Progeroid syndromes and UV-induced oxidative DNA damage

qMAP enabled microanatomical mapping of human skin aging

Aging is a major driver of diseases in humans. Identifying features associated with aging is essential for designing robust intervention strategies and discovering novel biomarkers of aging. Extensive studies at both the molecular and organ/whole-body physiological scales have helped determined features associated with aging. However, the lack of meso-scale studies, particularly at the tissue level, limits the ability to translate findings made at molecular scale to impaired tissue functions associated with aging. In this work, we established a tissue image analysis workflow - quantitative micro-anatomical phenotyping (qMAP) - that leverages deep learning and machine vision to fully label tissue and cellular compartments in tissue sections. The fully mapped tissue images address the challenges of finding an interpretable feature set to quantitatively profile age-related microanatomic changes. We optimized qMAP for skin tissues and applied it to a cohort of 99 donors aged 14 to 92. We extracted 914 microanatomic features and found that a broad spectrum of these features, represented by 10 cores processes, are strongly associated with aging. Our analysis shows that microanatomical features of the skin can predict aging with a mean absolute error (MAE) of 7.7 years, comparable to state-of-the-art epigenetic clocks. Our study demonstrates that tissue-level architectural changes are strongly associated with aging and represent a novel category of aging biomarkers that complement molecular markers. Our results highlight the complex and underexplored multi-scale relationship between molecular and tissue microanatomic scales.

[Progeroid syndromes : Aging, skin aging, and mechanisms of progeroid syndromes]

Progeroid syndromes (PSs) are characterized by the premature onset of age-related pathologies. PSs display a wide range of heterogeneous pathological symptoms that also manifest during natural aging, including vision and hearing loss, atrophy, hair loss, progressive neurodegeneration, and cardiovascular defects. Recent advances in molecular pathology have led to a better understanding of the underlying mechanisms of these diseases. The genetic mutations underlying PSs are functionally linked to genome maintenance and repair, supporting the causative role of DNA damage accumulation in aging. While some of those genes encode proteins with a direct involvement in a DNA repair machinery, such as nucleotide excision repair (NER), others destabilize the genome by compromising the stability of the nuclear envelope, when lamin A is dysfunctional in Hutchinson-Gilford progeria syndrome (HGPS) or regulate the DNA damage response (DDR) such as the ataxia telangiectasia-mutated (ATM) gene. Understanding the molecular pathology of progeroid diseases is crucial in developing potential treatments to manage and prevent the onset of symptoms. This knowledge provides insight into the underlying mechanisms of premature aging and could lead to improved quality of life for individuals affected by progeroid diseases.

A matter of delicate balance: Loss and gain of Cockayne syndrome proteins in premature aging and cancer

DNA repair genes are critical for preserving genomic stability and it is well established that mutations in DNA repair genes give rise to progeroid diseases due to perturbations in different DNA metabolic activities. Cockayne Syndrome (CS) is an autosomal recessive inheritance caused by inactivating mutations in CSA and CSB genes. This review will primarily focus on the two Cockayne Syndrome proteins, CSA and CSB, primarily known to be involved in Transcription Coupled Repair (TCR). Curiously, dysregulated expression of CS proteins has been shown to exhibit differential health outcomes: lack of CS proteins due to gene mutations invariably leads to complex premature aging phenotypes, while excess of CS proteins is associated with carcinogenesis. Thus it appears that CS genes act as a double-edged sword whose loss or gain of expression leads to premature aging and cancer. Future mechanistic studies on cell and animal models of CS can lead to potential biological targets for interventions in both aging and cancer development processes. Some of these exciting possibilities will be discussed in this review in light of the current literature.

Skin Conditions and Movement Disorders: Hiding in Plain Sight

Skin manifestations are well-recognized non-motor symptoms of Parkinson's disease (PD) and other hypokinetic and hyperkinetic movement disorders. Skin conditions are usually well visible during routine clinical examination and their recognition may play a major role in diagnostic work-up. In this educational review we: (1) briefly outline skin conditions related to Parkinson's disease, including therapy-related skin complications and their management; (2) discuss the role of skin biopsies in early diagnosis of PD and differential diagnosis of parkinsonian syndromes; and focus more on areas which have not been reviewed in the literature before, including (3) skin conditions related to atypical parkinsonism, and (4) skin conditions related to hyperkinetic movement disorders. In case of rare hyperkinetic movement disorders, specific dermatological manifestations, like presence of angiokeratomas, telangiectasias, Mongolian spots, lipomas, ichthyosis, progeroid skin changes and others may point to a very specific group of disorders and help guide further investigations.

