Effect of the Broad-Spectrum Caspase Inhibitor Q-VD-OPh on Neurodegeneration and Neuroinflammation of Sarin Exposed Mice

Organophosphates (OP) cause CNS hyperstimulation resulting in seizures, convulsions and brain damage. Sarin is a toxic nerve agent used in Syria, the Gulf War and in terrorist attacks in Japan. Exposure to sarin is associated with presence of dead neurons, activation of astrocytes, microglia and neuroinflammation. Since, cell death and neuroinflammation are found in sarin exposed animals, we evaluated the efficacy of Q-VD-OPh, a broad spectrum caspase inhibitor that prevents cell death and has anti-inflammatory properties. Currently, treatment for sarin exposures is effective only if administered within 30-40 minutes of exposure. In this study, adult female C57BL/6 mice were subjected to an injection of 1.5 mg/kg CBDP before a 0.04mg/kg injection of sarin followed by 20 mg/kg injection of Q-VD-OPh 30 minutes later. Mice were sacrificed at two and fourteen day time points followed by cytokine analysis of amygdala and hippocampus using Bio-Plex 200 Pro Mouse Cytokine Grp I Panel (23-Plex) kit. We found a significant increase in 13 out of 23 examined cytokines in amygdala after 2 days of sarin exposure. Also, sarin elicits a strong response in amygdala and hippocampus. After treatment with Q-VD-OPh, the cytokines did not change appreciably between 2 and 14 days in the sarin/Q-VD-OPh treated animals. Q-VE-OPh, a negative control for Q-VD-OPh was used and it showed no significant change at the two or fourteen day time points in amygdala and hippocampus. To detect DNA fragmentation, 12µm thick sections were TUNEL-stained using NeuroTacs Apoptosis kit. Q-VD-OPh effect on cholinesterase activity was detected by ChE assay. Frontal cortex was used to analyse apoptosis markers and for cholinesterase activity. TUNEL staining was increased in sarin treated sections but was seen to be less in sections treated with Q-VD-OPh at 2 days. At 14 days, there was not much difference seen. Also, Q-VE-OPh showed intense staining as compared to Q-VD-OPh. ChE assay showed that Q-VD-OPh did not appear to have an inhibitory effect in mice treated with it and sarin. These trends may be indicative of Q-VD-OPh being effective in attenuating neurodegeneration and neuroinflammation in sarin exposed mice