Zinc deficiency suppresses the development of oral tolerance in rats

Nutrition in chronic inflammatory conditions: Bypassing the mucosal block for micronutrients

Nutritional Immunity is one of the most ancient innate immune responses, during which the body can restrict nutrients availability to pathogens and restricts their uptake by the gut mucosa (mucosal block). Though this can be a beneficial strategy during infection, it also is associated with non-communicable diseases-where the pathogen is missing; leading to increased morbidity and mortality as micronutritional uptake and distribution in the body is hindered. Here, we discuss the acute immune response in respect to nutrients, the opposing nutritional demands of regulatory and inflammatory cells and particularly focus on some nutrients linked with inflammation such as iron, vitamins A, Bs, C, and other antioxidants. We propose that while the absorption of certain micronutrients is hindered during inflammation, the dietary lymph path remains available. As such, several clinical trials investigated the role of the lymphatic system during protein absorption, following a ketogenic diet and an increased intake of antioxidants, vitamins, and minerals, in reducing inflammation and ameliorating disease.

Lack of iron, zinc, and vitamins as a contributor to the etiology of atopic diseases

Micronutritional deficiencies are common in atopic children suffering from atopic dermatitis, food allergy, rhinitis, and asthma. A lack of iron, in particular, may impact immune activation with prolonged deficiencies of iron, zinc, vitamin A, and vitamin D associated with a Th2 signature, maturation of macrophages and dendritic cells (DCs), and the generation of IgE antibodies. In contrast, the sufficiency of these micronutrients establishes immune resilience, promotion of regulatory cells, and tolerance induction. As micronutritional deficiencies mimic an infection, the body's innate response is to limit access to these nutrients and also impede their dietary uptake. Here, we summarize our current understanding of the physiological function of iron, zinc, and vitamins A and D in relation to immune cells and the clinical consequences of deficiencies in these important nutrients, especially in the perinatal period. Improved dietary uptake of iron is achieved by vitamin C, vitamin A, and whey compounds, whereas zinc bioavailability improves through citrates and proteins. The addition of oil is essential for the dietary uptake of beta-carotene and vitamin D. As for vitamin D, the major source comes via sun exposure and only a small amount is consumed via diet, which should be factored into clinical nutritional studies. We summarize the prevalence of micronutritional deficiencies of iron, zinc, and vitamins in the pediatric population as well as nutritional intervention studies on atopic diseases with whole food, food components, and micronutrients. Dietary uptake via the lymphatic route seems promising and is associated with a lower atopy risk and symptom amelioration. This review provides useful information for clinical studies and concludes/emphasizes that a healthy, varied diet containing dairy products, fish, nuts, fruits, and vegetables as well as supplementing foods or supplementation with micronutrients as needed is essential to combat the atopic march.

Study of Serum Zinc and Copper Levels and Tumor Pathology: A Pilot Study in People Affected with Head and Neck Cancers

This study aimed to determine understanding the role of serum copper, zinc and copper/zinc ratio with tumor staging in people newly diagnosed to be affected with Head and Neck cancer and by comparing with age matched health individuals devoid of any orodental maladies. The study included patients confirmed to be affected with HN cancer with histological diagnosis of Head and Neck cancer (60) and age matched healthy volunteers (N = 23). The demographic details like age, domicile, menopausal status and pathological details (like tumor stage, number of lymph node involvement, tumor size) were collected from the patient's hospital data file. The serum levels of zinc and copper assayed as per standard procedures and the zinc/copper was calculated for the cancer patients and controls. The data were subjected to unpaired "t" test and ANOVA with Bonferroni's multiple comparisons. The association between zinc and copper levels with pathological details between the variables was ascertained using the Pearson correlation coefficient(r). A statistical value of p < 0.05 was considered to be significant in agreeance to the accepted norms. Results: This result of the study indicates that when compared to the healthy individuals, the serum levels of copper, and zinc, and copper/zinc ratio were high in patients with H&N cancer. Also when compared with controls, the levels of zinc decreased, while that of copper and copper/zinc ratio increased in people affected with H&N cancer (p = 0.017 to 0.0001) and with the stage of the tumor (p = 0.03 to 0.001). The results of the study suggest that levels of serum zinc were significantly lower and that of copper higher in H&N cancer patients than that in controls and also that it was dependent on the tumor stage. When analyzed cumulatively the results hint that zinc and copper, due to their role in free radical generation and prevention have an important role in cancer progression and possible prevention by judicious intervention.