Focus on the Contribution of Oxidative Stress in Skin Aging

Skin aging is one of the most evident signs of human aging. Modification of the skin during the life span is characterized by fine lines and wrinkling, loss of elasticity and volume, laxity, rough-textured appearance, and pallor. In contrast, photoaged skin is associated with uneven pigmentation (age spot) and is markedly wrinkled. At the cellular and molecular level, it consists of multiple interconnected processes based on biochemical reactions, genetic programs, and occurrence of external stimulation. The principal cellular perturbation in the skin driving senescence is the alteration of oxidative balance. In chronological aging, reactive oxygen species (ROS) are produced mainly through cellular oxidative metabolism during adenosine triphosphate (ATP) generation from glucose and mitochondrial dysfunction, whereas in extrinsic aging, loss of redox equilibrium is caused by environmental factors, such as ultraviolet radiation, pollution, cigarette smoking, and inadequate nutrition. During the aging process, oxidative stress is attributed to both augmented ROS production and reduced levels of enzymatic and non-enzymatic protectors. Apart from the evident appearance of structural change, throughout aging, the skin gradually loses its natural functional characteristics and regenerative potential. With aging, the skin immune system also undergoes functional senescence manifested as a reduced ability to counteract infections and augmented frequency of autoimmune and neoplastic diseases. This review proposes an update on the role of oxidative stress in the appearance of the clinical manifestation of skin aging, as well as of the molecular mechanisms that underline this natural phenomenon sometimes accelerated by external factors.

Blm helicase facilitates rapid replication of repetitive DNA sequences in early Drosophila development

The absence of functional BLM DNA helicase, a member of the RecQ family of helicases, is responsible for the rare human disorder Bloom Syndrome, which results in developmental abnormalities, DNA repair defects, genomic instability, and a predisposition to cancer. In Drosophila melanogaster, the orthologous Blm protein is essential during early development when the embryo is under the control of maternal gene products. We show that lack of functional maternal Blm during the syncytial cell cycles of Drosophila embryonic development results in severe nuclear defects and lethality. Amongst the small fraction of embryos from Blm mutant mothers that survive to adulthood, a prominent sex-bias favors the class that inherits less repetitive DNA content, which serves as an endogenous source of replication stress. This selection against repetitive DNA content reflects a role for Blm in facilitating replication through repetitive sequences during the rapid S-phases of syncytial cell cycles. During these syncytial cycles, Blm is not required for complex DNA double-strand break repair; however, the progeny sex-bias resulting from the absence of maternal Blm is exacerbated by repetitive DNA sequences and by the slowing of replication fork progression, suggesting that the essential role for Blm during this stage is to manage replication fork stress brought about by impediments to fork progression. Additionally, our data suggest that Blm is only required to manage this replication stress during embryonic development, and likely only during the early, rapid syncytial cell cycles, and not at later developmental stages. These results provide novel insights into Blm function throughout development.

Nevi, dysplastic nevi, and melanoma: Molecular and immune mechanisms involving the progression

