Lactobacillus species dominate the healthy vaginal ecological niche coexisting in a dynamic balance with the host mucosa. The vaginal lactobacilli play a crucial role in maintaining the homeostasis of the female genital tract by preventing the overgrowth of pathogens. Chlamydia trachomatis, a leading cause of sexually transmitted disease worldwide, can induce severe sequelae in women, i.e. pelvic inflammatory disease, infertility and ectopic pregnancy. C. trachomatis is an obligate intracellular bacterium with a unique cycle of development, alternating between two distinct bacterial forms: the infectious but non-dividing elementary bodies (EBs), and the non-infectious but replicative reticulate bodies (RBs). In the present study we investigated the interference of Lactobacillus crispatus, L. gasseri and L. vaginalis, dominant species in the vaginal microbiota, with C. trachomatis infection process. HeLa cells, a human cervical tumor cell line, were taken as an in vitro model. Firstly, we evaluated the capability of lactobacilli to inactivate C. trachomatis EBs in external killing experiments, that mimic the phase preceding the pathogen-host interaction. Lactobacilli cell free supernatants (CFS) exerted a strong killing activity on Chlamydia EBs in a concentration/pH dependent mode, especially when applied for short contact times. These results suggest a protective role of lactobacilli in the early steps of Chlamydia infection through the action of secreted metabolites. Lactobacillus CFS were analysed by 1H-NMR in order to delineate metabolic profiles related to anti-Chlamydia activity. Production of lactate and acidification of the vaginal environment seemed to be crucial for the activity, in addition to the consumption of the carbonate source represented by glucose. Secondly, we investigated the potential of the vaginal lactobacilli to interfere with C. trachomatis adhesion and entry into human epithelial cells. We found that lactobacilli cell pellets (CP) were more active than CFS in counteracting C. trachomatis penetration in HeLa cells, particularly by means of an exclusion strategy. L. crispatus strains showed the best anti-Chlamydia activity in all experiments. Finally, we studied the modulation activity of the vaginal lactobacilli on HeLa cells plasma membrane. The interaction of lactobacilli with the cervical cells determined the following effects on the plasma membrane: reduction of permeability and fluidity, modification of the polar lipid organization and modulation of integrins exposure. These effects can be at the basis of the protective role of lactobacilli CP against the entry of pathogens into epithelial cells. Furthermore, upon stimulation with all Lactobacillus strains, we observed a reduction of the basal oxidative stress in HeLa cells that could be related to modifications in physical properties and organization of the plasma membrane.
Vaginal lactobacilli and woman’s health: prevention of sexually transmitted infections and interaction with the cervico-vaginal epithelium
VITALI, BEATRICE
2017
Abstract
Lactobacillus species dominate the healthy vaginal ecological niche coexisting in a dynamic balance with the host mucosa. The vaginal lactobacilli play a crucial role in maintaining the homeostasis of the female genital tract by preventing the overgrowth of pathogens. Chlamydia trachomatis, a leading cause of sexually transmitted disease worldwide, can induce severe sequelae in women, i.e. pelvic inflammatory disease, infertility and ectopic pregnancy. C. trachomatis is an obligate intracellular bacterium with a unique cycle of development, alternating between two distinct bacterial forms: the infectious but non-dividing elementary bodies (EBs), and the non-infectious but replicative reticulate bodies (RBs). In the present study we investigated the interference of Lactobacillus crispatus, L. gasseri and L. vaginalis, dominant species in the vaginal microbiota, with C. trachomatis infection process. HeLa cells, a human cervical tumor cell line, were taken as an in vitro model. Firstly, we evaluated the capability of lactobacilli to inactivate C. trachomatis EBs in external killing experiments, that mimic the phase preceding the pathogen-host interaction. Lactobacilli cell free supernatants (CFS) exerted a strong killing activity on Chlamydia EBs in a concentration/pH dependent mode, especially when applied for short contact times. These results suggest a protective role of lactobacilli in the early steps of Chlamydia infection through the action of secreted metabolites. Lactobacillus CFS were analysed by 1H-NMR in order to delineate metabolic profiles related to anti-Chlamydia activity. Production of lactate and acidification of the vaginal environment seemed to be crucial for the activity, in addition to the consumption of the carbonate source represented by glucose. Secondly, we investigated the potential of the vaginal lactobacilli to interfere with C. trachomatis adhesion and entry into human epithelial cells. We found that lactobacilli cell pellets (CP) were more active than CFS in counteracting C. trachomatis penetration in HeLa cells, particularly by means of an exclusion strategy. L. crispatus strains showed the best anti-Chlamydia activity in all experiments. Finally, we studied the modulation activity of the vaginal lactobacilli on HeLa cells plasma membrane. The interaction of lactobacilli with the cervical cells determined the following effects on the plasma membrane: reduction of permeability and fluidity, modification of the polar lipid organization and modulation of integrins exposure. These effects can be at the basis of the protective role of lactobacilli CP against the entry of pathogens into epithelial cells. Furthermore, upon stimulation with all Lactobacillus strains, we observed a reduction of the basal oxidative stress in HeLa cells that could be related to modifications in physical properties and organization of the plasma membrane.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
