Biomedical subjects

A Slominski

Publications and source records attributed to A Slominski.

At least 19 recordsLinked to original sources

PubMed2007

What are subcutaneous adipocytes really good for?

Our acute awareness of the cosmetic, psychosocial and sexual importance of subcutaneous adipose tissue contrasts dramatically with how poorly we have understood the biology of this massive, enigmatic, often ignored and much-abused skin compartment. Therefore, it is timely to recall the exciting, steadily growing, yet underappreciated body of evidence that subcutaneous adipocytes are so much more than just 'fat guys', hanging around passively to conspire, at most, against your desperate attempts to maintain ideal weight. Although the subcutis, quantitatively, tends to represent the dominant architectural component of human skin, conventional wisdom confines its biological key functions to those of energy storage, physical buffer, thermoregulation and thermoinsulation. However, already the distribution of human superficial adipose tissue, by itself, questions how justified the popular belief is that 'skin fat' (which actually may be more diverse than often assumed) serves primarily thermoinsulatory purposes. And although the metabolic complications of obesity are well appreciated, our understanding of how exactly subcutaneous adipocytes contribute to extracutaneous disease - and even influence important immune and brain functions! - is far from complete. The increasing insights recently won into subcutaneous adipose tissue as a cytokine depot that regulates innate immunity and cell growth exemplarily serve to illustrate the vast open research expanses that remain to be fully explored in the subcutis. The following public debate carries you from the evolutionary origins and the key functional purposes of adipose tissue, via adipose-derived stem cells and adipokines straight to the neuroendocrine, immunomodulatory and central nervous effects of signals that originate in the subcutis - perhaps, the most underestimated tissue of the human body. The editors are confident that, at the end, you shall agree: No basic scientist and no doctor with a serious interest in skin, and hardly anyone else in the life sciences, can afford to ignore the subcutaneous adipocyte - beyond its ample impact on beauty, benessence and body mass.

Adipocytes↗

PubMed2006

CRH functions as a growth factor/cytokine in the skin.

We tested the effect of CRH and related peptides in a large panel of human skin cells for growth factor/cytokine activities. In skin cells CRH action is mediated by CRH-R1, a subject to posttranslational modification with expression of alternatively spliced isoforms. Activation of CRH-R1 induced generation of both cAMP and IP3 in the majority of epidermal and dermal cells (except for normal keratinocytes and one melanoma line), indicating cell type-dependent coupling to signal transduction pathways. Phenotypic effects on cell proliferation were however dependent on both cell type and nutrition conditions. Specifically, CRH stimulated dermal fibroblasts proliferation, by increasing transition from G1/0 to the S phase, while in keratinocytes CRH inhibited cell proliferation. In normal and immortalized melanocytes CRH effect showed dichotomy and thus, it inhibited melanocyte proliferation in serum-containing medium CRH through G2 arrest, while serum free media led instead to CRH enhanced DNA synthesis (through increased transition from G1/G0 to S phase and decreased subG1 signal, indicating DNA degradation). CRH also induced inhibition of early and late apoptosis in the same cells, demonstrated by analysis with the annexin V stains. Thus, CRH acts on epidermal melanocytes as a survival factor under the stress of starvation (anti-apoptotic) as well as inhibitor of growth factors induced cell proliferation. In conclusion, CRH and related peptides can couple CRH-R1 to any of diverse signal transduction pathways; they also regulate cell viability and proliferation in cell type and growth condition-dependent manners.

Apoptosis↗

PubMed2006

Melatonin increases survival of HaCaT keratinocytes by suppressing UV-induced apoptosis.

