Disrupted desmosomes in induced lesions of familial benign chronic pemphigus

Endoplasmic Reticulum Calcium Regulates Epidermal Barrier Response and Desmosomal Structure

Ca(2+) fluxes direct keratinocyte differentiation, cell-to-cell adhesion, migration, and epidermal barrier homeostasis. We previously showed that intracellular Ca(2+) stores constitute a major portion of the calcium gradient especially in the stratum granulosum. Loss of the calcium gradient triggers epidermal barrier homeostatic responses. In this report, using unfixed ex vivo epidermis and human epidermal equivalents we show that endoplasmic reticulum (ER) Ca(2+) is released in response to barrier perturbation, and that this release constitutes the major shift in epidermal Ca(2+) seen after barrier perturbation. We find that ER Ca(2+) release correlates with a transient increase in extracellular Ca(2+). Lastly, we show that ER calcium release resulting from barrier perturbation triggers transient desmosomal remodeling, seen as an increase in extracellular space and a loss of the desmosomal intercellular midline. Topical application of thapsigargin, which inhibits the ER Ca(2+) ATPase activity without compromising barrier integrity, also leads to desmosomal remodeling and loss of the midline structure. These experiments establish the ER Ca(2+) store as a master regulator of the Ca(2+) gradient response to epidermal barrier perturbation, and suggest that ER Ca(2+) homeostasis also modulates normal desmosomal reorganization, both at rest and after acute barrier perturbation.

The calcium ATPase SERCA2 regulates desmoplakin dynamics and intercellular adhesive strength through modulation of PKCα signaling

Darier's disease (DD) is an inherited autosomal-dominant skin disorder characterized histologically by loss of adhesion between keratinocytes. DD is typically caused by mutations in sarcoendoplasmic reticulum Ca(2+)-ATPase isoform 2 (SERCA2), a major regulator of intracellular Ca(2+) homeostasis in the skin. However, a defined role for SERCA2 in regulating intercellular adhesion remains poorly understood. We found that diminution of SERCA2 function by pharmacological inhibition or siRNA silencing in multiple human epidermal-derived cell lines was sufficient to disrupt desmosome assembly and weaken intercellular adhesive strength. Specifically, SERCA2-deficient cells exhibited up to a 60% reduction in border translocation of desmoplakin (DP), the desmosomal cytolinker protein necessary for intermediate filament (IF) anchorage to sites of robust cell-cell adhesion. In addition, loss of SERCA2 impaired the membrane translocation of protein kinase C α (PKCα), a known regulator of DP-IF association and desmosome assembly, to the plasma membrane by up to 70%. Exogenous activation of PKCα in SERCA2-deficient cells was sufficient to rescue the defective DP localization, desmosome assembly, and intercellular adhesive strength to levels comparable to controls. Our findings indicate that SERCA2-deficiency is sufficient to impede desmosome assembly and weaken intercellular adhesive strength via a PKCα-dependent mechanism, implicating SERCA2 as a novel regulator of PKCα signaling.

Dissociation of intra- and extracellular domains of desmosomal cadherins and E-cadherin in Hailey-Hailey disease and Darier's disease

In order to clarify the pathomechanism of acantholysis in Hailey-Hailey disease (HHD) and Darier's disease (DD), the distribution of desmosomal and adherens junction-associated proteins was studied in the skin of patients with HHD (n = 4) and DD (n = 3). Domain-specific antibodies were used to determine the cellular localization of the desmosomal transmembrane glycoproteins (desmogleins 1 and 3 and desmocollin), desmosomal plaque proteins (desmoplakin, plakophilin and plakoglobin) and adherens junction-associated proteins (E-cadherin, alpha-catenin, beta-catenin and actin). A significant difference in staining patterns between intra- and extracellular domains of desmosomal cadherins and E-cadherin was demonstrated in acantholytic cells in both HHD and DD, but not in those in pemphigus vulgaris and pemphigus foliaceus samples used as controls. In acantholytic cells in HHD and DD, antibodies against attachment plaque proteins and intracellular epitopes of desmosomal cadherins exhibited diffuse cytoplasmic staining, whereas markedly reduced staining was observed with antibodies against extracellular epitopes of the desmogleins. Similarly, membrane staining of an intracellular epitope of E-cadherin was preserved, while immunoreactivity of an extracellular epitope of E-cadherin was destroyed. While the DD gene has been identified as ATP2A2, the gene for HHD has not been clarified. The dissociation of intra- and extracellular domains of desmosomal cadherin and E-cadherin is characteristic of the acantholytic cells in HHD and DD, and not of pemphigus. This common phenomenon in HHD and DD might be closely related to the pathophysiological mechanisms in both conditions.

