Prostaglandins and activation of AC/cAMP prevents anoikis in IEC-18

Recent data indicates that chronic inflammation of the intestine such as Crohn's or ulcerative colitis puts those individuals at heightened risk for colorectal adenocarcinoma. In this study, we examine the effect of the inflammatory mediator PGE(2) and associated signalling on detachment-induced cell death (anoikis) in intestinal epithelial cells. Treatment of detached IEC-18 with 0.01-0.05 microM PGE(2) increased cell viability as well as induced aggregation. As EP4 prostaglandin receptors on IEC are coupled to adenylate cyclase, we next treated cells with agents that promote cAMP signalling (Forskolin, dbcAMP, and etazolate), all of which promoted IEC aggregation as well as survival. We next treated detached IECs with specific inhibitors of adenylate cyclase or PKA, which accelerated anoikis. To explore the mechanism of cell-cell adhesion, we next treated detached IECs with an anti-E-cadherin blocking antibody which dispersed aggregates induced by dbcAMP, and an adenovirus expressing a dominant negative E-cadherin (EcadDeltaEC) prevented aggregate formation. Interestingly EcadDeltaEC prevented aggregation of IEC induced by dbcAMP but did not significantly reduce viability. This suggests that cAMP signalling is important in both aggregate formation and promoting viability but these are distinct events. Taken together, these data support a mechanism whereby elevated PGE(2) levels characteristic of colitis prevent anoikis by activating an AC-, cAMP-, and PKA-dependent signalling pathway. The delay of apoptosis by PGE(2) may be one mechanism by which inflammation may contribute to carcinogenesis.

Pre-B-cell leukemia transcription factor 1 is a major target of promyelocytic leukemia zinc-finger-mediated melanoma cell growth suppression

Promyelocytic leukemia zinc-finger (PLZF) is a transcriptional repressor and tumor suppressor. PLZF is expressed in melanocytes but not in melanoma cells, and recovery of PLZF expression markedly suppresses melanoma cell growth. Several target genes regulated by PLZF have been identified, but the precise function of PLZF remains uncertain. Here, we searched for candidate target genes of PLZF by DNA microarray analysis. Pre-B-cell leukemia transcription factor 1 (Pbx1) was one of the prominently suppressed genes. Pbx1 was highly expressed in melanoma cells, and its expression was reduced by transduction with the PLZF gene. Moreover, the growth suppression mediated by PLZF was reversed by enforced expression of Pbx1. Knockdown of Pbx1 by specific small interfering RNAs suppressed melanoma cell growth. We also found that Pbx1 binds HoxB7. Reverse transcription-polymerase chain reaction analysis demonstrated that repression of Pbx1 by PLZF reduces the expression of HoxB7 target genes, including tumor-associated neoangiogenesis factors such as basic fibroblast growth factor, angiopoietin-2 and matrix metalloprotease 9. These findings suggest that deregulation of Pbx1 expression owing to loss of PLZF expression contributes to the progression and/or pathogenesis of melanoma.

Induction of the cytokine signal regulator SOCS3/CIS3 as a therapeutic strategy for treating inflammatory arthritis

Immune and inflammatory systems are controlled by multiple cytokines, including ILs and INFs. These cytokines exert their biological functions through Janus tyrosine kinases and STAT transcription factors. One such cytokine, IL-6, has been proposed to contribute to the development of rheumatoid arthritis (RA). We found that STAT3 was strongly tyrosine phosphorylated in synovial tissue of RA patients, but not those with osteoarthritis. Blockade of the IL-6-gp130-JAK-STAT3-signaling pathway might therefore be beneficial in the treatment of RA. We show here that the mRNA for the endogenous cytokine signaling repressor CIS3/SOCS3 is abundantly expressed in RA patients. To determine whether CIS3 is effective in treating experimental arthritis, a recombinant adenovirus carrying the CIS3 cDNA was injected periarticularly into the ankle joints of mice with antigen-induced arthritis or collagen-induced arthritis (CIA). Periarticular injection of CIS3 adenovirus drastically reduced the severity of arthritis and joint swelling compared with control groups. CIS3 was more effective than a dominant-negative form of STAT3 in the CIA model. Thus, induction of CIS3 could represent a new approach for effective treatment of RA.

