Methane-Rich Saline Alleviates CA/CPR Brain Injury by Inhibiting Oxidative Stress, Microglial Activation-Induced Inflammatory Responses, and ER Stress-Mediated Apoptosis

Brain injury induced by cardiac arrest/cardiopulmonary resuscitation (CA/CPR) is the leading cause of death among patients who have recovery of spontaneous circulation (ROSC). Inflammatory response, apoptosis, and oxidative stress are proven pathological mechanisms implicated in neuronal damage. Methane-rich saline (MRS) has been proven that exerts a beneficial protectiveness impact in several models of ischemia-reperfusion injury. The goal of this paper is to ascertain the role of MRS in CA/CPR-induced brain injury and its potential mechanisms. The tracheal intubation of Sprague-Dawley (SD) rats was clamped for 6 min to establish an asphyxiating cardiac arrest model. After that, chest compressions were applied; then, MRS or saline was administered immediately post-ROSC, the rats were sacrificed, and brain tissue was collected at the end of 6 hours. We observed that MRS treatment attenuated neuronal damage in the hippocampal CA1 region by inhibiting microglial activation, leading to a decrease in the overexpression of proinflammatory cytokines such as TNF-α, IL-6, and iNOS. The results also illustrated that MRS treatment diminished apoptosis in the hippocampal CA1 region , reduced the expression of apoptosis-associated proteins Bax and cleaved caspase9, and increased Bcl-2 expression, as well as inhibited the expression of endoplasmic reticulum (ER) stress pathway-related proteins GRP78, ATF4, and CHOP. Further findings showed that MRS treatment significantly attenuated hippocampal ROS and MDA levels and increased GSH and SOD antioxidant factor levels, which indicated that MRS treatment could inhibit oxidative stress. Our results suggest that MRS exerts a protective effect against CA/CPR brain injury, by inhibiting oxidative stress, microglial activation-induced inflammatory responses, and ER stress-mediated apoptosis.