Inhibition Of Lysozyme Activity Research Articles

Effects of preservatives on the activities of salivary enzymes

ObjectivesTo investigate the effects of common preservatives used in oral health care products on the enzymatic activities of lysozyme, peroxidase, and α-amylase in-solution and on-hydroxyapatite surface phases. DesignThe preservatives used in this study were sodium benzoate, methylparaben, propylparaben, and benzalkonium chloride. Hen egg-white lysozyme, bovine lactoperoxidase, and α-amylase from Bacillus sp. served as sources of purified enzymes. Human unstimulated whole saliva was used as a source of salivary enzymes. Hydroxyapatite beads were used as the surface phase. The preservatives were incubated with purified enzymes or saliva samples in-solution or on-hydroxyapatite surface phases, respectively. Enzymatic activities of lysozyme, peroxidase, and α-amylase were measured by hydrolysis of fluorescein-labelled Micrococcus lysodeikticus, oxidation of fluorogenic 2′,7′-dichlorofluorescin, and hydrolysis of fluorogenic starch, respectively. ResultsThe effects of the preservatives on the enzymatic activities of lysozyme and peroxidase were more distinct in the saliva samples than purified substances, and in the in-solution phase than on-hydroxyapatite surface phase, and the opposite was true for α-amylase. The most significant result was apparent decrease in peroxidase activities caused by the parabens in the in-solution phase (P<0.05). Sodium benzoate and parabens inhibited lysozyme activity in the in-solution phase, but differently for the purified and salivary lysozymes. Parabens and benzalkonium chloride inhibited the enzymatic activity of α-amylase from Bacillus sp., not saliva samples, only on-hydroxyapatite surface (P<0.05). ConclusionsEach preservative affected the enzymatic activities of lysozyme, peroxidase, and α-amylase differently. Based on the effects on salivary enzymes, sodium benzoate or benzalkonium chloride was recommended as preservatives rather than parabens.

Structural alterations and inhibition of lysozyme activity upon binding interaction with rotenone: Insights from spectroscopic investigations and molecular dynamics simulation

The pervasive employment of pesticides such as rotenone on a global scale represents a substantial hazard to human health through direct exposure. Therefore, exploring the interactions between such compounds and body macromolecules such as proteins is crucial in comprehending the underlying mechanisms of their detrimental effects. The present study aims to delve into the molecular interaction between rotenone and lysozyme by employing spectroscopic techniques along with Molecular dynamics (MD) simulation in mimicked physiological conditions. The binding interaction resulted in a fluorescence quenching characterized by both dynamic and static mechanisms, with static quenching playing a prominent role in governing this phenomenon. The analysis of thermodynamic parameters indicated that hydrophobic interactions primarily governed the spontaneous bonding process. FT-IR and circular dichroism findings revealed structural alternations of lysozyme upon complexation with rotenone. Also, complexation with rotenone declined the biological activity of lysozyme, thus rotenone could be considered an enzyme inhibitor. Further, the binding interaction substantially decreased the thermal stability of lysozyme. Molecular docking studies showed the binding location and the key residues interacting with rotenone. The findings of the spectroscopic investigations were confirmed and accurately supported by MD simulation studies.

Functional homology of tachykinin signalling: The influence of human substance P on the immune system of the mealworm beetle, Tenebrio molitor L.

Tachykinin-related peptides (TRPs) are one of the most prominent families of neuropeptides in the animal kingdom. Insect TRPs display strong structural and functional homology to vertebrate tachykinins (TKs). To study functional homologies between these two neuropeptide families, the influence of human substance P (SP, one of the essential vertebrate TKs) on the immune system of the mealworm beetle, Tenebrio molitor L., was analysed.Human SP influences the phagocytic abilities of T. molitor haemocytes. Peptide injection leads to an increase in the number of haemocytes participating in the phagocytosis of latex beads. In contrast, incubation of haemocytes from non-injected beetles in a solution of physiological saline and SP causes a decrease in phagocytic activity. Treatment with human SP also led to increased adhesion of haemocytes, but no changes in the arrangement of the F-actin cytoskeleton were observed. Interestingly, 6 h after human SP injection, increased DNA integrity in T. molitor haemocytes was reported. The opposite effects were observed 24 h after SP injection.Human SP caused the upregulation of humoral immune responses, such as phenoloxidase (PO) activity in the T. molitor haemolymph, and the downregulation of immune-related genes encoding coleoptericin A, tenecin 3 and Toll receptor. However, genes encoding attacin 2 and cecropin were upregulated. Despite these differences, the antimicrobial activity of T. molitor haemolymph was significantly lower in beetles injected with SP than in control beetles. Moreover, an analysis of the direct influence of SP on lysozyme activity was performed. Our results suggest that SP at a concentration of 10−6 M can directly inhibit lysozyme activity. However, an opposite effect was reported after the application of SP at a concentration of 10−4 M.The presented results suggest structural and functional homology between TK signalling in vertebrates and insects. Primarily, this was visible in the context of the humoral response and general antimicrobial activity of T. molitor haemolymph. However, some of the results related to haemocyte function may also indicate the importance of the TK and TRP sequences for evoking immunological effects.

