Project Summary
Intravenous lipid emulsions (ILEs) are important therapies. Though designed for parenteral nutrition, they
were discovered to be an antidote for local anesthetic systemic toxicity (LAST). With rising intravascular
concentrations of local anesthetics (LAs), which canonically inhibit voltage-gated sodium channels (Nav),
symptoms of central nervous system (CNS) toxicity progress to seizures, and cardiac arrest may ensue. LAST
is a major clinical challenge, and the identification of ILEs as treatment was a breakthrough that has made use
of LAs safer. Despite this important role, the molecular mechanisms by which ILEs treat LAST are not fully
understood. Furthermore, there is a paucity of studies examining whether Intralipid®, the emulsion
recommended in medical guidelines that is composed of long-chain triglycerides from soybean oil, is the best
choice. The most simplistic model for the effects of ILEs is that they form an intravascular compartment to
partition LAs and lower the effect-site concentration, but the degree to which concentrations fall in the aqueous
phase is debated. A competing hypothesis with strong evidence in cardiac models proposes ILEs serve as a fuel
via ß-oxidation of triglycerides (TGs), overcoming mitochondrial dysfunction caused by LAs. This mechanism
has been dismissed to explain reversal of CNS dysfunction because of the dogmatic belief that neurons rely on
glucose metabolism. Additionally, neurotoxicity due to LAs has been attributed, with limited evidence, to
preferential block of inhibitory neurons, but important effects in the CNS are unexplained by this hypothesis. My
preliminary in vitro data shows that neurons can use Intralipid® to sustain synaptic function in the absence of
other fuels, supporting the metabolic hypothesis of ILEs for LAST in the CNS.
This research proposal will test the hypothesis that ILEs reverse neurotoxicity by overcoming LA-induced
mitochondrial dysfunction. The experimental plan will systematically investigate the capacity for neurons to
metabolize components of ILEs. In doing so, I will comprehensively investigate the suitability of lipids to fuel
synaptic function. In Aim 1, I will use my developing expertise in optical imaging of cultured neurons expressing
genetically-encoded biosensors to compare lipids by their ability to sustain synaptic vesicle recycling and
produce ATP when deprived of glucose. Lipids will be tested as emulsions of both long- and medium-chain TGs
and free fatty acids of different lengths and saturation. In Aim 2, a metabolically optimized emulsion will be
compared in culture to Intralipid® in its ability to reverse LA-induced synaptic dysfunction. In Aim 3, the optimized
emulsion will be compared to Intralipid® in mice, quantifying effects on seizures with widefield calcium imaging,
local field potentials, and autofluorescence flavin imaging of metabolic activity. My five-year research and career
proposals capitalize on my excellent mentors and institutional environment. I will acquire the publication record
and expertise necessary for recognition as a national leader in anesthetic neuropharmacology and prepare for
independent investigation with R01 funding.