Gerardo Alvarez de Cienfuegos

Modulatory effects of dietary lipids on immune system functions.

Dietary lipid manipulation may affect a great number of immune parameters, such as lymphocyte proliferation, cytokine synthesis, natural killer (NK) cell activity, phagocytosis and so on. The immunomodulation induced by dietary fatty acids may be applied in the amelioration of inflammatory disorders, such as autoimmune diseases. However, the mechanisms that participate in these processes are still poorly understood. It is probable that modulation of immune system by fatty acids of the diet may occur by alteration of membrane fluidity, lipid peroxide formation, eicosanoid production or regulation of gene expression. However, recent studies have reported the effects of several free fatty acids on apoptosis induction of in vitro cultures. In fact, a possible explanation of the effects that fatty acids promote on the immune system cells could be associated with an apoptotic process performed in an irreversible way. In vivo studies have demonstrated the ability of fatty acids to alter the survival of animals fed diets containing oils and infected with a pathogenic bacterium. Experimental infection in animals fed dietary lipids produces a modification of resistance to micro‐organisms. The present review analyses all of these parameters that dietary fatty acids are capable of altering in order to modify the immune response. Further studies will be needed to establish the mechanisms involved in immune system regulation, reduction of symptoms derived from autoimmune pathologies and so on.

Dietary Antioxidants: Immunity and Host Defense

Natural antioxidants may be defined as molecules that prevent cell damage against free radicals and are critical for maintaining optimum health in both animals and humans. In all living systems, cells require adequate levels of antioxidant defenses in order to avoid the harmful effect of an excessive production of reactive oxygen species (ROS) and to prevent damage to the immune cells. During the inflammatory processes, the activation of phagocytes and/or the action of bacterial products with specific receptors are capable of promoting the assembly of the multicomponent flavoprotein NADPH oxidase, which catalyzes the production of high amounts of the superoxide anion radical (O(2)(-)). Under these particular circumstances, neutrophils and macrophages are recognized to produce superoxide free radicals and H(2)O(2), which are essential for defence against phagocytized or invading microbes. In this state, antioxidants are absolutely necessary to regulate the reactions that release free radicals. Antioxidant nutrients commonly included in the diet such as vitamin E, vitamin C, β-carotene, selenium, copper, iron and zinc improve different immune function exhibiting an important protective role in infections caused by bacteria, viruses or parasites. As a result, dietary antioxidants have been related to modulate the host susceptibility or resistance to infectious pathogens. Overall, numerous studies have suggested that the development of tolerance, and control of inflammation are strongly correlated with specific immune mechanisms that may be altered by an inadequate supply of either macronutrients or micronutrients. Therefore, the present paper will review the effects of dietary antioxidants on immune cell function and the impact on protection against infectious microorganisms.

Biomass production and detoxification of wastewaters from the olive oil industry by strains of Penicillium isolated from wastewater disposal ponds

Olive mill wastewater (OMW) usually has to be diluted before biological treatment. In the present work seven strains of Penicillium isolated from OMW disposal ponds were tested for biomass production and biodegradation of undiluted OMW. Best results were obtained by using strain P4, which formed 21.50 g (dry weight) of biomass per litre of undiluted wastewater after 20 days of cultivation. This and other strains also carried out an outstanding reduction of the chemical oxygen demand (COD) and the phenolic content of OMW, as well as a pH raise. The process could be accelerated by agitation. OMW fermented with Penicillium P4 was devoid of its initial antibacterial activity against Bacillus megaterium ATCC 25848.

Phenol-oxidase (laccase) activity in strains of the hyphomycete Chalara paradoxa isolated from olive mill wastewater disposal ponds.

