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PubMed1995

Decreased elastin synthesis in normal development and in long-term aortic organ and cell cultures is related to rapid and selective destabilization of mRNA for elastin.

We have previously shown that aortic organ cultures from 1- to 3-day-old chickens initially mimic the high levels of elastin production seen in vivo. However, more prolonged incubation of these tissues results in decreased synthesis of elastin. In the present study, we demonstrate that decreased production of elastin in these aortic organ cultures is selective for elastin compared with collagen and is correlated with decreased steady state levels of mRNA for elastin. These decreases in steady state levels of elastin mRNA are due at least in part to a rapid and selective destabilization of mRNA for elastin, the half-life of which falls from approximately 25 hours in fresh aortic tissues to approximately 15 hours after incubation for only 8 hours. Destabilization of elastin mRNA can be prevented by incubation in the presence of blockers of DNA transcription (5,6-dichlorobenzimidazole riboside and actinomycin D) and mRNA translation (cycloheximide). Furthermore, the half-life of aortic elastin mRNA decreases from approximately 25 hours in the 1-day-old chicken to approximately 7 hours in the 8-week-old chicken, demonstrating that destabilization of mRNA is an important contributing factor in the decline in production of aortic elastin taking place during normal postnatal growth.

Age Factors↗
PubMed1988

Elastin mRNA levels and insoluble elastin accumulation in neonatal rat smooth muscle cell cultures.

Insoluble elastin accumulation, elastin mRNA translational efficiencies, and elastin mRNA levels were evaluated in cultures of neonatal rat aortic smooth muscle cells grown for several days in consecutive passages. When the products of in vitro translation were immunoprecipitated with an anti-alpha-elastin antibody, a single 79,000-Da protein was obtained. Northern blot analysis also indicated an elastin mRNA species corresponding to approximately 4.2 kilobases. Insoluble elastin accumulation increased in cells cultured for 7-21 days in first through fourth passages, while with one exception, relative levels and translational activity of elastin mRNA decreased with time in culture. The data indicated that a simple relationship between elastin accumulation and elastin mRNA levels was not evident.

Animals↗
PubMed1999

Characterization of the elastin binding domain in the cell-surface 25-kDa elastin-binding protein of staphylococcus aureus (EbpS).

Our previous studies have established that a cell-surface 25-kDa elastin-binding protein of Staphylococcus aureus (EbpS) mediates binding of this pathogen to the extracellular matrix protein elastin. Results from binding assays examining the activity of various EbpS fragments suggested that the elastin recognition domain is contained within the first 59 amino acids. In this report, we have used functional analyses with synthetic peptides and recombinant truncated forms of EbpS to localize the elastin binding domain to a 21-amino acid region contained within residues 14-34 of EbpS. Further evidence for the importance of this domain was obtained by demonstrating that the inhibitory activity of anti-EbpS antibodies on staphylococcal elastin binding was neutralized when these antibodies were pre-absorbed with a truncated recombinant EbpS construct containing residues 1-34. Overlapping synthetic peptides corresponding to EbpS residues 14-36 were then generated and tested for elastin binding activity to define further the elastin binding domain, and results from these studies showed that sequences spanning amino acids Gln14-Asp23, Asp17-Asp23, and Thr18-Glu34 inhibit binding of Staphylococcus aureus to elastin. Our analyses indicate that the hexameric sequence Thr18-Asn-Ser-His-Gln-Asp23 is the minimal sequence common to all active synthetic peptides, proteolytic fragments, and recombinant constructs of EbpS. Furthermore, substitution of Asp23 with Asn abrogated the blocking activity of the synthetic peptides, demonstrating the requirement for a charged amino acid at this location. The composite data indicate that staphylococcal elastin binding is mediated by a discrete domain defined by short peptide sequences in the amino-terminal extracellular region of EbpS.

Amino Acid Sequence↗
PubMed1988

Isolation and characterization of human elastin cDNAs, and age-associated variation in elastin gene expression in cultured skin fibroblasts.

In attempts to isolate human elastin cDNAs, a human placental lambda gt11 cDNA library was screened with a 1.3 kilobase sheep genomic DNA subclone, corresponding to the 3'-end of the elastin mRNA. The four largest clones, the largest being approximately 3 kilobase, were characterized by Northern transfer analyses, restriction endonuclease digestions and dideoxy nucleotide sequencing. Northern transfer analyses of poly(A)+RNA revealed hybridization to mRNA transcripts in the region of 3.5 kilobase. Restriction endonuclease mapping and nucleotide sequencing demonstrated distinct domains characteristic of elastin, and identified areas of variability which apparently reflects alternative splicing of the primary elastin transcripts. To demonstrate the utilization of these cDNAs for studies on elastin gene expression in human cells, elastin mRNA was examined in fibroblast cultures established from the skin of several individuals of varying ages. Northern transfer analyses and slot blot hybridizations demonstrated that elastin gene expression is initiated early during fetal development, and continues at a relatively constant level through several decades. The lowest abundance of elastin mRNA was noted in the cell cultures established for the oldest individual studied (61-year-old female). Demonstration of elastin gene expression in cultured fibroblasts provides a system to study diseases affecting the elastic fibers.

