The downregulation of synaptic phagocytosis by P200 ELS microglia might seem counterintuitive considering the literature on ELS-induced reduction of dendritic and synaptic complexity [
99,
100,
101], which would imply increased phagocytosis.
In fact, we previously demonstrated increased CD68 immunoreactivity in two separate cohorts of adult ELS-exposed mice [
14,
38], and observed here the upregulation of genes regulating phagocytosis (e.g.,
C1qbp and
Gas6) in our adult transcriptomic data. These are in line with the increased phagocytosis of bacterial particles observed in mice exposed to maternal separation [
13], despite the difference in age. Our data, together with the reported findings by Delpech et al. [
13] and Bolton et al. [
96], suggest that ELS effects of phagocytosis, rather than being generalized, are complex and dependent on, e.g., specific substrates and possible eat-me signals. The identity of these different pathways, their regulators, and how ELS modulates them, is still unexplored and awaits future studies.\