Immunomodulatory Activity on Human Macrophages by Cell-Free Supernatants to Explore the Probiotic and Postbiotic Potential of Lactiplantibacillus plantarum Strains of Plant Origin

Abstract

Upon dietary administration, probiotic microorganisms can reach as live cells the human gut, where they interact with the microbiota and host cells, thereby exerting a beneficial impact on host functions, mainly through immune-modulatory activities. Recently, attention has been drawn by postbiotics, i.e. non-viable probiotic microbes, including their metabolic products, which possess biological activities that benefit the host. Lactiplantibacillus plantarum is a bacterial species that comprises recognised probiotic strains. In this study, we investigated in vitro the probiotic (and postbiotic) potential of seven L. plantarum strains, including five newly isolated from plant-related niches. The strains were shown to possess some basic probiotic attributes, including tolerance to the gastrointestinal environment, adhesion to the intestinal epithelium and safety. Besides, their cell-free culture supernatants modulated cytokine patterns in human macrophages in vitro, promoting TNF-α gene transcription and secretion, while attenuating the transcriptional activation and secretion of both TNF-α and IL-8 in response to a pro-inflammatory signal, and enhancing the production of IL-10. Some strains induced a high IL-10/IL-12 ratio that may correlate to an anti-inflammatory capacity in vivo. Overall, the investigated strains are good probiotic candidates, whose postbiotic fraction exhibits immunomodulatory properties that need further in vivo studies. The main novelty of this work consists in the polyphasic characterisation of candidate beneficial L. plantarum strains obtained from relatively atypical plant-associated niches, by an approach that explores both probiotic and postbiotic potentials, in particular studying the effect of microbial culture-conditioned media on cytokine pattern, analysed at both transcriptional and secretion level in human macrophages.

Postbiotic Fractions of Probiotics Lactobacillus plantarum 299v and Lactobacillus rhamnosus GG Show Immune-Modulating Effects

“…Postbiotics derived from Lactobacillus species have mainly immunoregulatory effects on immune-competent cells, such as macrophages. It has been found that lipoteichoic acid from the cell wall of L. plantarum attenuates pro-inflammatory TNF-α cytokine activation in response to LPS stimuli, but significantly upregulates IL-10 production [33]. Shi et al also examined the effect of probiotic bacteria of the Lactobacillus genus on the expression of the main pro-inflammatory cytokines, TNF-α, IL-6 and L-1β, in LPS-induced macrophage cultures.…”

Evaluation of immunomodulatory potential of probiotic conditioned medium on murine macrophages

“…So far, to the best of our knowledge, no study has investigated the immunostimulatory effect of "active" multi-species probiotic conditioned medium on RAW264.7 murine macrophages. Almost all studies in this field have investigated single-species probiotics 27 , 28 , the effect of a killed multi-species probiotic conditioned medium 29 . As such, in this study, we evaluated the effect of cell-free Probiotic Conditioned Medium (CM) using Advanced Multi-Billion Dophilus commercially available probiotics, which are mainly Lactobacilli and Bifidobacteria.…”