Electron paramagnetic resonance as a unique tool for skin and hair research

A methodological exploration of distinguishing hair quality based on hair proteomics

Hair is an advantageous biological sample due to its recordable, collectable, and storable nature. Hair's primary components are keratin and keratin-associated proteins. Owing to its abundance of cystine, keratin possesses impressive mechanical strength and chemical stability, formed by creating disulfide bonds as crosslinks within the protein peptide chain. Furthermore, keratin is cross-linked with keratin-associated proteins to create a complex network structure that provides the hair with strength and rigidity. Protein extraction serves as the foundation for hair analysis research. Bleaching hair causes damage to the structure between keratin and keratin-associated proteins, resulting in texture issues and hair breakage. This article outlines various physical treatment methods and lysate analysis that enhance the efficiency of hair protein extraction. The PLEE method achieves a three-fold increase in hair protein extraction efficiency when using a lysis solution containing SDS and combining high temperatures with intense shaking, compared to previous methods found in literature. We utilized the PLEE method to extract hair from both normal and damaged groups. Normal samples identified 156-157 proteins, including 51 keratin and keratin-associated proteins. The damaged group consisted of 155-158 identified proteins, of which 48-50 were keratin and keratin-associated proteins. Bleaching did not cause any notable difference in the protein identification of hair. However, it did reduce coverage of keratin and keratin-associated proteins significantly. Our hair protein extraction method provides extensive coverage of the hair proteome. Our findings indicate that bleaching damage results in subpar hair quality due to reduced coverage of protein primary sequences in keratin and keratin-associated proteins.

Spin Trapping of Nitric Oxide by Hemoglobin and Ferrous Diethyldithiocarbamate in Model Tumors Differing in Vascularization

Animal tumors serve as reasonable models for human cancers. Both human and animal tumors often reveal triplet EPR signals of nitrosylhemoglobin (HbNO) as an effect of nitric oxide formation in tumor tissue, where NO is complexed by Hb. In search of factors determining the appearance of nitrosylhemoglobin (HbNO) in solid tumors, we compared the intensities of electron paramagnetic resonance (EPR) signals of various iron-nitrosyl complexes detectable in tumor tissues, in the presence and absence of excess exogenous iron(II) and diethyldithiocarbamate (DETC). Three types of murine tumors, namely, L5178Y lymphoma, amelanotic Cloudman S91 melanoma, and Ehrlich carcinoma (EC) growing in DBA/2 or Swiss mice, were used. The results were analyzed in the context of vascularization determined histochemically using antibodies to CD31. Strong HbNO EPR signals were found in melanoma, i.e., in the tumor with a vast amount of a hemorrhagic necrosis core. Strong Fe(DETC)2NO signals could be induced in poorly vascularized EC. In L5178Y, there was a correlation between both types of signals, and in addition, Fe(RS)2(NO)2 signals of non-heme iron-nitrosyl complexes could be detected. We postulate that HbNO EPR signals appear during active destruction of well-vascularized tumor tissue due to hemorrhagic necrosis. The presence of iron-nitrosyl complexes in tumor tissue is biologically meaningful and defines the evolution of complicated tumor-host interactions.

mitfa deficiency promotes immune vigor and potentiates antitumor effects in zebrafish

The mitfa gene is a well-known transcription factor associated with microphthalmia and is essential for early melanophore development. However, little is known about how mitfa affects the immune system. Here, we generated a novel mitfa knock-out zebrafish line using the CRISPR/Cas9 system. The mitfa-/- zebrafish exhibited reduced melanin levels compared to the nacre mutant. We investigated the impact on the immune system after exposure to Edwardsiella tarda and bifenazate in zebrafish larvae, and observed that the macrophage numbers were reduced in both treated groups. Remarkably, the expression levels of immune-related genes exhibited significant increases after bacterial challenge or bifenazate exposure in the mitfa-/- zebrafish, except for tlr4 and rela. Furthermore, we conducted xenograft experiments using mouse B16 melanoma cells. Notably, the cancer cells didn't show a high cell migration ratio, implying that the immune system was highly activated after the loss of mifta. Taken together, our findings suggest that mitfa-/- zebrafish serve as a valuable model for investigating the relationship between the immune system and melanocytes, providing new insights into the role of mitfa in immune responses.

Accessing Properties of Molecular Compounds Involved in Cellular Metabolic Processes with Electron Paramagnetic Resonance, Raman Spectroscopy, and Differential Scanning Calorimetry

In this work, we review some physical methods of macroscopic experiments, which have been recently argued to be promising for the acquisition of valuable characteristics of biomolecular structures and interactions. The methods we focused on are electron paramagnetic resonance spectroscopy, Raman spectroscopy, and differential scanning calorimetry. They were chosen since it can be shown that they are able to provide a mutually complementary picture of the composition of cellular envelopes (with special attention paid to mycobacteria), transitions between their molecular patterning, and the response to biologically active substances (reactive oxygen species and their antagonists-antioxidants-as considered in our case study).

