1H and (13)C NMR spectroscopic analysis of human saliva

We have explored the ability of high-resolution NMR techniques to (1) index salivary biomolecules and (2) provide valuable data regarding intra- and inter-subject variability in the concentrations of a series of components readily determinable by this technique (organic acids and malodorous amines). Experiments were conducted on 'whole' saliva samples collected from 20 patients, either randomly during their daily activities, or, for investigations involving the quantification of salivary biomolecules, immediately after they woke in the morning throughout a three-day period. These NMR techniques permitted us to detect greater than 60 metabolites, together with agents arising from dietary, oral health care product, and pharmaceutical sources. Highly significant "between-subject" differences in the a.m. waking salivary metabolite concentrations were found for 9 out of 11 components monitored. It is concluded that NMR spectroscopy serves as a powerful technique for the multicomponent analysis of human saliva.

A multifactorial investigation of the ability of oral health care products (OHCPs) to alleviate oral malodour

AIM, BACKGROUND: Oral malodour (halitosis) is generally ascribable to oral microbial putrefaction generating malodorous volatile sulphur compounds which predominantly comprise dihydrogen sulphide and methyl mercaptan. This study assesses the relative effectiveness of 6 oral health care products in reducing oral cavity volatile sulphur compound concentrations.

METHOD

A mixed model 3-factor factorial experimental design involving 6 volunteers, 7 treatment regimens (products I-VI* and water placebo) and 5 time-points (0.00-5.29 h) was undertaken. Electron-donating volatile sulphur compound levels were determined in triplicate using a sulphide monitor (Interscan model 1170) both prior to (0.00 h) and following oral rinsing (20 ml of 5 of the products) or chewing (2 capsules of the remaining product) episodes with each product examined (0.29, 1.29, 2.29 and 5.29 h post-administration).

RESULTS

Results were recorded as peak and steady-state volatile sulphur compound equivalents (ppb). With the exception of one of the products, each oral health care product tested was found to reproducibly reduce volatile sulphur compound concentrations within 20 min of treatment; the mean % decreases in peak (and corresponding steady-state) levels ranging from 3.6 (0.0) to 16.8 (16.4)%. Subsequently, volatile sulphur compound concentrations returned to their zero-control (baseline) values within 5 h, the rate of this regression being in the reverse of the order observed for the magnitude of the primary 20 min reduction for both peak and steady-state measurements. As expected, the water placebo exerted no influence on oral cavity volatile sulphur compound levels. The most effective oral health care products contained admixtures of chlorite anion and chlorine dioxide (both of these agents have the ability to directly oxidise volatile sulphur compounds to non-malodorous products and the latter is also powerfully cidal towards odourigenic micro-organisms).

CONCLUSIONS

We therefore conclude that oral health care products containing such oxohalogen oxidants may provide a useful therapeutic strategy for the treatment of oral malodour.

1H-NMR analysis of microbial-derived organic acids in primary root carious lesions and saliva

In addition to lowered pH values, the molecular profile and concentrations of microbial-derived organic acids in carious dentin are important demineralization parameters involved in the induction, development and progression of dental caries. High-resolution proton ((1)H) NMR spectroscopy was employed to examine the organic acid status of primary root carious lesions. (1)H-NMR analysis of post-neutralized perchloric acid extracts of active carious lesions revealed that at an operating frequency of 600 MHz, the (1)H-NMR-detectable organic acid composition of carious dentin samples (mean molecular percentage content +/- standard error; the mean molecular percentage content is defined here as the mean of the concentration of each (1)H-NMR-visible organic acid/anion expressed as a percentage of total (1)H-NMR-detectable organic acid/anion level in each sample) was acetate 51 +/- 2%, formate 37 +/- 2%, lactate 5 +/- 1%, propionate 3 +/- 0.8%, pyruvate 2.4 +/- 0.3%, n-butyrate 1.2 +/- 0.2%; succinate 0.1 +/- 0.1%; iso-butyrate, n- and iso-valerate, and n- and iso-caproate (total) <0.2%. Further components detectable included alanine, glycine, choline, phosphorylcholine, trimethylamine oxide, methanol, glycolate and assorted saccharides. In view of their high dissociation constants (K(a)), our results demonstrate that formic and pyruvic acids (K(a) = 1.77 x 10(-4) and 3.20 x 10(-3) mol/dm(3), respectively) contribute substantially to the decreased pH values associated with active caries lesions (cf. lactate K(a) = 1.40 x 10(-4) mol/dm(3)), and hence the pathogenesis of primary root caries.

