Effect of age on the vasodilatory action of elastin peptides

We have recently shown, on young adult rat aorta rings, that elastin peptides induce a dose and endothelium-dependent vasodilation mediated by the 67 kDa subunit of the high affinity elastin-laminin receptor and, at least in part, by EDRF (NO). Here we have studied the effects of elastin peptides at circulating concentrations and below, on noradrenaline-contracted rat aortic rings, as a function of age. First, we have observed that, unlike 2-month-old (2M), 4-6-month-old (4M) and 12-month-old (12M) rat aorta rings, 30-month-old (30M) rat aorta rings were unable to maintain their contraction in long lasting experiments. Secondly, elastin peptides at physiological circulating concentrations (10(-6)-10(-3) mg/ml) induce a dose-dependent vasodilation on 4M rings. By contrast, only higher elastin peptide concentrations (10(-3) mg/ml) were effective on 12M rings, whereas rings from both younger (2M) and older animals (30M) did not respond to elastin peptides. Finally, using lactose and laminin as inhibitors, we have demonstrated that elastin peptide-induced vasodilation on 4M and 12M rings is mediated by the 67 kDa subunit of the elastin-laminin receptor. These experiments suggest that the functional availability of the 67 kDa subunit of the elastin-laminin receptor changes with age. It could be hypothesized that in young animals (0-2M) the reusable shuttle role recently demonstrated for the 67 kDa receptor subunit during elastic fiber formation leads to a major decrease in its availability for signal transduction. On the contrary, in adult animals. (4-12M), when developmental elastogenesis is completed, this subunit is essential for extracellular signal transduction. Inefficiency of this receptor in old animals (30M) can be attributed to its uncoupling from its transduction pathway, as previously shown on human cells. Finally, the age-dependent variations of circulating elastin peptide concentration and elastin-laminin receptor responsiveness to elastin peptides are two independent parameters which could influence the vascular tension regulation.

Corneal hyaluronan content during post-ablation healing: evidence for a transient depth-dependent contralateral effect

The hyaluronan content during wound healing following excimer laser photoablation was investigated. Rabbit corneas were photoablated (Summit Omnimed, 193 nm, 5 mm diameter, 50 microns and 100 microns depth). Central optical zones of photoablated and contralateral corneas were removed 7, 30 and 90 days after surgery. Corneas from 2 untreated rabbits were used as control. Hyaluronan content was determined after pepsin-solubilization using an alkaline-phosphatase linked hyaluronectin sorbent assay. The hyaluronan content of non-photoablated contralateral corneas was significantly increased and the changes appeared depth dependent. Hyaluronan content returned to control levels by the first month at 50 microns depth and by the third month at 100 microns depth in contralateral corneas. The hyaluronan content of the photoablated corneas was not significantly different from that of the non-photoablated contralateral sample regardless of the depth of photoablation. By contrast, the hyaluronan content of the treated corneas was significantly higher than that of the controls during the first month post-surgery and returned to control values by the third month. Thus the hyaluronan contents in the photoablated and contralateral corneas after excimer laser corneal photoablation were very similar during wound healing. This study shows that excimer laser photoablation induced transient depth-dependent contralateral alterations of the hyaluronan content.

[Hyaluronic acid (hyaluronan) levels in pathological human saphenous veins. Effects of procyanidol oligomers]

We investigated the hyaluronan content in the pathologic human venous wall using an ELSA assay with hyaluronectin according to the method of Delpech et al. The mean hyaluronan content in the 74 fragments from 12 venous walls studied was 596 +/- 528 ng/mg dry weight. These 12 venous walls could be separated in 3 distinct groups according to their hyaluronan content, low (277 +/- 141 ng/mg dry weight), moderate (552 +/- 361 ng/m dry weight) or high (1299 +/- 568 ng/mg dry weight). The differences between these groups are significant (p < 0.001). The presence of a veino-lymphatic oedema was generally associated with a high hyaluronan level (in 65% of cases). The 3H-glucosamine incorporation in cultured venous wall explants showed a 35% increase (p < 0.002) in varicosis as compared with the non or less modified segments of the vein and a 29% (p < 0.001) increase in presence of a veino-lymphatic oedema. The addition of 1 mg/ml of PCO (Procyanidolic Oligomers) to the culture media induced near to 20% decrease of the 3H-glucosamine incorporation and a 34% decrease of the hyaluronan content. Our results confirm the role of local overproduction of hyaluronan in the establishment of oedema and the potential effect of PCO to counteract it.

