Photoreactivity of Hair Melanin from Different Skin Phototypes-Contribution of Melanin Subunits to the Pigments Photoreactive Properties.

Photoreactivity of melanin has become a major focus of research due to the postulated involvement of the pigment in UVA-induced melanoma. However, most of the hitherto studies were carried out using synthetic melanin models. Thus, photoreactivity of natural melanins is yet to be systematically analyzed. Here, we examined the photoreactive properties of natural melanins isolated from hair samples obtained from donors of different skin phototypes (I, II, III, and V). X-band and W-band electron paramagnetic resonance (EPR) spectroscopy was used to examine the paramagnetic properties of the pigments. Alkaline hydrogen peroxide degradation and hydroiodic acid hydrolysis were used to determine the chemical composition of the melanins. EPR oximetry and spin trapping were used to examine the oxygen photoconsumption and photo-induced formation of superoxide anion, and time-resolved near infrared phosphorescence was employed to determine the singlet oxygen photogeneration by the melanins. The efficiency of superoxide and singlet oxygen photogeneration was related to the chemical composition of the studied melanins. Melanins from blond and chestnut hair (phototypes II and III) exhibited highest photoreactivity of all examined pigments. Moreover, melanins of these phototypes showed highest quantum efficiency of singlet oxygen photogeneration at 332 nm and 365 nm supporting the postulate of the pigment contribution in UVA-induced melanoma.

Topical RT1640 treatment effectively reverses gray hair and stem cell loss in a mouse model of radiation-induced canities.

Gray hair is a visible sign of tissue degeneration during aging. Graying is attributed to dysfunction of melanocyte stem cells (McSCs) that results in depletion of their melanin-producing progeny. This non-lethal phenotype makes the hair follicle and its pigment system an attractive model for investigating mechanisms that contribute to tissue aging and therapeutic strategies to combat this process. One potential combination therapeutic is RT1640, which is comprised of two drugs that are known to stimulate hair growth (cyclosporine A [CsA] and minoxidil), along with RT175, a non-immunosuppressive immunophilin ligand that is implicated in tissue regeneration. Using the ionizing radiation-induced acute mouse model of hair graying, we demonstrate that RT1640, over CsA alone, promotes regeneration of the hair pigment system during and following treatment. In non-irradiated mice, RT1640 is also physiologically active and successfully speeds hair growth and expands the McSC pool. It appears that this effect relies on the combined activities of the three drugs within RT1640 to simultaneously activate hair growth and McSCs as RT175 alone was insufficient to induce hair cycling in vivo, yet sufficient to drive the upregulation of the melanogenic program in vitro. This study sets the stage for further investigation into RT1640 and its components in McSC biology and, ultimately, melanocyte hypopigmentary disorders associated with disease and aging.

Keratinocyte stem cells but not melanocyte stem cells are the primary target for radiation-induced hair graying.

Ionizing radiation (IR)-induced hair graying is caused by the ectopic differentiation of melanocyte stem cells (MSCs) in their niche located at the bulge region of the hair follicle. Keratinocyte stem cells (KSCs) in the bulge region are an important component of that niche. However, little is known about the relationship between MSC differentiation and the KSC niche during IR-induced hair graying. We found that both follicular MSCs and KSCs were affected by IR by using immunohistochemical detection of γH2AX as a genotoxicity marker. We also found that KSCs prepared from irradiated mice were functionally affected by IR as indicated by their reduced colony-forming activity in culture and the delayed hair cycle in vivo. However, these effects of IR on KSCs were temporal. The MSC population, which proliferated and differentiated to melanocytes, was persistently maintained after irradiation. In addition to the loss of colony-forming activity, irradiated keratinocytes including KSCs suppressed the colony formation of MSCs in vitro. Furthermore, pigmented hairs were not reconstituted in vivo in the presence of irradiated KSCs or keratinocytes. These results provide a previously unreported insight that the primary target of IR during the induction of hair graying is follicular KSCs rather than MSCs.

UVA-induced oxidative degradation of melanins: fission of indole moiety in eumelanin and conversion to benzothiazole moiety in pheomelanin.

