Discordant expression of Bcl-x and Bcl-2 by keratinocytes in vitro and psoriatic keratinocytes in vivo.

Apoptosis is a required event in maintaining kinetic homeostasis within continually renewing tissues such as skin. However, no systematic study of the apoptotic process in epidermal keratinocytes of the skin has been performed. In this report, we examined the expression of proteins associated with promoting (Fas) or preventing (Bcl-2, Bcl-x, CD40) apoptosis in the normal, psoriatic, and malignant keratinocyte. Immunohistochemical staining and flow cytometry analysis revealed that normal cultured keratinocytes express low levels of Fas, CD40, and Bcl-x that was enhanced by cytokines including gamma-interferon (IFN-gamma) and a phorbol ester tumor promoter, TPA. Only faint Bcl-2 staining was detected in cultured keratinocytes exposed to IFN-gamma and TPA compared with the prominent expression of Bcl-x. Biopsies of normal skin, psoriatic plaques, and basal cell carcinomas were examined to extend the in vitro observations. Immunohistochemical staining revealed that while keratinocytes in normal epithelium express low to absent levels of Fas and Bcl-x, psoriatic keratinocytes expressed significantly higher levels of Fas and Bcl-x. In contrast, malignant keratinocytes in basal cell carcinomas expressed high levels of Bcl-2, but minimal Bcl-x, and no Fas. Immunoblot analysis revealed that the long form of Bcl-x (Bcl-xI), which prevents apoptosis in lymphocytes, is expressed by cultured keratinocytes and psoriatic plaque keratinocytes. We conclude that normal cytokine-activated keratinocytes can express an apoptotic (Fas) and an anti-apoptotic protein (Bcl-x). The overexpression of Bcl-x in psoriasis, or Bcl-2 in basal cell carcinomas, may contribute to the longevity of these cells by blocking the normal apoptotic process involved in the terminal differentiation program of epidermal keratinocytes.     

Apoptosis and Accidental Cell Death in Cultured Human Keratinocytes after Thermal Injury

The respective roles of apoptosis and accidental cell death after thermal injury were evaluated in normal human epidermal keratinocytes. By coupling the LIVE/DEAD fluorescence viability assay with the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method and ultrastructural morphology, these two processes could be distinguished. Cells were grown on glass coverslips with a microgrid pattern so that the results of several staining procedures performed sequentially could be visualized in the same cells after heating at temperatures of up to 72°C for 1 second. After exposure to temperatures of 58 to 59°C, cells died predominantly by apoptosis; viable cells became TUNEL positive, indicating degradation of DNA. After exposure to temperatures of 60 to 66°C, both TUNEL-positive viable cells and TUNEL-positive nonviable cells were observed, indicating that apoptosis and accidental cell death were occurring simultaneously. Cells died almost immediately after exposure to temperatures above 72°C, presumably from heat fixation. The fluorescent mitochondrial probe MitoTracker Orange indicated that cells undergoing apoptosis became TUNEL positive before loss of mitochondrial function. Nucleosomal fragmentation of DNA analyzed by enzyme-linked immunosorbent assay and gel electrophoresis occurred after exposure to temperatures of 58 to 59°C. The characteristic morphological findings of cells undergoing apoptosis, by transmission electron microscopy, included cellular shrinkage, cytoplasmic budding, and relatively intact mitochondria. Depending on temperature and time of exposure, normal human epidermal keratinocytes may die by apoptosis, accidental cell death, or heat fixation.     

