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Nutritional Immunology

Live and Ultraviolet-Inactivated Lactobacillus Rhamnosus GG Decrease Flagellin-Induced Interleukin-8 Production in Caco-2 Cells^1–3,

⁴ Department of Pediatrics, University of Florida, Gainesville, FL, 32610-0296 and ⁵ Mead Johnson Nutritionals, Evansville, Indiana 47721-0001

^* To whom correspondence should be addressed. E-mail: neuj{at}peds.ufl.edu.

Probiotics are widely used in the treatment and prevention of gastrointestinal problems. However, in some immune-compromised populations, the administration of live microorganisms may not be appropriate. A potential alternative to live microorganisms is to inactivate them as long as the beneficial function is retained. We hypothesized that UV-inactivated Lactobacillus rhamnosus GG (LGG) could downregulate interleukin-8 (IL-8) production in intestinal epithelial cells stimulated by the pathogenic ligand, flagellin, using similar mechanisms as live LGG. Caco-2 cells were pretreated with live or UV-inactivated LGG at 10¹¹ colony-forming units/L and stimulated by flagellin at a dose of 500 µg/L. IL-8 production was measured by ELISA, inhibitor of B (IB) and ubiquitinated-IB (Ub-IB) expression by immunoblotting and nuclear factor (NF) B localization by immunofluorescence staining. Flagellin induced a 17-fold increase in IL-8 production compared with control (P < 0.05), whereas pretreatment with either live LGG or UV-inactivated LGG resulted in 66 and 59% decreases, respectively, compared with the flagellin group (P < 0.05). Flagellin-induced NFB nuclear translocation was prevented by both live and UV-inactivated LGG. Flagellin decreased IB, which was reversed by either live or UV-inactivated LGG (P < 0.05). UV-inactivated LGG decreased Ub-IB expression (P < 0.05), although live LGG had no effect. This study supports the concept that UV-inactivated and live LGG are equally effective in decreasing IL-8 production in the intestinal epithelium. Although the mechanism involves different pathways, both alter cytoplasmic IB, thereby inhibiting NFB nuclear translocation.