Distinctive clinical and histological characteristics of atrophic and hypertrophic facial photoageing.

BACKGROUND: Photoageing describes complex cutaneous changes which occur following chronic exposure to solar ultraviolet radiation (UVR). Amongst White Northern Europeans, facial photoageing appears as distinct clinical phenotypes: 'hypertrophic' photoageing (HP) and 'atrophic' photoageing (AP). Deep, coarse wrinkles predominate in individuals with HP, whereas those with AP have relatively smooth, unwrinkled skin with pronounced telangiectasia. AP individuals have an increased propensity for developing keratinocyte cancers. OBJECTIVES: To investigate whether histological differences underlie these distinct phenotypes of facial photoageing. METHODS: Facial skin biopsies were obtained from participants with AP (10 M, 10 F; mean age: 78.7 years) or HP (10 M, 10 F; mean age: 74.5 years) and were assessed histologically and by immunohistochemistry. RESULTS: Demographic characterization revealed 95% of AP subjects, as compared to 35% with HP, were Fitzpatrick skin type I/II; of these, 50% had a history of one or more keratinocyte cancers. There was no history of keratinocyte cancers in the HP cohort. Analysis of UVR-induced mitochondrial DNA damage confirmed that all volunteers had received similar lifetime cumulative doses of sun exposure. Histologically, male AP had a significantly thicker epidermis than did AP females or those of either sex with HP. HP facial skin exhibited severe solar elastosis, whereas in AP facial skin, solar elastosis was apparent only in females. Loss of papillary dermal fibrillin-rich microfibrils occurred in all HP and AP female subjects, but not in AP males. Furthermore, male AP had a significant reduction in collagen VII at the dermal-epidermal junction than did AP females or those of either sex with HP. CONCLUSIONS: This study provides further evidence that AP and HP represent distinct clinical and histological entities. Knowledge of these two phenotypes is clinically relevant due to the increased prevalence of keratinocyte cancers in those - particularly males - with the AP phenotype.

In vitro protective effects of an aqueous extract of Clitoria ternatea L. flower against hydrogen peroxide-induced cytotoxicity and UV-induced mtDNA damage in human keratinocytes.

The traditional practice of eating the flowers of Clitoria ternatea L. or drinking their infusion as herbal tea in some of the Asian countries is believed to promote a younger skin complexion and defend against skin aging. This study was conducted to investigate the protective effect of C. ternatea flower water extract (CTW) against hydrogen peroxide-induced cytotoxicity and ultraviolet (UV)-induced mitochondrial DNA (mtDNA) damage in human keratinocytes. The protective effect against hydrogen peroxide-induced cytotoxicity was determined by 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay, and mtDNA damage induced by UV was determined by polymerase chain reaction. Preincubation of HaCaT with 100, 250, and 500 µg/ml CTW reduced cytotoxicity effects of H2 O2 compared with control (H2 O2 alone). CTW also significantly reduced mtDNA damage in UV-exposed HaCaT (p < .05). CTW was chemically-characterized using high resolution liquid chromatography-mass spectrometry. The main compounds detected were assigned as anthocyanins derived from delphinidin, including polyacylated ternatins, and flavonol glycosides derived from quercetin and kaempferol. These results demonstrated the protective effects of C. ternatea flower extracts that contain polyacylated anthocyanins and flavonol glycosides as major constituents, against H2 O2 and UV-induced oxidative stress on skin cells, and may provide some explanation for the putative traditional and cosmetic uses of C. ternatea flower against skin aging.

Oxidative stress and ageing.

