Increased survival after cecal ligation and puncture in mice consuming diets enriched with sesame seed oil

OBJECTIVES

Lignans that present in the nonfat portion of sesame seed oil (SSO) can inhibit delta-5 desaturase activity, resulting in an increase in the accumulation of dihomo-gamma-linolenic acid and, subsequently, decrease the production of proinflammatory dienoic eicosanoids with a concomitant increase in the secretion of less inflammatory monoenoic eicosanoids.

DESIGN

Female Balb/c mice were fed diets supplemented with 5wt% SSO or a physical mixture of oils (control) whose fatty acid composition resembled that of SSO for 3 wks.

MEASUREMENTS AND MAIN RESULTS

During a 4-day observation period after cecal ligation and puncture, only 20% of the controls and as many as 65% in the SSO group survived. Furthermore, the levels of cytokines and dienoic eicosanoids produced in response to an intraperitoneal injection of a nonlethal dose (50 microg/mouse) of endotoxin were measured in both groups. The interleukin (IL)-10 levels were markedly higher in mice fed SSO diets compared with the controls. However, the plasma concentrations of prostaglandin E1 + 2, tumor necrosis factor-alpha, IL-6, and IL-12 did not differ significantly between the two groups of mice.

CONCLUSIONS

Because the fatty acid composition is almost similar between the two diets, sesamin, sesamol and other lignans in SSO appear to be responsible for an increase in survival after cecal ligation and puncture and also for an increase in the IL-10 levels in response to a nonlethal dose of endotoxin in mice.

Effects of sesamin-supplemented dietary fat emulsions on the ex vivo production of lipopolysaccharide-induced prostanoids and tumor necrosis factor alpha in rats

BACKGROUND

Sesamin, a nonfat constituent of sesame oil, inhibits Delta(5)-desaturase activity, resulting in accumulation of dihomo-gamma-linolenic acid (DGLA), which displaces arachidonic acid (AA) and consequently decreases the formation of proinflammatory 2-series prostaglandins.

OBJECTIVE

We sought to determine whether dietary supplementation with sesamin augments the antiinflammatory effects of dietary linseed oil in rats.

DESIGN

We investigated the effects of continuous tube feedings of emulsions containing safflower oil or linseed oil with sesamin (SO+ and LO+) or without sesamin (SO and LO) on liver fatty acid composition and on endotoxin-induced production of prostaglandin E(2), 6-keto-prostaglandin F(1alpha), and tumor necrosis factor alpha (TNF-alpha) by whole blood from rats (n = 6 per diet group).

RESULTS

We found a significant accumulation of DGLA only in the liver phospholipids of animals fed SO+ and LO+ (1.8 +/- 0.2 and 1.4 +/- 0.3 mol%, respectively), which suggests that sesamin inhibited Delta(5)-desaturation of n-6 fatty acids. These changes were associated with significant reductions in plasma prostaglandin E(2) concentrations in animals fed SO+ compared with those fed SO (P: < 0. 05). Despite a significant reduction in tissue AA content in the LO group, the prostaglandin E(2) concentrations did not differ significantly from those of the SO group. Plasma concentrations of TNF-alpha were significantly lower (P: < 0.05) in the animals fed LO+ than in those fed SO (199 +/- 48 and 488 +/- 121 ng/L, respectively).

CONCLUSION

These data indicate that in rats, tube feedings of diets containing sesamin exerted antiinflammatory effects that were augmented by concurrent consumption of linseed oil.

Decreased production of interleukin-6 and prostaglandin E2 associated with inhibition of delta-5 desaturation of omega6 fatty acids in mice fed safflower oil diets supplemented with sesamol

