Regulation of UV-Protective Pathways Downstream of the Melanocortin 1 Receptor in Melanocytes

Malignant cutaneous melanoma is the deadliest form of skin cancer, and a majority of melanoma diagnoses are a result of exposure to ultraviolet (UV) radiation. UV radiation causes DNA damage, which if not repaired correctly via nucleotide excision repair (NER) can result in mutations and melanomagenesis. The melanocortin 1 receptor (MC1R) is a Gs protein coupled receptor located on melanocyte plasma membranes and is involved in protecting the skin from UV induced damage. MC1R signaling results in the activation of two protective pathways: 1) induction of eumelanin synthesis downstream of micropthalmia-associated transcription factor (MITF) and 2) acceleration of NER downstream of ataxia telangiectaseia mutated and Rad3 related (ATR). MC1R signaling, however, also promotes melanocyte proliferation, therefore, the activation of the MC1R pathway must be regulated. The overall hypothesis of this dissertation is that the pathways downstream of MC1R can be manipulated to protect against UV induced damage. Chapter 2 investigates the regulation of the MC1R neutral antagonist human β-defensin 3 (βD3). UV damage did not induce βD3 mRNA expression in ex vivo human skin explants. The induction of βD3 expression instead correlated with inflammatory cytokines including TNF. Chapter 3 investigates the interdependence and cross talk between the two protective pathways downstream of MC1R. We directly tested the effect of MITF on the acceleration of NER and the effect of ATR on the induction of eumelanin synthesis following MC1R activation. MITF was not required for the acceleration of NER as mediated by ATR, however, the induction of transcription of enzymes involved in eumelanin synthesis was dependent upon ATR kinase activity. Finally, Chapter 4 investigates the mechanism by which MC1R promoted proliferation and whether the two UV protective pathways downstream of MC1R could be selectively activated without the risk of melanocyte proliferation. MC1R signaling resulted in activation of the mechanistic target of rapamycin complex 1 (mTORC1), a major regulator of cell growth and proliferation. Inhibition of mTORC1 signaling via rapamycin prevented MC1R induced proliferation in vitro. Rapamycin, however, did not prevent MC1R induced eumelanin synthesis or the acceleration of NER in vitro or in vivo suggesting it is possible to selectively activate the beneficial signaling pathways without the risk of melanocyte proliferation. The results of this dissertation suggest that MC1R signaling could be augmented in individuals to prevent UV induced damage

Laparoscopic Partial Splenectomy for a Splenic Hamartoma

Objective We discuss current knowledge and management of splenic hamartoma, an uncommon form of benign tumor. Summary background data A splenic hamartoma is a rare form of benign splenic mass, often found incidentally while working up other complaints, and is typically treated by surgical resection of the mass. In this case, we discuss the management of an incidentally found splenic hamartoma that was treated with laparoscopic partial splenectomy. Methods The patient presented in the Emergency Department complaining of periumbilical pain after having been struck in the abdomen with a soccer ball the previous day. Following a physical exam and blood work, an ultrasound was performed that revealed a hypoechoic area within the spleen. The patient received a diagnosis of gastroenteritis and an appointment for follow-up at 2 months. At 2-month follow-up, an ultrasound indicated that the mass had grown. The mass appeared consistent with a splenic hemangioma, so the patient was scheduled for laparoscopic partial splenectomy. Results The mass was completely resected without any complications. The patient had an uncomplicated postoperative course. Conclusions When there are no other indications for a total splenectomy and malignancy is unlikely, laparoscopic partial splenectomy appears to be a reasonable treatment modality for a splenic hamartoma

