Fish oil ameliorates the allograft arteriosclerosis of intestine on rats

Six-month feeding of low-dose fish oil decreases vascular expression of high mobility group box1 and receptor for advanced glycation end-products in rat chronic allograft vasculopathy

Chronic allograft vasculopathy (CAV) is a typical feature of chronic rejection of small bowel transplantations (SBTx). Our previous studies revealed that feeding fish oil, a natural source of n-3 polyunsaturated fatty acids (PUFAs), protected against CAV. The underlying mechanism remains to be clarified. The pathway mediated by the receptor for advanced glycation end products (RAGE) and its ligand, high mobility group box-1 (HMGB1), which may contribute to the pathogenesis of CAV, is potentially regulated by n-3 PUFAs. Using a chronic rejection model of rat SBTx, the present study investigated whether amelioration of CAV by fish oil feeding was associated with regulation of the RAGE signaling pathway. Moreover, our previous studies also showed that feeding low-dose fish oil for 3 months had no effect. Since an relatively short duration of treatment might fail to produce a visible response, we fed low-dose fish oil for 190 postoperative days. Male inbred Lewis rats and F344 rats were used to establish a chronic rejection model of SBTx. The recipient rats were administered phosphate-buffered saline or fish oil at a daily dose of 3 mL/kg. All rats survived over 190 postoperative days. The expression of HMGB1 and RAGE increased in CAV-bearing vessels. Feeding low-dose fish oil for 6 months attenuated CAV, and significantly reduced HMGB1 and RAGE expressions, indicating beneficial effects of low-dose fish oil on CAV may occur via down-regulation of the HMGB1-RAGE pathway.

Attenuation of rat chronic small bowel allograft rejection by n-3 polyunsaturated fatty acids is associated with reduced expression of graft IL-15

Interleukin-15 was found to play key roles in various immunological processes including chronic rejection after renal and cardiac transplantation. n-3 polyunsaturated fatty acids (n-3 PUFA) have shown beneficial effects to chronic allograft rejection. The objective of this study is to search the possible mechanism of this inhibitory effect in chronic small bowel allograft rejection. Animals were divided into three groups: isograft (CsA + corn oil-supplemented diet); allograft (CsA + corn oil-supplemented diet); and allograft (CsA + fish oil-supplemented diet). Donor intestines from F344 rats were transplanted orthotopically into Lewis rat recipients. CsA was administered at 5 mg/kg/day for 2 wk post-operatively. Post-transplant weight was recorded. Histopathological changes and graft IL-15 expression were measured on POD 90. Chronic small bowel allograft rejection developed on POD 90. n-3 PUFA significantly decreased the score of chronic rejection and increased the post-operative weight gain rate. This attenuation is associated with reduced graft IL-15 expression. n-3 PUFA contributed to improved pathological and clinical outcome during chronic small bowel allograft rejection, and this improvement was associated with reduced graft IL-15 expression.

Fish oil enhances recovery of intestinal microbiota and epithelial integrity in chronic rejection of intestinal transplant

Background

The intestinal chronic rejection (CR) is the major limitation to long-term survival of transplanted organs. This study aimed to investigate the interaction between intestinal microbiota and epithelial integrity in chronic rejection of intestinal transplantation, and to find out whether fish oil enhances recovery of intestinal microbiota and epithelial integrity.

Methods/Principal Findings

The luminal and mucosal microbiota composition of CR rats were characterized by DGGE analysis at 190 days after intestinal transplant. The specific bacterial species were determined by sequence analysis. Furthermore, changes in the localization of intestinal TJ proteins were examined by immunofluorescent staining. PCR-DGGE analysis revealed that gut microbiota in CR rats had a shift towards Escherichia coli, Bacteroides spp and Clostridium spp and a decrease in the abundance of Lactobacillales bacteria in the intestines. Fish oil supplementation could enhance the recovery of gut microbiota, showing a significant decrease of gut bacterial proportions of E. coli and Bacteroides spp and an increase of Lactobacillales spp. In addition, CR rats showed pronounced alteration of tight junction, depicted by marked changes in epithelial cell ultrastructure and redistribution of occuldin and claudins as well as disruption in TJ barrier function. Fish oil administration ameliorated disruption of epithelial integrity in CR, which was associated with an improvement of the mucosal structure leading to improved tight junctions.