Melatonin is a potent antioxidant and direct radical scavenger. As keratinocytes represent the major population in the skin and UV light causes damage to these cells, the possible protective effects of melatonin against UV-induced cell damage in HaCaT keratinocytes were investigated in vitro. Cells were preincubated with melatonin at graded concentrations from 10(-9) to 10(-3) m for 30 min prior to UV irradiation at doses of 25 and 50 mJ/cm2. Biological markers of cellular viability such as DNA synthesis and colony-forming efficiency as well as molecular markers of apoptosis were measured. DNA synthesis was determined by [3H]-thymidine incorporation into insoluble cellular fraction, clonogenicity through plating efficiency experiments and apoptosis by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. DNA synthesis experiments showed a strong protective effect by preincubation with melatonin at concentrations of 10(-4) m (P < 0.01) and 10(-3) m (P < 0.001). Additional postirradiation treatment with melatonin showed no increase in the pre-UV incubation protective effect. These results indicate that preincubation is a requirement for melatonin to exert its protective effects. The mechanism of melatonin's protective effect (10(-6) to 10(-3) m) includes inhibition of apoptosis as measured by TUNEL assay. Moreover, the biological significance of these effects is supported by clonogenic studies showing a significantly higher number of colonies in cultures treated with melatonin compared to controls. Thus, pretreatment with melatonin led to strong protection against UVB-induced damage in keratinocytes.

Apoptosis↗

PubMed2006

Oncostatic effects of the indole melatonin and expression of its cytosolic and nuclear receptors in cultured human melanoma cell lines.

Melatonin has been shown to have oncostatic effects on malignant melanoma in vitro and in vivo. We studied the growth suppressive effects of melatonin over a wide range of concentrations in four melanoma cell lines (SBCE2, WM-98, WM-164 and SKMEL-188) representative for different growth stages and phenotype. Melanoma cells were incubated with melatonin 10(-12)-10(-3) M, and proliferation and clonogenicity was assessed at 12 h and 14 days, respectively. We also determined the expression of cytosolic quinone oxidoreductases NQO1, NQO2 (known as MT3 receptor) and nuclear receptor RORalpha by RT-PCR. Melatonin at pharmacological concentrations (10(-3)-10(-7) M) suppressed proliferation in all melanoma cell lines. In SKMEL-188 cells cultured in serum-free media, melatonin at low concentrations (10(-12)-10(-10) M) also slightly attenuated the proliferation. The effects of pharmacological doses of melatonin were confirmed in the clonogenic assay. Expression of NQO1 was detected in all cell lines, whereas NQO2 and nuclear receptor RORalpha including its isoform RORalpha4 were present only in SBCE2, WM-164 and WM-98. Thus, melatonin differentially suppressed proliferation in melanoma cell lines of different behaviour. The intensity of the oncostatic response to melatonin could be related to the cell-line specific pattern of melatonin cellular receptors and cytosolic binding protein expression.

Cell Nucleus↗

PubMed2003

Self-regulated endocrine systems in the skin.

The skin is the main physical barrier between the environment and internal homeostasis; functionally it is highly complex and expresses endocrine activities with self-regulatory properties. This skin neuroendocrine system comprises locally produced neuro-endocrine mediators that interact with corresponding specific receptors through para or autocrine mechanisms. While there are also systemic effects of cutaneously produced hormones exemplified by vitamin D3 and PTHrP, the most important function of this system would be the modulation of responses to noxious agents. Solar radiation, the most significant environmental stressor is already known to significantly affect cutaneous endocrine activities. Ultimately, the skin neuroendocrine system would act to preserve cutaneous structural and functional integrity to maintain systemic homeostasis.

Endocrine Glands↗

PubMed2001

Microassay of phosphate provides a general method for measuring the activity of phosphatases using physiological, nonchromogenic substrates such as lysophosphatidic acid.

Since measurement of lysophosphatidate phosphatase activity is important in studies of tumorigenesis, we attempted to develop a simpler alternative to the more complex methods currently available. Measuring the phosphate released would permit use of the same method for a variety of phosphatases with physiological substrates, many of which are nonchromogenic. The Malachite green method of K. Itaya and M. Ui (1966, Clin. Chim. Acta 14, 361) has adequate sensitivity for quantitating phosphatase activity in biological samples. In samples with high endogenous phosphate concentrations pretreatment with 50 mg Dowex 1 x 10 (100-200 mesh, OH- form) usually permitted reliable determination of phosphatase activity. For 34 consecutive runs the mean relative difference [(phosphorus activity--vitamer activity)/phosphorus activity] obtained from the simultaneous measurement of both the phosphate released and the corresponding organic product (pyridoxal and pyridoxine) was -0.03 +/- 0.09. The within run and between run coefficients of variation (three runs of four to five replicates) were 0.05 and 0.04, respectively. Pyridoxine 5'-phosphate hydrolase activity (pH 10) in cultured skin cells (normal and cancerous) ranged from 2 to 12 nmol phosphorus/min. mg protein. Lysophosphatidate phosphatase activity (pH 7.4) ranged from 3 to 14 nmol phosphorus/min. mg protein. The current approach permits the measurement of phosphatase activity with a single method using a variety of substrates and incubation conditions.

