Effects of alpha-linolenic acid on colonic secretion in rats with experimental colitis

Anti-inflammatory effect of Perilla frutescens seed oil rich in omega-3 fatty acid on dextran sodium sulfate-induced colitis in mice

Background and purpose

Ulcerative colitis is a chronic inflammatory bowel disease that involves diffused inflammation of the large intestine. Omega-3 fatty acid (FA) has been known to regulate the inflammatory response associated with ulcerative colitis pathogenesis. Perilla frutescens is a valuable source of omega-3 FA and α-linolenic acid (ALA) contained in its seed oil. Therefore, the aim of this study was to evaluate the anti-inflammatory effect of Perilla seed oil (PSO) on colitis induced by dextran sulfate sodium (DSS) in a mouse model.

Experimental approach

PSO was extracted using a cold-pressed extractor and FA composition of PSO was analyzed by GC-MS. Acute colitis in mice was induced with 3% DSS in drinking water for 7 days. Some mice were treated with PSO (20, 100, 200 mg/kg BW) for 3 weeks before the DSS administration. Sulfasalazine was used as a positive control. The clinical features, histopathologic, serum, and gene expression of proinflammatory cytokines in the colon were assessed.

Finding/Results

PSO contained the highest proportion of ALA (61.51%). Furthermore, PSO pretreatment evidently reduced body weight loss, diminished diarrhea, gross bleeding, and DSS-induced colon shortening. PSO pretreatment attenuated histopathological changes in response to DSS-induced colitis. PSO pretreatment also markedly decreased inflammatory response in serum and the colon tissue of DSS-induced mice.

Conclusion and implication

ALA in PSO is suggested to be mainly responsible for the reduction of DSS-induced colitis through suppressing inflammatory markers. PSO could be further developed as a functional health supplement, which would be beneficial for anti-inflammation in the colonic mucosa.

Frondanol, a Nutraceutical Extract from Cucumaria frondosa, Attenuates Colonic Inflammation in a DSS-Induced Colitis Model in Mice

Frondanol is a nutraceutical lipid extract of the intestine of the edible Atlantic sea cucumber, Cucumaria frondosa, with potent anti-inflammatory effects. In the current study, we investigated Frondanol as a putative anti-inflammatory compound in an experimental model of colonic inflammation. C57BL/6J male black mice (C57BL/6J) were given 3% dextran sodium sulfate (DSS) in drinking water for 7 days to induce colitis. The colitis group received oral Frondanol (100 mg/kg body weight/per day by gavage) and were compared with a control group and the DSS group. Disease activity index (DAI) and colon histology were scored for macroscopic and microscopic changes. Colonic tissue length, myeloperoxidase (MPO) concentration, neutrophil and macrophage marker mRNA, pro-inflammatory cytokine proteins, and their respective mRNAs were measured using ELISA and real-time RT-PCR. The tissue content of leukotriene B4 (LTB4) was also measured using ELISA. Frondanol significantly decreased the DAI and reduced the inflammation-associated changes in colon length as well as macroscopic and microscopic architecture of the colon. Changes in tissue MPO concentrations, neutrophil and macrophage mRNA expression (F4/80 and MIP-2), and pro-inflammatory cytokine content (IL-1β, IL-6 and TNF-α) both at the protein and mRNA level were significantly reduced by Frondanol. The increase in content of the pro-inflammatory mediator leukotriene B4 (LTB4) induced by DSS was also significantly inhibited by Frondanol. It was thus found that Frondanol supplementation attenuates colon inflammation through its potent anti-inflammatory activity.

Subepithelial trypsin induces enteric nerve-mediated anion secretion by activating proteinase-activated receptor 1 in the mouse cecum

Serine proteases are versatile signaling molecules and often exert this function by activating the proteinase-activated receptors (PAR(1)-PAR(4)). Our previous study on the mouse cecum has shown that the PAR(1)-activating peptide (AP) and PAR(2)-AP both induced electrogenic anion secretion. This secretion mediated by PAR(1) probably occurred by activating the receptor on the submucosal secretomotor neurons, while PAR(2)-mediated anion secretion probably occurred by activating the receptor on the epithelial cells. This present study was aimed at using trypsin to further elucidate the roles of serine proteases and PARs in regulating intestinal anion secretion. A mucosal-submucosal sheet of the mouse cecum was mounted in Ussing chambers, and the short-circuit current (I(sc)) was measured. Trypsin added to the serosal side increased I(sc) with an ED(50) value of approximately 100 nM. This I(sc) increase was suppressed by removing Cl(-) from the bathing solution. The I(sc) increase induced by 100 nM trypsin was substantially suppressed by tetrodotoxin, and partially inhibited by an NK(1) receptor antagonist, by a muscarinic Ach-receptor antagonist, and by 5-hydroxytryptamine-3 (5-HT(3)) and 5-HT(4) receptor antagonists. The I(sc) increase induced by trypsin was partially suppressed when the tissue had been pretreated with PAR(1)-AP, but not by a pretreatment with PAR(2)-AP. These results suggest that the serine protease, trypsin, induced anion secretion by activating the enteric secretomotor nerves. This response was initiated in part by activating PAR(1) on the enteric nerves. Serine proteases and PARs are likely to be responsible for the diarrhea occurring under intestinal inflammatory conditions.