Monosodium luminol reinstates redox homeostasis, improves cognition, mood and neurogenesis, and alleviates neuro- and systemic inflammation in a model of Gulf War Illness.

Enduring brain dysfunction is amid the highly manifested symptoms in veterans with Gulf War Illness (GWI). Animal studies have established that lasting brain dysfunction in GWI is concomitant with augmented oxidative stress, inflammation, and declined neurogenesis in the brain, and systemic inflammation. We hypothesize that drugs capable of restoring redox homeostasis in GWI will improve cognitive and mood function with modulation of neuroinflammation and neurogenesis. We examined the efficacy of monosodium luminol-GVT (MSL), a drug that promotes redox homeostasis, for improving cognitive and mood function in GWI rats. Young rats were exposed to GWI-related chemicals and moderate restraint stress for four weeks. Four months later, GWI rats received different doses of MSL or vehicle for eight weeks. Behavioral analyses in the last three weeks of treatment revealed that GWI rats receiving higher doses of MSL displayed better cognitive and mood function associated with reinstatement of redox homeostasis. Such restoration was evident from the normalized expression of multiple genes encoding proteins involved in combating oxidative stress in the brain and the return of several oxidative stress markers to control levels in the brain and the circulating blood. Sustained redox homeostasis by MSL also resulted in antiinflammatory and pro-neurogenic effects, which were apparent from reduced densities of hypertrophied astrocytes and activated microglia, and increased neurogenesis with augmented neural stem cell proliferation. Moreover, MSL treatment normalized the concentration of multiple proinflammatory markers in the circulating blood. Thus, MSL treatment reinstated redox homeostasis in an animal model of GWI, which resulted in alleviation of both brain and systemic inflammation, improved neurogenesis, and better cognitive and mood function.

Chronic Oxidative Stress, Mitochondrial Dysfunction, Nrf2 Activation and Inflammation in the Hippocampus Accompany Heightened Systemic Inflammation and Oxidative Stress in an Animal Model of Gulf War Illness.

Memory and mood dysfunction are the key symptoms of Gulf war illness (GWI), a lingering multi-symptom ailment afflicting >200,000 veterans who served in the Persian Gulf War-1. Research probing the source of the disease has demonstrated that concomitant exposures to anti-nerve gas agent pyridostigmine bromide (PB), pesticides, and war-related stress are among the chief causes of GWI. Indeed, exposures to GWI-related chemicals (GWIR-Cs) and mild stress in animal models cause memory and mood impairments alongside reduced neurogenesis and chronic low-level inflammation in the hippocampus. In the current study, we examined whether exposure to GWIR-Cs and stress causes chronic changes in the expression of genes related to increased oxidative stress, mitochondrial dysfunction, and inflammation in the hippocampus. We also investigated whether GWI is linked with chronically increased activation of Nrf2 (a master regulator of antioxidant response) in the hippocampus, and inflammation and enhanced oxidative stress at the systemic level. Adult male rats were exposed daily to low-doses of PB and pesticides (DEET and permethrin), in combination with 5 min of restraint stress for 4 weeks. Analysis of the hippocampus performed 6 months after the exposure revealed increased expression of many genes related to oxidative stress response and/or antioxidant activity (Hmox1, Sepp1, and Srxn1), reactive oxygen species metabolism (Fmo2, Sod2, and Ucp2) and oxygen transport (Ift172 and Slc38a1). Furthermore, multiple genes relevant to mitochondrial respiration (Atp6a1, Cox6a1, Cox7a2L, Ndufs7, Ndufv1, Lhpp, Slc25a10, and Ucp1) and neuroinflammation (Nfkb1, Bcl6, Csf2, IL6, Mapk1, Mapk3, Ngf, N-pac, and Prkaca) were up-regulated, alongside 73-88% reduction in the expression of anti-inflammatory genes IL4 and IL10, and nuclear translocation and increased expression of Nrf2 protein. These hippocampal changes were associated with elevated levels of pro-inflammatory cytokines and chemokines (Tnfa, IL1b, IL1a, Tgfb, and Fgf2) and lipid peroxidation byproduct malondialdehyde in the serum, suggesting the presence of an incessant systemic inflammation and elevated oxidative stress. These results imply that chronic oxidative stress, inflammation, and mitochondrial dysfunction in the hippocampus, and heightened systemic inflammation and oxidative stress likely underlie the persistent memory and mood dysfunction observed in GWI.

