Amita Quadros

Inflammatory cytokine levels correlate with amyloid load in transgenic mouse models of Alzheimer's disease

BackgroundInflammation is believed to play an important role in the pathology of Alzheimers disease (AD) and cytokine production is a key pathologic event in the progression of inflammatory cascades. The current study characterizes the cytokine expression profile in the brain of two transgenic mouse models of AD (TgAPPsw and PS1/APPsw) and explores the correlations between cytokine production and the level of soluble and insoluble forms of Aβ.MethodsOrganotypic brain slice cultures from 15-month-old mice (TgAPPsw, PS1/APPsw and control littermates) were established and multiple cytokine levels were analyzed using the Bio-plex multiple cytokine assay system. Soluble and insoluble forms of Aβ were quantified and Aβ-cytokine relationships were analyzed.ResultsCompared to control littermates, transgenic mice showed a significant increase in the following pro-inflammatory cytokines: TNF-α, IL-6, IL-12p40, IL-1β, IL-1α and GM-CSF. TNF-α, IL-6, IL-1α and GM-CSF showed a sequential increase from control to TgAPPsw to PS1/APPsw suggesting that the amplitude of this cytokine response is dependent on brain Aβ levels, since PS1/APPsw mouse brains accumulate more Aβ than TgAPPsw mouse brains. Quantification of Aβ levels in the same slices showed a wide range of Aβ soluble:insoluble ratio values across TgAPPsw and PS1/APPsw brain slices. Aβ-cytokine correlations revealed significant relationships between Aβ1–40, 1–42 (both soluble and insoluble) and all the above cytokines that changed in the brain slices.ConclusionOur data confirm that the brains of transgenic APPsw and PS1/APPsw mice are under an active inflammatory stress, and that the levels of particular cytokines may be directly related to the amount of soluble and insoluble Aβ present in the brain suggesting that pathological accumulation of Aβ is a key driver of the neuroinflammatory response.

Vasoactive effects of Aβ in isolated human cerebrovessels and in a transgenic mouse model of Alzheimer's disease: Role of inflammation

Abstract Aβ peptides are the major protein constituents of Alzheimers 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 Aβ on endothelin-1 induced vasoconstriction in isolated human cerebral arteries collected following rapid autopsies. We report that freshly solubilized Aβ enhances endothelin-1 induced vasoconstriction in isolated human middle cerebral and basilar arteries. The vasoactive effect of Aβ 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.

Impaired angiogenesis in a transgenic mouse model of cerebral amyloidosis

Abeta peptides are naturally occurring peptides, which are thought to play a key role in the pathophysiology of Alzheimers disease (AD). In AD cases, levels of soluble and insoluble Abeta peptides increase in the brain as well as in the cerebrovasculature, a phenomenon that does not occur in extra-cranial vessels. There are frequently anomalies in the cerebrovasculature in AD, and despite increases in several pro-angiogenic factors in AD brain, evidence for increased vascularity is lacking; in fact there is evidence to the contrary. It has also been recently shown that Abeta peptides may have profound anti-angiogenic effects in vitro and in vivo. We therefore investigated whether there is evidence for altered angiogenesis in the vasculature in a transgenic mouse model of Abeta amyloidosis (Tg APPsw line 2576). In vitro, the formation of capillary-like structures on a reconstituted extracellular matrix by endothelial cells isolated from Tg APPsw is impaired. Ex vivo, the sprouting of new capillaries from arterial explants (over expressing Abeta) isolated from 9-month-old Tg APPsw is reduced compared to arterial explants isolated from control littermates. In addition, Tg APPsw mice show a reduction in vascular density in the cortex and hippocampus compared to control littermates. Altogether, our data suggest that the over expression of APPsw in the vasculature may oppose angiogenesis.

Inhibition of Aβ production by NF-κB inhibitors

bstract The transcription factor nuclear factor B (NFB) is widely expressed in the nervous system and increased NFB immunoreactivity has been bserved in Alzheimer’s disease (AD) brains in the nuclei of neurons within the vicinity of diffuse -amyloid plaques. -Amyloid (A ) peptides re the main constituent of senile plaques and are known to stimulate NFB activity. In the present study, we investigated the effect of various FB inhibitors on the production of A 1–40, A 1–42, secreted APP (sAPP and sAPP ) and APP C-terminal fragments (APP-CTF) using CHO ells overexpressing the -amyloid precursor protein (APP). Our data show that NFB inhibitors decrease both A 1–40 and A 1–42 production.

Inhibition of angiogenesis by Abeta peptides.

Aβ peptides are naturally occurring peptides forming β-sheet aggregates that constitute an integral component of senile plaques and vascular deposits in Alzheimers disease. Since several peptides adopting a β-sheet conformation have been shown to be anti-angiogenic, we investigated the effect of Aβ on angiogenesis. We show that in vitro, Aβ dose-dependently inhibits the formation of capillaries by human brain endothelial cells plated on Matrigel and stimulates capillary degeneration at high doses. Preparations of Aβ peptides containing a higher content of β-sheet structures are more potently anti-angiogenic in vitro. Ex vivo, Aβ dose-dependently opposes angiogenesis in rat aortae and in human middle cerebral arteries. In vivo, Aβ 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 Aβ on human glioblastoma (U87MG) and human lung adenocarcinoma (A549) tumors. We show that intra-tumoral injection of Aβ 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, Aβ delivered intraperitoneally also suppressed the growth of human lung adenocarcinoma tumor xenografts. Altogether our data show that Aβ is an angiogenesis inhibitor.

