Molecular basis of sun-induced premature skin ageing and retinoid antagonism

Damage to skin collagen and elastin (extracellular matrix) is the hallmark of long-term exposure to solar ultraviolet irradiation, and is believed to be responsible for the wrinkled appearance of sun-exposed skin. We report here that matrix-degrading metalloproteinase messenger RNAs, proteins and activities are induced in human skin in vivo within hours of exposure to ultraviolet-B irradiation (UVB). Induction of metalloproteinase proteins and activities occurred at UVB doses well below those that cause skin reddening. Within minutes, low-dose UVB upregulated the transcription factors AP-1 and NF-kappa B, which are known to be stimulators of metalloproteinase genes. All-trans retinoic acid, which transrepresses AP-1 (ref. 8), applied before irradiation with UVB, substantially reduced AP-1 and metalloproteinase induction. We propose that elevated metalloproteinases, resulting from activation of AP-1 and NF-kappa B by low-dose solar irradiation, degrade collagen and elastin in skin. Such damage, if imperfectly repaired, would result in solar scars, which through accumulation from a lifetime of repeated low-dose sunlight exposure could cause premature skin ageing (photoageing).

The role of a mutant CCR5 allele in HIV-1 transmission and disease progression

A 32-nucleotide deletion (delta 32) within the beta-chemokine receptor 5 (CCR5) gene has been described in subjects who remain uninfected despite extensive exposure to HIV-1. This allele was found to be common in the Caucasian population with a frequency of 0.0808, but was not found in people of African or Asian ancestry. To determine its role in HIV-1 transmission and disease progression, we analyzed the CCRS genotype of 1252 homosexual men enrolled in the Chicago component of the Multicenter AIDS Cohort Study (MACS). No infected participant was found to be homozygous for the delta 32 allele, whereas 3.6% of at-risk but uninfected Caucasian participants were homozygous, showing the highly protective role of this genotype against sexual acquisition of HIV-1. No evidence was found to suggest that heterozygotes were protected against HIV-1 infection, but a limited protective role against disease progression was noted. The delta 32 allele of CCR5 is therefore an important host factor in HIV-1 transmission and pathogenesis.

Pathophysiology of premature skin aging induced by ultraviolet light

BACKGROUND

Long-term exposure to ultraviolet irradiation from sunlight causes premature skin aging (photoaging), characterized in part by wrinkles, altered pigmentation, and loss of skin tone. Photoaged skin displays prominent alterations in the collagenous extracellular matrix of connective tissue. We investigated the role of matrix-degrading metalloproteinases, a family of proteolytic enzymes, as mediators of collagen damage in photoaging.

METHODS

We studied 59 whites (33 men and 26 women, ranging in age from 21 to 58 years) with light-to-moderate skin pigmentation, none of whom had current or prior skin disease. Only some of the participants were included in each of the studies. We irradiated their buttock skin with fluorescent ultraviolet lights under standard conditions and obtained skin samples from irradiated and nonirradiated areas by keratome or punch biopsy. In some studies, tretinoin and its vehicle were applied to skin under occlusion 48 hours before ultraviolet irradiation. The expression of matrix metalloproteinases was determined by in situ hybridization, immunohistology, and in situ zymography. Irradiation-induced degradation of skin collagen was measured by radioimmunoassay of soluble cross-linked telopeptides. The protein level of tissue inhibitor of matrix metalloproteinases type 1 was determined by Western blot analysis.

RESULTS

A single exposure to ultraviolet irradiation increased the expression of three matrix metalloproteinases -- collagenase, a 92-kd gelatinase, and stromelysin -- in skin connective tissue and outer skin layers, as compared with nonirradiated skin. The degradation of endogenous type I collagen fibrils was increased by 58 percent in irradiated skin, as compared with nonirradiated skin. Collagenase and gelatinase activity remained maximally elevated (4.4 and 2.3 times, respectively) for seven days with four exposures to ultraviolet irradiation, delivered at two-day intervals, as compared with base-line levels. Pretreatment of skin with tretinoin (all-trans-retinoic acid) inhibited the induction of matrix metalloproteinase proteins and activity (by 70 to 80 percent) in both connective tissue and outer layers of irradiated skin. Ultraviolet irradiation also induced tissue inhibitor of matrix metalloproteinases-1, which regulates the enzyme. Induction of the inhibitor was not affected by tretinoin.

CONCLUSIONS

Multiple exposures to ultraviolet irradiation lead to sustained elevations of matrix metalloproteinases that degrade skin collagen and may contribute to photoaging. Treatment with topical tretinoin inhibits irradiation-induced matrix metalloproteinases but not their endogenous inhibitor.

