Photoprotection of Mammalian Acid-Soluble Collagen by Cuttlefish Sepia Melanin In Vitro

IBT-based quantitative proteomics identifies potential regulatory proteins involved in pigmentation of purple sea cucumber, Apostichopus japonicus

Sea cucumbers are an important economic species and exhibit high yield value among aquaculture animals. Purple sea cucumbers are very rare and beautiful and have stable hereditary patterns. In this study, isobaric tags (IBT) were first used to reveal the molecular mechanism of pigmentation in the body wall of the purple sea cucumber. We analyzed the proteomes of purple sea cucumber in early pigmentation stage (Pa), mid pigmentation stage (Pb) and late pigmentation stage (Pc), resulting in the identification of 5580 proteins, including 1099 differentially expressed proteins in Pb: Pa and 339 differentially expressed proteins in Pc: Pb. GO and KEGG analyses revealed possible differentially expressed proteins, including"melanogenesis", "melanosome", "melanoma", "pigment-biosynthetic process", "Epidermis development", "Ras-signaling pathway", "Wnt-signaling pathway", "response to UV light", and "tyrosine metabolism", involved in pigment synthesis and regulation in purple sea cucumbers. The large number of differentially expressed proteins identified here should be highly useful in further elucidating the mechanisms underlying pigmentation in sea cucumbers. Furthermore, these results may also provide the base for further identification of proteins involved in resistance mechanisms against melanoma, albinism, UV damage, and other diseases in sea cucumbers.

Host risk factors for the development of multiple non-melanoma skin cancers

Non-melanoma skin cancer (NMSC) is the most common cancer in the US, and having multiple lesions conveys substantial cost and morbidity for the individual involved. Although there are data available on risk factors for NMSC, there are currently few studies that identify specific risk factors for development of multiple NMSCs. We evaluated host risk factors for multiple NMSCs among men (Health Professionals Follow-up Study) and women (Nurses' Health Study). Compared with individuals with a single NMSC, having greater number of sunburns was a risk factor for developing ≥ 2 NMSCs [≥ 10 sunburns, cumulative relative risk (RR) = 1.21, 95% confidence interval (CI): 1.07-1.36] and a higher risk of developing ≥ 11 NMSCs (≥10 sunburns, RR = 2.33, 95% CI: 1.57-3.46). Inability-to-tan was associated with risk of developing ≥ 2 NMSCs (cumulative RR = 1.29, 95% CI: 1.18-1.40) and a higher risk of developing ≥ 11 NMSCs (RR = 1.91, 95% CI: 1.50-2.43). Men had an increased risk of developing ≥ 2 NMSCs (cumulative RR = 1.53, 95% CI: 1.40-1.66). Risk of developing 2-4, 5-10 and ≥11 NMSCs increased with age. Other risk factors for developing ≥ 2 NMSCs included red natural hair colour (cumulative RR = 1.23, 95% CI: 1.07-1.42), family history of melanoma (cumulative RR = 1.15, 95% CI: 1.03-1.28), and having ≥ 6 nevi on the left arm (cumulative RR = 1.22, 95% CI: 1.07-1.40). In conclusion, physicians caring for individuals with incident NMSCs may consider paying special attention to those at highest risk for developing additional tumours, especially males and those with a history of ≥ 10 lifetime sunburns, by performing routine full skin examinations and counselling for aggressive photoprotection.

Melanin protects melanocytes and keratinocytes against H2O2-induced DNA strand breaks through its ability to bind Ca2+

Reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) are produced in the skin under the influence of UV radiation. These compounds are highly reactive and can induce DNA lesions in epidermal cells. Melanin is considered to protect human skin against DNA damage by absorbing UV radiation. We have investigated whether melanin can, in addition, offer protection against the effects of H(2)O(2) in human melanocytes and HaCaT keratinocytes. In the present study, it was shown that 40 and 100 microM H(2)O(2) increased the number of DNA strand breaks as measured using the comet assay, in melanocytes of Caucasian origin. In melanocytes of the same origin in which melanin levels were increased by culturing in presence of 10 mM NH(4)Cl and elevated l-tyrosine, H(2)O(2)-induced DNA damage was reduced compared to that in control melanocytes. Similarly, HaCaT cells that were loaded with melanin were better protected against H(2)O(2)-induced DNA strand breaks than control HaCaT cells. These protective effects of melanin were mimicked by the intracellular Ca(2+)-chelator BAPTA. Thus, BAPTA reduced the level of H(2)O(2)-induced DNA strand breaks in melanocytes. Like BAPTA, melanin is known to be a potent chelator of Ca(2+) and this was confirmed in the present study. It was shown that melanin levels in melanocytic cells correlated directly with intracellular Ca(2+) binding capacity and, in addition, correlated inversely with H(2)O(2)-induced increases in intracellular Ca(2+). Our results show that melanin may have an important role in regulating intracellular Ca(2+) homeostasis and it is suggested that melanin protects against H(2)O(2)-induced DNA strand breaks in both melanocytes and keratinocytes and through its ability to bind Ca(2+).

Enzymatic dopamine peroxidation in substantia nigra of human brain

The main metabolic pathway affected in Parkinson's disease is that of dopamine oxidation and melanin formation in substantia nigra which involves both oxidative and reductive enzymes. The cyclic nature of the biosynthetic pathway from dopamine to melanin implies that a derangement at any of the steps may result in the disappearance of melanin. Possible pathogenetic events such as oxidative stress have therefore no clearcut interpretation since they may be both cause or consequence of the disease. This paper documents the existence of a peroxidase converting dopamine to dopaminochrome in the presence of hydrogen peroxide in the substantia nigra of autopsied human brain. The activatory effect of dopaminochrome on a purified peroxidase is shown, together with the inhibitory effect of dopaminochrome-derived melanin and the activatory effect of melanin/Fe. The toxic effect of dopaminochrome on murine neuroblastoma cells cultured in vitro is demonstrated together with the inhibition of dopaminochrome melanization induced by acetylcholine in vitro.