Isolation, chemical and biological characterization of sulphated glycoproteins synthesized by rat buccal and palatal minor salivary glands in vivo and in vitro

Induction of secretory and serum antibody responses following oral administration of antigen with bioadhesive degradable starch microparticles

Bioadhesive degradable starch microparticles were used to deliver antigen and immunoglobulin A (IgA)-enhancing cytokines to the oral mucosa. Degradable starch microparticle immunization groups consisted of rats dosed topically at the sublingual epithelium of the oral cavity, by subcutaneous injection in the vicinity of the major salivary glands or by oral intubation with degradable starch microparticles containing dinitrophenyl-bovine serum albumin +/- IL-5/IL-6 +/- penetration enhancer (alpha-lysophosphatidylcholine). Dinitrophenyl-bovine serum albumin was also adsorbed onto alum for salivary gland vicinity injection and administered to the oral cavity in soluble form. Animals were subjected to 3 immunization cycles, and sequential samples were assayed by radioimmunoassay for salivary IgA, tear IgA and serum IgG anti-dinitrophenyl antibodies after secondary and tertiary immunization. Salivary IgA responses were highest in degradable starch microparticle groups receiving penetration enhancer at 71 days post-secondary immunization and continued in one degradable starch microparticle((oral cavity) and two injected (salivary gland vicinity) groups for up to 88 days post-tertiary immunization. Long-term tear responses were also observed in degradable starch microparticle groups receiving penetration enhancer, but they dissipated before the salivary gland-alum responses following tertiary immunization. Serum IgG responses were most pronounced in salivary gland groups, but long-term low level responses were detectable in oral cavity groups receiving degradable starch microparticle formulations with penetration enhancer. Inclusion of IL-5 and IL-6 in oral cavity-delivered degradable starch microparticle formulations consistently enhanced tear IgA while only upregulating salivary IgA antibody responses at early time points post immunization. IL-5 and IL-6 did not enhance serum IgG antibodies in any group. These data indicate that bioadhesive degradable starch microparticles can be used as a vehicle to deliver antigen and cytokine signals to the oral cavity and, when delivered in combination with a penetration enhancer, can potentiate long-term salivary IgA responses.

High-performance liquid chromatography analysis of chondroitin sulphate isomers in human whole saliva in a variety of clinical conditions

OBJECTIVES

Tests have been carried out to assess the level of unsaturated disaccharide isomers obtained from chondroitin sulphate in whole saliva, which contains chondroitin sulphate derived from gingival crevicular fluid (GCF).

MATERIALS AND METHODS

Whole saliva was collected from periodontally diseased subjects (PDS), clinically healthy subjects (CHS) and edentulous subjects (ES). Glycosaminoglycans (GAG) were liberated by digestion with Pronase E, and precipitated with cetylpyridinium chloride and ethanol. The unsaturated disaccharides obtained by chondroitinase ACII digestion of the liberated GAG were analysed by high-performance liquid chromatography. The unsaturated disaccharides included delta Di-0S, delta Di-6S and delta Di-4S.

RESULTS AND CONCLUSIONS

Analysis of data indicated that delta Di-0S, delta Di-6S and delta Di-4S were found in all PDS samples. The amount (ng ml-1 collected whole saliva) of delta Di-0S, delta Di-6S and delta Di-4S (P < 0.01) indicated significant differences between CHS and PDS whole saliva samples. The quantities of delta Di-0S and delta Di-4S (P < 0.01) indicated significant differences between PDS and ES whole saliva. The amount of delta Di-0S (P < .05) and delta Di-6S (P < 0.01) also indicated significant differences between CHS and ES whole saliva. These results indicate that chondroitin sulphate in PDS and CHS whole saliva is representative of that previously reported in gingival crevicular fluid and so provides a useful and alternative means of assessing the role of GAG as indicators of periodontal disease.

Human glandular salivas: their separate collection and analysis

Human saliva is secreted by the three pairs of major salivary glands (parotid, submandibular, and sublingual), and numerous minor ones, e.g. labial, buccal and (glosso)palatine glands. Using individually adapted collection devices, sublingual, submandibular, parotid and palatine secretions of five individuals were collected and analyzed. Electrophoretic analysis revealed that each type of saliva possesses characteristic features, despite interindividual variations. Parotid salivas are characterized by intensely staining amylase and proline-rich protein bands, but contain minute amounts of cystatins, lysozyme and the extra-parotid glycoprotein. Sublingual salivas are characterized by high concentrations of both types of salivary mucins, MG1 and MG2, and contain relatively high levels of lysozyme. Submandibular salivas contain highest concentration of salivary cystatin S. Palatine secretions contain high molecular weight mucins and a relatively high amylase concentration.

