Use of fish oil to prevent graft rejection

A comparison of the effects of fish oil and flaxseed oil on cardiac allograft chronic rejection in rats

Both fish and flaxseed oils are major sources of different n-3 fatty acids. Beneficial effects of fish oil on posttransplantation complications have been reported. The current study aimed to compare the effects of flaxseed and fish oils in a rat cardiac allograft model. Male Fischer and Lewis rats were used as donors and recipients, respectively, to generate a heterotopic cardiac allograft model. Animals were randomly assigned into three groups and fed a diet supplemented with 1) 5% (wt/wt) safflower oil (control, n = 7), 2) 5% (wt/wt) flaxseed oil ( n = 8), or 3) 2% (wt/wt) fish oil ( n = 7), and an intraperitoneal injection of cyclosporine A (CsA; 1.5 mg·kg−1·day−1) over 12 wk. Body weight, blood pressure, plasma levels of lipids, CsA, select cytokines, as well as graft function and chronic rejection features were assessed. Body weight and blood CsA levels were similar among the groups. Relative to controls, both treated groups had lower systolic and diastolic blood pressure and plasma levels of macrophage chemotactic protein-1. Treatment with fish oil significantly ( P < 0.05) lowered plasma levels of triglycerides, total cholesterol, and LDL-cholesterol. HDL-cholesterol concentrations were significantly higher ( P < 0.05) in the flaxseed oil-treated group compared with the other two groups. Both flaxseed oil and fish oil may provide similar biochemical, hemodynamic, and inflammatory benefits after heart transplantation; however, neither of the oils was able to statistically significantly impact chronic rejection or histological evidence of apparent cyclosporine-induced nephrotoxicity in this model.

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.

Fish oil ameliorates the allograft arteriosclerosis of intestine on rats

Fish oil had been shown to have an immunomodulating effect and had favorable effect on the pathogenesis of atherosclerosis. The aim of this study was to estimate the effect of fish oil on the graft arteriosclerosis and graft immune response after rat allogenic small intestinal transplantation. Since two wk pretransplantation, the Lewis rats were supplemented by gavage with: (i) phosphate buffer saline, 0.6% volume of body weight (V/W), as control group; (ii) fish oil (0.6%, V/W); (iii) fish oil (0.3%, V/W). Total intestine from donor F344 was heterotopically transplanted into the Lewis recipient. The recipient rats were killed on the 60th day post-transplantation. The cytokine levels, the activity of NF-kappa B and the arteriosclerosis of grafts were analyzed. Intragastrical supplementation with 0.6% fish oil induced pronounced inhibition of the pro-inflammtory cytokine expression of interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha, and the increase of anti-inflammtory cytokine expression of IL-10 in graft. Suppression of the TNF-alpha and IL-6 expression by fish oil was attributed to its inhibitory effect on NF-kappaB activation. Intragastric 0.6% fish oil infusion ameliorated the development of graft arteriosclerosis. Fish oil was therefore considered to have an immunosuppressive effect on rat allogenic small intestinal transplant model based on the intra-graft IL-6, TNF-alpha and IL-10 levels. It might result in ameliorating the arteriosclerosis of the grafts.

Fatty acids, the immune response, and autoimmunity: a question of n-6 essentiality and the balance between n-6 and n-3

The essentiality of n-6 polyunsaturated fatty acids (PUFA) is described in relation to a thymus/thymocyte accretion of arachidonic acid (20:4n-6, AA) in early development, and the high requirement of lymphoid and other cells of the immune system for AA and linoleic acid (1 8:2n-6, LA) for membrane phospholipids. Low n-6 PUFA intakes enhance whereas high intakes decrease certain immune functions. Evidence from in vitro and in vivo studies for a role of AA metabolites in immune cell development and functions shows that they can limit or regulate cellular immune reactions and can induce deviation toward a T helper (Th)2-like immune response. In contrast to the effects of the oxidative metabolites of AA, the longer-chain n-6 PUFA produced by gamma-linolenic acid (18:3n-6, GLA) feeding decreases the Th2 cytokine and immunoglobulin (Ig)G1 antibody response. The n-6 PUFA, GLA, dihomo-gamma-linolenic acid (20:3n-6, DHLA) and AA, and certain oxidative metabolites of AA can also induce T-regulatory cell activity, e.g., transforming growth factor (TGF)-beta-producing T cells; GLA feeding studies also demonstrate reduced proinflammatory interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha production. Low intakes of long-chain n-3 fatty acids (fish oils) enhance certain immune functions, whereas high intakes are inhibitory on a wide range of functions, e.g., antigen presentation, adhesion molecule expression, Th1 and Th2 responses, proinflammatory cytokine and eicosanoid production, and they induce lymphocyte apoptosis. Vitamin E has a demonstrable critical role in long-chain n-3 PUFA interactions with immune functions, often reversing the effects of fish oil. The effect of dietary fatty acids on animal autoimmune disease models depends on both the autoimmune model and the amount and type of fatty acids fed. Diets low in fat, essential fatty acid deficient (EFAD), or high in long-chain n-3 PUFA from fish oils increase survival and reduce disease severity in spontaneous autoantibody-mediated disease, whereas high-fat LA-rich diets increase disease severity. In experimentally induced T cell-mediated autoimmune disease, EFAD diets or diets supplemented with long-chain n-3 PUFA augment disease, whereas n-6 PUFA prevent or reduce the severity. In contrast, in both T cell- and antibody-mediated autoimmune disease, the desaturated/elongated metabolites of LA are protective. PUFA of both the n-6 and n-3 families are clinically useful in human autoimmune-inflammatory disorders, but the precise mechanisms by which these fatty acids exert their clinical effects are not well understood. Finally, the view that all n-6 PUFA are proinflammatory requires revision, in part, and their essential regulatory and developmental role in the immune system warrants appreciation.

Dietary fatty acid modulation of mucosally-induced tolerogenic immune responses

Immunological unresponsiveness or hyporesponsiveness (tolerance) can be induced by feeding protein antigens to naive animals. Using a classical oral ovalbumin gut-induced tolerance protocol in BALB/c mice we investigated the effects of dietary n-6 and n-3 polyunsaturated fatty acids (PUFA) on high-and low-dose oral tolerance (and in non-tolerised animals, i.e. effects of antigen challenge alone) in relation to lymphoproliferative, cytokine and antibody responses. Fish oil rich in long-chain n-3 fatty acids decreased both T-helper (Th) 1- and Th2-like responses. In contrast, borage (Borago officinalis) oil rich in n-6 PUFA, of which gamma-linolenic acid is rapidly metabolised to longer-chain n-6 PUFA, increased Thl-like responses and decreased Th2-like responses, and possibly enhanced suppressor cell or Th3-like activity. These findings are in general agreement with other studies on the effects of long chain n-3 PUFA on immune system functions, and characterise important differences between long-chain n-3 and n-6 PUFA, defining more precisely and broadly the immunological regulatory mechanisms involved. They are also discussed in relation to autoimmune disease.