Pathological and biochemical consequences of acute and chronic neuroinflammation within the basal forebrain cholinergic system of rats

Chronic neuroinflammation during aging leads to cholinergic neurodegeneration in the mouse medial septum

BACKGROUND

Low-grade, chronic inflammation in the central nervous system characterized by glial reactivity is one of the major hallmarks for aging-related neurodegenerative diseases like Alzheimer's disease (AD). The basal forebrain cholinergic neurons (BFCN) provide the primary source of cholinergic innervation of the human cerebral cortex and may be differentially vulnerable in various neurodegenerative diseases. However, the impact of chronic neuroinflammation on the cholinergic function is still unclear.

METHODS

To gain further insight into age-related cholinergic decline, we investigated the cumulative effects of aging and chronic neuroinflammation on the structure and function of the septal cholinergic neurons in transgenic mice expressing interleukin-6 under the GFAP promoter (GFAP-IL6), which maintains a constant level of gliosis. Immunohistochemistry combined with unbiased stereology, single cell 3D morphology analysis and in vitro whole cell patch-clamp measurements were used to validate the structural and functional changes of BFCN and their microglial environment in the medial septum.

RESULTS

Stereological estimation of MS microglia number displayed significant increase across all three age groups, while a significant decrease in cholinergic cell number in the adult and aged groups in GFAP-IL6 mice compared to control. Moreover, we observed age-dependent alterations in the electrophysiological properties of cholinergic neurons and an increased excitability profile in the adult GFAP-IL6 group due to chronic neuroinflammation. These results complimented the significant decrease in hippocampal pyramidal spine density seen with aging and neuroinflammation.

CONCLUSIONS

We provide evidence of the significant impact of both aging and chronic glial activation on the cholinergic and microglial numbers and morphology in the MS, and alterations in the passive and active electrophysiological membrane properties of septal cholinergic neurons, resulting in cholinergic dysfunction, as seen in AD. Our results indicate that aging combined with gliosis is sufficient to cause cholinergic disruptions in the brain, as seen in dementias.

Cadmium-promoted thyroid hormones disruption mediates ROS, inflammation, Aβ and Tau proteins production, gliosis, spongiosis and neurodegeneration in rat basal forebrain

Cadmium (Cd) produces cognition decline following single and repeated treatment, although the complete mechanisms are still unrevealed. Basal forebrain (BF) cholinergic neurons innervate the cortex and hippocampus, regulating cognition. Cd single and repeated exposure induced BF cholinergic neuronal loss, partly through thyroid hormones (THs) disruption, which may cause the cognition decline observed following Cd exposure. However, the mechanisms through which THs disruption mediate this effect remain unknown. To research the possible mechanisms through which Cd-induced THs deficiency may mediate BF neurodegeneration, Wistar male rats were treated with Cd for 1- (1 mg/kg) or 28-days (0.1 mg/kg) with or without triiodothyronine (T3, 40 μg/kg/day). Cd exposure promoted neurodegeneration, spongiosis, gliosis and several mechanisms related to these alterations (increased H₂0₂, malondialdehyde, TNF-α, IL-1β, IL-6, BACE1, Aβ and phosphorylated-Tau levels, and decreased phosphorylated-AKT and phosphorylated-GSK-3β levels). T3 supplementation partially reversed the effects observed. Our results show that Cd induces several mechanisms that may be responsible for the neurodegeneration, spongiosis and gliosis observed in the rats' BF, which are partially mediated by a reduction in THs levels. These data may help to explain the mechanisms through which Cd induces BF neurodegeneration, possibly leading to the cognitive decline observed, providing new therapeutic tools to prevent and treat these damages.

A novel transgenic mouse model expressing primate-specific nuclear choline acetyltransferase: insights into potential cholinergic vulnerability

The acetylcholine (ACh) synthesizing enzyme choline acetyltransferase (ChAT) is an important cholinergic neuronal marker whose levels and/or activity are reduced in physiological and pathological aging. One isoform of ChAT, 82-kDa ChAT, is expressed only in primates and found primarily in nuclei of cholinergic neurons in younger individuals, but this protein becomes mostly cytoplasmic with increasing age and in Alzheimer's disease (AD). Previous studies suggest that 82-kDa ChAT may be involved in regulating gene expression during cellular stress. Since it is not expressed in rodents, we developed a transgenic mouse model that expresses human 82-kDa ChAT under the control of an Nkx2.1 driver. Behavioral and biochemical assays were used to phenotype this novel transgenic model and elucidate the impact of 82-kDa ChAT expression. The 82-kDa ChAT transcript and protein were expressed predominantly in basal forebrain neurons and subcellular distribution of the protein recapitulated the age-related pattern found previously in human necropsy brains. Older 82-kDa ChAT-expressing mice presented with better age-related memory and inflammatory profiles. In summary, we established a novel transgenic mouse expressing 82-kDa ChAT that is valuable for studying the role of this primate-specific cholinergic enzyme in pathologies associated with cholinergic neuron vulnerability and dysfunction.

Glial cells in Alzheimer's disease: From neuropathological changes to therapeutic implications

Alzheimer's disease (AD) is a neurodegenerative disorder that usually develops slowly and progressively worsens over time. Although there has been increasing research interest in AD, its pathogenesis is still not well understood. Although most studies primarily focus on neurons, recent research findings suggest that glial cells (especially microglia and astrocytes) are associated with AD pathogenesis and might provide various possible therapeutic targets. Growing evidence suggests that microglia can provide protection against AD pathogenesis, as microglia with weakened functions and impaired responses to Aβ proteins are linked with elevated AD risk. Interestingly, numerous findings also suggest that microglial activation can be detrimental to neurons. Indeed, microglia can induce synapse loss via the engulfment of synapses, possibly through a complement-dependent process. Furthermore, they can worsen tau pathology and release inflammatory factors that cause neuronal damage directly or through the activation of neurotoxic astrocytes. Astrocytes play a significant role in various cerebral activities. Their impairment can mediate neurodegeneration and ultimately the retraction of synapses, resulting in AD-related cognitive deficits. Deposition of Aβ can result in astrocyte reactivity, which can further lead to neurotoxic effects and elevated secretion of inflammatory mediators and cytokines. Moreover, glial-induced inflammation in AD can exert both beneficial and harmful effects. Understanding the activities of astrocytes and microglia in the regulation of AD pathogenesis would facilitate the development of novel therapies. In this article, we address the implications of microglia and astrocytes in AD pathogenesis. We also discuss the mechanisms of therapeutic agents that exhibit anti-inflammatory effects against AD.