Salivary mucins in oral mucosal defense

1. Salivary mucins are well recognized as an important factor in the preservation of the health of the oral cavity. These large glycoproteins play a major role in the formation of protective coatings covering tooth enamel and oral mucosa, which act as a dynamic functional barrier capable of modulating the untoward effects of oral environment, and are of significance to the processes occurring within the epithelial perimeter of mucosal defense. 2. Based on macromolecular characteristics, the mucins in saliva fall into high (> 1000 kDa) and low (200-300 kDa) molecular weight forms. The two forms, although differ with respect to bacterial clearance ability, display virtually identical carbohydrate chain make-up, ranging in size from 3 to 16 sugar units. 3. Of the two mucin forms, the low molecular weight form more efficient in bacterial aggregation, predominates in saliva and oral mucosal mucus coat of caries-resistant individuals, while the level of the high molecular weight form is higher in caries-susceptible subjects. The saliva of caries-resistant individuals also exhibits greater activity of protease capable of conversion of the high molecular weight mucin to the low molecular weight form. 4. The bacterial aggregating activity of salivary mucins appears to be associated with sulfomucins rather than sialomucins. While the removal of sialic acid causes only partial loss in mucin aggregating capacity, a complete loss in the bacterial aggregating activity occurs following mucin desulfation. 5. The mucins in oral mucosal mucus coat interact with the epithelial surfaces through specific membrane receptors. This interaction apparently involves the carbohydrate moiety of mucin molecule and may be rendered vulnerable to disruption by opportunistic bacteria colonizing the oral mucosa. 6. Salivary sulfo- and sialomucins actively participate in the modulation of the oral mucosal calcium channel activity through the inhibition of EGF-stimulated channel protein tyrosine phosphorylation. This function of salivary mucins is of paramount importance to mucosal calcium homeostasis.

Isolation of different high-Mr mucin species from human whole saliva

By using CsCl-density-gradient ultracentrifugation, two high-Mr mucin species were isolated from human whole saliva, having buoyant densities in 0.2 M-guanidinium chloride of approx. 1.56 g/ml (pool IA) and 1.48 g/ml (pool IIA). Analytical density-gradient centrifugation of submandibular, sublingual, labial and palatal saliva, followed by immunochemical analysis with anti-mucin monoclonal antibodies, indicated immunochemical and physicochemical similarities between the high-density mucins of pool IA and mucins from palatal salivary glands. Chemical analysis indicated that the putative palatal mucin was rich in sulphate, but poor in sialic acid. The lower-density mucins of pool IIA equated with the high-Mr mucins of submandibular-sublingual saliva, both immunochemically and physicochemically (buoyant density).

Comparative analysis of lysosomal hydrolases and natural glycoprotein substrates in the rat major salivary glands

1. The activities of some lysosomal hydrolases and the concentrations of their natural substrates were studied in the submandibular and sublingual glands of male and female rats using biochemical procedures. 2. In sublingual gland enzyme activities and substrate concentrations show the highest values. 3. The enzyme activities appear, in general, lower and the natural substrate concentrations higher in the females with respect to males. 4. In both glands beta-galactosidase shows the highest activity and beta-glucosidase the lowest. 5. These findings suggest that metabolic turnover of glycoproteins is slower in females than in males, probably because the oestrogens control the activity of lysosomal hydrolases.

Structure of two sulphated oligosaccharides from respiratory mucins of a patient suffering from cystic fibrosis. A fast-atom-bombardment m.s. and 1H-n.m.r. spectroscopic study

Human respiratory-mucin glycopeptides were isolated from the sputum of a patient suffering from cystic fibrosis. They were subjected to treatment with alkaline borohydride. Application of ion-exchange chromatography afforded carbohydrate fractions containing sulphate. One of these fractions containing a mixture of sulphated oligosaccharides was subsequently submitted to gel-filtration chromatography and h.p.l.c. Two sulphated oligosaccharide-alditols, A and B, were prepared; their structure was determined by means of 400 MHz 1H-n.m.r. spectroscopy and fast-atom-bombardment m.s. They had a core type 2 and the sulphate was 3-linked to a terminal galactose residue: (Formula; see text)

Enzymatic sulfation of mucus glycoprotein in rat submandibular salivary gland

1. The enzymic activity which catalyzes transfer of sulfate ester group from 3'-phosphoadenosine-5'-phosphosulfate to mucus glycoprotein was found associated with Golgi-rich membrane fraction of rat submandibular salivary gland. 2. Optimum enzyme activity was obtained with 0.5% Triton X-100, 4 mM MgCl2 and 25 mM NaF at a pH of 6.8 using desulfated submandibular salivary mucus glycoprotein. The apparent Km of the enzyme for mucus glycoprotein was 11.1 mg/ml. 3. Alkaline borohydride reductive cleavage of the synthesized 35S-labeled glycoprotein led to the liberation of the label into reduced oligosaccharides. A 75.4% of the label was found incorporated in four oligosaccharides. These were identified in order of abundance as sulfated penta-, tri-, hepta- and nonsaccharides. 4. Based on the results of chemical and enzymatic analyses of the intact and desulfated compounds the pentasaccharide was characterized as SO3H----GlcNAc beta----Gal beta----GlcNAc(NeuAc alpha----)GalNAc-ol and the trisaccharide as SO3H----GlcNAc beta----Gal beta----GalNAc-ol.

