Lysozyme is a component of human vascular elastic fibers

The defensive role of lysozyme in human gingiva in inflammatory periodontal disease

BACKGROUND AND OBJECTIVE

The presence of lysozyme in human gingiva has not previously been demonstrated. In this study, we looked for evidence for the potential role of lysozyme as a protector of gingival elastic fibres. The objective of this study was also to determine the ex vivo susceptibility to hydrolysis of gingival elastic fibres from patients with or without periodontal disease by human leukocyte elastase and by human cathepsin G.

MATERIALS AND METHODS

Using gingival tissue sections from eight control, 10 gingivitis and 10 periodontitis patients, we evaluated the area fraction occupied by gingival elastic fibres (after selective staining) by the use of automated image analysis. In the ex vivo experiments, serial tissue sections from four control, four gingivitis, four young periodontitis and four aged periodontitis patients were submitted to the action of human leukocyte elastase and cathepsin G, after which enzymatic activities were determined by image analysis. Indirect immunodetection of lysozyme was also done on tissue sections for all patients included in this study.

RESULTS

Large variations of the area fraction occupied by elastic fibres were observed in human gingiva from young and aged patients with and without periodontal disease. In control and gingivitis patients, leukocyte elastase and cathepsin G had high comparable elastin solubilizing activities. With young and aged periodontitis patients, the two serine proteinases had weak elastin solubilizing activities. Lysozyme appeared to be present at the periphery of gingival elastic fibres in periodontitis patients.

CONCLUSION

Lysozyme can be considered an important natural protector of elastic fibres in pathological gingiva.

Elastin changes during chronological and photo-ageing: the important role of lysozyme

Cutaneous ageing, as a result of combined chronological and photo-ageing in sun-exposed areas, is accompanied by major modifications of the elastic fibres. We aimed to investigate qualitative and quantitative changes of dermal elastin fibres during cutaneous chronological and photo-ageing and the involvement of lysozyme in these processes. Morphological, age-related changes and variations in the relative elastin content in sun-protected (buttock) and sun-exposed (forearm and face) skin of healthy volunteers were studied (145 samples). The deposition of lysozyme in elastin fibres was studied using light and immuno-electron microscopy and taking into consideration the relative efficacy of different UV wavebands (UVA or SSR (solar simulated radiation)). Our studies also included the proteolytic degradation of elastin by human leucocyte elastase (HLE) in situ. Our results indicate a reduction of elastin content with age in sun-protected and sun-exposed skin, associated for the latter with high elastin content, resulting in elastosis. Total UVA (320-400 nm), and in particular long wave UVA (UVA-1, 340-400 nm), induces lysozyme deposition in elastin fibres to a higher extent than solar simulated radiation (SSR, 280-400 nm). Immuno-electron microscopy revealed lysozyme association with the electron-dense granular amorphous elastin structures, corresponding to a basophilic degeneration induced by sun exposure. Lysozyme has no elastolytic activity in situ; however, its binding to elastin limits elastin degradation by human leucocyte elastase (HLE). In addition, a direct inhibitory effect of lysozyme on HLE was observed. Our data suggest that lysozyme prevents elastin degradation by HLE after binding to the damaged parts of the elastin network and by direct lysozyme-HLE interaction, which reduces HLE proteolytic activity. These observations contribute to a better understanding of the chronological and photo-induced changes of the dermal elastic network.

