Biomedical subjects

F Bernerd

Publications and source records attributed to F Bernerd.

27 records · Page 2Linked to original sources

PubMed1993

Expression of the carcinoma-associated keratin K6 and the role of AP-1 proto-oncoproteins.

The normal pattern of keratin expression in epidermis is altered in carcinomas as well as in nonmalignant diseases such as psoriasis and wound healing. Under these circumstances, the transcription of differentiation-specific keratins K1 and K10 is suppressed, whereas the activation- and hyperproliferation-associated keratins K6 and K16 are induced. Very little is known regarding transcriptional regulators involved in this switch. To investigate the nuclear factors that participate in regulation of expression of the K6 gene, we have characterized the binding sites for nuclear proteins on the promoter DNA of the K6 gene by gel retardation assays and site-specific deletion mutagenesis. We found four nuclear protein binding sites in the K6 gene promoter. Two are near the TATA box, but their ability to bind HeLa or keratinocyte nuclear extracts is independent of the TATA box-binding protein complex. The third binding site is a large palindrome. The sequences of these three sites do not correspond to any described target sequences for characterized transcriptional factors. The fourth is an AP-1 site, the target sequence for the proto-oncoproteins fos and jun. All four sites are independent of the previously characterized epidermal growth factor-responsive element, EGF-RE. These findings suggest that there may be two parallel pathways of induction of K6 transcription. One proceeds through the EGF-RE, which may be involved in nonmalignant hyperproliferation processes; the other, through the AP-1 site and the fos-jun proto-oncoproteins, may be related to induction in malignant processes.

Animals↗

PubMed1992

Delayed onset of epidermal differentiation in psoriasis.

In normal epidermis, as previously reported, the first signs of differentiation occur within the basal layer in a subpopulation of keratinocytes that start to express K1 and K10 "supra-basal" keratin transcripts (20-30% of the basal cells) and proteins (5-10% of the basal cells). We found that in psoriatic lesions, the basal layer was devoid of cells expressing these early differentiation markers. This was already the case at the periphery of the lesions, where epidermis, although slightly acanthotic, still completes the keratinization process. In the center of the lesions, not only the basal layer, but also several rows of suprabasal cells, were negative for keratin K10 transcripts or protein. Moreover, the upper nucleated layers of involved epidermis were also devoid of K10 keratin transcripts or proteins. In normal epidermis, as previously reported, transcripts for the "basal" K5 keratin were mainly restricted to the basal layer, whereas the protein persisted in a few suprabasal layers. We found that in psoriatic epidermis, K5 keratin transcripts persisted in several suprabasal layers up to the level where K10 keratin transcripts appeared. These data, although not contradictory with previous reports showing a reduction of K1-K10 keratins and other differentiation markers in psoriasis, demonstrate that these quantitative changes are in fact the result of major qualitative differences in the distribution of these markers in psoriatic versus normal skin. Our results indicating that the onset of differentiation is delayed in psoriasis show that, contrary to conclusions accepted so far, not only the suprabasal compartment, but also the basal one, is abnormal in psoriatic epidermis.

Cell Differentiation↗

PubMed1992

Expression of keratinocyte transglutamine mRNA revealed by in situ hybridization.

Plasma membrane-bound transglutaminase (TGm) catalyzes the formation of cornified envelopes (CE) in terminally differentiating keratinocytes. The recent cloning of cDNA encoding rabbit TGm allows detailed studies of its gene expression and regulation. In the present paper, we describe the localization of TGm mRNA in rabbit tissues, as well as in normal and psoriatic human skin, as assessed by in situ hybridization. Furthermore, we correlate TGm mRNA localization with the distribution of the TGm protein detected by immunohistochemistry with a specific monoclonal antibody. In rabbit epidermis, TGm mRNA was expressed in suprabasal cells. The TGm protein was detected in the upper stratum spinosum and stratum granulosum. In rabbit esophagus, TGm mRNA and protein were already expressed to a high level in the first suprabasal cell layer, and their expression decreased in the more differentiated cells. In normal human skin, a small amount of TGm mRNA, restricted to the stratum granulosum, was found, whereas psoriatic skin samples contained high amounts of TGm mRNA in the suprabasal layers with a decreasing gradient into the rete ridges, i.e., the involutions of the epidermis into the dermal compartment. The TGm protein was absent from the rete ridges and confined to several cell layers expressing high levels of mRNA. There was virtually no difference between uninvolved psoriatic and normal epidermis.

Animals↗

PubMed1992

Expression of loricrin is negatively controlled by retinoic acid in human epidermis reconstructed in vitro.

In epidermis, the last steps of keratinocyte differentiation are characterized by the covalent cross-linking of cornified envelope precursors such as involucrin and loricrin, a hydrophobic protein recently described in mouse and human epidermis. In situ hybridization of normal human skin sections with a human loricrin cRNA probe and immunolabeling with an antiserum directed against a synthetic peptide corresponding to the carboxyterminus of human loricrin revealed the presence of loricrin transcripts and protein in the granular layers of epidermis. In human epidermis reconstructed in vitro by growing keratinocytes on dermal equivalents, loricrin and loricrin mRNAs were also restricted to granular cells, but their amounts seemed higher than in epidermis from skin biopsies. The reactivities for both loricrin and loricrin mRNAs were abolished by a treatment of the cultures with a retinoic acid concentration (10(-6) M) provoking a complete inhibition of terminal epidermal differentiation (parakeratosis). Thus, the regulation of loricrin synthesis is different from that of another envelope precursor, involucrin, which does not seem to be significantly modulated by retinoic acid. Together with the well-documented inhibition of epidermal transglutaminase by retinoic acid, our results provide a molecular basis for the inhibition of cornified envelope formation by retinoic acid.

