Spinal toll-like receptor 4-mediated signalling pathway contributes to visceral hypersensitivity induced by neonatal colonic irritation in rats.
BACKGROUND
Although visceral hypersensitivity is a major pathophysiological feature of irritable bowel syndrome (IBS), its underlying mechanisms remain elusive. Toll-like receptor 4 (TLR4) is a critical pattern recognition molecule of the innate immune system. In this study, we investigated whether the TLR4/myeloid differentiation factor 88 (MyD88)/nuclear factor-kappa B (NF-κB) signalling pathway in the spinal cord contributed to the visceral hypersensitivity induced by neonatal colonic irritation (CI) in rats.


METHODS
The Sprague-Dawley rat model of IBS was induced by colon irritation on post-natal day (PND) 8, PND10 and PND12. Experiments were conducted in adult rats. TLR4 mRNA and protein, and its downstream signalling molecules, MyD88, inhibitory nuclear factor-kappa B (IκB) and NF-κB protein expressions in L2-S4 spinal segments were detected by quantitative real-time reverse transcription-polymerase chain reaction as well as Western blotting. TLR4 co-localization was determined by immunohistochemistry. Levels of tumour necrosis factor-alpha (TNF-α) and interleukin 1β (IL-1β) were measured with enzyme-linked immunosorbent assay.


RESULTS
We found that neonatal CI treatment induced long-lasting visceral hypersensitivity without identifiable structural abnormalities in descending colons of adult rats. Neonatal CI treatment evoked a significant up-regulation of the expressions of TLR4 in glia, MyD88, p-IκB-α and NF-κB in adult rats. Neonatal CI treatment also increased the levels of its downstream inflammatory agents TNF-α and IL-1β in the L2-S4 regions of the spinal cord of adult rats.


CONCLUSIONS
These results suggest that neonatal CI stimulates the production of IL-1β and TNF-α through the TLR4/MyD88/NF-κB signalling pathway in the spinal cord, which contributed to visceral hypersensitivity induced by neonatal CI in rats.
Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, China.
Z-Y
ZY
Chen
X-W
XW
Zhang
L
L
Yu
R
R
Hua
X-P
XP
Zhao
X
X
Qin
Y-M
YM
Zhang
D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D005260:Female; D020672:I-kappa B Proteins / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D043183:Irritable Bowel Syndrome / Q000378:metabolism*; D008297:Male; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D015854:Up-Regulation
D020672:I-kappa B Proteins; D053583:Interleukin-1beta; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; C000606206:Nfkbia protein, rat; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha