NR and NMN supplementation in relation to NAD⁺ biological activities and health benefits.
... Melanocytes become dysfunctional, and melanogenic activity decreases, resulting in a paler appearance [79,80]. However, melanocytes in sun-exposed areas demonstrate a tendency towards pigmentary changes, such as the formation of "aged spots", including melasma or senile lentigo [81][82][83]. The hydration level of the stratum corneum is decreased, as amino acids generated in aged skin show higher hydrophobicity [84]. ...
Several industries are increasingly focused on enhancing the delivery of active ingredients through the skin to optimize therapeutic outcomes. By facilitating the penetration of active ingredients through the skin barrier, these enhancers can significantly improve the efficacy of various formulations, ranging from skincare products to therapeutic agents targeting systemic circulation. As the understanding of skin physiology and the mechanisms of drug absorption deepen, these industries are adopting permeation enhancers more widely, ultimately leading to better patient outcomes and expanded treatment options. However, the structure and physiological function of the skin can vary according to different factors, such as the area of the body and between individuals. These variations, along with external environmental exposures, aging and pathological conditions, introduce complexities that must be carefully considered when designing effective delivery systems. Considering the intricacies of skin structure and physiology, tailoring systems to account for regional differences, individual variability, and changes induced by environmental factors or disease is critical to optimizing therapeutic outcomes. This review discusses the features of skin structure, physiology, and pathologies, as well as the application of permeation enhancers in these contexts. Furthermore, it addresses the use of animal skin models in transdermal delivery and dermatological studies, along with the latest developments in this field.
... Moreover, NMN has been found to mitigate skin-aging pigmentation issues. By downregulating the cyclic adenosine monophosphate (cAMP)/Wnt signaling pathway, NMN treatment reduces melanin production in senescent melanocytes, as supported by studies using human skin models (Brito et al., 2022). In summary, the antiaging mechanism of action of NMN is complex and involves multiple molecular pathways and biological processes. ...
Aging and age-related ailments have emerged as critical challenges and great burdens within the global contemporary society. Addressing these concerns is an imperative task, with the aims of postponing the aging process and finding effective treatments for age-related degenerative diseases. Recent investigations have highlighted the significant roles of nicotinamide adenine dinucleotide (NAD ⁺ ) in the realm of anti-aging. It has been empirically evidenced that supplementation with nicotinamide mononucleotide (NMN) can elevate NAD ⁺ levels in the body, thereby ameliorating certain age-related degenerative diseases. The principal anti-aging mechanisms of NMN essentially lie in its impact on cellular energy metabolism, inhibition of cell apoptosis, modulation of immune function, and preservation of genomic stability, which collectively contribute to the deferral of the aging process. This paper critically reviews and evaluates existing research on the anti-aging mechanisms of NMN, elucidates the inherent limitations of current research, and proposes novel avenues for anti-aging investigations.
... Furthermore, NMN exerts neuroprotective effects and improves cognitive and behavioral functions (Li et al., 2017;Johnson et al., 2018;Hosseini et al., 2019;Miao et al., 2020). Recent studies have reported that NMN supplementation exerts therapeutic effects on chronic inflammation and retinal damage, promotes melanogenesis (Chen et al., 2020;Liu et al., 2021;Lin et al., 2021b;Brito et al., 2022), and helps prevent skin photoaging, glaucoma, and cisplatin-induced ototoxicity (Katayoshi et al., 2021;Petriti et al., 2021;Zhan et al., 2021). ...
Introduction
β-nicotinamide mononucleotide (β-NMN) is an essential precursor of nicotinamide adenine dinucleotide (NAD⁺) and plays a key role in supplying NAD⁺ and maintaining its levels. Existing methods for NMN production have some limitations, including low substrate availability, complex synthetic routes, and low synthetic efficiency, which result in low titers and high costs.
Methods
We constructed high-titer, genetically engineered strains that produce NMN through a new pathway. Bacillus subtilis WB600 was used as a safe chassis strain. Multiple strains overexpressing NadE, PncB, and PnuC in various combinations were constructed, and NMN titers of different strains were compared via shake-flask culture.
Results
The results revealed that the strain B. subtilis PncB1-PnuC exhibited the highest total and extracellular NMN titers. Subsequently, the engineered strains were cultured in a 5-L fermenter using batch and fed-batch fermentation. B. subtilis PncB1-PnuC achieved an NMN titer of 3,398 mg/L via fed-batch fermentation and glucose supplementation, which was 30.72% higher than that achieved via batch fermentation.
Discussion
This study provides a safe and economical approach for producing NMN on an industrial scale.
... In niacin-deficient HaCaT cells, nicotinamide can regulate melanogenesis via the reduction in melanosome secretion [55]. NMN downregulates melanogenesis in aged melanocytes by inhibiting cAMP/Wnt signaling and, in the same way, the direct elevation of NAD + reduces both melanin production and cAMP/Wnt signaling [56]. ...
Nicotinamide adenine dinucleotide (NAD) is one of the most important and essential components within an organism. Extensive ongoing research is aimed at harnessing its potential in managing diverse diseases by supplying various forms of NAD in its oxidized state, NAD+. Ultraviolet radiation (UVR) is the most common environmental exposure factor, but also carries many risks. UVR affects the epidermis and contributes to sunburn, photo-allergy, DNA damage, and certain cancers, notably melanoma. Research has shown that NAD+ precursors, including nicotinamide riboside (NR), reduce melanogenesis in aged melanocytes. In this study, we used NR to determine whether melanin hyperpigmentation was suppressed after light stimulation. We found that melanogenesis was inhibited when B16F10 cells treated with α-melanocyte-stimulating hormone were exposed to specific doses of NR. Additionally, tyrosinase activity (a key step in melanin production) was suppressed. However, there was no difference in the expression level of melanogenic genes. Ultraviolet B light directly stimulated HaCaT cells, inducing the RNA expression of metalloproteinases. Treatment with NR suppressed the corresponding gene expression and reduced cytotoxicity. This study demonstrates the possibility of using NR as a new skin-whitening ingredient due to its inhibitory effect on hyperpigmentation and ability to maintain skin layers affected by UVR.
The differences in earlobe color of Jiangshan black-bone chickens have been reported to be caused by the combined effects of melanin and collagen. In this study, we conducted LC-MS untargeted metabolomics and 16S rDNA diversity sequencing on the cecal contents of two types of earlobes: peacock green (Blue and Green group) and dark reddish-purple (Black group). The metabolomic sequencing identified a total of 747 differential metabolites (DMs), in which the metabolites were primarily enriched in tyrosine and tryptophan metabolism pathways between peacock green and dark reddish-purple earlobes. There were 15 different bacterial taxa among the three groups of earlobes at the genus level, and correlation analysis between metabolites and microbes revealed that the DMs between peacock green and dark reddish-purple earlobes were positively correlated with the different bacterial taxa. In short, there are differences in gut microbiota and metabolites between Jiangshan black-bone chickens with peacock green earlobes and those with dark reddish-purple earlobes. Our results suggest that the bacterial phyla Firmicutes and Bacteroidota may influence melanin synthesis by affecting tryptophan metabolism, induced by 5-Methoxyindoleacetate, and tyrosine metabolism, induced by maleylacetoacetic acid and maleic acid, leading to differences in earlobe color.
The skin is considered the most important organ system in mammals, and as the population ages, it is important to consider skin aging and anti-aging therapeutic strategies. Exposure of the skin to various insults induces significant changes throughout our lives, differentiating the skin of a young adult from that of an older adult. These changes are caused by a combination of intrinsic and extrinsic aging. We report the interactions between skin aging and its metabolism, showing that the network is due to several factors. For example, iron is an important nutrient for humans, but its level increases with aging, inducing deleterious effects on cellular functions. Recently, it was discovered that ferroptosis, or iron-dependent cell death, is linked to aging and skin diseases. The pursuit of new molecular targets for ferroptosis has recently attracted attention. Prevention of ferroptosis is an effective therapeutic strategy for the treatment of diseases, especially in old age. However, the pathological and biological mechanisms underlying ferroptosis are still not fully understood, especially in skin diseases such as melanoma and autoimmune diseases. Only a few basic studies on regulated cell death exist, and the challenge is to turn the studies into clinical applications.
Background
Skin microbiota is essential for health maintenance. Photoaging is the primary environmental factor that affects skin homeostasis, but whether it influences the skin microbiota remains unclear.
Objective
The objective of this study is to investigate the relationship between photoaging and skin microbiome.
Methods
A cohort of senior bus drivers was considered as a long‐term unilateral ultraviolet (UV) irradiated population. 16S rRNA amplicon sequencing was conducted to assess skin microbial composition variations on different sides of their faces. The microbiome characteristics of the photoaged population were further examined by photoaging guinea pig models, and the correlations between microbial metabolites and aging‐related cytokines were analyzed by high‐throughput sequencing and reverse transcription polymerase chain reaction.