Conclusions/Significance

Our study have presented novel evidence that fish oil is involved in the maintenance of epithelial TJ integrity and recovery of gut microbiota, which may have therapeutic potential against CR in intestinal transplantation.

Acute effects of different types of oil consumption on endothelial function, oxidative stress status and vascular inflammation in healthy volunteers

Consumption of different types of oil may have different effects on cardiovascular risk. The exact role of maize oil, cod liver oil, soya oil and extra virgin olive oil on endothelial function, oxidative stress and inflammation is unknown. We evaluated the effect of acute consumption of these types of oil on endothelial function, oxidative stress and inflammation in healthy adults. Thirty-seven healthy volunteers were randomised to receive an oral amount of each type of oil or water. Endothelial function was evaluated by gauge-strain plethysmography at baseline and 1, 2 and 3 h after consumption. Oxidative stress status was determined by total lipid peroxides (PEROX), while inflammatory process was estimated by measuring the soluble form of vascular adhesion molecule 1. Serum levels of the two previous markers were measured at baseline and 3 h after oil consumption. Reactive hyperaemia (RH) was significantly decreased after maize oil consumption compared with controls (P < 0.05). However, the consumption of cod liver oil and soya oil induced a significant improvement of RH after 1 h, compared with controls (P < 0.05). There was no significant effect of any type of oil consumption on endothelium-independent dilatation, total lipid PEROX and vascular adhesion molecule 1 serum levels. Consumption of maize oil leads to impaired endothelial function, while soya oil and cod liver oil slightly improve endothelial function. However, all types of oils did not affect inflammatory process and systemic oxidative stress, suggesting that their effect on endothelial function may not be mediated by free radicals bioavailability.

Dietary n-3 fatty acids attenuate cardiac allograft vasculopathy via activating peroxisome proliferator-activated receptor-gamma

Recent in vitro data suggested that n-3 fatty acids could inhibit the activation of PPAR gamma. This study was designed to test the hypothesis that fish oil ameliorates CAV development via activating PPAR gamma in an inbred rat model of heart transplantation. Animals were divided into four groups: isograft, control (CsA + vehicle), LFO-treated group (CsA + 0.3% v/w fish oil), and HFO-treated group (CsA + 0.6% v/w fish oil). CsA was administered at 1.5 mg/kg/day for two wk postoperatively. Recipients were treated with fish oil or vehicle daily for eight wk. The histopathological and immunohistochemical examination, activity of NF-kappaB and PPAR gamma, intragraft chemokine levels, and chemokine receptor expression were analyzed. Both LFO and HFO significantly decreased the CAV score, inhibited recruitment of T lymphocytes and macrophages, elevated the activity of PPAR gamma, inhibited the activity of NF-kappaB, reduced levels of intragraft MCP-1 and IP-10 as well as downregulated expression of chemokine receptors CCR2. CXCR3 expression was not affected. Our results demonstrated that fish oil might attenuate CAV development, possibly through activating PPAR gamma and subsequently inhibiting the NF-kappaB activation, the chemokines secretion, as well as the CCR2 expression.

