Keratinocytes In Psoriasis Research Articles

Función efectora de linfocitos T CLA+ sobre queratinocitos autólogos en psoriasis

BackgroundCutaneous lymphocyte antigen (CLA) is expressed by a subgroup of memory T cells that exhibit skin homing and are implicated in cutaneous T-cell-mediated diseases. Material and methodsExpression of genes associated with psoriasis was analyzed in keratinocytes taken from patients and healthy individuals and cultured under different conditions, including activation using supernatants from CLA+ T lymphocytes activated with anti-CD3 and anti-CD28 antibodies. ResultsKeratinocytes from psoriasis patients activated by CLA+ T lymphocytes expressed higher levels of interferon-inducible protein 10, HLA-DR, intercellular cell adhesion molecule 1, and inducible nitric oxide synthase. ConclusionsOur results suggest that we have developed an in vitro model that will allow analysis of the effector role of CLA+ T lymphocytes on keratinocytes in psoriasis. This model may allow the identification of genes involved in the pathology of psoriasis through induction by CLA+ T lymphocytes.

Innate immune modulation of keratinocytes by antikeratin 16 antibodies

Chronic inflammation of psoriatic lesions may be due to an exaggerated innate immune response. Toll-like receptors (TLRs) are expressed by keratinocytes in psoriasis. Antikeratin 16 autoantibodies (AK16 autoAbs) are increased in serum from patients with psoriasis. Whether the elevated AK16 autoAbs play a role in psoriasis by exaggerating innate immune response is still unknown. To prove that AK16 autoAbs are involved in psoriasis, by exaggerating the innate immune response of keratinocytes. Keratinocytes were incubated with mouse antikeratin 16 monoclonal antibodies (AK16 mAbs) for a given length of time. Levels of TLR2, TLR4, involucrin and nascent polypeptide-associated complex (NACA) mRNA were measured by quantitative RT-PCR. Levels of TLR2, TLR4, involucrin, NF-kappaB and actin-related protein 2 (ARP2) protein were measured by flow cytometry or Western blot. Effects of the mAbs on keratinocytes were studied using DNA synthesis and cell cycle analysis. TLR2 mRNA increased 1.73-, 1.60- and 2.52-fold at 6, 24 and 36 h after incubation, respectively. TLR4 mRNA increased 3.62- and 2.21-fold after 12 and 36 h. Involucrin mRNA increased 2.33- and 2.0-fold after 12 and 36 h. NACA mRNA increased 5.93-, 3.35- and 3.54-fold after 12, 24 and 36 h. TLR2 protein increased 1.73-fold on the cell membrane and 2.22-fold on membrane plus intracytoplasm. NF-kappaB increased 2.64-fold after 6 h. Involucrin protein increased 4.5-fold, whereas Arp2 protein decreased 1.82-fold, after 36 h. The mAbs had an inhibitory effect on cultured keratinocytes. AK16 autoAbs may be involved in the chronic inflammation of psoriasis lesions by promoting TLR expression.

Expression of the L-fucose moiety on epidermal keratinocytes in psoriasis induced by the Koebner phenomenon: a sequential study.

The expression of Ulex europaeus agglutinin (UEA I) binding sites on cell-surface glycoproteins has been used as a marker for terminal differentiation. Increased number of UEA I binding sites of L-fucose specificity have been demonstrated in psoriatic epidermis. The results of lectin-binding studies in a series of biopsies taken sequentially (0 min, 5 min, 24 h, 7 days and 8 weeks) after tape-stripping of uninvolved skin in 12 psoriatic patients (three of whom were taking diltiazem, a calcium blocker at the time of the study) and six controls are presented. UEA I binding sites, which were expressed on the granular layer and upper layers of the stratum spinosum of pre-tape stripped uninvolved skin in psoriatic individuals, were progressively more numerous, with the expression of the L-fucose moiety on the lower stratum spinosum keratinocytes in the 7-day post-tape-stripping biopsies and 8-week biopsies, correlating with a moderate and marked increase in the proliferative index, respectively. In the Koebner-negative and non-psoriatic individuals who failed to develop psoriasis after tape-stripping, the UEA I binding sites were not expressed on keratinocytes of the lower stratum spinosum in any of the biopsies, although a mild increase in the proliferative index was noted in the 7-day biopsies. Our data suggest that the increased commitment of keratinocytes to terminally differentiate may be involved in the psoriatic process.(ABSTRACT TRUNCATED AT 250 WORDS)