Results
Photoaging decreased the relative abundance of microorganisms including Georgenia and Thermobifida in human skin and downregulated the generation of skin microbe‐derived antioxidative metabolites such as ectoin. In animal models, Lactobacillus and Streptobacillus abundance in both the epidermis and dermis dropped after UV irradiation, resulting in low levels of skin antioxidative molecules and leading to elevated expressions of the collagen degradation factors matrix metalloproteinase (MMP)‐1 and MMP‐2 and inflammatory factors such as interleukin (IL)‐1β and IL‐6.
Conclusions
Skin microbial characteristics have an impact in photoaging and the loss of microbe‐derived antioxidative metabolites impairs skin cells and accelerates the aging process. Therefore, microbiome‐based therapeutics may have potential in delaying skin aging.
Background
A wide variety of dermocosmetics (products with both active skincare and cosmetic activity) are available for the management of acne vulgaris. These products are important because they may be the first line of approach for patients desiring to self‐treat and they can also have beneficial effects—reducing lesion counts and improving global acne severity. When used in conjunction with medical therapy, dermocosmetics can improve tolerability and enhance results. We reviewed available evidence and combined it with our clinical experience to help guide clinicians in selecting skincare products with acne‐targeting ingredients.
Methods
An international panel of dermatologists with an interest and expertise in managing acne performed a literature review, formulated clinical questions related to the role of dermocosmetics in the acne setting, used a modified GRADE approach to evaluate available evidence and then utilized an online iterative Delphi process to create consensus recommendations. It should be noted that due to the limited number of available studies, the category of dermocosmetics was evaluated rather than specific ingredients.
Results
The quality of evidence was found to be low to moderate. Key recommendations were made based on available evidence for the use of dermocosmetics in acne to improve acne global assessment, reduce acne lesion counts, reduce superficial skin oiliness and serve as maintenance therapy after medical treatment, while providing a good tolerability. Recommendations were also made for using dermocosmetics as adjuncts to medical treatment.
Conclusions
While there is a need for better quality evidence, dermocosmetics have demonstrated some benefit for acne both when used alone in its milder clinical presentations or in maintenance post acne medication and as adjunct to acne treatments.
Background
In Eastern culture, a fair complexion is the standard of beauty, leading to appearance‐related distress among women with darker skin or facial pigmentation. Women seek whitening cosmetics to enhance their skin tone or correct their pigmentation, but their safety and effectiveness are paramount factors to consider. In this study, we evaluated the safety and whitening effects of a compound formula denoted as TEST comprising astaxanthin, nicotinamide, arbutin, and tranexamic acid.
Methods
Primary skin irritation and skin‐whitening efficacy were examined. Three qualified melanization areas were treated with TEST, 7% ascorbic acid, or a blank. Skin color, the individual type angle (ITA°), and the melanin index (MI) were compared among treatment areas.
Results
TEST did not induce a skin response and exhibited a significantly higher ITA° than the blank, while no significant difference was observed with that of 7% ascorbic acid. Furthermore, the MI of TEST was significantly reduced posttreatment.
Conclusions
TEST could be integrated into spot‐fading and skin‐whitening cosmeceuticals or functional cosmetics.
In recent years, skin aging has received increasing attention. Many factors affect skin aging, and research has shown that metabolism plays a vital role in skin aging, but there needs to be a more systematic review. This article reviews the interaction between skin metabolism and aging from the perspectives of glucose, protein, and lipid metabolism and explores relevant strategies for skin metabolism regulation. We found that skin aging affects the metabolism of three major substances, which are glucose, protein, and lipids, and the metabolism of the three major substances in the skin also affects the process of skin aging. Some drugs or compounds can regulate the metabolic disorders mentioned above to exert anti-aging effects. Currently, there are a variety of products, but most of them focus on improving skin collagen levels. Skin aging is closely related to metabolism, and they interact with each other. Regulating specific metabolic disorders in the skin is an important anti-aging strategy. Research and development have focused on improving collagen levels, while the regulation of other skin glycosylation and lipid disorders including key membrane or cytoskeleton proteins is relatively rare. Further research and development are expected.
Simple Summary
The color of wool is an essential trait in sheep which plays a significant role in the textile industry. The color of wool is determined by the presence of various pigments, which can range from white to various shades of brown, gray, black, etc. Understanding the genetics behind wool color is crucial for selective breeding and producing desirable colors for different textile products. By studying the genetic basis of wool color, researchers can identify genes related to pigmentation and develop strategies to enhance or modify wool color. This knowledge contributes to the improvement of wool quality, diversification of textile options, and economic development in the wool industry.
Abstract
Wool color is controlled by a variety of genes. Although the gene regulation of some wool colors has been studied in relative depth, there may still be unknown genetic variants and control genes for some colors or different breeds of wool that need to be identified and recognized by whole genome resequencing. Therefore, we used whole genome resequencing data to compare and analyze sheep populations of different breeds by population differentiation index and nucleotide diversity ratios (Fst and θπ ratio) as well as extended haplotype purity between populations (XP-EHH) to reveal selection signals related to wool coloration in sheep. Screening in the non-white wool color group (G1 vs. G2) yielded 365 candidate genes, among which PDE4B, GMDS, GATA1, RCOR1, MAPK4, SLC36A1, and PPP3CA were associated with the formation of non-white wool; an enrichment analysis of the candidate genes yielded 21 significant GO terms and 49 significant KEGG pathways (p < 0.05), among which 17 GO terms and 21 KEGG pathways were associated with the formation of non-white wool. Screening in the white wool color group (G2 vs. G1) yielded 214 candidate genes, including ABCD4, VSX2, ITCH, NNT, POLA1, IGF1R, HOXA10, and DAO, which were associated with the formation of white wool; an enrichment analysis of the candidate genes revealed 9 significant GO-enriched pathways and 19 significant KEGG pathways (p < 0.05), including 5 GO terms and 12 KEGG pathways associated with the formation of white wool. In addition to furthering our understanding of wool color genetics, this research is important for breeding purposes.
Orchidaceae are diverse plants whose bioactive compounds have various biological activities. New hybrids of Dendrobium have been generated to gain characteristics shared with their ancestors. Dendrobium Pearl Vera (designated as DH) is derived from parents used for dermatological treatments and cosmetics. However, the phytoconstituents and biological properties of DH have not been reported. The current study investigated extracts from DH plants using four solvents (water, methanol, ethanol, or 2-propanol). The propanolic extract (DH-P) contained the highest phenolic and flavonoid contents, along with a high scavenging performance for free radicals. In total, 25 tentative constituents in the DH-P matrix were identified, consisting of amino acids, nucleotides, and three types of secondary metabolites: furan, phenolics, and alkaloids. The DH-P inhibited human tyrosinase in vitro in a concentration-dependent manner of the phenolic content. Furthermore, there was no significant difference between DH-P with 10 μg/ml phenolic content and 0.75 mM kojic acid (a commercial whitening agent) on the inhibition of human tyrosinase. Incubation with DH-P containing at least 15 μg/ml phenolic content greatly inhibited the proliferation of human melanoma; however, the cell viability was not affected by the phenolic content at 5 μg/ml or less. The half-maximal inhibitory concentration (IC50) of the phenolic content in DH-P on melanoma viability was 12.90 ± 1.04 μg/ml. Melanin production in vivo by human melanoma incubated with 5 μg/ml phenolic content in DH-P was reduced significantly, compared to 2.5 μg/ml phenolic content in DH-P, 100 μg/ml arbutin, and in control. The identified components, including 5-hydroxymethyl-2-furaldehyde, salicylic acid, nicotinamide, acetophenone, cytidine, adenosine, proline, or valine, have been reported to be associated with depigmentation, antioxidant, and anticancer. This research revealed, for the first time, the tentative phytoconstituents of Dendrobium Pearl Vera and their biological activities, thus demonstrating the potential use of DH-P in dermal applications.
The importance of nicotinamide adenine dinucleotide (NAD+) in human physiology is well recognized. As the NAD+ concentration in human skin, blood, liver, muscle and brain are thought to decrease with age, finding ways to increase NAD+ status could possibly influence the ageing process and associated metabolic sequelae. Nicotinamide mononucleotide (NMN) is a precursor for NAD+ biosynthesis, and in vitro/in vivo studies have demonstrated that NMN supplementation increases NAD+ concentration and could mitigate ageing-related disorders such as oxidative stress, DNA damage, neurodegeneration and inflammatory responses. The promotion of NMN as an anti-ageing health supplement has gained popularity due to such findings; however, since most studies evaluating the effects of NMN have been conducted in cell or animal models, a concern remains regarding the safety and physiological effects of NMN supplementation in the human population. Nonetheless, a dozen human clinical trials with NMN supplementation are currently underway. This review summarizes the current progress of these trials and NMN/NAD+ biology to clarify the potential effects of NMN supplementation and to shed light on future study directions.
