Differential expression of nitric oxide synthases in human scalp epidermal and hair follicle pigmentary units: implications for regulation of melanogenesis

BACKGROUND: Nitric oxide (NO) is a ubiquitous gaseous lipophilic molecule generated from the conversion of L-arginine to L-citrulline by the NO synthases (NOSs). Ultraviolet radiation (UVR)-induced NO production appears to stimulate epidermal melanogenesis. However, given their relative protection from UVR, it is unclear whether NO plays a similar role in hair bulb melanocytes. OBJECTIVES: We aimed to identify the expression profiles of the NOS isoforms endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) and of phosphorylated eNOS and nitrotyrosine within the epidermal and follicular melanin units of normal human haired scalp during the hair growth cycle. METHODS: This study employed single and double immunohistochemical and immunofluorescence staining techniques using haired scalp from 10 healthy individuals (six women and four men). RESULTS: Melanocytes in the basal layer of the epidermis expressed eNOS, nNOS and nitrotyrosine. By contrast, melanogenically active melanocytes of the anagen hair bulb were wholly negative for these markers. However, other follicular melanocytes not actively involved in pigment production, including undifferentiated melanocytes located in the outer root sheath and melanocytes surviving the apoptosis-driven hair follicle (HF) regression during catagen/telogen, expressed eNOS, nNOS and nitrotyrosine. While iNOS was only weakly expressed in the basal layer of the human epidermis, it was highly expressed in keratinocytes of the inner root sheath (IRS), where it colocalized with trichohyalin, a differentiation-associated protein of the IRS that requires enzyme-catalysed conversion of arginine to citrulline. CONCLUSIONS: The NOS isoforms and nitrotyrosine are differentially expressed in different cutaneous melanocyte subpopulations. Results of this study suggest a possible role for eNOS, nNOS, iNOS and nitrotyrosine in melanocyte biology, particularly with respect to melanogenesis and melanocyte survival during HF regression. Another example of possible NO involvement in HF biology is the postsynthetic modification of trichohyalin in differentiating keratinocytes of the IRS. These results suggest that NO may influence several aspects of HF biology.     

Constitutive endothelial and inducible nitric oxide synthase in inflammatory dermatoses

We have used immunohistochemistry to localize the expression of the constitutive endothelial and inducible forms of the enzyme nitric oxide synthase (NOS) in skin from involved and uninvolved sites in patients with atopic dermatitis (AD) and allergic contact dermatitis (CD). Endothelial NOS (eNOS) immunoreactivity was localized to vascular endothelium in the dermis of both involved and uninvolved skin from all patients. Inducible NOS (iNOS) immunoreactivity was found to be closely associated with the upper dermal microvasculature in all the involved AD biopsies, but only in two of 10 uninvolved AD biopsies. CD biopsies were taken from 10 positive skin patch test sites and iNOS immunoreactivity was detected in all of these. iNOS immunoreactivity was detected in only one of the negative patch test biopsies. Both the extent and intensity of iNOS immunoreactivity was lower in CD than in AD skin lesions. The presence of eNOS in the skin is necessary for constitutive NO-mediated dilatation of the dermal vasculature. Induction of iNOS in the dermal endothelium and in perivascular inflammatory cells may be significant with respect to the roles of NO in both the vasodilatory component of the inflammatory response and in the modulation of immune responses in the skin.     

