Cocoa Diet Prevents Antibody Synthesis and Modifies Lymph Node Composition and Functionality in a Rat Oral Sensitization Model

Cocoa as immunomodulatory agent: an update

Cocoa is rich in polyphenols, mainly flavonoids, which correlate with several health benefits mediated by their antioxidant, anti-inflammatory and immunomodulatory properties. Cocoa and chocolate consumption have been reported to impact the regulation of the immune system, both in preclinical studies and in human trials. The mechanisms for immunomodulation can involve different effects of cocoa polyphenols on the immune system, acting as anti-inflammatory, antioxidant and anti-allergic agents, as well as the direct influence of cocoa on innate and acquired immunity, with cytokines production and activation of both lymphocyte-dependent and -independent pathways. Cocoa intake has been also correlated to changes in gut microbiota ecology and composition, also affecting the intestinal immune system. This review summarises the updates of the last two decades on cocoa as immunomodulatory agent and explores the health-related benefits of cocoa and chocolate intake.

Rat Mucosal Immunity following an Intensive Chronic Training and an Exhausting Exercise: Effect of Hesperidin Supplementation

Stressful situations such as a high-intensity exercise or exhausting training programs can act as immune disruptors leading to transitory immunodepression status, which can be accompanied by alterations of the gastrointestinal functions. Hesperidin intake has demonstrated ergogenic activity and is able to influence the intestinal ecosystem and immunity. We aimed to investigate the effect of hesperidin consumption in rats submitted to an intense training and a final exhaustion test, focusing on the functionality of the intestinal immune system and on the cecal microbiota. Rats, supplemented or not with hesperidin, were intensively trained on a treadmill for 5 weeks. Samples were obtained 24 h after a regular training session, and immediately and 24 h after a final exhaustion test. Cecal microbiota and composition and function of mesenteric lymph node (MLN) lymphocytes and mucosal immunoglobulin A (IgA) were determined. Results showed that chronic intense exercise followed by an exhausting test induced changes in the intestinal immune compartment such as the distribution and function of MLN lymphocytes. Although the hesperidin supplementation did not prevent these alterations, it was able to enhance IgA synthesis in the intestinal compartment. This could be important in enhancing the immune intestinal barrier in this stressful situation.

Influence of Diets Enriched with Flavonoids (Cocoa and Hesperidin) on the Systemic Immunity of Intensively Trained and Exhausted Rats

The aim of this study was to establish the influence of flavonoid-enriched diets on the immune alterations induced by an intensive training and a final exhaustion test in rats. A flavanol-enriched diet (with 10% cocoa, C10 diet) and a flavanol and flavanone-enriched diet (C10 plus 0.5% hesperidin, CH diet) were used. Lewis rats were fed either a standard diet, C10 diet or CH diet while they were submitted to an intensive running training on a treadmill. After 6 weeks, samples were obtained 24 h after performing a regular training (T groups) and after carrying out a final exhaustion test (TE groups). The C10 diet attenuated the increase in plasma cortisol induced by exhaustion, while both the C10 and the CH diets prevented the alterations in the spleen Th cell proportion. The experimental diets also induced an increase in serum immunoglobulin concentration and an enhancement of spleen natural killer cytotoxicity, which may be beneficial in situations with a weakened immunity. Most of the effects observed in the CH groups seem to be due to the cocoa content. Overall, a dietary intervention with flavonoids enhances immune function, partially attenuating the alterations in systemic immunity induced by intensive training or exhausting exercise.

A Cocoa Diet Can Partially Attenuate the Alterations in Microbiota and Mucosal Immunity Induced by a Single Session of Intensive Exercise in Rats

Background

Following intensive sports events, a higher rate of upper respiratory tract infections and the appearance of gastrointestinal symptomatology have been reported. We aimed to evaluate the effect of a cocoa-enriched diet on the cecal microbiota and mucosal immune system of rats submitted to high-intensity acute exercise, as well as to elucidate the involvement of cocoa fiber in such effects.

