Expression of retinoid receptors in sebaceous cell carcinoma

PURPOSE: The aim of this study is to investigate whether there are any abnormalities in the in vivo expression of retinoid acid receptors (RAR-alpha, RAR-beta and RAR-gamma) and retinoid X receptors (RXR-alpha, RXR-beta and RXR-gamma) in sebaceous cell carcinoma. METHODS: Expression of retinoid receptors in paired specimens of cancerous tissues (n = 10) and adjacent normal tissues (n = 10) from 10 patients with sebaceous cell carcinoma was studied immunohistochemically by using anti-retinoid receptor antibodies. RESULTS: In eight of the 10 normal tissue samples, all six receptors were expressed. In the other two samples, all receptors were expressed except RAR-gamma (one sample) or RXR-gamma (two samples). Five tumours (50%) lacked RAR-alpha; RAR-alpha expression was lower in tumours than in normal tissues in eight of 10 cases. RAR-beta was expressed in the cytoplasm of nine of 10 tumours; RAR-beta expression was at least as high in tumours as in normal tissue in eight of 10 cases. Two tumours lacked RAR-gamma; three tumours had lower RAR-gamma expression than paired normal epithelium; four had the same RAR-gamma expression, and one had higher RAR-gamma expression. RXR-alpha expression was strong in all normal tissues and tumour samples. Ten tumours lacked RXR-beta and all 10 tumours lacked RXR-gamma expression. CONCLUSIONS: Diminished RXR-beta and RXR-gamma expression might be related to the development of sebaceous cell carcinoma. Additional studies are required to establish whether the defects in RAR expression in sebaceous cell carcinoma might affect the potential response of this tumour to treatment with retinoids.     

The sebocyte culture: a model to study the pathophysiology of the sebaceous gland in sebostasis, seborrhoea and acne

Acne is the most common skin disease which affects millions of people worldwide. Seborrhea and sebostasis are major cosmetic problems but also lead occasionally to diseases. This article summarizes the data of newest research of sebostasis, seborrhoea and acne made possible through the development of human and animal sebocyte culture models.     

Glucocorticoid receptors and inhibition of neonatal mouse dermal fibroblast growth in primary culture

Summary Primary cultures of dermal fibroblasts from neonatal mice were used to investigate some of the anti-inflammatory effects of glucocorticoids in vitro as influenced by the genetic background of two different strains of mice (A/J and C57 B1/6J). Fibroblasts were cultured in the absence or presence of various glucocorticoids for 2–7 days. After 4–7 days in the presence of steroid, DNA synthesis was reduced by 50–85% while protein synthesis was inhibited by 50–60%. Corticosterone produced a dose-dependent inhibition of DNA synthesis in these cells with a 50% reduction occurring at 10 nM. Specific, high affinity, low capacity binding proteins for [³H]dexamethasone or [³H]triamcinolone acetonide were identified in the cytoplasm of neonatal dermal fibroblasts which had an apparent Kd of 9 nM and 5,200–6,400 binding sites/cell. Sedimentation analysis of the [³H]triamcinolone acetonide-receptor complexes on low salt glycerol gradients exhibited binding in the 7 to 8 S region of the gradients. These studies demonstrate that inhibition of growth of primary cultures of mouse neonatal dermal fibroblasts by glucocorticoids is probably mediated by a receptor-mediated pathway, and that this primary culture system might be useful in delineating other anti-inflammatory effects of glucocorticoids in vitro.This investigation was supported in part by a Public Health Service International Research Fellowship (FO-5-TWO 2236) to LAV     

Immunofluorescence localization of nuclear retinoid receptors in psoriasis versus normal human skin

