Mechanism of Carbamathione as a therapeutic agent for Stroke.

Stroke is the third leading cause of mortality in the United States, and so far, no clinical interventions have been shown completely effective in stroke treatment. Stroke may result in hypoxia, glutamate release and oxidative stress. One approach for protecting neurons from excitotoxic damage in stroke is to attenuate receptor activity with specific antagonists. Disulfiram requires bio-activation to S-methyl N, N-diethylthiolcarbamate sulfoxide (DETC-MeSO). In vivo, DETC-MeSO is further oxidized to the sulfone which is carbamoylated forming Carbamathione, a glutathione adducts. Carbamathione proved to be useful as a pharmacological agent in the treatment of cocaine dependence with the advantage that it lacks ALDH2 inhibitory activity. Carbamathione is a partial NMDA glutamate antagonist. The purpose of this dissertation study is to evaluate the neuroprotective effects of Carbamathione drug on PC-12 cell line and to understand the protective mechanisms underlying in three stroke-related models: excessive glutamate, hypoxia/reoxygenation and bilateral carotid artery occlusion (BCAO). Carbamathione was administered 14 mg/kg subcutaneously for 4 days with the first injection occurring 30 min after occlusion in the mouse BCAO stroke model. Mice were subjected to the locomotor test, and the brain was analyzed for infarct size. Heat shock proteins, key proteins involved in apoptosis and endoplasmic reticulum (ER) stress, were analyzed by immunoblotting. Carbamathione reduced both cell death following hypoxia/reoxygenation and brain infarct size. It improved performance on the locomotor test. The level of pro-apoptotic proteins declined, and anti-apoptotic, P-AKT and HSP27 protein expressions were markedly increased. We found that Carbamathione suppresses the up- regulation of Caspase-12, Caspase-3 and significantly declined ER stress protein markers GRP 78, ATF4, XBP-1, and CHOP. Carbamathione can down- regulate ATF 4 and XBP1 expression, indicating that Carbamathione inhibits the ER stress induced by hypoxia/reoxygenation through suppressing PERK and IRE1 pathways. Carbamathione elicits neuroprotection through the preservation of ER resulting in reduction of apoptosis by increase of anti-apoptotic proteins and decrease of pro-apoptotic proteins. Carbamathione can suppress the activation of both PERK and IRE1 pathways in PC-12 cell cultures and has no inhibitory effect on ATF6 pathway. These findings provide promising and rational strategies for stroke therapy.