James Humphrey

James A. Haley Veterans Hospital, Tampa, Florida, United States

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Publications (32)95.1 Total impact

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    ABSTRACT: Traumatic Brain Injury (TBI) is known to result in oxidative stress, and as variation at the Apolipoprotein E (APOE) gene has been shown to influence outcome following TBI, but through as yet unclear mechanisms, we used transgenic APOE mouse models to examine the relationship between APOE genotype and oxidative stress following TBI. We administered a controlled cortical impact (CCI) injury or sham injury to transgenic mice expressing either human APOE3 or APOE4 on a murine APOE-deficient background. RNA was prepared from the ipsilateral hippocampi and cortices retrieved at 24 h and 1 month post-TBI. Microarray analysis was performed on unpooled samples from three mice per group to determine the genomic response to TBI and to specifically investigate the response of genes involved in oxidative stress mechanisms. Our data demonstrated TBI-induced expression of many more anti-oxidant related genes in the APOE3 mice, suggesting a potential anti-oxidative role for ApoE3 compared to ApoE4. However, in an additional cohort of mice we isolated the ipsilateral hippocampi, cortices, and cerebella at 1 month after TBI or sham injury for immunohistochemical analysis of markers of oxidative stress: the formation and presence of carbonyls (indication of general oxidative modification), 3-nitrotyrosine (3NT; specific to protein modification), or 4-hydroxyl-2-nonenal (HNE; specific to lipid peroxidation). Although we observed significant increases in all three markers of oxidative stress in response to injury, and genotype was a significant factor for carbonyl and 3NT, we found no significant interaction between genotype and injury. This may be due to the overwhelming effect of injury compared to genotype in our ANOVA, but nonetheless suggests that an influence on oxidative stress response is not the primary mechanism behind the APOE-genotype dependent effects on outcome following TBI.
    Neuroscience 07/2010; 168(3):811-9. · 3.12 Impact Factor
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    ABSTRACT: The different alleles of the apolipoprotein E gene (APOE-gene, ApoE-protein) have been reported to influence recovery after traumatic brain injury (TBI) in both human patients and animal models, with the e4 allele typically conferring poorer prognosis for recovery. How the E4 allele, and consequently the ApoE4 isoform, affects recovery is unknown, but proposed mechanisms include neurogenesis, inflammatory response and amyloid processing or metabolism. Using the controlled cortical impact (CCI) model of brain injury and microarray technology we have characterized the genomic response to injury in the brains of APOE2, APOE3 and APOE4 transgenic mice and identified quantitatively and qualitatively significantly different profiles of gene expression in both the hippocampus and the cortex of the APOE3 mice compared to APOE4. The observed gene regulation predicts functional consequences including effects on inflammatory processes, cell growth and proliferation, and cellular signaling, and may suggest that the poor recovery post-TBI in APOE4 animals and human patients is less likely to result from a specific activation of neurodegenerative mechanisms than a loss of reparative capability.
    Neuroscience 05/2009; 159(4):1349-62. · 3.12 Impact Factor
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    ABSTRACT: Mounting evidence from in vitro and in vivo studies in transgenic mice overproducing β-amyloid peptides (Aβ) suggests that Aβ can induce vasoconstriction and decrease cerebral blood flow. In this report, we describe the vasoactive properties of Aβ, in particular the enhancement of endothelin-1-induced vasoconstriction and Aβ's induction of a long-lasting vasoconstrictive event. Furthermore, we show that low doses (as low as 50 nM) of freshly solubilized Aβ similar to those observed in the plasma of patients suffering from Alzheimer's disease are vasoactive. By using various inhibitors and activators of the phospholipase A2 (PLA2)/arachidonic acid (AA) cascade, we demonstrate that Aβ vasoactivity is dependent on activation of this intracellular signaling pathway, resulting in stimulation of downstream cyclooxygenase-2 and 5-lipoxygenase, which mediate production of proinflammatory eicosanoids. Taken together, our data show that Aβ directly activates an intracellular proinflammatory pathway, which is responsible for its vasoactive properties.
    Annals of the New York Academy of Sciences 01/2006; 903(1):97 - 109. · 4.38 Impact Factor
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    ABSTRACT: Bilateral temporoparietal hypoperfusion has been frequently observed early in the Alzheimer's disease (AD) process. The β-amyloid (Aβ) peptide is believed to play a central role in the pathogenesis of AD. In vitro experiments have shown that freshly solubilized Aβ enhances constriction of cerebral and peripheral vessels. We proposed that in vivo, Aβ would also have vasoactive properties. To test this hypothesis, we intraarterially infused freshly solubilized Aβ1–40 in rats and observed changes in peripheral blood pressure, cerebral blood flow, and cerebrovascular resistance. We found that infusion of Aβin vivo significantly increased the blood pressure in hypotensive rats but not in normotensive and hypertensive rats. Moreover, Aβ infusion also resulted in a decreased blood flow and increased vascular resistance specifically in cerebral cortex but not in heart or kidneys. These data suggest that Aβ has a direct and specific constrictive effect on cerebral vessels in vivo, which may contribute to the cerebral hypoperfusion observed early in the AD process.