The role of nitric oxide synthases in pemphigus vulgaris in a mouse model

Background  Pemphigus vulgaris (PV) is a blistering autoimmune disease characterized by IgG autoantibodies against desmoglein 3. Nitric oxide synthases (NOS) may contribute to the increase of inflammation in tissues by the generation of nitrotyrosine residues (NTR).
Objectives  To investigate whether the production of NTR mediated by NOS may participate in the development of inflammation and acantholysis in PV.
Methods  Mice were pretreated or not with NOS, tyrosine-kinase (TK) or nuclear factor (NF)-κB inhibitors, and then injected with PV-IgG. PV manifestations were examined in all mice. The expression of NTR, constitutive NOS (cNOS) [endothelial NOS (eNOS) and neuronal NOS (nNOS)], inducible NOS (iNOS) and NF-κB factor were studied in epidermis of mice using immunohistochemical techniques.
Results  After PV-IgG injection, expressions of NTR, iNOS, eNOS and nNOS increased in acantholytic cells, as did nuclear translocation of NF-κB in the basal cells of the epidermis. Pretreatment of mice with inhibitors of TK, nNOS and nonselective NOS, completely prevented NTR expression and the clinical and histological findings of PV in mice. TK inhibitor genistein inhibited both nNOS and iNOS expression on the membrane of basal keratinocytes, and nuclear translocation of NF-κB.
Conclusions  Upregulation of cNOS and iNOS, NTR generation and nuclear translocation of NF-κB may contribute to increased inflammation and tissue damage in PV lesions. The absence of the clinical and histological findings of PV and NTR expression in mice injected with PV-IgG, through pretreatment with TK and nNOS inhibitors, provides compelling evidence that these signalling molecules should be considered as potential therapeutic targets in PV.     

Sporadic dystrophic epidermolysis bullosa with albopapuloid and prurigo- and folliculitis-like lesions

A case of sporadic dystrophic epidermolysis bullosa (DEB) with albopapuloid and prurigo- and folliculitis-like lesions is reported. Histopathology of the scalp biopsy showed hyperkeratosis, a subepidermal cleft near the orifice of a hair follicle, dermal fibrosis, and a moderate perivascular and perifollicular lymphohistiocytic inflammatory cell infiltrate in the papillary dermis, without neutrophilic infiltrate in the orifice of the hair follicle. It is uncertain whether the present case should be classified as DEB pruriginosa or represents a new subtype of DEB.     

The human progenitor cell antigen (CD34) is localized on endothelial cells, dermal dendritic cells, and perifollicular cells in formalin-fixed normal skin, and on proliferating endothelial cells and stromal spindle-shaped cells in Kaposi's sarcoma

The human progenitor cell antigen (CD34) is selectively expressed on hematopoietic progenitor cells in the bone marrow. In either cryostat sections of snap-frozen skin, or formalin-fixed paraffin-embedded sections of normal skin, anti-CD34 monoclonal antibody immunostained vascular endothelial cells and perivascular/interstitial dendritic cells, particularly in the reticular dermis. A distinctive population of perifollicular spindle-shaped cells in the midportion of the follicle (ie, bulge area), which is the site of the putative hair follicle stem cells, were CD34 positive, as were spindle-shaped cells in and around the eccrine glands accentuating their basement membrane zone. In patch/plaque--and tumor-stage acquired immunodeficiency syndrome-associated Kaposi's sarcoma lesions, CD34 expression was present on both the proliferating endothelial cells as well as the spindle-shaped stromal cells. CD34 positive endothelial cells and spindle-shaped stromal cells may play important participatory and supportive functions in both normal and diseased skin.     

Expression of hair follicle stem cells detected by cytokeratin 15 stain: implications for pathogenesis of the scarring process in cutaneous lupus erythematosus

Background Discoid lupus erythematosus (DLE) is a scarring disease. Although the scarring and deformity may affect any part of the body, such changes have been reported to be most obvious on the face and scalp. The pathogenesis behind this scarring process is not well understood. Once lesions have scarred, recurrent disease tends to occur at the edge of the scarred lesions but not within them. Objectives The fact that inflammation in DLE generally involves the bulge area of the follicles raises the possibility that damage to the stem cells of the bulge region may be one process leading to the permanent loss of follicles. The aim of this study was to investigate the role of the hair follicle stem cells which reside in the bulge region in the scarring process in cutaneous lupus erythematosus (CLE). Methods We studied the reactivity of an antibody to the CD8 antigen (C8/144B), which recognizes cytokeratin (CK) 15 and preferentially immunostains hair follicle stem cells without staining the remaining hair follicle, on skin biopsies (scalp and body lesions) from patients with CLE (36 with discoid lesions and 10 with subacute lesions). Normal scalp and body biopsy specimens served as controls. The correlation between the extent of the cytotoxic inflammatory cell infiltrate (CD8+) and the presence of stem cells was investigated. Results were analysed semiquantitatively. Results The expression of CK15 in hair follicle stem cells was variable in the DLE lesions; there was normal to moderate CK15 expression at the bulge region of hair follicles when surrounded by mild or moderate inflammatory infiltrate (CD8+), but in cases of severe inflammation, CK15 expression was weak or absent. Conclusions The bulge region appears to be involved in this disease as part of a broader involvement of the hair follicles; it is secondarily affected by the surrounding inflammatory cell infiltrate. Expression of C8/144B diminished and was then absent, indicating either damage to stem cells or differentiation to help in the repair process. Damage to follicular stem cells may help to explain the irreversible alopecia and the scarring process which characterize this disease.     

