Biomarkers of connective tissue aging: biosynthesis of fibronectin, collagen type III, and elastase.
Explore the source record for details and available documents.
Aging↗
Biomedical subjects
J Labat-Robert
Publications and source records attributed to J Labat-Robert.
Cell-matrix interactions in the genesis of arteriosclerosis and atheroma. Effect of aging.
The progression of atheroarteriosclerosis was shown to be age dependent. This designation covers two separate entities: arteriosclerosis, the progressive and diffuse hardening of the walls of arteries with loss of elasticity, and atheromatous plaque formation, which can start early in life according to nutrition and genetic factors (LDL-receptor expression). Lipoprotein-receptor interactions play a crucial role in lipidic plaque formation. There is, however, no indication that the diffuse hardening of the vascular wall would also be influenced by these mechanisms. We described recently a high-affinity receptor for elastin peptides, present on smooth muscle cells, fibroblasts, and also on monocytes and PMNs. When activated, this receptor will increase intracellular calcium. Circulating elastin peptides were determined by a sensitive Elisa method and found to be between 0.1 and 20 micrograms/ml, in the range of activation of the elastin receptor. They increase in obliterative arteriopathies and type IIb hyperlipidemia. Elastolysis accompanies aging and vascular pathology; the sensitivity of this receptor changes with age, intracellular Ca++ increases, but the receptor appears to be uncoupled from its normal transmission mechanism. These results may well explain the increasing diffuse calcification of the vessel wall. The previously demonstrated potentiation of cholesterol deposition in elastic fibers by calcium is in agreement with simultaneous deposition of calcium and lipids. The recent demonstration of the efficient competition of fibronectin for LDL in proteoglycan-LDL complexes suggests that this reaction may be involved in foam cell formation by the opsonization of LDL for phagocytosis. Fibronectin was shown to accumulate in atherosclerotic plaques. Altogether these recent results confirm the importance of cell-matrix interactions in atherogenesis and lead to a better understanding of the age dependence of these disease processes.
Aging↗
UVA- and UVB-induced changes in collagen and fibronectin biosynthesis in the skin of hairless mice.
The modifications induced in hairless mouse skin by chronic UV irradiation were investigated. Skin explant cultures were used to study UVA- and UVB-induced changes occurring in interstitial collagen (type I and type III) and fibronectin biosynthesis. To study the long-term effects, albino hairless mice were irradiated with UVA radiation alone from two sources with different spectral qualities or with UVB. UVA and UVB radiation produced a significant increase in the ratio of type III to type I collagen (more than 100% for UVA-irradiated skin and about 60% for UVB-irradiated skin) accompanied by a significantly increased fibronectin biosynthesis (50% or more in all irradiated groups). Irradiation with either UVA or UVB alone had no significant effect on the total collagen synthesis and resulted in only a slight decrease in the total collagen content of the skin determined as hydroxyproline. This decrease was significant only in the case of the group irradiated with UVA (xenon) (decrease of 25%, expressed as micrograms of hydroxyproline per milligram wet weight). A significant decrease in collagen hydroxylation (expressed as radioactive hydroxyproline/radioactive hydroxyproline plus proline in neosynthesized collagen) was observed of about 50% in skin irradiated with UVA (xenon) but not in UVB-treated skin. Several of the above modifications (increased fibronectin biosynthesis, increased collagen type III to type I ratio) correspond to the modifications observed during the aging of non-irradiated hairless mice. Therefore it appears that UV irradiation accelerates the modifications of extracellular matrix biosynthesis observed during aging.
Amino Acids↗
In vivo evaluation of photoprotection against chronic ultraviolet-A irradiation by a new sunscreen Mexoryl SX.
In a previous study on the hairless mouse it was shown that sub-erythemal doses of pure UV-A enhanced the numerous changes normally observed during chronological aging. A new sunscreen (a bis-benzylidene campho sulfonic acid derivative) has been synthesized in our research laboratory (lambda max: 345 nm, epsilon: 47,000). Its photoprotective properties against UV-A induced damages were assessed in our mouse model. Three month old albino hairless mice were exposed for 1 y to suberythemal doses (35 J/cm2) of UV-A obtained from a xenon source filtered through a WG 345 filter. One group of animals was exposed untreated, the other received a formulation containing 5% of the sunscreen prior to irradiation. At the end of the study the cutaneous properties of protected mice were compared to those of unprotected animals and to 3 and 15 month old unirradiated controls. We found that the visible changes induced by UV-A irradiation were mainly sagging and wrinkling. Histological and electron microscopic alterations consisted of hyperkeratosis, increased density of elastic fibers with alteration of fiber orientation and increased glycosaminoglycan deposits. Biochemical changes consisted of decreases in total collagen and collagen hydroxylation and increases in both collagen III/I + III ratio and fibronectin biosynthesis. All these changes were reduced or abolished by the sunscreen.