Canalised and plastic components of melanin-based colouration: a diet-manipulation experiment in house sparrows

Whether melanin-based plumage colouration accurately reflects a bird's quality is still controversial. To better understand potential mechanisms behind the observed variation in plumage colouration, we shifted our attention from a high-level expression of colour to low-level physiological phenomena by targeting the microstructure and pigment content of the feather. In a well-studied model system, the house sparrow (Passer domesticus), we combined an experimental manipulation of birds' physiological condition and availability of resources that are key to the production of the studied colouration (phenylalanine and tyrosine (PT). We found that feathers from sparrows fed with the control diet had noticeably lower values of brightness, suggesting a higher quality of the ornamental "blackness" in comparison to those sampled from birds fed with a PT-reduced diet. Electron paramagnetic resonance (EPR) spectroscopy detected higher melanin concentrations in samples from the control than the PT-reduced group. Our multi-level analysis excluded mechanisms such as barbule density and melanosomes' distribution, clearly pointing to the finest-level proxy of colour: the concentration of melanin in melanosomes themselves. Despite melanins being manufactured by birds endogenously, the efficiency of melanogenesis can be noticeably limited by diet. As a result, the birds' plumage colouration is affected, which may entail consequences in social signalling.

In vivo imaging with a fast large-area multiphoton exoscope (FLAME) captures the melanin distribution heterogeneity in human skin

Melanin plays a significant role in the regulation of epidermal homeostasis and photoprotection of human skin. The assessment of its epidermal distribution and overall content is of great interest due to its involvement in a wide range of physiological and pathological skin processes. Among several spectroscopic and optical imaging methods that have been reported for non-invasive quantification of melanin in human skin, the approach based on the detection of two-photon excited fluorescence lifetime distinguishes itself by enabling selective detection of melanin with sub-cellular resolution, thus facilitating its quantification while also resolving its depth-profile. A key limitation of prior studies on the melanin assessment based on this approach is their inability to account for the skin heterogeneity due to the reduced field of view of the images, which results in high dispersion of the measurement values. Pigmentation in both normal and pathological human skin is highly heterogeneous and its macroscopic quantification is critical for reliable measurements of the epidermal melanin distribution and for capturing melanin-related sensitive dynamic changes as a response to treatment. In this work, we employ a fast large-area multiphoton exoscope (FLAME), recently developed by our group for clinical skin imaging, that has the ability to evaluate the 3D distribution of epidermal melanin content in vivo macroscopically (millimeter scale) with microscopic resolution (sub-micron) and rapid acquisition rates (minutes). We demonstrate significant enhancement in the reliability of the melanin density and distribution measurements across Fitzpatrick skin types I to V by capturing the intra-subject pigmentation heterogeneity enabled by the large volumetric sampling. We also demonstrate the potential of this approach to provide consistent measurement results when imaging the same skin area at different times. These advances are critical for clinical and research applications related to monitoring pigment modulation as a response to therapies against pigmentary skin disorders, skin aging, as well as skin cancers.

Unraveling the Structure and Function of Melanin through Synthesis

Melanin is ubiquitous in living organisms across different biological kingdoms of life, making it an important, natural biomaterial. Its presence in nature from microorganisms to higher animals and plants is attributed to the many functions of melanin, including pigmentation, radical scavenging, radiation protection, and thermal regulation. Generally, melanin is classified into five types-eumelanin, pheomelanin, neuromelanin, allomelanin, and pyomelanin-based on the various chemical precursors used in their biosynthesis. Despite its long history of study, the exact chemical makeup of melanin remains unclear, and it moreover has an inherent diversity and complexity of chemical structure, likely including many functions and properties that remain to be identified. Synthetic mimics have begun to play a broader role in unraveling structure and function relationships of natural melanins. In the past decade, polydopamine, which has served as the conventional form of synthetic eumelanin, has dominated the literature on melanin-based materials, while the synthetic analogues of other melanins have received far less attention. In this perspective, we will discuss the synthesis of melanin materials with a special focus beyond polydopamine. We will emphasize efforts to elucidate biosynthetic pathways and structural characterization approaches that can be harnessed to interrogate specific structure-function relationships, including electron paramagnetic resonance (EPR) and solid-state nuclear magnetic resonance (ssNMR) spectroscopy. We believe that this timely Perspective will introduce this class of biopolymer to the broader chemistry community, where we hope to stimulate new opportunities in novel, melanin-based poly-functional synthetic materials.

Mechanisms of skin moisturization with hyperharmonized hydroxyl modified fullerene substance

BACKGROUND

Hyper Harmonized Hydroxyl Modified Fullerene Substance (3HFWC⁺ ) establishes hydrogen bonds with the surrounding water molecules and organizes them in clusters with the liquid crystalline state, similar to the properties of water surrounding the biomolecules.

AIMS

To investigate the moisturizing properties of hyperharmonized fullerenol-3HFWC⁺ as an emulsion O/W ingredient on the skin.

