The long non-coding RNA FLJ46906 binds to the transcription factors NF-κB and AP-1 and regulates expression of aging-associated genes.

Several features differentiate aged cells from young cells, many of which are due to changes in gene expression during the aging process. The mechanisms of altered gene expression in aging cells remain incompletely understood, and we hypothesized that long non-coding (lnc) RNAs mediate at least some of these changes. We screened for alterations in lncRNA expression with aging in skin fibroblasts and identified the lncRNA FLJ46906 to be consistently upregulated with aging in-vivo and in-vitro. The function of this lncRNA has not been known. Here we show that FLJ46906 regulates several aging-associated genes, including IL1B, IL6, CXCL8, TGFB1, and ELN. We suggest that these effects are mediated through NF-κB and AP-1, because these aging-associated genes are regulated by NF-κB and AP-1, and because we found that FLJ46906 directly binds to these two transcription factors. This data supports a role of the lncRNA FLJ46906 in the aging process.

Mechanisms of Melanoma Promotion by Ultraviolet Radiation.

The mutagenic properties of ultraviolet radiation drive the initiation of melanoma. Induction of matrix metalloproteinases in melanoma cells by longwave UVA radiation, possibly via a Warburg-like effect, promotes melanoma invasiveness. This is one of several mechanisms by which ultraviolet radiation also promotes further growth of previously established melanomas.

Much remains to be learned about how UVR induces mutations.

Data on the wavelength dependence of UV-induced formation of DNA damage and skin cancer have been available for quite some time, but a detailed in vivo action spectrum of mutation formation has not yet been reported so far. This important information gap is filled by Ikehata et al. in this issue. Their findings question several aspects of our current thinking about UV-induced mutagenesis and carcinogenesis.

Longwave UV light induces the aging-associated progerin.

Premature aging in Hutchinson-Gilford progeria syndrome (HGPS) is caused by a mutation of the LMNA gene that activates a cryptic splice site. This results in expression of a truncated form of Lamin A, called progerin. Accumulation of progerin in the nuclei of HGPS cells impairs nuclear functions and causes abnormal nuclear morphology. Progerin accumulation has not only been described in HGPS, but also during normal intrinsic aging. We hypothesized that accumulation of progerin with abnormal nuclear shapes may also be accelerated by UV and with that contribute to photoaging of the skin. We exposed neonatal or aged cultured fibroblasts to single or repeated doses of longwave or shortwave UV (UVA or UVB) and found that UVA, but not UVB, induces progerin expression and HGPS-like abnormal nuclear shapes in all cells, but more in aged cells. The induction of progerin is mediated by UVA-induced oxidative damage and subsequent alternative splicing of the LMNA transcript, as progerin induction was suppressed by the singlet oxygen quencher sodium azide, and as mRNA expression of LMNA was not induced by UVA. These data suggest a previously unreported pathway of photoaging and support the concept that photoaging is at least in part a process of damage-accelerated intrinsic aging.

Primary cutaneous CD56 positive lymphoma: a diagnostic conundrum in an unusual case of lymphoma.

We present an unusual case of a CD56-positive T-cell lymphoma exhibiting immunophenotypic characteristics of both γδ T-cell lymphoma and extranodal NK/T-cell lymphoma, nasal-type. The patient presented with a 2-month history of rapidly progressive, pruritic and cutaneous nodules on his arms. A biopsy showed a dense pan-dermal infiltrate of markedly atypical CD3-positive lymphocytes, compatible with tumor stage cutaneous T-cell lymphoma. Retrospective review of a preceding biopsy and flow cytometric analysis, performed at an outside institution, showed strong expression of surface CD3, CD7, CD43 and γδ T-cell receptor (TCR), findings consistent with a diagnosis of cutaneous γδ T-cell lymphoma. In light of these data, we performed additional studies that showed diffuse positive staining of the atypical lymphocytes for CD56, CD4 and CD43 as well as Epstein-Barr virus-encoded small nonpolyadenylated RNA (EBER). Interestingly, this case displays characteristic features of γδ T-cell lymphoma, with strong surface expression of CD3 and γδ-TCR, as well as characteristics of natural killer (NK)/T-cell lymphoma, including expression of CD4 and EBER positivity, that represent two separate categories in the current classification of cutaneous lymphomas. Taken together, these findings underscore the difficulty of rendering an unambiguous classification of the presented neoplasm given the close ontogenetic relationship between NK and cytotoxic T-cells and highlight the need for continued reevaluation of the current classification system.