Animals↗
[Integrins].
Cells and extracellular matrix components have complex interactions which are involved in many biological processes throughout the life span. These cell-matrix interactions are mediated by receptors, of which some are integral membrane proteins. The aim of this short article is to review the integrin family, the overall structure of integrins, their distribution and their role. These new data will undoubtedly contribute to improved understanding of the physiological and pathological processes involving connective tissues.
Extracellular Matrix↗
The in vivo systemic effect of human recombinant interleukin-1 beta on fibronectin in rats.
The in vivo systemic effect of interleukin (IL)-1 beta on plasma and cartilage fibronectin was studied in arthritic rats, as well as alpha 1-acid glycoprotein and albumin. Plasma fibronectin showed a 27% increase in the arthritic group, while alpha 1-acid glycoprotein increased 22-fold and albumin decreased by 46%. IL-1 effect depended on the administered dose. 2 micrograms injection significantly increased plasma fibronectin and alpha 1-acid glycoprotein. In cartilage, fibronectin was significantly modified in arthritic animals but increased in a dose-related manner after IL-1 treatment. As IL-1 increases fibronectin-degrading enzyme production and as some of these fragments can develop properties that do not possess the intact molecule, one can postulate a vicious circle in matrix degradation in the inflammatory process of the joint.
Animals↗
[Fragmentation of fibronectin in cystic fibrosis].
Fibronectin (FN) plays an important role in mediating cell-matrix interactions and also as an opsonin in the phagocytosis of some microorganisms. Due to its domain structure FN is easily attacked by proteolytic enzymes and especially by elastases. Some of the fragments possess original properties as potentiation of viral transformation or proteolytic activity absent in the intact molecule. Cystic fibrosis is frequently accompanied by infection with protease generating microorganisms, such as Pseudomonas aeruginosa. Polyacrylamide gel electrophoresis and immunoblotting revealed the presence of FN fragments in the plasma of patients with molecular weight between 30 and 100 kD. Purified plasma FN was rapidly hydrolyzed in fragments by the sputum of patients as well as by purified Pseudomonas elastase. The comparison of fragments detected in patients' plasma with those produced by in vitro proteolysis confirms the probability of in vivo fragmentation of FN in cystic fibrosis and suggests that several proteolytic enzymes, endogenous and of bacterial origin, might be involved.
Cystic Fibrosis↗
Biosynthesis and distribution of fibronectin in normal and osteoarthritic human cartilage.
The biosynthesis of fibronectin was determined in explants from normal and osteoarthritic human cartilage after metabolic labeling and immunoprecipitation. Each sample of osteoarthritic cartilage was divided into three regions taken at different distances from the eburnated bone area. Only full depth cartilage samples were taken into consideration. We could detect a low level of fibronectin biosynthesis in normal cartilage. In osteoarthritic cartilage increased synthesis of fibronectin was demonstrated, the most important in the region close to the eburnated area. Increased synthesis, although to a lower extent, was also demonstrated in the two other regions at increasing distances from the eburnated areas. Immuno-histological examinations performed on tissue samples and similar studies on articular chondrocyte cell cultures confirmed the accumulation of newly synthesized fibronectin in pathological conditions.
Cartilage, Articular↗
Age-dependent variations of the biosyntheses of fibronectin and fibrous collagens in mouse skin.
Skin explant cultures from hairless mice of increasing age were incubated with radioactive precursors in order to determine the age-dependent variations of the biosyntheses of fibronectin and fibrous collagens (types I and III). Total collagen synthesis expressed as a percentage of total protein synthesis did not vary with age but, if expressed as micrograms hydroxyproline per mg wet weight of skin, decreased by about 30% between 2 and 22 months of age. Hydroxylation of collagen, expressed as the ratio of 3H-hypro over 3H (pro + hypro) incorporated in freshly synthesized collagen, decreased with age by about 40% between 2 and 22 months of age. The proportion of type III collagen expressed as % of type I + type III collagens increased progressively with age by about 25% at 12 months to 60% at 22 months of age. Fibronectin biosynthesis, determined by immunoprecipitation of 35S-methionine labeled peptides in SDS-extracts of skin increased progressively with age from about 2% of total incorporated radioactivity in fibronectin at 2 months to 4% at 22 months. Plasma fibronectin, of hepatic origin, was shown already to increase with age in humans. It appears thus that the expression of genes coding for extracellular matrix macromolecules is under age-dependent regulation. This regulation appears to be different for the investigated macromolecules.
