Biomedical subjects

B A Bernard

Publications and source records attributed to B A Bernard.

At least 37 records · Page 2Linked to original sources

PubMed1997

Biphasic effects of minoxidil on the proliferation and differentiation of normal human keratinocytes.

Minoxidil is the most used drug with proved effects in the treatment of androgenetic alopecia (AGA), but little is known about its pharmacological activity and target cells in hair follicles. As AGA is characterized by follicle atrophy, accelerated hair cycles and hair fiber thinning, we postulated that keratinocyte proliferation/differentiation is affected and we tested Minoxidil's effects on those parameters. Normal human keratinocytes (NHK) of follicular or epidermal origin were cultured in the presence of Minoxidil (0, 0.1, 1, 10, 100, 1,000 microM) during 5-8 days in various media (high-/low-calcium content, with or without serum). Proliferation was assessed by mitochondrial dehydrogenase activity (XTT), BrdU incorporation, lysosome numeration (neutral red incorporation) and total protein dosage. Drug-induced cytotoxicity was measured by lactate dehydrogenase release in culture supernatant, and pro-differentiating effects were evaluated by relative involucrin expression (ELISA dosage). On this basis, we showed that Minoxidil had biphasic effects on the proliferation and differentiation of NHK: Minoxidil stimulated NHK proliferation at micromolar doses, while antiproliferative, pro-differentiative and partially cytotoxic effects were observed with millimolar concentrations. We can hypothesize that Minoxidil hypertrichotic activity in vivo is possibly mediated by the maintenance of proliferative potential in follicular keratinocytes precociously committed to differentiation.

Cell Differentiation↗

PubMed1997

Expression of retinoid nuclear receptor superfamily members in human hair follicles and its implication in hair growth.

Since clinical evidence of hair loss and hair depigmentation following etretinate therapy has been reported, we decided to study the expression levels of several members of the retinoid nuclear receptor superfamily in dermal and epithelial compartments of the human hair follicle. Additionally, we evaluated the effects of several ligands for these receptors on human hair growth in culture in vitro. We observed that the cellular/ cytoplasmic retinoic acid (RA) binding protein-II and the retinoid-X-receptor-alpha were constantly and strongly expressed in both compartments at levels comparable to those of vitamin D receptor. In dermal papilla cells, by contrast with RAR beta which was always expressed, RAR alpha and RAR gamma were not constantly expressed. In dermal sheath fibroblasts, both RAR alpha, RAR beta and RAR gamma mRNAs were moderately expressed, while in the epithelial compartment, namely the plucked hair, we observed the expression of the same genes in the absence of RAR beta. We also observed that RAR agonists all-trans RA and CD367 inhibited the survival of human hair follicles in culture in vitro, while RXR agonist CD2425 stimulated hair growth and survival at levels comparable to those of 1 alpha,25-dihydroxyvitamin D3, suggesting that RXR agonists might stimulate hair growth in humans in vivo.

Base Sequence↗

PubMed1997

Adult epidermal keratinocytes are endowed with pilosebaceous forming abilities.

Pluristratified epithelia of adult vertebrate skin continuously regenerate from stem cells, and the question still arises as to whether those cells are committed to the production of only one cell lineage, or in contrast they conserve their embryonic pluripotentiality. In order to investigate the abilities of adult cultured as well as wound healing epidermis, heterospecific fibroblast-keratinocyte recombinations were performed, which allow unquestionable identification of the cells implicated in the structures that differentiate. Adult human cultured breast epidermal cells and full-thickness wound healing from human facial skin and foreskin were associated with either rabbit embryonic trichogenic dermis or cultured dermal papilla cells of adult rat, before grafting onto nude mice for two weeks to one month. In situ hybridization with a human specific sequence Alu probe labeled the human cells, whereas implanted rabbit or rat and host mouse cells were distinguished by the Hoechst staining of their nuclei. The results show that human adult cultured breast epidermal cells are able to form hair buds and to participate in hair follicle formation, while adult healing epidermis from a sparsely hairy skin as the human face or the dorsal skin of nude mouse, or even from a glabrous epidermis as the human foreskin, are able to differentiate pilosebaceous units. Although a follicular origin of the involved keratinocytes cannot be excluded in the three first cases, the formation of hair and sebaceous glands by foreskin keratinocytes of children 2 to 10 years-old establishes the cutaneous appendage ability of the interfollicular epidermal stem cells. The formation of interspecies mosaic follicles also highlights the fact that there must be a significant level of commonality in the interactive signaling molecules used by epithelial cells from different species.