Downregulation of E-cadherin and Desmoglein 1 by autocrine hepatocyte growth factor during melanoma development

During melanoma development, transformed cells evade keratinocyte-mediated control by downregulating cell adhesion molecules. This study investigated the regulation of cell adhesion by hepatocyte growth factor (HGF) in melanoma. Melanocytes and two melanoma lines, WM164 and WM35, expressed normal level E-cadherin and Desmoglein 1, whereas most melanomas (18 out of 20) expressed no E-cadherin and significantly reduced Desmoglein 1. Overexpression of dominant negative E-cadherin and Desmoglein in melanocytes demonstrated that both molecules contribute to adhesion between melanocytes and keratinocytes. In contrast to melanocytes, most melanomas expressed HGF. All melanocytic cells expressed the HGF receptor c-Met, and autocrine HGF caused constitutive activation of c-Met, MAPK and PI3K. When autocrine activation was induced with HGF-expressing adenovirus, E-cadherin and Desmoglein 1 were decreased in melanocytes, WM164 and WM35. MAPK inhibitor PD98059 and PI3K inhibitor wortmannin partially blocked the downregulation, suggesting that both pathways are involved in this process. c-Met was coimmunoprecipitated with E-cadherin, Desmoglein 1 and Plakoglobin, suggesting that they form a complex (es) that acts to regulate intercellular adhesion. Together, the results indicate that autocrine HGF decouples melanomas from keratinocytes by downregulating E-cadherin and Desmoglein 1, therefore frees melanoma cells from the control by keratinocytes and allows dissemination of the tumor mass.

Suppressor of cytokine signaling-3 is a biomechanical stress-inducible gene that suppresses gp130-mediated cardiac myocyte hypertrophy and survival pathways

The gp130 cytokine receptor activates a cardiomyocyte survival pathway during the transition to heart failure following the biomechanical stress of pressure overload. Although gp130 activation is observed transiently during transverse aortic constriction (TAC), its mechanism of inactivation is largely unknown in cardiomyocytes. We show here that suppressor of cytokine signaling 3 (SOCS3), an intrinsic inhibitor of JAK, shows biphasic induction in response to TAC. The induction of SOCS3 was closely correlated with STAT3 phosphorylation, as well as the activation of an embryonic gene program, suggesting that cardiac gp130-JAK signaling is precisely controlled by this endogenous suppressor. In addition to its cytoprotective action, gp130-dependent signaling induces cardiomyocyte hypertrophy. Adenovirus-mediated gene transfer of SOCS3 to ventricular cardiomyocytes completely suppressed both hypertrophy and antiapoptotic phenotypes induced by leukemia inhibitory factor (LIF). To our knowledge, this is the first clear evidence that these two separate cardiomyocyte phenotypes induced by gp130 activation lie downstream of JAK. Three independent signaling pathways, STAT3, MEK1-ERK1/2, and AKT activation, that are coinduced by LIF stimulation were completely suppressed by SOCS3 overexpression. We conclude that SOCS3 is a mechanical stress-inducible gene in cardiac muscle cells and that it directly modulates stress-induced gp130 cytokine receptor signaling as the key molecular switch for a negative feedback circuit for both myocyte hypertrophy and survival.

