Isabel Baeza

Changes with ageing in several leukocyte functions of male and female rats

The impairment of the immune system with aging, or ‘immunosenescence’, appears to contribute to the increased morbidity and mortality of aged subjects. T cell functions and Natural Killer activity seem to be the immune responses most affected by ageing. Since the immune system works more efficiently in females than in males, we have studied the changes of several immune functions with age in rats of both sexes. In addition, we have investigated if ovariectomy, a model of menopause in rats, produces a loss of this gender-related advantage. In the present work, the changes with age (2, 6, 12, 14, 18, 22 and 24 months old) in lymphocyte chemotaxis, T lymphoproliferative response to the mitogen ConA, IL-2 release and Natural Killer activity of cells from axillary nodes and spleen of male and female rats as well as of females ovariectomized at 12 months of age have been studied. An age-related decrease was found in all investigated functions, with a slightly different evolution depending on the immune organ and gender considered. In general, the data obtained show that a certain degree of immunosenescence takes place with age in rats, with males being less immunocompetent than intact age-matched females, but showing an immune response similar to that of ovariectomized animals.

Ovariectomy, a model of menopause in rodents, causes a premature aging of the nervous and immune systems

Ovariectomy in rodents is a good model for mimicking human ovarian hormone loss. This work studies the consequences of ovariectomy on the nervous and immune systems in the context of biological aging. Ovariectomy accelerates the process of aging by impairing the sensorimotor abilities (with loss of muscular vigor and impaired equilibrium and traction capacities) and the exploratory capacities (with reduction of vertical exploratory activity). It also leads to a premature immunosenescence with regard to chemotaxis index, lymphoproliferative response and natural killer activity, parameters investigated in the spleen and axillary nodes. Therefore, ovariectomy deteriorates homeostasis and may be a model of premature aging.

Environmental Enrichment Improves Age-Related Immune System Impairment: Long-Term Exposure Since Adulthood Increases Life Span in Mice

Age-related changes in immunity have been shown to highly influence morbidity and mortality. The aim of the present work was to study the effects of environmental enrichment (EE) (8-16 weeks) on several functions and oxidative stress parameters of peritoneal leukocytes, previously described as health and longevity markers, in mice at different ages, namely adult (44 +/- 4 weeks), old (69 +/- 4 weeks), and very old (92 +/- 4 weeks). Mortality rates were monitored in control and enriched animals, and effects on survival of long-term exposure to EE until natural death were determined. The results showed that exposure to EE was efficient in improving the function (i.e., macrophage chemotaxis and phagocytosis, lymphocyte chemotaxis and proliferation, natural killer cell activity, interleukin-2 and tumor necrosis factor-alpha levels) and decreasing the oxidative-inflammatory stress (i.e., lowered oxidized glutathione content, xanthine oxidase activity, expression of Toll-like receptors 2 and 4 on CD4 and CD8 cells, and increased reduced glutathione and glutathione peroxidase and catalase activities) of immune cells. These positive effects of EE were especially remarkable in animals at older ages. Importantly, long-term exposure to EE from adult age and until natural death stands out as a useful strategy to extend longevity. Thus, the present work confirms the importance of maintaining active mental and/or physical activity aiming to improve quality of life in terms of immunity, and demonstrates that this active life must be initiated at early stages of the aging process and preserved until death to improve life span.

Early Maternal Deprivation in Rats : A Proposed Animal Model for the Study of Developmental Neuroimmunoendocrine Interactions

Adult animals that had been subjected to a single prolonged episode of maternal deprivation (MD) [24 h, postnatal day (PND) 9–10] show long‐term behavioral alterations that resemble specific symptoms of schizophrenia. Moreover, at adolescence MD rats showed depressive‐like behavior and altered motor responses. According to the neurodevelopmental hypothesis, certain behavioral abnormalities observed in MD animals may be related to altered neurodevelopmental processes triggered by MD‐induced elevated glucocorticoids in relevant specific brain regions. We review here these neuroendocrine effects and show new data indicating that the MD procedure induces diverse detrimental effects on the immune system that are already revealed in the short term (PND 13) and persist into adulthood. These long‐lasting effects might be related to altered hypothalamus–pituitary–adrenal axis activity and to social as well as nutrition‐related factors. In fact, MD induces long‐lasting decreases in body weight. In view of our findings we propose the present MD procedure as a potentially useful model to analyze developmental interactions between early psychophysiological stress and immunodeficient states.