Aging↗
[Fibronectin, aging and related pathologies].
It could be demonstrated that plasma and tissue fibronectin (FN) increase with age. Some age dependent diseases as diabetes, osteoarthritis and Werner syndrome produce also an increase of tissue fibronectin biosynthesis. Plasma fibronectin decreases in diabetes and in breast cancer. Alternative splicing of the FN gene appears also to vary with age and in some related pathologies. Nutritional status and UV light also influence FN biosynthesis. It appears therefore that the determination of plasma FN and its isoforms as well as the study of tissue FN may be of interest for the study of chronological aging and related pathologies.
Age Factors↗
Extracellular matrix.
A succinct overview of recent results on the biochemistry of extracellular matrix (ECM) is presented. The rapid expansion of this discipline over the best decades renders impossible to give an even approximately complete coverage of matrix biology. Some selected results concerning the four major families of macromolecules composing the ECM, that is, collagens (14 types described), elastin(s), proteoglycans and structural glycoproteins (especially fibronectin) are described. Special attention is directed to a crucial aspect of matrix biology: cell-matrix interactions. A number of cell membrane receptors were recently described mediating the two way information flow from the cells to the matrix via the 'programme' of ECM synthesis coded in the genome and unfolding during differentiation and from the ECM to the cells through the membrane receptors which contact the cytoskeleton. One of them at least, the elastin receptor was shown to be linked through a G-protein-phospholipase C-IP3 mediated relay to the regulation of intracellular calcium. Modifications of the ECM will therefore influence cell behaviour. Derangements of this informational feed back mechanisms appear to be involved in most age-related connective tissue diseases.
Animals↗
Interaction between fibronectin, proteoglycans and lipoproteins.
The effect of purified human plasma fibronectin on LDL-GAG and LDL-PG complex formation was studied. Fibronectin added to LDL or to GAG or even to preformed LDL-GAG-Ca2+ complexes could inhibit complex formation and dissociated preformed complexes. Similar results were obtained with total serum instead of purified LDL: 1.2 mg fibronectin added to 1.0 mg LDL-cholesterol completely inhibited insoluble complex formation in the presence of Ca2+ between LDL and GAGs or LDL and PGs purified from aorta, whatever the order of mixing of the macromolecules. When fibronectin was added to preformed PG-LDL complexes however dissociation was less complete than with preformed LDL-GAG complexes (60% dissociation instead of 100% at similar concentration ratios). It appears therefore that the protein and GAG portions of PGs may not interact at the same sites of LDL and competition by fibronectin would be more efficient at the GAG binding site. Fibronectin could also dissociate LDL-heparin complexes formed on heparin-Sepharose affinity columns. As PG-LDL complexes were isolated from atherosclerotic plaques and fibronectin was also shown to increase in plaque area and exhibit opsonic-like functions, the above findings may well have physiopathological significance.
Binding Sites↗
[Contribution of proteolytic enzymes to the knowledge of biologic functions of fibronectin].
Proteolytic enzymes have been used to separate and analyze the fibronectin sequences responsible for the multiple interactions between fibronectin and collagens, proteoglycans, cell surfaces, etc. The location of these sequences on the molecule subunits has also been determined. This short article summarizes these results as well as future prospects.
Cell Membrane↗
Biosyntheses of interstitial collagens and fibronectin by porcine aorta smooth muscle cells. Modulation by low-molecular-weight heparin fragments.
The effect of low-molecular-weight heparin fragments (CY222) on the biosynthetic phenotype of porcine aortic smooth muscle cells (SMC) was investigated in vitro on overconfluent cell cultures. Addition of increasing concentrations of CY222 to the culture medium of early passage SMC resulted in a dose-dependent decrease of type III to type I collagen ratio without change in total collagen biosynthesis. In the same range of concentrations CY222 did not affect the biosynthesis of fibronectin. However, heparin fragments decreased the proportion of the freshly synthesized pericellular form of fibronectin with a concomitant increase of neosynthesized intracellular fibronectin, indicating an inhibitory effect of CY222 on fibronectin secretion. Our results demonstrate that the biosynthetic phenotype of SMC in vitro can be modulated by low-molecular-weight heparin fragments and confirm also that interactions between cells and extracellular matrix molecules can modify the biosynthetic pattern of mesenchymal cells.
