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The chemokine CX3CL1/fractalkine is expressed by neurons as a transmembrane-anchored protein that can be cleaved to yield a soluble isoform. However, the roles for these two types of endogenous CX3CL1 in neurodegenerative pathophysiology remain elusive. As such, it has been difficult to delineate the function of the two isoforms of CX3CL1, as both are natively present in the brain. In this study we examined each isoform's ability to regulate neuroinflammation in a mouse model of Parkinson's disease initiated by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We were able to delineate the function of both CX3CL1 isoforms by using adeno-associated virus-mediated gene therapy to selectively express synthetic variants of CX3CL1 that remain either permanently soluble or membrane bound. In the present study we injected each CX3CL1 variant or a GFP-expressing vector directly into the substantia nigra ofCX3CL1−/−mice. Our results show that only the soluble isoform of CX3CL1 is sufficient for neuroprotection after exposure to MPTP. Specifically, we show that the soluble CX3CL1 isoform reduces impairment of motor coordination, decreases dopaminergic neuron loss, and ameliorates microglial activation and proinflammatory cytokine release resulting from MPTP exposure. Furthermore, we show that the membrane-bound isoform provides no neuroprotective capability to MPTP-induced pathologies, exhibiting similar motor coordination impairment, dopaminergic neuron loss, and inflammatory phenotypes as MPTP-treatedCX3CL1−/−mice, which received the GFP-expressing control vector. Our results reveal that the neuroprotective capacity of CX3CL1 resides solely upon the soluble isoform in an MPTP-induced model of Parkinson's disease.

Adult hippocampal neurogenesis dramatically decreases with increasing age, and it has been proposed that this decline contributes to age-related memory deficits. Central inflammation contributes significantly to the decrease in neurogenesis associated with ageing. Interleukin-1beta is a proinflammatory cytokine initially synthesized as an inactive precursor that is cleaved by caspase-1 to generate the biologically active mature form. Whether IL-1beta affects neurogenesis in the aged hippocampus is unknown. Here we analysed cells positive for 5-bromo-2-deoxyuridine (BrdU; 50 mg/kg) in animals in which cleavage of IL-1beta was inhibited by the caspase-1 inhibitor Ac-YVAD-CMK (10 pmol). Aged (22 months) and young (4 months) rats received Ac-YVAD-CMK for 28 days intracerebroventricularly through a brain infusion cannula connected to an osmotic minipump. Starting on day 14, animals received a daily injection of BrdU for five consecutive days. Unbiased stereology analyses performed 10 days after the last injection of BrdU revealed that the total number of newborn cells generated over a 5-day period was higher in young rats than in aged rats. In addition, there was a 53% increase in the number of BrdU-labelled cells of the aged Ac-YVAD-CMK-treated rats compared to aged controls. Immunofluorescence studies were performed to identify the cellular phenotype of BrdU-labelled cells. The increase in BrdU-positive cells was not due to a change in the proportion of cells expressing neuronal or glial phenotypes in the subgranular zone. These findings demonstrate that the intracerebroventricular administration of Ac-YVAD-CMK reversed the decrease in hippocampal neurogenesis associated with ageing.

Neuroinflammation plays a critical role in loss of dopamine neurons during brain injury and in neurodegenerative diseases. Diets enriched in foods with antioxidant and anti-inflammatory actions may modulate this neuroinflammation. The model of 6-hydroxydopamine (6-OHDA) injected into the dorsal striatum of normal rats, causes a progressive loss of dopamine neurons in the ventral mesencephalon. In this study, we have investigated the inflammatory response following 6-OHDA injected into the striatum of adult rats treated with diet enriched in blueberry or spirulina. One week after the dopamine lesion, a similar size of dopamine degeneration was found in the striatum and in the globus pallidus in all lesioned animals. At 1 week, a significant increase in OX-6- (MHC class II) positive microglia was found in animals fed with blueberry- and spirulina-enriched diets in both the striatum and the globus pallidus. These OX-6-positive cells were located within the area of tyrosine hydroxylase (TH) -negativity. At 1 month after the lesion, the number of OX-6-positive cells was reduced in diet-treated animals while a significant increase beyond that observed at 1 week was now present in lesioned control animals. Dopamine recovery as revealed by TH-immunohistochemistry was significantly enhanced at 4 weeks postlesion in the striatum while in the globus pallidus the density of TH-positive nerve fibers was not different from control-fed lesioned animals. In conclusion, enhanced striatal dopamine recovery appeared in animals treated with diet enriched in antioxidants and anti-inflammatory phytochemicals and coincided with an early, transient increase in OX-6-positive microglia.

Diets high in antioxidant properties are known to reverse some deficits in neuronal and cognitive function that occur in aging animals. Antioxidants are also known to reduce levels of proinflammatory factors in the CNS. We report here that 6 weeks of a spinach-enriched diet ameliorates deficits in cerebellar-dependent delay classical eyeblink learning and reduces the proinflammatory cytokines tumor necrosis factor alpha (TNFalpha) and TNFbeta in the cerebelli of eyeblink-trained animals. Eighteen-month-old Fischer 344 rats were given spinach-enriched lab chow or regular lab chow for 6 weeks. The rats were then given 6 d of 30 trials per day training using a 3 kHz tone conditioned stimulus and airpuff unconditioned stimulus. Rats were killed 3 weeks after eyeblink training. Cytokine expression was measured using RNase protection assay analysis in the eyeblink-trained animals and in a group of young control animals given regular lab chow diet. Old animals on the spinach-enriched lab chow diet learned delay eyeblink conditioning significantly faster than old animals on the regular diet. Cerebelli from older animals on the spinach-enriched diet had significantly less TNFalpha and TNFbeta than cerebelli from older animals on the control diet.

