Cerebral amyloid angiopathy

A[beta] peptides are the major protein constituents of Alzheimer's disease (AD) senile plaques and also form some deposits in the cerebrovasculature leading to cerebral amyloid angiopathy and hemorrhagic stroke. Functional vascular abnormalities are one of the earlier clinical manifestations in both sporadic and familial forms of AD. Most of the cardiovascular risk factors (for instance, diabetes, hypertension, high cholesterol levels, atherosclerosis and smoking) constitute risk factors for AD as well, suggesting that functional vascular abnormalities may contribute to AD pathology. We studied the effect of A[beta] on endothelin-1 induced vasoconstriction in isolated human cerebral arteries collected following rapid autopsies. We report that freshly solubilized A[beta] enhances endothelin-1 induced vasoconstriction in isolated human middle cerebral and basilar arteries. The vasoactive effect of A[beta] in these large human cerebral arteries is inhibited by NS-398, a selective cyclooxygenase-2 inhibitor and by SB202190, a specific p38 Mitogen Activated Protein Kinase inhibitor suggesting the involvement of a pro-inflammatory pathway. Using a scanner laser Doppler imager, we observed that cerebral blood flow is decreased in the double transgenic APPsw Alzheimer mouse (PS1/APPsw) compared to PS1 litter/nates and can be improved by chronic treatment with either NS-398 or SB202190. Altogether, our data suggest a link between inflammation and the compromised cerebral hemodynamics in AD. [Neurol Res 2003; 25: 642-651]

Keywords: Cerebrovessels; microvessel; [beta]-amyloid; inflammation; Alzheimer; cerebral blood flow

INTRODUCTION

Alzheimer's disease (AD) is the major cause of dementia in the elderly in Western countries, and is characterized by the progressive accumulation of intracellular neurofibrillary tangles, extracellular parenchymal senile plaques and cerebrovascular deposits1. The principal component of senile plaques and cerebrovascular deposits is the 39-43 amino acid [beta]-amyloid peptide (A[beta]), which is proteolytically derived from the amyloid precursor protein (APP). Morphological abnormalities of cerebral capillaries and related deficient cerebral circulation observed in AD have gained increasing attention in recent years. Vascular pathology is the norm in advanced cases of AD, with cerebral amyloid angiopathy (CAA) being one of the most common abnormalities detected at autopsy2. Functional imaging techniques including positron emission tomography (PET) and single photon emission computerized tomography (SPECT) have revealed the existence of hypoperfusion in individuals prior to the clinical diagnosis of AD suggesting that vascular abnormalities occur early during the disease process3,4. The reduction in flow rate was found to be more pronounced in the hippocampus and temporal cortex, regions which are known to be first and most severely affected in AD5,6. A[beta] peptides are thought to be the key initiators of the pathophysiology of AD, however the mechanisms by which these peptides exert their deleterious effects is far from fully elucidated. At high doses (high micromolars), A[beta] peptides are known to be toxic both for neuronal and vascular cells7,8 and to contribute to the activation of glial cells9,10. We have shown previously that low doses of A[beta] (nanomolar to micromolar) can impair the vascular reactivity to various vasoconstrictors and vasorelaxants11-15 suggesting that A[beta] may contribute to brain dysfunction by decreasing the cerebral blood flow (CBF) in AD. We have previously shown that A[beta] peptides synergistically enhance the vasoconstriction induced by endothelin-1 (ET-1) via the stimulation of a proinflammatory pathway16 in rat aortae. ET-1 is one of the most potent cerebrovasoconstrictors known and in concert with nitric oxide is responsible for the second to second control of the cerebrovasotonus. We have confirmed in vivo that intra-arterial infusion of synthetic A[beta] acts as a cerebrovasoconstrictor17. Others have now reported that topical application of synthetic A[beta] peptides enhances vasoconstriction in the cerebrovasculature of rodents18. Moreover, Abgr; overexpression in young (2-3 month) Tg APPsw has been shown to reduce the increased CBF produced by activation of the vibrissae in the somatosensory cortex, suggesting that increased A[beta] levels produces a potentially deleterious mismatch between substrate delivery and energy demands imposed by neural activity19. The influence of A[beta] on constrictor responses of human cerebrovessels remains to be investigated. In the present study, we investigated the effect of A[beta] on the vasoconstriction induced by ET-1 in isolated human middle cerebral and basilar arteries and began to study the mechanism of the effect. In addition, CBF was also evaluated in the double transgenic APPsw Alzheimer mouse (PS1/APPsw) and the effect of two different anti-inflammatory drugs investigated in these animals.

