Role of lysozyme in the microbicidal activity of rat alveolar macrophages

Dietary supplementation of lysozyme can improve growth rate, laying performance, blood biochemistry, and mRNA levels of some related genes in different plumage-colored quails

The impact of dietary lysozyme (LZ) supplementation on the growth and laying performance was investigated over 4 weeks of growing and 6 weeks of laying periods in two different plumage color (white and brown-feathered) Japanese quail varieties. For each variety, 240 birds were randomly assigned into four groups with four replicates for each group. The first group (control) was fed a basal non-supplemented diet (BD). Whereas the 2nd, 3rd, and 4th received the BD supplemented with commercial LZ (CLZ) at 100 mg/kg diet, and natural LZ (NLZ) at 100 and 200 mg/kg diet, respectively. The main findings included significant increases in body weights and gains in the white-feathered quails supplemented with NLZ1 compared to the control and NLZ2. However, there were no significant differences in the case of brown-feathered quails in all LZ supplementations. Moreover, the different dietary LZ lowered FI in both quails with the lowest intake observed in the brown-feathered quails. Accordingly, enhanced FCR was reported in the CLZ groups for both quail varieties and in NLZ1 and NLZ2 for the white-feathered and brown-feathered quails, respectively. In both quail varieties, the NLZ2 significantly lowered serum creatinine and urea and increased albumen and globulin levels compared with other groups. Histologically, the best hepatic histological features were found in both quail' varieties fed the NLZ1-supplemented diet. Accompanying LZ-induced modulations in the expression levels of GHR, IGF-1, leptin, CCK, FAS, and ACC genes in both quail varieties were reported. Besides, both quail varieties in NLZ1& NLZ2 supplementation exhibited significant increases in hen day egg production, egg weight, egg mass, and hatchability percentages along with differences in external and internal egg qualities compared with LZ-free diet or CLZ. Therefore, NLZ could be used as an effective feed supplement to enhance the growth and egg performance of Japanese quail with caution being drawn to the supplementation dose about quail variety.

Postbiotic, anti-inflammatory, and immunomodulatory effects of aqueous microbial lysozyme in broiler chickens

Lysozymes, efficient alternative supplements to antibiotics, have several benefits in poultry production. In the present study, 120, one-day-old, Ross 308 broiler chickens of mixed sex, were allocated into 2 equal groups, lysozyme treated group (LTG) and lysozyme free group (LFG), to evaluate the efficacy of lysozyme (Lysonir®) usage via both drinking water (thrice) and spray (once). LTG had better (p = 0.042) FCR, and higher European production efficiency factor compared to LFG (p = 0.042). The intestinal integrity score of LTG was decreased (p = 0.242) compared to that of LFG; 0.2 vs. 0.7. Higher (p ≤ 0.001) intestinal Lactobacillus counts were detected in chickens of LTG. Decreased (p ≤ 0.001) IL-1β and CXCL8 values were reported in LTG. The cellular immune modulation showed higher (p ≤ 0.001) opsonic activity (MΦ and phagocytic index) in LTG vs. LFG at 25 and 35 days. Also, higher (p ≤ 0.001) local, IgA, and humoral, HI titers, for both Newcastle, and avian influenza H5 viruses were found in LTG compared to LFG. In conclusion, microbial lysozyme could improve feed efficiency, intestinal integrity, Lactobacillus counts, anti-inflammatory, and immune responses in broiler chickens.

Effects of dietary lysozyme supplementation on growth performance, nutrient digestibility, intestinal microbiota, and blood profiles of weanling pigs challenged with Escherichia coli

The aim of this was evaluate the efficacy of lysozyme on growth performance, nutrient digestibility, excreta microflora population, and blood profiles of weanling pigs under Escherichia coli (E. coli) challenge. A total of 30 piglets weaned at 25 days, 7.46 kg body weight, were assigned to three dietary treatments, composed of five replications, two piglets per replication, for 7 days. The dietary treatment groups were negative control (NC; without antibiotics and lysozyme), positive control (PC; NC + antibiotics), lysozyme (NC + 0.1% lysozyme). All piglets were challenged orally with 6 ml suspension, containing E. coli K88 (2 × 10⁹ CFU/mL). Dietary supplementation with lysozyme and PC resulted in no significant differences in average daily gain and gain to feed efficiency. Weanling pigs fed with E. coli challenge with lysozyme and PC treatments had significantly enhanced nutrient retentions of dry matter and energy (p < 0.05); however, there was a tendency to increase nitrogen digestibility. Furthermore, dietary inclusion of lysozyme and antibiotics treatment groups had a beneficial effect on excreta, ileal, and cecal of the fecal microbial population as decreased E. coli (p < 0.05) counts, without effects on lactobacillus counts. A significant effect were observed on a white blood cells, epinephrine and cortisol concentrations were reduced in piglets fed diets containing E. coli challenge with lysozyme and antibiotics supplementation comparison with the NC group. Therefore, the present data indicate that lysozyme in diet could ameliorate the experimental stress response induced by E. coli in piglets by decreasing intestinal E. coli, white blood cells and stress hormones and improving nutrient digestibility.

