A high isoflavone soy protein diet and intravenous genistein delay rejection of rat cardiac allografts

Elucidating the immunomodulatory effects of phytoestrogens and their groundbreaking applications in transplantation medicine

Phytoestrogens are natural compounds found in plants and plant-based foods. When ingested, they can affect the human body in the same way as estrogen produced by the body. Phytoestrogens affect the regulation, differentiation, and production of immune cells. People who consume polyphenol and flavonoid-rich foods have lower incidences of inflammation, autoimmune diseases, and cancer. In organ transplantation, immune rejection is a lifelong problem for patients. In clinical practice, acute rejection is treated with hormonal shock or immunosuppressive drugs. However, effective reversal measures for chronic rejection, specifically for prevention, are still lacking. Recipients are also prone to post-transplant complications such as new tumors, diabetes, hyperlipidemia, hyperuricemia, and cardiovascular and cerebrovascular diseases, owing to the long-term use of immunosuppressive drugs. Phytoestrogens play a promising role in immune regulation and exert curative effects on cardiovascular diseases and cancer. In this study, we reviewed the use of phytoestrogens in the fields of immune regulation and organ transplantation.

Dietary soy isoflavones during pregnancy suppressed the immune function in male offspring albino rats

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Less attention has been paid to the immune effects of phytoestrogens during pregnancy on the first generation.

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Soy isoflavones fed to pregnant rats could modulate the immune response of the male offspring.

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Isoflavones reduced spleen and thymus weights in rats born to dams fed dietary soy.

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Soy isoflavones possibly mediated its effect through reduction of IFN-γ that interacts with the IL-12 production pathway.

Phytoestrogens have an impact on both animals and humans due to use of legumes in animal diets as well as the increase of vegetarian diets in some human populations. Phytoestrogens thought to have varieties of adverse effects, among which immune system was involved. The present study aimed to investigate the effect of prenatal exposure to dietary soy isoflavones on some immunological parameters in male albino rat offspring. The pregnant rats were divided to three groups (12/group). Control group (free soy isoflavones), low soy isoflavones group (6.5%) and high soy isoflavones group (26%). The male offspring cell-mediated immune response was determined using phytohemagglutinin (PHA) injection and the intumesce index which was calculated on postnatal day 50 (PND 50). At PND 50, blood samples were collected for interleukin 12 (IL-12), interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α) determination. Spleen, thymus, and PHA injected footpads were fixed for histopathology. Intumesce index, IL-12, IFN-γ, spleen and thymus relative weights were significantly (P < 0.05) decreased in offspring born to dams fed low and high dietary soy isoflavones. In contrary, TNF-α was significantly (P < 0.05) increased in offspring born to dams fed high dietary soy isoflavones. Spleen of rats born to dams fed high dose of dietary soy isoflavones showed coagulative necrosis in white pulp. In conclusion, male offspring born to dams fed different levels of soy isoflavones showed marked immunosuppression after PHA stimulation. This effect was mediated through the reduced IFN-γ that interacts with the IL-12 production pathway.

Triptolide inhibits CD4+ memory T cell-mediated acute rejection and prolongs cardiac allograft survival in mice

