Uninvolved Psoriatic Epidermis Research Articles

Stress-Related Regulation Is Abnormal in the Psoriatic Uninvolved Skin.

Keratinocyte stress-response of the uninvolved psoriatic epidermis is known to be altered compared to healthy cells. Therefore, we aimed to reveal potential mechanisms underlying this alteration. We compared the expression of annotated cell-stress-related proteins between uninvolved psoriatic and healthy skin using the protein array method. Data were analyzed by the Reactome over-representation test. We found that p27/CDKN1B and cytochrome C showed at least a two-fold increase, while cyclooxygenase-2, indolamine-2,3-dioxygenase-1, serum paraoxonase 1, serum paraoxonase 3, serine-46-phosphorylated tumor protein p53, and superoxide-dismutase-2 showed a two-fold decrease in expression in the uninvolved skin. Over-representation analysis suggested the Forkhead-box protein O (FOXO)-mediated transcription as the most significant pathway affected by the differently expressed cell-stress-related proteins (DECSRPs). DECSRPs indicate increased FOXO-mediated transcription of cell-cycle genes and reduced interleukin-signaling in the psoriatic uninvolved skin. Nuclear positivity of the FOXO-signaling-related p27/CDKN1B and FOXO1 are negatively correlated with the disease severity and showed increased expression in the uninvolved epidermis and also in healthy primary keratinocytes, which were grown on cartilage oligomeric matrix protein-coated surfaces. Our results indicate a cell-cycle inhibitory process, as a stress-related compensatory mechanism in the uninvolved epidermis, that could be responsible for blocking keratinocyte hyperproliferation in the psoriatic uninvolved skin, thus maintaining the symptomless skin phenotype.

623 Genome-wide DNA methylation profiling identifies differential methylation in uninvolved psoriatic epidermis

623 Genome-wide DNA methylation profiling identifies differential methylation in uninvolved psoriatic epidermis

Genome-Wide DNA Methylation Profiling Identifies Differential Methylation in Uninvolved Psoriatic Epidermis

Psoriasis is a chronic inflammatory skin disease with both local and systemic components. Genome-wide approaches have identified more than 60 psoriasis-susceptibility loci, but genes are estimated to explain only one-third of the heritability in psoriasis, suggesting additional, yet unidentified, sources of heritability. Epigenetic modifications have been linked to psoriasis and altered DNA methylation patterns in psoriatic versus healthy skin have been reported in whole-skin biopsies. In this study, focusing on epigenetic modifications in the psoriatic uninvolved skin, we compared the lesional and non-lesional epidermis from psoriasis patients with epidermis from healthy controls. We performed an exhaustive genome-wide DNA methylation profiling using reduced representation bisulfite sequencing, which interrogates the methylation status of approximately 3-4 million CpG sites. More than 2,000 strongly differentially methylated sites were identified and a striking overrepresentation of the Wnt and cadherin pathways among the differentially methylated sites was found. In particular, we observe a strong differential methylation in several psoriasis candidate genes. A substantial number of differentially methylated sites present in the uninvolved versus healthy epidermis suggests the presence of a pre-psoriatic state in the clinically healthy skin type. Our exploratory study represents a starting point for identifying biomarkers for psoriasis-prone skin before disease onset.

Keratinocytes express functional CARD18, a negative regulator of inflammasome activation, and its altered expression in psoriasis may contribute to disease pathogenesis.

Caspase recruitment domain family member 18 (CARD18, Iceberg) is known as a negative regulatory molecule that inhibits inflammatory events by terminating inflammasome activation due to a direct interaction with pro-caspase-1. During the investigation of molecular mechanisms in keratinocytes that contribute to the pathogenesis of psoriasis, we found that CARD18 expression differs in healthy and psoriatic skin; moreover, CARD18 demonstrated altered response under inflammatory conditions in healthy and psoriatic skin. In healthy skin, low basal CARD18 expression was detected, which showed significant elevation in response to inflammatory stimuli (lymphokine treatment or mechanical injury). In contrast, higher basal expression was observed in psoriatic non-involved skin, but no further induction could be detected. We demonstrated that keratinocytes express CARD18 both at mRNA and protein levels and the expression increased in parallel with differentiation. The investigation of cellular inflammatory processes revealed that psoriasis-associated danger signals triggered the expression of inflammasome components (AIM2, Caspase-1) and CARD18 as well as IL-1β production of keratinocytes. Furthermore, gene-specific silencing of CARD18 in cells treated with cytosolic DNA (poly(dA:dT)) resulted in increased IL-1β secretion, suggesting a negative regulatory role for CARD18 in keratinocyte inflammatory signaling. The differential regulation of CARD18 in healthy and psoriatic uninvolved epidermis may contribute to the susceptibility of psoriasis. Furthermore, our in vitro results indicate that CARD18 may contribute to the fine tuning of keratinocyte innate immune processes.