Molecular cloning of human squamous cell carcinoma antigen 1 gene and characterization of its promoter

The squamous cell carcinoma antigen (SCCA) serves as a serological marker for squamous cell carcinomas. Molecular cloning of the SCCA genomic region has revealed the presence of two tandemly arrayed genes, SCCA1 and SCCA2, which are 95% identical in nucleotide sequence. SCCA1 is a papain-like cysteine proteinase inhibitor, while SCCA2 is a chymotrypsin-like serine proteinase inhibitor. We analyzed here the sequence and the promoter activity of the 5'-flanking region of the SCCA1 gene. Deletion analysis of SCCA1 and SCCA2 promoter identified a 471-bp core promoter region upstream of the transcription start site. The transcriptional activity of SCCA1 promoter was up-regulated in squamous cell carcinoma cells, compared with keratinocyte and adenocarcinoma cells. The ratios of SCCA1 to SCCA2 promoter activity in squamous cell carcinoma, keratinocyte and adenocarcinoma cells were respectively 1.6, 5.3 and 2.8. Position -50 of SCCA1 and SCCA2 promoters played an important role in determining the promoter activities of SCCA1 and SCCA2. These findings suggest that the transcriptional regulation of SCCA1 and SCCA2 might differ among squamous cell carcinoma, keratinocyte and adenocarcinoma cells, and that SCCA1 promoter might be a potential target of gene therapy for squamous cell carcinoma.

Gene expression of human squamous cell carcinoma antigens 1 and 2 in human cell lines

The squamous cell carcinoma antigen (SCCA) serves as a serological marker for squamous cell carcinomas. Molecular cloning of the SCCA genomic region has revealed the presence of two tandemly arrayed genes, SCCA1 and SCCA2. SCCA1 is a papain-like cysteine proteinase inhibitor, while SCCA2 is a chymotrypsin-like serine proteinase inhibitor. Little is known concerning how expression of the SCCA1 and SCCA2 genes is regulated in human cell lines. The purpose of this study was to determine whether the SCCA1 gene or SCCA2 gene is more strongly expressed in human cell lines. Squamous cell carcinoma cell lines secreted respectively 4 times and 50 times as much SCCA proteins into medium as normal human keratinocyte and non-squamous cell carcinoma cell lines, as measured by enzyme-linked immunosorbent assay. Quantitative RT-PCR ELISA digoxigenin-labeling assay demonstrated that SCCA1 mRNA expression in squamous cell carcinoma cell lines was respectively 2.8 times and 42 times that in keratinocyte and non-squamous cell carcinoma cell lines. The ratio of SCCA1 to SCCA2 mRNA expression differed distinctly among squamous cell carcinoma, keratinocyte and non-squamous cell carcinoma cell lines (2.8, squamous; 24.1, keratinocyte; 11.0, non-squamous). These findings suggest that SCCA1 is mainly expressed in squamous cell carcinoma, keratinocyte and non-squamous cell carcinoma cell lines and that the ratio of SCCA1 to SCCA2 expression might be a novel marker for the detection of squamous cell carcinoma.

Apoptosis signal-regulating kinase 1 (ASK1) is an intracellular inducer of keratinocyte differentiation

Cells differentiate in response to various extracellular stimuli. This cellular response requires intracellular signaling pathways. The mitogen-activated protein (MAP) kinase cascade is a core signal transduction pathway that determines the fate of many kinds of cell. MAP kinase kinase kinase activates MAP kinase kinase, which in turn activates MAP kinase. Apoptosis signal-regulating kinase (ASK1) was identified as a MAP kinase kinase kinase involved in the stress-induced apoptosis-signaling cascade that activates the SEK1-JNK and MKK3/MKK6-p38 MAP kinase cascades. Expression of the constitutively active form of ASK1 (ASK1-DeltaN) in keratinocytes induced significant morphological changes and differentiation markers, transglutaminase-1, loricrin, and involucrin. A transient increase in p21(Cip1/WAF1) reduced DNA synthesis, and cell cycle analysis verified the differentiation. p38 MAP kinase inhibitors, SB202190 and SB203580, abolished the induction of differentiation markers, transglutaminase-1, loricrin, and involucrin. In turn, the induction of differentiation with ceramide in keratinocytes caused an increase in ASK1 expression and activity. Furthermore, normal human skin expresses ASK1 protein in the upper epidermis, implicating ASK1 in in vivo keratinocyte differentiation. We propose that the ASK1-p38 MAP kinase cascade is a new intracellular regulator of keratinocyte differentiation.