Zinc deficiency as a possible risk factor for increased susceptibility and severe progression of Corona Virus Disease 19

The importance of Zn for human health becomes obvious during Zn deficiency. Even mild insufficiencies of Zn cause alterations in haematopoiesis and immune functions, resulting in a proinflammatory phenotype and a disturbed redox metabolism. Although immune system malfunction has the most obvious effect, the functions of several tissue cell types are disturbed if Zn supply is limiting. Adhesion molecules and tight junction proteins decrease, while cell death increases, generating barrier dysfunction and possibly organ failure. Taken together, Zn deficiency both weakens the resistance of the human body towards pathogens and at the same time increases the danger of an overactive immune response that may cause tissue damage. The case numbers of Corona Virus Disease 19 (COVID-19) are still increasing, which is causing enormous problems for health systems and economies. There is an urgent need to reduce both the number of severe cases and the resulting deaths. While therapeutic options are still under investigation, and first vaccines have been approved, cost-effective ways to reduce the likelihood of or even prevent infection, and the transition from mild symptoms to more serious detrimental disease, are highly desirable. Nutritional supplementation might be an effective option to achieve these aims. In this review, we discuss known Zn deficiency effects in the context of an infection with Severe Acute Respiratory Syndrome-Coronavirus-2 and its currently known pathogenic mechanisms and elaborate on how severe pre-existing Zn deficiency may pre-dispose patients to a severe progression of COVID-19. First published clinical data on the association of Zn homoeostasis with COVID-19 and registered studies in progress are listed.

Zinc intake and risk of Crohn’s disease and ulcerative colitis: a prospective cohort study

BACKGROUND

Diet plays a role in the pathogenesis of Crohn’s disease (CD) and ulcerative colitis (UC). Dietary zinc may influence risk of disease through effects on autophagy, innate and adaptive immune response and maintenance of the intestinal barrier.

METHODS

We analysed data from 170 776 women from the Nurses Health Study I and Nurses Health Study II, who were followed for 26 years. Zinc intake was assessed using semi-quantitative food frequency questionnaires administered every 4 years. Incident CD and UC were ascertained by medical record review. Cox proportional hazards models adjusting for potential confounders determined the independent association between zinc intake and incident disease.

RESULTS

Over 3 317 550 person-years (p-y) of follow-up, we identified 269 incident cases of CD and 338 incident cases of UC. Zinc intake ranged from 9 mg/day in the lowest quintile to 27 mg/day in the highest quintile. Compared with women with the lowest quintile of intake, the multivariate hazard ratios (HR) for CD were 0.92 [95% confidence interval (CI), 0.65 – 1.29) for women in the second quintile of intake, 0.60 (95% CI, 0.40 – 0.89) for the third quintile, 0.57 (95% CI, 0.38 – 0.86) for fourth quintile and 0.74 (95% CI, 0.50 – 1.10) for the highest quintile (Ptrend = 0.003). The association was stronger for dietary zinc (HR 0.63, 95% CI, 0.43 – 0.93, comparing extreme quintiles) than for zinc intake from supplements. Neither dietary nor supplemental zinc modified risk of UC.

CONCLUSIONS

In two large prospective cohorts of women, intake of zinc was inversely associated with risk of CD but not UC.

Lactobacillus rhamnosus GG and Bifidobacterium animalis MB5 induce intestinal but not systemic antigen-specific hyporesponsiveness in ovalbumin-immunized rats

Probiotics may modulate the host immune response by mechanisms not yet fully understood. We evaluated the modulation of intestinal and systemic antigen-specific immune response by Lactobacillus rhamnosus GG (LGG) or Bifidobacterium animalis MB5 in tolerized and immunized rats. Three groups of rats received orally LGG, B. animalis, or PBS (control) for 28 d. Each group was divided into two subgroups of tolerized or immunized rats receiving orally ovalbumin (OVA; 7 mg) or PBS on d 7, 9, and 11. All rats were immunized with OVA (300 μg) on d 14 and 21. In tolerized rats, the OVA-induced proliferative response of mesenteric lymph nodes (MLN) and spleen cells did not differ from control, indicating that the two probiotics maintained the tolerance. LGG and B. animalis in immunized rats reduced the OVA-induced proliferative response in MLN (P < 0.01) but not in spleen, whereas the proliferative response to anti-CD3 and concanavalin A of MLN and spleen cells as well as the delayed-type hypersensitivity reaction were not affected by probiotic treatment, indicating OVA-specific hyporesponsiveness restricted to intestinal immunity. This hyporesponsiveness was associated with CD4+CD25+Foxp3+ T cell expansion (P < 0.01) and increased IL-10 and TGFβ after LGG (P < 0.05), and increased apoptosis after B. animalis (P < 0.001) in MLN. In conclusion, we report a novel activity of LGG and B. animalis in inducing OVA-specific hyporesponsiveness in MLN of OVA-immunized rats that can be useful for a therapeutic strategy to prevent undesirable reactions to immunogenic antigens in the gut.