Extraction and Characterization of Lysozyme from Salted Duck Egg White.

Salted duck egg white (SDEW), as the main by-product in the production process of salted egg yolk, has not been effectively used as a food resource because of its high salt concentration. This study creatively used isoelectric point precipitation, ultrafiltration, and cation exchange to separate and purify lysozyme from SDEW and preliminarily explored the enzymatic properties of lysozyme. The results showed that the relative molecular weight of lysozyme was about 14 KDa, and the specific activity of lysozyme reached 18,300 U/mg. Lysozyme had good stability in the temperature range of 30 °C to 60 °C and pH of 4 to 7. Metal ions, Fe2+, Cu2+, and Zn2+, strongly inhibited lysozyme activity. Different surfactants showed certain inhibition effects on lysozyme from SDEW, among which glycerin had the strongest inhibitory effect. This study aimed to provide a theoretical reference for industrial purification and production of lysozyme from SDEW.

Effects of heavy metals and albumin on lysozyme activity

Lysozyme is an antibacterial enzyme that is found in most of body fluids. Lysozyme in tears plays a primary role in protecting eye from harmful environments; if lysozyme is degraded or inhibited, eyes are likely to be more vulnerable to bacterial infection. In this study, lysozyme activity was evaluated according to varying concentrations of heavy metals, copper, zinc, cobalt and manganese and light metal, calcium that are frequently found in airborne particulate matters and was assayed using a dyequenching lysozyme substrate, Micrococcus lysodeikticus. Less fluorescence intensity was observed with increasing amounts of copper, zinc, manganese and cobalt but not with calcium suggesting that these metals have some affinity with lysozyme and inhibit lysozyme activity. When albumin, the second most common protein in tears, was added on the reaction of lysozyme and metals, lysozyme activity was partially restored. This finding suggests that the albumin might protect damage caused by metals on lysozyme. To identify whether the decrease in enzymatic activity was related to structural changes of lysozyme, SDS-PAGE was conducted and only with copper did lysozyme show marked smearing bands on the SDS-gel, meaning that copper degraded lysozyme consistent with the sharpest activity decrease.

Autophagy counters LPS-mediated suppression of lysozyme.

Impaired Paneth cell expression of antimicrobial protein (AMP) lysozyme is found in patients with Crohn's disease with the autophagy gene ATG16L1 risk allele, in mice with mutations in autophagy genes Atg16L1, Atg5 and Atg7, and in Irgm1 knockout mice. Defective autophagy is also associated with expansion of resident Gram-negative bacteria in the intestinal lumen. These findings suggest that autophagy may control extracellular resident microbes by governing expression of lysozyme. To test the hypothesis that autophagy may have a defensive role in host response to resident extracellular microbes, we investigated the relationship between gut microbes, autophagy, and lysozyme. RAW 264.7 macrophages were treated with fecal slurry (FS), representing the resident microbial community; lipopolysaccharide (LPS); or butyrate, representing microbial products; or a representative resident Gram-negative bacterium Desulfovibrio vulgaris (DSV). FS, LPS, and DSV inhibited lysozyme expression, whereas butyrate had no effect. Induction of autophagy by rapamycin countered this inhibition, whereas silencing of the autophagy gene Irgm1 exacerbated the inhibitory effects of LPS on lysozyme expression. LPS also inhibited lysozyme activity against DSV and autophagy reversed this effect. Our results provide a novel insight into an interaction between gut bacteria, autophagy and AMP whereby autophagy may defend the host by countering the suppression of antimicrobial protein by Gram-negative bacteria.