Activation of microglia and astrocytes: a roadway to neuroinflammation and Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease that is of high importance to the neuroscience world, yet the complex pathogenicity is not fully understood. Inflammation is usually observed in AD and could implicate both beneficial or detrimental effects depending on the severity of the disease. During initial AD pathology, microglia and astrocyte activation is beneficial since they are involved in amyloid-beta clearance. However, with the progression of the disease, activated microglia elicit detrimental effects by the overexpression of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) bringing forth neurodegeneration in the surrounding brain regions. This results in decline in Aβ clearance by microglia; Aβ accumulation thus increases in the brain resulting in neuroinflammation. Thus, Aβ accumulation is the effect of increased release of pro-inflammatory molecules. Reactive astrocytes acquire gain of toxic function and exhibits neurotoxic effects with loss of neurotrophic functions. Astrocyte dysfunctioning results in increased release of cytokines and inflammatory mediators, neurodegeneration, decreased glutamate uptake, loss of neuronal synapses, and ultimately cognitive deficits in AD. We discuss the role of intracellular signaling pathways in the inflammatory responses produced by astrocytes and microglial activation, including the glycogen synthase kinase-3β, nuclear factor kappa B cascade, mitogen-activated protein kinase pathways and c-Jun N-terminal kinase. In this review, we describe the role of neuroinflammation in the chronicity of AD pathogenesis and an overview of the recent research towards the development of new therapies to treat this disorder.

Adolescent binge ethanol-induced loss of basal forebrain cholinergic neurons and neuroimmune activation are prevented by exercise and indomethacin

Basal forebrain cholinergic neurons mature in adolescence coinciding with development of adult cognitive function. Preclinical studies using the rodent model of adolescent intermittent ethanol (AIE; 5.0 g/kg, i.g., 2-days on/2-days off from postnatal day [P]25 to P55) reveal persistent increases of brain neuroimmune genes that are associated with cognitive dysfunction. Adolescent intermittent ethanol exposure also reduces basal forebrain expression of choline acetyltransferase (ChAT), an enzyme critical for acetylcholine synthesis in cholinergic neurons similar to findings in the post-mortem human alcoholic basal forebrain. We report here that AIE decreases basal forebrain ChAT+IR neurons in both adult female and male Wistar rats following early or late adolescent ethanol exposure. In addition, we find reductions in ChAT+IR somal size as well as the expression of the high-affinity nerve growth factor (NGF) receptor tropomyosin receptor kinase A (TrkA) and the low-affinity NGF receptor p75NTR, both of which are expressed on cholinergic neurons. The decrease in cholinergic neuron marker expression was accompanied by increased phosphorylation of NF-κB p65 (pNF-κB p65) consistent with increased neuroimmune signaling. Voluntary wheel running from P24 to P80 prevented AIE-induced cholinergic neuron shrinkage and loss of cholinergic neuron markers (i.e., ChAT, TrkA, and p75NTR) as well as the increase of pNF-κB p65 in the adult basal forebrain. Administration of the anti-inflammatory drug indomethacin (4.0 mg/kg, i.p prior to each ethanol exposure) during AIE also prevented the loss of basal forebrain cholinergic markers and the concomitant increase of pNF-κB p65. In contrast, treatment with the proinflammatory immune activator lipopolysaccharide (1.0 mg/kg, i.p. on P70) caused a loss of cholinergic neuron markers that was paralleled by increased pNF-κB p65 in the basal forebrain. These novel findings are consistent with AIE causing lasting activation of the neuroimmune system that contributes to the persistent loss of basal forebrain cholinergic neurons in adulthood.

Molecular and Cellular Mechanisms of Sporadic Alzheimer's Disease: Studies on Rodent Models in vivo

In this review, recent data are presented on molecular and cellular mechanisms of pathogenesis of the most widespread (about 95%) sporadic forms of Alzheimer's disease obtained on in vivo rodent models. Although none of the available models can fully reproduce the human disease, several key molecular mechanisms (such as dysfunction of neurotransmitter systems, especially of the acetylcholinergic system, β-amyloid toxicity, oxidative stress, neuroinflammation, mitochondrial dysfunction, disturbances in neurotrophic systems) are confirmed with different models. Injection models, olfactory bulbectomy, and senescence accelerated OXYS rats are reviewed in detail. These three approaches to in vivo modeling of sporadic Alzheimer's disease have demonstrated a considerable similarity in molecular and cellular mechanisms of pathology development. Studies on these models provide complementary data, and each model possesses its specific advantages. A general analysis of the data reported for the three models provides a multifaceted and the currently most complete molecular picture of sporadic Alzheimer's disease. This is highly relevant also from the practical viewpoint because it creates a basis for elaboration and preclinical studies of means for treatment of this disease.

The fate of the brain cholinergic neurons in neurodegenerative diseases

The aims of this review are: 1) to describe which cholinergic neurons are affected in brain neurodegenerative diseases leading to dementia; 2) to discuss the possible causes of the degeneration of the cholinergic neurons, 3) to summarize the functional consequences of the cholinergic deficit. The brain cholinergic system is basically constituted by three populations of phenotypically similar neurons forming a series of basal forebrain nuclei, the midpontine nuclei and a large population of striatal interneurons. In Alzheimer's disease there is an extensive loss of forebrain cholinergic neurons accompanied by a reduction of the cholinergic fiber network of the cortical mantel and hippocampus. The midpontine cholinergic nuclei are spared. The same situation occurs in the corticobasal syndrome and dementia following alcohol abuse and traumatic brain injury. Conversely, in Parkinson's disease, the midpontine nuclei degenerate, together with the dopaminergic nuclei, reducing the cholinergic input to thalamus and forebrain whereas the forebrain cholinergic neurons are spared. In Parkinson's disease with dementia, Lewis Body Dementia and Parkinsonian syndromes both groups of forebrain and midpontine cholinergic nuclei degenerate. In Huntington's disease a dysfunction of the striatal cholinergic interneurons without cell loss takes place. The formation and accumulation of misfolded proteins such as β-amyloid oligomers and plaques, tau protein tangles and α-synuclein clumps, and aggregated mutated huntingtin play a crucial role in the neuronal degeneration by direct cellular toxicity of the misfolded proteins and through the toxic compounds resulting from an extensive inflammatory reaction. Evidences indicate that β-amyloid disrupts NGF metabolism causing the degeneration of the cholinergic neurons which depend on NGF for their survival, namely the forebrain cholinergic neurons, sparing the midpontine and striatal neurons which express no specific NGF receptors. It is feasible that the latter cholinergic neurons may be damaged by direct toxicity of tau, α-synuclein and inflammations products through mechanisms not fully understood. Attention and learning and memory impairment are the functional consequences of the forebrain cholinergic neuron dysfunction, whereas the loss of midpontine cholinergic neurons results primarily in motor and sleep disturbances.

MicroRNA: Small RNA mediators of the brains genomic response to environmental stress

The developmental processes that establish the synaptic architecture of the brain while retaining capacity for activity-dependent remodeling, are complex and involve a combination of genetic and epigenetic influences. Dysregulation of these processes can lead to problems with neural circuitry which manifest in humans as a range of neurodevelopmental syndromes, such as schizophrenia, bipolar disorder and fragile X mental retardation. Recent studies suggest that prenatal, postnatal and intergenerational environmental factors play an important role in the aetiology of stress-related psychopathology. A number of these disorders have been shown to display epigenetic changes in the postmortem brain that reflect early life experience. These changes affect the regulation of gene expression though chromatin remodeling (transcriptional) and post-transcriptional influences, especially small noncoding microRNA (miRNA). These dynamic and influential molecules appear to play an important function in both brain development and its adaption to stress. In this review, we examine the role of miRNA in mediating the brain's response to both prenatal and postnatal environmental perturbations and explore how stress- induced alterations in miRNA expression can regulate the stress response via modulation of the immune system. Given the close relationship between environmental stress, miRNA, and brain development/function, we assert that miRNA hold a significant position at the molecular crossroads between neural development and adaptations to environmental stress. A greater understanding of the dynamics that mediate an individual's predisposition to stress-induced neuropathology has major human health benefits and is an important area of research.

