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

Inflammation 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 Abeta.

Our 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 Abeta present in the brain suggesting that pathological accumulation of Abeta is a key driver of the neuroinflammatory response.

Organotypic 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 Abeta were quantified and Abeta-cytokine relationships were analyzed.

Compared to control littermates, transgenic mice showed a significant increase in the following pro-inflammatory cytokines: TNF-alpha, IL-6, IL-12p40, IL-1beta, IL-1alpha and GM-CSF. TNF-alpha, IL-6, IL-1alpha 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 Abeta levels, since PS1/APPsw mouse brains accumulate more Abeta than TgAPPsw mouse brains. Quantification of Abeta levels in the same slices showed a wide range of Abeta soluble:insoluble ratio values across TgAPPsw and PS1/APPsw brain slices. Abeta-cytokine correlations revealed significant relationships between Abeta1-40, 1-42 (both soluble and insoluble) and all the above cytokines that changed in the brain slices.