Epidemiological time series studies of PM2.5 and daily mortality and hospital admissions: a systematic review and meta-analysis

Background

Short-term exposure to outdoor fine particulate matter (particles with a median aerodynamic diameter <2.5 μm (PM₂.₅)) air pollution has been associated with adverse health effects. Existing literature reviews have been limited in size and scope.

Methods

We conducted a comprehensive, systematic review and meta-analysis of 110 peer-reviewed time series studies indexed in medical databases to May 2011 to assess the evidence for associations between PM₂.₅ and daily mortality and hospital admissions for a range of diseases and ages. We stratified our analyses by geographical region to determine the consistency of the evidence worldwide and investigated small study bias.

Results

Based upon 23 estimates for all-cause mortality, a 10 µg/m³ increment in PM₂.₅ was associated with a 1.04% (95% CI 0.52% to 1.56%) increase in the risk of death. Worldwide, there was substantial regional variation (0.25% to 2.08%). Associations for respiratory causes of death were larger than for cardiovascular causes, 1.51% (1.01% to 2.01%) vs 0.84% (0.41% to 1.28%). Positive associations with mortality for most other causes of death and for cardiovascular and respiratory hospital admissions were also observed. We found evidence for small study bias in single-city mortality studies and in multicity studies of cardiovascular disease.

Conclusions

The consistency of the evidence for adverse health effects of short-term exposure to PM₂.₅ across a range of important health outcomes and diseases supports policy measures to control PM₂.₅ concentrations. However, reasons for heterogeneity in effect estimates in different regions of the world require further investigation. Small study bias should also be considered in assessing and quantifying health risks from PM₂.₅.

CTLA4Ig-mediated blockade of T-cell costimulation in patients with psoriasis vulgaris

Engagement of the B7 family of molecules on antigen-presenting cells with their T cell-associated ligands, CD28 and CD152 (cytotoxic T lymphocyte-associated antigen-4 [CTLA-4]), provides a pivotal costimulatory signal in T-cell activation. We investigated the role of the CD28/CD152 pathway in psoriasis in a 26-week, phase I, open-label dose-escalation study. The importance of this pathway in the generation of humoral immune responses to T cell-dependent neoantigens, bacteriophage phiX174 and keyhole limpet hemocyanin, was also evaluated. Forty-three patients with stable psoriasis vulgaris received 4 infusions of the soluble chimeric protein CTLA4Ig (BMS-188667). Forty-six percent of all study patients achieved a 50% or greater sustained improvement in clinical disease activity, with progressively greater effects observed in the highest-dosing cohorts. Improvement in these patients was associated with quantitative reduction in epidermal hyperplasia, which correlated with quantitative reduction in skin-infiltrating T cells. No markedly increased rate of intralesional T-cell apoptosis was identified, suggesting that the decreased number of lesional T cells was probably likely attributable to an inhibition of T-cell proliferation, T-cell recruitment, and/or apoptosis of antigen-specific T cells at extralesional sites. Altered antibody responses to T cell-dependent neoantigens were observed, but immunologic tolerance to these antigens was not demonstrated. This study illustrates the importance of the CD28/CD152 pathway in the pathogenesis of psoriasis and suggests a potential therapeutic use for this novel immunomodulatory approach in an array of T cell-mediated diseases.

Agrobacterium-Mediated Transformation of Fusarium oxysporum: An Efficient Tool for Insertional Mutagenesis and Gene Transfer

ABSTRACT Agrobacterium tumefaciens-mediated transformation (ATMT) has long been used to transfer genes to a wide variety of plants and has also served as an efficient tool for insertional mutagenesis. In this paper, we report the construction of four novel binary vectors for fungal transformation and the optimization of an ATMT protocol for insertional mutagenesis, which permits an efficient genetic manipulation of Fusarium oxysporum and other phytopathogenic fungi to be achieved. Employing the binary vectors, carrying the bacterial hygromycin B phosphotrans-ferase gene (hph) under the control of the Aspergillus nidulans trpC promoter as a selectable marker, led to the production of 300 to 500 hygromycin B resistant transformants per 1 x 10(6) conidia of F. oxysporum, which is at least an order of magnitude higher than that previously accomplished. Transformation efficiency correlated strongly with the duration of cocultivation of fungal spores with Agrobacterium tumefaciens cells and significantly with the number of Agrobacteruium tumefaciens cells present during the cocultivation period (r = 0.996; n = 3; P < 0.01). All transformants tested remained mitotically stable, maintaining their hygromycin B resistance. Growing Agrobacterium tumefaciens cells in the presence of acetosyringone (AS) prior to cocultivation shortened the time required for the formation of transformants but decreased to 53% the percentage of transformants containing a single T-DNA insert per genome. This increased to over 80% when Agrobacterium tumefaciens cells grown in the absence of AS were used. There was no correlation between the average copy number of T-DNA per genome and the colony diameter of the transformants, the period of cocultivation or the quantity of Agrobacterium tumefaciens cells present during cocultivation. To isolate the host sequences flanking the inserted T-DNA, we employed a modified thermal asymmetric interlaced PCR (TAIL-PCR) technique. Utilizing just one arbitrary primer resulted in the successful amplification of desired products in 90% of those transformants analyzed. The insertion event appeared to be a random process with truncation of the inserted T-DNA, ranging from 1 to 14 bp in size, occurring on both the right and left border sequences. Considering the size and design of the vectors described here, coupled with the efficiency and flexibility of this ATMT protocol, it is suggested that ATMT should be regarded as a highly efficient alternative to other DNA transfer procedures in characterizing those genes important for the pathogenicity of F. oxysporum and potentially those of other fungal pathogens.

