Low levels of amyloid-beta and its transporters in neonatal rats with and without hydrocephalus.

BACKGROUND: Previous studies in aging animals have shown that amyloid-beta protein (Abeta) accumulates and its transporters, low-density lipoprotein receptor-related protein-1 (LRP-1) and the receptor for advanced glycation end products (RAGE) are impaired during hydrocephalus. Furthermore, correlations between astrocytes and Abeta have been found in human cases of normal pressure hydrocephalus (NPH) and Alzheimer's disease (AD). Because hydrocephalus occurs frequently in children, we evaluated the expression of Abeta and its transporters and reactive astrocytosis in animals with neonatal hydrocephalus. METHODS: Hydrocephalus was induced in neonatal rats by intracisternal kaolin injections on post-natal day one, and severe ventriculomegaly developed over a three week period. MRI was performed on post-kaolin days 10 and 21 to document ventriculomegaly. Animals were sacrificed on post-kaolin day 21. For an age-related comparison, tissue was used from previous studies when hydrocephalus was induced in a group of adult animals at either 6 months or 12 months of age. Tissue was processed for immunohistochemistry to visualize LRP-1, RAGE, Abeta, and glial fibrillary acidic protein (GFAP) and with quantitative real time reverse transcriptase polymerase chain reaction (qRT-PCR) to quantify expression of LRP-1, RAGE, and GFAP. RESULTS: When 21-day post-kaolin neonatal hydrocephalic animals were compared to adult (6-12 month old) hydrocephalic animals, immunohistochemistry demonstrated levels of Abeta, RAGE, and LRP-1 that were substantially lower in the younger animals; in contrast, GFAP levels were elevated in both young and old hydrocephalic animals. When the neonatal hydrocephalic animals were compared to age-matched controls, qRT-PCR demonstrated no significant changes in Abeta, LRP-1 and RAGE. However, immunohistochemistry showed very small increases or decreases in individual proteins. Furthermore, qRT-PCR indicated statistically significant increases in GFAP. CONCLUSION: Neonatal rats with and without hydrocephalus had low expression of Abeta and its transporters when compared to adult rats with hydrocephalus. No statistical differences were observed in Abeta and its transporters between the control and hydrocephalic neonatal animals.

Hippocampal RAGE immunoreactivity in early and advanced Alzheimer's disease.

Microvascular accumulation and neuronal overproduction of amyloid-beta peptide (Abeta) are pathologic features of Alzheimer's disease (AD). In this study, we examined the receptor for advanced glycation endproducts (RAGE), a multi-ligand receptor found in both neurons and cerebral microvascular endothelia that binds Abeta. RAGE expression was assessed in aged controls (n = 6), patients with early AD-like pathology (n = 6), and severe, Braak V-VI AD (n = 6). Human hippocampi were stained with a specific polyclonal antibody directed against RAGE (Research Diagnostics, Flanders, NJ). Immunoreactivity was localized in both neurons and cerebral endothelial cells. Quantitative image-analyses were performed on grayscale images to assess the total surface area of endothelial RAGE immunoreaction product in cross sections of cerebral microvessels (5-20 microm). Confocal images were acquired for confirmation of RAGE immunoreactivity in both microvessels and neurons by coupling RAGE with CD-31 and neurofilament, respectively. A significant increase in endothelial RAGE immunoreactivity was found in severe Braak V-VI AD patients when compared to aged controls (p < 0.001), and when compared to patients with early AD pathology (p = 0.0125). In addition, a significant increase in endothelial RAGE immunoreactivity was witnessed when comparing aged controls having no reported AD pathology with patients having early AD-like pathology (p = 0.038). Our data suggest that microvascular RAGE levels increase in conjunction with the onset of AD, and continue to increase linearly as a function of AD pathologic severity (p < 0.0001).

Multiplicity of cerebrospinal fluid functions: New challenges in health and disease.