Methods

Wistar rats were fed either a standard diet, a diet containing 10% cocoa providing 5% fiber and a diet containing only 5% cocoa fiber. After 25 days, half of the rats of each diet performed an exhaustion running test. Sixteen hours later, samples were obtained to assess, among others, the cecal microbiota and short chain fatty acids (SCFAs) composition, mesenteric lymph nodes (MLNs) and Peyer’s patches (PPs) lymphocyte composition, and immunoglobulin (Ig) content in salivary glands.

Results

The intake of cocoa, partially due to its fiber content, improved the SCFA production, prevented some changes in PPs and in MLNs lymphocyte composition and also decreased the production of proinflammatory cytokines. Cocoa diet, contrary to cocoa fiber, did not prevent the lower salivary IgM induced by exercise.

Conclusion

A cocoa dietary intake can partially attenuate the alterations in microbiota and mucosal immunity induced by a single session of intensive exercise.

Protective Effect of a Cocoa-Enriched Diet on Oxidative Stress Induced by Intensive Acute Exercise in Rats

Intensive acute exercise can induce oxidative stress, leading to muscle damage and immune function impairment. Cocoa diet could prevent this oxidative stress and its consequences on immunity. Our aim was to assess the effect of a cocoa-enriched diet on the reactive oxygen species (ROS) production by peritoneal macrophages, blood immunoglobulin (Ig) levels, leukocyte counts, and the physical performance of rats submitted to an intensive acute exercise, as well as to elucidate the involvement of cocoa fiber in such effects. For this purpose, Wistar rats were fed either a standard diet, i.e., a diet containing 10% cocoa (C10), or a diet containing 5% cocoa fiber (CF) for 25 days. Then, half of the rats of each diet ran on a treadmill until exhaustion, and 16 h later, the samples were obtained. Both C10 and CF diets significantly prevented the increase in ROS production. However, neither the cocoa diet or the cocoa fiber-enriched diet prevented the decrease in serum IgG induced by acute exercise. Therefore, although the cocoa-enriched diet was able to prevent the excessive oxidative stress induced by intensive exercise, this was not enough to avoid the immune function impairment due to exercise.

Influence of Consumption of Two Peruvian Cocoa Populations on Mucosal and Systemic Immune Response in an Allergic Asthma Rat Model

Different cocoa populations have demonstrated a protective role in a rat model of allergic asthma by attenuating the immunoglobulin (Ig) E synthesis and partially protecting against anaphylactic response. The aim of this study was to ascertain the effect of diets containing two native Peruvian cocoa populations (“Amazonas Peru” or APC, and “Criollo de Montaña” or CMC) and an ordinary cocoa (OC) on the bronchial compartment and the systemic and mucosal immune system in the same rat model of allergic asthma. Among other variables, cells and IgA content in the bronchoalveolar lavage fluid (BALF) and serum anti-allergen antibody response were analyzed. The three cocoa populations prevented the increase of the serum specific IgG1 (T helper 2 isotype). The three cocoa diets decreased asthma-induced granulocyte increase in the BALF, which was mainly due to the reduction in the proportion of eosinophils. Moreover, both the OC and CMC diets were able to prevent the leukocyte infiltration caused by asthma induction in both the trachea and nasal cavity and decreased the IgA in both fecal and BALF samples. Overall, these results highlight the potential of different cocoa populations in the prevention of allergic asthma.

