Dimethyl sulfoxide inhibits killing of Staphylococcus aureus by polymorphonuclear leukocytes

Radical Scavenging Capacity and In Vitro Cytoprotective Effects of Great Salt Lake-Derived Processed Mineral Water

The Great Salt Lake, located in Utah, USA, is a saltwater lake with no outlet and is surrounded by vast mountains and salt deserts. We aimed to use Great Salt Lake-derived processed mineral water (hereafter termed as GSL-MW) for maintaining oral health. Therefore, we examined its radical scavenging activity as an antioxidant and its cytoprotective effect on human gingival fibroblasts (hGFs). The scavenging activity against O2•- radicals was determined by an electron spin resonance (ESR)-spin trapping technique using two kinds of O2•- generation systems; however, we could not reach any concrete conclusion because of the interference caused by GSL-MW in both systems. Detection of ·OH radicals using the ESR-spin trapping technique and kinetic analyses using double-reciprocal plots (corresponding to Lineweaver-Burk plots that are used to represent enzyme kinetics) revealed that GSL-MW has the ability to scavenge ·OH radicals. GSL-MW also showed a weak 2,2-diphenyl-1-picrylhydrazyl (DPPH; a stable radical)-scavenging activity. Regarding the cytoprotective effects, subconfluent hGFs pretreated with 10× and 100× dilutions of GSL-MW for 3 min and then exposed to harsh environmental conditions, such as pure water or 100 μM H2O2 for 3 min, showed enhanced cell viability rate. Moreover, 10× and 100× dilutions of GSL-MW reduced oxidative damage in confluent hGFs exposed to 12.5 and 25 mM H2O2. Our findings show that GSL-MW has antioxidant potential and cytoprotective effects on hGFs, suggesting that GSL-MW can be used to maintain oral health.

A Comprehensive Protocol for the Collection, Differentiation, Cryopreservation, and Resuscitation of Primary Murine Bone Marrow Derived Macrophages (BMDM)

BACKGROUND

The field of immunology has undoubtedly benefited from the in vitro use of cell lines for immunological studies; however, due to the "immortal" nature of many cell lines, they are not always the best model. Thus, direct collection and culture of primary cells from model organisms is a solution that many researchers utilize. To the best of our knowledge, there is not a singular protocol which encompasses the entire process of bone marrow cell collection through cryopreservation and resuscitation of cells from a murine model.

METHODS

Bone marrow cells were collected from mice with a C57BL6 genetic background. Cells were differentiated using L929 conditioned media. Cells were assessed using a combination of microscopy, differential staining, immunocytochemistry, and trypan blue. Results: Primary murine BMDMs that underwent cryopreservation followed by resuscitation retained a high degree of viability. Furthermore, these BMDMs retained on overall ability to clear S. aureus.

RESULTS

Primary murine BMDMs that underwent cryopreservation followed by resuscitation retained a high degree of viability. Furthermore, these BMDMs retained on overall ability to clear S. aureus.

CONCLUSION

Crypopreserved and resuscitated primary murine BMDMs were viable and retained their pverall S. aureus clearance ability.

Abiotic methanogenesis from organosulphur compounds under ambient conditions

Methane in the environment is produced by both biotic and abiotic processes. Biomethanation involves the formation of methane by microbes that live in oxygen-free environments. Abiotic methane formation proceeds under conditions at elevated temperature and/or pressure. Here we present a chemical reaction that readily forms methane from organosulphur compounds under highly oxidative conditions at ambient atmospheric pressure and temperature. When using iron(II/III), hydrogen peroxide and ascorbic acid as reagents, S-methyl groups of organosulphur compounds are efficiently converted into methane. In a first step, methyl sulphides are oxidized to the corresponding sulphoxides. In the next step, demethylation of the sulphoxide via homolytic bond cleavage leads to methyl radical formation and finally to methane in high yields. Because sulphoxidation of methyl sulphides is ubiquitous in the environment, this novel chemical route might mimic methane formation in living aerobic organisms.

A simple method to study the activity of natural compounds on the chemiluminescence of neutrophils upon stimulation by immune complexes

INTRODUCTION

Neutrophils (PMNs) are the main effector cells involved in the immune response to microorganisms. However, in various noninfectious states, such as autoimmune and immune complex (ICs) diseases, ICs are found to be deposited in various organs, leading to recruitment and activation of PMNs at these sites of deposition. Consequently, reactive oxygen species (ROS) and lysosomal enzymes are extensively released by activated PMNs into the extracellular milieu, leading to host tissue injury.

METHODS

In the present study, we discuss some experimental conditions of a luminol-enhanced chemiluminescence (LECL) assay to study the effect of natural compounds on the production of ROS by rabbit PMNs stimulated with precipitated ICs. Moreover, we evaluated the activities of quercetin and 7-allyloxycoumarin on this ROS-producing system and their toxicity to PMNs.

