Immunostimulatory effect of faecal Bifidobacterium species of breast-fed and formula-fed infants in a peripheral blood mononuclear cell/Caco-2 co-culture system.

Bifidobacterium spp. typical of the human intestinal microbiota are believed to influence the balance of immune responses in the intestinal mucosa. The aim of the present study was to investigate the effect of different bifidobacterial species and their mixtures in in vitro experiments with peripheral blood mononuclear cells (PBMC) and Caco-2 cells. Bifidobacterium adolescentis, B. angulatum, B. breve, B. catenulatum, B. infantis, B. longum and two combinations of these bifidobacteria simulating the species composition found in faecal samples from breast-fed (BF) and formula-fed (FF) infants were used. The levels of several cytokines were measured by direct stimulation of PBMC and by stimulation of a Caco-2/PBMC co-culture with bifidobacteria. B. catenulatum and B. breve were the strongest enhancers of interferon-γ (IFN-γ) production by direct stimulation of PBMC. B. longum was the highest inducer of IL-10 and the lowest TNF-α stimulus. In the Caco-2/PBMC system, B. breve was the highest inducer of IL-8 production by Caco-2 cells, significantly different from B. infantis, B. adolescentis and the FF mixture (P < 0·05). IFN-γ produced by PBMC stimulated with the BF mixture (containing 22 % B. breve, compared with 7 % in the FF mixture) was significantly higher compared with B. adolescentis, B. infantis and B. longum. B. adolescentis also inhibited IFN-γ production compared with the FF mixture and B. longum. The proportion of different Bifidobacterium strains seems to be an important determinant of the cytokine balance in the simulated intestinal environment studied. B. breve and the combination of the Bifidobacterium species typically found in the microbiota of BF infants have shown the most significant effects.

[Olive oil, immune system and infection]. / Aceite de oliva, sistema inmune e infección.

Polyunsaturated fatty acids contribute to the suppression of immune system functions. For this reason, n-3 polyunsaturated fatty acids have been applied in the resolution of inflammatory disorders. Although the inhibition of several immune functions promotes beneficial effects on the human health, this state may lead to a significant reduction of immune protection against infectious microorganisms (viruses, bacteria, fungi and parasites). Nevertheless, less attention has been paid to the action of olive oil in immunonutrition. Olive oil, a main constituent of the Mediterranean diet, is capable of modulating several immune functions, but it does not reduce host immune resistance to infectious microorganisms. Based on these criteria, we corroborate that olive oil administration may exert beneficial effects on the human health and especially on immune system, because it contributes to the reduction of typical inflammatory activity observed in patients suffering from autoimmune disorders, but without exacerbating the susceptibility to pathogen agents. The administration of olive oil in lipid emulsions may exert beneficial effects on the health and particularly on the immune system of immunocompromised patients. Therefore, this fact acquires a crucial importance in clinical nutrition. This review contributes to clarify the interaction between the administration of diets containing olive oil and immune system, as well as to determine the effect promoted by this essential component of Mediterranean diet in the immunomodulation against an infectious agent.

Effects of concentrated supernatants recovered from Lactobacillus plantarum on Escherichia coli growth and on the viability of a human promyelocytic cell line.

AIMS: The ability of concentrated supernatants from Lactobacillus plantarum to produce a disruption of plasma membrane in eukaryotic and prokaryotic cells has been examined. METHODS AND RESULTS: A strain of Lact. plantarum (tolerant to acid and bile salts and resistant to several antibiotics) was used. It inhibited the growth of pathogenic Escherichia coli and L. monocytogenes. Supernatants from Lact. plantarum were concentrated by centrifugation. Either E. coli or HL-60 cells (a human promyelocytic cell line) were treated in the presence of the concentrated supernatants. The effect of concentrated supernatants from Lact. plantarum on E. coli growth demonstrated a bacteriostatic activity and a loss of cell viability measured by sytox green staining. Concentrated supernatants were capable of disturbing plasma membrane in E. coli and of promoting a cytotoxic and lyctic action on HL-60 cells and on human erythrocytes, respectively. CONCLUSIONS: These results suggest that Lact. plantarum release an effective compound responsible for an important effect in the disruption of E. coli plasma membrane and for a cytototoxic activity on promyelocytic leukaemia cells. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first in vitro study about the antimicrobial and biological activities of concentrated supernatants from Lact. plantarum.

Analysis of caspase activities in rat mammary tumours induced by N-methyl-nitrosourea.

Normal breast development is controlled by a balance between cell proliferation and apoptosis. The balance between the two parameters is crucial for determining the growth or regression of breast tumours in response to therapies and treatments. Therefore, it is necessary to understand the role of apoptosis in tumour progression. Active caspases participate as essential elements in the execution of apoptotic mechanisms. In the present study, we analysed the activities of caspase-3, -8 and -9 as well as cytochrome c release in N-methyl-nitrosourea (NMU)-induced rat mammary tumours, in order to establish the apoptotic events that occur in tumour growth in this animal model. Forty female virgin Wistar rats were randomly divided into two groups. One group was injected intraperitoneally with three doses of 50 mg/kg body weight of NMU. The control group received the vehicle only. After 122 days of NMU injection, the rats were sacrificed and the tumours were excised and processed. Results showed that in mammary tumours induced by NMU, the apoptotic death receptor-mediated pathway is activated through caspase-3 and -8, but the apoptotic mitochondrial pathway is suppressed through a non-activating process of caspase-9 activity, despite the release of cytochrome c. In conclusion, these findings have demonstrated a suppression of the apoptotic mitochondrial pathway through a non-activating process of caspase-9 activity, despite the release of cytochrome c in mammary tumours induced by NMU. Although the apoptotic death receptor-mediated pathway is activated, it is not enough to maintain the balance between proliferation and apoptosis, and thus determine the overall growth of the tumour.

[Analysis of the immune resistance in an experimental murine model fed dietary lipids and infected with Listeria monocytogenes]. / Análisis de la resistencia inmune en un modelo murino experimental alimentado con dietas lipídicas e infectado con Listeria monocytogenes.

Several dietary lipids are capable of exerting an immunosupressor effect. This action may have undiserable effects on the host immune resistance to infectious diseases. The purpose of the present study was to determinate the immune status of mice fed dietary lipids and experimentally infected with a virulent strain of Listeria monocytogenes. Balb/c mice were divided into four groups and were fed with their respective diet: low fat diet (LF, 20%), olive oil diet (OO, 20%), fish oil diet (FO, 20%) and hydrogenated coconut oil (HCO, 20%). Mice were fed for four weeks and infected with L. monocytogenes by endovenous route. Results have shown a survival reduction in mice fed a diet containing FO, as well as a significant increase in the number of viable bacteria from spleen. In addition, we have observed an increase in the bactericidal activity in peritoneal cells from OO group, although the invasion of L. monocytogenes in cells from this group was larger. Finally, a significant reduction of lymphocyte proliferation was observed in the group fed an FO diet, whereas natural killer (NK) cell activity was not modified. These results indicate that dietary lipids constituted by polyunsaturated n-3 fatty acids reduce the murine immune resistance, whereas a diet constituted by OO-does not exert an immunosuppressor effect as relevant as FO diet, and it does not reduce the immune resistance leading to an efficient L. monocytogenes elimination.