Oxidative stress is the resultant damage due to redox imbalances (increase in destructive free radicals [reactive oxygen species (ROS)] and reduction in antioxidant protection/pathways) and is linked to ageing in many tissues including skin. In ageing skin there are bioenergetic differences between keratinocytes and fibroblasts which provide a potential ageing biomarker. The differences in skin bioenergy are part of the mitochondrial theory of ageing which remains one of the most widely accepted ageing theories describing subsequent increasing free radical generation. Mitochondria are the major source of cellular oxidative stress and form part of the vicious cycle theory of ageing. External and internal sources of oxidative stress include UVR/IR, pollution (environment), lifestyle (exercise and diet), alcohol and smoking all of which may potentially impact on skin although many exogenous actives and endogenous antioxidant defence systems have been described to help abrogate the increased stress. This also links to differences in skin cell types in terms of the UVR action spectrum for nuclear and mitochondrial DNA damage (the latter a previously described UVR biomarker in skin). Recent work associates bioenergy production and oxidative stress with pigment production thereby providing another additional potential avenue for targeted anti-ageing intervention in skin. This new data supporting the detrimental effects of the numerous wavelengths of UVR may aid in the development of cosmetic/sunscreen design to reduce the effects of photoageing. Recently, complex II of the mitochondrial electron transport chain appears to be more important than previously thought in the generation of free radicals (suggested predominantly by non-human studies). We investigated the relationship between complex II and ageing using human skin as a model tissue. The rate of complex II activity per unit of mitochondria was determined in fibroblasts and keratinocytes cultured from skin covering a wide age range. Complex II activity significantly decreased with age in fibroblasts (P = 0·015), but not in keratinocytes. This was associated with a significant decline in transcript expression (P = 0·008 and P = 0·001) and protein levels (P = 0·0006 and P = 0·005) of the SDHA and SDHB catalytic subunits of complex II respectively. In addition there was a significant decrease in complex II activity with age (P = 0·029) that was specific to senescent skin cells, our study being the first to investigate these differences with senescence and skin age. There was no decrease in complex IV activity with increasing age, suggesting possible locality to complex II. Our study provides a future potential biomarker for monitoring the progression of skin ageing.

Oxidative stress--a key emerging impact factor in health, ageing, lifestyle and aesthetics.

Oxidative stress is the resultant damage that arises due to redox imbalances, more specifically an increase in destructive free radicals and reduction in protection from antioxidants and the antioxidant defence pathways. Oxidation of lipids by reactive oxygen species (ROS) can damage cellular structures and result in premature cell death. At low levels, ROS-induced oxidative stress can be prevented through the action of antioxidants, however, when ROS are present in excess, inflammation and cytotoxicity eventually results leading to cellular oxidative stress damage. Increasing evidence for the role of oxidative stress in various diseases including neurological, dermatological, and cardiovascular diseases is now emerging. Mitochondria are the principal source (90%) of ROS in the cell, with superoxide radicals being generated when molecular oxygen is combined with free electrons. Given the key role of mitochondria in the generation of cellular oxidative stress it is worth considering this organelle and the process in more detail and to provide methods of intervention.

Mitochondrial DNA damage as a biomarker for ultraviolet radiation exposure and oxidative stress.

The skin is regularly exposed to the harmful effects of sunlight, such as ultraviolet radiation (UVR), which leads to ageing effects as well as clinical precancerous lesions and skin cancer. The accumulation of mitochondrial DNA (mtDNA) damage has been strongly associated as an underlying cause of the general ageing process in tissues and mtDNA damage has been associated with cancer development in many tissues including human skin. This scenario is linked to the key roles of mitochondrial function and mtDNA both in terms of energy production and also oxidative stress production as well as a mediator of apoptosis. We and others have pioneered the use of mtDNA damage as a highly sensitive biomarker of UVR exposure and oxidative stress in human skin; furthermore, ageing-dependent mtDNA mutations can be accelerated by exposure to sunlight. In addition, this review will also highlight useful applications of mtDNA as a biomarker of UVR-induced oxidative stress including effects of antioxidants.

Increasing the therapeutic efficacy of docetaxel for cutaneous squamous cell carcinoma through the combined inhibition of phosphatidylinositol 3-kinase/AKT signalling and autophagy.

