MAPK/AP-1 signal pathway in tobacco smoke-induced cell proliferation and squamous metaplasia in the lungs of rats

Overwhelming evidence has demonstrated tobacco smoke (TS) is causally associated with various types of cancers, especially lung cancer. Sustained epithelial cell hyperplasia and squamous metaplasia are considered as preneoplastic lesions during the formation of lung cancer. The cellular and molecular mechanisms leading to lung cancer due to TS are not clear. Mitogen-activated protein kinases (MAPK)/activator protein-1 (AP-1) can be activated by various stimuli and play a critical role in the control of cell proliferation and differentiation. To date, information on the response of the MAPK/AP-1 pathway during hyperplasia and squamous metaplasia induced by TS is lacking. We therefore investigated the effects of TS on the development of epithelial hyperplasia and squamous metaplasia, regulation of MAPK/AP-1 activation, and expression of AP-1-regulated cell cycle proteins and differentiation markers in the lungs of rats. Exposure of rats to TS (30 mg/m(3) or 80 mg/m(3), 6 h/day, 3 days/week for 14 weeks) dramatically induced cell proliferation and squamous metaplasia in a dose-dependent manner, effects that paralleled the activation of AP-1-DNA binding activity. Phosphorylated ERK1/2, JNK, p38 and ERK5 were significantly increased by exposure to TS, indicating the activation of these MAPK pathways. Expression of Jun and Fos proteins were differentially regulated by TS. TS upregulated the expression of AP-1-dependent cell cycle proteins including cyclin D1 and proliferating cell nuclear antigen (PCNA). Among the AP-1-dependent cell differentiation markers, keratin 5 and 14 were upregulated, while loricrin, filaggrin and involucrin were downregulated following TS exposure. These findings suggest the important role of MAPK/AP-1 pathway in TS-induced pathogenesis, thus providing new insights into the molecular mechanisms of TS-associated lung diseases including lung cancers.

A7445G mtDNA mutation present in a Portuguese family exhibiting hereditary deafness and palmoplantar keratoderma

Mitochondrial DNA (mtDNA) A7445G point mutation has been shown to be responsible for familial nonepidermolytic palmoplantar keratoderma (NEPPK) associated with deafness without any additional features. To date, only a few cases have been described. We report a Portuguese pedigree presenting an inherited combination of NEPPK and sensorineural deafness compatible with maternal transmission. Clinical expression and age of onset of NEPPK and deafness were variable. Normal expression patterns of epidermal keratins and filaggrin, intercellular junction proteins including connexin 26, loricrin and cornified envelope proteins, were observed. Molecular analysis revealed that all the affected members, previously screened for Cx26 mutations with negative results, presented the mtDNA A7445G point mutation in the homoplasmic form. To our knowledge, this is the fifth family in whom inherited NEPPK and hearing loss are related to this mitochondrial mutation.

Apoptosis coordinates with proliferation and differentiation during human hair follicle morphogenesis

BACKGROUND

Apoptosis sculptures the most complicated skin appendage, feathers, out of epidermal layers by playing a variety of roles (1). Human hair follicle formation is different from feathers in growth direction and pattern formation of proliferative zone.

OBJECTIVE

To delineate the apoptotic events together with proliferation and differentiation in developing human hair follicle and emphasis on the mechanism and biological meaning of epidermal hair canal.

METHODS

We used TUNEL to examine apoptosis and Ki-67, involucrin, filaggrin immuno-localization to examine proliferation and differentiation.

RESULTS

In hair germs, apoptosis was diffuse in periderm, basal keratinocytes, and mesenchymal cells with high Ki-67 expression, but spared follicular germinative cells with low Ki-67 and high bcl-2 expression. In hair pegs, apoptosis was active in high Ki-67 expression area, like outer root sheath, hair follicle sheath, but spared dermal papilla with low Ki-67 and high bcl-2 expression. In bulbous pegs, apoptosis appeared in companion layer, precortical area, inner root sheath and outer root sheath, but spared bulge area with high bcl-2 expression. Apoptosis resulted in epidermal and subepidermal hair canal formation. Filaggrin and involucrin were expressed in the lining cells of hair canal. CD1a+ cells were densely distributed alone the hair canal before its opening.

CONCLUSION

During human hair follicle morphogenesis, apoptosis coordinates with proliferation to shape the growth zone, creates space to free the hair shaft from follicular wall, and directs a driving force on hair shaft extension. Apoptosis accompanies the terminal differentiation of epidermal hair canal. The bottom becomes interfollicular epidermis after roof shedding and hair exposure. Langerhans cells also populate in the hair canal before its opening. The biological meaning of epidermal hair canal is supposed to prepare the barrier when hair perturbing the intact of epidermis.