Antioxidants and diets supplemented with foods high in oxygen radical absorbance capacity (ORAC) reverse age-related decreases in cerebellar beta-adrenergic receptor function. We examined whether this effect was related to the antioxidant capacity of the food supplement and whether an antioxidant-rich diet reduced the levels of proinflammatory cytokines in the cerebellum. Aged male Fischer 344 rats were given apple (5 mg dry weight), spirulina (5 mg), or cucumber (5 mg) either in 0.5 ml water by oral gavage or supplied in the rat chow daily for 14 d. Electrophysiologic techniques revealed a significant decrease in beta-adrenergic receptor function in aged control rats. Spirulina reversed this effect. Apple (a food with intermediate ORAC) had an intermediate effect on cerebellar beta-adrenergic receptor physiology, and cucumber (low ORAC) had no effect, indicating that the reversal of beta-adrenergic receptor function decreases might be related to the ORAC dose. The mRNA of the proinflammatory cytokines tumor necrosis factor-alpha (TNFalpha) and TNFbeta was also examined. RNase protection assays revealed increased levels of these cytokines in the aged cerebellum. Spirulina and apple significantly downregulated this age-related increase in proinflammatory cytokines, whereas cucumber had no effect, suggesting that one mechanism by which these diets work is by modulation of an age-related increase in inflammatory responses. Malondialdehyde (MDA) was measured as a marker of oxidative damage. Apple and spirulina but not cucumber decreased MDA levels in the aged rats. In summary, the improved beta-adrenergic receptor function in aged rats induced by diets rich in antioxidants is related to the ORAC dose, and these diets reduce proinflammatory cytokine levels.

Our view of microglia has dramatically changed in the last decade. From cells being silent in the healthy brain, microglia have emerged to be actively involved in several brain physiological functions, including adult hippocampal neurogenesis, cognitive and behavioral function. In light of recent discoveries revealing a role of microglia as important effectors of neuronal circuit reorganization, considerable attention has been focused on how microglia and hippocampal neurogenesis could be an interdependent phenomenon. In this review the role of microglia in the adult hippocampal neurogenesis under physiological condition will be discussed.

Alzheimer's disease is characterized by amyloid plaques, neurofibrillary tangles, glial activation, and neurodegeneration. In mouse models, inflammatory activation of microglia accelerates tau pathology. The chemokine fractalkine serves as an endogenous neuronal modulator to quell microglial activation. Experiments with fractalkine receptor null mice suggest that fractalkine signaling diminishes tau pathology, but exacerbates amyloid pathology. Consistent with this outcome, we report here that soluble fractalkine overexpression using adeno-associated viral vectors significantly reduced tau pathology in the rTg4510 mouse model of tau deposition. Furthermore, this treatment reduced microglial activation and appeared to prevent neurodegeneration normally found in this model. However, in contrast to studies with fractalkine receptor null mice, parallel studies in an APP/PS1 model found no effect of increased fractalkine signaling on amyloid deposition. These data argue that agonism at fractalkine receptors might be an excellent target for therapeutic intervention in tauopathies, including those associated with amyloid deposition.

Tumor necrosis factor alpha (TNF-α) is a multifunctional proinflammatory cytokine, which is a critical inflammatory mediator involved in aging and neurodegenerative diseases of aging. Previous work has shown that diets enriched with antioxidants reduce levels of the cytokine TNF-α and improve classical eyeblink conditioning performance. Therefore we tested the hypothesis that the proinflamatory cytokine TNF-α may be a critical factor that modulates classical conditioning behavior. If increased levels of endogenous cerebellar TNF-α negatively affect performance on the eyeblink conditioning task in aged rats, then exogenous administration of TNF-α in young rats should result in an impaired acquisition and/or retention of eyeblink conditioning memory. On the other hand, the reduction or blockage of the age-related increase in cerebellar TNF-α levels in aged rats should result in an improvement in memory. Young (3 month old) F344 rats were pretreated with an intracerebellar injection of recombinant rat (rr)TNF-α or denatured (rr)TNF-α prior to eyeblink conditioning coupled to microdialysis. The results showed that young rats treated with rrTNF-α have a decreased rate of learning compared to the control group. Norepinephrine which has been shown to play a critical role in cerebellar learning tasks presented a shift on training day one of young rats resembling that observed in aged rats. In a second experiment aged (22 month old) F344 rats were pretreated with intracerebellar microinjection of anti-rat TNF-α three times a week for 4 weeks prior to eyeblink conditioning training couple to microdialysis. Aged rats showed a better performance in the conditioned responses when compared to controls. The release of norepinephrine in this group reached basal levels sooner than the control group but not as early as the young rats. The results of these experiments demonstrate a critical correlation between TNF-α and the rate of learning and the pattern of NE release during eyeblink conditioning.

Inflammation is by definition a protective phase of the immune response. The very first goal of inflammation is destroying and phagocytosing infected or damaged cells to avoid the spread of the pathogen or of the damage to neighboring, healthy, cells. However, we now know that during many chronic neurological disorders, inflammation and degeneration always coexist at certain time points. For example, inflammation comes first in multiple sclerosis, but degeneration follows, while in Alzheimer’s or Parkinson’s disease degeneration starts and inflammation is secondary. Either way these are the two pathological detectable problems. The central nervous system (CNS) has long been viewed as exempt from the effects of the immune system. The brain has physical barriers for protection, and it is now clear that cells in the nervous system respond to inflammation and injury in unique ways. In recent years, researchers have presented evidence supporting the idea that in the CNS there is an ongoing protective inflammatory mechanism, which involves macrophage, monocytes, T cells, regulatory T-cells, effector T cells and many others; these, in turn, promote repair mechanisms in the brain not only during inflammatory, and degenerative disorders but also in healthy people. This “repair mechanism” can be considered as an intrinsic part of the physiological activities of the brain. It is now well known that the microenvironment of the brain is a crucial player in determining the relative contribution of the two different outcomes. Failure of molecular and cellular mechanisms sustaining the “brain-repair programme” might be, at least in part, a cause of neurological disorders. Today, the neurotoxic and neuroprotective roles of the innate immune reactions in aging, brain injury, ischemia, autoimmune and neurodegenerative disorders of the CNS are widely investigated and highly debated research topics. Nevertheless, several issues remain to be elucidated, notably the earlier cellular events that initiate dysregulation of brain inflammatory pathways. If these inflammatory processes could be identified and harnessed, then cognitive function may be protected during aging and age-related neurodegenerative diseases through early interventions directed against the negative consequences of inflammation. This commentary highlights the major issues/opinions presented by experts on the involvement of the brain immune system in aging and age-related diseases in a special edition of the journal Aging and Disease.

