UC Davis

Current therapeutic strategies for organophosphate (OP)-induced status epilepticus (SE) prevent mortality, but not chronic neurotoxic outcomes, which may be mediated in part by neuroinflammation. The plasminogen activation system (PAS) is implicated in diverse models of neuroinflammation but has yet to be evaluated after acute OP intoxication. Here, we characterized the PAS in a rat model of acute intoxication with diisopropylfluorophosphate (DFP). Adult male Sprague Dawley rats exposed to DFP (4 mg/kg, sc) followed 1 min later by atropine sulfate (2 mg/kg, im) and 2-pralidoxime (25 mg/kg, im) exhibited prolonged SE as determined using behavioral criteria. Electron microscopy of the hippocampus and piriform cortex at 1 day post-exposure (DPE) was consistent with metabolic stress and acute neurodegeneration. At 1 DPE, concentrations of plasminogen activator inhibitor-1 (PAI-1) were significantly increased in serum from DFP rats. Protein levels of the plasminogen activators (PA), tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA), as determined by ELISA, were elevated in the cerebellum, cortex and hippocampus in a time- and region-dependent manner after DFP exposure. Similarly, normalized protein levels of the primary PA inhibitor, PAI-1, was also elevated in the same brain regions. At 1 DPE, tPA, uPA and PAI-1 were significantly increased in the cortex and hippocampus. Normalized concentrations of uPA and PAI-1 returned to control values by 3-7 DPE, whereas tPA concentrations remained persistently elevated in the cortex and hippocampus up to 28 DPE. Immunohistochemistry confirmed increased PAI-1 immunoreactivity in multiple regions of the DFP brain up to 28 DPE. Co-localization of PAI-1 with neuronal, microglial and astrocytic biomarkers indicated that PAI-1 predominantly localized to astrocytic subsets, with intense immunofluorescence in astrocytic endfeet associated with endothelial cells. Collectively, these data indicate that acute DFP intoxication activates the PAS, identifying this enzymatic cascade as a potential therapeutic target for mitigating the long-term neurologic consequences of acute OP intoxication.