Humoral immune response to citrullinated collagen type II determinants in early rheumatoid arthritis

Collagen type II (CII) is a relevant joint-specific autoantigen in the pathogenesis of rheumatoid arthritis (RA). Whereas the reasons for the breakage of self tolerance to this major cartilage component are still enigmatic, T cell responses to glycosylated CII determinants in RA patients indicate that post-translational modifications play a role. Since the conversion of arginine into citrulline by peptidylarginine deiminases (PAD) in some non-joint-specific antigens such as filaggrin or fibrin has been shown to give rise to RA-specific humoral immune responses, we investigated whether PAD modification of cartilage-specific CII might affect its recognition by circulating autoantibodies in early RA. In vitro treatment with purified PAD led to arginine deimination of native CII or of synthetic CII peptides as evidenced by amino acid analysis. The citrullination resulted in modified recognition of the immunodominant CII epitope C1(III) (amino acid residues 359-369) by murine and human antibodies. In a cohort of early RA patients (n=286), IgG antibodies directed toward a synthetic citrullinated C1(III) peptide (citC1(III)-P) were detectable with a prevalence of 40.4%. The partial autoantibody cross-reactivity between citC1(III)-P and citrullinated peptides mimicking epitopes of the cytoskeletal autoantigen filaggrin suggests that autoimmunity to cartilage-specific modified self might be a critical intermediate bridging recognition of PAD-modified extra-articular autoantigens with the disruption of tolerance to native cartilage constituents.

Nitric oxide regulates synthesis of gene products involved in keratinocyte differentiation and ceramide metabolism

During terminal differentiation of keratinocytes the expression of various proteins, which are required for the formation of the epidermal water barrier in the skin of land dwelling animals, is upregulated. Using a cell culture model for the differentiation of human keratinocytes and real-time PCR, we quantified the mRNA levels of several proteins involved in differentiation and ceramide metabolism. A calcium shift (1.1 mM CaCl2, 10 microM linoleic acid) for 8 days triggered an increase in mRNA levels of keratin 10 (75-fold), profilaggrin (55-fold), glucosylceramide synthase (40-fold), beta-glucocerebrosidase (30-fold), prosaposin (15-fold), acid sphingomyelinase (5-fold), and serine palmitoyltransferase (SPTLC2, 4-fold). However, mRNA levels of keratin 14 and acid ceramidase did not change significantly. On the other hand nitric oxide added at concentrations lower than 0.25mM stimulates proliferation of keratinocytes (Krischel et al., J. Invest. Dermatol. 111, 286-291, 1998). Accordingly, the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 0.2 mM) had no effect on the morphology of cultured keratinocytes, whereas in cultured human fibroblasts apoptosis was induced. The expression patterns obtained suggest that keratinocytes remain in a basal proliferative state, with a 3-fold increase in keratin 14 expression, a marked decrease in mRNA levels of differentiation markers and of most ceramide-metabolizing enzymes to negligible levels. The inhibitor of the NO synthase, N(G)-nitro-L-arginine-methyl ester (L-NAME, 10 mM), induced a transient increase in ceramide formation, followed by apoptosis in keratinocytes but not in fibroblasts. Both, SNAP and L-NAME, decreased the mRNA levels of all proteins involved in ceramide metabolism.

Effect of bee venom on aromatase expression and activity in leukaemic FLG 29.1 and primary osteoblastic cells

The effect of bee venom aqua-acupuncture (BVA) (api-toxin), a traditional immunosuppressive Korean aqua-acupuncture, on the bone function in human osteoblastic cells was studied. To provide insights into the effect of BVA on aromatase activity in bone-derived cells, we examined the human leukaemic cell line FLG 29.1, which is induced to differentiate toward the osteoclastic phenotype by TPA and TGF-beta1, and the primary first-passage osteoblastic cells (hOB). Southern blot of RT-PCR products with a 32P-labeled cDNA probe for the human aromatase demonstrated that FLG 29.1 and hOB cells express aromatase mRNA. Gene expression and enzyme activity were stimulated in a time-dependent fashion by 5.0 microl/ml BV and by either 1-50 nM TPA or 0.01-0.5 ng/ml TGF-beta1, with maximal responses after 2-3 h exposure. After 24 h incubation of the cells in the absence of these stimuli the aromatase mRNA and the protein were barely detectable. These findings demonstrate that cells of the osteoclastic lineage synthesize aromatase in vitro by the local cytokine of TGF-beta1 and BVA. These can offer an explanation for the lack of development of osteoarthritis in BVA-treated patients.

