Tissue amyloid P component in normal human dermis is non-covalently associated with elastic fiber microfibrils

Synchronous granulomatous cholecystitis and fibroelastosis of the gallbladder

We describe an unusual form of xanthogranulomatous cholecystitis in a 69-year-old man, with abundant intramural concrement formation and a local fibroelastosis of the adjacent interstitium and arteries. The gallbladder was obtained following resection of an adenocarcinoma of the gastro-esophageal junction without evidence of metastases. Only two cases of fibroelastosis of the gallbladder have previously been reported, and its pathogenesis is unknown. The influence of bile that leaked into the interstitium or a specific local tissue response to cytokines secreted by histiocytes are among the possible explanations for its development in our case.

Codistribution analysis of elastin and related fibrillar proteins in early vertebrate development

Elastin is an extracellular matrix protein found in adult and neonatal vasculature, lung, skin and connective tissue. It is secreted as tropoelastin, a soluble protein that is cross-linked in the tissue space to form an insoluble elastin matrix. Cross-linked elastin can be found in association with several microfibril-associated proteins including fibrillin-1, fibrillin-2 and fibulin-1 suggesting that these proteins contribute to elastic fiber assembly, structure or function. To date, the earliest reported elastin expression was in the conotruncal region of the developing avian heart at 3.5 days of gestation. Here we report that elastin expression begins at significantly earlier developmental stages. Using a novel immunolabeling method, the deposition of elastin, fibrillin-1 and -2 and fibulin-1 was analyzed in avian embryos at several time points during the first 2 days of development. Elastin was found at the midline associated with axial structures such as the notochord and somites at 23 h of development. Fibrillin-1 and -2 and fibulin-1 were also expressed at the embryonic midline at this stage with fibrillin-1 and fibulin-1 showing a high degree of colocalization with elastin in fibers surrounding midline structures. The expression of these genes was confirmed by conventional immunoblotting and mRNA detection methods. Our results demonstrate that elastin polypeptide deposition occurs much earlier than was previously appreciated. Furthermore, the results suggest that elastin deposition at the early embryonic midline is accompanied by the deposition and organization of a number of extracellular matrix polypeptides. These filamentous extracellular matrix structures may act to transduce or otherwise stabilize dynamic forces generated during embryogenesis.

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.

Proteoglycans associated with the ciliary zonule of the rat eye: a histochemical and immunocytochemical study

The structural organization of integral and associated components of the ciliary zonule is still not fully understood. The present study is to localize and characterize the proteoglycans associated with the ciliary zonule of the rat eye by Cuprolinic blue (CB) staining and immunocytochemistry. After CB staining, the proteoglycans appeared as electron dense elongated rodlets and were localized with the zonular fibers. They were seen lying on the periphery of the zonular fibers or along the length of the individual fibrils. Most of the CB rodlets had a size of 60-170 nm long (average 130 nm) and 25 nm wide. Smaller CB rodlets measuring 25-60 nm long (average 45 nm) and 12 nm wide were sometimes found associated with the individual zonular fibrils. The CB rodlets were removed after chondroitinase ABC or chondroitinase AC treatment, but were resistant to heparitinase, nitrous acid, keratanase or Streptomyces hyaluronidase digestions. The ciliary zonule was also immunostained with three monoclonal antibodies: 2-B-6 specific for chondroitin 4-sulfate, 3-B-3 for chondroitin 6-sulfate and 1-B-5 for unsulfated chondroitin, using indirect immunoperoxidase or immuno-colloidal gold methods. The zonular fibers were immunoperoxidase stained and immunogold labeled by 2-B-6, but were not reactive to 3-B-3 and 1-B-5. The results demonstrate that chondroitin sulfate proteoglycan is associated with the ciliary zonule of the rat eye.

The distribution of fibronectin and P component in Descemet's membrane: an immunoelectron microscopic study

Descemet's membrane consists of two zones, the 'anterior banded zone' which contains wide-spaced collagen and the amorphous 'posterior non-banded zone'. It is attached anteriorly to the corneal stroma by a narrow transitional zone termed the 'interfacial matrix'. The distribution of fibronectin and P component within the different layers of Descemet's membrane was investigated using an ultrastructural immunogold technique. Seven normal human corneas from an eye bank and one specimen from an orbital exenteration were examined. Fibronectin was predominantly present in the posterior part of the posterior non-banded zone and in the anterior banded zone. The anterior part of the posterior non-banded zone contained less fibronectin. P component was present throughout the anterior banded and posterior non-banded zones. There was a sharp demarcation at the interfacial matrix since neither substance was observed in the corneal stroma. The differences shown in the distribution of fibronectin and P component within Descemet's membrane may have resulted from their binding to other substances or alternatively from differences in the quantities laid down during the evolution of this basement membrane.

