Narrowband ultraviolet B inhibits innate cytosolic double-stranded RNA receptors in psoriatic skin and keratinocytes.

BACKGROUND: The mode of action of narrowband ultraviolet B (NB-UVB) therapy in clearing psoriasis is incompletely understood, and in vivo studies at the molecular level in patients undergoing NB-UVB therapy are limited. We previously demonstrated increased expression and activity of double-stranded RNA (dsRNA) receptors in psoriasis lesions, and suggested that this enhanced innate signalling contributed to the maintenance of psoriatic inflammation. OBJECTIVES: We investigated whether NB-UVB affects dsRNA receptor expression and function in vivo as well as in vitro. METHODS: Skin samples of patients with psoriasis undergoing NB-UVB treatment were analysed for epidermal messenger RNA (mRNA) expression of the various dsRNA receptors by microarray and quantitative reverse transcription-polymerase chain reaction. Primary human keratinocytes were irradiated with NB-UVB and stimulated with interferon (IFN)-α or IFN-γ, critical cytokines in psoriasis. The dsRNA analogue polyriboinosinic-polyribocytidylic acid was used to assess the functional responsiveness of the cells to dsRNA. RESULTS: NB-UVB therapy of patients with psoriasis resulted in a significantly reduced mRNA expression of the activating dsRNA receptors MDA5 (IFIH1) and RIG-I (DDX58). On the other hand, expression of LGP2 (DHX58), toll-like receptor 3 (TLR3) and PKR (EIF2AK2) was not affected. In vitro, NB-UVB irradiation completely blocked the upregulation of four of the dsRNA receptors in primary human keratinocytes stimulated with IFN-α or IFN-γ, resulting in an attenuated inflammatory response to dsRNA. CONCLUSIONS: Our results show that NB-UVB irradiation inhibits the local innate inflammatory response to dsRNA, and suggest a novel mechanism of action of NB-UVB phototherapy in psoriasis.

A restricted clonal T-cell receptor αß repertoire in Sézary syndrome is indicative of superantigenic stimulation.

BACKGROUND: Sézary syndrome (SS) is a cutaneous T-cell lymphoma characterized by erythroderma, lymphadenopathy and malignant clonal T cells in the skin, lymph nodes and peripheral blood. A role for superantigens in the pathogenesis of SS has been postulated before. OBJECTIVES: To investigate a putative involvement of chronic (super-)antigenic stimulation in driving T-cell expansion in SS. METHODS: Antigenic specificity of the T-cell receptor (TCR) was assayed by molecular analysis of the TCRA (n=11) and TCRB (n=28) genes, followed by detailed in silico analysis. RESULTS: Sequence analysis of clonally rearranged TCRB genes showed over-representation of Vß8, Vß13, Vß17, Vß21 and Vß22, and under-representation of Vß2 and Jß1.1 when compared with healthy controls. No similarity was detected in amino acid motifs of the complementarity determining region 3 (CDR3). Analysis of TCRA rearrangements showed that there was no common Vα or Jα gene usage, and that TCRA CDR3 amino acid motifs were not highly similar. CONCLUSIONS: The lack of clear stereotypic TCRA and TCRB CDR3 amino acid motifs would argue against involvement of a single common antigen in the pathogenesis of SS. Nevertheless, the skewing of Vß and Jß gene usage does seem to point to a restricted TCR repertoire, possibly as a result of superantigenic selection prior to neoplastic transformation.

ORCA3, a jasmonate-responsive transcriptional regulator of plant primary and secondary metabolism.

Biosynthesis of many classes of secondary metabolites in plants is induced by the stress hormone jasmonate. The gene for ORCA3, a jasmonate-responsive APETALA2 (AP2)-domain transcription factor from Catharanthus roseus, was isolated by transferred DNA activation tagging. Orca3 overexpression resulted in enhanced expression of several metabolite biosynthetic genes and, consequently, in increased accumulation of terpenoid indole alkaloids. Regulation of metabolite biosynthetic genes by jasmonate-responsive AP2-domain transcription factors may link plant stress responses to changes in metabolism.

[The pathogenesis of inflammatory dermatoses, especially psoriasis]. / Pathogenese van inflammatoire dermatosen, in het bijzonder psoriasis.