Vitamin A antagonizes decreased cell growth and elevated collagen-degrading matrix metalloproteinases and stimulates collagen accumulation in naturally aged human skin

Damage to human skin due to ultraviolet light from the sun (photoaging) and damage occurring as a consequence of the passage of time (chronologic or natural aging) are considered to be distinct entities. Photoaging is caused in part by damage to skin connective tissue by increased elaboration of collagen-degrading matrix metalloproteinases, and by reduced collagen synthesis. As matrix metalloproteinase levels are known to rise in fibroblasts as a function of age, and as oxidant stress is believed to underlie changes associated with both photoaging and natural aging, we determined whether natural skin aging, like photoaging, gives rise to increased matrix metalloproteinases and reduced collagen synthesis. In addition, we determined whether topical vitamin A (retinol) could stimulate new collagen deposition in sun-protected aged skin, as it does in photoaged skin. Sun-protected skin samples were obtained from 72 individuals in four age groups: 18-29 y, 30-59 y, 60-79 y, and 80+ y. Histologic and cellular markers of connective tissue abnormalities were significantly elevated in the 60-79 y and 80+ y groups, compared with the two younger age groups. Increased matrix metalloproteinase levels and decreased collagen synthesis/expression were associated with this connective tissue damage. In a separate group of 53 individuals (80+ y of age), topical application of 1% vitamin A for 7 d increased fibroblast growth and collagen synthesis, and concomitantly reduced the levels of matrix-degrading matrix metalloproteinases. Our findings indicate that naturally aged, sun-protected skin and photoaged skin share important molecular features including connective tissue damage, elevated matrix metalloproteinase levels, and reduced collagen production. In addition, vitamin A treatment reduces matrix metalloproteinase expression and stimulates collagen synthesis in naturally aged, sun-protected skin, as it does in photoaged skin.

High-Performance High-Tc Superconducting Wires

We demonstrated short segments of a superconducting wire that meets or exceeds performance requirements for many large-scale applications of high-temperature superconducting materials, especially those requiring a high supercurrent and/or a high engineering critical current density in applied magnetic fields. The performance requirements for these varied applications were met in 3-micrometer-thick YBa2Cu3O(7-delta) films epitaxially grown via pulsed laser ablation on rolling assisted biaxially textured substrates. Enhancements of the critical current in self-field as well as excellent retention of this current in high applied magnetic fields were achieved in the thick films via incorporation of a periodic array of extended columnar defects, composed of self-aligned nanodots of nonsuperconducting material extending through the entire thickness of the film. These columnar defects are highly effective in pinning the superconducting vortices or flux lines, thereby resulting in the substantially enhanced performance of this wire.

GLI3 frameshift mutations cause autosomal dominant Pallister-Hall syndrome

Pallister-Hall syndrome (PHS, M146510) was first described in 1980 in six newborns. It is a pleiotropic disorder of human development that comprises hypothalamic hamartoma, central polydactyly, and other malformations. This disorder is inherited as an autosomal dominant trait and has been mapped to 7p13 (S. Kang et al. Autosomal dominant Pallister-Hall syndrome maps to 7p13. Am. J. Hum. Genet. 59, A81 (1996)), co-localizing the PHS locus and the GLI3 zinc finger transcription factor gene. Large deletions or translocations resulting in haploinsufficiency of the GLI3 gene have been associated with Greig cephalopolysyndactyly syndrome (GCPS; M175700) although no mutations have been identified in GCPS patients with normal karyotypes. Both PHS and GCPS have polysyndactyly, abnormal craniofacial features and are inherited in an autosomal dominant pattern, but they are clinically distinct. The polydactyly of GCPS is commonly preaxial and that of PHS is typically central or postaxial. No reported cases of GCPS have hypothalamic hamartoma and PHS does not cause hypertelorism or broadening of the nasal root or forehead. The co-localization of the loci for PHS and GCPS led us to investigate GLI3 as a candidate gene for PHS. Herein we report two PHS families with frameshift mutations in GLI3 that are 3' of the zinc finger-encoding domains, including one family with a de novo mutation. These data implicate mutations in GLI3 as the cause of autosomal dominant PHS, and suggest that frameshift mutations of the GLI3 transcription factor gene can alter the development of multiple organ systems in vertebrates.