Ultrastructural and immunohistochemical studies of microfibril-associated components in the posterior chamber of the eye

Connective tissue microfibrils were observed in tissues prepared with methods believed to minimize the loss of tissue components. The eyes of C57BL/6J mice were fixed with glutaraldehyde followed by either freeze substitution, or embedding in glycol methacrylate, a water-miscible embedding medium, after limited or no dehydration. In these preparations, microfibrils were present within sheet-like layers observed in the posterior chamber of the eye. The material enclosing the microfibrils that formed the layer was also preserved, at least partially, by fixation of the tissue with uranyl acetate or potassium permanganate (KMnO4) as observed in the chick eye. This microfibril-associated material was found to be composed of heparan sulfate proteoglycan (HSPG) as shown by positive immunostaining for HSPG, as well as by identification of 4.5 nm-wide HSPG double tracks as its major constituent. When a considerable amount of this material was lost in KMnO4-fixed tissues, the remaining portion was preserved in the form of clusters of about 50 nm in width which were periodically adhered along the length of microfibrils. At the center of each cluster, a minute dark particulate structure was present. It was composed of an approximately 10 nm-wide polygonal assembly of 3.5 nm-wide ring-like structures, and was, in unfixed chick eyes, positively immunostained for fibrillin. The periodicity of HSPG clusters, and of fibrillin, along the length of immunostained microfibrils was similar, ranging from 45 nm to 65 nm. These observations indicate that fibrillin is periodically associated at the surface of "classical" microfibrils, and it may mediate the association of large amounts of HSPG to microfibrils.

Ultrastructural organization of connective tissue microfibrils in the posterior chamber of the eye in vivo and in vitro

The ultrastructural organization of connective tissue microfibrils was studied in the mouse eye and also by means of in vitro experiments for reconstituting microfibrils. In the posterior chamber of the eye of the C57BL/6J mouse, 3 nm-wide ribbon-like double-tracked structures were present and were periodically associated on either side with 3.5 nm-wide particulate structures identified as pentosomes, the subunits of amyloid P component (AP). At certain sites, such composite structures were observed in various stages of helical winding, and in these helices, pentosomes were preferentially localized internally. In helices in the final stages of winding, the resulting rods appeared increasingly similar to those of microfibrils. In experiments in vitro, incubation of chondroitin sulfate proteoglycan (CSPG) in TRIS buffer, pH 7.4, at 35 degrees C for 1 h produced random aggregates of 3 nm-wide double-tracked structures similar to those observed in the eye. Co-incubation of CSPG and AP resulted in the formation of rod-like structures arranged parallel to one another in approximately 50 nm-thick sheet-like layers. These rods were ultrastructurally similar to microfibrils and were made up of helically wound, 3 nm-wide double-tracked structures containing pentosomes within their core. The results of in vivo as well as in vitro experiments suggest the possibility that the connective tissue microfibril is composed of helically wound, CSPG-containing, 3 nm-wide double-tracked structures periodically associated with pentosomes which, as the helix becomes progressively tighter, fit with one another at the core of the helix to form successive 8.5 nm-wide disks of AP segments.

Tissue vitronectin in normal adult human dermis is non-covalently bound to elastic tissue

Vitronectin is a multifunctional human plasma glycoprotein that is also found in constant association with elastic tissue fibers in normal adults. We have investigated the nature of the association of vitronectin with elastic tissue, and compared it to that of other elastic fiber-associated proteins, namely fibrillin and amyloid P component. Samples of normal human dermis were incubated with a variety of extraction agents, including high molar salt solution, non-ionic detergent (Nonidet P-40), the reducing agents dithiothreitol or 2-mercaptoethanol, and the chaotropic agents sodium dodecyl sulfate or guanidine hydrochloride. Vitronectin purified from serum typically migrates as two bands of 75 and 65 kD. By contrast, immunoblotting studies of residual dermal material after extraction with the various agents revealed only lower molecular weight (58, 50, 42, 35, and 27 kD) anti-vitronectin reactive bands. Although these bands may represent degradation products of vitronectin generated as a result of the extraction procedure, we cannot exclude the possibility that tissue vitronectin is distinct from plasma vitronectin. Anti-vitronectin reactive polypeptides co-migrating with the 58-, 50-, and 42-kD bands were solubilized following extraction with sodium dodecyl sulfate or guanidine hydrochloride, but not with the other extraction agents. Immunofluorescence studies using residual dermal material after extraction with guanidine hydrochloride demonstrated a marked reduction in elastic fiber staining intensity with anti-vitronectin and anti-amyloid P component, but not with anti-fibrillin. Thus the majority, if not all of dermal vitronectin, is, like amyloid P component, non-covalently associated with, and not an integral constituent of, elastic fibers.