Diagnostic performances of anti-cyclic citrullinated peptides antibody and antifilaggrin antibody in Korean patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease of unknown etiology. We studied the diagnostic performances of anti-cyclic citrullinated peptides antibody (anti-CCP) assay and recombinant anti-citrullinated filaggrin antibody (AFA) assay by enzyme linked immunosorbent assay (ELISA) in patients with RA in Korea. Diagnostic performances of the anti-CCP assay and AFA assay were compared with that of rheumatoid factor (RF) latex fixation test. RF, anti-CCP, and AFA assays were performed in 324 RA patients, 251 control patients, and 286 healthy subjects. The optimal cut off values of each assay were determined at the maximal point of area under the curve by receiver-operator characteristics (ROC) curve. Sensitivity (72.8%) and specificity (92.0%) of anti-CCP were better than those of AFA (70.3%, 70.5%), respectively. The diagnostic performance of RF showed a sensitivity of 80.6% and a specificity of 78.5%. Anti-CCP and AFA showed positivity in 23.8% and 17.3% of seronegative RA patients, respectively. In conclusion, we consider that anti-CCP could be very useful serological assay for the diagnosis of RA, because anti-CCP revealed higher diagnostic specificity than RF and AFA at the optimal cut off values and could be performed by easy, convenient ELISA method.

Genomic profiling of neutrophil transcripts in Asian Qigong practitioners: a pilot study in gene regulation by mind-body interaction

BACKGROUND AND OBJECTIVES

The great similarity of the genomes of humans and other species stimulated us to search for genes regulated by elements associated with human uniqueness, such as the mind-body interaction. DNA microarray technology offers the advantage of analyzing thousands of genes simultaneously, with the potential to determine healthy phenotypic changes in gene expression. The aim of this study was to determine the genomic profile and function of neutrophils in Falun Gong (FLG, an ancient Chinese Qigong) practitioners, with healthy subjects as controls.

SUBJECTS AND DESIGN

Six (6) Asian FLG practitioners and 6 Asian normal healthy controls were recruited for our study. The practitioners have practiced FLG for at least 1 year (range, 1-5 years). The practice includes daily reading of FLG books and daily practice of exercises lasting 1-2 hours. Selected normal healthy controls did not perform Qigong, yoga, t'ai chi, or any other type of mind-body practice, and had not followed any conventional physical exercise program for at least 1 year. Neutrophils were isolated from fresh blood and assayed for gene expression, using microarrays and RNase protection assay (RPA), as well as for function (phagocytosis) and survival (apoptosis).

RESULTS

The changes in gene expression of FLG practitioners in contrast to normal healthy controls were characterized by enhanced immunity, downregulation of cellular metabolism, and alteration of apoptotic genes in favor of a rapid resolution of inflammation. The lifespan of normal neutrophils was prolonged, while the inflammatory neutrophils displayed accelerated cell death in FLG practitioners as determined by enzyme-linked immunosorbent assay. Correlating with enhanced immunity reflected by microarray data, neutrophil phagocytosis was significantly increased in Qigong practitioners. Some of the altered genes observed by microarray were confirmed by RPA.

CONCLUSION

Qigong practice may regulate immunity, metabolic rate, and cell death, possibly at the transcriptional level. Our pilot study provides the first evidence that Qigong practice may exert transcriptional regulation at a genomic level. New approaches are needed to study how genes are regulated by elements associated with human uniqueness, such as consciousness, cognition, and spirituality.

The cornified envelope: a model of cell death in the skin

The epidermis functions as a barrier against the environment by means of several layers of terminally differentiated, dead keratinocytes - the cornified layer, which forms the endpoint of epidermal differentiation and death. The cornified envelope replaces the plasma membrane of differentiating keratinocytes and consists of keratins that are enclosed within an insoluble amalgam of proteins, which are crosslinked by transglutaminases and surrounded by a lipid envelope. New insights into the molecular mechanisms and the physiological endpoints of cornification are increasing our understanding of the pathological defects of this unique form of programmed cell death, which is associated with barrier malfunctions and ichthyosis.

