Lactobacillus rhamnosus Lcr35 as an effective treatment for preventing Candida albicans infection in the invertebrate model Caenorhabditis elegans: First mechanistic insights

Abstract

The increased recurrence of Candida albicans infections is associated with greater resistance to antifungal drugs. This involves the establishment of alternative therapeutic protocols, such as probiotic microorganisms whose antifungal potential has already been demonstrated using preclinical models (cell cultures, laboratory animals). Understanding the mechanisms of action of probiotic microorganisms has become a strategic need for the development of new therapeutics for humans. In this study, we investigated the prophylactic anti-C. albicans properties of Lactobacillus rhamnosus Lcr35® using the in vitro Caco-2 cell model and the in vivo Caenorhabditis elegans model. In Caco-2 cells, we showed that the strain Lcr35® significantly inhibited the growth (~2 log CFU.mL-1) and adhesion (150 to 6,300 times less) of the pathogen. Moreover, in addition to having a pro-longevity activity in the nematode (+42.9%, p = 3.56.10−6), Lcr35® protects the animal from the fungal infection (+267% of survival, p < 2.10−16) even if the yeast is still detectable in its intestine. At the mechanistic level, we noticed the repression of genes of the p38 MAPK signalling pathway and genes involved in the antifungal response induced by Lcr35®, suggesting that the pathogen no longer appears to be detected by the worm immune system. However, the DAF-16/FOXO transcription factor, implicated in the longevity and antipathogenic response of C. elegans, is activated by Lcr35®. These results suggest that the probiotic strain acts by stimulating its host via DAF-16 but also by suppressing the virulence of the pathogen.

Role of glucosyltransferase R in biofilm interactions between Streptococcus oralis and Candida albicans

“…Exposure to a high sucrose diet changes the composition of the endogenous microbial communities in the alimentary tract of mice [38]. Such changes may involve overgrowth of endogenous lactic acid bacteria which curtail C. albicans growth and/or hyphal morphogenesis [39].…”

Curative Treatment of Candidiasis by the Live Biotherapeutic Microorganism Lactobacillus rhamnosus Lcr35® in the Invertebrate Model Caenorhabditis elegans: First Mechanistic Insights

“…To elucidate the mechanisms involved in the action of Lcr35 ® against C. albicans, we studied the expression of seven C. elegans genes (Table 2) divided into three groups: daf-2 and daf-16 (insulin signaling pathway) involved in host longevity and antipathogenicity response, sek-1 and pmk-1 (p38 MAPK signaling pathway) which concern the immunity reaction as well as abf-2, cnc-4 and fipr-22/fipr-23 which encode antimicrobial proteins. The interest in targeting these genes has been demonstrated by various studies showing that the insulin and p38 MAPK pathways were involved in the pro-longevity properties of lactobacilli and bifidobacteria [12,[18][19][20], while the antimicrobial genes were involved in the anti-Candida effect [21]. In comparison with the E. coli OP50 control condition, we noted that Lcr35 ® induced an overexpression of daf-16 (p = 0.0004) and had no effect on daf-2 (p = 0.9459), while C. albicans tended to induce an up regulation of daf-2 (p = 0.0922) and a down-regulation of daf-16 (p = 0.4959).…”

“…Deciphering these mechanisms therefore requires the use of cellular and animal models having enough homology with humans. This type of approach, implemented during our previous work [12], highlighted the preventive protective capacities of the LBM on intestinal Caco-2 cells and the invertebrate Caenorhabditis elegans, with respectively an inhibition of the growth of the yeast and an optimal survival of the host. So far, most studies have been conducted in contexts of fungal infection prevention.…”

“…These have provided answers about the mechanisms of action allowing an LBM to prevent the installation of a pathogen with, for instance, the reduction of C. albicans hyphae formation [12][13][14][15][16]. However, few studies showing the efficacy of LBM against candidiasis have been conducted and no "curative" study relative to C. albicans was conducted using the nematode C. elegans [12,16]. The only curative study was carried out by Sharma and colleagues against infections with E. coli pathogenic strains [17].…”

“…In this context, we wanted to evaluate the effect of Lactobacillus rhamnosus Lcr35 ® strain to cure a fungal infection due to C. albicans. In order to overcome the experimental limits of the Caco-2, an enterocyte-like cell line in vitro model, we conducted the mechanistic study on C. elegans, an in vivo model relevant for interaction and mechanistic investigations [12]. The worm survival and gene expression, in response to the pathogen and/or the LBM, were evaluated.…”