Effects of dietary supplementation with lysozyme on the structure and function of the cecal microbiota in broiler chickens

Lysozyme is known to eliminate intestinal pathogens in poultry and improve their growth performance. However, whether it can replace antibiotic growth promoters without the associated risk of the emergence of antibiotic-resistant bacterial strains is not known, and the effects of lysozyme supplementation on the composition, biodiversity, and function of the chicken gut microbiota remain unclear. Here, we used the 16S rRNA gene and ITS fragment Illumina sequencing combined with transcriptomic analysis to address this issue. A total of 400 1-d-old Di Gao chicks were allocated randomly to five groups, each consisting of four replicates (20 birds/group). The chicks were fed a starter (1–21 d) and a grower (22–42 d) diet supplemented with 0 (control), 40 (LYS40), 100 (LYS100), or 200 ppm (LYS200) lysozyme, or 400 ppm flavomycin as an antibiotic control for 6 weeks. Lysozyme administration did not contribute significantly (P > 0.05) to the growth of the broiler chickens. No significant (P > 0.05) differences in the diversity and composition of the bacterial and fungal communities in the cecal microbiota of chickens in the different diet groups were found. However, lysozyme supplementation led to a significant (P < 0.05) enrichment of genes involved in the synthesis/degradation of bacterial outer membranes and cell walls, cross-cell substrate transport, and carbohydrate metabolic processes, thus possibly promoting the cecal microbiota carbon and energy metabolism. Bacteroides contributed 31.9% of glycoside hydrolase genes (17,681–24,590), 26.1% of polysaccharide lyase genes (479–675), 20.7% of carbohydrate esterase genes (3,509–4,101), 8.8% of auxiliary activity genes (705–1,000), 16.2% of glycosyltransferase genes (5,301–6,844), and 13.9% of carbohydrate-binding module genes (8838–15,172) identified in the cecal samples. Thus, they were the main players in the breakdown of non-starch polysaccharides in the cecum, although Parabacteroides, Alistipes, Prevotella, Clostridium, Blastocystis, Barnesiella, Blautia, Faecalibacterium, Subdoligranulum, Megamonas, Eubacterium, Ruminococcus, Paenibacillus, Bifidobacterium, Akkermansia, and other bacteria also participated.

Enzymatic Changes in Alveolar Macrophages of Rats Exposed to Lead and Nickel by Inhalation

In previous inhalation studies, rats exposed to aerosol concentrations of lead oxide (Pb2O3), 150 μg/m3; lead chloride (PbCl2), 100 μg/m3; nickel oxide (NiO), 120 μg/m3; and nickel chloride (NiCl2), 109 μg/m3; significant changes were observed in the lungs and alveolar macrophages. In this study the hydroiytic enzymes, acetylesterase, acid and alkaline phos-phatases, lysozyme, and beta-glucuronidase, in alveolar macrophages and lung washout fluid from rats subjected to the inhalation of the lead and nickel aerosols were examined. Washed alveolar macrophages from animals exposed to lead and nickel aerosols were found to contain reduced quantities of the various hydrolytic enzymes (except for acetylesterase) when compared with those from control rats. On the other hand, a significant increase in enzymatic activity was noted in lung washout fluid from exposed animals. The functional efficiency of macrophages, relative enzyme changes, and the mechanism of action of metals are discussed. It is important to note that the changes observed in these studies were from animals exposed to metallic concentrations near their Threshold Limit Values.

Genetics of immunocompetent traits in a synthetic broiler dam line

Three hundred and three chicks of both sexes, from a synthetic dam line (SDL) of broiler chickens, were studied for economic traits (body weights at 4, 5 and 6 weeks of age) and immunological traits (humoral and cell mediated immune responses, and serum lysozyme concentration). The objective was to evaluate these traits and to estimate their genetic and non-genetic parameters. The humoral immune response was assessed by estimating the antibody response to sheep red blood cells using the haemagglutination (HA) test and serum IgG concentration using single radial immunodiffusion (SRID). The cell mediated immune (CMI) response was estimated as in vivo response to a mitogen (PHA-P). Serum lysozyme was measured by lysoplate assay. Least squares means for body weight at 4, 5 and 6 weeks were 684 +/- 20, 920 +/- 19 and 1205 +/- 28 g, HA titre was 6.289 +/- 0.246, CMI was 0.438 +/- 0.015 mm, lysozyme was 1.860 +/- 0.047 microg/ml and IgG was 6.287 +/- 0.194 mg/ml. There was an effect of sire on HA titre and on body weight at 4, 5 and 6 weeks of age; males were heavier than females. Heritability estimates were high for body weights but low for immunological traits. Phenotypic correlations (rp) among body weights were high and positive but were very low between body weights and most immunological traits. Among the immunological traits all rp were very low. Genetic correlations (rg) of body weights were positive and medium to high with CMI and HA and negative with serum IgG.