Lipopolysaccharides upregulate hepcidin in neuron via microglia and the IL-6/STAT3 signaling pathway

Neuroinflammation is closely related to brain iron homeostasis. Our previous study demonstrated that lipopolysaccharides (LPS) can regulate expression of iron-regulatory peptide hepcidin; however, the mechanism is undefined. Here, we demonstrated that intracerebroventricular injection of LPS in rat brain upregulated hepcidin and downregulated ferroportin 1 in the cortex and substantia nigra. LPS increased hepcidin expression in neurons only when they were co-cultured with BV-2 microglia, and the upregulation was suppressed by IL-6 neutralizing antibody in vitro. In addition, IL-6 but not IL-1α, IL-1β, or tumor necrosis factor-alpha increased hepcidin expression and signal transducer and activator of transcription 3 (STAT3) phosphorylation in cortical neurons and MES23.5 dopaminergic neurons. These effects were blocked by the STAT3 inhibitor, stattic. Our results show that neurons are the major source of increased hepcidin expression in response to LPS challenge but microglia play a key mediator role by releasing IL-6 and recruiting the STAT3 pathway. We conclude that LPS upregulates hepcidin expression in neurons via microglia and the IL-6/STAT3 signaling pathway.

Biomarkers of postoperative delirium and cognitive dysfunction

Elderly surgical patients frequently experience postoperative delirium (POD) and the subsequent development of postoperative cognitive dysfunction (POCD). Clinical features include deterioration in cognition, disturbance in attention and reduced awareness of the environment and result in higher morbidity, mortality and greater utilization of social financial assistance. The aging Western societies can expect an increase in the incidence of POD and POCD. The underlying pathophysiological mechanisms have been studied on the molecular level albeit with unsatisfying small research efforts given their societal burden. Here, we review the known physiological and immunological changes and genetic risk factors, identify candidates for further studies and integrate the information into a draft network for exploration on a systems level. The pathogenesis of these postoperative cognitive impairments is multifactorial; application of integrated systems biology has the potential to reconstruct the underlying network of molecular mechanisms and help in the identification of prognostic and diagnostic biomarkers.

Interaction of basal forebrain cholinergic neurons with the glucocorticoid system in stress regulation and cognitive impairment

A substantial number of studies on basal forebrain (BF) cholinergic neurons (BFCN) have provided compelling evidence for their role in the etiology of stress, cognitive aging, Alzheimer’s disease (AD), and other neurodegenerative diseases. BFCN project to a broad range of cortical sites and limbic structures, including the hippocampus, and are involved in stress and cognition. In particular, the hippocampus, the primary target tissue of the glucocorticoid stress hormones, is associated with cognitive function in tandem with hypothalamic-pituitary-adrenal (HPA) axis modulation. The present review summarizes glucocorticoid and HPA axis research to date in an effort to establish the manner in which stress affects the release of acetylcholine (ACh), glucocorticoids, and their receptor in the context of cognitive processes. We attempt to provide the molecular interactive link between the glucocorticoids and cholinergic system that contributes to BFCN degeneration in stress-induced acceleration of cognitive decline in aging and AD. We also discuss the importance of animal models in facilitating such studies for pharmacological use, to which could help decipher disease states and propose leads for pharmacological intervention.

Systemic inflammation, blood-brain barrier vulnerability and cognitive/non-cognitive symptoms in Alzheimer disease: relevance to pathogenesis and therapy

The incidence of dementia is increasing at an alarming rate, and has become a major public health concern. Alzheimer disease (AD) is the most common form of dementia and is characterized by progressive cognitive impairment. In addition to classical neuropathological features such as amyloid plaques and neurofibrillary tangles (NFT), accumulation of activated immune cells has been documented in the AD brain, suggesting a contribution of neuroinflammation in the pathogenesis of AD. Besides cognitive deterioration, non-cognitive symptoms, such as agitation, aggression, depression and psychosis, are often observed in demented patients, including those with AD, and these neuropsychological symptoms place a heavy burden on caregivers. These symptoms often exhibit sudden onset and tend to fluctuate over time, and in many cases, they are triggered by an infection in peripheral organs, suggesting that inflammation plays an important role in the pathogenesis of these non-cognitive symptoms. However, there is no mechanistic explanation for the relationship between inflammation and neuropsychiatric symptoms. Observations from experimental mouse models indicate that alteration of brain blood vessels, especially blood-brain barrier (BBB) dysfunction, may contribute to the relationship. The current review summarizes the results from recent studies on the relationship between inflammation and AD, while focusing on cerebrovascular alterations, which might provide an insight into the pathogenesis of cognitive/non-cognitive symptoms in AD patients and suggest a basis for the development of new therapeutic treatments for these conditions.

The association between C-reactive protein and delirium in 710 acute elderly hospital admissions

BACKGROUND

Delirium is a common neuropsychiatric syndrome associated with poor outcomes. Evidence supports a neuroinflammatory etiology, but the role of the inflammatory marker C-reactive protein (C-RP) remains unclear. We investigated the relationship between C-RP and delirium and its severity as well as interaction with medical diagnosis.

METHODS

From an existing database (710 patients over 70 years old admitted to a Medical Acute Admissions Unit) we analyzed data which included C-RP levels, delirium (using the Confusion Assessment Method), and other clinical and demographic factors. Primary diagnoses were grouped (cardiovascular, musculoskeletal, infection, metabolic, and other).

RESULTS

There was a strong association between elevated C-RP and delirium (t = 5.09; p < 0.001), independent of other potential risk factors for delirium (odds ratio (OR) = 1.32 (95% CI: 1.10-1.58) p = 0.003). There was no significant association between C-RP and delirium severity, and between C-RP and delirium in the populations with cardiovascular disease, infection upon admission, or from the metabolic group despite an OR of 2.24 (95% CI: 0.92-5.45). There was an association in the musculoskeletal group (OR 2.19 (95% CI: 1.19-4.02)).

CONCLUSIONS

There is an association between elevated C-RP and delirium. This is strongest in patients admitted with musculoskeletal disease but not in others, implying that C-RP is involved in the genesis of delirium in musculoskeletal disease, but that other factors or processes may be more important in those with cardiovascular disease or infection.

