Interaction between cells and extracellular matrix: signaling by integrins and the elastin-laminin receptor.
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Extracellular Matrix↗
Biomedical subjects
L Robert
Publications and source records attributed to L Robert.
[Venlafaxine withdrawal syndrome: report of six cases and review of the literature].
INTRODUCTION: Venlafaxine is an antidepressant that selectively inhibits serotonin reuptake and is a norepinephrine inhibitor. Withdrawal syndromes can occur after abrupt drug discontinuation of long-term regimens. EXEGESIS: We report six cases of withdrawal symptoms after venlafaxine discontinuation. CONCLUSION: Physicians must be aware of the frequency, rapidity and potent severity of these withdrawal syndromes.
Adult↗
Age dependent increase of elastase type protease activity in mouse skin. Effect of UV-irradiation.
The effect of chronological aging and photoaging (UV-radiation) on elastase-type enzyme activity of hairless mouse skin was studied. Aging resulted in the increase of elastase type endopeptidase activity extractable from mouse skins. Both chronic UVA and UVB radiation resulted in a significant increase of elastase type activity. PBS extracted only small part of the elastase activity, UV-A produced an increase of about 90-120% according to the type of irradiation (xenon or UV-A SUN) and UV-B produced a 72% increase. Extraction by Triton X-100 suggested that most of the activity is bound to cells and fibrous structures. EDTA inhibited 80-90% of the elastase activity in chronologically aged skin extracts and also the activity induced by UVA radiation suggesting that metallo-elastase(s) are involved. About 30% of the UVB induced activity could only be inhibited by EDTA and about 50% by PMSF suggesting that irradiation by UVB increased more serine endopeptidase activity but also MMP-activity. Chronic UVA radiation produced an increase of skin elastase activity equivalent to that observed after 24 months of aging in non-irradiated animals (approximately 100 weeks) corresponding to approximately 90% of total life span of these mice. The total increase produced by UVB was less, but the strong increase of a serine elastase, presumably from PMN-s, appear to produce a much more pronounced biological activity as shown by the presence of fibronectin degradation products in skin extracts. Such degradation products were shown to exert harmful effects on tissues. These results may well have biological significance and distinguish chronological aging and photoaging.
Aging↗
Aging of connective tissues: from genetic to epigenetic mechanisms.
The mechanisms of aging and of age-dependent pathologies can be studied at the tissue level. Such studies concern cell aging within tissues, where cells are surrounded by their matrix. Matrix components undergo post-synthetic modifications such as the Maillard reaction and proteolytic degradations. Finally, cell matrix interactions, mediated by cell membrane receptors also undergo age-dependent modifications. These three aspects of tissue-aging are discussed succinctly in this review with several examples, as the age-dependent increase of fibronectin and the potential harmful effects of its degradation products and the age-dependent degradation of elastin and the harmful effects of elastin peptides mediated by the elastin-laminin receptor. These examples clearly show the intricate cooperation of gene-mediated processes (increased expression of fibronectin and some elastolytic enzymes) and of post-synthetic processes as the novel properties of fibronectin and elastin derived peptides. Such epigenetic mechanisms appear to play a crucial role in age-dependent tissue alterations and pathologies.
Aging↗
Serum elastase activity is elevated in migraine.
Migraine has been associated with diseases considered to be related to extracellular matrix disorders--in particular, cervical artery dissection. In this population-based study, we found a highly significant association between migraine and the activity of serum elastase, a metalloendopeptidase degrading specific elastin-type amino acid sequences. Such enzymes are involved in matrix degradation. This association was seen in both sexes and was stronger for migraine with aura. These findings could help in the understanding of why patients with migraine are at higher risk of stroke. Further study is needed to establish whether extracellular matrix abnormalities play a broader role in the pathophysiology of migraine.
Aged↗
Effect of in vitro aging on the biosynthesis of glycosaminoglycans by human skin fibroblasts. Modulation by the elastin-laminin receptor.