PATIENTS/METHODS

We have analyzed the reflexion of the blue light from the skin, in vivo, with different levels of moisturization and compared the influence of three groups of cosmetic products (with various active ingredients, 3HFWC⁺ or water in same percentage in the "vehiculum") on skin moisturization by measuring paramagnetic/diamagnetic properties by Optomagnetic Imaging Spectroscopy.

RESULTS

Regenerating Cream and Body Lotion have shown statistically significant increase of diamagnetic features predominantly in all 3 types of creams, while the Hand Cream formulations have not shown statistically significant results after 4 weeks of treatment. Anti-aging cream with 3HFWC⁺ demonstrated statistically significant increase of paramagnetic properties of the skin (p⁺ /p^- from 0.90 to 0.62) and showed beneficial effects on information transfer and water content in stratum corneum.

CONCLUSION

Although it does not act as a classical moisturizing agent on the skin, 3HFWC⁺ can increase moisturization as a result of hydrogen bonds established among 3HFWC⁺ and water or biomolecules, liquid crystalline state of water in 3HFWC⁺ resembling the properties of water surrounding the biomolecules, and finally, liquid crystalline state of water in the products.

Melanins as Sustainable Resources for Advanced Biotechnological Applications

Melanins are a class of biopolymers that are widespread in nature and have diverse origins, chemical compositions, and functions. Their chemical, electrical, optical, and paramagnetic properties offer opportunities for applications in materials science, particularly for medical and technical uses. This review focuses on the application of analytical techniques to study melanins in multidisciplinary contexts with a view to their use as sustainable resources for advanced biotechnological applications, and how these may facilitate the achievement of the United Nations Sustainable Development Goals.

Free radical imaging of endogenous redox molecules using dynamic nuclear polarisation magnetic resonance imaging

Redox reactions accompanied by the oxidation-reduction of endogenous molecules play important roles in maintaining homeostasis in living organisms. In humans, numerous endogenous molecules that contribute towards maintaining physiological conditions form free radicals via electron transfer. A typical example of this is the mitochondrial electron transport chain, which is involved in energy production. If free radicals derived from endogenous molecules could be visualised and exploited as biological and functional probes, redox reactions mediated by endogenous molecules could be detected non-invasively. We succeeded in visualising the free radicals derived from endogenous molecules using an in vivo dynamic nuclear polarisation (DNP) magnetic resonance imaging (MRI) system. In this review, we describe the visualisation of endogenous redox molecules, such as flavins and ubiquinones, which are mitochondrial electron carriers, as well as vitamin E and vitamin C (ascorbate). In addition, we describe the application of melanin free radicals for the in vivo visualisation of metabola without using probes via in vivo DNP-MRI.

Forensic determination of hair deposition time in crime scenes using electron paramagnetic resonance

Several types of biological samples, including hair strands, are found at crime scenes. Apart from the identification of the value and the contributor of the probative evidence, it is important to prove that the time of shedding of hair belonging to a suspect or victim matches the crime window. To this end, to estimate the ex vivo aging of hair, we evaluated time-dependent changes in melanin-derived free radicals in blond, brown, and black hairs by using electron paramagnetic resonance spectroscopy (EPR). Hair strands aged under controlled conditions (humidity 40%, temperature 20-22°C, indirect light, with 12/12 hour of light/darkness cycles) showed a time-dependent decay of melanin-derived radicals. The half-life of eumelanin-derived radicals in hair under our experimental settings was estimated at 22 ± 2 days whereas that of pheomelanin was about 2 days suggesting better stabilization of unpaired electrons by eumelanin. Taken together, this study provides a reference for future forensic studies on determination of degradation of shed hair in a crime scene by following eumelanin radicals by utilizing the non-invasive, non-destructive, and highly specific EPR technique.

Paramagnetism and Relaxation Dynamics in Melanin Biomaterials

Spectroscopical characterization of melanins is a prior requirement for the efficient tailoring of their radical scavenging, ultraviolet-visible radiation absorption, metal chelation, and natural pigment properties. Electron paramagnetic resonance (EPR), exploiting the common persistent paramagnetism of melanins, represents the elective standard for the structural and dynamical characterization of their constituting radical species. Although melanins are mainly investigated using X-band (9.5 GHz) continuous wave (CW)-EPR, an integration with the application of Q-band (34 GHz) in CW and pulse EPR for the discrimination of melanin pigments of different compositions is presented here. The longitudinal relaxation times measured highlight faster relaxation rates for cysteinyldopa melanin, compared to those of the most common dopa melanin pigment, suggesting pulse EPR spin-lattice relaxation time measurements as a complementary tool for characterization of pigments of interest for biomimetic materials engineering.