Converging lines of evidence indicate dysregulation of the key immunoregulatory molecule CD45 (also known as leukocyte common antigen) in Alzheimer's disease (AD). We report that transgenic mice overproducing amyloid-β peptide (Aβ) but deficient in CD45 (PSAPP/CD45−/−mice) faithfully recapitulate AD neuropathology. Specifically, we find increased abundance of cerebral intracellular and extracellular soluble oligomeric and insoluble Aβ, decreased plasma soluble Aβ, increased abundance of microglial neurotoxic cytokines tumor necrosis factor-α and interleukin-1β, and neuronal loss inPSAPP/CD45−/−mice compared with CD45-sufficient PSAPP littermates (bearing mutant human amyloid precursor protein and mutant human presenilin-1 transgenes). After CD45 ablation,in vitroandin vivostudies demonstrate an anti-Aβ phagocytic but proinflammatory microglial phenotype. This form of microglial activation occurs with elevated Aβ oligomers and neural injury and loss as determined by decreased ratio of anti-apoptotic Bcl-xL to proapoptotic Bax, increased activated caspase-3, mitochondrial dysfunction, and loss of cortical neurons inPSAPP/CD45−/−mice. These data show that deficiency in CD45 activity leads to brain accumulation of neurotoxic Aβ oligomers and validate CD45-mediated microglial clearance of oligomeric Aβ as a novel AD therapeutic target.

Background: Parkinson’s disease is characterized by a progressive loss of dopaminergic neurons in the substantia nigra. The cause of the neurodegeneration is unknown. Neuroinflammation has been clearly shown in Parkinson’s disease and may be involved in the progressive nature of the disease. Microglia are capable of producing neuronal damage through the production of bioactive molecules such as cytokines, as well as reactive oxygen species (ROS), and nitric oxide (NO). The inflammatory response in the brain is tightly regulated at multiple levels. One form of immune regulation occurs via neurons. Fractalkine (CX3CL1), produced by neurons, suppresses the activation of microglia. CX3CL1 is constitutively expressed. It is not known if addition of exogenous CX3CL1 beyond otherwise physiologically normal levels could decrease microglia activation and thereby minimize the secondary neurodegeration following a neurotoxic insult. Methods: The intrastriatal 6-hydroxydopamine (6-OHDA) rat model of Parkinson disease, was used to test the hypothesis that exogenous CX3CL1 could be neuroprotective. Treatment with recombinant CX3CL1 was delivered to the striatum by an osmotic minipump for 28 days beginning 7 days after the initial insult. Unbiased stereological methods were used to quantify the lesion size in the striatum, the amount of neuronal loss in the substantia nigra, and the amount of microglia activation. Results: As hypothesized, CX3CL1 was able to suppress this microglia activation. The reduced microglia activation was found to be neuroprotective as the CX3CL1 treated rats had a smaller lesion volume in the striatum and importantly significantly fewer neurons were lost in the CX3CL1 treated rats. Conclusion: These findings demonstrated that CX3CL1 plays a neuroprotective role in 6-OHDA-induced dopaminergic lesion and it might be an effective therapeutic target for many neurodegenerative diseases, including Parkinson disease and Alzheimer disease, where inflammation plays an important role. Background Parkinson’s disease (PD) is a neurodegenerative disorder affecting the motor system including motor coordination and speed as well as producing rigidity and tremor. The symptoms of PD are mainly due to a progressive loss of dopaminergic neurons within the pars compacta of the substantia nigra (SNpc). This degeneration decreases the levels of the neurotransmitter dopamine in the nigrostriatal system. In the past 15 years, an increasing amount of evidence has emerged to suggest

The process of aging is linked to oxidative stress, microglial activation, and proinflammatory factors, which are known to decrease cell proliferation and limit neuroplasticity. These factors may lead the transition from normal aging to more severe cognitive dysfunction associated with neurodegenerative diseases. We have shown that natural compounds such as polyphenols from blueberry and green tea and amino acids like carnosine are high in antioxidant and antiinflammatory activity that decreases the damaging effects of reactive oxygen species (ROS), in the blood, brain, and other tissues of the body. Furthermore, we have shown that the combination of these nutrients (called NT-020) creates a synergistic effect that promotes the proliferation of stem cells in vitro and in vivo. In the current study, we examined the effects of NT-020 on neurogenesis and performance on a Morris water maze (MWM). Aged (20-month-old) male Fischer 344 rats were treated with 135.0 mg/kg per day (n = 13) of NT-020. Young (3-month-old) (n = 10) and aged (20-month-old) (n = 13) control male Fischer 344 rats were treated with water by oral gavage. All groups were treated for a period of 4 weeks. Although there was no difference in performance in the MWM when comparing all aged rats, when the data for aged impaired rats were compared, there was a significant difference between groups on the last day of training with the treatment group performing better than controls. Using the cell cycle-regulating protein (Ki67), doublecortin (DCX), and OX6 antibody markers, cell proliferation, neurogenesis, and microglial activation were estimated in the dentate gyrus (DG) of young and aged animals. Cell proliferation was also examined in the subventricular zone (SVZ). A decreased number of OX6 MHC II-positive cells, increased neurogenesis, and increased number of proliferating cells were found in rats treated with NT-020 in comparison with aged control rats. In sum, NT-020 may promote health, proliferation, and maintenance of neurons in the age animals and exert antiinflammatory actions that promote function in the aged stem cell niche.

