Stimulation of lysozyme release by selected microbial preparations

Lysozyme is an important factor of innate immunity and a unique enzybiotic in that it exerts not only antibacterial activity, but also antiviral, anti-inflammatory, anticancer, and immunomodulatory activities. The purpose of the present study was to investigate whether in vitro exposure to microbial preparations can affect the release and production of lysozyme activity in human monocytic cell line THP-1. Lysozyme activity levels in cell culture fluids were measured using highly sensitive fluorescence-based lysozyme activity assay. Different preparations of bacteria and ascomycetes stimulated lysozyme release result in a higher lysozyme activity after one hour exposure. The demonstrated ability of selected microbial preparations to enhance the release of lysozyme activity can present a new mechanism contributing to explaining biological characteristics of microbial preparations, including their antibacterial and immune-stimulating properties.

In vitro Effects of Selected Saponins on the Production and Release of Lysozyme Activity of Human Monocytic and Epithelial Cell Lines

Lysozyme is one of the most important factors of innate immunity and a unique enzybiotic in that it exerts not only antibacterial activity, but also antiviral, anti-inflammatory, anticancer and immunomodulatory activities. The purpose of the present study was to investigate whether in vitro exposure to saponins can affect the release and production of lysozyme activity in human monocytic cells THP-1, and in human epithelial cells HT-29. Lysozyme activity levels in cell culture fluids were measured using highly sensitive fluorescence-based lysozyme activity assay. Majority of the examined saponins were demonstrated to stimulate significantly the release of lysozyme activity of monocytes and epithelial cells after one hour treatment at non-toxic concentrations. On the contrary, cells treated with saponins for longer periods up to 72 hours showed tendency to decrease in the secretion and production of lysozyme activity. However, these inhibitory effects of saponins observed with long-term treatment periods were mostly associated with toxic effects of saponins to cells. The results suggested positive contribution of some saponins to lysozyme release of monocytes and epithelial cells upon short exposure. Furthermore, demonstrated ability of these saponins to enhance the release of lysozyme activity can present a new mechanism contribute to explaining important biological characteristics of saponins, including the antibacterial, antiviral, anti-inflammatory or immune-stimulating properties.

New aspects in the synthesis and secretion of lysozyme by cultured human monocyte cell lines

The main purpose of this study was to investigate lysozyme synthesis and secretion in three human monocyte cell lines: U-937, HL-60, and THP-1, using sensitive fluorescence-based assay of lysozyme activity. PMA and hIFN-gamma were evaluated for inducing lysozyme activity. Using well-defined cell lines from the cell culture collection, no lysozyme activity could be detected in the cultured U-937 cells either with or without addition of the inducing factors. These data suggested, contrary to previous reports, that U-937 cell line cannot synthesize or secrete active lysozyme. THP-1 and HL-60 cells were proved to produce enzymatically active lysozyme in increasing amounts with the time course. PMA and hIFN-gamma had no significant inducing effect on the production or the release of active lysozyme in THP-1 and HL-60 cells. We showed inhibiting effect of PMA and hIFN-gamma on the lysozyme activity, particularly in HL-60 cell line.

Determination of lysozyme activity by a fluorescence technique in comparison with the classical turbidity assay

The aim of this comparable study was to evaluate two different methods for the assay of lysozyme activity. Lysozyme activity was assayed by turbidimetric and fluorescence-based methods with hen egg white lysozyme as standard. The standard activity of each assay was calibrated in units of activity per mg under the experimental conditions (37 degrees C) so that direct comparison between these two assays could be made. The turbidimetric assay was performed using a 0.36 mg/ml Micrococcus lysodeikticus suspension and a microtiter plate reader capable of analyzing enzyme kinetics at 450 nm, and the linearity, in the range of 2.3-23.8 units/ml, presented a correlation coefficient (R2) as high as 0.9967. The fluorescence-based assay was performed with EnzChek kit using a suspension of Micrococcus lysodeikticus labeled with fluorescein and a fluorescence microplate reader. The linearity in the range of 0.47-5.28 units/ml, presented a correlation coefficient (R2) as high as 0.9881. Thus, the turbidimetric assay provides a simple rapid accurate and specific method for the determination of lysozyme activity but with relatively low sensitivity in comparison with the fluorescence-based method which was demonstrated to be a high sensitivity assay, and hence a reliable applicable technique to determine lysozyme activity at low levels e.g. in cell culture systems.

Hemodynamic effects of external continuous negative pressure ventilation compared with those of continuous positive pressure ventilation in dogs with acute lung injury

Patients with noncardiogenic pulmonary edema requiring ventilatory assistance are usually supported with CPPV using positive end-expiratory pressure (PEEP), but CPPV requires endotracheal intubation and may decrease cardiac output (QT). The purpose of this study was to examine thoracoabdominal continuous negative pressure ventilation (CNPV) using external negative end-expiratory pressure (NEEP). The effects on gas exchange and hemodynamics were compared with those of CPPV with PEEP, with the premise that CNPV might sustain venous return and improve QT. In 6 supine, anesthetized and paralyzed dogs with oleic-acid-induced pulmonary edema, 30 min of CNPV was alternated twice with 30 min of CPPV. Positive and negative pressure ventilation were carefully matched for fractional inspired oxygen concentration (FIO2 = 0.56), breathing frequency, and tidal volume. In addition, we matched the increase in delta FRC obtained with the constant distending pressures produced by both modes of ventilation. An average of -9 cm H2O of NEEP produced the same delta FRC as 10.8 cm H2O of PEEP. Gas exchange did not differ significantly between the 2 modes. However, QT was 15.8% higher during CNPV than during CPPV (p less than 0.02). Mixed venous oxygen saturation also improved during CNPV compared with that during CPPV (58.3 versus 54.5%, p less than 0.01). Negative pressure ventilation using NEEP may be a viable alternative to positive pressure ventilation with PEEP in the management of critically ill patients with noncardiogenic pulmonary edema. It offers comparable improvement in gas exchange with the advantages of less cardiac depression and the possible avoidance of endotracheal intubation.