Induction of apoptosis underlies the Radix Rubiae-mediated anti-proliferative action on human epidermal keratinocytes: implications for psoriasis treatment

Psoriasis is a chronic inflammatory skin disease characterized histologically by hyperproliferation and aberrant differentiation of epidermal keratinocytes. While screening 60 psoriasis-treating Chinese herbs for their anti-proliferative properties using a cultured human HaCaT keratinocyte model, we found Radix Rubiae to be highly effective. Evidence is now provided that induction of apoptosis is the underlying mechanism for the observed anti-proliferative action of Radix Rubiae. Analysis of cell cycle with PI staining showed that Radix Rubiae induced the appearance of a sub-G1 peak and cell arrest at the G1 phase. Radix Rubiae was also capable of inducing morphological changes as evidenced by nuclear condensation. DNA fragmentation was clearly demonstrated by gel electrophoresis and by the TUNEL method. Quantitative analyses by Annexin V-PI staining revealed that Radix Rubiae-induced apoptosis was dose- and time-dependent. Furthermore, Radix Rubiae was able to activate caspase-3 expression when examined by Western blot analysis. The cellular, morphological and molecular data unequivocally demonstrated that induction of cellular apoptosis was mainly responsible for the previously observed anti-proliferation induced Radix Rubiae on HaCaT keratinocytes. Our experimental results suggest that Radix Rubiae is a promising source from which a herb-based topical agent could be developed for psoriasis treatment.     

Revisiting the Koebner phenomenon: role of NGF and its receptor system in the pathogenesis of psoriasis

Nerve growth factor (NGF) influences the key pathological events of psoriasis: keratinocyte proliferation, angiogenesis, and T-cell activation. We have systematically examined the kinetics of NGF expression, keratinocyte proliferation, and migration of T lymphocytes in the epidermis in Koebner-induced developing psoriatic plaques. In skin traumatized by the tape-stripping method (n = 12), a marked up-regulation of NGF in Koebner-positive lesions (n = 7) was observed 24 hours after trauma. Synthesis of NGF reached its maximum level in the 2nd week. Furthermore, cultured keratinocytes from nonlesional skin of psoriasis patients produced 10 times higher levels of NGF compared with keratinocytes from healthy individuals. To substantiate the in vivo effect of NGF secreted by keratinocytes in psoriatic plaques, we studied psoriatic plaques and normal human skin in a SCID-human skin xenograft model. The transplanted psoriatic plaques demonstrated marked proliferation of NGF-R (p75)-positive nerve fibers compared with only a few nerves in the transplanted normal human skin. Our results demonstrate that 1) in a developing psoriatic lesion, up-regulation of NGF together with keratinocyte proliferation are early events and precede epidermotropism of T lymphocytes; 2) keratinocytes in patients with psoriasis are primed to produce elevated levels of NGF; and 3) NGF synthesized by these keratinocytes is functionally active.     

Expression of Bcl-2 family proteins in psoriasis

Aim

To elucidate the mechanisms involved in apoptosis of psoriatic keratinocytes by examining the expression of pro-apoptotic (Bak, Bax) and anti-apoptotic (Bcl-2, Bcl-X) Bcl-2 family of proteins, as well as the expression of p53 and Ki-67 proteins in normal skin, and uninvolved and involved psoriatic skin.

Methods

A total of 90 skin samples (30 cases of involved and uninvolved psoriatic skin and normal skin) were examined immunohistochemicaly to determine the protein expression of p53, Ki-67, Bcl-2, Bcl-X, Bax, and Bak. The results were quantified and expressed as a percentage of positive keratinocytes.

Results

There was a significant increase in Ki-67 (17.05 vs 3.65; P<0.001), Bcl-X (40.21 vs 13.97; P<0.001), Bak (89.46 vs 73.36; P<0.001), and Bax (50.00 vs 29.25; P<0.001) expression and a decrease in Bcl-2 (3.23 vs 6.25; P=0.008) expression in involved psoriatic skin, as well as an increase in Bcl-X (25.13 vs 13.97; P<0.001) expression in uninvolved psoriatic skin, when compared to normal skin. Samples with higher percentage of Ki-67 positive cells showed a higher percentage of p53 positive cells (correlation coefficient r = 0.75 in involved psoriatic samples, P<0.001; r = 0.88 in uninvolved psoriatic samples, P<0.001; and r = 0.85 in normal skin samples, P<0.001). Samples with higher percentage of p53 positive cells expressed pro-apoptotic Bak and Bax in higher percentage of cells; the correlation coefficients were r = 0.74 and r = 0.68 in involved psoriatic samples (P<0.001 for both), r = 0.75 and r = 0.69 in uninvolved psoriatic samples (P<0.001, for both), and r = 0.87 and r = 0.70 in normal skin samples (P<0.001, for both).