Microglia have neuroprotective capacities, yet chronic activation can promote neurotoxic inflammation. Neuronal fractalkine (FKN), acting on CX(3)CR1, has been shown to suppress excessive microglia activation. We found that disruption in FKN/CX(3)CR1 signaling in young adult rodents decreased survival and proliferation of neural progenitor cells through IL-1β. Aged rats were found to have decreased levels of hippocampal FKN protein; moreover, interruption of CX(3)CR1 function in these animals did not affect neurogenesis. The age-related loss of FKN could be restored by exogenous FKN reversing the age-related decrease in hippocampal neurogenesis. There were no measureable changes in young animals by the addition of exogenous FKN. The results suggest that FKN/CX(3)CR1 signaling has a regulatory role in modulating hippocampal neurogenesis via mechanisms that involve indirect modification of the niche environment. As elevated neuroinflammation is associated with many age-related neurodegenerative diseases, enhancing FKN/CX(3)CR1 interactions could provide an alternative therapeutic approach to slow age-related neurodegeneration.

It is now well accepted that the brain is able to generate newborn neurons from a population of resident multipotential neural stem cells (NSCs) located in two discrete regions of the brain. The capacity for neurogenesis appears to diminish over the lifespan of an organism. Methods to potentiate the proliferation of new neuronal or glial cells within the central nervous system from resident NSCs could have therapeutic potential following an insult, such as stroke, or to replace lost cells as a result of a neurodegenerative disease. We implanted cells from a human NSC cell line, CTX0E03, originally derived from fetal cortical tissue directly into the ventricles of aged rats. CTX0E03 cells have angiogenic properties via secretion of growth factors, so we investigated if the implanted cells would stimulate proliferation of NSCs within the subgranular zone (SGZ) of the dentate gyrus. Bromodeoxyuridine staining demonstrated significantly increased proliferation in the SGZ. Absence of double labeling for human nuclear antigen suggested that the increased proliferation was from endogenous neural progenitor cells. The acute treatment also led to an increased number of immature neurons as demonstrated by immunohistochemical staining for the immature neuronal marker doublecortin. The data suggest that implants of exogenous NSCs may promote regeneration in aging organisms through stimulation of endogenous neurogenesis.

Adult hippocampal neurogenesis dramatically decreases with increasing age, and it has been proposed that this decline contributes to age-related memory deficits. Central inflammation contributes significantly to the decrease in neurogenesis associated with ageing. Interleukin-1beta is a proinflammatory cytokine initially synthesized as an inactive precursor that is cleaved by caspase-1 to generate the biologically active mature form. Whether IL-1beta affects neurogenesis in the aged hippocampus is unknown. Here we analysed cells positive for 5-bromo-2-deoxyuridine (BrdU; 50 mg/kg) in animals in which cleavage of IL-1beta was inhibited by the caspase-1 inhibitor Ac-YVAD-CMK (10 pmol). Aged (22 months) and young (4 months) rats received Ac-YVAD-CMK for 28 days intracerebroventricularly through a brain infusion cannula connected to an osmotic minipump. Starting on day 14, animals received a daily injection of BrdU for five consecutive days. Unbiased stereology analyses performed 10 days after the last injection of BrdU revealed that the total number of newborn cells generated over a 5-day period was higher in young rats than in aged rats. In addition, there was a 53% increase in the number of BrdU-labelled cells of the aged Ac-YVAD-CMK-treated rats compared to aged controls. Immunofluorescence studies were performed to identify the cellular phenotype of BrdU-labelled cells. The increase in BrdU-positive cells was not due to a change in the proportion of cells expressing neuronal or glial phenotypes in the subgranular zone. These findings demonstrate that the intracerebroventricular administration of Ac-YVAD-CMK reversed the decrease in hippocampal neurogenesis associated with ageing.