Bacterial lipopolysaccharide induces a dose-dependent activation of neuroglia and loss of basal forebrain cholinergic cells in the rat brain

In a rat model of neuroinflammation induced with a low-dose infusion lipopolysaccharide (5.0 ng/hr, LPS), we reported that brain arachidonic acid (ARA, 20:4 n-6), but not docosahexaenoic acid (DHA, 22:6n-3), metabolism is increased compared to control rats. To further characterize the impact LPS has on the induction of injury in this model, we quantified the dose-dependent activation of neuroglia and the loss of cholinergic cells in rats subjected to increasing doses of LPS. In this study, we found that LPS produced a statistically significant and linear dose-dependent increase in the percentage of activated CD11b-positive microglia ranging from 26% to 82% following exposure to doses ranging between 0.05 and 500 ng/hr, respectively. The percentage of activated GFAP-positive astrocytes also increased linearly and significantly from 35% to 91%. Significant astroglial scaring was evident at the lateral ventricular boarder of rats treated with 50 and 500 ng/hr LPS, but not evident in control treated rats or rats treated with lower doses of LPS. A dose-dependent decrease in the numbers of ChAT-positive cells in the basal forebrain of LPS-treated rats was found at higher doses of LPS (5, 50, and 500 ng/hr) but not at lower doses. The numbers of ChAT-positive cells within individual regions of the basal forebrain (medial septum and diagonal bands) and the composite basal forebrain were similar in their response. These data demonstrate that extremely low doses of LPS are sufficient to induce significant neuroglia activation while moderate doses above 5.0 ng/hr are required to induce cholinergic cell loss.

Age and duration of inflammatory environment differentially affect the neuroimmune response and catecholaminergic neurons in the midbrain and brainstem

Neuroinflammation and degeneration of ascending catecholaminergic systems occur early in the neurodegenerative process. Age and the duration of a pro-inflammatory environment induced by continuous intraventricular lipopolysaccharide (LPS) differentially affect the expression profile of pro- and anti-inflammatory genes and proteins as well as the number of activated microglia (express major histocompatibility complex II; MHC II) and the integrity and density of ascending catecholaminergic neural systems originating from the locus coeruleus (LC) and substantia nigra pars compacta (SNpc) in rats. LPS infusion increased gene expression and/or protein levels for both pro- and anti-inflammatory biomarkers. Although LPS infusion stimulated a robust increase in IL-1ß gene and protein expression, this increase was blunted with age. LPS infusion also increased the density of activated microglia cells throughout the midbrain and brainstem. Corresponding to the development of a pro-inflammatory environment, LC and SNpc neurons immunopositive for tyrosine-hydroxylase (the rate-limiting synthetic enzyme for dopamine and norepinephrine) decreased in number, along with a decrease in tyrosine-hydroxylase gene expression in the midbrain and/or brainstem region. Our data support the concept that continuous exposure to a pro-inflammatory environment drives exaggerated changes in the production and release of inflammatory mediators that interact with age to impair functional capacity of the SNpc and LC.

Lipopolysaccharide-induced blood brain barrier permeability is enhanced by alpha-synuclein expression

Because α-synuclein (Snca) is involved in neuroinflammatory response, we determined if its expression altered blood-brain barrier (BBB) permeability. To induce increased BBB permeability, Snca gene-ablated (KO) and wild-type (WT) mice were injected (i.p.) with lipopolysaccharide (LPS). To assess changes in BBB permeability, Evans blue was injected (i.p.) and extravasation into the brain assessed using fluorescence spectroscopy. WT mice had a significant increase in BBB permeability at 1, 3, and 6h post-injection of LPS relative to untreated mice. Contrary to WT mice, LPS did not induce a time-dependent change in BBB permeability in KO mice. Although brain edema is associated with increased BBB permeability, no significant difference in edema was found between groups. These results show that Snca expression is associated with increased reactive opening of the BBB in response to LPS.

Association between intraoperative blood transfusions and early postoperative delirium in older adults

OBJECTIVES

To determine whether intraoperative blood transfusion, a known trigger and amplifier of inflammation, is an independent risk factor for early postoperative delirium (POD), an acute state of confusion with fluctuating consciousness and inattention after surgery, in older adults undergoing surgery.

DESIGN

Secondary analysis using a database created for a prospective cognitive outcomes study.

SETTING

University hospital.

PARTICIPANTS

Four hundred seventy-two individuals aged 65 and older undergoing major noncardiac surgery.

MEASUREMENTS

Perioperative data were examined for association with POD on the first postoperative day. Multivariable logistic regression analysis was conducted to determine whether intraoperative blood transfusion independently predicts POD after adjusting for covariates known to be associated with onset of delirium and blood transfusions.

RESULTS

One hundred thirty-seven individuals (29%) developed delirium on the first postoperative day. The multivariable logistic regression model identified age, sex, history of central nervous system disorder, preoperative cognitive dysfunction, and pain, as well as blood transfusions, as independent risk factors for POD. Intraoperative administration of more than 1,000 mL of red blood cells (RBCs) was the strongest predictor of POD on the first postoperative day (odds ratio = 3.68; 95% confidence interval = 1.32–10.94; P < .001).

CONCLUSION

Intraoperative blood transfusion of more than 1,000 mL of RBCs increases the risk of delirium on the first postoperative day in older adults undergoing noncardiac surgery.

Sevoflurane anesthesia in pregnant mice induces neurotoxicity in fetal and offspring mice

BACKGROUND

Each year, over 75,000 pregnant women in the United States undergo anesthesia care. The authors set out to assess the effects of the anesthetic sevoflurane on neurotoxicity in pregnant mice and on learning and memory in fetal and offspring mice.

METHODS

Pregnant mice (gestational day 14) and mouse primary neurons were treated with 2.5% sevoflurane for 2 h and 4.1% sevoflurane for 6 h, respectively. Brain tissues of both fetal and offspring mice (P31) and the primary neurons were harvested and subjected to Western blot and immunohistochemistry to assess interleukin-6, the synaptic markers postsynaptic density-95 and synaptophysin, and caspase-3 levels. Separately, learning and memory function in the offspring mice was determined in the Morris water maze.

RESULTS

Sevoflurane anesthesia in pregnant mice induced caspase-3 activation, increased interleukin-6 levels (256 ± 50.98% [mean ± SD] vs. 100 ± 54.12%, P = 0.026), and reduced postsynaptic density-95 (61 ± 13.53% vs. 100 ± 10.08%, P = 0.036) and synaptophysin levels in fetal and offspring mice. The sevoflurane anesthesia impaired learning and memory in offspring mice at P31. Moreover, interleukin-6 antibody mitigated the sevoflurane-induced reduction in postsynaptic density-95 levels in the neurons. Finally, environmental enrichment attenuated the sevoflurane-induced increases in interleukin-6 levels, reductions of synapse markers, and learning and memory impairment.

CONCLUSIONS

These results suggest that sevoflurane may induce detrimental effects in fetal and offspring mice, which can be mitigated by environmental enrichment. These findings should promote more studies to determine the neurotoxicity of anesthesia in the developing brain.

Regional sensitivity to neuroinflammation: in vivo and in vitro studies

BACKGROUND

Neuroinflammation is involved in several acute-onset neuropathologies such as meningitis, encephalitis, stroke, and traumatic brain injury as well as in neurodegenerative diseases. All of these patholologies are associated with cognitive deficits. Using a model of pure neuroinflammation (intracisternal injection of endotoxin in mice), we tested the hypothesis that brain regions involved in cognition are the most vulnerable to inflammatory insults, and this vulnerability is an inherent property of neocortical neurons.

