Chemistry Reference
In-Depth Information
Produce
antimicrobial
substances
Stimulation of
immunity
Compete for
nutrients
Pathogens
PROBIOTICS
Competition for
receptors
Degradation of
toxin pathogen
receptors
Mucin secretion
Block receptors
Receptors on intestinal walls
where pathogens attach
Figure 18.2
Mechanism of action of probiotics.
5. Possible modification of toxin receptors and blockage of toxin-mediated pathology
by probiotics.
12,19
Saccharomyces boulardii
degrades
Clostridium
difficile
toxin
receptors in the rabbit ileum
20
and blocks cholera-induced secretion in rat jejunum
by the production of polyamines.
21
6. Possible promotion by probiotics of nonspecific stimulation of the host immune
system, including immune cell proliferation, enhanced phagocytic activity of mac-
rophages, and increased production of secretory immunoglobulin A (IgA) and
IgM.
12,22
Probiotics have also been reported to stimulate the production of inter-
feron gamma (IFN-γ), interleukin 2 (IL-2), IL-12, and IL-18.
23,24
IL-12 may in
turn downregulate the Th2 response, thereby decreasing IL-4 and IgE production,
which would explain the role of probiotics in allergy prevention.
24
7. Stabilization of intestinal permeability barrier, which restricts colonization by
pathogens, eliminates foreign antigens, which have penetrated the mucosa, and
regulates the antigen-specific immune responses.
23
8. Probiotic bacterial “priming” of gut-associated lymphoid tissue (GALT) and immu-
nomodulation of gut-associated lymphoid and epithelial tissue response.
4,24
18.3 sAlvAgE oF vArIous DIsorDErs
Through ProbIoTIC ThErAPy
18.3.1 Intestinal Disorders
Intestinal homeostasis relies on the equilibrium between absorption (nutrients,
ions), secretion (ions, IgA) and barrier capacity (to pathogens and macromolecules)
of the digestive epithelium. Disturbance of this homeostatic control results in inflam-
mation, diarrhea, and various intestinal diseases. To better understand the benefi-
cial effects of probiotics in digestive diseases, it is important to take into account
the mechanisms involved in the derangement of epithelial functions (Figure 18.3),
such as (1) dysregulation of ion-coupled nutrient absorption and (2) an abnormal
stimulation of ion secretion, in turn driving water losses.
25,26
Water movements are