Effector Function of CLA+ T Lymphocytes on Autologous Keratinocytes in Psoriasis

Background Cutaneous lymphocyte antigen (CLA) is expressed by a subgroup of memory T cells that exhibit skin homing and are implicated in cutaneous T-cell-mediated diseases. Material and methods Expression of genes associated with psoriasis was analyzed in keratinocytes taken from patients and healthy individuals and cultured under different conditions, including activation using supernatants from CLA + T lymphocytes activated with anti-CD3 and anti-CD28 antibodies. Results Keratinocytes from psoriasis patients activated by CLA + T lymphocytes expressed higher levels of interferon-inducible protein 10, HLA-DR, intercellular cell adhesion molecule 1, and inducible nitric oxide synthase. Conclusions Our results suggest that we have developed an in vitro model that will allow analysis of the effector role of CLA + T lymphocytes on keratinocytes in psoriasis. This model may allow the identification of genes involved in the pathology of psoriasis through induction by CLA + T lymphocytes.

Overexpression of vascular endothelial growth factor (VEGF) receptors on keratinocytes in psoriasis: regulated by calcium independent of VEGF

Psoriasis is a common chronic inflammatory disease of the skin characterized by epidermal hyperplasia and angiogenesis. Recently, vascular endothelial growth factor receptors (VEGFRs, including VEGFR-1, VEGFR-2 and VEGFR-3) were found to be expressed in normal human epidermis and associated with proliferation and migration of keratinocytes. The purpose of this study is to investigate the expression of VEGFRs on psoriatic keratinocytes and the roles of calcium and VEGF in regulating VEGFR expression. Skin samples from 17 patients with chronic plaque psoriasis and 11 normal controls were included. The expression of VEGFRs in psoriatic keratinocytes at mRNA and protein levels was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis. Localization of the VEGFRs in skin lesions was determined by immuno-fluorescent method. Since keratinocyte proliferation and differentiation rely on calcium concentrations, and VEGF is overexpressed in psoriatic epidermis, we further investigated the roles of calcium and VEGF in regulating the expression of VEGFRs. Overexpression of VEGFR-1, VEGFR-2 and VEGFR-3 in psoriatic epidermis was demonstrated both at mRNA and protein levels in vitro. VEGFRs were strongly labeled in non-lesional, perilesional and lesional psoriatic keratinocytes in all viable epidermal stratums in vivo. Furthermore, both exogenous VEGF165 and calcium enhanced the expression of VEGFRs. Calcium also enhanced the expression of VEGF in non-lesional psoriatic keratinocytes, while targeted blockade of VEGF activity by bevacizum-ab could not inhibit calcium-induced up-regulation of protein levels of VEGFRs. We conclude from these results that VEGFRs are overexpressed in lesional psoriatic epidermal keratinocytes. Both calcium and VEGF regulate VEGFRs expression in psoriatic epidermis. More importantly, calcium is a potential regulator for VEGFR independent of VEGF.

Elevated serum levels of calcium-binding S100 proteins A8 and A9 reflect disease activity and abnormal differentiation of keratinocytes in psoriasis

The expression of calcium-binding S100 molecules organized within the epidermal differentiation complex on chromosome 1q21 is disturbed in hyperproliferative skin diseases such as psoriasis. We studied whether serum levels of S100 proteins A8 (S100A8) and A9 (S100A9) are elevated in psoriasis, correlated their amounts with disease activity and identified potential cellular sources. Serum obtained from psoriasis patients or from healthy individuals was studied for S100A8 and S100A9 levels by enzyme-linked immunosorbent assay. Data were correlated to disease activity as reflected by the Psoriasis Area and Severity Index (PASI). Cellular sources of S100A8 and S100A9 were identified by in situ hybridization and immunohistochemistry of lesional psoriatic and nonlesional, nonpsoriatic skin. A significant increase of S100A8/S100A9 serum levels was found in patients with psoriasis compared with healthy controls. Grading the patients into two groups of severity, individuals with a PASI of <15 showed serum levels of 705+/-120 ng mL-1 (mean+/-SEM, n=18), those with a PASI of >or=15 showed levels of 1315+/-150 ng mL-1 (n=32) while controls presented with 365+/-50 ng mL-1. Performing in situ hybridization of lesional psoriatic skin we detected a dramatic induction of both S100A8 and S100A9 mRNA and protein primarily in the suprabasal layers of the epidermis while expression was negligible in nonlesional, nonpsoriatic interfollicular epidermis. Our data demonstrate that hyperproliferation and abnormal differentiation of psoriatic skin is associated with a massive upregulation and secretion of S100A8 and S100A9, suggesting not only a prominent role of these molecules during intracellular calcium-dependent signalling but also implying distinct extracellular functions.