[Relation between genetic and epigenetic mechanisms in aging]

The recent identification of genes involved in the regulation of the longevity of some invertebrates (drosophila, nematodes) as well as the presence of human genes exhibiting homologies to those identified in invertebrates, revived the deterministic theories of aging. It appears however that those mechanisms which were shown experimentally to be involved in aging in vertebrates and in particular in humans belong to the epigenetic mechanisms such as the Maillard reaction and free radical attack in particular. Some diseases which imitate an accelerated aging as Progeria and the Werner syndrome are due to mutations, some of them mutagenic themselves. Reflections based on such arguments concerning reactions with catalysers coded in the genome but with activities escaping strict control, suggest an indirect determinism of phenomena involved directly in cell- and tissue aging. These considerations are illustrated by the example of the elastin-laminin receptor studied in our laboratory. Its sustained activation by circulating elastin peptides appears to be involved in cell and tissue aging.

[Epigenetic mechanisms of aging: relations between Maillard reactions and radical generation]

Aging is under the influence of both genetic and epigenetic factors. We are particularly interested in these latter mechanisms which play an important role in the aging of most if not all pluricellular organisms. Genetic factors on the contrary appear to differ among the species investigated. We studied two major epigenetic mechanisms: the Maillard reaction or nonenzymatic glycosylation and generation of free radicals. Using a sensitive method of free radical detection based on the degradation of hyaluronan, we could show that Maillard products are able to produce the depolymerization of this glycosaminoglycan. This may be of special importance in tissues rich in hyaluronan as the vitrous of the eye. Its degradation with age, accelerated in diabetes may well depend on such reactions, intensifyed in diabetes and involved in its complications as diabetic retinopathy.

[Aging and brain circulation. Role of the extracellular matrix of brain microvessels]

Maintenance of normal brain activity is dependent among other factors on the maintenance of a functional blood-brain barrier (BBB), localised mainly at the capillary wall of cerebral microcirculation. The modifications of the BBB during aging play an important role in cognitive decline with aging as well as in dementias. A review of the experiments of our laboratory over the last decades is presented, on the interaction of endothelial cells with their basement membranes, both together representing a functional unit of BBB. The action of proteolytic enzymes on the basement membrane increases BBB permeability by increasing the transcellular transport activity of endothelial cells. Flavonoid drugs protect BBB from proteolytic activity by interacting with collagen fibers and protecting sensitive peptide bonds from attack by proteolytic enzymes. These drugs enhance also the resynthesis of degraded basement membranes.

Severity of asthma is related to endotoxin in house dust

In sensitized subjects, exposure to the mite allergen appears to be only one of several factors leading to asthma. We hypothesized that in association with allergen exposure, endotoxin, a proinflammatory agent present in house dust (HD), influences the severity of asthma. Using a cross-sectional study design, we investigated a group of 69 consecutive dust mite (HDM)-sensitized subjects defined as having rhinitis (n = 20) or asthma (n = 49); the latter were evaluated functionally and clinically by three different scores and by their need for daily medication. Concentrations of Dermatophagoides pteronyssinus p I allergen (Der p I) (by two-site monoclonal antibody enzyme-linked immunosorbent assay [ELISA]), guanine (by high-pressure liquid chromatography [HPLC]), and endotoxin (by modified Limulus. amebocyte lysate assay) were measured in HD collected in duplicate from the mattresses and floors in each subject's home. The concentrations of Der p I and of guanine in HD collected from mattresses were significantly higher in asthmatic subjects than in those with rhinitis (p < 0.05 and < 0.04, respectively). In subjects (n = 37) exposed to a high level of HDM allergen (i.e., Der p I > or = 10 micrograms/g HD and/or guanine > or = 0.10 mg/100 mg HD), the severity of asthma was unrelated to mite allergen concentration in HD. On the contrary, the severity of asthma was related to concomitant exposure to endotoxin in HD, since the concentration of HD endotoxin was significantly and inversely correlated with FEV1 (p < 0.05), FEV1/FVC (p < 0.02), daily need for oral (p < 0.01) and inhaled (p < 0.01) corticosteroids, daily need for beta 2 agonists (p < 0.001) and xanthines (p < 0.01), and clinical scores such as the modified Aas score (p < 0.01). In HDM-sensitized subjects exposed to a high level of allergen, the concentration of endotoxin measured in HD is an important determinant of asthma severity.

