Eduardo Luzía França

Oxidative and Nitrosative Stress on Phagocytes’ Function: from Effective Defense to Immunity Evasion Mechanisms

Although oxygen, nitrogen, and chlorine reactive species have been associated with disease pathogenesis, their partial absence is very harmful to the body’s innate immune defense. Lacking of adequate release of free radicals from activated phagocytes is related to impaired ability on fungi, bacteria, and protozoa killing. We constructed an updated conceptual landmark regarding the paramount role of free radicals in phagocyte defense systems (phagocyte oxidase, myeloperoxidase, and nitric oxide/peroxynitrite system) on natural immunity. Diverse fungal, bacterial and protozoal pathogens evade the phagocytes’ oxidative/nitrosative burst though antioxidant genes, enzymes and proteins. The most important evasion mechanisms were also described and discussed. These interconnected systems were reviewed and discussed on the basis of knowledge from relevant research groups around the globe. Phagocyte-derived free radicals are essential to destroy important human pathogens during the course of innate immunity.

Time-dependent alterations of soluble and cellular components in human milk

This study sought to determine the chronobiological variations in soluble and cellular components of human breast milk. The material was collected from 36 mothers at three stages of maturity – 3 days (colostrum), 10 days (transitional milk) and 30 days (mature milk) postpartum – and at two times of day – diurnal (12:00 h) and nocturnal (24:00 h) – making a total of 216 samples. Fat and calorie content, antibody concentration, C3 and C4 proteins of the complement system, superoxide anion release by milk mononuclear (MN) and polymorphonuclear (PMN) phagocytes, and concentration of the superoxide dismutase enzyme (CuZn-SOD) were determined. No difference in fat concentration was found between milk collected at the different times or between milk maturation stages but in the transitional milk the calorie concentration was higher in the nocturnal period. IgA was higher in milk collected in the diurnal period regardless of milk maturation. IgG and IgM were at higher concentrations in the diurnal period for both transitional and mature milk. The C3 protein increased significantly in the diurnal period regardless of milk maturation, and the C4 protein increased significantly during the diurnal period in the colostrum and transitional milk stages. Mature milk MN phagocytes had the highest superoxide during the diurnal period. Superoxide release by PMN phagocytes was higher in colostrum and mature milk collected in the diurnal period. CuZn-SOD increased significantly in diurnal and nocturnal colostrum. This chronobiological variation during the first month postpartum may represent an additional breastfeeding mechanism to improve adaptation to environmental changes and establish biological rhythms in the temporal synchronization process.

Human colostral phagocytes eliminate enterotoxigenic Escherichia coli opsonized by colostrum supernatant

BACKGROUND Several elements in colostrum and human milk, including antibodies and nonspecific factors with bactericidal and antiviral activity, may play an important anti-infectious and protective role. In developing countries, enterotoxigenic Escherichia coli (ETEC) is the main etiological agent of diarrhea in low-socioeconomic level children. In the present work, we studied the functional activity of mononuclear (MN) and polymorphonuclear (PMN) phagocytes of human colostrum against ETEC, as well as the interactions between these cells and colostral or serum opsonins. METHODS Colostrum samples were collected from 33 clinically healthy women between 48 and 72 hours postpartum. We verified superoxide release in colostral MN and PMN using cytochrome C reduction methods, phagocytosis, and bactericidal activity using acridine orange methods and superoxide dismutase (SOD) in the colostrum supernatants. RESULTS Colostral MN and PMN phagocytes exposed to ETEC opsonized with colostrum supernatants caused a significant increase (p<0.05) in superoxide release. Phagocytosis by colostral PMN cells increased significantly (p<0.5) when the phagocytes were incubated with both sources of opsonins (sera and colostrum). Increases in superoxide release in the presence of opsonized bacteria triggered the bactericidal activity of the phagocytes. Phagocyte treatment with SOD decreased their ability to eliminate ETEC. Colostrum supernatant had higher SOD concentrations (p<0.05) compared with normal human sera. CONCLUSIONS These results suggest that the ability of phagocytes to eliminate ETEC depends on the activation of cellular oxidative metabolism; moreover, activation of colostral phagocytes is likely an additional breast-feeding protection mechanism against intestinal infections in infants.

Diabetes induced immunological and biochemical changes in human colostrum

Aim:  This article describes the changes and relationships between biochemical and immunological parameters in the colostrum and serum of diabetic women.

Phagocytosis of Giardia lamblia trophozoites by human colostral leukocytes.

Aim: To determine the phagocytic activity of the polymorphonuclear and mononuclear cells present in human colostrum, and to verify the influence of opsonins in the adherence, ingestion and killing of Giardia lamblia trophozoites. Methods: Polymorphonuclear and mononuclear phagocytes were incubated with G. lamblia trophozoites, in the presence as well as the absence of supernatant of human colostrum (the source of opsonins) for 30, 60 and 120 min. The trophozoites/phagocytes ratio was 1:1, and the percentage of phagocytosed trophozoites was determined by microscopic examination of acridine orange‐stained cells. Results: The mononuclear phagocytes presented more functional activity than the polymorphonuclear. The highest indexes of adherence (77.6±5.1), ingestion (68.9±5.5) and killing (48.5±4.9) were obtained through the incubation of mononuclear cells in the presence of colostrum supernatant for 120 min.