    Annals of the New York Academy of Sciences 01/2006; 903(1):156 - 163. · 4.38 Impact Factor
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    ABSTRACT: The involvement of beta-secretase and gamma-secretase in producing the beta-amyloid component of senile plaques found in the brain of Alzheimer's patients has fueled a major research effort to design selective inhibitors of these proteases. Interestingly, gamma-secretase cleaves several proteins including Notch, E-cadherin, CD44 and ErbB-4 (erythroblastic leukemia viral oncogene homolog 4), which are important modulators of angiogenesis. The beta-amyloid precursor protein, which is cleaved by beta-secretase and gamma-secretase to produce beta-amyloid, is highly expressed in the endothelium of neoforming vessels suggesting that it might play a role during angiogenesis. These data prompted us to explore the effects of beta and gamma-secretase inhibitors of different structures on angiogenesis and tumor growth. Both the gamma and beta-secretase inhibitors tested reduce endothelial cell proliferation without inducing cellular toxicity, suppress the formation of capillary structures in vitro and oppose the sprouting of microvessel outgrowths in the rat aortic ring model of angiogenesis. Moreover, they potently inhibit the growth and vascularization of human glioblastoma and human lung adenocarcinoma tumors xenotransplanted into nude mice. Altogether these data suggest that the gamma and beta-secretases play an essential role during angiogenesis and that inhibitors of the beta and gamma-secretases may constitute new classes of anti-angiogenic and anti-tumoral compounds.
    European Journal of Pharmacology 06/2005; 514(1):1-15. · 2.59 Impact Factor
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    ABSTRACT: The development of Alzheimer's disease (AD) is generally thought to correlate with cerebral accumulation of Abeta. It has previously been shown that Abeta peptides enhance vasoconstriction in isolated arteries and oppose certain vasorelaxants. Moreover, exogenous application of Abeta peptides causes cerebral vasoconstriction in rodents and in transgenic mouse models of AD that overexpress Abeta there is reduced cerebral blood flow. In the present study, we investigated the effect of nilvadipine, a dihydropyridine-type calcium channel blocker, on Abeta induced vasoconstriction in isolated arteries and in vivo on cerebral blood flow (CBF) of an AD transgenic mouse model overexpressing Abeta (Tg APPsw line 2576). Nilvadipine completely inhibited the vasoactivity elicited by Abeta in rat aortae and in human middle cerebral arteries. The effect of a short treatment duration (2 weeks) with nilvadipine on regional CBF was investigated in 13-month-old Tg APPsw mice and control littermates using a laser Doppler imager. Additionally, CBF was also measured in 20-month-old Tg APPsw mice and control littermates that were chronically treated with nilvadipine for 7 months. Untreated Tg APPsw mice showed a reduction of regional CBF compared to their untreated control littermates. Nilvadipine restored cortical perfusion levels in Tg APPsw to values similar to those observed in control littermates without notably affecting the CBF of control mice. All together, these data suggest that nilvadipine might be useful for the treatment of oligemia associated with AD.
    Brain Research 03/2004; 999(1):53-61. · 2.88 Impact Factor
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    ABSTRACT: Abeta peptides are naturally occurring peptides forming beta-sheet aggregates that constitute an integral component of senile plaques and vascular deposits in Alzheimer's disease. Since several peptides adopting a beta-sheet conformation have been shown to be anti-angiogenic, we investigated the effect of Abeta on angiogenesis. We show that in vitro, Abeta dose-dependently inhibits the formation of capillaries by human brain endothelial cells plated on Matrigel and stimulates capillary degeneration at high doses. Preparations of Abeta peptides containing a higher content of beta-sheet structures are more potently anti-angiogenic in vitro. Ex vivo, Abeta dose-dependently opposes angiogenesis in rat aortae and in human middle cerebral arteries. In vivo, Abeta dose dependently inhibits angiogenesis in the chick chorioallantoic membrane assay and suppresses bFGF-induced blood vessel formation in the corneal micropocket and Matrigel plug assays. Since angiogenesis is required for tumor growth, we explored the effect of Abeta on human glioblastoma (U87MG) and human lung adenocarcinoma (A549) tumors. We show that intra-tumoral injection of Abeta potently inhibits the growth and vascularization of human glioblastoma and human lung adenocarcinoma tumor xenografts in nude mice. Similarly to the intra-tumoral injection regimen, Abeta delivered intraperitoneally also suppressed the growth of human lung adenocarcinoma tumor xenografts. Altogether our data show that Abeta is an angiogenesis inhibitor.