The Special DNA Methylation Status in the Promoter of IL-12B in Psoriatic Epidermis

Background: It is unclear the metylation status of CpG islands within interleukin-12B (IL-12B) in psoriasis, although increasing evidence indicates that the abnormal DNA methylation is involved in the pathogenesis of psoriasis. Objective: We investigated the methylation status of IL-12B gene in psoriatic epidermis. Methods: The DNA specimens were obtained from the involved and uninvolved epidermis of 30 patients with plaque psoriasis and 28 healthy persons as the control group. Methylation of 26 CpG sites in the promoter within IL-12B gene was examined by bisulfite sequencing. The severity of disease was evaluated by psoriasis area and severity index (PASI). Results: The mean methylation rate in the promoter of IL-12B in involved psoriatic epidermis, uninvolved psoriatic epidermis and healthy control is 0.0230 ± 0.0101, 0.0188 ± 0.0118 and 0.0105 ± 0.0114, respectively. The methylation rate of IL-12B in both involved psoriatic epidermis (p<0.001) and uninvolved psoriatic epidermis (p<0.05) is significantly higher than in healthy controls, respectively. The methylation rate of IL-12B in uninvolved psoriatic epidermis is lower than in involved psoriatic epidermis (p=0.031). The mean methylation rate in involved psoriatic epidermis was correlated to patient PASI scores (r=0.633, p<0.001). Conclusions: Abnormal methylation in the promoter of IL-12B have been found in psoriatic epidermis, and is associated with severity of the disease, which suggests the promoter methylation of IL-12B may be involved to the pathogenesis of psoriasis.

Expressions of CD1a and Ki-67 in psoriatic lesions before and after narrow-band ultraviolet B phototherapy

Objective To investigate the effect of narrow-band ultraviolet B phototherapy on the expression of CDla and Ki-67 in psoriatic lesions. Methods The expression and distribution of CDla and Ki-67 antigens were detected by immunohistochemistry in involved and uninvolved psoriatic skin of 27 patients before and after ultraviolet B phototherapy. Psoriasis area and severity index （PASI） was assessed to evaluate the severity of disease. Results The count of CD1a-expressing dendritic cells and Ki-67-expressing keratinoeytes per square millimeter under high power field was higher in untreated involved psoriatic epidermis than that in uninvolved psoriatic epidermis and involved psoriatic epidermis after narrow-band UVB therapy （15 ± 4 vs 9± 3 and 9 ±3, 53 ± 12 vs 22 ±6 and 25 ±1, all P〈 0.05）. The PASI score significantly correlated with the expression level of Ki-67 （ r = 0.29, P 〈 0.05）, but unrelated to that of CD1a （r =-0.27, P 〉 0.05 ）. Conclusions Narrow-band UVB may improve psoriasis via modulating the immune system of skin. The expression level of Ki-67 in psoriatic epidermis is associated with PASI. Key words: Psoriasis; Ultraviolet rays; Immune system; CD1a^＋; Ki-67; Dendritic cells

Increased activities of Akt in psoriatic epidermis.

