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Biomedical subjects

Barbara A Gilchrest

Publications and source records attributed to Barbara A Gilchrest.

At least 19 recordsLinked to original sources
PubMed2003

Noggin overexpression inhibits eyelid opening by altering epidermal apoptosis and differentiation.

Contact of developing sensory organs with the external environment is established via the formation of openings in the skin. During eye development, eyelids first grow, fuse and finally reopen, thus providing access for visual information to the retina. Here, we show that eyelid opening is strongly inhibited in transgenic mice overexpressing the bone morphogenetic protein (BMP) antagonist noggin from the keratin 5 (K5) promoter in the epidermis. In wild-type mice, enhanced expression of the kinase-inactive form of BMPR-IB mediated by an adenovirus vector also inhibits eyelid opening. Noggin overexpression leads to reduction of apoptosis and retardation of cell differentiation in the eyelid epithelium, which is associated with downregulation of expression of the apoptotic receptors (Fas, p55 kDa TNFR), Id3 protein and keratinocyte differentiation markers (loricrin, involucrin). BMP-4, but not EGF or TGF-alpha, accelerates opening of the eyelid explants isolated from K5-Noggin transgenic mice when cultured ex vivo. These data suggest that the BMP signaling pathway plays an important role in regulation of genetic programs of eyelid opening and skin remodeling during the final steps of eye morphogenesis.

Adenoviridae↗
PubMed2003

UV induces VEGF through a TNF-alpha independent pathway.

Vascular endothelial growth factor (VEGF) is a potent keratinocyte-derived angiogenic factor. Prior reports suggest that following UV irradiation VEGF in keratinocytes is induced primarily by tumor necrosis factor (TNF)- alpha, a cytokine synthesized and secreted by keratinocytes after UV irradiation. We investigated whether blocking TNF-alpha binding to its receptors would inhibit UV-induced VEGF expression and secretion in the keratinocyte-derived line SCC-12F. Irradiation with physiologic UV doses (30 mJ/cm2) substantially induced VEGF mRNA in this cell line, as expected, and mRNA induction was followed by increased VEGF in medium conditioned by UV-irradiated cells. Also as expected, TNF-alpha induced VEGF expression and secretion in a dose-dependent manner. Addition of a hexapeptide (Ac-KWIIVW-NH2), known to block TNF-alpha binding to its receptors, abrogated this TNF-alpha effect on VEGF mRNA induction. However, addition of the peptide to cells immediately after UV irradiation did not substantially affect VEGF mRNA induction or secretion into the medium. Our results suggest that VEGF induction after UV irradiation is mediated by multiple mechanisms and that blocking a single pathway does not affect the response.

Animals↗
PubMed2003

Evidence that exposure of the telomere 3' overhang sequence induces senescence.

Normal human cells cease proliferation after a finite number of population doublings, a phenomenon termed replicative senescence. This process, first convincingly described by Hayflick and Moorhead [Hayflick, L. & Moorhead, P. S. (1961) Exp. Cell Res. 25, 595-621] for cultured human fibroblasts 40 years ago, is suggested to be a fundamental defense against cancer. Several events have been demonstrated to induce the senescent phenotype including telomere shortening, DNA damage, oxidative stress, and oncogenic stimulation. The molecular mechanisms underlying senescence are poorly understood. Here we report that a 1-week exposure to oligonucleotide homologous to the telomere 3'-overhang sequence TTAGGG (T-oligo) similarly specifically induces a senescent phenotype in cultured human fibroblasts, mimicking serial passage or ectopic expression of a dominant negative form of the telomeric repeat binding factor, TRF2(DN). We propose that exposure of the 3' overhang due to telomere loop disruption may occur with critical telomere shortening or extensive acute DNA damage and that the exposed TTAGGG tandem repeat sequence then triggers DNA-damage responses. We further demonstrate that these responses can be induced by treatment with oligonucleotides homologous to the overhang in the absence of telomere disruption, a phenomenon of potential therapeutic importance.