Aging is characterized by a progressive decline in the efficiency of physiological function and by the increased susceptibility to disease and death. Currently, one of the most plausible and acceptable explanations for the mechanistic basis of aging is the “free radical theory of aging.” This theory postulates that aging and its related diseases are the consequence of free radical-induced damage to cellular macromolecules and the inability to counterbalance these changes by endogenous anti-oxidant defenses. The origin of this explanation has a foundation in the “rate of living theory” [1], according to which the lifespan of an individual depends on its rate of energy utilization (metabolic rate) and on a genetically determined amount of energy consumed during adult life. Pearl [1] proposed that the longevity of an organism is inversely correlated to its mass-specific metabolic rate: increasing an organism’s metabolic rate will decrease longevity, whereas factors that decrease the metabolic rate will increase longevity. The correlation between metabolic rate and longevity has been questioned due to the exception posed by birds, which have a high metabolic rate yet live much longer than mammals [2]. However, despite their high rate of oxygen consumption, it has been shown that birds have a low rate of free radical production in brain and in other tissues; their mitochondria produce up to 10-fold fewer reactive oxygen species (ROS) in vitro [3, 4]. This observation suggests that the mitochondrial rate of free radical production may be more important than the metabolic rate in terms of longevity. Indeed, the mitochondrial rate of free radical production seems to have a much stronger correlation with maximum longevity.Harman [5] originally proposed the “free-radical theory” of aging in the mid-1950s. He suggested that free radicals produced during aerobic respiration have deleterious effects on cell components and connective tissues, causing cumulative damage over time that ultimately results in aging and death. He initially speculated that free radicals were most likely produced through reactions involving molecular oxygen catalyzed in the cells by the oxidative enzymes and enhanced by trace metals such as iron, cobalt, and manganese. The skepticism first spread around this theory was weakened by the discovery in 1969 of the enzyme superoxide dismutase (SOD) [6]. The existence of an intracellular enzyme whose sole function is to remove superoxide anions (O2−•) has provided strong biological evidence that free radicals are involved in the aging process. In 1972, Harman expanded his original studies to include the involvement of mitochondria in the physiological processes of aging [7]. Harman proposed that mitochondria generate a significant amount of cellular energy and, through consumption of most of the intracellular oxygen, set the limit on the lifespan. Approximately 90% of cellular oxygen is consumed within the mitochondria, mainly in the inner membrane, where oxidative phosphorylation occurs. Since the early 1970s, several studies have emerged to give support to this theory, and the free radical theory of aging has been expanded to the mitochondrial free radical theory of aging. The premise of the mitochondrial free radical theory of aging is that mitochondria are both producers and targets of reactive oxidative species. According to the theory, oxidative stress attacks mitochondria, leading to increased oxidative damage. As a consequence, damaged mitochondria progressively become less efficient, losing their functional integrity and releasing more oxygen molecules, increasing oxidative damage to the mitochondria, and culminating in an accumulation of dysfunctional mitochondria with age.Although the deleterious effects of free radicals in the aging process have been demonstrated, ROS also are important in maintaining homeostasis. Recent studies have shown that ROS act as an additional class of small molecules that function as cellular messengers. For example, oxidants (nitrous oxide [NO]) act as signaling molecules to promote long-term potentiation (LTP) [8]. Moreover, it has been shown that stimulation of growth factors induces the production of free radicals that are subsequently involved in regulating the proliferative response [9]. The human organism is equipped with very efficient antioxidative defense mechanisms that, among others, include antioxidative enzymes such as SOD, catalase, glutathione peroxidase, and glutathione reductase [10]. When the production of ROS is prolonged, the endogenous reserves of antioxidants become insufficient, leading to cell damage. Similarly, the production of ROS below physiological levels induces a decreased proliferative response.

Evidence suggests that tumor necrosis factor alpha (TNF) is a leading cause of dopaminergic neuronal cell death. TNF also, however, has neuroprotective effects. Thus, TNF might have a dual role following injury: immediate release after injury is protective, whereas chronic increases are detrimental. In the present study, 6-hydroxydopamine was used to lesion the dorsal striatum in male Fisher 344 rats at 2 different time points. Group 1 received a daily injection of TNFalpha antisense oligodeoxyribonucleotide (ODN) or control on days 1 through 7 post-lesion. Group 2 received a daily injection of TNF antisense ODN or control on days 5 through 15 post-lesion. Rats were killed on the day following the last injection of TNF antisense ODN. Injection of TNF antisense ODN on days 1 through 7 increased the area of the tyrosine-hydroxylase-negative zone ipsilateral to the injection when compared to controls. In contrast, when inhibition of TNF was delayed, the area of tyrosine hydroxylase loss was significantly reduced. These findings suggest that TNF release is neuroprotective in the early stages of injury but becomes neurotoxic when chronically induced.

Scientific research on the unprecedented and growing number of older adults in the United States and other industrialized countries has focused much attention on the health consequences of aging. Over the last few decades, inflammation in the brain and its implication in the progression of aging and age-related cognitive dysfunction has been an area of increasing importance to neuroscientists and is now considered as one of the most interesting and promising topics for aging research. One of the critical aspects of inflammatory processes is that the activation of one upstream inflammatory molecule initiates a cascade of self-sustaining inflammatory events which leads to the activation of a number of different downstream functions. Recently, a great deal of attention has been given to the interplay between inflammatory and apoptotic processes and the regulation of these processes by the caspases. The caspase family of proteases can be divided into proapoptotic and pro-inflammatory members. The present review summarizes recent observations of the interactions between the inflammatory cytokine interleuldn-1 (IL-1) beta and the inflammatory/apoptotic caspase-1 and their involvement in age-related impairments in cognition. A comprehensive understanding of these mechanisms could potentially lead to the development of preventive or protective therapies that reduce or inhibit the cognitive decline associated with aging and age-related neurodegenerative disease.

Disorders of sleep and wakefulness have been reported in up to 73% individuals who have experienced traumatic brain injury (TBI). Specifically, increased sleep need and excessive daytime sleepiness are often reported post-TBI. The etiology of post-TBI sleep disturbances is not well understood, and current pharmacological therapies have limited efficacy. Here, we investigate the effects of TBI on sleep-wake behavior and on hypocretin (Hcrt) and melanin-concentrating hormone (MCH), two neuropeptides important for regulating sleep and wakefulness. Adult male C57BL/6J mice ( n = 6–10/group) were implanted with EEG recording electrodes and baseline recordings were obtained. TBI was then induced using controlled cortical impact (CCI). EEG recordings were obtained from the same animals at 7 and 15 days post-surgery. Another group of animals ( n = 6–8/group) underwent sham or TBI surgery and was sacrificed 7 or 15 days later. Brains from these animals were used for immunohistochemistry to determine the number of Hcrt- or MCH-producing neurons in the hypothalamus. At 15 days post-surgery, wakefulness was decreased and NREM sleep was increased during the dark period in moderately injured animals. Moderate injury resulted in significantly fewer Hcrt-producing neurons. There were no significant differences among groups in MCH-producing neurons. Because Hcrt is an important promoter of wakefulness, the decrease in number of Hcrt-producing neurons may be one mechanism underlying the observed decrease in wakefulness and increase in NREM sleep after TBI.

