VSL3 Probiotics in animal models
The use of VSL3 probiotics resulted in a complete normalization of physiological transport function and barrier integrity, in conjunction with a reduction in mucosal secretion of TNF-a. and IFN-y in the IL-10 gene-deficient mouse. Madsen et al. (74) described numerous studies that have characterized the ability of various strains of probiotics, especially the probiotic VSL#3, to modify the activity and cytokine expression of gut-associated lymphoid tissue and epithelial cells.
The rationale behind the use of a probiotic compound containing high levels 'of a mixture of different bacterial species was to attempt to influence the microbial composition of the colon through a synergistic action of the different strains in the mixture. One of the bacteria in this mixture, Lactobacillus delbruekii subsp. bulgaricus enhanced the mucus binding of Bifidobacterium lactis in vitro, suggesting that combinations of adherent probiotic strains can influence other strains' adhesion and activity in the human intestinal tract (74).
In their study, Madsen et al. (74), showed that, compared with controls, IL-10 gene-deficient mice spontaneously secreted higher amounts of TNF-a. from both the ileum and the colon. One of the observations showed that IL-10 gene-deficient mice developed spontaneous colitis similar to the inflammation observed in patients with Crohn's disease. Histological damage began within 4 weeks and reached a plateau after 8 weeks.
In these mice within 2 weeks of age and before appearance of injury, there was an alteration in bacterial colonization and an increase in translocated and mucosal-adhered bacteria. These alterations reached a steady state 1month before maximal histological injury and persisted for months. It was important that the concentration of Lactobacillus spp., a species that prevents adhesion of pathogens, was reduced within 2 weeks and reduced in a pattern paralleling mucosal injury (62).
Colonic tissue from IL-10 gene-deficient mice responded to the presence of LPS with an enhanced release of TNF-a., thus suggesting the presence of monocytes and active inflammation. On the other hand, ileal tissue from IL-10 gene-deficient mice showed a twofold increase in the spontaneous basal TNF-a. secretion, but compared to controls, there was no response to LPS with a significant increase in TNF-a. secretion and no histological inflammation in this region. Control mice did not respond to the presence of LPS increase in TNF-a. secretion in the ileum or in the colon.
In a study by Madsen et al. (74), IL-10 gene-deficient mice received VSL3 for 4 weeks and showed, compared to untreated IL-10 mice, a significantly reduced TNF-a secretion in the ileum and colon. VSL#3 had no effects on cytokine secretion from the ileum of control mice. Compared to controls, IL10 gene-deficient mice also showed an increase in spontaneous IFN-y secretion both in ileum and colon, which was not stimulated by LPS. VSL#3 treatment normalized basal IFN-y secretion in the ileum but not in the colon. These results suggested that the luminal microflora modulated the immune cytokine responses, both under normal and inflammatory conditions. It was also found that, even in the absence of the regulatory cytokine IL-10, the intestinal mucosa in IL-10 gene-deficient mice responded to the presence of the Lactobacillus and Bifidobacterium found in the VSL#3 mixture with a down-regulation of a proinflammatory immune response.
This study showed that treatment of IL-10 gene-deficient mice with VSL#3 resulted in normalization of colonic physiologic function and barrier integrity in combination with reduction in mucosal levels of proinflammatory cytokines and a significant improvement in histological features.
Another study, carried out in alcohol-fed rodents, demonstrated that intestinal bacteria, bacterial endotoxin, and the endotoxin-inducible cytokine, TNF-a, modulated alcohol-induced liver damage (13). Treatments such as antibiotics and Lactobacillus, that inhibit endotoxin production by the intestinal flora, or treatments that inhibit the activity of TNF-a itself, significantly inhibited the development of steatohepatitis in animals ingesting large amounts of alcohol. In this respect, Li et al. (13) observed mice for 4 weeks and found that intestinal bacteria, endotoxin LPS- and LPS-induced cytokines such as TNF-a are important modulators of alcoholic fatty liver disease. Treatments that partially decontaminate intestinal flora and treatments that inhibit activity of TNF-a itself inhibited alcoholic fatty liver disease in experimental animals. In this regard, Li et al. (13) hypothesized that treatment with VSL3 or anti-TNF-a antibodies would improve nonalcoholic fatty liver disease in these mice by down-regulating NFKB and JNK (13).