Structure of the Neisseria Adhesin Complex Protein (ACP) and its role as a novel lysozyme inhibitor.

Pathogenic and commensal Neisseria species produce an Adhesin Complex Protein, which was first characterised in Neisseria meningitidis (Nm) as a novel surface-exposed adhesin with vaccine potential. In the current study, the crystal structure of a recombinant (r)Nm-ACP Type I protein was determined to 1.4 Å resolution: the fold resembles an eight-stranded β-barrel, stabilized by a disulphide bond between the first (Cys38) and last (Cys121) β-strands. There are few main-chain hydrogen bonds linking β4-β5 and β8-β1, so the structure divides into two four-stranded anti-parallel β-sheets (β1-β4 and β5-β8). The computed surface electrostatic charge distribution showed that the β1-β4 sheet face is predominantly basic, whereas the β5-β8 sheet is apolar, apart from the loop between β4 and β5. Concentrations of rNm-ACP and rNeisseria gonorrhoeae-ACP proteins ≥0.25 μg/ml significantly inhibited by ~80–100% (P<0.05) the in vitro activity of human lysozyme (HL) over 24 h. Specificity was demonstrated by the ability of murine anti-Neisseria ACP sera to block ACP inhibition and restore HL activity. ACP expression conferred tolerance to HL activity, as demonstrated by significant 3–9 fold reductions (P<0.05) in the growth of meningococcal and gonococcal acp gene knock-out mutants in the presence of lysozyme. In addition, wild-type Neisseria lactamica treated with purified ACP-specific rabbit IgG antibodies showed similar fold reductions in bacterial growth, compared with untreated bacteria (P<0.05). Nm-ACPI is structurally similar to the MliC/PliC protein family of lysozyme inhibitors. However, Neisseria ACP proteins show <20% primary sequence similarity with these inhibitors and do not share any conserved MliC/PliC sequence motifs associated with lysozyme recognition. These observations suggest that Neisseria ACP adopts a different mode of lysozyme inhibition and that the ability of ACP to inhibit lysozyme activity could be important for host colonization by both pathogenic and commensal Neisseria organisms. Thus, ACP represents a dual target for developing Neisseria vaccines and drugs to inhibit host-pathogen interactions.

Influence of graphene oxide and reduced graphene oxide on the activity and conformation of lysozyme

The dramatically different bio-effects of graphene and graphene oxide (GO) have been widely observed in diverse biological systems, which determine the applications and toxicity of graphene materials. To elucidate the mechanism at molecular level, it is urgent to investigate the enzyme-graphene interaction and its consequences. In this study, we comparatively studied the influence of GO and reduced GO (RGO) on the activity and conformation of lysozyme to provide better understandings of their different bio-effects. Both GO and RGO adsorbed large quantities of lysozyme after incubation. GO inhibited lysozyme activity seriously, while RGO nearly had no influence on the enzyme activity. The different inhibitions of enzyme activity could be explained by the lysozyme conformational changes, where GO induced more changes to the protein conformation according to UV–vis absorbance, far-UV circular dichroism spectra, intrinsic fluorescence quenching, and infrared spectra. Based on the spectroscopic changes of lysozyme, GO induced the loss of secondary structure and exposed the active site of lysozyme more to the aqueous environment. In addition, neither GO nor RGO induced the fibrillation of lysozyme after 12d incubation. The results collectively indicated that the oxidation degree significantly impacted the enzyme-graphene interaction. The implications to the designs of enzyme-graphene system for bio-related applications and the toxicological effects of graphene materials are discussed.