Nicotinamide mononucleotide (NMN), a naturally occurring biologically active nucleotide, mainly functions via mediating the biosynthesis of NAD⁺. In recent years, its excellent pharmacological activities including anti-aging, treating neurodegenerative diseases, and protecting the heart have attracted increasing attention from scholars and entrepreneurs for production of a wide range of formulations, including functional food ingredients, health care products, active pharmaceuticals, and pharmaceutical intermediates. Presently, the synthesis methods of NMN mainly include two categories: chemical synthesis and biosynthesis. With the development of biocatalyst engineering and synthetic biology strategies, bio-preparation has proven to be efficient, economical, and sustainable methods. This review summarizes the chemical synthesis and biosynthetic pathways of NMN and provides an in-depth investigation on the mining and modification of enzyme resources during NMN biosynthesis, as well as the screening of hosts and optimization of chassis cells via metabolic engineering, which provide effective strategies for efficient production of NMN. In addition, an overview of the significant physiological functions and activities of NMN is elaborated. Finally, future research on technical approaches to further enhance NMN synthesis and strengthen clinical studies of NMN are prospected, which would lay the foundation for further promoting the application of NMN in nutrition, healthy food, and medicine in the future.
Key points
• NMN supplementation effectively increases the level of NAD⁺.
• The chemical and biological synthesis of NMN are comprehensively reviewed.
• The impact of NMN on the treatment of various diseases is summarized.
Graphical abstract
This study aimed to reveal the potential genetic basis for litter size, coat colour, black middorsal stripe and skin colour by combining genome-wide association analysis (GWAS) and selection signature analysis and ROH detection within the Youzhou dark (YZD) goat population (n = 206) using the Illumina GoatSNP54 BeadChip. In the GWAS, we identified one SNP (snp54094-scaffold824-899720) on chromosome 11 for litter size, two SNPs on chromosome 26 (snp11508-scaffold142-1990450, SORCS3) and chromosome 12 (snp55048-scaffold842-324525, LOC102187779) for coat colour and one SNP on chromosome 18 (snp56013-scaffold873-22716, TCF25) for the black middorsal stripe. In contrast, no SNPs were identified for skin colour. In selection signature analysis, 295 significant iHS genomic regions with a mean |iHS| score > 2.66, containing selection signatures encompassing 232 candidate genes were detected. In particular, 43 GO terms and one KEGG pathway were significantly enriched in the selected genes, which may contribute to the excellent environmental adaptability and characteristic trait formation during the domestication of YZD goats. In ROH detection, we identified 4446 ROH segments and 282 consensus ROH regions, among which nine common genes overlapped with those detected using the iHS method. Some known candidate genes for economic traits such as reproduction (TSHR, ANGPT4, CENPF, PIBF1, DACH1, DIS3, CHST1, COL4A1, PRKD1 and DNMT3B) and development and growth (TNPO2, IFT80, UCP2, UCP3, GHRHR, SIM1, CCM2L, CTNNA3 and CTNNA1) were revealed by iHS and ROH detection. Overall, this study is limited by the small population size, which affects the results of GWAS to a certain extent. Nevertheless, our findings could provide the first overview of the genetic mechanism underlying these important traits and provide novel insights into the future conservation and utilisation of Chinese goat germplasm resources.
β-Nicotinamide mononucleotide (β-NMN), a key precursor in the biosynthesis of nicotinamide adenine dinucleotide (NAD+) in mammals, has significant effects in replenishing NAD+ levels in the body, so it has obvious ameliorative effects on metabolic and age-related degenerative diseases. β-NMN is widely used in healthcare products, food, and cosmetics. It has considerable commercial worth and promising medical application prospects. Hence, the development of methods for preparing β-NMN is of great research significance. This review summarized and analyzed recent developments in the chemical synthesis of β-NMN from various starting materials, which could provide helpful references for the investigation of new synthetic techniques for β-NMN and encourage its further development and large-scale application.
Background
Increasing knowledge regarding the deleterious effects of sun exposure and the mechanisms of photodamage has enabled the development of tailored photoprotection strategies based on skin type and the existence of underlying conditions. Dermatologists play an essential role as they identify the specific skin photoprotection needs of their patients. This translates into specific recommendation of suitable protection measures, both in terms of the length and time of the day these patients can be exposed to the sun, and use of sun protection products.
Purpose
Our purpose was to overview of optimal photoprotection strategies for patients with dermatological pathologies or alterations. Methods: Increasing evidence supports the use of sunscreens containing not only organic and inorganic filters, but also non-filtering biological ingredients that can enhance sunscreen protection efficacy. Examples of these biologicals include DNA repair enzymes, antioxidants including vitamins and other biological agents, including those of botanical origin have been reviewed.
Results
Oral photoprotection is also an area of increasing interest that contributes to an integral protection against sun-related alterations.
Conclusion
This article provides the skin care specialist with a simple, easy-to-use guide to identify appropriate measures for patients presenting pathologies or conditions requiring specific sun protection needs, including (but not limited to) photodermatoses (polymorphic light eruption, porphyrias); inflammatory dermatoses (atopic dermatitis, rosacea, psoriasis); pigmentation disorders (hyperpigmentation, vitiligo), photoaging, skin pre-cancerous lesions and cancers, and photosensitive or sensitized skin (patients undergoing specific drugs treatments or skin-related procedures), ensuring the choice of personalized protection for susceptible groups within the general population.
Many compounds containing the β-phenyl-α,β-unsaturated carbonyl (PUSC) scaffold, including cinnamamide derivatives, have been shown to inhibit tyrosinase potently in vitro and in vivo. Structural changes to cinnamamide derivatives were produced by adding a dithionate functional group to provide eight (Z)-5-(substituted benzylidene)-3-cyclohexyl-2-thioxothiazolidin-4-one analogs with high log p values for skin. These analogs were synthesized using a two-step reaction, and their stereochemistry was confirmed using the 3JC4-Hβ values of C4 measured in proton-coupled 13C mode. Analogs 2 (IC50 = 5.21 ± 0.86 µM) and 3 (IC50 = 1.03 ± 0.14 µM) more potently inhibited mushroom tyrosinase than kojic acid (IC50 = 25.26 ± 1.10 µM). Docking results showed 2 binds strongly to the active site of tyrosinase, while 3 binds strongly to an allosteric site. Kinetic studies using l-tyrosine as substrate indicated 2 and 3 competitively and non-competitively inhibit tyrosinase, respectively, which was supported by our docking results. In B16F10 cells, 3 significantly and concentration-dependently reduced α–MSH plus IBMX induced increases in cellular tyrosinase activity and melanin production and the similarity between these inhibitory patterns implied that the anti-melanogenic effect of 3 might be due to its tyrosinase-inhibitory ability. In addition, 2 and 3 exhibited strong antioxidant effects; for example, they reduced ROS and ONOO– levels and exhibited radical scavenging activities, suggesting that these effects might underlie their anti-melanogenic effects. Furthermore, 3 suppressed the expressions of melanogenesis-associated proteins and genes in B16F10 cells. These results suggest (Z)-5-(substituted benzylidene)-3-cyclohexyl-2-thioxothiazolidin-4-one analogs offer a means of producing novel anti-melanogenesis agents.
The beneficial effect on health of argan oil is recognized worldwide. We have previously reported that the cake that remains after argan oil extraction (argan press-cake or APC) inhibits melanogenesis in B16 melanoma cells in a time-dependent manner without cytotoxicity. In this study, the global gene expression profile of B16 melanoma cells treated with APC extract was determined in order to gain an understanding of the possible mechanisms of action of APC. The results suggest that APC extract inhibits melanin biosynthesis by down-regulating microphthalmia-associated transcription factor (Mitf) and its downstream signaling pathway through JNK signaling activation, and the inhibition of Wnt/β-catenin and cAMP/PKA signaling pathways. APC extract also prevented the transport of melanosomes by down-regulating Rab27a expression. These results suggest that APC may be an important natural skin whitening product and pharmacological agent used for clinical treatment of pigmentary disorders.
NAD+, a co-enzyme involved in a great deal of biochemical reactions, has been found to be a network node of diverse biological processes. In mammalian cells, NAD+ is synthetized, predominantly through NMN, to replenish the consumption by NADase participating in physiologic processes including DNA repair, metabolism, and cell death. Correspondingly, aberrant NAD+ metabolism is observed in many diseases. In this review, we discuss how the homeostasis of NAD+ is maintained in healthy condition and provide several age-related pathological examples related with NAD+ unbalance. The sirtuins family, whose functions are NAD-dependent, is also reviewed. Administration of NMN surprisingly demonstrated amelioration of the pathological conditions in some age-related disease mouse models. Further clinical trials have been launched to investigate the safety and benefits of NMN. The NAD+ production and consumption pathways including NMN are essential for more precise understanding and therapy of age-related pathological processes such as diabetes, ischemia–reperfusion injury, heart failure, Alzheimer’s disease, and retinal degeneration.