The polymorphism of lysozyme gene in Zhikong scallop (Chlamys farreri) and its association with susceptibility/resistance to Listonella anguillarum

Lysozyme functions as a crucial biodefence effector against the infection of bacterial pathogens in innate immunity. The nucleotide sequence polymorphisms in promoter region of a nuclear goose type lysozyme gene from Zhikong scallop Chlamys farreri (designated as CFLysG) were investigated to explore their association with susceptibility/resistance to Listonella anguillarum infection. Eight sites of single nucleotide polymorphisms (SNPs) and two sites of insert-deletion (ins-del) polymorphisms were identified in the promoter region of CFLysG. Two of them, -753 TATCTCGATCAGG ins-del polymorphism and -391 A-G SNP were selected to analyze their distribution in the susceptible and resistant stocks, which were identified according to the survival time after L. anguillarum challenge. Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), two genotypes were found at each site, which were ins/del and ins/ins at locus -753, and A/A and A/G at locus -391, respectively. The -753 ins/del genotype was more prevalent in the resistant stock than that in the susceptible stock, 30% vs 16.67% in frequency, but there was no significant difference in the frequency distribution between these two stocks (P=0.15). In contrast, the frequency of -391A/G genotype in the resistant stock was significantly higher (30%) than that in the susceptible stock (7.14%) (P=0.007), indicating a significant association with the resistance of Zhikong scallop to L. anguillarum. To confirm the presumption, another independent challenge experiment was performed, in which the cumulative mortality of scallops with -391 A/A genotype (96.8%) was significantly higher than those with -391 A/G genotype (64.5%) (P=0.001), which further validate the association between -391 A/G genotype and the resistance of Zhikong scallop to L. anguillarum. These results suggested that the -391 A/G could be a potential marker applied in future selection of Zhikong scallop with enhanced resistance to L. anguillarum.

Macrophage elastase kills bacteria within murine macrophages

Macrophages are aptly positioned to function as the primary line of defence against invading pathogens in many organs, including the lung and peritoneum. Their ability to phagocytose and clear microorganisms has been well documented. Macrophages possess several substances with which they can kill bacteria, including reactive oxygen species, nitric oxide, and antimicrobial proteins. We proposed that macrophage-derived proteinases may contribute to the antimicrobial properties of macrophages. Macrophage elastase (also known as matrix metalloproteinase 12 or MMP12) is an enzyme predominantly expressed in mature tissue macrophages and is implicated in several disease processes, including emphysema. Physiological functions for MMP12 have not been described. Here we show that Mmp12(-/-) mice exhibit impaired bacterial clearance and increased mortality when challenged with both gram-negative and gram-positive bacteria at macrophage-rich portals of entry, such as the peritoneum and lung. Intracellular stores of MMP12 are mobilized to macrophage phagolysosomes after the ingestion of bacterial pathogens. Once inside phagolysosomes, MMP12 adheres to bacterial cell walls where it disrupts cellular membranes resulting in bacterial death. The antimicrobial properties of MMP12 do not reside within its catalytic domain, but rather within the carboxy-terminal domain. This domain contains a unique four amino acid sequence on an exposed beta loop of the protein that is required for the observed antimicrobial activity. The present study represents, to our knowledge, the first report of direct antimicrobial activity by a matrix metallopeptidase, and describes a new antimicrobial peptide that is sequentially and structurally unique in nature.

Histopathological Characteristics of Ito Cells and Kupffer Cells in the Feline Liver

The histopathological characteristics of Ito cells and Kupffer cells were investigated in the liver of 21 cats (age range: 6 months -18 years) autopsied in our laboratory during 2003. Immunohistochemical examinations were performed using antibodies against lysozyme, desmin and alpha-smooth muscle actin. No Kupffer cells reacted with the antibody against lysozyme. However, macrophages in the lung and spleen showed a positive reaction with the antibody. This finding suggests a possibility that the amount of lysozyme in the Kupffer cells of feline liver is comparatively small. On the other hand, large vacuole-laden cells were observed in the hepatic perisinusoid of some feline cases, and these cells showed a positive reaction with antibodies against desmin and alpha-smooth muscle actin. These cells could be Ito cells with large lipid vacuoles. This conclusion was supported by electron microscopic observation and oil red O staining. However, no such large vacuole-laden perisinusoidal cells were detected in the liver of young cats less than 2 years old. The present study revealed the histopathological features of Kupffer cells and Ito cells in the feline liver.

