Sabine Fimmel

Enzymes involved in the biosynthesis of leukotriene B4 and prostaglandin E2 are active in sebaceous glands.

The expression of enzymes involved in leukotriene and prostaglandin signalling pathways, of interleukins 6 and 8 and of peroxisome proliferator-activated receptors in sebaceous glands of acne-involved facial skin was compared with those of non-involved skin of acne patients and of healthy individuals. Moreover, 5-lipoxygenase and leukotriene A4 hydrolase were expressed at mRNA and protein levels in vivo and in SZ95 sebocytes in vitro (leukotriene A4 hydrolase > 5-lipoxygenase), while 15-lipoxygenase-1 was only detected in cultured sebocytes. Cyclooxygenase-1 and cyclooxygenase-2 were also present. Peroxisome proliferator-activated receptors were constitutively expressed. Enhanced 5-lipoxygenase, cyclooxygenase 2 and interleukin 6 expression was detected in acne-involved facial skin. Arachidonic acid stimulated leukotriene B4 and interleukin 6 release as well as prostaglandin E2 biosynthesis in SZ95 sebocytes, induced abundant increase in neutral lipids and down-regulated peroxisome proliferator-activated receptor-α, but not receptor-γ1 mRNA levels, which were the predominant peroxisome proliferator-activated receptor isotypes in SZ95 sebocytes. In conclusion, human sebocytes possess the enzyme machinery for functional leukotriene and prostaglandin pathways. A comprehensive link between inflammation and sebaceous lipid synthesis is provided.

Involvement of the corticotropin-releasing hormone system in the pathogenesis of acne vulgaris

Background  The sebaceous gland exhibits an independent peripheral endocrine function and expresses receptors for neuropeptides. Previous reports have confirmed the presence of a complete corticotropin‐releasing hormone (CRH) system in human sebocytes in vitro. The capability of hypothalamic CRH to induce lipid synthesis, induce steroidogenesis and interact with testosterone and growth hormone implicates a possibility of its involvement in the clinical development of acne.

Interplay of IGF-I and 17β-estradiol at age-specific levels in human sebocytes and fibroblasts in vitro

In order to obtain greater insights into the molecular mechanisms accompanying hormonal aging the effects of growth hormone (GH), insulin-like growth factor-I (IGF-I), 17beta-estradiol, progesterone and dehydroepiandrosterone were tested as single agents in concentrations corresponding to 20- and 60-year-old females on human SZ95 sebocytes and fibroblasts. Cell proliferation and viability were measured by 4-methylumbelliferyl heptanoate and lactate dehydrogenase microassays, respectively, whereas lipid accumulation was documented via nile red microassay and fluorescence microscopy. mRNA and protein expression were evaluated via real-time RT-PCR and Western blotting or ELISA, accordingly. Our results depict the importance of IGF-I for lipid synthesis in SZ95 sebocyte and demonstrate the lack of 17beta-estradiol, dehydroepiandrosterone and progesterone activity on lipid synthesis and SZ95 sebocyte proliferation suggesting that the action of these hormones in vivo may be implemented through indirect pathways. Fibroblast showed to be more susceptible to 17beta-estradiol treatment, while IGF-I could significantly stimulate fibroblast proliferation in a dose-dependent manner. Furthermore, an interplay between the 17beta-estradiol and IGF-I signaling pathway was documented in both cell types. In conclusion, IGF-I is a key regulator of human skin aging and declining IGF-I levels with age may play a significant role in the reduction of skin surface lipids and thickness.

Desensitization of melanoma cells to autocrine TGF‐β isoforms

Previous studies have suggested that transforming growth factor‐beta 1 (TGF‐β1) acts as an autocrine growth inhibitor on normal human melanocytes, while melanoma cells may not respond to this stimulus. The role of other TGF‐β isoforms such as TGF‐β2 and TGF‐β3 remained less well characterized. In the present study, the mRNA and protein levels of all three isoforms of TGF‐β were analyzed in a panel of human melanoma cell lines and in cultures of normal human melanocytes in vitro. Northern analysis showed that the degree of TGF‐β1, ‐β2, ‐β3 mRNA expression varied considerably in melanoma cells, whereas TGF‐β expression was very low in melanocytes. In melanoma cells, secreted amounts of TGF‐β1 and TGF‐β3 were found increased in comparison to normal melanocytes: 615 pg/ml vs. 118 pg/ml and 193 pg/ml vs. 30 pg/ml (mean values). In addition, low levels of TGF‐β2 were detected (mean value: 28 pg/ml). Although TGF‐β secretion increased, the proliferation of melanoma cells was found to be only moderately inhibited by TGF‐β isoforms, in contrast to its strong antiproliferative effect on normal human melanocytes: −15%, −11%, and −18% vs. −52%, −46%, and −50% average inhibition at 0.5 ng/ml TGF‐β1, ‐β2, and ‐β3, respectively. The different efficacy of TGF‐β on melanocyte and melanoma cells was highly significant (P < 0.0001); in addition, TGF‐β–dependent growth inhibition of melanoma cells from primary tumors vs. cells from metastases showed a trend for further decreased response for the metastatic populations (P ≤ 0.075). Measurements of DNA synthesis revealed even more pronounced differences between melanocytes (−86%, −78%, and −80% inhibition, respectively, for TGF‐β1, ‐β2, and ‐β3) and melanoma cells (no inhibition). Our data show loss of responsiveness of melanoma cells to the growth‐inhibitory function of TGF‐β isoforms but not of melanocytes. Although melanoma cells are not growth‐inhibited by all three TGF‐β isoforms, they secrete significantly higher levels of TGF‐β, as compared to melanocytes. The reduced response indicates their escape from TGF‐β surveillance with ongoing tumor progression. J Cell Physiol 178:179–187, 1999.