Evolutionary changes of immunohistological characteristics of secondary lesions in pityriasis rosea

Summary In 15 patients with pityriasis rosea, we studied the evolutionary changes of the immunohistological characteristics of the secondary lesions. Many CD1a⁺ cells were seen in the epidermis and dermis of early lesions. In the well-developed lesions, the number of CD1a⁺ cells greatly increased in the dermis. In the late lesions, CD1a⁺ cells in the dermis significantly decreased as compared with the well-developed lesions. Early lesions showed a moderate T-cell infiltrate. In the well-developed lesions, the dermal T-cell infiltrate was dense, and the CD4 CD8 ratio was 2.9. The late lesions had a moderate T-cell infiltrate, in which the CD4 CD8 ratio significantly decreased as compared with the well-developed lesions. Thus, the relative decrease in CD4⁺ helper inducer cells during lesion regression, concomitant with a decrease in number of CD1a⁺. Langerhans cells, is in accordance with a broader concept of increased suppressor mechanisms during healing.     

Immunohistochemical Localization of Nitric Oxide Synthase in Normal Human Skin: Expression of Endothelial-type and Inducible-type Nitric Oxide Synthase in Keratinocytes

Nitric oxide (NO) is a critical mediator of various biological functions. NO is generated from L-arginine by nitric oxide synthase (NOS), which has three isoforms; endothelial-type NOS (eNOS) and brain-type NOS (bNOS) are constitutive enzymes, and inducible-type NOS (iNOS) is expressed after stimulation. We investigated the expression of NOS in normal human skin by an immunohistochemical technique and western blotting analysis. In human skin, epidermal keratinocytes and the outer root sheath were labeled with not only eNOS antibody but also with iNOS antibody. Both eNOS and iNOS protein in epidermal keratinocytes were confirmed by western blotting. eNOS immunoreactivity was observed in endothelial cells, fibroblasts, the arrector pili muscle, apocrine secretory gland, eccrine coiled duct, and eccrine secretory gland. bNOS immunoreactivity was observed in mast cells. No staining with anti-bNOS antibody was observed in any other cell type. Our present findings suggest that epidermal keratinocytes in normal human skin contain both eNOS and iNOS.     

Nitric oxide: a key mediator in cutaneous physiology

Nitric oxide (NO) is a free radical synthesized from l-arginine by a family of NO synthase (NOS) enzymes, all of which are present in the skin, and also by reduction of sweat nitrate. NO synthesis is regulated by NOS activation (eNOS and nNOS) or synthesis (iNOS) and by substrate availability. Elevated arginase concentrations in psoriatic skin suggest that substrate competition may affect NO production. The balance of NO and reactive oxygen species is probably also important in regulating the biological actions of NO. The physiological functions of NO in the skin are being elaborated. NO release is increased following exposure to ultraviolet radiation (UVR); in eNOS null mice, dermal and epidermal apoptosis following UVR exposure is increased. Experiments in which keratinocytes and melanocytes were cocultured show melanogenesis being dependent on keratinocyte-generated NO, and UVR-induced guinea pig pigmentation is delayed following application of a NOS antagonist to the skin. Wound healing is delayed in eNOS and iNOS null mice.     