Melanocytic nevi, dysplastic nevi, and melanoma are all derived from the pigment-producing cells, namely melanocytes. Concerning the clinical spectrum, cutaneous melanoma is the most aggressive skin cancer with a low survival rate, while nevi are the most common benign lesions in the general population, and dysplastic nevi place in between nevi and melanoma. Ultraviolet (UV) radiation is a well-recognized extrinsic risk factor for all three. BRAF^V600E is a well-recognized driver mutation that activates the RAS-BRAF-mitogen-activated protein kinase (MAPK) signaling pathway among 40%–60% of melanoma cases. Interestingly, BRAF^V600E mutation is detected even more in acquired nevi, approximately 80%. However, in nevi, several tumor suppressors such as p53 and phosphatase and tensin homolog (PTEN) are intact, and senescence factors, including p15^INK4b, p16^INK4a, p19, and senescence-associated acidic β-galactosidase, are expressed, leading to cell senescence and cell cycle arrest. Although loss of p53 function is rarely found in melanoma, decreased or loss of PTEN with an activated PI3k/Akt signaling pathway is common in nevi, which may abolish senescence status and allow further progression into dysplastic nevi or melanoma. At present, mouse models closely resembling human nevi are used for investigating these phenomena. Melanocortin 1 receptor deficiency, an intrinsic risk factor for melanomagenesis, is related to the production of procarcinogenic pheomelanin and the inhibition of PTEN function. Immune response escape via programmed cell death-1/programmed cell death ligand-1 interaction plays further roles in monitoring the spectrum. Here, we review the current literature on the molecular and immune mechanisms involving the transition from benign nevi to malignant melanoma.

Type I Interferon Induction in Cutaneous DNA Damage Syndromes

Type I interferons (IFNs) as part of the innate immune system have an outstanding importance as antiviral defense cytokines that stimulate innate and adaptive immune responses. Upon sensing of pattern recognition particles (PRPs) such as nucleic acids, IFN secretion is activated and induces the expression of interferon stimulated genes (ISGs). Uncontrolled constitutive activation of the type I IFN system can lead to autoinflammation and autoimmunity, which is observed in autoimmune disorders such as systemic lupus erythematodes and in monogenic interferonopathies. They are caused by mutations in genes which are involved in sensing or metabolism of intracellular nucleic acids and DNA repair. Many authors described mechanisms of type I IFN secretion upon increased DNA damage, including the formation of micronuclei, cytosolic chromatin fragments and destabilization of DNA binding proteins. Hereditary cutaneous DNA damage syndromes, which are caused by mutations in proteins of the DNA repair, share laboratory and clinical features also seen in autoimmune disorders and interferonopathies; hence a potential role of DNA-damage-induced type I IFN secretion seems likely. Here, we aim to summarize possible mechanisms of IFN induction in cutaneous DNA damage syndromes with defects in the DNA double-strand repair and nucleotide excision repair. We review recent publications referring to Ataxia teleangiectasia, Bloom syndrome, Rothmund–Thomson syndrome, Werner syndrome, Huriez syndrome, and Xeroderma pigmentosum. Furthermore, we aim to discuss the role of type I IFN in cancer and these syndromes.

Aging-Related Disorders and Mitochondrial Dysfunction: A Critical Review for Prospect Mitoprotective Strategies Based on Mitochondrial Nutrient Mixtures

A number of aging-related disorders (ARD) have been related to oxidative stress (OS) and mitochondrial dysfunction (MDF) in a well-established body of literature. Most studies focused on cardiovascular disorders (CVD), type 2 diabetes (T2D), and neurodegenerative disorders. Counteracting OS and MDF has been envisaged to improve the clinical management of ARD, and major roles have been assigned to three mitochondrial cofactors, also termed mitochondrial nutrients (MNs), i.e., α-lipoic acid (ALA), Coenzyme Q10 (CoQ10), and carnitine (CARN). These cofactors exert essential–and distinct—roles in mitochondrial machineries, along with strong antioxidant properties. Clinical trials have mostly relied on the use of only one MN to ARD-affected patients as, e.g., in the case of CoQ10 in CVD, or of ALA in T2D, possibly with the addition of other antioxidants. Only a few clinical and pre-clinical studies reported on the administration of two MNs, with beneficial outcomes, while no available studies reported on the combined administration of three MNs. Based on the literature also from pre-clinical studies, the present review is to recommend the design of clinical trials based on combinations of the three MNs.

