TLR5 as an Anti-Inflammatory Target and Modifier Gene in Cystic Fibrosis

Abstract

New treatments are needed to improve the health of people with cystic fibrosis (CF). Reducing lung-damaging inflammation is likely to be beneficial, but specific anti-inflammatory targets have not been identified. By combining cellular immunology with a population-based genetic modifier study, we examined TLR5 as an anti-inflammatory target and modifier gene in CF. Using two pairs of human CF and control airway epithelial cells, we demonstrated that the TLR5–flagellin interaction is a major mediator of inflammation following exposure to Pseudomonas aeruginosa. To validate TLR5 as an anti-inflammatory target, we analyzed the disease modifying effects of the TLR5 c.1174C>T single nucleotide polymorphism (rs5744168) in a large cohort of CF patients (n = 2219). rs5744168 encodes a premature stop codon and the T allele is associated with a 45.5–76.3% reduction in flagellin responsiveness (p < 0.0001). To test the hypothesis that reduced TLR5 responsiveness would be associated with improved health in CF patients, we examined the relationship between rs5744168 and two clinical phenotypes: lung function and body weight. Adults with CF carrying the TLR5 premature stop codon (CT or TT genotype) had a higher body mass index than did CF patients homozygous for the fully functional allele (CC genotype) (p = 0.044); however, similar improvements in lung function associated with the T allele were not statistically significant. Although follow-up studies are needed to confirm the impact of TLR5 on nutritional status, this translational research provides evidence that genetic variation in TLR5 resulting in reduced flagellin responsiveness is associated with improved health indicators in adults with CF.

Impaired TLR5 Functionality Is Associated with Survival in Melioidosis

“…It is therefore tempting to postulate that the hypofunctional TLR5 variant broadly impairs the inflammatory response to flagellated infection, resulting in reduced sepsisinduced organ failure and death. This idea is consistent with other studies showing that carriage of the variant is protective in inflammatory conditions, including systemic lupus erythematosus, cystic fibrosis (the variant is associated with a higher body mass index), and Crohn's disease (29)(30)(31). However, IL-10 is the sole cytokine that is consistently reduced in carriers of TLR5 1174T from Whole blood was stimulated with media, E. coli 0111:B4 LPS 10 ng/ml, S. typhimurium flagellin 500 ng/ml, heat-killed B. pseudomallei 1026b 2.5 3 10 6 CFU/ml, or heat-killed B. pseudomallei K96243 2.5 3 10 6 CFU/ml (K9) for 6 h. Inflammatory mediators were measured in plasma by multiplex bead assay or ELISA (IL-1b for B. pseudomallei only), normalized to monocyte count, and log 10 transformed for statistical analysis by linear regression.…”

Flagellin Induces Myeloid-Derived Suppressor Cells: Implications for Pseudomonas aeruginosa Infection in Cystic Fibrosis Lung Disease

“…3A). To dissect which mechanism(s) induce(s) MDSCs in chronic P. aeruginosa infection, we focused on flagellin because 1) infection with flagellated P. aeruginosa was associated with MDSC induction in our CF patient cohort, whereas nonflagellated microbes did not show any association with MDSCs in vivo; and 2) previous studies showed that among different PAMPs, flagellin recognition through TLR5 in particular plays a key role in leukocyte-P. aeruginosa interactions in CF lung disease (4,5,17,18). Our studies demonstrated that flagellin efficiently and dose-dependently induced MDSCs with a more potent capacity than GM-CSF did (Fig.…”

“…P. aeruginosa potently activates the innate arm of the immune system, an effect mainly mediated through pathogenassociated molecular patterns (PAMPs) and pattern recognition receptors. Among those, the TLR 5 ligand flagellin was found to play a key role in the recognition of P. aeruginosa (1)(2)(3)(4)(5). However, patients with chronic lung diseases, prototypically cystic fibrosis (CF) patients (6), are unable to eradicate the bacterium efficiently.…”

Acetylbritannilactone Modulates MicroRNA-155-Mediated Inflammatory Response in Ischemic Cerebral Tissues

“…These cytokines cause postischemic inflammation in the brain, subsequently leading to exacerbated primary brain damage (3,4). Previous work has demonstrated that activation of TLRs either by microbial or endogenous ligands results in an inflammatory response by delivering a signal from the intracellular TIR (Toll/IL-1 receptor) domain of TLR through a series of intracellular adaptor molecules, including MyD88, interleukin-1 receptorassociated kinase (IRAK) and TNF receptor associated factor 6 (TRAF6) (5,6). For example, IRAK and TRAF6 are recruited to the TLR complex via interaction with MyD88 (7) and activate nuclear factorkappa B (NF-κB), a transcription factor that regulates the expression of a wide array of genes involved in inflammatory responses, as well as the mitogenactivated protein kinases (MAPKs), such as extracellular signal-regulated kinase (ERK), p38 and c-jun N-terminal kinase (JNK) (8,9).…”