Alkaline Phosphatase↗

PubMed2001

Steroidogenesis in the human skin: 21-hydroxylation in cultured keratinocytes.

We have evaluated the metabolism of radiolabeled progesterone (P) by the microsomal fraction isolated from HaCaT keratinocytes. P was widely metabolized to different compounds that included DOC (5-7% conversion) thus demonstrated 21-hydroxylase (21-OHase) activity, a key step in adrenal synthesis of gluco- and mineralocorticoids. However, RT-PCR amplification for the CYPc21 transcript of the corresponding gene showed no evidence for gene expression in HaCaT cells suggesting that the 21-OHase enzyme present in keratinocytes is different from that described in adrenal gland. Further characterization showed that whereas estradiol stimulated markedly P metabolism by HaCaT microsomes, with generation of new unidentified compounds, Lineweaver-Burk analysis of keratinocyte 21-OHase activity showed that the K(m) and V(max) were unaffected by estrogen. The apparent K(m) was 0.6 microM without estradiol and 0.7 microM with estradiol, while the respective V(max) values were 60 and 76 nmol/l/min. To conclude, we found extensive metabolism of P in human keratinocytes, we also provide the first demonstration of 21-OHase activity in this cell system and further showed that it is coded by a gene different from the adrenal CYPc21.

Adrenal Glands↗

PubMed2001

Cutaneous expression of corticotropin-releasing hormone (CRH), urocortin, and CRH receptors.

Studies in mammalian skin have shown expression of the genes for corticotropin-releasing hormone (CRH) and the related urocortin peptide, with subsequent production of the respective peptides. Recent molecular and biochemical analyses have further revealed the presence of CRH receptors (CRH-Rs). These CRH-Rs are functional, responding to CRH and urocortin peptides (exogenous or produced locally) through activation of receptor(s)-mediated pathways to modify skin cell phenotype. Thus, when taken together with the previous findings of cutaneous expression of POMC and its receptors, these observations extend the range of regulatory elements of the hypothalamic-pituitary-adrenal axis expressed in mammalian skin. Overall, the cutaneous CRH/POMC expression is highly reactive to common stressors such as immune cytokines, ultraviolet radiation, cutaneous pathology, or even the physiological changes associated with the hair cycle phase. Therefore, similar to its central analog, the local expression and action of CRH/POMC elements appear to be highly organized and entrained, representing general mechanism of cutaneous response to stressful stimuli. In such a CRH/POMC system, the CRH-Rs may be a central element.

Animals↗

PubMed2001

Pleiotropic effects of corticotropin releasing hormone on normal human skin keratinocytes.

The hypothalamic-pituitary-adrenal (HPA) axis is the major stress response system. Several components of the HPA axis, such as corticotropin-releasing hormone (CRH) and POMC peptides and their receptors are also present in the skin. In earlier studies, we showed that CRH inhibits cellular proliferation of immortalized human keratinocytes. We now examine further the functional activity of the HPA axis in the skin, by characterizing the actions of CRH on normal foreskin keratinocytes. The CRH receptor was detected as CRH-R1 antigen at 47 kDa in the cultured keratinocytes by Western blotting, and immunohistochemistry demonstrated its presence in the epidermal and follicular keratinocytes. CRH is also biologically active in cultured keratinocytes, where it inhibits proliferation and enhances the interferon-gamma-stimulated expression of the hCAM and ICAM-1 adhesion molecules and of the HLA-DR antigen. These effects were concentration-dependent, with maximal activity at CRH 10(-7) M. Thus, in the keratinocyte, the most important cellular component of the epidermis, CRH appears to induce a shift in energy metabolism away from proliferation activity, and toward the enhancement of immunoactivity. Therefore, similar to its central actions, cutaneous CRH may also he involved in the stress response, but at a highly localized level.