Changes in Matrix Gene and Protein Expressions After Single or Repeated Exposure to One Minimal Erythemal Dose of Solar-simulated Radiation in Human Skin In Vivo

Damage to the skin extracellular matrix (ECM) is the hallmark of long-term exposure to solar UV radiation. The aim of our study was to investigate the changes induced in unexposed human skin in vivo after single or repeated (five times a week for 6 weeks) exposure to 1 minimal erythemal dose (MED) of UV solar-simulated radiation. Morphological and biochemical analyses were used to evaluate the structural ECM components and the balance between the degrading enzymes and their physiologic inhibitors. A three-fold increase in matrix metalloproteinase 2 messenger RNA (mRNA) (P < 0.02, unexposed versus exposed) was observed after both single and repeated exposures. Fibrillin 1 mRNA level was increased by chronic exposure (P < 0.02) and unaltered by a single MED. On the contrary, a single MED significantly enhanced mRNA levels of interleukin-1alpha (IL-1alpha), IL-1beta (P < 0.02) and plasminogen activator inhibitor-1 (P < 0.05). Immunohistochemistry demonstrated a significant decrease in Type-I procollagen localized just below the dermal-epidermal junction in both types of exposed sites. At the same location, the immunodetected tenascin was significantly enhanced, whereas a slight increase in Type-III procollagen deposits was also observed in chronically exposed areas. Although we were unable to observe any change in elastic fibers in chronically exposed buttock skin, a significant increase in lysozyme and alpha-1 antitrypsin deposits on these fibers was observed. These results demonstrate the existence of a differential regulation, after chronic exposure compared with an acute one, of some ECM components and inflammatory mediators.

Lysozyme binds to elastin and protects elastin from elastase-mediated degradation

Lysozyme has been shown to be associated with damaged elastic fibers in many tissues and organs. To better characterize this interaction, binding of lysozyme to elastin was studied using solution-based binding assays. Under physiologic conditions, radio-labeled lysozyme bound specifically to elastin in a time- and concentration-dependent manner. Binding was reversible and was inhibited by unlabeled human and hen lysozyme but not by other proteins. Lysozyme had no elastolytic activity as assessed by a standard tritium-release assay, but, importantly, prevented the proteolytic degradation of elastin by human leukocyte elastase, pancreatic elastase, thermolysin, and Pseudomonas elastase. A striking feature of lysozyme's anti-elastase activity was that it did not function in the classical sense of inhibiting directly the enzymatic activity of the protease. Instead, by binding to elastin, lysozyme prevented the protease from interacting with the elastin substrate in ways that normally favor proteolysis. These results show that lysozyme binds to the elastin component of elastic fibers and that this interaction has important biological consequences for elastic fiber degradation. By preventing degradation of elastin, lysozyme can function as an important natural inhibitor that exerts a protective effect on elastic fibers at sites of tissue injury.

Cumulative effects from repeated exposures to suberythemal doses of UVB and UVA in human skin

BACKGROUND

The skin is repeatedly exposed to solar UV radiation. Long-term photodamage is a consequence of cumulative UV radiation injury. Hence an examination of the repetitive effects of UV exposure is more likely to yield clues to the early alterations that lead to photoaged skin than a single exposure.

OBJECTIVE

We examined the effects of repetitive low-dose UV irradiation on human skin with the aim of identifying UVA-induced effects that may have a different wavelength dependence than acute erythema.

METHODS

Areas on the lower part of the back were each exposed to a suberythemal dose (0.5 minimal erythema dose [MED]) of solar simulated radiation (290 to 400 nm) and of UVA (320 to 400 nm) once daily, 5 days a week, for 28 doses. One site was also treated daily with a sunscreen having a sun protection factor of 22 and then exposed to 11 MEDs of solar simulated radiation for the same duration. Epidermal and dermal changes were analyzed and quantified by histochemical stains in combination with computer-assisted image analysis of tissue sections.

RESULTS

At equal 0.5 MED doses, UVA induced greater cumulative changes than solar simulated radiation, as assessed by development of a greater cumulative erythema response in the first week of treatment, the presence of epidermal hyperplasia and stratum corneum thickening, depletion of Langerhans cells, dermal inflammatory infiltrates, and deposition of lysozyme on elastin fibers. These changes were not prevented by the sunscreen. A single short-term dose of UVA did not elicit these changes.

CONCLUSION

These findings suggest that UVA may contribute significantly to long-term actinic damage and that the spectral dependence for cumulative damage does not parallel the action spectrum for acute injury (erythema) in human beings.

