198 - Dendrimer conjugated glutaminase inhibitor improves the neurobehavioral phenotype in a mouse model of Rett syndrome

Friday, April 28, 2023

5:15 PM – 7:15 PM ET

Poster Number: 198
Publication Number: 198.142

Preeti Vyas, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Elizabeth L. Wilkinson, Johns Hopkins University Center for Nanomedicine, Johns Hopkins University Chemical and Biomolecular Engineering, Baltimore, MD, United States; Amanda Y. Fowler, Johns Hopkins University School of Medicine, Washington, DC, United States; Nirnath Sah, Johns Hopkins School of Medicine, Baltimore, MD, United States; Elizabeth Khoury, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Jinhuan Liu, Johns Hopkins University(Department ACCM), Baltimore, MD, United States; Anjali Sharma, Washington State University, Pullman, WA, United States; Ashley Bedner, Johns Hopkins Children's Center, Dundalk, MD, United States; Ajit G. Thomas, JHU School of Medicine, Baltimore, MD, United States; Rana Rais, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Barbara S. Slusher, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Tomas Tichy, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Hlavni mesto Praha, Czech Republic; Pavel Majer, Institute of Organic Chemistry and Biochemistry / Czech Academy of Sciences, Prague, Hlavni mesto Praha, Czech Republic; Kannan Rangaramanujam, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Sujatha Kannan, Johns Hopkins University SOM, Baltimore, MD, United States

Presenting Author(s)

PV

Preeti Vyas, PhD (she/her/hers)

Post Doc Fellow
Department of Anesthesiology and Critical Care Medicine , Johns Hopkins University School of Medicine
Baltimore, Maryland, United States

Background:

Rett Syndrome (RTT) is a progressive neurodevelopmental disorder, caused by mutations in gene encoding for methyl-CpG binding protein 2 (MeCP2). Although therapies are being explored for symptomatic management, there are currently no therapies that modify the course of disease progression in RTT. Recent work with MeCP2 deficient mouse models has demonstrated a major role for glutamatergic pathways, specifically microglial-produced glutamate, due to upregulation of glutaminase in the pathology of RTT. The glutaminase antagonist 6-diazo-5-oxo-L-norleucine (DON) inhibits glutamine-utilizing reactions, however it is rapidly cleared from periphery and is associated with systemic toxicities. Considering, we have used a prodrug of DON (DON020) synthesized specifically for conjugation with our generation-4 hydroxyl PAMAM dendrimers (~4 nm, non-toxic) that target activated/dysregulated glia and astrocytes in MeCP2 deficient mice, but not in WT upon systemic administration.

Objective: To determine if systemic targeted monotherapy with dendrimer conjugated DON020 (D-DON020) results in microglial glutaminase inhibition and improvement in behavior phenotype in MeCP2 KO and Het mice, while eliminating the peripheral toxicity of free DON.

Design/Methods:

We first conjugated DON020 with hydroxyl PAMAM dendrimers and studied the effects on the microglial glutaminase activity in 5-6 week old Cx3CR1-GFP^/+ Mecp2 KO male mice. Next, the WT and the symptomatic Mecp2^-/+ Het mice were treated biweekly for 8 weeks with saline or 1 mg/Kg ip of DON or D-DON020, and their neurobehavioral phenotype was examined pre and post treatment.

Results:

D-DON020 (1 mg/Kg ip) treatment resulted in selective glutaminase inhibition in the isolated microglia from Cx3CR1-GFP^/+ MeCP2 KO male mice. The MeCP2 Het mice treated with D-DON020 showed improvement in neurobehavioral scores, particularly paw-clench, while DON and saline treated groups did not. D-DON020 also restored the long term retrieval of conditioned fear memory and improved cue-response during fear extinction after 8 weeks of treatment.

Conclusion(s):

Glia-targeted glutaminase inhibition with DON020 using PAMAM dendrimer drug delivery system may be a potential therapeutic avenue for treating glutamate dysregulation in Rett syndrome. Further work is being carried out to understand the effect of D-DON020 on glutamine and glutamate levels within the brain and the subsequent impact on neuronal morphology in MeCP2 Het mice.