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G Armand

Publications and source records attributed to G Armand.

At least 19 recordsLinked to original sources
PubMed2000

The effect of hyaluronan on elastic fiber injury in vitro and elastase-induced airspace enlargement in vivo.

This laboratory has previously described a method of preventing air-space enlargement in experimental pulmonary emphysema using aerosolized hyaluronan (HA). Although it was found that HA preferentially binds to elastic fibers (which undergo breakdown by elastases in emphysema), it remains to be shown that such attachment actually prevents damage to the fibers. In the current study, cell-free radiolabeled extracellular matrices, derived from rat pleural mesothelial cells, were used to test the ability of low molecular weight ( approximately 100 kDa) streptococcal HA to prevent elastolysis. Coating the matrices with HA significantly decreased elastolysis (P<0.05) induced by porcine pancreatic elastase (43%), human neutrophil elastase (53%), and human macrophage metalloelastase (80%). Concomitant in vivo studies examined the ability of an aerosol preparation of the streptococcal HA to prevent experimental emphysema induced by intratracheal administration of porcine pancreatic elastase. As seen with earlier studies involving bovine tracheal HA, a single aerosol exposure significantly decreased elastase-induced airspace enlargement, as measured by the mean linear intercept (107.5 vs 89.6 microm; P < 0. 05). Furthermore, repeated exposure to the HA aerosol for 1 month did not reveal any morphological changes in the lung. The results provide further evidence that aerosolized HA may be an effective means of preventing pulmonary emphysema and perhaps other lung diseases that involve elastic fiber injury.

Aerosols↗
PubMed1999

The pulmonary matrix, glycosaminoglycans and pulmonary emphysema.

This paper reviews recent evidence of the effect of intratracheal hyaluronan (HA) to limit the induction of experimental emphysema in hamsters. Experimental emphysema was induced by both neutrophil and pancreatic elastase instilled intratracheally. Emphysema was quantified anatomically by measurement of alveolar mean linear intercept. Hyaluronidase, instilled intratracheally, enhanced the induction of experimental emphysema. Air-space size measured one week after intratracheal instillation of elastase showed that administration of 1 mg HA immediately following elastase administration resulted in a marked reduction in air-space enlargement (82 microM vs 122 microM, p < 0.01). Similarly, animals given either 1 or 2 mg HA 2 h before elastase or 2mg HA 1 h after elastase showed a significant decrease in air-space enlargement compared to controls (96 microM, 88 microM vs 120 microM and 66 microM vs 104 microM, respectively; p < 0.05. Experimental emphysema induced by neutrophil elastase was also limited by the administration of 1 or 4 mg of HA, administered 2 h prior to elastase (57 and 59 microM, respectively vs 64 for controls, p < 0.05). Characterization of administered HA showed a mean molecular weight of 104,800 Da, less than 5% protein and a uronic acid/hexosamine ratio of 1, which is characteristic of HA. Studies using fluorescein-labeled hyaluronan (HA) showed fluorescence associated with interstitial, pleural and vascular elastic fibers. The mechanism of attachment of the administered HA to elastin remains unknown. Fluorescein labeling of elastin was visible for at least 4 h post-instillation. These studies indicate a protective effect of hyaluronan against elastase degradation of pulmonary elastin in vivo by both pancreatic and neutrophil elastases. The anatomical studies further suggest a mechanism of protective coating of hyaluronan which may limit access to pulmonary elastin from neutrophils and alveolar macrophages. Results also suggest that a reduction in pulmonary hyaluronan content increases the susceptibility of elastin to degradation by elastases. These studies provide evidence for an antielastase effect of hyaluronan which is not dependent upon enzyme inhibition but on anatomical protection of pulmonary elastin by other mechanisms.

Animals↗
PubMed1998

Aerosolized hyaluronic acid decreases alveolar injury induced by human neutrophil elastase.