Recent studies have revealed that decline in cellular nicotinamide adenine dinucleotide (NAD⁺) levels causes aging-related disorders and therapeutic approaches increasing cellular NAD⁺ prevent these disorders in animal models. The administration of nicotinamide mononucleotide (NMN) has been shown to mitigate aging-related dysfunctions. However, the safety of NMN in humans have remained unclear. We, therefore, conducted a clinical trial to investigate the safety of single NMN administration in 10 healthy men. A single-arm non-randomized intervention was conducted by single oral administration of 100, 250, and 500 mg NMN. Clinical findings and parameters, and the pharmacokinetics of NMN metabolites were investigated for 5 h after each intervention. Ophthalmic examination and sleep quality assessment were also conducted before and after the intervention. The single oral administrations of NMN did not cause any significant clinical symptoms or changes in heart rate, blood pressure, oxygen saturation, and body temperature. Laboratory analysis results did not show significant changes, except for increases in serum bilirubin levels and decreases in serum creatinine, chloride, and blood glucose levels within the normal ranges, independent of the dose of NMN. Results of ophthalmic examination and sleep quality score showed no differences before and after the intervention. Plasma concentrations of N-methyl-2-pyridone-5-carboxamide and N-methyl-4-pyridone-5-carboxamide were significantly increased dose-dependently by NMN administration. The single oral administration of NMN was safe and effectively metabolized in healthy men without causing any significant deleterious effects. Thus, the oral administration of NMN was found to be feasible, implicating a potential therapeutic strategy to mitigate aging-related disorders in humans.
Nicotinamide mononucleotide (NMN) is a biosynthetic precursor of NAD+ known to promote cellular NAD+ production and counteract age-associated pathologies associated with a decline in tissue NAD+ levels. How NMN is taken up into cells has not been entirely clear. Here we show that the Slc12a8 gene encodes a specific NMN transporter. We find that Slc12a8 is highly expressed and regulated by NAD+ in the murine small intestine. Slc12a8 knockdown abrogates the uptake of NMN in vitro and in vivo. We further show that Slc12a8 specifically transports NMN, but not nicotinamide riboside, and that NMN transport depends on the presence of sodium ion. Slc12a8 deficiency significantly decreases NAD+ levels in the jejunum and ileum, which is associated with reduced NMN uptake as traced by doubly labeled isotopic NMN. Finally, we observe that Slc12a8 expression is upregulated in the aged murine ileum, which contributes to the maintenance of ileal NAD+ levels. Our work identifies the first NMN transporter and demonstrates that Slc12a8 has a critical role in regulating intestinal NAD+ metabolism.
Skin color diversity is the most variable and noticeable phenotypic trait in humans resulting from constitutive pigmentation variability. This paper will review the characterization of skin pigmentation diversity with a focus on the most recent data on the genetic basis of skin pigmentation, and the various methodologies for skin color assessment. Then, melanocyte activity and amount, type and distribution of melanins, which are the main drivers for skin pigmentation, are described. Paracrine regulators of melanocyte microenvironment are also discussed. Skin response to sun exposure is also highly dependent on color diversity. Thus, sensitivity to solar wavelengths is examined in terms of acute effects such as sunburn/erythema or induced-pigmentation but also long-term consequences such as skin cancers, photoageing and pigmentary disorders. More pronounced sun-sensitivity in lighter or darker skin types depending on the detrimental effects and involved wavelengths is reviewed.
Nicotinamide adenine dinucleotide (NAD+) biosynthesis and its regulation have recently been attracting markedly increasing interest. Aging is marked by a systemic decrease in NAD+ across multiple tissues. The dysfunction of NAD+ biosynthesis plays a critical role in the pathophysiologies of multiple diseases, including age-associated metabolic disorders, neurodegenerative diseases, and mental disorders. As downstream effectors, NAD+-dependent enzymes, such as sirtuins, are involved in the progression of such disorders. These recent studies implicate NAD+ biosynthesis as a potential target for preventing and treating age-associated diseases. Indeed, new studies have demonstrated the therapeutic potential of supplementing NAD+ intermediates, such as nicotinamide mononucleotide and nicotinamide riboside, providing a proof of concept for the development of an effective anti-aging intervention.
Photoreceptor death is the endpoint of many blinding diseases. Identifying unifying pathogenic mechanisms in these diseases may offer global approaches for facilitating photoreceptor survival. We found that rod or cone photoreceptor-specific deletion of nicotinamide phosphoribosyltransferase (Nampt), the rate-limiting enzyme in the major NAD⁺ biosynthetic pathway beginning with nicotinamide, caused retinal degeneration. In both cases, we could rescue vision with nicotinamide mononucleotide (NMN). Significantly, retinal NAD⁺ deficiency was an early feature of multiple mouse models of retinal dysfunction, including light-induced degeneration, streptozotocin-induced diabetic retinopathy, and age-associated dysfunction. Mechanistically, NAD⁺ deficiency caused metabolic dysfunction and consequent photoreceptor death. We further demonstrate that the NAD⁺-dependent mitochondrial deacylases SIRT3 and SIRT5 play important roles in retinal homeostasis and that NAD⁺ deficiency causes SIRT3 dysfunction. These findings demonstrate that NAD⁺ biosynthesis is essential for vision, provide a foundation for future work to further clarify the mechanisms involved, and identify a unifying therapeutic target for diverse blinding diseases.
DAVID bioinformatics resources consists of an integrated biological knowledgebase and analytic tools aimed at systematically extracting biological meaning from large gene/protein lists. This protocol explains how to use DAVID, a high-throughput and integrated data-mining environment, to analyze gene lists derived from high-throughput genomic experiments. The procedure first requires uploading a gene list containing any number of common gene identifiers followed by analysis using one or more text and pathway-mining tools such as gene functional classification, functional annotation chart or clustering and functional annotation table. By following this protocol, investigators are able to gain an in-depth understanding of the biological themes in lists of genes that are enriched in genome-scale studies.
We survey the historical development of scientific knowledge surrounding Vitamin B3, and describe the active metabolite forms of Vitamin B3, the pyridine dinucleotides NAD+ and NADP+ which are essential to cellular processes of energy metabolism, cell protection and biosynthesis. The study of NAD+ has become reinvigorated by new understandings that dynamics within NAD+ metabolism trigger major signaling processes coupled to effectors (sirtuins, PARPs, and CD38) that reprogram cellular metabolism using NAD+ as an effector substrate. Cellular adaptations include stimulation of mitochondrial biogenesis, a process fundamental to adjusting cellular and tissue physiology to reduced nutrient availability and/or increased energy demand. Several metabolic pathways converge to NAD+, including tryptophan-derived de novo pathways, nicotinamide salvage pathways, nicotinic acid salvage and nucleoside salvage pathways incorporating nicotinamide riboside and nicotinic acid riboside. Key discoveries highlight a therapeutic potential for targeting NAD+ biosynthetic pathways for treatment of human diseases. A recent emergence of understanding that NAD+ homeostasis is vulnerable to aging and disease processes has stimulated testing to determine if replenishment or augmentation of cellular or tissue NAD+ can have ameliorative effects on aging or disease phenotypes. This experimental approach has provided several proof of concept successes demonstrating that replenishment or augmentation of NAD+ concentrations can provide ameliorative or curative benefits. Thus NAD+ metabolic pathways can provide key biomarkers and parameters for assessing and modulating organism health.
The regulation of melanin production is important for managing skin darkness and hyperpigmentary disorders. Numerous anti-melanogenic agents that target tyrosinase activity/stability, melanosome maturation/transfer, or melanogenesis-related signaling pathways have been developed. As a rate-limiting enzyme in melanogenesis, tyrosinase has been the most attractive target, but tyrosinase-targeted treatments still pose serious potential risks, indicating the necessity of developing lower-risk anti-melanogenic agents. Sugars are ubiquitous natural compounds found in humans and other organisms. Here, we review the recent advances in research on the roles of sugars and sugar-related agents in melanogenesis and in the development of sugar-based anti-melanogenic agents. The proposed mechanisms of action of these agents include: (a) (natural sugars) disturbing proper melanosome maturation by inducing osmotic stress and inhibiting the PI3 kinase pathway and (b) (sugar derivatives) inhibiting tyrosinase maturation by blocking N-glycosylation. Finally, we propose an alternative strategy for developing anti-melanogenic sugars that theoretically reduce melanosomal pH by inhibiting a sucrose transporter and reduce tyrosinase activity by inhibiting copper incorporation into an active site. These studies provide evidence of the utility of sugar-based anti-melanogenic agents in managing skin darkness and curing pigmentary disorders and suggest a future direction for the development of physiologically favorable anti-melanogenic agents.