Objective To investigate the significance of Akt in the pathogenesis of psoriasis.Methods Tissue specimens were obtained from involved and uninvolved skin of 30 patients with progressive psoriasis vulgaris and normal skin of 20 human controls.Immunohistochemistry.immunobloting and kinase activity assay were performed to detect the expressions of Akt and phosphorylated Akt as well as Akt activities in these specimens.Immunostaining intensity Was assessed by optical density detection and the results of immunobiot and activity assay by grey scanning.Statistical analyses were performed by variance analysis and student's t test.Results As immunohistochemistry revealed.there was no significant difierence in Akt protein expression among normal epidermis,psoriatic epidermis and uninvolved epidermis(F=0.611,P＞0.05):the level of phosphorylated Akt in psoriatic epidermis was significantly higher than that in normal epidermis and psoriatic uninvolved epidermis(F=19.081.P＜0.01).while no significant difierence was observed between normal epidermis and psoriatic uninvolved epidermis (t=0.624.P＞0.05).Immunoblot showed a significant difierence in phosphorylated Akt(t=237.75.P＜0.01)but not in Akt(t=1.378,P＞0.05)between psoriatic involved epidermis and normal epidermis.In comparison with normal epidermis,the activity of Akt in psoriatic involved epidermis was increased significantly(t=138.44 1.P＜0.0 1).Conclusion The overproliferation of psoriatic keratinocytcs may be associated with increased activation of Akt. Key words: Psoriasis; Protcin kinase B:Immunocompetence

Proliferating keratinocytes are putative sources of the psoriasis susceptibility-related EDA+ (extra domain A of fibronectin) oncofetal fibronectin.

The extra domain A of fibronectin (EDA+ oncofetal isoform of fibronectin was recently reported to be overexpressed in psoriatic uninvolved epidermis. It has been proposed that the abnormal presence of EDA+ oncofetal protein at the dermal-epidermal junction in the uninvolved skin may provide the "psoriatic" environment in which keratinocytes are in a preactivated state with regard to mitogenic signals (e.g., T cell lymphokines). To determine the possible sources of cellular fibronectin in the non-lesional psoriatic skin, we aimed to investigate whether keratinocytes could produce the EDA+ oncofetal form of fibronectin. RT-PCR studies revealed that both cultured normal keratinocytes and HaCaT cells express the EDA+ splice variant of fibronectin mRNA, and in HaCaT cells the EDA+/EDA- transcript ratio was elevated compared with normal keratinocytes. Cultured keratinocytes and HaCaT cells showed intracytoplasmic staining with an EDA+ fibronectin-specific antibody and among the positively stained cells many showed mitosis. Using RT-PCR, western blot analysis, and flow cytometry, we showed that in synchronized HaCaT cells the amount of both total fibronectin and its EDA+ isoform change with the proliferation/differentiation state of HaCaT cells and peak in highly proliferating cells. We show that in short-term ex vivo cultures, a small population of EDA+ fibronectin containing cell population appear among psoriatic uninvolved, but not normal epidermal cells. We also demonstrate that cell attachment has a strong influence on the expression of both total and EDA+ fibronectin. Our results suggest that proliferating keratinocytes could be the sources of the psoriasis susceptibility-related EDA+ oncofetal fibronectin in the epidermis.

Decreased Deiminated Keratin K1 in Psoriatic Hyperproliferative Epidermis

Citrulline-containing proteins, mainly originating from keratin K1 and formed by enzymatic deimination of arginine residues, have been identified in the cornified layers of human epidermis. We analyzed the localization and nature of the deiminated proteins in psoriatic epidermis. Immunostaining based on chemical modification of citrulline residues showed that the normal and psoriatic uninvolved epidermis contained deiminated proteins diffusely in the cornified cell layer, whereas the involved epidermis had no detectable or markedly reduced levels of deiminated proteins. Immunolabeling with polyclonal antibodies against a synthetic citrulline-containing peptide corresponding to a deiminated sequence of mouse K1 also suggested markedly decreased deiminated K1 in psoriatic involved lesions. Keratin analyses indicated that deiminated K1 present in normal and psoriatic uninvolved epidermis was not detected in the psoriatic involved epidermis. Double staining with a monoclonal antibody, 34betaB4, and the polyclonal antibodies demonstrated that epidermis with low suprabasal keratin expression was negative for deiminated K1. In contrast, intralesional acrosyringia showing decreased suprabasal keratin immunoreactivity like that of the surrounding psoriatic epidermis showed strong deiminated K1 staining. This suggests that abnormal keratin deimination is restricted to the psoriatic hyperproliferative epidermis, without affecting sweat ductal epithelia.