Premature cell senescence in human skin: Dual face in chronic acquired pigmentary disorders

Although senescence was originally described as an in vitro acquired cellular characteristic, it was recently recognized that senescence is physiologically and pathologically involved in aging and age-related diseases in vivo. The definition of cellular senescence has expanded to include the growth arrest caused by various cellular stresses, including DNA damage, inadequate mitochondria function, activated oncogene or tumor suppressor genes and oxidative stress. While senescence in normal aging involves various tissues over time and contributes to a decline in tissue function even with healthy aging, disease-induced premature senescence may be restricted to one or a few organs triggering a prolonged and more intense rate of accumulation of senescent cells than in normal aging. Organ-specific high senescence rate could lead to chronic diseases, especially in post-mitotic rich tissue. Recently, two opposite acquired pathological conditions related to skin pigmentation were described to be associated with premature senescence: vitiligo and melasma. In both cases, it was demonstrated that pathological dysfunctions are not restricted to melanocytes, the cell type responsible for melanin production and transport to surrounding keratinocytes. Similar to physiological melanogenesis, dermal and epidermal cells contribute directly and indirectly to deregulate skin pigmentation as a result of complex intercellular communication. Thus, despite senescence usually being reported as a uniform phenotype sharing the expression of characteristic markers, skin senescence involving mainly the dermal compartment and its paracrine function could be associated with the disappearance of melanocytes in vitiligo lesions and with the exacerbated activity of melanocytes in the hyperpigmentation spots of melasma. This suggests that the difference may arise in melanocyte intrinsic differences and/or in highly defined microenvironment peculiarities poorly explored at the current state of the art. A similar dualistic phenotype has been attributed to intratumoral stromal cells as cancer-associated fibroblasts presenting a senescent-like phenotype which influence the behavior of neoplastic cells in either a tumor-promoting or tumor-inhibiting manner. Here, we present a framework dissecting senescent-related molecular alterations shared by vitiligo and melasma patients and we also discuss disease-specific differences representing new challenges for treatment.

HDAC inhibition improves autophagic and lysosomal function to prevent loss of subcutaneous fat in a mouse model of Cockayne syndrome

Cockayne syndrome (CS), a hereditary form of premature aging predominantly caused by mutations in the csb gene, affects multiple organs including skin where it manifests with hypersensitivity toward ultraviolet (UV) radiation and loss of subcutaneous fat. There is no curative treatment for CS, and its pathogenesis is only partially understood. Originally considered for its role in DNA repair, Cockayne syndrome group B (CSB) protein most likely serves additional functions. Using CSB-deficient human fibroblasts, Caenorhabditiselegans, and mice, we show that CSB promotes acetylation of α-tubulin and thereby regulates autophagy. At the organ level, chronic exposure of csb^m/m mice to UVA radiation caused a severe skin phenotype with loss of subcutaneous fat, inflammation, and fibrosis. These changes in skin tissue were associated with an accumulation of autophagic/lysosomal proteins and reduced amounts of acetylated α-tubulin. At the cellular level, we found that CSB directly interacts with the histone deacetylase 6 (HDAC6) and the α-tubulin acetyltransferase MEC-17. Upon UVA irradiation, CSB is recruited to the centrosome where it colocalizes with dynein and HDAC6. Administration of the pan-HDAC inhibitor SAHA (suberoylanilide hydroxamic acid) enhanced α-tubulin acetylation, improved autophagic function in CSB-deficient models from all three species, and rescued the skin phenotype in csb^m/m mice. HDAC inhibition may thus represent a therapeutic option for CS.

Premature aging and cancer development in transgenic mice lacking functional CYLD

CYLD is a deubiquitinating enzyme known for its role as a tumor suppressor whose mutation leads to skin appendages tumors and other cancers. In this manuscript we report that the tumor suppressor CYLD, similarly to other renowned tumor suppressor genes, protects from premature aging and cancer. We have generated transgenic mice expressing the mutant CYLDC/S protein, lacking its deubiquitinase function, under the control of the keratin 5 promoter, the K5-CYLDC/S mice. These mice express the transgene in different organs, including those considered to be more susceptible to aging, such as skin and thymus. Our results show that K5-CYLDC/S mice exhibit epidermal, hair follicle, and sebaceous gland alterations; and, importantly, they show signs of premature aging from an early age. Typically, 3-month-old K5-CYLDC/S mice exhibit a phenotype characterized by alopecia and kyphosis, and, the histological examination reveals that transgenic mice show signs of accelerated aging in numerous organs such as skin, thymus, pancreas, liver and lung. Additionally, they spontaneously develop tumors of diverse origin. Over-activation of the NF-κB pathway, along with hyperactivation of Akt, JNK and c-Myc, and chronic inflammation, appear as the mechanisms responsible for the premature aging of the K5-CYLDC/S mice.