Psoriasis responds favourably to treatment with retinoids but the cellular pathways mediating these effects are poorly understood. Retinoids regulate keratinocyte proliferation and maturation via binding to nuclear retinoic acid receptors (mainly RARalpha and RARgamma) which form heterodimers with the 9-cis-RA receptor, RXRalpha. We have previously shown that mRNA expression of RARalpha and RXRalpha is down-regulated in psoriatic lesions as compared with non-lesional human skin. In the present study, we investigated the protein expression of RARalpha, RARgamma and RXRalpha in normal and psoriatic skin using indirect immunofluorescence analysis. Epidermal keratinocytes of normal and non-lesional psoriatic skin displayed similar nuclear localization of all three receptors; RARalpha was detected with decreasing intensity from basal to suprabasal layers, RARgamma showed the opposite trend, whereas RXRalpha was evenly expressed throughout the epidermis. In lesional psoriatic skin, however, all three receptor proteins showed a much higher staining intensity in the lower half of the epidermis; in particular, RARalpha immunoreactivity was low or even absent in the upper layers of epidermis. The results support the idea that psoriasis is associated with abnormal retinoid signalling in lesional epidermis.     

Heparin-binding epidermal-growth-factor-like growth factor activation of keratinocyte ErbB receptors Mediates epidermal hyperplasia, a prominent side-effect of retinoid therapy

Sun-protected human skin was maintained in organ culture and treated with all-trans retinoic acid in the presence or absence of reversible or irreversible pharmacologic antagonists of c-erbB receptor tyrosine kinase activity. In the absence of these inhibitors, all-trans retinoic acid induced epidermal hyperplasia comparable to that induced in intact skin by all-trans retinol or all-trans retinoic acid itself. There was a strong correlation between inhibition of epidermal hyperplasia in organ culture and inhibition of epidermal-growth-factor-dependent keratinocyte growth in monolayer culture. In additional studies it was shown that all-trans retinoic acid could overcome the known inhibitory effects of calcium on expression of HB-EGF-like growth factor mRNA in organ-cultured skin. Further, it was shown that an antibody to HB-EGF-like growth factor inhibited retinoid-stimulated epidermal hyperplasia in organ culture and reduced proliferation in cultured keratinocytes. In contrast, the c-erbB receptor tyrosine kinase antagonists and the neutralizing HB-EGF-like growth factor antibody were ineffective in inhibiting all-trans-retinoic-acid-dependent survival and proliferation of human dermal fibroblasts. Taken together, these data indicate (i) that retinoid-induced epidermal hyperplasia in human skin proceeds through c-erbB, and (ii) that HB-EGF-like growth factor is one of the c-erbB ligands mediating this effect.     

The role of the TRAF-interacting protein in proliferation and differentiation

Ubiquitination of proteins is a post-translational modification, which decides on the cellular fate of the protein. Addition of ubiquitin moieties to proteins is carried out by the sequential action of three enzymes: E1, ubiquitin-activating enzyme; E2, ubiquitin-conjugating enzyme; and E3, ubiquitin ligase. The TRAF-interacting protein (TRAIP, TRIP, RNF206) functions as Really Interesting New Gene (RING)-type E3 ubiquitin ligase, but its physiological substrates are not yet known. TRAIP was reported to interact with TRAF [tumor necrosis factor (TNF) receptor-associated factors] and the two tumor suppressors CYLD and Syk (spleen tyrosine kinase). Ectopically expressed TRAIP was shown to inhibit nuclear factor-kappa B (NF-κB) signalling. However, recent results suggested a role for TRAIP in biological processes other than NF-κB regulation. Knock-down of TRAIP in human epidermal keratinocytes repressed cellular proliferation and induced a block in the G1/S phase of the cell cycle without affecting NF-κB signalling. TRAIP is necessary for embryonal development as mutations affecting the Drosophila homologue of TRAIP are maternal effect-lethal mutants, and TRAIP knock-out mice die in utero because of aberrant regulation of cell proliferation and apoptosis. These findings underline the tight link between TRAIP and cell proliferation. In this review, we summarize the data on TRAIP and put them into a larger perspective regarding the role of TRAIP in the control of tissue homeostasis.     

The role of Eph receptors and Ephrins in the skin

Eph receptors and Ephrin ligands are widely expressed in the skin. Various studies have been carried out to identify the effects of these molecules on many aspects of skin development. Here we summarize the literature that has identified roles for Eph receptors and Ephrins in the skin, focusing mainly on the epidermis, hair follicles, and cutaneous innervation. This review may help direct and focus further investigations into the role of Eph receptors and Ephrins in the development, maintenance, and repair processes in cutaneous biology.     

