Degradation of hyaluronic acid by polymorphonuclear leukocytes

Immune-responsive biodegradable scaffolds for enhancing neutrophil regeneration

Neutrophils are essential effector cells for mediating rapid host defense and their insufficiency arising from therapy-induced side-effects, termed neutropenia, can lead to immunodeficiency-associated complications. In autologous hematopoietic stem cell transplantation (HSCT), neutropenia is a complication that limits therapeutic efficacy. Here, we report the development and in vivo evaluation of an injectable, biodegradable hyaluronic acid (HA)-based scaffold, termed HA cryogel, with myeloid responsive degradation behavior. In mouse models of immune deficiency, we show that the infiltration of functional myeloid-lineage cells, specifically neutrophils, is essential to mediate HA cryogel degradation. Post-HSCT neutropenia in recipient mice delayed degradation of HA cryogels by up to 3 weeks. We harnessed the neutrophil-responsive degradation to sustain the release of granulocyte colony stimulating factor (G-CSF) from HA cryogels. Sustained release of G-CSF from HA cryogels enhanced post-HSCT neutrophil recovery, comparable to pegylated G-CSF, which, in turn, accelerated cryogel degradation. HA cryogels are a potential approach for enhancing neutrophils and concurrently assessing immune recovery in neutropenic hosts.

Rapid Aggregation of Staphylococcus aureus in Synovial Fluid Is Influenced by Synovial Fluid Concentration, Viscosity, and Fluid Dynamics, with Evidence of Polymer Bridging

Early bacterial survival in the postsurgical joint is still a mystery. Recently, synovial fluid-induced aggregation was proposed as a potential mechanism of bacterial protection upon entry into the joint. As synovial fluid is secreted back into the joint cavity following surgery, rapid fluctuations in synovial fluid concentrations, composition, and viscosity occur. These changes, along with fluid movement resulting from postoperative joint motion, modify the environment and potentially affect the kinetics of aggregate formation. Through this work, we sought to evaluate the influence of exposure time, synovial fluid concentration, viscosity, and fluid dynamics on aggregation. Furthermore, we aimed to elucidate the primary mechanism of aggregate formation by assessing the interaction of bacterial adhesins with the synovial fluid polymer fibrinogen. Following incubation under each simulated postoperative joint condition, the aggregates were imaged using confocal microscopy. Our analysis revealed the formation of two distinct aggregate phenotypes, depending on whether the incubation was conducted under static or dynamic conditions. Using a surface adhesin mutant, we have narrowed down the genetic determinants for synovial fluid aggregate formation and identified essential host polymers. We report here that synovial fluid-induced aggregation is influenced by various changes specific to the postsurgical joint environment. While we now have evidence that select synovial fluid polymers facilitate bridging aggregation through essential bacterial adhesins, we suspect that their utility is limited by the increasing viscosity under static conditions. Furthermore, dynamic fluid movement recovers the ability of the bacteria with surface proteins present to aggregate under high-viscosity conditions, yielding large, globular aggregates.

Endothelial Glycocalyx Impairment in Disease: Focus on Hyaluronan Shedding

Hyaluronan (HA) is a ubiquitous glycosaminoglycan of the extracellular matrix. It is present in the endothelial glycocalyx covering the apical surface of endothelial cells. The endothelial glycocalyx regulates blood vessel permeability and homeostasis. HA plays a central role in numerous functions of the endothelial surface layer, protecting the endothelial cells, regulating the barrier permeability, and ensuring mechanosensing, which is essential to nitric oxide production and flow-induced vasodilation. During acute injury, inflammatory conditions, or many other pathologic conditions, the endothelial glycocalyx is damaged, and its degradation is accompanied by shedding of one or more glycocalyx components into the blood. Syndecan-1, heparan sulfate, and HA are the main components whose shedding has been claimed to represent the endothelial glycocalyx state of health. This review focuses on endothelial glycocalyx HA and highlights its key roles in the functions of the endothelial glycocalyx, its shedding in several pathologic conditions such as sepsis, diabetes, chronic and acute kidney injury, ischemia/reperfusion, atherosclerosis, and inflammation, which are all accompanied by increased circulating HA levels. Plasma/serum HA level is becoming recognized as a biomarker of endothelial glycocalyx damage in select pathologies. Hyaluronidase, the main HA-degrading enzyme, and its involvement in the impairment of endothelial glycocalyx are also addressed.

Role of hyaluronan in angiogenesis and its utility to angiogenic tissue engineering

Angiogenesis represents the outgrowth of new blood vessels from existing ones, a physiologic process that is vital to supply nourishment to newly forming tissues during development and tissue remodeling and repair (wound healing). Regulation of angiogenesis in the healthy body occurs through a fine balance of angiogenesis-stimulating factors and angiogenesis inhibitors. When this balance is disturbed, excessive or deficient angiogenesis can result and contribute to development of a wide variety of pathological conditions. The therapeutic stimulation or suppression of angiogenesis could be the key to abrogating these diseases. In recent years, tissue engineering has emerged as a promising technology for regenerating tissues or organs that are diseased beyond repair. Among the critical challenges that deter the practical realization of the vision of regenerating functional tissues for clinical implantation, is how tissues of finite size can be regenerated and maintained viable in the long-term. Since the diffusion of nutrients and essential gases to cells, and removal of metabolic wastes is typically limited to a depth of 150-250 microm from a capillary (3-10 cells thick), tissue constructs must mandatorily permit in-growth of a blood capillary network to nourish and sustain the viability of cells within. The purpose of this article is to provide an overview of the role and significance of hyaluronan (HA), a glycosaminoglycan (GAG) component of connective tissues, in physiologic and pathological angiogenesis, its applicability as a therapeutic to stimulate or suppress angiogenesis in situ within necrotic tissues in vivo, and the factors determining its potential utility as a pro-angiogenic stimulus that will enable tissue engineering of neo-vascularized and functional tissue constructs for clinical use.

Oxidative depolymerization of polysaccharides by reactive oxygen/nitrogen species

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are constantly produced and are tightly regulated to maintain a redox balance (or homeostasis) together with antioxidants (e.g. superoxide dismutase and glutathione) under normal physiological circumstances. These ROS/RNS have been shown to be critical for various biological events including signal transduction, aging, apoptosis, and development. Despite the known beneficial effects, an overproduction of ROS/RNS in the cases of receptor-mediated stimulation and disease-induced oxidative stress can inflict severe tissue damage. In particular, these ROS/RNS are capable of degrading macromolecules including proteins, lipids and nucleic acids as well as polysaccharides, and presumably lead to their dysfunction. The purpose of this review is to highlight (1) chemical mechanisms related to cell-free and cell-based depolymerization of polysaccharides initiated by individual oxidative species; (2) the effect of ROS/RNS-mediated depolymerization on the successive cleavage of the glycosidic linkage of polysaccharides by glycoside hydrolases; and (3) the potential biological outcome of ROS/RNS-mediated depolymerization of polysaccharides.