The skin contains a variety of cell types and mediators, which together constitute the skin's immune system and play a key role in protecting the human body against dangers from outside. Dysregulation of the skin's immune system, however, frequently occurs and can result in undesirable inflammatory processes in the skin. A typical example of an undesirable inflammation in the skin is the chronic inflammatory skin disease psoriasis. In the pathogenesis of psoriasis, both genetic and environmental factors play a key role. In psoriasis, the complex interactions between T-lymphocytes, antigen-presenting cells, keratinocytes and pro-inflammatory cytokines and chemokines are disturbed. The two most widely accepted hypotheses are: (a) psoriasis is a T-cell mediated autoimmune disease, and (b) psoriasis is the result of a too finely adjusted system for regulating inflammation in the skin. The result of both mechanisms is a chronic inflammatory reaction fuelled by pro-inflammatory type-I cytokines that lead to the psoriasis-skin phenotype. With the development ofbiologicals, it has become feasible to target specific molecules in the immune process, for example type-I cytokines and the molecules present on pathogenic T-cells. This approach has already proved successful in the treatment of rheumatoid arthritis and Crohn's disease, creating novel therapeutic options for psoriasis and other inflammatory dermatoses.

[New systemic treatments for psoriasis: etanercept, infliximab, adalimumab, efalizumab and alefacept]. / Nieuwe systemische behandelingen bij psoriasis: etanercept, infliximab, adalimumab, efalizumab en alefacept.

The chronic skin disease psoriasis frequently requires long-term systemic treatment with agents that suppresses the immune system with little specificity, which can lead to systemic side effects. Today, using recombinant techniques, it is possible to produce modified proteins, the so-called biologicals, that target specific molecules in the inflammatory process. For the biologicals etanercept, infliximab, adalimumab, efalizumab and alefacept, the clinical efficacy expressed in the rates of partial remission (75% reduction in skin lesions) in patients with plaque psoriasis range from 12 to 88%, compared with 22 to 87% for existing systemic therapies for psoriasis. The side effects of biologicals are usually mild to moderate, but can sometimes be severe. The biologicals should be prescribed with caution, given that they have been on the market for a relatively short period, and because all forms of immune suppression carry an increased risk of oncologic degeneration. The guideline of the Dutch Society of Dermatology and Venereology states that the use of a biological may be considered when a patient cannot tolerate or is unresponsive to conventional systemic therapy, or has an increased risk of adverse events. Biologicals increase the number of options for treatment-resistant plaque psoriasis, which allows therapy to be tailored to the individual patient.

The histone deacetylase inhibitors vorinostat and romidepsin downmodulate IL-10 expression in cutaneous T-cell lymphoma cells.

BACKGROUND AND PURPOSE: Vorinostat and romidepsin are histone deacetylase inhibitors (HDI), approved for the treatment of cutaneous T-cell lymphoma (CTCL). However, the mechanism(s) by which these drugs exert their anti-cancer effects are not fully understood. Since CTCL is associated with immune dysregulation, we investigated whether these HDI modulated cytokine expression in CTCL cells. EXPERIMENTAL APPROACH: CTCL cell lines and primary CTCL cells were treated in vitro with vorinostat or romidepsin, or with STAT3 pathway inhibitors. Cell cycle parameters and apoptosis were analysed by propidium iodide and annexin V/propidium iodide staining respectively. Cytokine expression was analysed using QRT-PCR and elisa assays. STAT3 expression/phosphorylation and transcriptional activity were analysed using immunoblotting and transfection/reporter assays respectively. KEY RESULTS: Vorinostat and romidepsin strongly down-regulated expression of the immunosuppressive cytokine, interleukin (IL)-10, frequently overexpressed in CTCL, at both the RNA and protein level in CTCL cell lines and at the RNA level in primary CTCL cells. Vorinostat and romidepsin also increased expression of IFNG RNA and decreased expression of IL-2 and IL-4 RNA, although to a lesser extent compared to IL-10. Transient exposure to vorinostat was sufficient to suppress IL-10 secretion but was not sufficient to irreversibly commit cells to undergo cell death. STAT3 pathway inhibitors decreased production of IL-10 and vorinostat/romidepsin partially decreased STAT3-dependent transcription without effects on STAT3 expression or phosphorylation. CONCLUSIONS AND IMPLICATIONS: These results demonstrate that HDI modulate cytokine expression in CTCL cells, potentially via effects on STAT3. Immunomodulation may contribute to the clinical activity of HDI in this disease.

