Mast cell density and IL-8 expression in nonlesional and lesional psoriatic skin.

BACKGROUND: An important cellular aberration at sites of psoriatic inflammation is an increase in the number of dermal mast cells. Being multifactorial immune effector cells, it is believed that mast cells play an essential role in perpetuating the inflammatory process of psoriasis. However, factors responsible for the infiltration and accumulation of mast cells in psoriatic lesions are largely unknown. Recent studies have demonstrated that Interleukin-8 (IL-8) exerts strong chemotactic effects on mast cells in vitro. Overexpression of IL-8 has also been reported in psoriatic lesions. In this study, we have found a correlation between the expression of IL-8 and dermal mast cell density in lesional psoriatic skin as compared to nonlesional psoriatic skin. METHODS: Four-mm punch biopsies were taken from 14 psoriatic patients and eight healthy volunteers. Using immunohistochemical techniques, 8 microm sections of lesional psoriatic, nonlesional psoriatic, and normal control samples were evaluated for dermal mast cell density and the density of IL-8 expressing keratinocytes. RESULTS: It was found that dermal mast cell density in lesional psoriatic, nonlesional psoriatic, and normal skin was 105.4 +/- 71.2, 42.3 +/- 30.1, and 47.5 +/- 32.5 mast cells/mm(2), respectively. IL-8+ keratinocyte density in lesional psoriatic, non lesional psoriatic, and normal skin was 171.5 +/- 67.1, 25.4 +/- 14.9 and 20.6 +/- 8.7 IL-8+ Keratinocytes/mm(2), respectively. CONCLUSIONS: The results of this study suggest that increased levels of IL-8 in the keratinocytes of psoriatic plaques play a contributing role in the migration of mast cells to lesion sites.

Effect of nerve growth factor on endothelial cell biology: proliferation and adherence molecule expression on human dermal microvascular endothelial cells.

In addition to its effect on the central nervous system, nerve growth factor (NGF) appears to play a key role in the initiation and maintenance of inflammation in many organs. NGF degranulates mast cells, recruits inflammatory cellular infiltrates and activates T cells. Extravascular migration of leukocytes is initially controlled by the interaction of cell surface adhesion molecules of leukocytes and endothelial cells. A marked upregulation of NGF in keratinocytes is also observed in conditions characterized by angiogenesis such as psoriasis and wound healing. In this study we investigated the role of NGF in inflammation by studying its effects on endothelial cell proliferation and intracellular adhesion molecule expression by endothelial cells. The effect of NGF on human dermal microvascular endothelial cell (HDMEC) proliferation was measured using the hexosaminidase assay. ICAM-1 expression on HDMEC was measured by ELISA. The function of ICAM-1 was assessed by adherence of peripheral blood mononuclear cells (PBMC) to HDMEC using 51Cr-labeled PBMC. There was a significant increase in proliferation of HDMEC stimulated with NGF as compared to unstimulated HDMEC (P < 0.001). NGF-neutralizing antibody decreased the mitogenic effect of NGF significantly (P < 0.05). NGF also increased ICAM expression on HDMEC as compared to unstimulated HDMEC (P < 0.05). NGF-neutralizing antibody decreased ICAM expression on NGF-stimulated HDMEC (P < 0.05). The percentage of PBMC adherence was higher in NGF-stimulated HDMEC (P < 0.001). Anti-ICAM antibody decreased PBMC adherence. In the study reported here, the role of NGF in two important aspects of inflammation, i.e. angiogenesis and inflammatory cell recruitment at the site of inflammation, was investigated.

Cellular localization of fractalkine at sites of inflammation: antigen-presenting cells in psoriasis express high levels of fractalkine.