VEGF, bFGF, and their receptors in the endometrium of rhesus monkey during menstrual cycle and early pregnancy

A number of cytokines and growth factors are known to modulate proliferation and differentiation of human endometrium. In this study, the expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and VEGF receptors, fms-like tyrosine kinase (Flt1) and kinase insert domain-containing region (KDR), and bFGF receptor 1 (Flg) were examined in the endometrium of rhesus monkey on Day 5, 10, 16, 20, 25 of menstrual cycle and on Day 19 of early pregnancy. Western blot analysis showed the specificity of the anti-human antibodies with the monkey tissue. The expression of mRNA and protein of VEGF was correlated with that of its receptor KDR, which was detected in epithelial, vascular, and myometrial cells. The localization of bFGF and its receptor Flg was similar to that of VEGF, except that the Flg was absent in the endothelial cells. Strong expression of VEGF and bFGF in the glandular epithelial cells was observed in the proliferative phase, declined in the secretory phase during the cycle. Stronger staining of these factors was also observed in the decidual cells of the pregnant uterus, as compared with the stromal cells of cycling uterus. No expression of Flt1 was detected in the tissue examined in this study. These data suggest that VEGF, bFGF, and their receptors play important roles in epithelial and stromal development, angiogenesis, and blood vessel function in the endometrium during the menstrual cycle and early pregnancy of the rhesus monkey.

Large-scale DNA microarray analysis of atopic skin lesions shows overexpression of an epidermal differentiation gene cluster in the alternative pathway and lack of protective gene expression in the cornified envelope

BACKGROUND

Atopic dermatitis (AD)-specific genes have not yet been clarified. Objectives To identify gene expression specific to active atopic skin lesions.

METHODS

We analysed 23,000 genes in skin biopsy samples from 17 patients with AD and four normal controls using Affymetrix oligonucleotide arrays.

RESULTS

Four of the 10 genes with the greatest differences in expression between patients and controls, S100A8 and S100A7 (upregulated), and loricrin and filaggrin (downregulated), were epidermal differentiation genes located on 1q21, a locus previously reported to have a genetic linkage with AD.

CONCLUSIONS

Our results, showing downregulation of the cornified envelope genes and upregulation of the alternative keratinization pathway, are the first to suggest abnormal epidermal differentiation and defective defences as key abnormalities in AD.

The differentiation profile of the epithelium of the human lip

The aim of this study was to analyse the immunohistochemical differentiation profile of the stratified squamous epithelium of the adult human lip. Full-thickness lower lips taken from 31 cadavers were analysed. Sections were stained with haematoxylin and eosin, periodic acid-Schiff (PAS), cytokeratins (CK), loricrin, involucrin, profilaggrin and filaggrin. The stratified squamous epithelium covering the lip could be divided into: (i) appendage-bearing, orthokeratinised epidermis; (ii) orthokeratinised vermilion which had a more prominent rete pattern than the epidermis; (iii) parakeratinised, PAS-positive intermediate zone; and (iv) non- or parakeratinised labial mucosal epithelium. Epithelial thickness increased gradually from the skin to the mucosal aspect. The CK pattern changed across the intermediate zone, with gradual loss of CK 1 and 10 from the skin, and CK 4, 13 and 19 from the mucosal, aspect. CK 5 and 14 were consistently expressed basally, and variably expressed suprabasally. Apart from labelling Merkel cells, CK 8, 18 and 20 were negative. Involucrin, which was present at all sites, was restricted to the stratum granulosum in skin, but extended into the stratum spinosum, and gradually into parabasal keratinocytes, across the vermilion and mucosa. Loricrin, profilaggrin and filaggrin were present in the stratum granulosum of orthokeratinised sites, but expression was abruptly lost at the junction between the vermilion and the intermediate zone. In conclusion, the phenotype of the stratified squamous epithelium covering the lip changes at, or across, the intermediate zone of the adult vermilion. It is possible that changes in the composition of the stratified squamous epithelium affect the colour of the vermilion.