活血化瘀法治愈Fox—Fordyce病1例报告

报告1例Fox—Fordyce病。患者女，37岁，因腋窝、乳晕、外阴瘙痒性丘疹lO年余而就诊，皮肤科检查可见双侧腋窝、乳晕、外阴对称性多发米粒至绿豆大毛囊性圆形丘疹，组织病理检查符合Fox-Fordyce病。本例患者用活血化瘀中药治疗取得显著效果，随访3个月无复发。     

Dermatophytic granuloma caused by Microsporum canis in a heart-lung recipient.

We present a case of dermatophytic granuloma caused by Microsporum canis in a heart-lung recipient. This 66-year-old man was seen for erythematous pustules and papules on the forearm. The diagnosis was suspected after histological examination showing an inflammatory infiltrate in the upper dermis with giant cells containing intracytoplasmic fungal elements. Cultures of the skin biopsy confirmed the diagnosis identifying M. canis. Our case emphasizes the possibility of deep dermatophytic infections in immunocompromised patients. There are only 4 additional reports of M. canis infection responsible for invasion of the dermis in such patients. The follicle involvement probably explains these dermal lesions due to the progression of the dermatophyte from the hair follicle to the dermis. In our observation topical antifungal therapy alone was unsuccessful and fluconazole seems to be the treatment of choice for these M. canis invasive dermal cutaneous infections.     

Effects of Transforming Growth Factor β1 in the Hair Cycle

Hair follicle growth is thought to be regulated by a complex interplay of stimulatory and inhibitory signals. From among such signals, we examined the effects of transforming growth factor β1 (TGFβ1) on the murine hair growth cycle. Quantitation of TGFβ1 per wet tissue weight was performed at different stages of the hair cycle. TGFβ1 was extracted with 10 mM HCl, and its level was measured with ELISA. The level of TGFβ1 did not change markedly during the hair cycle. Immunohistochemical observations revealed that hair follicle cells and epidermal cells were negative for TGFβ1 at all stages of the hair cycle. Mast cells in the dermis were positive throughout the cycle. To confirm whether TGFβ1 inhibits the proliferation of hair follicles, we injected it subcutaneously. TGFβ1 inhibited the proliferation of hair follicles. Our observations suggest that TGFβ1 is at least partly responsible for regulating hair follicles as a negative growth factor.     

Functional expression of AQP3 in human skin epidermis and reconstructed epidermis

The purpose of this study was to examine the presence of aquaporin water channels in human skin and to assess their functional role. On western blots of human epidermis obtained from plastic surgery, a strong signal was obtained with polyclonal anti-aquaporin-3 antibodies. By indirect immunofluorescence on 5 microm cryosections, anti-aquaporin-3 antibodies strongly stained keratinocyte plasma membranes in human epidermis, whereas no staining was observed in the dermis or the stratum corneum or when anti-aquaporin-3 antibodies were preabsorbed with the peptide used for immunization. Similarly, a strong signal with anti-aquaporin-3 antibodies was observed in keratinocyte plasma membranes of reconstructed human epidermis in culture at the air-liquid interface for up to 3 wk. The keratinocyte plasma membrane localization of aquaporin-3 was confirmed at the electron microscope level in prickle cells. In addition an intracellular localization of aquaporin-3 was also detected in epidermis basal cells. Osmotically induced transepidermal water permeability was measured on stripped human skin and on reconstructed epidermis. Water transport across both stripped human skin and 2-3 wk reconstructed epidermis was comparable, inhibited by > 50% by 1 mM HgCl2 and fully inhibited by acid pH. By stopped-flow light scattering, keratinocyte plasma membranes, where aquaporin-3 is localized, exhibited a high, pH-sensitive, water permeability. Although human skin is highly impermeable to water, this is primarily accounted for by the stratum corneum, where a steep water content gradient was demonstrated. In contrast, the water content of viable strata of the epidermis is remarkably constant. Our results suggest that the human epidermis, below the stratum corneum, exhibits a high, aquaporin-3-mediated, water permeability. We propose that the role of aquaporin-3 is to water-clamp viable layers of the epidermis in order to improve the hydration of the epidermis below the stratum corneum.     

