The publication data currently available has been vetted by Vanderbilt faculty, staff, administrators and trainees. The data itself is retrieved directly from NCBI's PubMed and is automatically updated on a weekly basis to ensure accuracy and completeness.
If you have any questions or comments, please contact us.
Lichenoid lesions of the skin are characterized by a band-like dermal inflammatory infiltrate and structural alterations of the basement membrane (BM). The etiopathogenesis of these lesions, of which lichen planus (LP) is perhaps the prototypic example, is unknown. Acute cases of LP are accompanied by the destruction of epidermal BM, degeneration of basal keratinocytes with loss of tonofilaments and hemidesmosomes, vesicular alterations, and even blister formation. Chronic LP is characterized by hyperkeratosis and acanthosis in the epidermis, fibrosis, and dense infiltrate in dermis. We found that acute LP lesions are characterized by uneven or absent immunostaining for laminin-5, laminin-1, and collagen type IV. Distribution and activity of gelatinases matrix metalloproteinase (MMP)-9 and MMP-2, and a specific inhibitor of MMP-2, tissue inhibitor of metalloprotein-2, were analyzed. The expression and activity of MMP-2 were increased, whereas tissue inhibitor of metalloprotein-2 expression was weak in the involved areas during the acute phase of LP. Moreover, we demonstrated in vitro that MMP-2 is directly capable of digesting laminin-5 gamma 2 chains to yield a 80-kd fragment. We also observed a weak or absent staining of all examined integrin receptors in the acute LP lesions. In chronic lesions, the staining of BM components was similar to normal controls. In these sections, normal expression of gelatinases and inhibitor was observed. There was, however, up-regulation and altered polarity of integrin receptors. These results indicate a link between overexpression of gelatinases, BM disruption, and altered integrin expression. In LP, the digestion of BM by MMP-2 may contribute to the pathogenesis by inducing altered integrin expression in basal keratinocytes and ultimately blister formation.
Melanoma growth stimulatory activity (MGSA/GRO), a cytokine originally characterized as an autocrine growth factor for melanoma cells, is highly chemotactic for neutrophils and releases neutrophil elastase as well as other matrix-degrading enzymes. Previous work has demonstrated the presence of MGSA/GRO in melanocytic lesions and in the epidermal keratinocytes of non-lesional skin and psoriatic scale. Herein, MGSA/GRO localization was examined in a variety of human skin lesions exhibiting proliferative and/or differentiative disorders using immunohistochemical methods. Most lesions showed greater MGSA/GRO immunoreactivity in the more differentiated suprabasal keratinocytes of the stratum spinosum and stratum granulosum than in the stratum basalis, where the dividing basal cells are found. Hair follicles, sebaceous glands, and sweat glands were also frequently positive for MGSA/GRO. The highest level of immunoreactive MGSA/GRO in diseased epidermis was detected in verruca vulgaris, followed by psoriasis, keratoacanthoma, and squamous cell carcinoma. Detection of MGSA/GRO in basal cell carcinoma was variable, being present in the sclerosing variant and absent in the more common nodular variant. Melanocytic lesions stained less intensely for MGSA/GRO than keratinocytic lesions, where the levels of MGSA/GRO expression correlated with the inflammatory response and degree of keratinocyte differentiation.
Psoriatic lesions are relatively frequent in patients with chronic liver disease. Furthermore, therapy with interferons tends to exacerbate the symptoms. The pathogenesis of psoriatic lesions is unclear. An important question is whether such lesions may be linked to the underlying chronic liver disease in these patients, or whether they are incidental manifestations of psoriasis vulgaris. We collected biopsy specimens from involved and uninvolved skin areas of chronic liver disease patients with psoriatic manifestations, as well as from psoriasis vulgaris patients, and investigated the patterns of integrin adhesion receptors by means of immunohistochemical methods. Integrin expression is known to be characteristically altered in psoriasis vulgaris. We found some of these changes in chronic liver disease psoriatic lesions-namely pericellular redistribution and suprabasal expression of the basement membrane receptor alpha 6 beta 4 and of the intercellular integrins alpha 2 beta 1 and alpha 3 beta 1. However, psoriasis vulgaris causes two other typical changes: One is the induction of the prototype fibronectin receptor alpha 5 beta 1, and the other is the alteration of integrin expression in areas of the epidermis that are macroscopically normal. These two changes were not found in chronic liver disease psoriasis biopsy specimens in 14 patients investigated. Thus integrin expression may be useful in differentiating chronic liver disease psoriatic lesions from psoriasis vulgaris lesions. Even though the two types of lesions are indistinguishable on inspection or by their histological features, they may be caused by distinct pathogenetic mechanisms. It remains to be seen whether the underlying chronic liver disease has a role, albeit indirect, in such mechanisms.
We have investigated lipid peroxidation in the skin of CD1 mice following single or repeated topical applications of the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA). A substantial accumulation of hydroxyphospholipids, to levels 3-5 times control values, followed exposure to two or more TPA treatments (24-72 h intervals), whereas single applications were ineffective. Sodium borohydride reduction increased the yield of product by approximately 50%, suggesting the additional presence of phospholipid hydroperoxides in the oxidized lipids. Straight phase HPLC analysis of the constituent hydroxy fatty acids, followed by gas chromatography/mass spectrometry, revealed that oxidized derivatives of linoleic acid, including 9- and 13-hydroxyoctadecadienoic acids (9- and 13-HODE), were the primary products. Stereochemical analysis showed ratios of S to R stereoisomers of 1.3 for 13-HODE and 1.27 for 9-HODE, which implied that TPA-induced peroxidation was primarily due to free radical oxidation, although a partial contribution of enzyme (lipoxygenase) activity is possible. The TPA-induced peroxidation was greater in the epidermis than in the dermis. Pre-exposure of mouse skin to the anti-inflammatory agent fluocinolone acetonide, antioxidants and enzyme (phospholipase A2 and lipoxygenase) inhibitors lowered the peroxidation response to subsequent exposure to TPA. Phospholipid peroxidation products may be useful markers of oxygen radical production in TPA-exposed mouse skin with possible relevance to tumor promotion.
