α7 nicotinic acetylcholine receptor signaling modulates the inflammatory and iron homeostasis in fetal brain microglia

Neuroinflammation in utero may result in life-long neurological disabilities. Microglia play a pivotal role, but the mechanisms are poorly understood. No early postnatal treatment strategies exist to enhance neuroprotective potential of microglia. We hypothesized that agonism on 7 nicotinic acetylcholine receptor (7nAChR) in fetal microglia will augment their neuroprotective transcriptome profile, while the antagonistic stimulation of 7nAChR will achieve the opposite. Using an in vivo - in vitro model of developmental programming of neuroinflammation induced by lipopolysaccharide (LPS), we validated this hypothesis in primary fetal sheep microglia cultures re-exposed to LPS in presence of a selective 7nAChR agonist or antagonist. Our RNAseq and protein level findings show that a pro-inflammatory microglial phenotype acquired in vitro by LPS stimulation is reversed with 7nAChR agonistic stimulation. Conversely, antagonistic 7nAChR stimulation potentiates the pro-inflammatory microglial phenotype. Surprisingly, under conditions of LPS double-hit an interference of a postulated 7nAChR - ferroportin signaling pathway may impede this mechanism. These results suggest a therapeutic potential of 7nAChR agonists in early re-programming of microglia in neonates exposed to in utero inflammation via an endogenous cerebral cholinergic anti-inflammatory pathway. Future studies will assess the role of interactions between inflammation-triggered microglial iron sequestering and 7nAChR signaling in neurodevelopment.