UNLABELLED: This review integrates eight aspects of cerebrospinal fluid (CSF) circulatory dynamics: formation rate, pressure, flow, volume, turnover rate, composition, recycling and reabsorption. Novel ways to modulate CSF formation emanate from recent analyses of choroid plexus transcription factors (E2F5), ion transporters (NaHCO3 cotransport), transport enzymes (isoforms of carbonic anhydrase), aquaporin 1 regulation, and plasticity of receptors for fluid-regulating neuropeptides. A greater appreciation of CSF pressure (CSFP) is being generated by fresh insights on peptidergic regulatory servomechanisms, the role of dysfunctional ependyma and circumventricular organs in causing congenital hydrocephalus, and the clinical use of algorithms to delineate CSFP waveforms for diagnostic and prognostic utility. Increasing attention focuses on CSF flow: how it impacts cerebral metabolism and hemodynamics, neural stem cell progression in the subventricular zone, and catabolite/peptide clearance from the CNS. The pathophysiological significance of changes in CSF volume is assessed from the respective viewpoints of hemodynamics (choroid plexus blood flow and pulsatility), hydrodynamics (choroidal hypo- and hypersecretion) and neuroendocrine factors (i.e., coordinated regulation by atrial natriuretic peptide, arginine vasopressin and basic fibroblast growth factor). In aging, normal pressure hydrocephalus and Alzheimer's disease, the expanding CSF space reduces the CSF turnover rate, thus compromising the CSF sink action to clear harmful metabolites (e.g., amyloid) from the CNS. Dwindling CSF dynamics greatly harms the interstitial environment of neurons. Accordingly the altered CSF composition in neurodegenerative diseases and senescence, because of adverse effects on neural processes and cognition, needs more effective clinical management. CSF recycling between subarachnoid space, brain and ventricles promotes interstitial fluid (ISF) convection with both trophic and excretory benefits. Finally, CSF reabsorption via multiple pathways (olfactory and spinal arachnoidal bulk flow) is likely complemented by fluid clearance across capillary walls (aquaporin 4) and arachnoid villi when CSFP and fluid retention are markedly elevated. A model is presented that links CSF and ISF homeostasis to coordinated fluxes of water and solutes at both the blood-CSF and blood-brain transport interfaces. OUTLINE: 1 Overview2 CSF formation2.1 Transcription factors2.2 Ion transporters2.3 Enzymes that modulate transport2.4 Aquaporins or water channels2.5 Receptors for neuropeptides3 CSF pressure3.1 Servomechanism regulatory hypothesis3.2 Ontogeny of CSF pressure generation3.3 Congenital hydrocephalus and periventricular regions3.4 Brain response to elevated CSF pressure3.5 Advances in measuring CSF waveforms4 CSF flow4.1 CSF flow and brain metabolism4.2 Flow effects on fetal germinal matrix4.3 Decreasing CSF flow in aging CNS4.4 Refinement of non-invasive flow measurements5 CSF volume5.1 Hemodynamic factors5.2 Hydrodynamic factors5.3 Neuroendocrine factors6 CSF turnover rate6.1 Adverse effect of ventriculomegaly6.2 Attenuated CSF sink action7 CSF composition7.1 Kidney-like action of CP-CSF system7.2 Altered CSF biochemistry in aging and disease7.3 Importance of clearance transport7.4 Therapeutic manipulation of composition8 CSF recycling in relation to ISF dynamics8.1 CSF exchange with brain interstitium8.2 Components of ISF movement in brain8.3 Compromised ISF/CSF dynamics and amyloid retention9 CSF reabsorption9.1 Arachnoidal outflow resistance9.2 Arachnoid villi vs. olfactory drainage routes9.3 Fluid reabsorption along spinal nerves9.4 Reabsorption across capillary aquaporin channels10 Developing translationally effective models for restoring CSF balance11 Conclusion.

Choroid plexus genes for CSF production and brain homeostasis are altered in Alzheimer's disease.