Involvement of the nuclear structural proteins in aging-related responses of human skin to the environmental stress

Human skin is a stratified endocrine organ with primary roles in protection against detrimental biochemical and biophysical factors in the environment. Environmental stress causes gradual accumulation of the macromolecular damage and clinical manifestations consistent with chronic inflammatory conditions and premature aging of the skin. Structural proteins of cell nucleus, the nuclear lamins and lamina-associated proteins, play an important role in the regulation of a number of signal transduction pathways associated with stress. The nuclear lamina proteins have been implicated in a number of degenerative disorders with frequent clinical manifestations of the skin conditions related to premature aging. Analysis of the molecular signatures in response of the skin to a range of damaging factors not only points at the likely involvement of the nuclear lamina in transmission of the signals between the environment and cell nucleus but also defines skin's sensitivity to stress, and therefore the capacities to counteract external damage in aging.

Fighting against Skin Aging: The Way from Bench to Bedside

As the most voluminous organ of the body that is exposed to the outer environment, the skin suffers from both intrinsic and extrinsic aging factors. Skin aging is characterized by features such as wrinkling, loss of elasticity, laxity, and rough-textured appearance. This aging process is accompanied with phenotypic changes in cutaneous cells as well as structural and functional changes in extracellular matrix components such as collagens and elastin. In this review, we summarize these changes in skin aging, research advances of the molecular mechanisms leading to these changes, and the treatment strategies aimed at preventing or reversing skin aging.

Ultraviolet Radiation-Induced Skin Aging: The Role of DNA Damage and Oxidative Stress in Epidermal Stem Cell Damage Mediated Skin Aging

Skin is the largest human organ. Skin continually reconstructs itself to ensure its viability, integrity, and ability to provide protection for the body. Some areas of skin are continuously exposed to a variety of environmental stressors that can inflict direct and indirect damage to skin cell DNA. Skin homeostasis is maintained by mesenchymal stem cells in inner layer dermis and epidermal stem cells (ESCs) in the outer layer epidermis. Reduction of skin stem cell number and function has been linked to impaired skin homeostasis (e.g., skin premature aging and skin cancers). Skin stem cells, with self-renewal capability and multipotency, are frequently affected by environment. Ultraviolet radiation (UVR), a major cause of stem cell DNA damage, can contribute to depletion of stem cells (ESCs and mesenchymal stem cells) and damage of stem cell niche, eventually leading to photoinduced skin aging. In this review, we discuss the role of UV-induced DNA damage and oxidative stress in the skin stem cell aging in order to gain insights into the pathogenesis and develop a way to reduce photoaging of skin cells.

Practice parameter for the diagnosis and management of primary immunodeficiency

The American Academy of Allergy, Asthma & Immunology (AAAAI) and the American College of Allergy, Asthma & Immunology (ACAAI) have jointly accepted responsibility for establishing the "Practice parameter for the diagnosis and management of primary immunodeficiency." This is a complete and comprehensive document at the current time. The medical environment is a changing environment, and not all recommendations will be appropriate for all patients. Because this document incorporated the efforts of many participants, no single individual, including those who served on the Joint Task Force, is authorized to provide an official AAAAI or ACAAI interpretation of these practice parameters. Any request for information about or an interpretation of these practice parameters by the AAAAI or ACAAI should be directed to the Executive Offices of the AAAAI, the ACAAI, and the Joint Council of Allergy, Asthma & Immunology. These parameters are not designed for use by pharmaceutical companies in drug promotion.