Alterations in the mucosal immune system by a chronic exhausting exercise in Wistar rats

Exhausting exercise can disturb immune and gastrointestinal functions. Nevertheless, the impact of it on mucosal-associated lymphoid tissue has not been studied in depth. Here, we aim to establish the effects of an intensive training and exhausting exercise on the mucosal immunity of rats and to approach the mechanisms involved. Rats were submitted to a high-intensity training consisting of running in a treadmill 5 days per week for 5 weeks, involving 2 weekly exhaustion tests. At the end, samples were obtained before (T), immediately after (TE) and 24 h after (TE24) an additional final exhaustion test. The training programme reduced the salivary production of immunoglobulin A, impaired the tight junction proteins’ gene expression and modified the mesenteric lymph node lymphocyte composition and function, increasing the ratio between Tαβ+ and B lymphocytes, reducing their proliferation capacity and enhancing their interferon-γ secretion. As a consequence of the final exhaustion test, the caecal IgA content increased, while it impaired the gut zonula occludens expression and enhanced the interleukin-2 and interferon-γ secretion. Our results indicate that intensive training for 5 weeks followed or not by an additional exhaustion disrupts the mucosal-associated lymphoid tissue and the intestinal epithelial barrier integrity in rats.

Attenuating Effect of Peruvian Cocoa Populations on the Acute Asthmatic Response in Brown Norway Rats

Cocoa contains bioactive components, which vary according to genetic and environmental factors. The present study aimed to ascertain the anti-allergic properties of native Peruvian cocoa populations ("Blanco de Piura" or BPC, "Amazonas Peru" or APC, "Criollo de Montaña" or CMC, "Chuncho" or CCC, and an ordinary cocoa or OC). To do so, after an initial in vitro approach, an in vivo study focused on the induction of an anaphylactic response associated with allergic asthma in Brown Norway rats was carried out. Based on their polyphenol content, antioxidant activity and in vitro effects, the APC and CMC were selected to be included in the in vivo study. Cocoa diets were tested in a model of allergic asthma in which anaphylactic response was assessed by changes in body temperature, motor activity and body weight. The concentration of specific immunoglobulin E (IgE), mast cell protease and leukotrienes was also quantified in serum and/or bronchoalveolar lavage fluid. CMC and OC populations exhibited a protective effect on the allergic asthma rat model as evidenced by means of a partial protection against anaphylactic response and, above all, in the synthesis of IgE and the release of mast cell protease.

Influence of Hesperidin on Systemic Immunity of Rats Following an Intensive Training and Exhausting Exercise

Intensive training and exhausting exercise can disrupt innate and acquired immunity. The flavanone hesperidin has shown immunomodulatory properties in physiological and some pathological conditions, and positive effects on exercise-induced oxidative stress. Nevertheless, it remains uncertain whether it also prevents exhausting exercise-induced immune alterations. The aim of this study was to establish the effect of oral hesperidin supplementation on the systemic immune system in rats following an intensive training and exhausting exercise. For this purpose, female Wistar rats were randomized into an intensive training group or a sedentary group. Intensive training was induced by running in a treadmill 5 days per week (including two exhausting tests) for five weeks. Throughout the training period, 200 mg/kg of hesperidin or vehicle was administered by oral gavage three times per week. At the end, blood, thymus, spleen and macrophages were collected before, immediately after and 24 h after an additional final exhaustion test. Hesperidin supplementation enhanced natural killer cell cytotoxicity and the proportion of phagocytic monocytes, attenuated the secretion of cytokines by stimulated macrophages, prevented the leukocytosis induced by exhaustion and increased the proportion of T helper cells in the thymus, blood and spleen. These results suggest that hesperidin can prevent exhausting exercise-induced immune alterations.

The gut microbiota, environmental factors, and links to the development of food allergy

Food allergy appears to have its roots in an insufficient exposure to a diverse range of environmental microbiota during early life. Microbial exposure ensures the colonization of the gastrointestinal tract with commensal microbes, which is necessary for the induction of a balanced and tolerogenic immune function. High-throughput sequencing technology has facilitated in-depth studies of the gut microbiota as well as bacterial-derived metabolites. Although the role of the microbiota in allergies is now widely studied, its importance for food allergy was only recently noted. Studies in human cohorts have shown that there is an association of dysbiosis and pathogenesis of food allergy, while studies from animal models have demonstrated the capacity of specific species in the gut microbiota to alter immune response, which may lead to the desensitization of food allergy. This article reviews the role of the gut microbiota in food allergy, and discusses the influence of environmental factors as well as prevention and management strategies relating to such regulatory mechanism.