The growth and structure of human oral keratinocytes in culture

Human keratinocytes derived from explants of cheek (buccal) mucosa grow vigorously in culture and can be subcultivated twice. The structure of the oral keratinocytes in vitro is the same in primary cultures and subcultures. The cells stratify, are characterized by well-developed tonofibrillar-desmosomal complexes, and rarely exhibit signs of terminal differentiation. Unique features of the culture system that favor keratinocyte growth are: incubation at 34 degrees C, inclusion of 0.5% dimethyl sulfoxide in the culture medium, and initiating subcultures as 5.0 mm colonies containing 100,000/20 microliter of medium. One primary culture can yield 6 first-passage subcultures, which subsequently achieve confluence in 10-12 days. Such cultures are a useful source of human keratinocytes that stratify but generally do not undergo terminal differentiation.     

The growth and differentiation of cultured newborn rat keratinocytes

Keratinocytes were cultured from adult and newborn rat epidermis using the 3T3 feeder cell technique. By modifying culture conditions a long-lived line of newborn rat keratinocytes was developed which showed a plating efficiency of 40% and a doubling time of 16 h. The cells produced stratified colonies with tonofilaments, desmosomes, cell envelopes, and keratohyaline granules. When the cells were grown on a collagen gel they formed a thick stratum corneum and many keratohyaline granules. The fibrous proteins synthesized by the newborn rat cultured keratinocytes were different than those of newborn rat epidermis but similar to those of adult rat cultured keratinocytes. A histidine-rich basic protein was identified by immunologic techniques but it appeared to be more heterogeneous than that of newborn rat epidermis. A cell envelope precursor protein was identified by dansyl cadaverine incorporation studies and was identical to a major envelope precursor of newborn rat epidermis. The growth characteristics, colony morphology, and biochemical markers did not change for up to 40 passages and there was no evidence of malignant transformation. Because of their case of growth and long-term survival these cells are useful for studying a variety of problems related to keratinization.     

The role of toll-like receptors in the pathophysiology of acne

Acne vulgaris is a common cutaneous disorder of the pilosebaceous follicle, affecting more than 45 million people in the United States alone. The pathogenesis of acne is multifactorial, involving abnormal hyperkeratinization, increased sebum production, hormones, cutaneous microbes, and immunological mechanisms. Many of the immunological processes that contribute to the formation of acne lesions take place at the very site of disease, the skin. Skin is an important component of the innate immune system, providing both physical barriers and rapid cellular responses by keratinocytes, Langerhans cells, and other infiltrating inflammatory cells. In this review, we discuss the ability of the innate immune system to use Toll-like receptors (TLRs) to recognize microbial patterns and initiate immune responses in cutaneous disorders. Because TLRs are vital players in infectious and inflammatory diseases, they are potential therapeutic targets. Indeed, the ability of TLRs to combat disease already has been harnessed through the development of drugs that act as TLR agonists. A better understanding of TLRs will allow for the development of new therapeutic options for cutaneous inflammatory diseases such as acne.     

Maintenance of human skin in organ culture: role for insulin-like growth factor-1 receptor and epidermal growth factor receptor

