Abstract
Lactobacillus plantarum species (recently re-named Lactiplantibacillus (Lpb.) plantarum subsp. plantarum) can be isolated from both either the mammalian gut or specific fermented foods where they may be present at high concentrations. Whilst Lpb. plantarum strains have been proposed as potential probiotic candidates, the ability of resident strains consumed in fermented foods to interact with the host is unclear. The main objective of this study was to investigate the cellular location and ability of three different food-borne Lpb. plantarum strains isolated from different sources (table olives and cheese) to modulate the immune response of a murine macrophage-like cell line (J774A.1). For that purpose, macrophages were exposed to the three different Lpb. plantarum strains for 24 h and the expression of a panel of genes involved in the immune response, including genes encoding pattern-recognition receptors (TLRs and NLRs) and cytokines was evaluated by qRT-PCR. We also utilized chemical inhibitors of intracellular pathways to gain some insight into potential signaling mechanisms. Results showed that the native food strains of Lpb. plantarum were able to modulate the response of J774A.1 murine macrophages through a predominately NOD signaling pathway that reflects the transient intracellular location of these strains within the macrophage. The data indicate the capacity of food-dwelling Lpb. plantarum strains to influence macrophage-mediated host responses if consumed in sufficient quantities.
Highlights
The original genus Lactobacillus (L.) comprised a heterogeneous group of non-sporeforming, nonmotile and rod-shaped bacteria (Plot et al, 2014)
In accordance with the regulations outlined by FAO/WHO (2006), a potential probiotic strain should be able to survive in the gastrointestinal tract by exhibiting acid and bile tolerance, transiently colonize the gut and be able to exert any benefits on the host (Hill et al, 2014)
The results show that Lpb. plantarum strains increase the expression of Tlr2, Tlr9, and Nod2
Summary
The original genus Lactobacillus (L.) comprised a heterogeneous group of non-sporeforming, nonmotile and rod-shaped bacteria (Plot et al, 2014). A recent phylogenetic and ecological revaluation of the genus has led to reclassification of Lactobacillus species into 25 proposed genera (Zheng et al, 2020). Immunomodulation by Food-Borne Lactiplantibacillus plantarum plantarum subsp. Lpb. plantarum has been used as a starter culture in food fermentation processes due to its organoleptic fermentative properties and a capacity to produce lactic acid and other antimicrobial compounds (Seddik et al, 2017; Behera et al, 2018). We have recently shown that Lpb. plantarum strains are likely to be consumed at high concentrations in table olives where they are one of the predominant species (107–108 CFU/g) (Hurtado et al, 2012; Heperkan, 2013; Perpetuini et al, 2020). The potential impact of these autochthonous food strains on the host, when either consumed directly or re-employed as starter cultures, is currently unclear
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