Aged↗

PubMed1997

Immunohistochemical analysis of tissue remodelling during the anagen-catagen transition of the human hair follicle.

The transition from the growth phase (anagen) to the involution phase (catagen) involves profound morphological changes in the human hair follicle. Club hair and epithelial column formation, for example, are key features of the catagen phase, which result in the disruption of physical interaction between the bulb and the dermal papilla. However, the dynamics and tissue remodelling that occur during this involution process remain largely unknown. Using monoclonal antibodies directed against K14 keratin, trichohyalin, transglutaminase I, desmoglein and Ki67 antigen, we followed the movements of each of the main hair follicle compartments during the onset of catagen. Our results indicate that the inner root sheath is an early target in this process, suggesting a key role for this compartment in the maintenance of hair follicle homeostasis.

Biomarkers↗

PubMed1996

Messenger RNA expression of steroidogenesis enzyme subtypes in the human pilosebaceous unit.

In order to define the respective involvement of steroidogenesis enzymes subtypes in the control of hair follicle homeostasis, we evaluated, by semiquantitative RT/PCR, the expression levels of mRNAs coding for 17 beta-hydroxysteroid dehydrogenase type 1 and type 2, 3 beta-hydroxysteroid dehydrogenase, Cyt.P450-aromatase, steroid 5 alpha-reductase type 1 and type 2 and 11 beta-hydroxysteroid dehydrogenase. These assays were performed for several components of the pilosebaceous unit (PSU); fresh plucked anagen hairs, sebaceous glands and primary culture of dermal papilla, as well as other tissues involved in an active steroid metabolism (human testis, liver, placenta, prostate, ovary, uterus and adrenals) as controls. We found that plucked hair (i.e. mainly keratinocytes from the inner and outer root sheaths) expressed: (1) very high levels of 17 beta-hydroxysteroid dehydrogenase type 2 corresponding to levels found in liver and placenta; (2) high levels of steroid 5-alpha-reductase type 1 corresponding to levels found in testis, liver and ovary, and moderate levels of 17 beta-hydroxysteroid dehydrogenase type 1, which corresponded to the expression in testis, prostate and uterus. In contrast, Cyt.P450-aromatase, 3 beta-hydroxysteroid dehydrogenase and steroid 5 alpha-reductase type 2 were poorly expressed in the pilosebaceous unit as compared with other tissues. Interestingly, expression patterns of these enzymes in primary cultures of dermal papilla were distinctive since 5 alpha-reductase type 1 and 11 beta-hydroxysteroid dehydrogenase were the only mRNA detected. Taken together, these results suggest that not only sebaceous gland but also outer root sheath keratinocytes may contribute, through the activity of the steroid 5 alpha-reductase type 1, to the pathogenesis of androgen-dependent alopecia.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1996

A minoxidil-related compound lacking a C6 substitution still exhibits strong anti-lysyl hydroxylase activity in vitro.

It has been previously reported that minoxidil inhibits the activity of lysyl hydroxylase (LH), an enzyme which catalyzes the formation of hydroxylysine, which is necessary for proper maturation of collagen at the transcriptional and enzymatic levels. Using the reverse transcriptase-polymerase chain reaction, we confirmed that this inhibition occurred at least at the transcriptional level. Furthermore, we took advantage of this sensitive and rapid method to perform a quantitative structure activity relation study using several compounds structurally related to minoxidil. We found that when the C6 of the pyrimidinyl moiety was substituted, it had to be by a tertiary nitrogen, i.e. an N-piperidin ring for the inhibition of LH mRNA synthesis to be observed. Surprisingly, however, we found that 2,4-diamino-pyrimidin-3-oxide, a new compound lacking an organic moiety para to the nitroxide oxygen, also retained a high inhibitory effect on LH mRNA expression, comparable to that of minoxidil. We thus conclude that the presence of a substituent para to the nitroxide oxygen is dispensable for inhibition of LH mRNA to be observed in vitro. This brings new insights into the design of therapeutic agents useful in any condition where an overproduction of mature collagen is unwanted, i.e. accelerated wound healing, keloids and localized scleroderma.

Antihypertensive Agents↗

PubMed1996

Pro-inflammatory cytokine cascade in human plucked hair.