BACKGROUND: Chemokines play a key role in cell trafficking at sites of inflammation. The fractalkine CX3C chemokine is unique in several aspects. Fractalkine is expressed on activated endothelial cells and exists in two forms, either membrane anchored or in a soluble form. The soluble form is a potent chemotactic agent for T cells/monocytes and the anchored form functions as an adhesion molecule. In view of these specific functions fractalkine is capable of controlling the key regulatory mechanisms of cell trafficking at sites of inflammation. OBJECTIVES: Little is known about the significance of this important molecule in inflammatory diseases. We undertook this study to elucidate the role of fractalkine in inflammatory diseases of the skin. METHODS: We used a polyclonal antifractalkine antibody (immunoperoxidase and immunofluorescence stainings) in cryosections obtained from tissues of normal skin and that of selected cutaneous inflammatory diseases (psoriasis, lichen planus, eczema). RESULTS: Increased expression of fractalkine was observed in the dermal blood vessels of lichen planus, eczema and psoriasis tissues. The most striking finding was that the dermal dendrocytes in the papillary dermis of psoriasis tissues expressed high levels of fractalkine. Compared with 186.64 +/- 51.69 fractalkine positive dermal dendrocytes per mm2 of the upper dermis of psoriatic tissue, the number of positive cells in lichen planus, eczema, and normal skin were 17.29 +/- 12.50, 12.50 +/- 6.75 and 5.93 +/- 3.53, respectively. We also performed double label immunofluorescence staining with nerve growth factor receptor (NGF-R) antibody and fractalkine antibody. NGF-R-positive terminal cutaneous nerves were in close contact with the fractalkine-positive dermal dendrocytes in psoriatic lesions. CONCLUSIONS: The results of this study confirm that fractalkine is upregulated at sites of inflammation. Thus, it is likely that this molecule plays a key part in cell trafficking. An increased expression of fractalkine at the dermal papillae provides a plausible explanation for the migration and accumulation of T cells at these sites in psoriasis. Earlier studies have reported an increased number of dermal dendrocytes in psoriatic tissue; however, the functional role of these cells in the pathogenesis of psoriasis is largely unknown. Expression of fractalkine on the surface of dermal dendrocytes suggests an active role for these cells in localization and activation of lesional T cells.

Severe combined immunodeficiency mouse-human skin chimeras: a unique animal model for the study of psoriasis and cutaneous inflammation.

Elucidation of the molecular and cellular mechanisms responsible for the pathogenesis of psoriasis had been significantly handicapped due to lack of an ideal animal model. To overcome this hurdle several investigators have developed a number of animal models for psoriasis. Recent establishment of the SCID-human skin chimeras with transplanted psoriasis plaques has opened new vistas to study the molecular complexities involved in psoriasis. This model also offers a unique opportunity to investigate various key biological events such as cell proliferation, angiogenesis, homing in of T cells in target tissues, neurogenic inflammation and cytokine/chemokine cascades involved in an inflammatory reaction. The SCID mouse model will be of immense help to target the cellular and molecular events associated with these pathogenic processes and develop novel drugs for psoriasis and other inflammatory diseases. In this article we have reviewed the prospects and the limitations of the SCID mouse model of psoriasis.

Is psoriasis a T-cell disease?

The etiology and pathogenesis of psoriasis--one of the most common chronic, inflammatory, hyperproliferative skin disorders of man--have long fascinated dermatologists, pathologists and biologists alike. Here, we have a model disease that offers to study neuroectodermal-mesenchymal interactions in the widest sense possible. Epithelial, endothelial, and hematopoietic cells as well as neurons projecting into the skin apparently all interact with each other to generate the characteristic psoriatic lesion. For decades, the ongoing controversy on the molecular nature, choreography and hierarchy of these complex interactions e.g. between epidermal keratinocytes, T cells, neurotrophils, endothelial cells and sensory nerves has served as a driving force propelling investigative dermatology to ever new horizons. This debate has not only been at the heart of our quest to develop more effective forms of therapy for this socially crippling disease, but it also has profoundly influenced how we view the skin as a whole: the numerous competing theories on the pathogenesis of psoriasis published so far also are reflections on the evolution of mainstream thought in skin biology over the last decades. These days, conventional wisdom infatuated with a T-cell-centered approach to inflammatory skin diseases-- portrays psoriasis as an autoimmune disease, where misguided T lymphocyte activities cause secondary epithelial abnormalities. And yet, as this CONTROVERSIES feature reminds us, some authoritative "pockets of academic resistance" are still quite alive, and interpret psoriasis e.g. as a genetically determined, abnormal epithelial response pattern to infectious and/or physicochemical skin insults. Weighing the corresponding lines of argumentation is not only an intriguing, clinically relevant intellectual exercise, but also serves as a wonderful instrument for questioning our own views of the skin universe and its patterns of deviation from a state of homeostasis.