Aging is a complex, multifaceted process that induces a myriad of physiological changes over an extended period of time. Aging is accompanied by major biochemical and biomechanical changes at macroscopic and microscopic length scales that affect not only tissues and organs but also cells and subcellular organelles. These changes include transcriptional and epigenetic modifications; changes in energy production within mitochondria; and alterations in the overall mechanics of cells, their nuclei, and their surrounding extracellular matrix. In addition, aging influences the ability of cells to sense changes in extracellular-matrix compliance (mechanosensation) and to transduce these changes into biochemical signals (mechanotransduction). Moreover, following a complex positive-feedback loop, aging is accompanied by changes in the composition and structure of the extracellular matrix, resulting in changes in the mechanics of connective tissues in older individuals. Consequently, these progressive dysfunctions facilitate many human pathologies and deficits that are associated with aging, including cardiovascular, musculoskeletal, and neurodegenerative disorders and diseases. Here, we critically review recent work highlighting some of the primary biophysical changes occurring in cells and tissues that accompany the aging process.
Mitochondrial dysfunction is a hallmark of neurodegenerative diseases including Alzheimer's disease (AD), with morphological and functional abnormalities limiting the electron transport chain and ATP production. A contributing factor of mitochondrial abnormalities is loss of nicotinamide adenine dinucleotide (NAD), an important cofactor in multiple metabolic reactions. Depletion of mitochondrial and consequently cellular NAD(H) levels by activated NAD glycohydrolases then culminates in bioenergetic failure and cell death. De Novo NAD(+) synthesis from tryptophan requires a multi-step enzymatic reaction. Thus, an alternative strategy to maintain cellular NAD(+) levels is to administer NAD(+) precursors facilitating generation via a salvage pathway. We administered nicotinamide mononucleotide (NMN), an NAD(+) precursor to APP(swe)/PS1(ΔE9) double transgenic (AD-Tg) mice to assess amelioration of mitochondrial respiratory deficits. In addition to mitochondrial respiratory function, we examined levels of full-length mutant APP, NAD(+)-dependent substrates (SIRT1 and CD38) in homogenates and fission/fusion proteins (DRP1, OPA1 and MFN2) in mitochondria isolated from brain. To examine changes in mitochondrial morphology, bigenic mice possessing a fluorescent protein targeted to neuronal mitochondria (CaMK2a-mito/eYFP), were administered NMN.
Mitochondrial oxygen consumption rates were examined in N2A neuroblastoma cells and non-synaptic brain mitochondria isolated from mice (3 months). Western blotting was utilized to assess APP, SIRT1, CD38, DRP1, OPA1 and MFN2 in brain of transgenic and non-transgenic mice (3-12 months). Mitochondrial morphology was assessed with confocal microscopy. One-way or two-way analysis of variance (ANOVA) and post-hoc Holm-Sidak method were used for statistical analyses of data. Student t-test was used for direct comparison of two groups.
We now demonstrate that mitochondrial respiratory function was restored in NMN-treated AD-Tg mice. Levels of SIRT1 and CD38 change with age and NMN treatment. Furthermore, we found a shift in dynamics from fission to fusion proteins in the NMN-treated mice.
This is the first study to directly examine amelioration of NAD(+) catabolism and changes in mitochondrial morphological dynamics in brain utilizing the immediate precursor NMN as a potential therapeutic compound. This might lead to well-defined physiologic abnormalities that can serve an important role in the validation of promising agents such as NMN that target NAD(+) catabolism preserving mitochondrial function.
Motivation:
A large choice of tools exists for many standard tasks in the analysis of high-throughput sequencing (HTS) data. However, once a project deviates from standard workflows, custom scripts are needed.
Results:
We present HTSeq, a Python library to facilitate the rapid development of such scripts. HTSeq offers parsers for many common data formats in HTS projects, as well as classes to represent data, such as genomic coordinates, sequences, sequencing reads, alignments, gene model information and variant calls, and provides data structures that allow for querying via genomic coordinates. We also present htseq-count, a tool developed with HTSeq that preprocesses RNA-Seq data for differential expression analysis by counting the overlap of reads with genes.
Availability and implementation:
HTSeq is released as an open-source software under the GNU General Public Licence and available from http://www-huber.embl.de/HTSeq or from the Python Package Index at https://pypi.python.org/pypi/HTSeq.
Many tissues of the human body encounter hyperosmotic stress. The effect of extracellular osmotic changes on melanin production has not yet been elucidated. In this study, we determined that hyperosmotic stress induced by organic osmolytes results in reduced melanin production in human melanoma MNT-1 cells. Under hyperosmotic stress, few pigmented mature melanosomes were detected, but there was an increase in swollen vacuoles. These vacuoles were stained with an anti-M6PR antibody that recognizes late endosomal components and with anti-TA99 and anti-HMB45 antibodies, implying that melanosome formation was affected by hyperosmotic stress. Electron microscopic analysis revealed that the M6PR-positive swollen vacuoles were multi-layered and contained melanized granules, and they produced melanin when L-DOPA was applied, indicating that these vacuoles were still capable of producing melanin, but the inner conditions were not compatible with melanin production. The vacuolation phenomenon induced by hyperosmotic conditions disappeared with treatment with the PI3K activator 740 Y-P, indicating that the PI3K pathway is affected by hyperosmotic conditions and is responsible for the proper formation and maturation of melanosomes. The microarray analysis showed alterations of the vesicle organization and transport under hyperosmotic stress. Our findings suggest that melanogenesis could be regulated by physiological conditions, such as osmotic pressure.
Hyper-pigmentation causes skin darkness and medical disorders, such as post-inflammatory melanoderma and melasma. Therefore, the development of anti-melanogenic agents is important for treating these conditions and for cosmetic production. In our previous paper, we demonstrated that the anti-diabetic drug voglibose, a valiolamine derivative, is a potent anti-melanogenic agent. In addition, we proposed an alternative screening strategy to identify valiolamine derivatives with high skin permeability that act as anti-melanogenic agents when applied topically. In this study, we synthesized several valiolamine derivatives with enhanced lipophilicity and examined their inhibitory effects in a human skin model. N-(2-hydroxycyclohexyl)valiolamine (HV) possesses a stronger inhibitory effect on melanin production than voglibose in a human skin model, suggesting that HV is a more potent anti-melanogenic agent for the skin.
Epidermal melanocytes are particularly vulnerable to oxidative stress owing to the pro-oxidant state generated during melanin synthesis, and to the intrinsic antioxidant defenses that are compromised in pathologic conditions. Melanoma is thought to be oxidative stress driven, and melanocyte death in vitiligo is thought to be instigated by a highly pro-oxidant state in the epidermis. We review the current knowledge about melanin and the redox state of melanocytes, how paracrine factors help counteract oxidative stress, the role of oxidative stress in melanoma initiation and progression and in melanocyte death in vitiligo, and how this knowledge can be harnessed for melanoma and vitiligo treatment.Journal of Investigative Dermatology advance online publication, 27 February 2014; doi:10.1038/jid.2014.65.
Sirtuin 1 (Sirt1), a NAD(+)-regulated deacetylase with numerous known positive effects on cellular and whole-body metabolism, is expressed in the renal cortex and medulla. It is known to have protective effects against age-related disease, including diabetes. Here we investigated the protective role of Sirt1 in diabetic renal damage. We found that Sirt1 in proximal tubules (PTs) was downregulated before albuminuria occurred in streptozotocin-induced or obese (db/db) diabetic mice. PT-specific SIRT1 transgenic and Sirt1 knockout mice showed prevention and aggravation of the glomerular changes that occur in diabetes, respectively, and nondiabetic knockout mice exhibited albuminuria, suggesting that Sirt1 in PTs affects glomerular function. Downregulation of Sirt1 and upregulation of the tight junction protein Claudin-1 by SIRT1-mediated epigenetic regulation in podocytes contributed to albuminuria. We did not observe these phenomena in 5/6 nephrectomized mice. We also demonstrated retrograde interplay from PTs to glomeruli using nicotinamide mononucleotide (NMN) from conditioned medium, measurement of the autofluorescence of photoactivatable NMN and injection of fluorescence-labeled NMN. In human subjects with diabetes, the levels of SIRT1 and Claudin-1 were correlated with proteinuria levels. These results suggest that Sirt1 in PTs protects against albuminuria in diabetes by maintaining NMN concentrations around glomeruli, thus influencing podocyte function.
Free radicals and oxidants play a dual role as both toxic and beneficial compounds, since they can be either harmful or helpful to the body. They are produced either from normal cell metabolisms in situ or from external sources (pollution, cigarette smoke, radiation, medication). When an overload of free radicals cannot gradually be destroyed, their accumulation in the body generates a phenomenon called oxidative stress. This process plays a major part in the development of chronic and degenerative illness such as cancer, autoimmune disorders, aging, cataract, rheumatoid arthritis, cardiovascular and neurodegenerative diseases. The human body has several mechanisms to counteract oxidative stress by producing antioxidants, which are either naturally produced in situ, or externally supplied through foods and/or supplements. This mini-review deals with the taxonomy, the mechanisms of formation and catabolism of the free radicals, it examines their beneficial and deleterious effects on cellular activities, it highlights the potential role of the antioxidants in preventing and repairing damages caused by oxidative stress, and it discusses the antioxidant supplementation in health maintenance.