Inhibitory effect of dietary n-3 polyunsaturated fatty acids to intestinal IL-15 expression is associated with reduction of TCRαβ+CD8α+CD8β− intestinal intraepithelial lymphocytes

Intestinal intraepithelial lymphocytes (IELs) and their cytokines play an important role in the regulation of gut immune response and take part in gut immune barrier function. n-3 polyunsaturated fatty acid (PUFA) is an immunoregulator that has been shown to influence the process of gut inflammation. Interleukin (IL)-15 is a T-cell growth factor that has been shown to influence the differentiation of IEL. The aim of this study was to analyze the effects of dietary n-3 PUFA on IEL. IEL phenotype and cytokine (TNF-alpha, IFN-gamma, IL-4, IL-10 and TGF-beta1) profile were measured by FACS and real-time RT-PCR in healthy adult rats fed with fish oil diet for 90 days. Rats fed with corn oil diet served as controls. Intestinal IL-15 expression was measured by immunohistochemistry and real-time RT-PCR. The results demonstrated a decrease of intestinal IL-15 expression in the fish oil group. Associated with this deduction, n-3 PUFA significantly decreased the proportion of TCRalphabeta+CD8alpha+CD8beta- cells and IEL-derived TNF-alpha, IFN-gamma, IL-4 and IL-10. In conclusion, n-3 PUFA could inhibit intestinal mucosal expression of IL-15 and may influence phenotype and function of IEL through this mechanism.

Effect of n-3 polyunsaturated fatty acids on membrane microdomain localization of tight junction proteins in experimental colitis

Ulcerative colitis (UC) is a gastrointestinal disorder characterized by an inflammatory process associated with mucosal damage. Many studies have shown that n-3 polyunsaturated fatty acids (PUFAs) possess anti-inflammatory effects in inflammatory bowel disease. The aim of this study was to investigate whether n-3 PUFAs could alleviate intestinal damage in experimental UC. In the present study, we found that in 2,4,6-trinitrobenzenesulfonic acid-induced colitic rats, the damage to the intestinal mucosa was accompanied by a disrupted tight junction (TJ) structure. In accordance with these changes, the distribution and expression of TJ proteins, including occludin, claudin-1, claudin-3, claudin-5, claudin-8 and ZO-1, in membrane microdomains was altered. The distribution of flotillin-1, a lipid raft marker protein, was also changed. Moreover, we found for the first time that n-3 PUFAs prevented redistribution of TJ proteins from Triton X-100-insoluble raft-like membrane microdomains to Triton X-100-soluble fractions. The expression of ZO-1, claudin-1, claudin-5 and claudin-8 was significantly elevated by n-3 PUFAs. n-3 PUFAs also attenuated the disruption of TJ structure and improved the histological score. Our results demonstrate that the expression and distribution of TJ proteins in TJ membrane microdomains might be affected in UC, and that such altered expression of TJ proteins in membrane microdomains in experimental UC is affected by n-3 PUFAs. These findings may have therapeutic potential in intestinal inflammation.

Long-term n-3 polyunsaturated fatty acids administration ameliorates arteriosclerosis by modulating T-cell activity in a rat model of small intestine transplantation

BACKGROUND

Fish oil, rich in n-3 polyunsaturated fatty acids (n-3 PUFAs), has been found to reduce graft rejection and increase allografts survival. But these studies mainly focused on acute rejection. We imitated long-term fish oil administration to investigate the effects of n-3 PUFAs on graft arteriosclerosis, and T cells in a rat model of small intestine transplantation.

METHODS

From 2 weeks pre-transplantation to the 60th day post-transplantation, the Lewis rats were supplemented by gavage with phosphate buffer saline, corn oil and fish oil respectively. Total small intestine was heterotopically transplanted from F344 to Lewis rat. Graft arteriosclerosis was assessed by histological grading of intimal thickening. The expression of CD25 and CD154, IL-2 level, and NF-kappaB activation in T cells were analyzed by western blotting, ELISA, and electrophoretic mobility shift assay respectively.

RESULTS

Compared with corn oil, graft arteriosclerosis was ameliorated by fish oil significantly. The expression of CD25 and CD154, IL-2 level, and NF-kappaB activation were markedly reduced by fish oil.

CONCLUSIONS

Long-term n-3 PUFAs administration pre- and post-transplantation could inhibit T-cell activity by reducing CD154 expression and NF-kappaB activation, which might contribute to amelioration of graft arteriosclerosis.