MATERIALS AND METHODS

Vessel experiments

Freshly dissected human basilar and middle cerebral arteries were collected from 17 different elderly patients (average post-mortem delay: 4.5 h+ or -12 min including the time necessary to perform the autopsy; mean age: 77.4+ or -2.5 years). Arteries were first rinsed in ice-cold HBSS containing 2x penicillin-streptomycin-fungizone and washed in 50 ml PBS (only the segments of arteries presenting no deposits were selected for this study). Human basilar and middle cerebral arteries were segmented into 3 mm rings and suspended in Kreb's buffer on hooks connected to a tensiometer linked to a MacLab system (AD Instruments, Castle Hill, Australia). Artery rings were equilibrated for 2 h in 7 ml tissue baths containing Kreb's buffer (changed every 30 min) oxygenated with 95% O2 : CO2, and thermoregulated at 37[degrees]C. A baseline tension of 2 g was applied to each ring, 2 min prior to their treatment with either 1 [mu]M A[beta], 10 [mu]M NS-398, 5 [mu]M SB202190, a combination of A[beta] and NS-398 or A[beta] and SB202190 as previously described16. Following 5 min of treatment, artery rings were submitted to a dose range of ET-1 ranging from 1 nM to 5 nM. Each dose of ET-1 was added only after the constriction response to the previous dose had reached a plateau. Arteries presenting deposits were not used and arteries that did not show the expected increased vasoconstriction in response to ET-1 treatment were excluded from the study. Results were expressed as the means + or - SE of the tension (in g) obtained for each dose of ET-1 and for the different treatments.

Isolation of human brain microvessels and prostaglandin measurement

Human brain microvessels were isolated as previously described20. Immediately following the autopsies, fragments of frontal and temporal cortex (1 cm^sup 3^) were washed with cold Hanks' balanced salt solution (HBSS) containing 2x penni-strepto-fungizone mixture (Biowhittaker, Walkersville, MD, USA) and homogenized in 20-25 ml of HBSS with a dounce homogenizer at 4[degrees]C under sterile conditions. Briefly, the homogenates were centrifuged at 2000xg and the pellets were resuspended in four volumes of HBSS containing 15% dextran and 5% fetal calf serum. Following 20 min centrifugation at 4000xg, the pellets were resuspended in two volumes of HBSS. Microvessels were then collected on 53 [mu]m filters and washed with 30 ml of HBSS. Microvessels were then centrifuged at 2000xg for 15 min and resuspended in Dulbecco's Modified Eagle Medium (DMEM, Life Technologies, Inc., Rockville, MD, USA) containing 5% fetal calf serum. Microvessels were then transferred to 24-well tissue culture plates and incubated at 37[degrees]C following treatment with 2 [mu]M A[beta]^sub 1-40^ (control microvessels were untreated), 10 [mu]M of NS298, or a combination of A[beta] and NS398. Cell culture medium (100 [mu]l) was collected at 2, 4 and 6 h of incubation and assayed for PGF^sub 2a^ and PGE^sub 2^ using competitive ELISA following the recommendation of the manufacturer (Cayman Chemical Company, Ann Arbor, MI, USA). At the end of the experiments, microvessels were collected by centrifugation and sonicated in mammalian lysis buffer (Pierce, Rockford, IL, USA). Protein concentrations were determined in the lysis buffer using Biorad reagent, and results of the prostaglandin ELISAs were standardized against the amount of protein.

