4R-cembranoid protects against diisopropylfluorophosphate-mediated neurodegeneration

Abstract

Many organophosphorous esters synthesized for applications in industry, agriculture, or warfare irreversibly inhibit acetylcholinesterase, and acute poisoning with these compounds causes life-threatening cholinergic overstimulation. Following classical emergency treatment with atropine, an oxime, and a benzodiazepine, surviving victims often suffer brain neurodegeneration. Currently, there is no pharmacological treatment to prevent this brain injury. Here we show that a cyclic diterpenoid, (1S,2E,4R,6R,7E,11E)-cembra-2,7,11-triene-4,6-diol (4R) ameliorates the damage caused by diisopropylfluorophosphate (DFP) in the hippocampal area CA1. DFP has been frequently used as a surrogate for the warfare nerve agent sarin. In rats, DFP is lethal at the dose used to cause brain damage. Therefore, to observe brain damage in survivors, the death rate was reduced by pre-administration of the peripherally acting antidotes pyridostigmine and methyl atropine or its analogue ipratropium. Pyridostigmine bromide, methyl atropine nitrate, and ipratropium bromide were dissolved in saline and injected intramuscularly at 0.1 mg/kg, 20 mg/kg, and 23 mg/kg, respectively. DFP (9 mg/kg) dissolved in cold water was injected intraperitoneally. 4R (6 mg/kg) dissolved in DMSO was injected subcutaneously, either 1 hour before or 5 or 24 hours after DFP. Neurodegeneration was assessed with Fluoro-Jade B and amino cupric silver staining; neuroinflammation was measured by the expression of nestin, a marker of activated astrocytes. Forty-eight hours after DFP administration, 4R decreased the number of dead neurons by half when injected before or after DFP. 4R also significantly decreased the number of activated astrocytes. These data suggest that 4R is a promising new drug that could change the therapeutic paradigm for acute poisoning with organophosphorous compounds by the implementation of a second-stage intervention after the classical countermeasure treatment.

Neuroprotection Against Diisopropylfluorophosphate in Acute Hippocampal Slices

“…As mentioned in the introduction, the neurotoxicity and neuroprotection observed in slices is a good predictor of the result in vivo. In the present case, the neuroprotection by 4R, first observed in slices [32], was reproduced in vivo [14]. A puzzling finding is the very early onset of the caspase-dependent neurotoxic effect, which is most likely apoptosis.…”

“…Remarkably, the neuroprotective effect observed in vitro has been repeatedly confirmed in vivo proving the usefulness of this method [14-18]. …”

Neuroprotective activity of (1S,2E,4R,6R,-7E,11E)-2,7,11-cembratriene-4,6-diol (4R) in vitro and in vivo in rodent models of brain ischemia

“…4R neuroprotective activity was found to be mediated by activation of the PI3K/Akt antiapoptotic cascade (Ferchmin et al, 2005). In vivo experiments demonstrated that 4R ameliorated brain degeneration caused by diisopropylfluorophosphate when injected 24 hours after organophosphate poisoning (Ferchmin et al, 2014). For the first time, the present study demonstrated that 4R protected brain against ischemic stroke-induced injury in rodents.…”

Chronic Treatment with Naltrexone Prevents Memory Retention Deficits in Rats Poisoned with the Sarin Analog Diisopropylfluorophosphate (DFP) and Treated with Atropine and Pralidoxime

“…Based on what is known about the pathophysiology of organophosphate-induced neurodegeneration, targeting neuroinflammation and apoptosis may provide an effective strategy [16]. The diterpenoid 4R-cembranoid has been found to decrease the number of dead neurons and astrocyte activation in rats poisoned with DFP [17].…”