Mrp14 deficiency ameliorates amyloid β burden by increasing microglial phagocytosis and modulation of amyloid precursor protein processing.

Neuroinflammation plays a fundamental role in the pathogenesis of Alzheimer's disease (AD), resulting in the extensive activation of microglial and astroglial cells. Here we describe the role of myeloid-related protein Mrp14, a recently described amplifier of inflammation, in Alzheimer's disease and in the related amyloid precursor protein/presenilin1 (APP/PS1) mouse model. Detection of Mrp14 in control, mildly cognitive impaired, and AD patients revealed a strong induction of Mrp14 in protein extracts as well as in the cerebrospinal fluid, but not in blood plasma. In APP/PS1 mice, Mrp14 and its heterodimeric partner Mrp8 was found to be upregulated in microglial cells surrounding amyloid plaques. Functionally, loss of Mrp14 led to increased phagocytosis of fibrillar amyloid β (Aβ) in microglia cells in vitro and in vivo. Generating APP/PS1-transgenic mice deficient for Mrp14, we observed a decrease of key cytokines involved in APP processing, a reduction of BACE1 expression and activity, and consequently overall Aβ deposition. We therefore conclude that Mrp14 promotes APP processing and Aβ accumulation under neuroinflammatory conditions.