5 - Can Cholinergic Forebrain System Neurons be Rescued with Intranasal p75NTR Small Molecule Ligand after Hypoxia-Ischemia (HI) in Neonatal Mice?

Monday, May 1, 2023

9:30 AM – 11:30 AM ET

Poster Number: 5
Publication Number: 5.433

Nazli Kuter, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Leslie Doucette, Johns Hopkins, Baltimore, MD, United States; Victoria Turnbill, Johns Hopkins University, Baltimore, MD, United States; Debbie Flock, Johns Hopkins University School of Medicine, Fallston, MD, United States; Jesse Alt, Johns Hopkins University, Baltimore, MD, United States; Raul Chavez-Valdez, Johns Hopkins University School of Medicine, CATONSVILLE, MD, United States; Lauren Jantzie, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Rana Rais, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Lee J. Martin, Johns Hopkins University School of Medicine Department of Pathology, Baltimore, MD, United States; Frances J.. Northington, Johns Hopkins University School of Medicine, Baltimore, MD, United States

Presenting Author(s)

Nazli Kuter, MD

Neonatal-Perinatal Medicine Fellow
Johns Hopkins University School of Medicine
Baltimore, Maryland, United States

Background: Despite therapeutic hypothermia, memory and executive function, controlled by neocortex, hippocampus, and forebrain cholinergic systems, are affected in child survivors of hypoxic-ischemic encephalopathy. Cholinergic basal forebrain (cBF) neurons are severely disrupted in a neonatal mouse model of HI. p75 neurotrophin receptor (p75NTR) modulates survival of cBF neurons. LM11A-31 is an orally bioavailable, brain-penetrant, nonpeptide, small molecule p75NTR ligand with neuroprotective effects in mouse models of adult acute stroke and neurodegenerative disease.

Objective:

To determine if LM11A-31 could be a late treatment of HI, by providing rescue of cBF neurons.

Design/Methods:

Dosing experiments were designed to determine whether LM11A-31 accumulates in postweaning mouse brain with chronic dosing and whether HI affects brain [drug]. Plasma and brain tissue levels of LM11A-31 were measured by liquid chromatography-tandem mass spectrometry. P10 mice were injured by a modified Rice-Vannucci model. Littermates exposed to anesthesia served as Shams. LM11A-31 (dissolved in sterile water) or vehicle (veh, sterile water) was administered intranasally (IN) (50 mg/kg/day, 5 of 7 days/week) to Sham and HI mouse pups from P14-P60. After behavioral testing, mice were sacrificed at P270 and immunohistochemistry for choline acetyltransferase (ChAT) was done to determine if LM11A-31 treatment has a permanent effect on cBF neurons after HI.

Results:

Sham and HI brain [drug] did not differ with chronic dosing (n=6 HI, 3 Sham). Prolonged dosing (35 vs 10 doses) did not result in drug accumulation in brain (n=6 HI, 3 Sham, 6 Naive). LM11A-31 had a positive effect on ChAT neuron number in sublenticular regions at P270 (KW p=0.006, n=6 HI veh, 6 HI drug, 7 Sham), with decreased loss of neurons in HI drug compared to HI veh (p=0.0414) and while HI veh had fewer ChAT neurons than Sham (p=0.0194). There was no difference in Sham vs HI drug. In nucleus basalis of Meynert (NBM), HI veh had less ChAT neurons than Shams (p=0.011) whereas neuron numbers in HI drug were not different than Sham. ChAT soma areas in NBM neurons in both HI groups were smaller than Sham (p=0.011) and LM11A-31 did not ameliorate the effect of HI on soma size. Microscopically, LM11A-31 treated ChAT NBM neurons had prominent processes and robust ChAT staining.

Conclusion(s):

Chronic IN dosing of LM11A-31 achieves target therapeutic levels in mouse brain without accumulating and mediates neuroprotective effects evident 8 months post HI injury with preservation of cholinergic neurons in NBM and sublenticular regions of the basal forebrain.