Numerous reports elucidate that tissue-specific stem cells are phenotypically plastic and their differentiation pathways are not strictly delineated. Although the identity of all the epigenetic factors which may trigger stem cells to make a lineage selection are still unknown, the plasticity of adult stem cells opens new approaches for their application in the treatment of various disorders. There is increasing researcher interest in hematopoietic stem cells for treatment of not only blood-related diseases but also various unrelated disorders including neurodegenerative diseases. Human umbilical cord blood (hUCB) cells, due to their primitive nature and ability to develop into nonhematopoietic cells of various tissue lineages, including neural cells, may be useful as an alternative cell source for cell-based therapies requiring either the replacement of individual cell types and/or substitution of missing substances. Here we focus on recent findings showing the robustness of adult stem cells derived from hUCB and their potential as a source of transplant cells for the treatment of diseased or injured brains and spinal cords. Depending upon the pathological microenvironment in which the hUCB cells are introduced, neuroprotective and/or trophic effects of these cells, from release of various growth or anti-inflammatory factors to moderation of immune-inflammatory effectors, may be more likely than neural replacement. These protective effects may prove essential to maintaining restored tissue integrity over the course of various diseases or injuries.

The neuroprotective mechanism of human umbilical cord blood cells (HUCBC) in the rat middle cerebral artery occlusion (MCAO) stroke model remains uncertain. Given the inflammatory sequelae that occur following stroke, we investigated whether HUCBC protection could be derived from the modulation of this immuno-inflammatory event, suggested by the attraction of the HUCBC to the spleen. We found that, following MCAO, rat spleen size was reduced concomitantly with their CD8+ T-cell counts. Interestingly, MCAO-induced spleen size reduction correlated with the extent of ischemic damage, however, HUCBC treatment rescued the spleen weight, splenic CD8+ T-cell counts, as well as the amount of brain injury. Additionally, splenocyte proliferation assays demonstrated that HUCBC treatment opposed MCAO-associated T-cell proliferation by increasing the production of IL-10 while decreasing IFN-gamma. Taken together, these results suggest a novel immunomodulatory mechanism by which HUCBC mediate protection in the rat MCAO model of stroke.

Numerous reports elucidate that tissue-specific stem cells are phenotypically plastic and their differentiation pathways are not strictly delineated. Although the identity of all the epigenetic factors which may trigger stem cells to make a lineage selection are still unknown, the plasticity of adult stem cells opens new approaches for their application in the treatment of various disorders. There is increasing researcher interest in hematopoietic stem cells for treatment of not only blood-related diseases but also various unrelated disorders including neurodegenerative diseases. Human umbilical cord blood (hUCB) cells, due to their primitive nature and ability to develop into nonhematopoietic cells of various tissue lineages, including neural cells, may be useful as an alternative cell source for cell-based therapies requiring either the replacement of individual cell types and/or substitution of missing substances. Here we focus on recent findings showing the robustness of adult stem cells derived from hUCB and their potential as a source of transplant cells for the treatment of diseased or injured brains and spinal cords. Depending upon the pathological microenvironment in which the hUCB cells are introduced, neuroprotective and/or trophic effects of these cells, from release of various growth or anti-inflammatory factors to moderation of immune-inflammatory effectors, may be more likely than neural replacement. These protective effects may prove essential to maintaining restored tissue integrity over the course of various diseases or injuries.

When human umbilical cord blood cells (HUCBCs) are administered intravenously after a middle cerebral artery occlusion, they reliably produce behavioral and anatomical recovery, and protect neural tissue from progressive change. However, our results indicate that the cells do not exert their effects by engraftment in the peri-infarct region, even though they migrate to the site of injury. The objective of the present study was to determine if the cells induce recovery by decreasing inflammation. We used a combination of in vivo and in vitro studies to show that HUCBCs decrease inflammation in the brain after stroke and thereby enhance neuroprotection. After stroke and transplantation, there was a decrease in CD45/CD11b- and CD45/B220-positive (+) cells. This decrease was accompanied by a decrease in mRNA and protein expression of pro-inflammatory cytokines and a decrease in nuclear factor kappaB (NF-kappaB) DNA binding activity in the brain of stroke animals treated with HUCBCs. In addition to modulating the inflammatory response, we demonstrate that the cord blood cells increase neuronal survival through non-immune mechanisms. Once thought of as "cell replacement therapy," we now propose that cord blood treatment in stroke reduces inflammation and provides neuroprotection. Both of these components are necessary for effective therapy.

Impaired learning and memory is a common pathologic feature associated with numerous neurologic disorders. There is strong evidence that central inflammation contributes significantly to the progression of several neurodegenerative diseases as well as to the ageing process. For example, in aged rats an increase in interleukin-1beta (IL-1beta) is implicated in the decline of synaptic plasticity in the hippocampus and impaired performance on cognitive tasks such as contextual fear conditioning. IL-1beta is a proinflammatory cytokine initially synthesized in an inactive precursor form that is cleaved by caspase-1 to generate the biologically mature form. In the present study, cleavage of IL-1beta was chronically inhibited using a specific caspase-1 inhibitor (Ac-YVAD-CMK; 10 pmol) in both aged (22 month) and young (4 month) rats. Both groups received Ac-YVAD-CMK for 28 days intracerebroventricularly through a brain infusion cannula connected to an osmotic minipump. On day 20 the animals were trained in contextual fear conditioning, and memory for context was tested on day 22. Chronic infusion of a specific caspase-1 inhibitor in aged rats ameliorated age-related increases in hippocampal IL-1beta and improved memory for context.