1alpha,24-dihydroxyvitamin D3 (tacalcitol) is effective against Hailey-Hailey disease both in vivo and in vitro

We report a case of Hailey-Hailey disease (HHD) in which 1alpha, 24-dihydroxyvitamin D3 (tacalcitol) was effective both clinically (in vivo) and in explant cultures (in vitro) of a skin lesion. The patient was a 65-year-old man with HHD lesions in the axillary and inguinal areas bilaterally. We applied ointment containing 1alpha, 24-dihydroxyvitamin D3 (tacalcitol), an analogue of active vitamin D3, to the lesions and assessed its clinical effectiveness. The HHD lesions in both groins disappeared after treatment with the 1alpha, 24-dihydroxyvitamin D3 ointment, and the remission has continued to the present. A punch biopsy specimen of the lesion that had remitted showed no acantholysis. In addition, dissociation of migrating keratinocytes was observed when biopsy specimens of the HHD skin lesion were cultured in medium without 1alpha,24-dihydroxyvitamin D3, but inhibition of keratinocyte dissociation was observed in medium containing it. These results suggest the effectiveness of 1alpha, 24-dihydroxyvitamin D3 against HHD both in vivo and in vitro.

Ultrastructural localization of gap junction protein connexin 43 in normal human skin, basal cell carcinoma, and squamous cell carcinoma

The expression and localization of connexin 43 (Cx43) were investigated in normal human epidermis, pilosebaceous apparatus, basal cell carcinoma, and squamous cell carcinoma by immunofluorescence as well as by immunoelectron microscopy. In the normal epidermis the immunofluorescence was weak in the basal layer, increased in spinous layer and negative in the horny layer. In the sebaceous gland, peripheral lobular cells showed weak cell membrane dotted pattern. Cell membrane and cytoplasmic fluorescence was strong in the central lobular cells. In the lower hair follicle, the cortex, inner and outer root sheath cells showed cell membrane fluorescence. As cortical cells underwent keratinization, they lost Cx43 epitopes. Basal cell carcinoma and squamous cell carcinoma were poorly stained, and eccrine and apocrine glands were unstained. In immunoelectron microscopy, close membrane appositions of typical gap junctions were often observed in the spinous layers of the epidermis and the immunolabeling for Cx43 was seen along the gap junction structures. Circular and long gap junctions often were found in follicular root sheaths and sebaceous glands. Gold particles labeling Cx43 in these gap junctions were found on the gap junctions or localized in the cytoplasm near the gap junction membranes. Basal cell carcinoma and squamous cell carcinoma had a small number of small gap junctions, and gold particles were not only localized to gap junctions but scattered in the cytoplasm. No gap junctions were labeled in eccrine and apocrine glands. These findings confirmed that 1) long, curved or circular membrane appositions found in hair follicle and sebaceous gland are true gap junctions, 2) immature cells such as epidermal basal cells, peripheral germinative cells of sebaceous gland and basal and squamous cell carcinoma cells do not have fully developed gap junctions, and 3) Cx43 or its precursors are present in the cytoplasm as well as on poorly developed gap junctions in these immature cells. Immunofluorescence findings generally corresponded to ultrastructural distribution and structural maturity of gap junctions.

Hailey-Hailey disease keratinocytes: normal assembly of cell-cell junctions in vitro

The blisters in the inherited disorder, Hailey-Hailey disease, may be caused by defective epidermal junctional complexes. We evaluated these structural complexes in vivo and in vitro. We induced a vesicular lesion in the apparently normal skin of a patient with Hailey-Hailey disease and studied a biopsy of this lesion by transmission electron microscopy. To determine whether acantholysis was related to a defect in the number or assembly of intercellular junctions, we cultured Hailey-Hailey disease keratinocytes in medium containing 0.1 mM Ca2+ and increased the [Ca2+] to 1.1 mM in order to induce assembly of cell-cell junctions. Keratinocytes were examined by double immunofluorescence with antibodies to the desmosome protein, desmoplakin, and the adherens junction protein, vinculin, at intervals after the increase in [Ca2+]. Characteristic Hailey-Hailey disease histopathology was observed by electron microscopy of the patient's skin after trauma, but we found no splitting of desmosomes. Based on the location, intensity, and rate of change of immunofluorescent staining, Hailey-Hailey and normal keratinocytes did not differ in their ability to assemble desmosomes and adherens junctions. Furthermore, we observed no significant morphologic differences between normal and Hailey-Hailey keratinocytes cultured in low and high [Ca2+]-containing media; Hailey-Hailey cells contained abundant normal-appearing desmosomes in 1.1 mM [Ca2+]. Since Hailey-Hailey disease keratinocytes can assemble normal-appearing adherens junctions and desmosomes in vitro, the functional defect may not lie in assembly of cell-cell adhering junctions, or additional perturbation may be required to expose the defect.

