Lactobacillus paracasei and Lactobacillus plantarum strains downregulate proinflammatory genes in an ex vivo system of cultured human colonic mucosa

Significant health benefits have been demonstrated for certain probiotic strains through intervention studies; however, there is a shortage of experimental evidence relative to the mechanisms of action. Here, noninvasive experimental procedure based on a colon organ culture system has been used that, in contrast to most experimental in vitro models reported, can preserve natural immunohistochemical features of the human mucosa. This system has been used to test whether commensal lactobacilli (Lactobacillus paracasei BL23, Lactobacillus plantarum 299v and L. plantarum 299v (A(-))) were able to hinder inflammation-like signals induced by phorbol 12-myristate 13-acetate (PMA)/ionomycin (IO). Whole genome microarrays have been applied to analyze expression differences, from which mRNA markers could be inferred to monitor the effect of putative probiotic strains under such conditions. Regarding the gene expression, PMA/IO treatment induced not only interleukin (IL)-2 and interferon gamma (IFN-gamma), as expected, but also other relevant genes related to immune response and inflammation, such as IL-17A, chemokine (C-X-C motif) ligand (CXCL) 9 and CXCL11. The ex vivo culturing did not modify the pattern of expression of those genes or others related to inflammation. Interestingly, this study demonstrated that lactobacilli downregulated those genes and triggered a global change of the transcriptional profile that indicated a clear homeostasis restoring effect and a decrease in signals produced by activated T cells.