Zinc and its role in age-related inflammation and immune dysfunction

Zinc is an essential micronutrient required for many cellular processes, especially for the normal development and function of the immune system. Zinc homeostasis and signaling are critical in immune activation, and an imbalance in zinc homeostasis is associated with the development of chronic diseases. Zinc deficiency causes significant impairment in both adaptive and innate immune responses, and promotes systemic inflammation. The elderly are a population particularly susceptible to zinc deficiency. National surveys indicate that a significant portion of the aged population has inadequate zinc intake, and a decline in zinc status is observed with age. There are remarkable similarities between the hallmarks of zinc deficiency and immunological dysfunction in aged individuals. Both zinc deficiency and the aging process are characterized by impaired immune responses and systemic low grade chronic inflammation. It has been hypothesized that age-related zinc deficiency may be an important factor contributing to immune dysfunction and chronic inflammation during the aging process. In this review, we discuss the effects of zinc status on aging, potential molecular and epigenetic mechanisms contributing to age-related decline in zinc status, and the role of zinc in age-related immune dysfunction and chronic inflammation.

Aminoguanidine administered during the induction of oral tolerance alters the systemic response of the tolerised rats

Herewith we investigated the role of nitric oxide synthase (NOS)-II in the establishment of oral tolerance induced by low antigen dose. To accomplish this, we used a rat model of oral tolerance induced by intragastric administration of low doses of ovalbumin (OVA). NOS-II was inhibited in vivo during the onset of tolerance by intraperitoneal (i.p.) treatment with aminoguanidine (AMG), a selective NOS-II inhibitor. Four experimental groups were generated: (TOL), tolerised rats, receiving OVA but no AMG; (TAG), rats tolerised with OVA and simultaneously receiving AMG i.p.; (CAG), controls treated with AMG but no oral antigen; and (CONT), controls receiving neither OVA nor AMG treatment. The state of oral tolerance was evaluated in all groups by analysing several immune parameters upon subcutaneous administration of OVA in Freund's complete adjuvant. First, we were able to determine that NOS-II inhibition altered the TH1/TH2 balance in tolerised rats, driving the TH2 anti-OVA response in TOL rats towards TH1 in TAG animals, which showed enhanced delayed hypersensitivity responses. Second, splenocyte cultures from TAG rats showed lower levels of IL-10 production compared to TOL samples as determined by ELISA analysis. Last, we detected the presence of a functional distinct Tr1 regulatory T cell population in spleen samples recovered from TAG animals. Contrary to what happened with TOL Tr1 cells, the levels of Tr1 cells in TAG samples were modified by in vitro stimulation with OVA. All together, these data indicate a preponderant role for NOS-II in the process of oral tolerance induced by low antigen dose.

The ubiquitous role of zinc in health and disease

OBJECTIVE

To review zinc physiology and pathophysiology and the importance of zinc toxicity and deficiency in veterinary patients.

DATA SOURCES

A review of human and veterinary medical literature.

HUMAN DATA SYNTHESIS

There is a significant amount of original research in humans and animals on the role of zinc in multiple organ systems. There is also significant data available on human patients with zinc abnormalities.

VETERINARY DATA SYNTHESIS

Zinc deficiency has been studied in dogs with genetic disease and dietary deficiency leading to dermatological disease and immune deficiency. Zinc toxicity has been described after ingestion of metallic foreign bodies containing zinc.