Psoriasis: dysregulation of innate immunity

The current understanding of the function of natural killer (NK) T cells in innate immunity and their potential to control acquired specific immunity, as well as the remarkable efficacy of antitumour necrosis factor-alpha biological treatments in psoriasis, forces us to refine the current T-cell hypothesis of psoriasis pathogenesis, and to give credit to the role of innate immunity. Psoriasis might be envisioned to be a genetically determined triggered state of otherwise dormant innate immunity. This aggravated state of innate immunity is represented by the activity of NK T cells, dendritic cells, neutrophils and keratinocytes, leading to the recruitment and activation of preferentially type 1 T cells, possibly in an antigen-independent way. Keratinocytes in psoriasis then are sensitive to the effects of T-cell activation and cytokine production, interferon (IFN)-gamma, by responding with psoriasiform hyperplasia. The chronic inflammation of psoriatic lesions suggests that this might be due to a deficiency in downregulation processes (e.g. a defect in the regulatory T-cell repertoire) and/or the persistence of an unknown trigger resulting in an exaggerated innate immune response.

Immunohistochemical analysis of keratinocyte growth factor and fibroblast growth factor 10 expression in psoriasis

The pathogenic mechanism underlying the hyperproliferation of keratinocytes in psoriasis is still not completely clarified. The production of cytokines released by activated T lymphocytes infiltrating the upper dermis probably has a crucial role. Even dermal fibroblasts can participate in the process through the secretion of growth factors, and some studies have reported an increased expression of the insulin-like growth factor 1. Few studies, however, have focused on the possible involvement of the keratinocyte growth factor (KGF/FGF-7) and the fibroblast growth factor 10 (FGF-10/KGF-2), which are secreted by fibroblasts and stimulate keratinocyte proliferation acting through a receptor specifically expressed by epithelial cells. The aim of this study was to investigate the expression of KGF and FGF-10 on the skin of patients with psoriasis by immunohistochemical analysis and to evaluate the correlation with the lymphocyte infiltrate and the epidermal proliferation. Immunostaining for KGF and FGF-10 showed that both the growth factors are upregulated in the upper dermis of psoriatic skin, and that the expression is correlated with the presence of T-cell infiltrate and with keratinocyte proliferation. Our data suggest that in psoriatic lesions activated lymphocytes can stimulate fibroblasts to produce KGF and FGF-10, which in turn contribute to sustain the hyperproliferative status of the keratinocytes.

Expression of Krox‐20 is Increased in Psoriasis

Psoriasis is a common and chronic inflammatory skin disease that afflicts 2–3% of the world population. There is no cure and the precise cause of psoriasis is unknown. Cytokines however, have been established as critical mediators in the immunopathogenesis of psoriasis. EGR‐2 is an immediate early serum response gene that codes for Krox‐20, a zinc finger transcription factors that is important in resisting TGF‐? mediated apoptosis. The aim of this study was to evaluate Krox‐20 expression in epidermal keratinocytes in psoriasis where aberrant response to TGF‐? signaling has been shown to occur. Formalin‐fixed paraffin‐embedded tissue (N = 38) including nine psoriatic plaques (PP), nine lichen planus (LP), ten lichen simplex chronicus (LSC), and ten normal skin (NS) were evaluated for expression of Krox‐20 by immunohistochemistry. Frequency and relative intensity of nuclear labeling were evaluated. Strong and diffuse nuclear labeling of keratinocytes was observed in all PP and LSC. The frequency of labeling was significantly greater (p &lt; 0.05) in PP and LSC compared to NS. Lichen planus tended toward absent to weak nuclear labeling of keratinocytes. The increased frequency of Krox‐20 expression in PP and LSC may lead to resistance of TGF‐? mediated apoptosis and contribute to epidermal hyperplasia common to these disorders.