Conclusion

Increased expression of Bcl-X protein was associated with psoriatic epidermal hyperplasia. Strong Bax and Bak expression in involved psoriatic skin are probably inhibitory mechanisms counteracting intensive proliferation.Psoriasis is a chronic, relapsing, inflammatory, and hyperproliferative skin disorder characterized by well-circumscribed erythematosquamous lesions (1). Clinically, psoriasis is characterized by significant epidermal keratinocyte hyperplasia with proliferation, keratinocyte maturation, and turn-over rates as important mechanisms in its pathogenesis (2,3).In normal human skin, keratinocytes in the superficial layer of the epidermis undergo apoptosis and regulate proliferation of cells in the basal layer (4). As opposed to normal skin, keratinocytes derived from psoriatic plaques were shown to be resistant to apoptosis (5). Numerous TUNEL-positive keratinocytes were also positive for proliferating nuclear antigen and Ki-67, which are indicative of proliferating cells (5). Inappropriate regulation of apoptosis was proposed as a possible explanation for epidermal thickening in hyperproliferative inflammatory skin disorders (6).The list of molecular mediators influencing apoptosis is rapidly expanding with Bcl-2 and its homologous proteins, emerging as one of the most important regulators of programmed cell death and playing a crucial role in the balance between cell survival and cell death. Protein p53 is a well described tumor suppressor that plays a central role in the initiation of apoptosis and cell cycle control (2,7,8).The mechanisms involved in the psoriatic plaque formation are not completely elucidated. In the era of biological therapy, better understanding of different apoptotic cell cycle regulatory mechanisms involved in this process would enable a development of novel specific therapeutic approaches for treating psoriatic patients. In this study, we examined the expression and distribution of the pro-apoptotic (Bak, Bax) and anti-apoptotic (Bcl-2, Bcl-X) Bcl-2 family proteins, as well as the expression of p53 protein in psoriatic epidermis and normal human skin. High TUNEL-positive rate in psoriatic keratinocytes was linked to high proliferation rate, so staining of Ki-67 was also performed.     

Aberrant production of interleukin-8 and thrombospondin-1 by psoriatic keratinocytes mediates angiogenesis.

Psoriasis is a common inherited skin disease that is characterized by hyperproliferation of epidermal keratinocytes and excessive dermal angiogenesis. A growing body of evidence supports a key pathogenetic role for activated keratinocytes in the angiogenic response that accompanies psoriasis. We investigated the role of psoriatic epidermis in the aberrant expression of angiogenesis by examining the ability of pure populations of multipassaged keratinocytes obtained from the skin of normal individuals and psoriatic patients to induce angiogenesis in vivo in the rat corneal bioassay and endothelial cell chemotaxis in vitro. Media conditioned by keratinocytes from psoriatic patients, including both symptomless skin and psoriatic plaques, induced vigorous angiogenic responses in over 90% of corneas tested and potently stimulated directional migration of capillary endothelial cells in vitro. In contrast, conditioned medium from normal keratinocyte cultures was weakly positive in less than 10% of corneas assayed and failed to stimulate endothelial cell chemotaxis. Furthermore, keratinocytes from psoriatic skin exhibited a 10- to 20-fold increase in interleukin-8 production and a seven-fold reduction in thrombospondin-1 production. The angiogenic activity present in keratinocyte-conditioned media from psoriatic patients was suppressed by adding either highly purified thrombospondin-1 (125 ng) or following the addition of either normal keratinocyte-conditioned media or neutralizing interleukin-8 antibody. We conclude that psoriatic keratinocytes are phenotypically different from normal keratinocytes with respect to their angiogenic capacity and that this aberrant phenotype is attributable to a defect in the overproduction of interleukin-8 and a deficiency in the production of the angiogenesis inhibitor thrombospondin-1.     