Immunological functions of hyaluronan and its receptors in the lymphatics

The lymphatic system is best known for draining interstitial fluid from the tissues and returning it to the blood circulation. However, the lymphatic system also provides the means for immune surveillance in the immune system, acting as conduits that convey soluble antigens and antigen-presenting cells from the tissues to the lymph nodes, where primary lymphocyte responses are generated. One macromolecule that potentially unites these two functions is the large extracellular matrix glycosaminoglycan hyaluronan (HA), a chemically simple copolymer of GlcNAc and GlcUA that fulfills a diversity of functions from danger signal to adhesive substratum, depending upon chain length and particular interaction with its many different binding proteins and a small but important group of receptors. The two most abundant of these receptors are CD44, which is expressed on leukocytes that traffic through the lymphatics, and LYVE-1, which is expressed almost exclusively on lymphatic endothelium. Curiously, much of the HA within the tissues is turned over and degraded in lymph nodes, by a poorly understood process that occurs in the medullary sinuses. Indeed there are several mysterious aspects to HA in the lymphatics. Here we cover some of these by reviewing recent findings in the biology of lymphatic endothelial cells and their possible roles in HA homeostasis together with fresh insights into the complex and enigmatic nature of LYVE-1, its regulation of HA binding by sialylation and self-association, and its potential function in leukocyte trafficking.

Oxidative damage to extracellular matrix and its role in human pathologies

The extracellular compartments of most biological tissues are significantly less well protected against oxidative damage than intracellular sites and there is considerable evidence for such compartments being subject to a greater oxidative stress and an altered redox balance. However, with some notable exceptions (e.g., plasma and lung lining fluid) oxidative damage within these compartments has been relatively neglected and is poorly understood. In particular information on the nature and consequences of damage to extracellular matrix is lacking despite the growing realization that changes in matrix structure can play a key role in the regulation of cellular adhesion, proliferation, migration, and cell signaling. Furthermore, the extracellular matrix is widely recognized as being a key site of cytokine and growth factor binding, and modification of matrix structure might be expected to alter such behavior. In this paper we review the potential sources of oxidative matrix damage, the changes that occur in matrix structure, and how this may affect cellular behavior. The role of such damage in the development and progression of inflammatory diseases is discussed.

Reactive oxygen species mediate modification of glycocalyx during ischemia-reperfusion injury

The glycocalyx (Gcx) is a complex and poorly understood structure covering the luminal surface of endothelial cells. It is known to be a determinant of vascular rheology and permeability and may be a key control site for the vascular injuries caused by ischemia-reperfusion (I/R). We used intravital-microscopy to evaluate the effects of I/R injury on two properties of Gcx in mouse cremasteric microvessels: exclusion of macromolecules (anionic-dextrans) and intracapillary distribution of red blood cells (RBC). In this model, the Gcx is rapidly modified by I/R injury with an increase in 70-kDa anionic-dextran penetration without measurable effect on the penetration of 580-kDa anionic-dextran or on RBC exclusion. The effects of I/R injury appear to be mediated by the rapid production of reactive oxygen species (ROS) because they are ameliorated by the addition of exogenous superoxide dismutase-catalase. Intravenous application of allopurinol or heparin also inhibited the effects of I/R injury, and we interpret efficacy of allopurinol as evidence for a role for xanthine-oxidoreductase (XOR) in the response to I/R injury. Heparin, which is hypothesized to displace XOR from a heparin-binding domain in the Gcx, reduced the effects of I/R. The effects of I/R injury were also partially prevented or fully reversed by the intravascular infusion of exogenous hyaluronan. These data demonstrate: 1) the liability of Gcx during I/R injury; 2) the importance of locally produced ROS in the injury to Gcx; and 3) the potential importance of heparin-binding sites in modulating the ROS production. Our findings further highlight the relations between glycosaminoglycans and the pathophysiology of Gcx in vivo.

Size selectivity of hyaluronan molecular sieving by extracellular matrix in rabbit synovial joints

In joint fluid the polymer hyaluronan (HA) confers viscous lubrication and greatly attenuates trans-synovial fluid loss (outflow buffering). Outflow buffering arises from the molecular sieving (reflection) and concentration polarization of HA at the synovial membrane surface. Outflow buffering declines if HA chain length is reduced, as in arthritis, and this has been attributed to reduced HA reflection. This was tested directly in the present study. Infused solutions of HA of approximately 2200 kDa (HA2000, 0.2 mg ml(-1)) or approximately 500 kDa (HA500, 0.2 mg ml(-1)) or approximately 140 kDa (HA140, 0.2-4.0 mg ml(-1)) were filtered across the synovial lining of the knee joint cavity of anaesthetized rabbits at a constant rate, along with a freely permeating reference solute, 20 kDa fluorescein-dextran (FD20). After a priming period the femoral lymph was sampled over 3 h. Mixed intra-articular (i.a.) fluid and subsynovial fluid were sampled at the end. Fluids were analysed by gel exclusion chromatography. The trans-synovial concentration profile was found to depend on polymer size. The i.a. concentration of HA2000 increased substantially relative to infusate and the subsynovial and lymph concentrations fell substantially. For HA500 and HA140 the trans-synovial concentration gradients were less pronounced, and absent for FD. The reflected fractions for HA2000, HA500 and HA140 across the cavity-to-lymph barrier were 0.65 +/- 0.05 (n = 10), 0.43 +/- 0.09 (n = 3) and 0.19 +/- 0.05 (n = 7), respectively, at matched filtration rates (P < 0.0001, analysis of variance). Reflected fractions calculated from HA i.a. accumulation or subsynovial dilution showed the same trend. The results demonstrate size-selective molecular sieving by the synovial extracellular matrix, equivalent to steric exclusion from cylindrical pores of radius 33-59 nm. The findings underpin the concentration polarization-outflow buffering theory and indicate that reduced HA chain length in arthritis exacerbates lubricant loss from a joint.

Study of Hyaluronan-Binding Proteins and Receptors Using Iodinated Hyaluronan Derivatives

This chapter detailed methodology for the purification of high molecular weight HA, as well as procedures to fragment the HA to prepare large oligosaccharides in the range of 40,000-80,000 Da. The aforementioned procedures used to prepare HA-alkylamine and HA-Bolton-Hunter adducts, as well as 125I-labeled HA, have been very reproducible, and the latter preparations are of adequate length to retain high-affinity interactions and specific binding, e.g., to human fibrinogen and HARE. For example, we were able to isolate, characterize, and clone the rat HARE using 125I-labeled HA initially with the dot blot assay to monitor solubilization and partial purification, and later with the ligand blot assay, to identify the protein after SDS-PAGE. The ligand blot assay enabled us to determine that HARE is actually present as two discrete isoreceptors of different molecular masses. These techniques should provide a means to analyze purification strategies and to characterize additional HA receptors and binding proteins involved in a variety of physiologic processes.

Human monocytes synthesize hyaluronidase

The involvement of hyaluronic acid (HA) oligosaccharides and blood-derived mononuclear cells in inflammatory processes prompted us to determine whether peripheral blood mononuclear cells (PBMC) possess hyaluronidase activity. PBMC were incubated with macromolecular-tritiated HA at pH 3.8 and supernatants were analysed by size exclusion chromatography to reveal digestion of HA. This digestion was due to the CD14-positive (CD14+), adherent, non-specific esterase-positive, subpopulation of PBMC. Hyaluronidase activity (72 kDa) was found in aqueous and non-ionic detergent PBMC extracts but not in the medium in which the cells had been cultured. These results indicate that hyaluronidase is, at least in part, linked to the membrane rather than excreted. Hence, monocytes have one or more hyaluronidases that can generate a pool of active HA fragments within tissues. Hyaluronidase activity was also found in 3/3 myelomonocytic lineage leukaemias but not in 3/3 lymphoblastic leukaemias.

