Differences in Involucrin Immunolabeling Within Cornified Cell Envelopes in Normal and Psoriatic Epidermis

Epidermal keratinocytes form a cornified cell envelope (CE) beneath the plasma membrane during the late stages of differentiation, This CE is stabilized by cross linking of several precursor proteins, including involucrin, In psoriasis, the expression pattern of the precursor proteins is known to be deranged; involucrin expression is increased and loricrin expression is decreased. However, these changes have not been previously evaluated ultrastructurally. In the present study, we performed light and electron microscopic immunohistochemistry in conjunction with conventional transmission electron microscopy to assess the nature of involucrin involvement in normal and psoriatic CEs. In normal epidermis, CEs were observed from the deepest cornified cells or, when present, from the transitional cells, increasing In thickness and changing electron densities with maturation. In psoriatic epidermis, CE formation started earlier, one to several cells below the cornified layer. Psoriatic CEs were generally thinner and showed a constant high electron density. Immunoelectron microscopy revealed that the normal CE was involucrin positive only at a very early stage, whereas psoriatic CE showed persistent involucrin immunoreactivity. These results suggest that in normal skin, involucrin is the major constituent of the CE only In its early stages of assembly. In contrast, CE formation seems to be initiated prematurely in psoriatic skin, where involucrin remains the major constituent of the CE during maturation

Decreased Deiminated Keratin K1 in Psoriatic Hyperproliferative Epidermis

Citrulline-containing proteins, mainly originating from keratin K1 and formed by enzymatic deimination of arginine residues, have been identified in the cornified layers of human epidermis. We analyzed the localization and nature of the deiminated proteins in psoriatic epidermis. Immunostaining based on chemical modification of citrulline residues showed that the normal and psoriatic uninvolved epidermis contained deiminated proteins diffusely in the cornified cell layer, whereas the involved epidermis had no detectable or markedly reduced levels of deiminated proteins. Immunolabeling with polyclonal antibodies against a synthetic citrulline-containing peptide corresponding to a deiminated sequence of mouse K1 also suggested markedly decreased deiminated K1 in psoriatic involved lesions. Keratin analyses indicated that deiminated K1 present in normal and psoriatic uninvolved epidermis was not detected in the psoriatic involved epidermis. Double staining with a monoclonal antibody, 34βB4, and the polyclonal antibodies demonstrated that epidermis with low suprabasal keratin expression was negative for deiminated K1. In contrast, intralesional acrosyringia showing decreased suprabasal keratin immunoreactivity like that of the surrounding psoriatic epidermis showed strong deiminated K1 staining. This suggests that abnormal keratin deimination is restricted to the psoriatic hyperproliferative epidermis, without affecting sweat ductal epithelia

Corneodesmosomal Cadherins Are Preferential Targets of Stratum Corneum Trypsin- and Chymotrypsin-like Hyperactivity in Netherton Syndrome

SPINK5 (serine protease inhibitor Kazal-type 5), encoding the protease inhibitor LEKTI (lympho-epithelial Kazal-type related inhibitor), is the defective gene in Netherton syndrome (NS), a severe inherited keratinizing disorder. We have recently demonstrated epidermal protease hyperactivity in Spink5−/− mice resulting in desmosomal protein degradation. Herein, we investigated the molecular mechanism underlying the epidermal defect in 15 patients with NS. We demonstrated that, in a majority of patients, desmoglein 1 (Dsg1) and desmocollin 1 (Dsc1) were dramatically reduced in the upper most living layers of the epidermis. These defects were associated with premature degradation of corneodesmosomes. Stratum corneum tryptic enzyme (SCTE)-like and stratum corneum chymotryptic enzyme (SCCE)-like activities were increased, suggesting that these proteases participate in the premature degradation of corneodesmosomal cadherins. SCTE and SCCE expression was extended to the cell layers where Dsg1 and Dsc1 immunostaining was reduced. In contrast, a subset of six patients with normal epidermal protease activity or residual LEKTI expression displayed apparently normal cadherin expression and less severe disease manifestations. This suggests a degree of correlation between cadherin degradation and clinical severity. This work further supports the implication of premature corneodesmosomal cadherin degradation in the pathogenesis of NS and provides evidence for additional factors playing a role in disease expression