Studies on immunocompetence status in two turkey varieties in India

(1) Two hundred and twenty-seven adult turkeys of both sexes, of two varieties (104 Black and 123 White) were used to evaluate their immunocompetence status and body weights. (2) Response to sheep red blood cells (SRBC) (humoral immunity) was measured by Haemagglutination (HA) test 5 days post immunisation (dpi) and expressed as log2 values. Mercaptoethanol resistant (MER) antibodies representing IgG were determined by Mercaptoethanol HA test and Mercaptoethanol sensitive (MES) antibodies, representing IgM as the difference in total HA titre and IgG. Serum lysozyme concentrations were estimated by 'Lysoplate assay' and expressed in log2 values. (3) Least squares analysis of variance revealed that the White variety had higher adult body weight (4.788 +/- 0.040 kg) than the Black (3.774 +/- 0.044 kg). Sexual dimorphism was apparent and meals were heavier than females in both varieties. The interaction effect of variety and sex on body weight was also significant. (4) Least squares means for immunological traits, namely, total anti-SRBC antibodies, MER, MES titres and serum lysozyme were 7.161 +/- 0.189, 0.801 +/- 0.071, 6.362 +/- 0.160 and 1.766 +/- 0.043 microg/ml, respectively. The Black variety had a higher MES antibody titre than the White. (5) Sex had an effect on all the immunological traits except on MER titres. Females generally had higher anti-SRBC, MER and MES titres and serum lysozyme. The variety x sex interaction effect was significant for MES titres and serum lysozyme. White males had the lowest MES titres.

Expression and prognostic significance of lysozyme in male breast cancer

BACKGROUND

Lysozyme, one of the major protein components of human milk that is also synthesized by a significant percentage of breast carcinomas, is associated with lesions that have a favorable outcome in female breast cancer. Here we evaluate the expression and prognostic value of lysozyme in male breast cancer (MBC).

METHODS

Lysozyme expression was examined by immunohistochemical methods in a series of 60 MBC tissue sections and in 15 patients with gynecomastia. Staining was quantified using the HSCORE (histological score) system, which considers both the intensity and the percentage of cells staining at each intensity. Prognostic value of lysozyme was retrospectively evaluated by multivariate analysis taking into account conventional prognostic factors.

RESULTS

Lysozyme immunostaining was negative in all cases of gynecomastia. A total of 27 of 60 MBC sections (45%) stained positively for this protein, but there were clear differences among them with regard to the intensity and percentage of stained cells. Statistical analysis showed that lysozyme HSCORE values in relation to age, tumor size, nodal status, histological grade, estrogen receptor status, metastasis and histological type did not increase the statistical significance. Univariate analysis confirmed that both nodal involvement and lysozyme values were significant predictors of short-term relapse-free survival. Multivariate analysis, according to Cox's regression model, also showed that nodal status and lysozyme levels were significant independent indicators of short-term relapse-free survival.

CONCLUSION

Tumor expression of lysozyme is associated with lesions that have an unfavorable outcome in male breast cancer. This milk protein may be a new prognostic factor in patients with breast cancer.

Lysozyme expression by breast carcinomas, correlation with clinicopathologic parameters, and prognostic significance

BACKGROUND

Here we evaluate the expression and prognostic value of lysozyme, a milk protein that is also synthesized by a significant percentage of breast carcinomas, in women with breast cancer.

METHODS

Lysozyme expression was examined by immunohistochemical methods in a series of 177 breast cancer tissue sections. Staining was quantified by using the HSCORE system, which considers both the intensity and the percentage of cells staining at each intensity. The prognostic value of lysozyme was retrospectively evaluated by multivariate analysis that took into account conventional prognostic factors.

RESULTS

A total of 126 of 177 carcinomas (69.4%) stained positive for this protein, but there were clear differences among them with regard to the intensity and percentage of stained cells. Lysozyme values were higher in well-differentiated and moderately differentiated tumors than in poorly differentiated tumors (P < .05). Similarly, lysozyme levels were higher in small and node-negative tumors than in large and node-positive tumors (P < .05). Moreover, results indicated that low lysozyme content predicted shorter relapse-free survival and overall survival (P < .005). Separate Cox multivariate analysis in subgroups of patients as defined by node status showed that lysozyme expression was an independent prognostic factor able to predict both relapse-free survival and overall survival in node-negative patients (P < .05).

CONCLUSIONS

Tumoral expression of lysozyme is associated with lesions of favorable evolution in breast cancer. This milk protein may be a new prognostic factor in patients with breast cancer.