Influence of physiological androgen levels on wound healing and immune status in men.

Aging in men is associated with a progressive decline in the production of several hormones, including androgens. The extent to which an age-dependent decline in androgen levels lead to health problems or can affect quality of life remains under debate. Clinical results on replacement therapy do not yet provide a definitive clue on the benefit/risk balance. A sexual dimorphism of the immune system is well established, and the differences between female and male immune responses under normal, as well as pathological, conditions are generally attributed to the influence of estrogens, progestins, and androgens. The suppressive effects of male sex hormones on immune functions have been observed in a wide variety of disease processes and appear to be testosterone-mediated. Endogenous testosterone inhibits skin wound healing response in males and is associated with an enhanced inflammatory response. Although there are no known gender-related differences in permeability barrier function in adults, estrogens accelerates—whereas testosterone retards—barrier development in fetal skin, and male fetuses demonstrate slower barrier development than female littermates.

The role of neuropeptides in the multifactorial pathogenesis of acne vulgaris

Background Central or peripheral stress may induce the development of clinical inflammation in the pilosebaceous unit (PSU) leading to the development or to exacerbation of pre-existing acne. The presence of a complete corticotropin-releasing hormone (CRH) system has been confirmed in human sebocytes in vitro. CRH is capable to induce lipid synthesis, steroidogenesis and interact with testosterone and growth hormone. α-Melanocyte-stimulating hormone (α-MSH) and its receptors can regulate melanogenesis as well as affect inflammation, apoptosis, and sebogenesis. Objectives The purpose of the study was to investigate by immunohistochemistry if changes of CRH/CRH-binding protein (CRHBP)/CRH receptors (CRHR) as well as melanocortin-1 receptor (MC-1R) expression are detectable in acne lesions vs normal skin, especially in the sebaceous gland (SG). Methods 33 patients with acne vulgaris and 8 age-matched volunteers without acne participated in the study. Skin biopsies were taken from acne-involved face, the non-involved thigh skin of the same patients and from normal human skin. Results Very strong expression of CRH was observed in acne-involved skin in SG cells comparing with weaker expression in non-involved and normal skin SG. The strongest reaction for CRHBP in acne-involved SG was in differentiating sebocytes. CRHR-1 and –2 exhibited the strongest expression in sweat glands and SG, respectively. Sebocytes and cells of the ductus seboglandularis (DSG) of acne-involved and non-involved skin showed very intense MC-1R expression in contrast to less intense scattered immunoreactivity in normal skin samples. Conclusions These data suggest that NP, such as the complete CRH system and MC-1R, are involved in the pathogenesis of acne.

IL-8 production and AP-1 transactivation induced by UVA in human keratinocytes: Roles of d-α-tocopherol

Identification of individual response-signal pathway induced by UVA-irradiation is necessary for understanding photo-biological and -pathological mechanisms with respect to the prevention of UV-irradiated skin damage and aging. Here, we investigated the role of D-alpha-tocopherol in the regulation of IL-8 production and AP-1 binding activity in UVA-irradiated human keratinocytes. UVA dramatically upregulated IL-8 mRNA expression and protein secretion and enhanced the AP-1-DNA binding activity. These effects of UVA irradiation were effectively reduced by D-alpha-tocopherol in a dose-dependent manner. The human keratinocytes expressed various NAD(P)H oxidase components, gp91phox homologues Nox1, and p22phox, p47phox, p67phox, as well as NOXO1, suggesting that cellular stress induced by UVA included the activation of non-phagocytic NADPH oxidase system, leading to AP-1 transactivation and IL-8 expression. D-alpha-tocopherol significantly inhibited the NADPH oxidase activity and the formation of malondialdehyde-thiobarbituric acid under UVA exposure. These results demonstrated that D-alpha-tocopherol may be able to prevent the IL-8 upregulation and the increase in AP-1 activation induced by UVA irradiation through down-modulating cellular oxidative stress.