Probing the toxic mechanism of Ag+ with lysozyme

Silver (Ag) is widely used in human activities, which provides possibilities to distribute in organisms and tissues, resulting in harmful effects on human health. In this work, lysozyme was chosen as the target molecule to study the mechanism of toxic interactions between Ag+ and protein using fluorescence emission spectra, synchronous fluorescence spectra, UV–vis absorption spectra, circular dichroism (CD) spectra, isothermal titration calorimetry (ITC), and enzyme activity assay. The results of fluorescence emission and synchronous fluorescence showed that there were interactions between Ag+ and lysozyme by eliminating the inner filter effect (IFE). Data from UV–vis spectra indicated that the frame structure of lysozyme became looser with Ag+ existent, while the micro-environment of aromatic amino acid residues did not show any significant alteration. CD results suggested that the secondary structure of lysozyme presented a decrease in α-helix contents with the increasing amount of Ag+. ITC results showed Ag+ can spontaneously bind with lysozyme through hydrogen bonding and van der Waals forces with one binding site (Ka=1.93×106). The lysozyme activity was inhibited by Ag+ according to the enzyme activity assay, revealing that Ag+ bound to lysozyme at the active site which resulted in inhibition of lysozyme activity. This work showed that Ag+ can cause damages to the structure and function of lysozyme.

The trenbolone acetate affects the immune system in rainbow trout, Oncorhynchus mykiss

In aquatic systems, the presence of endocrine-disrupting chemicals (EDC) can disrupt the reproductive function but also the immune system of wildlife. Some studies have investigated the effects of androgens on the fish immune parameters but the mechanisms by which the xenoandrogens alter the immunity are not well characterized. In order to test the effects of trenbolone acetate (TbA) on fish immune system, we exposed rainbow trout male juveniles during three weeks to TbA levels at 0.1 and 1μg/L. The present results suggest that TbA impacts, in a tissue-dependent manner, the rainbow trout immunity by affecting primarily the humoral immunity. Indeed, TbA inhibited lysozyme activity in plasma and liver and enhanced the alternative complement pathway activity (ACH50) in kidney. In plasma, the modulation of the complement system was time-dependent. The mRNA expression of genes encoding some cytokines such as renal TGF-β1, TNF-α in skin and hepatic IL-1β was also altered in fish exposed to TbA. Regarding the cellular immunity, no effect was observed on the leucocyte population. However, the expression of genes involved in the development and maturation of lymphoid cells (RAG-1 and RAG-2) was decreased in TbA-treated fish. Among those effects, we suggest that the modulation of RAG-1 and mucus apolipoprotein-A1 gene expression as well as plasma and hepatic lysozyme activities are mediated through the action of the androgen receptor. All combined, we conclude that trenbolone affects the rainbow trout immunity.

Immunological and histopathological responses of the kidney of common carp (Cyprinus carpio L.) sublethally exposed to glyphosate

Glyphosate is a broad-spectrum herbicide frequently used world widely in agricultural and non-agricultural areas to control unwanted plants. Health risk of chronic and subchronic exposure of glyphosate on animals and humans has received increasing attention in recent years. The aim of this study was to evaluate the effects of glyphosate on the immunoglobulin M (IgM), complement C3 (C3), and lysozyme (LYZ) in the kidney of common carp exposed to 52.08 or 104.15mgL−1 of glyphosate for 168h. The results showed that the transcriptions of IgM, C3, or LYZ were altered due to glyphosate-exposure, for example, IgM and C3 initially increased at 24h later it decreased (except for a increase of C3 in higher dose group at 24h) while the expression of G-type LYZ were not affected at 24h, then increased at 72h, but decreased at the end of test, however C-type LYZ expression was initially up-regulated (24–72h) but down-regulated at the end of exposure (168h). However, glyphosate-exposure generally decreased the contents of IgM and C3 or inhibited LYZ activity in the kidney of common carp. In addition, glyphosate-exposure also caused remarkable histopathological damage, mainly including vacuolization of the renal parenchyma and intumescence of the renal tubule in fish kidney. The results of this study indicate that glyphosate causes immunotoxicity on common carp via suppressing the expressions of IgM, C3, and LYZ and also via damaging the fish kidney.

Efficient production of anti-fluorescein and anti-lysozyme as single-chain anti-body fragments (scFv) by Brevibacillus expression system

Expression of scFv in Brevibacillus choshinensis was tested using combinations of three different promoters and four different secretion signals. Two model scFv constructs, i.e., His-scFvFLU and His-scFvHEL, were successfully expressed with some of the combinations. Ni Sepharose column and size exclusion chromatography resulted in fairly pure preparations of these two proteins. The purified His-scFvFLU inhibited fluorescence from fluorescein, while the purified His-scFvHEL inhibited lysozyme activity. Relatively high yield of His-scFvFLU (∼40%) and His-scFvHEL (∼30%) was achieved with the expression and purification system described here.