There have been numerous investigations into the immunosuppressive effects of triptolide; however, its inhibitory effects on memory T cells remain to be elucidated. Using a cluster of differentiation (CD)4⁺ memory T-cell transfer model, the aim of the present study was to determine the inhibitory effects of triptolide on CD4⁺ memory T cell-mediated acute rejection and to determine the potential underlying mechanisms. At 4 weeks after skin transplantation, mouse cervical heart transplantation was performed following the transfer of CD4⁺ memory T cells. Mice were divided into two groups: A Control [normal saline, 30 ml/kg/day; intraperitoneal injection (ip)] and a triptolide group (triptolide, 3 mg/kg/day; ip). Graft survival, pathological examination and the corresponding International Society for Heart & Lung Transplantation (ISHLT) scores were assessed 5 days following heart transplantation, and levels of interleukin (IL)-2, interferon-γ (IFN-γ), IL-10 and transforming growth factor β1 (TGF-β1) in cardiac grafts and peripheral blood were assessed using reverse transcription-quantitative polymerase chain reaction and ELISA. The duration of cardiac graft survival in the triptolide group was significantly increased compared with the control group (14.3±0.4 vs. 5.3±0.2 days; P<0.001). Further pathological examinations revealed that the infiltration of inflammatory cells and myocardial damage in the cardiac grafts was notably reduced by triptolide, and the corresponding ISHLT scores in the triptolide group were significantly lower than those of the control group (grade 2.08±0.15 vs. 3.67±0.17; P<0.001). In addition, triptolide was able to significantly reduce IL-2 and IFN-γ secretion (P<0.01), significantly increase TGF-β1 secretion in the cardiac grafts and peripheral blood (P<0.01) and increase IL-10 secretion in the cardiac grafts. Therefore, the present study suggests that triptolide inhibits CD4⁺ memory T cell-mediated acute rejection and prolongs cardiac allograft survival in mice. This effect may be mediated by the inhibition of cytokine secretion by type 1 T helper cells and promotion of regulatory T cell proliferation.

Prenatal Exposure to Soy Isoflavones Altered the Immunological Parameters in Female Rats

Information on the effects of phytoestrogens on animals has increased recently; however, there were only few studies on prenatal exposure on cellular immune response. Pregnant rats were assigned to 3 groups (12 rats per group), the first was fed control diet, the second was fed low-dose (6.5 g/100 g of diet) soy isoflavones, while the third was fed high-dose (26 g/100 g of diet) soy isoflavones. The female offspring cell-mediated immune response was determined using phytohemagglutinin (PHA) injection, and intumesce index was calculated on postnatal day 50. After 24 hours of PHA injection, blood samples were collected for tumor necrosis factor α, interferon γ (IFN-γ), and interleukin (IL)-12 determination. Spleen, thymus, and PHA-injected footpads were fixed for histopathology. Intumesce index was significantly (P < 0.05) reduced in rats' offspring born from dams fed low- and high-dietary soy isoflavones than that in control groups. Thymic relative weights in offspring of rats fed high-dietary soy isoflavones showed a significant (P < 0.05) decrease compared to that in the control group. Female offspring where low and high-dietary soy isoflavones were fed to their dams showed a significant (P < 0.05) decrease in IFN-γ and IL-12 than that in control ones. Spleen of rats born from dams fed high dose of dietary soy isoflavones showed lymphocytic depletion in white pulp. Taking together, it is clear that dietary soy isoflavones at prenatal period had immunosuppressive effect on female offspring after PHA stimulation. This effect was mediated through reduced IFN-γ that interplayed in IL-12 production pathway thus reducing its level.

Comparison of natural estrogens and synthetic derivative on genioglossus function and estrogen receptors expression in rats with chronic intermittent hypoxia

The pathogenesis of obstructive sleep apnea--hypopnea syndrome (OSAHS) is summarized as the narrow anatomic structure of upper airway (UA) and the defective function of UA dilator muscles. Up to now, there have been no specific treatments for the UA dilator muscle deficiency. We previously found that some estrogen-like compounds exert protective effects on genioglossus, but this protection tends to be less satisfactory. A novel phytoestrogen derivative was synthesized in recent years and was verified to have some cytoprotective activity. This study was designed to compare the effects of natural estrogens and the synthetic resveratrol dimer on genioglossus contraction and expression of estrogen receptors (ERs) under chronic intermittent hypoxia (CIH) condition. Genioglossus myoblasts of rat were isolated and cultured in a culture medium with different agents (estradiol, genistein, resveratrol, and resveratrol dimer, respectively) under hypoxia condition, and ERs expressions were detected. In vivo study, 48 ovariectomized female rats were randomized into six groups. After CIH exposure and agents injection, rats were tested for genioglossus contractile properties and further analysis of ERs expression. Estradiol up-regulated ERα level and exerted the best protective effect of fatigue resistance. Genistein, resveratrol and resveratrol dimer primarily up-regulated the expression of ERβ. Resveratrol dimer exhibited better protection of fatigue resistance than genistein and resveratrol, and expressed higher binding affinity for ERβ than for ERα. Besides estrogenic effects, there may be some other mechanisms for the fatigue resistance improvement contributed by phytoestrogens and their derivatives.