Electron Paramagnetic Resonance Imaging of Melanin in Honey Bee

Honey bees play a crucial role in the nature by pollinating wild flowers. Over the past years, there has been an increasing concern regarding the honey bee colony decline. Pesticides or environmental effects targeting the biochemistry of insect chitin and cuticle coating may be in part responsible for honey bee pathologies. We here propose the use of electron paramagnetic resonance imaging (EPRI) as a tool to image the melanin-chitin complexes as part of the exoskeleton of the honey bee. EPRI at 9.65 GHz was applied on intact freeze-dried bees. The imaging data were collected on the melanin peak. High-resolution images revealed that this compound is extensively distributed in the periphery of the animal, data consistent with the localization in the cuticle of the bee. While EPR of melanin has been so far explored in the context of melanoma characterization, it may offer new opportunities in research on honey bees and other insects.

Formation of methyl radicals derived from cumene hydroperoxide in reconstructed human epidermis: an EPR spin trapping confirmation by using 13C-substitution

Dermal exposure to cumene hydroperoxide (CumOOH) during manufacturing processes is a toxicological issue for the industry. Its genotoxicity, mutagenic action, ability to promote skin tumour, capacity to induce epidermal hyperplasia, and aptitude to induce allergic and irritant skin contact dermatitis are well known. These toxic effects appear to be mediated through the activation to free radical species such as hydroxyl, alkoxyl, and alkyl radicals characterised basically by electron paramagnetic resonance (EPR) and spin-trapping (ST) techniques. To be a skin sensitiser CumOOH needs to covalently bind to skin proteins in the epidermis to form the antigenic entity triggering the immunotoxic reaction. Cleavage of the O-O bond allows formation of unstable CumO^•/CumOO^• radicals rearranging to longer half-life specific carbon-centred radicals R^• proposed to be at the origin of the antigen formation. Nevertheless, it is not still clear which R^• is precisely formed in the epidermis and thus involved in the sensitisation process. The aim of this work was to elucidate in conditions closer to real-life sensitisation which specific R^• are formed in a 3D reconstructed human epidermis (RHE) model by using ¹³C-substituted CumOOH at carbon positions precursors of potentially reactive radicals and EPR-ST. We demonstrated that most probably methyl radicals derived from β-scission of CumO^• radicals occur in RHE through a one-electron reductive pathway suggesting that these could be involved in the antigen formation inducing skin sensitisation. We also describe a coupling between nitroxide radicals and β position ¹³C atoms that could be of an added value to the very few examples existing for the coupling of radicals with ¹³C atoms.

Characterization of Melanin Radicals in Paraffin-embedded Malignant Melanoma and Nevus Pigmentosus Using X-band EPR and EPR Imaging

Continuous wave electron paramagnetic resonance (CW EPR) and X-band (9 GHz) EPR imaging (EPRI) were used to nondestructively investigate the possible differentiation between malignant melanoma (MM) and nevus pigmentosus (NP) melanin radicals in paraffin-embedded specimens. The EPR spectra of both samples were analyzed using linewidth, spectral pattern, and X-band EPRI. The CW-EPR spectra of the MM showed an additional signal overlap. Eumelanin- and pheomelanin-related radicals were observed in the MM specimens. The EPR results revealed that the peak-to-peak linewidths (ΔH_pp) of paraffin-embedded MM and NP samples were 0.65 ± 0.01 and 0.69 ± 0.01 mT, respectively. The g-value was 2.005 for both samples. Moreover, the two-dimensional (2D) EPRI of the MM showed different signal intensities at the different tumor stages, unlike the NP, which displayed fewer variations in signal intensity. Thus, the present results suggest that EPR and 2D EPRI can be useful for characterization of the two melanin radicals in the MM and for determination of their size and concentration.

Spectroscopic Characterization of Natural Melanin from a Streptomyces cyaneofuscatus Strain and Comparison with Melanin Enzymatically Synthesized by Tyrosinase and Laccase

An actinobacteria strain was isolated from Algerian Sahara soil and assigned to Streptomyces cyaneofuscatus Pridham et al. 1958 species. This strain was selected for its ability to produce melanin exopigments in liquid and solid media. Melanin synthesis was associated with tyrosinase activity and the enzyme from this strain was isolated and biochemically characterized. Synthetic melanin was then enzymatically produced using the S. cyaneofuscatus Pridham et al. 1958 tyrosinase. As this enzyme showed a higher diphenolase activity, a synthetic melanin from the enzymic oxidation of 3,4-dihydroxyphenylalanine (dopa) was obtained by the use of a Trametes versicolor (L.) Lloyd laccase for comparison. The natural and synthetic pigments were physico-chemically characterized by the use of ultraviolet (UV)-Visible, and Fourier transform infrared (FT-IR) and multifrequency electron paramagnetic resonance (EPR) spectroscopies. All the melanin samples displayed a stable free radical when analyzed by X-band EPR spectroscopy. Once the samples were recorded at Q-band EPR, a copolymer derived from a mixture of different constituents was evident in the natural melanin. All radical species were analyzed and discussed. The use of water-soluble melanin naturally produced by S. cyaneofuscatus Pridham et al. 1958 represents a new biotechnological alternative to commercial insoluble pigments.