Using reverse transcriptase polymerase chain reaction we showed that freshly plucked human anagen hair expressed both type 1 (80 kD) and type 2 (60 kD) interleukin (IL)-1 receptor mRNAs. The IL-1 receptor type 1 was functional since after in vitro stimulation of plucked hair with IL-1 alpha, we observed the induction of mRNA(s) for the inflammatory cytokines IL-1 beta, tumour necrosis factor alpha and IL-6 as well as for the chemokines monocyte chemotactic and activating factor and IL-8. In addition, the growth of dissected human anagen hairs in culture in vitro was significantly and dose-dependently inhibited by IL-1 alpha as a consequence of hair bulb degradation. These observations, together with those of other authors in IL-1 alpha transgenic mice evidence the inhibitory role of IL-1 on human hair growth. Therefore, in order to identify individuals with high inflammatory potential in their hair follicle environment, we designed a rapid and simple assay to detect variations in the level of IL-1 alpha production in the overnight supernatant of plucked hairs in culture. We observed that 32.7% of the specimens from the volunteers tested (n = 116) could be considered highly inflammatory in terms of IL-1 alpha production. Altogether, these results suggest that in alopecia androgenetica, hair growth might be negatively influenced by IL-1, directly produced by the outer root sheath keratinocytes. Consequently, identifying the "inflammatory alopecic individual' might be of clinical interest to discriminate among individuals for whom anti-IL-1 strategies might be of therapeutic relevance.

Adult↗

PubMed1995

Constitutive and inducible expression of drug metabolizing enzymes in cultured human keratinocytes.

Drug metabolizing enzymes, particularly those involved in the metabolism of carcinogenic chemicals, were characterized in cultured human keratinocytes. Using immunoblotting experiments, we analysed the expression of phase I enzymes, cytochrome P4501A1 (CYP1A1) and NADPH reductase, and phase II enzymes, phenol UDP-glucuronosyltransferase (UGT) and glutathione S-transferase (GST) isoform pi, in the presence of either classical inducers (i.e. 3-methylcholanthrene, dimethylbenz[a]anthracene, phenobarbital, and clofibrate) or all-trans retinoic acid (RA). This study has shown that the expression of CYP1A1 and UGT is concomitantly induced by 3-methylcholanthrene, dimethylbenz[a]anthracene, and RA, and that of NADPH reductase is only enhanced by phenobarbital and RA. In contrast, the expression of GST pi was not affected by the inducers. Using the reverse transcriptase-polymerase chain reaction, we have demonstrated that the effects of 3-methylcholanthrene, dimethylbenz[a]anthracene and RA on CYP1A1 expression correlate with an increase of CYP1A1 mRNA level. Our results indicate that, with the exception of clofibrate, xenobiotics and RA differentially modulate the expression of drug metabolizing enzymes.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1995

Epidemiology of injury in people with Alzheimer's disease.

BACKGROUND: Previous studies have suggested that the risk of injury is elevated among persons with dementia, but these studies have focused primarily on falls and fractures. This study characterizes all injuries incurred in a large sample of community-dwelling persons with a specific form of dementia, Alzheimer's disease (AD). SUBJECTS AND METHODS: The sample consisted of 281 community-dwelling persons diagnosed with AD according to NINCDS/ADRDA guidelines. Information regarding all injuries occurring within the previous 6 months was obtained through a structured interview of a caregiver. RESULTS: The rate of injuries was 58.4 per 100 persons per year. Although falling was the single most common mechanism by which injuries occurred, it accounted for only 43.8% of all injuries. Fractures accounted for 13.7% of injuries. Medical treatment was sought for 52.1% of the injuries. After adjustment for age and gender, the likelihood of injury was significantly associated with cognitive impairment and with ADL limitation, but the independent contribution of these two factors could not be assessed. CONCLUSIONS: The findings suggest that injuries are a significant problem in persons with AD.

Activities of Daily Living↗

PubMed1994

Presence of a retinoid responsive element in the promoter region of the human cytochrome P4501A1 gene.

Cytochrome P4501A1 (CYP1A1) plays a key role in the metabolic activation of procarcinogenic compounds, leading to skin carcinogenesis. It is therefore important to determine whether its enzymatic activity is altered by topically administered drugs. We investigated, in cultured normal human keratinocytes (NHK), the effects of retinoic acid (RA) and synthetic analogs on the regulation of the CYP1A1 gene. Using transient transfections and gel shift assays, we demonstrated that the human CYP1A1 gene promoter was differentially regulated by retinoid receptors. We report, for the first time, that a RA responsive element 5'-CTTAGGTCACCACGGGGCA-3' (RARE1A1) is present within the promoter region of the CYP1A1 gene.

Base Sequence↗

PubMed1994

[Molecular approach of hair biology].

