Expression of Toll-like Receptors, Pro-, and Anti-inflammatory Cytokines in Relation to Gut Microbiota in Irritable Bowel Syndrome: The Evidence for Its Micro-organic Basis

Abstract

Background/AimsA Subset of patients with irritable bowel syndrome (IBS) may have mild inflammation due to immune activation. Toll-like receptors (TLRs) and cytokines may cause intestinal inflammation. We studied their expression in relation to gut microbiota.MethodsExpression of TLRs and cytokines was assessed in 47 IBS patients (Rome III) and 25 controls using quantitative real-time polymerase chain reaction. Immunohistochemistry was further performed to confirm the expression of TLR-4 and TLR-5.ResultsOf 47 patients with IBS, 20 had constipation (IBS-C), 20 diarrhea (IBS-D), and 7 unclassified (IBS-U). The mRNA levels of TLR-4 and TLR-5 were up-regulated in IBS patients than controls (P = 0.013 and P < 0.001, respectively). Expression of TLR-4 and TLR-5 at protein level was 4.2-folds and 6.6-folds higher in IBS-D than controls. The mRNA levels of IL-6 (P = 0.003), C-X-C motif chemokine ligand 11 (CXCL-11) (P < 0.001) and C-X-C motif chemokine receptor 3 (CXCR-3) (P < 0.001) were higher among IBS patients than controls. Expression of IL-6 (P = 0.002), CXCL-11 (P < 0.001), and CXCR-3 (P < 0.001) were up-regulated and IL-10 (P = 0.012) was down-regulated in IBS-D patients than controls. Positive correlation was seen between TLR-4 and IL-6 (P = 0.043), CXCR-3, and CXCL-11 (P = 0.047), and IL-6 and CXCR-3 (P = 0.003). Stool frequency per week showed positive correlation with mRNA levels of TLR-4 (P = 0.016) and CXCR-3 (P = 0.005), but inversely correlated with IL-10 (P = 0.002). Copy number of Lactobacillus (P = 0.045) and Bifidobacterium (P = 0.011) showed correlation with IL-10 in IBS-C, while Gram-positive (P = 0.031) and Gram-negative bacteria (P = 0.010) showed correlation with CXCL-11 in IBS-D patients.ConclusionsAltered immune activation in response to dysbiotic microbiota may promote intestinal inflammation in a subset of patients with IBS.

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“…Of 15/82 patients with IBS having SIBO on quantitative upper gut aspirate culture, mucosal IL‐1 α and β (pro‐inflammatory cytokine) levels were higher than those without SIBO, and higher IL‐1 β levels were associated with loose stool and abdominal bloating 45 . In a recent study on 47 IBS patients, colonic biopsy messenger ribonucleic acid (mRNA) levels of toll‐like receptor (TLR)‐4 and TLR‐5, their protein expression, Il‐6, C‐X‐C motif chemokine ligand‐11 (CXCL‐11), and C‐X‐C motif chemokine receptor (CXCR‐3), which are pattern recognition receptors or pro‐inflammatory cytokine or chemokine, were up‐regulated in patients than controls 46 ; in contrast, anti‐inflammatory cytokine mRNA of IL‐10 was down‐regulated among IBS patients. Interestingly, number of gene copies of the good bugs such as Lactobacillus and Bifidobacteria showed correlation with anti‐inflammatory cytokine IL‐10 46 .…”

“…In a recent study on 47 IBS patients, colonic biopsy messenger ribonucleic acid (mRNA) levels of toll‐like receptor (TLR)‐4 and TLR‐5, their protein expression, Il‐6, C‐X‐C motif chemokine ligand‐11 (CXCL‐11), and C‐X‐C motif chemokine receptor (CXCR‐3), which are pattern recognition receptors or pro‐inflammatory cytokine or chemokine, were up‐regulated in patients than controls 46 ; in contrast, anti‐inflammatory cytokine mRNA of IL‐10 was down‐regulated among IBS patients. Interestingly, number of gene copies of the good bugs such as Lactobacillus and Bifidobacteria showed correlation with anti‐inflammatory cytokine IL‐10 46 . Weekly stool frequency had positive correlation with mRNA levels of TLR‐4 and CXCR‐3 but inversely correlated with IL‐10 46 .…”

“…Interestingly, number of gene copies of the good bugs such as Lactobacillus and Bifidobacteria showed correlation with anti‐inflammatory cytokine IL‐10 46 . Weekly stool frequency had positive correlation with mRNA levels of TLR‐4 and CXCR‐3 but inversely correlated with IL‐10 46 . Most of the evidences mentioned above suggest that patients with IBS, particularly those with IBS‐D, have immune activation in the gut suggesting the condition to be a low‐grade inflammatory state.…”

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“…55 Expression levels of the TLR-4 and TLR-5 genes in biopsy samples from the sigmoid colon of patients with IBS (n = 47) were 1.2-and 6-fold greater, respectively, compared with those of healthy individuals (n = 25; p = 0.01 and p < 0.001, respectively); further, for patients with IBS-D (n = 20), TLR-4, and TLR-5 gene expression levels were increased 1.3-and 8-fold, respectively, compared with healthy individuals (p < 0.02 for both). 56 As well, TLR-4 and TLR-5 protein levels in colonic crypts and the luminal surface were 4.2-and 6.6-fold greater, respectively, in patients with IBS-D compared with healthy individuals, and TLR-4 gene expression levels correlated with stool frequency in patients with IBS. 56 Although the data are inconsistent, increased serum levels of proinflammatory cytokines have been reported in patients with IBS compared with healthy individuals.…”

“…56 As well, TLR-4 and TLR-5 protein levels in colonic crypts and the luminal surface were 4.2-and 6.6-fold greater, respectively, in patients with IBS-D compared with healthy individuals, and TLR-4 gene expression levels correlated with stool frequency in patients with IBS. 56 Although the data are inconsistent, increased serum levels of proinflammatory cytokines have been reported in patients with IBS compared with healthy individuals. 57,58 In one study, patients with IBS (n = 74) had significantly greater serum levels of interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α compared with healthy individuals (n = 75; p < 0.001 for IL-6 and IL-8; p = 0.04 for TNF-α).…”