Potential mechanism of action of intra-articular hyaluronan therapy in osteoarthritis: are the effects molecular weight dependent?

BACKGROUND

Hyaluronan, or hyaluronic acid (HA), is the major hydrodynamic nonprotein component of joint synovial fluid (SF). Its unique viscoelastic properties confer remarkable shock absorbing and lubricating abilities to SF, while its enormous macromolecular size and hydrophilicity serve to retain fluid in the joint cavity during articulation. HA restricts the entry of large plasma proteins and cells into SF but facilitates solute exchange between the synovial capillaries and cartilage and other joint tissues. In addition, HA can form a pericellular coat around cells, interact with proinflammatory mediators, and bind to cell receptors, such as cluster determinant (CD)44 and receptor for hyaluronate-mediated motility (RHAMM), where it modulates cell proliferation, migration, and gene expression. All these physicochemical and biologic properties of HA have been shown to be molecular weight (MW) dependent.

OBJECTIVE

Intra-articular (IA) HA therapy has been used for the treatment of knee osteoarthritis (OA) for more than 30 years. However, the mechanisms responsible for the reported beneficial clinical effects of this form of treatment remain contentious. Furthermore, there are a variety of pharmaceutic HA preparations of different MW available for the treatment of OA, but the significance of their MWs with respect to their pharmacologic activities have not been reviewed previously. The objective of the present review is to redress this deficiency.

METHODS

We reviewed in vitro and in vivo reports to identify those pharmacologic activities of HA that were considered relevant to the ability of this agent to relieve symptoms and protect joint tissues in OA. Where possible, reports were selected for inclusion when the pharmacologic effects of HA had been studied in relation to its MW. In many studies, only a single HA preparation had been investigated. In these instances, the experimental outcomes reported were compared with similar studies undertaken with HAs of different MWs.

RESULTS

Although in vitro studies have generally indicated that high MW-HA preparations were more biologically active than HAs of lower MW, this finding was not confirmed using animal models of OA. The discrepancy may be partly explained by the enhanced penetration of the lower MW HA preparation through the extracellular matrix of the synovium, thereby maximizing its concentration and facilitating its interaction with target synovial cells. However, there is accumulating experimental evidence to show that the binding of HAs to their cellular receptors is dependent on their molecular size; the smaller HA molecular species often elicits an opposite cellular response to that produced by the higher MW preparations. Studies using large animal models of OA have shown that HAs with MWs within the range of 0.5 x 10(6)-1.0 x 10(6) Da were generally more effective in reducing indices of synovial inflammation and restoring the rheological properties of SF (visco-induction) than HAs with MW > 2.3 x 10(6) Da. These experimental findings were consistent with light and electron microscopic studies of synovial membrane and cartilage biopsy specimens obtained from OA patients administered 5 weekly IA injections of HA of MW = 0.5 x 10(6)-0.73 x 10(6) Da in which evidence of partial restoration of normal joint tissue metabolism was obtained.

CONCLUSIONS

By mitigating the activities of proinflammatory mediators and pain producing neuropeptides released by activated synovial cells, HA may improve the symptoms of OA. In addition, HAs within the MW range of 0.5 x 10(6)-1.0 x 10(6) Da partially restore SF rheological properties and synovial fibroblast metabolism in animal models. These pharmacologic activities of HA could account for the reported long-term clinical benefits of this OA therapy. However, clinical evidence has yet to be described to support the animal studies that indicated that HAs with MW > 2.3 x 10(6) Da may be less effective in restoring SF rheology than HAs of half this size.

Chlorination of pyridinium compounds. Possible role of hypochlorite, N-chloramines, and chlorine in the oxidation of pyridinoline cross-links of articular cartilage collagen type II during acute inflammation

Reactive oxygen species produced by activated neutrophils and monocytes are thought to be involved in mediating the loss of collagen and other matrix proteins at sites of inflammation. To evaluate their potential to oxidize the pyridinoline (Pyd) cross-links found in collagen types I and II, we reacted hydrogen peroxide (H(2)O(2)), hypochlorous acid/hypochlorite (HOCl/OCl(-)), and singlet oxygen (O(2)((1)delta g)) with the Pyd substitutes, pyridoxamine dihydrochloride and vitamin B(6), which share the same chemical structure and spectral properties of Pyd cross-links. Neither H(2)O(2) (125-500 microm) nor O(2)((1)delta g) (10-25 microm) significantly changed the spectral properties of pyridoxamine or vitamin B(6). Reaction of HOCl/OCl(-) (12.5-50 microm) with pyridoxamine at pH 7.2 resulted in a concentration-dependent appearance of two new absorbance peaks and a decrease in fluorescence at 400 nm (excitation 325 nm). The new absorbance peaks correlated with the formation of an N-chloramine and the product of its subsequent reaction with pyridoxamine. In contrast, the extent to which HOCl reacted with vitamin B(6), which lacks a primary amine group, was variable at this pH. At lysosomal pH 5.5, Cl(2)/HOCl/OCl(-) reacted with both pyridoxamine and vitamin B(6). Four of the chlorinated products of this reaction were identified by gas chromatography-mass spectrometry and included 3-chloropyridinium, an aldehyde, and several chlorinated products with disrupted rings. To evaluate the effects of Cl(2)/HOCl/OCl(-) on Pyd cross-links in collagen, we exposed bone collagen type I and articular cartilage type II to HOCl. Treatment of either collagen type with HOCl at pH 5. 0 or 7.2 resulted in the oxidation of amine groups and, for collagen type II, the specific decrease in Pyd cross-link fluorescence, suggesting that during inflammation both oxidations may be used by neutrophils and monocytes to promote the loss of matrix integrity.

Role of hyaluronan chain length in buffering interstitial flow across synovium in rabbits

1. Synovial fluid drains out of joints through an interstitial pathway. Hyaluronan, the major polysaccharide of synovial fluid, attenuates this fluid drainage; it creates a graded opposition to outflow that increases with pressure (outflow 'buffering'). This has been attributed to size-related molecular reflection at the interstitium-fluid interface. Chain length is reduced in inflammatory arthritis. We therefore investigated the dependence of outflow buffering on hyaluronan chain length. 2. Hyaluronan molecules of mean molecular mass approximately 2200, 530, 300 and 90 kDa and concentration 3.6 mg ml-1 were infused into the knees of anaesthetized rabbits, with Ringer solution as control in the contralateral joint. Trans-synovial drainage rate was recorded at known joint pressures. Pressure was raised in steps every 30-60 min (range 2-24 cmH2O). 3. With hyaluronan-90 and hyaluronan-300 the fluid drainage rate was reduced relative to Ringer solution (P < 0.001, ANOVA) but increased steeply with pressure. The opposition to outflow, defined as the pressure required to drive unit outflow, did not increase with pressure, i.e. there was no outflow buffering. 4. With hyaluronan-530 and hyaluronan-2000 the fluid drainage rate became relatively insensitive to pressure, causing a near plateau of flow. Opposition to outflow increased markedly with pressure, by up to 3.3 times over the explored pressures. 5. Hyaluronan concentration in the joint cavity increased over the drainage period, indicating partial reflection of hyaluronan by synovial interstitium. Reflected fractions were 0.12, 0.33, 0.25 and 0.79 for hyaluronan-90, -300, -530 and -2200, respectively. 6. Thus the flow-buffering effect of hyaluronan depended on chain length, and shortening the chains reduced the degree of molecular reflection. The latter should reduce the concentration polarization at the tissue interface, and hence the local osmotic pressure opposing fluid drainage. In rheumatoid arthritis the reduced chain length will facilitate the escape of hyaluronan and fluid.