Micro-methods for serial determinations of elastin metabolism parameters in blood plasma and serum

Micro-methods are described for the serial determinations of elastin metabolism related parameters in human serum or plasma samples: serum elastase activity, elastase inhibitor titers and elastin peptide conc-s. These methods were used in an epidemiological study (the EVA study, " Etude du vieillissement vasculaire") carried out in Nantes, west of France on several thousand individuals. Blood samples obtained from the first-1389 individuals (574 males, 815 females) were used for the determinations. In order to carry out this large number of determinations previously described procedures had to be modified. These methods used for the large serial determinations of the above mentioned three elastin metabolism related serum (or plasma) parameters are described because of their potential interest for serial clinical investigations.

Presence of the elastin-laminin receptor on human activated lymphocytes

A variety of cells - fibroblasts, vascular smooth muscle cells, endothelial cells, monocytes and polymorphonuclear leukocytes (PMNs) - carry the elastin-laminin receptor. The activation of this receptor by elastin peptides triggers a variety of reactions as chemotactic movements to an elastin peptide gradient, release of lytic enzymes and oxygen-free radicals, modifications of ion fluxes. We now show that human lymphocytes also express this receptor. Membrane labelling of the receptor by specific antibodies shows capping. In the presence of elastin peptides lymphocytes show increased proliferation and increased production of an elastase type serine protease apparently identical to PMN-elastase, inhibited by cycloheximide and by anti-PMN elastase antibodies. T-lymphocytes are present in atherosclerotic plaques where elastin degradation occurs and could contribute to the chronicity of the lesion by the above mechanism.

Aging of the vascular wall and atherogenesis: role of the elastin-laminin receptor

Aging of the vascular wall, arteriosclerosis and focal lipidic plaques, atheromatosis, often occur together but may occur separately as lipidic lesions in young children or vascular aging in some animal species resistant to lipid-rich diet as the rat. Most theories of athero-arteriosclerosis claim an endothelial lesion for its initiation, without proposing a detailed mechanism. The elastin-laminin receptor present also on endothelial cells, mediates NO.-dependent vasorelaxation. It could be shown that chronic exposure to higher concentrations of the agonist, elastin peptides, present in human blood at microgram/ml concentrations, and also during aging, the receptor gets "uncoupled" from its transmission pathway (G-protein, PLC, PKC) but continues releasing free radicals as superoxyde. NO. and O2-. give peroxynitrite, a toxic anion, needing GSH for its neutralisation. GSH production decreases with age. This process decreases available NO. for vasorelaxation and could then contribute to age-dependent blood pressure increase and produce the endothelial lesions leading to the development of athero-arteriosclerosis.

Elastin degradation in systemic vasculitis

The elastin peptide level (EP) and elastase-type activity (EA) were investigated in 89 patients with different types of systemic vasculitis (polyarteritis nodosa-14, non-specific aortoarteritis-33, temporal arteritis-23 and thromboangiitis obliterans-18) and compared to the controls: 31 patients with leg atherosclerosis and 12 aged subjects with no evident vascular pathology. EP and EA levels in patients with thromboangiitis obliterans were significantly lower as compared to leg atherosclerosis and the aged control group (p < 0.02 for EA, p < 0.05 for EP). The increase of EP predominated in giant-cell arteritis as compared to the other vasculitic groups (18/56 vs. 5/32, p < 0.05); EA in these patients was the lowest. The activation of elastin degradation after corticosteroid treatment was demonstrated by an increase of EP in temporal arteritis (p < 0.05) and of EA in thromboangiitis obliterans (p < 0.03). We suggest that the determination of the above parameters of elastin degradation may be helpful in the search for differences in mechanisms of vascular damage between atherosclerosis and inflammatory vascular diseases.