Early-stage cutaneous squamous cell carcinoma (cSCC) has a favourable prognosis. Metastatic disease is probably associated with chemoresistance mediated through the activation of pro-survival phosphatidylinositol 3-kinase/AKT signalling. Inhibition of activated AKT partially increases chemosensitivity but induces autophagy, the principal lysosomal mechanism for the bulk degradation and recycling of proteins and damaged organelles. The aim of the current study was to test the hypothesis that combined inhibition of AKT signalling and autophagy by the lysosomal inhibitor chloroquine increases the susceptibility to docetaxel-induced apoptosis of cSCC cells isolated from a lymph-node metastasis. Combined AKT inhibition and chloroquine treatment of MET 4 cSCC cells resulted in significantly enhanced inhibition of cell viability and apoptosis induced by clinically achievable concentrations of docetaxel (P < 0.001). Inhibition of both autophagy and AKT thus represents an effective and viable therapeutic strategy to increase the cytotoxicity of docetaxel for the treatment of advanced cSCC.

Tomato paste rich in lycopene protects against cutaneous photodamage in humans in vivo: a randomized controlled trial.

BACKGROUND: Previous epidemiological, animal and human data report that lycopene has a protective effect against ultraviolet radiation (UVR)-induced erythema. OBJECTIVES: We examined whether tomato paste--rich in lycopene, a powerful antioxidant--can protect human skin against UVR-induced effects partially mediated by oxidative stress, i.e. erythema, matrix changes and mitochondrial DNA (mtDNA) damage. METHODS: In a randomized controlled study, 20 healthy women (median age 33 years, range 21-47; phototype I/II) ingested 55 g tomato paste (16 mg lycopene) in olive oil, or olive oil alone, daily for 12 weeks. Pre- and postsupplementation, UVR erythemal sensitivity was assessed visually as the minimal erythema dose (MED) and quantified with a reflectance instrument. Biopsies were taken from unexposed and UVR-exposed (3 × MED 24 h earlier) buttock skin pre- and postsupplementation, and analysed immunohistochemically for procollagen (pC) I, fibrillin-1 and matrix metalloproteinase (MMP)-1, and by quantitative polymerase chain reaction for mtDNA 3895-bp deletion. RESULTS: Mean ± SD erythemal D(30) was significantly higher following tomato paste vs. control (baseline, 26·5 ± 7·5 mJ cm(-2); control, 23 ± 6·6 mJ cm(-2); tomato paste, 36·6 ± 14·7 mJ cm(-2); P = 0·03), while the MED was not significantly different between groups (baseline, 35·1 ± 9·9 mJ cm(-2); control, 32·6 ± 9·6 mJ cm(-2); tomato paste, 42·2 ± 11·3 mJ cm(-2)). Presupplementation, UVR induced an increase in MMP-1 (P = 0·01) and a reduction in fibrillin-1 (P = 0·03). Postsupplementation, UVR-induced MMP-1 was reduced in the tomato paste vs. control group (P = 0·04), while the UVR-induced reduction in fibrillin-1 was similarly abrogated in both groups, and an increase in pCI deposition was seen following tomato paste (P = 0·05). mtDNA 3895-bp deletion following 3 × MED UVR was significantly reduced postsupplementation with tomato paste (P = 0·01). CONCLUSIONS: Tomato paste containing lycopene provides protection against acute and potentially longer-term aspects of photodamage.

Real-time polymerase chain reaction analysis of a 3895-bp mitochondrial DNA deletion in epithelial swabs and its use as a quantitative marker for sunlight exposure in human skin.

BACKGROUND: The use of mitochondrial DNA (mtDNA) damage as a reliable and highly sensitive biomarker of ultraviolet (UV) radiation exposure in both the dermis and epidermis has now been well developed by our group and others. We have previously identified a 3895-bp mtDNA deletion which occurred more frequently and to a higher level in usually sun-exposed skin as opposed to occasionally sun-exposed skin. This work focused on older-aged individuals and, in particular, perilesional, histologically normal skin biopsies taken from patients with skin cancer. OBJECTIVES: To develop novel, less-invasive methods of obtaining skin samples (i.e. epidermis) from volunteers covering a much wider age range and larger number of individuals (n = 239). METHODS: The 3895-bp deletion was quantified by a specific real-time polymerase chain reaction assay in normal human epidermis samples taken from three body sites with differing sun exposure. RESULTS: The results show a statistical increase of the level of the 3895-bp deletion with increasing sun exposure in the epidermal swabs of human skin (P < 0·001) and with increasing age of the donor in the needle biopsy samples. CONCLUSIONS: These data suggest that the upper layers of the epidermis are an accessible and reliable site for assessing mtDNA damage caused by UV exposure.