Development of Hair Fibres

The growth of hairs occurs during the anagen phase of the follicle cycle. Hair growth begins with basement membrane-bound stem cells (mother cells) around the dermal papilla neck which continuously bud off daughter cells which further divide as a transient amplifying population. Division ceases as cell line differentiation begins, which entails changes in cell junctions, cell shape and position, and cell-line specific cytoplasmic expression of keratin and trichohyalin. As the differentiating cells migrate up the bulb, nuclear function ceases in cortex, cuticle and inner root sheath (IRS) layers. Past the top of the bulb, cell shape/position changes cease, and there is a period of keratin and keratin-associated protein (KAP) synthesis in fibre cell lines, with increases, in particular of KAP species. A gradual keratinization process begins in the cortex at this point and then non-keratin cell components are increasingly broken down. Terminal cornification, or hardening, is associated with water loss and precipitation of keratin. In the upper follicle, the hair, now in its mature form, detaches from the IRS, which is then extracted of material and becomes fragmented to release the fibre. Finally, the sebaceous and sudoriferous (if present) glands coat the fibre in lipid-rich material and the fibre emerges from the skin. This chapter follows the origin of the hair growth in the lower bulb and traces the development of the various cell lines.

Functional Role of Cyclin-Dependent Kinase 5 in the Regulation of Melanogenesis and Epidermal Structure

The mammalian integumentary system plays important roles in body homeostasis, and dysfunction of melanogenesis or epidermal development may lead to a variety of skin diseases, including melanoma. Skin pigmentation in humans and coat color in fleece-producing animals are regulated by many genes. Among them, microphthalmia-associated transcription factor (MITF) and paired-box 3 (PAX3) are at the top of the cascade and regulate activities of many important melanogenic enzymes. Here, we report for the first time that cyclin-dependent kinase 5 (Cdk5) is an essential regulator of MITF and PAX3. Cdk5 knockdown in mice causes a lightened coat color, a polarized distribution of melanin and hyperproliferation of basal keratinocytes. Reduced expression of Keratin 10 (K10) resulting from Cdk5 knockdown may be responsible for an abnormal epidermal structure. In contrast, overexpression of Cdk5 in sheep (Ovis aries) only produces brown patches on a white background, with no other observable abnormalities. Collectively, our findings show that Cdk5 has an important functional role in the regulation of melanin production and transportation and in normal development of the integumentary system.

A Randomized Controlled Trial of Green Tea Beverages on the in vivo Radical Scavenging Activity in Human Skin

BACKGROUND

Oxidative stress plays an important role in the pathogenesis of various skin diseases. Thus, the antioxidant network of the skin relies on the uptake of exogenous antioxidants to ensure cell protection against radical formation. Green tea is one of the main sources of polyphenolic antioxidant compounds, but only few data are available on its cutaneous antioxidant effects.

METHODS

The radical scavenging properties of Benifuuki and Yabukita green tea were investigated in the human skin. Thirty-two participants who met the inclusion criteria were randomized to consume 3 cups per day of either Benifuuki tea, Yabukita tea, or water (control group) for 2 weeks. Electron paramagnetic resonance (EPR) spectroscopy was applied to measure the radical scavenging capacity of the skin in vivo before and after the intervention.

RESULTS

Both Yabukita and Benifuuki tea led to an increase in the radical scavenging activity of the skin by 28 and 29%, respectively, and the difference was significant when compared to the control group. Benifuuki tea, previously reported to be superior in bioavailability due to a highly absorbable methylated catechin, did not prove to be more effective than the common Yabukita tea.

CONCLUSION

The results show that green tea enhances the radical scavenging capacity of the skin and support the hypothesis that green tea may offer protection against cutaneous oxidative stress.

Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo

We demonstrate a superior method of 2D spectral-spatial imaging of stable radical reporter molecules at 250 MHz using rapid-scan electron-paramagnetic-resonance (RS-EPR), which can provide quantitative information under in vivo conditions on oxygen concentration, pH, redox status and concentration of signaling molecules (i.e., OH^•, NO^•). The RS-EPR technique has a higher sensitivity, improved spatial resolution (1 mm), and shorter acquisition time in comparison to the standard continuous wave (CW) technique. A variety of phantom configurations have been tested, with spatial resolution varying from 1 to 6 mm, and spectral width of the reporter molecules ranging from 16 µT (160 mG) to 5 mT (50 G). A cross-loop bimodal resonator decouples excitation and detection, reducing the noise, while the rapid scan effect allows more power to be input to the spin system before saturation, increasing the EPR signal. This leads to a substantially higher signal-to-noise ratio than in conventional CW EPR experiments.

Reducing the Harmful Effects of Infrared Radiation on the Skin Using Bicosomes Incorporating β-Carotene

AIM

In this work the effect of infrared (IR) radiation, at temperatures between 25 and 30°C, on the formation of free radicals (FRs) in the skin is studied. Additionally, the influence of IR radiation at high temperatures in the degradation of skin collagen is evaluated. In both experiments the protective effect against IR radiation of phospholipid nanostructures (bicosomes) incorporating β-carotene (Bcb) is also evaluated.