Eumelanin is photoprotective while pheomelanin is phototoxic to pigmented tissues. Ultraviolet A (UVA)-induced tanning seems to result from the photooxidation of pre-existing melanin and contributes no photoprotection. However, data available for melanin biodegradation remain limited. In this study, we first examined photodegradation of eumelanin and pheomelanin in human black hairs and found that the ratio of Free (formed by peroxidation in situ) to Total (after hydrogen peroxide oxidation) pyrrole-2,3,5-tricarboxylic acid (PTCA) increases with hair aging, indicating fission of the dihydroxyindole moiety. In red hair, the ratio of thiazole-2,4,5-tricarboxylic acid (TTCA) to 4-amino-3-hydroxyphenylalanine (4-AHP) increases with aging, indicating the conversion from benzothiazine to benzothiazole moiety. These photodegradation of melanins were confirmed by UVA (not UVB) irradiation of melanins from mice and human hairs and synthetic eumelanin and pheomelanin. These results show that both eumelanin and pheomelanin degrade by UVA and that Free/Total PTCA and TTCA/4-AHP ratios serve as sensitive indicators of photodegradation.

Protective effect of Kit signaling for melanocyte stem cells against radiation-induced genotoxic stress.

Radiation-induced hair graying is caused by irreversible defects in the self-renewal and/or development of follicular melanocyte stem cells in the hair follicles. Kit signaling is an essential growth and differentiation signaling pathway for various cell lineages including melanocytes, and its radioprotective effects have been shown in hematopoietic cells. However, it is uncertain whether Kit signaling exerts a radioprotective effect for melanocytes. In this study, we found that various loss-of-function mutations of Kit facilitate radiation-induced hair graying. In contrast, transgenic mice expressing the ligand for Kit (Kitl) in the epidermis have significantly reduced levels of radiation-induced hair graying. The X-ray doses used did not show a systemic lethal effect, indicating that the in vivo radiosensitivity of Kit mutants is mainly caused by the damaged melanocyte stem cell population. X-ray-damaged melanocyte stem cells seemed to take the fate of ectopically pigmented melanocytes in the bulge regions of hair follicles in vivo. Endothelin 3, another growth and differentiation factor for melanocytes, showed a lesser radioprotective effect compared with Kitl. These results indicate the prevention of radiation-induced hair graying by Kit signaling.

Tanning and increased nevus development in very-light-skinned children without red hair.

OBJECTIVE: To examine the relationship between tanning and nevus development in very-light-skinned children. DESIGN: Prospective cohort nested within a randomized controlled trial. Skin examinations in 3 consecutive years (2004, 2005, and 2006) included full-body counts of nevi, skin color and tanning measurement using colorimetry, and hair and eye color evaluation by comparison with charts. Telephone interviews of parents provided sun exposure, sun protection, and sunburn history. SETTING: Large managed-care organization and private pediatric offices in the Denver, Colorado, metropolitan area. PARTICIPANTS: A total of 131 very-light-skinned white children without red hair and 444 darker-skinned white children without red hair born in Colorado in 1998. MAIN OUTCOME MEASURES: Full-body nevus counts at ages 6 to 8 years. RESULTS: Among very-light-skinned white children, geometric mean numbers of nevi for minimally tanned children were 14.8 at age 6 years; 18.8 at age 7 years; and 22.3 at age 8 years. Mean numbers of nevi for tanned children were 21.2 at age 6 years; 27.9 at age 7 years; and 31.9 at age 8 years. Differences in nevus counts between untanned and tanned children were statistically significant at all ages (P < .05 for all comparisons). The relationship between tanning and number of nevi was independent of the child's hair and eye color, parent-reported sun exposure, and skin phototype. Among darker-skinned white children, there was no relationship between tanning and nevi. CONCLUSIONS: Very-light-skinned children who tan (based on objective measurement) develop more nevi than children who do not tan. These results suggest that light-skinned children who develop tans may be increasing their risk for developing melanoma later in life.

Burning, paradoxical hypertrichosis, leukotrichia and folliculitis are four major complications of intense pulsed light hair removal therapy.

