Spatiotemporal pattern of neuronal injury induced by DFP in rats: A model for delayed neuronal cell death following acute OP intoxication

Abstract

Organophosphate (OP) neurotoxins cause acute cholinergic toxicity and seizures resulting in delayed brain damage and persistent neurological symptoms. Testing novel strategies for protecting against delayed effects of acute OP intoxication has been hampered by the lack of appropriate animal models. In this study, we characterize the spatiotemporal pattern of cellular injury after acute intoxication with the OP diisopropylfluorophosphate (DFP). Adult male Sprague Dawley rats received pyridostigmine (0.1 mg/kg, im) and atropine methylnitrate (20 mg/kg, im) prior to DFP (9 mg/kg, ip) administration. All DFP-treated animals exhibited moderate to severe seizures within minutes after DFP injection but survived up to 72 h. AChE activity was significantly depressed in the cortex, hippocampus, subcortical brain tissue and cerebellum at 1 h post-DFP injection and this inhibition persisted for up to 72 h. Analysis of neuronal injury by FluoroJade-B (FJB) labeling revealed delayed neuronal cell death in the hippocampus, cortex, amygdala and thalamus, but not the cerebellum, starting at 4 h and persisting until 72 h after DFP treatment, although temporal profiles varied between brain regions. At 24 h post-DFP injection, the pattern of FJB labeling corresponded to TUNEL staining in most brain regions, and FJB-positive cells displayed reduced NeuN immunoreactivity but were not immunopositive for astrocytic (GFAP), oligodendroglial (O4) or macrophage/microglial (ED1) markers, demonstrating that DFP causes a region-specific delayed neuronal injury mediated in part by apoptosis. These findings indicate the feasibility of this model for testing neuroprotective strategies, and provide insight regarding therapeutic windows for effective pharmacological intervention following acute OP intoxication.

Methylene Blue Reduces Acute Cerebral Ischemic Injury via the Induction of Mitophagy

“…TUNEL labeling represents apoptotic cells, and FJB labeling represents degenerating cells, including apoptotic and necrotic cells (41). We observed that MB did not decrease apoptosis, but actually increased it (see Supplemental Figure 1); however, the percentage of necrotic cells, as determined by FJB labeling, excluding the TUNEL-positive cells, was significantly less in the MB treatment group than in the VC group (Figures 3A-C).…”

“…The brains were rapidly removed and cryoprotected in 30% sucrose. FJB and TUNEL labeling were performed using in situ death detection kits as described previously (41). Fluorescence signals were visualized via fluorescence microscopy.…”

Characterization of Seizures Induced by Acute and Repeated Exposure to Tetramethylenedisulfotetramine

“…Sections adjacent to those stained with DAPI and H&E were stained with Fluoro-Jade B as described previously (Li et al, 2011). As a positive control, paraformaldehyde-fixed sections from the brain of a rat treated with diisopropylfluorophosphate (DFP) (9 mg/kg i.p.)…”

The effect of exposure to chlorfenvinphos on lipid metabolism and apoptotic and necrotic cells death in the brain of rats

“…OP pesticides are characterized by high acute toxicity to mammals associated with an inhibition of activity of cholinesterases regulating the function of the nervous system such as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) (Lotti, 2001;Li et al, 2011). These compounds are known to damage to the different organs and systems at both acute and chronic exposure (Lasram et al, 2009;Singh et al, 2011;Dirican and Kalender, in press;Solati et al, in press); however, the main unfavorable effect of their action in mammals is the impact on the nervous system.…”

“…These compounds are known to damage to the different organs and systems at both acute and chronic exposure (Lasram et al, 2009;Singh et al, 2011;Dirican and Kalender, in press;Solati et al, in press); however, the main unfavorable effect of their action in mammals is the impact on the nervous system. Numerous experimental, epidemiological and clinical data show on the connection between exposure to OP pesticides and damage to the nervous system (Lotti, 2001;Sekar Babu et al, 2010;Kaur et al, 2007;Celik and Isik, 2009;Li et al, 2011;Solati et al, in press). The neurotoxic action of these compounds has been mainly explained by their ability to inhibit the activities of AChE and BChE.…”