Intralesional T-Lymphocyte Activation as a Mediator of Psoriatic Epidermal Hyperplasia.

An early cellular event in the development of psoriatic lesions is infiltration of target tissue by macrophages and activated T lymphocytes. Lesional psoriatic skin contains activated memory T lymphocytes with production of mRNA for lymphokines such as interleukin-2, interferon-gamma, and tumor necrosis factor-alpha that is elevated relative to normal or uninvolved psoriatic skin. That the T-cell activation and cellular lymphokine production have a crucial role in the maintenance of epidermal hyperplasia in the psoriatic lesion is indicated by the beneficial effect of immunosuppressive agents in the treatment of psoriasis (cyclosporin A, FK506, anti-CD3, anti-CD4). A link between immune activation and psoriasis is also indicated by immunogenetic associations in this disease. Also, psoriatic keratinocytes appear to have been modulated by T-cell lymphokines in vivo, because they abnormally express molecules uniquely induced on keratinocytes by the T-cell product interferon-gamma. Indeed, T cells producing interferon-gamma have been cloned from psoriatic lesions, and they are able to induce keratinocyte class II major histocompatibility complex and intercellular adhesion molecule expression. These lesion-derived T-cell clones can induce growth of keratinocytes, and specifically lesional psoriatic T cells produce factors that induce increased keratinocyte colony formation, as well as increased cell cycle entry of the normally quiescent stem cell population. Interferon-gamma, although a growth inhibitor on its own, acts cooperatively with other T-cell-produced growth factors to cause keratinocyte growth induction. Furthermore, relative to normal stem cells, keratinocyte stem cells (beta 1 integrin+ K1/K10-) in psoriatic uninvolved epidermis are significantly hyperresponsive to the growth-stimulatory lymphokine milieu created by lesional T lymphocytes. Whether such abnormalities in responsiveness are associated with new genetic linkages reported in families of psoriasis patients is unknown. As the epidermis of lesional psoriatic skin can be demonstrated to produce elevated levels of factors that can further potentiate T-cell activation, a self-sustaining cycle can be constructed of T-cell recruitment, intralesional activation, release of factors that preferentially stimulate psoriatic epidermal stem cells to proliferate, and further epidermal potentiation of the T-cell-mediated lesions.

Intralesional T-Lymphocyte Activation as a Mediator of Psoriatic Epidermal Hyperplasia

An early cellular event in the development of psoriatic lesions is infiltration of target tissue by macrophages and activated T lymphocytes. Lesional psoriatic skin contains activated memory T lymphocytes with production of mRNA for lymphokines such as interleukin-2, interferon-gamma, and tumor necrosis factor-alpha that is elevated relative to normal or uninvolved psoriatic skin. That the T-cell activation and cellular lymphokine production have a crucial role in the maintenance of epidermal hyperplasia in the psoriatic lesion is indicated by the beneficial effect of immunosuppressive agents in the treatment of psoriasis (cyclosporin A, FK506, anti-CD3, anti-CD4). A link between immune activation and psoriasis is also indicated by immunogenetic associations in this disease. Also, psoriatic keratinocytes appear to have been modulated by T-cell lymphokines in vivo, because they abnormally express molecules uniquely induced on keratinocytes by the T-cell product interferon-gamma. Indeed, T cells producing interferon-gamma have been cloned from psoriatic lesions, and they are able to induce keratinocyte class II major histocompatibility complex and intercellular adhesion molecule expression. These lesion-derived T-cell clones can induce growth of keratinocytes, and specifically lesional psoriatic T cells produce factors that induce increased keratinocyte colony formation, as well as increased cell cycle entry of the normally quiescent stem cell population. Interferon-gamma, although a growth inhibitor on its own, acts cooperatively with other T-cell-produced growth factors to cause keratinocyte growth induction. Furthermore, relative to normal stem cells, keratinocyte stem cells (beta 1 integrin+ K1/K10-) in psoriatic uninvolved epidermis are significantly hyperresponsive to the growth-stimulatory lymphokine milieu created by lesional T lymphocytes. Whether such abnormalities in responsiveness are associated with new genetic linkages reported in families of psoriasis patients is unknown. As the epidermis of lesional psoriatic skin can be demonstrated to produce elevated levels of factors that can further potentiate T-cell activation, a self-sustaining cycle can be constructed of T-cell recruitment, intralesional activation, release of factors that preferentially stimulate psoriatic epidermal stem cells to proliferate, and further epidermal potentiation of the T-cell-mediated lesions.

