Differential expression of inflammatory cytokines and chemokines in lipopolysaccharide‐stimulated melanocytes from lightly and darkly pigmented skin

Increasing evidence suggests that human epidermal melanocytes play an important role in the skin immune system; however, a role of their pigmentation in immune and inflammatory responses is poorly examined. In the study, the expression of Toll‐like receptor 4 (TLR4) and inflammatory cytokines and chemokines by cultured normal melanocytes derived from lightly and darkly pigmented skin was investigated after cell stimulation with lipopolysaccharide (LPS). The basal TLR4 mRNA level in heavily pigmented cells was higher as compared to their lightly pigmented counterparts. Melanocyte exposure to LPS upregulated the expression of TLR4 mRNA and enhanced the DNA‐binding activity of NF‐κB p50 and p65. We found substantial differences in the LPS‐stimulated expression of numerous genes encoding inflammatory cytokines and chemokines between the cells with various melanin contents. In lightly pigmented melanocytes, the most significantly upregulated genes were nicotinamide phosphoribosyltransferase (NAMPT/visfatin), the chemokines CCL2 and CCL20, and IL6, while the genes for CXCL12, IL‐16 and the chemokine receptor CCR4 were the most significantly upregulated in heavily pigmented cells. Moreover, the lightly pigmented melanocytes secreted much more NAMPT, CCL2 and IL‐6. The results of our study suggest modulatory effect of melanogenesis on the immune properties of normal epidermal melanocytes.     

Niacinamide and 12‐hydroxystearic acid prevented benzo(a)pyrene and squalene peroxides induced hyperpigmentation in skin equivalent

Skin surface is constantly exposed to environmental and secreted stressors such as UV, air pollution and peroxidized sebum. The current study aims to use reconstructed human skin equivalents to demonstrate topical stressor‐induced hyperpigmentation and evaluate bioactives’ potential protective effect. Given that polycyclic aromatic hydrocarbons are representative airborne particle‐bound organic compounds with known relevance to pigmentation pathways, benzo(a)pyrene was selected as surrogate environmental toxin. On the other hand, squalene monohydroperoxides are well‐characterized sebum peroxidation product under UV and pollutant exposure, thus are used as another representative skin stressor. With 3‐day continuous exposure, 30 pmol/cm² of benzo(a)pyrene and 3.4 nmol/cm² of squalene monohydroperoxides induced significant viability loss, inflammatory response, and approximately 10 shades of pigmentation increase in pigmented living skin equivalents. At the same time, pretreatment and co‐treatment with 12‐hydroxystearic acid (12‐HSA, 20 μmol/L) or niacinamide (5 mmol/L) ameliorated such stressor‐induced consequences. Niacinamide was particularly effective against benzo(a)pyrene damage, probably as a substrate for important NAD+ dependent detoxification pathways, while 12‐HSA was potent against squalene monohydroperoxides through barrier enhancing, anti‐inflammatory, and anti‐oxidative mechanisms. In summary, topical stressor‐induced hyperpigmentation was achieved in vitro, with known bioactives showing protective benefits.     

The natural phytochemical trans‐communic acid inhibits cellular senescence and pigmentation through FoxO3a activation

Ageing is characterized by the accumulation of chronic and irreversible oxidative damage, chronic inflammation and organ dysfunction. To attenuate these ageing‐related changes, various natural phytochemicals are often applied. Trans‐communic acid (TCA), an active component of brown pine leaf extract, has antimicrobial and cancer chemopreventive activity and inhibits ultraviolet B (UVB)‐induced MMP‐1 expression. To determine whether the phytochemical TCA could affect the lifespan of an ageing model, Caenorhabditis elegans prevent ageing‐related phenotypes of the skin. Caenorhabditis elegans (C. elegans) wild‐type N2 and mutant strains were used in this study to explore the lifespan extension effect of TCA and its mechanism. We estimated lipofuscin accumulation and melanin levels, which are closely associated with skin senescence. Moreover, we explored the mechanism of action associated with ageing attenuation. We performed oxidative stress resistance and thermotolerance assays in C. elegans and surface plasmon resonance analysis of TCA binding with the forkhead box‐O3a (FoxO3a) protein. TCA, which is the active component in Korean red pine (Pinus densiflora), attenuated ageing‐related changes in skin cells. TCA lowered lipofuscin accumulation in fibroblasts and decreased melanin levels in melanocytes. These protective effects were mediated by activation of the representative longevity gene FoxO3a, which was induced by direct binding with TCA. Interestingly, TCA extended the lifespan of C. elegans, although it did not affect stress resistance, oxidative stress or thermotolerance. These results strongly suggest that TCA prevents the senescent phenotype of model organisms and exhibits beneficial effects on ageing‐related skin phenotypes through direct FoxO3a activation.     