Reactive oxygen species (ROS) are a family of compounds that can oxidatively damage cellular macromolecules and may influence lifespan. Sirtuins are a conserved family of nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases that regulate lifespan in many model organisms including yeast and mice. Recent work suggests that sirtuins can modulate ROS levels notably during a dietary regimen known as calorie restriction which enhances lifespan for several organisms. Although both sirtuins and ROS have been implicated in the aging process, their precise roles remain unknown. In this review, we summarize current thinking about the oxidative stress theory of aging, discuss some of the compelling data linking the sirtuins to ROS and aging, and propose a conceptual model placing the sirtuins into an ROS-driven mitochondria-mediated hormetic response.
Cytoscape is a free software package for visualizing, modeling and analyzing molecular and genetic interaction networks. This protocol explains how to use Cytoscape to analyze the results of mRNA expression profiling, and other functional genomics and proteomics experiments, in the context of an interaction network obtained for genes of interest. Five major steps are described: (i) obtaining a gene or protein network, (ii) displaying the network using layout algorithms, (iii) integrating with gene expression and other functional attributes, (iv) identifying putative complexes and functional modules and (v) identifying enriched Gene Ontology annotations in the network. These steps provide a broad sample of the types of analyses performed by Cytoscape.
Daily skin exposure to solar radiation causes cells to produce reactive oxygen species (ROS), which are a primary factor in skin damage. Although the contribution of the UV component to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology. Solar radiation comprises <10% of UV, and thus the purpose of this study was to examine the physiological response of skin to visible light (400-700 nm). Irradiation of human skin equivalents with visible light induced production of ROS, proinflammatory cytokines, and matrix metalloproteinase (MMP)-1 expression. Commercially available sunscreens were found to have minimal effects on reducing visible light-induced ROS, suggesting that UVA/UVB sunscreens do not protect the skin from visible light-induced responses. Using clinical models to assess the generation of free radicals from oxidative stress, higher levels of free radical activity were found after visible light exposure. Pretreatment with a photostable UVA/UVB sunscreen containing an antioxidant combination significantly reduced the production of ROS, cytokines, and MMP expression in vitro, and decreased oxidative stress in human subjects after visible light irradiation. Taken together, these findings suggest that other portions of the solar spectrum aside from UV, particularly visible light, may also contribute to signs of premature photoaging in skin.
Kyoto Encyclopedia of Genes and Genomes (KEGG, http://www.genome.jp/kegg/ or http://www.kegg.jp/) is a database resource that integrates genomic, chemical and systemic functional information. In particular, gene catalogs
from completely sequenced genomes are linked to higher-level systemic functions of the cell, the organism and the ecosystem.
Major efforts have been undertaken to manually create a knowledge base for such systemic functions by capturing and organizing
experimental knowledge in computable forms; namely, in the forms of KEGG pathway maps, BRITE functional hierarchies and KEGG
modules. Continuous efforts have also been made to develop and improve the cross-species annotation procedure for linking
genomes to the molecular networks through the KEGG Orthology system. Here we report KEGG Mapper, a collection of tools for
KEGG PATHWAY, BRITE and MODULE mapping, enabling integration and interpretation of large-scale data sets. We also report a
variant of the KEGG mapping procedure to extend the knowledge base, where different types of data and knowledge, such as disease
genes and drug targets, are integrated as part of the KEGG molecular networks. Finally, we describe recent enhancements to
the KEGG content, especially the incorporation of disease and drug information used in practice and in society, to support
translational bioinformatics.
The fine detail provided by sequencing-based transcriptome surveys suggests that RNA-seq is likely to become the platform of choice for interrogating steady state RNA. In order to discover biologically important changes in expression, we show that normalization continues to be an essential step in the analysis. We outline a simple and effective method for performing normalization and show dramatically improved results for inferring differential expression in simulated and publicly available data sets.
A new protocol for sequencing the messenger RNA in a cell, known as RNA-Seq, generates millions of short sequence fragments in a single run. These fragments, or 'reads', can be used to measure levels of gene expression and to identify novel splice variants of genes. However, current software for aligning RNA-Seq data to a genome relies on known splice junctions and cannot identify novel ones. TopHat is an efficient read-mapping algorithm designed to align reads from an RNA-Seq experiment to a reference genome without relying on known splice sites.
We mapped the RNA-Seq reads from a recent mammalian RNA-Seq experiment and recovered more than 72% of the splice junctions reported by the annotation-based software from that study, along with nearly 20,000 previously unreported junctions. The TopHat pipeline is much faster than previous systems, mapping nearly 2.2 million reads per CPU hour, which is sufficient to process an entire RNA-Seq experiment in less than a day on a standard desktop computer. We describe several challenges unique to ab initio splice site discovery from RNA-Seq reads that will require further algorithm development.
TopHat is free, open-source software available from http://tophat.cbcb.umd.edu.
Supplementary data are available at Bioinformatics online.
Melanin pigments provide efficient protection against ultraviolet B (UVB) radiation but DNA repair also plays a key role in eliminating UV-induced damage and preventing the development of skin cancers. In this study, we demonstrate that forskolin (FSK), an agent that increases intracellular levels of cAMP, protects keratinocytes from UVB-induced apoptosis independently from the amount of melanin in the skin. FSK enhances the removal of the two major types of UVB-induced DNA damage, cyclobutane pyrimidine dimers and 6,4-photoproducts, by facilitating DNA repair. These findings suggest new preventive approaches with topical formulations of FSK or other bioactive agents that could be applied to the skin before sun exposure to increase its ability to repair DNA damage.
Ultraviolet (UV) light and incompletely understood genetic and epigenetic variations determine skin color. Here we describe an UV- and microphthalmia-associated transcription factor (MITF)-independent mechanism of skin pigmentation. Targeting the mitochondrial redox-regulating enzyme nicotinamide nucleotide transhydrogenase (NNT) resulted in cellular redox changes that affect tyrosinase degradation. These changes regulate melanosome maturation and, consequently, eumelanin levels and pigmentation. Topical application of small-molecule inhibitors yielded skin darkening in human skin, and mice with decreased NNT function displayed increased pigmentation. Additionally, genetic modification of NNT in zebrafish alters melanocytic pigmentation. Analysis of four diverse human cohorts revealed significant associations of skin color, tanning, and sun protection use with various single-nucleotide polymorphisms within NNT. NNT levels were independent of UVB irradiation and redox modulation. Individuals with postinflammatory hyperpigmentation or lentigines displayed decreased skin NNT levels, suggesting an NNT-driven, redox-dependent pigmentation mechanism that can be targeted with NNT-modifying topical drugs for medical and cosmetic purposes.
Background
The skin is the first organ that manifests changes in response to zinc deficiency. However, the molecular mechanism underlying how zinc is involved in skin homeostasis, especially in its epigenetic regulation, is largely unknown.
Objectives
In this study, we demonstrate the importance of zinc levels and the zinc transporter ZIP10 in the epigenetic maintenance of human epidermal homeostasis.
Methods
Adult human skin, including skin appendages were stained with anti‐ZIP10 antibody. HAT activity was assessed after treating human keratinocytes with ZIP10 siRNAs or a zinc chelator TPEN. ZIP10‐ or HAT‐regulated genes were analyzed based on limma bioinformatics analysis for keratinocytes treated with ZIP10 siRNAs or HAT inhibitor, or using a public database for transcription factors. A reconstituted human skin model was used to validate the role of ZIP10 in epidermal differentiation and the functional association between ZIP10 and HAT.
Results
ZIP10 is predominantly expressed in the interfollicular epidermis, epidermal appendages, and hair follicles. ZIP10 depletion resulted in epidermal malformations in a reconstituted human skin model via down‐regulation of the activity of the epigenetic enzyme HAT. The decreased HAT activity, resulting from either ZIP10 depletion or treatment with the zinc chelator TPEN, was readily restored by zinc supplementation. Through bioinformatics analysis for gene sets regulated by ZIP10 knockdown and HAT inhibition, we demonstrated that ZIP10 and HATs were closely linked with the regulation of genes related to epidermal homeostasis, particularly filaggrin and metallothionein.
Conclusions
Our study suggests that ZIP10‐mediated zinc distribution is crucial for epidermal homeostasis via HATs; therefore, zinc‐dependent epigenetic regulation could provide alternatives to maintaining healthy skin or alleviating disorders with the skin barrier defects.
This article is protected by copyright. All rights reserved.
Research on the biology of NAD+ has been gaining momentum, providing many critical insights into the pathogenesis of age-associated functional decline and diseases. In particular, two key NAD+ intermediates, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), have been extensively studied over the past several years. Supplementing these NAD+ intermediates has shown preventive and therapeutic effects, ameliorating age-associated pathophysiologies and disease conditions. Although the pharmacokinetics and metabolic fates of NMN and NR are still under intensive investigation, these NAD+ intermediates can exhibit distinct behavior, and their fates appear to depend on the tissue distribution and expression levels of NAD+ biosynthetic enzymes, nucleotidases, and presumptive transporters for each. A comprehensive concept that connects NAD+ metabolism to the control of aging and longevity in mammals has been proposed, and the stage is now set to test whether these exciting preclinical results can be translated to improve human health.