The incorporation of a radioactive precursor 3H-glucosamine in glycoconjugates, essentially glycosaminoglycans (GAG) was evaluated in the culture medium and cell fraction of human skin fibroblasts. Using increasing passage numbers, we could estimate the effect of in vitro aging on these biosynthetic activities. The incorporation in different free (hyaluronan) and protein bound (proteoglycans) GAGs was evaluated after specific enzymatic digestion. Most newly synthesized GAGs were excreted in the extracellular medium. Incorporation of the tracer in hyaluronan, the major biosynthetic product, increased with passage number but its titratable concentration decreased with in vitro aging, suggesting a rapid post-synthetic degradation. The proportion of chondroitin sulfates 4 (A) and 6 (C) and heparan sulfate decreased and that of dermatan sulfate increased with increasing passage number. We explored the modulation of these biosynthetic activities by the elastin laminin receptor. Using agonists (elastin peptides) and an antagonist (melibiose) of the receptor, their action on GAG biosynthesis was evaluated. Both elastin peptides and melibiose increased incorporation of the tracer in GAGs, but only melibiose inhibited post-synthetic degradation of hyaluronan, therefore increasing its concentration. The effect of passage number on the receptor mediated modulations was also investigated.
Adolescent↗
Aging of the vascular-wall and atherosclerosis.
The rapid increase of life expectancy during the last half of the 20th century is changing the expression of cardiovascular disease and of its risk factors. These findings are examined by the separate consideration of atheromatous plaque formation and vascular wall stiffening, known as arteriosclerosis. in humans, these processes may progress together, but in some other species as the rat, only vascular wall stiffening is observed. A saturated fat- and cholesterol-rich diet produces the early appearance of lipidic plaques, which progress to fibrous, sometimes ulcerated, thrombotic lesions. This progression is age dependent; the establishment of lipidic plaques is not. Vascular wall stiffening, characterized by an increase of the collagen-elastin ratio and diffuse deposition of calcium and lipids is also age dependent (arteriosclerosis). Although hyperlipidemia appears to be involved both in plaque formation and wall thickness progression, the detailed mechanisms are not identical. In the oldest age group (above 80 years and in centenarians), high cholesterol values may not be a risk factor as in younger individuals. Among the cellular and molecular mechanisms involved, immune factors and modifications in receptor coupling appear to play a major role. These mechanisms are described in some detail.
Aging↗
Cell death by overload of the elastin-laminin receptor on human activated lymphocytes: protection by lactose and melibiose.
BACKGROUND: Activated human lymphocytes were shown to express the elastin-laminin receptor in vitro and also in vivo in atherosclerotic plaques. In the presence of the agonist, elastin peptides, this receptor was shown to mediate an increased cell proliferation and an increased synthesis and excretion of an elastase-type serine endopeptidase. In this study, we investigated the variation of the above reaction as a function of agonist concentration. MATERIALS AND METHODS: Human lymphocytes were obtained by tonsillectomy and cultured in the presence of phytohaemagglutinin and elastin peptides. Cell viability was evaluated by vital dye exclusion. Elastase and cathepsin G activities were determined in culture supernates and cell lysates using synthetic substrates. Apoptotic cells were identified by the TUNEL method and by electron microscopy. RESULTS: At increasing concentrations of elastin peptides, a dose-dependent increase in cell death was observed. Up to 100 micrograms mL-1 elastin peptides and an increasing fraction of lymphocytes were found permeable to trypan blue, and a large proportion was in apoptosis. Elastin peptide-induced cell death was inhibited by 1 microgram mL-1 lactose and melibiose. CONCLUSION: We describe here cell death of human activated lymphocytes expressing the elastin-laminin receptor in the presence of increasing concentrations of elastin peptides, agonists of the receptor. The mechanism of cell death appears to be related to the triggering of the release of elastase and free radicals mediated by the elastin-laminin receptor. Antagonists of this receptor, lactose and melibiose, protected the lymphocytes from the receptor-mediated cell death.
Apoptosis↗
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↗
[Management of time by the cell and by the organism].