CONCLUSIONS

Historically, the role of zinc in health and disease has been studied through patients with toxicity or severe deficiency with obvious clinical signs. As the ubiquitous contribution of zinc to structure and function in biological systems was discovered, clinically significant but subtle deficiency states have been revealed. In human medicine, mild zinc deficiencies are currently thought to cause chronic metabolic derangement leading to or exacerbating immune deficiency, gastrointestinal problems, endocrine disorders, neurologic dysfunction, cancer, accelerated aging, degenerative disease, and more. Determining the causal relationships between mild zinc deficiency and concurrent disease is complicated by the lack of sensitive or specific tests for zinc deficiency. The prevalence of zinc deficiency and its contribution to disease in veterinary patients is not well known. Continued research is warranted to develop more sensitive and specific tests to assess zinc status, to determine which patients are at risk for deficiency, and to optimize supplementation in health and disease.

(Xeno)estrogen regulation of food allergy

Food allergy and other types of allergies are becoming epidemic in both the developed and developing countries. A large amount of information is available in literature that (xeno)estrogens can regulate the immune response in general, and the development of allergy in particular; however, the effect of (xeno)estrogens on food allergy is basically unknown. With increasing use of xenobiotics worldwide, chemicals with estrogenic activity have been accumulating in our environment. This review has summarized the current literature relating to the topic (xeno)estrogen regulation of food allergy. The effect of (xeno)estrogens on enterocytes, proteases for protein hydrolysis, dendritic cells and T-regulatory cells in the gastrointestinal tract has been discussed. Finally, considering the current confusion in literature regarding the effect of phytoestrogen genistein on the immune system, a brief discussion has been included for its effect on T(H)1-T(H)2 polarization, and possibly food allergy in its relation to windows of exposure. Sufficient evidences exist to support the notion that (xeno)estrogens can regulate food allergy, with the developmental periods more sensitive. Further clinical and animal studies are needed to determine the causal relationship between the exposure of (xeno)estrogens and incidence of food allergy, and the underlying mechanisms.

Zinc, copper, and magnesium and risks for all-cause, cancer, and cardiovascular mortality

BACKGROUND

Experimental data suggest that zinc, copper, and magnesium are involved in carcinogenesis and atherogenesis. Few longitudinal studies have related these minerals to cancer or cardiovascular disease mortality in a population.

METHODS

Data from the Paris Prospective Study 2, a cohort of 4035 men age 30-60 years at baseline, were used to assess the association between serum zinc, copper, and magnesium and all-cause, cancer, and cardiovascular disease mortality. Serum mineral values measured at baseline were divided into quartiles and classified into low (1st quartile, referent group), medium (2nd-3rd quartiles), and high (4th quartile) values. During 18-year follow up, 339 deaths occurred, 176 as a result of cancer and 56 of cardiovascular origin. Relative risks (RRs) for each element were inferred using Cox's proportional hazard model after controlling for various potential confounders.

RESULTS

High copper values (4th quartile) were associated with a 50% increase in RRs for all-cause deaths (RR = 1.5; 95% confidence interval = 1.1-2.1), a 40% increase for cancer mortality (1.4; 0.9-2.2), and a 30% increase for cardiovascular mortality (1.3; 0.6-2.8) compared with low values (1st quartile). High magnesium values were negatively related to mortality with a 40% decrease in RR for all-cause (0.6; 0.4-0.8) and cardiovascular deaths (0.6; 0.2-1.2) and by 50% for cancer deaths (0.5; 0.3-0.8). Additionally, subjects with a combination of low zinc and high copper values had synergistically increased all-cause (2.6; 1.4-5.0) and cancer (2.7; 1.0-7.3) mortality risks. Similarly, combined low zinc and high magnesium values were associated with decreased all-cause (0.2; 0.1-0.5) and cancer (0.2; 0.1-0.8) mortality risks.

CONCLUSIONS

High serum copper, low serum magnesium, and concomitance of low serum zinc with high serum copper or low serum magnesium contribute to an increased mortality risk in middle-aged men.

Probiotic bacteria Bifidobacterium animalis MB5 and Lactobacillus rhamnosus GG protect intestinal Caco-2 cells from the inflammation-associated response induced by enterotoxigenic Escherichia coli K88