Determination of regional CBF by laser scanner Doppler imaging

Mice expressing mutant APP^sub K670N,M671L^ (Tg APPsw line 2576)21 were crossed with mice expressing mutant PS1 (mutant PS1, line 6.2) in order to produce the PS/APPsw line (Tg PS/APPsw)22. Transgenic PS1/APPsw (n = 15), PS1 mice (n = 13), Tg PS1/APPsw mice treated with NS-398 (n = 10), PS1 mice treated with NS-398 (n = 8), Tg PS1/APPsw treated with SB202190 (n = 8) and PS1 treated with SB202190 (n = 10) were studied at nine months of age. PS1 and Tg PS/APPsw mice (at six months of age) were injected intraperitoneally with 20 mg kg^sup -1^ of NS-398, with 5 mg kg^sup -1^ SB202190 or with the vehicle alone three times a week for a period of three months. NS-398 and SB202190 were dissolved in PBS containing 50% DMSO. For CBF measurement, mice were anesthetized with a gas mixture of 3%) isofluorane, 0.9 l min^sup -1^ nitrous oxide and 0.5 l min^sup -1^ oxygen. Animals were then immobilized on a mouse stereotaxic table and maintained under anesthesia with a mouse anesthetic mask (Kopf Instruments, Tunjunga, CA, USA) delivering 3% isofluorane, 0.5 l min^sup -1^ nitrous oxide, 0.3 l min^sup -1^ oxygen. Rectal temperature was maintained at 37[degrees]C using a mice homeothermic blanket system (Harvad Apparatus, Holliston, MA, USA). An incision was made through the scalp and the skin retracted to expose the skull, which was then cleaned with a sterile cotton swab. Animals were maintained on a mixture of 1.5% isofluorane, 0.5 l min^sup -1^ nitrous oxide and 0.3 l min^sup -1^ oxygen. Cortical perfusion was measured with the Laser-Doppler Perfusion Imager from Moor Instruments (Wilmington, DE, USA) as previously described23. A computer-controlled optical scanner directed a low-power He-Ne laser beam over the exposed cortex. The scanner head was positioned parallel to the cerebral cortex at a distance of 26 cm. The scanning procedure took 1 min and 21 sec for measurements of 5538 pixels covering an area of 0.8 cm x 0.8 cm. At each measuring site, the beam illuminated the tissue to a depth of 0.5 mm. An image color-coded to denote specific relative perfusion levels was displayed on a video monitor. All images were acquired at 2-min intervals for a period of 30 min (15 images for each animal). All images were stored in computer memory for subsequent analysis. For each animal, a square area of 0.05 cm^sup 2^ (360 pixels) equally distributed between the right and left hemispheres was defined and applied to each image of the series in order to measure the CBF in the frontal, parietal and occipital cortex. CBF was also measured in the entire cortex by manually delineating for each mouse the cortex area (0.51 to 0.54 cm^sup 2^ corresponding to 3504 to 3714 pixels). Relative perfusion values for each area studied were normalized against the CBF values obtained in control mice and expressed as a percentage of control CBF.

Data analysis

Data are expressed as means + or - SE. Multiple comparisons were evaluated by analysis of variance and post hoc comparisons performed using Scheffe test. Probability values inferior to 5% were considered statistically significant.

RESULTS

Effect of A[beta] on the vasoconstriction elicited by ET-1 on human middle cerebral and basilar arteries

Human middle cerebral and basilar arteries were isolated following rapid autopsies. As shown in Figures 1 and 2, A[beta] synergistically enhances the vasoconstriction induced by ET-1 in both human middle cerebral and basilar arteries confirming that A[beta] displays some vasoactive properties in isolated human cerebrovessels. To assess the specificity of the A[beta] effects, a scrambled A[beta] peptide was used and displayed no enhancement of ET-1 induced vasoconstriction in human middle cerebral artery (data not shown). We have previously shown that soluble forms of A[beta] peptides exert their vasoactive effects in rodent aortae by stimulating a pro-inflammatory pathway involving p38 MAPK and COX-2 activation16. Therefore, we tested whether the vasoactive effect of A[beta] in human cerebrovessels would also be mediated via a similar mechanism. Pharmacological inhibition of COX-2 and p38 MAPK by the selective inhibitors NS-398 and SB202190 respectively resulted in a complete inhibition of A[beta] vasoactivity in human basilar and middle cerebral arteries (Figures 1 and 2).

