Abstract
Tissue-resident macrophages exist in unique environments, or niches, that inform their identity and function. There is an emerging body of literature suggesting that the qualities of this environment, such as the types of cells and debris they eat, the intercellular interactions they form, and the length of time spent in residence, collectively what we call habitare, directly inform their metabolic state. In turn, a tissue-resident macrophage’s metabolic state can inform their function, including whether they resolve inflammation and protect the host from excessive perturbations of homeostasis. In this review, we summarize recent work that seeks to understand the metabolic requirements for tissue-resident macrophage identity and maintenance, for how they respond to inflammatory challenges, and for how they perform homeostatic functions or resolve inflammatory insults. We end with a discussion of the emerging technologies that are enabling, or will enable, in situ study of tissue-resident macrophage metabolism.
Highlights
In his “An Essay Concerning Human Understanding” [1], John Locke famously argued against “innate principles” or the notion that we are born with knowledge that informs our identity
It will be interesting to see how different tissue-resident macrophages (TRMs) populations respond to the combination of inflammatory stimuli and unique tissue environment factors, such as the unique factors in adipose tissue highlighted above. This is exemplified by a recent study which found that alveolar macrophages, who reside in a glucose-restricted environment, rely on oxidative phosphorylation (OXPHOS) and not glycolysis to mount an inflammatory response to acute inflammation induced by LPS or to influenza infection [121]
We believe habitare is apt, because it carries with it a quality that is more than just the cold residence in which one resides, but instead includes the richness and warmth that makes the place one resides in a home
Summary
In his “An Essay Concerning Human Understanding” [1], John Locke famously argued against “innate principles” or the notion that we are born with knowledge that informs our identity. It will be important for future studies of TRM metabolism to take into consideration the unique intra-tissue environment differences, including nutrient [63, 64] and oxygen [65, 66] availability, as well as the cell types and debris they engulf [24].
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