Loricrin and human skin diseases: molecular basis of loricrin keratodermas

The cornified cell envelope (CE) is a tough structure formed beneath the plasma membrane of terminally differentiated keratinocytes. Recent progress in understanding the molecular organization of the CE has disclosed the complex, yet orderly structure that functions as a protective barrier against the environment. We have recently demonstrated that two inherited skin diseases, Vohwinkel's syndrome (VS) and progressive symmetric erythrokeratoderma (PSEK) may result from mutations in the gene encoding loricrin, a major constituent of the CE. In adult human epidermis, loricrin is diffusely distributed within the superficial granular cells. In the cornified cells, loricrin is associated with CEs. In some patients with VS and PSEK skin, however, granular cells contain many intranuclear granules which are labeled with an amino-terminal loricrin antibody. CEs are thinner than normal and sparsely labeled with the loricrin antibody. Parakeratotic cornified cells contain loricrin-positive granules. Sequencing of the loricrin gene has disclosed heterozygous mutations; insertion of one nucleotide (730insG, 709insC) that shifts the reading frame in these patients. Consequently the carboxyl-terminus are replaced by highly charged missense sequences that override the endogeneous termination codon extending the protein with an additional 22 amino acids. Elucidation of the molecular biology of "loricrin keratodermas" adds to our understanding of the complexity and biological significance of the CE

Immunoelectron microscopic analysis of cornified cell envelopes and antigen retrieval

The original publication is available at www.springerlink.com authorIn this chapter, postembedding immunoelectron microscopy methods for studies of cornified cell envelopes are provided. Human epidermal tissue samples are used as the material. The samples are cryo-fixed without chemical fixation, freeze-substituted at a low temperature, and embedded in Lowicryl K11M resin. For immunostaining, colloidal gold-conjugated secondary antibodies are used. Methods for retrieval of masked epitopes are also described

Loricrin keratoderma: a novel disease entity characterized by nuclear accumulation of mutant loricrin

Elsevier Science Ireland Ltd., Akemi Ishida-Yamamoto, Journal of Dermatological Science, 31(1), 2003, 3-8. authorLoricrin is the major protein of the cornified cell envelope, a structure that replaces the plasma membrane during keratinocyte terminal differentiation. Recently, unique heterozygous, insertion mutations in the loricrin gene have been found to underlie certain congenital skin abnormalities, the phenotypes of which vary considerably. Clinically, these patients can be diagnosed as suffering from an ichthyotic variant of Vohwinkel's syndrome, progressive symmetric erythrokeratoderma, or congenital ichthyosiform erythroderma born as a collodion baby. Common clinical features include hyperkeratosis of the palms and soles with digital constriction. Histologic characteristics are parakeratotic hyperkeratosis with hypergranulosis and nuclear accumulation of mutant loricrin. The unique mutations in the glycine rich domain of the mutant loricrin form arginine rich nuclear localization sequences that disrupts differentiation of keratinocytes. This group of unique genodermatoses caused by distinct loricrin mutations is collectively termed loricrin keratoderma

Pruritic Palpable Purpura on the Lower Legs: A Quiz

Abstract is missing (Quiz

Localized Myxedema on the Upper Eyelids in a Patient of Hypothyroidism

A 42-year-old Japanese woman presented with upper eyelid swelling of 2 months duration (Figure 1a). She did not complain muscle weakness or myalgia. She showed no dry coarse skin, tremors of the hands, thick tongue, or loss of hair. Histopathology of the skin biopsy revealed swelling of the collagen bundles with splitted individual fibers accompanied with pale material (Figure 1b), which was stained with blue with colloidal iron (Figure 1c).Laboratory investigation revealed decreased free T4 (0.88 ng/ml(1-1.8)), decreased free T3 (1.12 pg/ml (2.73-4.5)), and increased TSH (10.34 IU/ml (0.27-4.29). Anti-thyroid, anti-microsome, antithyrogloblin and anti-thyroid peroxidase antibodies were positive.Total cholesterol (286 mg/dl) and triglyceride (342 mg/dl) were elevated. Other laboratory findings including anti-nuclear antibody, aldolase, creatine kinase, and angiotensin-converting enzyme showed normal results. Echo examination disclosed slight but diffuse swelling of thyroid gland. Chest X-rays showed no abnormality and no malignant disease was detected in CT. The patient was diagnosed as localized myxedema with hypothyroidism due to Hashimoto disease.After three months of thyroid hormone replacement therapy, the skin lesions gradually improved accompanied with euthyrodic state. We got the informed consent form the patient.</p