Amino Acid Sequence↗

PubMed1991

The rhino mouse model: the effects of topically applied all-trans retinoic acid and CD271 on the fine structure of the epidermis and utricle wall of pseudocomedones.

The histological and ultrastructural effects following 3 weeks' topical treatment with two agents (all-trans retinoic acid and a new synthetic retinoid-like substance, CD271) were evaluated on the epidermis and the epithelial wall of the pseudocomedones in rhino mouse skin. The comedolytic effects of these drugs were similar, and consisted of a reduction of the utricular diameter, with normalization of follicular units. Morphological examinations revealed a hyperplastic response with an increase in the number of cell layers of both epidermis and follicular epithelium, and modifications in keratinocyte differentiation. Ultrastructural changes in the epidermis and epithelial wall were observed mainly in the granular and horny layers, with increased desquamation, and a decrease in the cohesiveness of corneocytes. During the first week of treatment, some cutaneous toxic effects were noticed, but they normalized within two weeks. On the other hand, a fine granular material persisted in the intercellular spaces. It is confirmed that the skin of the rhino mouse is a good model for the evaluation of the comedolytic effects of drugs. Moreover, it reveals the specific effects of retinoids on epidermal differentiation. We have demonstrated that topically applied CD271 induces modifications similar to those obtained with all-trans retinoic acid. It is thus concluded that CD271 is a potentially effective anti-acne agent.

Adapalene↗

PubMed1991

Sequence of morphological events during topical application of retinoic acid on the rhino mouse skin.

In a study of the comedolytic action of retinoids on the epidermal pseudocomedones of rhino mouse skin, the earliest changes and the sequence of events induced by the treatment were investigated. Rhino mice were treated topically with all-trans retinoic acid and at various time intervals from day 0 to 3 weeks, histological and ultrastructural studies as well as quantification of mast cells were performed. The earliest changes occurred in the dermis after 2 days of treatment and were characterized by degranulation of mast cells, clumping and association of Langerhans cells and lymphocytes. During the second week of treatment there was hyperplasia, hypergranulosis and an increase in the number of membrane coating granules with disorganization of the horny layer both of the epidermis and the follicular epithelium. These changes in the proliferation and the differentiation of keratinocytes resulted in a comedolytic effect. Associated with these epidermal changes there were changes in the dermis with an increased number of mast cells and a decreased number of Langerhans cells.

Acne Vulgaris↗

PubMed1988

Normal Merkel cells express a synaptophysin-like immunoreactivity.

Synaptophysin (SY), a specific component of the membrane of presynaptic vesicles, has been reported as a novel marker for neurons, certain neuroendocrine cells and their neoplasms including neuroendocrine carcinomas of the skin. The origin of the Merkel cells (MC) being far from clear, this study was performed to establish if normal MC express SY. It is demonstrated by immunofluorescence and immunoelectron microscopy using a monoclonal antibody SY38 to this glycoprotein that normal MC in man, rabbit and pigs express an SY-like reactivity. Although immunoblotting identification of the immunoreactive material gave negative results, it is likely that normal MC contain SY. By immunoelectron microscopy, the staining was located at the surface of cytoplasmic vesicles. In view of the possible involvement of SY in the Ca2+-dependent neurotransmitter release, the observation of an SY-like immunoreactivity in MC supports the view that they are epithelial neuroendocrine cells and that they may possess a neurosecretory function.

Animals↗

PubMed1987

Herpes gestationis factor reacts with the amniotic epithelial basement membrane.

Sera from five patients with clinically and immunopathologically proven herpes gestationis were studied by complement fixing immunofluorescence and complement fixing immuno-electron microscopy using specimens of skin, amniochorion and placenta. The results demonstrated that the complement fixation antibody (herpes gestationis factor) could bind to the basement membrane zone of skin, amnion and chorion laeve but not to that of the placental syncytiotrophoblast. These data suggest that the herpes gestationis factor may be induced by the basement membrane zone antigens of extra-villous cytotrophoblasts.

Amnion↗

PubMed1987

Ultrastructural aspects of skin after cryoultramicrotomy.

Skin was studied by transmission electron microscopy after cryoultramicrotomy. Global and ultrastructural preservation of the tissue was obtained with satisfactory cohesion between dermis and epidermis. The main constitutive elements could be observed with good definition allowing easy recognition of all the organelles and therefore absolute identification of each cellular type encountered. The methodology provided a comparable quality to the conventional technique. Ice crystal artefacts were minimized but slight enlargement of intercellular spaces persisted. One of the main advantages of this procedure is that neither lipidic solvents nor embedding resins, are used, so that one can envisage cytochemical studies.

Animals↗