Reactive oxygen species: a potential role in the pathogenesis of periodontal diseases

The pathological events leading to the destruction of the periodontium during inflammatory periodontal diseases are likely to represent complex interactions involving an imbalance in enzymic and non-enzymic degradative mechanisms. This paper aims to review the increasing body of evidence implicating reactive oxygen species (ROS), derived from many metabolic sources, in the pathogenesis of periodontal tissue destruction. ROS are generated predominantly by polymorphonuclear leukocytes (PMN) during an inflammatory response and are regarded as being highly destructive in nature. The detection of ROS oxidation products, the elevation of iron and copper ions, which catalyse the production of the most reactive radical species, and the identification of an imbalance in the oxidant/antioxidant activity within periodontal pockets, suggests a significant role for ROS in periodontal tissue destruction. In vitro studies have shown that ROS are capable of degrading a number of extracellular matrix components including proteoglycans, resulting in the modification of amino acid functional groups, leading to fragmentation of the core protein, whilst the constituent glycosaminoglycan chains undergo limited depolymerisation. The identification and characterisation of connective tissue metabolites in gingival crevicular fluid (GCF) resulting from the degradation of periodontal tissues, notably alveolar bone, provides further evidence for a role for ROS in tissue destruction associated with inflammatory periodontal diseases.

The role of low molecular weight hyaluronic acid contained in Wharton's jelly in necrotizing funisitis

The purpose of this research was to study the changes in the molecular weight of hyaluronic acid in Wharton's jelly altered by necrotizing funisitis. Umbilical cords were collected at delivery from 20 newborns without funisitis, 6 newborns with acute funisitis, and 4 newborns with necrotizing funisitis. Agarose gel electrophoresis of Wharton's jelly was performed to analyze the molecular weight of hyaluronic acid (HA). We also investigated the effects of low or high molecular weight HA on the production of interleukin-8 in human umbilical fibroblasts. In Wharton's jelly without funisitis, HA was 1150 +/- 280 kD in preterm newborns, regardless of gestational week at birth, and that in full-term newborns was 1100 +/- 200 kD. When acute funisitis was present, HA was 700 +/- 250 kD, and when necrotizing funisitis was present, HA was 520 +/- 100 kD. The molecular weight of HA was significantly below normal in newborns with necrotizing funisitis. Low molecular weight HA was associated with increased levels of IL-8 in the supernatant of cultured human umbilical fibroblasts in a time- and dose-dependent manner. High molecular weight HA did not induce the production of IL-8 in the same cells. Low molecular weight HA has a potent inflammatory action. The conversion from high to low molecular weight HA in Wharton's jelly may be important in the pathophysiology of necrotizing funisitis.

Proteoglycans at the bone-implant interface

The widespread success of clinical implantology stems from bone's ability to form rigid, load-bearing connections to titanium and certain bioactive coatings. Adhesive biomolecules in the extracellular matrix are presumably responsible for much of the strength and stability of these junctures. Histochemical and spectroscopic analyses of retrievals have been supplemented by studies of osteoblastic cells cultured on implant materials and of the adsorption of biomolecules to titanium powder. These data have often been interpreted to suggest that proteoglycans permeate a thin, collagen-free zone at the most intimate contact points with implant surfaces. This conclusion has important implications for the development of surface modifications to enhance osseointegration. The evidence for proteoglycans at the interface, however, is somewhat less than compelling due to the lack of specificity of certain histochemical techniques and to possible sectioning artifacts. With this caveat in mind, we have devised a working model to explain certain observations of implant interfaces in light of the known physical and biological properties of bone proteoglycans. This model proposes that titanium surfaces accelerate osseointegration by causing the rapid degradation of a hyaluronan meshwork formed as part of the wound-healing response. It further suggests that the adhesive strength of the thin, collagen-free zone is provided by a bilayer of decorin proteoglycans held in tight association by their overlapping glycosaminoglycan chains.

Lipid peroxidation products and antioxidants in human disease

Lipid peroxidation (LPO) is a free radical-related process that in biologic systems may occur under enzymatic control, e.g., for the generation of lipid-derived inflammatory mediators, or nonenzymatically. This latter form is associated mostly with cellular damage as a result of oxidative stress, which also involves cellular antioxidants in this process. This article focuses on the relevance of two LPO products, malondialdehyde (MDA) and 4-hydroxynonenal (HNE), to the pathophysiology of human disease. The former has been studied in human serum samples of hepatitis C virus-infected adults and human immunodeficiency virus-infected children. In these two cases it is shown that the specific assay of serum MDA is useful for the clinical management of these patients. The presence of MDA in subretinal fluid of patients with retinal detachment suggests the involvement of oxidative stress in this process. Moreover, we were able to report the dependence of this involvement on the degree of myopia in these patients. The assay of MDA contents in the peripheral nerves of rats fed a chronic alcohol-containing diet or diabetic mice also confirms the pathophysiologic role of oxidative stress in these experimental models. In these two cases, associated with an increase in tissue LPO products content, we detected a decrease of glutathione peroxidase (GSHPx) activity in peripheral nerve, among other modifications. We have demonstrated that in vitro HNE is able to inhibit GSHPx activity in an apparent competitive manner, and that glutathione may partially protect and/or prevent this inactivation. The accumulation of LPO products in the brain of patients with Alzheimer's disease has also been described, and it is on the basis of this observation that we have tried to elucidate the role of oxidative stress and cellular antioxidants in beta-amyloid-induced apoptotic cell death of rat embryo neurons. Finally, we discuss the possible role of the observed vascular effects of HNE on human arteries.