Elevated expression of human nonpancreatic phospholipase A2 in psoriatic tissue.

In involved psoriatic tissue, which is characterized by chronic inflammation in both epidermis and dermis, elevated levels of arachidonic acid and eicosanoids have been measured. This implies that a phospholipase A2 (PLA2) may be involved in the pathogenesis of psoriasis. The PLA2's are a group of enzymes that release unsaturated fatty acids from the sn2-position of membrane phospholipids. Once released, the fatty acids are converted by various enzymes into biologically very important signaling molecules. Release of arachidonate initiates the arachidonate cascade, leading to the synthesis of eicosanoids such as prostaglandins, thromboxanes, leukotrienes, and lipoxines. Eicosanoids are important in a variety of physiological processes and play a central role in inflammatory mediators, such as lyso-PAF (a precursor for PAF) and other lysophospholipids, may also be formed through the action of a PLA2. We report for the first time the detection of transcripts of nonpancreatic phospholipase A2 (npPLA2, type II) and cytosolic (c) PLA2 in human skin, and overexpression of npPLA2 in involved skin from patients with psoriasis (plaque psoriasis and pustular psoriasis). Limited amounts of npPLA2 enzyme are detected immunologically in the uppermost layers of epidermis from healthy persons. Both involved and uninvolved psoriatic epidermis contain higher levels of npPLA2 than normal skin. Positive cells in dermis showed significantly higher levels of npPLA2 than epidermal cells. In dermis from healthy persons, only weak staining of a few cells could be detected. The two PLA2 enzymes detected in psoriatic skin (cytosolic and nonpancreatic) may both be involved in eicosanoid overproduction in psoriatic tissue, and the npPLA2 may also be involved in potentiating cell activation, especially T cells.

Expression of Keratinocyte Transglutamine mRNA Revealed by In Situ Hybridization

Plasma membrane-bound transglutaminase (TGm) catalyzes the formation of cornified envelopes (CE) in terminally differentiating keratinocytes. The recent cloning of cDNA encoding rabbit TGm allows detailed studies of its gene expression and regulation. In the present paper, we describe the localization of TGm mRNA in rabbit tissues, as well as in normal and psoriatic human skin, as assessed by in situ hybridization. Furthermore, we correlate TGm mRNA localization with the distribution of the TGm protein detected by immunohistochemistry with a specific monoclonal antibody. In rabbit epidermis, TGm mRNA was expressed in suprabasal cells. The TGm protein was detected in the upper stratum spinosum and stratum granulosum. In rabbit esophagus, TGm mRNA and protein were already expressed to a high level in the first suprabasal cell layer, and their expression decreased in the more differentiated cells. In normal human skin, a small amount of TGm mRNA, restricted to the stratum granulosum, was found, whereas psoriatic skin samples contained high amounts of TGm mRNA in the suprabasal layers with a decreasing gradient into the rete ridges, i.e., the involutions of the epidermis into the dermal compartment. The TGm protein was absent from the rete ridges and confined to several cell layers expressing high levels of mRNA. There was virtually no difference between uninvolved psoriatic and normal epidermis.

Normal psoriatic epidermis expression of hyperproliferation-associated keratins

Keratin expression in lesional, marginal and uninvolved psoriatic epidermis was analysed by one- and two-dimensional gel electrophoresis and immunoblotting. Keratins K1, K5, K6, K10, K14, and K16 were identified in lesional epidermis. Keratins K6 and K16 were found in all epidermis probes of uninvolved skin, but never occurred in normal epidermis of control skin samples. By means of laser-densitometric evaluation of one-dimensional gels a downregulation of K1 and K10 and an upregulation of K6 and K16 was found in psoriatic epidermis. Unexpectedly, the level of K5 was considerably lower and the level of K14 considerably higher in lesional skin than in normal epidermis. These results demonstrate that not only basal keratinocytes in lesional epidermis but also suprabasal keratinocytes in uninvolved psoriatic epidermis express an altered differentiation pattern. The latter phenomenon could be very important in understanding the development of the so-called "Köbner effect" in psoriatic epidermis.