High resolution 1H NMR investigations of the reactivities of alpha-keto acid anions with hydrogen peroxide

The chemical reactivity of various alpha-keto acid anions (beta-hydroxypyruvate, beta-phenylpyruvate, 2-ketobutyrate and 2-ketoglutarate) with hydrogen peroxide (H2O2) was investigated at physiological pH (7.4) and a temperature of 25 degrees C. The initial concentration of the alpha-keto acid anions was kept constant at 1.00 mM whilst that of added H2O2 was varied from 0.25 to 1.00 mM, and the rate and extent of these reactions was evaluated using 1H NMR spectroscopy. At all H2O2 concentrations utilised, the order of reactivity of the alpha-keto acid anions was beta-hydroxypyruvate > beta-phenylpyruvate > 2-ketobutyrate > 2-ketoglutarate. The results obtained are in agreement with a proposed mechanism for these reactions, involving nucleophilic attack of the mono-deprotonated peroxide species (HO2-) at the C-2 carbonyl group carbon centre. The antioxidant capacity of such alpha-keto acids is discussed in terms of their potential use as therapeutic agents in clinical conditions where H2O2 has been shown to play a critical role in the disease process, i.e., those involving 'oxidative stress'.

Metabolism of glycoprotein-derived sialic acid and N-acetylglucosamine by Streptococcus oralis

Nine strains of Streptococcus oralis, isolated from blood cultures of patients with infective endocarditis or from the oral cavity as part of the normal flora, were examined for their ability to elaborate sialidase (neuraminidase) and N-acetylglucosaminidase, enzymes which are involved in the degradation of glycoproteins. Both glycosidases were induced when bacteria were grown in a minimal medium supplemented with porcine gastric mucin, a model glycoprotein, and repressed when growth occurred in the presence of glucose. Cell-free extracts mucin-grown cultures expressed elevated levels of N-acetylneuraminate pyruvate-lyase (the first intracellular enzyme in the pathway of N-acetylneuraminate catabolism), N-acetylglucosamine (glcNAc)-6-phosphate deacetylase and glucosamine-6-phosphate deaminase (enzymes involved in the intracellular catabolism of GlcNAc 6-phosphate); activity of each of these intracellular enzymes was markedly repressed when bacteria were grown in media supplemented with alpha 1-acid glycoprotein, a major component of human plasma. Cells from these cultures expressed high levels of sialidase, N-acetylglucosaminidase, and the intracellular enzymes involved in the catabolism of N-acetyl-sugars released by action of these glycosidases. High-resolution 1H-NMR spectroscopy of spent culture supernatants revealed that sialic acid and GlcNAc residues of the molecularly mobile oligosaccharide side-chains of alpha 1-acid glycoprotein had been hydrolysed and the released sugars internalized by the bacteria. These data indicate that S. oralis has the ability to hydrolyse constituents of oligosaccharide side-chains of host-derived glycoproteins and to utilize simultaneously these released carbohydrates. The biochemical characteristics induced by the growth of S. oralis on glycoproteins may play a role in the survival and persistence of these bacteria at the infection site in vivo.

Effect of mu, delta and kappa opioid receptor agonists on a reactive oxygen species mediated model of skin inflammation

Opioid agents have been shown to protect against tissue damage caused by hypoxia/reperfusion, an event which has a significant reactive-oxygen-species (ROS) involvement. We have investigated the potential anti-inflammatory activity of three opioid agonists, DAMGO, DPDPE and U50488 in rat skin inflammation induced by the ROS hydrogen peroxide. The model involves the intradermal injection of the enzyme glucose oxidase which converts glucose to D-gluconic acid and H2O2 which is locally released. Following injection, a well-delineated inflammatory response develops rapidly, is maximal at 5 h and still measurable after 48 h. Co-administration of the delta or kappa opioid agonist DPDPE or U50488 (7.5-60 micrograms per site) significantly reduced the inflammation, in a dose-dependent manner, for periods of up to 3 h for DPDPE, and up to 5 h with U50488. The mu-opioid agonist DAMGO (7.5-60 micrograms per site) was ineffective. Co-administration of the opioid antagonist naltrexone (120 micrograms) partially reversed the anti-inflammatory effects of DPDPE and U50488. We conclude that the delta and kappa opioid receptor agonists DPDPE and U50488 are able to inhibit ROS-induced skin inflammation and that this may have clinical implications.