Interaction betweenPlectranthus barbatusherbal tea components and human serum albumin and lysozyme: Binding and activity studies

Anti-cholinesterase and antioxidant active constituents ofPlectranthus barbatusaqueous extract were found in plasma of rats after its administration – rosmarinic acid, luteolin and apigenin. The aim of the present work is to determine if the extract components can interact with human plasma proteins, namely albumin and lysozyme. Protein intrinsic fluorescence analysis showed that the plant phenolic compounds may bind to albumin, the main transport protein in plasma, and to lysozyme. The estimated thermodynamic parameters suggest that the main intermolecular interaction is hydrophobic association. FTIR analysis of the protein amide bands showed that the plant extract components do not alter the secondary structure of either albumin or lysozyme, however the rate of hydrogen–deuterium exchange suggests that tertiary structure changes might have occurred. An increase of hydrogen deuterium exchange suggests that rosmarinic acid may bind to the fatty acid binding sites in albumin, while luteolin and apigenin may bind to the drug binding sites. The plant extract components also inhibit lysozyme activity with IC50values around 100 μM. ThereforeP. barbatusherbal tea, rosmarinic acid, luteolin and apigenin interact and may be transported by albumin and lysozyme. The inhibition of lysozyme activity may be an additional mechanism for its anti-inflammatory activity.

Interaction between Plectranthus barbatus herbal tea components and human serum albumin and lysozyme: Binding and activity studies

Anti-cholinesterase and antioxidant active constituents of Plectranthus barbatus aqueous extract were found in plasma of rats after its administration - rosmarinic acid, luteolin and apigenin. The aim of the present work is to determine if the extract components can interact with human plasma proteins, namely albumin and lysozyme. Protein intrinsic fluores- cence analysis showed that the plant phenolic compounds may bind to albumin, the main transport protein in plasma, and to lysozyme. The estimated thermodynamic parameters suggest that the main intermolecular interaction is hydrophobic associa- tion. FTIR analysis of the protein amide bands showed that the plant extract components do not alter the secondary structure of either albumin or lysozyme, however the rate of hydrogen-deuterium exchange suggests that tertiary structure changes might have occurred. An increase of hydrogen deuterium exchange suggests that rosmarinic acid may bind to the fatty acid binding sites in albumin, while luteolin and apigenin may bind to the drug binding sites. The plant extract components also inhibit lysozyme activity with IC50 values around 100 µM. Therefore P. barbatus herbal tea, rosmarinic acid, luteolin and apigenin interact and may be transported by albumin and lysozyme. The inhibition of lysozyme activity may be an additional mechanism for its anti-inflammatory activity.

Steady-State and Time-Resolved Studies of the Photocleavage of Lysozyme by Co(III) Complexes

Steady-state and time-resolved studies of site-selective photocleavage of lysozyme by cobalt(III) complexes [Co(NH(3))(5)Br](2+) and ([Co(NH(3))(4)CO(3)](+) are reported. Photocleavage resulted in two fragments of molecular masses approximately 10.5 kDa and approximately 3.5 kDa, and the yield increased (8-33%) with irradiation time (0.16-0.8 h) as well as with the metal complex concentration (0.1-5 mM). The reaction proceeded to a significant extent even when nearly stoichiometric amounts of the reagents were used. Photocleavage was effective at wavelengths ranging from 310 to 390 nm, and cleavage was inhibited by the addition of selected metal ions such as Gd(III) at moderate concentrations (2 mM). Gd(III) is known to bind at Asp52/Glu35 residues on lysozyme, and these residues are located at the enzyme active site. Current and previous studies suggest that Co(III) metal complexes bind at this site on lysozyme. Consistent with this hypothesis, [Co(NH(3))(4)CO(3)](+) (8 mM) inhibited lysozyme activity by 67%. Laser flash photolysis studies show that excitation of the metal complexes [Co(NH(3))(5)Br](2+) and ([Co(NH(3))(4)CO(3)](+) (308 nm, 20 ns pulse width) resulted in the corresponding ligand-derived radical intermediates. For example, photoexcitation of an aqueous solution of [Co(NH(3))(5)Br](2+) at 308 nm resulted in the formation of Br(2)(-*). When the excitation was carried out in the presence of lysozyme, Br(2)(-*) was quenched with a bimolecular rate constant of 1.4 x 10(9) M(-1) s(-1). Quenching resulted in protein-derived radicals (Trp(+*) and Tyr(+*)), as identified by their characteristic known transient absorption bands. Steady-state studies correlated with the time-resolved data, and taken together, these illustrated the reactivities of Co(III) metal complexes to direct protein photocleavage with high selectivity.