In situ expression of messenger RNA of interleukin-1 and interleukin-6 in psoriasis: interleukin-6 involved in formation of psoriatic lesions

Psoriasis is a disease of abnormal proliferation and differentiation of epidermal cells. Several cytokines released by keratinocytes are implicated as factors responsible for this pathological condition of the epidermis. In order to elucidate the role of these cytokines in psoriasis, messenger RNA (mRNA) expression of interleukin-1 (IL-1) and IL-6 in psoriatic epidermis was investigated using biotin-labelled complementary DNA (cDNA) of the cytokines. Messenger RNA of IL-1 alpha was weakly detected in some normal healthy epidermis specimens and more strongly in all the perilesional uninvolved psoriatic epidermis specimens. It was also expressed in the transitional zone between uninvolved and fully developed psoriatic skin, but was not expressed in lesional skin. In contrast, IL-6 mRNA was rarely expressed in normal healthy epidermis, but was expressed in perilesional uninvolved psoriatic epidermis, in the transitional zone and in the fully developed lesional epidermis, with the maximum intensity in the transitional zone. Expression of mRNA of IL-6 receptor showed a similar tendency to that of IL-6. It was expressed in psoriatic epidermis, most strongly in the transitional zone, but not in normal healthy epidermis. IL-6 was demonstrated immunohistochemically in psoriatic epidermis, but IL-6 receptor was demonstrated only in the transitional zone. Thus IL-6 and its receptor expression correlated well with the formation of psoriatic lesions where IL-1 may initiate their expression. IL-6 may play an important role in the pathogenesis of psoriasis.

The effect of PUVA therapy on glycoprotein biosynthesis in uninvolved psoriatic epidermis

Protein and N-linked glycoprotein biosynthesis was studied in the uninvolved epidermis of patients with psoriasis by the incorporation of radiolabelled leucine and mannose prior to and during PUVA treatment. Analysis of the polyacrylamide gel electrophoresis (PAGE) patterns of the 3[H]-labelled proteins and glycoproteins showed that the major changes in untreated uninvolved psoriatic epidermis compared to normal epidermis were: (a) a shift towards the synthesis of low-molecular-weight glycoproteins; (b) the absence of a 48-kDa peak labelled with mannose; (c) the appearance of 3[H]-mannose-labelled peaks at 40-36 kDa. PUVA treatment gradually changed the PAGE profile back more towards that expected for normal epidermis, with the reintroduction of a 52-48-kDa glycoprotein and reduction of the peaks in the 40-34-kDa region. This effect was dependent on uninterrupted treatment. The PUVA-treated PAGE profiles were compared to those expected in skin tumours (i.e. increased 3[H]-mannose-labelled peaks at 95 and 40-34 kDa with an absence of 62-kDa peaks). It appeared that these criteria were not seen generally as a result of PUVA treatment. However, the results indicate that tumour development may be possible if a patient responds to PUVA treatment by showing an increased peak at 95 and 40-34 kDa in association with a loss of an 3[H]-mannose-labelled peak at 62 kDa.

Ultrastructural Localization of Calcium in Psoriatic and Normal Human Epidermis

With ion capture cytochemistry, we previously demonstrated the distribution of calcium ions in murine epidermis, a pattern consistent with a role for this ion in the regulation of epidermal differentiation. Because of the known proliferation and differentiation defects in psoriasis, we compared the calcium distribution of involved vs uninvolved psoriatic lesions and normal human epidermis. Whereas normal human and uninvolved psoriatic epidermis revealed increased calcium-containing precipitates in the uppermost stratum granulosum, in contrast the basal layer of psoriatic lesions contained less extracellular calcium, a condition that favored enhanced proliferation. Moreover, all psoriatic suprabasal cell layers displayed heavier than normal concentrations of calcium, indicating loss of the normal calcium gradient that programs terminal differentiation. This abnormal profile may account for the differentiation defects (eg, parakeratosis) that occur in psoriasis. Finally, psoriatic lesions displayed retained ionic Ca in intercellular domains of the upper stratum granulosum with absence of normal intercellular bilayers, findings that may underlie the abnormal desquamation and permeability barrier in psoriasis.