METHODS

The formation of FRs in skin under IR exposure was measured near physiological temperatures (25-30°C) using 5,5-dimethyl-1-pyrroline-N-oxide spin trap and electron paramagnetic resonance (EPR) spectroscopy. The study of the collagen structure was performed by small-angle X-ray scattering using synchrotron radiation.

RESULTS

EPR results showed an increase in the hydroxyl radical in the irradiated skin compared to the native skin. The skin collagen was degraded by IR exposure at high temperatures of approximately 65°C. The treatment with Bcb reduced the formation of FRs and kept the structure of collagen.

CONCLUSIONS

The formation of FRs by IR radiation does not depend on the increase of skin temperature. The decrease of FRs and the preservation of collagen fibers in the skin treated with Bcb indicate the potential of this lipid system to protect skin under IR exposure.

New Whitening Constituents from Taiwan-Native Pyracantha koidzumii: Structures and Tyrosinase Inhibitory Analysis in Human Epidermal Melanocytes

Nontoxic natural products useful in skin care cosmetics are of considerable interest. Tyrosinase is a rate-limiting enzyme for which its inhibitor is useful in developing whitening cosmetics. Pyracantha koidzumii (Hayata) Rehder is an endemic species in Taiwan that exhibits tyrosinase-inhibitory activity. To find new active natural compounds from P. koidzumii, we performed bioguided isolation and studied the related activity in human epidermal melanocytes. In total, 13 compounds were identified from P. koidzumii in the present study, including two new compounds, 3,6-dihydroxy-2,4-dimethoxy-dibenzofuran (9) and 3,4-dihydroxy-5-methoxybiphenyl-2'-O-β-d-glucopyranoside (13), as well as 11 known compounds. The new compound 13 exhibited maximum potency in inhibiting cellular tyrosinase activity, the protein expression of cellular tyrosinase and tyrosinase-related protein-2, as well as the mRNA expression of Paired box 3 and microphthalmia-associated transcription factor in a concentration-dependent manner. In the enzyme kinetic assay, the new compound 13 acted as an uncompetitive mixed-type inhibitor against the substrate l-3,4-dihydroxyphenylalanine and had a Km value against this substrate of 0.262 mM, as calculated using the Lineweaver-Burk plots. Taken together, our findings show compound 13 exhibits tyrosinase inhibition in human melanocytes and compound 13 may be a potential candidate for use in cosmetics.

Effect of ascorbic acid (vitamin C) on the ESR spectra of the red and black hair: pheomelanin free radicals are not always present in red hair

Increased incidence of melanoma in the population with red hair is conditioned by synthesis of pheomelanin pigments in the skin and their phototoxic properties. The recent research has shown that free radicals of pheomelanin are produced not only by the influence of UV irradiation, but also in UV-independent pathways of oxidative stress. It has been ascertained, that the color of the hair is not always determinant of the amount of pheolemanin radicals in red hair. Therefore, in order to evaluate the risk of melanoma in different individuals, it is necessary to define the amount of free radicals of pheomelanin in red hair using ESR spectroscopy method. Besides, it is very important to find effective antioxidant, capable of neutralizing free radicals of pheomelanin. It was proved that ascorbic acid neutralizes free radicals of pheomelanin very effectively. The main goal of our research was to define the presumably optimal concentration of ascorbic acid as an antioxidant and study the kinetics of the influence of this concentration on red and black hair. It has been found out, that ascorbic acid influences the free radicals of red and black hair, and its appropriate optimal concentration is 10 mM. The obtained results can be considered in dermatology and cosmetology.

Curcumin does not switch melanin synthesis towards pheomelanin in B16F10 cells

Melanin, the basic skin pigment present also in the majority of melanomas, has a huge impact on the efficiency of photodynamic, radio- or chemotherapies of melanoma. Moreover, the melanoma cells produce more melanin than normal melanocytes in adjacent skin do. Thus, attention has been paid to natural agents that are safe and effective in suppression of melanogenesis. B16F10 cells were studied by electron paramagnetic resonance (EPR) spectroscopy. The cells were cultured for 24-72 h in RPMI or DMEM with or without curcumin. The results confirmed that curcumin has no significant effect on B16F10 cells viability at concentrations of 1-10 µM. Curcumin at concentration of 10 µM significantly inhibited their proliferation and stimulated differentiation. We have not stimulated melanogenesis hormonally but we found a strong increase in melanogenesis in DMEM, containing more L-Tyr, as compared to RPMI. The EPR studies revealed that the effect of curcumin on melanogenesis in RPMI-incubated cells was not significant, and only in DMEM was curcumin able to inhibit melanogenesis. The effect of curcumin was only quantitative, as it did not switch eumelanogenesis towards pheomelanogenesis under any conditions. Interestingly, we observed elevation of production of hydrogen peroxide in DMEM-incubated cells, in parallel to the facilitation of melanogenesis. Curcumin significantly but transiently intensified the already pronounced generation of H2O2 in DMEM. We conclude that the quantitative effect of curcumin on melanogenesis in melanoma is intricate. It depends on the basic melanogenetic efficiency of the cells, and can be observed only in strongly pigmented cells. Qualitatively, curcumin does not switch melanogenesis towards pheomelanogenesis, either in strongly, or in weakly melanized melanoma cells.

