The objective of this study was to determine the specific relationship between brain aging and changes in the level of oxidative stress, lipid peroxidation (LPO) and in the activities of antioxidant enzymes. We used four different age groups (2-3 months, 10-11 months, 16-17 months and 20-21 months) which represented young adults, adults, beginning senescence and senescence, respectively. Basal levels of LPO products measured as malondialdehyde increased gradually with age in mouse brain homogenate. The extent of stimulated LPO products, however, was clearly decreased in the brain of adult mice compared to young mice but increased again in the brain of senescent mice. We could not detect any appreciable age-related changes in the basal as well as in stimulated levels of ROS measured with the fluorescent dyes dichlorofluorescein and dihydrorhodamine123. Nevertheless, there was a significant delay in the time course of ROS-generation in brain cells from old mice. The activities of the antioxidant enzymes CuZn-superoxide dismutase and glutathione reductase increased with age whereas glutathione peroxidase remained unchanged. On the basis of our present findings, we envisage a potential model that integrates several divergent findings described in the literature about the role of oxidative stress in brain aging.

The Venus Kinase Receptor (VKR) is a single transmembrane molecule composed of an intracellular tyrosine kinase domain close to that of insulin receptor and an extracellular Venus Flytrap (VFT) structure similar to the ligand binding domain of many class C G Protein Coupled Receptors. This receptor tyrosine kinase (RTK) was first discovered in the platyhelminth parasite Schistosoma mansoni, then in a large variety of invertebrates. A single vkr gene is found in most genomes, except in S. mansoni in which two genes Smvkr1 and Smvkr2 exist. VKRs form a unique family of RTKs present only in invertebrates and their biological functions are still to be discovered. In this work, we show that SmVKRs are expressed in the reproductive organs of S. mansoni, particularly in the ovaries of female worms. By transcriptional analyses evidence was obtained that both SmVKRs fulfill different roles during oocyte maturation. Suppression of Smvkr expression by RNA interference induced spectacular morphological changes in female worms with a strong disorganization of the ovary, which was dominated by the presence of primary oocytes, and a defect of egg formation. Following expression in Xenopus oocytes, SmVKR1 and SmVKR2 receptors were shown to be activated by distinct ligands which are L-Arginine and calcium ions, respectively. Signalling analysis in Xenopus oocytes revealed the capacity of SmVKRs to activate the PI3K/Akt/p70S6K and Erk MAPK pathways involved in cellular growth and proliferation. Additionally, SmVKR1 induced phosphorylation of JNK (c-Jun N-terminal kinase). Activation of JNK by SmVKR1 was supported by the results of yeast two-hybrid experiments identifying several components of the JNK pathway as specific interacting partners of SmVKR1. In conclusion, these results demonstrate the functions of SmVKR in gametogenesis, and particularly in oogenesis and egg formation. By eliciting signalling pathways potentially involved in oocyte proliferation, growth and migration, these receptors control parasite reproduction and can therefore be considered as potential targets for anti-schistosome therapies.

Since oxidative stress plays an important role in the pathogenesis of Alzheimer's disease (AD) and since the age-adjusted incidence of AD is higher in females than males, we examined a possible influence of gender on antioxidant metabolism in brains from male and female AD patients and age-matched controls. Activities of copper/zinc-dependent superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-disulfide reductase (GR) were elevated in AD samples compared to controls. Upon in vitro stimulation, levels of malondialdehyde formation were significantly lower in AD samples, probably due to the increased antioxidant capacity. Overall, our results indicate that antioxidant metabolism is functionally still intact but increased in AD implying that oxidative damage is caused rather by overproduction than by insufficient detoxification of ROS. Among AD patients, a gender-specific partial upregulation of antioxidant defence was present: activities of SOD and GPx were even further increased in female patients, and levels of 4-hydroxynonenal, a marker of oxidative damage, were higher than in male patients. Importantly, our results are in line with epidemiological studies indicating a higher risk for AD in females. Thus, gender differences in oxidative stress parameters might be related to the higher prevalence of AD in females.