Role of nerve growth factor in RANTES expression by keratinocytes.

A role of neurogenic inflammation induced by the neuropeptides and nerve growth factor (NGF) has been attributed to the pathogenesis of several cutaneous disorders such as psoriasis, wound healing and eczematous dermatitis. The underlying mechanisms of the inflammatory process induced by NGF are not clearly established. This study explored whether NGF influences the inflammatory process by inducing chemokines. The effects of NGF were investigated on induction of 2 important chemokines, interleukin-8 and RANTES, which are known to be upregulated in the keratinocytes of various inflammatory conditions. NGF significantly increased RANTES production by the keratinocytes (p < 0.001, 2-tailed Student's t-test). Induction of RANTES expression in the keratinocytes by NGF provides further insight regarding the role of NGF-NGF receptor system in cutaneous inflammatory conditions.

Childhood psoriasis.

Psoriasis is a common skin disease in infants, children, and adolescents. A review of the clinical, epidemiologic, genetic, and therapeutic aspects of childhood psoriasis is presented. Population studies indicate that the first signs of psoriatic lesions occur in the pediatric age group, birth to 18 years of age, and that both genetic and environmental factors interact to precipitate the development of psoriasis. Koebner reactions are the result of external or internal triggering factors, such as physical injury to the skin, low humidity, and certain drugs. The most frequently observed variant to psoriasis is the plaque type, followed by guttate psoriasis, and juvenile psoriatic arthritis. Pustular psoriasis and erythrodermic psoriasis are rare forms of the disease, but are seen in children from infancy to adolescence. The scalp is the most frequently affected site of involvement in pediatric psoriasis, followed by the appearance of lesions on the extensor surfaces of the extremities, trunk, and nails. Although not common in adult psoriasis, the face and ears are often involved. Topical medications such as corticosteroids, calcipotriol, coal tar preparations, anthralin formulations, and ultraviolet B are recommended in monotherapy or in combination therapy, whereas psoralen plus ultraviolet A, methotrexate, and retinoids should only be administered in crisis situations. The treatment objectives in childhood psoriasis are to preserve skin surfaces, to afford physical relief from the disease, and to employ treatments that do not endanger the health or future development of the child.

Search for the psoriasis susceptibility gene: the Newfoundland Study.

The authors review early pioneering research on the genetics of psoriasis and recently published independent and collaborative investigations searching for the psoriasis susceptibility genes. We describe the research design and current plans for a joint pursuit between the Psoriasis Research Institute, the Memorial University of Newfoundland, and Chiroscience R&D, Inc., for susceptibility genes. A unique study sample from Newfoundland, drawn from affected and unaffected members of multiplex families and relatives, provides a nearly homogeneous isolated population. Families reflect English, Scottish, and Irish ancestry, and have been in residence in Newfoundland for over 300 years. The prevalence of psoriasis is estimated to be 2 to 3%. Familial psoriasis occurs in over 85% of families, with at least one affected member. The experimental strategy using linkage analysis and linkage disequilibrium analysis of the collected tissue bank are discussed, emphasizing prospects for the future outcome of the research findings.

Immunomodulatory effects of peptide T on Th 1/Th 2 cytokines.

Peptide T is an octapeptide from the V2 region of HIV-1 gp120. It has been shown to resolve psoriatic lesions--an inflammatory skin disease. The mechanisms of anti-inflammatory actions of peptide T are not well understood. Th1 cytokines such as IL-2, and IFN-gamma are upregulated in psoriasis. These cytokines play a key role in the inflammatory and proliferative processes of psoriasis. The effects of peptide T on Th1 and Th2 cytokines were studied in order to elucidate the mechanisms of antiinflammatory actions of peptide T. It was observed that peptide T at 10(-8) M induces IL-10 production by the human Th2 cell line and PBMC (P < 0.05, ANOVA). Also peptide T at 10(-9) M concentration significantly inhibited IFN-gamma production by PBMC (P < 0.001, ANOVA). Anti IL-10 antibody inhibited the anti-IFN-gamma effect of peptide T (P < 0.05, t-test). Our study shows that peptide T induces IL-10 production and inhibits IFN-gamma production. IL-10 is a potent anti-inflammatory cytokine. It inhibits IL-2 and IFN-gamma production from the T cells and downregulates the expression of TNF-alpha in the antigen presenting cells. Recently, IL-10 has been shown to resolve psoriatic lesions. The effects of peptide T on IL-10 and IFN-gamma production provides a plausible explanation for its clinical efficacy in psoriasis.

