ABSTRACT
Human pigmentation involves production and dispersion of melanin by epidermal melanocytes to neighboring keratinocytes. Melanin synthesis or melanogenesis occurs within the specialized organelle termed melanosomes where the amino acid L-tyrosine serves as the starting precursor. Melanocytes from individuals of different pigmentary phenotypes differ in their rate and types of melanin synthesis, as well as in the rate and manner of melanosome transfer. Modern molecular biology methods and the use of transgenic animals have greatly advanced our understanding in the molecular and cellular mechanisms regulating human pigmentation and its disorders. This review examines recent advances in the regulation of human pigmentation and their implication in treatments for the pigmentary disorders.
Subject(s)
Pigmentation Disorders/genetics , Skin Pigmentation/genetics , Animals , Estrogens/metabolism , Humans , Intramolecular Oxidoreductases/metabolism , Keratinocytes/metabolism , Melanins/biosynthesis , Melanocytes/metabolism , Melanosomes/metabolism , Membrane Glycoproteins/metabolism , Monophenol Monooxygenase/metabolism , Mutation , Nitric Oxide/metabolism , Oxidoreductases/metabolism , Phenotype , Pigmentation Disorders/enzymology , Tyrosine/metabolism , Ultraviolet Rays/adverse effectsABSTRACT
The color of the skin, hair and eye is controlled by multiple genes and is among the most visible examples of human phenotypic variation. Genetics correlate phenotypic with genotypic variation. Recent scientific work reveals DNA polymorphisms at least partially responsible for some of the differences observed in human pigmentation. These are the focus of this review.
Subject(s)
DNA/genetics , Polymorphism, Genetic , Skin Pigmentation/genetics , Albinism, Oculocutaneous/genetics , HumansABSTRACT
The popularity of sunscreens dramatically increased since ultraviolet irradiation was implicated in the pathogenesis of skin cancer and skin ageing. The absorption properties, safety, photostability of different organic and inorganic filters are reviewed: para-aminobenzoic acid, salicylates, cinnamates, benzophenones, butylmethoxydibenzoylmethane (Parsol 1789), drometrizole trisulphonic (Mexoryl XL), terephthalydene dicamphor sulphonic acid (Mexoryl SX), methylene bisbenzotriazol tetramethylbutylphenol (Tinasorb M), anisotriazine (Tinasorb S), titanium dioxide and zinc oxide. Furthermore, this review discusses the optimal methods for measuring the protection that a sunscreen offers, the role of sunscreen use in melanoma prevention and future trends in sunscreen filters development.
Subject(s)
Sunscreening Agents , Humans , Melanoma/prevention & control , Skin Neoplasms/prevention & control , Ultraviolet RaysABSTRACT
Recent work has substantially elucidated the mechanisms of skin aging and photoaging. In particular, a central role for telomere-based signaling can be inferred. Intrinsic aging is largely controlled by progressive telomere shortening, compounded by low grade oxidative damage to telomeres and other cellular constituents, the consequence of aerobic cellular metabolism. In sun exposed skin, UV irradiation also damages DNA and accelerates telomere shortening. Aging and photodamage appear to share a common final pathway that involves signaling through p53 following disruption of the telomere. These telomere-initiated responses, in combination with UV-induced damage to critical regulatory genes, lead to the familiar picture of "photoaging." These and other insights into the molecular basis for skin aging/photoaging may lead to enhanced management options.
Subject(s)
Skin Aging/pathology , Skin/ultrastructure , Telomere/physiology , Apoptosis , Cell Division , Cellular Senescence/physiology , DNA/radiation effects , DNA Damage , Humans , Oxidative Stress , Skin/radiation effects , Sunlight/adverse effects , Tandem Repeat Sequences , Telomerase/physiology , Telomere/ultrastructure , Telomeric Repeat Binding Protein 2/physiologyABSTRACT
OBJECTIVES: We investigated whether the mean platelet volume would be a useful marker in the evaluation of inflammatory bowel disease activity. METHODS: Complete blood count, C-reactive protein, erythrocyte sedimentation rate, serum thrombopoietin and erythropoietin, plasma beta-thromboglobulin, and platelet factor 4 were measured in 93 patients with ulcerative colitis, 66 patients with Crohn's disease, and 38 healthy blood donors. Disease activity was assessed by the Clinical Colitis Activity Index in patients with ulcerative colitis and by the Crohn's Disease Activity Index in patients with Crohn's disease. RESULTS: Mean platelet count was increased in patients with active compared to inactive ulcerative colitis (p < 0.05), and in patients with active compared to inactive Crohn's disease (p = 0.0002) or healthy controls (p < 0.0001). On the other hand, mean platelet volume was significantly decreased in patients with active compared to inactive ulcerative colitis (p = 0.02) or healthy controls (p < 0.0001), and in patients with active compared to inactive Crohn's disease (p = 0.0005) or healthy controls (p < 0.0001). Mean platelet volume was inversely correlated with the white blood cell count (r = -0.17, p = 0.02), C-reactive protein (r = -0.46, p = 0.009) and erythrocyte sedimentation rate (r = -0.28, p = 0.008). No significant correlations were found between mean platelet volume and serum thrombopoietin or erythropoietin levels; however, a strong negative correlation between mean platelet volume and beta-thromboglobulin (r = -0.34, p < 0.0001) and platelet factor 4 (r = -0.30, p = 0.0002) was observed. CONCLUSIONS: Mean platelet volume is significantly reduced in active inflammatory bowel disease and is negatively correlated with the known inflammatory bowel disease activity markers and the platelet activation products. We propose that mean platelet volume provides a useful marker of activity in inflammatory bowel disease.