Peptidoglycan and peptidoglycan-specific Th1 cells in psoriatic skin lesions.

We have previously demonstrated, in psoriatic skin lesions, the presence of a subset of dermal CD4+ T cells that produce interferon-gamma (IFN-gamma) in response to a mixture of cell wall proteins extracted from group A streptococci. However, the identity of the antigen(s) involved is unknown. To investigate the hypothesis that peptidoglycan (PG), the major constituent of the streptococcal cell wall, acts as a T cell activator in psoriasis, we performed in situ analysis to detect antigen-presenting cells containing PG in lesional versus non-lesional skin, and determined proliferation and IFN-gamma responses of lesional skin T cells. Increased numbers of PG-containing cells were detected in the dermal papillae and cellular infiltrates of guttate and chronic plaque skin lesions compared with normal and non-lesional psoriatic skin. A varying proportion of these were CD68+ macrophages, but the remaining cells did not double stain for either Langerhans' or dendritic cell markers. Psoriatic dermal streptococcal-specific CD4+ T cell lines proliferated and produced IFN-gamma in a self HLA-DR allele-restricted manner in response to streptococcal PG, excluding mitogenic or superantigenic stimulation, but were unresponsive to staphylococcal PG. Similarly, psoriatic staphylococcus-specific T cell lines recognized staphylococcal, but not streptococcal, PG by IFN-gamma production. The presence of PG-containing macrophages in close association with PG-specific CD4+ T cells in lesional skin suggests that PG may be responsible, at least in part, for T cell activation in psoriasis.

Comparison of the activities of CaMV 35S and FMV 34S promoter derivatives in Catharanthus roseus cells transiently and stably transformed by particle bombardment.

Activities of several CaMV 35S and FMV 34S promoter derivatives fused to the gusA reporter gene were compared in suspension-cultured Catharanthus roseus cells that were transiently and stably transformed using particle bombardment. Our data demonstrate that the 35S and a deletion derivative of the 34S promoter combined with particle bombardment form useful tools for genetic engineering of C. roseus cells. Our results disagree on several points with activities of 35S and 34S promoter derivatives reported for tobacco, indicating that absolute and relative promoter activities can differ between plant species.

The jasmonate-inducible AP2/ERF-domain transcription factor ORCA3 activates gene expression via interaction with a jasmonate-responsive promoter element.

The AP2/ERF-domain transcription factor ORCA3 is a master regulator of primary and secondary metabolism in Catharanthus roseus (periwinkle). Here we demonstrate that ORCA3 specifically binds to and activates gene expression via a previously characterized jasmonate- and elicitor-responsive element (JERE) in the promoter of the terpenoid indole alkaloid biosynthetic gene Strictosidine synthase (Str). Functional characterization of different domains in the ORCA3 protein in yeast and plant cells revealed the presence of an N-terminal acidic activation domain and a serine-rich C-terminal domain with a negative regulatory function. Orca3 mRNA accumulation was rapidly induced by the plant stress hormone methyljasmonate with biphasic kinetics. A precursor and an intermediate of the jasmonate biosynthetic pathway also induced Orca3 gene expression, further substantiating the role for ORCA3 in jasmonate signaling. The protein synthesis inhibitor cycloheximide did not inhibit jasmonate-responsive expression of Orca3, nor of its target genes Str and Tryptophan decarboxylase (Tdc). In conclusion, ORCA3 regulates jasmonate-responsive expression of the Str gene via direct interaction with the JERE. The activating activities of ORCA proteins do not seem to depend on jasmonate-induced de novo protein synthesis, but presumably occur via modification of pre-existing ORCA protein.

T-DNA activation tagging as a tool to isolate regulators of a metabolic pathway from a genetically non-tractable plant species.