Time-dependent regulations of cells and organisms can be analysed at different levels. One of these levels is the periodicity of cell functions such as cell division, metabolic processes (generation of ATP by glycolysis or oxidative mitochondrial processes) and the biosynthesis of cell constituents. Studies carried out on unicellular eukaryotes revealed the periodic, oscillatory nature of most of these processes. Time constants of these reactions vary from nanoseconds to hours-days, necessitating coupling mechanisms. Comparative studies revealed the coupling of the rapid processes (mitochondrial ATP generation) to the slower rhythms of the biosynthetic processes of macromolecules. Adenine nucleotides are involved in the coupling mechanisms between rapid and slow processes ("the slow dance of life to the music of time"). The mechanisms underlying these rhythmic processes involve either key allosteric regulatory enzymes (PFK for glycolysis) or "desensitization" of receptors by phosphorylation-dephosphorylation. At the organismic level the study of rhythmic processes is illustrated by the periodicity of heart beats, shown to exhibit multifractality, following apparently the formalism of deterministic chaos. Another example is the rhythmic oscillatory discharges of neuronal networks. The existence of subrhythmes mostly of epigenetic nature, facilitated probably the progressive adjustment of cells during evolution to the slow increase of day time since the separation of the moon from the earth. We analysed the mechanisms underlying the decline of these processes during aging. Loss of receptors or/and their uncoupling from their transmission pathway appear to be involved in most of these processes of decline. One conclusion of this review is the importance of epigenetic mechanisms both in the genesis and in the decline of these rythmic processes involved in time keeping by the cell.
Activity Cycles↗
Quantification and localization of hyaluronan in a PTFE polymer implanted in the corneal stroma.
The amount and distribution of hyaluronan in a PTFE polymer used to support an artificial cornea implanted in the rabbit cornea were determined. The findings were used to describe the polymer-corneal stroma interface and the reason for the translucence and wettability of this originally opaque and hydrophobic biomaterial. PTFE disks (6 mm in diameter, 0.2 mm thick, 50 microns in pore size) were implanted after a free-hand intralamellar dissection. The corneas were removed 15 days, 1 month, and 3 months after implantation. The hyaluronan content of pepsin-solubilized corneal stromal extracts and its distribution (7 microns cryostat sections) were investigated using an alkaline phosphatase-linked hyaluronectin assay that specifically detects nanogram amounts of hyaluronan. A PTFE polymer implant caused large, transient increases in hyaluronan density in the implanted stroma. The presence of amphiphilic hyaluronan in the polymer 15 days post implantation probably produced translucence and wettability of this opaque, hydrophobic implant despite the absence of cells. The hyaluronan density in the PTFE polymer increased considerably during the first month and then decreased to stabilize at a moderate level by the third month. These changes in hyaluronan density parallel the invasion of the polymer by inflammatory cells during the first month and the subsequent replacement of these cells by fibroblasts. The PTFE polymer is a good interface that is compatible with the native corneal stroma, and our results indicate that hyaluronan, because of its amphiphilic character, plays a major role in the polymer wettability and translucence and in the production of typical corneal extracellular matrix within the pores of the polymer.
Alkaline Phosphatase↗
Nuclear and cytoplasmic free calcium level changes induced by elastin peptides in human endothelial cells.
The extracellular matrix protein "elastin" is the major component of elastic fibers present in the arterial wall. Physiological degradation of elastic fibers, enhanced in vascular pathologies, leads to the presence of circulating elastin peptides (EP). EP have been demonstrated to influence cell migration and proliferation. EP also induce, at circulating pathophysiological concentrations (and not below), an endothelium- and NO- dependent vasorelaxation mediated by the 67-kDa subunit of the elastin-laminin receptor. Here, by using the techniques of patch-clamp, spectrofluorimetry and confocal microscopy, we demonstrate that circulating concentrations of EP activate low specificity calcium channels on human umbilical venous endothelial cells, resulting in increase in cytoplasmic and nuclear free calcium concentrations. This action is independent of phosphoinositide metabolism. Furthermore, these effects are inhibited by lactose, an antagonist of the elastin-laminin receptor, and by cytochalasin D, an actin microfilament depolymerizer. These observations suggest that EP-induced signal transduction is mediated by the elastin-laminin receptor via coupling of cytoskeletal actin microfilaments to membrane channels and to the nucleus. Because vascular remodeling and carcinogenesis are accompanied by extracellular matrix modifications involving elastin, the processes here described could play a role in the elastin-laminin receptor-mediated cellular migration, differentiation, proliferation, as in atherogenesis, and metastasis formation.