Regulation of the immune response by soybean isoflavones

Soybeans are rich in immuno-modulatory isoflavones such as genistein, daidzein, and glycitein. These isoflavones are well-known antioxidants, chemopreventive and anti-inflammatory agents. Several epidemiological studies suggest that consumption of traditional soy food containing isoflavones is associated with reduced prevalence of chronic health disorders. Isoflavones are considered to be phytoestrogens because of their ability to bind to estrogen receptors. The literature is extensive on the chemistry, bio-availability, and bio-activity of isoflavones. However, their effects on immune response are yet to be fully understood, but are beginning to be appreciated. We review the role of isoflavones in regulation of the immune response and their potential clinical applications in immune-dysfunction. Special emphasis will be made regarding in vivo studies including humans and animal model systems.

Immunomodulatory effects of environmental endocrine disrupting chemicals

During recent decades more than 100,000 new chemicals have been introduced as common consumer products into our environment. Among these chemicals, endocrine-disrupting chemicals (EDCs) are of particular concern owing to their toxicity in animal studies and their impacts on human health. EDCs are ubiquitous in the environment, including the air, water, and soil. The endocrine-disrupting effect of EDCs has been found to imitate the action of steroid hormones and promote several endocrine and reproductive disorders in both animal and human studies. In the present review, we focus on the effects of EDCs on the immune system. EDCs interfere with the synthesis of cytokines, immunoglobulins, and inflammatory mediators, and they also affect the activation and survival of immune cells. The dysfunction of the immune system caused by EDCs may lead to the attenuation of immunity (immunodeficiency) against infection or hyperreactivity of immune responses (allergy and autoimmune disease). In this review, we summarize epidemiologic, animal, and cell studies to demonstrate the potential effects of EDCs on immunity, allergy, and autoimmune diseases. We also address the impact of EDCs on epigenetic regulation.

Comparison of the effects of genistein and daidzein with dexamethasone and soy protein on rheumatoid arthritis in rats

INTRODUCTION

We have already shown the protective effects of soy protein on rheumatoid arthritis in rats. In this study, the effects of genistein and daidzein, two isoflavones from soy on rheumatoid arthritis prognosis and prevention in rats have been investigated.

METHODS

Rheumatoid arthritis was induced in female Sprague-Dawley rats using collagen type II plus adjuvant. Rats were then treated with soy protein (7 g/kg), dexamethasone (1 mg/kg), genistein (20 mg/kg genistein), daidzein (20 mg/kg genistein) and casein (in control groups) by daily gavage feedings for 50 days. Scores of arthritis were recorded every day for each paw of animal. Serum concentrations of TNF-α, IL-6, adiponectin and leptin were characterized. Tibiotarsal tissue was used for histopathologic analyses.

RESULTS

Treatment with genistein and daidzein resulted in not only a reduction in disease symptoms but also a delay in the onset of symptoms. Results from delayed-type hypersensitivity test demonstrated that the ear thickness in treated rats was significantly lower than that in the control group (p<0.05). There was a reduction in TNF-α, IL-6, adiponectin and leptin serum concentrations after treatment with genistein and daidzein. Dexamethasone reduced the serum concentrations of TNF-α, IL-6 and adiponectin but increased leptin serum level. Prevention of the tissue damage and joint inflammation was also observed following treatment with two soy isoflavones.

CONCLUSION

soy isoflavones, daidzein and especially genistein, could significantly improve rheumatoid arthritis symptoms in rats. The structural similarity of isoflavones to estrogen could be the possible underlying mechanism involved in the function.

17beta-Estradiol and soy phytochemicals selectively induce a type 2 polarization in mesenteric lymph nodes of ovariectomized rats

OBJECTIVE

This study was designed to compare the effects of 17beta-estradiol (17beta-E2) and a phytoestrogen-containing soy extract on the immune system in an ovariectomized rat model of menopause. Specifically, T- and B-lymphocyte subsets, the balance of type 1 and 2 immune responses in the mesenteric lymph nodes, and serum levels of different classes of immunoglobulin were examined as study endpoints.