The differences in the immune responses in mice fed sesame oil diets and those fed sesamin may be attributed to the presence of other lignans in the non-fat portion of the oil. The fatty acid composition (mean +/- SD mol. %) of liver membrane phospholipids and the levels of endotoxin-induced prostaglandin (PG) E2, interleukin (IL)-6, IL-10, IL-12 and tumor necrosis factor (TNF)-alpha were determined in mice fed diets supplemented with 5% safflower oil (SO) in the absence or presence of 1% sesamol. The levels of dihomo-gamma-linolenic acid (20:3omega6) were markedly higher (P<0.025) in the livers from mice fed sesamol supplemented SO diets (1.6 +/- 0.1) compared to the controls (1.4 +/- 0.1). These data suggest that sesamol or its metabolite could inhibit the in vivo delta-5 desaturation of omega6 fatty acids. Further, in animals fed sesamol supplemented SO diets, the levels of PGE2 (228 +/- 41 pg/ml) were markedly lower (P<0.01) compared to those fed SO diet alone (1355 +/- 188 pg/ml). Concomitantly, the concentrations of IL-6 were also lower (P<0.01) in mice fed sesamol diet (63 +/- 11 ng/ml) compared to the controls (143 +/- 22 ng/ml). A marked reduction in the levels of PGE2 in animals fed sesamol diets suggests that sesamol or its metabolite could inhibit the activity of cyclooxygenase enzyme.

Increased production of TNF-alpha and decreased levels of dienoic eicosanoids, IL-6 and IL-10 in mice fed menhaden oil and juniper oil diets in response to an intraperitoneal lethal dose of LPS

Eicosapentaenoic acid (EPA) and the non-methylene interrupted fatty acids (NMIFA) displace arachidonic acid (AA: 20:4omega6 -5,8,11,14) in the membrane phospholipids. Unlike EPA (20:5omega3 -5,8,11,14,17), the NMIFA (20:3omega6 -5,11,14 and 20:4omega3 -5,11,14,17) lacking the delta-8 double bond are not substrates for the formation of eicosanoids. For 20 days, the mice were fed diets containing 5wt% dietary fats from various sources. The magnitudes in the production of eicosanoids and cytokines produced in response to an intraperitoneal injection of endotoxin in mice fed menhaden fish oil (MO) diets enriched with EPA were compared with those maintained on juniper oil (JO) containing NMIFA or on safflower oil (SO), a major source of the AA precursor, linoleic acid. The levels of PGE2, 6-keto-PGF1alpha and TXB2 were markedly lower (P < 0.01) in animals fed either MO or JO diets compared to the controls. The plasma levels of tumor necrosis factor (TNF)-alpha were significantly higher (P < 0.05) with a concomitant decrease of interleukin (IL)-6 and of IL-10 in mice fed MO or JO diets (P < 0.01) compared to those fed SO diet. These data suggest that the effects of consuming NMIFA of JO despite their inability to form eicosanoids are similar to those of feeding EPA which forms biologically active alternate metabolites.

Dietary alpha-linolenic acid increases TNF-alpha, and decreases IL-6, IL-10 in response to LPS: effects of sesamin on the delta-5 desaturation of omega6 and omega3 fatty acids in mice

Sesamin (a non-fat portion of sesame seed oil) inhibits delta-5 desaturase activity resulting in an accumulation of dihomo-gamma-linolenic acid (DGLA) which can displace arachidonic acid (AA) and decrease the formation of pro-inflammatory mediators. We investigated the effects of consumption of diets containing 0.25wt% sesamin and 15 wt% safflower oil (SO) (providing 12% of the added fat as linoleic acid) or a 15 wt% 2:1 mixture of linseed oil and SO (LOSO) (providing 6% alpha-linolenic acid and 6% linoleic acid) for 3 weeks on the liver membrane fatty acid composition and on the production of prostaglandin (PG) E2, TNF-alpha, IL-6 and IL10 in mice. Consumption of sesamin-supplemented SO and LOSO diets resulted in a significant increase in the levels of 20:3omega6 (DGLA), suggesting that sesamin inhibited delta-5 desaturation of omega6 fatty acids. In animals fed LOSO diets, the levels of alpha-linolenic acid, eicosapentaenoic acid (EPA) and of docosahexaenoic acid (DHA) were elevated with a concomitant decrease of arachidonic acid (AA) in the liver membrane phospholipids. Further, in animals fed LOSO diets with or without sesamin, an increase in the circulating levels of TNF-alpha was associated with a concomitant decrease in PGE2. Despite a lack of differences in the levels of AA, the PGE2 levels were significantly lower in mice fed sesamin-supplemented SO compared to those fed SO alone. Thus, these data suggest that irrespective of the availability of a specific fatty acid as a substrate, through regulating the PGE2 synthesis, the production of TNF-alpha could be modulated.