The pilo-sebaceous unit is the site of numerous cell interactions, involving epithelial cells--hair follicle and sebaceous gland--, fibroblasts--dermal papilla--, nerve fibres, melanocytes, endothelial cells, and the immune system--Langerhans cells and lymphocytes--. From these timely and spacely regulated interactions results a complex process, namely the hair cycle comprising three main phases: anagen, catagen and telogen. Anagen is the growing phase of the follicle, catagen is a phase of involution, and telogen is a resting phase. Although the structure and the histology of the follicle is well known today, the molecular events controlling the hair cycle, namely the anagen-catagen and telogen-anagen transitions, remain obscure. The development of in vitro and in vivo models, however, has given some insights on the role growth factors such as IGF-1, TGF alpha, HGF, and EGF, as well as androgens such as the 5 alpha-dihydrotestosterone, cytokines such as IL-1 and potassium channel openers such as minoxidil. Many other mediators are likely to be discovered in the next future, the toughest task being to understand the integration of the diverse signals resulting in the harmonious development of the hair follicle.

Androgens↗

PubMed1993

Epidermis reconstructed from the outer root sheath of human hair follicle. Effect of retinoic acid.

In the present paper, we show that a multilayered and well-differentiated epidermis can easily and rapidly be generated in vitro from the outer root sheath of human hair follicles deposited on de-epidermized demis. Histologically, this epidermis presented characteristic features of normal human epidermis in vivo. Moreover, markers specific for interfollicular keratinocyte terminal differentiation, such as the K10 keratin, involucrin, membrane-bound transglutaminase, filaggrin and loricrin, were expressed in the reconstructed tissue. By in situ hybridization, keratin K5 and K10 mRNAs were detected in the basal and suprabasal cells, respectively, as in normal human epidermis. The differentiation pattern achieved in this reconstructed epidermis confirms the already reported phenotypical shift from outer root sheath cells to interfollicular keratinocytes and shows that this transition takes place in the absence of living fibroblasts. The differentiation of the reconstructed epidermis thus obtained was modulated by retinoic acid in a dose-dependent manner. This culture system on dead dermis is easier to handle than similar cultures on collagen-fibroblast lattices because of the resistance of dermis to mechanical forces and to collagenolysis. It could represent a valuable wound-healing model and a promising tool for pharmacological studies on in vitro reconstructed skin.

Cell Differentiation↗

PubMed1993

Comparison of CD271 (adapalene) and all-trans retinoic acid in human skin: dissociation of epidermal effects and CRABP-II mRNA expression.

A new synthetic retinoid analogue, adapalene (6-[3-(1-adamantyl)-4-methoxyphenyl]-2-naphthoic acid, CD271), which is relatively selective for retinoic acid receptor beta, was noted to be an effective comedolytic agent in the rhino mouse model and to have clinical efficacy against acne. In pursuit of this observation, we studied the effects of CD271 on the development of erythema, spongiosis, and epidermal hyperplasia as well as other well-characterized markers of in vivo retinoid action after 4 d of occluded topical treatment. The objective of the study was to elucidate further those parameters associated with potential clinical efficacy. Twenty-five subjects were treated with 0.1% all-trans retinoic acid cream, all-trans retinoic acid vehicle, 0.1% CD271 gel, or CD271 vehicle under occlusion for 4 d. Only all-trans retinoic acid induced erythema (p < 0.01 versus all other treatments). Similarly, histologic analysis revealed that epidermal hyperplasia and spongiosis were induced only by all-trans retinoic acid (p < 0.01 versus all other treatments). By immunohistochemical analysis: all-trans retinoic acid increased expression of epidermal transglutaminase, involucrin, and calgranulin (p < 0.05 versus all other treatments). In contrast to these data, both CD271 and all-trans retinoic acid caused marked and significant (p < 0.05) elevation of cellular retinoic acid-binding protein-II (CRABP-II) messenger ribonucleic acid steady-state levels as judged by quantitative RNA blot analysis. Although CD271 treatment did not lead to erythema or affect epidermal morphology, its ability to induce a marker of retinoid action (i.e., CRABP-II) was 70% the potency of all-trans retinoic acid. This study suggests that CRABP-II gene expression may be a more sensitive indicator of retinoid biologic activity in skin than are erythema or changes in epidermal morphology and differentiation.

Adapalene↗

PubMed1993

Adapalene, a new chemical entity with retinoid activity.