Glutaminolysis as a target for cancer therapy

Cancer cells display an altered metabolic circuitry that is directly regulated by oncogenic mutations and loss of tumor suppressors. Mounting evidence indicates that altered glutamine metabolism in cancer cells has critical roles in supporting macromolecule biosynthesis, regulating signaling pathways, and maintaining redox homeostasis, all of which contribute to cancer cell proliferation and survival. Thus, intervention in these metabolic processes could provide novel approaches to improve cancer treatment. This review summarizes current findings on the role of glutaminolytic enzymes in human cancers and provides an update on the development of small molecule inhibitors to target glutaminolysis for cancer therapy.

Measurements of energetic particle radiation in transit to Mars on the Mars Science Laboratory

The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011, and for most of the 253-day, 560-million-kilometer cruise to Mars, the Radiation Assessment Detector made detailed measurements of the energetic particle radiation environment inside the spacecraft. These data provide insights into the radiation hazards that would be associated with a human mission to Mars. We report measurements of the radiation dose, dose equivalent, and linear energy transfer spectra. The dose equivalent for even the shortest round-trip with current propulsion systems and comparable shielding is found to be 0.66 ± 0.12 sievert.

Monomeric insulins and their experimental and clinical implications

Due to the inherent pharmacokinetic properties of available insulins, normoglycemia is rarely, if ever, achieved in insulin-dependent diabetic patients without compromising their quality of life. Subcutaneous insulin absorption is influenced by many factors, among which the associated state of insulin (hexameric) in pharmaceutical formulation may be of importance. This review describes the development of a series of human insulin analogues with reduced tendency to self-association that, because of more rapid absorption, are better suited to meal-related therapy. DNA technology has made it possible to prepare insulins that remain dimeric or even monomeric at high concentration by introducing one or a few amino acid substitutions into human insulin. These analogues were characterized and used for elucidating the mechanisms involved in subcutaneous absorption and were investigated in preliminary clinical studies. Their relative receptor binding and in vitro potency (free-fat cell assay), ranging from 0.05 to 600% relative to human insulin, were strongly correlated (r = 0.97). In vivo, most of the analogues exhibited approximately 100% activity, explainable by a dominating receptor-mediated clearance. This was confirmed by clamp studies in which correlation between receptor binding and clearance was observed. Thus, an analogue with reduced binding and clearance gives higher circulating concentrations, counterbalancing the reduced potency at the cellular level. Absorption studies in pigs revealed a strong inverse correlation (r = 0.96) between the rate of subcutaneous absorption and the mean association state of the insulin analogues. These studies also demonstrated that monomeric insulins were absorbed three times faster than human insulin. In healthy subjects, rates of disappearance from subcutis were two to three times faster for dimeric and monomeric analogues than for human insulin. Concomitantly, a more rapid rise in plasma insulin concentration and an earlier hypoglycemic response with the analogues were observed. The monomeric insulin had no lag phase and followed a monoexponential course throughout the absorption process. In contrast, two phases in rate of absorption were identified for the dimer and three for the normal hexameric human insulin. The initial lag phase and the subsequent accelerated absorption of soluble insulin can now be explained by the associated state of native insulin in pharmaceutical formulation and its progressive dissociation into smaller units during the absorption process. In the light of these results, the effects of insulin concentration, injected volume, temperature, and massage on the absorption process are now also understood.(ABSTRACT TRUNCATED AT 400 WORDS)

Expansion and deletion of CTG repeats from human disease genes are determined by the direction of replication in E. coli

Several human hereditary neurological and neurodegenerative disease genes are associated with the expansion of CTG repeats. Here we show that the frequency of genetic expansions or deletions in Escherichia coli depends on the direction of replication. Large expansions occur predominantly when the CTGs are in the leading strand template rather than the lagging strand. However, deletions are more prominent when the CTGs are in the opposite orientation. Most deletions generated products of defined size classes. Strand slippage coupled with non-classical DNA structures may account for these observations and relate to expansion-deletion mechanisms in eukaryotic chromosomes for disease genes.