Detection of aldehydes and their conjugated hydroperoxydiene precursors in thermally-stressed culinary oils and fats: investigations using high resolution proton NMR spectroscopy

High field (400 and 600 MHz) proton NMR spectroscopy has been employed to investigate the thermally-induced autoxidation of glycerol-bound polyunsaturated fatty acids present in intact culinary frying oils and fats. Heating of these materials at 180 degrees C for periods of 30, 60 and 90 min. generated a variety of peroxidation products, notably aldehydes (alkanals, trans-2-alkenals and alka-2,4-dienals) and their conjugated hydroperoxydiene precursors. Since such aldehydes appear to be absorbed into the systemic circulation from the gut in vivo, the toxicological significance of their production during standard frying practices is discussed.

Hypoxia, oxidative stress and rheumatoid arthritis

The synovial cavity has a negative pressure in health. When the joint is exercised, vascular patency is maintained, allowing for nutrition of the avascular cartilage. In rheumatoid synovitis, the situation is altered. The cavity pressure is raised and upon movement this pressure exceeds the capillary perfusion pressure, causing collapse of the blood vessels. This leads to the production of multiple episodes of 'hypoxic-reperfusion injury' generating reactive oxygen species (ROS). Such ROS oxidise: (a) IgG, inducing rheumatoid factor production (b) Hyaluronan, leading to hyaluronan fragmentation products which may alter immune function (c) Lipids, generating aldehydes which are toxic and may alter T cell/macrophage interactions (d) lipoproteins, leading to the production of monocyte chemotactic peptides Progressive hypoxia alters immune function, predominantly by calcium mediated pathways.

Degradation of hyaluronate by Streptococcus intermedius strain UNS 35

Streptococcus intermedius strain UNS 35, a brain abscess isolate, produced extracellular hyaluronidase when grown in brain heart infusion broth. Chemical assays with this enzyme indicated that hyaluronate depolymerisation resulted in the formation of carbohydrate moieties with N-acetylglucosamine at the reducing terminal and containing an unsaturated carbon-carbon double bond. The nature of the products of this hyaluronidase were investigated further by high-field (400 MHz) proton (1H) NMR spectroscopy. Treatment of hyaluronate with the enzyme resulted in a series of new, sharp resonances in spectra (acetamido methyl group singlets located at 2.03 and 2.07 ppm, sugar ring proton multiplets in the 3.5-4.2 ppm chemical shift range, and doublets at 5.16 and 5.87 ppm) characteristic of low-M(r) oligosaccharide species, predominantly those containing glucuronosyl residues with delta 4,5-carbon-carbon double bonds. Comparison of spectra acquired from hyaluronidase-treated samples with that of an authentic sample of 4-deoxy-L-threo-hex-4-enopyranosyluronic-acid-N-acetylglucosamine (delta UA GlcNAc) indicated that this disaccharide was a major product arising from the actions of this enzyme. When used in minimal media, hyaluronate supported growth of S. intermedius, with lactate as the major metabolic end-product.

Generation of lipid peroxidation products in culinary oils and fats during episodes of thermal stressing: a high field 1H NMR study

The oxidative deterioration of glycerol-bound polyunsaturated fatty acids (PUFAs) in culinary oils and fats during episodes of heating associated with normal usage (30-90 min at 180 degrees C) has been monitored by high field 1H NMR spectroscopy. Thermal stressing of PUFA-rich culinary oils generated high levels of n-alkanals, trans-2-alkenals, alka-2,4-dienals and 4-hydroxy-trans-2-alkenals via decomposition of their conjugated hydroperoxydiene precursors, whereas only low concentrations of selected aldehydes were produced in oils with a low PUFA content, lard and dripping when subjected to the above heating episodes. Samples of repeatedly used, PUFA-rich culinary oils obtained from restaurants also contained high levels of each class of aldehyde. The dietary, physiological and toxicological ramifications of the results obtained are discussed.

