BackgroundInflammation is believed to play an important role in the pathology of Alzheimer's 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.

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.

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