Alterations in the innate immune system due to exhausting exercise in intensively trained rats

It is known that intensive physical activity alters the immune system's functionality. However, the influence of the intensity and duration of exercise needs to be studied in more depth. We aimed to establish the changes in the innate immune response induced by two programmes of intensive training in rats compared to sedentary rats. A short training programme included 2 weeks of intensive training, ending with an exhaustion test (short training with exhaustion, S-TE). A second training programme comprised 5-week training including two exhaustion tests and three trainings per week. In this case, immune status was assessed before (T), immediately after (TE) and 24 h after (TE24) an additional final exhaustion test. Biomarkers such as phagocytic activity, macrophage cytokine and reactive oxygen species (ROS) production, and natural killer (NK) cell activity were quantified. S-TE was not enough to induce changes in the assessed innate immunity biomarkers. However, the second training was accompanied by a decrease in the phagocytic activity, changes in the pattern of cytokine secretion and ROS production by macrophages and reduced NK cell proportion but increased NK cytotoxic activity. In conclusion, a 5-week intense training programme, but not a shorter training, induced alterations in the innate immune system functionality.

Changes in Lymphocyte Composition and Functionality After Intensive Training and Exhausting Exercise in Rats

Exhausting exercise can have a deleterious effect on the immune system. Nevertheless, the impact of exercise intensity on lymphocyte composition and functionality remains uncertain. The aim of this study was to establish the influence of intensive training on lymphoid tissues (blood, thymus, and spleen) in Wistar rats. Two intensive training programs were performed: a short program, running twice a day for 2 weeks and ending with a final exhaustion test (S-TE group), and a longer program, including two exhaustion tests plus three runs per week for 5 weeks. After this last training program, samples were obtained 24 h after a regular training session (T group), immediately after an additional exhaustion test (TE group) and 24 h later (TE24 group). The composition of lymphocytes in the blood, thymus, and spleen, the function of spleen cells and serum immunoglobulins were determined. In the blood, only the TE group modified lymphocyte proportions. Mature thymocytes' proportions decreased in tissues obtained just after exhaustion. There was a lower percentage of spleen NK and NKT cells after the longer training program. In these rats, the T group showed a reduced lymphoproliferative activity, but it was enhanced immediately after the final exhaustion. Cytokine secretion was modified after the longer training (T group), which decreased IFN-γ and IL-10 secretion but increased that of IL-6. Higher serum IgG concentrations after the longer training program were detected. In conclusion, the intensive training for 5 weeks changed the lymphocyte distribution among primary and secondary lymphoid tissues and modified their function.

Role of Theobromine in Cocoa's Metabolic Properties in Healthy Rats

Cocoa is rich in polyphenols and methylxanthines, and it has been reported that its consumption, among other properties, has beneficial effects on metabolism. This study aimed to investigate the role of theobromine in cocoa's metabolic properties in healthy rats. In addition to morphometric measurements, biochemical markers of lipids and glucose metabolism and gene expression of molecules related to immune cells in adipose and hepatic tissues were assessed after 7 or 18 days of diet. Additionally, a metabolomic analysis was carried out at day 7. This study revealed the presence of six discriminant metabolites in plasma due to the diets. Moreover, the results showed that theobromine is the main responsible factor for cocoa's effects on body weight gain as well as on lipid and glucose metabolism. The effects on body weight and lipids appeared as early as after 7 days of diet, whereas those affecting glucose metabolism required a longer intervention.