Detection of apoptotic alterations in sperm in subfertile patients and their correlations with sperm quality

BACKGROUND: The aim of the present study was to define the effect of apoptosis on sperm quality and function. METHODS: The apoptotic features in sperm were assessed in 60 subfertile subjects, using Annexin-V staining for phosphatidylserine (PS) externalization and Tdt-mediated dUTP nick end labelling (TUNEL) assay for DNA fragmentation. RESULTS: On average, about 45% of the sperm were found to be apoptotic based on the results from Annexin-V staining, including both early (Annexin-V-positive, PI-negative) and late apoptosis (Annexin-V-positive, PI-positive). TUNEL-positive cells (median value 15%) significantly correlated to late apoptosis but not early apoptosis, indicating that DNA fragmentation only occurs at the later stage of sperm apoptosis. TUNEL-positive and late apoptotic cells (Annexin-V-positive, PI-positive) were found to be inversely correlated to sperm motility and vitality, and positively to abnormal sperm morphology. On the other hand, it is surprising to note that the apoptotic alterations in sperm positively correlated to sperm concentration or total sperm counts. CONCLUSIONS: Overall results from this study support the abortive apoptosis theory; apoptosis in mature sperm is initiated during spermatogenesis, after which some cells earmarked for elimination via apoptosis may escape the removal mechanism and contribute to poor sperm quality.     

Changes in numbers of epidermal cell adhesion molecules caused by oral cyclosporin in psoriasis.

AIM--To determine the effects of a three month course of low dose cyclosporin on the expression of epidermal cell adhesion molecules. METHODS--Eighteen patients with psoriasis were treated for 12 weeks with either 2.5 or 5 mg/kg/day of oral cyclosporin. Biopsy specimens taken from skin before, during, and after cyclosporin treatment were stained immunohistochemically for CD 54 (ICAM-1), CD 29 (beta-1 integrins), and CD18 (beta-2 integrins). RESULTS--There was a highly significant (p < 0.01) clinical response after 12 weeks of cyclosporin as assessed by the Psoriasis Area and Severity Index (PASI) score. The staining of CD 29 on keratinocytes of affected and unaffected psoriatic skin was not affected by cyclosporin. Epidermal CD54 was variably expressed in active psoriatic plaques and changed unpredictably after cyclosporin (p = NS). Staining for CD18 on large epidermal dendritic cells was reduced after cyclosporin (p < 0.02). The expression of CD18 by large epidermal dendritic cells during treatment correlated strongly with the PASI score at that time and one month after stopping cyclosporin (p < 0.02). CONCLUSIONS--Persistence of epidermal staining for CD 54 in psoriasis is compatible with a good clinical response to cyclosporin. Residual staining for CD 18 on large epidermal dendritic cells may be a useful marker for early clinical relapse.     

Ultrastructural and confocal laser scanning microscopic examination of TUNEL-positive cells

TdT-mediated dUTP-biotin nick end labelling (TUNEL) has been widely used for detecting cells with DNA fragmentation or apoptotic cells. However, since the concept of apoptosis is based on cellular ultrastructure, it is important to identify the morphological features of TUNEL-positive cells. In this study, we performed TUNEL and electron microscopic observation on serial semithin and ultrathin sections of pancreas from bilaterally adrenalectomized rats with caerulein-induced pancreatitis. TUNEL-positive cells were identified with two different ultrastructural patterns. One was characteristic of apoptosis, with condensed nuclei, intact mitochondria, and zymogen granules. The other pattern was one of marked cellular degeneration, possibly representing the end stage of cell death. Cells which did not demonstrate these ultrastructural patterns were not labelled by the TUNEL method. The three-dimensional structure of TUNEL-positive cells was also investigated by confocal laser scanning microscopy (CLSM), which showed the apoptotic nuclei exhibited various three-dimensional structures. These results confirm the utility of the TUNEL method in detecting apoptosis; application of the technique reported in this study will contribute to the further characterization of individual TUNEL-positive cells. © 1997 John Wiley & Sons, Ltd.     