Localization and Characterization of Specific Cornification Proteins in Avian Epidermis

Little is known about proteins involved in the formation of the stratum corneum in the avian apteric epidermis. The present immunocytochemical, autoradiographic and electrophoretic study shows that antibodies against characteristic proteins of mammalian cornification (alpha-keratins, loricrin, sciellin, filaggrin, transglutaminase) recognize avian epidermal proteins. This suggests the presence of avian protein with epitopes common to related mammalian proteins. These proteins may also be involved in the formation of the cornified core and cell envelope of mature avian corneocytes. The immunoblotting study suggests that protein bands, cross-reactive for antibodies against loricrin (45, 52-57 kDa), sciellin (54, 84 kDa), filaggrin (32, 38, 45-48 kDa), and transglutaminase (40, 50, 58 kDa), are present in the avian epidermis. Immunocytochemistry shows that immunoreactivity for the above proteins is localized in the transitional and lowermost corneous layer of apteric epidermis. Their epitopes are rapidly masked/altered in cornifying cells and are no longer detectable in mature corneocytes. In scaled epidermis a thick layer made of beta-keratins of 14-18, 20-22, and 33 kDa is formed. Only in feathered epidermis (not in scale epidermis), an antifeather chicken beta-keratin antibody recognized a protein band at 8-12 kDa. This small beta-keratin is probably suitable for the formation of long, axial filaments in elongated barb, barbule and calamus cells. Conversely, the larger beta-keratins in scales are irregularly deposited forming flat plates. Tritiated histidine coupled to autoradiography show an absence of both keratohyalin and histidine-rich proteins in adult feathered and scaled epidermis. Most of the labeling appears in proteins within the range of beta- and alpha-keratins. These data on apteric epidermis support the hypothesis of an evolution of the apteric and interfollicular epidermis from the expansion of hinge regions of protoavian archosaurians.

Comparison of enzymatic properties between hPADI2 and hPADI4

In the sera of rheumatoid arthritis (RA) patients, autoantibodies directed to citrullinated proteins are found with high specificity for RA. Peptidylarginine deiminases (PADIs) are enzymes responsible for protein citrullination. Among many isoforms of PADIs, only PADI4 has been identified as an RA-susceptibility gene. To understand the mechanisms of the initiation and progression of RA, we compared the properties of two PADIs, human PADI2 and human PADI4, which are present in the synovial tissues of RA patients. We confirmed their precise distribution in the RA synovium and compared the stability, Ca2+ dependency, optimal pH range, and substrate specificity. Small but significant differences were found in the above-mentioned properties between hPADI2 and hPADI4. Using LC/MS/MS analysis, we identified the sequences in human fibrinogen indicating that hPADI2 and hPADI4 citrullinate in different manners. Our results indicate that hPADI2 and hPADI4 have different roles under physiological and pathological conditions. Further studies are needed for the better understanding of the role of hPADIs in the initiation and progression of RA.

Tetracycline-regulated gene expression in epidermal keratinocytes

The tetracycline-regulated expression system developed by Gossen and Bujard is a powerful genetic tool that permits the expression of any gene construct introduced into either cultured cells or transgenic animals to be precisely controlled. It involves two components, a regulatory component based on the prokaryotic tetracycline repressor (TetR) and a response plasmid that expresses the gene of interest under control of the tetracycline-response element. In this paper, we review the Tet system methodology, discuss the available vector systems, and describe how to prepare and characterize keratinocyte cell lines that express a gene under tetracycline control. The methodology involves the development of stable cell lines expressing the TetR protein (either tTA or rtTA, expressed as a fusion with the VP16 activation domain), and a second set of double-stable cell lines that contain both TetR and the response plasmid (tetracycline-response element-gene X) expressed under tetracycline control. As an example of this methodology, we discuss our recently developed keratinocyte cell lines that express human filaggrin in a tetracycline- regulated manner. This technique, now also available in retrovirus and adenovirus-based vectors, is applicable both to the study of genes that are toxic to cells and more generally to understand how genes regulate cell structure/function, growth, and differentiation.

PKCalpha induces differentiation through ERK1/2 phosphorylation in mouse keratinocytes

Epidermal keratinocyte differentiation is a tightly regulated stepwise process that requires protein kinase C (PKC) activation. Studies on cultured mouse keraitnocytes induced to differentiate with Ca2+ have indirectly implicated the involvement of PKCa isoform. When PKCalpha was overexpressed in undifferentiated keratinocytes using adenoviral system, expressions of differentiation markers such as loricrin, filaggrin, keratin 1 (MK1) and keratin 10 (MK10) were increased, and ERK1/2 phosphorylation was concurrently induced without change of other MAPK such as p38 MAPK and JNK1/2. Similarly, transfection of PKCalpha kinase active mutant (PKCalpha- CAT) in the undifferentiated keratinocyte, but not PKCbeta-CAT, also increased differentiation marker expressions. On the other hand, PKCalpha dominant negative mutant (PKCbeta-KR) reduced Ca2+ -mediated differentiation marker expressions, while PKCbeta-KR did not, suggesting that PKCalpha is responsible for keratinocyte differentiation. When downstream pathway of PKCalpha in Ca2+ -mediated differentiation was examined, ERK1/2, p38 MAPK and JNK1/2 phosphorylations were increased by Ca2+ shift. Treatment of keratinocytes with PD98059, MEK inhibitor, and SB20358, p38 MAPK inhibitor, before Ca2+ shift induced morphological changes and reduced expressions of differentiation markers, but treatment with SP60012, JNK1/2 inhibitor, did not change at all. Dominant negative mutants of ERK1/2 and p38 MAPK also inhibited the expressions of differentiation marker expressions in Ca2+ shifted cells. The above results indicate that both ERK1/2 and p38 MAPK may be involved in Ca2+ -mediated differentiation, and that only ERK1/2 pathway is specific for PKCalpha-mediated differentiation in mouse keratinocytes.