Inhibition of Angiogenesis by Aβ Peptides

Aβ peptides are naturally occurring peptides forming β-sheet aggregates that constitute an integral component of senile plaques and vascular deposits in Alzheimers disease. Since several peptides adopting a β-sheet conformation have been shown to be anti-angiogenic, we investigated the effect of Aβ on angiogenesis. We show that in vitro, Aβ dose-dependently inhibits the formation of capillaries by human brain endothelial cells plated on Matrigel and stimulates capillary degeneration at high doses. Preparations of Aβ peptides containing a higher content of β-sheet structures are more potently anti-angiogenic in vitro. Ex vivo, Aβ dose-dependently opposes angiogenesis in rat aortae and in human middle cerebral arteries. In vivo, Aβ 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 Aβ on human glioblastoma (U87MG) and human lung adenocarcinoma (A549) tumors. We show that intra-tumoral injection of Aβ 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, Aβ delivered intraperitoneally also suppressed the growth of human lung adenocarcinoma tumor xenografts. Altogether our data show that Aβ is an angiogenesis inhibitor.

Nilvadipine antagonizes both Aβ vasoactivity in isolated arteries, and the reduced cerebral blood flow in APPsw transgenic mice

The development of Alzheimers 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.

The influence of diagnosis, intra- and inter-person variability on serum and plasma Aβ levels

Evidence suggests that high peripheral beta-amyloid (Abeta)(1-40) levels and low ratios of Abeta(1-42)/Abeta(1-40) are associated with increased risk for Alzheimers disease (AD). In this cross-sectional design, serum and plasma samples from 67 AD patients and 146 controls (similar in age and gender) were evaluated using Abeta(1-40) and Abeta(1-42) ELISA. Coefficient of variance was calculated for intra- and inter-person variability of Abeta(1-40) and Abeta(1-42). Abeta(1-40) correlated with age, MMSE and their Abeta(1-42)/Abeta(1-40) ratios (p<0.05). Significantly higher Abeta(1-40) levels were observed in AD patients than controls (p<0.05) but no difference was observed for Abeta(1-42) (p>0.05). Serum Abeta(1-42)/Abeta(1-40) ratios were also significantly lower in AD patients than controls (p<0.05). Lower intra-person than inter-person variability was observed for serum and plasma Abeta(1-40) and Abeta(1-42) and these were higher in controls than in AD patients. The intra-person variability of serum Abeta(1-40) did not influence the group differences observed between AD patients and controls. Significant interaction was observed between diagnosis and intra-person variability for serum Abeta(1-40) levels (p<0.05) and was supported by our finding of higher intra-person variability for serum Abeta(1-40) in controls (26.97%) than in AD patients (18.35%). We confirm the previously observed differences in blood Abeta levels between AD and control groups. In addition, we now report the presence of high intra- and inter-person variability possibly due to factors that influence peripheral Abeta levels and warrant further investigation before the potential use of Abeta as an AD biomarker can be fully exploited.

Inhibition of Angiogenesis by A Peptides

Aβ peptides are naturally occurring peptides forming β-sheet aggregates that constitute an integral component of senile plaques and vascular deposits in Alzheimers disease. Since several peptides adopting a β-sheet conformation have been shown to be anti-angiogenic, we investigated the effect of Aβ on angiogenesis. We show that in vitro, Aβ dose-dependently inhibits the formation of capillaries by human brain endothelial cells plated on Matrigel and stimulates capillary degeneration at high doses. Preparations of Aβ peptides containing a higher content of β-sheet structures are more potently anti-angiogenic in vitro. Ex vivo, Aβ dose-dependently opposes angiogenesis in rat aortae and in human middle cerebral arteries. In vivo, Aβ 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 Aβ on human glioblastoma (U87MG) and human lung adenocarcinoma (A549) tumors. We show that intra-tumoral injection of Aβ 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, Aβ delivered intraperitoneally also suppressed the growth of human lung adenocarcinoma tumor xenografts. Altogether our data show that Aβ is an angiogenesis inhibitor.

Increased TNFα production and Cox-2 activity in organotypic brain slice cultures from APPsw transgenic mice

beta-Amyloid (Abeta) peptides are the principal component of senile plaques and vascular deposits in Alzheimers disease and are derived from the proteolytic cleavage of the beta-amyloid precursor protein (APP). We have previously shown that synthetic Abeta can stimulate cyclooxygenase-2 (Cox-2) activity in brain organotypic slice cultures. In the present study, we used brain slices from transgenic APP Swedish (TgAPPsw) mice and control littermates of different age groups to determine the effect of APP overexpression on the levels of prostaglandin and tumor necrosis factor alpha (TNFalpha) release. The production of eicosanoid and TNFalpha was increased as a function of age in organotypic brain slice culture from TgAPPsw mice compared to age matched control littermates. We also showed that the selective Cox-2 inhibitor NS-398 reduces the production of eicosanoid and TNFalpha in organotypic brain slice cultures of TgAPPsw mice. In conclusion, our data suggest that either activity or expression of Cox-2 is increased in TgAPPsw mice brains as a function of age, contributing to an increased production of pro-inflammatory eicosanoids and TNFalpha.