Disclosing CO-induced cytoprotection in astrocytes: role of FosB

Cerebral ischemia is a serious health problem, causing disability and death worldwide. Therefore, it is essential to develop strategies to protect and repair the brain. Recently, some studies on preconditioning started to emerge, where a toxic stimulus below the threshold of injury is given, inducing tolerance, preparing and strengthening the brain for a potential greater injury. In this project, it will be used carbon monoxide (CO) as a preconditioning agent, since its administration is able to produce several beneficial effects, namely acting as an anti-apoptotic and anti-inflammatory agent. The purpose of this work is to disclose CO-induced cytoprotection and the potential role of FosB associated to it. The experiments were developed using primary cultures of astrocytes isolated from newborn mice. As CO source the CO-releasing molecule CORM-A1 was used. CORM-A1 showed the ability to induce FosB protein expression in astrocytes, which was analyzed by western blot. However, it is not know yet how this increase is mediated. Reactive oxygen species (ROS) signaling is involved in CO and in FosB related pathways. Consequently, astrocytes were pre-treated with antioxidants (β-carotene or N-acetylcysteine) for decreasing cellular ROS levels. In addition P2X7 receptor also appears to be associated with FosB activation. Thus, P2X7 inhibitor (A-438079) was added to astrocytic culture in order to assess if FosB increased expression could be mediated by P2X7 receptor. Nevertheless, inhibition of ROS signaling did not change CO-induced FosB levels, while prevention of P2X7 activation showed a slight tendency to revert FosB expression, indicating that this pathway is independent on ROS but it could be mediated by P2X7 receptor. Although it is still a long way to go, these results gave more insight about CO-induced FosB activation, which is important for understanding the molecular mechanisms underlying CO-induced cytoprotection. Potential therapeutic applications of CO will depend on a clear understanding of its pathways ...