BACKGROUND: The roles of the choroid plexus (CP) and cerebrospinal fluid (CSF) production have drawn increasing attention in Alzheimer's disease (AD) research. Specifically, studies document markedly decreased CSF production and turnover in moderate-to-severe AD. Moreover, reduced CP function and CSF turnover lead to impaired clearance of toxic metabolites, likely promote neuroinflammation, and may facilitate neuronal death during AD progression. We analyzed CP gene expression in AD compared with control subjects, specifically considering those genes involved with CSF production and CP structural integrity. METHODS: The Brown-Merck Gene Expression Omnibus (GEO) database (CP transcripts) was mined to examine changes in gene expression in AD compared to controls with a focus on assorted genes thought to play a role in CSF production. Specifically, genes coding for ion transporters in CP epithelium (CPE) and associated enzymes like Na-K-ATPase and carbonic anhydrase, aquaporins, mitochondrial transporters/enzymes, blood-cerebrospinal fluid barrier (BCSFB) stability proteins, and pro-inflammatory mediators were selected for investigation. Data were analyzed using t test p-value and fold-change analysis conducted by the GEO2R feature of the GEO database. RESULTS: Significant expression changes for several genes were observed in AD CP. These included disruptions to ion transporters (e.g., the solute carrier gene SLC4A5, p = 0.004) and associated enzyme expressions (e.g., carbonic anhydrase CA4, p = 0.0001), along with decreased expression of genes involved in BCSFB integrity (e.g., claudin CLDN5, p = 0.039) and mitochondrial ATP synthesis (e.g., adenosine triphosphate ATP5L, p = 0.0004). Together all changes point to disrupted solute transport at the blood-CSF interface in AD. Increased expression of pro-inflammatory (e.g., interleukin IL1RL1, p = 0.00001) and potential neurodegenerative genes (e.g., amyloid precursor APBA3, p = 0.002) also implicate disturbed CP function. CONCLUSIONS: Because the altered expression of numerous transcripts in AD-CP help explain decreased CSF production in AD, these findings represent a first step towards identifying novel therapeutic targets in AD.

Comparative transcriptomics of choroid plexus in Alzheimer's disease, frontotemporal dementia and Huntington's disease: implications for CSF homeostasis.

BACKGROUND: In Alzheimer's disease, there are striking changes in CSF composition that relate to altered choroid plexus (CP) function. Studying CP tissue gene expression at the blood-cerebrospinal fluid barrier could provide further insight into the epithelial and stromal responses to neurodegenerative disease states. METHODS: Transcriptome-wide Affymetrix microarrays were used to determine disease-related changes in gene expression in human CP. RNA from post-mortem samples of the entire lateral ventricular choroid plexus was extracted from 6 healthy controls (Ctrl), 7 patients with advanced (Braak and Braak stage III-VI) Alzheimer's disease (AD), 4 with frontotemporal dementia (FTD) and 3 with Huntington's disease (HuD). Statistics and agglomerative clustering were accomplished with MathWorks, MatLab; and gene set annotations by comparing input sets to GeneGo ( http://www.genego.com ) and Ingenuity ( http://www.ingenuity.com ) pathway sets. Bonferroni-corrected hypergeometric p-values of < 0.1 were considered a significant overlap between sets. RESULTS: Pronounced differences in gene expression occurred in CP of advanced AD patients vs. Ctrls. Metabolic and immune-related pathways including acute phase response, cytokine, cell adhesion, interferons, and JAK-STAT as well as mTOR were significantly enriched among the genes upregulated. Methionine degradation, claudin-5 and protein translation genes were downregulated. Many gene expression changes in AD patients were observed in FTD and HuD (e.g., claudin-5, tight junction downregulation), but there were significant differences between the disease groups. In AD and HuD (but not FTD), several neuroimmune-modulating interferons were significantly enriched (e.g., in AD: IFI-TM1, IFN-AR1, IFN-AR2, and IFN-GR2). AD-associated expression changes, but not those in HuD and FTD, were enriched for upregulation of VEGF signaling and immune response proteins, e.g., interleukins. HuD and FTD patients distinctively displayed upregulated cadherin-mediated adhesion. CONCLUSIONS: Our transcript data for human CP tissue provides genomic and mechanistic insight for differential expression in AD vs. FTD vs. HuD for stromal as well as epithelial components. These choroidal transcriptome characterizations elucidate immune activation, tissue functional resiliency, and CSF metabolic homeostasis. The BCSFB undergoes harmful, but also important functional and adaptive changes in neurodegenerative diseases; accordingly, the enriched JAK-STAT and mTOR pathways, respectively, likely help the CP in adaptive transcription and epithelial repair and/or replacement when harmed by neurodegeneration pathophysiology. We anticipate that these precise CP translational data will facilitate pharmacologic/transgenic therapies to alleviate dementia.

Aging alters mRNA expression of amyloid transporter genes at the blood-brain barrier.