Effect of A[beta] on isolated human brain microvessels

We previously showed that freshly solubilized A[beta] (fsA[beta]) peptides stimulate eicosanoid production in the peripheral vasculature, resulting in an increased vaso-constriction by ET-116. In the present study, we considered whether fsA[beta] could also stimulate prostaglandin formation in isolated human brain microvessels. Our data show that fsA[beta] increased the accumulation of PGE^sub 2^ and PGF^sub 2^sub [alpha]^^ in the culture medium of isolated human brain microvessels (Figure 3). Human brain microvessels were found to constitutively express COX-2 (data not shown), therefore we incubated human brain microvessels with the selective COX-2 inhibitor NS-398 to determine whether the increased prostaglandin production stimulated by fsA[beta] was COX-2 dependent. We observed that NS-398 treatment reduced the basal production of PGE^sub 2^ by isolated human brain microvessels suggesting that a part of the basal PGE^sub 2^ production is mediated by COX-2 in human brain microvessels. Furthermore, fsA[beta] increased production of PGE^sub 2^ and PGF^sub 2[alpha]^ is inhibited by NS-398 suggesting that fsA[beta] stimulates COX-2 activity in human brain microvessels (Figure 3).

Reduced CBF in transgenic mouse models of Alzheimer's disease

A laser scanner Doppler imager (LDI) was used to measure regional variation of CBF in Tg PSI/APPsw mice compared to their PS1 littermates. CBF was analyzed in the entire cortex (area covering approximately 0.5 cm^sup 2^ to 0.6 cm^sup 2^) and in selected areas of the cortex defined as parietal, occipital and frontal areas (Figure 4). Regional CBF was found to be reduced in nine-month-old Tg PS/APPsw mice compared to PS1 littermates (Figure 4). Interestingly, chronic treatment of the mice with NS-398 or with SB202190 prevented the decline in CBF observed in Tg PS/APP mice compared to their control PS1 littermates (Figure 4).

DISCUSSION

Previous studies have revealed a high correlation between regional capillary density, local CBF and glucose utilization24,25. The precise matching of glucose and oxygen delivery to metabolic demand via changes in local CBF is a crucial process, which sustains all neuronal activity. Insufficient cerebral circulation is associated with memory deficits and cognitive impairments in laboratory animals26,27. We observed that A[beta] synergistically enhanced ET-1 induced vasoconstriction in isolated human cerebrovessels reproducing the vasoactive effect of the peptide originally described in rodent aortae and suggesting that A[beta] may exert a vasoactive action in the human cerebrovasculature. The in vitro vasoactive effect of A[beta] is completely reversed by NS-398 and by SB202190 in isolated human cerebrovessels. At the concentrations used SB202190 (5 [mu]M) selectively inhibits p38 MAPK activity without affecting ERK2, SAPK3 or SAPK4 activities28,29 and NS-398 (10 [mu]M) preferentially inhibits COX-2 compared to COX-130. These results suggest that the vasoactive effects of A[beta] in human middle cerebral and basilar arteries are mediated via a pro-inflammatory pathway involving the activation of p38 MARK and COX-2. Chronically disturbed capillary blood flow is likely to impair normal delivery of essential nutrients to the brain as well as impede catabolic outflow of central nervous system waste products31. Therefore, we investigated the impact of A[beta] on isolated human brain microvessels. Our data suggest that A[beta] stimulates COX-2 activity in isolated brain microvessels resulting in an increased production of vasoactive prostaglandins.