Proteomic analysis of psoriatic skin tissue for identification of differentially expressed proteins: up-regulation of GSTP1, SFN and PRDX2 in psoriatic skin

Psoriasis is a chronic inflammatory skin disease, characterized by a combination of abnormal proliferation of keratinocytes, immunology and vascular proliferation. Proteomic analyses have revealed some clues regarding the pathogenesis of psoriasis. In the present study, we conducted an investigation of different proteomes of psoriatic lesional skin, and compared them with those of normal and non-lesional psoriatic skin. We performed 2-D gel electrophoresis, liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis and database searches. Expression of proteins were evaluated by immunoblot and immunohistochemistry analyses. Our data showed differential expression of 74 and 145 protein spots in non-lesional and lesional psoriatic skin, respectively. Eleven of 36 proteins, which were identified by LC-MS/MS, were categorized as apoptosis-regulating proteins. Other protein spots were categorized as proteins with involvement in the negative regulation of apoptosis, defense response-related proteins and inflammatory response. Of particular interest, increased expression of glutathione S transferase 1 (GSTP1) and peroxiredoxin 2 (PRDX2), which are involved in the Redox balance system, and SFN, which is involved in the cellular proliferation system, was observed in psoriatic lesional skin. Localization of GSTP1 and SFN was observed above the middle layer of the epidermis in psoriatic skin lesions. Expression of PRDX2 was clearly observed below the middle layer of the epidermis in chronic type psoriatic skin lesions. Taken together, 36 identified proteins were associated with biological regulation, including regulation of cell death, defense response, inflammatory response and reactive oxygen species (ROS) regulation. PRDX2 and GSTP1 may play roles in compensating mechanisms for reduction of ROS stress, and SFN may play roles in prevention of cancer development in proliferating cells through G2/M cell cycle arrest upon accidental DNA damage within psoriatic skin lesions.     

The tunel assay in the diagnosis of graft-versus-host disease: caveats for interpretation

Acute graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality following bone marrow transplantation, and early detection is important to allow effective therapy. Since the presence of apoptotic keratinocytes (dyskeratotic bodies) has been suggested as a useful diagnostic criterion for GVHD, attention has focused on the use of the TUNEL assay to detect apoptosis in clinical specimens. We reviewed clinical specimens upon which TUNEL had been performed for possible artifacts that might interfere with accurate evaluation for GVHD. Several distinct types of artifact were found and could be re-created in experimental systems. Artifacts in TUNEL staining generally resulted from the lack of specificity of this reaction for apoptotic cell death. Artifacts were found resulting from inadequate fixation, over-exposure of the TUNEL reaction, and proximity to the section edge. In addition, a novel artifact, apparently resulting from DNA shearing during the sectioning process, was noted and confirmed using confocal microscopy of experimental specimens. The TUNEL assay must therefore must be interpreted with caution in the clinical setting. In our laboratory, we consider TUNEL-positive cells as apoptotic only when accompanied by apoptotic morphology. Although these criteria clearly miss some cells in the early stages of apoptosis, they provide the highest specificity for apoptotic cell death.     