Expression of epidermal N-methyl-D-aspartate receptors (NMDAR1) depends on formation of the granular layer--analysis in diseases with parakeratotic cornification

Ionotrope glutamate receptors of the N-methyl-D-aspartate (NMDA) receptor type are expressed on keratinocytes and influence the intracellular calcium concentration. The importance of NMDA receptors in pathophysiological processes in the skin is, however, still unclear. Epidermal distribution patterns of NMDA receptors were investigated in dermatoses with parakeratotic cornification (psoriasis vulgaris and verrucae vulgares) and compared to the expression of filaggrin. The expression of NMDA receptors (R1 component) in paraffin-embedded normal epidermis (n = 22), psoriasis vulgaris (n = 21) and verrucae vulgares (n = 23) was examined and evaluated by means of digital image analysis. For quantitative characterization of the distribution patterns, a quotient was formed of the expression in the stratum granulosum and stratum basale ("NMDA ratio"). The distribution of NMDAR1 was compared to the immunohistochemical expression of filaggrin. Additionally the expression of filaggrin was investigated in HaCaT cells after treatment with the NMDA receptor antagonist MK-801. NMDA receptors were demonstrated in the epidermis of all preparations. In healthy skin, the highest receptor density was found in the stratum granulosum. This distribution pattern was basically also present in the dermatoses examined. Thus, the occurrence of parakeratosis in psoriasis vulgaris, but not in verrucae vulgares, was characterized by a significant reduction in the NMDA ratio (reduced expression of NMDAR1 in the upper epidermis). The immunohistochemical distribution of filaggrin was similar to that of NMDAR1. In HaCaT cells MK-801 suppressed the expression of filaggrin. NMDA receptors are expressed in human epidermis under physiological conditions especially in the stratum granulosum. Their reduced expression within parakeratotic epidermis in psoriasis vulgaris may be evidence of impaired intracellular calcium influx in this disease.

Chronic ultraviolet radiation modulates epidermal differentiation as it up-regulates transglutaminase 1 and its substrates

BACKGROUND

Ultraviolet radiation (UVR) stimulates cellular mitosis, which leads to epidermal hyperplasia. On the basis of hypothesis that chronic UVR may modulate differentiation as well as epidermal hyperplasia, we evaluated the modulation of markers of epidermal differentiation, such as transglutaminase 1 (TGase 1), filaggrin and loricrin, by chronic UVR in vivo.

METHODS

Total TGase activities assay or in situ TGase activities were measured in human and mouse skin. TGase 1 expression was identified by immunohistochemical staining in human skin. In the human, the pre-auricular skin of face was used for samples of chronic UVR, and the post-auricular skin was selected as non-UVR control. The changes of filaggrin and loricrin were identified by western immunoblots.

RESULTS

In human and mouse epidermis, chronic UVR induced the increase of in situ TGase activities or total TGase activities as it up-regulated TGase 1 expression in the epidermis. As the substrates of TGase 1, chronic UVR induced the up-regulation of filaggrin and loricrin in mouse epidermis as well. At the same time, chronic UVR induced the marked epidermal hyperplasia in human and mouse skin.

CONCLUSION

Chronic UVR stimulates epidermal differentiation as it up-regulates TGase 1 and its substrates. The modified epidermal differentiation is balanced with epidermal hyperplasia, leading to the maintenance of epidermal homeostasis in the UV-irradiated epidermis.

