Cinnamaldehyde protects against rat intestinal ischemia/reperfusion injuries by synergistic inhibition of NF-κB and p53.

Our preliminary study shows that cinnamaldehyde (CA) could protect against intestinal ischemia/reperfusion (I/R) injuries, in which p53 and NF-κB p65 play a synergistic role. In this study, we conducted in vivo and in vitro experiments to verify this proposal. SD rats were pretreated with CA (10 or 40 mg · kg-1 · d-1, ig) for 3 days, then subjected to 1 h mesenteric ischemia followed by 2 h reperfusion. CA pretreatment dose-dependently ameliorated morphological damage and reduced inflammation evidenced by decreased TNF-α, IL-1ß, and IL-6 levels and MPO activity in I/R-treated intestinal tissues. CA pretreatment also attenuated oxidative stress through restoring SOD, GSH, LDH, and MDA levels in I/R-treated intestinal tissues. Furthermore, CA pretreatment significantly reduced the expression of inflammation/apoptosis-related NF-κB p65, IKKß, IK-α, and NF-κB p50, and downregulated apoptotic protein expression including p53, Bax, caspase-9 and caspase-3, and restoring Bcl-2, in I/R-treated intestinal tissues. We pretreated IEC-6 cells in vitro with CA for 24 h, followed by 4 h hypoxia and 3 h reoxygenation (H/R) incubation. Pretreatment with CA (3.125, 6.25, and 12.5 µmol · L-1) significantly reversed H/R-induced reduction of IEC-6 cell viability. CA pretreatment significantly suppressed oxidative stress, NF-κB activation and apoptosis in H/R-treated IEC-6 cells. Moreover, CA pretreatment significantly reversed mitochondrial dysfunction in H/R-treated IEC-6 cells. CA pretreatment inhibited the nuclear translocation of p53 and NF-κB p65 in H/R-treated IEC-6 cells. Double knockdown or overexpression of p53 and NF-κB p65 caused a synergistic reduction or elevation of p53 compared with knockdown or overexpression of p53 or NF-κB p65 alone. In H/R-treated IEC-6 cells with double knockdown or overexpression of NF-κB p65 and p53, CA pretreatment caused neither further decrease nor increase of NF-κB p65 or p53 expression, suggesting that CA-induced synergistic inhibition on both NF-κB and p53 played a key role in ameliorating intestinal I/R injuries. Finally, we used immunoprecipitation assay to demonstrate an interaction between p53 and NF-κB p65, showing the basis for CA-induced synergistic inhibition. Our results provide valuable information for further studies.

Geniposide ameliorates TNBS-induced experimental colitis in rats via reducing inflammatory cytokine release and restoring impaired intestinal barrier function.

Geniposide is an iridoid glycosides purified from the fruit of Gardenia jasminoides Ellis, which is known to have antiinflammatory, anti-oxidative and anti-tumor activities. The present study aimed to investigate the effects of geniposide on experimental rat colitis and to reveal the related mechanisms. Experimental rat colitis was induced by rectal administration of a TNBS solution. The rats were treated with geniposide (25, 50 mg·kg-1·d-1, ig) or with sulfasalazine (SASP, 100 mg·kg-1·d-1, ig) as positive control for 14 consecutive days. A Caco-2 cell monolayer exposed to lipopolysaccharides (LPS) was used as an epithelial barrier dysfunction model. Transepithelial electrical resistance (TER) was measured to evaluate intestinal barrier function. In rats with TNBS-induced colitis, administration of geniposide or SASP significantly increased the TNBS-decreased body weight and ameliorated TNBS-induced experimental colitis and related symptoms. Geniposide or SASP suppressed inflammatory cytokine (TNF-α, IL-1ß, and IL-6) release and neutrophil infiltration (myeloperoxidase activity) in the colon. In Caco-2 cells, geniposide (25-100 µg/mL) ameliorated LPS-induced endothelial barrier dysfunction via dose-dependently increasing transepithelial electrical resistance (TER). The results from both in vivo and in vitro studies revealed that geniposide down-regulated NF-κB, COX-2, iNOS and MLCK protein expression, up-regulated the expression of tight junction proteins (occludin and ZO-1), and facilitated AMPK phosphorylation. Both AMPK siRNA transfection and AMPK overexpression abrogated the geniposide-reduced MLCK protein expression, suggesting that geniposide ameliorated barrier dysfunction via AMPK-mediated inhibition of the MLCK pathway. In conclusion, geniposide ameliorated TNBS-induced experimental rat colitis by both reducing inflammation and modulating the disrupted epithelial barrier function via activating the AMPK signaling pathway.