Somatostatin limits intestinal ischemia-reperfusion injury in macaques via suppression of TLR4-NF-kappaB cytokine pathway.
OBJECTIVE
Intestinal ischemia-reperfusion (IIR)-induced gut injury remains a challenge for critically ill patients despite the oxidative stress theory that has been elaborated. This study aimed to test whether Toll-like receptor 4 (TLR4) is involved in gut injury during IIR and whether somatostatin (SST) affects TLR4-nuclear factor-kappaB (NF-kappaB) cytokine pathway in the intestinal mucosa of macaques.


METHODS
Fifteen macaques were randomized into control, IIR, and SST + IIR groups. Pieces of isolated ileal epithelium from each animal were incubated with lipopolysaccharide (LPS), interferon-gamma, or SST. Expression of TLR4 and NF-kappaBp65 was evaluated by immunohistochemical staining, Western blot analysis and reverse transcription polymerase chain reaction. Cytokine levels were measured by ELISA. Radioimmunoassay was used to determine of SST levels.


RESULTS
Significant overexpression (IIR vs control) of ileal TLR4 (0.17 +/- 0.03 vs 0.05 +/- 0.02), NF-kappaBp65 (0.55 +/- 0.11 vs 0.15 +/- 0.05), and TNF-alpha (213.2 +/- 29.2 vs 56.0 +/- 10.04) after IIR was greatly decreased (p < 0.05) by prophylactic use of SST (TLR4: 0.06 +/- 0.02; NF-kappaBp65: 0.26 +/- 0.09; TNF-alpha: 97.1 +/- 32.3) in vivo. TLR4 expression in the ileal epithelium treated with LPS and SST (1,330 +/- 93) was significantly lower than that in the ileal epithelium treated with LPS alone (2,088 +/- 126) in vitro. SST levels in plasma (3.67 +/- 0.41 ng/ml) and ileal mucosa (1,402.3 +/- 160 ng/mg protein) of the IIR group were significantly lower than those (6.09 +/- 1.29 ng/ml, 2,234. 8 +/- 301.8 ng/mg protein) in the control group (p < 0.05).


CONCLUSIONS
Endogenous SST is a crucial inhibitor of massive inflammatory injury in the intestinal mucosa via direct suppression of the TLR4-NF-kappaB cytokine pathway induced by LPS in ileal epithelium. IIR attacks caused shortages of endogenous SST in the plasma and intestinal mucosa of macaques in this study. Therefore, preventive supplements of SST may limit intestinal injury of macaques by IIR.
Wu
Hao
H
Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu, 610041, People's Republic of China.
Liu
Ling
L
Tan
Qinghua
Q
Wang
Chunhui
C
Guo
Meimei
M
Xie
Yongmei
Y
Tang
Chengwei
C
D000818:Animals; D018929:Cell Culture Techniques; D016207:Cytokines / Q000502:physiology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006728:Hormones / Q000494:pharmacology*; D007082:Ileum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D007410:Intestinal Diseases / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051218:Lymphocyte Antigen 96 / Q000502:physiology; D008253:Macaca mulatta; D008297:Male; D016328:NF-kappa B / Q000502:physiology*; D015427:Reperfusion Injury / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D013004:Somatostatin / Q000494:pharmacology* / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000502:physiology*
D016207:Cytokines; D006728:Hormones; D051218:Lymphocyte Antigen 96; D016328:NF-kappa B; D051197:Toll-Like Receptor 4; D013004:Somatostatin