Upregulation of RANTES in psoriatic keratinocytes: a possible pathogenic mechanism for psoriasis.

Intraepidermal collections of neutrophils and lymphocytes are unique features of the inflammatory reaction of psoriasis. Migration of leukocytes from dermis to the epidermis suggests a role for chemotactic agent(s). In recent years, increased levels of chemokines such as IL-8 , GRO-a and MCP-1 have been reported in the keratinocytes of psoriatic tissue. IL-8 and GRO-alpha belong to a subfamily (C x C) class and MCP-1 is a beta chemokine. In this study, we investigated RANTES, which is a beta chemokine (C-C class); RANTES has been found to be associated with various cell-mediated hypersensitive disorders. We obtained eight skin biopsies from chronic psoriatic plaques, and five biopsies each from non-lesional psoriatic skin, lichen planus, eczematous dermatitis and skin from healthy controls. Snap-frozen samples were cut into 7 microm cryosections and stained with 6 mg/ml of monoclonal anti-RANTES mouse IgG (DNAX, Palo Alto, CA). Standard immunohistochemistry techniques were applied. RANTES was detected only in the keratinocytes. The number of keratinocytes in per mm2 of epidermis stained for RANTES were 116.79+/-98.42 in psoriatic tissues compared to 32.00+/-46.05 (p<0.05), 6.39+/-3.59 (p<0.01), 2.64 +/-1.15 (p<0.01) and 3.53+/-5.26 (p<0.01), respectively, in the non-lesional, lichen planus, eczematous lesions and normal skin. This is the first study to report that the keratinocytes of psoriatic tissue express high levels of RANTES compared to the controls. IL-8 and related molecules (C x C class) are predominantly chemotactic for neutrophils and MCP-1 is a strong chemotactic factor for monocytes. In contrast, RANTES is chemotactic for memory T cells and activated naive T cells. Increased amounts of RANTES as reported here provide an explanation for migration of the activated T cells to the epidermis of the psoriatic lesions. In addition, RANTES activates T cells. These results suggest that RANTES may have a significant role in the inflammatory process of psoriasis. Our findings further substantiate a regulatory role for keratinocytes in the inflammatory process of psoriasis.

Experimental studies on topoisomerase inhibitor camptothecin as an antipsoriatic agent.

OBJECTIVES: To elucidate the therapeutic mechanism of topical camptothecin (CPT) in treating psoriasis and to detect the effects of CPT on keratinocyte proliferation, differentiation and apoptosis. METHODS: Mitotic numbers in mouse vaginal epithelium at estrus and numbers of scale with granular layer per 100 scales in mouse tail epidermis were determined in vivo. Experiments on cultured normal human keratinocytes were performed using the methods of crystal violet staining, absorbance-cell number converting, cell counting and quantitation of morphologic changes during differentiation, transglutaminase assay and nucleosomal enrichment assay. RESULTS: Inhibition of cell proliferation and promotion of cell differentiation by camptothecin were showed in animal models and were reconfirmed in cultured keratinocytes. Apoptosis was induced by camptothecin and was showed by activation of "tissue" transglutaminase and increase in nucleosomes. The endonuclease activity was reduced by an endonuclease inhibitor aurintricarboxylic acid. CONCLUSION: The therapeutic effects of camptothecin on psoriasis can at least partly be explained by its multiple effects on DNA as a topoisomerase inhibitor.

Anti-chemotactic activities of peptide-T: a possible mechanism of actions for its therapeutic effects on psoriasis.