Degradation of glycosaminoglycans by reactive oxygen species derived from stimulated polymorphonuclear leukocytes

The effect of reactive oxygen species (ROS), generated by in vitro stimulation of isolated PMN upon the main GAG components of mineralised and non-mineralised connective tissues was investigated. PMN were isolated from whole blood and the production of the ROS superoxide (O2.-) and hydroxyl radicals (.OH) was stimulated by the addition of phorbol myristyl acetate (PMA) and PMA/FeCl3-EDTA chelate respectively and their production assessed over a 24 h period. The glycosaminoglycans (GAG), hyaluronan, chondroitin 4-sulphate and dermatan sulphate, were exposed to the ROS fluxes, incubated at 37 degrees C for 1 h and 24 h. GAG fragmentation was examined by gel exclusion chromatography and modification to hexuronic acid and hexosamine residues determined. Stimulation of PMN with PMA resulted in a burst of O2.- production for 1 h, which was sustained at a reduced level for 24 h. Fragmentation of GAG was observed for all GAG examined. Modification to the GAG was evident, with hyaluronan being more susceptible to loss of GAG residues than sulphated GAG. Modification of sugar residues increased with the incubation time and loss of the hexuronic acid residues was greater than loss of hexosamine residues. Addition of FeCl3-EDTA chelate, which led to the generation of .OH and was sustained over the 24 h period, demonstrated similar trends of GAG modification although increased degradation and loss of hexosamine and hexuronic acid were observed. GAG chains are constituents of PGs and their modification is likely to affect the function of these macromolecules and be of importance in considering the pathogenesis of inflammatory diseases, including periodontal diseases.

Urinary excretion of sulfated polysaccharides administered to Wistar rats suggests a renal permselectivity to these polymers based on molecular size

Sulfated polysaccharides were administered to Wistar rats and their elimination from the blood as well as their urinary excretion were evaluated. Sulfated polysaccharides with differences in molecular mass, charge density and molecular structure were obtained from algae, marine invertebrates and vertebrates. A simple methodology based on the metachromatic property of these polysaccharides with 1,9-dimethylmethylene blue was used to estimate their concentration in urine and blood. Renal permselectivity to these macromolecules was based on molecular size, but the upper limit of molecular mass for excretion of a sulfated polysaccharide in urine varies among polymers with different structures. For dextran sulfates the upper limit is approximately 8 kDa. Chondroitin 4- and 6-sulfates were excreted as fragments of approximately 30 kDa, which is smaller than the injected polysaccharide. This suggests that they were degraded enzymatically in vivo. Large synthetic polymers (dextran sulfate > 8 kDa) were not excreted in urine, but slowly disappeared from the blood. Evaluation of their tissue distribution after intravenous administration indicated that these molecules are preferentially accumulated in the kidney.

Reactive oxygen species contribute to epidermal hyaluronan catabolism in human skin organ culture

Hyaluronan (HA) is produced by keratinocytes in human skin organ culture, and degraded locally in epidermis by an unknown metabolic route. The present work tested whether reactive oxygen species (ROS), spontaneously produced in the tissue, could contribute to HA catabolism in epidermis. Epidermal HA was endogenously labeled with 3H-glucosamine for 24 h, then chased for 24 h in the presence of superoxide dismutase (SOD) and catalase to reduce the concentration of ROS. In control cultures, 35% of labeled HA was degraded during the 24 h chase while the corresponding figures in the presence of SOD and catalase were 19% and 23%, respectively (p < 0.05). Methionine, a quencher of hypochlorous acid, did not significantly inhibit the degradation. In additional experiments, the iron and copper chelator Detapac was even more effective, reducing the degradation to 8-9%, and suggesting that the ROS responsible for the degradation were produced in the Fenton reaction. Dermal HA, and proteoglycans in both epidermis and dermis were not influenced by the treatments, indicating that the inhibition by SOD, catalase and Detapac on epidermal HA catabolism was specific. It is suggested that endogenous ROS is involved in the catabolism human epidermal HA.

Middle ear catalase distribution in an animal model of otitis media

Increasing evidence implicates free radicals in the pathogenesis of inflammatory disease, including otitis media. The anti-oxidant enzymes catalase, glutathione peroxidase and superoxide dismutase protect tissues from the destructive effects of free radicals. Our previous work has shown depressed levels of superoxide dismutase in the infected middle ears of a guinea pig model of otitis media in comparison with normal control ears. We studied the distribution and relative abundance of catalase in the middle ear of this animal model in an effort to elucidate the role free radicals play in the pathogenesis of otitis media. Catalase distribution was mapped immunohistochemically in the middle ears of guinea pigs with induced streptococcus otitis media, and compared with normal control ears. In the control ears, catalase was localized to the epithelium of the middle ear mucosa, with scant distribution in the submucosa. The infected ears demonstrated inflammatory cell invasion with hyperemia and submucosal edema. Catalase was localized to the epithelium and had scant distribution in the submucosa. This distribution was similar to that found previously with superoxide dismutase. Enzyme-linked immunosorbent assay of catalase demonstrated a mean value of 1.00 +/- 0.06 microgram/mg protein in the control ears, and 1.06 +/- 0.12 microgram/mg in the infected ears, but these two values were not statistically different.

Compositional and structural alterations of arterial glycosaminoglycans associated with the complications brought about by thalassemia major. A case report

A biochemical analysis of glycosaminoglycans was performed in arteries of a fifteen-year old white male who died of beta thalassemia major. The patient presented the severe clinical complications resulting from hemochromatosis, which was evidenced at autopsy and by histologic examination. The arteries under study comprised the thoracic and abdominal aortas and the iliac and pulmonary arteries, which were compared with the same arteries from normal individuals. Data on total glycosaminoglycan and total collagen, including the determination of the relative contents of the different glycosaminoglycans, suggest an as yet undescribed fibrotic process in the thalassemic arteries. Also altered were the proportions of the disaccharides making up chondroitin sulfate and heparin sulfate. A reduction in the molecular weight of arterial heparin sulfate, presumably with free radical involvement, was also detected. All these changes in the extracellular matrix may be ascribed to the presence of large amounts of iron in the tissue, and as such they should be expected in other disorders with chronic iron overload.

Lipid peroxidation products in human subretinal fluid

The concentrations of thiobarbituric acid reacting substances (TBARS) and proteins in the subretinal fluid (SF) of patients undergoing retinal detachment surgery have been determined. We have tried to establish the correlations between these biochemical and other clinical features of these patients: evolution time of the retinal detachment, age, degree of myopia, and macular affection. Caucasian patients, 19 men and 19 women (57.42 +/- 12.85 average age, interval 20-80) were randomly selected for this study. SF samples were obtained by puncture after scleral indentation. TBARS and protein concentrations were determined by the corresponding colorimetric assays. A linear correlation exists between TBARS and protein contents in these samples. No correlation could be established between evolution time of the retinal detachment and TBARS content in SF. TBARS in SF increases with increasing age in nonmyopic patients. In the samples of myopic patients the correlation was established between TBARS content and degree of myopia. The group of patients with more than 10 dioptres show a significant higher TBARS concentration in SF than any of the other groups studied. It can be concluded that lipid peroxidation products in SF originate, at least partially, from rod outer segments, and that lipid peroxidation is a process that might play a role in the pathogenesis of retinal detachment, specially in myopic patients.

