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

Racha Helal

doi:10.3797/scipharm.1012-15

Abstract

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.

Highlights

Human lysozyme (1,4-N-acetylmuramidase, E.C.3.2.1.17) is a ubiquitous low molecular– weight enzyme present in a wide range of biological fluids and tissues within animal and plant kingdoms [1]
Most examined saponins, which have been reportedly known for their influence on the immune response, stimulated the release of lysozyme activity after one hour incubation with monocytes (Fig. 1)
Percent change in the secreted lysozyme activity of 1×10+6 cells/ml THP-1 cell cultures treated with various saponins for 1 hour using sensitive fluorescencebased lysozyme activity assay

Summary

Introduction

Human lysozyme (1,4-N-acetylmuramidase, E.C.3.2.1.17) is a ubiquitous low molecular– weight enzyme present in a wide range of biological fluids and tissues within animal and plant kingdoms [1]. Among major cell types responsible for the production of lysozyme are monocytes/macrophages and neutrophilic granulocytes as a part of their surveillance functions in the immune system [3]. This antimicrobial peptide tends to be found abundantly in animal tissues that are likely to come in contact with pathogens, such as airway epithelia and other epithelial tissues [4]. The purpose of the present study was to investigate whether in vitro exposure to various concentrations of selected saponins can affect the release and production of lysozyme activity in human monocytic cells THP-1, and in human epithelial cells HT-29. The selection of the investigated saponins was based on their proven antibacterial, antiviral, anti-inflammatory or immune-stimulating properties

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