Modulation of Macrophage Function by Lactobacillus-Conditioned Medium

Abstract

Probiotics are used as microbial food supplements for health and well-being. They are thought to have immunomodulatory effects although their exact physiological mechanism of action is not clear. This study investigated the influence of probiotic Lactobacillus rhamnosus GG conditioned media (LGG-CM) on macrophage phagocytosis of non-pathogenic Escherichia coli HfrC. The gentamicin protection assay was used to study the bacterial killing phases of phagocytosis. Macrophages coincubated with E. coli for an hour allowed them to ingest bacteria and then the rate of E. coli killing was monitored for up to 300 min to determine the killing or digestion of the bacteria by recovering them from the macrophage lysate. We found that the LGG-CM significantly increased the bacterial killing by approximately 6-fold when compared with that of controls. By contrast, this killing process was found to be associated with enhanced free radical production via the activation of NADPH oxidase, stimulated by the LGG conditioned medium. We also found that the conditioned medium had small effect on nitric oxide (NO) generation, albeit to a lesser extent. This work suggests that LGG-CM may play an important role in suppressing the total microbial load within the macrophages and hence, the extent to which pro-inflammatory molecules such as free radicals and NO are generated. The modulation of inflammation-promoting signals by LGG-CM may be beneficial as it modulates bacterial killing, and thereby prevents any collateral damage to host.

Extracellular Proteins Isolated from L. acidophilus as an Osteomicrobiological Therapeutic Agent to Reduce Pathogenic Biofilm Formation, Regulate Chronic Inflammation, and Augment Bone Formation In Vitro

“…***p < 0.001. phagocytic bacterial clearance. In support of this, and using a conditioned medium obtained from cultures of L. rhamnsosus, Nanjundaiah et al [119] showed a dose-dependent increase in the bacterial killing ability of macrophages against E. coli, and that this was found to be associated with the enhanced production of reactive oxygen species (ROS) and nitric oxide (NO) in differential amounts, within macrophages. Similarly, Rocha-Ramirez et al [120] demonstrated that the pretreatment of macrophages with varying Lactobacillus strains increased their phagocytic and bactericidal activity toward pathogens including S. aureus and E. coli.…”

“…[106] Regulating phagocytic macrophage activity by probiotics has been shown to enhance their ability to engulf and kill pathogenic bacteria, thereby augmenting the innate host immune response to infection. [119] However, the mechanisms that impact macrophage phagocytic capacity and downstream phagosomal processing remain poorly understood. The phagocytic response to S. aureus was not investigated in this study and as a dose-dependent response was measured, further investigation is essential to determine the role of LaEP-induced enhanced [B] Cell viability was assessed using a live/ dead assay, where live cells stain green and dead cells, red.…”

The commensal bacterium Lactiplantibacillus plantarum imprints innate memory-like responses in mononuclear phagocytes

“…that may activate innate immune cells. Lactobacilli produce a wide array of proteins and metabolites, such as short-chain fatty acids, 40 , 41 that are secreted to the extracellular medium and might exert immunomodulatory properties.…”

Phagocytosis: Inflammation-Obesity Relationship

“…When macrophages were exposed to LGG-conditioned media, their phagocytic and bactericidal activity was increased up to sixfold. This activity was associated with an increment in free radicals production, with the activation of NADPH oxidase, and a slight increase in nitric oxide generation [78].…”