Calcium↗
Action of tropoelastin and synthetic elastin sequences on vascular tone and on free Ca2+ level in human vascular endothelial cells.
The elastic properties of extensible tissues such as arteries and skin are mainly due to the presence of elastic fibers whose major component is the extracellular matrix protein elastin. Pathophysiological degradation of this protein leads to the generation of elastin peptides that have been identified in the circulation in the ng/mL to microg/mL range. Similar concentrations of an elastin peptide preparation (kappa-elastin) were previously demonstrated to induce, among other biological actions, a dose- and endothelium-dependent vasorelaxation mediated by the elastin/laminin receptor and by endothelial NO production. To determine the elastin sequence(s) responsible for vasomotor activity and to learn more about possible signaling pathways, we have compared the action of different concentrations (10(-13) to 10(-7) mol/L) of recombinant human tropoelastin, eight synthetic elastin peptides, and a control peptide (VPVGGA) on both rat aortic ring tension and [Ca2+]i of cultured human umbilical vein endothelial cells. No vasoactivity could be detected for VPVGGA and for the elastin-related sequences VGVGVA, PGVGVA, and GVGVA. Tropoelastin, VGV, PGV, and VGVAPG were found to induce an endothelium- and dose-dependent vasorelaxation and to increase endothelial [Ca2+]i, whereas PVGV and VGVA produced these effects only at low concentration (10(-11) mol/L). A likely candidate for mediating the elastin peptide-related effects is the elastin/laminin receptor, since the presence of lactose strongly inhibited the vasoactivity associated with these compounds. Our results show that although the flanking amino acids modulate its activity, VGV seems to be the core sequence recognized by the elastin receptor.
Animals↗
Localization of vascular endothelial growth factor in synovial membrane mast cells: examination with "multi-labelling subtraction immunostaining".
Mast cells are believed to play a novel part in the development of destructive synovial pannus in rheumatoid arthritis (RA). This study was undertaken to investigate the localization of vascular endothelial growth factor (VEGF) in the synovial membrane using a unique immunostaining technique. Synovial specimens of RA patients were examined immunohistochemically and were compared with specimens from non-RA controls. Multi-labelling subtraction immunostaining, a modification of double- and triple-labelling immunostaining, revealed that the VEGF-positive cells were identical to tryptase-positive cells (mast cells). No other cell types were found to be positive for VEGF. The synovium of RA patients showed a larger number of VEGF-positive mast cells than that of non-RA controls (P<0.001). The study suggests that mast cell-derived VEGF may contribute to the development of synovial pannus in RA.
Arthritis, Rheumatoid↗
Elastin-elastase-atherosclerosis revisited.
This review proposes reinvestigation of a topic studied in the author's laboratory over the last decades concerning the age-dependent modifications of the vascular extracellular matrix (ECM) as related to atherogenesis and its recognized risk-factors: blood lipids, lipoproteins. Most salient previous results are confronted with recent publications in this field. Age-dependent modifications of the vascular wall discussed in this review include upregulation of elastolytic enzymes, demonstrated for the first time in the vascular wall in this laboratory, matrix biosynthesis and receptor function. The progressive deposition of lipids in elastic tissues as well as the addition of lipoproteins or lipids to cell and organ cultures were shown to modify matrix biosynthesis and upregulate elastase expression. Lipid-elastin interactions exhibit a great deal of specificity as shown by the nature and amount of lipids accumulating in elastin in vivo and in vitro. Recent epidemiological studies (the EVA study) enables the confrontation of blood lipid parameters with matrix related components (serum elastase and inhibitors, elastin peptides, fibronectin) in the same blood samples. The elastin laminin receptor present on vascular cells was shown to trigger NO dependent vasodilation, and downregulation of cholesterol synthesis. Both of these functions decrease or disappear with age except the upregulation of elastase release which is preserved and increased. Recent experiments extended these findings to T-lymphocytes present also in the atherosclerotic plaque. Finally several recent publications are analyzed which give more precision on the cellular mechanisms underlying the above-described modifications.