Ectodomain shedding of epidermal growth factor receptor ligands is required for keratinocyte migration in cutaneous wound healing

Keratinocyte proliferation and migration are essential to cutaneous wound healing and are, in part, mediated in an autocrine fashion by epidermal growth factor receptor (EGFR)-ligand interactions. EGFR ligands are initially synthesized as membrane-anchored forms, but can be processed and shed as soluble forms. We provide evidence here that wound stimuli induce keratinocyte shedding of EGFR ligands in vitro, particularly the ligand heparin-binding EGF-like growth factor (HB-EGF). The resulting soluble ligands stimulated transient activation of EGFR. OSU8-1, an inhibitor of EGFR ligand shedding, abrogated the wound-induced activation of EGFR and caused suppression of keratinocyte migration in vitro. Soluble EGFR-immunoglobulin G-Fcgamma fusion protein, which is able to neutralize all EGFR ligands, also suppressed keratinocyte migration in vitro. The application of OSU8-1 to wound sites in mice greatly retarded reepithelialization as the result of a failure in keratinocyte migration, but this effect could be overcome if recombinant soluble HB-EGF was added along with OSU8-1. These findings indicate that the shedding of EGFR ligands represents a critical event in keratinocyte migration, and suggest their possible use as an effective clinical treatment in the early phases of wound healing.

Superantigen production by Staphylococcus aureus in psoriasis

BACKGROUND

Activation of T cells is believed to play a critical role in the pathogenesis of psoriasis. Recently, it has been proposed that psoriasis is a T-cell-mediated autoimmune reaction triggered by bacterial superantigen.

OBJECTIVE

We investigated whether patients with chronic plaque psoriasis bear superantigen-producing Staphylococcus aureus on the skin or the throat.

METHODS

S. aureus producing exfoliative toxin, staphylococcal enterotoxin B or toxic shock syndrome toxin 1 was isolated from the skin and throat of 100 psoriasis patients using Western blot analysis and polymerase chain reaction.

RESULTS

Only 5, 4 and 9 patients had super-antigen producing S. aureus identified on lesional skin, nonlesional skin and throat, respectively. The vast majority of patients did not bear superantigen-producing S. aureus.

CONCLUSION

We believe that superantigens are not essential in sustaining disease activity but may, instead, be exacerbating or triggering factors for some psoriasis patients.

Different effects of dominant negative mutants of desmocollin and desmoglein on the cell-cell adhesion of keratinocytes

Desmosomes contain two types of cadherin: desmocollin (Dsc) and desmoglein (Dsg). In this study, we examined the different roles that Dsc and Dsg play in the formation of desmosomes, by using dominant-negative mutants. We constructed recombinant adenoviruses (Ad) containing truncated mutants of E-cadherin, desmocollin 3a, and desmoglein 3 lacking a large part of their extracellular domains (EcaddeltaEC, Dsc3adeltaEC, Dsg3deltaEC), using the Cre-loxP Ad system to circumvent the problem of the toxicity of the mutants to virus-producing cells. When Dsc3adeltaEC Ad-infected HaCaT cells were cultured with high levels of calcium, E-cadherin and beta-catenin, which are marker molecules for the adherens junction, disappeared from the cell-cell contact sites, and cell-cell adhesion was disrupted. This also occurred in the cells infected with EcaddeltaEC Ad. With Dsg3deltaEC Ad infection, keratin insertion at the cell-cell contact sites was inhibited and desmoplakin, a marker of desmosomes, was stained in perinuclear dots while the adherens junctions remained intact. Dsc3adeltaEC Ad inhibited the induction of adherens junctions and the subsequent formation of desmosomes with the calcium shift, while Dsg3deltaEC Ad only inhibited the formation of desmosomes. To further determine whether Dsc3adeltaEC directly affected adherens junctions, mouse fibroblast L cells transfected with E-cadherin (LEC5) were infected with these mutant Ads. Both Dsc3adeltaEC and EcaddeltaEC inhibited the cell-cell adhesion of LEC5 cells, as determined by the cell aggregation assay, while Dsg3deltaEC did not. These results indicate that the dominant negative effects of Dsg3deltaEC were restricted to desmosomes, while those of Dsc3adeltaEC were observed in both desmosomes and adherens junctions. Furthermore, the cytoplasmic domain of Dsc3adeltaEC coprecipitated both plakoglobin and beta-catenin in HaCaT cells. In addition, beta-catenin was found to bind the endogenous Dsc in HaCaT cells. These findings lead us to speculate that Dsc interacts with components of the adherens junctions through beta-catenin, and plays a role in nucleating desmosomes after the adherens junctions have been established.