Hyaluronan and CD44 in psoriatic skin. Intense staining for hyaluronan on dermal capillary loops and reduced expression of CD44 and hyaluronan in keratinocyte-leukocyte interfaces

The distributions of hyaluronan (HA) and its presumptive receptor, CD44, were studied in skin samples from 13 psoriasis vulgaris patients, using an HA-specific probe (HABC), and monoclonal antibodies, respectively. The general distribution of HA and CD44 in psoriatic lesional epidermis resembled that in normal epidermis. However, areas of epidermis invaded by leukocytes showed a local depletion of HA and CD44, particularly at the contact areas of keratinocytes to lymphocytes and neutrophils. Removal by cellular uptake or extracellular degradation of CD44 and HA may be required for tight adherence between a keratinocyte and a leukocyte. On the dermal side, the tips of the prolonged dermal papillae in psoriatic lesions were intensively stained with HABC. The dilated capillaries and the space below the tip basal lamina, in particular, were heavily covered with HA. Occasionally, a similar intense staining was seen around an enlarged capillary in uninvolved psoriatic skin. CD44-positive leukocytes were found around the affected capillaries. The accumulation of HA in the dermal papillae may support the growth of psoriatic lesions, since HA stimulates the growth of capillaries as well as attracting inflammatory cells.

Differential effects of reactive oxygen species on native synovial fluid and purified human umbilical cord hyaluronate

The ability of reactive oxygen species produced by triggered neutrophilic leukocytes, hypoxanthine/xanthine oxidase (HX/XAO), hydrogen peroxide, and hypochlorous acid/myeloperoxidase (HOCl/MPO) systems to degrade hyaluronate (HA) in human synovial fluid (SF) and purified umbilical cord HA was compared by measuring the molecular weight distribution of HA using high-performance liquid chromatography with a size-exclusion column. The exposure of noninflammatory SF to phorbol myristic acetate (PMA)-activated neutrophils or to hydrogen peroxide (H2O2) caused depolymerization of SF HA to the degree corresponding to that found in rheumatoid SFs. When HX/XAO was used as radical generator, the molecular weight of SF HA decreased from 3.42 x 10(6) to 1.40 x 10(4) daltons with concomitant decrease of SF viscosity to 36% from the original value. The HOCl/MPO system caused no depolymerization of SF HA, even at very high unphysiological HOCl concentrations that induced the precipitation of SF HA together with SF proteins. This effect was found to be comparable to conventional mucin clot formation in SF. However, purified human umbilical cord HA was easily depolymerized with HOCl/MPO or with H2O2, but these effects were sensitive to the hydroxyl radical scavenger mannitol and iron chelator desferrioxamine, indicating that the formation of reactive hydroxyl radical (OH.) is likely to participate in these reactions. Thus we conclude that in inflammatory SF HA is mainly depolymerized by OH. produced by decomposition of H2O2 catalyzed by iron, free or locally bound to HA itself. In contrast to what has been reported earlier, HOCl/MPO only depolymerizes purified umbilical cord HA (in a hydroxyl radical-dependent manner) but does not depolymerize HA in SF. As a matter of fact, HOCl/MPO has a scavenging action on SF HA by consuming H2O2 and thus preventing the formation of reactive hydroxyl radicals.

The effects of intraarticular administration of hyaluronan in a model of early osteoarthritis in sheep. II. Cartilage composition and proteoglycan metabolism

A model of early osteoarthritis (OA) induced in ovine joints by medial meniscectomy was used to study the effects of two hyaluronan (HA) preparations (AHA and DHA) on cartilage composition and proteoglycan (PG) metabolism. DHA was an HA preparation with an average molecular weight (MW) of approximately 2.0 x 10(6) d, and AHA had an MW of approximately 8.0 x 10(5) d. Both preparations were administered intraarticularly once a week for 5 weeks starting 16 weeks after meniscectomy, and animals (n = 5) were killed 5 weeks after the last injection. Meniscectomized, saline-injected (n = 5) and nonoperated (n = 5) animals were used for controls. At necropsy, 3-mm-diameter full-depth cartilage plugs were sampled under sterile conditions from specific locations on the medial and lateral femoral condyles, tibial plateaus, patella, and trochlear groove. The cartilage plugs were cultured in Hams-F12 medium supplemented with 10% fetal calf serum for 24 hours, then for a further 48 hours in the presence of H2(35)SO4 to determine the biosynthesis of PGs. The percentage of 35S-PGs and sulfated glycosaminoglycans released into the media was also ascertained. The cartilage adjacent to the plugs was analyzed for collagen and proteoglycan content and differential extractability with guanidine hydrochloride (GuHCl) solutions. The extractability of PGs with 0.4 mol/L GuHCl (nondissociative conditions) was lower from the medial femoral cartilages of the DHA-treated group than from the corresponding saline-treated group. In contrast, the release of 35S-PGs from the tibial cartilages of the DHA-treated animals was higher than in the saline-treated group. The biosynthesis of 35S-PGs, determined in vitro, for cartilage derived from the medial compartment was generally lower than for the lateral regions of the meniscectomized joints. The biosynthetic activity was further reduced in joints injected with the two HA preparations, but DHA reduced 35SO4 incorporation into PGs more than AHA. It was concluded that reduced biosynthesis of 35S-PGs and secretion into media was a consequence of increased loading of joints in the HA-treated animals rather than a direct effect of these preparations on chondrocyte metabolism.

Evaluation of sodium hyaluronate therapy in induced septic arthritis in the horse

This study was conducted to determine the efficacy of sodium hyaluronate (SH) with antibiotic therapy and joint lavage for reducing acute inflammatory and degenerative changes induced by septic arthritis. Septic arthritis was induced in six adult horses by inoculating the tarsocrural joints with 1 x 10(4) colony-forming units of Staphylococcus aureus. When clinical signs appeared, trimethoprim-sulphamethoxazole (30 mg/kg bodyweight [bwt] daily) and phenylbutazone (4.4 mg/kg bwt sid) were administered and continued until termination of the study (Treatment Day 18). Twenty-four hours post inoculation, all joints were lavaged with sterile lactated Ringer's solution. Following lavage, one joint of each horse was injected with 10 mg of SH, and the contralateral joint served as the control. Sodium hyaluronate treated joints showed significant reductions in lameness, tarsal circumference and synovial fluid protein and WBC concentrations. The synovial membrane of the SH-treated joints contained less cellular infiltrate, less granulation tissue formation and retained a more normal villous structure compared with controls. The total glycosaminoglycan loss from the articular cartilage in the SH treated joints was consistently less than that from the control joints; however, this difference was not statistically significant. Sodium hyaluronate with joint lavage appears to be more beneficial than lavage alone for treatment of septic arthritis.

Active oxygen species, articular inflammation and cartilage damage

Rheumatoid arthritis and osteoarthritis are age-related diseases, in which degenerative changes (arthrosis) and superimposed inflammatory reactions (arthritis) lead to progressive destruction of the joints. Active oxygen species derived from various sources play a role in this process, which may be influenced by appropriate treatment with antioxidants and free radical scavengers.

Effect of hylan on cartilage and chondrocyte cultures

The protective role of hylan, a hyaluronan [hyaluronic acid (HA)] derivative, was studied in explanted bovine cartilage and isolated chondrocytes. Cartilage and chondrocytes were exposed to degradative enzymes (lysate from activated polymorphonuclear leukocytes), oxygen-derived free radicals (ODFR), conditioned media from mononuclear cells (MCCM), and interleukin-1 (IL-1), in the presence and absence of hylan. The effect of HA was also studied. In cartilage explants susceptibility to pertubation was evaluated in terms of 35S release and proteoglycan depletion and was compared to control cultures; high viscosity hylan was found to reduce 35S release in cartilage explants caused by degradative enzymes, ODFR, MCCM, and IL-1. The hylan effect was reversible and viscosity-dependent. In chondrocyte cultures, high viscosity hylan was effective in reducing cell injury caused by degradative enzymes and ODFR. The data suggest that the glycosaminoglycan hylan, as well as native HA, may mediate exposure to and/or response to stimuli associated with initiation of degenerative processes in cartilage tissues.