Phospholipid profiling of plasma from GW veterans and rodent models to identify potential biomarkers of Gulf War Illness.

Gulf War Illness (GWI), which affects at least one fourth of the 700,000 veterans deployed to the Gulf War (GW), is characterized by persistent and heterogeneous symptoms, including pain, fatigue and cognitive problems. As a consequence, this illness remains difficult to diagnose. Rodent models have been shown to exhibit different symptomatic features of GWI following exposure to particular GW agents (e.g. pyridostigmine bromide, permethrin and DEET) and/or stress. Preclinical analyses have shown the activation of microglia and astroglia as a pathological hallmark in these mouse and rat models. Although much has been learned in recent years from these different rodent models and independent clinical studies, characterization studies to identify overlapping features of GWI in animals and humans have been missing. Thus, we aimed to identify biomarkers that co-occur in the plasma of rodent models of GWI and human GWI patients. We observed increases of multiple phospholipid (PL) species across all studied cohorts. Furthermore, these data suggested dysfunction within ether and docosahexaenoic acid and arachidonic acid containing PL species in relation to GWI. As these PL species play a role in inflammatory processes, these findings suggest a possible role for inflammatory imbalance in GWI. Overall, we show that the peripheral lipid disturbances are present both in human GWI patients and in the preclinical rodent models of GWI, highlighting the importance of lipidomics as a potential platform for further biomarker discovery and supporting the value of GW agent exposed models of GWI.

Neural Stem Cell or Human Induced Pluripotent Stem Cell-Derived GABA-ergic Progenitor Cell Grafting in an Animal Model of Chronic Temporal Lobe Epilepsy.

Grafting of neural stem cells (NSCs) or GABA-ergic progenitor cells (GPCs) into the hippocampus could offer an alternative therapy to hippocampal resection in patients with drug-resistant chronic epilepsy, which afflicts >30% of temporal lobe epilepsy (TLE) cases. Multipotent, self-renewing NSCs could be expanded from multiple regions of the developing and adult brain, human embryonic stem cells (hESCs), and human induced pluripotent stem cells (hiPSCs). On the other hand, GPCs could be generated from the medial and lateral ganglionic eminences of the embryonic brain and from hESCs and hiPSCs. To provide comprehensive methodologies involved in testing the efficacy of transplantation of NSCs and GPCs in a rat model of chronic TLE, NSCs derived from the rat medial ganglionic eminence (MGE) and MGE-like GPCs derived from hiPSCs are taken as examples in this unit. The topics comprise description of the required materials, reagents and equipment, methods for obtaining rat MGE-NSCs and hiPSC-derived MGE-like GPCs in culture, generation of chronically epileptic rats, intrahippocampal grafting procedure, post-grafting evaluation of the effects of grafts on spontaneous recurrent seizures and cognitive and mood impairments, analyses of the yield and the fate of graft-derived cells, and the effects of grafts on the host hippocampus. © 2016 by John Wiley & Sons, Inc.

Resveratrol Treatment after Status Epilepticus Restrains Neurodegeneration and Abnormal Neurogenesis with Suppression of Oxidative Stress and Inflammation.

Antiepileptic drug therapy, though beneficial for restraining seizures, cannot thwart status epilepticus (SE) induced neurodegeneration or down-stream detrimental changes. We investigated the efficacy of resveratrol (RESV) for preventing SE-induced neurodegeneration, abnormal neurogenesis, oxidative stress and inflammation in the hippocampus. We induced SE in young rats and treated with either vehicle or RESV, commencing an hour after SE induction and continuing every hour for three-hours on SE day and twice daily thereafter for 3 days. Seizures were terminated in both groups two-hours after SE with a diazepam injection. In contrast to the vehicle-treated group, the hippocampus of animals receiving RESV during and after SE presented no loss of glutamatergic neurons in hippocampal cell layers, diminished loss of inhibitory interneurons expressing parvalbumin, somatostatin and neuropeptide Y in the dentate gyrus, reduced aberrant neurogenesis with preservation of reelin + interneurons, lowered concentration of oxidative stress byproduct malondialdehyde and pro-inflammatory cytokine tumor necrosis factor-alpha, normalized expression of oxidative stress responsive genes and diminished numbers of activated microglia. Thus, 4 days of RESV treatment after SE is efficacious for thwarting glutamatergic neuron degeneration, alleviating interneuron loss and abnormal neurogenesis, and suppressing oxidative stress and inflammation. These results have implications for restraining SE-induced chronic temporal lobe epilepsy.