In order to explore whether increased level of A[beta] could exert similar vasoactive effects in vivo, we next measured the regional cortical blood flow in Tg PS1/APPsw mice and PS1 littermates using an LDI. This instrument produces a two-dimensional image of the movement of red blood cells (perfusion) in the area being scanned32. Compared with the conventional laser Doppler perfusion monitoring, the LDI technique presents the advantage of not requiring contact with the tissue, integrating flow reading over a large area instead of a single point, which allows determination of regional differences, and also makes possible studies of relative red blood cell velocity changes from smaller tissue volume than is possible by available probe configuration33. The Tg PS2/APPsw mice used for this study develop a partial AD-like phenotype including learning and memory deficits and pathological findings of amyloid plaque deposition, increased A[beta]^sub 1-40^ and A[beta]^sub 1-42^ levels, gliosis, inflammatory responses, phosphorylated tau epitopes, but not neurofibrillary tangles or neuronal loss21,34-37. Alterations in the vasodilatation produced by pharmacological agents applied to cerebral blood vessels have been observed previously in 2-3 month-old Tg APPsw mice18. Moreover, A[beta] overexpression has been shown to diminish the increased neocortical CBF produced by physiological activation of the somatosensory pathway in Tg APPsw mice18,19. We measured the CBF in nine-month-old double transgenic PS1/APPsw and observed a reduction of CBF in these mice compared to their PS1 littermates for all the areas of the brain examined. In isolated human cerebrovessels, A[beta] vasoactivity appears to be mediated via a pro-inflammatory pathway and can be antagonized by the selective COX-2 inhibitor NS-398 and by the p38 MAPK inhibitor SB202190. Therefore, we also studied the impact of SB202190 and NS-398 treatments on the CBF of PS1 and Tg PS/APPsw mice. Our data reveal that a chronic treatment with SB202190 or NS-398 can improve cerebral perfusion in Tg PS/APPsw mice suggesting that the alteration of CBF observed in these animals involves an inflammatory mechanism.

Sufficient cerebral perfusion is essential for proper memory processing. With a lower perfusion rate, the delivery of oxygen and the nutrient transport to the brain may not be adequate, which may reduce neuronal metabolism, and consequently affect cognition. Such deprivation of the neuronal tissue can either be consequent to the reduced CBF itself or due to abnormal structural features. Most likely, the two factors are dynamically connected and equally affect nutrient trafficking in the brain. Reciprocally, cerebral hypoperfusion might lead to cerebral capillary damage39.

The present results provide evidence that cortical CBF is impaired in a transgenic mouse model of AD and suggest a link between inflammation and CBF alteration. Nonsteroidal anti-inflammatory drugs (NSAIDs) can slow the progression of AD or reduce the risk of its development40,41, suggesting that inflammatory events may be important in the initiation of AD pathology. In particular, NSAIDs reduce prostaglandin production by inhibiting cyclooxygenases42, suggesting that prostaglandins may contribute to AD development. Several converging lines of evidence suggest that A[beta] peptides and inflammation may be linked in AD pathogenesis. For example, senile plaques observed in AD brain are sites of classical inflammatory processes, as shown by the presence of numerous degenerating neurons, reactive microglia and astrocytes, cytokines, and complement proteins43,44. An elevated PGE^sub 2^ concentration in the cerebrospinal fluid and an increased COX-2 immunoreactivity have been found in patients with AD45,46. The role of elevated prostaglandin production in AD pathogenesis is far from understood. Prostaglandins are important modulators of arterial vasotonus; for example PGF^sub 2^sub [alpha]^^ can reduce CBF by inducing vasoconstriction in the cerebrovasculature47,48. CBF is depressed in AD brain, and the Mini-Mental Status Examination score (a sensitive marker of neuropsychological deficit) correlates with the hippocampal perfusion level49. Perhaps A[beta]-induced vasoconstriction contributes to AD pathophysiology and the reduction of CBF observed in AD may be associated to a neuroinflammatory process. It is interesting to note that the coupling of neuronal activation to cerebral blood vessel responses has been shown to involve the release of a cyclo-oxygenase product from astrocytes50. Prostaglandins might also contribute to AD pathophysiology via other mechanisms; for instance, PGE^sub 2^ can activate the expression of the amyloid precursor protein in astrocytes51, and thus may play a role in modulating A[beta] production. Additionally, our data suggest that the vasculature could constitute an important source of prostaglandins in response to elevated levels of A[beta] leading possibly to an increased vasoconstriction by endogenous vasoconstrictors such as ET-1 hence resulting in alteration of CBF.

ACKNOWLEDGEMENTS

We wish to thank Mr Bob and Mrs Diane Roskamp for their generous support, which helped to make this work possible. This work was supported in part by National Institutes of Health Grant AG19250-01.

