Intraluminal Flagellin Differentially Contributes to Gut Dysbiosis and Systemic Inflammation following Burn Injury

Abstract

Burn injury is associated with a loss of gut barrier function, resulting in systemic dissemination of gut-derived bacteria and their products. The bacterial protein and TLR5 agonist, flagellin, induces non-specific innate immune responses. Because we detected flagellin in the serum of burn patients, we investigated whether gut-derived flagellin was a primary or secondary contributor to intestinal dysfunction and systemic inflammation following burn injury. The apical surface of polarized human intestinal epithelial cells (IECs), Caco-2BBe, were exposed to 50 or 500 ng of purified flagellin and 1 x 105 of an intestinal E. coli (EC) isolate as follows: 1) flagellin added 30 min prior to EC, 2) flagellin and EC added simultaneously, or 3) EC added 30 min prior to flagellin. Our results showed that luminal flagellin and EC modulated each other's biological actions, which influenced their ability to induce basolateral secretion of inflammatory cytokines and subsequent translocation of bacteria and their products. A low dose of flagellin accompanied by an enteric EC in the lumen, tempered inflammation in a dose- and time-dependent manner. However, higher doses of flagellin acted synergistically with EC to induce both intestinal and systemic inflammation that compromised barrier integrity, increasing systemic inflammation following burn injury, a process we have termed flagellemia. In a murine model of burn injury we found that oral gavage of flagellin (1 μg/mouse) significantly affected the gut microbiome after burn injury. In these mice, flagellin disseminated out of the intestine into the serum and to distal organs (mesenteric lymph nodes and lungs) where it induced secretion of monocyte chemoattractant protein (MCP-1) and CXCL1/KC (mouse equivalent of human IL-8) at 24 and 48h post-burn. Our results illustrated that gut-derived flagellin alone or accompanied by a non-pathogenic enteric EC strain can function as an initiator of luminal and systemic inflammation following burn injury.

MiR‐150 alleviates neuropathic pain via inhibiting toll‐like receptor 5

“…TLR5‐dependent signaling pathway is involved in the anti‐microbial peptide TP359 attenuating inflammation in human lung cells infected with pseudomonas aeruginosa . TLR5 agonist flagellin contributes to gut dysbiosis and systemic inflammation following burn injury by inducing non‐specific innate immune responses . CBLB502, a kind of TLR5 agonist exhibits anticancer and radioprotective activities via modulation of inflammation responses in ulcerative colitis (UC) treatment .…”

Edaravone reduces oxidative stress and intestinal cell apoptosis after burn through up-regulating miR-320 expression

“…Physiological barrier injury caused by intestinal damage after burn injury is an important factor for causing the mortality of burn patients (Grimes et al, 2016; Ng et al, 2016). Severe burn injury, increases intestinal microvascular permeability increases, damages intestinal cell necrosis, apoptosis and intestinal mucosal barrier function impair, lead to displacement of intestinal bacterial and toxin, induction of systemic inflammatory response syndrome and multiple organ dysfunction syndromes (Zhang et al, 2017a; Osuka et al, 2017) .…”

Altered Fecal Microbiome Years after Traumatic Brain Injury

“…To rigorously confirm the differences identified through Illumina 16S V4 and metagenomic comparisons, we also used a novel NGS approach that utilized Ion Torrent sequencing of five overlapping contigs created by amplification of the bacterial 16S rRNA gene. 34 This method produced bidirectional sequences from >90% of the bacterial 16S rRNA gene, including all of the variable regions, but had lower throughput relative to Illumina NGS. As a result, we created 10 biopools of fecal DNA (equivalent bacterial genomic contributions of the indicated samples mixed into a single DNA pool), by stratifying the cohorts by BMI, and by time, post-TBI (Table 1).…”