Impaired mitochondrial beta-oxidation in a patient with an abnormality of the respiratory chain. Studies in skeletal muscle mitochondria.

Defects of complex I of the mitochondrial respiratory chain are important causes of neurological disease. We report studies that demonstrate a severe deficiency of complex I activity with less severe abnormalities of complexes III and IV (less than 5, 63, and 30% of control values, respectively) in a skeletal muscle mitochondrial fraction from a 22-yr-old female with weakness, lactic acidemia, and the deposition of intramuscular neutral lipid. The observation that lipid accumulates in this and other patients with complex I deficiency suggests impaired mitochondrial fatty acid oxidation. To investigate this mechanism we have shown impaired flux through beta-oxidation [( U-14C]hexadecanoate oxidation was 66% of control rate) and accumulation of specific acyl-CoA ester intermediates. The changes in fatty acid metabolism in complex I deficiency are secondary to the reduced state within the mitochondrial matrix with low NAD+/NADH ratios.

Effects of chelating agents on the Ca2+-stimulated ATPase of rat liver plasma membranes.

Using strictly controlled ionic conditions we have demonstrated, in agreement with previous findings (Lotersztajn et al. (1981) J. Biol. Chem. 256, 11209-11215; Lotersztajn, S. and Pecker, F. (1982) J. Biol. Chem. 257, 6638-6641) a Ca2+-stimulated ATPase in rat liver plasma membranes which is detectable at low free Mg2+ concentrations (normally fulfilled by endogenous levels) but not at free Mg2+ concentrations greater than about 10(-5) M. The findings reported here also suggest that this (Ca2+ + Mg2+)-ATPase is activated by EGTA or one of its liganded species. Furthermore, this is probably an intrinsic property of the enzyme as it was found to be independent of the isolation technique. The stimulation by EGTA appears to be a function both of free Ca2+ concentration and of one or more liganded species of EGTA and it is also inhibited at high free Mg2+ concentrations (approx. 10(-5) M). The specificity of the EGTA effect on ATPase activity is studied with respect to other, widely used, chelating agents namely HEEDTA, EDTA and CDTA. Of these, only CDTA shares the effect, although the concentration dependence of the activation is different from EGTA, suggesting that there is some degree of structural specificity involved rather than a generalised effect of complexed Ca2+.

Ca2+ transport by rat liver plasma membranes: the transporter and the previously reported Ca2+-ATPase are different enzymes.

A rat liver plasma membrane fraction showed an ATP-dependent uptake of Ca2+ which was released by the ionophore A23187. This activity represents a plasma membrane component and is not due to microsomal contamination. The Ca2+ transport displayed several properties which were different from those of the high-affinity Ca2+-ATPase previously observed in these membranes (Lotersztajn et al. (1981) J. Biol. Chem. 256, 11209-11215; Birch-Machin, M.A. and Dawson, A.P. (1986) Biochim. Biophys. Acta 855, 277-285). These observations have shown that Ca2+-ATPase does not require added Mg2+ whereas we have demonstrated that, in the same membrane preparation, Ca2+ uptake required millimolar concentrations of added Mg2+. The Ca2+-ATPase has a broad specificity for the nucleotides ATP, GTP, UTP and ITP while Ca2+ uptake remains specific for ATP. Ca2+ uptake also displayed different affinities for free Ca2+ and MgATP compared to Ca2+-ATPase activity, with apparent Km values of 0.25 microM Ca2+, 0.15 mM MgATP and 1.0 microM Ca2+, 4 microM MgATP respectively. The apparent maximum rate of Ca2+ uptake was about 150-fold less than Ca2+-ATPase activity. These features suggest that the high-affinity Ca2+-ATPase is not the enzymic expression of the ATP-dependent Ca2+ transport mechanism.