Peptidylarginine Deiminase Isoforms 1–3 Are Expressed in the Epidermis and Involved in the Deimination of K1 and Filaggrin

Post-translational conversion of arginine to citrulline residues is catalyzed by peptidylarginine deiminases (PAD). Although the existence of five isoforms of PAD has been reported in rodents and humans, their tissue distribution, substrate specificity, and physiological function have yet to be explored. In the epidermis, deimination of filaggrin and keratins is involved in maintaining hydration of the stratum corneum (SC), and hence the cutaneous barrier function. Here, RT-PCR, western blotting, and confocal microscopy analyses with anti-peptide antibodies highly specific for each of the PAD1-4 demonstrated that only PAD1-3 are expressed in mouse and human epidermis. PAD1 was detected in all layers, including the SC, and PAD2 in all the living layers, whereas PAD3 expression was shown to be restricted to the granular layer and lower SC. Moreover, PAD1 and 3 were observed to co-localize with (pro)filaggrin, and PAD2 to be located at the keratinocyte periphery in the stratum granulosum. We also detected PAD1 in extracts of superficial SC, where K1 is deiminated. Moreover, we showed that PAD1 and 3 are able to modify filaggrin in vitro. These data strongly suggest that each enzyme exerts a specific role in the course of epidermis differentiation.

Receptor-mediated tobacco toxicity: regulation of gene expression through alpha3beta2 nicotinic receptor in oral epithelial cells

Tobacco is a known cause of oral disease but the mechanism remains elusive. Nicotine (Nic) is a likely culprit of pathobiological effects because it displaces the local cytotransmitter acetylcholine from the nicotinic receptors (nAChRs) expressed by oral keratinocytes (KCs). To gain a mechanistic insight into tobacco-induced morbidity in the oral cavity, we studied effects of exposures to environmental tobacco smoke (ETS) versus equivalent concentration of pure Nic on human and murine KCs. Both ETS and Nic up-regulated expression of cell cycle and apoptosis regulators, differentiation marker filaggrin, and signal transduction factors at both the mRNA and protein levels. These changes could be abolished in cultured human oral KCs transfected with anti-alpha3 small interfering RNA or treated with the alpha3beta2-preferring antagonist alpha-conotoxin MII. Functional inactivation of alpha3-mediated signaling in alpha3-/- mutant KCs prevented most of the ETS/Nic-dependent changes in gene expression. To determine relevance of the in vitro findings to the in vivo situation, we studied gene expression in oral mucosa of neonatal alpha3+/+ and alpha3-/- littermates delivered by heterozygous mice soon after their exposures to ETS or equivalent concentration of pure Nic in drinking water. In addition to reverse transcriptase-polymerase chain reaction and Western blot, the ETS/Nic-dependent alterations in gene expression were also detected by semiquantitative immunofluorescence assay directly in KCs comprising murine oral mucosa. Only wild-type mice consistently developed significant (P < 0.05) changes in the gene expression. These results identified alpha3beta2 nAChR as a major receptor mediating effects of tobacco products on KC gene expression. Real-time polymerase chain reaction demonstrated that in all three model systems the common genes targeted by alpha3beta2-mediated ETS/Nic toxicity were p21, Bcl-2, NF-kappaB, and STAT-1. The expression of the nAChR subunits alpha5 and beta2 and the muscarinic receptor subtypes M(2) and M(3) was also altered. This novel mechanism offers innovative solutions to ameliorate the tobacco-related cell damage and intercede in disease pathways, and may shed light on general mechanisms regulating and driving tobacco-related morbidity in human cells.

The mitogen-activated protein kinase kinase kinase dual leucine zipper-bearing kinase (DLK) acts as a key regulator of keratinocyte terminal differentiation

In the skin, epithelial cells undergo a terminal differentiation program leading to the formation of the stratum corneum. Although it is expected that the last phases of this process must be tightly regulated since it results in cell death, the signaling pathways involved in this induction remain ill defined. We now report that a single kinase, the mitogen-activated protein kinase kinase kinase dual leucine zipper-bearing kinase (DLK), acts in the epidermis to promote the terminal differentiation of human keratinocytes. In support of this notion, we showed that DLK expression was restricted to the granular layer in situ. In addition, cultured keratinocytes infected with a recombinant adenovirus expressing DLK exhibited morphological and biochemical changes, including a suprabasal localization, altered cell shape, compacted cytoplasm, DNA fragmentation, and the up-regulation of filaggrin, that are reminiscent of a terminally differentiated phenotype. Moreover the expression of wild-type DLK in keratinocytes stimulated transglutaminase activity and the consequent formation of the cornified cell envelope, while a kinase-inactive variant of DLK did not. Together these results identify DLK as a signaling molecule implicated in the regulation of keratinocyte terminal differentiation and cornification.