Experimental, clinical, and epidemiologic studies indicate that non-steroidal anti-inflammatory drugs (NSAIDs) are beneficial in Alzheimer's disease and other neuroinflammatory processes. One possible mechanism is an interaction with peroxisome proliferator-activated receptors (PPARs). We examined the effect of a specific PPARgamma agonist, rosiglitazone, on contextual fear conditioning in aged rats. Male rats (20-months-old) were administered rosiglitazone in the diet for 2 months prior to behavioral testing. Young control and aged rats fed rosiglitazone froze significantly more than did the aged control rats in a hippocampal-dependent fear conditioning task. Rosiglitazone had no effect hippocampal interleukin-1beta levels, markers of oxidative damage, and NMDA receptor expression. Therefore, activation of PPARgamma prevented age-related deficits in hippocampal function.

Inflammatory processes in the central nervous system are thought to contribute to Alzheimer's disease (AD). Chronic administration of nonsteroidal anti-inflammatory drugs (NSAIDs) decreases the incidence of Alzheimer's disease. There are very few studies, however, on the cognitive impact of chronic NSAID administration. The N-methyl-d-aspartate (NMDA) receptor is implicated in learning and memory, and age-related decreases in the NMDA NR2B subunit correlate with memory deficits. Sulindac, an NSAID that is a nonselective cyclooxygenase (COX) inhibitor was chronically administered to aged Fischer 344 rats for 2 months. Sulindac, but not its non-COX active metabolite, attenuated age-related deficits in learning and memory as assessed in the radial arm water maze and contextual fear conditioning tasks. Sulindac treatment also attenuated an age-related decrease in the NR1 and NR2B NMDA receptor subunits and prevented an age-related increase in the pro-inflammatory cytokine, interleukin 1beta (IL-1beta), in the hippocampus. These findings support the inflammation hypothesis of aging and have important implications for potential cognitive enhancing effects of NSAIDs in the elderly.

Adult stem cells are present in many tissues including, skin, muscle, adipose, bone marrow, and in the brain. Neuroinflammation has been shown to be a potent negative regulator of stem cell and progenitor cell proliferation in the neurogenic regions of the brain. Recently we demonstrated that decreasing a key neuroinflammatory cytokine IL-1beta in the hippocampus of aged rats reversed the age-related cognitive decline and increased neurogenesis in the age rats. We also have found that nutraceuticals have the potential to reduce neuroinflammation, and decrease oxidative stress. The objectives of this study were to determine if spirulina could protect the proliferative potential of hippocampal neural progenitor cells from an acute systemic inflammatory insult of lipopolysaccharide (LPS). To this end, young rats were fed for 30 days a control diet or a diet supplemented with 0.1% spirulina. On day 28 the rats were given a single i.p. injection of LPS (1 mg/kg). The following day the rats were injected with BrdU (50 mg/kg b.i.d. i.p.) and were sacrificed 24 hours after the first injection of BrdU. Quantification of the BrdU positive cells in the subgranular zone of the dentate gyrus demonstrated a decrease in proliferation of the stem/progenitor cells in the hippocampus as a result of the LPS insult. Furthermore, the diet supplemented with spirulina was able to negate the LPS induced decrease in stem/progenitor cell proliferation. In a second set of studies we examined the effects of spirulina either alone or in combination with a proprietary formulation (NT-020) of blueberry, green tea, vitamin D3 and carnosine on the function of bone marrow and CD34+ cells in vitro. Spirulina had small effects on its own and more than additive effects in combination with NT-020 to promote mitochondrial respiration and/or proliferation of these cells in culture. When examined on neural stem cells in culture spirulina increased proliferation at baseline and protected against the negative influence of TNFalpha to reduce neural stem cell proliferation. These results support the hypothesis that a diet enriched with spirulina and other nutraceuticals may help protect the stem/progenitor cells from insults.

Background Amyotrophic Lateral Sclerosis (ALS) is a multicausal disease characterized by motor neuron degeneration in the spinal cord and brain. Cell therapy may be a promising new treatment for this devastating disorder. We recently showed that a single low dose (106 cells) of mononuclear human umbilical cord blood (MNC hUCB) cells administered intravenously to G93A mice delayed symptom progression and modestly prolonged lifespan. The aim of this pre-clinical translation study is to optimize the dose of MNC hUCB cells to retard disease progression in G93A mice. Three different doses of MNC hUCB cells, 10×106, 25×106 and 50×106, were administered intravenously into pre-symptomatic G93A mice. Motor function tests and various assays to determine cell effects were performed on these mice. Methodology/Principal Findings Our results showed that a cell dose of 25×106 cells significantly increased lifespan of mice by 20–25% and delayed disease progression by 15%. The most beneficial effect on decreasing pro-inflammatory cytokines in the brain and spinal cord was found in this group of mice. Human Th2 cytokines were found in plasma of mice receiving 25×106 cells, although prevalent human Th1 cytokines were indicated in mice with 50×106 cells. High response of splenic cells to mitogen (PHA) was indicated in mice receiving 25×106 (mainly) and 10×106 cells. Significantly increased lymphocytes and decreased neutrophils in the peripheral blood were found only in animals receiving 25×106 cells. Stable reduction in microglia density in both cervical and lumbar spinal cords was also noted in mice administered with 25×106 cells. Conclusions/Significance These results demonstrate that treatment for ALS with an appropriate dose of MNC hUCB cells may provide a neuroprotective effect for motor neurons through active involvement of these cells in modulating the host immune inflammatory system response.

Background Neurogenesis continues to occur throughout life but dramatically decreases with increasing age. This decrease is mostly related to a decline in proliferative activity as a result of an impoverishment of the microenvironment of the aged brain, including a reduction in trophic factors and increased inflammation. Results We determined that human umbilical cord blood mononuclear cells (UCBMC) given peripherally, by an intravenous injection, could rejuvenate the proliferative activity of the aged neural stem/progenitor cells. This increase in proliferation lasted for at least 15 days after the delivery of the UCBMC. Along with the increase in proliferation following UCBMC treatment, an increase in neurogenesis was also found in the aged animals. The increase in neurogenesis as a result of UCBMC treatment seemed to be due to a decrease in inflammation, as a decrease in the number of activated microglia was found and this decrease correlated with the increase in neurogenesis. Conclusion The results demonstrate that a single intravenous injection of UCBMC in aged rats can significantly improve the microenvironment of the aged hippocampus and rejuvenate the aged neural stem/progenitor cells. Our results raise the possibility of a peripherally administered cell therapy as an effective approach to improve the microenvironment of the aged brain.