Growth-inhibitory effects of 1,25-dihydroxyvitamin D3 on normal and psoriatic keratinocytes

The effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on the growth and DNA synthesis of cultured human keratinocytes obtained from involved and uninvolved psoriatic epidermis and normal epidermis were studied. Treatment with 10(-8) M and 10(-7) M of 1,25(OH)2D3 inhibited cell growth as follows: 58.5 +/- 19.3% and 21.3 +/- 13.6% in normal keratinocytes (n = 6); 43.8 +/- 22.8% and 17.8 +/- 12.3% in psoriatic uninvolved keratinocytes (n = 4); 51.7 +/- 18.2% and 13.2 +/- 6.4% in psoriatic involved keratinocytes (n = 6). Inhibition was virtually complete at 10(-6) M. DNA synthesis was also inhibited by 10(-8) M, 10(-7) M and 10(-6) M of 1,25(OH)2D3 as follows: 70.0 +/- 8.3%, 59.0 +/- 6.8% and 16.7 +/- 4.0%, respectively, in normal keratinocytes (n = 3); 78.5 +/- 13.5%, 51.5 +/- 25.5% and 24.5 +/- 21.5%, respectively, in psoriatic uninvolved keratinocytes (n = 2); and 69.3 +/- 14.5%, 41.3 +/- 19.1% and 14.8 +/- 11.2%, respectively, in psoriatic involved keratinocytes (n = 4). These results indicate that 1,25(OH)2D3 functions as a growth inhibitor for cultured human keratinocytes derived from both normal and psoriatic skin.

Dolichos biflorus agglutinin (DBA) reveals a similar basal cell differentiation in normal and psoriatic epidermis

Binding of N-acetyl galactosamine (GalNAc)-specific Dolichos biflorus agglutinin (DBA) conjugates to frozen sections of normal epidermis and of psoriatic uninvolved and lesional skin was studied in fluorescence microscopy. The DBA conjugates bound only to single basal cell layer in normal and uninvolved psoriatic epidermis from patients with different blood group status. In the lesional area of psoriatic skin a similar reaction with a single basal cell layer was revealed. Other lectin-conjugates applied, presenting also GalNAc specificity, reacted with most cell layers of normal and both uninvolved and lesional psoriatic epidermis and gave an attenuated reaction with the middle epidermal layers. The results show that the basal cell characteristics are confined only to the cells along the basal membrane also in psoriatic epidermis, although cells in three lowest layers may be able to proliferate.

A novel histone-stimulated protein kinase in normal and psoriatic epidermis.

During the course of studies on protein kinases in psoriatic epidermis, a novel histone-activated protein kinase activity was identified. This activity (referred to as PK-II because it was the second peak of protein kinase activity eluted from a DEAE column) was partially purified from the supernatant of an epidermal homogenate by DEAE-cellulose column chromatography. Although histone was not a substrate for phosphorylation, in the presence of histone, endogenous proteins of Mr 105 and 95 kDa were phosphorylated. Activity was not affected by Ca2+/phospholipid, cAMP, cGMP, cAMP-dependent kinase inhibitor, spermine, spermidine, calmodulin, EGF, or phorbol ester. Phosphorylation was specific for serine and threonine residues. A major peak of PK-II activity eluted from sepharose 6B with an apparent Mr of 100 kDa, suggesting that histone may stimulate autophosphorylation. The properties of PK-II resemble those recently described for a class of polypeptide-dependent protein kinases isolated from placenta, Ehrlich ascites tumor cells, and bakers' yeast. PK-II was significantly higher in psoriatic involved epidermis (32.6 +/- 11.6 pmol/min/mg protein) compared to psoriatic uninvolved epidermis (5.7 +/- 0.6 pmol/min/mg; p = 0.03) and normal epidermis (9.5 +/- 2.2 pmol/min/mg; p = 0.05). The function of histone stimulated protein kinase in epidermal function and its role in the pathophysiology of psoriasis remain to be explored.