Peptide T is an octapeptide (ASTTTNYT) from the V2 region of gpl20 of HIV. D-[Ala]-Ser-Thr-Thr-Thr-Asn-Tyr-Thr-amide (DAPTA) is one of its analogue. DAPTA has been shown to resolve the psoriatic lesions. The mechanisms of action of peptide T for its therapeutic effect is not clearly understood. Lymphomononuclear cells play an important roles in inflammatory disease processes. Intraepidermal collection of lymphocytes is a unique feature of the inflammatory processes of psoriasis. It is believed that chemokine such as RANTES (C-C class) plays an important role for intraepidermal localization of the inflammatory infiltrates in psoriasis. In order to study the mechanisms, we have analyzed the effects of DAPTA on monocyte and lymphocyte chemotaxis. Chemotaxis of cells was measured by using Boyden chamber. DAPTA inhibited significantly the monocyte and lymphocyte chemotactic activity of RANTES (p < 0.005, < 0.001). Antichemotactic activities of peptide T analogue could be a possible explanation for its therapeutic efficacy in psoriasis.

Camptothecin induces differentiation, tissue transglutaminase and apoptosis in cultured keratinocytes.

Cultured normal human adult keratinocytes were exposed to (S)-(+)- camptothecin over the concentration range 10(-5) to 10(-10) M. The dose-dependent inhibition of growth was recorded using cell counting. The induction of terminal differentiation was demonstrated by the relative increase in squamous and cornified cells, and the concomitant decrease in small, proliferative cells, with an overall decrease in total cell numbers on going from 10(-10) to 10(-6) M concentration of the drug. The induction of apoptosis was studied by assay of two types of transglutaminase, "tissue" and "keratinocyte", and by assay of histone-linked mono- and oligonucleosomes. Induction of apoptosis was accompanied with increase in "tissue" transglutaminase and in the amount of nucleosomes, the latter being indicative of endonuclease activity. This activity was sharply increased at a camptothecin concentration of 10(-5) M, and may have been facilitated by "tissue" transglutaminase at lower concentrations. The data suggest that camptothecin restricts keratinocyte growth by several mechanisms including apoptosis and emphasize its possible use in topical therapy for psoriasis.

Double-labeled immunofluorescence study of cutaneous nerves in psoriasis.

BACKGROUND AND OBJECTIVE: In recent years, many reports have suggested an active role of neuropeptides in the pathogenesis of psoriasis. Increased numbers of neuropeptide-containing nerves positive for substance P (SP), vasoactive intestinal polypeptide (VIP), and calcium gene-related peptide (CGRP) have been reported in psoriatic tissue. As psoriatic epidermis has a larger mass/volume, however, it is expected to have more nerves and a higher number of neuropeptergic fibers. Therefore, instead of demonstrating a larger number of neuropeptergic fibers, a more significant study is to investigate whether the neuropeptergic fibers are denser in psoriatic tissue. In this study, we applied a double labeled immunofluorescence technique. This method allows the identification of the total number of nerve fibers and the number of nerves positive for specific neuropeptides. MATERIALS AND METHODS: We obtained biopsies from nine lesional and seven non-lesional psoriatic skins and six normal controls. Biopsies were snap frozen and then cut into 14 microm cryosections. The tissues were first treated with anti-microtubule associated protein (MAP)2 antibody to stain the nerves. This was followed by a second set of stainings for SP, VIP, and CGRP. Primary antibodies were used in dilutions of 1:200 for anti-MAP2, 1:200 for anti-SP, 1:800 for anti-VIP, and 1:400 for anti-CGRP. RESULTS: We found that the percentage of SP-positive fibers was twofold greater and the percentage of CGRP-positive fibers was 2.5 times greater in the psoriatic epidermis than in the epidermis of normal skin. Psoriatic epidermis had 30.1 +/- 3.9% SP-positive nerve fibers compared with 15.7 +/- 3.7% in the normal control. The corresponding values for CGRP-positive nerve fibers were 30.1 +/- 3.9% and 12.0 +/- 4.2%. CONCLUSIONS: The results of our study suggest that SP- and CGRP-containing neuropeptide nerve fibers are more dense in the psoriatic epidermis. Both SP and CGRP are chemotactic to neutrophils and mitogenic to keratinocytes and endothelial cells. In addition, SP activates T lymphocytes and induces adhesion molecules on the endothelial cells. Our observations suggest that neuropeptides may play a significant role in the inflammatory and proliferative process of psoriasis.