Isomerization of urocanic acid after ultraviolet radiation is influenced by skin pigmentation

Natural moisturising factor constituents in South African nursing students

BACKGROUND

The majority of South African healthcare workers are Black Africans with dark-pigmented skin. Studies on how the markers of skin barrier function and natural moisturising factor (NMF) compare between dark and light-pigmented skin are limited. Quantifying NMF in a nursing student population during their practical training at university may provide valuable insight into their potential susceptibility to skin conditions associated with low NMF.

OBJECTIVES

The objectives of this study were to quantify and compare NMF content of Black African, Mixed Race and White nursing students from their dominant dorsal hand.

METHODS

Forty-nine White, 32 Black African and 5 Mixed Race nursing students participated in this study. Tape strip samples were collected from the participants' dominant dorsal hand and NMF content was measured, including histidine (HIS), pyrrolidone carboxylic acid (PCA), trans-urocanic acid (t-UCA) and cis-urocanic acid (c-UCA), as well as cytokines interleukin-1 alpha (IL-1α) and interleukin-1 receptor antagonist (IL-1RA).

RESULTS

No statistically significant differences in PCA, t-UCA, c-UCA, IL-1α or IL-1RA were found between Black African and White nursing students. HIS was significantly (p = 0.001) higher in White nursing students when compared to Black African students. The ratio of tot-UCA/HIS was significantly higher in Black Africans (p = 0.0002) when compared to White nursing students.

CONCLUSION

No significant differences were established in NMF content between White and Black African nursing students, other than HIS which was significantly higher in White students than in Black African students. Different HIS levels between the racial groups suggest variation in histidase activity which may be related to skin pH and pigmentation. This finding may suggest that nursing students at the beginning of their careers may have similar susceptibility to skin diseases related to NMF.

Analytical tools for urocanic acid determination in human samples: A review

Urocanic acid is a chromophore found in the skin that has been identified as an important immunosuppressant and carcinogenesis mediator through its photoisomerization from trans to cis form induced by ultraviolet radiation. Research on analytical methods that explore urocanic acid isomerization is indispensable to fully understand the deleterious effects mediated by this biomarker. In this context, the current relevant analytical methods for determination of these isomers in human samples are summarized in this review. The methods presented here are applicable to human samples collected by noninvasive methods (or minimally invasive), encompassing an array of analytical techniques, including high-performance capillary electrophoresis, confocal Raman spectroscopy, gas chromatography, high-performance liquid chromatography, and mass spectrometry, among others. Developed high-performance liquid chromatography methods have proven to be advantageous, allowing noninvasive collections for in vivo analysis and the confocal Raman, specially, for real-time analysis. Among all these methods, high-performance liquid chromatography is the most investigated one with mass spectrometry or ultraviolet detector, and the mass spectrometry detector being the most studied in the last years, demonstrating high sensitivity, very low detection limits, and accurate identification, especially for clinical investigations.

NK1R/5-HT1AR interaction is related to the regulation of melanogenesis

Substance P (SP) is a candidate mediator along the brain-skin axis and can mimic the effects of stress to regulate melanogenesis. Previously, we and others have found that the regulation of SP for pigmentary function was mediated by neurokinin 1 receptor (NK1R). Emerging evidence has accumulated that psychologic stress can induce dysfunction in the cutaneous serotonin 5-hydroxytryptamine (5-HT)-5-HT1A/1B receptor system, thereby resulting in skin hypopigmentation. Moreover, NK1R and 5-HTR (except 5-HT3) belong to GPCR. The present study aimed at assessing the possible existence of NK1R-5-HTR interactions and related melanogenic functions. Western blot and PCR detection revealed that SP reduced expression of 5-HT1A receptor via the NK1 receptor. Biochemical analyses showed that NK1R and 5-HT1AR could colocalize and interact in a cell and in the skin. When the N terminus of the NK1R protein was removed NK1R surface targeting was prevented, the interaction between NK1R-5-HT1AR decreased, and the depigmentation caused by SP and WAY100635 could be rescued. Importantly, pharmaceutical coadministration of NK1R agonist (SP) and 5-HT1A antagonist (WAY100635) enhanced the NK1-5-HT1A receptor coimmunoprecipitation along with the depigmentary response. SP and WAY100635 cooperation elicited activation of a signaling cascade (the extracellular, regulated protein kinase p-JNK signaling pathway) and inhibition of p70S6K1 phosphorylation and greatly reduced melanin production in vitro and in vivo in mice and zebrafish. Moreover, the SP-induced depigmentation response did not be occur in 5-htr1aa^+/- zebrafish embryos. Taken together, the results of our systemic study increases our knowledge of the roles of NK1R and 5-HT1AR in melanogenesis and provides possible, novel therapeutic strategies for treatment of skin hypo/hyperpigmentation.-Wu, H., Zhao, Y., Huang, Q., Cai, M., Pan, Q., Fu, M., An, X., Xia, Z., Liu, M., Jin, Y., He, L., Shang, J. NK1R/5-HT1AR interaction is related to the regulation of melanogenesis.

EFFECT OF FUCOIDAN ON B16 MURINE MELANOMA CELL MELANIN FORMATION AND APOPTOSIS

Background: :

Fucoidan is a complex sulfated polysaccharide extracted from brown seaweed and has a wide variety of biological activities. It not only inhibits cancer cell growth but also inhibits tyrosinase in vitro. Therefore, it is of interest to investigate the effect of fucoidan on B16 murine melanoma cells as the findings may provide new insights into the underlying mechanism regarding the inhibition of melanin formation by fucoidan. In the present study, we aimed to investigate the anti-melanogenic effect of fucoidan and its inhibitory effect on B16 cells.