T-DNA activation tagging is a method used to generate dominant mutations in plants or plant cells by the insertion of a T-DNA which carries constitutive enhancer elements that can cause transcriptional activation of flanking plant genes. We applied this approach to the species Catharanthus roseus (L.) G. Don (Madagascar periwinkle), in an attempt to isolate regulators of genes that are involved in the biosynthesis of secondary metabolites of the terpenoid indole alkaloid (TIA) class. Several TIAs have pharmaceutically interesting activities, including the anti-tumour agents vincristine and vinblastine. The use of suspension-cultured cells enabled us to screen in a relatively easy way hundreds of thousands of T-DNA-tagged cells for resistance to a toxic substrate of one of the TIA biosynthetic enzymes: tryptophan decarboxylase. This screening yielded several interesting tagged cell lines. Further characterisation of one of the tagged cell lines led to the isolation of Orca3, a gene encoding an AP2/ERF-domain transcription factor that acts as a master regulator of primary and secondary metabolism. The T-DNA activation tagging results described in detail in this paper illustrate the usefulness of this approach to isolate regulators of a complex metabolic pathway from a genetically non-tractable plant species.

The ternary transformation system: constitutive virG on a compatible plasmid dramatically increases Agrobacterium-mediated plant transformation.

This paper describes a so-called ternary transformation system for plant cells. We demonstrate that Agrobacterium tumefaciens strain LBA4404 supplemented with a constitutive virG mutant gene (virGN54D) on a compatible plasmid is capable of very efficient T-DNA transfer to a diverse range of plant species. For the plant species Catharanthus roseus it is shown that increased T-DNA transfer results in increased stable transformation frequencies. Analysis of stably transformed C. roseus cell lines showed that, although the T-DNA transfer frequency is greatly enhanced by addition of virGN54D, only one or a few T-DNA copies are stably integrated into the plant genome. Thus, high transformation frequencies of different plant species can be achieved by introduction of a ternary plasmid carrying a constitutive virG mutant into existing A. tumefaciens strains in combination with standard binary vectors.

A Catharanthus roseus BPF-1 homologue interacts with an elicitor-responsive region of the secondary metabolite biosynthetic gene Str and is induced by elicitor via a JA-independent signal transduction pathway.

Plants respond to pathogen attack by induction of various defence responses, including the biosynthesis of protective secondary metabolites. In Catharanthus roseus, the elicitor-induced expression of the terpenoid indole alkaloid biosynthetic gene Strictosidine synthase (Str) is mediated via the plant stress hormonejasmonate. In the promoters of several defence-related genes, cis-acting elements have been identified that are important for transcriptional regulation upon stress signals. Here we show that an upstream region in the Str promoter confers responsiveness to partially purified yeast elicitor and jasmonate. Yeast one-hybrid screening with this element as a bait identified a MYB-like protein, which shows high homology to parsley box P-binding factor-1 (PcBPF-1). In vitro analyses showed that the Str promoter fragment contained a novel binding site for BPF-1-like proteins with higher binding affinity than the previously described box P. CrBPF-1 mRNA accumulated rapidly in elicitor-treated C. roseus suspension cells, whereas no induction was observed with jasmonate. Inhibitor studies indicated that CrBPF-1 plays a role in an elicitor-responsive but jasmonate-independent signal transduction pathway, acting downstream of protein phosphorylation and calcium influx.

A site-specific recombinase is required for competitive root colonization by Pseudomonas fluorescens WCS365.

A colonization mutant of the efficient root-colonizing biocontrol strain Pseudomonas fluorescens WCS365 is described that is impaired in competitive root-tip colonization of gnotobiotically grown potato, radish, wheat, and tomato, indicating a broad host range mutation. The colonization of the mutant is also impaired when studied in potting soil, suggesting that the defective gene also plays a role under more natural conditions. A DNA fragment that is able to complement the mutation for colonization revealed a multicistronic transcription unit composed of at least six ORFs with similarity to lppL, lysA, dapF, orf235/233, xerC/sss, and the largely incomplete orf238. The transposon insertion in PCL1233 appeared to be present in the orf235/233 homologue, designated orf240. Introduction of a mutation in the xerC/sss homologue revealed that the xerC/sss gene homologue rather than orf240 is crucial for colonization. xerC in Escherichia coli and sss in Pseudomonas aeruginosa encode proteins that belong to the lambda integrase family of site-specific recombinases, which play a role in phase variation caused by DNA rearrangements. The function of the xerC/sss homologue in colonization is discussed in terms of genetic rearrangements involved in the generation of different phenotypes, thereby allowing a bacterial population to occupy various habitats. Mutant PCL1233 is assumed to be locked in a phenotype that is not well suited to compete for colonization in the rhizosphere. Thus we show the importance of phase variation in microbe-plant interactions.

