Brain Region-Specific nAChR and Associated Protein Abundance Alterations Following Chronic Nicotine and/or Menthol Exposure

The identification of biomarkers
that are altered following nicotine/tobacco
exposure can facilitate the investigation of tobacco-related diseases.
Nicotinic acetylcholine receptors (nAChRs) are pentameric cation channels
expressed in the mammalian central and peripheral nervous systems
and the neuromuscular junction. Neuronal nAChR subunits (11) have
been identified in mammals (α2-7, α9-10, β2-4).
We examined changes in β2 nAChR subunit protein levels after
chronic nicotine, (±)-menthol, or nicotine co-administered with
(±)-menthol in nine murine brain regions. Our investigation of
β2 nAChR subunit level changes identified the hypothalamus as
a novel region of interest for menthol exposure that demonstrated
increased β2 nAChR levels after (±)-menthol plus nicotine
exposure compared to nicotine exposure alone. Using mass spectrometry,
we further characterized changes in membrane protein abundance profiles
in the hypothalamus to identify potential biomarkers of (±)-menthol
plus nicotine exposure and proteins that may contribute to the elevated
β2 nAChR subunit levels. In the hypothalamus, 272 membrane proteins
were identified with altered abundances after chronic nicotine plus
menthol exposure with respect to chronic nicotine exposure without
menthol. A comprehensive investigation of changes in nAChR and non-nAChR
protein expression resulting from (±)-menthol plus nicotine in
the brain may establish biomarkers to better understand the effects
of these drugs on addiction and addiction-related diseases.