Hamartomas of the breast: six novel diagnostic features in three-dimensional thick sections

Fifteen hamartomas of the breast have been studied by dissecting microscopy of thick sections at a depth of 1.0 to 2.5 mm, and by conventional 5 microns deep sections. This combined approach has revealed six distinctive features, three in the parenchymal structure and three in the connective tissue components. Ducts (invariably of penetrating or arcuate configuration) and discrete lobules, neither of which are seen in lesions accepted as fibroadenomas, were invariably found. In one-third of hamartomas, up to 10% of the surface area was occupied by Herãti-style nodules composed of concentric rings of epithelium. In the hyaline interlobular connective tissue characteristic drifts of caraway seed-like fibrocytes, encasement of adipocytes by hyaline collagen, or spider-naevus vascular abnormalities were found in approximately half of the mammary hamartomas when examined in thick sections. Hitherto the positive diagnosis of hamartomas of the breast has relied on a combined clinical, radiological and pathological assessment. We suggest that the additional features described here, taken in conjunction with those already known, may facilitate the recognition of mammary hamartomas by histopathological examination alone.

Backprocessing paraffin wax blocks for subgross examination

A method called "backprocessing", for subgross examination of sections, ranging between 50 microns and 1 mm in thickness using a dissecting microscope was developed. It requires either archival or current diagnostic breast tissue. In this study tissue is assumed to have been already embedded in paraffin wax for immediate diagnostic purposes. The advantages of backprocessing include the ability to select valuable or rare diagnostic tissue from archival histopathological material, and the preservation of histological structure should further examination at 5 microns thickness be required at a later date.

Diagnostic and therapeutic aspects of fine-wire localization biopsy for impalpable breast cancer

During the first 2 years (July 1989 to July 1991) of the Avon Breast Screening Service, fine-wire localization biopsy was indicated in 213 impalpable breast lesions. A total of 144 lesions were benign and 69 malignant. Only four of 213 lesions (1.9 per cent) were not excised at the first localization. Factors influencing reoperation in the 69 patients with malignant impalpable lesions were examined. There was a significant association (P < 0.001) between parenchymal disturbances on mammography and invasive carcinoma, and between non-invasive carcinoma and microcalcification (P < 0.001). In 31 patients the localization biopsy was the only surgical procedure. Thirty-eight patients required further surgery: 12 underwent further local excision and 26 mastectomy. Reoperation was more frequent in patients with calcification than in those with parenchymal disturbance (P < 0.001). The most frequent indications for mastectomy were inadequate excision of widespread comedo ductal carcinoma in situ or invasive ductal carcinoma combined with extensive ductal carcinoma in situ. Fine-wire localization biopsy was a combined therapeutic and diagnostic procedure in 31 of 69 women with impalpable screen-detected lesions. The majority of patients required further surgery because radiological abnormalities underestimated the extent of disease.

Lysozyme in abnormal dermal elastic fibers of cutaneous aging, solar elastosis and pseudoxanthoma elasticum

Staining of elastic fibres with antilysozyme antibodies has been noted previously. In this study, we examined the staining pattern of dermal elastic fibres in aging, solar elastosis, and lesional skin of pseudoxanthoma elasticum (PXE) using an antibody to lysozyme and the indirect-peroxidase technique. To assess the effects of aging, sun-protected skin (buttock) from a younger and an older group of patients was used. Sun damage was studied in skin specimens from varying sun-exposed body regions (trunk; head and neck). No staining was seen in sun-protected skin from younger individuals, whereas sun-protected skin from older persons had scattered positive fibres. Solar elastotic material was intensely positive and the number of positive fibres appeared to correlate with the amount of sun damage. Abnormal elastic fibres in PXE also stained positively, but less intensely, than fibres in solar elastosis. This study shows that changes in the elastic fibres due to degenerative processes or genetic factors results in altered antigenic expression of the fibres. This may be an epiphenomenon secondary to changes in proteoglycans, which are known to occur with solar elastosis and PXE, or may represent an adaptive phenomenon to maintain the elastic properties of the altered fibres or to decrease their antigenicity.