Improvement of leucocyte functions in ovariectomised aged rats after treatment with growth hormone, melatonin, oestrogens or phyto-oestrogens

Ageing is accompanied by an impairment of the physiological activity of the nervous, endocrine and immune system, as well as in neuroendocrine-immune communication. However, age-related changes in this communication axis have been scarcely studied. In mammals, the process of ageing is associated with an important decline in the secretion of several hormones, such as growth hormone (GH), melatonin (MEL) and oestrogens (Os). Ovariectomy, a model of menopause in rats, has been found to lead to premature immunosenescence. In the present study, the effect of ovariectomy and the role of replacement therapies with GH, MEL, O and natural phyto-oestrogens (POs) have been assessed on several functions in leucocytes from the spleen and the axillary nodes of intact and ovariectomised rats. Chemotaxis, lymphoproliferative response to the mitogen concanavalin A (Con A), the release of interleukin-2 (IL-2) and the natural killer (NK) cell activity have been investigated. Age-controlled rats were used to compare immune functions in hormone treated aged rats with those in younger untreated animals. In all experimental groups, the immune impairment caused by ageing and ovariectomy was partially or completely reversed by hormone treatments. Since the immune system is a marker of health and a predictor of longevity, the results suggest that treatment with hormones could slow down the effects of the ageing process.

Effect of Environmental Enrichment on the Immunoendocrine Aging of Male and Female Triple-Transgenic 3xTg-AD Mice for Alzheimer's Disease

We have previously shown that 3xTgAD mice (triple-transgenic mice for Alzheimers disease, harboring PS1(M146V), AβPP(Swe), tau(P301L) transgenes) suffer detrimental changes in some key lymphocyte functions, described as health and longevity markers, with males being more affected than females and showing higher mortality rates. In the present work, 3xTgAD and wild type 129/C57BL6 male and female non- and environmentally enriched mice were used. The enriched environment (EE) began in the adulthood (6 months) and lasted for 5.5 months. The animals were sacrificed at advanced stages of the disease (15 month-old), and spleen, thymus, and plasma were obtained. The results indicate that 3xTg-AD males are especially benefitted from EE exposure, as shown by the improvement in lymphocyte functional activities such as chemotaxis and natural killer cytotoxicity, as well as in plasma corticosterone levels. By contrast, wild type females seem to be highly sensitive to EE removal, as regards the proliferation capacity of lymphocytes and their intracellular glutathione content. These results support the relevance of gender differences in AD when screening for new strategies for the control of the disease, and suggest that active life, by means of EE, should be maintained until natural death in order to preserve all the positive effects that this strategy exerts on the immune system.

Improvement of immune cell functions in aged mice treated for five weeks with soybean isoflavones.

Abstract:  Aging is associated with an impaired immune system as well as with a decline of several hormones, such as estrogens. Dietary phytoestrogens have been proposed as an alternative to hormone replacement therapy. The beneficial action of soybean compounds is probably due to isoflavones, whose role as immunomodulators has been investigated with increasing interest. The aim of the present work was to study whether a 5‐week administration of a diet enriched in soybean isoflavones and green tea could influence the immune function of mice that were sham‐operated or ovariectomized. Natural killer activity (NK) and lymphoproliferation in response to the mitogens concanavaline A (Con A) and lipopolysaccharide (LPS), were studied in peritoneal leukocytes. Both treatments with soybean or green tea plus soybean were highly effective in improving these immune parameters with respect to control groups. Since the immune system is a marker of health and a predictor of longevity, an adequate treatment with isoflavones could be useful in slowing down the effects of the aging process through an improvement in the two relevant immune functions studied.