Retinoic acid inhibits induction of c-Jun protein by ultraviolet radiation that occurs subsequent to activation of mitogen-activated protein kinase pathways in human skin in vivo

Human skin is exposed daily to solar ultraviolet (UV) radiation. UV induces the matrix metalloproteinases collagenase, 92-kD gelatinase, and stromelysin, which degrade skin connective tissue and may contribute to premature skin aging (photoaging). Pretreatment of skin with all-trans retinoic acid (tRA) inhibits UV induction of matrix metalloproteinases. We investigated upstream signal transduction pathways and the mechanism of tRA inhibition of UV induction of matrix metalloproteinases in human skin in vivo. Exposure of human skin in vivo to low doses of UV activated EGF receptors, the GTP-binding regulatory protein p21Ras, and stimulated mitogen-activated protein (MAP) kinases, extracellular signal-regulated kinase (ERK), c-Jun amino-terminal kinase (JNK), and p38. Both JNK and p38 phosphorylated, and thereby activated transcription factors c-Jun and activating transcription factor 2 (ATF-2), which bound to the c-Jun promoter and upregulated c-Jun gene expression. Elevated c-Jun, in association with constitutively expressed c-Fos, formed increased levels of transcription factor activator protein (AP) 1, which is required for transcription of matrix metalloproteinases. Pretreatment of human skin with tRA inhibited UV induction of c-Jun protein and, consequently, AP-1. c-Jun protein inhibition occurred via a posttranscriptional mechanism, since tRA did not inhibit UV induction of c-Jun mRNA. These data demonstrate, for the first time, activation of MAP kinase pathways in humans in vivo, and reveal a novel posttranscriptional mechanism by which tRA antagonizes UV activation of AP-1 by inhibiting c-Jun protein induction. Inhibition of c-Jun induction likely contributes to the previously reported prevention by tRA of UV induction of AP-1-regulated matrix-degrading metalloproteinases in human skin.

A genome-wide scan for linkage to human exceptional longevity identifies a locus on chromosome 4

Substantial evidence supports the familial aggregation of exceptional longevity. The existence of rare families demonstrating clustering for this phenotype suggests that a genetic etiology may be an important component. Previous attempts at localizing loci predisposing for exceptional longevity have been limited to association studies of candidate gene polymorphisms. In this study, a genome-wide scan for such predisposing loci was conducted by using 308 individuals belonging to 137 sibships demonstrating exceptional longevity. By using nonparametric analysis, significant evidence for linkage was noted for chromosome 4 at D4S1564 with a MLS of 3.65 (P = 0.044). The analysis was corroborated by a parametric analysis (P = 0.052). These linkage results indicate the likelihood that there exists a gene, or genes, that exerts a substantial influence on the ability to achieve exceptional old age. Identification of the genes in humans that allow certain individuals to live to extreme old age should lead to insights on cellular pathways that are important to the aging process.

Application of retinol to human skin in vivo induces epidermal hyperplasia and cellular retinoid binding proteins characteristic of retinoic acid but without measurable retinoic acid levels or irritation

We investigated the clinical, histologic, and molecular responses of normal human skin to all-trans-retinol (ROL) application, compared to those induced by topical all-trans-retinoic acid (RA), and measured ROL-derived metabolites. Up to 1.6% ROL, 0.025% RA in vehicle (70% ethanol/30% propylene glycol), or vehicle alone were applied in a double-blind fashion to normal buttock skin and occluded for 4 d. ROL produced from none to only trace erythema, which was clinically and statistically insignificant, whereas RA induced a significant 3.7-fold increase in erythema score compared to vehicle (n = 10, p < 0.01). However, ROL induced significant epidermal thickening (1.5-fold at 1.6% ROL, p < 0.01), similar to RA (1.6-fold at 0.025% RA, p < 0.01), relative to the vehicle. ROL, compared with vehicle, also increased mRNA levels of cellular retinoic acid binding protein (CRABP-II) and cellular retinol binding protein (CRBP) genes as determined by Northern analysis (5-6-fold and 6-7-fold, respectively) and riboprobe in situ hybridization. CRABP-II and CRBP protein levels were also higher following ROL than vehicle treatment, as measured by ligand binding (3.2-fold, p < 0.001; n = 7) and Western analysis (3.6-fold, p < 0.003; n = 6), respectively. Epidermal retinyl ester (RE) content, measured after removal of stratum corneum, rose 240-fold (p < 0.005, n = 5) by 24 h of ROL occlusion. RA content, however, was undetectable or detectable only at trace amounts in all samples obtained at 0, 6, 24, and 96 h after ROL occlusion. Detectability of RA was not correlated with ROL treatment (compared to untreated normal skin, p = 0.86) or baseline skin ROL levels (average r = -0.1, p > 0.3). These data demonstrate that ROL application 1) produces trace erythema not significantly different from vehicle, whereas RA causes erythema; 2) induces epidermal thickening and enhances expression of CRABP-II and CRBP mRNAs and proteins as does RA; 3) causes marked accumulation of retinyl ester; and 4) does not significantly increase RA levels. Taken together, the data are compatible with the idea that ROL may be a prohormone of RA, because it produces changes in skin similar to those produced by RA but without measurable RA or irritation.

