Mónica De la Fuente

An update of the oxidation-inflammation theory of aging: the involvement of the immune system in oxi-inflamm-aging.

The aging process is one of the best examples of the effects of a deterioration of homeostasis, since aging is accompanied by an impairment of the physiological systems including the homeostatic systems such as the immune system. We propose an integrative theory of aging providing answers to the how (oxidation), where first (mitochondria of differentiated cells) and why (pleiotropic genes) this process occurs. In agreement with this oxidation-mitochondrial theory of aging, we have observed that the age-related changes of immune functions have as their basis an oxidative and inflammatory stress situation, which has among its intracellular mechanisms the activation of NFkappaB in immune cells. Moreover, we have also observed that several functions of immune cells are good markers of biological age and predictors of longevity. Based on the above we have proposed the theory of oxidation-inflammation as the main cause of aging. Accordingly, the chronic oxidative stress that appears with age affects all cells and especially those of the regulatory systems, such as the nervous, endocrine and immune systems and the communication between them. This fact prevents an adequate homeostasis and, therefore, the preservation of health. We have also proposed a key involvement of the immune system in the aging process of the organism, concretely in the rate of aging, since there is a relation between the redox state and functional capacity of the immune cells and the longevity of individuals. Moreover, the role of the immune system in senescence could be of universal application. A confirmation of the central role of the immune system in oxi-inflamm-aging is that the administration of adequate amounts of antioxidants in the diet, improves the immune functions, decreasing their oxidative stress, and consequently increases the longevity of the subjects.

VIP modulation of immune cell functions

Neuropeptides have recently been shown to modulate the immune response. Vasoactive intestinal peptide (VIP) released from nerve endings and from immune cells modulates the mobility and adherence of lymphocytes and macrophages, phagocytic cell functions (phagocytosis and free radical production), the lymphocyte proliferative response, lymphokine and immunoglobulin production and the natural killer cell activity, with opposite effects in vitro on these immune cell functions. The VIP receptor heterogeneity and the different action mechanisms of VIP-mediated immunoregulation could explain, at least in part, the different VIP effects observed on lymphoid and phagocytic cells. The evidence supports the theory that VIP acts not as an inhibitor, but as a modulator of immune functions, as previously thought, and that this neuropeptide may play a relevant role in vivo.

Increased cerebrospinal fluid Fas (Apo-1) levels in Alzheimer’s disease: Relationship with IL-6 concentrations

Increasing lines of evidence suggest a role of apoptosis in the neurodegeneration associated with Alzheimers disease, in which it has been implicated in increasing the expression of p53 and Fas. On the other hand, inflammatory cytokines have also been implicated as important factors in the progression of neuronal damage in this disease. In an attempt to investigate the possible in vivo relationship between programmed cell death and the inflammatory response in patients with dementia of the Alzheimer type (DAT), we measured the levels of soluble Fas, interleukin-1beta (IL-lbeta) and IL-6 in cerebrospinal fluid (CSF) from ten DAT patients and ten age-matched controls. Our results show a significant increase in IL-6 and soluble Fas concentrations in the CSF of DAT patients compared with those from nondemented controls. Moreover, linear regression analysis demonstrated a significant correlation (r=0.703; P<0.05) between soluble Fas and IL-6 levels in the CSF in DAT patients. These results suggest that Fas is implicated in the inflammatory response observed in Alzheimers brains.

Differential effects of gastrin-releasing peptide, neuropeptide Y, somatostatin and vasoactive intestinal peptide on interleukin-1β, interleukin-6 and tumor necrosis factor-α production by whole blood cells from healthy young and old subjects