El aislamiento social durante la vejez empeora el deterioro cognitivo, conductual e inmunitario

INTRODUCTION Several studies by the World Health Organization indicate that widows and widowers show lower physical and mental health indexes than the age-matched general population. In addition, widowhood and social isolation are common in the elderly, with women being more affected than men due to their longer life span. Thus, the aim of the present study was to create an animal model of solitude in old age to study the behavioral, cognitive and immunological changes induced by social isolation at this late stage of life. MATERIAL AND METHODS Twenty female C57b/129sv mice, housed in groups of 4-5 until their old age (18 months), remained in groups (controls, n=10) or were isolated after reaching the age of 18 months and until they reached the age of 24 months (isolated, n=10). At this advanced age, the animals were submitted to a battery of tests to assess neophobia (corner test), anxiety (open-field test), and learning and memory (Morris water maze). Thereafter, the animals were sacrificed and the thymus was removed. The natural killer (NK) activity of the thymic cells against the YAC-1 murine tumor cell line was evaluated. RESULTS Animals isolated during old age showed functional and cognitive decline, with increased neophobia and anxiety as well as learning and memory deficits. In addition, isolation reduced the NK activity of thymic cells. CONCLUSIONS We demonstrate the importance of social isolation and solitude during old age. Both social isolation and solitude exacerbate mental and immunological involution during this period, despite normal social life during previous stages of life.

Soybean and Green Tea Polyphenols Improve Immune Function and Redox Status in Very Old Ovariectomized Mice

In previous work we have observed that ovariectomy in rodents, a good model of mimicking human ovarian hormone loss, causes premature aging of the immune system. The prooxidative and inflammatory state that underlies the aging process is the base of that premature immunosenescence. It has been found that nutritional interventions with polyphenolic antioxidants constitute a good alternative to rejuvenate age-affected immune functions. In this study, we administered a diet supplemented with polyphenols (coming from soybean isoflavones and green tea) to sham-operated and ovariectomized mature mice for 15 weeks, until they reached a very old age. We have studied the effect of this supplementation on a broad range of parameters of immune function (in macrophages and lymphocytes) and oxidative stress (enzymatic and nonenzymatic antioxidant defences, oxidant compounds, and lipid peroxidation damage) in peritoneal leukocytes. The results showed that ovariectomy accelerates the age-related impairment of immune functions in very old mice as well as the oxidative and proinflammatory imbalance, and that the administration of soybean isoflavones and green tea improve the immune and redox state in these animals. Because the immune system is a good marker of health and a predictor of longevity, we suggest that an adequate nutritional treatment with polyphenols could be a highly recommended tool to fight against the detrimental effects of the lack of female sex hormones, through an improvement of the immune cell functions and redox state.

Effect of Growth Hormone Treatment on Lymphocyte Functions in Old Male Rats

Introduction: Age-related changes in the communication between the neuroendocrine and the immune system have been scarcely studied. Aging in mammals is associated with an impairment of the immune response, especially regarding lymphocyte functions. Furthermore, the endocrine system is also affected by aging, one of the most significant changes being the decrease in the secretion of several hormones such as growth hormone (GH). Objective: The aim of the present work was to study whether GH replacement therapy in old male rats could improve several lymphocyte functions. Methods: Spleen and axillary node lymphocytes from old (24 months of age) male Wistar rats were used in the present study to investigate the effect of GH (2 mg/kg daily during 10 weeks) on chemotaxis, lymphoproliferative response to the mitogen concanavalin A, interleukin 2 release and natural killer cell activity. Results: We have found that the administration of GH can reduce or even reverse the age-related changes observed in these key immune function parameters. Moreover, we have observed that the recovery of such immune functions is able to reach similar values as those exhibited by young control animals of 6 months of age. Conclusion: Considering that the immune system is a marker of health and a predictor of longevity, hormone replacement therapies with GH, by increasing the immune function and thus delaying or slowing down some aspects of the aging process, could facilitate successful aging.