Protective effect of beta-glucan against mycobacterium bovis, BCG infection in BALB/c mice

Beta-1,3-glucan is a potent stimulator of macrophage functions and has a protective effect against a range of infections in rodent models. We examined whether the agent could also protect against the intracellular Mycobacterium bovis, bacillus Calmette-Guérin (BCG) infection in mice. BCG-susceptible BALB/c mice were injected intravenously (i.v.) with beta-glucan or vehicle 3 days before, or with beta-glucan 7 days after i.v. challenge with live BCG bacilli. The animals were killed 4 or 8 weeks later, their organs were homogenized and applied to object slides and stained with auramin for counting of bacilli, or seeded onto agar in Petri dishes. Mice treated with beta-glucan both pre- and postchallenge had significantly lower numbers of BCG bacilli and BCG colony-forming units in spleen homogenates compared with controls 4 weeks after challenge. A similar, but not statistically significant, tendency was observed in spleen homogenates from mice killed 8 weeks after challenge. In homogenates of liver and lungs there were similar findings, but less pronounced. There was a dose-dependent effect of beta-glucan injected before BCG challenge on the number of BCG bacilli found in spleen and liver homogenates. In addition, antibody cross-reactivity was demonstrated between M. tuberculosis cell wall and beta-glucan. The results suggest that beta-glucan has a protective effect against M. bovis, BCG infection in susceptible mice.

Viscosity of human seminal fluid: role of lysozyme

The aim of this research was to evaluate the role of lysozyme in the phenomenon of seminal hyper-viscosity. The enzyme was determined in 142 samples of seminal plasma either leucospermic or not, with or without active macrophages classified according to their consistency (normal or high). The kinetic method with Micrococcus lysodeikticus as substrate was employed. No difference was found in enzymatic concentration expressed in nmol/L of enzymatic protein (mean +/- 2 SEM) on comparing normal and high seminal consistency groups, while differences proved highly significant in batches either leucospermic or not (n = 44, 197.2 +/- 51.3 vs. n = 98, 108.3 +/- 12.8; p < .0005). On subdividing the normal and high-consistency groups according to the count of polymorphonuclear leucocytes and the macrophagic responses, differences were also significant (p < .005 in both cases). Lysozyme concentration increases in presence of leucospermic reaction. In vitro lysozyme addition showed no significant effect on samples with high consistency. The results indicate that lysozyme plays no direct role in the phenomenon of seminal hyperviscosity, although its deficiency in cases of chronic infections may prove a factor aggravating the clinical picture.

Biological properties of bacterial peptidoglycan

Synthetic and natural muramyl peptides have a variety of biological actions in mammals, including the abilities to enhance sleep and body temperature. Although muramyl peptides can be detected constitutively in mammalian organisms, no biochemical synthetic pathways are known for muramyl peptides in mammals. However, muramyl peptides are well known as components of bacterial cell wall peptidoglycan (synonym: murein). Isolated bacterial cell walls elicit host responses similar to those produced by bacterial infections or by purified muramyl peptides. Mammalian cells which phagocytize bacteria can digest bacterial cell walls and release biologically active muramyl peptides. The released muramyl peptides then express some or all of the biological effects observed with synthetic muramyl peptides. Also, cell-free systems consisting of isolated bacterial cell walls and lysozyme produce substances with similar biological activities.

Intrapulmonary growth of Staphylococcus aureus in rats during induced atelectasis

Intrinsic pulmonary antibacterial defenses are mediated by alveolar macrophages and by noncellular factors. Mechanical ventilation in the resting tidal volume range leads to alterations in the physical characteristics of alveolar surfactant, alveolar instability, regional hypoxia, and systemic hypoxemia. While a number of experimental manipulations diminish the activity of the intrinsic antibacterial defense system, the effects of mechanical ventilation per se have not been systematically evaluated previously. We found that normal rats ventilated without sighing (periodic large breaths) manifested severe defects in pulmonary clearance of Staphylococcus aureus during 6-h experiments, such that growth of the inoculum occurred. Addition of a timer-controlled mechanism to cause the animals to sigh every 2 min, without other modifications in the experimental conditions, caused significant improvement in clearance. Analysis of cellular response, compartmentalization of viable bacteria, surfactant quantities and sedimentation characteristics, and protein influx indicated that the defect in clearance paralleled alterations in the physical state of surfactant and alveolar stability but was not strongly correlated with alterations in the other parameters we measured. The data show that defective pulmonary bacterial clearance is rapidly induced by measures which alter alveolar stability and suggest that intrinsic pulmonary defenses require maintenance of normal air-liquid interfaces for optimal function.