In the present study, we have investigated the effect in vitro of gastrin-releasing peptide (GRP, 10(-10) M), neuropeptide Y (NPY, 10(-10) M), somatostatin (10(-10) M) and vasoactive intestinal peptide (VIP, 10(-9) M) on the production of IL-1 beta, IL-6 and TNF alpha by peripheral whole blood cells from healthy young and old people. We have found that GRP, NPY, somatostatin and VIP stimulated the production of IL-1 beta in old subjects, and NPY, somatostatin and VIP in young ones. In addition, the production of IL-6 was enhanced by GRP, NPY and VIP in young and old people. The TNF alpha production was stimulated by NPY and somatostatin in young subjects, and by NPY, somatostatin and VIP in old ones, whereas GRP produced a decrease of TNF alpha in young persons. GRP in old subjects and VIP in young and old subjects stimulated in a great degree the LPS-induced IL-6 production by whole blood cells. On the contrary, GRP and VIP inhibited highly the LPS-induced TNF alpha production in young controls. Our results show that these neuropeptides, when added to whole blood cells at physiological concentrations, are able to stimulate the production of IL-1 beta, IL-6 and TNF alpha in a differential way according to the subject age.

N-acetylcysteine protects mice from lethal endotoxemia by regulating the redox state of immune cells.

The excessive production of reactive oxygen species (ROS) associated with inflammation leads to oxidative stress, which is involved with the high mortality from several diseases such as endotoxic shock and can be controlled to a certain degree by antioxidants. The immune cells use ROS in order to support their functions and, therefore, need adequate levels of antioxidant defenses in order to avoid the harmful effect of an excessive ROS production. In the present work, the effect of the administration of the antioxidant N-acetylcysteine (NAC) on the redox state of peritoneal macrophages and lymphocytes from mice with lethal endotoxic shock (100 mg/kg i.p. of lipopolysaccharide, LPS), was studied. In both types of immune cells at 0, 2, 4, 12 and 24 h after LPS injection, an increase of ROS, of the proinflammatory cytokine tumor necrosis factor alpha (TNFα), the lipid peroxidation (malonaldehyde levels, MDA), inducible nitric oxide synthase (iNOS) expression and the oxidized/reduced glutathione (GSSG/GSH) ratio, as well as a decrease of enzymatic antioxidant defenses, such as superoxide dismutase (SOD) and catalase (CAT) activity, was observed. The injection of NAC (150 mg/kg i.p. at 30 min after LPS injection) decreased the ROS, the TNFα the MDA levels, iNOS expression and the GSSG/GSH ratio, and increased the antioxidant defenses in both macrophages and lymphocytes. Moreover, the NAC treatment prevented the activation of nuclear translocation of the nuclear factor κB (NF-κB), which regulates ROS, inflammatory cytokines and antioxidant levels. Our present results provide evidence that both cell types have a relevant role in the pathogenesis of endotoxic shock, and that NAC, by improving the redox state of these immune cells, could increase mouse survival. Thus, antioxidants could offer an alternative treatment of human endotoxic shock.

Regulation of macrophage function by the antioxidant N-acetylcysteine in mouse-oxidative stress by endotoxin

Changes in several functions of peritoneal macrophages from mice with oxidative stress caused by intraperitoneal injection of endotoxin (Escherichia coli lipopolysaccharide, LPS) (100 mg/kg), and associated with a high production of reactive oxygen species (ROS), have been observed in our previous studies. Antioxidants such as N-acetylcysteine (NAC) are free radical scavengers that improve and modulate the immune response, especially in oxidative stress situations. Therefore, in the present work, we have studied the effects of the administration of NAC (150 mg/kg i.p.) on different functions of peritoneal macrophages from Swiss mice suffering that oxidative stress, caused by LPS (100 mg/kg). NAC was injected 30 min after LPS injection, and the peritoneal macrophages were obtained at 2, 4, 12, and 24 h after endotoxin injection. The following functions, key stages of the phagocytic process, were studied: adherence to substrate, chemotaxis, ingestion of particles, and production of ROS (reactive oxygen species), as well as tumor necrosis factor (TNFalpha) release. The decrease in chemotaxis and the increase in adherence, ingestion, superoxide anion production, and TNFalpha release shown by macrophages from animals with oxidative stress were counteracted by NAC injection. These data suggest that NAC administration may be useful for the treatment of oxidative stress-linked endotoxic shock, modulating the function of macrophages, specifically in decreasing the production of ROS and of inflammatory cytokines such as TNFalpha.