Morphea-like skin reactions in patients treated with the cathepsin K inhibitor balicatib.

BACKGROUND: In a multicenter clinical trial in North America and Europe that tested the cathepsin K (catK) inhibitor balicatib for the treatment of osteoporosis, several patients developed hardening of the skin. OBJECTIVE: We sought to characterize these observed adverse events. METHODS: Patients with skin hardening were examined by a local dermatologist. All of those patients except one had at least one biopsy specimen taken from affected skin, which was read by local and two central dermatopathologists. Workup was directed for consideration of systemic scleroderma. RESULTS: Nine patients of 709 treated with balicatib developed skin hardening and were given a diagnosis of morphea-like skin changes. No such events were observed in patients taking placebo or the lowest balicatib dose. After discontinuation of balicatib, skin changes resolved completely in 8 and partially in one patient. LIMITATIONS: Each patient was seen by a different dermatologist in 6 different countries. CONCLUSIONS: These observations are likely dose-related adverse effects of balicatib. Although catK was originally thought to be expressed only in osteoclasts, it has more recently also been found in lung and dermal fibroblasts and been implicated in the degradation of the extracellular matrix in the lung and the skin. It is therefore plausible that the observed dermal fibrosis in balicatib-treated patients is a result of impaired degradation of extracellular matrix proteins and may represent a class effect of catK inhibitors. We recommend that further exploration of catK inhibition for the treatment of osteoporosis or cancer should include monitoring for similar adverse effects.

Comparison of DNA damage responses following equimutagenic doses of UVA and UVB: a less effective cell cycle arrest with UVA may render UVA-induced pyrimidine dimers more mutagenic than UVB-induced ones.

Mechanisms of UVA-mutagenesis remain a matter of debate. Earlier described higher rates of mutation formation per pyrimidine dimer with UVA than with UVB and other evidence suggested that a non-pyrimidine dimer-type of DNA damage contributes more to UVA- than to UVB-mutagenesis. However, more recently published data on the spectra of UVA-induced mutations in primary human skin cells and in mice suggest that pyrimidine dimers are the most common type of DNA damage-inducing mutations not only with UVB, but also with UVA. As this rebuts a prominent role of non-dimer type of DNA damage in UVA-mutagenesis, we hypothesized that the higher mutation rate at UVA-induced pyrimidine dimers, as compared to UVB-induced ones, is caused by differences in the way UVA- and UVB-exposed cells process DNA damage. Therefore, we here compared cell cycle regulation, DNA repair, and apoptosis in primary human fibroblasts following UVB- and UVA-irradiation, using the same physiologic and roughly equimutagenic doses (100-300 J m(-2) UVB, 100-300 kJ m(-2) UVA) we have used previously for mutagenesis experiments with the same type of cells. ELISAs for the detection of pyrimidine dimers confirmed that much fewer dimers were formed with these doses of UVA, as compared to UVB. We found that cell cycle arrests (intra-S, G1/S, G2/M), mediated at least in part by activation of p53 and p95, are much more prominent and long-lasting with UVB than with UVA. In contrast, no prominent differences were found between UVA and UVB for other anti-mutagenic cellular responses (DNA repair, apoptosis). Our data suggest that less effective anti-mutagenic cellular responses, in particular different and shorter-lived cell cycle arrests, render pyrimidine dimers induced by UVA more mutagenic than pyrimidine dimers induced by UVB.

No formation of DNA double-strand breaks and no activation of recombination repair with UVA.