High field proton NMR investigations of the metabolic profiles of multidrug-sensitive and -resistant leukaemic cell lines: evidence for diminished taurine levels in multidrug-resistant cells

High field proton (1H) nuclear magnetic resonance (NMR) spectroscopy has for the first time been employed to investigate and compare the metabolic profiles of vinblastine-sensitive and -resistant T-lymphoid leukaemic cell lines (CCRF-CEM and CEM/VLB100 respectively) and evidence is presented for a significantly lower taurine content in the CEM/VLB100 resistant subline when expressed relative to that of its drug-sensitive parental counterpart. These data suggest differences in the nature and relative involvements of taurine biosynthetic pathways between the two cell lines, a phenomenon that may be related to their differing sensitivities towards chemotherapeutic agents such as adriamycin which promote the generation of cytotoxic reactive oxygen species (ROS) in vivo. However, the 1H NMR data obtained provided no evidence for an increased metabolic consumption of hypotaurine (a metabolic precursor of taurine with powerful .OH radical scavenging properties) in CCRF-CEM cells since differences observed in the hypotaurine: taurine concentration ratio between the drug-sensitive and -resistant cell lines were not statistically significant. Furthermore, hypotaurine is unlikely to compete with alternative endogenous .OH radical scavengers present such as lactate since its level in either of the two cell lines investigated (ca. 6.0 x 10(-8) mol./10(8) cells) is insufficient for it to act as an antioxidant in this context. The biochemical and therapeutic significance of these results are discussed.

Application of methionine as a detector molecule for the assessment of oxygen radical generation by human neutrophils and endothelial cells

Diverse cell types can generate reactive oxygen species (ROS) which are implicated in many disease processes and are ascribed both beneficial and deleterious roles. In vitro studies of this phenomenon indicate that properties of the microenvironment in culture influence the cells' behaviour with regard to ROS generation in vivo. To date, however, the assessment of cellular ROS generation has been limited to techniques which are invasive of the culture environment, or require cells to be in suspension. This study describes the application of NMR spectroscopy to the detection of ROS generation, a technique which is non-invasive of the cell culturing environment.

Reactions of triethylphosphine gold(I) complexes with heme proteins: novel spin-state changes in cytochrome b562, myoglobin, and hemoglobin

Reactions of bacterial Fe(III) cyt b562, HbO2, met Hb and met Mb with Et3PAuCl and Et3PAuNO3 (and some related complexes) have been investigated by electronic absorption and EPR and NMR spectroscopy. Except for met Hb, which denatured, the products were novel high-spin Fe(III) heme proteins. The reactions of cyt b562 and Mb were reversible. Two distinct kinetic steps were observed in the autoxidation of HbO2 and MbO2. These may involve the liberation of superoxide. Autoxidation of HbO2 occurred more rapidly than that of MbO2. The kinetics of the spin-state change of cyt b562 were too fast to measure by conventional (spectrophotometric) methods. The reaction of Et3PAuCl with HbO2 was not blocked by N-ethylmaleimide. The reactions are discussed in terms of attack by Et3PAu+ on histidine residues in the hydrophobic haem pockets of the proteins.

1H, 13C NMR, and electronic absorption spectroscopic studies of the interaction of cyanide with aurothiomalate

The reaction between cyanide and aurothiomalate (Autm) has been studied by 1H and 13C NMR spectroscopy and by uv spectroscopy. At cyanide:Autm ratios greater than or equal to 2, aurocyanide, [Au(CN)2]-, is the sole product but was also produced at lower ratios. Two intermediates were also identified. These were a mixed ligand complex, [tmAuCN]-, which accounted for over 80% of the gold at a ratio of cyanide to Autm of 1, and a bisthiomalato complex, [Autm2]-, which accounted for 6.8% of the total gold at this ratio of cyanide to Autm. The formation of these complexes may be significant in the antiarthritic activity of Autm since cyanide is produced by potential target cells such as polymorphonuclear leukocytes.

Progress in the characterization of gold drugs

As used clinically, Myocrisin appears to contain largely polymeric (Autm)n, in which thiomalate (tm) sulphurs bridge between Au(I) ions, together with small amounts of a more reactive gold-bound thiomalate, and free thiomalate, as well as glycerol, unidentified yellow-products from autoclaving and phenylmercury adducts. Solganal usually contains thioglucose sulphinic acid as an impurity. Auranofin, on the other hand, has been crystallised. It is monomeric and Au(I) is almost linearly coordinated by P and S from triethylphosphine and tetraacetyl-beta-D-thioglucose, the latter adopting the chair conformation in the solid state and in solution. The major reaction of auranofin in acidic aqueous solutions appears to be hydrolysis of the sugar acetyl groups but other products arise if methanol is also present in the medium. NMR methods are used to examine in vitro the partition of auranofin between plasma and blood cells. The displacement of the thioglucose ligand and release of PEt3 from gold as OPEt3 are discussed.