Propagation of protein glycation damage involves modification of tryptophan residues via reactive oxygen species: inhibition by pyridoxamine

Nonenzymatic modification of proteins is one of the key pathogenic factors in diabetic complications. Uncovering the mechanisms of protein damage caused by glucose is fundamental to understanding this pathogenesis and in the development of new therapies. We investigated whether the mechanism involving reactive oxygen species can propagate protein damage in glycation reactions beyond the classical modifications of lysine and arginine residues. We have demonstrated that glucose can cause specific oxidative modification of tryptophan residues in lysozyme and inhibit lysozyme activity. Furthermore, modification of tryptophan residues was also induced by purified albumin–Amadori, a ribose-derived model glycation intermediate. The AGE inhibitor pyridoxamine (PM) prevented the tryptophan modification, whereas another AGE inhibitor and strong carbonyl scavenger, aminoguanidine, was ineffective. PM specifically inhibited generation of hydroxyl radical from albumin–Amadori and protected tryptophan from oxidation by hydroxyl radical species. We conclude that oxidative degradation of either glucose or the protein–Amadori intermediate causes oxidative modification of protein tryptophan residues via hydroxyl radical and can affect protein function under physiologically relevant conditions. This oxidative stress-induced structural and functional protein damage can be ameliorated by PM via sequestration of catalytic metal ions and scavenging of hydroxyl radical, a mechanism that may contribute to the reported therapeutic effects of PM in the complications of diabetes.

Effects of tributyltin on the immune system of Japanese flounder ( Paralichthys olivaceus)

Effects of tributyltin (TBT) which has been used for antifouling paint of ship's hulls and fishing nets on the immune system in Japanese flounder ( Paralichthys olivaceus) were investigated. After short-term exposure to a high level of TBT, leucocytes in the head kidney from 1-year-old flounder were examined for the proportion of neutrophils in total leucocytes. Also examined were their respiratory burst activities using flow cytometry, the reduction of nitroblue tetrazolium (NBT) and lysozyme activities. Furthermore, long-term exposures to a relatively low level of TBT using young flounder were also carried out. The proportion of neutrophils in total leucocytes prepared from head kidney in each fish exposed to TBT at 20 μg/L for 5 days and the reduction of NBT by leucocytes prepared from the same experimental conditions increase compared to the control group. The contents were 42.0 ± 6.8 and 52.5 ± 6.3%, respectively. Significant differences of the NBT reduction were observed between 0 and 20 μg/L TBT exposure groups. On the other hand, the respiratory burst activity of cells in the exposure group clearly showed a tendency to decrease compared to the control group. Furthermore, high level of TBT also inhibited lysozyme activity which plays an important role for the bacteriocidal procedures. However, similar results were not obtained in the exposure group with a relatively low level of TBT. To determine the immunotoxic effects of TBT, infection experiments using pathogens which are naturally occurring should be further investigated.

Influences of animal mucins on lysozyme activity in solution and on hydroxyapatite surfaces