Aging↗
PubMed1990

Changes in distribution of elastin and elastin receptor during intimal cushion formation in the ductus arteriosus.

Changes in distribution of elastin and elastin receptor were studied during maturation of the ductus arteriosus. In this vessel intimal thickening is a normal process. It starts with separation of endothelial cells from the internal elastic lamina by the formation of a wide subendothelial region, followed by an increase in number of radially orientated cells in the inner media and subendothelial region. For the first time the nature of these originally inner media cells could be definitely determined as being derived from smooth muscle cells. Areas rich in these modified smooth muscle cells contained less elastin as compared with regions rich in circularly orientated smooth muscle cells. The internal elastic lamina had disappeared underneath intimal cushions of the canine ductus arteriosus, whereas in the fetal human ductus arteriosus, splitting of the internal elastic lamina was observed. Elastin was not present underneath separated endothelial cells, which suggests that these cells do not synthesize elastin, at least not after separation. Both smooth muscle cells and endothelial cells demonstrated the presence of the elastin receptor. Changes in its distribution were not observed. The temporal and spatial association between the altering distribution of elastin and the absence of normal cushion formation in the persistent ductus arteriosus suggests a role of the elastin receptor in the process of intimal thickening.

Animals↗
PubMed1995

Elastin morphology in normal and obstructed guinea-pig bladders. Localization of elastin to the trigone.

Elastin is the major component of elastic fibers in aortic tissue and has been suggested to be important for the stretch and recoil of the bladder. We have mapped the histologic distribution of elastin throughout the entire guinea-pig bladder as well as changes in the distribution of elastin during bladder-outlet obstruction. We used an animal model in which a jeweler's ring is placed around the urethra of the young guinea pig. As the animal grows, outlet obstruction is gradually induced, and the bladder gradually increases in total weight to as much as 8-fold that of controls. We localized the elastin histologically in normal and obstructed bladders by serially sectioning entire bladders and staining the sections with an elastin-specific stain, Verhoff-van Gieson stain (VVG). Surprisingly, we found that the elastin was predominantly localized only to the trigone of the bladder and that the elastin in this area was increased during obstruction. These results are consistent with the predominantly mesodermal embryologic origin of the trigone, since mesodermal tissues are more often associated with elastin expression.

Animals↗
PubMed1992

Serum anti-tropo:anti-alpha-elastin antibody ratio assessing elastin turnover in scleroderma.

Serum antibodies to native (tropo) and denatured (alpha) elastins appear to correlate with the production and breakdown respectively of elastic tissue. Elastin may be degraded as a part of autoimmune diseases. This possibility was tested by measuring IgG antibodies to tropo- and alpha-elastins by ELISA in the sera of 111 patients with a variety of connective tissue diseases compared with 18 healthy individuals. Anti-alpha-elastin antibodies were significantly higher in sera from 18 scleroderma patients than from healthy controls (p less than 0.008). Conversely, anti-tropoelastin antibody levels for scleroderma patients (p less than 0.03) and for patients with a variety of other connective tissue diseases (p less than 0.02) were lower than in healthy controls. Low antibody levels to native elastin and high levels of antibodies to denatured elastin suggest a low synthesis: degradation ratio for elastin in scleroderma. Scleroderma may be a unique model for elastin turnover because of its heretofore unrecognized accelerated elastolysis.

Adolescent↗
PubMedDate not supplied

Elastin-lipid interaction in the arterial wall. Part 2. In vitro binding of lipoprotein-lipids to arterial elastin and the inhibitory effect of high density lipoproteins on the process.

The mechanism of lipoprotein binding to arterial elastin, and the inhibitory effect of high density lipoprotein (HDL) on the in vitro complex formation between plasma low density lipoprotein (LDL) and elastin were studied. The binding of LDL-cholesterol, phospholipids and triacylglycerols to delipidated elastin increased progressively with time over 24 h of incubation. The results of a kinetic study on lipoprotein-cholesterol concentration in the incubation medium, suggesting that the ability to bind cholesterol to elastin decreases in the following order: very low density lipoprotein (VLDL), LDL, intermediate density lipoprotein (IDL) and HDL, and that the capacities to bind to a fixed amount of elastin decrease in the order: LDL, IDL, VLDL and HDL. When a definite amount of LDL was incubated with elastin in the presence of increasing concentrations of HDL, the binding of lipids to elastin progressively decreased. On the other hand, no release of cholesterol, bound to elastin during preincubation with LDL, could be detected in additional incubations with HDL, apoHDL or apoHDL-phospholipid complex.