Succinate-cytochrome c reductase: assessment of its value in the investigation of defects of the respiratory chain.

Defects of the respiratory chain are important causes of human disease and one of the most commonly used assays in the investigation of these patients is the measurement of succinate-cytochrome c reductase. However, this assay measures several components of the respiratory chain and the ability to detect a partial defect in one enzyme complex will depend on the amount of control exerted by that enzyme step on overall electron flux. We show that measurement of succinate-cytochrome c reductase activity may fail to detect partial defects of complex III and therefore is of limited diagnostic value in the identification of complex III defects. However, complex II is a major point of control of flux through succinate-cytochrome reductase and it is likely that measurement of the latter will detect defects of complex II.

The cDNA sequence of the flavoprotein subunit of human heart succinate dehydrogenase.

We report the full-length cDNA sequence for the flavoprotein subunit of human heart succinate dehydrogenase (succinate: (acceptor) oxidoreductase EC 1.3.99.1). Identical sequence was obtained for part of the cDNA of the human placental flavoprotein, in contrast to a previously published sequence. The human sequence, like the bovine one, contains a cysteine triplet and at the active site there is an additional cysteine when compared with yeast or prokaryotes.

The spectrum of mitochondrial DNA deletions is a ubiquitous marker of ultraviolet radiation exposure in human skin.

We and colleagues have suggested that deletions of mitochondrial DNA may be useful as a biomarker of ultraviolet radiation exposure in skin. In this study using a southwestern approach involving monoclonal antibodies against thymine dimers we provide direct evidence for the presence of ultraviolet-induced damage in mitochondrial DNA purified from any nuclear DNA contamination. Previous studies have been limited, as they have focused on the frequency of a single mitochondrial DNA deletion. Therefore we have addressed the question of the spectrum of mitochondrial DNA deletions in skin and whether this can be used as an index of overall DNA damage. We have used a long polymerase chain reaction technique to determine the mitochondrial DNA deletion spectrum of almost the entire mitochondrial genome in 71 split skin samples in relation to sun exposure. There was a significant increase in the number of deletions with increasing ultraviolet exposure in the epidermis (Kruskal-Wallis test, p = 0.0015) but not the dermis (p = 0.6376). The findings in the epidermis are not confounded by any age-dependent increases in mitochondrial DNA deletions also detected by the long polymerase chain reaction technique. The large spectrum of deletions identified in our study highlights the ubiquitous nature and the high mutational load of mitochondrial DNA associated with ultraviolet exposure and chronologic aging. Compared with the detection of single deletions using competitive polymerase chain reaction, we show that long polymerase chain reaction is a sensitive technique and may therefore provide a more comprehensive, although not quantitative, index of overall mitochondrial DNA damage in skin.

Mitochondrial DNA deletions in human skin reflect photo- rather than chronologic aging.

We have examined the use of mitochondrial DNA (mtDNA) as a molecular marker to study the relation between chronologic aging and photoageing in human skin. Using a 3-primer quantitative polymerase chain reaction method we have studied changes in the ratio of the 4977 bp deleted to wild-type mtDNA in relation to sun exposure and chronologic age of human skin. Based on previous studies, samples showing greater than 1% deleted mtDNA were classed as abnormal. There was a significant increase in the incidence of high levels (i.e., >1%) of the 4977 bp deleted mtDNA in sun-exposed sites (27%, 27 of 100) compared with sun-protected sites (1.1%, one of 90) (Fisher's exact test, p < 0.0001). There appeared to be no relation between the frequency of the mtDNA deletion and age. Analysis of split skin samples showed that most deletions (93%, n = 27) were confined to the dermal rather than the epidermal component, and in keeping with this deletions were found in three of six primary cultures of fibroblasts from sun-exposed sites. Deletions were not seen in the epidermal component of several epidermal tumors nor were deletions seen in fibroblasts cultured from an individual with Werner's syndrome. We propose that deletions or mutations of mitochondrial DNA may be useful as a marker of cumulative ultraviolet radiation exposure.