Cell Division↗
PubMed2003

Modulations of nerve growth factor and Bcl-2 in ultraviolet-irradiated human epidermis.

BACKGROUND: Ultraviolet (UV) irradiation to the skin causes apoptosis of keratinocytes. Melanocytes are more resistant to UV-induced apoptosis, due, in part, to high levels of antiapoptotic proteins such as Bcl-2. In vitro studies have shown that nerve growth factor (NGF), a neurotrophic polypeptide, is produced by keratinocytes and exerts a protective role for melanocytes by upregulating Bcl-2. The purpose of this study was to determine NGF and Bcl-2 modulations in UV-irradiated human skin. METHODS: Nine volunteers were irradiated with two minimal erythema doses using solar-simulated UV irradiation. Seventy-two hours post irradiation, skin biopsies were obtained from irradiated and sun-protected skin. The skin specimens were stained with anti-tyrosinase-related protein-1 monoclonal antibody IgG2a (Mel-5), anti-Bcl-2 (monoclonal antibody IgG-kappa), and with anti-NGF (polyclonal antibody IgG). RESULTS: NGF staining was identified within the cytoplasm of epidermal melanocytes, similar to the staining observed for TRP-1 and Bcl-2. While no significant difference in the number of TRP-1- and Bcl-2-positive melanocytes was observed between irradiated and non-irradiated skin within 72 h, the number of NGF-positive melanocytes decreased significantly, 72 h after UV irradiation (p < 0.024). NGF was also identified within keratinocytes, and while non-irradiated skin exhibited cytoplasmic NGF staining throughout the epidermis, NGF staining was reduced in the lower epidermal layers after UV irradiation. CONCLUSIONS: This is the first in vivo study showing NGF to be present in melanocytes, as well as showing modulations of NGF and Bcl-2 in melanocytes, following solar-simulated UV irradiation.

Adult↗
PubMed2003

Inhibition of the elicitation phase of contact hypersensitivity by thymidine dinucleotides is in part mediated by increased expression of interleukin-10 in human keratinocytes.

The production of immunomodulatory cytokines such as interleukin-10 (IL-10) from keratinocytes and other target cells in the skin plays a crucial role in UV-induced immunosuppression. Substantial evidence supports an association between DNA damage and immunomodulation. It is also known that small DNA fragments such as thymidine dinucleotides (pTpT) can mimic several UV-induced effects, including inhibition of the induction phase of the contact hypersensitivity response and up-regulation of tumor necrosis factor-alpha (TNF-alpha). To determine whether pTpT also induces IL-10 secretion by keratinocytes, and by inference whether IL-10 production after UV irradiation is a response to DNA damage, we compared the effects of pTpT with those of UV irradiation on primary human keratinocyte cultures. Subconfluent cultures of primary human keratinocytes were treated either with 10 micro M or 100 micro M pTpT or diluent alone, or exposed to solar-simulated light (100 J/m2 of UVB) or sham irradiated. An increase in IL-10 mRNA expression was observed 6-24 h after irradiation and at 24-48 h after treatment with pTpT. Detection of secreted IL-10 protein coincided with up-regulation of IL-10 gene expression at 48 and 72 h as determined by ELISA. Conditioned media from human keratinocytes treated with pTpT, like that from irradiated cells, significantly inhibited lymphocyte proliferation in the allogeneic-mixed lymphocyte reaction (MLR) assay. To determine whether pTpT mimics the suppressive influence of UVB on the elicitation phase of contact hypersensitivity, believed to result largely from IL-10 release, we compared the effects of topical application of pTpT with those of UVB irradiation on C57Bl/6 mice sensitized with dinitrofluorobenzene. Sensitized mice treated with pTpT or UVB irradiation showed markedly suppressed elicitation of ear-swelling responses. These results demonstrate that increased keratinocyte IL-10 mRNA level and IL-10 protein release are among the effects of pTpT and support the hypothesis that pTpT treatment triggers many of the biologic effects of UV irradiation by mimicking UV-induced DNA damage. Finally, regardless of mechanism, the data suggest that topical treatment with pTpT may provide a novel means of suppressing contact hypersensitivity or other lymphocyte-mediated reactions in skin.