Decreased production of interleukin-1-beta, prostaglandin-E2 and thromboxane-B2, and elevated levels of interleukin-6 and -10 are associated with increased survival during endotoxic shock in mice consuming diets enriched with sesame seed oil supplemented with Quil-A saponin

Sesamin, present in sesame seed oil (SSO), can inhibit delta-5-desaturase activity and cause accumulation of dihomo-gamma-linolenic acid (DGLA), which displaces arachidonic acid, and subsequently decrease production of dienoic eicosanoids. The effects of diets containing both SSO and Quil A, a saponin that emulsifies fats and potentiates the immune responses, were also studied. A mixture of oils having a fatty-acid composition similar to that of SSO served as a control diet. The levels of docosapentaenoic acid in mice fed Quil-A-supplemented diets and of DGLA in those fed SSO diets were markedly higher in the liver. These changes were associated with a significant reduction in the plasma prostaglandin-E(1+2) and thromboxane-B2 levels in response to an intraperitoneal injection of a lethal dose of lipopolysaccharide (LPS) endotoxin (LD50 20 mg/kg). The levels of interleukin (IL-)6 were elevated and those of IL-1beta were decreased in mice consuming Quil-A-supplemented diets. The IL-10 levels that were elevated in all mice after LPS exposure, remained higher (even at 9 h) only in those fed Quil-A-supplemented diets, but declined rapidly in others. During a 48-hour observation period following LPS injection, all control animals died, and survival was 40% in the SSO group, and 27 and 50%, respectively, in those fed Quil-A-supplemented control and SSO diets. These data suggest that SSO and Quil A when present in the diet exerted cumulative effects that resulted in a decrease in the levels of dienoic eicosanoids with a reduction in IL-1beta and a concomitant elevation in the levels of IL-10 that were associated with a marked increase in survival in mice.

The effect of dietary polyunsaturated fatty acids (PUFA) on acute rejection and cardiac allograft blood flow in rats

For six weeks, recipient (Lewis RT11) and donor rats (LBNF11/n) were fed three diets that varied only in their lipid content. Diet A (MO) contained 19.5% menhaden oil and 0.5% safflower oil and was rich in omega 3 PUFA; diet B (SO) was 20% safflower oil rich in omega 6 PUFA; and diet C (BT) was 20% beef tallow rich in omega 9 monounsaturated fatty acids and saturated fat. In the first set of graft survival studies a group fed laboratory chow was included (CHOW). Heterotopic cardiac transplantation from donor to recipient animals was performed after the six-week feeding period. The effect of these diets on cardiac allograft survival, mixed lymphocyte response, and blood flow in the rejecting grafts was investigated. The median graft survival in days was significantly prolonged in the rats maintained on either MO (12 days) or SO (14.5 days) compared with the BT (8 days)-or lab chow (7.5 days)-fed animals (P < 0.05). Cyclosporine (CsA) administered at subtherapeutic levels further increased the differences between the PUFA-fed animals and the BT-fed group. The myocardial blood flow of the rejecting allografts was measured using an 85Sr-labeled microsphere technique on the fifth posttransplant day. Flow was greatest in the MO-fed group, and both MO and SO groups had significantly higher myocardial blood flow than BT-fed rats (P < 0.05) or those bearing isografts. The allogenic mixed lymphocyte responses of peripheral blood mononuclear cells (PBMC) and splenic lymphocytes were suppressed in MO- and SO-fed groups compared with BT-fed animals. The immunosuppressive effect of dietary PUFA warrants further investigation, and their use as a possible adjunctive treatment in organ transplantation should be considered.

Effects of prostaglandin E2, cholera toxin and 8-bromo-cyclic AMP on lipopolysaccharide-induced gene expression of cytokines in human macrophages