The purpose of this study was to investigate the influence of animal mucins on lysozyme activity in solution and on the surface of hydroxyapatite (HA) beads. The effects of animal mucins on lysozyme activity in solution were examined by incubating porcine gastric mucin (PGM) or bovine submaxillary mucin (BSM) with hen egg-white lysozyme (HEWL) or salivary samples. HA-immobilised animal mucins or lysozyme were used to determine the influence of animal mucins on lysozyme activity on HA surfaces. Lysozyme activity was determined by turbidity measurement of a Micrococcus lysodeikticus substrate suspension. Protein concentration was determined by ninhydrin assay. PGM inhibited the activity of HEWL and salivary lysozyme in solution. The amount of inhibition was dependent on mucin concentration, incubation time and temperature, and the structural integrity of the mucin. The inhibition of salivary lysozyme activity by PGM was greater in submandibular/sublingual saliva than in parotid saliva. The inhibition of lysozyme activity by PGM was markedly dependent on pH. However, BSM did not inhibit the in-solution lysozyme activities of HEWL and clarified saliva. Both PGM and BSM bound to HA surfaces, and HA-adsorbed animal mucins increased the subsequent adsorption of lysozyme. When HA beads were exposed to a mixture of HEWL and PGM or BSM, lysozyme activity on the HA surfaces was significantly increased. The results suggest that animal mucins affect lysozyme activity, and the effects are different on HA surfaces compared with in solution. Further research is needed to determine the effect of animal mucins on lysozyme activity in vivo.

Effect of Sertraline on Glucocorticoid Sensitivity of Mononuclear Leukocytes in Post-Traumatic Stress Disorder

This study examined the effects of sertraline (SER) on glucocorticoid sensitivity in mononuclear leukocytes (MNL) from eight subjects with current post-traumatic stress disorder (PTSD) and nine comparison subjects. In all, 60 ml of blood was withdrawn by venipuncture at 0800, and MNL were isolated from blood and divided into two portions: the first contained live cells incubated with a series of concentrations of dexamethasone (DEX); the second contained cells incubated with similar concentrations of DEX+2 muM SER. Group difference in the concentrations of DEX required to inhibit lysozyme activity by 50% were evaluated under conditions of DEX-only and DEX+SER using analysis of covariance (ANCOVA). A significant Group x Condition interaction reflected that SER altered the lysozyme IC(50-DEX) in the direction of decreasing sensitivity to glucocorticoids in PTSD while having no uniform effect in cells from comparison subjects. The data provide support for the idea that glucocorticoid receptors might be more responsive to antidepressants in PTSD than in persons without PTSD. Insofar as increased sensitivity to glucocorticoids has been linked with PTSD, the actions of SER on the lysozyme IC(50-DEX) suggest that this medication may target a biologic alteration associated with PTSD pathophysiology.

The influence of intravenous anaesthetics on the activity of enzymes released from polymorphonuclear leucocytes in vitro.

Polymorphonuclear leucocytes make a decisive contribution to defence against bacterial infections. In particular, the effects of anaesthetics on non-oxidative bactericidal mechanisms have previously only been superficially examined. Although the influence of anaesthetic agents on oxidative bactericidal activity has been thoroughly examined, our study concentrated on the effect on non-oxidative processes, which appears to have been a neglected field of research. The effects of methohexital, etomidate, ketamine, fentanyl and morphine on the activity of lysozyme and beta-glucuronidase released from polymorphonuclear leucocytes have been studied in vitro. The activity of lysozyme was determined by recording the changes in the turbidity of a suspension of micrococcus lysodeicticus caused by the enzymatic action of lysozyme. beta-glucuronidase activity was photometrically measured by the enzymatic cleavage of phenolphthalein glucuronic acid. High concentrations of methohexital inhibited lysozyme activity; however, etomidate and morphine caused an increase of beta-glucuronidase activity in therapeutic plasma concentrations. While there was no effect of etomidate on lysozyme activity, all concentrations tested significantly stimulated beta-glucuronidase activity. This result was unexpected because intravenous anaesthetics have previously shown a tendency to suppress polymorphonuclear leucocyte functions. Whereas the inhibition of lysozyme activity by the high concentration of methohexital was no surprise, the increase of beta-glucuronidase activity caused by etomidate, ketamine, fentanyl and morphine was quite unexpected. At present, the underlying mechanism for the increase of beta-glucuronidase activity caused by etomidate, ketamine, fentanyl and morphine is unknown. The fact that there was no influence of these agents on lysozyme activity possibly suggests that the anaesthetic agents have different effects on azurophilic and specific granules. Since in vitro investigations have their limitations, it is too early to draw practical consequences from our study. Moreover, at present it is unclear whether an increase of beta-glucuronidase activity in vivo is an advantage or not. In any case, we think it advisable to perform further investigations on the influence of anaesthetic agents on oxygen-independent bactericidal mechanisms.