Oxidative stress and antioxidant response in fibroblasts from Werner and atypical Werner syndromes

Werner Syndrome (WS, ICD-10 E34.8, ORPHA902) and Atypical Werner Syndrome (AWS, ICD-10 E34.8, ORPHA79474) are very rare inherited syndromes characterized by premature aging. While approximately 90% of WS individuals have any of a range of mutations in the WRN gene, there exists a clinical subgroup in which the mutation occurs in the LMNA/C gene in heterozygosity. Although both syndromes exhibit an age-related pleiotropic phenotype, AWS manifests the onset of the disease during childhood, while major symptoms in WS appear between the ages of 20 and 30. To study the molecular mechanisms of progeroid diseases provides a useful insight into the normal aging process. Main changes found were the decrease in Cu/Zn and Mn SOD activities in the three cell lines. In AWS, both mRNA SOD and protein levels were also decreased. Catalase and glutathione peroxidases decrease, mainly in AWS. Glutaredoxin (Grx) and thioredoxin (Trx) protein expression was lower in the three progeroid cell lines. Grx and Trx were subjected to post-transcriptional regulation, because protein expression was reduced although mRNA levels were not greatly affected in WS.

The melanocyte lineage in development and disease

Melanocyte development provides an excellent model for studying more complex developmental processes. Melanocytes have an apparently simple aetiology, differentiating from the neural crest and migrating through the developing embryo to specific locations within the skin and hair follicles, and to other sites in the body. The study of pigmentation mutations in the mouse provided the initial key to identifying the genes and proteins involved in melanocyte development. In addition, work on chicken has provided important embryological and molecular insights, whereas studies in zebrafish have allowed live imaging as well as genetic and transgenic approaches. This cross-species approach is powerful and, as we review here, has resulted in a detailed understanding of melanocyte development and differentiation, melanocyte stem cells and the role of the melanocyte lineage in diseases such as melanoma.

Summary: This Review discusses melanocyte development and differentiation, melanocyte stem cells, and the role of the melanocyte lineage in diseases such as melanoma.

Premature skin aging features rescued by inhibition of NADPH oxidase activity in XPC-deficient mice

Xeroderma pigmentosum type C (XP-C) is characterized mostly by a predisposition to skin cancers and accelerated photoaging, but little is known about premature skin aging in this disease. By comparing young and old mice, we found that the level of progerin and p16(INK4a) expression, β-galactosidase activity, and reactive oxygen species, which increase with age, were higher in young Xpc(-/-) mice than in young Xpc(+/+) ones. The expression level of mitochondrial complexes and mitochondrial functions in the skin of young Xpc(-/-) was as low as in control aged Xpc(+/+)animals. Furthermore, the metabolic profile in young Xpc(-/-) mice resembled that found in aged Xpc(+/+) mice. Furthermore, premature skin aging features in young Xpc(-/-) mice were mostly rescued by inhibition of nicotinamide adenine dinucleotide phosphate oxidase 1 (NOX1) activity by using a NOX1 peptide inhibitor, suggesting that the continuous oxidative stress due to overactivation of NOX1 has a causative role in the underlying pathophysiology.

Reactive oxygen species, vascular Noxs, and hypertension: focus on translational and clinical research

SIGNIFICANCE

Reactive oxygen species (ROS) are signaling molecules that are important in physiological processes, including host defense, aging, and cellular homeostasis. Increased ROS bioavailability and altered redox signaling (oxidative stress) have been implicated in the onset and/or progression of chronic diseases, including hypertension.

RECENT ADVANCES

Although oxidative stress may not be the only cause of hypertension, it amplifies blood pressure elevation in the presence of other pro-hypertensive factors, such as salt loading, activation of the renin-angiotensin-aldosterone system, and sympathetic hyperactivity, at least in experimental models. A major source for ROS in the cardiovascular-renal system is a family of nicotinamide adenine dinucleotide phosphate oxidases (Noxs), including the prototypic Nox2-based Nox, and Nox family members: Nox1, Nox4, and Nox5.

CRITICAL ISSUES

Although extensive experimental data support a role for increased ROS levels and altered redox signaling in the pathogenesis of hypertension, the role in clinical hypertension is unclear, as a direct causative role of ROS in blood pressure elevation has yet to be demonstrated in humans. Nevertheless, what is becoming increasingly evident is that abnormal ROS regulation and aberrant signaling through redox-sensitive pathways are important in the pathophysiological processes which is associated with vascular injury and target-organ damage in hypertension.