Prostaglandin E2 (PGE2) appears to regulate macrophage cytokine production through the stimulatory GTP-binding protein (Gs protein)-mediated cyclic AMP (cAMP)-dependent transmembrane signal transduction pathway. In this study, we used PGE2, cholera toxin (CT; a direct G alpha s protein stimulator) and 8-bromo-cAMP (a membrane permeable cAMP analogue) to stimulate this pathway, and investigated their influence on cytokine gene expression in lipopolysaccharide (LPS)-activated human macrophages. The mRNA expression for interleukin-1 alpha (IL-1 alpha), IL-1 beta, tumour necrosis factor-alpha (TNF-alpha), IL-6 and IL-8 were determined employing reverse transcription polymerase chain reaction (RT-PCR) using specific primers. We demonstrated that PGE2, CT and 8-bromo-cAMP inhibited the LPS-induced gene activation of TNF-alpha and IL-1 alpha, and had no effect on the gene activation of IL-1 beta and IL-8. Further, our data indicate that PGE2 suppressed the gene activation of IL-6 following LPS stimulation, but neither CT nor 8-bromo-cAMP had an effect. These data suggest that PGE2 alters LPS-stimulated gene activation of only some of the early macrophage cytokines, and does so either by a Gs transmembrane cAMP-dependent or an independent system.

Effects of continuous tube feeding of dietary fat emulsions on eicosanoid production and on fatty acid composition during an acute septic shock in rats

The effects of a short-term (5 days) continuous intragastric tube feeding of diets containing n - 6 polyunsaturated fatty acids (PUFA) from safflower oil (SO) or n - 3 PUFA from menhaden oil (MO) on the production of proinflammatory mediators, and on the number of animals surviving after an intravenous injection of lipopolysaccharide (LPS) were investigated in rats. The phospholipid fatty acid composition of cell membranes from several organs and of plasma were also analyzed. No marked differences in the number of animals surviving or in the production of tumor necrosis factor-alpha were observed between the 2 groups of animals. However, 90 min after LPS exposure the plasma levels of prostaglandin (PG) E2 and 6-keto-PGF1 alpha decreased significantly (40% and 60%, respectively) for the group of rats fed MO diet compared to those fed SO diet (P < 0.05). Following continuous infusion of liquid MO diet, the amount of arachidonic acid (AA) detected was significantly lower in plasma (23%), spleen (43%), lungs (41%), and liver (38%), but was unchanged in the heart tissues. The percent of eicosapentaenoic acid (EPA) incorporated into phospholipids of plasma, spleen, lungs, liver, and heart were 7.6, 4.4, 2.1, 7.2, and 1.1%, respectively. These data indicate that after continuous MO feeding, a significant decrease in the production of proinflammatory eicosanoids was associated with a marked reduction in AA content. Further, these data suggest that nutritional intervention may have a therapeutic potential to ameliorate clinical symptoms due to excessive productions of eicosanoids during acute septic complications.

Effect of prostaglandin E2 and other intracellular cyclic AMP elevating agents on the mitogen induced mouse splenocyte proliferation in a serum free culture condition

Prostaglandins (PGs) play an important role in the regulation of the host's immune responses to infection and inflammation. However, the mechanisms through which the PGs regulate immune functions are not well known. In the present study, we investigated the T cell specific mitogen Concanavalin A (Con A) induced mouse splenocyte proliferation in a serum free condition in vitro in the presence of absence of different doses of PGE2, indomethacin, cholera toxin and forskolin. The Con A induced splenocyte proliferative responses were significantly inhibited following the addition of PGE2 and were markedly enhanced in the presence of indomethacin (PG synthase inhibitor). As with PGE2, both cholera toxin and forskolin, which increase intracellular cyclic AMP by activating stimulatory GTP binding protein (Gs protein) and adenylate cyclase respectively, inhibited splenocyte proliferation in a dose dependent manner. These data indicate that PGE2 down regulated mitogen induced splenocyte proliferation and that blocking the production of endogenous PGs potentiated T-cell mitogen response. Further, these findings suggest that PGE2 regulation of splenocyte proliferation is due to increasing intracellular cAMP through G protein transmembrane regulation of adenylate cyclase. This study also provided a defined experimental model to investigate mechanisms of the regulation of cellular function through the exogenous and endogenous mediators such as PGs and their intracellular signal transductions.

Immunopotentiation by orally-administered Quillaja saponins: effects in mice vaccinated intraperitoneally against rabies

Orally fed Quillaja saponins amplified the immunopotentiating ability of an intraperitoneally (IP) administered inactivated rabies vaccine in mice. The number of animals surviving rabies infection was markedly higher (90-100%) in groups of animals receiving a combined treatment of oral saponin (SAP) and IP vaccine, compared to groups receiving vaccine alone (25%), or to unimmunized mice (0%). Antibody production was significantly higher in animals fed SAP 2 weeks after primary or secondary sensitization with an IP-injected vaccine. In mice given 2 IP doses of vaccine, 1 week apart, simultaneous feeding of SAP resulted in an enhanced production of rabies-specific (whole Ig) antibodies. On the other hand, animals preconditioned with SAP 3 days prior to administration of the vaccine exhibited greatly increased IgG antibody levels. Moreover, SAP-preconditioned mice vaccinated with a very low dosage produced significantly higher levels of antibodies.