c-Jun-dependent inhibition of cutaneous procollagen transcription following ultraviolet irradiation is reversed by all-trans retinoic acid

The aged appearance of skin following repeated exposure to solar ultraviolet (UV) irradiation stems largely from damage to cutaneous connective tissue, which is composed primarily of type I and type III collagens. We report here that a single exposure to UV irradiation causes significant loss of procollagen synthesis in human skin. Expression of type I and type III procollagens is substantially reduced within 24 hours after a single UV exposure, even at UV doses that cause only minimal skin reddening. Daily UV exposures over 4 days result in sustained reductions of both type I and type III procollagen protein levels for at least 24 hours after the final UV exposure. UV inhibition of type I procollagen synthesis is mediated in part by c-Jun, which is induced by UV irradiation and interferes with procollagen transcription. Pretreatment of human skin in vivo with all-trans retinoic acid inhibits UV induction of c-Jun and protects skin against loss of procollagen synthesis. We have reported previously that UV irradiation induces matrix-degrading metalloproteinases in human skin and that pretreatment of skin with all-trans retinoic acid inhibits this induction. UV irradiation, therefore, damages human skin connective tissue by simultaneously inhibiting procollagen synthesis and stimulating collagen breakdown. All-trans retinoic acid protects against both of these deleterious effects and may thereby retard premature skin aging.

Identification, cloning, and characterization of PWL2, a gene for host species specificity in the rice blast fungus

Genetic analysis of host specificity in the rice blast fungus (Magnaporthe grisea) identified a single gene, PWL2 (for Pathogenicity toward Weeping Lovegrass), that exerts a major effect on the ability of this fungus to infect weeping lovegrass (Eragrostis curvula). The allele of the PWL2 gene conferring nonpathogenicity was genetically unstable, with the frequent appearance of spontaneous pathogenic mutants. PWL2 was cloned based on its map position. Large deletions detected in pathogenic mutants guided the gene cloning efforts. Transformants harboring the cloned PWL2 gene lost pathogenicity toward weeping lovegrass but remained fully pathogenic toward other host plants. Thus, the PWL2 host species specificity gene has properties analogous to classical avirulence genes, which function to prevent infection of certain cultivars of a particular host species. The PWL2 gene encodes a glycine-rich, hydrophilic protein (16 kD) with a putative secretion signal sequence. The pathogenic allele segregating in the mapping population, pwl2-2, differed from PWL2 by a single base pair substitution that resulted in a loss of function. The PWL2 locus is highly polymorphic among rice pathogens from diverse geographic locations.

Blockade of T lymphocyte costimulation with cytotoxic T lymphocyte-associated antigen 4-immunoglobulin (CTLA4Ig) reverses the cellular pathology of psoriatic plaques, including the activation of keratinocytes, dendritic cells, and endothelial cells

Efficient T cell activation is dependent on the intimate contact between antigen-presenting cells (APCs) and T cells. The engagement of the B7 family of molecules on APCs with CD28 and CD152 (cytotoxic T lymphocyte-associated antigen 4 [CTLA-4]) receptors on T cells delivers costimulatory signal(s) important in T cell activation. We investigated the dependence of pathologic cellular activation in psoriatic plaques on B7-mediated T cell costimulation. Patients with psoriasis vulgaris received four intravenous infusions of the soluble chimeric protein CTLA4Ig (BMS-188667) in a 26-wk, phase I, open label dose escalation study. Clinical improvement was associated with reduced cellular activation of lesional T cells, keratinocytes, dendritic cells (DCs), and vascular endothelium. Expression of CD40, CD54, and major histocompatibility complex (MHC) class II HLA-DR antigens by lesional keratinocytes was markedly reduced in serial biopsy specimens. Concurrent reductions in B7-1 (CD80), B7-2 (CD86), CD40, MHC class II, CD83, DC-lysosomal-associated membrane glycoprotein (DC-LAMP), and CD11c expression were detected on lesional DCs, which also decreased in number within lesional biopsies. Skin explant experiments suggested that these alterations in activated or mature DCs were not the result of direct toxicity of CTLA4Ig for DCs. Decreased lesional vascular ectasia and tortuosity were also observed and were accompanied by reduced presence of E-selectin, P-selectin, and CD54 on vascular endothelium. This study highlights the critical and proximal role of T cell activation through the B7-CD28/CD152 costimulatory pathway in maintaining the pathology of psoriasis, including the newly recognized accumulation of mature DCs in the epidermis.