Longwave UVA is an independent class I carcinogen. A complete understanding of UVA-induced DNA damage and how this damage is processed in skin cells is therefore of utmost importance. A particular question that has remained contentious is whether UVA induces DNA double-strand breaks (DSBs), either directly or through processing of other types of DNA damage, such as recombination repair of replication forks stalled at DNA photoproducts. We therefore studied activation of the recombination repair pathway by solar available doses of UVA and assessed formation of DNA DSBs in primary skin fibroblasts. We found that, unlike ionizing radiation or UVB, UVA does not activate the Fanconi anemia/BRCA DNA damage response pathway or the "recombinase" RAD51 in primary skin fibroblasts. The fact that this pathway mediates recombination repair of DNA DSBs suggests that DNA DSBs are not formed by UVA. This is further supported by findings that UVA did not induce DNA DSBs, as assayed by neutral single-cell electrophoresis or by formation of γ-H2AX nuclear foci, considered the most sensitive assay for DNA DSBs. The lack of sufficient evidence for formation of DNA DSBs underlines the pivotal role of UVA-induced DNA photoproducts in UVA mutagenesis and carcinogenesis.

Telomeric DNA induces p53-dependent reactive oxygen species and protects against oxidative damage.

BACKGROUND: Reactive oxygen species (ROS) are generated by cellular metabolism as well as by exogenous agents. While ROS can promote cellular senescence, they can also act as signaling molecules for processes that do not lead to senescence. Telomere homolog oligonucleotides (T-oligos) induce adaptive DNA damage responses including increased DNA repair capacity and these effects are mediated, at least in part, through p53. OBJECTIVE: Studies were undertaken to determine whether such p53-mediated protective responses include enhanced antioxidant defenses. METHODS: Normal human fibroblasts as well as R2F fibroblasts expressing wild type or dominant negative p53 were treated with an 11-base T-oligo, a complementary control oligo or diluents alone and then examined by western blot analysis, immunofluorescence microscopy and various biochemical assays. RESULTS: We now report that T-oligo increases the level of the antioxidant enzymes superoxide dismutase 1 and 2 and protects cells from oxidative damage; and that telomere-based gammaH2AX (DNA damage) foci that form in response to T-oligos contain phosphorylated ATM and Chk2, proteins known to activate p53 and to mediate cell cycle arrest in response to oxidative stress. Further, T-oligo increases cellular ROS levels via a p53-dependent pathway, and these increases are abrogated by the NAD(P)H oxidase inhibitor diphenyliodonium chloride. CONCLUSION: These results suggest the existence of innate telomere-based protective responses that act to reduce oxidative damage to cells. T-oligo treatment induces the same responses and offers a new model for studying intracellular ROS signaling and the relationships between DNA damage, ROS, oxidative stress, and cellular defense mechanisms.

Intracellular degradation of elastin by cathepsin K in skin fibroblasts--a possible role in photoaging.

Solar elastosis is observed in the dermis of photoaged skin and is characterized by an accumulation of abnormal elastin in the extracellular space. Several proteases that degrade elastin in the extracellular space have been implicated in its formation. The lysosomal protease cathepsin K (catK) has recently been described to be highly expressed in skin fibroblasts under certain pathologic conditions. As cat K is one of the most potent mammalian elastases, we hypothesized that catK-mediated intracellular elastin degradation may play a role in the formation of solar elastosis. Immunostaining of cultured skin fibroblasts incubated with labeled elastin demonstrated internalization of extracellular elastin to lysosomes and its degradation by catK. Induction of catK expression in fibroblasts was observed both in vitro and in vivo after exposure to longwave UVA. In contrast to fibroblasts from young donors, cells from old donors failed to activate catK in response to UVA. These data suggest a role of intracellular elastin degradation by catK in the formation of solar elastosis. We propose that an age-related decline in catK activity, in particular after UV exposure, may promote the formation of actinic elastosis through a decline of orderly intracellular elastin degradation and subsequent accumulation of elastin in the extracellular space.