    Angiogenesis 02/2004; 7(1):75-85. · 4.41 Impact Factor
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    ABSTRACT: 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 littermates 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.
    Neurological Research 10/2003; 25(6):642-51. · 1.18 Impact Factor
  • Neurological Research - NEUROL RES. 01/2003; 25(6):642-651.
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    ABSTRACT: Clinical and animal studies have demonstrated that nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, can delay the onset of Alzheimer’s disease (AD). We have recently shown that soluble amyloid-beta mediates vasoactivity via activation of a pro-inflammatory pathway involving the COX-2 enzyme. To further determine the therapeutic potentials of COX-2 inhibitors for AD, in transgenic mouse models (6 month old PSAPP or PS1), we repeatedly administered a selective COX-2 inhibitor (NS398), a selective p38 MAPK inhibitor (SB202190), or saline during a three month period. Open field exploration test showed that PSAPP mice have increased overall activity and decreased neophobia. Balance beam ability, a sensorimotor test, was diminished in the PSAPP mice as compared to the PS1 mice. Spatial memory was assessed using the Morris water maze, and on the final probe trial, PSAPP mice performance was impaired compared to PS1 mice. NS398 or SB202190 produced attenuation of the behavioral differences between PSAPP and PS1 mice. Cerebral blood flow (CBF) was determined using non-invasive scanning laser Doppler flowmetry. A reduction in CBF was found in PSAPP mice compared to the PS1 mice. NS398 or SB202190 was associated with an increase in CBF in both the PS1 and PSAPP though a marked increase was seen in the PSAPP animals. These results suggest that COX-2 and p38 MAPK acting drugs reduce the behavioral impairments and CBF losses associated with amyloid pathology typical of AD.
    Society for Neuroscience, 2002, Orlando, FL; 11/2002
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    ABSTRACT: It has recently been shown that the level of soluble beta-amyloid (Abeta) peptides correlates well with the severity of synaptic loss and the density of neurofibrillary tangles observed in Alzheimer's disease (AD) brain. However, the biological activity of soluble forms of Abeta peptides in the brain remains to be determined. We have investigated ex vivo the effect of freshly solubilized Abeta1-40 peptides (fsAbeta) on prostaglandin E2 (PGE2) production in rat brain slices. PGE2 levels increased rapidly following treatment with fsAbeta, an effect that was prevented by SB202190, a selective inhibitor of p38 mitogen-activated protein kinase (p38 MAPK), and by NS-398, which preferentially inhibits cyclooxygenase-2 (COX-2) compared to COX-1. In an attempt to determine the cellular systems of the brain responsible for prostaglandin production in response to fsAbeta, the effect of fsAbeta was tested on isolated brain microvessels, primary cultures of brain smooth muscle cells/pericytes and endothelial cells, and a human neuron-like cell line (IMR32). Our data show that fsAbeta ex vivo can stimulate prostaglandin accumulation in incubates of isolated rat brain microvessels. In addition, fsAbeta appears to cause a concentration-dependent enhancement of prostaglandin accumulation in primary cultures of brain microvessel-derived smooth muscle cells/pericytes but not of brain endothelial cells. Finally, fsAbeta also stimulated PGF2alpha accumulation in cultures of differentiated IMR32 cells, but to a lesser extent than in brain smooth muscle cell/pericyte cultures. Deposition of aggregated forms of Abeta in the brain has been thought to trigger an inflammatory response which accompanies the neuropathologic events of AD. Our data provide evidence that fsAbeta triggers a pro-inflammatory reaction in rat brain, and suggest that the cerebrovasculature may constitute an important source of pro-inflammatory eicosanoids.