FUTURE DIRECTIONS

There is a paucity of clinical information related to the mechanisms of oxidative stress and blood pressure elevation, and a few assays accurately measure ROS directly in patients. Such further ROS research is needed in humans and in the development of adequately validated analytical methods to accurately assess oxidative stress in the clinic.

Genome stability pathways in head and neck cancers

Genomic instability underlies the transformation of host cells toward malignancy, promotes development of invasion and metastasis and shapes the response of established cancer to treatment. In this review, we discuss recent advances in our understanding of genomic stability in squamous cell carcinoma of the head and neck (HNSCC), with an emphasis on DNA repair pathways. HNSCC is characterized by distinct profiles in genome stability between similarly staged cancers that are reflected in risk, treatment response and outcomes. Defective DNA repair generates chromosomal derangement that can cause subsequent alterations in gene expression, and is a hallmark of progression toward carcinoma. Variable functionality of an increasing spectrum of repair gene polymorphisms is associated with increased cancer risk, while aetiological factors such as human papillomavirus, tobacco and alcohol induce significantly different behaviour in induced malignancy, underpinned by differences in genomic stability. Targeted inhibition of signalling receptors has proven to be a clinically-validated therapy, and protein expression of other DNA repair and signalling molecules associated with cancer behaviour could potentially provide a more refined clinical model for prognosis and treatment prediction. Development and expansion of current genomic stability models is furthering our understanding of HNSCC pathophysiology and uncovering new, promising treatment strategies.

From clinical description, to in vitro and animal studies, and backward to patients: oxidative stress and mitochondrial dysfunction in Fanconi anemia

Fanconi anemia (FA) is a rare genetic disease associated with deficiencies in DNA repair pathways. A body of literature points to a pro-oxidant state in FA patients, along with evidence for oxidative stress (OS) in the FA phenotype reported by in vitro, molecular, and animal studies. A highlight arises from the detection of mitochondrial dysfunction (MDF) in FA cell lines of complementation groups A, C, D2, and G. As yet lacking, in vivo studies should focus on FA-associated MDF, which may help in the understanding of the mitochondrial basis of OS detected in cells and body fluids from FA patients. Beyond the in vitro and animal databases, the available analytical devices may prompt the direct observation of metabolic and mitochondrial alterations in FA patients. These studies should evaluate a set of MDF-related endpoints, to be related to OS endpoints. The working hypothesis is raised that, parallel to OS, nitrosative stress might be another, so far unexplored, hallmark of the FA phenotype. The expected results may shed light on the FA pathogenesis and might provide grounds for pilot chemoprevention trials using mitochondrial nutrients.

Cockayne-Syndrom

Das Cockayne-Syndrom (CS) ist eine seltene, autosomal-rezessive Erkrankung, charakterisiert durch vorzeitige Alterungssymptomatik mit Degeneration des zentralen Nervensystems, Verlust des subkutanen Fettgewebes und Kachexie. Auslöser dieser Erkrankung sind autosomal-rezessiv vererbte Mutationen im CSA- und CSB-Gen. Im Zellkern sind das CSA- und das CSB-Protein sowohl an der DNA-Reparatur als auch der Transkription beteiligt. Außerhalb des Zellkerns schützen die CS-Proteine im Mitochondrium vor oxidativ induzierten mitochondrialen (mt) DNA-Schäden und spielen somit möglicherweise eine wichtige Rolle beim altersbedingten Verlust des subkutanen Fettgewebes. Damit ist das CS nicht nur wichtig als Modellerkrankung zur Untersuchung molekularer Mechanismen der DNA-Reparatur, sondern auch für das Verständnis der Ursachen des Alterungsprozesses.