Decreased clearance of potentially toxic metabolites, due to aging changes, likely plays a significant role in the accumulation of amyloid-beta (Aß) peptides and other macromolecules in the brain of the elderly and in the patients with Alzheimer's disease (AD). Aging is the single most important risk factor for AD development. Aß transport receptor proteins expressed at the blood-brain barrier are significantly altered with age: the efflux transporters lipoprotein receptor-related protein 1 and P-glycoprotein are reduced, whereas the influx transporter receptor for advanced glycation end products is increased. These receptors play an important role in maintaining brain biochemical homeostasis. We now report that, in a rat model of aging, gene transcription is altered in aging, as measured by Aß receptor gene messenger RNA (mRNA) at 3, 6, 9, 12, 15, 20, 30, and 36 months. Gene mRNA expression from isolated cerebral microvessels was measured by quantitative polymerase chain reaction. Lipoprotein receptor-related protein 1 and P-glycoprotein mRNA were significantly reduced in aging, and receptor for advanced glycation end products was increased, in parallel with the changes seen in receptor protein expression. Transcriptional changes appear to play a role in aging alterations in blood-brain barrier receptor expression and Aß accumulation.

Brain amyloid accumulates in aged rats with kaolin-induced hydrocephalus.

Amyloid beta-peptide (Abeta) accumulation in aged Sprague-Dawley rats (12 months) with kaolin-induced hydrocephalus was investigated by Abeta(1-40) and Abeta(1-42) immunohistochemistry at 2, 6 and 10 weeks after induction. The low-density lipoprotein receptor-related protein-1 transporting Abeta across the blood-brain barrier was assayed. Age-matched controls showed some positive Abeta staining, mainly in the choroid plexus. At 2 weeks after induction, Abeta staining of the arachnoid and subependymal layer was observed. At 6 weeks, larger Abeta accumulations were prominent at the endothelial and perivascular sites. Intraparenchymal Abeta positively stained accumulations occurred at 10 weeks. Microvessel lipoprotein receptor-related protein-1 staining was progressively reduced from 2 to 10 weeks. The pattern of Abeta deposition and lipoprotein receptor-related protein-1 loss suggests reduced Abeta clearance in chronic hydrocephalus.

Elevated cerebrospinal fluid pressure in patients with Alzheimer's disease.

BACKGROUND: Abnormalities in cerebrospinal fluid (CSF) production and turnover, seen in normal pressure hydrocephalus (NPH) and in Alzheimer's disease (AD), may be an important cause of amyloid retention in the brain and may relate the two diseases. There is a high incidence of AD pathology in patients being shunted for NPH, the AD-NPH syndrome. We now report elevated CSF pressure (CSFP), consistent with very early hydrocephalus, in a subset of AD patients enrolled in a clinical trial of chronic low-flow CSF drainage. Our objective was to determine the frequency of elevated CSFP in subjects meeting National Institutes of Neurological and Communicative Diseases and Stroke-Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria for AD, excluding those with signs of concomitant NPH. METHODS: AD subjects by NINCDS-ADRDA criteria (n = 222), were screened by history, neurological examination, and radiographic imaging to exclude those with clinical or radiographic signs of NPH. As part of this exclusion process, opening CSFP was measured supine under general anesthesia during device implantation surgery at a controlled pCO2 of 40 Torr (40 mmHg). RESULTS: Of the 222 AD subjects 181 had pressure measurements recorded. Seven subjects (3.9%) enrolled in the study had CSFP of 220 mmH20 or greater, mean 249 +/- 20 mmH20 which was significantly higher than 103 +/- 47 mmH2O for the AD-only group. AD-NPH patients were significantly younger and significantly less demented on the Mattis Dementia Rating Scale (MDRS). CONCLUSION: Of the AD subjects who were carefully screened to exclude those with clinical NPH, 4% had elevated CSFP. These subjects were presumed to have the AD-NPH syndrome and were withdrawn from the remainder of the study.

Memory encoding in Alzheimer's disease: an fMRI study of explicit and implicit memory.