RESULTS

Both compounds had concentration-dependent inhibitory effects on LECL. Quercetin at concentration of 5 micromol/l inhibited 94.5+/-1.0% of LECL, whereas 7-allyloxycoumarin at concentration of 200 micromol/l inhibited 53.8+/-2.4% of LECL. Neither compound was toxic to PMNs under the tested conditions.

DISCUSSION

The proposed method may be useful for the screening of nontoxic compounds that can modulate ROS production by IC-stimulated PMNs. Special attention should be devoted to natural compounds from higher plants, since their potential as sources of new drugs is still largely unexplored.

Ethanol-induced injury to the rat gastric mucosa. Role of neutrophils and xanthine oxidase-derived radicals

Ethanol-induced gastric mucosal injury closely resembles an inflammatory response. Thus, in vivo and in vitro experimental models were used to assess whether ethanol is proinflammatory in concentrations likely to be encountered by the gastric mucosa during acute intoxication. Perfusing the rat gastric lumen with progressively increasing concentrations of ethanol (10%, 20%, and 30%) resulted in a dose-dependent increase in 51Cr-ethylenediaminetetraacetic acid clearance from blood-to-gastric lumen. Rendering the animals neutropenic (with antineutrophil serum) ameliorated the ethanol-induced mucosal injury; the degree of protection was directly related to the severity of neutropenia. Neither superoxide dismutase, catalase, nor sodium benzoate offered any protection against ethanol-induced injury, indicating that neither superoxide anion, hydrogen peroxide, nor the hydroxyl radical is involved. To assess further whether ethanol could exert proinflammatory effects an in vitro model consisting of cultured bovine microvascular endothelial cells and isolated human neutrophils was used. Ethanol at concentrations of 1.0%-4.0% (but not at 0.1%-0.5%) increased neutrophil adherence to endothelial cells and enhanced neutrophil-mediated endothelial cell injury. We conclude that ethanol is proinflammatory at concentrations that may be achieved in the gastric mucosa during acute intoxication. The ethanol-induced, neutrophil-mediated cell injury does not appear to involve oxy radicals.

Thiourea and dimethylthiourea decrease human neutrophil bactericidal function in vitro

Addition of thiourea (TU) or dimethylthiourea (DMTU) decreased killing of Staphylococcus aureus, 502A, and decreased concentrations of hydrogen peroxide (H2O2), and hydroxyl radical (.OH), but not superoxide anion (O2-.) or lysozyme concentrations, in mixtures containing human neutrophils in vitro. Addition of TU or DMTU also decreased concentrations of H2O2, .OH, or hypochlorous acid (HOCl) in neutrophil-free mixtures exposed to beta-D-glucose and glucose oxidase, gamma irradiation, or HOCl, respectively. Our results suggest that TU or DMTU can decrease neutrophil-mediated killing of bacteria by inhibiting O2 metabolite-dependent bactericidal mechanisms.

Neutrophil-mediated injury to endothelial cells. Enhancement by endotoxin and essential role of neutrophil elastase

The neutrophil has been implicated as an important mediator of vascular injury, especially after endotoxemia. This study examines neutrophil-mediated injury to human microvascular endothelial cells in vitro. We found that neutrophils stimulated by formyl-methionyl-leucyl-phenylalanine (FMLP), the complement fragment C5a, or lipopolysaccharide (LPS) (1-1,000 ng/ml) alone produced minimal endothelial injury over a 4-h assay. In contrast, neutrophils incubated with endothelial cells in the presence of low concentrations of LPS (1-10 ng/ml) could then be stimulated by FMLP or C5a to produce marked endothelial injury. Injury was maximal at concentrations of 100 ng/ml LPS and 10(-7) M FMLP. Pretreatment of neutrophils with LPS resulted in a similar degree of injury, suggesting that LPS effects were largely on the neutrophil. Endothelial cell injury produced by LPS-exposed, FMLP-stimulated neutrophils had a time course similar to that induced by the addition of purified human neutrophil elastase, and different from that induced by hydrogen peroxide (H2O2). Further, neutrophil-mediated injury was not inhibited by scavengers of a variety of oxygen radical species, and occurred with neutrophils from a patient with chronic granulomatous disease, which produced no H2O2. In contrast, the specific serine elastase inhibitor methoxy-succinyl-alanyl-alanyl-prolyl-valyl-chloromethyl ketone inhibited 63% of the neutrophil-mediated injury and 64% of the neutrophil elastase-induced injury. However, neutrophil-mediated injury was not inhibited significantly by 50% serum, 50% plasma, or purified alpha 1 proteinase inhibitor. These results suggest that, in this system, chemotactic factor-stimulated human neutrophil injury of microvascular endothelial cells is enhanced by small amounts of LPS and may be mediated in large part by the action of neutrophil elastase.