Lysozyme activity in ultrastructurally defined fractions of alveolar macrophages after inhalation exposure to nickel

Rabbits were exposed to 0.6 mg/m3 of nickel as NiCl2 for about one month. After exposure, alveolar macrophages were lavaged from the lung and divided into three fractions by elutriation. Laminated structures in the macrophages were related to fraction number so that the fractions with the largest cells contained the highest number of structures. The lysozyme activity decreased in unfractionated as well as in fractionated macrophages from nickel exposed rabbits. The decrease was most pronounced in the fraction with the smallest macrophages and smallest number of laminated structures. Therefore the pronounced decrease in lysozyme activity seen in this and earlier studies is not caused by the increased amount of surfactant material. Increased amount of surfactant is a hallmark of nickel inhalation exposure and the surfactant material is responsible for the morphological and metabolic effects of the macrophages. The decreased lysozyme activity is probably a direct effect of nickel on the macrophages.

Characterization of cytoplasmic lysozyme immunoreactivity as a histiocytic marker in normal canine tissues

The immunoreactive lysozyme distribution in normal canine tissues was determined to assess the value of lysozyme as a marker of histiocytic differentiation. Lysozyme was largely confined to monocytes, neutrophils, macrophages, serous cells in mucosal associated exocrine glands, and renal proximal tubular epithelium. Macrophages in the majority of tissues stained intensely for lysozyme, although in lymphoid tissues not all acid phosphatase and nonspecific esterase positive cells contained lysozyme. In particular, dendritic antigen presenting cells, including Langerhans cells, follicular dendritic cells, and interdigitating reticulum cells, lacked immunoreactive lysozyme; hence lysozyme appeared to represent a discriminatory marker with respect to these cells. Also, a small proportion of non-dendritic macrophages appeared to lack lysozyme. It was concluded that the demonstration of immunoreactive lysozyme was a useful adjunct to conventional morphological techniques for the identification of tissue macrophages provided that due caution was exercised in the interpretation of the results of lysozyme staining.

Modulation of pulmonary clearance of bacteria by antioxidants

To further delineate the mechanisms underlying murine pulmonary defenses against bacterial infection, we studied the effects of antioxidant enzymes and hydroxyl radical scavengers on pulmonary clearance processes. Intratracheal injection of catalase and superoxide dismutase resulted in prolonged intraalveolar residence of the enzymes, but caused no decrease in rates of clearance of either Staphylococcus aureus 502A or Pseudomonas aeruginosa PAO1. In contrast, dimethylsulfoxide and dimethylthiourea caused significant depression of clearance of P. aeruginosa without altering clearance of S. aureus. These results provide further differentiation between clearance processes affecting gram-negative and gram-positive bacteria and suggest that murine clearance of gram-negative organisms may be in part mediated by reactions which generate hydroxyl anion. In vivo administration of agents which inhibit hydrogen peroxide-, superoxide-, or hydroxyl anion-mediated reactions do not alter normal clearance of S. aureus.

Oxidative metabolism of neonatal and adult rabbit lung macrophages stimulated with opsonized group B streptococci

We compared the oxidative metabolism of alveolar macrophages (AM) from adult and neonatal (1- and 7-day-old) rabbits before and after their in vitro exposure to type Ia group B streptococci (GBS) opsonized with immune rabbit serum. Nonstimulated AM from 1-day-old, 7-day-old, or adult rabbits consumed O2 at a rate of 17 to 20 nmol/10(6) AM per 10 min under basal conditions and released minimal amounts of superoxide (O2-) into the medium. Approximately 80% of this basal respiration was of mitochondrial origin, based on its inhibition by NaCN. Exposure to GBS opsonized with immune rabbit serum stimulated O2 consumption approximately half as effectively in the neonatal AM as in the adult AM. Little O2- was released into the medium unless the cells were pretreated with dihydrocytochalasin B. Under such conditions, 1-day-old, 7-day-old, and adult AM released 3.6, 5.3, and 13.9 nmol of O2-/10(6) AM per 10 min, respectively. The uptake of opsonized GBS by 1-day-old AM was not affected by 1 mM NaCN, whereas phagocytosis by adult AM was substantially reduced under these conditions. Overall, our findings suggest that neonatal AM have less-well-developed postphagocytic oxidative metabolic responses and release less superoxide after exposure to opsonized GBS than do adult AM. They also demonstrate that the energy for phagocytosis is derived principally from mitochondrial metabolism in adult AM but not in neonatal AM. We conclude that metabolic differences between neonatal and adult AM may contribute to neonatal pulmonary susceptibility to GBS infections and account, in part, for the ability of GBS to succeed as neonatal pulmonary pathogens.

What's new in lysozyme research? Always a model system, today as yesterday

The present review is focused on the main achievements realized in the lysozyme research field since the meeting held in 1972 to commemorate the fiftieth anniversary of the discovery of this enzyme. Despite of extensive structural, physico-chemical, crystallographic, genetic, immunological and evolutionary studies devoted to lysozymes, their biological role is still not exactly known.