Materials and Methods:

The influence of fucoidan on B16 melanoma cells and cellular tyrosinase was examined. Cell viability was examined by the cell counting kit-8 assay. Cellular tyrosinase activity and melanin content were determined using spectrophotometric methods and protein expression was analyzed by immunoblotting. Morphological changes in B16 melanoma cells were examined by phase contrast microscopy and apoptosis was analyzed by flow cytometry.

Results:

In vitro studies were performed using cell viability analysis and showed that fucoidan significantly decreased viable cell number in a dose-response manner with an IC₅₀ of 550 ±4.3 µg/mL. Cell morphology was altered and significant apoptosis was induced when cells were exposed to 550 µg/mL fucoidan for 48 h.

Conclusion:

This study provides substantial evidence to show that fucoidan inhibits B16 melanoma cell proliferation and cellular tyrosinase activity. Fucoidan may be useful in the treatment of hyperpigmentation and as a skin-whitening agent in the cosmetics industry.

The impact of skin colour on human photobiological responses

Terrestrial solar ultraviolet radiation (UVR) exerts both beneficial and adverse effects on human skin. Epidemiological studies show a lower incidence of skin cancer in people with pigmented skins compared to fair skins. This is attributed to photoprotection by epidermal melanin, as is the poorer vitamin D status of those with darker skins. We summarize a wide range of photobiological responses across different skin colours including DNA damage and immunosuppression. Some studies show the generally modest photoprotective properties of melanin, but others show little or no effect. DNA photodamage initiates non‐melanoma skin cancer and is reduced by a factor of about 3 in pigmented skin compared with white skin. This suggests that if such a modest reduction in DNA damage can result in the significantly lower skin cancer incidence in black skin, the use of sunscreen protection might be extremely beneficial for susceptible population. Many contradictory results may be explained by protocol differences, including differences in UVR spectra and exposure protocols. We recommend that skin type comparisons be done with solar‐simulated radiation and standard erythema doses or physical doses (J/m²) rather than those based solely on clinical endpoints such as minimal erythema dose (MED).

Activation of neurokinin-1 receptor by substance P inhibits melanogenesis in B16-F10 melanoma cells

Skin pigmentation plays a number of valuable roles and its regulation is a complex process that is controlled by different factors. Substance P (SP) regulates many biological functions, including neurogenic inflammation, pain, and stress. However, to date, the regulatory role of SP in the control of melanogenesis has not been elucidated. The present study was designed to investigate the effects of SP on melanogenesis and to elucidate its underlying mechanism(s). After treatment for 48 h in mouse B16-F10 melanoma cells, SP (1 and 10nM) significantly down-regulated tyrosinase activity and melanin content. Importantly, western blot analysis revealed the presence of neurokinin-1 receptor (NK-1 R) in B16-F10 cells and the activation of it after SP treatment. It was also found that preincubation with NK-1 receptor antagonist Spantide I could partially reversed SP-induced down-regulations of tyrosinase activity, melanin content and the expression of tyrosinase and tyrosinase-related protein 1. Furthermore, SP could remarkably inhibit the expressions of microphtalmia-associated transcription factor (MITF) and p-p38 MAPK and stimulated p-p70 S6K1. These effects could also be partially reversed by the pretreatment with Spantide I. These results collectively suggested that SP inhibited melanogenesis in B16-F10 cells, which might be attributed to the fact that SP induces the activation of NK-1 receptor, stimulates the phosphorylation of p70 S6K1 and inhibits that of p38 MAPK, decreases the tyrosinase and tyrosinase-related protein 1 expression through MITF, finally resulting in the suppression of melanogenesis. These observations in vitro indicated that the regulation of the SP/NK-1 receptor system might be a useful novel management for skin pigmentation.

Recent advances in urocanic acid photochemistry, photobiology and photoimmunology

Urocanic acid (UCA), produced in the upper layers of mammalian skin, is a major absorber of ultraviolet radiation (UVR). Originally thought to be a 'natural sunscreen', studies conducted a quarter of a century ago proposed that UCA may be a chromophore for the immunosuppression that follows exposure to UVR. With its intriguing photochemistry, its role in immunosuppression and skin cancer development, and skin barrier function, UCA continues to be the subject of intense research effort. This review summarises the photochemical, photobiological and photoimmunological findings regarding UCA, published since 1998.

Seasonal fluctuations of incubation, healing delays, and clinical presentation of cutaneous leishmaniasis in French Guiana

An investigation was conducted to determine whether seasonal variations affected the development of cutaneous leishmaniasis. Data from 499 cases treated between July 1994 and December 1998 were analyzed. The interval between infection and consultation and between treatment and clinical cure varied significantly between cases with an incubation period during the dry season compared with the rainy season (P < 0.001). When the incubation period occurred during the dry season, the standard pentamidine isethionate treatment seemed to be less effective (i.e.. the odds ratio for failure was 1.9 [1.1-3.4], P = 0.01). The presence of lymphangitis was more frequent during the dry season (i.e., the odds ratio was 0.26 [0.15-0.45], P < 0.001). These results suggested that the observed seasonal variations were due to variations in the host/parasite balance. Converging indirect elements that suggest a role for variations in solar ultraviolet radiation are discussed.