Aberrant signalling and transcription factor activation as an explanation for the defective growth control and differentiation of keratinocytes in psoriasis: a hypothesis.

Psoriasis is a chronic inflammatory skin disease characterized by the accumulation of red, scaly plaques on the skin. The plaques result from hyperproliferation and incomplete differentiation of keratinocytes (KC) in a process that seems to be driven, in part by skin-infiltrating leucocytes. We believe that the KC have inherent defects in intracellular signalling which could be usefully targeted to allow the development of more effective therapies. We suggest that there are defects in the regulation of the transcription factors: signal transducer and activator of transcription (STAT-1alpha), interferon regulated factor-1 (IRF-1) and NFkappaB which lead to loss of growth and differentiation control when the cells are subjected to physico-chemical and immunological stress. We also highlight recent studies that suggest that peroxisome proliferator-activated receptors, the notch receptor and defects in calcium and other ion transporting proteins may contribute to impairment in the ability of psoriatic KC to differentiate. The role of these systems in the development of the psoriatic phenotype and tests of these hypotheses are proposed.

Matrix metalloproteinase-19 is expressed by keratinocytes in psoriasis.

Keratinocyte hyperproliferation, inflammatory infiltrates, neoangiogenesis and alterations in cytokine levels are hallmarks of psoriatic skin. Matrix metalloproteinases (MMPs) have been associated with the remodeling of the extracellular matrix during inflammation, neovascularization, and malignant transformation. We have previously shown that particularly MMP-12 is abundantly expressed by macrophages and MMP-9 in macrophages and neutrophils of psoriatic lesions. In this work the expression of two novel metalloproteinases, MMP-19 and MMP-28, was investigated in psoriatic lesional and non-lesional skin. MMP-19 protein was detected by immunohistochemistry in 28/29 samples in keratinocytes in the same regions as Ki67 (marker of proliferating keratinocytes) and p63 (marker of keratinocyte stem cells). Immunosignaling was also seen in endothelial cells and fibroblasts. Furthermore, MMP-19 mRNA was upregulated in psoriatic keratinocytes and skin as assessed by quantitative real-time polymerase chain reaction. In lichen planus and lichenoid chronic dermatitis, MMP-19 staining was found in keratinocytes in areas where the basement membrane was abnormal. MMP-28 was not detected in psoriatic or non-lesional skin. Our results suggest that keratinocytes as well as the previously reported cell types (smooth muscle, endothelial and macrophages) can express MMP-19 in psoriasis and lichen planus. Upregulation of MMP-19 in keratinocytes may be influenced by changes in the architecture of the basement membrane zone.

Overexpression of CD1d by keratinocytes in psoriasis and CD1d-dependent IFN-gamma production by NK-T cells.

The MHC class I-like protein CD1d is a nonpolymorphic molecule that plays a central role in development and activation of a subset of T cells that coexpress receptors used by NK cells (NK-T cells). Recently, T cells bearing NK receptors were identified in acute and chronic lesions of psoriasis. To determine whether NK-T cells could interact with epidermal cells, we examined the pattern of expression of CD1d in normal skin, psoriasis, and related skin disorders, using a panel of CD1d-specific mAbs. CD1d was expressed by keratinocytes in normal skin, although expression was at a relatively low level and was generally confined to upper level keratinocytes immediately beneath the lipid-rich stratum corneum. In contrast, there was overexpression of CD1d in chronic, active psoriatic plaques. CD1d could be rapidly induced on keratinocytes in normal skin by physical trauma that disrupted barrier function or by application of a potent contact-sensitizing agent. Keratinocytes displayed enhanced CD1d following exposure to IFN-gamma. Combining CD1d-positive keratinocytes with human NK-T cell clones resulted in clustering of NK-T cells, and while no significant proliferation ensued, NK-T cells became activated to produce large amounts of IFN-gamma. We conclude that CD1d can be expressed in a functionally active form by keratinocytes and is up-regulated in psoriasis and other inflammatory dermatoses. The ability of IFN-gamma to enhance keratinocyte CD1d expression and the subsequent ability of CD1d-positive keratinocytes to activate NK-T cells to produce IFN-gamma, could provide a mechanism that contributes to the pathogenesis of psoriasis and other skin disorders.