Cell death and immunohistochemistry of p53, c-Fos and c-Jun after spermine injection into the rat striatum

Administration of polyamines into the central nervous system results in tissue damage, possibly through the excitotoxic actions of the NMDA receptor. Direct injection of 100 nmol of spermine into the rat striatum produced a lesion equivalent to approximately 50% of the striatum. Analysis of the DNA in this region revealed the distinct ladder-like pattern of degradation often associated with apoptosis. This DNA fragmentation was confirmed in vivo using terminal deoxynucleotidyl-transferase-mediated biotinylated deoxyuridine triphosphate nick end labelling (TUNEL). The morphology of the TUNEL-positive cells showed marked differences at the needle tract when compared with cells in damaged areas away from the needle tract, suggesting a differential mechanism of cell death in these two regions. The patterns of p53, c-Fos and c-Jun protein expression were determined using immunohistochemistry. The number of p53-immunoreactive cells increased up to 14 h and returned to basal levels by 24 h. c-Fos protein expression transiently increased, peaking at 8 h after injection. c-Jun exhibited a protracted pattern of expression, remaining elevated up to 24 h. p53 protein expression was colocalised with TUNEL staining in areas away from the needle tract, but not in cells at the needle tract, suggesting once again a differential mechanism of cell death. At 14 h, c-Fos and c-Jun were not colocalised with TUNEL staining, suggesting that they are either not involved with the cell death process or that the time course of protein expression and the onset of DNA fragmentation do not overlap. This work represents the first characterisation of processes associated with cell death induced by spermine in vivo.     

Influence of infliximab on keratinocyte apoptosis in psoriasis patients

Biological drugs targeting tumor necrosis factor-α, such as infliximab, are highly effective in psoriasis. The interference with keratinocyte apoptosis has been included among the possible effects of infliximab in psoriasis, although the available data are still controversial. The purpose of our study was to verify the action of infliximab on psoriatic keratinocytes. Keratinocyte apoptosis was evaluated in the lesional psoriatic skin of 11 patients at baseline and a different time point during treatment with infliximab. Infliximab (5?mg/kg) was given intravenously at weeks 0, 2, and 6, followed by maintenance infusions every 8 weeks. Pretreatment with intravenous hydrocortisone was performed prior to each infusion. Keratinocytes with apoptotic features were histologically identified according to the following changes: chromatin condensation at the periphery of the nucleus, cytoplasmic vesiculation, nuclear fragmentation, nuclear pyknosis. Immunohistochemical assessment of p53 and caspase-3 expression was also performed. At baseline, prior to treatment with infliximab, lesional epidermis showed 1.2–3.2% p53-positive apoptotic keratinocytes in the basal zone. The number of p53-positive apoptotic keratinocytes increased after treatment with infliximab, already at day 1–2 after the first infusion, and such cells were localized at basal and suprabasal layers or were through all layers. There was no immunoreactivity for caspase-3 at any time point examined. Our results suggest that induction of p53-related keratinocyte apoptosis might be one of the mechanisms of infliximab action in psoriasis.     

Cellular localization of interleukin-8 and its inducer, tumor necrosis factor-alpha in psoriasis.

The importance of immunologic mechanisms in psoriasis has been deduced from the ability of immunosuppressive therapies to ameliorate this common and chronic skin disease. Certainly the histology of psoriatic lesions suggests a dialogue between the hyperplastic keratinocytes and infiltrating T lymphocytes and macrophages. To begin dissecting the cytokine network involved in the pathophysiology of psoriasis, the location, in both epidermal and dermal compartments, of tumor necrosis factor-alpha, interleukin-8, intercellular adhesion molecule-1, and transforming growth factor-alpha at the protein and/or mRNA levels were identified. Tumor necrosis factor-alpha was selected as a potentially key regulatory cytokine, first because it induces cultured keratinocyte interleukin-8, intercellular adhesion molecule-1, and transforming growth factor-alpha production, and second because intercellular adhesion molecule-1 expression by keratinocytes in psoriatic epidermis had been identified previously. Using immunohistochemical localization, tumor necrosis factor-alpha was identified in 12 psoriatic lesions as intense and diffuse expression by dermal dendrocytes (macrophages) in the papillary dermis (without significant staining of endothelial cells, mast cells, or dermal Langerhans cells), and focally by keratinocytes and intraepidermal Langerhans cells. Functional interaction between the dermal dendrocytes and keratinocytes was suggested by the presence of interleukin-8 expression of suprabasal keratinocytes immediately above the tumor necrosis factor-alpha-positive dermal dendrocytes. Interleukin-8 mRNA and transforming growth factor-alpha mRNA were detectable in the epidermal roof of psoriatic lesions, but neither was detectable at the protein or mRNA levels in any normal skin specimens. Treatment of cultured human keratinocytes with phorbol ester (which experimentally produces psoriasiform changes on mouse skin) or tumor necrosis factor-alpha also increased interleukin-8 and transforming growth factor-alpha mRNAs. Further elucidation of the cellular and molecular basis for the genesis and evolution of psoriasis will provide the framework for a better evaluation of the cause and treatment of this skin disease.     

