Emotional regulatory function of receptor interacting protein 140 revealed in the ventromedial hypothalamus

Receptor-interacting protein (RIP140) is a transcription co-regulator highly expressed in macrophages to regulate inflammatory and metabolic processes. However, its implication in neurological, cognitive and emotional conditions, and the cellular systems relevant to its biological activity within the central nervous system are currently less clear. A transgenic mouse line with macrophage-specific knockdown of RIP140 was generated (M Phi RIPKD mice) and brain-region specific RIP140 knockdown efficiency evaluated. Mice were subjected to a battery of tests, designed to evaluate multiple behavioral domains at naive or following site-specific RIP140 re-expression. Gene expression analysis assessed TNF-alpha, IL-1 beta, TGF-1 beta, IL1 -RA and neuropeptide Y (NPY) expression, and in vitro studies examined the effects of macrophage's RIP140 on astrocytes' NPY production. We found that RIP140 expression was dramatically reduced in macrophages within the ventromedial hypothalamus (VMH) and the cingulate cortex of M Phi RIPKD mice. These animals exhibited increased anxiety-and depressive-like behaviors. VMH-targeted RIP140 re-expression in M Phi RIPKD mice reversed its depressive-but not its anxiety-like phenotype. Analysis of specific neurochemical changes revealed reduced astrocytic-NPY expression within the hypothalamus of M Phi RIPKD mice, and in vitro analysis confirmed that conditioned medium of RIP140-silnenced macrophage culture could no longer stimulate NPY production from astrocytes. The current study revealed an emotional regulatory function of macrophage-derived RIP140 in the VMH, and secondary dysregulation of NPY within hypothalamic astrocyte population, which might be associated with the observed behavioral phenotype of M Phi RIPKD mice. This study highlights RIP140 as a novel target for the development of potential therapeutic and intervention strategies for emotional regulation disorders. (C) 2014 Elsevier Inc. All rights reserved.