Blotting, Western↗

PubMed2001

Malignant melanoma.

CONTEXT: The rapidly developing fields of melanoma research are revolutionizing the current concepts on melanoma etiology and pathogenesis and are introducing newer diagnostic techniques and potential therapeutic approaches. OBJECTIVES: To present the most current concepts on the etiology and pathogenesis of melanoma and to introduce the recent diagnostic techniques and the potential therapeutic approaches. METHODS: Data sources were reports on melanoma published in the English language literature and observations made using specimens available at Harvard University, Johns Hopkins Medical Center, Albany Medical College, Loyola University Medical Center, and University of Tennessee Health Science Center. RESULTS: Studies on melanoma containing chromosomal or genetic evaluation were selected for further analysis. Current clinical and pathologic categories with the reported genetic abnormalities were related to the latest information on pigment biology. The data extracted were used to develop a conceptual framework on the pathogenesis of melanoma; the generated model was then evaluated and used to suggest potential therapeutic approaches. CONCLUSIONS: (1) Melanoma is not genetically homogeneous, and the existing differences between the pathologic categories, particularly in areas such as type of growth phase (radial vs vertical growth), total vertical dimension, ulceration of primary tumor, and metastatic process, have profound prognostic and therapeutic implications. (2) Chromosomal aberrations and gene mutations are found in sporadic and familial melanomas; among the most important are those affecting the 9p21, which contains the p16 locus, a site known to be critical for normal progression of the cell cycle. Aberrant p16 expression is associated with more aggressive behavior. (3) Melanoma cells possess a remarkable repertoire of biosynthetic capacities represented by the production of hormones, growth factors, and their receptors that may sustain and accelerate tumor development and progression. For example, expression of the tumoral products alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone is regulated in vitro by ultraviolet light, a known carcinogen. (4) Melanomas differ from other tumors in their intrinsic capability to express melanogenic enzymes with the corresponding structural proteins to actually synthesize melanin. Melanogenesis-related proteins are rapidly entering the clinical arena, being used not only as diagnostic markers, but also as potential targets for melanoma therapy.

Chromosome Aberrations↗

PubMed2000

Active steroidogenesis in the normal rat skin.

Using the radiolabeled precursors of adrenal steroids (14)C-11-deoxycorticosterone (DOC) and (14)C-progesterone ((14)C-PROG) we demonstrate that rat skin can synthesize a number of steroids. TLC separation of labeled metabolites show that among the (14)C-steroid products, two co-migrate with corticosterone (B) and 11-dehydrocorticosterone (A) standards. Thus, normal rodent skin possesses steroidogenic activity that can be shown using progesterone or DOC as primary substrates.

Animals↗

PubMed2000

What is the most promising strategy for the treatment of metastasizing melanoma?

The treatment of patients with metastasizing melanoma, still one of the most deadly diseases in modern medicine, ranks among the greatest challenges that a clinician has to face. Metastatic melanoma also is one of the most profound sources of clinical frustration, since it provides far more ultimately defeating experiences than clinical victories. At the same time, the fascinating biology of melanoma has invited the study of this neuroectodermal tumor as a model system for dissecting many of the key problems of modern oncology, ranging from molecular oncogenesis via the controls of tumor proliferation, apoptosis, invasion, metastasis, and angiogenesis to tumor immunosurveillance and tumor drug resistance. Together with the dire need to develop more effective treatment modalities for improving both life expectancy and quality of life of affected patients, this has made metastatic melanoma a favorite model for the exploration of innovative strategies for tumor management. Encouragingly, many of these have already generated very promising results in animal models. However, this impressive level of research progress in conquering melanoma in the animal room contrasts rather pitifully with the actual progress made on the ward. This CONTROVERSIES feature, therefore, critically and soberly reviews the state of the art of treating metastatic melanoma today (distinguishing between nodal and distant metastases), and sharply defines unresolved or comparatively neglected key problems. In addition, this feature highlights several novel, provocative, hitherto underappreciated, yet potentially promising treatment approaches that deserve systematic exploration. Hopefully, this will offer further inspiration for the design and pursuit of innovative anti-melanoma strategies off-the-beaten-track.