Alzheimer's disease is the most common cause of dementia in older adults. Although the cognitive deficits and pathologic hallmarks of Alzheimer's disease have been well characterized, few functional imaging studies have examined the functional competency of specific brain regions and their relationship to specific behavioural memory deficits in Alzheimer's disease. We used functional MRI (fMRI) to examine seven early stage Alzheimer's disease patients and seven healthy age-matched neurologically normal control subjects during intentional encoding of scenes. Subjects viewed blocks of novel scenes, repeated scenes or baseline. Data were analysed using whole-brain statistical parametric mapping and region of interest approaches. The Alzheimer's disease group demonstrated impaired explicit recognition memory, but intact implicit memory (repetition priming), for the scenes. Alzheimer's disease patients demonstrated a graded deficit in activation for novel versus repeated scenes along the ventral visual stream, with most impaired activation changes in the mesial temporal lobe (MTL) and fusiform regions, most preserved activations in primary visual cortex and variably affected activations in secondary visual areas. Group-level correlations with behavioural measures of explicit memory were found in MTL, lingual and fusiform areas, whereas correlations with priming were found in lateral occipital, parietal and frontal areas. Together, these fMRI findings indicate a dissociation in Alzheimer's disease between impaired explicit memory encoding in MTL and fusiform regions and intact implicit encoding in earlier-stage occipital cortex.

P-glycoprotein expression and amyloid accumulation in human aging and Alzheimer's disease: preliminary observations.

P-glycoprotein (P-gp), part of the blood-brain barrier, limits drug access to the brain and is the target for therapies designed to improve drug penetration. P-gp also extrudes brain amyloid-beta (Aß). Accumulation of Aß is a hallmark of Alzheimer's disease (AD). Aß accumulates in normal aging and in AD primarily due to decreased Aß clearance. This is a preliminary report on the relative protein and messenger RNA expression of P-gp in human brains, ages 20-100 years, including AD subjects. In these preliminary studies, cortical endothelial P-gp expression decreased in AD compared with controls (p < 0.001). Trends in P-gp expression in human aging are similar to aging rats. Microvessel P-gp messenger RNA remained unchanged with aging and AD. Aß plaques were found in 42.8% of normal subjects (54.5% of those older than 50 years). A qualitative analysis showed that P-gp expression is lower than the group mean in subjects older than 75 years but increased if younger. Decreased P-gp expression may be related to Aß plaques in aging and AD. Downregulating P-gp to allow pharmaceuticals into the central nervous system may increase Aß accumulation.

Kaolin-induced chronic hydrocephalus accelerates amyloid deposition and vascular disease in transgenic rats expressing high levels of human APP.

BACKGROUND: Normal pressure hydrocephalus (NPH) is most common in the elderly and has a high co-morbidity with Alzheimer's disease (AD) and cerebrovascular disease (CVD). To understand the relationship between NPH, AD and CVD, we investigated how chronic hydrocephalus impacts brain amyloid-beta peptide (Aß) accumulation and vascular pathology in an AD transgenic rodent model. Previously we showed that the altered CSF physiology produced by kaolin-hydrocephalus in older wild-type Sprague-Dawley rats increased Aß and hyperphosphorylated Tau (Silverberg et. al. Brain Res. 2010, 1317:286-296). We postulated that hydrocephalus would similarly affect an AD rat model. METHODS: Thirty-five transgenic rats (tgAPP21) that express high levels of human APP and naturally overproduce Aß40 were used. Six- (n = 7) and twelve-month-old (n = 9) rats had hydrocephalus induced by cisternal kaolin injection. We analyzed Aß burden (Aß40, Aß42 and oligomeric Aß) and vascular integrity (Masson trichrome and Verhoeff-Van Gieson) by immunohistochemistry and chemical staining at 10 weeks (n = 8) and 6 months (n = 5) post hydrocephalus induction. We also analyzed whether the vascular pathology seen in tgAPP21 rats, which develop amyloid angiopathy, was accelerated by hydrocephalus. Age-matched naïve and sham-operated tgAPP21 rats served as controls (n = 19). RESULTS: In hydrocephalic tgAPP21 rats, compared to naïve and sham-operated controls, there was increased Aß 40 and oligomeric Aß in hippocampal and cortical neurons at 10 weeks and 6 months post-hydrocephalus induction. No dense-core amyloid plaques were seen, but diffuse Aß immunoreactivity was evident in neurons. Vascular pathology was accelerated by the induction of hydrocephalus compared to controls. In the six-month-old rats, subtle degenerative changes were noted in vessel walls at 10 weeks post-kaolin, whereas at six months post-kaolin and in the 12-month-old hydrocephalic rats more pronounced amyloid angiopathic changes were seen, with frequent large areas of infarction noted. CONCLUSIONS: Kaolin-hydrocephalus can accelerate intraneuronal Aß40 accumulation and vascular pathology in tgAPP21 rats. In addition, disrupted CSF production and reduced CSF turnover results in impaired Aß clearance and accelerated vascular pathology in chronic hydrocephalus. The high co-morbidity seen in NPH, AD and CVD is likely not to be an age-related coincidence, but rather a convergence of pathologies related to diminished CSF clearance.