Adult↗
Free radical depolymerization of hyaluronan by Maillard reaction products: role in liquefaction of aging vitreous.
The degradation of hyaluronan was followed by viscosimetry and by HPLC in order to study the possible role of Maillard products (lysine-glucose) on the alteration of the vitreous gel in aging and diabetes. Lysine-glucose generated Maillard products produced a decrease of viscosity and of the number average molecular weight (Mn) of hyaluronan during a 1 h incubation at 37 degrees C. This effect was comparable to that produced by 1 U/ml of testicular hyaluronidase but was weaker than the effect of a Fenton-type reagent (Udenfriend's reagent). The polydispersity of hyaluronan incubated with Maillard products appeared higher than with hyaluronidase suggesting a more random reaction. Antioxydant enzymes (SOD, catalase), the iron chelators (desferrioxamine, transferrin) and the free radical scavengers (uric acid, carnosine) inhibited the degradation by Maillard products confirming its free radical nature and the intervention of trace metals. Maillard products have been detected in diabetic vitreous and may play a role in its accelerated modifications (liquefaction) in diabetes as compared to normal aging.
Aging↗
Effect of high-glucose concentrations on the expression of collagens and fibronectin by fibroblasts in culture.
Extracellular matrix macromolecules such as collagen and fibronectin are progressively altered during aging and age-related diseases like diabetes. We investigated the effect of high-glucose concentration (mimicking diabetic conditions) and the influence of in vitro cell aging [comparing 4th-passage fibroblasts (P4) to 15th-passage fibroblasts (P15)] on collagen and fibronectin synthesis. Fibroblasts were incubated at postconfluency with radiolabeled precursors, [3H] proline for collagen, [35S] methionine for fibronectin. We report that in control conditions (5 mM glucose) collagen III production increased with in vitro cell aging. High glucose concentrations (10 and 15 mM) increased specifically collagen III synthesis both at the mRNA and protein levels, without alteration of collagen I production in P4 and P15 cells. Fibronectin synthesis was also increased both during in vitro cell aging and in high glucose-treated P4 fibroblasts. Taken together, these data suggest similarities between changes of phenotypic expression of collagen and fibronectin induced by in vitro cell aging and conditions imitating diabetes.
Adolescent↗
Cell death induced in lymphocytes expressing the elastin-laminin receptor by excess agonists: necrosis and apoptosis.
This manuscript summarizes our experiments carried out during the last years on the expression of the elastin-laminin receptor on human activated lymphocytes and cell death triggered by the activation of this receptor by its agonists, elastin peptides. We could distinguish two types of cell reactions, depending on the elastin peptide concentration added to the cell culture media of lymphocytes. At low concentrations (1-10 micrograms/mL, 1.3-13 x 10(-8) M) of kappa-elastin, there was a stimulation of cell proliferation, elastase biosynthesis and release. As the concentration of kappa-elastin was increased in the culture medium up to 100 micrograms/mL, lymphocyte proliferation and elastase production decreased and the proportion of dead cells increased. Cell death was shown to be due to both apoptotic and non-apoptotic mechanisms. Apoptotic cell death increased with agonist concentration and reached approximately 60% of the lymphocyte population at mg/mL elastin peptide concentrations. This observation was confirmed by the concomitant use of several different methodologies, such as flow cytometry and electron microscopy. The precise nature of the non-apoptotic cell death remains to be established.
Apoptosis↗