    Prostaglandins & other lipid mediators 10/2002; 70(1-2):1-12. · 2.42 Impact Factor
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    ABSTRACT: Freshly solubilized A beta peptides synergistically increase the magnitude of the constriction induced by endothelin-1 (ET-1), via the activation of a pro-inflammatory pathway. We report that mevinolin and mevastatin, two inhibitors of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase are able to completely abolish the vasoactive properties of A beta in rat aortae. Mevinolin also appears to oppose the increased vascular reactivity to ET-1 induced by interleukin 1-beta and phospholipase A(2) suggesting that statins display some anti-inflammatory properties. We show that freshly solubilized A beta stimulates prostaglandin E(2) and F(2 alpha) production (by 6 and 3.6 times, respectively) in isolated rat aortae and that mevinolin completely antagonizes this effect confirming the anti-inflammatory action of mevinolin ex vivo in rat aortae. In addition, we observed that A beta vasoactivity is not mediated nor modulated by mevalonic acid suggesting that the anti-inflammatory action of the statins are not related to an inhibition of HMG-CoA reductase activity. Differentiated human neuroblastoma cells (IMR32) were used to assess the neurotoxic effect of pre-aggregated A beta by quantifying the release of lactate dehydrogenase (LDH) in the cell culture medium. A beta appears to enhance LDH release by 30% in IMR32 cells, an effect that can be completely opposed by mevastatin. Taken together these data show that statins can antagonize the effect of A beta in different assays and provide new clues to understand the prophylactic action of the statins against Alzheimer's disease.
    Atherosclerosis 05/2002; 161(2):293-9. · 3.71 Impact Factor
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    ABSTRACT: Freshly solubilized Aβ peptides synergistically increase the magnitude of the constriction induced by endothelin-1 (ET-1), via the activation of a pro-inflammatory pathway. We report that mevinolin and mevastatin, two inhibitors of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase are able to completely abolish the vasoactive properties of Aβ in rat aortae. Mevinolin also appears to oppose the increased vascular reactivity to ET-1 induced by interleukin 1-β and phospholipase A2 suggesting that statins display some anti-inflammatory properties. We show that freshly solubilized Aβ stimulates prostaglandin E2 and F2α production (by 6 and 3.6 times, respectively) in isolated rat aortae and that mevinolin completely antagonizes this effect confirming the anti-inflammatory action of mevinolin ex vivo in rat aortae. In addition, we observed that Aβ vasoactivity is not mediated nor modulated by mevalonic acid suggesting that the anti-inflammatory action of the statins are not related to an inhibition of HMG-CoA reductase activity. Differentiated human neuroblastoma cells (IMR32) were used to assess the neurotoxic effect of pre-aggregated Aβ by quantifying the release of lactate dehydrogenase (LDH) in the cell culture medium. Aβ appears to enhance LDH release by 30% in IMR32 cells, an effect that can be completely opposed by mevastatin. Taken together these data show that statins can antagonize the effect of Aβ in different assays and provide new clues to understand the prophylactic action of the statins against Alzheimer's disease.
    Atherosclerosis 04/2002; 161(2):293-299. · 3.71 Impact Factor
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    ABSTRACT: Mounting evidence suggests that cholesterol may contribute to the pathogenesis of Alzheimer disease (AD). We examined whether cholesterol might be present in senile plaques, a hallmark neuropathological feature of AD. We employed 2 different fluorometric-staining techniques (filipin staining and an enzymatic technique) for the determination of cholesterol in brains of postmortem confirmed AD patients and in nondemented, age-matched histopathologically normal controls. AD patient brains showed abnormal accumulation of cholesterol in congophilic/birefringent dense cores of senile plaques that was essentially absent in histopathologically normal controls. To determine whether increased senile plaque-associated cholesterol occurred generally in all plaques or was restricted to a specific subset, quantitative analysis was performed. Data indicate abnormal accumulation of cholesterol in cores of mature plaques but not in diffuse or immature plaques. Additionally, transgenic mice that overexpress the “Swedish” amyloid precursor protein (Tg APPsw, line 2576) exhibited a similar pattern of abnormal cholesterol accumulation in mature, congophilic amyloid plaques at 24 months of age that was absent in their control littermates or in 8-month-old Tg APPsw mice (an age prior to amyloid deposition). Taken together, our results imply a link between cholesterol and AD pathogenesis and suggest that cholesterol plays an important role in the formation and/or progression of senile plaques.
    Journal of Neuropathology and Experimental Neurology 07/2001; 60(8):778–785. · 4.35 Impact Factor
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    ABSTRACT: Hypercholesterolemia (HC) is associated with coronary endothelial dysfunction and increased circulating levels of endothelin-1. We show that pre-treatment of intact rat aortic rings with cholesterol synergistically enhances the vasoconstriction induced by endothelin-1 suggesting that elevated levels of cholesterol may predispose to hypertension by modulating the vascular reactivity to endogenous vasoconstrictors. Moreover, we report that SB202190, a selective inhibitor of p38 MAPK, and PD98059 an inhibitor of MEK1/2 are able to abolish the vasoactive properties of cholesterol. MK-886, an inhibitor of 5-lipoxygenase is inefficient at blocking the vasoactive properties of cholesterol whereas NS-398, a selective inhibitor of cyclooxygenase-2 (COX-2) completely abolishes cholesterol-induced vasoconstriction. In intact rat aortae, cholesterol stimulates prostaglandin E2 and prostaglandin F2α production, an effect that can be completely prevented by inhibiting p38 MAPK, or COX-2. In vitro, cholesterol appears to stimulate a similar pro-inflammatory pathway in human cerebrovascular smooth muscle cells. Disruption of the MAPK/COX-2 pathway may represent a valuable therapy to block the hypertension associated with HC, as well as the development of atherosclerosis.