Differential marking of excision planes in screened breast lesions by organically coloured gelatins

Traditionally India ink has been used to mark surgical resection margins, more recently with acetone to aid drying. Alternative methods have been suggested in recent months, including solutions of alcian blue, and Tippex. These methods use one colour only and Tippex is radiodense. Artists' pigments have been used, but their radiodensity makes them unsuitable for the detailed mammograms of the sliced screened specimens. An alternative method was specifically designed for impalpable breast lesions. It is based on coloured gelatins that are painted on to the biopsy specimen before dissection. The markers are radiolucent, quick to set, and do not penetrate the connective tissue. They can be applied to both fresh and fixed tissues, and the cost is about 0.05 pounds a specimen. The system is also suitable for marking other large specimens.

Marking planes of surgical excision on breast biopsy specimens: use of artists' pigments suspended in acetone

The performance of carbon and metallic inks, silver nitrate solution, and artists' pigments mounted in acetone was compared for marking the surface of surgical biopsy specimens. Using India ink is an unsatisfactory procedure because of slow drying, messiness, and spreading of the ink. It is concluded that use of artists' pigments has many advantages over other reagents, because of their rapid drying, resistance to tissue processing, and the ability to mark simultaneously many different planes of excision. Furthermore, the pigments are readily visible, are distinguishable from each other on microscopical examination, and the method entails little extra cost.

Elastic fibres in normal and sun-damaged skin: an immunohistochemical study

Sun-exposed and sun-protected skin obtained at post mortem from the nape of the neck in 14 subjects was immunostained using antisera to elastin, lysozyme, amyloid P component, and the plasma protease inhibitors alpha-I antitrypsin, alpha-I antichymotrypsin and alpha-2 macroglobulin. Both the normal elastic fibres in sun-protected skin, and elastosis in sun-exposed skin were positively immunostained for elastin, lysozyme and amyloid P component. Collagen fibres were unstained. No immunostaining of normal elastic fibres or elastosis in the skin was obtained with antisera to alpha-I antitrypsin, alpha-I antichymotrypsin or alpha-2 macroglobulin. It was concluded that the elastosis in sun-exposed skin does contain elastic fibres. The absence of immunostaining for plasma protease inhibitors probably indicates that the elastic material is mature, and not newly-formed.

Elastosis in breast carcinoma: I. Immunohistochemical characterization of elastic fibres

Elastosis associated with invasive ductal and lobular carcinomas of the breast was examined by tinctorial and immunohistochemical staining methods, enzyme digestion, and electron microscopy. The elastotic material exhibited the tinctorial staining properties of elastic fibres, and the ultrastructural appearances were those of elastic fibres although there was a higher proportion of microfibrils than in normal mature elastic fibres. The elastosis was immunostained by antisera to human fetal elastin, lysozyme and amyloid P component, as in other sites where elastic fibres are found. These findings indicate that immunohistochemically intact elastic fibres are present in the elastosis of breast cancer. They also demonstrate that lysozyme and amyloid P component are co-distributed with elastic fibres in elastosis of breast carcinoma, as distinct components with different susceptibilities to enzyme digestion. The cellular origin of elastosis in breast carcinoma remains uncertain.

Lectin binding to elastic fibres and associated components during development of the human aorta

A panel of peroxidase-conjugated lectins was used to stain frozen sections of human foetal, neonatal, infant and adult aortae. Two main distinctive staining patterns were observed at the light microscope level, depending on the lectin employed. Lectins from Concanavalin A, Triticum vulgaris, Arachis hypogaea and Glycine max resulted in staining of the surfaces of aortic elastic lamellae and the interlamellar areas. With lectins from Dolichos biflorus and Bandeiraea simplicifolia staining was seen predominantly in the interlamellar areas. The findings indicate the presence of several different glycoconjugates at various sites within the aorta. In addition, there were alterations in the lectin binding affinities of the aortae that were dependent upon age. The findings are interpreted as indicating sequential changes in the composition of glycoprotein or proteoglycan moieties in the development of the human aorta.

