Selective Inhibition of Microglial Glutaminase Alleviates Chronic Stress-Induced Neurobehavioral and Cognition Deficits

Major depressive disorder (MDD) is a prevalent and debilitating psychiatric condition with significant societal and economic impacts. Many patients exhibit resistance to current antidepressant therapies, underscoring the need for novel treatments targeting MDD's underlying mechanisms. We previously discovered that the enzyme glutaminase (GLS1), which converts glutamine to glutamate, is upregulated in activated microglia of mice exposed to Chronic Social Defeat Stress (CSDS), a model for stress-induced depression. In this study, we developed hydroxyl-terminated poly (amidoamine) (PAMAM) G4 dendrimer nanoparticle delivery systems designed to specifically target microglial GLS1. Using structurally distinct GLS1 inhibitors, we synthesized two hydroxyl-dendrimer-GLS1 inhibitor conjugates. A DON analog (TTM020) and a BPTES analog (JHU29) were conjugated to the dendrimer, resulting in dendrimer-TTM020 (D-TTM020) and dendrimer-JHU29 (D-JHU29). Using the CSDS-exposed mice model, we evaluated the target engagement and efficacy of these inhibitors through GLS1 enzymatic activity assays, immunohistochemistry, and behavioral tests. Using a Cy5-labeled hydroxyl-terminated dendrimer (D-Cy5), we demonstrated that D-Cy5 was selectively engulfed by activated microglia in mice after CSDS. In addition, D-TTM020 and D-JHU29 treatment significantly reduced the CSDS-induced elevation in GLS1 activity specifically in microglia isolated from the prefrontal cortex or the hippocampus. Furthermore, both drugs improved the neurobehavioral and cognition deficits in the CSDS murine model without side effects, especially gastrointestinal-related toxicities, which has been an issue with previous GLS1 inhibitors. These findings suggest that the development of dendrimer-based GLS1 inhibitors improved drug selectivity and reduced off-target toxicity, making them suitable candidates for clinical development. P30MH075673 (B.S.S.), R01AG063831 (R.R.), R01AG078181 (B.S.S.), JHU Catalyst Award (X.Z.), JH CAHN Pilot Award (X.Z.), K01AT010984 (X.Z.), R56MH135895 (X.Z.) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.