Cathepsin D is involved in the regulation of transglutaminase 1 and epidermal differentiation

We previously demonstrated that the aspartate protease cathepsin D is activated by ceramide derived from acid sphingomyelinase. Increased expression of cathepsin D in the skin has been reported in wound healing, psoriasis and skin tumors. We explored specific functions of cathepsin D during epidermal differentiation. Protein expression and enzymatic activity of cathepsin D increased in differentiated keratinocytes in both stratified organotypic cultures and in mouse skin during epidermal barrier repair. Treatment of cultured keratinocytes with exogenous cathepsin D increased the activity of transglutaminase 1, known to cross-link the cornified envelope proteins involucrin and loricrin during epidermal differentiation. Inhibition of cathepsin D by pepstatin A suppressed the activity of transglutaminase 1. Cathepsin D-deficient mice revealed reduced transglutaminase 1 activity and reduced protein levels of the cornified envelope proteins involucrin and loricrin. Also, amount and distribution of cornified envelope proteins involucrin, loricrin, filaggrin, and of the keratins K1 and K5 were significantly altered in cathepsin D-deficient mice. Stratum corneum morphology in cathepsin D-deficient mice was impaired, with increased numbers of corneocyte layers and faint staining of the cornified envelope only, which is similar to the human skin disease lamellar ichthyosis. Our findings suggest a functional link between cathepsin D activation, transglutaminase 1 activity and protein expression of cornified envelope proteins during epidermal differentiation.

FOXN1 is critical for onycholemmal terminal differentiation in nude (Foxn1) mice

Nude mice have a mutation in the transcription factor Foxn1(nu), resulting in downregulation of hair keratins. Although hair follicles develop normally, the hair fibers become structurally weak, curl, and break off at the surface. Nails in nude mice are deformed, based on alterations of the onychocyte differentiation process. Elemental microanalysis of the nail plate reveals marked decreases in sulfur concentrations in the nude mouse nail plates. Immunohistochemistry shows a lack of keratin 1 expression in terminally differentiating keratinocytes of the nail matrix. Instead, the typical differentiation process of the matrix is altered toward an epidermis-like differentiation pattern, comprising the production of filaggrin-containing keratohyalin granules in cells resembling those of the stratum granulosum, which are never observed in normally haired mice. The nail plate has diffuse basophilic stippling. It is thinner than normal, weak, and in most Foxn1(nu)/Foxn1(nu) mice breaks where it separates from the hyponychium. These studies indicate that the Foxn1(nu) mutated gene has effects beyond downregulating keratin expression, including changes in filaggrin expression, and is critical for normal onycholemmal differentiation. The nails of nude mice provide new insights into the molecular controls of onychocyte differentiation, and they offer a useful model to investigate the pathogenesis of nail hypergranulosis, a common feature in human nail diseases.

[Comparative characteristics of specific autoantibodies in rheumatoid arthritis]

AIM

To assess diagnostic informative value of specific autoantibodies (AAB)--antikeratin antibodies (AKA), antiperinuclear factor (APF) and antibodies to cyclic peptide containing citrullin (CCP) from the family of antifilaggrine autoantibodies (AFA)--in rheumatoid arthritis (RA).

MATERIAL AND METHODS

A total of 121 patients with RA and 45 patients with seronegative spondylarthropathies. Rheumatoid factor was detected with latex agglutination. AKA and APF were estimated with indirect immunofluorescence the substrate of which was series frozen sections of rat esophagus in the middle third of 4 mcm and cells of the epithelium of the internal surface of healthy donor's cheek. For detection of antibodies to cyclic peptide, the test DIASTAT Anti-CCP ELISA (Axis Shield, Great Britain) was made.

RESULTS

The RF was detected in 67.8% patients with RA; AKA, APF and antibodies to CCP--in 43.6, 52.9 and 68.0% patients, respectively. AKA were most specific for RA (100%) while the RF was least specific among the AAB studied (87%). Simultaneous use of RF and AFA allows AAB detection in 84% RA patients at early stages of the disease. AFA were detected in patients with high clinico-laboratory activity of the process, high indices of functional joint insufficiency. 95% of all cases of destructive arthritis were detected in patients with RF, AKA, APF and antibodies to CCP.

CONCLUSION

For RA patients it is necessary to determine both RF and AFA. Detection of AFA allows early diagnosis of RA as well as to single out patients with more aggressive course of the disease and unfavourable prognosis.