This laboratory has previously shown that an intratracheally instilled solution of hyaluronic acid (HA) protects the lung from elastase-induced airspace enlargement. In those studies, fluorescein-labeled HA was found to bind preferentially to lung elastic fibers, suggesting a mechanism for the protective effect. The current investigation extends these findings by examining the capacity of an aerosol preparation of HA to similarly inhibit elastase-induced lung injury. Syrian hamsters were exposed to aerosolized bovine tracheal HA (0.1% solution in water) for either 25 or 50 min, then immediately instilled intratracheally with 80 units of human neutrophil elastase. One week later the lungs were examined for airspace enlargement, using the mean linear intercept method. Animals exposed to HA for 50 min showed a significant decrease in airspace enlargement compared to controls exposed to aerosolized water alone (68.2 microm vs 85.9 microm; P < 0.05). The 25-min exposure to the HA aerosol also reduced the mean linear intercept compared to controls (73.7 microm vs 85.9 microm), but this decrease was not statistically significant. With regard to possible inflammatory effects of HA, there was no difference in the percentage of lavaged neutrophils between HA-treated and control lungs at 24 hr (1.4% vs 1.8%, respectively). As with earlier experiments using intratracheally instilled HA, aerosolized fluorescein-labeled HA was found to bind to lung elastic fibers. These results suggest that aerosolized HA may prevent elastase-mediated injury in pulmonary emphysema.

Administration, Inhalation↗
PubMed1994

Synthetic polysulfated hyaluronic acid is a potent inhibitor for tumor necrosis factor production.

Based on the premise that naturally occurring glycosaminoglycans could serve as building blocks for synthesizing nontoxic drugs for suppression of tumor necrosis factor (TNF) production by inflammatory cells, we have chemically modified hyaluronic acid (HA) and tested its effects in blocking TNF-alpha and TNF-beta production in vitro. HA was chosen mainly for its structural simplicity, nonimmunogenicity, and readiness for chemical modifications. When HA was chemically polysulfated to a sulfate/hexosamine molar ratio of 3.9, the sulfated HAs was shown to be a potent inhibitor of TNF-alpha production in lipopolysaccharide (LPS)- or interferon-gamma-activated THP-1 cells. For example, a concentration of HAs as low as 10 ng/ml reduced TNF-alpha production in LPS-activated THP-1 cells more than 50%, whereas achieving a similar extent of reduction required 50 micrograms/ml native HA. By decreasing the extent of polysulfation, the inhibitory effect of HAs on TNF-alpha production was diminished. Other chemical modifications, including deacetylation, thiolation, or reduction of the carboxylic groups, could not increase the efficacy of HA in suppression of TNF-alpha production. Naturally polysulfated glycosaminoglycans, such as chondroitin sulfates, keratan sulfate, heparan sulfate, and heparin, failed to inhibit TNF-alpha production. HAs also restricted TNF-beta (lymphotoxin) secretion in an Epstein-Barr virus-transformed B cell line, Roha-9, which constitutively produces TNF-beta. HAs had no inhibitory effect on the proliferation of THP-1 or Roha-9 cells, which would account for the reduced TNF-alpha or TNF-beta production. Furthermore, time-course metabolic labeling studies revealed that HAs could not restrict overall protein synthesis and secretion in THP-1 cells. However, HAs increased complement C1q secretion in THP-1 in a dose-dependent manner, but it had no effect on biosynthesis of complement C1 inhibitor, factor D, and Fc gamma receptor type II (Fc gamma RII). These results indicate that HA, selectively restricts the production of TNF-alpha, TNF-beta, and probably several other protein species.

Cell Division↗
PubMed1987

Conformational differences between hyaluronates of gel and liquid human vitreous: fractionation and circular dichroism studies.

Post-mortem human vitreous samples (liquid and gel) of comparable intrinsic viscosity values (n approximately equal to 3000 cc/g) were chromatographed on DEAE-Sephacel columns at 4 degrees C using a linear salt gradient ranging from 0----0.4 M NaCl. All samples examined produced numerous discrete hyaluronic acid (HA) fractions. The HA fractions from liquid vitreous were eluted at lower salt concentrations than those from gel vitreous. Several HA fractions from vitreous analyzed by circular dichroism (CD) displayed CD minima at 210 nm, with an ellipticity value of 14 to 16 X 10(3) deg X cm2d mole-1. However, all HA fractions from liquid vitreous showed lower ellipticity values and a weak positive signal above 240 nm. This signal was absent in HA fractions from gel vitreous. Results suggest that subtle but definite conformational differences involving carboxylic groups exist between gel and liquid vitreous hyaluronate.

Chemical Fractionation↗
PubMed1985

Hyaluronic acid-complement interactions--I. Reversible heat-induced anticomplementary activity.