Leukocyte-mediated inactivation of alpha 1-proteinase inhibitor is inhibited by amino analogues of alpha-tocopherol

Human leukocytes stimulated by opsonized zymosan increase their NADPH oxidase-catalysed reduction of molecular oxygen. This leads to enhanced formation of superoxyl radicals and subsequently hydrogen peroxide. The leukocyte enzyme myeloperoxidase generates the strong microbicidal oxidant hypochlorite from hydrogen peroxide and chloride anions. Hypochlorite inactivates serum alpha 1-proteinase inhibitor, a protein which protects host tissue from digestion by proteinases, that are also secreted by stimulated leukocytes. Micromolar concentrations of a water-soluble, quaternary ammonium analogue of alpha-tocopherol (vitamin E) (3,4-dihydro-6-hydroxy-N,N,N-2,5,7,8-heptamethyl-2H-1-benzopyran-2 -ethanaminium 4-methylbenzenesulfonate) and its tertiary amine derivative (3,4-dihydro-2- (2-dimethylaminoethyl)-2,5,7,8-tetramethyl-2H-1-benzopyran-6-ol hydrochloride) were able to protect alpha 1-proteinase inhibitor from inactivation by stimulated human leukocytes. The mechanism of action of the quaternary ammonium analogue was further investigated. Selective inhibition of hydrogen peroxide formation is assumed to be the reason for its protective effect. This compound rapidly reacts with superoxyl radicals, but not with hydrogen peroxide, and is only a weak hypochlorite scavenger. It neither impedes exocytosis of elastase, nor effectively inhibits NADPH oxidase or myeloperoxidase. In contrast, superoxide dismutase, which enhances hydrogen peroxide formation, cannot protect alpha 1-proteinase inhibitor from inactivation.

Oxygen derived free radicals and synovial fluid hyaluronate

High performance liquid chromatography with TSK 5000 PW or TSK 6000 PW size exclusion columns combined with a 125I labelled hyaluronic acid binding protein assay was used to study the effects of oxygen derived free radicals on synovial fluid hyaluronate. A continuous flux of free radicals was generated by the xanthine oxidase/hypoxanthine system. When the free radical flux was generated with xanthine oxidase/hypoxanthine in the presence of the iron chelator desferrioxamine and the hydroxyl radical scavenger mannitol a 30-50% decrease in hyaluronate peak was detected, but the molecular weight of synovial fluid hyaluronate remained almost unchanged as a result of reaction with superoxide radicals and hydrogen peroxide. When trace amounts of iron and EDTA were present in the reaction mixture depolymerisation of synovial fluid hyaluronate occurred, and it reached a final molecular weight of about 13,500 daltons. These results suggest that superoxide and hydroxyl radicals may have a different mode of action on synovial fluid hyaluronate. Superoxide radicals and hydrogen peroxide do not induce depolymerisation but, rather, change the molecular configuration of synovial fluid hyaluronate.

Oxygen radicals, inflammation, and arthritis: pathophysiological considerations and implications for treatment

A vast amount of circumstantial evidence implicates oxygen-derived free radicals, especially superoxide and hydroxyl radical (and to lesser extent, hydrogen peroxide), as mediators of inflammation and/or tissue destruction in inflammatory and arthritic disorders. The substrates for radical generation, namely properly stimulated phagocytic cells, transition metal catalysts, and (to a limited extent) ischemia, are all amply present, although there is no particular rheumatic disease in which a consistent abnormality of radical generation has been identified. These radical species can clearly degrade hyaluronic acid, modify collagen and perhaps proteoglycan structure and/or synthesis, alter and interact with immunoglobulins, activate enzymes and inactivate their inhibitors, and possibly participate in chemotaxis. In most situations, however, there is ample scavenging ability to detoxify these radicals before they hit their target, and many rheumatic disease drugs can decrease their production and/or effects. Despite the apparent sufficiency of natural scavengers and the lack of direct evidence that oxygen radicals are pathogenetically important, substantial pharmaceutical effort is still being made to develop free radical scavengers as therapeutic agents. Although individual free radicals die out quickly, rheumatologic interest in them has been sustained for nearly two decades.

Oxidative damage to hyaluronate and glucose in synovial fluid during exercise of the inflamed rheumatoid joint. Detection of abnormal low-molecular-mass metabolites by proton-n.m.r. spectroscopy

Proton Hahn spin-echo n.m.r. spectroscopy was employed to detect abnormal metabolites present in rheumatoid synovial fluid that are derived from the deleterious generation of reactive oxygen radical species during exercise of the inflamed rheumatoid joint. A resonance attributable to a low-molecular-mass N-acetylglucosamine-containing oligosaccharide formed by the oxygen-radical-mediated depolymerization of synovial-fluid hyaluronate was clearly demonstrable when subjects with inflammatory joint disease were exercised. Moreover, formate, which may be derived from the attack of OH.radical on synovial-fluid carbohydrates, was also readily detectable in these samples. gamma-Radiolysis of rheumatoid synovial fluid samples and aqueous solutions of hyaluronate also gave rise to the production of the low-molecular-mass hyaluronate-derived oligosaccharide species and markedly elevated concentrations of (non-protein-bound) formate in the biological fluids. As expected, corresponding spectra of gamma-irradiated blood serum samples obtained from normal volunteers did not contain the signal attributable to the low-molecular-mass oligosaccharide species, but the formate resonance (barely detectable in non-irradiated normal serum samples) became clearly visible. Additionally, a curious increase in the effective concentration of non-protein-bound low-molecular-mass metabolites such as acetate, citrate, lactate and glutamine was observed after gamma-radiolysis of all biological fluids studied. The hyaluronate-derived low-molecular-mass oligosaccharide species and formate are suggested as novel markers of reactive oxygen radical activity in the inflamed rheumatoid joint during exercise-induced hypoxic/reperfusion injury.

Oxidant defense mechanisms in the human colon

Reactive oxygen metabolites have been implicated as important mediators of inflammation-induced intestinal injury associated with ischemia (and reperfusion), radiation, and inflammatory bowel disease. Because the colonic mucosa may be subjected to significant oxidant stress during times of acute and chronic inflammation, knowledge of the oxidant defense mechanisms in the colon is of biologic and potential clinical importance. Therefore, the objective of this study was to quantify the specific activities of superoxide dismutase (SOD), catalase, and GSH peroxidase in the normal human colon. We found low, but significant, amounts of all three enzymes in the mucosa, submucosa, and muscularis/serosa of the human colon. However, the mucosal, levels of SOD (3.6 +/- 0.3 units/mg protein), catalase (11 +/- 3 units/mg), and GSH peroxidase (15.2 +/- 0.8 mU/mg) represented only 8%, 4%, and 40%, respectively, of those values determined for human liver. Colonic epithelial cells derived from mucosal biopsies exhibited significantly higher specific activities for SOD (12 +/- 0.5 units/mg) and catalase (26 +/- 6 units/mg) when compared to whole mucosa, suggesting most of the mucosal activity was associated with the epithelial cells and not the lamina propria. In a comparative study, we found that a human colonic carcinoma cell line (CaCo-2) contained significantly lower SOD (6 +/- 0.5 units/mg) and catalase (6 +/- 0.6 units/mg) activities when compared to colonic epithelial cells. Taken together, our data suggest that: (1) the colonic mucosa is relatively deficient in antioxidant enzymes when compared to liver, and (2) most of the protective enzyme activity is localized within the epithelium and not the mucosal interstitium.