Recent studies have shown that adult skin incubated in low-Ca2+ (0.15 mM) medium rapidly degenerates but that normal architecture is maintained when the tissue is incubated in high-Ca2+ medium (1.4 mM Ca2+). To investigate whether the skin cell-produced growth factors insulin-like growth factor-1 (IGF-1) and epidermal growth factor (EGF) play a role in these events, 2-mm skin punch biopsies were obtained and maintained for 8 to 10 days in a basal medium containing 0.15 mM Ca2+ with and without growth factors, or containing 1.4 mM Ca2+ with and without antibodies to the same growth factors. In parallel experiments, cultured human keratinocytes were incubated for 2 days in the same basal medium in the presence or absence of the same growth factors and antibodies. Consistent with previous reports, organ cultures incubated in the low-Ca2+ (0.15 mM) medium rapidly degenerated. Neither IGF-1 nor EGF prevented the complete degeneration of epidermis and dermis in these organ cultures. Interestingly, the addition of an anti-IGF-1 receptor (IGF-1R) antibody to the organ cultures maintained in high-Ca2+ medium induced changes reminiscent of those seen when the organ cultures were maintained in low-Ca2+ medium, i.e. tissue degeneration. In contrast, antibodies to EGF receptor, used for comparison, only produced focal areas of epidermal necrosis. In vitro, IGF-1 is a known mitogen for keratinocytes. In cultured human keratinocytes, anti-IGF-1R antibody partially inhibited the IGF-1-mediated stimulation of human keratinocyte proliferation without affecting normal spontaneous growth. Additionally, IGF-1R immunolocalized to basal keratinocytes in vivo, exhibited specific binding to IGF-1 in vitro. This indicated a critical role for IGF-1R in both organ cultures ex vivo and cultured cells in vitro. Messenger RNA encoding both IGF-1 and IGF-1R were readily detected by RT-PCR in organ cultures incubated in both low- and high-Ca2+ medium. There were no detectable differences in IGF-1 mRNA in organ cultures growing in the low- or high-Ca2+ medium, but lower levels of IGF-1R mRNA were observed in the organ cultures maintained in low-Ca2+ medium than in those in high Ca2+ medium. These findings are consistent with homeostatic changes in the tissue grown under different calcium concentrations. IGF-1 mRNA was detected in several skin cell populations in vitro, even though it was undetectable in cultured keratinocytes. Taken together these findings indicate that (1) the IGF-1/ IGF-1R loop is critically involved in maintenance of human skin organ cultures ex vivo, and (2) IGF-1, locally produced by skin cells other than keratinocytes, interacts with its receptor, predominantly expressed in basal keratinocytes, to maintain tissue homeostasis.     

雄激素及雄激素受体在痤疮发病中的作用

雄激素和雄激素受体在某些皮肤相关疾病中发挥着重要作用,如雄激素性脱发及痤疮。目前可通过对这些疾病进行针对雄激素的合成或阻止其结合雄激素受体来达到治疗的目的,但这种治疗可能引起不良反应。目前对于AR基因敲除小鼠的最新研究已表明雄激素受体和雄激素在皮肤病的发病中起着不同的作用,而AR在皮肤病治疗中优于雄激素。现就雄激素及AR在痤疮发病中的作用综述如下。     

Decreased retinoid concentration and retinoid signalling pathways in human atopic dermatitis

Atopic dermatitis (AD) is one of the most common skin diseases. Various features present in AD like inflammation, reduced apoptosis, altered epidermal differentiation and hyperproliferation as well as permeability dysfunction are also regulated by retinoids. The aim of our study is to identify the retinoid signalling pathways and retinoid concentration profiles in AD skin. Human skin biopsies were obtained from healthy volunteers (HS) (n=6) and patients with AD (n=6), with both affected (AS) and non-affected (NAS) skin. The gene expression of retinoid receptors, retinoid-binding proteins and retinoid-metabolizing enzymes was investigated by QRT-PCR. Retinoid concentrations in serum and skin were measured via high performance liquid chromatography mass spectrometry-mass spectrometry. Our results show that the target gene expression of retinoid receptor regulated pathways is significantly decreased in AS and NAS of patients with AD. CYP26A1, transglutaminase 2 and retinoic acid receptor responder 1 decreased in NAS and AS in comparison with HS. The main retinoic acid synthesizing enzyme, retinal dehydrogenase 1, was significantly lower expressed in NAS (0.1%) and AS (1%) in patients with AD. Analysis of retinoid concentration in serum and skin showed comparable all-trans retinoic acid (ATRA) and retinol (ROL) concentrations from AD and healthy serum, but strongly reduced ATRA and ROL concentrations in affected and non-affected skin in comparison with healthy skin. Our data indicate that retinoid transport, synthesis, concentrations and signalling are strongly decreased in the affected but also in non-affected skin of patients with AD suggesting a general intrinsic influence on skin retinoid signalling pathway in patients with AD.