Early maternal deprivation and neonatal single administration with a cannabinoid agonist induce long-term sex-dependent psychoimmunoendocrine effects in adolescent rats

Maternal deprivation [24h on postnatal day 9] might represent an animal model of schizophrenia and behavioural and neurochemical alterations observed in adulthood may be mediated by hippocampal impairments induced by abnormally increased glucocorticoids due to neonatal stress. We aimed to provide new data for psychoimmunoendocrine characterization of this animal model by evaluating its effects in adolescent rats of both genders. In previous studies we found that cannabinoid compounds counteracted the enhanced impulsivity of maternally deprived animals and that the cannabinoid receptor agonist WIN 55,212-2 showed neuroprotective properties in neonatal rats. So, we hypothesised that this compound could counteract at least some of the detrimental effects that we expected to find in maternally deprived animals. Accordingly, the drug was administered immediately after the maternal deprivation period. Maternally deprived males showed significantly decreased motor activity in the holeboard and the plus-maze. The cannabinoid agonist induced, exclusively in males, a significant anxiogenic-like effect, which was reversed by maternal deprivation. In the forced swimming test, both treatments independently induced depressive-like responses. Maternal deprivation reduced immunological function whereas the drug exerted tissue-dependent effects on the immune parameters analysed. Maternally deprived females showed reduced corticosterone levels whereas the cannabinoid agonist increased hormone concentration in all groups. In general, the results show detrimental effects of both treatments as well as intriguing interactions, notably in relation to emotional behaviour and certain immunological responses.

Bombesin, gastrin-releasing peptide, and neuromedin C modulate murine lymphocyte proliferation through adherent accessory cells and activate protein kinase C

Recent data have shown the ability of bombesin-related peptides to stimulate murine macrophage functions. In the present study, we have investigated the effect of bombesin, gastrin-releasing peptide (GRP), and neuromedin C on the proliferative response of lymphocytes from murine axillary nodes, spleen, and thymus. The results show that these neuropeptides at 10(-9), 10(-10), and 10(-11) M concentrations modulate the lymphoproliferative response, stimulating to a small but significant extent the spontaneous proliferation and inhibiting to a great extent the lymphoproliferative response to the mitogen concanavalin A (Con A). This regulation is probably mediated through adherent accessory cells, since their presence for the neuropeptides to produce their effect. The increased interleukin-1 beta production by Con A in cultures of peritoneal macrophages (a model of adherent accessory cells) decreased after the addition of bombesin, GRP, and neuromedin C; this diminution is a possible mechanism for their inhibitory action on the lymphoproliferative response to Con A. In addition, these neuropeptides caused a significant protein kinase C activation in total leukocyte population and T-enriched lymphocytes from axillary nodes, as well as in peritoneal macrophages.

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.

Immune cells redox state from mice with endotoxin-induced oxidative stress. involvement of NF-κB

The immune cells, such as phagocytes and lymphocytes, which use reactive oxygen species (ROS) for carrying out many of their functions, need appropriate levels of intracellular antioxidants to avoid the harmful effect of oxidative stress. In previous studies, we have observed changes in several functions of those leukocytes from female BALB/c mice with lethal endotoxic shock caused by intraperitoneal injection of Escherichia coli 055:B5 lipopolysaccharide (LPS) (100 mg/kg), which were associated with high ROS production. In the present study, we have investigated the redox state of the above mentioned immune cells in that lethal endotoxic shock model measuring the oxidant/antioxidant balance through the following parameters: production of ROS, proinflammatory cytokine TNF f reduced glutathione (GSH), oxidized glutathione (GSSG), superoxide dismutase (SOD) and catalase (CAT) activities, malonaldehyde (MDA) and transcription factor NF- s B expression at different times after LPS injection. The results show an increase in ROS, TNF f and MDA production in both cell types, being higher in macrophages than in lymphocytes. GSSG/GSH ratio was increased in both macrophages and lymphocytes after LPS injection. With respect to the activity of the antioxidant enzymes SOD and CAT were decreased in both macrophages and lymphocytes. The activation of the transcription factor NF- s B was stimulated in macrophages and lymphocytes. These results point out that both lymphocytes and macrophages, which are able to play an important role in host response to endotoxin, show an oxidative stress thus contributing to the pathogenesis of this septic shock.