Leptin and adiponectin supplementation modifies mesenteric lymph node lymphocyte composition and functionality in suckling rats

At birth, when immune responses are insufficient, there begins the development of the defence capability against pathogens. Leptin and adiponectin, adipokines that are present in breast milk, have been shown to play a role in the regulation of immune responses. We report here, for the first time, the influence of in vivo adipokine supplementation on the intestinal immune system in early life. Suckling Wistar rats were daily supplemented with leptin (0·7 μg/kg per d, n 36) or adiponectin (35 μg/kg per d, n 36) during the suckling period. The lymphocyte composition, proliferation and cytokine secretion from mesenteric lymph node lymphocytes (on days 14 and 21), as well as intestinal IgA and IgM concentration (day 21), were evaluated. At day 14, leptin supplementation significantly increased the TCRαβ + cell proportion in mesenteric lymph nodes, in particular owing to an increase in the TCRαβ + CD8+ cell population. Moreover, the leptin or adiponectin supplementation promoted the early development CD8+ cells, with adiponectin being the only adipokine capable of enhancing the lymphoproliferative ability at the end of the suckling period. Although leptin decreased intestinal IgA concentration, it had a trophic effect on the intestine in early life. Supplementation of both adipokines modulated the cytokine profile during (day 14) and at the end (day 21) of the suckling period. These results suggest that leptin and adiponectin during suckling play a role in the development of mucosal immunity in early life.

Enhancement of immune maturation in suckling rats by leptin and adiponectin supplementation

Leptin and adiponectin, adipokines present in breast milk, have shown immunomodulatory properties. The current study aimed to ascertain whether a nutritional supplementation with leptin or adiponectin in neonatal rats was able to influence the maturation of the systemic immune response in early life. To achieve this, suckling Wistar rats were supplemented with either leptin (0.7 μg/kg/day) or adiponectin (35 μg/kg/day) during the whole suckling period. Plasmatic immunoglobulins were quantified, and spleen lymphocyte composition and their ability to proliferate and release cytokines were evaluated during (day 14) and at the end (day 21) of the suckling period. Rats fed with either adipokine showed higher plasma IgM and IgG1 concentrations and adiponectin supplementation also increased IgG2a at both studied days (P < 0.05). With regard to the lymphocyte composition, both adipokine supplementations increased T cell proportion and both CD4⁺ and CD8⁺ T cell subsets after two weeks of supplementation (P < 0.05). Moreover, only leptin administration increased NK and NKT cell proportions at the end of the suckling period. Finally, both adipokines influenced the cytokine secretion pattern by splenocytes. In conclusion, these results suggest that leptin and adiponectin play a role in the maturation of the systemic immune response during the suckling period.

Hesperidin Effects on Gut Microbiota and Gut-Associated Lymphoid Tissue in Healthy Rats

Hesperidin, found in citrus fruits, has shown a wide range of biological properties. Nonetheless, a more in-depth investigation is required on the effects on the immune system, and in particular, on the gut-associated lymphoid tissue, together with its relationship with the gut microbiota. Therefore, we aimed to establish the influence of oral hesperidin administration on the intestinal lymphoid tissue and on the gut microbiota composition in healthy animals. Lewis rats were orally administrated 100 or 200 mg/kg hesperidin three times per week for four weeks. Microbiota composition and IgA-coated bacteria were determined in caecal content. Mesenteric lymph node lymphocyte (MLNL) composition and functionality were assessed. IgA, cytokines, and gene expression in the small intestine were quantified. Hesperidin administration resulted in a higher number of bacteria and IgA-coated bacteria, with changes in microbiota composition such as higher Lactobacillus proportion. Hesperidin was also able to increase the small intestine IgA content. These changes in the small intestine were accompanied by a decrease in interferon-γ and monocyte chemotactic protein-1 concentration. In addition, hesperidin increased the relative proportion of TCRαβ+ lymphocytes in MLNL. These results show the immunomodulatory actions of hesperidin on the gut-associated lymphoid tissue and reinforce its role as a prebiotic.