Keratinocytes Express the CD146 (Muc18/S-Endo) Antigen in Tissue Culture and During Inflammatory Skin Diseases

The CD146 (or MUC18/MEL-CAM) antigen is a cell adhesion molecule of the immunoglobulin superfamily. Besides in melanoma, expression of CD146 antigen has been demonstrated in breast epithelia and hair follicles. We studied its expression by human keratinocytes in culture as well as in neoplastic and inflammatory skin diseases. Staining of primary cultured keratinocytes revealed expression of CD146 on the cell membrane, preferentially on cell-cell contact sites. Western blot analysis of keratinocytes detected a band of approximately 113 kDa, corresponding to the CD146 protein. In contrast to primary keratinocytes, neither CD146 protein nor mRNA expression was found in the keratinocyte-derived cell lines A431 and HaCaT. Treatment of keratinocytes with the proinflammatory cytokines interleukin-1 and interleukin-6, tumor necrosis factor-alpha, and interferon-gamma, resulted in no change of CD146 expression and incubation with phorbol 12-myristate 13-acetate led to a reduction of CD146 on keratinocytes. By contrast, when culturing keratinocytes in medium devoid of growth supplements, a distinct upregulation was observed as compared with culture in fully supplemented medium. In normal human epidermis expression of the CD146 antigen was not detectable. It was strongly upregulated, however, on suprabasal keratinocytes in psoriasis, in lichen planus, in the epidermis overlying skin neoplasms, and in viral warts. In squamous cell carcinomas and basal cell carcinomas only a minority of tumor cells expressed CD146. Our findings suggest that the CD146 antigen represents an activation marker of keratinocytes and may be involved in cutaneous inflammatory tissue reaction.

Flow-cytometric characterization of normal versus psoriatic epidermis using improved cell separation methodology.

Recently a new approach for epidermal cell characterization was developed: three-parameter flow cytometrical analysis of pure and complete epidermal cell suspensions prepared from punch biopsies followed by dermoepidermal separation by thermolysin. The aim of the present communication is the comparison between psoriatic lesional skin and normal skin using this new approach with respect to the percentage of suprabasal keratinocytes (keratin 10+ cells), mesenchymal cells, including the infiltrate cells (vimentin+ cells) and the percentage of basal cells in SG2 M phase, in order to validate this methodology in studies on psoriatic skin. Punch biopsies were taken from 7 healthy volunteers and in 7 psoriatic patients 4 biopsies were taken in each of them from comparable lesions. The present study reconfirmed that the percentage of basal keratinocytes in psoriasis was increased and the percentage of keratin 10+ cells was substantially decreased as compared to normal skin. The new methodology revealed data with a narrow range. In psoriatic lesional skin the intra individual variation was less compared to the inter individual variation.

Changes in Keratin 6 and Keratin 10 (Co-)Expression in Lesional and Symptomless Skin of Spreading Psoriasis