The in vitro interaction of hyaluronic acid (HA) with complement (C) classical-pathway activity has been investigated. It was found that native HA, even at a high concn (greater than 3 mg/ml), has a relatively weak anticomplementary activity. However, we report here that native HA can be reversibly altered by heat treatment such that C-inhibitory properties are manifested. We have determined in this study that a potent C-inhibitory activity can be obtained if HA solutions are thermally treated (100 degrees C), and stabilized by prompt freezing with prompt thawing just prior to the interaction with human serum complement. Several investigators have proposed that the intermolecular-associated strands of HA undergo a reversible decoupling upon thermal treatment and this decoupled state of HA can be semi-stabilized by quickly cooling the sample. This heat-treated HA strongly inhibits C1 as well as classical-pathway-mediated C3 conversion. However, if heat-treated HA samples are not stabilized but, rather, slowly cooled after heating or if heated HA samples are snapfrozen and then slowly thawed, the anticomplementary activity is gradually lost. Interestingly, the activity for this same sample can be regenerated by retreatment of the same sample with heat followed by low-temp stabilization, indicating the reversibility of the physical state of HA responsible for the anticomplementary effect. Since no detectable molecular degradation of thermally-treated HA was found, it was assumed that a heat-induced physical transition of HA (decoupled state) was responsible for the C-inhibitory effect.

Chromatography, Gel↗
PubMed1983

A new chromatographic method for the fractionation of hyaluronic acid.

Sodium hyaluronate from rooster comb, umbilical cord, bovine vitreous and a special commercial hyaluronic acid preparation, "HealonR" have been fractionated at 4 degrees C on DEAE-Sephacel columns using salt gradients from 0 leads to 0.4M NaCl. All samples examined displayed a high degree of polydispersity. The number of well separated fractions observed in these chromatograms ranges from 10-30 depending on the source of the material. A molecular weight distribution effect does not seem to be the main factor controlling this fractionation as no differences could be observed when the limiting viscosity numbers (eta) for numerous fractions isolated from the same sample were compared with each other. As no galactosamine, sulfate or phosphate is found directly linked to these fractions, it is suggested that disaggregation of an hyaluronate molecular aggregate could be the basis for this fractionation.

Animals↗
PubMed1983

Isolation and characterization of ichthyosan from tuna vitreous.

Ichthyosan has been prepared from tuna vitreous. Glucuronic acid was found to account for the total uronic acid content of the macromolecule, while the hexosamine content was a mixture of N-acetyl-glucosamine and N-acetyl-galactosamine. When ichthyosan was gel filtered on Sepharose 2B or Sephacryl S-300, using sodium or calcium chloride, the elution profile of the column gave only one peak indicating no separation between glucosamine and galactosamine containing fractions. Similar results were obtained when ichthyosan was chromatographed on DEAE-cellulose using a salt gradient both in the presence and absence of 7.0 M urea. When ichthyosan was gel filtered in 4.0 M guanidine-HCL and subsequently chromatographed on DEAE-Sephacel or DEAE-cellulose, three well separated fractions were present. The two major fractions (II and III) were characterized as chondroitin and hyaluronic acid respectively; while fraction I representing about 3-5% of the total polysaccharide content of ichthyosan was identified as a keratan-like molecule. The same pattern was obtained when ichthyosan was digested with proteolytic enzymes and subsequently chromatographed on DEAE-cellulose or DEAE-Sephacel. Based on these findings it is concluded that in ichthyosan chondroitin, hyaluronate and keratan-like molecular chains are bound to proteins in non-covalent linkages.

Animals↗
PubMed1978

Structure-function relationships of heparin species.

We have fractionated porcine heparin species of low molecular weight, with an average specific anticoagulant activity of 96 units/mg by affinity chromotography. Highly active and relatively inactive preparations of similar size were obtained with specific anticoagulant activities of 360 and 4 units/mg, respectively. The highly active heparin fraction possesses 1.1 additional residues of glucuronic acid and 1.5 fewer residues of N-sulfated glucosamine per molecule compared to the relatively inactive species. This decrease in N-sulfated glucosamine appears to be secondary to a corresponding increase in N-acetylated glucosamine. This form also contains a tetrasaccharide sequence with a N-sulfated glucosamine at its reducing end as well as equivalent amounts of glucuronic acid and iduronic acid. Furthermore, the internal glucosamine residue of this sequence appears to be N-acetylated. Sufficient amounts of this tetrasaccharide sequence are present within the highly active preparation such that each molecule may be endowed with this structure. The relatively inactive product contains a significantly decreased quantity of this tetrasaccharide sequence such that only [unk]20% of these molecules may possess this structure. The mean distance between nonsulfated uronic acid residues of the highly active species is smaller than that separating similar residues of the relatively inactive product. In addition, a larger number of the nonsulfated uronic acid residues of the highly active material appears either to be present in a restricted region of the molecule separated only by glucosamine residues or to be located at penultimate positions within the polysaccharide chain.

Animals↗