Neural stem cell- and neurogenesis-related gene expression profiles in the young and aged dentate gyrus.

Hippocampal neurogenesis, important for memory and mood function, wanes greatly in old age. Studies in rat models have implied that this decrease is not due to loss of neural stem cells (NSCs) in the subgranular zone of the dentate gyrus (DG) but rather due to an increased quiescence of NSCs. Additional studies have suggested that changes in the microenvironment, particularly declines in the concentrations of neurotrophic factors, underlie this change. In this study, we compared the expression of 84 genes that are important for NSC proliferation and neurogenesis between the DG of young (4 months old) and aged (24 months old) Fischer 344 rats, using a quantitative real-time polymerase chain reaction array. Interestingly, the expression of a vast majority of genes that have been reported previously to positively or negatively regulate NSC proliferation was unaltered with aging. Furthermore, most genes important for cell cycle arrest, regulation of cell differentiation, growth factors and cytokine levels, synaptic functions, apoptosis, cell adhesion and cell signaling, and regulation of transcription displayed stable expression in the DG with aging. The exceptions included increased expression of genes important for NSC proliferation and neurogenesis (Stat3 and Shh), DNA damage response and NF-kappaB signaling (Cdk5rap3), neuromodulation (Adora1), and decreased expression of a gene important for neuronal differentiation (HeyL). Thus, age-related decrease in hippocampal neurogenesis is not associated with a decline in the expression of selected genes important for NSC proliferation and neurogenesis in the DG.

Stem/progenitor cell proliferation factors FGF-2, IGF-1, and VEGF exhibit early decline during the course of aging in the hippocampus: role of astrocytes.

Dentate neurogenesis, important for learning and memory, declines dramatically by middle age. Although studies have shown that this age-related decrease can be reversed to some extent by exogenous applications of mitogenic factors, it is unclear whether one or more of these factors exhibits decline by middle age. We hypothesize that multiple stem/progenitor cell proliferation factors exhibit early decline during the course of aging in the hippocampus, and some of these declines are linked to age-related alterations in hippocampal astrocytes. We measured the concentrations of fibroblast growth factor-2 (FGF-2), insulin-like growth factor-1 (IGF-1), and vascular endothelial growth factor (VEGF) in the hippocampus of young, middle-aged, and aged F344 rats, using enzyme-linked immunosorbent assay (ELISA). In addition, we quantified the total number of FGF-2 immunopositive (FGF-2+) and glial fibrillary acidic protein immunopositive (GFAP+) cells in the dentate gyrus and the entire hippocampus. Our results provide new evidence that the concentrations of FGF-2, IGF-1, and VEGF decline considerably by middle age but remain steady between middle age and old age. Further, decreased concentrations of FGF-2 during aging are associated with decreased numbers of FGF-2+ astrocytes. Quantification of GFAP+ cells, and GFAP and FGF-2 dual immunostaining analyses, reveal that aging does not decrease the total number of astrocytes but fractions of astrocytes that express FGF-2 decline considerably by middle age. Thus, dramatically decreased dentate neurogenesis by middle age is likely linked to reduced concentrations of FGF-2, IGF-1, and VEGF in the hippocampus, as each of these factors can individually influence the proliferation of stem/progenitor cells in the dentate gyrus. Additionally, the results demonstrate that decreased FGF-2 concentration during aging is a consequence of age-related impairment in FGF-2 synthesis by astrocytes.

Brain-derived neurotrophic factor, phosphorylated cyclic AMP response element binding protein and neuropeptide Y decline as early as middle age in the dentate gyrus and CA1 and CA3 subfields of the hippocampus.