Background: Keratin 6 (K6) and keratin 10 (K10) are markers for epidermal hyperproliferation and differentiation, respectively, and are both expressed in the suprabasal layers of the epidermis. They may be co-expressed in different stages of the spreading psoriatic lesion, but single expression can also occur. Objective: To investigate to what extent keratinocytes express K6 and K10, and to what extent they co-express K6 and K10 in different stages of the psoriatic lesion. We studied this in spreading psoriatic plaques. Methods: Three 3-mm punch biopsies were obtained from the inner involved margin of a spreading lesion, from the uninvolved skin immediately adjacent to the spreading plaque, and from the distant uninvolved skin of 8 patients with incipient psoriasis. From 9 healthy volunteers, 3-mm punch biopsies were obtained as controls. After preparation of single cell suspensions of these biopsies, a triple staining protocol was performed with markers for K6 (monoclonal antibody LHK6B), K10 (monoclonal antibody RKSE60) and DNA content (TO-PRO-3 iodide). Subsequently, cells were measured with a flow cytometer and the proportion of the markers was calculated using specific software. Results: We observed a population of K6/K10-co-expressing cells, but also populations expressing only K6. These subpopulations varied with the involvement of the lesion. There was a statistically significant difference between the inner margin and the outer margin with respect to the proportion of K6- and K10-expressing cells, whereas more K6-positive and K10-negative cells were detected in the inner margin of the lesions. The proportion of K6/K10-co-expressing cells in the inner margin was significantly different from the distant uninvolved skin. Conclusion: We confirmed that individual keratinocytes in psoriasis can express K6 or K10 depending on their localization in involved or uninvolved skin. There is a unique subpopulation of cells in the psoriatic plaques which co-express K6 and K10. More studies are required to fully understand the pathogenic relevance of co-expression and single expression of K6 and K10.

Human Keratinocytes Constitutively Express Interleukin-18 and Secrete Biologically Active Interleukin-18 After Treatment with Pro-Inflammatory Mediators and Dinitrochlorobenzene

Interleukin-18 is a potent inducer of interferon-gamma by activated T cells, macrophages, and monocytes and is synthesized as an inactive precursor. Pro-interleukin-18 must be cleaved by interleukin-1-beta-converting enzyme for secretion of the biologically active form. We report that among selected non-bone marrow derived skin cells, interleukin-18 mRNA is constitutively expressed by human keratinocytes and not by dermal microvascular endothelial cells, dermal fibroblasts, or melanocytes. Interleukin-18 mRNA and intracellular protein levels are neither changed in human keratinocytes nor induced in human dermal microvascular endothelial cells, dermal fibroblasts, or melanocytes by exposure to pro-inflammatory stimuli. Exposure of human keratinocytes to phorbol 12-myrisate 13-acetate, lipopolysaccharides or the contact sensitizer DNCB results in the secretion of immunoprecipitable interleukin-18 protein. Human keratinocyte-secreted interleukin-18 is biologically active, in that conditioned media from phorbol 12-myrisate 13-acetate, lipopolysaccharide and DNCB-treated human keratinocytes induce interferon-gamma expression by peripheral blood mononuclear cells. This bioactivity is neutralized by anti-interleukin-18, but not anti-interleukin-12 antibodies. By immunohistochemistry, interleukin-18 protein is detected in basal keratinocytes of normal human skin, but its expression is markedly upregulated in suprabasal keratinocytes in psoriasis. These findings indicate that human keratinocytes are a source of biologically functional interleukin-18 and thus are capable of playing an initiating part in the local interferon-gamma-dependent inflammatory processes through expression, activation, and secretion of interleukin-18.

Keratin 15 Expression in Stratified Epithelia: Downregulation in Activated Keratinocytes

Keratin 15 (K15) is a type I keratin without a defined type II partner whose expression in epidermal diseases has not been investigated. In this study we have used LHK15, a monoclonal antibody raised against the last 17 amino acids of the K15 polypeptide, to show that K15 is expressed primarily in the basal keratinocytes of stratified tissues, including the fetal epidermis and fetal nail. Although K15 in normal hair follicles was virtually absent from hair bulbs, it was expressed by a subset of keratinocytes in the outer root sheath. By comparison, K14 expression was found throughout the outer root sheath of hair follicles; however, when both K14 alleles were naturally ablated, the expression of K15 was also observed throughout the outer root sheath of the follicles. Expression of K15 mRNA was assessed by in situ hybridization and corroborated the data from immunostaining. An increase in K15 mRNA and protein expression in hair follicles from the K14 ablated epidermis suggested an upregulation of the K15 gene in the absence of the K14 protein. In organotypical cultures where differentiating keratinocytes expressed markers of activated phenotype, i.e., K6 and K16, expression of K15 was undetectable. The expression of K15 mRNA and protein was also downregulated in two hyperproliferating situations, psoriasis and hypertrophic scars. Because keratinocytes in psoriasis and hypertrophic scars are activated, we conclude that K15 expression is not compatible with keratinocyte activation and the K15 gene is downregulated to maintain the activated phenotype.

