Chemistry Reference
In-Depth Information
12.5.2 Probiotic supernatants
Recently, there has been increasing interest in the use of probiotic supernatants
in the treatment of intestinal disorders. Probiotic supernatants are devoid of bacte-
rial cells, but contain a mixture of secreted products. If deemed to have therapeutic
potential, the use of bacterial supernatants would reduce the minor risk of sepsis
associated with administration of live bacteria. The use of supernatants will also
facilitate the delivery of these secreted products in a more controlled manner, which
does not require the colonization and survival of the bacterium.
109
Bacterial superna-
tants could also be more effective therapeutics as they would have a longer shelf life
than live bacteria, facilitating greater quality control during production. The exact
composition of the secreted products is not known, but would vary dependent on
species, strain, and culture conditions. Studies have reported probiotic supernatants
to contain SCFAs,
110
phospholipids,
111
bacteriocins,
112
and proteins.
109
Frick and colleagues investigated the ability of
L. fermentum
supernatant to
inhibit the proinflammatory responses of HeLa 229 cells on
Yersinia enterocolitica
infection.
111
Yersinia enterocolitica
treatment was shown to induce two proinflam-
matory responses: NF-κB activation and increased IL-8 production. Treatment with
L. fermentum
supernatant inhibited IL-8 secretion and decreased NF-κB activation
following infection. The antiinflammatory effect of
L. fermentum
supernatant was
diminished upon treatment with phospholipase C, indicating a key role for a secreted
phospholipid in the antiinflammatory effect. Similarly, Roselli and colleagues dem-
onstrated the efficacy of both
B. animalis
MB5 and LGG in the treatment of E
.
coli
K88-infected Caco-2 cells.
104
Supernatant administration decreased
E. coli
K88
adhesion, counteracted IL-8 upregulation, and inhibited neutrophil translocation.
This supernatant exerted identical beneficial effects following protease digestion,
suggesting that proteins were not the active constituent.
Escherichia coli
viabil-
ity was unaffected by treatment, eliminating bactericidal activity of the probiotic
or its supernatant. The mechanism for these beneficial effects needs to be further
elucidated. Interestingly, only treatment with live bacteria prevented the pathogen-
induced increase in expression of IL-1β and TNF-α and the decrease of TGF-α. This
study provided an example of the differing impact of live bacteria and supernatants,
and highlights that not all therapeutic benefits of probiotic bacteria are mediated by
their secreted products.
Yan and colleagues performed the first study in which proteins were character-
ized and purified from a probiotic supernatant, and shown to exert beneficial effects
on colonic epithelial cells.
109
In this experiment, two proteins (p75 and p40) were
isolated from LGG and tested in four settings: young adult mouse colon epithelial
cells, kinase suppressor of Ras
-1
knockout mouse colon epithelial cells, human HT-29
colon cells, and cultured C57BL/6 mouse colon explants. Cells and colon explants
treated with p75 and p40 displayed increased Akt activation, inhibition of cytokine-
induced epithelial cell apoptosis, and growth promotion. TNF-induced epithelial cell
apoptosis was also significantly reduced by both p75 and p40. These findings eluci-
date key mechanisms behind the therapeutic effects of LGG, and indicate potential