Amyloid-β (Aβ) oligomers have been accepted as major neurotoxic agents in the therapy of Alzheimer's disease (AD). It has been shown that the activity of nicotinamide adenine dinucleotide (NAD + ) is related with the decline of Aβ toxicity in AD. Nicotinamide mononucleotide (NMN), the important precursor of NAD+, is produced during the reaction of nicotinamide phosphoribosyl transferase (Nampt). This study aimed to figure out the potential therapeutic effects of NMN and its underlying mechanisms in APPswe/PS1dE9 (AD-Tg) mice. We found that NMN gave rise to a substantial improvement in behavioral measures of cognitive impairments compared to control AD-Tg mice. In addition, NMN treatment significantly decreased β-amyloid production, amyloid plaque burden, synaptic loss, and inflammatory responses in transgenic animals. Mechanistically, NMN effectively controlled JNK activation. Furthermore, NMN potently progressed nonamyloidogenic amyloid precursor protein (APP) and suppressed amyloidogenic APP by mediating the expression of APP cleavage secretase in AD-Tg mice. Based on our findings, it was suggested that NMN substantially decreases multiple AD-associated pathological characteristically at least partially by the inhibition of JNK activation.
Acrodermatitis enteropathica (AE) is an autosomal recessive disorder that is characterized by scaly eczematous dermatosis accompanied by alopecia and diarrhea. Various mutations in the SLC39A4 gene (ZIP4), which encodes a zinc transporter, are responsible for this disorder. However, the molecular mechanism underlying the involvement of ZIP4 in the pathogenesis of this condition has yet to be established. In this study, we report the role of ZIP4 in human epidermis. ZIP4 is predominantly expressed in human keratinocytes, and its expression is dramatically reduced upon epidermal differentiation. ZIP4 knockdown in human keratinocytes down-regulates Zn levels and the transcriptional activity of a key epidermal Zn-binding protein, ΔNp63, and dysregulates epidermal differentiation in a reconstituted human skin model, resulting in the appearance of proliferating keratinocytes even in the uppermost layers of the skin. We verified that, among the amino acid residues in its Zn-binding motif, Cys205 is critical for the processing and nuclear distribution of ΔNp63 and, therefore, Zn-dependent transcriptional activity. Our results suggest that ZIP4 is essential for maintaining human epidermal homeostasis through the regulation of Zn-dependent ΔNp63 activity and can provide insight into the molecular mechanisms responsible for the cutaneous symptoms observed in AE patients.
NAD⁺ availability decreases with age and in certain disease conditions. Nicotinamide mononucleotide (NMN), a key NAD⁺ intermediate, has been shown to enhance NAD⁺ biosynthesis and ameliorate various pathologies in mouse disease models. In this study, we conducted a 12-month-long NMN administration to regular chow-fed wild-type C57BL/6N mice during their normal aging. Orally administered NMN was quickly utilized to synthesize NAD⁺ in tissues. Remarkably, NMN effectively mitigates age-associated physiological decline in mice. Without any obvious toxicity or deleterious effects, NMN suppressed age-associated body weight gain, enhanced energy metabolism, promoted physical activity, improved insulin sensitivity and plasma lipid profile, and ameliorated eye function and other pathophysiologies. Consistent with these phenotypes, NMN prevented age-associated gene expression changes in key metabolic organs and enhanced mitochondrial oxidative metabolism and mitonuclear protein imbalance in skeletal muscle. These effects of NMN highlight the preventive and therapeutic potential of NAD⁺ intermediates as effective anti-aging interventions in humans.
Oxidative stress is the resultant damage due to redox imbalances (increase in destructive free radicals [reactive oxygen species (ROS)] and reduction in antioxidant protection/pathways) and is linked to ageing in many tissues including skin. In ageing skin there are bioenergetic differences between keratinocytes and fibroblasts which provide a potential ageing biomarker. The differences in skin bioenergy are part of the mitochondrial theory of ageing which remains one of the most widely accepted ageing theories describing subsequent increasing free radical generation. Mitochondria are the major source of cellular oxidative stress and form part of the vicious cycle theory of ageing. External and internal sources of oxidative stress include UVR/IR, pollution (environment), lifestyle (exercise and diet), alcohol and smoking all of which may potentially impact on skin although many exogenous actives and endogenous antioxidant defence systems have been described to help abrogate the increased stress. This also links to differences in skin cell types in terms of the UVR action spectrum for nuclear and mitochondrial DNA damage (the latter a previously described UVR biomarker in skin). Recent work associates bioenergy production and oxidative stress with pigment production thereby providing another additional potential avenue for targeted anti-ageing intervention in skin. This new data supporting the detrimental effects of the numerous wavelengths of UVR may aid in the development of cosmetic/sunscreen design to reduce the effects of photoageing. Recently, complex II of the mitochondrial electron transport chain appears to be more important than previously thought in the generation of free radicals (suggested predominantly by non-human studies). We investigated the relationship between complex II and ageing using human skin as a model tissue. The rate of complex II activity per unit of mitochondria was determined in fibroblasts and keratinocytes cultured from skin covering a wide age range. Complex II activity significantly decreased with age in fibroblasts (P = 0·015), but not in keratinocytes. This was associated with a significant decline in transcript expression (P = 0·008 and P = 0·001) and protein levels (P = 0·0006 and P = 0·005) of the SDHA and SDHB catalytic subunits of complex II respectively. In addition there was a significant decrease in complex II activity with age (P = 0·029) that was specific to senescent skin cells, our study being the first to investigate these differences with senescence and skin age. There was no decrease in complex IV activity with increasing age, suggesting possible locality to complex II. Our study provides a future potential biomarker for monitoring the progression of skin ageing.
Skin melanocytes are activated by exposure to UV radiation to secrete melanin-containing melanosomes to protect the skin from UV-induced damage. Despite the continuous renewal of the epidermis, the turnover rate of melanocytes is very slow, and they survive for long periods. However, the mechanisms underlying the survival of melanocytes exposed to UV radiation are not known. Here, we investigated the role of melanocyte-derived extracellular vesicles in melanocyte survival. Network analysis of the melanocyte extracellular vesicle proteome identified the extracellular matrix component fibronectin at a central node, and the release of fibronectin-containing extracellular vesicles was increased after exposure of melanocytes to UVB radiation. Using an anti-fibronectin neutralizing antibody and specific inhibitors of extracellular vesicle secretion, we demonstrated that extracellular vesicles enriched in fibronectin were involved in melanocyte survival following UVB radiation. Furthermore, we observed that in the hyperpigmented lesions of melasma patients, the extracellular space around melanocytes contained more fibronectin compared with normal skin, suggesting that fibronectin is involved in maintaining melanocytes in pathological conditions. Collectively, our findings suggest that melanocytes secrete fibronectin-containing extracellular vesicles to increase their survival following UVB radiation. These data provide important insight into how constantly stimulated melanocytes can be maintained in pathological conditions such as melasma.
Nicotinamide adenine dinucleotide (NAD+) is a coenzyme found in all living cells. It serves both as a critical coenzyme for enzymes that fuel reduction-oxidation reactions, carrying electrons from one reaction to another, and as a cosubstrate for other enzymes such as the sirtuins and poly(adenosine diphosphate-ribose) polymerases. Cellular NAD+ concentrations change during aging, and modulation of NAD+ usage or production can prolong both health span and life span. Here we review factors that regulate NAD+ and discuss how supplementation with NAD+ precursors may represent a new therapeutic opportunity for aging and its associated disorders, particularly neurodegenerative diseases.
Hyperpigmentation problems, such as postinflammatory hyperpigmentation, solar lentigos, and melasma, can occur across all skin types with aging. Basic understanding of the pigmentation process and of these skin problems has led to their management by attacking proven targets with proven technologies. To name just a few examples, tyrosinase inhibition, blocking melanosome transfer, inhibition of tyrosinase glycosylation, increasing tyrosinase turnover, and blocking inflammation are clinically demonstrated approaches using, respectively, kojic acid, niacinamide, N-acetyl glucosamine, hexyldecanol, and phytosterol. Yet, because of the complexity of the pigmentation process, changes in skin with aging, and the involvement of a variety of cells (melanocytes, keratinocytes, fibroblasts, and inflammatory cells) in initiation, production, and processing of melanin, there are likely many more potential targets still to be characterized and fully exploited.
This review chapter explores these topics. Also, it briefly discusses other important skin chromophores that likely contribute to the color of aging skin, opening further approaches to understand skin color and to develop approaches for treatment of discoloration. Additionally, investigative tools such as laboratory model systems for understanding the pigmentation process and screening for potential active technologies are presented. Furthermore, since evaluating the effectiveness of technology on human subjects is a key step in validating any new approach to treatment, clinical methods are also briefly discussed.