Humans↗

PubMed2000

Human skin expresses growth hormone but not the prolactin gene.

Using sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) methods, we showed the expression of mRNA for growth hormone (GH) but not prolactin (PRL) in whole human skin (normal and basal cell carcinoma (BCC)). These RNAs for PRL and GH were below detectability in human epidermal keratinocytes and in human and hamster malignant melanocytes. This is in agreement with previous studies showing GH gene expression in dermal fibroblasts. GH peptide was not detected (by immunocytochemistry) in human skin specimens (normal and pathologic) in either dermal or epidermal compartments. The mRNA coding for the GH mediator insulin-like growth factor-1 (IGF-1) was detectable in whole skin and in malignant melanocytes. Therefore, in the present investigation of hormonal mediators of the cutaneous (epidermal) response to environmental stress, we have excluded the direct participation of PRL and GH in that reaction. Thus the analogy previously noted between the systemic (central) and skin responses to stress, as represented by cutaneous expression of hypothalamic-pituitary-adrenal axis components, does not extend to other pituitary hormones also involved in that response such as PRL and GH.

Adult↗

PubMed2000

Corticotropin releasing hormone and proopiomelanocortin involvement in the cutaneous response to stress.

The skin is a known target organ for the proopiomelanocortin (POMC)-derived neuropeptides alpha-melanocyte stimulating hormone (alpha-MSH), beta-endorphin, and ACTH and also a source of these peptides. Skin expression levels of the POMC gene and POMC/corticotropin releasing hormone (CRH) peptides are not static but are determined by such factors as the physiological changes associated with hair cycle (highest in anagen phase), ultraviolet radiation (UVR) exposure, immune cytokine release, or the presence of cutaneous pathology. Among the cytokines, the proinflammatory interleukin-1 produces important upregulation of cutaneous levels of POMC mRNA, POMC peptides, and MSH receptors; UVR also stimulates expression of all the components of the CRH/POMC system including expression of the corresponding receptors. Molecular characterization of the cutaneous POMC gene shows mRNA forms similar to those found in the pituitary, which are expressed together with shorter variants. The receptors for POMC peptides expressed in the skin are functional and include MC1, MC5 and mu-opiate, although most predominant are those of the MC1 class recognizing MSH and ACTH. Receptors for CRH are also present in the skin. Because expression of, for example, the MC1 receptor is stimulated in a similar dose-dependent manner by UVR, cytokines, MSH peptides or melanin precursors, actions of the ligand peptides represent a stochastic (predictable) nonspecific response to environmental/endogenous stresses. The powerful effects of POMC peptides and probably CRH on the skin pigmentary, immune, and adnexal systems are consistent with stress-neutralizing activity addressed at maintaining skin integrity to restrict disruptions of internal homeostasis. Hence, cutaneous expression of the CRH/POMC system is highly organized, encoding mediators and receptors similar to the hypothalamic-pituitary-adrenal (HPA) axis. This CRH/POMC skin system appears to generate a function analogous to the HPA axis, that in the skin is expressed as a highly localized response which neutralizes noxious stimuli and attendant immune reactions.

Animals↗

PubMed2000

Spatiotemporal expression, distribution, and processing of POMC and POMC-derived peptides in murine skin.

In murine skin, after depilation-induced anagen, there was a differential spatial and temporal expression of pro-opiomelanocortin (POMC) mRNA, of the POMC-derived peptides beta-endorphin, ACTH, beta-MSH, and alpha-MSH, and of the prohormone convertases PC1 and PC2 in epidermal and hair follicle keratinocytes and in the cells of sebaceous units. Using a combination of in situ hybridization histochemistry and immunohistochemistry, we found cell-specific variations in the expression of POMC mRNA that were consistent with immunoreactivities for POMC-derived peptides. Cells that contained POMC peptide immunoreactivity (IR) also expressed POMC mRNA, and where the IR increased there was a parallel increase in mRNA. The levels of PC1-IR and PC2-IR also showed cell-specific variations and were present in the same cells that contained the POMC peptides. Based on the cleavage specificities of these convertases and on the spatial and temporal expression of the convertases and of ACTH, beta-endorphin, beta-MSH, and alpha-MSH, we can infer that the activities of PC1 and PC2 are responsible for the cell-specific differential processing of POMC in murine skin.