Pathways for repairing and tolerating the spectrum of oxidative DNA lesions

Reactive oxygen species (ROS) arise from both endogenous and exogenous sources. These reactive molecules possess the ability to damage both the DNA nucleobases and the sugar phosphate backbone, leading to a wide spectrum of lesions, including non-bulky (8-oxoguanine and formamidopyrimidine) and bulky (cyclopurine and etheno adducts) base modifications, abasic sites, non-conventional single-strand breaks, protein-DNA adducts, and intra/interstrand DNA crosslinks. Unrepaired oxidative DNA damage can result in bypass mutagenesis during genome copying or gene expression, or blockage of the essential cellular processes of DNA replication or transcription. Such outcomes underlie numerous pathologies, including, but not limited to, carcinogenesis and neurodegeneration, as well as the aging process. Cells have adapted and evolved defense systems against the deleterious effects of ROS, and specifically devote a number of cellular DNA repair and tolerance pathways to combat oxidative DNA damage. Defects in these protective pathways trigger hereditary human diseases that exhibit increased cancer incidence, developmental defects, neurological abnormalities, and/or premature aging. We review herein classic and atypical oxidative DNA lesions, outcomes of encountering these damages during DNA replication and transcription, and the consequences of losing the ability to repair the different forms of oxidative DNA damage. We particularly focus on the hereditary human diseases Xeroderma Pigmentosum, Cockayne Syndrome and Fanconi Anemia, which may involve defects in the efficient repair of oxidative modifications to chromosomal DNA.

When not to treat cutaneous vascular lesions with the pulsed dye laser

The availability of effective laser treatment for cutaneous vascular lesions has risen dramatically in recent years. At the same time, there has been a proliferation of laser providers with varying amounts of training-both medical and nonmedical. We report a series of four cases where patients presented for cosmetic evaluation of vascular lesions and were discovered to have more significant pathologic disease. In presenting these cases, we hope to illuminate a basic differential diagnosis that exists for cutaneous vascular lesions and remind healthcare providers that not all "cosmetic" concerns are benign in origin. There is a differential diagnosis that exists for cutaneous vascular lesions that is worth reviewing, and it should be considered in all patients presenting for laser treatment.

Research in practice: More than skin deep -aging of subcutaneous fat tissue

Mitochondria, responsible for the generation of energy in our cells, contain their own genome, mitochondrial (mt)DNA. It is known that mutations of mtDNA accumulate during normal aging and that this can be accelerated by oxidative stress, i.e. induced by ultraviolet radiation. These mutations are functionally relevant and they play a causative role in normal aging as well as premature aging induced by ultraviolet radiation. While the focus of scientific research was more on epidermis and dermis within the last years, alterations of subcutaneous fat tissue were not investigated thus far. Cockayne syndrome (CS) A and B are two proteins known to repair oxidatively induced DNA damage via nucleotide excision repair (NER) in the nucleus. We could show that these two proteins enrich in mitochondria upon oxidative stress, directly interact with mtDNA and the two repair-associated proteins mtSSBP-1 and mtOGG-1 and protect from deletions of mtDNA. If CSA or CSB are lacking, mtDNA mutations accumulate particularly in the cells of subcutaneous fat tissue which appears to mediate loss of adipocytes via apoptosis. Therefore, the two NER-associated proteins CSA and CSB appear to play a direct role in protection from mutations which in turn are causative in aging-associated loss of subcutaneous fat tissue.

True lies: the double life of the nucleotide excision repair factors in transcription and DNA repair

Nucleotide excision repair (NER) is a major DNA repair pathway in eukaryotic cells. NER removes structurally diverse lesions such as pyrimidine dimers, arising upon UV irradiation or bulky chemical adducts, arising upon exposure to carcinogens and some chemotherapeutic drugs. NER defects lead to three genetic disorders that result in predisposition to cancers, accelerated aging, neurological and developmental defects. During NER, more than 30 polypeptides cooperate to recognize, incise, and excise a damaged oligonucleotide from the genomic DNA. Recent papers reveal an additional and unexpected role for the NER factors. In the absence of a genotoxic attack, the promoters of RNA polymerases I- and II-dependent genes recruit XPA, XPC, XPG, and XPF to initiate gene expression. A model that includes the growth arrest and DNA damage 45α protein (Gadd45α) and the NER factors, in order to maintain the promoter of active genes under a hypomethylated state, has been proposed but remains controversial. This paper focuses on the double life of the NER factors in DNA repair and transcription and describes the possible roles of these factors in the RNA synthesis process.