Animals↗
PubMed2003

Fas and c-kit are involved in the control of hair follicle melanocyte apoptosis and migration in chemotherapy-induced hair loss.

Chemotherapy alters the structure and function of hair follicle melanocytes. Molecular mechanisms controlling melanocyte responses during chemotherapy-induced hair loss, however, remain largely unknown. Using immunohistology and multicolor confocal microscopy, we show here that cyclophosphamide administration to C57BL/6 mice alters the activity and fate of hair follicle melanocytes. After 24-48 h, hair bulb melanocytes expressing Fas undergo apoptosis. The number of apoptotic follicular melanocytes is significantly reduced (p<0.01) in cyclophosphamide-treated Fas knockout mice compared to wild-type controls, suggesting that Fas signaling contributes to chemotherapy-induced melanocyte death. After 3-5 d, surviving hair bulb melanocytes express c-kit receptor, proliferate, and appear to migrate up the outer root sheath. Tyrosinase-positive and melanogenically active cells then appear in the epidermis. By Western blotting and immunohistochemistry, expression levels of the c-kit ligand, stem cell factor, in skin and epidermis are strongly increased after cyclophosphamide treatment. Cyclophosphamide-induced migration of the hair follicle melanocytes into epidermis is completely abrogated by administration of c-kit neutralizing antibody. These data suggest that chemotherapy induces a complex response in the hair follicle melanocytes, which includes apoptosis, proliferation, and migration. Pharmacologic manipulation of Fas and c-kit signaling pathways might be useful for the correction of skin hyperpigmentation as a side-effect of chemotherapy.

Alopecia↗
PubMed2003

Fate of melanocytes during development of the hair follicle pigmentary unit.

During hair follicle morphogenesis, melanocyte precursors migrate into developing hair follicles and give rise to differentiated melanocytes that actively produce and transport pigment into the keratinocytes that form the hair shaft; however, patterns of melanocyte proliferation and differentiation during formation of the hair pigmentation unit remain to be elucidated. Using multicolor confocal microscopy and double immunofluorescence of melanogenic proteins (tyrosinase-related proteins 1 and 2, tyrosinase) and the proliferative marker Ki67, we have studied melanocyte development in C57BL/6 mouse embryonic hair follicles. Proliferating melanocyte precursors (tyrosinase-related protein-2/Ki67+ cells) are seen in the hair follicles at stages 1-2 of morphogenesis, as follicular invagination begins. In stage 3-4 hair follicles, the majority of intrafollicular melanocytes remain tyrosinase-related protein-2+ and Ki67+, whereas some located adjacent to the forming dermal papilla begin to express tyrosinase-related protein-1, an early marker of differentiation. Melanin granules appear in stage 5 hair follicles coincident with tyrosinase expression in nonproliferating tyrosinase-related protein-2+/tyrosinase-related protein-1+ melanocytes. Stage 6-8 hair follicles, those actively producing hair, show nonproliferating tyrosinase-related protein-2+ melanocytes in the bulge area, tyrosinase-related protein-2+/tyrosinase-related protein-1+ melanocytes in the outer root sheath, and tyrosinase-related protein-2+/tyrosinase-related protein-1+/tyrosinase+ melanocytes above the dermal papilla. These data suggest that melanocyte precursor cells proliferate extensively at the onset of follicle development. Progeny of these cells migrate down the developing follicle, differentiating further until reaching the area immediately above the dermal papilla, where fully differentiated nonproliferative melanin-producing melanocytes persist, contributing pigment to the growing hair shaft.