Theobromine Is Responsible for the Effects of Cocoa on the Antibody Immune Status of Rats

Background

A 10% cocoa-enriched diet influences immune system functionality including the prevention of the antibody response and the induction of lower immunoglobulin (Ig) concentrations. However, neither cocoa polyphenols nor cocoa fiber can totally explain these immunoregulatory properties.

Objectives

This study aimed to establish the influence of cocoa theobromine in systemic and intestinal Ig concentrations and to determine the effect of cocoa or theobromine feeding on lymphoid tissue lymphocyte composition.

Methods

Three-week-old female Lewis rats were fed either a standard diet (AIN-93M; RF group), a 10% cocoa diet (CC group), or a 0.25% theobromine diet (the same amount provided by the cocoa diet; TB group) in 2 separate experiments that lasted 19 (experiment 1) or 8 (experiment 2) d. Serum IgG, IgM, IgA, and intestinal secretory IgA (sIgA) concentrations were determined. In addition, at the end of experiment 2, thymus, mesenteric lymph node (MLN), and spleen lymphocyte populations were analyzed.

Results

Both CC and TB groups in experiments 1 and 2 showed similar serum IgG, IgM, and IgA and intestinal sIgA concentrations, which were lower than those in the RF group (46-98% lower in experiment 1 and 23-91% lower in experiment 2; P < 0.05). In addition, in experiment 2, the cocoa and theobromine diets similarly changed the thymocyte composition by increasing CD4-CD8- (+133%) and CD4+CD8- (+53%) proportions (P < 0.01), changed the MLN composition by decreasing the percentage of T-helper (Th) lymphocytes (-3%) (P = 0.015), and changed the spleen composition by increasing the proportion of Th lymphocytes (+9%) (P < 0.001) after 1 wk of diet treatment.

Conclusions

The theobromine in cocoa plays an immunoregulatory role that is responsible for cocoa's influence on both systemic and intestinal antibody concentrations and also for modifying lymphoid tissue lymphocyte composition in young healthy Lewis rats. The majority of these changes are observed after a single week of being fed a diet containing 0.25% theobromine.

Cocoa Diet and Antibody Immune Response in Preclinical Studies

The ability of cocoa to interact with the immune system in vitro and in vivo has been described. In the latter context, a cocoa-enriched diet in healthy rats was able to modify the immune system's functionality. This fact could be observed in the composition and functionality of lymphoid tissues, such as the thymus, spleen, and lymph nodes. Consequently, immune effector mechanisms, such as antibody synthesis, were modified. A cocoa-enriched diet in young rats was able to attenuate the serum levels of immunoglobulin (Ig) G, IgM, and IgA and also the intestinal IgM and IgA secretion. Moreover, in immunized rats, the intake of cocoa decreased specific IgG1, IgG2a, IgG2c, and IgM concentrations in serum. This immune-regulator potential was then tested in disease models in which antibodies play a pathogenic role. A cocoa-enriched diet was able to partially prevent the synthesis of autoantibodies in a model of autoimmune arthritis in rats and was also able to protect against IgE and T helper 2-related antibody synthesis in two rat models of allergy. Likewise, a cocoa-enriched diet prevented an oral sensitization process in young rats. In this review, we will focus on the influence of cocoa on the acquired branch of the immune function. Therefore, we will focus on how a cocoa diet influences lymphocyte function both in the systemic and intestinal immune system. Likewise, its potential role in preventing some antibody-induced immune diseases is also included. Although further studies must characterize the particular cocoa components responsible for such effects and nutritional studies in humans need to be carried out, cocoa has potential as a nutraceutical agent in some hypersensitivity status.