Summary. Enhanced apoptosis and elevated levels of reactive oxygen species (ROS) play a major role in aging. In addition, several neurodegenerative diseases are associated with increased oxidative stress and apoptosis in neuronal tissue. Antioxidative treatment has neuro-protective effects. The aim of the present study was to evaluate changes of susceptibility to apoptotic cell death by oxidative stress in aging and its inhibition by the antioxidant Ginkgo biloba extract EGb761. We investigated basal and ROS-induced levels of apoptotic lymphocytes derived from the spleen in young (3 months) and old (24 months) mice. ROS were induced by 2-deoxy-D-ribose (dRib) that depletes the intracellular pool of reduced glutathione. Lymphocytes from aged mice accumulate apoptotic cells to a significantly higher extent under basal conditions compared to cells from young mice. Treatment with dRib enhanced this difference, implicating a higher sensitivity to ROS in aging. Apoptosis can be reduced in vitro by treatment with EGb761. In addition, mice were treated daily with 100 mg/kg EGb761 per os over a period of two weeks. ROS-induced apoptosis was significantly reduced in the EGb761 group. Interestingly, this effect seemed to be more pronounced in old mice.

Apoptosis seems to be involved in irnmunosenescence associated with aging. Moreover, in lymphocytes (PBL) of patients with Akheimer's disease, an increased susceptibirity to the apoprotic pathway has been described possibly due to impaired protection o f oxidative stress. Accordingly. it seemed to be of particular interest to investigate the contribution of normal aging to the susceptibility from human lymphocytes 20 programmed cell death. We coiild show that PBL from elderly individuals (>60 years) accumuIate apoptosing cells to a significant higher extent in spontaneous and activation-induced cell death compared to younger controls (<35 years). Treatment with the oxidative Stressor 2-deoxy-D-ribose or with agonistic-CD95-antibody pronounced this effect even more implicating a higher sensitivity to reactive oxygen species and a higher functionril CD95 expression, respectively. In addition, expression of the activation markerc HLA-DR and CD95 was significantly increased in CD3 "-cells of aged subjects, while expression of CD25 did not seem to be affected by age.Expression of Bcl-2 was increased in aging and comlated with the number o f apoptotic cells.Kqwordv. &in& Apoptosis: 1,yrnphocytes; Oxidativc stress; dctivation markers; Bcl-2 Programmed cell death (PCD) or apoptosis is of particular interest in aging, as it is thought X o play an irnportant role in various age-related degenerative diseases. Apoptosis of white bIood cells could be one reason for the decrease of the total number of leukocytes and the decrease of the immune response with aging related Z o Cancer, infections, and autoirnmune disorders [3]. Several changes in lymphocytes have been observed related to aging: diminished synthesis of g r o~h and survive factos 146,511, impaired intracellular calcium regulation [18], different surface malecule expression 1431, and defects of signal transdi~ction [36]. Some of these pathological changes are additionally altered in patients witl~ Alzheimer's disease (AD), but are not present in vascular dementia [13][14][15]171. In order to differentiate common and divergent mechanisms of an enhanced susceptibility of lymphocytes to apoptosis in aging and sporadic AD, we investigated in detail the molecular basis of enhanced apoptosis in aged human lymphocytes. Oxidative Stress increases with aging and ltads to enhanced cellular damage (e.g. Iipidperoxidation, protein oxidation, DNA damage (for review see ref.[IO]). In addition, reactive axygen species (ROS) can trigger cells to undergo pragrammed cell death and can act as second rnessenger by influencing transcription factors like NF-KB and AP-I. Increased oxidative stress and decreased ability to cope with ROS could ampliQ apoptotic cell death in aging lymphocytes. BcI-2 acts in an antioxidative and antiapoptotic way and can interfcre with the apoptotic pathway 17,471.One oF the best known and characterized surface receptors related to PCD in lymphocytes is ApollFas (CD95), a rnernber of the himor necrosis factor (W) superfamily. Stimulation of this recep...