Collagen synthesized in fluorocarbon polymer implant in the rabbit cornea

The integration of microporous polymer into tissues is of great interest for the production of keratoprosthetic devices. Our previous studies showed functional differentiated cells and collagen synthesis in the pore of an expanded polytetrafluoroethylene implant. This study identifies and quantifies collagen types synthesized in the implant. Expanded polytetrafluoroethylene polymers were implanted in the rabbit corneas. The collagen extracted from the polymer and implanted stroma after 1, 3 and 6 months was quantified by measuring hydroxyproline. The relative proportions of collagen types were determined by densitometric analysis after SDS-PAGE. The collagen-to-protein ratio in the polymer increased from 0.22 to 0.70 between the first and third month after implantation becoming similar to control cornea. So that of the protein and collagen densities in the polymer and implanted stroma were similar to the control from the third month. The collagen synthesized in the polymer was mainly type I (87%) plus a small amount of type III (8%) 1 month after implantation. The collagen distribution from the third month after implantation was similar to that of the controls and remained constant thereafter in the polymer implant and in the implanted stroma. Immunogold labelling techniques confirmed these results. Implantation of this PTFE disc induced no obvious modification of the corneal stroma, confirming that this polymer is a good interface that is compatible with the native corneal stroma. The keratocytes in this polymer rapidly adopted a corneal phenotype, distinct from the dermal or scaring phenotype as shown by the collagen types produced in the implant.

Relation of serum elastase activity to ultrasonographically assessed carotid artery wall lesions and cardiovascular risk factors. The EVA study

The potential interest of serum elastase activity (SEA) as a marker of vascular aging and atherosclerosis was studied as part of an epidemiological study on vascular and cognitive aging (EVA Study). SEA was measured in 555 men and 774 women aged 59-71 years with a synthetic substrate, suc(ala)3pNA, according to a modified enzyme-linked immunosorbant assay (ELISA)-type procedure. The distribution of SEA-values was skewed to the right in men and women, the mean value was 0.52 +/- 0.55 U/ml in males and 0.43 +/- 0.52 U/ml for females. This difference could be entirely explained by alcohol consumption. SEA increased strongly with alcohol consumption in males and females. It was also positively and significantly correlated with body mass index (BMI) and systolic blood pressure (SBP). SEA significantly decreased with age in men and was not influenced by smoking in either sex. SEA was significantly increased in diabetic men compared with non-diabetics and a similar trend, although not significant, was observed in women. When both sexes were combined, the association between diabetes and SEA was independent of other clinical risk factors. No significant associations were observed with intima-media thickness or atherosclerotic plaques assessed by B-mode carotid ultrasonography. Among biological risk factors, triglycerides (in both sexes) and glucose (in men) appeared the strongest correlates of increase in SEA. In multivariate analysis, independent determinants of an increased SEA were age, alcohol consumption, triglycerides and glucose in men, and alcohol consumption and triglycerides in women.

[Randomized study comparing the safety and efficacy of albendazole and metronidazole in the treatment of giardiasis in children]

An open, randomized study was carried out with 100 children to compare the efficacy and security of albendazole and metronidazole to eradicate Giardia lamblia. We included 100 patients in primary school age with giardiasis confirmed by parasitoscopic test who had not received treatment during the 2 previous months. A complete clinical study was performed. By using an aleatory code, the children were distributed in 2 groups: A and B. The clinical data was corroborated and the following tests were made: cell blood count, blood chemistry, direct and concentrated coproparasitoscopic study. Both groups were given an antiparasite treatment consisting of albendazole for group A or metronidazole for group B. Clinical, parasitological and blood controls were conducted before, during and after the treatment. A therapeutic efficacy of 94% and 98% for group A and B, respectively, was found. We concluded that albendazole and metronidazole are equally effective in a 5 days treatment period, but some undesirable effects may occur with metronidazole.