REFERENCES

1 Sisodia SS, Price DL. Role of the beta-amyloid protein in Alzheimer's disease. FASEB J 1995; 9: 366-370

2 Ellis RJ, Olichney JM, Thai LJ, Mirra SS, Morris JC, Beekly D, Heyman A. Cerebral amyloid angiopathy in the brains of patients with Alzheimer's disease: The CERAD experience, Part XV. Neurology 1996; 46: 1592-1596

3 Nagata K, Kondoh Y, Atchison R, Sato M, Satoh Y, Watahiki Y, Hirata Y, Yokoyama E. Vascular and metabolic reserve in Alzheimer's disease. Neurobiol Aging 2000; 21: 301-307

4 Johnson KA, Albert MS. Perfusion abnormalities in prodromal AD. Neurobiol Aging 2000; 21: 289-292

5 Braak H, Braak E. Neuropathological staging of Alzheimer-related changes. Acta Neuropathol (Ben) 1991; 82: 239-259

6 DeKosky ST, Shih WJ, Schmitt FA, Coupai J, Kirkpatrick C. Assessing utility of single photon emission computed tomography (SPECT) scan in Alzheimer disease: Correlation with cognitive severity. Alzheimer Dis Assoc Disord 1990; 4: 14-23

7 Roher AE, Chaney MO, Kuo YM, Webster SD, Stine WB, Haverkamp LJ, Woods AS, Cotter RJ, Tuohy JM, Krafft GA, Bonnell BS, Emmerling MR. Morphology and toxicity of Abeta-(1-42) dimer derived from neuritic and vascular amyloid deposits of Alzheimer's disease. J Biol Chem 1996; 271: 20631-20635

8 Van Nostrand WE, Melchor JP, Cho HS, Greenberg SM, Rebeck GW. Pathogenic effects of D23N Iowa mutant amyloid beta-protein. J Biol Chem 2001; 276: 32860-32866

9 Tan J, Town T, Paris D, Mori T, Suo Z, Crawford F, Mattson MP, Flavell RA, Mullan M. Microglial activation resulting from CD40-CD40L interaction after beta-amyloid stimulation. Science 1999; 286: 2352-2355

10 Lue LF, Walker DG, Rogers J. Modeling microglial activation in Alzheimer's disease with human postmortem microglial cultures. Neumbiol Aging 2001; 22: 945-956

11 Thomas T, Thomas G, McLendon C, Sutton T, Mullan M. Beta-Amyloid-mediated vasoactivity and vascular endothelial damage. Nature 1996; 380: 168-171

12 Crawford F, Suo Z, Fang C, Mullan M. Characteristics of the in vitro vasoactivity of beta-amyloid peptides. Exp Neurol 1998; 150: 159-168

13 Paris D, Town T, Parker TA, Tan J, Humphrey J, Crawford F, Mullan M. Inhibition of Alzheimer's beta-amyloid induced vasoactivity and proinflammatory response in microglia by a cGMP-dependent mechanism. Exp Neurol 1999; 157: 211-221

14 Paris D, Town T, Parker TA, Humphrey J, Mullan M. Isoform-specific vasoconstriction induced by apolipoprotein E and modulation of this effect by Alzheimer's beta-amyloid peptide. Neurosci Lett 1998; 256: 73-76

15 Paris D, Parker TA, Town T, Suo Z, Fang C, Humphrey J, Crawford F, Mullan M. Role of peroxynitrite in the vasoactive and cytotoxic effects of Alzheimer's beta-amyloid 1-40 peptide. Exp Neurol 1998; 152: 116-122

16 Paris D, Town T, Mori T, Parker TA, Humphrey J, Mullan M. Soluble beta-amyloid peptides mediate vasoactivity via activation of a pro-inflammatory pathway. Neurobiol Aging 2000; 21: 183-197

17 Suo Z, Humphrey J, Kundtz A, Sethi F, Placzek A, Crawford F, Mullan M. Soluble Alzheimers beta-amyloid constricts the cerebral vasculature in vivo. Neurosci Lett 1998; 257: 77-80

18 Niwa K, Carlson GA, Iadecola C. Exogenous A beta 1-40 reproduces cerebrovascular alterations resulting from amyloid precursor protein overexpression in mice. J Cereb Blood Flow Metab 2000; 20: 1659-1668