DESIGN

Ovariectomized rats were treated with either the phytoestrogen-containing soy extract (50 or 100 mg/kg/day PO), 17beta-E2 (0.5 mg/kg/day PO), or vehicle; a sham control was included in the study. After the rats were killed, mesenteric lymph nodes and blood samples were collected. B- and T (CD4 and CD8)-lymphocyte subsets in mesenteric lymph nodes were evaluated by flow cytometry analysis. Cytokine-producing T lymphocytes were identified within each T-lymphocyte subset as TH1 (interferon-gamma CD4), TH2 (interleukin-4 CD4), TC1 (interferon-gamma CD8), and TC2 (interferon-4 CD8) lymphocytes. Serum levels of immunoglobulin classes were determined by enzyme-linked immunosorbent assay.

RESULTS

There were no differences in the proportions of B lymphocytes and CD4 and CD8 T lymphocytes among groups. Treatment with 17beta-E2 and phytoestrogen-containing soy extract induced a reduction in TH1 and TC1 lymphocytes paralleled by a slight, nonsignificant, increase in the frequency of TH2. Data expressed as TH1/TH2 and TC1/TC2 ratios depicted a significant polarization of local immunity toward a humoral response. Evaluation of immunoglobulin serum levels did not show any significant difference among groups.

CONCLUSIONS

Here we show that estrogens and soy phytochemicals similarly polarize the immune system toward a type 2 immune response in a preclinical model of menopause; our data draw attention to the crucial need to evaluate in clinical studies the potential side effects on the immune system of the complex soy products that are actually consumed in the postmenopausal setting.

Drugs modulating endothelial function after transplantation

Endothelial cells play a vital role in the success or failure of a transplant procedure. The procedure itself can be viewed as a series of insults that damages the endothelium thereby triggering an inflammatory cascade that may, if uncontrolled, drive the proliferative and fibrotic processes characteristic of chronic graft vasculopathy. Unfortunately, many immunosuppressant agents contribute to this process. Glucocorticoids and the calcineurin inhibitor cyclosporine induce endothelial dysfunction, and although tacrolimus may not have the same disruptive effects on endothelial function as cyclosporine, its endothelial activity is still being established. In contrast, antiproliferative agents slow the proliferation and migration of endothelial cells and so help protect against graft vasculopathy. Researchers agree that endothelial cell dysfunction is a potentially treatable stage in the multifactorial process of graft vasculopathy and rejection. A number of cardiovascular agents (statins, angiotensin converting enzyme inhibitors, calcium channel blockers), immunoregulatory drugs, and dietary compounds have been shown to have beneficial effects on endothelial function. We briefly review the evidence supporting their use as protection for endothelial cells in transplant recipients.

Genistein, estrogen receptors, and the acquired immune response

Estrogen regulates thymic development and immune function. Despite the critical role of estrogens in inducing thymic involution and modulating immune responses, the mechanism of this effect is unclear. Similarly, humans and animals are exposed to increasing amounts of the estrogenic soy isoflavone genistein in the diet, but whether genistein can induce immune changes has not been definitively established. We reported previously that genistein induces thymic atrophy in mice, and decreases both humoral and cell-mediated immunity. These thymic effects of genistein occur via estrogen receptor (ER)-mediated and non-ER-mediated pathways. Genistein injections produced the most pronounced effects, but dietary administration to mice that produced serum genistein concentrations similar to those reported in human infants consuming soy formula also had demonstrable effects. Microarray analysis of the effects of estradiol and genistein on neonatal thymus indicated that estradiol affected genes involved in transcription, apoptosis, cell cycle, and thymic development and function; genistein had similar effects on many estradiol target genes, but also had unique actions not replicated by estradiol. Despite extensive work showing inhibitory effects of genistein on immunity, other rodent studies reported that genistein or other phytoestrogens stimulate various aspects of immune function. Although the present data strongly indicate that genistein can regulate immune function, possibly at physiologic concentrations, further work is required to definitively establish overall thymic and immune effects of genistein and soy, which may vary with age, species, and specific end point.