Electron spin resonance (ESR/EPR) of free radicals observed in human red hair: a new, simple empirical method of determination of pheomelanin/eumelanin ratio in hair

The definition of the concentration of pheomelanin in the skin is an issue of great interest because in the case of being influenced by UV radiation, it manifests itself as a prooxidant, causing various skin disorders including melanoma that might help to explain the relatively high incidence of skin cancer among individuals with red hair. The ESR spectra of red hair samples were investigated. It was found that at low microwave power, they are characterized by two types of spectra. Red hair ESR signals result from a superposition of two spectral shapes, a singlet spectrum as a result of the existence of eumelanin and a triplet spectrum as a result of the existence of pheomelanin. At high microwave power, only triplet spectra shape was detected, caused by saturation of the eumelanin singlet. Using different concentration ratios of black to red hair, we measured ESR spectra and plotted the ratio values in each sample against a measured 'g-factor' (experimental). We found that there is a linear relationship between these two parameters. So, it is evident that using these results, the concentration ratio of pheomelanin to eumelanin in a sample of hair can be easily determined by an almost noninvasive method. This can be considered a potential advantage for many practical activities compared with other invasive methods. The concentration dependence curve of pheomelanin (µg/mg) on gexp-factor in an ESR spectrum of hair has been designed, which allows the determination of the amount of pheomelanin in hair of any color.

Premature graying as a consequence of compromised antioxidant activity in hair bulb melanocytes and their precursors

Intricate coordinated mechanisms that govern the synchrony of hair growth and melanin synthesis remain largely unclear. These two events can be uncoupled in prematurely gray hair, probably due to oxidative insults that lead to the death of oxidative stress-sensitive melanocytes. In this study, we examined the gene expression profiles of middle (bulge) and lower (hair bulb) segments that had been micro-dissected from unpigmented and from normally pigmented hair follicles from the same donors using quantitative real-time RT-PCR (qPCR) arrays. We found a significant down-regulation of melanogenesis-related genes (TYR, TYRP1, MITF, PAX3, POMC) in unpigmented hair bulbs and of marker genes typical for melanocyte precursor cells (PAX3, SOX10, DCT) in unpigmented mid-segments compared with their pigmented analogues. qPCR, western blotting and spin trapping assays revealed that catalase protein expression and hydroxyl radical scavenging activities are strongly repressed in unpigmented hair follicles. These data provide the first clear evidence that compromised antioxidant activity in gray hair follicles simultaneously affects mature hair bulb melanocytes and their immature precursor cells in the bulge region.

Parallel image-acquisition in continuous-wave electron paramagnetic resonance imaging with a surface coil array: Proof-of-concept experiments

This article describes a feasibility study of parallel image-acquisition using a two-channel surface coil array in continuous-wave electron paramagnetic resonance (CW-EPR) imaging. Parallel EPR imaging was performed by multiplexing of EPR detection in the frequency domain. The parallel acquisition system consists of two surface coil resonators and radiofrequency (RF) bridges for EPR detection. To demonstrate the feasibility of this method of parallel image-acquisition with a surface coil array, three-dimensional EPR imaging was carried out using a tube phantom. Technical issues in the multiplexing method of EPR detection were also clarified. We found that degradation in the signal-to-noise ratio due to the interference of RF carriers is a key problem to be solved.

HGF/SF increases number of skin melanocytes but does not alter quality or quantity of follicular melanogenesis

Melanins are an important factor determining the vulnerability of mammalian skin to UV radiation and thus to UV-induced skin cancers. Transgenic mice overexpressing hepatocyte growth factor/scatter factor (HGF/SF) have extra-follicular dermal melanocytes, notably in the papillary upper dermis, and are susceptible to UV-induced melanoma. Pigmented HGF/SF neonatal mice are more susceptible than albino HGF/SF animals to UVA -induced melanoma, indicating an involvement of melanin in melanoma formation. This raises the question of the effect of transgenic HGF/SF on melanization. We developed a methodology to accurately quantitate both the production of melanin and the efficiency of melanogenesis in normal, and HGF/SF transgenic mice in vivo. Skin and hair shafts of 5 day old and adult (3 week old) C57BL/6-HGF/SF and corresponding C57BL/6 wild type mice were investigated by electron paramagnetic resonance spectroscopy (EPR) to quantitate melanin, by transmission electron microscopy (TEM) for the presence of melanosomes, and by standard histology and by Western blotting and zymography to determine the expression and activity of melanogenesis-related proteins. Eumelanin but no phaeomelanin was detected in transgenic C57BL/6-HGF and C57BL/6 wild type mice. Transgenic HGF/SF overexpression did not change the type of melanin produced in the skin or hair, did not affect the terminal content of melanin production in standard samples of hair and did not influence hair cycle/morphogenesis-related changes in skin thickness. No melanocytes were found in the epidermis and no melanosomes were found in epidermal keratinocytes. HGF/SF transgenic mice thus lack the epidermal melanin UV-protection found in constitutively dark human skin. We conclude that melanocytes in the HGF/SF transgenic mouse, particularly in the papillary dermis, are vulnerable to UVA which interacts with eumelanin but not phaeomelanin to induce melanoma.

