Disease-modifying effects of NRF2 activators in a nerve agent exposure model - ABSTRACT Organophosphate (OP) nerve agents (OPNA) are increasingly used to target civilians and often as chemical warfare agents. There is no treatment for OPNA survivors. Limiting the life-long health consequences of OPNA exposure is as important as preventing deaths due to acute exposure to OPNAs, which are cholinesterase inhibitors and potent seizurogenic agents. In animal models, acute OPNA exposure induces status epilepticus (SE) and other cholinergic symptoms. The current medical countermeasures (MCM), such as atropine, oxime, and diazepam/midazolam, control symptoms but do not prevent long-term neurotoxicity and the development of epilepsy that are primarily due to persistent brain injury. We predict that combining neuroprotectants and MCMs will prevent OPNA-induced long-term neurotoxicity. We will investigate the long-term neuroprotective effect of novel activators of the Nuclear factor erythroid-2–Related Factor 2 (NRF2), a potential regulator of endogenous antioxidants. We will test the non-electrophilic small molecules of NRF2 activators as novel disease-modifying drugs in a rat diisopropylfluorophosphate (DFP) model. DFP is a surrogate for OPNAs. We and others have demonstrated nitrooxidative stress, neuroinflammation, and neurodegeneration in OPNA models. Treating with either an inducible nitric oxide synthase (iNOS) inhibitor, 1400W, or an NADPH oxidase 2 (NOX2) inhibitor, diapocynin, mitigated the DFP-induced nitrooxidative stress and brain pathology, suggesting the antioxidant mechanism as a potential therapeutic target for disease- modification. Our studies also indicated that 1400W and diapocynin/mitoapocynin increased the total glutathione in the serum. Therefore, the drugs that directly promote endogenous glutathione synthesis could be useful as a therapeutic agent to mitigate OPNA-induced long-term neurotoxicity. We will test two NRF2 activators, RTA408 and IND22. RTA408 is in clinical trials for other diseases and demonstrated its’ disease- modifying potential in a rat kainate model of chronic epilepsy. Therefore, RTA408 will be a positive control for testing the efficacy of a novel NRF2 activator, IND22, which is also a non-electrophilic small molecule, blood- brain-barrier permeable, and its pharmacokinetics are promising. Our overarching hypothesis is that NRF2 activators will counteract OPNA-induced oxidative stress, neurodegeneration, and epileptogenesis and restore brain function. We will investigate the short-term effects of the test drugs in a mixed-sex cohort of a rat DFP model (Specific Aim 1) and validate the lead compound for behavioral, structural, and functional MRI, video- EEG, and histological outcomes in the long-term study (Specific Aim 2). To determine the protective effect of NRF2 activators, we will quantify nitrooxidative stressors, cytokines, and brain immunohistochemistry for neurodegeneration and neuroinflammation markers. Our research proposal, per (PAR-25-114), “directly advances the discovery of novel treatment strategies that address serious morbidity (due to long-term neurotoxicity and seizures) and mortality after acute exposure to highly toxic chemical threats.”