Curvicircular intracytoplasmic membranous structures in keratinocytes of pemphigus foliaceus

We noticed intracytoplasmic membranous, annular, or circular structures in the lesion of pemphigus foliaceus and studied these by regular transmission electron microscopy and immunoelectron microscopy. These curvicircular bodies were observed in the preacantholytic keratinocytes of the blister wall as well as in acantholytic cells in 6 out of 6 patients with pemphigus foliaceus. They were absent in samples from 3 patients with pemphigus vulgaris. These structures were about 60-70 nm wide and consisted of 4 electron-dense layers. They were continuous with intact desmosomal structures and gap junctions in the periphery of the keratinocytes. These curvicircular membranous bodies were well labeled with immunogold particles for desmoglein, plakoglobin, connexin 43, and IgG. In contrast to pemphigus vulgaris, splitting of desmosomes through dissolution of intercellular desmoglea was seldom observed in all 6 specimens of pemphigus foliaceus. These findings suggest that in pemphigus foliaceus 1) curvicircular bodies are derived from internalized desmosomes and gap junctions, and 2) cell-to-cell adhesions are weakened by this internalization and acantholysis is initiated, while in pemphigus vulgaris the dissolution of desmoglea is the initial event. It is suggested that in pemphigus foliaceus the binding of autoantibody induces internalization of many intact desmosomes and gap junctions rather than splitting them.

Effects of steroid, retinoid, and protease inhibitors on the formation of acantholysis induced in organ culture of skins from patients with benign familial chronic pemphigus

Skin explants from two lesional areas and four normal-appearing areas of four patients with benign familial chronic pemphigus (BFCP) were organ cultured with and without various reagents. After 24-h culturing of involved skin with medium only, dissociation of keratinocytes, which was also observed prior to culturing, was exacerbated, and the epidermis became edematous, with a large section detaching from the dermis. These phenomena were not suppressed even when betamethasone, retinol acetate, or camostat mesilate (serine protease inhibitor) was added to the medium. On the other hand, in the cultures of uninvolved skin explants with medium only, widened intercellular spaces were observed 24-48 h after initiation of culture, and dissociation of keratinocytes and acantholytic clefts became apparent after 72 h. Such culture-induced acantholysis was almost completely suppressed by the addition of betamethasone, but not suppressed by the addition of retinol acetate, EDTA, N-ethylmaleimaide, or pepstatin A. Camostat and SBTI incompletely suppressed the acantholysis. These findings suggest the possibility that steroid may reduce blistering and that an organ culture of non-lesional benign familial chronic pemphigus (BFCP) skin may be useful for clarifying the pathogenesis, as well as for discovering new drugs for the treatment of BFCP. Further experiments are required to clarify the role of serine proteases in the acantholysis in this disease.

Immunolocalization of desmoglein I ("band 3" polypeptide) on acantholytic cells in pemphigus vulgaris, Darier's disease, and Hailey-Hailey's disease

Acantholysis is defined as loss of coherence between epithelial cells and is histologically shown in several bullous diseases. It was postulated that desmoglein I, one of the major transmembrane glycoproteins of the desmosome, may adhere to the attachment plaque inside the cell and contribute to desmoglea outside the cell. In this study we used a well characterized antibody against desmoglein I for immunofluorescence and immunoelectron microscopic techniques on 2 cases each of pemphigus vulgaris and Darier's disease and one case of Hailey-Hailey's disease. In the normal epidermis desmosomes were demonstrated in dotted or rim-like patterns along cell periphery on immunofluorescence study. In pemphigus vulgaris dotted or rim-like patterns were still identified in many acantholytic cells, particularly in early phase of acantholysis. In Darier's disease and Hailey-Hailey's disease, dotted or rim-like patterns were already lost in early acantholysis and immunoreactive desmoglein I proteins were observed diffusely in the cytoplasm. Immunoelectron microscopy confirmed these immunofluorescence observations. It was suggested that in pemphigus vulgaris desmoglein I is unlikely to be the primary site of acantholysis because dotted or rim-like patterns of immunoreactive desmoglein I are relatively preserved on lesional cells, whereas in genodermatoses such as Darier's disease and Hailey-Hailey's disease primary abnormalities of desmosomes may be involved in their acantholysis.