Animals↗
PubMed2003

Topical photodynamic therapy: a new tool in cosmetic dermatology.

Topical photodynamic therapy is an evolving relatively new modality in dermatology. While widely used in Europe for treatment of actinic keratoses and skin cancer, topical photodynamic therapy is still relatively unfamiliar in the United States. Approved by the US Food and Drug Administration in 1999, photodynamic therapy is now being evaluated for superficial epidermal tumors, acne, and cosmetic applications. This article reviews recent advances in this field, with emphasis on skin rejuvenation, acne, and hair removal.

Acne Vulgaris↗
PubMed2003

The first 15 years of the American Academy of Dermatology skin cancer screening programs: 1985-1999.

BACKGROUND: In response to the precipitous increase of melanoma, the American Academy of Dermatology (AAD) has coupled melanoma/skin cancer education with free skin cancer screening programs throughout the United States since 1985. The purpose of this analysis is to investigate the risk factors, access to dermatologic services, and screening results of participants in AAD-sponsored programs during the first 15 years that this service was available to the US public. METHODS: Before screening, participants completed a standardized AAD screening form. Screening forms were counted in the AAD central office and recorded in annual summaries. Forms were sent for keypunching and returned to the AAD on a computer disk annually. In 1999, disks were sent to Boston University and a master file was created. RESULTS: Computerized records were available for 819,019 screening forms and 639,835 individuals. In all, 65% of screenees had at least 1 risk factor and 33% had at least 2 risk factors. Of screenees, 33% reported a changing mole and 37% had skin type I or II. Among all screenees, nearly 80% did not have a regular dermatologist, 78% reported no prior AAD skin cancer screening, 60% had never had their skin checked by any doctor, and 51% would not have seen a doctor for skin cancer without the free screening. Nearly 30% of screenees had a presumptive diagnosis of skin cancer or a precursor lesion. Melanomas confirmed by postscreening biopsy were more likely than those in population-based registries to be less than 1.50 mm in thickness. CONCLUSIONS: AAD national screening and educational programs have expanded to all 50 states, provided educational messages about sun protection and early detection to millions, and served many US citizens with an above average risk for skin cancer and suboptimal access to dermatologic care. Screenees had a disturbingly high point prevalence of malignant and premalignant skin lesions. Sustained commitment by the AAD leadership and membership to the screening program is critical to reducing the morbidity and mortality of skin cancer.

Adolescent↗
PubMed2003

Induction of a p95/Nbs1-mediated S phase checkpoint by telomere 3' overhang specific DNA.

Telomere shortening induces a nonproliferative senescent phenotype, believed to reduce cancer risk, and telomeres are involved in a poorly understood manner in responses to DNA damage. Although telomere disruption induces p53 and triggers apoptosis or cell cycle arrest, the features of the disrupted telomere that trigger this response and the precise mechanism involved are poorly understood. Using human cells, we show that DNA oligonucleotides homologous to the telomere 3' overhang sequence specifically induce and activate p53 and activate an S phase checkpoint by modifying the Nijmegen breakage syndrome protein, known to mediate the S phase checkpoint after DNA damage. These responses are mediated, at least in part, by the ATM kinase and are not attributable to disruption of cellular telomeres. Based on these and earlier data, we propose that these oligonucleotides mimic a physiological signal, exposure of the telomere 3' overhang due to opening of the normal telomere loop structure, and hence evoke these protective antiproliferative responses in the absence of DNA damage or telomere disruption.

Ataxia Telangiectasia Mutated Proteins↗
PubMed2002

Strategies for improving melanoma education and screening for men age >or= 50 years: findings from the American Academy of Dermatological National Skin Cancer Sreening Program.