Adapalene is a novel chemical entity which, in terms of pharmacology, behaves similar to tretinoin, but is chemically and photochemically stable. It has a particular selectivity profile for the known nuclear retinoic acid receptors with low affinity for RAR alpha and no transactivating potential for RXR alpha. This receptor profile could imply that adapalene, in contrast to tretinoin, affects the terminal differentiation pathway of epidermal cells rather than their proliferation. Furthermore, adapalene does not bind to members of the cellular retinoic acid binding protein family. Adapalene has comedolytic activity in the topical rhino mouse model. It exerts a moderate-to-potent anti-inflammatory effect in a series of in vitro and in vivo models. In comparative clinical studies involving 72 acne patients, the efficacy of adapalene was comparable, if not superior, to tretinoin, but adapalene was better tolerated. The data reviewed in this paper indicate that adapalene should be particularly beneficial in the treatment of acne.

Acne Vulgaris↗

PubMed1992

Identification of synthetic retinoids with selectivity for human nuclear retinoic acid receptor gamma.

The action of retinoids on gene regulation is mediated by three distinct nuclear retinoic acid receptor (RAR) subtypes called RAR alpha, beta and gamma. Since RAR gamma is predominantly expressed in adult skin, specific ligands for this subtype could (i) represent valuable tools to evaluate the biological role of RAR gamma in skin and (ii) provide therapeutic entities with a higher therapeutic index at lower teratogenic risk. Using in vitro binding studies and a functional transactivation assay, we have identified three compounds with high RAR gamma selectivity.

Animals↗

PubMed1991

Predictors of behavioral disturbance in Alzheimer's disease.

The relationship of behavioral disturbances in Alzheimer's disease to disease severity, age at onset, and the presence of extrapyramidal signs was investigated in three studies. Five categories of behavior disturbance were ascertained through structured interview with the patient's primary caregiver: apathy, agitation, psychotic symptoms, disinhibition, and irritability. In Study 1, measures of disease severity accounted for 42% of the variance in the Apathy scale but less than 20% of the variance in the remaining scales. In Study 2, the presence of extrapyramidal signs was associated with increased Apathy and moderated the association between disease severity and the Psychotic Symptoms and Irritability scales. In Study 3, age at onset was associated with the Agitation scale and moderated the association between disease severity and the Apathy, Psychotic Symptoms, and Irritability scales. The findings are discussed in terms of the clinical heterogeneity within Alzheimer's disease, the possible biological bases of these behavioral disturbances, and the psychometric issues pertinent to their measurement.

Age Factors↗

PubMed1991

Selective high affinity retinoic acid receptor alpha or beta-gamma ligands.

Biological effects of retinoic acid (RA) are mediated through its binding to three closely related nuclear receptors (RAR alpha, RAR beta, and RAR gamma) belonging to the steroid-thyroid nuclear receptor family. RARs are able to modulate the transcription of specific genes by binding to responsive elements located in the promoter-enhancer region of these genes. As demonstrated by in situ hybridization, the distribution of each RAR type in the developing embryo, as well as in the adult, is not uniform. In this context, synthetic retinoids that would behave as selective ligands would be invaluable for studying the respective roles of each RAR type in cultured cells, whole animals, and embryos. Moreover, from a pharmacological point of view, such selective compounds may possess a higher therapeutic index and a lower teratogenic risk, because they might affect specific tissues and spare some others. As an approach to this problem, we have set up two complementary assays, (i) an in vitro binding assay to determine the Kd values of retinoids for RAR alpha, RAR beta, and RAR gamma and (ii) a functional assay in cultured cells to evaluate the potential of retinoids to transactivate, through their binding to one type of RAR, a reporter gene. The binding assay uses nuclear extracts of COS-7 cells transfected with vectors expressing RAR alpha, RAR beta, or RAR gamma. The functional assay is a measure of chloramphenicol acetyltransferase (CAT) activity in HeLa cells co-transfected with the expression vectors used in the binding assay and the reporter gene TRE-tk-CAT. Selective agonists for RAR alpha (Am80 and Am580) and RAR beta-RAR gamma (CD495 and CD564) were identified. However, compounds with pure RAR beta or RAR gamma selectivity have not yet been identified.

Carrier Proteins↗

PubMed1991

Cessation of driving and unsafe motor vehicle operation by dementia patients.

We surveyed 522 consecutive patients from a dementia clinic to assess duration of driving after disease onset and instances of unsafe motor vehicle operation in the preceding 6 months. Among the 333 patients licensed to drive at the onset of dementia, the median duration of driving after onset was 28.6 months. Patients with a clinical diagnosis of Alzheimer's disease drove significantly longer than those with other dementia syndromes. Of the 93 patients still driving at the time of the survey, approximately one third were reported to have had at least one form of unsafe motor vehicle operation in the past 6 months, including 21 patients with motor vehicle accidents. Motor vehicle accidents were associated with use of prescription medications with sedative properties and with lower subjective ratings of the patient's driving ability by the informant.

Accidents, Traffic↗