Epiregulin, a novel member of the epidermal growth factor family, is an autocrine growth factor in normal human keratinocytes

Epiregulin is a new member of the epidermal growth factor (EGF) family purified from conditioned medium of NIH-3T3 clone T7. Some EGF family growth factors play essential roles in human keratinocytes in an autocrine manner. We show here that epiregulin is another autocrine growth factor for human keratinocytes. Epiregulin stimulated human keratinocyte proliferation under both subconfluent and confluent culture conditions in the absence of exogenous EGF family growth factors. Immunoprecipitation of [(35)S]methionine-labeled conditioned medium revealed a 5-kDa band corresponding to epiregulin. Northern blot analysis detected a 4. 8-kilobase transcript of epiregulin, and the addition of epiregulin up-regulated epiregulin mRNA synthesis. Furthermore, an anti-epiregulin blocking antibody reduced DNA synthesis by 25%. Epiregulin up-regulated the mRNA levels of heparin-binding EGF-like growth factor (HB-EGF), amphiregulin, and TGF-alpha. In turn, the addition of EGF, HB-EGF, amphiregulin, and TGF-alpha increased epiregulin mRNA levels. These results demonstrate that epiregulin acts as an autocrine growth factor in human epidermal keratinocytes and is part of auto- and cross-induction mechanisms involving HB-EGF, amphiregulin, and TGF-alpha. The mRNA expression profile resulting from induction of differentiation with high calcium and fetal calf serum revealed the differential expression of epiregulin, HB-EGF, amphiregulin, and TGF-alpha in keratinocytes. This indicates that these four growth factors have distinct, non-redundant biological functions.

Expression of vitamin D receptor in cultured human keratinocytes and fibroblasts is not altered by corticosteroids

Topical vitamin D3 therapy is one of the mainstays of psoriasis treatment. However, the effectiveness of combination therapy with topical vitamin D3 and corticosteroids is still controversial. It has been reported that topical vitamin D3 treatment following topical corticosteroids is less effective than that without preceding corticosteroid treatment. We hypothesized that vitamin D receptor (VDR) in the skin is down-regulated by topical corticosteroids. To obtain support for this hypothesis, we determined VDR protein levels in cultured keratinocytes and fibroblasts after corticosteroid treatment. VDR levels were quantified by Western blot analysis with a Fluorolmager. Keratinocytes and fibroblasts were obtained from four psoriasis patients and four normal controls. VDR levels were altered in neither normal nor psoriatic keratinocytes by 2-day incubation with dexamethasone (1x10(-9)-1x10(-6) M) or clobetasol propionate (1x10(-9)-1x10(-6) M). Similarly, VDR levels in normal and psoriatic fibroblasts were not affected by 2-day incubation with dexamethasone (1x10(-6) M). These findings suggest that down-regulation of VDR by topical corticosteroids in keratinocytes and fibroblasts of psoriasis is unlikely.