BACKGROUND: Recently, the Institute of Medicine (2000) and the Third United States Preventive Services Task Force (2001) called for studies to help clinicians identify patients, especially elderly patients, who are at high risk for melanoma. In the current study, the authors sought to identify factors associated with a high yield in skin cancer screening and to explore strategies for improving mass screenings for melanoma. METHODS: The authors analyzed the data base of the 242,374 skin cancer screenings conducted on more than 206,000 Americans who attended the American Academy of Dermatology National Skin Cancer Screening Programs during the period 1992-1994. RESULTS: Ninety-six percent of 3476 screenees with a presumptive diagnosis of melanoma or possible melanoma were contacted, and follow-up records were obtained for 73% of screenees. Of these, 363 screenees had histologically proven melanoma. Middle-aged and older men (age >or= 50 years) comprised only 25% of screenees but comprised 44% of those with a confirmed diagnosis of melanoma. The overall yield of melanoma (the number of confirmed diagnoses per the number of screenees) was 1.5 per 1000 screenings (363 diagnoses of 242,374 screenees) compared with a yield of 2.6 per 1000 screenings among men age >or= 50 years. The yield was improved further for men age >or= 50 years who reported either a changing mole (4.6 per 1000 screenings) or skin types I and II (3.8 per 1000 screenings). The predictive value of a screening diagnosis of melanoma was more than twice as high for men age >or= 50 years with either a changing mole or skin types I and II compared with all other participants. CONCLUSIONS: The yield of mass screening for melanoma would be improved by outreach to middle-aged and older men, with particular focus on men with changing moles or with skin types I and II. Primary care physicians should be attuned to the risk factors among all of their patients but should be alerted in particular to the heightened risk of melanoma for men age >or= 50 years. Formal assessment of the impact of targeted screening on mortality warrants further study.

Age Factors↗
PubMed2002

Induction of apoptosis by telomere 3' overhang-specific DNA.

Telomeres are tandem repeats of a specific TTAGGG nucleotide sequence at the ends of chromosomes. Telomere shortening is proposed to act as a biological clock and cancer prevention mechanism by inducing a nonproliferative, senescent phenotype after a limited number of cellular divisions. Recent evidence also suggests that telomere disruption can trigger apoptosis in certain cell types, mimicking a major cellular response to DNA damage. Here, we show that addition of DNA oligonucleotides homologous to the telomere 3' overhang sequence causes lymphocytic (Jurkat) cells to undergo apoptosis, as described for lymphocytes following telomere loop disruption. We further implicate the p53 tumor suppressor and transcription factor, as well as the p53 homolog p73 and the E2F1 transcription factor, in mediating the apoptotic response. We propose that exposure of the telomere 3' overhang due to opening of the normal telomere loop structure is a physiologic signal for these DNA damage-like responses in vivo and that oligonucleotides partially or completely homologous to the telomere overhang mimic this signal in the absence of DNA damage or telomere disruption.

3' Flanking Region↗
PubMed2002

DNA oligonucleotide treatment corrects the age-associated decline in DNA repair capacity.

Age-related decline in DNA repair capacity (DRC) is associated with decreased constitutive levels of p53 and other nucleotide excision repair proteins. To determine whether pretreatment of cells with small DNA oligonucleotides compensates for decreased DRC in the elderly, fibroblasts from donors of different ages were pretreated with thymidine dinucleotide (pTT), a 5' phosphorylated 9 base oligonucleotide (p9mer) or diluent alone for 48 h, then UV-irradiated with solar-simulated light. Western blot analysis revealed age-associated decreases of 40%-80% between newborn and old adult donor cells in the constitutive protein levels of p53, p21, XPA, RPA, ERCC1, and PCNA. Treatment with pTT or p9mer up-regulated these proteins by 200%-650% at 24, 48, and 72 h. Moreover, pretreatment with oligonucleotides significantly increased the removal rate of photoproducts as determined by reacting DNA with thymine dimer-specific antibodies: 40+/-5% vs. 20+/-9% and 15+/-11% remained after 24 h in diluent, pTT and p9mer treated cells, respectively. Oligonucleotide-treated adult cells removed thymine dimers at least as rapidly as diluent treated newborn cells, demonstrating that pTT and p9mer completely corrected the age-associated decrease in DRC. Our studies suggest that topical oligonucleotide treatment may enhance DRC in older adults and thus reduce the carcinogenic risk from solar UV irradiation in this age group.