Lysozyme levels in rabbit lung after inhalation of nickel, cadmium, cobalt, and copper chlorides

Groups of rabbits were exposed to chlorides of nickel, cadmium, copper, and cobalt at concentrations ranging from 0.2 to 0.6 mg/m3 (as metal) for 4-6 weeks (5 days/week, 6 hr/day). Activity of lysozyme (muramidase) in lavage fluid, in alveolar macrophages, and in culture medium from macrophages incubated at 37 degrees C for 1 and 20 hr was estimated using the lyso-plate technique, agar plates with heat-killed Micrococcus lysodeikticus. In the nickel-exposed rabbits lysozyme activity in the mucous membrane from the left main bronchus was also estimated. Following nickel exposure the lysozyme level was significantly decreased in lavage fluid, macrophages, and in culture medium from incubated macrophages but remained unchanged in the mucous membrane. After exposure to cadmium, copper, and cobalt, lysozyme levels increased or were unchanged.

Nonphagocytic clearance of Staphylococcus aureus from murine lungs

Several investigations of host and bacterial factors critical to staphylococcal clearance from lungs suggest that alveolar macrophages may not provide the principal defense against inhaled staphylococci. We evaluated possible contributions of extracellular bactericidal activities in lungs with a standard aerosol challenge model by using methods which allowed recovery of macrophages for in vitro bactericidal assays and recovery of intrapulmonary staphylococci for clearance studies. Macrophages recovered by a gentle lavage technique immediately after aerosol exposure contained 6.0 +/- 2.3 colony-forming units of viable staphylococci per 100 glass-adherent macrophages. These intracellular staphylococci were killed in vitro with a half-life of 10.8 +/- 2.1 h, which is identical to our results with a completely in vitro system for ingestion and killing. However, 99.4 +/- 0.2% and 94.9 +/- 1.5% of the viable cocci recovered in bronchoalveolar lavage at 0.5 and 6.0 h after aerosol exposure were sensitive to lysostaphin, a rapidly bactericidal enzyme with no demonstrable activity against intracellular organisms and therefore, presumably extracellular. Photomicrographs from lavage pellets obtained 0.5, 1.5, 3.0, and 5.5 h after aerosol exposure confirmed the presence of numerous extracellular cocci. These extracellular cocci were eliminated at the same rate as whole lung cocci (half-life = 3.07 and 3.14 h, respectively) and at a much faster rate than intracellular cocci. In summary, we found large numbers of extracellular staphylococci in bronchoalveolar spaces during the first 6 h after aerosol exposure that are inactivated at the same rate as the whole lung bacterial population. Since only a small number of staphylococci are ingested by macrophages and intracellular bactericidal activity appears too slow to explain intrapulmonary killing, we conclude that an as yet unidentified extracellular killing process contributed to staphylococcal clearance.

Cell wall degradation of Staphylococcus aureus by lysozyme

In contrast to former findings lysozyme was able to attack the cell walls of Staphylococcus aureus under acid conditions. However, experiments with 14C-labelled cell walls and ribonuclease indicated that, under these conditions, lysozyme acted less as an muralytic enzyme but more as an activator of pre-existing autolytic wall enzymes. Electron microscopic studies showed that under these acid conditions the cell walls were degraded by a new mechanism (i.e. "attack from the inside"). This attack on the cell wall started asymmetrically within the region of the cross wall and induced the formation of periodically arranged lytic sites between the cytoplasmic membrane and the cell wall proper. Subsequently, a gap between the cell wall and the cytoplasmic membrane resulted and large cell wall segments became detached and suspended in the medium. The sequence of lytic events corresponded to processes known to take place during wall regeneration and wall formation. In the final stage of lysozyme action at pH 5 no cell debris but "stabilized protoplasts" were to be seen without detectable alterations of the primary shape of the cells. At the same time long extended ribbon-like structures appeared outside the bacteria. The origin as well as the chemical nature of this material is discussed. Furthermore, immunological implications are considered.

Drug-induced lipidosis and the alveolar macrophage

The alveolar macrophage is the principal component of the defense mechanisms of the lung. As a result, alterations in its function can predispose the host organism to pulmonary disease or damage. This cell shows toxic responses to a wide variety of chemicals which are delivered to the lungs by either inhalation or via the systemic circulation. In this regard, this review will focus on the effects of a group of cationic amphiphilic drugs which when administered to humans and animals causes a lysosomal storage disorder of lipids, principally phospholipids, in alveolar macrophages. The susceptibility to the disorder is species-dependent and can be induced in fetal, neonatal and adult animals. Evidence exists that the accumulation of lipids within the cells occurs as a result of an impairment in lipid catabolism, however, not all of the available data are consistent with this theory. In light of this, other mechanisms to explain the etiology of this lipidosis are discussed. Associated with the increase in lipid content within the cell, striking morphological, biochemical and functional changes occur to the alveolar macrophage. Available data indicate that afflicted cells have an increased phagocytic activity and exhibit enhanced killing of one strain of bacteria. While these data suggest an enhancement in certain cellular functions, inadequate information presently exists to allow conclusions to be drawn concerning the consequences of this disorder.