UV-Independent Induction of Beta Defensin 3 in Neonatal Human Skin Explants

In order to determine the effect of UV radiation on β-defensin 3 (BD3) expression in human skin, freshly-isolated UV-naïve skin was obtained from newborn male infants undergoing planned circumcision. Skin explants sustained ex vivo dermis side down on RPMI media were exposed to 0.5 kJ/m2 UVB, and biopsies were taken from the explant through 72 hours after radiation. mRNA expression was measured by qRTPCR and normalized to TATA-binding protein. BD3 expression at each time point was compared with an untreated control taken at time 0 within each skin sample. Extensive variability in both the timing and magnitude of BD3 induction across individuals was noted and was not predicted by skin pigment phenotype, suggesting that BD3 induction was not influenced by epidermal melanization. However, a mock-irradiated time course demonstrated UV-independent BD3 mRNA increases across multiple donors which was not further augmented by treatment with UV radiation, suggesting that factors other than UV damage promoted increased BD3 expression in the skin explants. We conclude that BD3 expression is induced in a UV-independent manner in human skin explants processed and maintained in standard culture conditions, and that neonatal skin explants are an inappropriate model with which to study the effects of UV on BD3 induction in whole human skin

Wave function-dependent mobility and suppression of interface roughness scattering in a strained SiGe p-channel field-effect structure

The 4 K Hall mobility has been measured in a top-gated, inverted, modulation-doped Si/Si0.8Ge0.2 structure having a Si:B doping layer beneath the alloy. From comparisons with theoretical calculations, we argue that, unlike an ordinary enhancement-mode SiGe p-channel metal–oxide–semiconductor structure, this configuration leads to a decrease of interface roughness scattering with increasing sheet carrier density. We also speculate on the nature of the interface charge observed in these structures at low temperature

Melanocortin 1 Receptor: Structure, Function, and Regulation

The melanocortin 1 receptor (MC1R) is a melanocytic Gs protein coupled receptor that regulates skin pigmentation, UV responses, and melanoma risk. It is a highly polymorphic gene, and loss of function correlates with a fair, UV-sensitive, and melanoma-prone phenotype due to defective epidermal melanization and sub-optimal DNA repair. MC1R signaling, achieved through adenylyl cyclase activation and generation of the second messenger cAMP, is hormonally controlled by the positive agonist melanocortin, the negative agonist agouti signaling protein, and the neutral antagonist β-defensin 3. Activation of cAMP signaling up-regulates melanin production and deposition in the epidermis which functions to limit UV penetration into the skin and enhances nucleotide excision repair (NER), the genomic stability pathway responsible for clearing UV photolesions from DNA to avoid mutagenesis. Herein we review MC1R structure and function and summarize our laboratory’s findings on the molecular mechanisms by which MC1R signaling impacts NER

A return to strong radio flaring by Circinus X-1 observed with the Karoo Array Telescope test array KAT-7

Circinus X-1 is a bright and highly variable X-ray binary which displays strong and rapid evolution in all wavebands. Radio flaring, associated with the production of a relativistic jet, occurs periodically on a ~17-day timescale. A longer-term envelope modulates the peak radio fluxes in flares, ranging from peaks in excess of a Jansky in the 1970s to an historic low of milliJanskys during the years 1994 to 2007. Here we report first observations of this source with the MeerKAT test array, KAT-7, part of the pathfinder development for the African dish component of the Square Kilometre Array (SKA), demonstrating successful scientific operation for variable and transient sources with the test array. The KAT-7 observations at 1.9 GHz during the period 13 December 2011 to 16 January 2012 reveal in temporal detail the return to the Jansky-level events observed in the 1970s. We compare these data to contemporaneous single-dish measurements at 4.8 and 8.5 GHz with the HartRAO 26-m telescope and X-ray monitoring from MAXI. We discuss whether the overall modulation and recent dramatic brightening is likely to be due to an increase in the power of the jet due to changes in accretion rate or changing Doppler boosting associated with a varying angle to the line of sight.Comment: 7 pages, 5 figures, accepted for publication in MNRAS 14 May 201

Divergence of cAMP Signalling Pathways Mediating Augmented Nucleotide Excision Repair and Pigment Induction in Melanocytes