Probiotic bacteria may provide protection against intestinal damage induced by pathogens, but the underlying mechanisms are still largely unknown. We investigated whether Bifidobacterium animalis MB5 and Lactobacillus rhamnosus GG (LGG) protected intestinal Caco-2 cells from the inflammation-associated response induced by enterotoxigenic Escherichia coli (ETEC) K88, by inhibiting pathogen attachment to the cells, which is the first step of ETEC pathogenicity, and regulating neutrophil recruitment, a crucial component of inflammation. A partial reduction of ETEC adhesion was exerted by probiotics and their culture supernatant fractions either undigested or digested with proteases. ETEC viability was unaffected by the presence of B. animalis, LGG or their supernatant fractions in the culture medium, indicating an absence of probiotic bactericidal activity. Probiotics and their supernatant fractions, either undigested or digested with proteases, strongly inhibited the neutrophil transmigration caused by ETEC. Both B. animalis and LGG counteracted the pathogen-induced up regulation of IL-8, growth-related oncogene-alpha and epithelial neutrophil-activating peptide-78 gene expression, which are chemokines essential for neutrophil migration. Moreover, the probiotics prevented the ETEC-induced increased expression of IL-1beta and TNF-alpha and decrease of transforming growth factor-alpha, which are regulators of chemokine expression. These results indicate that B. animalis MB5 and LGG protect intestinal cells from the inflammation-associated response caused by ETEC K88 by partly reducing pathogen adhesion and by counteracting neutrophil migration, probably through the regulation of chemokine and cytokine expression.

The antibacterial effects of zinc ion migration from zinc-based glass polyalkenoate cements

Zinc-based glass polyalkenoate cements have been synthesised and their potential use in orthopaedic applications investigated. Zinc ions were released from the materials in a rapid burst over the first 24 h after synthesis, with the release rate falling below detectable levels after 7 days. Cement-implanted bone samples were prepared and the released zinc was shown, using energy dispersive X-ray analysis, to penetrate from the cement into the adjacent bone by up to 40 microm. Finally, the cements exhibited antibacterial activity against Streptococcus mutans and Actinomyces viscosus that reflected the pattern of zinc release, with the inhibition of growth greatest shortly after cement synthesis and little or no inhibition measureable after 30 days.

Oral-tolerance induction in diet-induced obese mice

OBJECTIVE

It is known that immune functions are altered in various ways by obesity. However, changes in the intestinal immune system resulting from obesity remain poorly understood. Oral tolerance is a system that suppresses antigen specific immune responses to orally administrated antigens. The intestinal immune system is intimately associated with the oral tolerance system, that acts to prevent allergic and inflammatory diseases. In this study we investigated the effect of obesity on induction of oral tolerance to ovalbumin (OVA) in an animal model of obesity.

RESEARCH METHODS AND PROCEDURES

Obese mice induced by a high fat diet and control mice were allowed free access for 3 days to a 1%-ovalbumin (OVA) solution in drinking water. After continuous feeding of the antigen, all the mice were immunized by two intraperitoneal injections of OVA administered 7 days apart.

RESULTS

In the control mice, induction of oral tolerance caused an increase in antigen specific IgG1 levels and a decrease in IgG2a levels. In contrast, the IgG1/IgG2a ratio was reversed in obese mice. OVA-specific IL-2 production was suppressed by antigen feeding in both the control and obese mice; however, suppression of OVA-specific IL-10 was observed only in the control mice. Although OVA-specific IgA and IgM were not affected by antigen feeding, the obese groups of mice had significantly lower titers of antibodies.

DISCUSSION

These findings suggest that obesity may affect induction of oral tolerance following antigen feeding and that these changes may be related to the inflammatory reaction.

Immune response in relation to zinc status, sex and antioxidant defence in Italian elderly population: the ZENITH study

OBJECTIVE

Evaluation of some immune markers in Italian elderly population in relation to zinc status, gender and antioxidant defence.

DESIGN

Observational study.

SETTING

Italian population.

SUBJECTS

Apparently healthy, free-living subjects, 56 men and 52 women, aged 70-85 y, enrolled in Italy.

METHODS

Lymphocytes were unstimulated or stimulated with the mitogen phytohemoagglutinin (PHA). The proliferative capacity was measured as incorporation of [3H]-thymidine and reported as stimulation index (SI). Cytokine secretion by lymphocytes was determined by ELISA. The antioxidant enzyme activities were measured using commercial kits.