Cerebral hypoperfusion and delayed hippocampal response after induction of adult kaolin hydrocephalus.

BACKGROUND AND PURPOSE: In chronic hydrocephalus, a role for tissue hypoxia resulting from cerebrovascular compression is suggested. The purpose of this study was to evaluate whether changes in cerebral blood flow (CBF) in the time course of adult kaolin-induced hydrocephalus correlated with immunohistochemical neuronal responses. METHODS: In 46 adult Sprague-Dawley rats, kaolin hydrocephalus was induced and immunostaining of neurofilament protein (NF68), synaptophysin (SYN38), and neuronal nitric oxide synthase (NOS) was performed at 2 (short term), 4 (intermediate term), and 6 and 8 (long term) weeks. Local CBF was measured quantitatively by [14C]iodoantipyrine ([14C]IAP) autoradiography in the short-term stage and in both long-term stages. RESULTS: At 2 weeks, neuronal NOS immunoreactivity was globally increased in cortical areas and within the hippocampus. Four weeks after hydrocephalus induction, a reactive increase of SYN38 and NF68 immunoreactivity in the periventricular cortex was seen. At 6 and 8 weeks, when the ventricular size was decreasing, immunohistochemical changes in the hippocampus became most evident. A maintained toxic NOS reactivity in the CA1 subfield was accompanied by a loss of NF68 staining. In the CA3 subfield, however, focal increases in NF68 and SYN38 immunoreactivity were found. Cortical and hippocampal blood flow showed prolonged decreases of 25% to 55% compared with control animals. At 8 weeks, control levels were reached. CONCLUSIONS: The observed temporary CBF decrease appears to correlate with an early global neuronal ischemic response. In addition, it may also account for the delayed selective response of ischemia-vulnerable structures, eg, hippocampus, in chronic adult kaolin-induced hydrocephalus.

Alzheimer's disease, normal-pressure hydrocephalus, and senescent changes in CSF circulatory physiology: a hypothesis.

There is evidence that production and turnover of CSF help to clear toxic molecules such as amyloid-beta peptide (Abeta) from the interstitial-fluid space of the brain to the bloodstream. Two changes in CSF circulatory physiology have been noted as part of ageing: first, a trend towards lower CSF production, hence a decrease in CSF turnover; and second, greater resistance to CSF outflow. Our hypothesis is that, all else being equal, the initially dominant physiological change determines whether CSF circulatory failure manifests as Alzheimer's disease (AD) or as normal-pressure hydrocephalus (NPH). If CSF production failure predominates, AD develops. However, if resistance to CSF outflow predominates, NPH results. Once either disease process takes hold, the risk of the other disorder may rise. In AD, increased deposition of Abeta in the meninges leads to greater resistance to CSF outflow. In NPH, raised CSF pressure causes lower CSF production and less clearance of Abeta. The disorders may ultimately converge in vulnerable individuals, resulting in a hybrid as has been observed in several clinical series. We postulate a new nosological entity of CSF circulatory failure, with features of AD and NPH. NPH-AD may cover an important subset of patients who carry the diagnosis of either AD or NPH.

Reduction of brain lipid peroxidation by CSF drainage in Alzheimer's disease patients.

Alzheimer's disease (AD) is associated with an increase in cerebrospinal fluid (CSF) levels of the isoprostane 8,12-iso-iPF2alpha-VI, a specific marker of in vivo lipid peroxidation. Poor cerebral clearance of end products of oxidative reactions via CSF circulation may contribute to and sustain ongoing stress. CSF drainage via a low-flow ventriculoperitoneal (VP) shunt may improve removal of these products, reducing oxidative stress. We quantified this biomarker in patients with AD undergoing to VP shunt placement at baseline and after one-year period. CSF sampling occurred at baseline and quarterly visits for one year. Levels of this isoprostane were determined simultaneously at the end of the study by gas chromatography negative ion chemical ionization mass spectrometry. Over one-year, CSF 8,12-iso-iPF2alpha-VI levels consistently decreased versus baseline (51% of initial level), while CSF protein, glucose, cell count and IgG concentrations remained within normal limits. This finding supports the hypothesis that improving CSF drainage enhances extra-cellular clearance of end products of oxidative reactions and lowers brain lipid peroxidation.