An Endogenous Electron Spin Resonance (ESR) signal discriminates nevi from melanomas in human specimens: a step forward in its diagnostic application

Given the specific melanin-associated paramagnetic features, the Electron Spin Resonance (ESR, called also Electron Paramagnetic Resonance, EPR) analysis has been proposed as a potential tool for non-invasive melanoma diagnosis. However, studies comparing human melanoma tissues to the most appropriate physiological counterpart (nevi) have not been performed, and ESR direct correlation with melanoma clinical features has never been investigated. ESR spectrum was obtained from melanoma and non-melanoma cell-cultures as well as mouse melanoma and non-melanoma tissues and an endogenous ESR signal (g = 2.005) was found in human melanoma cells and in primary melanoma tissues explanted from mice, while it was always absent in non-melanoma samples. These characteristics of the measured ESR signal strongly suggested its connection with melanin. Quantitative analyses were then performed on paraffin-embedded human melanoma and nevus sections, and validated on an independent larger validation set, for a total of 112 sections (52 melanomas, 60 nevi). The ESR signal was significantly higher in melanomas (p = 0.0002) and was significantly different between “Low Breslow’s and “High Breslow’s” depth melanomas (p<0.0001). A direct correlation between ESR signal and Breslow’s depth, expressed in millimetres, was found (R = 0.57; p<0.0001). The eu/pheomelanin ratio was found to be significantly different in melanomas “Low Breslow’s” vs melanomas “High Breslow’s” depth and in nevi vs melanomas “High Breslow’s depth”. Finally, ROC analysis using ESR data discriminated melanomas sections from nevi sections with up to 90% accuracy and p<0.0002. In the present study we report for the first time that ESR signal in human paraffin-embedded nevi is significantly lower than signal in human melanomas suggesting that spectrum variations may be related to qualitative melanin differences specifically occurring in melanoma cells. We therefore conclude that this ESR signal may represent a reliable marker for melanoma diagnosis in human histological sections.

Nitroxides: Versatile Reporters and Reactants

Stable nitroxyl radicals are important tools in chemistry, biophysics, biology, and materials science. Their stability and the sensitivity of their EPR spectra to the local environment make them valuable molecular probes. This review seeks to give an overview of the developments in the field of nitroxide spin probes and their various applications, with the main focus on the pH-sensitive imidazoline nitroxide family.

Interaction between carotenoids and free radicals in human skin

Environmental factors like air pollutants, radiation of the sun and stress factors such as illness, smoking, or alcohol abuse produce free radicals in the human tissue as well as in the skin. Free radicals serve as the main cause for premature skin aging. Additionally, they also contribute towards immunosuppression and the formation of skin diseases including cancer. The human organism has developed a protection system against the destructive action of free radicals by means of the antioxidant network. In the present study, the interaction of free radicals and carotenoid antioxidants in the human skin under in vivo conditions was investigated and summarized. The measurement of carotenoids in human skin was performed in vivo using resonance Raman spectroscopy.

Determination of the antioxidative capacity of the skin in vivo using resonance Raman and electron paramagnetic resonance spectroscopy

BACKGROUND

Non-invasive measurements are of major interest for investigating the effects of stress, nutrition, diseases or pharmaceuticals on the antioxidative capacity of the human skin. However, only a few non-invasive methods are available.

MATERIAL AND METHODS

The resonance Raman spectroscopy is well established to monitor carotenoids in the skin, but correlations with other antioxidants have not yet been described. Electron paramagnetic resonance spectroscopy used for measurements of free radicals has already been used elsewhere to investigate the reduction of applied long-living nitroxide radicals, caused by skin antioxidants and UV irradiation, but only a single or up to four volunteers were included in these studies. Therefore, in this study, the two methods were applied in parallel on 17 volunteers, and the rate constant of the nitroxide decrease was correlated with the cutaneous carotenoid concentration.

RESULTS AND DISCUSSION

A correlation with R = 0.65 was found, supporting the thesis that different antioxidants protect each other and build an antioxidative network in the skin. The results also give first indications that the carotenoids serve as marker substances for the antioxidative capacity, if the nutrition is well balanced.