Animals↗
Heparin fragments regulate collagen phenotype and fibronectin synthesis in the skin of genetically diabetic mice.
The biosyntheses of interstitial collagens of type I and III and of fibronectin were studied in genetically diabetic KK mice, as compared to control C57 Black mice, as well as the effect of low-Mr heparin fragments (CY 222) on these biosyntheses. An increased production of type III collagen, as compared to type I collagen, could be demonstrated in explant cultures of KK mice skins. Fibronectin biosynthesis was also increased. In vivo treatment of KK mice with 1 mg/kg of CY 222 decreased the biosyntheses of type III collagen and of fibronectin to normal levels. These experiments suggest that low-Mr heparin fragments can modulate the expression of extracellular matrix macromolecules.
Animals↗
Aging of the extracellular matrix and its pathology.
Recent concepts on the mechanisms of aging of extracellular matrix (EM) are reviewed as well as its involvement in age-associated diseases. Cell differentiation, histogenesis and organogenesis can be analyzed in terms of the program of the biosynthesis of EM macromolecules during development, maturation and aging. The most important biological role of EM is the integration of cells in tissues, of tissues in organs and of organs in the whole organism. EM can directly influence cell behavior through the contact between EM and the genome mediated by structural glycoproteins (fibronectin, laminin, elastonectin, etc.) interacting with other EM macromolecules (collagen, proteoglycans, elastin) and the cytoskeleton by trans-membrane receptors (integrins). Most age-associated diseases exhibit a deviation (qualitative or quantitative) from the normal program of EM biosynthesis. Three examples are analyzed in some detail: atherosclerosis, diabetes and malignant tumors. The degradation of elastic fibers catalyzed by cellular elastase-type enzymes is observed in atherosclerosis and also in emphysema and skin aging. Several of these enzymes were isolated and characterized from platelets, fibroblasts, smooth muscle cells and lipoproteins. The biosynthesis of some of them increases with age and facilitates cell migration. Plasma fibronectin increases with age exponentially. This increase is absent or strongly attenuated in diabetes and some cancers. Tissue fibronectin increases in diabetes, Werner syndrome and in the peritumoral desmoplastic reaction while most tumor cells can no more retain fibronectin on their membrane facilitating their movement in the organism. These examples demonstrate the importance of the study of cell matrix interactions for gerontology.
Aging↗
[Study of an optimal biological profile for demonstrating pancreatic involvement in acute abdominal syndrome].
The authors have studied several seric, plasmatic and urinary constituents in patients hospitalized for an acute abdominal syndrome to be able to characterize an eventual pancreatic lesion; mainly seric and urinary amylase as well as its isoenzymes, lipase, liver profile and trypsin. In acute pancreatitis, the means of the maximal increases of seric amylase, lipase and trypsin are respectively: 10.7; 21.6 and 19.2 X N (upper normal limit) whereas in chronic pancreatitis, these elevations are 6.5 X N for amylase and 9.5 XN for lipase. The authors observed at J1 (first day of hospitalisation) and at J2 an increase in seric amylase, lipase and/or liver profile respectively in 95, 90 and 25 p. cent of acute pancreatitis; in 86, 86 and 14 p. cent of chronic pancreatitis and 43, 39 and 86 p. cent of bili duct diseases. In conclusion, it appears compulsory to run a liver profile with the pancreatic enzymes (amylase and lipase) to diagnose a pancreatitis in presence of an acute abdominal syndrome.
Abdomen, Acute↗
Plasma fibronectin in mammary and uterine carcinomas.
Plasma fibronectin was determined in cancer patients and in age- and sex-matched controls and analyzed as a function of age, size of tumor, receptor content of the tumor, metastases and treatment. In the control population, plasma fibronectin increased with age exponentially. The age-dependent increase in plasma fibronectin was strongly attenuated in the cancer population. As normal and cancer curves intersect at about 40-46 years, below this age cancer plasmas have slightly higher values than normal, above this age the inverse is true. No correlation was found between estrogen or progesterone receptor levels and plasma fibronectin values, nor with plasma albumin. Tumor patients with distant metastases gave slightly but significantly higher values than those with local or no metastases. No significant difference was found between tumors when Bloom grading was taken as the second parameter instead of age. The size of the tumor or the type of treatment had no influence. Increased proteolytic activity, increased trapping of plasma fibronectin in tissues and especially in the stromal (desmoplastic) reaction and/or modifications in plasma fibronectin biosynthesis may well be responsible for these results.
Adenocarcinoma↗