The phytoestrogen biochaninA weakens acute cardiac allograft rejection without affecting the reproductive system

BACKGROUND

Since the two estrogen receptor isoforms ERalpha and ERbeta have been discovered it is unclear by which receptor immunomodulating or feminizing effects are mediated. In this study, the effects of the two selective ERalpha- and ERbeta-agonists ethinylestradiol and biochaninA, respectively, on acute cardiac allograft rejection, uterus growth, vascular adhesion molecule and MHC-II expression were investigated and verified using in vitro cell culture.

METHODS

Heterotopic Lewis to ovarectomized F344 cardiac transplantations were performed. The study groups received supplemental biochaninA or ethinylestradiol, the control group received no treatment. Grafts and uteri were harvested on the fifth postoperative day and blood was taken for hormone plasma level quantifications. Purified Lewis aortic endothelial cell cultures were pre-treated with biochaninA or ethinylestradiol and stimulated with TNF-alpha or IFN-gamma for quantification of ICAM-1/VCAM-1 and MHC-II expression. Endothelium-lymphocyte adhesion assays were performed using purified F344 lymphocytes.

RESULTS

Both biochaninA and ethinylestradiol treatment significantly reduced graft mononuclear infiltration of CD8(+) and ED1(+) cells and markedly reduced ISHLT grading compared to untreated controls. Either agent significantly inhibited lymphocyte adhesion, endothelial VCAM-1 upregulation during graft rejection and during TNF-alpha-stimulation in vitro, whereas no effect was observed for ICAM-1 upregulation. BiochaninA but not ethinylestradiol significantly reduced endothelial MHC-II upregulation in vivo and in vitro. Only ethinylestradiol treatment strongly affected uterus growth in ovarectomized recipients.

CONCLUSIONS

Only the treatment with the phytoestrogen biochaninA reduced endothelial MHC-II expression in vivo and in vitro and weakened allograft rejection without affecting the reproductive system. Supplemental phytoestrogens may therefore provide further benefits in the clinical setting.

Gene Expression Profiling of 17β-Estradiol and Genistein Effects on Mouse Thymus

Estrogen regulates thymic development and involution and modulates immune function. Despite its critical role in thymus, as well as in autoimmune disorders, the mechanism by which estrogen affects the thymus is not well understood. We previously reported that the estrogenic soy isoflavone genistein, as well as 17beta-estradiol (E2), could induce thymic involution, but genistein effects were only partially mediated through estrogen receptors. To provide insights into mechanisms of estrogenic effects in the thymus, we investigated thymic gene expression changes induced by E2 (125 ng/day) and genistein (1500 ppm in feed) in weanling mice using high-density DNA arrays. We identified several E2-responsive genes involved in thymic development and thymocyte signaling during selection and maturation. Functional characterization indicated effects on genes involved in transcription, apoptosis, and the cell cycle. This study also identified changes in several E2-regulated transcripts essential to maintain immune self-tolerance. E2 upregulated more genes than genistein, while genistein downregulated more genes than E2. Though each treatment regulated several genes not altered by the other, there was considerable overlap in the genes regulated by E2 and genistein. Changes in transcription factors and cell cycle factors were consistent with decreases in cell proliferation induced by both genistein and E2. As indicated by the regulation of non-E2-responsive genes, genistein also induced unique effects through non-estrogenic mechanisms. The specific downregulation of the CD4 coreceptor transcript by genistein was consistent with the decline of CD4+ thymocytes in genistein-treated mice in our previous study. This is the first study identifying E2 and genistein target genes in the thymus. These findings provide new mechanistic insights toward explaining estrogen action on thymocyte development, selection, and maturation, as well as the effects of genistein on prenatal and neonatal thymic development and function.