Desmoplakin I and II in acantholytic dermatoses: preservation in pemphigus vulgaris and pemphigus erythematosus and dissolution in Hailey-Hailey's disease and Darier's disease

Desmoplakin I and II are important components of the attachment plaque of the desmosome which mediates cell to cell adhesion, in epithelial cells. In this study we used well-characterized antibody against desmoplakin I and II immunohistochemically and immunoelectron microscopically on two cases of pemphigus vulgaris and one case of pemphigus erythematosus and two cases each of Hailey-Hailey's disease and Darier's disease. In the normal human epidermis the desmosomes were demonstrated in a dotted pattern along cell periphery. In pemphigus vulgaris and pemphigus erythematosus acantholytic cells and the perilesional cells exhibited normal dotted pattern along the cell periphery. In Hailey-Hailey's disease and Darier's disease, the dotted pattern is lost in acantholysed and perilesional areas and anti-desmoplakin I + II positive proteins were observed diffusely in the cytoplasm. Immunoelectron microscopical findings correspond to these light microscopical observations. It is concluded that in autoimmune acantholytic disease such as pemphigus vulgaris and pemphigus erythematosus, desmoplakins are intact even in acantholytic cells, whereas in genodermatoses such as vulgaris and pemphigus erythematosus, desmoplakins are intact even in acantholytic cells, whereas in genodermatoses such as Hailey-Hailey's disease and Darier's disease primary or secondary abnormalities abnormalities of desmosomes may be involved in their pathogenesis.

Ultrastructural studies of acantholysis induced in vivo by passive transfer of IgG from endemic pemphigus foliaceus (Fogo Selvagem)

Intraperitoneal (IP) injections of IgG from patients with Endemic Pemphigus Foliaceus [Fogo Selvagem (FS)] cause acantholysis in BALB/c mice (JID. 85:538, 1985). The dynamic ultrastructural changes of FS IgG-induced acantholysis in mice are the subject of this study. FS IgG was injected IP into neonatal BALB/c mice. Skin and serum was studied at 0, 1, 3, 6, 12, 18, and 24 h post injection by immunofluorescence (IF), electron microscopy (EM), and immuno-EM. Binding of FS IgG in the intercellular spaces (ICS) of the basal cell layer was seen by IF within 1 h and was strongest at 12 h. IgG binding affected the spinous and granular cell layer by 12 h, then faded and remain localized only in the basal cell layer at 24 h. By immuno-EM, IgG binding was diffuse along the keratinocyte surface. Edema of the ICS in the basal cell layer was present at 1 h by EM. At 12 h, there was microvillous formation with intact desmosomes at the tip of the projections. Splitting of desmosomes (forming half desmosomes) and acantholysis primarily affecting the granular cell layer were most prominent between 12 and 24 h. The plaques of the half desmosomes gradually disappeared and tonofilaments retracted into the cytoplasm. Detaching keratinocytes showed vacuolization, swollen mitochondria, and internalization of intact desmosomes and half desmosomes (remnants of split desmosomes). This investigation shows that the ultrastructural changes observed in the epidermis of patients with FS can be duplicated in experimental animals by IP injection of FS IgG. Further, FS IgG may have direct effects on the assembly/disassembly of desmosomes.

Carbon dioxide laserabrasion: a new approach to management of familial benign chronic pemphigus (Hailey-Hailey disease)

Familial benign chronic pemphigus (FBCP), or Hailey-Hailey disease, can be a debilitating condition. Treatment is palliative and only excision of lesional skin followed by split-thickness grafting may be curative. The success of surgery is attributed to the removal of adnexal structures and a decrease in sweating and maceration. This is the first report of successful carbon dioxide (CO2) laserabrasion of a patient with FBCP. The procedure spared the underlying adnexae which contributed to the reepithelialization of the epidermis. The selective destructive property of the CO2 laser may contribute to understanding the pathophysiology of FBCP.

Relapsing linear acantholytic dermatosis

A 5-year-old girl with a unilateral linear systematized skin lesion showing the clinical, histological and ultrastructural features of Hailey-Hailey disease is described. We suggest that this relapsing linear acantholytic dermatosis represents a new distinct entity within the spectrum of unilateral linear skin diseases.