Oral melanin pigmentation related to smoking in a Turkish population

OBJECTIVE: Besides genetic factors, tobacco smoking has been found to be the major cause of oral melanin pigmentation. The purpose of the present study was to evaluate the frequency of oral melanin pigmentation in a Turkish population and to present its correlation with clinical parameters relevant to periodontal status in current smokers, non-smokers, former smokers. METHOD: A sample of 496 patients was randomly selected. The subjects were interviewed regarding their smoking habits. They were clinically examined by a single examiner for the presence of oral melanin pigmentation in different oral mucosal regions. The same examiner recorded the clinical parameters including GI (gingival index), PI (plaque index), BOP (bleeding on probing), PD (probing depth) and GR (gingival recession). Examiner 2 completed a questionnaire concerning skin color and smoking habits. RESULTS: In the study group, 41% were current smokers, 46% nonsmokers and 13% former smokers. The frequencies of pigmented areas were significantly higher in current smokers than in those without any smoking habits. The clinical parameters revealed similar findings for all groups. Low GI and BOP values were observed for current smokers when compared with non-smokers and former smokers, respectively. GI values were significantly associated with the pigmentations in gingiva. CONCLUSIONS: The results of our study show that smokers in a Turkish population had significantly more pigmented oral surfaces than nonsmokers.     

Optogenetic activation of melanin‐concentrating hormone neurons increases non‐rapid eye movement and rapid eye movement sleep during the night in rats

Neurons containing melanin‐concentrating hormone (MCH) are located in the hypothalamus. In mice, optogenetic activation of the MCH neurons induces both non‐rapid eye movement (NREM) and rapid eye movement (REM) sleep at night, the normal wake‐active period for nocturnal rodents [R. R. Konadhode et al. (2013) J. Neurosci., 33, 10257–10263]. Here we selectively activate these neurons in rats to test the validity of the sleep network hypothesis in another species. Channelrhodopsin‐2 (ChR2) driven by the MCH promoter was selectively expressed by MCH neurons after injection of rAAV‐MCHp‐ChR2‐EYFP into the hypothalamus of Long–Evans rats. An in vitro study confirmed that the optogenetic activation of MCH neurons faithfully triggered action potentials. In the second study, in Long–Evans rats, rAAV‐MCH‐ChR2, or the control vector, rAAV‐MCH‐EYFP, were delivered into the hypothalamus. Three weeks later, baseline sleep was recorded for 48 h without optogenetic stimulation (0 Hz). Subsequently, at the start of the lights‐off cycle, the MCH neurons were stimulated at 5, 10, or 30 Hz (1 mW at tip; 1 min on – 4 min off) for 24 h. Sleep was recorded during the 24‐h stimulation period. Optogenetic activation of MCH neurons increased both REM and NREM sleep at night, whereas during the day cycle, only REM sleep was increased. Delta power, an indicator of sleep intensity, was also increased. In control rats without ChR2, optogenetic stimulation did not increase sleep or delta power. These results lend further support to the view that sleep‐active MCH neurons contribute to drive sleep in mammals.     

天然产物对毛发色素的调节作用研究进展

毛发的颜色不仅受年龄、环境因素的影响,还受到众多因子的调控,其中主要有阿黑皮素原(POMC)、黑色素细胞刺激素(α-MSH)、黑色素1受体(MCIR)、小眼畸形相关蛋白因子(MITF)、酪氨酸酶(TYR)、酪氨酸相关蛋白酶1(TRP-1)、酪氨酸相关蛋白酶2(TRP-2)、刺鼠信号蛋白(ASIP)等。毛发颜色的异常常被认为是衰老的特征,给患者带来巨大的心理压力,但相关的治疗药物目前尚属空白。总结了天然药物对毛发颜色的影响程度和作用方式,以期阐明天然药物在治疗须发早白方面可能的作用途径及靶点,为从天然产物中寻找发掘新的药物奠定基础。     

Gentamicin affects melanogenesis in normal human melanocytes

Background: Aminoglycoside antibiotics, including gentamicin, despite their ability to induce adverse effects on pigmented tissues, remain valuable and sometimes indispensable for the treatment of various infections. It is known that gentamicin binds to melanin biopolymers, but the relation between this drug affinity to melanin and its toxicity is not well documented. The aim of this work was to examine the impact of gentamicin on viability and melanogenesis in HEMa-LP (light pigmented) and HEMn-DP (dark pigmented) normal human melanocytes.

Methodology/principal findings: The effect of gentamicin on cell viability was determined by 4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST-1) assay; melanin content and tyrosinase activity were measured spectrophotometrically. It has been demonstrated that gentamicin induces concentration-dependent loss in melanocytes viability. The application of antibiotic in concentration of 10?mM causes higher reduction in viability of the light pigmented melanocytes (by about 74%) when compared with the dark pigmented ones (by about 62%). The value of the concentration of a drug that produces loss in cell viability by 50% (EC₅₀) for both cell lines was found to be ～7.5?mM. It has been shown that gentamicin causes inhibition of tyrosinase activity and reduces melanin content in light pigmented melanocytes significantly more than in the dark pigmented cells.

Conclusion/significance: We have found that gentamicin modulates melanization process in melanocytes in vitro, what may explain the potential role of melanin biopolymer in the mechanisms of undesirable toxic effects of this drug in vivo, as a result of its accumulation in pigmented tissues. We have also stated that the melanogenesis process in light pigmented melanocytes is more sensitive to the inhibitory effect of gentamicin than in the dark pigmented cells.