Low frequency of genetic change in p53 immunopositive clones in human epidermis.

Sun-exposed skin of Caucasians harbors thousands of p53-mutated clones, which are clinically invisible. Using whole mount immunostaining for p53 or Ki67 antigens, p53 sequencing, and loss of heterozygosity analysis, we have further characterised these clones. Loss of heterozygosity for the alleles examined is uncommon with the exception of 9q, which occurred in 28.3% of the samples. P53 clones are more common and larger in individuals with basal cell carcinoma than in control subjects (p < 0.03). Loss of heterozygosity is also more common in clones from individuals with basal cell carcinoma than in clones from subjects without a history of basal cell carcinoma, as would be expected if both relate to ultraviolet radiation exposure. p53 sequencing of clones is in keeping with the mutagenic role of ultraviolet radiation. Surprisingly, skin found to harbor p53 clones showed no clusters of Ki67 positive cells, unlike the situation for actinic keratoses or basal cell carcinomas. These results show that in human skin p53 mutation is not directly associated with genomic instability or abnormal cell cycling; that the p53 immunopositive clones are either genetically distinct or precursors to other squamous cell lesions of skin; and that p53 immunopositive clones are early lesions, in that gross disturbance of proliferation has not already occurred.

The relation between melanocortin 1 receptor genotype and experimentally assessed ultraviolet radiation sensitivity.

Pigmentary phenotype is a key determinant of an individual's response to ultraviolet radiation with the presence of phaeomelanin thought to be of particular importance. Reports of minimal erythema testing, however, have failed to show a consistent difference between skin type I and other skin types. The melanocortin 1 receptor is a key genetic determinant of the cutaneous response to ultraviolet radiation. In this study we investigate the relation between experimentally induced erythemal response to ultraviolet radiation and the melanocortin 1 receptor genotype. Phototesting was performed in 20 redheads and 20 nonredheaded subjects, the majority of whom were also screened for the presence of melanocortin 1 receptor variants. The majority of redheads sequenced (89%) had two melanocortin 1 receptor variants previously found to be associated with red hair compared to none of the controls. There was no significant difference between the groups in minimal erythema dose: the median minimal erythema dose in redheads was 44 mJ per cm2 (interquartile range 34-56) and in the nonredheaded group was 40 mJ per cm2 (interquartile range 40-56). Objective measurements of ultraviolet-B-induced erythema were performed using reflectance instrument measurements of erythema intensity and dose-response curves constructed for each subject. The slope of the dose-response curve in the redheaded group was statistically greater than in the nonredheaded group (median in redheads 4.08 vs 3.56 for controls, 95% confidence interval for the difference between the medians being 0.01-1.23, p = 0.043). In addition the ratio D0.05:D0.025 was significantly lower for the redheaded group (median in redheads 1.22, interquartile range 1.18-1.26; median in nonreds 1.28, interquartile range 1.23-1.32; p < 0.05). Thus, although the minimal erythema dose values were not different, subjects with red hair develop greater intensity of erythema than nonredheaded individuals when doses greater than the minimal erythema dose are given. Importantly, when analyzed by genotype alone rather than phenotype, the slope of the erythema dose-response differed between those persons who were homozygous or heterozygous mutants and wildtype/pseudo-wildtype (p = 0.026).

Expression, candidate gene, and population studies of the melanocortin 5 receptor.