Aging↗
PubMed2002

Effect of sunscreen application on UV-induced thymine dimers.

BACKGROUND: Exposure to UV radiation is a major risk factor for skin cancer, including malignant melanoma. Photocarcinogenesis is caused largely by mutations at sites of incorrectly repaired DNA photoproducts, of which the most common is the thymine dimer. Over the past decade, controversy has arisen over the use of sunscreens to prevent UV-induced skin cancer. OBJECTIVES: To determine if daily application of a broad-spectrum sunscreen with a sun protection factor (SPF) of 15 protects human skin against UV-induced DNA damage as determined by the formation of thymine dimers after repeated exposures to simulated solar light and, if so, to determine whether daily applications are required to achieve this protective effect. METHODS: Over 4 consecutive days, an SPF 15 sunscreen was applied homogeneously to each of 4 buttock sites of 18 women 30 minutes before exposure to 2 minimum erythemal doses of UV radiation. Of these 4 sites, 1 was treated with SPF 15 daily, and the remaining 3 were treated on 3 of the 4 irradiation days, skipping application on day 2, 3, or 4. A fifth site served as the untreated control and was also not irradiated. The number of cells per square millimeter positive for thymine dimer formation was determined using immunohistochemical and image analyses. RESULTS: There was no significant difference in thymine dimer formation between nonirradiated and irradiated skin when application of sunscreen preceded each irradiation. However, when sunscreen application was omitted even once prior to irradiation, a statistically significant increase in thymine dimer formation was apparent. At 48 hours after irradiation of unprotected skin, 50% of epidermal dimers present 24 hours after irradiation had been removed; at 72 hours, more than 75% were gone. CONCLUSIONS: Our study indicates that regular use of a broad-spectrum sunscreen is effective in preventing a major form of UV-induced DNA damage. Irregular and inadequate use of sunscreen during exposure to UV radiation results in thymine dimer formation, which may lead to mutation and subsequent cancer development.

Administration, Topical↗
PubMed2002

Should the skin cancer examination be taught in medical school?

BACKGROUND: The fact that thin melanomas are associated with a greater than 95% survival rate, while later, more deeply invasive melanomas have a 5-year survival rate of less than 10%, demonstrates the potential personal and public health impact of early detection. The majority of patients with skin lesions are seen by nondermatologists who infrequently counsel patients about skin cancer prevention or perform a complete skin examination as part of routine care. We documented the antecedents of physician practice by evaluating medical students' observation, training, performance, and self-reported skill level for the skin cancer examination and sun protection counseling. METHODS: Surveys were administered and completed in classrooms and student workshops in each of the 4 medical school years during the spring of 1996 and 1997. We concentrate our analysis on the graduating fourth-year students. RESULTS: Of the 302 fourth-year students enrolled at Boston University School of Medicine, Boston, Mass, in 1996 and 1997, 223 (74%) completed surveys. Among fourth-year students, 52% rated themselves as unskilled in skin cancer examinations. Twenty-eight percent of fourth-year students had never observed a skin cancer examination, 40% had received no training, and 35% had never practiced the examination. However, fourth-year students reporting at least 1 opportunity to observe, train, or practice an examination were 3 times as likely to report themselves as moderately to very skilled as students without such opportunities. CONCLUSION: If medical student training rates for the skin cancer examination are equally low elsewhere, as is likely, the present data suggest that even brief additions to the current curriculum, integrated into systems teaching, would augment student exposure and likely boost student skill levels.

Adult↗