Brief Isoflurane Anesthesia Produces Prominent Phosphoproteomic Changes in the Adult Mouse Hippocampus

Anesthetics are widely used in medical
practice and experimental
research, yet the neurobiological basis governing their effects remains
obscure. We have here used quantitative phosphoproteomics to investigate
the protein phosphorylation changes produced by a 30 min isoflurane
anesthesia in the adult mouse hippocampus. Altogether 318 phosphorylation
alterations in total of 237 proteins between sham and isoflurane anesthesia
were identified. Many of the hit proteins represent primary pharmacological
targets of anesthetics. However, findings also enlighten the role
of several other proteinsimplicated in various biological
processes including neuronal excitability, brain energy homeostasis,
synaptic plasticity and transmission, and microtubule functionas
putative (secondary) targets of anesthetics. In particular, isoflurane
increases glycogen synthase kinase-3β (GSK3β) phosphorylation
at the inhibitory Ser9 residue and regulates the phosphorylation
of multiple proteins downstream and upstream of this promiscuous kinase
that regulate diverse biological functions. Along with confirmatory
Western blot data for GSK3β and p44/42-MAPK (mitogen-activated
protein kinase; reduced phosphorylation of the activation loop), we
observed increased phosphorylation of microtubule-associated protein
2 (MAP2) on residues (Thr1620,1623) that have been shown
to render its dissociation from microtubules and alterations in microtubule
stability. We further demonstrate that diverse anesthetics (sevoflurane,
urethane, ketamine) produce essentially similar phosphorylation changes
on GSK3β, p44/p42-MAPK, and MAP2 as observed with isoflurane.
Altogether our study demonstrates the potential of quantitative phosphoproteomics
to study the mechanisms of anesthetics (and other drugs) in the mammalian
brain and reveals how already a relatively brief anesthesia produces
pronounced phosphorylation changes in multiple proteins in the central
nervous system.