BACKGROUND: Lasers and intense pulsed light (IPL) are now used worldwide for prolonged photo-epilation. OBJECTIVE: To study the side effects of IPL hair removal therapy among 2541 female hirsute patients as the largest series reported so far in the literature. METHODS: The first series of 1000 patients were treated by the Lumina IPL system. (Lynton Lasers, UK). The second series of 1541 patients were treated by Vasculight-SR, a multi-functional laser and IPL system (Lumenis, Inc., USA). The fluences used for Lumina varied between 16 and 30 J/cm2. The parameters used for Vasculight-SR were as follows: fluences ranged from 33 to 42 J/cm2; pulse duration was 3-5 ms, and pulse delay was 20-80 ms. The pulse mode was either double or triple. The parameters were chosen according to the patients' Fitzpatrick skin types and tolerance. The cut-off filters frequently used were 695, 755, 645 and 615 nm in descending order of their frequencies. Patients were treated every 4-6 weeks and for eight sessions or more. All patients were followed for up to 20 months. RESULTS: Series 1 - burning and its sequelae presented as post-inflammatory hyperpigmentation (PIH), post-inflammatory hypopigmentation (PIHPO), bulla and erosion, and finally scar formation in 75, 10, 64 and one case, respectively. Leukotrichia, folliculitis, and paradoxical hypertrichosis were recorded in 40, 35, and 12 more cases, respectively. Series 2 - PIH and PIHPO were recorded in 28 and four patients. Erosion and crust formation were recorded in 28 patients. Paradoxical effect, leukotrichia and acne formation were seen in 79, 27 and 19 cases, respectively. CONCLUSION: Burning and its sequellae, leukotrichia, paradoxical hypertrichosis and folliculitis are four major side effects of IPL hair removal therapy in our study.

Hair color changes and protein damage caused by ultraviolet radiation.

Ultraviolet and visible radiations are known to damage hair. However, quantitative data relating damage to hair type, proteins and color to the radiation wavelength are missing. We studied the effect of UV plus visible, UVA plus visible, visible mercury-vapor lamp radiation and sunlight on (blended) virgin dark-brown, blond and red hair and (one head) virgin black and curly dark-brown hair. All hair types showed a substantial increase in protein loss in water after lamp and sun irradiation. The damaging effect of UVB was about 2-5 times higher than that of UVA plus visible radiation, depending on the hair type. Significant color changes were also observed in every hair type, after lamp and sun irradiation, being more pronounced for the light colored hairs. The luminosity difference parameter was the major contributor to the hair color changes, but significant changes in the red-green and yellow-blue parameters of every hair were observed. In this case, the damaging effect is ascribable mainly to UVA radiation. No significant changes in the mechanical properties or topography were observed in any case. We discuss these results in terms of hair type and composition and melanin types.

Silicones used in permanent and semi-permanent hair dyes to reduce the fading and color change process of dyed hair occurred by wash-out or UV radiation.

Different kinds of silicones were incorporated directly into permanent and semi-permanent hair dyes. To ensure that the silicone was deposited to the hair fibers Si deposition was measured. Hair treated with a silicone free control or the silicone modified hair dyes was tested for color and lightness change (fading) by washing the treated tresses several times and measuring the color change. In a second experiment, hair treated with permanent hair dye was treated with UV radiation to show if silicones can reduce the color change initiated by UV light. The influence of the silicones to dry combing forces of permanent dyed hair untreated and treated with UV was also investigated. The tests showed that dimethiconol/dimethicone mixtures can reduce the washout of hair colorant clearly and silicone resins like trimethylsiloxysilcate or propylphenylsilsesquioxane are able to decrease the color change occurred by UV radiation in dyed hair.

Leukotrichia developed following application of intense pulsed light for hair removal.