Possible involvement of p21 but not of p16 or p53 in keratinocyte senescence

It has been reported that p21, p53, and p16 affect the cell cycle and cell senescence. However, their roles in keratinocyte senescence are not clear. We established primary keratinocyte strains from 15 donors and maintained them until replicative senescence; their population doublings ranged from 5.7-45.2. These strains were classified based on their population doublings as short (5.7-10.4), intermediate (13.9-17.4), and long (21.5-45.2). To investigate the roles of p21, p53, and p16 in the cellular senescence of the cultured keratinocytes, we quantitatively analyzed p21, p53, and p16 levels of keratinocyte strains with different life spans by Western blot with Fluorol mager. p21 levels increased in the senescent phase but not in the nonsenescent phase in all of the short, intermediate, and long life-span strains. Northern blot analysis also revealed induction of p21 mRNA was similar to that of p21 protein levels. There were no apparent differences in p53 levels between senescent and nonsenescent cells. The short life-span strains exhibited a significant increase in p16 levels in the senescent phase (eighth or tenth passage). However, in two long life-span strains, p16 levels were increased in the nonsenescent phase (eighth passage) but then declined as the cells reached senescence (twenty-seventh passage). Therefore, induction of p16 appeared not to be associated with senescence in long life-span strains. In conclusion, p21 but not p16 or p53 may play roles in keratinocyte senescence.

Food-dependent exercise-induced anaphylaxis: a case related to the amount of food allergen ingested

A 24-year-old Japanese woman had suffered for 2 years from attacks of urticaria, dyspnoea and syncope associated with exercise after the ingestion of wheat. Specific IgE measurements revealed RAST class 2 for wheat and gluten (a major wheat protein), and class 3 for rye. Skin prick tests with wheat, bread, gluten and udon (a Japanese noodle made of wheat) were all positive. Food-dependent exercise-induced anaphylaxis (FDEIA) caused by wheat was suspected. Challenge tests with bread were performed. Exercise following ingestion of 64 g, but not 45 g, of bread induced generalized urticaria. Challenge tests with udon also triggered allergic reaction in a dose-dependent manner: 200 g, but not 100 g or 150 g, of udon elicited wealing and erythema with exercise. Ingestion of bread or udon alone failed to elicit any allergic reaction. This is the first case of FDEIA in which the dependence of the triggering allergic reaction on the amount of allergen ingested was clearly confirmed.

Lack of mucosal involvement in pemphigus foliaceus may be due to low expression of desmoglein 1

Oral mucosal lesions are seen in most cases of pemphigus vulgaris, whereas they are only rarely seen in pemphigus foliaceus; however, both pemphigus vulgaris and pemphigus foliaceus sera show positive immunofluorescence staining on oral mucosa. To explain this apparent paradox, we examined the expression level of desmoglein (Dsg)3, pemphigus vulgaris antigen, and Dsg1, pemphigus foliaceus antigen, in human squamous mucosal epithelia and epidermis by immunofluorescence staining and immunoblotting. For immunofluorescence staining, Dsg isotype-specific antibodies were produced by immunoadsorbing pemphigus vulgaris sera with either recombinant Dsg1 or Dsg3 baculoprotein. In oral mucosa and esophagus both Dsg were immunoreactive on cell surfaces throughout the entire epithelia, but staining intensity was weaker for Dsg1 than for Dsg3. Immunoblotting was performed to compare Dsg1 and Dsg3 expression levels in extracts from epidermis and oral mucosa. The total amount of desmosomal proteins applied was adjusted to give the same degree of staining intensity for desmoplakin, a cytoplasmic plaque protein of desmosomes. In the mucosal extract, the Dsg1 band was much weaker than Dsg3, whereas in the epidermal extract the Dsg1 band was stronger than Dsg3. These data suggest that although Dsg1 and Dsg3 are expressed in a similar distribution throughout squamous mucosal epithelia, Dsg1 is expressed at a much lower level than Dsg3. This finding provides a good explanation for the paradox: even though anti-Dsg1 autoantibodies block the function of Dsg1 in the mucosal epithelia, Dsg3 may be sufficient for cell-cell adhesion, with consequently no apparent oral involvement in pemphigus foliaceus patients.