Characterization of a low-temperature-induced cDNA from winter Brassica napus encoding the 70 kDa subunit of tonoplast ATPase

A cDNA clone, pBN59, was isolated by differential screening of a cDNA library of winter Brassica napus during cold acclimation. Nucleotide sequence of BN59 was found to be homologous to that encoding the 70 kDa subunit of the vacuolar H(+)-ATPase in plants. Transcripts hybridizing to BN59 accumulated during exposure to low temperatures and to the exogenous application of abscisic acid (ABA). Western blot analyses also indicated an increase in the 70 kDa subunit during cold acclimation. The accumulation of an endomembrane H(+)-ATPase is consistent with the observation of osmotic adjustment, increases in endogenous ABA and the proliferation of endomembranes during cold acclimation.

[Role of glycosoaminoglycans in venous disease. Mode of action of some flavonoid drugs]

Varicose vein walls differ from normal venous walls by an important loss of their collagen content and an increase of their glycosaminoglycan content, essentially of hyaluronan. The decrease in fibrous protein content can be attributed to increased proteolytic (collagenolytic) activity as well as to free radicals. Glycosaminoglycan increase reflects a disregulation of the normal program of matrix biosynthesis by the cells of varicose vein wall, essentially smooth muscle cells. Some flavonoid drugs are capable of correcting these deviations by decreasing proteolytic attack on fibrous proteins and the accumulation of proteoglycans and hyaluronan. These effects, due to interactions between flavonoid drugs and the cells and fibrous proteins of the venous wall differ according to the nature of such drugs. A hypothesis is proposed to explain these differences in the intensity of action of flavonoid drugs with apparently closely related structures, based on the conformation of these drugs and their interaction with the triple helical structure of collagen fibers as well as with the cell membranes.

Derivatized dextrans modulate collagen synthesis in aortic smooth muscle cells

The effect of specifically derivatized dextrans, with or without antiproliferative activity on smooth muscle cells (SMC), was investigated on type I and type III collagen biosynthesis and mRNA levels in post-confluent SMC cultures. Our results indicate that dextran derivatives decreased total protein and collagen synthesis independently of their antiproliferative activities. However, the most substituted dextran, the one exhibiting the strongest antiproliferative activity towards SMC, was the most active in modulating type III collagen expression. In addition, only the two dextran derivatives bearing benzylamide groups inhibited collagen excretion.

Effect of elastin peptides on vascular tone

Elastin peptides are present in human blood. As elastin receptors exist on several cell types, especially endothelial cells, this investigation was carried out to study the effect of elastin peptides on vascular tone. For this purpose, rat aortic rings were mounted in an organ bath for isometric tension measurements. Elastin peptides (kappa-elastin) were added in the concentration range of 0.1 ng/ml to 1 microgram/ml, concentrations similar to those found in the circulating blood. In rat aortic rings, precontracted or not with noradrenaline (10(-6) M), elastin peptides induced an endothelium-dependent vasodilation. The pretreatment of aortic rings with N-omega-nitro-L-arginine methyl ester (10(-5) M), an inhibitor of nitric oxide (NO) production, or with indomethacin (10(-5) M), an inhibitor of cyclooxygenase, prevented elastin peptide-induced vasodilation. These findings suggest that elastin peptides act through the synthesis of prostanoids, leading to the production of NO. Moreover, this relaxant effect of elastin peptides was decreased or inhibited when aortic rings were treated with lactose (10(-5) to 10(-2) M) or laminin (10(-6) to 10(-4) mg/ml) whereas lactose or laminin was unable to inhibit acetylcholine-induced vasodilation. These findings suggest that the inhibitory effects of lactose and laminin are specific for elastin peptide receptors and are in agreement with previous studies on these receptors. As there is evidence of the degradation of elastin in several vascular diseases, the concept that elastin peptides may contribute to the control of vascular tone is discussed.