Expression of the neuronal isoform of nitric oxide synthase (nNOS) and its inhibitor, protein inhibitor of nNOS, in pigment cell lesions of the skin

Nitric oxide (NO) is involved in many physiological processes. In cancer, low levels of NO are thought to enhance tumour progression and metastasis. NO is generated from arginine by NO synthase (NOS); the Ca2+-dependent neuronal isoform or nNOS (expressed by neurones and inhibited by the protein inhibitor of nNOS, PIN), is also expressed by cultured normal melanocytes and by all malignant melanoma (MM) cell lines. We studied the expression of nNOS and PIN in paraffin sections of 177 and 58 pigment cell lesions, respectively, using immunohistochemistry; the activity of the necessary cofactor NADPH was studied in 26 frozen cases. Normal melanocytes in situ lacked nNOS and PIN expression, but were NADPH +. Almost half of common acquired benign naevi expressed nNOS; however, halo naevi and congenital naevi expressed nNOS very frequently. Dysplastic naevi and MM showed variable nNOS immunoreactivity in 72% and 83% of cases, respectively. Early (Clark I and Clark II) MM displayed nNOS staining most frequently, and all MM with an invasive radial growth phase expressed nNOS in the papillary dermis. In contrast, only 67% of metastatic MM were nNOS +. PIN was coexpressed with nNOS in 40 of 58 lesions. NADPH activity was present in all nNOS + naevi, but in two malignant cases, NADPH activity was not accompanied by nNOS expression. We conclude that nNOS expression is induced de novo in benign and malignant pigment cell lesions which have all the requirements (NADPH, PIN) necessary for the production and modulation of NO. We postulate that the frequent expression of nNOS in the junctional part of dysplastic naevi may be responsible for their particular histological features. NO generated by the neoplastic dermal cells in the invasive radial growth phase may contribute to the increased number of blood vessels in the papillary dermis.     

Expression of endothelial nitric oxide synthase in human eccrine clear cells

Nitric oxide is generated from L-arginine by nitric oxide synthase (NOS), which has at least three isoJorms: endothelial-type NOS (eNOS) and brain-type NOS (bNOS) are constitutive enzymes, and inducible-type NOS (iNOS) is expressed after stimulation. Studies by the avidin-biotin immunocomplex method, revealed eNOS immunoreactivity exclusively in the human eccrine clear cells. No eNOS immunoreactivity was observed in the eccrine dark cells or myoepithelial cells. No staining of iNOS or bNOS was observed in the eccrine yland. These findings indicate that NO pUiys a physiological part in the production and/or excretion of sweat in the human skin eccritie gland.     

Possible role of the bulge region in the pathogenesis of inflammatory scarring alopecia: lichen planopilaris as the prototype

BACKGROUND: Lichen planopilaris (LPP) is the prototype of scarring alopecias that mainly target the infundibuloisthmic (bulge) region of hair follicle. Hair follicle stem cells have been shown to reside in the bulge. METHODS: We carried out this study to better define the possible pathogenetic role of the bulge in LPP. Thirty-five cases of LPP were studied. Multiple serial sections of biopsy specimens stained with hematoxylin and eosin, periodic acid Schiff-diastase, and Elastic van Gieson. The following immunostains were applied: CD3, CD4, CD8, CD1a, and Ki-67. Uninvolved follicles and normal scalp biopsy specimens served as normal controls. RESULTS: All cases showed a lichenoid lymphocytic infiltrate at the bulge region. The bulb area was spared. CD8(+) T cells were increased compared with CD4(+) T-cell population. Langerhans' cells were decreased. Proliferating stem cells, highlighted by Ki-67, showed a marked decrease in the bulge compared with uninvolved follicles. CONCLUSION: Our study supports the finding that in LPP, the inflammatory infiltrate mainly involves the bulge region, where the stem cells reside. Once this area is damaged, the hair loses its potential of regrowth with resulting scarring alopecia. This is in contrast with inflammatory non-scarring alopecias such as alopecia areata, where the bulb region is targeted, sparing the stem cells.     