RESULTS

Dietary zinc intake, as well as zinc in serum, red blood cells and urine were on the normal range of values and did not show any difference between men and women. The proliferative response showed a high variability without significant differences between men and women. The amount of secreted pro- and anti-inflammatory cytokines was similar in men and women. No differences were found in the activity of antioxidant enzymes in lymphocytes, namely superoxide dismutase, glutathione peroxidase and catalase, between men and women. An association between SI and serum zinc level in men was found. SI resulted negatively correlated with interleukin (IL)-1beta (R2 = 0.036 and P = 0.012) and IL-10 (R2 = 0.34 and P = 0.040) only in men. IL-10 of PHA-stimulated lymphocytes was negatively correlated with red blood zinc in men (R2 = 0.41 and P = 0.008), while IL-10 of unstimulated and PHA-stimulated lymphocytes were negatively correlated with serum zinc in women (R2 = 0.38 and P = 0.020; R2 = 0.31 and P = 0.040, respectively). No correlation was observed between immune markers and antioxidant enzyme activities.

CONCLUSIONS

Only weak differences on immune response between men and women were observed. However, zinc status appears to have more influence on the ability of lymphocytes to proliferate in men than in women.

Reprogramming of the immune system during zinc deficiency

Thymic atrophy, lymphopenia, and compromised cell- and antibody-mediated responses that cause increased rates of infections of longer duration are the immunological hallmarks of zinc deficiency (ZD) in humans and higher animals. As the deficiency advances, a reprogramming of the immune system occurs, beginning with the activation of the stress axis and chronic production of glucocorticoids that accelerate apoptosis among pre-B and -T cells. This reduces lymphopoiesis and causes atrophy of the thymus. In contrast, myelopoiesis is preserved, thereby providing protection for the first line of immune defense or innate immunity. Changes in gene expression for cytokines, DNA repair enzymes, zinc transporters, signaling molecules, etc., suggest that cells of the immune system are attempting to adapt to the stress of suboptimal zinc. Better understanding of the molecular and cellular changes made in response to inadequate zinc should lead to the development of immunotherapeutic interventions.

Immunonutrition and cancer

The immune system is the body's primary defence against invading pathogens, non-self components and cancer cells. Inflammatory processes, including the release of pro-inflammatory cytokines and formation of reactive oxygen and nitrogen species, are an essential part of these processes. Although such actions are usually followed rapidly by anti-inflammatory effects, excessive production of pro-inflammatory cytokines, or their production in the wrong biological context may lead to situations of chronic inflammation. Whether such conditions arise as a result of exogenous chemicals, invading pathogens or disease processes, the long-term implications include an increased risk of cancer. A number of nutrients have the ability to modulate immune response and counter inflammatory processes. Zinc, epigallocatechin galate (EGCG), omega-3 polyunsaturated fatty acids and probiotics all act differently to modulate immune response, but all appear to have the potential to protect against cancer development and progression. We suggest that immunonutrition may provide a less invasive alternative to immunotherapy in protection against cancers associated with chronic inflammation.

Zinc Oxide Protects Cultured Enterocytes from the Damage Induced by Escherichia coli

There is some evidence that zinc oxide (ZnO) protects against intestinal diseases. However, despite the suggestions that ZnO may have an antibacterial effect, the mechanisms of this protective effect have not yet been elucidated. We investigated the potential benefits of ZnO in protecting intestinal cells from damage induced by enterotoxigenic Escherichia coli (ETEC, strain K88) and the related mechanisms, using human Caco-2 enterocytes. Cell permeability, measured as transepithelial electrical resistance (TEER), was unaffected by 0.01 and 1 mmol/L ZnO treatments and moderately increased by 5 mmol/L ZnO, compared with untreated cells. Transfer of (14)C-inulin was slightly increased by 5 mmol/L ZnO compared with untreated cells; transfer was unaffected by lower concentrations. The TEER and (14)C-inulin transfer were lower in ETEC-infected cells than in uninfected cells. Treatment of ETEC exposure with 0.2 mmol/L ZnO prevented disruption of membrane integrity. The ETEC was able to adhere to enterocytes and, to some extent, invade the cells. The ZnO treatment reduced bacterial adhesion and blocked bacterial invasion. The ETEC infection upregulated the expression of the inflammatory cytokines interleukin-8, growth-related oncogene-alpha and tumor necrosis factor-alpha, and reduced that of the anti-inflammatory cytokine transforming growth factor-beta, compared with uninfected cells. The addition of 0.2 or 1 mmol/L ZnO counteracted the alteration of cytokine mRNA levels caused by ETEC. The protective effects of ZnO were not due to any antibacterial activity, because the viability of ETEC grown in a medium containing ZnO was unaffected. In conclusion, ZnO may protect intestinal cells from ETEC infection by inhibiting the adhesion and internalization of bacteria, preventing the increase of tight junction permeability and modulating cytokine gene expression.