METHODS

Mice (n = 10/group) injected with endotoxin (LPS) or saline in the cisterna magna underwent neurobehavioral and cognitive testing followed by quantitative autoradiographic assessment of regional neuroinflammation with [3H]PK11195, an established marker of microgliosis. In parallel, cocultures of cortical and striatal neurons taken from embryonic day 19 rat embryos or postnatal day 1 mice expressing green fluorescent protein were exposed for 24 h to the proinflammatory cytokine TNFalpha, glutamate, or a combination of the two agents.

RESULTS

LPS-treated mice exhibited significant deficits in memory and significant increases in specific PK11195 binding in cortical and hippocampal regions, but not in striatum. Cultured neurons of cortical origin showed significantly lower survival rate relative to striatal neurons in response to TNFalpha, glutamate, or a combination of the two agents. Furthermore, TNFalpha exerted neuroprotective rather than neurotoxic effects in the striatal but not in the cortical neurons.

CONCLUSIONS

These results suggest that the cortex is inherently more sensitive than the striatum to the deleterious effects of neuroinflammation, and may offer an explanation for the preponderance of cognitive deficits in neuropathologies with a neuroinflammatory component.

Acetate supplementation attenuates lipopolysaccharide-induced neuroinflammation

Glyceryl triacetate (GTA), a compound effective at increasing circulating and tissue levels of acetate was used to treat rats subjected to a continual 28 day intra-ventricular infusion of bacterial lipopolysaccharide (LPS). This model produces a neuroinflammatory injury characterized by global neuroglial activation and a decrease in choline acetyltransferase immunoreactivity in the basal forebrain. During the LPS infusion, rats were given a daily treatment of either water or GTA at a dose of 6 g/kg by oral gavage. In parallel experiments, free-CoA and acetyl-CoA levels were measured in microwave fixed brains and flash frozen heart, liver, kidney and muscle following a single oral dose of GTA. We found that a single oral dose of GTA significantly increased plasma acetate levels by 15 min and remained elevated for up to 4 h. At 30 min the acetyl-CoA levels in microwave-fixed brain and flash frozen heart and liver were increased at least 2.2-fold. The concentrations of brain acetyl-CoA was significantly increased between 30 and 45 min following treatment and remained elevated for up to 4 h. The concentration of free-CoA in brain was significantly decreased compared to controls at 240 min. Immunohistochemical and morphological analysis demonstrated that a daily treatment with GTA significantly reduced the percentage of reactive glial fibrillary acidic protein-positive astrocytes and activated CD11b-positive microglia by 40-50% in rats subjected to LPS-induced neuroinflammation. Further, in rats subjected to neuroinflammation, GTA significantly increased the number of choline acetyltransferase (ChAT)-positive cells by 40% in the basal forebrain compared to untreated controls. These data suggest that acetate supplementation increases intermediary short chain acetyl-CoA metabolism and that treatment is potentially anti-inflammatory and neuroprotective with regards to attenuating neuroglial activation and increasing ChAT immunoreactivity in this model.

The galanin peptide family in inflammation

The immune system defends the organism against invading pathogens. In recent decades it became evident that elimination of such pathogens, termination of inflammation, and restoration of host homeostasis all depend on bidirectional crosstalk between the immune system and the neuroendocrine system. This crosstalk is mediated by a complex network of interacting molecules that modulates inflammation and cell growth. Among these mediators are neuropeptides released from neuronal and non-neuronal components of the central and peripheral nervous systems, endocrine tissues, and cells of the immune system. Neuropeptide circuitry controls tissue inflammation and maintenance, and an imbalance of pro- and anti-inflammatory neuropeptides results in loss of host homeostasis and triggers inflammatory diseases. The galanin peptide family is undoubtedly involved in the regulation of inflammatory processes, and the aim of this review is to provide up-to-date knowledge from the literature concerning the regulation of galanin and its receptors in the nervous system and peripheral tissues in experimental models of inflammation. We also highlight the effects of galanin and other members of the galanin peptide family on experimentally induced inflammation and discuss these data in light of an anti-inflammatory role for this family of peptides.

Neuroinflammation not associated with cholinergic degeneration in aged-impaired brain

Degeneration of the cholinergic neurons in the basal forebrain and elevation of inflammatory markers are well-established hallmarks of Alzheimer's disease; however, the interplay of these processes in normal aging is not extensively studied. Consequently, we conducted a neuroanatomical investigation to quantify cholinergic neurons and activated microglia in the medial septum/vertical diagonal band (MS/VDB) of young (6 months) and aged (28 months) Fisher 344 × Brown Norway F(1) rats. Aged rats in this study were impaired relative to the young animals in spatial learning ability as assessed in the Morris water maze. Stereological analysis revealed no difference between aged and young rats in the total numbers of cholinergic neurons, demonstrating that loss of cholinergic neurons is not a necessary condition to observe impaired spatial learning in aged rats. In this same region, the total number of activated microglia was substantially greater in aged rats relative to young rats. Jointly, these data demonstrate that aging is characterized by an increase in the basal inflammatory state within the MS/VDB, but this inflammation is not associated with cholinergic neuron death.

Systemic infection and delirium: when cytokines and acetylcholine collide

Systemic infection and drugs with anticholinergic effects are well-recognised and prevalent risk factors for delirium in elderly people. Experimental findings and neuropathological observations suggest that activation of microglia is pivotal for mediation of the behavioural effects of systemic infections. The microglial response is usually regulated tightly, but defensive features could turn neurotoxic once microglial cells escape from cholinergic inhibition. A self-propelling neuroinflammatory reaction might follow, and this cascade could account for the strong association between delirium and long-term cognitive impairment and even dementia. Here, we propose a hypothetical model, suggesting that poor outcome after delirium can be averted in vulnerable elderly people by use of readily available drugs. Agents that either restore cholinergic control of microglia or directly inhibit neuroinflammation warrant testing in clinical trials.

Rat brain docosahexaenoic acid metabolism is not altered by a 6-day intracerebral ventricular infusion of bacterial lipopolysaccharide

In a rat model of neuroinflammation, produced by a 6-day intracerebral ventricular infusion of bacterial lipopolysaccharide (LPS), we reported that the brain concentrations of non-esterified brain arachidonic acid (AA, 20:4 n-6) and its eicosanoid products PGE(2) and PGD(2) were increased, as were AA turnover rates in certain brain phospholipids and the activity of AA-selective cytosolic phospholipase A(2) (cPLA(2)). The activity of Ca(2+)-independent iPLA(2), which is thought to be selective for the release of docosahexaenoic acid (DHA, 22:6 n-3) from membrane phospholipid, was unchanged. In the present study, we measured parameters of brain DHA metabolism in comparable artificial cerebrospinal fluid (control) and LPS-infused rats. In contrast to the reported changes in markers of AA metabolism, the brain non-esterified DHA concentration and DHA turnover rates in individual phospholipids were not significantly altered by LPS infusion. The formation rates of AA-CoA and DHA-CoA in a microsomal brain fraction were also unaltered by the LPS infusion. These observations indicate that LPS-treatment upregulates markers of brain AA but not DHA metabolism. All of which are consistent with other evidence that suggest different sets of enzymes regulate AA and DHA recycling within brain phospholipids and that only selective increases in brain AA metabolism occur following a 6-day LPS infusion.