Differential proliferation of endothelial cells and keratinocytes in psoriasis and spongiotic dermatitis.

This study used MIB-1 monoclonal antibody to quantify the proliferating keratinocytes and endothelial cells and their proliferation fractions in cases of normal skin, acute and established plaque psoriasis, and acute and chronic spongiotic dermatitis. The number and the proliferation fraction of MIB-1 positive cells were higher in psoriatic and chronic spongiotic lesions than in normal skin (p < 0.05). Established plaque psoriasis had a higher number of proliferating keratinocytes and a higher keratinocytic proliferation fraction than did acute psoriasis (p < 0.05). The number of proliferating endothelial cells decreased as acute psoriatic lesion became chronic, but the number in acute spongiotic lesion increased as it became chronic. The endothelial proliferation fraction was higher in acute psoriasis than in established plaque psoriasis (p < 0.05). The ratio of keratinocytic proliferation fraction to endothelial cell proliferation fraction of the psoriatic and spongiotic lesions suggested the presence of different reaction patterns to inflammation in psoriasis and spongiotic dermatitis.

Regulation of 12-lipoxygenase expression by epidermal growth factor in human epidermoid carcinoma A431 cells.

Arachidonate 12-lipoxygenase in the platelet was the first mammalian lipoxygenase discoverved1. It catalyzes the transformation of arachidonic acid into 12(S)-hydroperoxyeicosatetraenoic acid, which is subsequently converted to 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) by a glutathione-dependent peroxidase2. We recently identified a human 12-lipoxygenase as the platelet-type enzyme in human epidermoid carcinoma A431 cells, and found that epidermal growth factor (EGF) increased the 12-lipoxygenase mRNA level by about 2-fold with a lag peroid of 10 h, which was parallel to the increase in enzyme activity3. This was the first evidence indicating the inducibility of a human 12-lipoxygenase gene expression by growth factor. In studying the signal transduction of EGF in the induction of 12-lipoxygenase expression, we recently reported the possible involvement of protein kinase C activation in the expression of EGF-induced 12-lipxoygenase4. The biological activities of 12(S)-HETE induces the expression of glycoprotein Ilb-IIIa on the cell membrane of Lewis lung carcinoma cells5 and may also play a significant role in the pathogenesis of some epidermal and epithelial inflammation6. Takahashi et al.7 identified 12-lipoxygenase in human epidermal cells as a platelet-type enzyme and Hussain et al.8 recently found an overexpression of the human platelet-type 12-lipoxygenase in germinal layer keratinocytes in psoriasis.

Epidermal expression of 65 and 72 kd heat shock proteins in psoriasis and AIDS-associated psoriasiform dermatitis

Background: Psoriasiform dermatitis is common in patients with AIDS. The expression of heat shock proteins by keratinocytes has been postulated to be a significant factor in the physiopathology of psoriasis and might be subject to modulation in HIV-infected patients. Objective: We sought to evaluate the epidermal expression of 65 and 72 kd heat shock proteins (HSPs) in lesions of AIDS-associated psoriasiform dermatitis (AIDS-PD) and compare it with that in psoriasis vulgaris and seborrheic dermatitis in patients not infected with HIV. Methods: Sections from paraffin-embedded blocks of biopsy specimens of AIDS-PD (eight cases), psoriasis vulgaris (eight cases), seborrheic dermatitis (four cases), and normal skin (four cases) in non-HIV-infected patients were immunohistochemically stained by the avidin-biotin-peroxidase method and two monoclonal antibodies directed against the major 65 kd HSP antigen (HSP65) and against 70 72 kd HSP. The intensity, distribution, and cellular pattern of the epidermal stain were graded and assessed blindly. Results: The epidermal expression of HSP65 in biopsy specimens from AIDS-PD lesions was irregular, with less intensity and less tendency to perinuclear arrangement than in psoriasis or seborrheic dermatitis not associated with AIDS. The expression of HSP72 was also less intense and more uniform in AIDS-PD. Conclusion: The altered interplay of T cells and keratinocytes in a situation of immune derangement such as AIDS might account for the differences observed in the expression of HSP65 and HSP72 by keratinocytes in psoriasis and AIDS-PD.