Decreased level of lysozyme in rabbit lung lavage fluid after inhalation of low nickel concentrations

Six rabbits were exposed for 4 months (5 days/week, 6 h/day) and 6 rabbits for 8 months to approx. 0.1 mg/m3 of metallic nickel dust (U.S. threshold limit value (TLV) 1 mg/m3). Another 8 rabbits were exposed for 4-6 weeks (5 days/week, 6 h/day) to 0.3 mg/m3 (as Ni) of nickel chloride (U.S. TLV 0.1 mg/m3). After exposure lungs were lavaged. Concentration of lysozyme in the lavage fluid was estimated with the lyso-plate technique (agar plates with heat-killed Micrococcus lysodeikticus) after macrophages had been removed. All 3 exposed groups had markedly lower concentrations of lysozyme than corresponding controls. Mean values in controls and exposed rabbits were: for 4 months metallic nickel dust exposure 2.3 and less than or equal to 0.04 microgram/ml; for 8 months metallic nickel dust exposure 1.4 and less than or equal to 0.5 microgram/ml; and for nickel chloride exposure 1.9 and less than or equal to 0.4 microgram/ml.

Effects of viral pneumonia on lung macrophage lysosomal enzymes

During viral pneumonitis in mice, lung fluid protein and free lysosomal enzyme activity are increased while macrophage lysosomal enzymes are decreased.

Effect of phorbol myristate acetate on cellular metabolism and lysozyme release from alveolar macrophages and polymorphonuclear leukocytes

Phorbol myristate acetate stimulated oxidative metabolism in alveolar macrophages and blood neutrophils. This compound also stimulated lysozyme release from neutrophils but not from alveolar macrophages. These findings suggest that the regulation of lysozyme release from alveolar macrophages is different than for polymorphonuclear leukocytes.

Increased resistance to Staphylococcus aureus infection and enhancement in serum lysozyme activity by glucan

Glucan is a potent reticuloendothelial stimulant whose immunobiological activity is mediated, in part, by an increase in the number and function of macrophages. In studying the role of glucan as a mediator of antibacterial activity, we attempted to ascertain the ability of glucan to modify the mortality of mice with experimentally induced Gram-positive bacteremia, and to enhance antibacterial defenses in rats as denoted by serum lysozyme and phagocytic activity. After intravenous administration of glucan, serum lysozyme concentrations were increased approximately sevenfold over control concentrations. The increase in serum lysozyme appeared to parallel the glucan-induced increase in phagocytosis and induced hyperplasia of macrophages. Prior treatment of mice with glucan significantly enhanced their survival when they were challenged systemically with Staphylococcus aureus. These studies indicate that glucan confers an enhanced state of host defense against bacterial infections.

Hydrogen peroxide release by rat alveolar macrophages: comparison with blood neutrophils

Hydrogen peroxide release was examined using biochemical and cytochemical techniques in rat alveolar macrophages, at rest and during phagocytosis, and compared with rat blood neutrophils. Using biochemical techniques, alveolar macrophages released small amounts of hydrogen peroxide at rest, and no increase was observed after challenge with opsonized and nonopsonized zymosan particles at several particle-cell ratios (1:1 to 1:1,000). Neutrophils released similar quantities of hydrogen peroxide at rest but showed a 12-fold increase in hydrogen peroxide release following exposure to opsonized zymosan particles. Using cytochemical techniques to localize sites of hydrogen peroxide release, resting neutrophils showed little deposition of reaction product at the cell surface and occasional deposits in endocytotic vesicles. After exposure to latex particles, a dense reaction product was observed between the particle and the cell membrane, indicating significant increases in hydrogen peroxide release at the sites of particle contact with the neutrophil. The resting macrophage displayed a light, uniform precipitation of cerium over the cell surface and lining intracellular channels and endocytotic vesicles and vacuoles. Following particle exposure, there was no significant difference in the density or distribution of reaction product. These findings, together with previous studies of oxidative metabolism, suggest that alveolar macrophages do not release increased quantities of hydrogen peroxide during phagocytosis. In contrast to neutrophils, oxidative-dependent metabolic pathways may not be of primary importance for microbial killing by alveolar macrophages.