The alpha-chemokines have been implicated as regulators of proliferation and differentiation of normal keratinocytes and as mediators of keratinocyte maturation and migration in inflammatory processes that involve the skin. Using the cutaneous wound repair model, we examined the sites and temporal sequence of the appearance of melanoma growth stimulatory activity or growth-regulated gene (MGSA/GRO;ligand) and the type B interleukin (IL)-8 receptor (IL-8RB) to which MGSA/GRO binds. Human burn tissues (n = 44) representing days 2 to 12 after injury were obtained during surgical debridement, fixed in 4% paraformaldehyde, and embedded in paraffin. Immunolocalizations were performed with polyclonal antisera for both ligand and receptor, as well as a monoclonal antibody for the IL-8 RB. Western blot analysis confirmed the presence of the IL-8 RB in immunoprecipitates of epidermal keratinocyte lysates. In normal skin, MGSA/GRO protein was restricted to sites populated by differentiated keratinocytes (suprabasal compartments, inner root sheath cells, and dermal sweat ducts). MGSA/GRO protein was barely detectable within epithelial margins and islands of burn wounds where the migrating/proliferating keratinocyte populations reside, but staining intensities increased as cells matured into the outer layers. Weak diffuse staining was detected in areas of neutrophilic infiltration (granulation tissue and overlying exudates). By contrast, in normal skin the IL-8 RB was detected in specific locations within epidermal and dermal compartments of healing wounds. In the dermis, polyvalent antibodies detected receptor immunoreactivity most prominently in dermal sweat ducts and endothelium of capillaries, whereas this immunoreactivity was inconspicuous in sections stained with the monoclonal antibody. Receptor immunostaining was noted in migrating/proliferating keratinocytes in epithelial margins and islands but was in the outer layers or in hypertrophic epidermis adjacent to wounds. This same pattern was observed in epidermal appendages such as hair follicles and eccrine sweat ducts. In granulation tissues, IL-8 RB was noted in numerous fibroblasts and in subpopulations of macrophages and smooth muscle. The presence of both MGSA/GRO and its receptor in human burn wounds implicate this cytokine as an autocrine or paracrine mediator of epidermal regeneration in both the inflammatory and proliferative phases of cutaneous wound repair.
Previously we showed that epidermal cells are able to use fibrinogen (FGN) as a migration substratum during wound closure. The goal of the present study was to determine the structural features of FGN that allow this migration. Pieces of glass coated with native, fragmented, or other modified forms of FGN were implanted into full-thickness skin wounds of adult newts such that migrating epidermal cells would encounter the implant. In this system, a coating of FGN allowed considerably more migration than a coating of BSA. At high concentrations, heat-denatured FGN supported as much migration as the same amount of intact FGN. Fraction I-9, a circulating form of FGN missing a 20-30K (K = 10(3) Mr) carboxy-terminal segment of the A alpha chain, was no less effective than intact FGN. Comparison of the isolated D1 and E fragments of FGN showed migration only on D1, but never to the extent seen on intact FGN containing the same amount of D1. Plasmin digestion of D1 in the presence of EDTA, a process which produces D3, a fragment differing from D1 by the loss of the carboxy-terminal 109 amino acids of the gamma chain, caused a significant loss of activity in the D fragment. Migration was good on implants coated with relatively high concentrations of purified A alpha chains but gamma chains were inactive. Migration over intact FGN was almost totally blocked by 230 microM-Arg-Gly-Asp-Ser (RGDS), a peptide known to interact with integrin-type receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
The effects of exogenously added transforming growth factor (TGF alpha and TGF beta on the growth of BALB/MK cells were examined. TGF alpha supplanted the epidermal growth factor (EGF) requirement in these cells. In contrast, TGF beta reversibly inhibited the growth of BALB/MK cells by abrogating the stimulatory actions of EGF or TGF alpha. The inhibitory effects of TGF beta appeared to be mediated by events distal to EGF ligand-receptor interactions. Growth inhibition of BALB/MK cells by TGF beta did not result in the induction of differentiation. This finding is different from the growth inhibition of these cells induced by elevated calcium levels (1.5 mM) which was tightly coupled to terminal differentiation. The BALB/MK cells were found to express TGF alpha mRNA, as well as TGF beta mRNA and protein. In addition, TGF alpha, as well as EGF, enhanced TGF alpha gene expression. These studies suggest a role for endogenous TGFs in regulating BALB/MK proliferation. TGF alpha provides a positive growth signal, while TGF beta is a potent inhibitor of growth even in the presence of such positive modulators as TGF alpha and EGF.
Transforming growth factor-alpha (TGF-alpha) is a polypeptide which is structurally related to epidermal growth factor (EGF) and binds to the EGF receptor. TGF-alpha synthesis occurs in a variety of neoplastic cells and during early fetal development but has not been reported in normal cells of the adult organisms. TGF-alpha has therefore been regarded as an embryonic growth factor which is inappropriately expressed during neoplasia. Here we report that primary cultures of normal human keratinocytes synthesize TGF-alpha. Furthermore, we show that addition of EGF or TGF-alpha to these cultures induces TGF-alpha gene expression, suggesting that a mechanism of auto-induction exists. Analysis of normal skin biopsies using in situ hybridization and immunohistochemistry demonstrates the in vivo presence of TGF-alpha messenger RNA and protein in the stratified epidermis.