Lipoprotein cholesterol uptake mediates up-regulation of bile-acid synthesis by increasing cholesterol 7alpha-hydroxylase but not sterol 27-hydroxylase gene expression in cultured rat hepatocytes.

Lipoproteins may supply substrate for the formation of bile acids, and the amount of hepatic cholesterol can regulate bile-acid synthesis and increase cholesterol 7alpha-hydroxylase expression. However, the effect of lipoprotein cholesterol on sterol 27-hydroxylase expression and the role of different lipoproteins in regulating both enzymes are not well established. We studied the effect of different rabbit lipoproteins on cholesterol 7alpha-hydroxylase and sterol 27-hydroxylase in cultured rat hepatocytes. beta-Migrating very-low-density lipoprotein (betaVLDL) and intermediate-density lipoprotein (IDL) caused a significant increase in the intracellular cholesteryl ester content of cells (2. 3- and 2-fold, respectively) at a concentration of 200 microgram of cholesterol/ml, whereas high-density lipoprotein (HDL, 50% v/v), containing no apolipoprotein E (apo E), showed no effect after a 24-h incubation. betaVLDL and IDL increased bile-acid synthesis (1. 9- and 1.6-fold, respectively) by up-regulation of cholesterol 7alpha-hydroxylase activity (1.7- and 1.5-fold, respectively). Dose- and time-dependent changes in cholesterol 7alpha-hydroxylase mRNA levels and gene expression underlie the increase in enzyme activity. Incubation of cells with HDL showed no effect. Sterol 27-hydroxylase gene expression was not affected by any of the lipoproteins added. Transient-expression experiments in hepatocytes, transfected with a promoter-reporter construct containing the proximal 348 nucleotides of the rat cholesterol 7alpha-hydroxylase promoter, showed an enhanced gene transcription (2-fold) with betaVLDL, indicating that a sequence important for a cholesterol-induced transcriptional response is located in this part of the cholesterol 7alpha-hydroxylase gene. The extent of stimulation of cholesterol 7alpha-hydroxylase is associated with the apo E content of the lipoprotein particle, which is important in the uptake of lipoprotein cholesterol. We conclude that physiological concentrations of cholesterol in apo E-containing lipoproteins increase bile-acid synthesis by stimulating cholesterol 7alpha-hydroxylase gene transcription, whereas HDL has no effect and sterol 27-hydroxylase is not affected.

Effects of over-expression of strictosidine synthase and tryptophan decarboxylase on alkaloid production by cell cultures of Catharanthus roseus.

Cells of Catharanthus roseus (L.) G. Don were genetically engineered to over-express the enzymes strictosidine synthase (STR; EC 4.3.3.2) and tryptophan decarboxylase (TDC; EC 4.1.1.28), which catalyze key steps in the biosynthesis of terpenoid indole alkaloids (TIAs). The cultures established after Agrobacterium-mediated transformation showed wide phenotypic diversity, reflecting the complexity of the biosynthetic pathway. Cultures transgenic for Str consistently showed tenfold higher STR activity than wild-type cultures, which favored biosynthetic activity through the pathway. Two such lines accumulated over 200 mg.L-1 of the glucoalkaloid strictosidine and/or strictosidine-derived TIAs, including ajmalicine, catharanthine, serpentine, and tabersonine, while maintaining wild-type levels of TDC activity. Alkaloid accumulation by highly productive transgenic lines showed considerable instability and was strongly influenced by culture conditions, such as the hormonal composition of the medium and the availability of precursors. High transgene-encoded TDC activity was not only unnecessary for increased productivity, but also detrimental to the normal growth of the cultures. In contrast, high STR activity was tolerated by the cultures and appeared to be necessary, albeit not sufficient, to sustain high rates of alkaloid biosynthesis. We conclude that constitutive over-expression of Str is highly desirable for increased TIA production. However, given its complexity, limited intervention in the TIA pathway will yield positive results only in the presence of a favorable epigenetic environment.