Metabolic studies of radioiodinated serum amyloid P component in normal subjects and patients with systemic amyloidosis

125I-Serum amyloid P component (SAP), injected intravenously into 10 normal subjects, remained predominantly intravascular with mean (SD) T1/2 (half time) in plasma of 24.5 (5.9) h. The fractional catabolic rate of 68 (19)% of the plasma pool per day was more rapid than other reported human plasma proteins. All radioactivity was excreted in the urine by 14 d. In 16 patients with monoclonal gammopathy or chronic inflammatory diseases, but without amyloidosis, 125I-SAP metabolism was normal. However, among 45 patients with biopsy-proven systemic amyloidosis (25, amyloid A type; 20, amyloid L type), 125I-SAP was cleared from the plasma more rapidly, accumulated in the amyloid deposits, and persisted there. The T1/2 in amyloid, measured directly with 131I-SAP, was 24 d. Repeat studies after 6-18 mo were notably consistent in normals but changed significantly in amyloid patients, generally correlating with clinical signs of disease progression. Measurements of 125I-SAP turnover may thus be of value for diagnosis and monitoring of amyloidosis. Analysis of SAP metabolism in amyloidosis suggests that plasma SAP is in dynamic equilibrium with a very large amyloid pool, and in two autopsies the total mass of SAP in the amyloid deposits was 2,100 and 21,000 mg, respectively.

Amyloid elastosis: analysis of the role of amyloid P component

We report the second case of amyloid elastosis. Our patient had an underlying primary systemic amyloidosis with lambda light chain paraproteinemia. Salient clinical features included a sclerodermatous facial appearance, cordlike thickening of superficial blood vessels, neck skin resembling that in pseudoxanthoma elasticum, livedo reticularis-like changes on the trunk, Raynaud's phenomenon, arterial and venous thromboses, and the nephrotic syndrome. Amyloid deposits were present in the dermis, around appendages, in blood vessel walls, and in a striking distribution surrounding individual elastic fibers, that appeared shortened and fragmented. Immunofluorescence, electron microscopic, and immunoultrastructural studies with antibodies to lambda light chain, localized the amyloid deposits to the region of the elastic fiber microfibrils, with which amyloid P component (AP) is invariably associated in normal tissues. Because AP binds amyloid fibrils, codistribution of amyloid deposits and AP in amyloid elastosis strongly supports the theory that elastic fiber-associated AP may act as a nidus for amyloid deposition.

Vitronectin shows complement-independent binding to isolated keratin filament aggregates

Keratinocyte cell death, whether produced by skin disease or by physiologic apoptosis in normal skin, may result in formation of dermal keratin bodies, consisting mainly of keratin intermediate filament aggregates. Vitronectin, a multifunctional plasma and tissue glycoprotein, which inhibits the complement membrane attack complex and promotes cell attachment and spreading, is, like amyloid P component, associated with keratin bodies in vivo. To investigate a potential role for vitronectin in the removal of keratin bodies, we studied the interaction of vitronectin with keratin intermediate filaments in normal human skin and in Hep-2 cells, as well as with isolated keratin intermediate filament aggregates in vitro. Following pre-incubation of skin sections and Hep-2 cells with normal human serum (as a source of vitronectin), cytoplasmic staining of keratinocytes and of cytoskeletal filaments in Hep-2 cells was observed by immuno-fluorescence staining with polyclonal and monoclonal anti-vitronectin antibodies. Vitronectin binding to keratin intermediate filament aggregates extracted from normal human epidermis was demonstrated by immunofluorescence and by immunoblotting, and was not dependent on complement activation, because it occurred even when heat-inactivated human serum or C4-deficient serum was used as a source of vitronectin. Amyloid P component shows Ca++- dependent binding to keratin intermediate filament aggregates. does not involve amyloid P component because it occurred when binding of the latter protein was inhibited by EDTA buffer. Moreover, purified vitronectin also bound to keratin intermediate filament aggregates in immunofluorescence studies. Vitronectin binding to keratin intermediate filaments may play a role both in limiting complement-mediated tissue damage (because keratin bodies may activate complement) and in promoting removal of keratin bodies by fibroblasts and/or macrophages.

Serum amyloid P component binds to cell nuclei in vitro and to in vivo deposits of extracellular chromatin in systemic lupus erythematosus

Serum amyloid P component (SAP) is the single plasma protein that, from the milieu of whole normal human serum, undergoes specific calcium-dependent binding to isolated DNA and chromatin in vitro. We now report for the first time that SAP in whole serum also undergoes calcium-dependent binding to nuclei of epidermal cells in sections of normal human skin and to nuclei of fixed Hep-2 cells, a human epithelial cell line. Furthermore, and most importantly, SAP was detected in association with unusual globular dermal deposits of nuclear material in skin biopsies from two patients with systemic lupus erythematosus. This is the first evidence for binding of SAP to extracellular chromatin in vivo and supports the idea that SAP may have an important physiological role in the disposal of this material.