Ever since eukaryotes subsumed the bacterial ancestor of mitochondria, the nuclear and mitochondrial genomes have had to closely coordinate their activities, as each encode different subunits of the oxidative phosphorylation (OXPHOS) system. Mitochondrial dysfunction is a hallmark of aging, but its causes are debated. We show that, during aging, there is a specific loss of mitochondrial, but not nuclear, encoded OXPHOS subunits. We trace the cause to an alternate PGC-1α/β-independent pathway of nuclear-mitochondrial communication that is induced by a decline in nuclear NAD(+) and the accumulation of HIF-1α under normoxic conditions, with parallels to Warburg reprogramming. Deleting SIRT1 accelerates this process, whereas raising NAD(+) levels in old mice restores mitochondrial function to that of a young mouse in a SIRT1-dependent manner. Thus, a pseudohypoxic state that disrupts PGC-1α/β-independent nuclear-mitochondrial communication contributes to the decline in mitochondrial function with age, a process that is apparently reversible.
When small RNA is sequenced on current sequencing machines, the resulting reads are usually longer than the RNA and therefore contain parts of the 3' adapter. That adapter must be found and removed error-tolerantly from each read before read mapping. Previous solutions are either hard to use or do not offer required features, in particular support for color space data. As an easy to use alternative, we developed the command-line tool cutadapt, which supports 454, Illumina and SOLiD (color space) data, offers two adapter trimming algorithms, and has other useful features.
Cutadapt, including its MIT-licensed source code, is available for download at http://code.google.com/p/cutadapt/
Mitochondrial dysfunctions activate retrograde signaling from mitochondria to the nucleus. To identify transcription factors and their associated pathways that underlie mitochondrial retrograde signaling, we performed gene expression profiling of the cells engineered to have varying amounts of mitochondrial DNA with an A3243G mutation (mt3243) in the leucine transfer RNA (tRNA(Leu)), which reduces the abundance of proteins involved in oxidative phosphorylation that are encoded by the mitochondrial genome. The cells with the mutation exhibited reduced mitochondrial function, including compromised oxidative phosphorylation, which would activate diverse mitochondrial retrograde signaling pathways. By analyzing the gene expression profiles in cells with the mutant tRNA(Leu) and the transcription factors that recognize the differentially regulated genes, we identified 72 transcription factors that were potentially involved in mitochondrial retrograde signaling. We experimentally validated that the mt3243 mutation induced a retrograde signaling pathway involving RXRA (retinoid X receptor α), reactive oxygen species, kinase JNK (c-JUN N-terminal kinase), and transcriptional coactivator PGC1α (peroxisome proliferator-activated receptor γ, coactivator 1 α). This RXR pathway contributed to the decrease in mRNA abundances of oxidative phosphorylation enzymes encoded in the nuclear genome, thereby aggravating the dysfunction in oxidative phosphorylation caused by the reduced abundance of mitochondria-encoded enzymes of oxidative phosphorylation. Thus, matching transcription factors to differentially regulated gene expression profiles was an effective approach to understand mitochondrial retrograde signaling pathways and their roles in mitochondrial dysfunction.
Type 2 diabetes (T2D) has become epidemic in our modern lifestyle, likely due to calorie-rich diets overwhelming our adaptive metabolic pathways. One such pathway is mediated by nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in mammalian NAD(+) biosynthesis, and the NAD(+)-dependent protein deacetylase SIRT1. Here, we show that NAMPT-mediated NAD(+) biosynthesis is severely compromised in metabolic organs by high-fat diet (HFD). Strikingly, nicotinamide mononucleotide (NMN), a product of the NAMPT reaction and a key NAD(+) intermediate, ameliorates glucose intolerance by restoring NAD(+) levels in HFD-induced T2D mice. NMN also enhances hepatic insulin sensitivity and restores gene expression related to oxidative stress, inflammatory response, and circadian rhythm, partly through SIRT1 activation. Furthermore, NAD(+) and NAMPT levels show significant decreases in multiple organs during aging, and NMN improves glucose intolerance and lipid profiles in age-induced T2D mice. These findings provide critical insights into a potential nutriceutical intervention against diet- and age-induced T2D.
The significance of human cutaneous pigmentation lies in its protective role against sun-induced DNA damage and photocarcinogenesis. Fair skin and red hair are characterized by a low eumelanin to pheomelanin ratio, and have been associated with increased risk of skin cancer. Cutaneous pigmentation is a complex genetic trait, with more than 120 genes involved in its regulation, among which the melanocortin 1 receptor gene (MC1R) plays a key role. Although a large number of single nucleotide polymorphisms (SNPs) have been identified in pigmentation genes, very few SNPs have been examined in relation to human pigmentary phenotypes and skin cancer risk. Recent GWAS have identified new candidate determinants of pigmentation traits, but MC1R remains the best characterized genetic determinant of human skin and hair pigmentation as well as the more firmly validated low-penetrance skin cancer susceptibility gene. In this review, we will address how the melanocortin system regulates pigmentation, the effect of MC1R variants on the physiologic function of the MC1 receptor, and how specific MC1R variants are associated with distinct human pigmentation phenotypes.
It has been reported that melanocytes play important roles in skin and hair pigmentation and are differentiated from melanocyte stem cells (MSCs) residing in the bulge area of hair follicles. Recently, interest has been growing in MSCs because regulation of the upstream of differentiated melanocytes is essential for the determination of skin and hair pigmentation; however, their precise characteristics remain to be elucidated. The aim of this study is to explore cell-surface markers expressed on MSCs in order to understand their characteristics. To explore genes specifically expressed in the bulge region, we classified a hair follicle into four areas, hair bulb, hair bulb to bulge (lower bulge), bulge, and epidermis to bulge (upper bulge), and collected these areas from back skin sections of C57BL/6 mice by laser microdissection. Real-time RT-PCR performed on these areas revealed that Frizzled (Fzd)-4, Fzd7, low density lipoprotein receptor-related protein 5 (Lrp5), and Lrp6, receptors for Wnt molecules, were expressed higher in the bulge area than other areas. Furthermore, FACS analysis showed that populations of Fzd4(+) cells and Fzd7(+) cells were different from those of Kit(+) cells (precursor of melanocytes: melanoblasts). Fzd4(+) and Fzd7(+) cells isolated by FACS required a longer culture period to differentiate into mature melanocytes than Kit(+) cells. Up-regulation of mRNA expressions of melanocyte markers (dopa chrometautomerase: Dct, tyrosinase: Tyr, tyrosinase-related protein 1: Tyrp1) was observed in Fzd4(+) and Fzd7(+) cells following Kit(+) cells during differentiation. These results suggested that Fzd4(+) and Fzd7(+) cells were more immature than melanoblasts, therefore raising the possibility that Fzd4(+) and Fzd7(+) cells are MSCs.
With aging, melanocytes become unevenly distributed in the epidermis. In light skin individuals, hypo-pigmentation is found in association with focal hyper-pigmentation (lentigo senilis). Apparently this results from progressive loss of active melanocytes and focal increase in melanocyte proliferation and/or aggregation. This paper summarizes the present knowledge on aging of melanocytes in vivo and in vitro, with a focus on the role of melanin as a determinant for proliferation and terminal differentiation. We describe that excessive melanin deposition by cyclic AMP-inducing agents results in increased expression of the cyclin-dependent kinase inhibitors P27Kip-1 and p21SDI-1/Waf-1, increased binding of p16 to CDK4, and terminal differentiation. Journal of Investigative Dermatology Symposium Proceedings 3:36– 40, 1998
Importantly, the efficiency with which the melanocytes exit the cell cycle depends on the melanin background of the donor's cells. Melanocytes from skin types IV–VI that accumulate large amounts of brown black melanin (eumelanin), lose expression of the transcription factors E2F1 and E2F2, two key regulatory proteins, and withdraw from the cell cycle more rapidly than melanocytes from skin types I and II that accumulate red/yellow melanin (pheomelanin). Thus, we propose that terminal differentiation is a tumor suppressor mechanism that becomes less efficient under imperfect eumelanization.
Nicotinamide adenine dinucleotide (NAD(+)) is both a coenzyme for hydride-transfer enzymes and a substrate for NAD(+)-consuming enzymes, which include ADP-ribose transferases, poly(ADP-ribose) polymerases, cADP-ribose synthases and sirtuins. Recent results establish protective roles for NAD(+) that might be applicable therapeutically to prevent neurodegenerative conditions and to fight Candida glabrata infection. In addition, the contribution that NAD(+) metabolism makes to lifespan extension in model systems indicates that therapies to boost NAD(+) might promote some of the beneficial effects of calorie restriction. Nicotinamide riboside, the recently discovered nucleoside precursor of NAD(+) in eukaryotic systems, might have advantages as a therapy to elevate NAD(+) without inhibiting sirtuins, which is associated with high-dose nicotinamide, or incurring the unpleasant side-effects of high-dose nicotinic acid.
Neuronal SIRT1 activation as a novel mechanism underlying the prevention of Alzheimer disease amyloid neuropathology by calorie restriction
- Qin