BACKGROUND: Lasers and light sources are now used worldwide for permanent or prolonged hair removal. Patients now prefer lasers and light sources for hair removal because of their noninvasiveness and fewer reported side effects. OBJECTIVE: To study and report on leukotrichia that developed following application of intense pulsed light (IPL). METHODS: From February 9, 2001 to February 14, 2002 a total of 821 patients were treated for unwanted hair. The system used was a noncoherent IPL system, with a 650 nm flashlamp filter; the parameters used varied with different Fitzpatrick skin types. The patients were treated monthly, with the rate of hair loss, measured by hair counts, and possible side effects recorded. RESULTS: Twenty-nine of 821 patients treated developed leukotrichia. Thirteen patients had no white or gray hairs before IPL therapy; the remaining 16 patients, who had few white hairs before treatment reported accelerated development of new white hairs starting after the first or second IPL therapy. Restoration of hair color occurred in 9 patients and the remaining 20 patients had no improvement or worsening of the condition within the next 2-6 months. CONCLUSION: Temporary or permanent leukotrichia may develop following IPL and laser hair removal therapy. This finding may be explained by the difference in the thermal relaxation times of melanocytes and germinative cells. The light absorbed and the heat produced by melanin may be sufficient enough to destroy or impair the function of melanocytes but insufficient to damage the hair follicle cells.

Reversion of the mouse pink-eyed unstable mutation induced by low doses of x-rays.

Deletions and other genome rearrangements can be caused by radiation and are associated with carcinogenesis and inheritable diseases. The pink-eyed unstable (p(un)) mutation in the mouse is caused by a gene duplication and reverts to wild type by deletion of one copy. Reversion events in the mouse embryo were detected as black spots on the fur of the animals or microscopically as partially black hair in a background of colorless hair. The frequency of partially black hair was increased by x-rays at very low doses. A linear dose-response relation was found between 1 and 100 centigray.

Effect of Fluosol-DA 20% and oxygen on response of C57BL/6 mice to whole-body irradiation.

Normal tissue effects in mice due to combinations of a perfluorochemical emulsion, Fluosol-DA 20%, 100% oxygen, and whole-body irradiation were investigated. Eight-to-10-week-old C57BL/6 male mice were injected via the tail vein with 10 ml/kg of Fluosol-DA with and without subsequent exposure to oxygen for 60 minutes. Animals then received graded doses of whole-body radiation (4 MV photons) at a dose rate of 2.85 +/- .015 Gy/minute. Using linear regression analysis, the lethal doses of radiation to 50% and 10% of the animals within 30 days in the absence of Fluosol-DA and oxygen were 8.35 Gy (95% c.l.:7.77-8.93 Gy) and 6.73 Gy (95% cl.:6.21-7.25 Gy), respectively, and were unaffected by Fluosol-DA and/or oxygen pre-treatment. However, Fluosol-DA given alone or in combination with oxygen produced increased balding and decreased graying incidence in mice within 60 days, and resulted in depressed weight gain 15 to 60 days post-treatment. Normal tissue effects due to administration of Fluosol-DA and oxygen in combination with whole-body irradiation have been demonstrated but appear minimal compared to other anti-tumor modalities currently under investigation.

Late tissue-specific toxicity of total body irradiation and busulfan in a murine bone marrow transplant model.

Total body irradiation (TBI) and busulfan were compared for late effects in a murine model of bone marrow transplantation (BMT). Male C57BL/6 mice were given fractionated TBI or busulfan given in 4 equal daily doses followed by infusion of 10(7) syngeneic bone marrow cells. Total doses of 16.4 Gy TBI and 3.4 mg busulfan were chosen for their equivalence in inducing near complete engraftment of allogeneic marrow from donor mice of the LP strain. The two treatment groups had a late wave of mortality starting at about 80 weeks after transplantation. Specific tissue damage was manifested in bone marrow stem cells, splenic T-cell precursors, hair greying and cataract formation for both TBI and busulfan but to varying degrees. Severe nephrotoxicity and anemia were observed only after TBI. Although both busulfan and TBI kill early marrow stem cells and are effective preparative agents in bone marrow transplantation, their effects on other stem cell and organ systems are not similar. In addition, many of the injuries seen are late to occur. The delayed expression of injury deserves careful long-term evaluation of BMT recipients before the therapeutic potential of effective preparative regimens can be fully appreciated.