Loss‐of‐function melanocortin 1 receptor (MC1R) polymorphisms are common in UV‐sensitive fair‐skinned individuals and are associated with blunted cAMP second messenger signalling and higher lifetime risk of melanoma because of diminished ability of melanocytes to cope with UV damage. cAMP signalling positions melanocytes to resist UV injury by upregulating synthesis of UV‐blocking eumelanin pigment and by enhancing the repair of UV‐induced DNA damage. cAMP enhances melanocyte nucleotide excision repair (NER), the genome maintenance pathway responsible for the removal of mutagenic UV photolesions, through cAMP‐activated protein kinase (protein kinase A)‐mediated phosphorylation of the ataxia telangiectasia‐mutated and Rad3‐related (ATR) protein on the S435 residue. We investigated the interdependence of cAMP‐mediated melanin upregulation and cAMP‐enhanced DNA repair in primary human melanocytes and a melanoma cell line. We observed that the ATR‐dependent molecular pathway linking cAMP signalling to the NER pathway is independent of MITF activation. Similarly, cAMP‐mediated upregulation of pigment synthesis is independent of ATR, suggesting that the key molecular events driving MC1R‐mediated enhancement of genome maintenance (eg PKA‐mediated phosphorylation of ATR) and MC1R‐induced pigment induction (eg MITF activation) are distinct

Proteomic Analysis of Media from Lung Cancer Cells Reveals Role of 14-3-3 Proteins in Cachexia

Aims: At the time of diagnosis, 60% of lung cancer patients present with cachexia, a severe wasting syndrome that increases morbidity and mortality. Tumors secrete multiple factors that contribute to cachectic muscle wasting, and not all of these factors have been identified. We used Orbitrap electrospray ionization mass spectrometry to identify novel cachexia-inducing candidates in media conditioned with Lewis lung carcinoma cells (LCM). Results: One-hundred and 58 proteins were confirmed in three biological replicates. Thirty-three were identified as secreted proteins, including 14-3-3 proteins, which are highly conserved adaptor proteins known to have over 200 binding partners. We confirmed the presence of extracellular 14-3-3 proteins in LCM via western blot and discovered that LCM contained less 14-3-3 content than media conditioned with C2C12 myotubes. Using a neutralizing antibody, we depleted extracellular 14-3-3 proteins in myotube culture medium, which resulted in diminished myosin content. We identified the proposed receptor for 14-3-3 proteins, CD13, in differentiated C2C12 myotubes and found that inhibiting CD13 via Bestatin also resulted in diminished myosin content. Conclusions: Our novel findings show that extracellular 14-3-3 proteins may act as previously unidentified myokines and may signal via CD13 to help maintain muscle mass

Chronic disease self-management education courses: utilization by low-income, middle-aged participants

BACKGROUND: Individuals living in lower-income areas face an increased prevalence of chronic disease and, oftentimes, greater barriers to optimal self-management. Disparities in disease management are seen across the lifespan, but are particularly notable among middle-aged adults. Although evidence-based Chronic Disease Self-management Education courses are available to enhance self-management among members of this at-risk population, little information is available to determine the extent to which these courses are reaching those at greatest risk. The purpose of this study is to compare the extent to which middle-aged adults from lower- and higher-income areas have engaged in CDSME courses, and to identify the sociodemographic characteristics of lower-income, middle aged participants. METHODS: The results of this study were produced through analysis of secondary data collected during the Communities Putting Prevention to Work: Chronic Disease Self-Management Program initiative. During this initiative, data was collected from 100,000 CDSME participants across 45 states within the United States, the District of Columbia, and Puerto Rico. RESULTS: Of the entire sample included in this analysis (19,365 participants), 55 people lived in the most impoverished counties. While these 55 participants represented just 0.3% of the total study sample, researchers found this group completed courses more frequently than participants from less impoverished counties once enrolled. CONCLUSION: These results signal a need to enhance participation of middle-aged adults from lower-income areas in CDSME courses. The results also provide evidence that can be used to inform future program delivery choices, including decisions regarding recruitment materials, program leaders, and program delivery sites, to better engage this population