    Biochemical and Biophysical Research Communications 09/2000; · 2.28 Impact Factor
  • D Paris, T Town, T Parker, J Humphrey, M Mullan
    Annals of the New York Academy of Sciences 05/2000; 903:446-50. · 4.38 Impact Factor
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    ABSTRACT: Bilateral temporoparietal hypoperfusion has been frequently observed early in the Alzheimer's disease (AD) process. The beta-amyloid (A beta) peptide is believed to play a central role in the pathogenesis of AD. In vitro experiments have shown that freshly solubilized A beta enhances constriction of cerebral and peripheral vessels. We proposed that in vivo, A beta would also have vasoactive properties. To test this hypothesis, we intraarterially infused freshly solubilized A beta 1-40 in rats and observed changes in peripheral blood pressure, cerebral blood flow, and cerebrovascular resistance. We found that infusion of A beta in vivo significantly increased the blood pressure in hypotensive rats but not in normotensive and hypertensive rats. Moreover, A beta infusion also resulted in a decreased blood flow and increased vascular resistance specifically in cerebral cortex but not in heart or kidneys. These data suggest that A beta has a direct and specific constrictive effect on cerebral vessels in vivo, which may contribute to the cerebral hypoperfusion observed early in the AD process.
    Annals of the New York Academy of Sciences 05/2000; 903:156-63. · 4.38 Impact Factor
  • D Paris, T Town, T Parker, J Humphrey, M Mullan
    [Show abstract] [Hide abstract]
    ABSTRACT: Mounting evidence from in vitro and in vivo studies in transgenic mice overproducing beta-amyloid peptides (A beta) suggests that A beta can induce vasoconstriction and decrease cerebral blood flow. In this report, we describe the vasoactive properties of A beta, in particular the enhancement of endothelin-1-induced vasoconstriction and A beta's induction of a long-lasting vasoconstrictive event. Furthermore, we show that low doses (as low as 50 nM) of freshly solubilized A beta similar to those observed in the plasma of patients suffering from Alzheimer's disease are vasoactive. By using various inhibitors and activators of the phospholipase A2 (PLA2)/arachidonic acid (AA) cascade, we demonstrate that A beta vasoactivity is dependent on activation of this intracellular signaling pathway, resulting in stimulation of downstream cyclooxygenase-2 and 5-lipoxygenase, which mediate production of proinflammatory eicosanoids. Taken together, our data show that A beta directly activates an intracellular proinflammatory pathway, which is responsible for its vasoactive properties.
    Annals of the New York Academy of Sciences 05/2000; 903:97-109. · 4.38 Impact Factor
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    ABSTRACT: Freshly solubilized β-amyloid (Aβ) peptides display vasoactive properties, increasing both the magnitude and the duration of endothelin-1-induced vasoconstriction. We show that Aβ vasoactivity is mediated by the stimulation of a pro-inflammatory pathway involving activation of secretory phospholipase A2 (PLA2), mitogen activated protein kinase (MAPK) kinase (MEK1/2), p38 MAPK, cytosolic PLA2, and the release of arachidonic acid. Ultimately, arachidonic acid is metabolized into proinflammatory eicosanoids via the 5-lipoxygenase and cyclooxygenase-2 (COX-2) enzymes, both of which we show to be required for Aβ vasoactivity. Accordingly, p38 MAPK activity is higher in the brains of transgenic mice that overproduce Aβ, and COX-2 immunoreactivity is increased in the cerebrovasculature of these transgenic animals. Taken together, our data show that freshly solubilized Aβ peptides can trigger a pro-inflammatory reaction in the vasculature that can be blocked by inhibiting specific target molecules, providing the basis for novel therapeutic intervention.
    Neurobiology of Aging 05/2000; 21(2):183-197. · 6.17 Impact Factor
  • 04/2000: chapter A vasoactivity and pro-inflammation in microglia can be blocked by cGMP-elevating agents.: pages 446-450; Ann. N.Y. Acad. Sci..