银屑病皮损组织中PPIL6基因的下调表达与功能

目的：分析人类脯氨酸异构酶基因PPIL6（ peptidylprolyl isomerase-like 6）在银屑病皮损组织中的表达异常,并研究PPIL6对信号通路及皮肤细胞增殖的影响。方法利用生物信息学方法从已经发表的基因芯片表达谱数据中分析脯氨酸异构酶（ PPIase）家族基因在银屑病皮损组织和正常皮肤中的表达差异。通过双荧光素酶报告系统研究PPIL6对Rb信号通路的影响。通过Western印迹研究PPIL6对Rb磷酸化的调控。通过染色质免疫沉淀（ ChIP）研究PPIL6敲降表达后E2 F1与下游基因EZH2启动子结合能力的变化。通过MTT实验检测PPIL6对人永生化表皮细胞HaCat增殖能力的影响。结果 PPIL6在银屑病皮损组织中下调表达, PPIL6过表达能够激活Rb信号通路,其机制可能是抑制Rb磷酸化。 PPIL6敲降表达上调E2 F1与EZH2启动子的结合。功能实验表明PPIL6过表达抑制HaCat细胞的增殖。结论 PPIL6可能在银屑病的发生发展过程中发挥重要作用。     

BCL-2 expression in adult and embryonic non-haematopoietic tissues

The B-cell leukaemia/lymphoma-2 (bcl-2) proto-oncogene is unusual as its product appears to provide survival advantage to B cells by blocking apoptosis. In this study, the expression of bcl-2 has been examined in normal nonhaematopoietic tissues, embryos, and psoriatic skin by immunohistochemical staining. Bcl-2 protein expression is mainly observed in cell populations with a long life and/or proliferating ability such as duct cells in exocrine glands, basal keratinocytes, cells at the bottom of colon crypts, and neurons. In the skin of both adult and embryo and also embryonic kidney and cartilage, bcl-2 expression was observed in cells which were undergoing morphological transition from undifferentiated stem cells to committed precursor cells. The finding of bcl-2 expression in the terminal differentiated syncytial trophoblast, but not cytotrophoblast, and in some cells responsive to hormone stimulation such as in the endometrium and myometrium suggests that the gene expression may be related too hormone responsiveness. As no bci-2 localization was seen in the benign hyperproliferative skin condition psoriasis, this does not suggest a straightforward link to proliferation. These observations support the view that the bcl-2 gene may have an important role in cell development, maturation, and the path to terminal differentiation.     

Cytochemical identification of programmed cell death in the fusing fetal mouse palate by specific labelling of DNA fragmentation

The process of palate fusion was examined in 13- and 14-day-old mouse fetuses by using in situ staining for nuclear DNA fragmentation (TUNEL method) and immunofluorescent staining for keratin, with special reference to the disruption of the midline epithelial seam. TUNEL-positive cells were found in the disappearing midline seam and the oral and nasal epithelial triangles at some late stages of palate fusion, but not in the palatal shelves prior to contact or in the intact midline epithelial seam. It seems that DNA fragmentation or apoptosis is required for the midline epithelial seam to disrupt, but may not be necessary for initial contact of palatal shelves or for the epithelial fusion of opposing palatal shelves. A similar sign of apoptotic cell death was observed in the disappearing epithelial seam between the fusing nasal septum and dorsal palate. We have demonstrated that apoptotic programmed cell death does occur at some stages of palate fusion, although the present results do not exclude the possibility of epithelial-mesenchymal transformation and the oral and nasal migration of midline epithelial cells.     

