Heat-killed preparations of L. rhamnosus GR-1 marginally augmented NF-κB, in a manner similar to using viable L. rhamnosus GG (below twofold). It is possible this augmentation is due to surface-associated structures shared by both strains. Lactobacilli

surface components have previously been shown to modulate NF-κB in a contact-dependent manner [17]. T24 cells express TLR2, and can recognize lipoteichoic acid (LTA) found on the surface of lactobacilli with increased NF-κB activation as a consequence [28]. However, since heat-killed lactobacilli only slightly induced AR-13324 mw NF-κB activation that is not a likely mechanism given that LTA is anchored to the Gram-positive cell wall. A more probable mechanism is that products released during bacterial growth are responsible for the NF-κB augmentation by L. rhamnosus GR-1. We have previously shown that spent culture

supernatant from L. rhamnosus GR-1 can augment NF-κB activation in E. coli-challenged T24 cells [29]. There are no published studies on the identity of the secreted proteins from L. rhamnosus GR-1. However L. rhamnosus GG is known to release a small number of proteins during growth, none of which have an established immunomodulatory effect [30]. A comparison of secretory proteins from the two strains might help explain the differences in terms of immune potentiation. The role of TLR4 was evaluated by blocking LPS binding to the receptor using polymyxin B, which eliminated the observed NF-kB potentiation. We initially saw that expression of TLR4 at genetic and protein levels was increased CBL0137 during co-XAV939 stimulation compared to controls, or during individual stimulation with E. coli or lactobacilli. Although TLR4 has LPS as a natural ligand, other E. coli components such as pili have been shown

to be able to activate TLR4. However, in this study, polymyxin B completely inhibited NF-κB activation in E. coli stimulated cells, therefore pili or other surface structures could not have contributed PLEKHM2 to this effect [31]. We consider that an increased number of TLR4 present on the cell facilitated activation by ligands on E. coli and lactobacilli alike. TLRs are important in UTI disease progression, as shown in C3H/HeJ mice with a mutation in the Tlr4 gene. After an E. coli infection, these mutant mice have problems removing the pathogens from their urinary tract [32]. A recent study scoring TLR4 expression levels in healthy control subjects and UTI patients showed that the latter have a lower TLR4 expression than healthy controls [9]. This important feature of TLR4 is consistent with the effect that certain E. coli strains expressing immunomodulatory compounds have on TLR signaling and NF-κB activation. The effect of lactobacilli on NF-κB, TNF and TLR4 represents one possibility that increases the urothelial immune cell responses. This augmentation might facilitate early detection and clearance of pathogens.