Effect of dimethyl sulfoxide on the in vitro and in vivo bactericidal activity of human and mouse neutrophils and mononuclear phagocytes

Dimethyl sulfoxide (DMSO) is reported to have antiinflammatory activity in various systems. Since resistance to bacterial infection can be thought of as a specialized type of inflammation, we were interested in determining the effect of DMSO on phagocyte bactericidal activity. The results indicated that in vitro DMSO treatment of human and mouse neutrophils and mononuclear phagocytes caused a dose-dependent inhibition of the killing of Escherichia coli and Listeria monocytogenes. However, pretreatment of mice with DMSO in vivo caused only a slight decrease in the subsequent in vitro bactericidal activity of neutrophils and macrophages from those mice. In addition, repeated injection of mice with a physiologically relevant dosage of DMSO did not enhance the lethality of either E. coli or L. monocytogenes, nor did it affect the clearance of a sublethal Listeria challenge from the spleen and liver. These results suggest that clinical usage of DMSO should not predispose human subjects to bacterial infection.

Nonoxidative antimicrobial reactions of leukocytes

Increasingly abundant evidence supports the hypothesis that PMNs and perhaps alveolar macrophages have antimicrobial mechanisms independent of the presences of molecular oxygen for effective action against an array of bacteria and against some fungi. Eosinophils have mechanisms toxic for schistosomula and Trichinella larvae. In all instances the antimicrobial substances isolated have been cationic proteins and, in PMNs, associated with the azurophil cytoplasmic granules of the PMNs. Several of these substances have thus far demonstrated no enzymic function. Two of these substances are serine proteases but in one, chymotrypsin-like protein, the antimicrobial action depends on the cationic properties of the protein and is independent of the proteolytic action of the substance. In most instances, these proteins are cationic due to relatively large proportions of arginine. In two instances, a large proportion of lysine is present. All have high proportions (about 50%) of hydrophobic amino acid. Such proteins occur in the PMNs of man, rabbit, guinea pig, rat, cow, and chicken. The present view is that they are most active against gram-negative bacteria. At least two of them-37-kd and 57-kd proteins (Shafer and Spitznagel, 1983)-act on S. typhimurium in a manner analogous to that of polymyxin B through binding to lipid A. Currently available results shows that anaerobic PMNs have substantial antimicrobial capacity. Whether this capacity is due to the O2-independent mechanisms discussed in this chapter remains to be established with greater certainty.

Dimethyl sulfoxide inhibits phagocyte influx into infected pleural spaces and phagocyte locomotion in vitro

Influx of polymorphonuclear leukocytes (PMNs) and monocytes (MNs) into pleural spaces was decreased in dimethyl sulfoxide (DMSO)-treated rabbits infected intrapleurally with Staphylococcus aureus. In addition, pleural fluids contained S. aureus longer and marked pleural thickening with fibrosis occurred in DMSO-treated rabbits. DMSO also inhibited stimulated locomotion of PMN and MN in vitro, suggesting that the aforementioned responses in vivo may have occurred because of DMSO-mediated inhibition of the locomotion of PMN and MN.

Outer membrane mutants of Salmonella typhimurium LT2 have lipopolysaccharide-dependent resistance to the bactericidal activity of anaerobic human neutrophils

The capacity of neutrophil polymorphonuclear granulocytes (PMNs) to phagocytize bacteria under anaerobic as well as aerobic conditions afforded the opportunity to compare the bactericidal activities of oxygen-independent and oxygen-dependent antimicrobial mechanisms in human PMNs challenged with Salmonella typhimurium LT2 and its lipopolysaccharide mutants (outer membrane mutants). Anaerobic human PMNs challenged with either opsonized LT2 or serum-treated zymosan failed to produce detectable superoxide anion (O2-) or to reduce nitroblue tetrazolium, although aerobic PMNs readily produced O2- in response to such challenge. Anaerobic PMNs killed these bacteria in an ordered fashion that appeared to be dependent on their lipopolysaccharide chemotype. As the carbohydrate content of the mutant lipopolysaccharide decreased, the bacteria became less resistant to the oxygen-independent bactericidal activity. The results resembled the ordered resistance to oxygen-independent killing observed with LT2 and its mutants in PMN-free systems with PMN granule proteins. Studies on the kinetics of killing showed these to be less rapid in anaerobic as compared with aerobic conditions. Opsonization increased the rate of phagocytosis, but such factors as opsonization and the rate of phagocytosis did not appear to affect intraleukocytic bactericidal capacity in that the resultant proportion of bacteria remaining viable after ingestion was similar regardless of which serum was used (normal serum, C6-deficient serum, C8-deficient serum, or no serum at all). The results are consistent with an active and substantial participation by oxygen-independent systems in the antimicrobial effects of neutrophils.