Homeostatic capabilities of the choroid plexus epithelium in Alzheimer's disease.

As the secretory source of vitamins, peptides and hormones for neurons, the choroid plexus (CP) epithelium critically provides substances for brain homeostasis. This distributive process of cerebrospinal fluid (CSF) volume transmission reaches many cellular targets in the CNS. In ageing and ageing-related dementias, the CP-CSF system is less able to regulate brain interstitial fluid. CP primarily generates CSF bulk flow, and so its malfunctioning exacerbates Alzheimers disease (AD). Considerable attention has been devoted to the blood-brain barrier in AD, but more insight is needed on regulatory systems at the human blood-CSF barrier in order to improve epithelial function in severe disease. Using autopsied CP specimens from AD patients, we immunocytochemically examined expression of heat shock proteins (HSP90 and GRP94), fibroblast growth factor receptors (FGFr) and a fluid-regulatory protein (NaK2Cl cotransporter isoform 1 or NKCC1). CP upregulated HSP90, FGFr and NKCC1, even in end-stage AD. These CP adjustments involve growth factors and neuropeptides that help to buffer perturbations in CNS water balance and metabolism. They shed light on CP-CSF system responses to ventriculomegaly and the altered intracranial pressure that occurs in AD and normal pressure hydrocephalus. The ability of injured CP to express key regulatory proteins even at Braak stage V/VI, points to plasticity and function that may be boosted by drug treatment to expedite CSF dynamics. The enhanced expression of human CP 'homeostatic proteins' in AD dementia is discussed in relation to brain deficits and pharmacology.

Downregulation of cerebrospinal fluid production in patients with chronic hydrocephalus.

OBJECT: The goal of this study was to determine the effect of hydrocephalus on cerebrospinal fluid (CSF) production rates in patients with acute and chronic hydrocephalus. METHODS: The authors studied CSF production both in patients presenting with acute and chronic hydrocephalus, and patients with Parkinson disease (PD) of a similar mean age, whose CSF production was known to be normal. A modification of the Masserman method was used to measure CSF production through a ventricular catheter. The CSF production rates (means +/- standard deviations) in the three groups were then compared. The patients with PD had a mean CSF production rate of 0.42 +/- 0.13 ml/minute; this value lies within the normal range measured using this technique. Patients with acute hydrocephalus had a similar CSF production rate of 0.4 +/- 0.13 ml/minute, whereas patients with chronic hydrocephalus had a significantly decreased mean CSF production rate of 0.25 +/- 0.08 ml/minute. CONCLUSIONS: The authors postulate that chronic increased intracranial pressure causes downregulation of CSF production.

Effects of tumor suppressor gene (p53) on brain tumor angiogenesis and expression of angiogenic modulators.

BACKGROUND: p53 retarded tumor growth by several known mechanisms, including suppression of cell proliferation and inhibition of tumor angiogenesis. Vascular endothelial growth factors (VEGF) and angiopoietins (Ang-1, Ang-2) are major angiogeneic modulators. The current study examined the effect of p53 on the expression of these factors in conjunction with tumor growth and vascular formation. MATERIALS AND METHODS: Growth characteristics of rat glioma cells (RT-2) infected with retrovirus (MSCV) encoding a full-length human wild-type p53 gene were examined by clonogenic assay. Expression of the transgene in vitro was verified by RT-PCR and immunoprecipitation. Tumor morphology, vascular architecture and the expression of VEGF, Ang-1, Ang-2 and Tie-2 were examined by immunohistochemistry and semi-quantitative RT-PCR. RESULTS: p53-infected cells showed retardation in growth and colony formation. In vivo, expression of the transgene resulted in prolonged survival and reduction of tumor volume (62%) and reduced the expression of VEGF (57.8%) and Tie-2 (15.4%) but not Ang-1 and Ang-2. The tumor exhibited increased necrosis (38%), hemorrhage and abnormal vascular architecture. CONCLUSION: p53 causes tumor regression by suppressing tumor proliferation and indirectly induces involution of tumor vessels by fostering unopposed activity of Ang-2 in an environment of diminishing VEGF.