Soy Isoflavones Modify Liver Free Radical Scavenger Systems and Liver Parameters in Sprague–Dawley Rats

Soyfoods contain estrogenic isoflavones--namely, genistein (G) and daidzein (D)--that, like estrogens, display physiological effects in humans and animals. Previously we and others have demonstrated antioxidant and cardioprotective effects of orally ingested soy diets and soy isoflavones. The overall objective of this study was to test the effects of injected soy isoflavones, G and D, on liver lipids, liver free radical scavenger systems, and parameters of cardiovascular risk. Forty male rats were injected with G, D, estradiol (E), or a vehicle control (V) for 6 weeks. At the end of the study, body weight, food intake, feed efficiency ratio (FER), plasma glucose and cholesterol, abdominal fat pad weight, reproductive organ weight, liver weight, liver lipids, and liver free radical scavenger systems were compared. Food intake was significantly (P < .04) higher in the D-, G-, and E-treated animals compared with V-treated animals. FER was lower (P < .001) in D-, G-, and E-treated animals compared with the V- and the E-treated animals. Body weight, testis weight, and prostate weight were markedly (P < .001) lower in the E-treated animals compared with D-, G-, and V-treated animals. Intraabdominal fat pad weights were also significantly (P < .001) lower in the E group, although this effect was lost when corrected for body weight. Liver weights were considerably lower in the D-, G-, and E-treated animals versus the V group (P < .001). Total plasma cholesterol was reduced (P < .05) in D- and E-treated animals versus the V group. Liver lipids appeared to be unchanged by the isoflavones and slightly elevated by E treatment (P < .02). Liver catalase levels were numerically higher in the D- and E-treated animals compared with the V group (P < .1). Similarly, Cu/Zn superoxide dismutase (SOD) activity was significantly elevated in the D and E groups (P < .01), while G treatment (P < .03) elevated SOD to a lesser degree, versus the V group. These results suggest that subcutaneous injections of the naturally occurring soy isoflavone D and, to a lesser extent, G exert cardioprotective effects and stimulate antioxidant systems, while minimizing the undesirable effects elicited by E treatment.

Dietary isoflavones suppress endotoxin-induced inflammatory reaction in liver and intestine

Dietary isoflavone intake has been linked to cancer prevention and their anti-inflammation activity was examined. Intraperitoneal lipopolysaccharide (LPS) injection in mice led to a decrease in the liver antioxidant glutathione level but this decrease was prevented in mice fed with an isoflavone-containing diet. Similarly, isoflavone diet prevented the inflammation-associated induction of metallothionein (MT) in the intestine; and the induction of manganese superoxide dismutase (Mn-SOD) in the liver. Results from the intestinal cell studies suggest that isoflavones suppress the intestinal response to inflammation by modulating the action of pro-inflammatory cytokine, IL-6. IL-6 secretion and the STAT3 (signal transducer and activator of transcription protein 3) nuclear translocation in response to IL-6 were both decreased by genistein.

Soy isoflavones exert antidiabetic and hypolipidemic effects through the PPAR pathways in obese Zucker rats and murine RAW 264.7 cells

The hypocholesterolemic and anti-atherosclerotic mechanism by which soy may exert a beneficial effect remains unclear. Peroxisome-proliferator activated receptors (PPAR) are promiscuous nuclear receptors that regulate the transcription of genes involved in lipid and glucose homeostasis and lipid metabolism within the cell. We hypothesize that the isoflavones improve lipid and glucose metabolism by acting as an antidiabetic PPAR agonist. Male and female obese Zucker rats (OZR) were used as a model of Type 2 diabetes, and OZR fed a high isoflavone soy protein diet displayed improvements in lipid metabolism consistent with results in humans treated with antidiabetic PPAR agonists such as the fibrates or glitazones. Liver triglyceride and cholesterol concentrations were lower in all OZR fed high-isoflavone soy protein diets than in rats fed low-isoflavone and casein diets (P < 0.05). Concurrently, PPAR-directed gene expression was evaluated in a cell culture model. An isoflavone-containing soy extract doubled PPAR-directed gene expression (P < 0.05) in RAW 264.7 cells containing either a PPARalpha or PPARgamma expression plasmid. A similar induction was observed when the soy isoflavones genistein or daidzein were used to treat cells. Both isoflavones doubled PPARalpha-directed gene expression (P < 0.05), whereas they increased PPARgamma-directed gene expression 200-400% (P < 0.05). This study suggests that soy isoflavones improve lipid metabolism, produce an antidiabetic effect, and activate PPAR receptors.