Influence of Hesperidin on the Systemic and Intestinal Rat Immune Response

Polyphenols, widely found in edible plants, influence the immune system. Nevertheless, the immunomodulatory properties of hesperidin, the predominant flavanone in oranges, have not been deeply studied. To establish the effect of hesperidin on in vivo immune response, two different conditions of immune system stimulations in Lewis rats were applied. In the first experimental design, rats were intraperitoneally immunized with ovalbumin (OVA) plus Bordetella pertussis toxin and alum as the adjuvants, and orally given 100 or 200 mg/kg hesperidin. In the second experimental design, rats were orally sensitized with OVA together with cholera toxin and fed a diet containing 0.5% hesperidin. In the first approach, hesperidin administration changed mesenteric lymph node lymphocyte (MLNL) composition, increasing the TCRαβ+ cell percentage and decreasing that of B lymphocytes. Furthermore, hesperidin enhanced the interferon (IFN)-γ production in stimulated MLNL. In the second approach, hesperidin intake modified the lymphocyte composition in the intestinal epithelium (TCRγδ+ cells) and the lamina propria (TCRγδ+, CD45RA+, natural killer, natural killer T, TCRαβ+CD4+, and TCRαβ+CD8+ cells). Nevertheless, hesperidin did not modify the level of serum anti-OVA antibodies in either study. In conclusion, hesperidin does possess immunoregulatory properties in the intestinal immune response, but this effect is not able to influence the synthesis of specific antibodies.

Gut Microbiota in a Rat Oral Sensitization Model: Effect of a Cocoa-Enriched Diet

Increasing evidence is emerging suggesting a relation between dietary compounds, microbiota, and the susceptibility to allergic diseases, particularly food allergy. Cocoa, a source of antioxidant polyphenols, has shown effects on gut microbiota and the ability to promote tolerance in an oral sensitization model. Taking these facts into consideration, the aim of the present study was to establish the influence of an oral sensitization model, both alone and together with a cocoa-enriched diet, on gut microbiota. Lewis rats were orally sensitized and fed with either a standard or 10% cocoa diet. Faecal microbiota was analysed through metagenomics study. Intestinal IgA concentration was also determined. Oral sensitization produced few changes in intestinal microbiota, but in those rats fed a cocoa diet significant modifications appeared. Decreased bacteria from the Firmicutes and Proteobacteria phyla and a higher percentage of bacteria belonging to the Tenericutes and Cyanobacteria phyla were observed. In conclusion, a cocoa diet is able to modify the microbiota bacterial pattern in orally sensitized animals. As cocoa inhibits the synthesis of specific antibodies and also intestinal IgA, those changes in microbiota pattern, particularly those of the Proteobacteria phylum, might be partially responsible for the tolerogenic effect of cocoa.

Effect of a cocoa diet on the small intestine and gut-associated lymphoid tissue composition in an oral sensitization model in rats

Previous studies have attributed to the cocoa powder the capacity to attenuate the immune response in a rat oral sensitization model. To gain a better understanding of cocoa-induced mechanisms at small intestinal level, 3-week-old female Lewis rats were fed either a standard diet or a diet containing 10% cocoa for 4 weeks with or without concomitant oral sensitization with ovalbumin (OVA). Thereafter, we evaluated the lymphocyte composition of the Peyer's patches (PPL), small intestine epithelium (IEL) and lamina propria (LPL). Likewise, gene expression of several immune molecules was quantified in the small intestine. Moreover, histological samples were used to evaluate the proportion of goblet cells, IgA+ cells and granzyme+cells as well. In cocoa-fed animals, we identified a five-time reduction in the percentage of IgA+ cells in intestinal tissue together with a decreased proportion of TLR4+ IEL. Analyzing the lymphocyte composition, almost a double proportion of TCRγδ+cells and an increase of NK cell percentage in PPL and IEL were found. In addition, a rise in CD25+, CD103+ and CD62L- cell proportions was observed in CD4+ PPL from cocoa-fed animals, along with a decrease in gene expression of CD11b, CD11c and IL-10. These results suggest that changes in PPL and IEL composition and in the gene expression induced by the cocoa diet could be involved, among other mechanisms, on its tolerogenic effect.