In mouse the melanocortin 5 receptor is known to regulate sebaceous gland function. To clarify its role in man, we have studied melanocortin 5 receptor expression in skin, and allelic variation at the melanocortin 5 receptor locus in diverse human populations and candidate disease groups. Melanocortin 5 receptor protein and mRNA expression were studied by immunohistochemistry and reverse transcriptase polymerase chain reaction. Melanocortin 5 receptor mRNA was detected in normal skin and cultured keratinocytes but not in cultured fibroblasts or melanocytes. Immunohistochemistry revealed melanocortin 5 receptor immunoreactivity in the epithelium and appendages, including the sebaceous gland, eccrine glands, and apocrine glands, as well as low level expression in the interfollciular epidermis. In order to screen for genetic diversity in the melanocortin 5 receptor that might be useful for allelic association studies we sequenced the entire melanocortin 5 receptor coding region in a range of human populations. One nonsynonymous change (Phe209Leu) and four synonymous changes (Ala81Ala, Asp108Asp, Ser125Ser, and Thr248Thr) were identified. Similar results were found in each of the populations except for the Inuit in which only the Asp108Asp variant was seen. The apparent "global distribution" of melanocortin 5 receptor variants may indicate that they are old in evolutionary terms. Variation of melanocortin 5 receptor was examined in patients with acne (n = 21), hidradenitis supprativa (n = 4), and sebaceous gland lesions comprising sebaceous nevi, adenomas, and hyperplasia (n = 13). No additional mutations were found. In order to determine the functional status of the Phe209Leu change, increase in cAMP in response to stimulation with alpha-melanocyte-stimulating hormone was measured in HEK-293 cells transfected with either wild-type or the Phe209Leu variant. The variant melanocortin 5 receptor was shown to act in a concentration-dependent manner, which did not differ from that of wild type. We have therefore found no evidence of a causative role for melanocortin 5 receptor in sebaceous gland dysfunction, and in the absence of any association between variation at the locus and disease group, the pathophysiologic role of the melanocortin 5 receptor in man requires further study.

Melanocortin 1 receptor variants in an Irish population.

The identification of an association between variants in the human melanocortin 1 receptor (MC1R) gene and red hair and fair skin, as well as the relation between variants of this gene and coat color in animals, suggests that the MC1R is an integral control point in the normal pigmentation phenotype. In order to further define the contribution of MC1R variants to pigmentation in a normal population, we have looked for alterations in this gene in series of individuals from a general Irish population, in whom there is a preponderance of individuals with fair skin type. Seventy-five per cent contained a variant in the MC1R gene, with 30% containing two variants. The Arg151Cys, Arg160Trp, and Asp294His variants were significantly associated with red hair (p = 0.0015, p < 0.001, and p < 0.005, respectively). Importantly, no individuals harboring two of these three variants did not have red hair, although some red-haired individuals only showed one alteration. The same three variants were also over-represented in individuals with light skin type as assessed using a modified Fitzpatrick scale. Despite these associations many subjects with dark hair/darker skin type harbored MC1R variants, but there was no evidence of any particular association of variants with the darker phenotype. The Asp294His variant was similarly associated with red hair in a Dutch population, but was infrequent in red-headed subjects from Sweden. The Asp294His variant was also significantly associated with nonmelanoma skin cancer in a U.K. population. The results show that the Arg151Cys, Arg160Trp, and Asp294His variants are of key significance in determining the pigmentary phenotype and response to ultraviolet radiation, and suggest that in many cases the red-haired component and in some cases fair skin type are inherited as a Mendelian recessive.

Respiratory chain abnormalities in skeletal muscle from patients with Parkinson's disease.

Parkinson's disease is one of the commonest neurodegenerative disorders in Western society. Although the neuropathological changes have been well documented, the underlying biochemical defect is unknown. Toxins may play a part in the aetiology of this disorder. It has been shown that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces a Parkinson-like syndrome in both man and primates and 1-methyl-4-phenylpyridine (MPP+), a metabolite of MPTP, inhibits NADH-ubiquinone oxidoreductase (complex I) of the mitochondrial respiratory chain. We studied mitochondrial respiratory chain function in skeletal muscle from patients with Parkinson's disease because, like brain, it has a high dependence on oxidative metabolism. Our results show low activity in all complexes studied (I, II and IV). The implications of these findings are discussed in relation to the aetiology of Parkinson's disease.