Production of laccase activity by nine strains of Chalara paradoxa isolated from olive mill wastewater disposal ponds were studied. Enzyme extracts obtained from cultured broths by adsorption on hydroxyapatite showed a single band of laccase activity on ABTS after polyacrylamide gel electrophoresis (PAGE). They showed small mobility differences, with molecular masses of 67 to 68 kDa. Enzymes from the different strains oxidized a variety of phenolic and non-phenolic substances, and they could be divided into two groups according to their relative activities on substrates. All laccases showed a dual pH dependence of activity, with a maximum in the range of pH 3.0 to 4.5 for ABTS, o-dianisidine and 2,6-dimethoxyphenol, and pH 6.0 (Group 1) or pH 6.5 (Group 2) for syringaldazine and other substrates. Optimal temperatures were in the range of 10 to 28 degrees C for two strains (maximum at 10 degrees C) and 10 to 37 degrees C for the rest. The different enzymes were partially inactivated by heating at 60 degrees C and totally inactivated at 70 degrees C. Laccases were stable in a pH range of 3.0 to 9.0 (except for strain 36A, which was partially inactivated at pH 3.0), but became inactivated at pH 2.0. Altogether these data suggest that Ch. paradoxa strains produce different laccase isoenzymes.

The antimicrobial peptide cecropin A induces caspase-independent cell death in human promyelocytic leukemia cells

Most antimicrobial peptides have been shown to have antitumoral activity. Cecropin A, a linear 37-residue antimicrobial polypeptide produced by the cecropia moth, has exhibited cytotoxicity in various human cancer cell lines and inhibitory effects on tumor growth. In this study, we investigated the apoptosis induced by cecropin A in the promyelocytic cell line HL-60. Treatment of cells with cecropin A was characterized by loss of viability in a dose-dependent manner, lactate dehydrogenase (LDH) leakage, and modest attenuation of lysosomal integrity measured by neutral red assay. An increase of reactive oxygen species (ROS) generation, DNA fragmentation, and phosphatidylserine externalization were quantified following cecropin A exposure at a concentration of 30 microM, whereas cecropin A-induced apoptosis was independent of caspase family members, because the activity of caspase-8 and -9 were irrelevant. Nevertheless, caspase-3 activity showed a significant increase at concentrations of 20-40 microM, but a considerable reduction at 50 microM. Flow cytometry analysis revealed a dissipation of the mitochondrial transmembrane potential (Deltapsi(m)), and the accumulation of cells at sub-G1 phase measured by FACS analysis of propidium iodide (PI) stained nuclei suggested induction of apoptosis. Morphological changes measured by Hoechst 33342 or acridine orange/ethidium bromide staining showed nuclear condensation, corroborating the apoptotic action of cecropin A. Overall, these data indicate that cecropin A is able to induce apoptosis in HL-60 cells through a signaling mechanism mediated by ROS, but independently of caspase activation.

In vitro biological activities of magainin alone or in combination with nisin.

Antimicrobial peptides have received increasing attention not only as potential candidates to their administration as antimicrobial agents, but also as potential drugs applied in cancer therapy. Here, we have examined the action of both nisin and magainin on human promyelocytic leukemia HL-60 cells. Cells were cultured in presence of either nisin or magainin 1 as well as in combination with both nisin and magainin 1. Results have revealed that magainin, but not nisin, produces a loss of cell viability in HL-60 cells, and a minor increase of hemolysis, whereas it is not responsible for cell membrane disruption and lactate dehydrogenase (LDH) leakage. In addition, magainin is involved in a significant generation of reactive oxygen species (ROS), as well as in an augment of caspase-3 activity. Magainin-induced apoptosis was verified by DNA fragmentation and annexin V-FITC/propidium iodide (PI) staining of the cells. Promotion of cell death by magainin occurs via cytochrome c release accompanied by a substantial increase of proteasome activity. These results underline the importance of magainin as a drug capable of exerting an in vitro antitumoral activity by triggering apoptosis.

Relevance of Dietary Lipids as Modulators of Immune Functions in Cells Infected with Listeria monocytogenes