MY7 monoclonal antibody for diagnosis of cutaneous T-cell lymphoma

Infiltrate in cutaneous T-cell lymphomas (CTCLs) is composed mainly of CD4 helper cells with a phenotype very similar to that of benign cutaneous lymphoid infiltrate. MY7 (CD13) is a monoclonal antibody that is normally expressed on peripheral granulocytes and monocytes but also cross-reacts with an antigen expressed on epidermal basal cells. We studied MY7 expression on basal cells of the epidermis and CD4 cell infiltrate in 34 CTCLs, 11 pseudolymphomas, and 29 other benign cutaneous lesions. An indirect immunofluorescence technique with double labeling and an immunoperoxidase technique were used. We found that in benign inflammatory infiltrate, less than 10% of CD4 cells expressed MY7 antigen associated with normal MY7 monoclonal antibody labeling of basal cells, whereas in CTCLs more than 50% of CD4 tumoral cells in dermis expressed MY7 antigens; however, basal cells were MY7 negative. Thus, it is demonstrated that MY7 monoclonal antibody with its double modulation on epidermis (basal cells) and dermis (CD4 cells) has diagnostic value for differentiating CTCLs with CD4+ MY7+ tumor cells in dermis and MY7-negative basal cells from benign inflammatory lesions with CD4+ MY7- cells in dermis and MY7-positive basal cells. This modulation of MY7 labeling could be related to the secretion of epidermal cytokines.     

Type 1 interferon signature in the scalp lesions of alopecia areata

Background Autoimmune attack of the bulbar region of anagen phase hair follicles by CD8+ T cells and Th1 cytokines has been proposed to result in hair loss in alopecia areata (AA). The initiating stimuli are unknown. As interferon‐α therapy may trigger AA, we propose that type 1 interferons are involved in the induction of disease. Objectives To compare lesional scalp from patients with AA with scalp lesions of cutaneous diseases associated with local type 1 interferon‐related protein expression. Methods Lesional scalp of patients with AA, discoid lupus erythematosus, lichen planopilaris and androgenetic alopecia was examined by immunohistochemistry for expression of the type 1 interferon‐inducible myxovirus protein A (MxA), the chemokine receptor CXCR3, and the cytotoxic proteins granzyme B (GrB) and T‐cell intracytoplasmic antigen 1 (TiA‐1). Results MxA was expressed in the intradermal and subcutaneous compartments of the hair follicle including sebaceous glands in inflammatory AA similar to lesions of cicatricial alopecia (discoid lupus erythematosus, lichen planopilaris) but not in the epidermal compartment of AA, and not at all in noninflammatory AA or androgenetic alopecia. The location of CXCR3‐expressing cells correlated with MxA expression. The inflammatory cells around the hair follicle in AA included a lower number of GrB+ and TiA‐1+ cells compared with cicatricial alopecia and demonstrated predominant TiA‐1+ expression. Conclusions We demonstrate the expression of type 1 interferon‐related proteins in the inflammatory lesions of AA. The distribution pattern of the interferon signature and cytotoxicity‐associated proteins in AA differs from cicatricial alopecia.     

Effect of endothelial nitric oxide synthase on epidermal permeability barrier recovery after disruption

Background We previously demonstrated that neuronal nitric oxide synthase (nNOS) in epidermal keratinocytes is associated with epidermal permeability barrier homeostasis. Objectives In the present study, we examined the contributions of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) to epidermal permeability barrier homeostasis. Methods We measured the barrier recovery rate after tape stripping of the epidermis of iNOS and eNOS knockout mice, and carried out electron‐microscopic observation of the epidermis after acetone treatment. Results The barrier recovery rate of eNOS knockout mice was significantly faster than that of the wild‐type control, while no significant difference was observed between iNOS knockout mice and wild‐type mice. Electron‐microscopic observation at 1 h after acetone treatment indicated that barrier recovery of both nNOS and eNOS mice was faster than that of wild‐type mice, and lamellar body secretion was accelerated in both types of knockout mice. Conclusions These results suggested that both nNOS and eNOS play roles in epidermal barrier homeostasis and lamellar body secretion.