Apoptosis mediated by cytolytic molecules might be responsible for maintenance of psoriatic plaques

Psoriasis is a chronic hyperproliferative skin disease characterized by keratinocyte hyperproliferation and inflammation. It is generally considered as an autoimmune disease mediated by T cells. The precise mechanism of triggering keratinocyte hyperproliferation is as yet unknown. Apoptosis seems to be important in the maintenance of skin cell homeostasis as well as in the pathogenesis of some skin diseases. We hypothesize how apoptosis mediated by cytolytic mechanisms could be involved in initiating and maintenance of psoriatic plaque. Increased keratinocyte hyperproliferation might develop as a consequence of failure to remove self-reactive T cells by apoptosis that in other way cause significant keratinocyte damage. Apoptotic keratinocytes might trigger an injury response program causing regenerative hyperplasia of epidermal keratinocytes. Another possibility is that the failure to eliminate these abnormal keratinocytes could result in the persistence of chronic inflammatory conditions constantly recruiting specific T cells. Increased epidermal thickness in psoriasis could be also explained by imbalance between the expression of pro- and anti-apoptotic proteins. Epidermal keratinocytes have the ability to produce cytolytic molecules, thus they might also have the potential to protect the epidermis from T cell-mediated damage. In conclusion, hyperproliferation of psoriatic keratinocytes might be partly due to changes in the keratinocyte expression of pro- and anti-apoptotic genes, partly to the damaged keratinocytes triggering an inappropriate wound repair response and partly by the failure to eliminate these abnormal keratinocytes resulting in the persistence of chronic inflammation. Each of the proposed mechanisms might be a possible therapeutic target mainly by new immunomodulatory agents.     

In situ demonstration of CD40- and CD154-positive cells in psoriatic lesions and keratinocyte production of chemokines by CD40 ligation in vitro

In psoriatic lesions, T cells and keratinocytes are in an activated state. Ligation of CD40 expressed on activated keratinocytes with CD154 expressed on activated T cells is thought to be involved in the pathogenesis of psoriasis. However, the presence of CD40(+) and CD154(+) cells in psoriatic skin has not been thoroughly studied. The present study has therefore examined their presence by immunohistochemistry in the lesional and non-lesional skin of ten patients. The influence of CD154-CD40 ligation on the release of chemokines (IL-8, RANTES, and MCP-1) and complement components (C3 and factor B) from keratinocytes was also investigated in vitro. Studies using single and double staining showed that clusters of CD40(+) keratinocytes were present in both lesional and non-lesional skin; CD40(+)CD1a(+) Langerhans cells in lesional, non-lesional, and normal skin; and numerous CD40(+)CD83(+) cells in lesional skin. CD1a(+) and CD83(+) cells always expressed CD40 strongly. Numerous T cells were seen in lesional skin. A small number of T cells expressed CD154. CD154(+) T cells were seen in the lesional epidermis of seven of ten patients-in six, in juxtaposition to CD40(+) cells including keratinocytes. In non-lesional epidermis, CD154(+) T cells were seen in two patients-in one, in juxtaposition to CD40(+) keratinocytes. In vitro studies showed that IFN-gamma-treated keratinocytes released small amounts of IL-8, RANTES, and MCP-1; ligation of these cells with CD154-transfected J558 cells or soluble CD154 greatly enhanced the release. This ligation did not enhance the release of C3 and factor B. These results warrant further studies on the role of CD40 ligation in the pathogenesis of psoriasis.