Aorta↗
PubMed1999

Interaction between cells and elastin, the elastin-receptor.

This article dedicated to Ines Mandl at her 80th birthday is a short review of the recent work of our team on the elastin receptor. Our studies started in the early nineteen eighties aimed at the understanding of cell-elastin interactions. The first experiments reviewed demonstrated the inducible interaction of cells--smooth muscle cells, fibroblasts--with elastic fibers. Their strong adhesion was accelerated and amplified by elastin peptides and cell adhesion to elastin needed protein neosynthesis. The demonstration of the presence of the elastin receptor on leukocytes facilitated the detailed description of the transmission pathway from receptor to the intracellular sites activated by the receptor: modifications of ion fluxes, increase of elastase production and excretion of reactive oxygen species, superoxide and NO*. The calcium transients triggered by elastin peptides acting on the receptor decrease with age, the receptor appears to be uncoupled from the G-proteins, but superoxide release is increased. As circulating blood was shown to contain elastin peptides at concentrations saturating for the receptor (microg/ml conc-s for a Kd in the nanomolar range), the receptor on cells in contact with excess agonists is constantly overstimulated. The continuous release of lytic enzymes and free radicals might well be involved in cell damage. This was demonstrated with human lymphocytes undergoing cell death by necrosis and apoptosis in presence of higher concentrations of elastin peptides.

Elastin↗
PubMed1997

[Properties in elastin of different arteries: cross-links, hydrophobicity and fibronectin in elastin fraction].

In order to evaluate the quantitative and qualitative changes of elastin in different arteries, biochemical properties were measured; that is, elastin content, isodesmosine (ID) as cross-links content, free thiol content (free SH/total SH), hydrophobic properties and coexisting fibronectin (FN) content in elastin fraction from different arteries, correlation coefficients of these properties and these their effect with aging were also calculated. The results from different arteries in regard to changes in elastin can be summarized as follows: 1. The basilar artery in the quantitative changes of elastin. There was no correlation of these parameters in the basial artery from the other arteries. 2. The content of ID in the coronary artery was lower than that of the other arteries. The level of ID was negatively associated with aging, FN, elastin and free SH. On the other hand, the level of free SH was positively associated with aging, cholesterol and FN. 3. The contents of free SH, hydrohobicity and FN in elastin from the arch to the thoracic artery were lower than that of the other arteries. Hydrohobicity was negatively correlated with ID, and FN was positively correlated with cholesterol. 4. In the abdominal artery, FN content was higher than that of other arteries. There was a correlation between FN and free SH. However, free SH was inversely associated with elastin, ID and hydrohobicity.

Adult↗
PubMed1994

Three dimensional structures of pulmonary elastin; airway vs vascular elastin.

Elastin is known to occur in the lung parenchyma and pleura as well as in the pulmonary vessels, but no detailed studies of this elastin's linkage between them have been done in three dimensions. For many years we have known that there is abundant elastin in the mammalian lungs, which may be associated with etiology of causing emphysema. We have developed selective casting methods to allow us to determine the location where elastin is found morphologically. The method involves casting either the vasculature via the right ventricle, or the airways via the trachea in the air sacs. Studies of the vasculature were done with the lung inflated to 80% of the vital capacity. The casted lungs were then put in 0.1 N NaOH at 75 degrees C for 48 hours, turning them frequently. THis method removed all non-elastin tissues. The scanning electron microscopy (SEM) was used to reveal the three dimensional pictures of elastin structures from both lung parenchyma and pulmonary vessels. Elastin was seen as fenestrated sheets and some fibers in both the vessels and the airways. Elastin in the two different locations was often interconnected. Studies on 6 dogs, 8 rabbits, and 2 pigs showed no significant species difference at the level of resolution of the SEM, which was used to study the specimens after they had been freeze-dried.

Animals↗
PubMed1982

Regulation of elastin synthesis in developing sheep nuchal ligament by elastin mRNA levels.

Levels of elastin production in explant culture of fetal sheep nuchal ligament and corresponding levels of translatable elastin mRNA were determined in parallel studies during a period of rapid growth of the embryo. The identity of the explant culture and cell-free products was confirmed by peptide mapping, immunoprecipitation, and the characteristic lack of histidine and methionine. Elastin production was quantitated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and radioimmune precipitation. The translation products could be labeled with methionine only when NH2-terminally donated as f-Met-tRNAfMet. Explant cultures showed a large rise in elastin production from 70 days after conception to 150 days after conception. Cell-free translation of RNA demonstrated a parallel in elastin mRNA levels and in elastin mRNA per cell. It appears, therefore, that the marked emphasis the differentiating nuchal ligament places on elastin production is modulated, at least in part, by the quantities of available elastin mRNA.