Transfer of Maternal Immunity to Newborns of Diabetic Mothers

This study was carried out with hyperglycemic pregnant women to investigate the transfer of antibody classes to newborns across the placenta or by colostrum and the functional activity of phagocytes in maternal blood, cord blood, and colostrum from diabetes mothers. Samples from maternal blood, cord blood, and colostrum were collected from 20 normoglycemic and 20 hyperglycemic pregnant women. We determined antibodies levels, superoxide release, phagocytosis and bactericidal activity of phagocytes. We demonstrated that IgG levels in cord blood were higher in the hyperglycemic group. IgA and IgM levels were higher in maternal than in cord blood samples. Plasma antibody levels were lower in hyper- than in normoglycemic women. The colostrum of diabetic mothers had lower IgA and IgG levels. Colostrum and maternal blood phagocytes when exposed to EPEC increased the superoxide release. Cord blood phagocytes of hyperglycemic group, independently of bacteria, had higher superoxide release. Colostrum and blood phagocytes from diabetic group exhibited some phagocytic and microbicidal activity in response to EPEC. Mononuclear phagocytes from cord blood had the lowest phagocytosis, and bactericidal activity for EPEC, regardless of glycemic status. These data showed that hyperglycemia altered IgG transfer across the placenta and decreases immunoglobulin levels in maternal blood and colostrum.

Antioxidant Effect of Melatonin on the Functional Activity of Colostral Phagocytes in Diabetic Women

Melatonin is involved in a number of physiological and oxidative processes, including functional regulation in human milk. The present study investigated the mechanisms of action of melatonin and its effects on the functional activity of colostral phagocytes in diabetic women. Colostrum samples were collected from normoglycemic (N = 38) and diabetic (N = 38) women. We determined melatonin concentration, superoxide release, bactericidal activity and intracellular Ca2+ release by colostral phagocytes treated or not with 8-(Diethylamino) octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8) and incubated with melatonin and its precursor (N-acetyl-serotonin-NAS), antagonist (luzindole) and agonist (chloromelatonin-CMLT). Melatonin concentration was higher in colostrum samples from hyperglycemic than normoglycemic mothers. Melatonin stimulated superoxide release by colostral phagocytes from normoglycemic but not hyperglycemic women. NAS increased superoxide, irrespective of glycemic status, whereas CMTL increased superoxide only in cells from the normoglycemic group. Phagocytic activity in colostrum increased significantly in the presence of melatonin, NAS and CMLT, irrespective of glycemic status. The bactericidal activity of colostral phagocytes against enterophatogenic Escherichia coli (EPEC) increased in the presence of melatonin or NAS in the normoglycemic group, but not in the hyperglycemic group. Luzindole blocked melatonin action on colostrum phagocytes. Phagocytes from the normoglycemic group treated with melatonin exhibited an increase in intracellular Ca2+ release. Phagocytes treated with TMB-8 (intracellular Ca2+ inhibitor) decreased superoxide, bactericidal activity and intracellular Ca2+ release in both groups. The results obtained suggest an interactive effect of glucose metabolism and melatonin on colostral phagocytes. In colostral phagocytes from normoglycemic mothers, melatonin likely increases the ability of colostrum to protect against EPEC and other infections. In diabetic mothers, because maternal hyperglycemia modifies the functional activity of colostrum phagocytes, melatonin effects are likely limited to anti-inflammatory processes, with low superoxide release and bactericidal activity.

Secretory IgA-Fc alpha receptor interaction modulating phagocytosis and microbicidal activity by phagocytes in human colostrum of diabetics

França EL, Morceli G, Fagundes DLG, Rudge MVC, Calderon I de MP, Honorio‐França AC. Secretory IgA–Fcα receptor interaction modulating phagocytosis and microbicidal activity by phagocytes in human colostrum of diabetics. APMIS 2011; 119: 710–19.

Breastfeeding and its Relationship with Reduction of Breast Cancer: A Review

In this review, we describe the patterns of known immunological components in breast milk and examine the relationship between breastfeeding and reduced risk of breast cancer. The top risk factors for breast cancer are a womans age and family history, specifically having a first-degree relative with breast cancer. Women that have a history of breastfeeding have been shown to have reduced rates of breast cancer. Although the specific cause has not been elucidated, previous studies have suggested that breastfeeding reduces the risk of breast cancer primarily through two mechanisms: the differentiation of breast tissue and reduction in the lifetime number of ovulatory cycles. In this context, one of the primary components of human milk that is postulated to affect cancer risk is alpha-lactalbumin. Tumour cell death can be induced by HAMLET (a human milk complex of alpha-lactalbumin and oleic acid). HAMLET induces apoptosis only in tumour cells, while normal differentiated cells are resistant to its effects. Therefore, HAMLET may provide safe and effective protection against the development of breast cancer. Mothers should be encouraged to breastfeed their babies because the complex components of human milk secretion make it an ideal food source for babies and clinical evidence has shown that there is a lower risk of breast cancer in women who breastfed their babies.

Melatonin reduces the severity of experimental amoebiasis

BackgroundMelatonin has immunomodulatory effects but very little is known about its influence in protozoan infections, such as Entamoeba histolytica, which causes amoebiasis, a disease with significant morbidity and mortality. In this study, we evaluated the effects of exogenous melatonin interference in experimental amoebiasis and on interactions between human blood cells and E. histolytica trophozoites.MethodsThe effect of melatonin was investigated in models of experimental amoebiasis in hamsters and rats by evaluating the area of necrosis induced by E. histolytica. The activity of melatonin on the interactions between leukocytes and amoebae was determined by examining leukophagocytosis. For in vitro tests, polymorphonuclear and mononuclear human blood leucocytes were incubated with E. histolytica trophozoites.ResultsThe areas of amoebic necrosis were significantly reduced in animals treated with melatonin. Melatonin treatment increased leukophagocytosis but was associated with a greater number of dead amoebae.ConclusionsThese results suggest that melatonin may play a beneficial role in the control of amoebic lesions, raising the possibility that this drug may be used as an adjuvant in anti-amoebic therapy.