The hippocampus is very susceptible to aging. Severely diminished dentate neurogenesis at middle age is one of the most conspicuous early changes in the aging hippocampus, which is likely linked to an early decline in the concentration of neurotrophic factors and signaling proteins that influence neurogenesis. We analyzed three proteins that are well-known to promote dentate neurogenesis and learning and memory function in the dentate gyrus and the hippocampal CA1 and CA3 subfields of young, middle-aged and aged F344 rats. These include the brain-derived neurotrophic factor (BDNF), the transcription factor phosphorylated cyclic AMP response element binding protein (p-CREB) and the neuropeptide neuropeptide Y (NPY). The BDNF was analyzed via ELISA and BDNF immunohistochemistry, the p-CREB through densitometric analysis of p-CREB immunopositive cells, and the NPY via stereological counting of NPY-immunopositive interneurons. We provide new evidence that the BDNF concentration, the p-CREB immunoreactivity and the number of NPY immunopositive interneurons decline considerably by middle age in both dentate gyrus and CA1 and CA3 subfields of the hippocampus. However, both BDNF concentration and NPY immunopositive interneuron numbers exhibit no significant decrease between middle age and old age. In contrast, the p-CREB immunoreactivity diminishes further during this period, which is also associated with reduced BDNF immunoreaction within the soma of dentate granule cells and hippocampal pyramidal neurons. Collectively, these results suggest that severely dampened dentate neurogenesis observed at middle age is linked at least partially to reduced concentrations of BDNF, p-CREB and NPY, as each of these proteins is a positive regulator of dentate neurogenesis. Dramatically diminished CREB phosphorylation (and persistently reduced levels of BDNF and NPY) at old age may underlie the learning and memory impairments observed during senescence.

Hippocampal neurotrophin levels in a kainate model of temporal lobe epilepsy: a lack of correlation between brain-derived neurotrophic factor content and progression of aberrant dentate mossy fiber sprouting.

A significant upregulation of neurotrophins particularly brain-derived neurotrophic factor (BDNF) is believed to be involved in the initiation of epileptogenic changes such as the aberrant axonal sprouting and synaptic reorganization in the injured hippocampus. However, it is unknown which of the neurotrophins are upregulated during the peak period of aberrant mossy fiber sprouting in the chronically injured hippocampus. We measured chronic changes in the levels of BDNF, nerve growth factor (NGF) and neurotrophin-3 (NT-3) in the adult hippocampus using enzyme-linked immunosorbent assay (ELISA) after a unilateral intracerebroventricular administration of kainic acid (KA), a model of temporal lobe epilepsy. For comparison, neurotrophins were also measured from the control intact hippocampus. Further, to see the association between changes in neurotrophin levels and the progression of mossy fiber sprouting, chronic changes in the mossy fiber distribution within the dentate supragranular layer (DSGL) were quantified. In the KA-lesioned hippocampus, the neurotrophins BDNF and NGF were upregulated at 4 days post-lesion, in comparison to their levels in the intact hippocampus. However, the concentration of BDNF reached the baseline level at 45 days post-lesion and dramatically diminished at 120 days post-lesion. In contrast, the upregulation of NGF observed at 4 days post-lesion was sustained at both 45 days and 120 days post-lesion. The concentration of NT-3 was upregulated at 45 days post-lesion but remained comparable to baseline levels at 4 days and 120 days post-lesion. Interestingly, analysis of mossy fiber sprouting revealed that most of the aberrant sprouting in the lesioned hippocampus occurs between 45 days and 120 days post-lesion. Taken together, these results suggest that the period of robust mossy fiber sprouting does not correlate with the phase of post-lesion BDNF upregulation. Rather, it shows a relationship with the time of upregulation of neurotrophins NGF and NT-3.

Hippocampal neurotrophin levels after injury: Relationship to the age of the hippocampus at the time of injury.

Aging impairs the competence of the hippocampus for synaptic reorganization after injury. This potentially is due to the inability of the aging hippocampus to up-regulate the critical neurotrophic factors for prolonged periods after injury to levels at which they can stimulate neurite outgrowth and facilitate synaptic reorganization. We hypothesize that the concentrations of neurotrophins in the hippocampus after injury depend on the age at the time of injury. We quantified the concentrations of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin-3 (NT-3) in the hippocampus of young, middle-aged, and aged Fischer 344 rats at 4 days after kainic acid (KA)-induced injury. In comparison with the age-matched intact hippocampus, the KA-lesioned hippocampus exhibited increased levels of BDNF and NGF in all three age groups. In contrast, the NT-3 concentration was unaltered after KA lesion. Notwithstanding similar percentage increases in BDNF after injury, the lesioned middle-aged and aged hippocampus contained 45-52% less BDNF than the lesioned young hippocampus. NGF and NT-3 levels after injury were comparable across the three age groups, however. Furthermore, lower BDNF concentration in the injured aging hippocampus was associated with normal astrocytic response but significantly diminished microglial reaction. Thus, in comparison with the injured young hippocampus, the injured aging hippocampus contains considerably less BDNF but similar levels of NGF and NT-3. Lower BDNF levels in the injured aging hippocampus might underlie the diminished spontaneous healing response observed in the aging hippocampus after injury, particularly in terms of synaptic reorganization and dentate neurogenesis.