Cryotherapy modifies synthetic activity and differentiation of keloidal fibroblasts in vitro

Abstract:  In order to obtain a persuasive explanation for the beneficial clinical effect of cryotherapy on keloids, we developed a reproducible model to apply freezing temperatures on cell cultures, and investigated their influence on proliferation, viability, synthetic activity and differentiation of dermal fibroblasts in vitro. Cell cultures were established from 13 untreated keloids and 10 healthy skin specimens matched for age and skin localization to the donors. No significant influence of cell freezing on the proliferation rates of both keloidal and normal fibroblasts was documented, but mechanical cell destruction with a wide variation in lethality rates (29% average lethal effect on keloidal fibroblasts and 41% on normal ones) was observed. When comparing specimens of keloidal and normal tissue derived from the same four donors, the keloidal fibroblasts were similar regarding their synthetic activity but presented enhanced tenascin‐C expression compared with the normal fibroblasts. After cryotherapy, delayed collagen III increase was detected in both cell types (P = 0.03). The collagen III/collagen I ratio increased from 1.6 to 2.8 in the keloidal and only from 1.9 to 2.2 in the normal fibroblasts after subcultivation. Normal fibroblasts exhibited a significantly lasting increase in fibronectin synthesis after freezing (P = 0.03). The intensity of staining against tenascin‐C was decreased in five of nine keloidal fibroblast cultures after cryotherapy (P < 0.05) but increased in four of five normal fibroblast cultures (P = 0.016), so that the intensity of tenascin‐C staining after freezing became identical in both cell types. Immunoblot studies in four patients and two controls confirmed a temporary decrease of tenascin‐C in keloidal but not in normal fibroblasts immediately after freezing. Significantly decreased staining with two markers of myogenic differentiation, myosin in keloidal fibroblasts (P = 0.002) and desmin (P = 0.007) in normal fibroblasts, could also be detected after treatment. In summary, with the help of a model for controlled cell freezing in vitro, cryotherapy was found to modify collagen synthesis and differentiation of keloidal fibroblasts.

2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin alters sebaceous gland cell differentiation in vitro

Abstract:  Chloracne is a characteristic marker of intoxication by 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) or related compounds. Decreased lipogenesis is a prominent clinical sign in this disease. However, the activity of dioxins on human sebaceous glands is still unclear. In this study, the effects of TCDD on sebaceous gland differentiation were studied both in human skin samples maintained ex vivo and in cultured SZ95 sebocytes. Aryl hydrocarbon receptor (AhR) protein expression, the receptor for dioxin, was detected in SZ95 sebocytes. Its expression was markedly inhibited by TCDD. Furthermore, we detected a reduced release of neutral lipids (10−10–10−8 m; P < 0.001) and decreased expression of epithelial membrane antigen and keratin 7, all of which are specific markers of sebaceous differentiation. Markedly, increased expression of the keratinocyte differentiation marker keratin 10 and of peroxisome proliferators‐activated receptor‐δ was assessed in SZ95 sebocytes treated with TCDD. To corroborate these in vitro data, an ex vivo sebaceous gland‐rich skin culture model was investigated. Obvious shrinkage of sebaceous glands with sebaceous duct hyperplasia and increased expression of keratin 10 in the atrophic sebaceous glands were observed on the 5th day of TCDD treatment. In conclusion, TCDD affects the differentiation of sebaceous gland cells probably by switching human sebaceous into keratinocyte‐like differentiation. In addition and together with the results of a parallel study (J Dermatol Sci 58, 2010, 211), we provide evidence that TCDD effects on human sebocytes are mediated through the AhR signalling pathway.

Psoriasin and Follicular Hyperkeratinization in Acne Comedones

pathological circumstances [5] . In the meantime, psoriasin has been suggested to be involved in the pathogenesis of inflammatory skin diseases, and its levels were found to increase in response to inflammatory stress. In addition, retinoic acid (RA) and inflammatory agents have been implicated in the upregulation of psoriasin [6, 7] . Psoriasin was shown to be induced not only in psoriatic epidermis [4] , but also in keratinocytes after alltrans -RA treatment in vitro [8] . In this work we suggest that psoriasin may be involved in the abnormal follicular hyperkeratinization detected in acne lesions. The purpose of the study was to detect changes of psoriasin expression in acne lesions versus normal skin, especially in the ductus seboglandularis, and to identify a possible psoriasin involvement in acne pathogenesis.