Adrenocorticotropic Hormone↗

PubMed2000

Neuroendocrinology of the skin.

The classical observations of the skin as a target for melanotropins have been complemented by the discovery of their actual production at the local level. In fact, all of the elements controlling the activity of the hypothalamus-pituitary-adrenal axis are expressed in the skin including CRH, urocortin, and POMC, with its products ACTH, alpha-MSH, and beta-endorphin. Demonstration of the corresponding receptors in the same cells suggests para- or autocrine mechanisms of action. These findings, together with the demonstration of cutaneous production of numerous other hormones including vitamin D3, PTH-related protein (PTHrP), catecholamines, and acetylcholine that share regulation by environmental stressors such as UV light, underlie a role for these agents in the skin response to stress. The endocrine mediators with their receptors are organized into dermal and epidermal units that allow precise control of their activity in a field-restricted manner. The skin neuroendocrine system communicates with itself and with the systemic level through humoral and neural pathways to induce vascular, immune, or pigmentary changes, to directly buffer noxious agents or neutralize the elicited local reactions. Therefore, we suggest that the skin neuroendocrine system acts by preserving and maintaining the skin structural and functional integrity and, by inference, systemic homeostasis.

Homeostasis↗

PubMed2000

Liquid chromatography-mass spectrometry detection of corticotropin-releasing hormone and proopiomelanocortin-derived peptides in human skin.

We have previously shown expression of CRH and POMC genes and peptides in the human skin. To ascertain the identity of those peptides, we used methods of peptide extraction and purification combined with the highly specific technique of liquid chromatography-mass spectrometry. Testing extracts of human skin, we identified endogenous peptides with masses and retention times corresponding to CRH, ACTH 1-39, ACTH 1-13, and alpha-MSH standards. Thus, conclusive evidence is provided for the presence of CRH and the POMC-derived ACTH 1-39, ACTH 1-13, and alpha-MSH peptides in human skin. Direct identification of these peptides is consistent with translation of the corresponding genes, and it also suggests intermediate pituitary lobe-like POMC peptide processing.

Chromatography, Liquid↗

PubMed2000

The skin produces urocortin.

Since the skin produces POMC peptides, in the present work we investigated local production of urocortin, a peptide related to CRH, the normal endogenous stimulant for POMC. Urocortin immunoreactivity was detected by direct RIA in extracts of human skin, mouse skin (C57BL-6 strain), cultured cells from established lines of human melanoma and squamous cell carcinoma, human keratinocytes (Ha-CaT), and hamster melanomas. Addition of a reverse phase high performance liquid chromatography step before the RIA confirmed the presence of urocortin, as the immunoreactivity eluted at the same retention time as urocortin standard in extracts from HaCaT keratinocytes and mouse skin. Using the tandem technique of liquid chromatography-mass spectrometry, we identified a peptide with the same mass and retention time as the urocortin standard in human skin extracts. The urocortin antigen could be immunolocalized to normal keratinocytes of the epidermis and hair follicle, epithelium of sweat and sebaceous glands, dermal skeletal muscle, and nevocytes; it was also detected in melanoma and basal cell carcinoma cells. RT-PCR amplification of ribonucleic acid from human skin, cultured keratinocytes, and melanoma cells showed a 145-kb fragment from the coding region of exon 2 of the urocortin gene in all of the tested sources. Lastly, sequencing of the amplified fragment confirmed 100% homology with the known sequence of the urocortin gene. In conclusion, we now demonstrate that human skin and mouse skin as well as cultured keratinocytes and melanoma cells exhibit functional expression of the urocortin gene with actual production of urocortin peptide.

Animals↗