Highlighting new phylogenetic specificities of Crohn's disease microbiota

BACKGROUND

Recent studies suggest that gastrointestinal (GI) microbes play a part in the pathogenesis of Crohn's disease (CD).

METHODS

Fecal samples were collected from 16 healthy individuals and 16 CD patients (age- and sex-matched). The DNA extracted from these samples were subjected to two different methods of microbiome analysis. Specific bacterial groups were quantified by real-time polymerase chain reaction (PCR) methods using primers designed using a high-throughput in-house bioinformatics pipeline. The same DNA extracts were also used to produce fluorescently labeled cRNA amplicons to interrogate a custom-designed phylogenetic microarray for intestinal bacteria.

RESULTS

Even though the intersubject variability was high, differences in the fecal microbiomes of healthy and CD patients were detected. Faecalibacterium prausnitzii and Escherichia coli were more represented in healthy and ileal CD patients, respectively. Additionally, probes specific for Ruminococcus bromii, Oscillibacter valericigenes, Bifidobacterium bifidum, and Eubacterium rectale produced stronger hybridization signals with the DNA samples from healthy subjects. Conversely, species overrepresented in CD patients were E. coli, Enterococcus faecium, and species from the Proteobacteria not normally found in the healthy human GI tract. Furthermore, we detected "healthy specific" molecular species or operational taxonomic units (OTUs) that are not closely related to any known species (Faecalibacterium, Subdoligranulum, and Oscillospora species), indicating that the phylogenetic dysbiosis is broader than at strain or species level.

CONCLUSIONS

These two techniques of microbiome analysis provided a statistically robust new picture of the dysbiosis in fecal microbiota from ileal CD patients. Specifically, we identified a set of six species discriminant for CD, which provides a preliminary diagnostic tool.

Phosphorylation-mediated activation of LDHA promotes cancer cell invasion and tumour metastasis

Metastases remain the major cause of death from cancer. Recent molecular advances have highlighted the importance of metabolic alterations in cancer cells, including the Warburg effect that describes an increased glycolysis in cancer cells. However, how this altered metabolism contributes to tumour metastasis remains elusive. Here, we report that phosphorylation-induced activation of lactate dehydrogenase A (LDHA), an enzyme that catalyses the interconversion of pyruvate and lactate, promotes cancer cell invasion, anoikis resistance and tumour metastasis. We demonstrate that LDHA is phosphorylated at tyrosine 10 by upstream kinases, HER2 and Src. Targeting HER2 or Src attenuated LDH activity as well as invasive potential in head and neck cancer and breast cancer cells. Inhibition of LDH activity by small hairpin ribonucleic acid or expression of phospho-deficient LDHA Y10F sensitized the cancer cells to anoikis induction and resulted in attenuated cell invasion and elevated reactive oxygen species, whereas such phenotypes were reversed by its product lactate or antioxidant N-acetylcysteine, suggesting that Y10 phosphorylation-mediated LDHA activity promotes cancer cell invasion and anoikis resistance through redox homeostasis. In addition, LDHA knockdown or LDHA Y10F rescue expression in human cancer cells resulted in decreased tumour metastasis in xenograft mice. Furthermore, LDHA phosphorylation at Y10 positively correlated with progression of metastatic breast cancer in clinical patient tumour samples. Our findings demonstrate that LDHA phosphorylation and activation provide pro-invasive, anti-anoikis and pro-metastatic advantages to cancer cells, suggesting that Y10 phosphorylation of LDHA may represent a promising therapeutic target and a prognostic marker for metastatic human cancers.