Hyaluronan in experimental serous and purulent otitis media

The concentration of hyaluronan (hyaluronic acid; sodium hyaluronate; HA), a major component of connective tissue, was analyzed by a specific radioassay in tissue samples from normal rat middle ears and in tissue and effusions from middle ears affected by experimentally induced otitis media. In normal ears the pars flaccida of the tympanic membrane contained a considerably higher concentration of HA (60 to 200 micrograms/g) than the pars tensa and areas of the medial wall (2 to 7 micrograms/g). In purulent otitis media the pars flaccida contained less HA than in normal ears. The HA concentrations were lower in purulent (3 to 40 micrograms/mL) than in serous (20 to 190 micrograms/mL) effusions. The weight average molecular weight of HA in serous fluid was high (greater than 10(6] and comparable to that in lymph. It is inferred from the study that the subepithelial tissue and its matrix components, eg, HA, must be considered when attempting to understand the function of the middle ear normally and in otitis media.

Degradation of human proteoglycan aggregate induced by hydrogen peroxide. Protein fragmentation, amino acid modification and hyaluronic acid cleavage

We have previously shown that treatment of neonatal human articular-cartilage proteoglycan aggregates with H2O2 results in loss of the ability of the proteoglycan subunits to interact with hyaluronic acid and in fragmentation of the link proteins [Roberts, Mort & Roughley (1987) Biochem. J. 247, 349-357]. We now show the following. (1) Hyaluronic acid in proteoglycan aggregates is also fragmented by treatment with H2O2. (2) Although H2O2 treatment results in loss of the ability of the proteoglycan subunits to interact with hyaluronic acid, the loss of this function is not attributable to substantial cleavage of the hyaluronic acid-binding region of the proteoglycan subunits. (3) In contrast, link proteins retain the ability to bind to hyaluronic acid following treatment with H2O2. (4) The interaction between the proteoglycan subunit and link protein is, however, abolished. (5) N-Terminal sequence analysis of the first eight residues of the major product of link protein resulting from H2O2 treatment revealed that cleavage occurred between residues 13 and 14, so that the new N-terminal amino acid is alanine. (6) In addition, a histidine (residue 16) is converted into alanine and an asparagine (residue 21) is converted into aspartate by the action of H2O2. (7) Rat link protein showed no cleavage or modifications in similar positions under identical conditions. (8) This species variation may be related to the different availability of histidine residues required for the co-ordination of the transition metal ion involved in hydroxyl-radical generation from H2O2. (9) Changes in function of these structural macromolecules as a result of the action of H2O2 may be consequences of both fragmentation and chemical modification.

Changes in the viscosity of hyaluronic acid after exposure to a myeloperoxidase-derived oxidant

Both purified hyaluronic acid (HA) and bovine synovial fluid react with OCI-, the major oxidant produced by the myeloperoxidase (MPO)/H2O2/CI- system, resulting in a decrease in their specific viscosity. This reaction is inhibited in the presence of excess methionine. H2O2 alone decreases the viscosity of HA, presumably by the Fenton reaction, in the absence (but not in the presence) of the iron chelator, diethyltriaminepentacetic acid (DETAPAC). In the presence of DETAPAC, incubation of HA with the complete MPO/H2O2/CI- system lowered the viscosity of HA. Analysis of 3H-HA exposed to OCI- by gel filtration chromatography indicated that cleavage of HA occurred only at higher OCI- concentrations. We suggest that the reduction in viscosity of HA by the MPO/H2O2/CI- system may be due to a combination of oxidative cleavage and changes in the conformation of the molecule. We speculate that the changes in the molecular size of rheumatoid synovial fluid HA may be due to the action of the neutrophil MPO/H2O2/CI- system.

Conversion of superoxide generated by polymorphonuclear leukocytes to hydroxyl radical: a direct spectrophotometric detection system based on degradation of deoxyribose

Hydroxyl radical is produced secondarily after phagocytic cells have been stimulated to generate superoxide anion. The systems used most commonly for detection of cell-generated hydroxyl radical are often inconvenient for routine biomedical research. We have modified an assay used heretofore in cell-free systems, that is, the degradation of deoxyribose, and adapted it for use with neutrophils. The time and dose responses of the system, requirement for chelated iron, inhibition profiles with various scavengers, and correlation with superoxide production have been ascertained. The method correlated strongly with a standard but more cumbersome technique. Values for a normal population are provided. The method can readily be used to study the parameters of superoxide-hydroxyl radical conversion by cells in various disease or treatment states.

Immunogenicity of liposome-bound hyaluronate in mice. At least two different antigenic sites on hyaluronate are identified by mouse monoclonal antibodies

Hyaluronate (HA) was previously demonstrated to be immunogenic in rabbits. The immunogenicity of HA in mice was studied. Hyaluronidase-digested streptococcal HA (IA1) covalently linked to liposomes (IA1-liposomes) were produced for immunization. Mice immunized with IA1-liposomes developed measurable serum antibodies to IA1, while mice immunized with IA1 in Freund's adjuvant did not. mAbs produced by two stable hybridomas (10G6 and 5F11) from mice immunized with IA1-liposomes produced IgG antibody reactive with HA in ELISA. 10G6 had a much higher avidity for liposome-bound IA1 than free IA1, while 5F11 did not, suggesting that the mode of presentation of IA1 is important in HA immunogenicity and antigenicity. Both mAbs recognized terminal HA immunodeterminants exposed by hyaluronidase treatment. Sonication had no effect on HA reactivity for either mAb. However, ascorbic acid treatment significantly reduced the antigenicity of HA for mAb 5F11, but not 10G6. Only 10G6 was inhibited by glucuronic acid. Electrostatic forces appear to play a role in the binding site of 5F11, but not 10G6. 5F11 crossreacts with heparan sulfate and phosphorylcholine, while 10G6 did not crossreact with any glycosaminoglycans or phosphorylated compounds tested. These results confirm that HA is immunogenic. They suggest that the mode of presentation of HA is important for the induction of the immune response, and in HA antigenicity. At least two different antigenic sites on HA were demonstrated. 10G6 recognizes a terminal HA antigenic site expressed on IA1-liposomes that contains glucuronic acid in its immunodominant site. 5F11 recognizes an HA antigenic site in which electrostatic forces appear to play a role, is sensitive to ascorbic acid treatment, and is crossreactive with heparan sulfate. The use of mAbs should facilitate immunologic studies of HA.