Cholinergic protection via alpha7 nicotinic acetylcholine receptors and PI3K-Akt pathway in LPS-induced neuroinflammation

The present study was planned to investigate the effect of anti-cholinesterase drugs donepezil and neostigmine on neuroinflammation induced by intracerebroventricular administration of lipopolysaccharide (LPS, 50 microg) in rat. Proinflammatory cytokines (TNF-alpha and IL-1beta), expressions of iNOS and COX-2, acetylcholinesterase activity, malondialdehyde and reduced glutathione were studied in different brain regions at 24h of LPS injection. Donepezil was found to decrease the LPS-induced AChE activity and oxidative stress in all the brain regions. It also inhibited the LPS-induced proinflammatory cytokines and iNOS expression but did not affect the increased COX-2 expression whereas neostigmine treatment had no effect on LPS-induced proinflammatory cytokines. Methyllycaconitine (MLA), a alpha7 nicotinic acetylcholine receptor antagonist, significantly antagonized the donepezil mediated inhibition of LPS-induced proinflammatory cytokines, indicating that alpha7 nicotinic acetylcholine receptor subunit was playing a role in regulation of neuroinflammation. The phosphorylation of Akt, an effector of PI3K, increased with donepezil treatment. These results suggest that increased cholinergic activity in brain by donepezil prevents LPS-induced neuroinflammation via alpha7-nAChRs, followed by the PI3K-Akt pathway and this system may form the basis for the development of novel agents for reversing neuroinflammation or provide new indications for existing drugs.

Influence of LPS-induced neuroinflammation on acetylcholinesterase activity in rat brain

In the present study, neuroinflammation was induced by bilateral intracerebroventricular (ICV) administration of Lipopolysaccharide (LPS). Proinflammatory cytokines (TNF-alpha and IL-1beta), acetylcholinesterase (AChE) activity, malondialdehyde (MDA) and reduced glutathione (GSH) were studied as markers for neuroinflammation, cholinergic activity and oxidative stress respectively in different brain regions at different time points after LPS injection. LPS produced increase in proinflammatory cytokines, MDA and the decrease in level of GSH at 24 h indicating a state of inflammation in brain regions, which was significantly blocked by Ibuprofen, a non steroidal anti-inflammatory drug. Enhanced AChE activity with these inflammatory markers after LPS administration indicates a possible relationship between neuroinflammation and cholinergic system during the development of neurodegenerative diseases.

Cholinergic deficiency hypothesis in delirium: a synthesis of current evidence

Deficits in cholinergic function have been postulated to cause delirium and cognitive decline. This review examines current understanding of the cholinergic deficiency hypothesis in delirium by synthesizing evidence on potential pathophysiological pathways. Acetylcholine synthesis involves various precursors, enzymes, and receptors, and dysfunction in these components can lead to delirium. Insults to the brain, like ischemia and immunological stressors, can precipitously alter acetylcholine levels. Imbalances between cholinergic and other neurotransmitter pathways may result in delirium. Furthermore, genetic, enzymatic, and immunological overlaps exist between delirium and dementia related to the cholinergic pathway. Important areas for future research include identifying biomarkers, determining genetic contributions, and evaluating response to cholinergic drugs in delirium. Understanding how the cholinergic pathway relates to delirium may yield innovative approaches in the diagnosis, prevention, and treatment of this common, costly, and morbid condition.

Cholinergic status modulations in human volunteers under acute inflammation

Cholinergic Status, the total soluble circulation capacity for acetylcholine hydrolysis, was tested for putative involvement in individual variabilities of the recruitment of immune cells in response to endotoxin challenge. Young (average age 26) and elderly (average age 70) volunteers injected with either Escherichia coli endotoxin or saline on two different occasions were first designated Enhancers and Suppressors if they showed increase or decrease, respectively, in plasma acetylcholinesterase (AChE) activity 1.5 h after endotoxin administration compared to saline. Enhancers showed significant co-increases in plasma butyrylcholinesterase (BChE) and paraoxonase (PON1) activities, accompanied by rapid recovery of lymphocyte counts. Young Enhancers alone showed pronounced post-exposure increases in the pro-inflammatory cytokine interleukin-6 (IL-6), and upregulation of the normally rare, stress-induced AChE-R variant, suggesting age-associated exhaustion of the cholinergic effects on recruiting innate immune reactions to endotoxin challenge. Importantly, IL-6 injected to young volunteers or administered in vitro to primary mononuclear blood cells caused upregulation of AChE, but not BChE or PON1, excluding it from being the sole cause for this extended response. Interestingly, Suppressors but not Enhancers showed improved post-exposure working memory performance, indicating that limited cholinergic reactions may be beneficial for cognition. Our findings establish Cholinergic Status modulations as early facilitators and predictors of individual variabilities in the peripheral response to infection.

Cytokines and acute phase response in delirium

OBJECTIVE

This study aimed to examine the expression patterns of pro- and anti-inflammatory cytokines in elderly patients with and without delirium who were acutely admitted to the hospital.

METHODS

All consecutive patients aged 65 years and older, who were acutely admitted to the Department of Internal Medicine of the Academic Medical Center, Amsterdam, a tertiary university teaching hospital, were invited. Members of the geriatric consultation team completed a multidisciplinary evaluation for all study participants within 48 h after admission, including cognitive and functional examination by validated measures of delirium, memory, and executive function. C-reactive protein and cytokines (IL-1beta, IL-6, TNF-alpha, IL-8, and IL-10) were determined within 3 days after admission.

RESULTS

In total, 185 patients were included; mean age was 79 years; 42% were male; and 34.6% developed delirium within 48 h after admission. Compared to patients without delirium, patients with delirium were older and had experienced preexistent cognitive impairment more often. In patients with delirium, significantly more IL-6 levels (53% vs. 31%) and IL-8 levels (45% vs. 22%) were above the detection limit as compared with patients who did not have delirium. After adjusting for infection, age, and cognitive impairment, these differences were still significant.

CONCLUSIONS

Proinflammatory cytokines may contribute to the pathogenesis of delirium in acutely admitted elderly patients.

Potent anti-inflammatory activity of 3-aminovinylphosphonates as inhibitors of reactive oxygen intermediates, nitric oxides generation, and tumor necrosis factor-alpha release

Two 3-aminoalkenylphosphonate compounds 1, 2, and a hydroxyl derivative, 2-(3-hydroxy-3-phenylpropyl)hex-1-enylphosphonate 3, recently synthesized in our lab, have been evaluated for their ability to modulate the production of reactive oxygen intermediates, nitric oxide (NO) and tumor necrosis factor (TNF-alpha) by murine macrophages. We found that all three molecules suppressed generation of reactive oxygen intermediates, NO, and TNF-alpha. However, although 2-(3-hydroxy-3-phenylpropyl)hex-1-enylphosphonate 3 possessed higher activity in suppression of reactive oxygen intermediates and nitric oxide compared to 3-aminoalkenylphosphonates 1 and 2, it showed less activity in the inhibition of tumor necrosis factor release.