The temporal-spatial expression of VEGF, angiopoietins-1 and 2, and Tie-2 during tumor angiogenesis and their functional correlation with tumor neovascular architecture.

Angiopoietins play a pivotal role in tumor angiogenesis by modulating vascular endothelial proliferation and survival. The expression of angiopoietins 1 and 2 (Ang-1 and Ang-2) and vascular endothelial growth factor (VEGF) has been documented in human malignant glioma. The expression of Ang-1, Ang-2, VEGF, and Tie-2, a member of the receptor tyrosine kinases and the natural receptor for both Ang-1 and Ang-2, follows a distinct transcriptional profile in vivo. Ang-2 and VEGF were expressed early in tumor formation and their levels increased throughout tumor growth. Their expression coincided with the expansion of the tumor mass and the formation of the vascular tree. There was no significant change in the expression of Tie-2 and Ang-1. The expression of Ang-1 and Tie-2 was more noticeable at the periphery of the tumor. The expression of Ang-2 was more robust at the periphery and within the tumor mass, and VEGF was more concentrated within the center of the tumor. This distinct expression profile may explain the morphology of the newly formed vessels at various times and regions of the tumor. The lack of concomitant expression of Ang-1 may underscore the unopposed endovascular induction by Ang-2 and VEGF resulting in the chaotic appearance and fragility of tumor vessels.

Amyloid-beta accumulation, neurogenesis, behavior, and the age of rats.

The goals of this research were to describe age-related changes in brain biochemistry and behavior, and the relationships between them. The chronological ages of greatest change are particularly important for targeting interventions. In this experiment, 36 Fischer 344/Brown-Norway rats (3, 12, 20, and 30 months old) were trained in lever boxes on temporal discrimination tasks. The greatest response rate decrease and response pattern change occurred between 12 and 20 months. The biochemical results showed that amyloid-beta peptides (Aß40 and Aß42) increased with age. The endothelial expression of the Aß influx transporter (RAGE) also increased, and the expression of Aß efflux transporter (LPR-1) decreased, with age. The greatest change in the biochemical measures also were between 12 and 20 months. Twenty additional rats were analyzed for stem cell proliferation, and neurogenesis decreased with age, particularly between about 12 and 20 months. These early changes in brain, biochemistry, and behavior provide opportunity for new therapies or prophylaxis.

Temporal course of cerebrospinal fluid dynamics and amyloid accumulation in the aging rat brain from three to thirty months.

BACKGROUND: Amyloid accumulation in the brain parenchyma is a hallmark of Alzheimer's disease (AD) and is seen in normal aging. Alterations in cerebrospinal fluid (CSF) dynamics are also associated with normal aging and AD. This study analyzed CSF volume, production and turnover rate in relation to amyloid-beta peptide (Aß) accumulation in the aging rat brain. METHODS: Aging Fischer 344/Brown-Norway hybrid rats at 3, 12, 20, and 30 months were studied. CSF production was measured by ventriculo-cisternal perfusion with blue dextran in artificial CSF; CSF volume by MRI; and CSF turnover rate by dividing the CSF production rate by the volume of the CSF space. Aß40 and Aß42 concentrations in the cortex and hippocampus were measured by ELISA. RESULTS: There was a significant linear increase in total cranial CSF volume with age: 3-20 months (p < 0.01); 3-30 months (p < 0.001). CSF production rate increased from 3-12 months (p < 0.01) and decreased from 12-30 months (p < 0.05). CSF turnover showed an initial increase from 3 months (9.40 day-1) to 12 months (11.30 day-1) and then a decrease to 20 months (10.23 day-1) and 30 months (6.62 day-1). Aß40 and Aß42 concentrations in brain increased from 3-30 months (p < 0.001). Both Aß42 and Aß40 concentrations approached a steady state level by 30 months. CONCLUSIONS: In young rats there is no correlation between CSF turnover and Aß brain concentrations. After 12 months, CSF turnover decreases as brain Aß continues to accumulate. This decrease in CSF turnover rate may be one of several clearance pathway alterations that influence age-related accumulation of brain amyloid.