19 Niwa K, Younkin L, Ebeling C, Turner SK, Westaway D, Younkin S, Ashe KH, Carlson GA, Iadecola C. Abeta 1-40-related reduction in functional hyperemia in mouse neocortex during somatosensory activation. Proc Natl Acad Sci USA 2000; 97: 9735-9740

20 Grammas P, Moore P, Weigel PH. Microvessels from Alzheimer's disease brains kill neurons in vitro. Am J Pathol 1999; 154: 337-342

21 Hsiao K, Chapman P, Nilsen S, Eckman C, Harigaya Y, Younkin S, Yang F, Cole G. Correlative memory deficits, Abeta elevation, and amyloid plaques in transgenic mice. Science 1996; 274: 99-102

22 Duff K, Eckman C, Zehr C, Yu X, Prada CM, Perez-tur J, Hutton M, Buee L, Harigaya Y, Yager D, Morgan D, Gordon MN, Holcomb L, Refolo L, Zenk B, Hardy J, Younkin S. Increased amyloid-beta42(43) in brains of mice expressing mutant presenilin 1. Nature 1996; 383: 710-713

23 Liu Y, Belayev L, Zhao W, Busto R, Belayev A, Ginsberg MD. Neuroprotective effect of treatment with human albumin in permanent focal cerebral ischemia: Histopathology and cortical perfusion studies. Eur J Pharmacol 2001; 428: 193-201

24 Borowsky IW, Collins RC. Metabolic anatomy of brain: A comparison of regional capillary density, glucose metabolism, and enzyme activities. J Comp Neurol 1989; 288: 401-413

25 Klein B, Kuschinsky W, Schrock H, Vetterlein F. Interdependency of local capillary density, blood flow, and metabolism in rat brains. Am J Physiol 1986; 251: H1333-H1340

26 Sopala M, Dunysz W. Chronic cerebral hypoperfusion in the rat enhances age-related deficits in spatial memory. J Neural Transm 2001; 108: 1445-1456

27 Ohta H, Nishikawa H, et al. Chronic cerebral hypoperfusion by permanent internal carotid ligation produces learning impairment without brain damages in rats. Neuroscience 1997; 79: 1039-1050

28 Li Z, Jiang Y, Ulevitch RJ, Han J. The primary structure of p38 gamma: A new member of p38 group of MAP kinases. Biochem Biophys Res Commun 1996; 228: 334-340

29 Manthey CL, Wang SW, Kinney SD, Yao Z. SB202190, a selective inhibitor of p38 mitogen-activated protein kinase, is a powerful regulator of LPS-induced mRNAs in monocytes. J Leukoc Biol 1998; 64: 409-417

30 Futaki N, Takahashi S, Yokoyama M, Arai I, Higuchi S, Otomo S. NS-398, a new anti-inflammatory agent, selectively inhibits prostaglandin G/H synthase/cyclooxygenase (COX-2) activity in vitro. Prostaglandins 1994; 47: 55-59

31 de la Torre JC. Hemodynamic consequences of deformed microvessels in the brain in Alzheimer's disease. Ann NY Acad Sci 1997; 826: 75-91

32 Essex TJ, Byrne PO. A laser Doppler scanner for imaging blood flow in skin. J Biomed Eng 1991; 13: 189-194

33 Golster H, Linden M, Bertuglia S, Colantuoni A, Nilsson G, Sjoberg F. Red blood cell velocity and volumetric flow assessment by enhanced high-resolution laser Doppler imaging in separate vessels of the hamster cheek pouch microcirculation. Microvasc Res 1999; 58: 62-73

34 Irizarry MC, McNamara M, Fedorchak K, Hsiao K, Hyman BT. APPSw transgenic mice develop age-related A beta deposits and neuropil abnormalities, but no neuronal loss in CA1. J Neuropathol Exp Neurol 1997; 56: 965-973

35 Frautschy SA, Yang F, Irrizarry M, Hyman B, Saido TC, Hsiao K, Cole GM. Microglial response to amyloid plaques in APPsw transgenic mice. Am J Pathol 1998; 152: 307-317

36 Chapman PF, White GL, Jones MW, Cooper-Blacketer D, Marshall VJ, Irizarry M, Younkin L, Good MA, Bliss TV, Hyman BT, Younkin SG, Hsiao KK. Impaired synaptic plasticity and learning in aged amyloid precursor protein transgenic mice. Nat Neurosci 1999; 2: 271-276