Potential role of N-methyl-D-aspartate receptors as executors of neurodegeneration resulting from diverse insults: focus on memantine

Glutamatergic neurotransmission is critical to normal learning and memory and when the activity of glutamate neurons becomes excessive, or the normal function of its primary receptors becomes dysfunctional, this may lead to pathological changes associated with age-related neurodegenerative diseases. Anomalous glutamatergic activity associated with Alzheimer's disease may be due to a postsynaptic receptor and downstream defects that produce inappropriately timed or sustained glutamate activation of N-methyl-D-aspartate receptors, leading to neuronal injury and death and cognitive deficits associated with dementia. The mechanisms leading to the condition of chronically depolarized membranes on vulnerable neurons in the Alzheimer's disease brain are likely due to a complex interaction between oxidative stress, mitochondrial failure, chronic brain inflammation and the presence of amyloid-beta and hyperphosphorylated-tau; each of these factors are highly interrelated with each other and are discussed with an emphasis upon potential therapeutic mechanisms underlying the neuroprotective actions of memantine.

Long-term cognitive impairment, neuronal loss and reduced cortical cholinergic innervation after recovery from sepsis in a rodent model

Sepsis is a disease with a high and growing prevalence worldwide. Most studies on sepsis up to date have been focused on reduction of short-term mortality. This study investigates cognitive and neuroanatomical long-term consequences of sepsis in a rat model. Sepsis was induced in male Wistar rats weighing 250-300 g by an i.p. injection of bacterial lipopolysaccharide (LPS, 10 mg/kg). Three months after complete recovery from sepsis, animals showed memory deficits in the radial maze and changes in open field exploratory patterns but unaffected inhibitory avoidance learning. Behavioral findings were matched by sepsis-induced loss of neurons in the hippocampus and the prefrontal cortex on serial sections after NeuN-staining and reduced cholinergic innervation in the parietal cortex measured by immunoradiography of vesicular acetylcholine transporter (VAChT). Together these results suggest that sepsis can induce persistent behavioral and neuroanatomical changes and warrant studies of the neurological long-term consequences of sepsis in humans.

Interaction of interleukin-1beta with muscarinic acetylcholine receptor-mediated signaling cascade in cholinergically differentiated SH-SY5Y cells

Increased expression of interleukin (IL)-1beta has been found in Alzheimer brain, raising the question whether plaque-associated up-regulation of IL-1beta may contribute to neurodegeneration. IL-1beta is capable to induce a number of events that also occur in Alzheimer's disease such as stimulation of the amyloidogenic pathway of amyloid precursor protein processing. However, less is known on participation of IL-1beta in specific cholinergic cell loss. To reveal whether IL-1beta affects muscarinic acetylcholine receptor (mAChR)-mediated intracellular signaling, cholinergically differentiated SH-SY5Y cells were exposed to IL-1beta for various periods of time followed by stimulation of mAChR with carbachol for 1 h, and key molecules of cholinergic signaling cascades were determined including phosphoinositide hydrolysis, DNA-binding capacity of NFkappaB and AP-1, and activity of acetylcholinesterase (AChE). Carbachol stimulation of SH-SY5Y cells dose-dependently stimulated the activation of the transcription factors NFkappaB and AP-1 as revealed by electrophoretic mobility shift assay (EMSA), while pre-exposure of SH-SY5Y cells for 24 h with 1 ng/ml IL-1beta completely suppressed the carbachol response. mAChR-mediated enhancements of AChE activity by carbachol were impaired following pre-exposure of SH-SY5Y cells with IL-1beta, already detectable at a concentration of 1 ng/ml and 1 h of exposure time. The data indicate that IL-1beta may interfere with the cholinergic signal transduction cascade by inhibiting transcription factor activation, thus providing another mechanism by which IL-1beta may induce cholinergic dysfunction in Alzheimer's disease.

Stress increases vulnerability to inflammation in the rat prefrontal cortex

Inflammation could be involved in some neurodegenerative disorders that accompany signs of inflammation. However, because sensitivity to inflammation is not equal in all brain structures, a direct relationship is not clear. Our aim was to test whether some physiological circumstances, such as stress, could enhance susceptibility to inflammation in the prefrontal cortex (PFC), which shows a relative resistance to inflammation. PFC is important in many brain functions and is a target for some neurodegenerative diseases. We induced an inflammatory process by a single intracortical injection of 2 microg of lipopolysaccharide (LPS), a potent proinflammogen, in nonstressed and stressed rats. We evaluated the effect of our treatment on inflammatory markers, neuronal populations, BDNF expression, and behavior of several mitogen-activated protein (MAP) kinases and the transcription factor cAMP response element-binding protein. Stress strengthens the changes induced by LPS injection: microglial activation and proliferation with an increase in the levels of the proinflammatory cytokine tumor necrosis factor-alpha; loss of cells such as astroglia, seen as loss of glial fibrillary acidic protein immunoreactivity, and neurons, studied by neuronal-specific nuclear protein immunohistochemistry and GAD67 and NMDA receptor 1A mRNAs expression by in situ hybridization. A significant increase in the BDNF mRNA expression and modifications in the levels of MAP kinase phosphorylation were also found. In addition, we observed a protective effect from RU486 [mifepristone (11beta-[p-(dimethylamino)phenyl]-17beta-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one)], a potent inhibitor of the glucocorticoid receptor activation. All of these data show a synergistic effect between inflammation and stress, which could explain the relationship described between stress and some neurodegenerative pathologies.

Diverse microglial responses after intrahippocampal administration of lipopolysaccharide

Inflammation has been argued to play a primary role in the pathogenesis of Alzheimer's disease by contributing to the development of neuropathology and clinical symptoms. However, the mechanisms underlying these effects remain obscure. Lipopolysaccharide (LPS) activates the innate immune response and triggers gliosis when injected into the central nervous system. In the studies described in the present work, we evaluated the time course of microgliosis after a single intrahippocampal injection of LPS. Mice were injected bilaterally with 4 mug of LPS. Post-injection survival times were 1, 6, and 24 h, as well as 3, 7, 14, and 28 days. Protein and RNA analyses were performed for inflammatory markers. Significant elevations of cluster differentiation marker CD45, glial fibrillary acidic protein (GFAP), scavenger receptor A (SRA), and Fcgamma receptor mRNA were seen after 24 h. Immunohistochemistry revealed a complex pattern of protein expression by microglia, as well as changes in cell morphologies. RNA and protein for Fcgamma receptor and SRA were transiently elevated, peaked at 3 days, and returned to basal levels after 1 week. In contrast, microglia remained significantly activated through the 28-day time point, as determined by CD45 and complement receptor 3 levels. These findings indicate a multivariate response to LPS, and evaluation of microglial phenotypes may lead to a better understanding of neuroinflammatory diseases.