Aging↗
PubMed1985

Bovine elastin cDNA clones: evidence for the occurrence of a new elastin-related protein in fetal calf ligamentum nuchae.

Poly (A+) mRNA was isolated from fetal calf ligamentum nuchae and used for the construction of cDNA libraries. A fraction highly enriched in elastin mRNA was used to prepare the cDNA probes for screening the libraries. A 2 kb clone, pRE1, gave the most positive signal in colony hybridization. It hybridized to a mRNA of the same size as reported for elastin mRNAs from chick and sheep. Hybrid-arrested translation showed that translation of mRNAs for proteins other than elastin doublet was not inhibited by pRE1. Southern blot analysis showed that pRE1 has sequence homology with pVE6 and pVE10, which were tentatively identified as elastin-related cDNA clones representing two distinct mRNAs. DNA sequence data from the 5' end of pRE1 show that the translated amino acid sequence is not typical of known elastin sequences but contains some elastin-like sequences. All of this evidence strongly suggests the occurrence in fetal calf nuchal ligament of a mRNA which codes for a previously unknown elastin-related protein.

Amino Acid Sequence↗
PubMed1990

Pattern of accumulation of elastin and the level of mRNA for elastin in aortic tissue of growing chickens.

Synthesis and accumulation of elastin in many elastic tissues begins in the last third of fetal development, reaches a maximum shortly after birth, and then declines rapidly. For the aorta of the chick and the pig and the ligamentum nuchae and lung of the sheep, it has been shown that increased levels of elastin production with fetal development are correlated with increased levels of elastin mRNA in the tissue, measured both by cell-free translation and by hybridization to cDNA probes. In this study we examine the relationship between insoluble elastin accumulation and message levels for tropoelastin in aortic tissue of chickens during posthatching development and growth. Whether evaluated by cell-free translation or by dot blot hybridization, steady state levels of tropoelastin message increase to a maximum at 2 weeks after hatching, and then fall rapidly with further development and growth. This pattern correlates well with production of insoluble elastin by the aorta, determined either by direct measurements of synthesis or by rate of accumulation of insoluble elastin. The data indicate that the major site of regulation of elastin production is pretranslational throughout the entire period of development and growth of the chicken aorta.

Animals↗
PubMed1986

Influence of elastin on the inhibition of leucocyte elastase by alpha 1-proteinase inhibitor and bronchial inhibitor. Potent inhibition of elastin-bound elastase by bronchial inhibitor.

We have investigated the effect of human lung elastin on the inhibition of human leucocyte elastase by human alpha 1-proteinase inhibitor and bronchial inhibitor. Elastin was unable to dissociate the elastase-inhibitor complexes during the 150 min of the elastolysis reaction. When elastase was added to mixtures of elastin and alpha 1-proteinase inhibitor, it was fully bound to the latter. The competition between elastin and bronchial inhibitor was also in favour of the latter, but a 1.5 molar excess of inhibitor over elastase was required to achieve total binding of the enzyme. About 25% of elastin-bound elastase was found to be resistant to the inhibitory effect of alpha 1-proteinase inhibitor. The major isoenzyme and the mixture of the three minor isoenzymes of elastase exhibited similar behaviour. By contrast, bronchial inhibitor was as efficient in inhibiting the elastin-bound elastase as it was in inhibiting the free enzyme. This inhibitor was also able to inhibit fully the fraction of elastin-bound elastase that was resistant to alpha 1-proteinase inhibitor. We also describe a rapid procedure for the isolation of gram quantities of alpha 1-proteinase inhibitor.

Blood Proteins↗
PubMed1995

Bovine elastin and kappa-elastin secondary structure determination by optical spectroscopies.

Elastin is the macromolecular polymer of tropoelastin molecules responsible for the elastic properties of tissues. The understanding of its specific elasticity is uncertain because its structure is still unknown. Here, we report the first experimental quantitative determination of bovine elastin secondary structures as well as those of its corresponding soluble kappa-elastin. Using circular dichroism and Fourier transform infrared and near infrared Fourier transform Raman spectroscopic data, we estimated the secondary structure contents of elastin to be approximately 10% alpha-helices, approximately 45% beta-sheets, and approximately 45% undefined conformations. These values were very close to those we had previously determined for the free monomeric tropoelastin molecule, suggesting thus that elastin would be constituted of a closely packed assembly of globular beta structural class tropoelastin molecules cross-linked to form the elastic network (liquid drop model of elastin architecture). The presence of a strong hydration shell is demonstrated for elastin, and its possible contribution to elasticity is discussed.

Amino Acids↗
PubMed1996

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.

Elastin↗