Neurogenesis occurs throughout life but significantly decreases with age. Human umbilical cord blood mononuclear cells (HUCB MNCs) have been shown to increase the proliferation of neural stem cells (NSCs) in the dentate gyrus (DG) of the hippocampus and the subgranular zone of aging rats (Bachstetter et al., BMC Neurosci 9:22, 2008), but it is unclear which fraction or combination of the HUCB MNCs are responsible for neurogenesis. To address this issue, we examined the ability of HUCB MNCs, CD4+, CD8+, CD3+, CD14+, and CD133+ subpopulations to increase proliferation of NSCs both in vitro and in vivo. NSCs were first grown in conditioned media generated from HUCB cultures, and survival and proliferation of NSC were determined with the fluorescein diacetate/propidium iodide and 5-bromo-2′-deoxyuridine incorporation assays, respectively. In a second study, we injected HUCB cells intravenously in young and aged Fisher 344 rats and examined proliferation in the DG at 1 week (study 2.1) and 2 weeks (study 2.2) postinjection. The effects of the HUCB MNC fractions on dendritic spine density and microglial activation were also assessed. HUCB T cells (CD3+, CD4+, and CD8+ cells) induced proliferation of NSCs (p < 0.001) and increased cell survival. In vivo, HUCB-derived CD4+ cells increased NSC proliferation at both 1 and 2 weeks while also enhancing the density of dendritic spines at 1 week and decreasing inflammation at 2 weeks postinjection. Collectively, these data indicate that a single injection of HUCB-derived T cells induces long-lasting effects and may therefore have tremendous potential to improve aging neurogenesis.

Disorders of sleep and wakefulness occur in the majority of individuals who have experienced traumatic brain injury (TBI), with increased sleep need and excessive daytime sleepiness often reported. Behavioral and pharmacological therapies have limited efficacy, in part, because the etiology of post-TBI sleep disturbances is not well understood. Severity of injuries resulting from head trauma in humans is highly variable, and as a consequence so are their sequelae. Here, we use a controlled laboratory model to investigate the effects of TBI on sleep-wake behavior and on candidate neurotransmitter systems as potential mediators. We focus on hypocretin and melanin-concentrating hormone (MCH), hypothalamic neuropeptides important for regulating sleep and wakefulness, and two potential downstream effectors of hypocretin actions, histamine and acetylcholine. Adult male C57BL/6 mice (n=6–10/group) were implanted with EEG recording electrodes and baseline recordings were obtained. After baseline recordings, controlled cortical impact was used to induce mild or moderate TBI. EEG recordings were obtained from the same animals at 7 and 15 days post-surgery. Separate groups of animals (n=6–8/group) were used to determine effects of TBI on the numbers of hypocretin and MCH-producing neurons in the hypothalamus, histaminergic neurons in the tuberomammillary nucleus, and cholinergic neurons in the basal forebrain. At 15 days post-TBI, wakefulness was decreased and NREM sleep was increased during the dark period in moderately injured animals. There were no differences between groups in REM sleep time, nor were there differences between groups in sleep during the light period. TBI effects on hypocretin and cholinergic neurons were such that more severe injury resulted in fewer cells. Numbers of MCH neurons and histaminergic neurons were not altered under the conditions of this study. Thus, we conclude that moderate TBI in mice reduces wakefulness and increases NREM sleep during the dark period, effects that may be mediated by hypocretin-producing neurons and/or downstream cholinergic effectors in the basal forebrain., Highlights • Effects of TBI on mouse sleep-wake behavior and selected neurotransmitters were determined. • Moderate TBI decreases wakefulness and increases NREM sleep during the dark period. • Responses to moderate TBI in this model persist for at least 15 days. • Reduced wakefulness may be due to hypocretinergic and/or cholinergic dysfunction.

Background Neuroinflammation is an important secondary mechanism that is a key mediator of the long-term consequences of neuronal injury that occur in traumatic brain injury (TBI). Microglia are highly plastic cells with dual roles in neuronal injury and recovery. Recent studies suggest that the chemokine fractalkine (CX3CL1, FKN) mediates neural/microglial interactions via its sole receptor CX3CR1. CX3CL1/CX3CR1 signaling modulates microglia activation, and depending upon the type and time of injury, either protects or exacerbates neurological diseases. Methods In this study, mice deficient in CX3CR1 were subjected to mild controlled cortical impact injury (CCI), a model of TBI. We evaluated the effects of genetic deletion of CX3CR1 on histopathology, cell death/survival, microglia activation, and cognitive function for 30 days post-injury. Results During the acute post-injury period (24 h–15 days), motor deficits, cell death, and neuronal cell loss were more profound in injured wild-type than in CX3CR1−/− mice. In contrast, during the chronic period of 30 days post-TBI, injured CX3CR1−/− mice exhibited greater cognitive dysfunction and increased neuronal death than wild-type mice. The protective and deleterious effects of CX3CR1 were associated with changes in microglia phenotypes; during the acute phase CX3CR1−/− mice showed a predominant anti-inflammatory M2 microglial response, with increased expression of Ym1, CD206, and TGFβ. In contrast, increased M1 phenotypic microglia markers, Marco, and CD68 were predominant at 30 days post-TBI. Conclusion Collectively, these novel data demonstrate a time-dependent role for CX3CL1/CX3CR1 signaling after TBI and suggest that the acute and chronic responses to mild TBI are modulated in part by distinct microglia phenotypes.