Basal forebrain cholinergic dysfunction in Alzheimer's disease--interrelationship with beta-amyloid, inflammation and neurotrophin signaling

Alzheimer's disease, the most common neurodegenerative disorder of senile dementia, is characterized by two major morpho-pathological hallmarks. Deposition of extracellular neuritic, beta-amyloid peptide-containing plaques (senile plaques) in cerebral cortical regions of Alzheimer patients is accompanied by the presence of intracellular neurofibrillary tangles in cerebral pyramidal neurons. Basal forebrain cholinergic dysfunction is also a consistent feature of Alzheimer's disease, which has been suggested to cause, at least partly, the cognitive deficits observed in patients with Alzheimer's disease. Impaired cortical cholinergic neurotransmission may also contribute to beta-amyloid plaque pathology in Alzheimer's disease by affecting expression and processing of the beta-amyloid precursor protein (APP). Vice versa, low level of soluble beta-amyloid has been observed to inhibit cholinergic synaptic function. Deposition of beta-amyloid plaques in Alzheimer's disease is also accompanied by a significant plaque-associated glial up-regulation of interleukin-1, which has been attributed to affect expression and metabolism of APP and to interfere with cholinergic transmission. Understanding the molecular mechanisms underlying the interrelationship between cortical cholinergic dysfunction, beta-amyloid formation and deposition, as well as local inflammatory upregulation, would allow to derive potential treatment strategies to pharmacologically intervene in the disease-causing signaling cascade.

Phenotype dependent differential effects of interleukin-1beta and amyloid-beta on viability and cholinergic phenotype of T17 neuroblastoma cells

Amyloid-beta accumulation in brains of Alzheimer's disease (AD) victims is accompanied by glial inflammatory reactions and preferential loss of cholinergic neurons. Therefore, the aim of this study was to find out whether proinflamatory cytokine interleukin 1beta (IL1beta) modifies effects of amyloid-beta (Abeta) on viability and cholinergic phenotype of septum derived T17 cholinergic neuroblastoma cells. In nondifferentiated T17 cells (NC) Abeta(25-35) (1 microg/ml) caused no changes in choline acetyltransferase (ChAT) activity, acetylcholine (ACh) release, subcellular distribution of acetyl-CoA, but doubled content of trypan blue positive cells. IL1beta (10 ng/ml) increased ACh release (125%) but did not change other parameters of NC. In the presence of Abeta IL1beta also increased ChAT activity (47%), ACh release (100%) but had no effect on acetyl-CoA distribution and cell viability. Differentiation with retinoic acid and dibutyryl cyclic AMP caused over two-fold increase of ChAT activity and ACh content, four-fold increase of ACh release and about 50% decrease of acetyl-CoA level in the mitochondria. In differentiated cells (DC), Abeta decreased ChAT activity (31%), ACh release (47%) and content of acetyl-CoA (80%) in cell cytoplasmic compartment, whereas IL1beta elevated ChAT activity (54%) and ACh release (32%). IL1beta totally reversed Abeta-evoked inhibition of ChAT activity and ACh release and restored control level of cytoplasmic acetyl-CoA but increased fraction of nonviable cells to 25%. Thus, IL1beta could compensate Abeta-evoked cholinergic deficits through the restoration of adequate expression of ChAT and provision of acetyl-CoA to cytoplasmic compartment in cholinergic neurons that survive under such pathologic conditions. These data indicate that IL1beta possess independent cholinotrophic and cholinotoxic activities that may modify Abeta effects on cholinergic neurons.

Cognitive deficit associated with cholinergic and nerve growth factor down-regulation in experimental allergic encephalomyelitis in rats

Clinical symptoms in multiple sclerosis include cognitive dysfunction. Difficulties in learning and remembering new information represent the most common cognitive deficit and are associated with a general and progressive brain pathology. Possible pathogenetic mechanisms for neuronal damage such as neuroprotective strategies are under active investigation also in experimental allergic encephalomyelitis, the most widely used experimental model for multiple sclerosis. In this paper we demonstrate that a selective deficit in learning and memory performance, as investigated by the Morris water maze test, is a consistent feature in rat encephalomyelitis, which correlates with a decline in choline acetyltransferase activity and nerve growth factor mRNA level in cerebral cortex, hippocampus, and basal forebrain. Treatment aimed to restore acetylcholine content through chronic administration of selective acetylcholinesterase inhibitors (rivastigmine and donepezil) restores cognitive performance, choline acetyltransferase activity, and nerve growth factor mRNA expression.

Plasma insulin growth factor-1 and incident delirium in older people

BACKGROUND

A variety of demographic and clinical variables are acknowledged as risk factors for delirium; a syndrome thought to be mediated by abnormalities in a wide range of neurotransmitters. However, little research has been conducted in this field and the role of neuro-immunological factors as a mechanism of medication has received very little attention.

AIMS

To determine if low base line (on admission) IGF-1 levels (a protective cytokine released by brain cells in response to insult) is a risk factor for incident delirium in patients aged 75 and over admitted to an acute medical ward.

METHOD

Base line demographic and clinical variables and serum IGF-1 levels were measured in a consecutive series of 100 non-delirious subjects on inpatient admission. Subjects were assessed daily regarding the development of delirium during the inpatient episode.

RESULTS

Twelve patients developed incident delirium. IGF-1 (OR: 0.822, CI: 0.69, 0.97, p = 0.027), pre-admission cognitive deterioration (assessed by IQCODE) (OR; 3.26, CI: 1.18, 9.04, p = 0.023) and depression (GDS four item: cut-off score > or = 3) (OR; 8.99, CI 1.59,50.76, p = 0.013) were identified as risk factors for developing subsequent delirium.

CONCLUSIONS

Despite the small size of this study our findings suggest that low, pre-morbid IGF-1 is a risk factor for subsequent delirium in this population, emphasizing the potential protective role of this anabolic cytokine and the need for replication of these findings.

Time-dependent reduction in Abeta levels after intracranial LPS administration in APP transgenic mice

Inflammation has been argued to play a primary role in the pathogenesis of Alzheimer's disease (AD). Lipopolysaccharide (LPS) activates the innate immune system, triggering gliosis and inflammation when injected in the central nervous system. In studies described here, APP transgenic mice were injected intrahippocampally with 4 or 10 microg of LPS and evaluated 1, 3, 7, 14, or 28 days later. Abeta load was significantly reduced at 3, 7, and 14 days but surprisingly returned near baseline 28 days after the injection. No effects of LPS on congophilic amyloid deposits could be detected. LPS also activated both microglia and astrocytes in a time-dependent manner. The GFAP astrocyte reaction and the Fcgamma receptor microglial reaction peaked at 7 days after LPS injection, returning to baseline by 2 weeks postinjection. When stained for CD45, microglial activation was detected at all time points, although the morphology of these cells transitioned from an ameboid to a ramified and bushy appearance between 7 and 14 days postinjection. These results indicate that activation of brain glia can rapidly and transiently clear diffuse Abeta deposits but has no effect on compacted fibrillar amyloid.