Frozen section diagnosis: an audit

A consecutive series of 1000 operative frozen section diagnoses was reviewed. Correct diagnosis was made at the time in 96.5% of the cases. Clinically relevant errors were found in 1.3% of the cases and unimportant errors in 0.9%. Diagnosis was deferred, to await subsequent paraffin sections, in a further 1.3%. All the errors and provisional diagnoses in the deferred cases were conservative false negative results; no false positive diagnosis of malignancy was made. The cases of incorrect or deferred diagnosis were analysed to ascertain the origin of the difficulties, which comprised: technical imperfection (three cases); the focal nature of the lesion (14); and pathological misinterpretation (28). More than one of these factors played a part in eight cases. Further retrospective assessment indicated that the factors leading to error or deferred diagnosis were avoidable in 57% and potentially avoidable in 43% of cases. Misinterpretation was the single factor responsible for all avoidable misdiagnoses or deferred diagnosis. None the less, unavoidable factors led to erroneous or deferred diagnosis in about 2% of operative frozen section requests. Using present methods this seems to be the irreducible minimum of failures to make the correct diagnosis when frozen sections are assessed.

The effects of preliminary proteolysis on the immunohistochemical and dye staining properties of elastic fibres

Antibodies to alpha-elastin peptides, amyloid P component, lysozyme and plasma protease inhibitors have been used in an immunoperoxidase method to stain elastic fibres in frozen sections of human breast tissues. A loss of immunoreactivity seen in formalin-fixed, paraffin-embedded sections was reversed by a preliminary proteolysis. Differences in the tinctorial dye and immunohistochemical staining patterns following proteolysis by a variety of enzymes suggests a selective unmasking or removal of elastic fibre components and thus the presence of separate binding sites for individual antibodies and tinctorial dyes. Antibody blocking experiments and double immunoenzymatic labelling support the existence of several different epitopes within elastic fibres.

Differential Congo red staining: the effects of pH, non-aqueous solvents and the substrate

Congo red is an acid-base indicator dye. In free solution the colour and absorption characteristics of Congo red depend not only on the pH but are also governed by the nature of the solvent environment. In tissue sections stained by Congo red, alteration of the pH and the use of non-aqueous solvents can effect differential colouring of the tissue components. Stained sections of unmodified and chemically substituted celluloses show that differential red or blue coloration reflects the acidic or basic character of the substrate. In stained tissue sections, secondary protein structure and porosity of the substrate may also influence their colour. The effect of non-aqueous solvents is probably to modify the ionization state of the dye-substrate complex, thus altering the colour of the Congo red. Such solvents may also change the aggregation or solvation states of the dye, with consequent modification in the colour of tissue components.

Phenotypic expression of immune secretory function in focal pregnancy-like change of the human breast

Fibrocystic disease of the breast in middle-aged women characteristically shows focal epithelial lesions of a very varied nature. The functional immunohistochemical changes in such lesions have been little studied. Focal Pregnancy-like Change in the breast has a striking morphological similarity to the secretory breast lobules in pregnancy and in lactation. We show that the epithelial cells in all the lesions of Focal Pregnancy-like Change studied simultaneously express secretory component, Ig A and J chain in their cytoplasm. Additionally these epithelial cells, unlike those in resting breast lobules, contain lysozyme and lactoferrin. All these phenotypic immunohistochemical changes in Focal Pregnancy-like Change resemble the breast lobules of late pregnancy and lactation. Possibly, the very focality of Focal Pregnancy-like Change reflects a peculiar and local sensitivity of 'resting' breast lobules to unidentified hormonal stimulation.