37 King DL, Arendash GW, Crawford F, Sterk T, Menendez J, Mullan MJ. Progressive and gender-dependent cognitive impairment in the APP(SW) transgenic mouse model for Alzheimer's disease. Behav Brain Res 1999; 103: 145-162

38 Iadecola C, Zhang F, Niwa K, Eckman C, Turner SK, Fischer E, Younkin S, Borchelt DR, Hsiao KK, Carlson GA. SOD1 rescues cerebral endothelial dysfunction in mice overexpressing amyloid precursor protein. Nat Neurosci 1999; 2: 157-161

39 De Jong GI, Farkas E, Stienstra CM, Plass JR, Keijser JN, de la Torre JC, Luiten PG. Cerebral hypoperfusion yields capillary damage in the hippocampal CA1 area that correlates with spatial memory impairment. Neuroscience 1999; 91: 203-210

40 Andersen K, Launer LJ, Ott A, Hose AW, Breteler MMB, Hofman A. Do nonsteroidal anti-inflammatory drugs decrease the risk for Alzheimer's disease? The Rotterdam Study. Neurology 1995; 45: 1441-1445

41 Breitner JCS, Gau BA, Welsh KA, Plassman BL, McDonald WM, Helms MJ, Anthony JC. Inverse association of anti-inflammatory treatments and Alzheimer's disease: Initial results of a co-twin control study. Neurology 1994; 44: 227-244

42 Meade EA, Smith WL, Dewitt DL. Differential inhibition of prostaglandin endoperoxide synthase (cyclooxygenase) isozyme by aspirin and other non-steroidal anti-inflammatory drugs. J Biol Chem 1993; 268: 6610-6614

43 Itagaki S, McGeer PL, Akiyama H, Zhu S, Selkoe D. Relationship of microglia and astrocytes to amyloid deposits of Alzheimer's disease. J Neuroimmunol 1989; 24: 173-182

44 McGeer PL, McGeer EG. Inflammation of the brain in Alzheimer's disease: Implications for therapy. J Leukoc Biol 1999; 409-415

45 Ho L, Luterman JD, Aisen PS, Pasinetti GM, Montine TJ, Morrow JD. Elevated CSF prostaglandin E2 levels in patients with probable AD. Neurology 2000; 55: 323

46 Montine TJ, Sidell KR, Crews BC, et al. Elevated CSF prostaglandin E2 levels in patients with probable AD. Neurology 1999; 53: 1495-1498

47 Hoffman SW, Moore S, Ellis EF. Isoprostanes: Free radical-generated prostaglandins with constrictor effects on cerebral arterioles. Stroke 1997; 28: 844-849

48 Li DY, Hardy P, Abran D, et al. Key role for cyclooxygenase-2 in PGE2 and PGF2alpha receptor regulation and cerebral blood flow of the newborn. Am J Physiol 1997; 273: R1283-R1290

49 Rodriguez G, Nobili F, Copello F, et al. 99mTc-HMPAO regional cerebral blood flow and quantitative electroencephalography in Alzheimer's disease: A correlative study. J Nucl Med 1999; 40: 522-529

50 Zonta M, Angulo MC, Gobbo S, Rosengarten B, Hossmann KA, Pozzan T, Carmignoto G. Neuron-to-astrocyte signaling is central to the dynamic control of brain microcirculation. Nat Neurosci 2003; 6: 43-50

51 Lee RK, Knapp S, Wurtman RJ. Prostaglandin E2 stimulates amyloid precursor protein gene expression: Inhibition by immuno-suppressants. J Neurosci 1999; 19: 940-947

Daniel Paris, James Humphrey, Amita Quadros, Nikunj Patel, Robert Crescentini, Fiona Crawford and Michael Mullan

The Roskamp Institute, Sarasota, FL, USA

Correspondence and reprint requests to: Daniel Paris, The Roskamp Institute, 2040 Whitfield Avenue, Sarasota, FL 34243, USA.

[dparis@rfdn.org] Accepted for publication April 2003.

Copyright Forefront Publishing Group Sep 2003
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