Inhibition of type I procollagen synthesis by damaged collagen in photoaged skin and by collagenase-degraded collagen in vitro

Type I and type III procollagen are reduced in photodamaged human skin. This reduction could result from increased degradation by metalloproteinases and/or from reduced procollagen synthesis. In the present study, we investigated type I procollagen production in photodamaged and sun-protected human skin. Skin samples from severely sun-damaged forearm skin and matched sun-protected hip skin from the same individuals were assessed for type I procollagen gene expression by in situ hybridization and for type I procollagen protein by immunostaining. Both mRNA and protein were reduced ( approximately 65 and 57%, respectively) in photodamaged forearm skin compared to sun-protected hip skin. We next investigated whether reduced type I procollagen production was because of inherently reduced capacity of skin fibroblasts in severely photodamaged forearm skin to synthesize procollagen, or whether contextual influences within photodamaged skin act to down-regulate type I procollagen synthesis. For these studies, fibroblasts from photodamaged skin and matched sun-protected skin were established in culture. Equivalent numbers of fibroblasts were isolated from the two skin sites. Fibroblasts from the two sites had similar growth capacities and produced virtually identical amounts of type I procollagen protein. These findings indicate that the lack of type I procollagen synthesis in sun-damaged skin is not because of irreversible damage to fibroblast collagen-synthetic capacity. It follows, therefore, that factors within the severely photodamaged skin may act in some manner to inhibit procollagen production by cells that are inherently capable of doing so. Interactions between fibroblasts and the collagenous extracellular matrix regulate type I procollagen synthesis. In sun-protected skin, collagen fibrils exist as a highly organized matrix. Fibroblasts are found within the matrix, in close apposition with collagen fibers. In photodamaged skin, collagen fibrils are shortened, thinned, and disorganized. The level of partially degraded collagen is approximately 3.6-fold greater in photodamaged skin than in sun-protected skin, and some fibroblasts are surrounded by debris. To model this situation, skin fibroblasts were cultured in vitro on intact collagen or on collagen that had been partially degraded by exposure to collagenolytic enzymes. Collagen that had been partially degraded by exposure to collagenolytic enzymes from either bacteria or human skin underwent contraction in the presence of dermal fibroblasts, whereas intact collagen did not. Fibroblasts cultured on collagen that had been exposed to either source of collagenolytic enzyme demonstrated reduced proliferative capacity (22 and 17% reduction on collagen degraded by bacterial collagenase or human skin collagenase, respectively) and synthesized less type I procollagen (36 and 88% reduction, respectively, on a per cell basis). Taken together, these findings indicate that 1) fibroblasts from photoaged and sun-protected skin are similar in their capacities for growth and type I procollagen production; and 2) the accumulation of partially degraded collagen observed in photodamaged skin may inhibit, by an as yet unidentified mechanism, type I procollagen synthesis.

Long-term safety and efficacy of tacrolimus ointment for the treatment of atopic dermatitis in children

Tacrolimus ointment is a nonsteroidal topical immunomodulator that was formulated specifically for the treatment of atopic dermatitis. A total of 255 children, 2 to 15 years of age, with moderate to severe atopic dermatitis applied 0.1% tacrolimus ointment twice daily for up to 12 months to assess long-term safety and efficacy. Patients on average were treated with tacrolimus ointment for 279 days or 87% of study days. Substantial improvements in the signs and symptoms of atopic dermatitis, percent body surface area affected, and the patient's or parent's assessment of pruritus were observed during the first week of treatment and were maintained throughout the study. Transient skin burning and itching were the most common drug application site adverse events. Occurrence of these symptoms decreased after the first few days of treatment. There was no increased incidence of infections or other significant adverse events. Effectiveness of tacrolimus was maintained with prolonged daily use. Tacrolimus ointment (0.1%) is safe and effective for long-term treatment of atopic dermatitis in children.

N-linked glycosylation of the HIV type-1 gp120 envelope glycoprotein as a major determinant of CCR5 and CXCR4 coreceptor utilization

The variable V1V2 and V3 regions of the human immunodeficiency virus type-1 (HIV-1) envelope glycoprotein (gp120) can influence viral coreceptor usage. To substantiate this we generated isogenic HIV-1 molecularly cloned viruses that were composed of the HxB2 envelope backbone containing the V1V2 and V3 regions from viruses isolated from a patient progressing to disease. We show that the V3 amino acid charge per se had little influence on altering the virus coreceptor phenotype. The V1V2 region and its N-linked glycosylation degree were shown to confer CXCR4 usage and provide the virus with rapid replication kinetics. Loss of an N-linked glycosylation site within the V3 region had a major influence on the virus switching from the R5 to X4 phenotype in a V3 charge-dependent manner. The loss of this V3 N-linked glycosylation site was also linked with the broadening of the coreceptor repertoire to incorporate CCR3. By comparing the amino acid sequences of primary HIV-1 isolates, we identified a strong association between high V3 charge and the loss of this V3 N-linked glycosylation site. These results demonstrate that the N-linked glycosylation pattern of the HIV-1 envelope can strongly influence viral coreceptor utilization and the R5 to X4 switch.