ABSTRACT Nutritional status may have significant importance for the immune system, and particularly, unsaturated fatty acids may serve as modulators of immune functions. Clinical and epidemiological studies have demonstrated that fatty acids are involved in the reduction of the inflammatory processes that occur in diseases characterized by an overactivation of the immune system. At the same time, an increase in susceptibility to infection has also been reported. The importance of immune system modulation by dietary lipids in the presence of an intracellular bacterial pathogen, such as Listeria monocytogenes, was evaluated in the present study. BALB/c mice were divided into four groups which were each fed a low-fat (2.5% by weight) diet, an olive oil (OO; 20% by weight) diet, a fish oil (FO; 20% by weight) diet, or a hydrogenated coconut oil (HCO; 20% by weight) diet for 4 weeks. In each group, lymphocye proliferation was measured, and a reduction in the stimulation index was observed in the FO and HCO groups. Cytotoxicity exerted by L. monocytogenes was increased in the groups fed diets containing OO and FO after 6 h of incubation with the bacterium. An important increase in the production of reactive oxygen species was found in the groups fed the HCO diet after 12 h of incubation with L. monocytogenes. Finally, invasion and adhesion factors were not modified substantially by the action of dietary lipids, although these factors were reduced in cells from mice fed an FO diet. These results underline the importance of several dietary lipids as biological modulators of immune functions and their crucial role in the alteration of host natural resistance.

Changes in the immune functions and susceptibility to Listeria monocytogenes infection in mice fed dietary lipids

The direct examination of the effects that fish oil diets (composed of long‐chain n‐3 polyunsaturated fatty acids) exert on immune system function indicates a reduction of host natural resistance to infectious diseases mainly because of a suppression of immune function generated by the fatty acids contained in this diet. Here, we evaluated the concentration of IL‐12, IL‐4, prostaglandin E2 and leukotriene B4 in the serum from BALB/c mice receiving four different diets. Each group was fed a diet that differed only in the source of fat: a low‐fat diet (2.5% by weight), an olive oil diet (20% by weight), a fish oil diet (20% by weight) or a hydrogenated coconut oil diet (20% by weight). Mice were fed for 4 weeks and then infected with the intracellular pathogen Listeria monocytogenes. An initial reduction in the Th1‐type response as a result of a decrease in IL‐12p70 secretion, an inefficient action of IL‐4 (Th2‐type response) and no modification of pro‐inflammatory lipid‐mediator production could be, at least in part, the key events responsible for the inadequate elimination of L. monocytogenes from the spleens of mice fed a fish oil diet. Furthermore, our results suggest that the type of dietary lipids may affect the circulating concentration of IL‐12p70 and IL‐4, leading to a modulation in the protective cellular immune response to L. monocytogenes infection.

A study on the microbiota from olive-mill wastewater (OMW) disposal lagoons, with emphasis on filamentous fungi and their biodegradative potential.

The microbial composition of olive mill wastewater (OMW) from four disposal ponds has been studied. Such OMW samples contained a variable (but high) number of bacteria, yeasts and molds. Among the latest, members of twelve different genera (Acremonium, Alternaria, Aspergillus, Chalara, Fusarium, Lecytophora, Paecilomyces, Penicillium, Phoma, Phycomyces, Rhinocladiella and Scopulariopsis) were found. Members of five genera (Chalara, Fusarium, Paecilomyces, Penicillium and Scopulariopsis) were widely distributed, and they were able to grow efficiently in undiluted OMW as a sole source of nutrients. Strains of Fusarium, Paecilomyces, Penicillium and Scopulariopsis showed a marked capacity for OMW detoxification, depleting its antibacterial activity almost completely.

Significance of olive oil in the host immune resistance to infection

The effects exerted by polyunsaturated fatty acids (PUFA) on immune system functions have been investigated in recent years. These studies have reported the important role that n-3 PUFA play in the diminution of incidence and severity of inflammatory disorders. Nevertheless, less attention has been paid to the action of monounsaturated fatty acids (MUFA) upon the immune system. The administration of a diet containing a high amount of olive oil in experimental animals produces a suppression of lymphocyte proliferation, an inhibition of cytokine production and a reduction in natural killer (NK) cell activity. Despite these alterations in immune functions, it has been reported that olive oil-rich diets are not as immunosuppressive as fish oil diets. An important aspect in immunonutrition is focused on the relationship between fats, the immune system and host resistance to infection, particularly when these nutrients are supplied to patients at risk of sepsis. Different studies have determined that olive oil-rich diets do not impair the host resistance to infection. Therefore, olive oil constitutes a suitable fat that may be applied in clinical nutrition and administered to critically ill patients. In the present review, we summarize the current knowledge on olive oil and immune system functions, the biological consequences derived from the administration of diets containing olive oil and the impact of olive oil on immune defence.