Adjuvant effects of orally administered saponins on humoral and cellular immune responses in mice

We have described adjuvant effects of orally administered Quillaja saponins on the immune responses of mice fed inactivated rabies antigen (AG). The in vivo lymphocyte proliferation in mice fed antigen + saponin (AG + SAP) was significantly greater than that in mice fed antigen (AG) alone. Further, the mitogen-induced cell proliferative responses in animals primed with AG + SAP was markedly increased compared with those in the AG group. These changes in clonal expansion were associated with an enhanced helper T cell (Th) and B cell co-operation. The in vivo cell proliferation and in vitro mitogen-induced responses of mice fed AG + SAP correlated with enhanced antibody synthesis. In mice fed saponin alone, there were significant increases in clonal expansion and lymphocyte function. Our present data indicate that the immunocompetence in animals fed AG + SAP was indeed evoked by saponins. Cytotoxic T lymphocyte activity in mice fed SAP or AG + SAP was detected 7 days after booster, in contrast to 21 days in mice fed AG alone. The natural killer cell activity in mice fed SAP alone was greatly enhanced and persisted for an extended period of time.

An in vitro study of immunomodulatory effects of some saponins

The in vitro immunomodulatory activities of a number of saponins (crude Quillaja saponin, Quillayanin, Quil-A and glycyrrhizic acid) are described. Addition of these saponin preparations to mouse spleen cell cultures resulted in significant cell proliferation. B-cells were induced to proliferate in the presence of the crude saponin, and T-cells in the presence of Quil-A. On the other hand, Quillayanin and glycyrrhizic acid stimulated both T- and B-lymphocytes equally. The selective proliferation of subtypes of lymphocytes correlated with restimulation responses by polyclonal mitogens. Pretreatment by lymphocytes with crude saponins induced significant T-cell responses to PHA and Con A, and to T-independent B-cell stimulation by LPS. Pulse exposure of spleen cells to Quil-A resulted in enhanced cell proliferation when restimulated with PHA, Con A and PWM. In comparison, similar exposure of lymphocytes to Quillayanin or glycyrrhizic acid produced markedly increased responses to PHA, Con A, PWM and LPS. Incubation of lymphocytes in the presence of Quillaja saponins and Quillayanin caused effector cell generation as determined in a one-way mixed lymphocyte reaction. In the case of lymphocytes cultured in the presence of crude saponins or glycyrrhizic acid, the supernatants contained active soluble factors. This was demonstrated by the observation that the addition of supernatants to spleen cell cultures induced spontaneous cell proliferation, and also amplified their responses to a suboptimal dose of PHA. The experimental data suggest that different components in the Quillaja saponin preparations may have selective effects on various subtypes of cell populations. Glycyrrhizic acid has the most profound immunomodulatory activity in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunomodulatory effects of orally-administered saponins and nonspecific resistance against rabies infection

We present evidence that orally fed Quillaja saponins offer nonspecific resistance to mice against rabies viral infection. Adoptive transfer of spleen cells and thymocytes from animals preconditioned with saponin (SAP), inactivated rabies antigen (AG), or a mixture of AG+SAP has offered significant protection against an intracerebral challenge with live rabies virus. Levels of serum rabies-neutralizing antibodies in the different groups of recipient animals did not correlate with the respective survival rates. Culture supernatants of concanavalin A-stimulated spleen cells from animals fed SAP or AG+SAP induced marked T cell and B cell proliferation, and also greatly enhanced the plaque-forming cell activity of unprimed spleen B cells. Irrespective of the presence or absence of rabies-specific antibodies, sera from animals fed a mixture of AG+SAP induced significant levels of cell proliferation and augmented phytohemagglutinin (PHA)-induced responsiveness of spleen lymphocytes in vitro. The addition of sera from animals fed AG alone resulted in inhibition of cell proliferation and suppressed PHA-induced responses.