Effect of L.pentosus extract on host defence and microbiota

These dynamic interactions play a crucial role in establishment of the protection against pathogens by spatial and nutritional competition, production of antimicrobial peptides and stimulation of host immunity. Production of antimicrobial peptides by epithelia is an essential defence against infection by pathogens. The protection ensured by the host defence peptides (HDPs) is widely recognised for multifunctional roles in both the innate and adaptive immune responses. 

Using an ex vivoskin model approach, we evaluated whether an extract from the bacteria Lactobacillus pentosus(Lp) may enhance the production of host defence peptides such as (psoriasin) S100A7 and ß-defensin 2 (hBD-2). We also evaluated the compatibility of Lp extract with the skin microbiota of healthy volunteers. The skin microbiota analysis was performed based on 16 rRNA gene sequencing to observe the dynamism of populations and the diversity after 7 days of application. We noted a significant increase of 237% (p<0.01) for S100A7 and 229% (p<0.01) for hBD-2). L. pentosusextract maintains the preservation of healthy status of skin microbiota through the composition of commensal bacteria and protection against pathogen invasion. 

The skin is constantly exposed to external and internal disruptive factors (ultraviolet radiation, pollution) that can alter the balanced relationship between the skin and its microbiota.1 Disruption may result in increased risk for infections, chronic inflammatory skin diseases (atopic dermatitis, psoriasis, acne) and complaints of sensitive and irritated skin.2 To prevent disruption, skin has established a complex system of immune control composed by the actions of epithelial cells, lymphocytes and antigen-presenting cells.3 One of these fundamental processes involves defined components of the skin microbiota called PAMP (pathogen-associated molecular pattern) that can bind to the innate immune receptor, Toll-like receptors (TLRs) (Fig 1). This family of receptors is able to modulate the defense of the host, via the innate immunity and the inflammatory response.4, 5 Skin commensal microorganisms can participate in the regulation of the expression of various innate immune factors, including host defence peptides (HDPs). HDPs belong to multiple protein families, which, in the skin are dominated by cathelicidins and ß-defensins.6 To date, only four ß-defensins and one cathelicidin have been identified in human skin. Their expression has been studied in healthy as well as inflamed skin (e.g. atopic dermatitis and psoriasis). The defensins are the most represented family in mammals with a broad spectrum of actions against bacteria, viruses and fungi. The antimicrobial activity of human ß-defensin-2 has been reported to be predominantly effective against gramnegative bacteria such as Escherichia coli and Pseudomonas aeruginosaand less against Staphylococcus aureus.7 Within the epidermis, ß-defensins following exposure to microorganisms is differentially expressed according to the degree of keratinocyte differentiation.8 Among the HDPs, the S100 proteins, low molecular weight proteins are involved in multiple functions in many cell and tissue types. It appears that S100 proteins serve as calcium sensors that, after activation, regulate the function and/or subcellular distribution of specific target proteins.9 Among them, S100A7 (also known as psoriasin) has been identified as an anti-microbial peptide expressed by keratinocytes and playing a key role in the response against Escherichia coli.10