Sulfation in vitro of mucus glycoprotein by submandibular salivary gland: effects of prostaglandin and acetylsalicylic acid

Enzymatic sulfation of mucus glycoprotein by rat submandibular salivary gland and the effect of prostaglandin and acetylsalicylic acid on this process were investigated in vitro. The sulfotransferase enzyme which catalyzes the transfer of sulfate ester group from 3'-phosphoadenosine-5'-phosphosulfate to submandibular gland mucus glycoprotein has been located in the detergent extracts of Golgi-rich membrane fraction of the gland. Optimum enzyme activity was obtained at pH 6.8 with 0.5% Triton X-100, 25 mM NaF and 4 mM MgCl2, using the desulfated glycoprotein. The enzyme was also capable of sulfation of the intact mucus glycoprotein, but the acceptor capacity of such glycoprotein was 68% lower. The apparent Km of the submandibular gland sulfotransferase for salivary mucus glycoprotein was 11.1 microM. The 35S-labeled glycoprotein product of the enzyme reaction gave in CsCl density gradient a 35S-labeled peak which coincided with that of the glycoprotein. This glycoprotein upon reductive beta-elimination yielded several acidic 35S-labeled oligosaccharide alditols which accounted for 75% of the 35S-labeled glycoprotein label. Based on the analytical data, the two most abundant oligosaccharides were identified as sulfated tri- and pentasaccharides. The submandibular gland sulfotransferase activity was stimulated by 16,16-dimethyl prostaglandin E2 and inhibited by acetylsalicylic acid. The rate of enhancement of the glycoprotein sulfation was proportional to the concentration of prostaglandin up to 2.10(-5) M, at which point a 31% increase in sulfation was attained. The inhibition of the glycoprotein sulfation by acetylsalicylic acid was proportional to the drug concentration up to 2.5.10(-4) M at which concentration a 48% reduction in the sulfotransferase activity occurred. The apparent Ki value for sulfation of salivary mucus glycoprotein in presence of acetylsalicylic acid was 58.9 microM. The results suggest that prostaglandins may play a role in salivary mucin sulfation and that this process is sensitive to such nonsteroidal anti-inflammatory agents as acetylsalicylic acid.

Role of associated and covalently bound lipids in salivary mucin hydrophobicity: effect of proteolysis and disulfide bridge reduction

The hydrophobic properties of salivary mucus glycoprotein were investigated by fluorescence spectroscopy using bis(8-anilino-1-naphthalene-sulfonate). The mucin, purified from rat submandibular salivary gland, was subjected to removal of associated and covalently bound lipids, degradation with pronase, and reduction with beta-mercaptoethanol, and titrated with the probe. Analyses of fluorescence data revealed the presence of 49 +/- 5 hydrophobic binding sites in the intact mucin molecule, a 69% increase in the number of binding sites occurred following extraction of associated lipids, while the removal of covalently bound fatty acids caused a 25% decrease in the binding sites. Proteolytic destruction of the nonglycosylated regions of the glycoprotein essentially abolished the probe binding, whereas reduction produced glycoprotein subunits whose combined number of hydrophobic binding sites was 2.4 times greater than that of mucus glycoprotein polymer. The results suggest that associated and covalently bound lipids contribute to hydrophobic characteristics of salivary mucin and that the hydrophobic binding sites reside on the nonglycosylated regions of this glycoprotein buried within its core.

Enzymatic sulphation of mucus glycoprotein in rat sublingual salivary gland

Sulphotransferase activity catalysing the transfer of sulphate ester group from 3'-phosphoadenosine-5'-phosphosulphate to salivary mucus glycoprotein was located in detergent extracts of the Golgi-rich membrane fraction of rat sublingual salivary glands. Optimum enzyme activity was obtained with 0.5 per cent Triton X-100, 20 mM NaF and 2 mM MgCl2, at pH 6.8, using desulphated sublingual salivary mucus glycoprotein. The enzyme was equally capable of sulphation of the proteolytically degraded and desulphated glycoprotein, whereas the acceptor capacity of intact salivary mucus glycoprotein was about four times lower. The Golgi enzyme preparation also catalysed the sulphation of galactosylceramide. However, the sulphation of mucus glycoprotein was not affected by the presence of this glycolipid, suggesting that the sulphotransferase involved in mucin sulphation is different from that responsible for the synthesis of galactosylceramide sulphate. The apparent Km of the sublingual-gland mucus glycoprotein sulphotransferase for salivary mucin was 7.7 microM. The 35S-labelled glycoprotein product of the enzyme reaction gave, in CsCl density gradient, a band in which the 35S label coincided with the glycoprotein. Alkaline borohydride reductive cleavage of this glycoprotein released the label into the reduced acidic oligosaccharide fraction. Upon thin-layer chromatography, two [35S]-oligosaccharides were detected. These were identified as penta- and heptasaccharides, each bearing a labelled sulphate ester group on the terminal N-acetylglucosamine residue. Based on the results of chemical and enzymatic analyses of the intact and desulphated compounds the following structures for these oligosaccharides are suggested: SO3----GlcNAc beta----Gal beta----GlcNAc beta----Gal beta----GlcNAc beta----(NeuAc----)GalNAc-ol and SO3----GlcNAc beta----Gal beta----GlcNAc beta----(NeuAc----)GalNAc-ol.