Delayed encephalopathy after acute carbon monoxide (CO) poisoning (DEACMP) is the most severe and clinically intractable complication that occurs following acute CO poisoning. Unfortunately, the mechanism ofDEACMPis still vague. Growing evidence indicates that delayed cerebral damage afterCOpoisoning is related to oxidative stress, abnormal neuro‐inflammation, apoptosis and immune‐mediated injury. Our recent report indicated that methylene blue (MB) may be a promising therapeutic agent in the prevention of neuronal cell death and cognitive deficits after transient global cerebral ischaemia (GCI). In this study, we aimed to investigate the potential ofMBtherapy to ameliorate the signs and symptoms of DEACMP. Rats were exposed to 1000 ppmCOfor 40 min. in the first step;COwas then increased to 3000 ppm, which was maintained for another 20 min. The rats were implanted with 7‐day release Alzet osmotic mini‐pumps subcutaneously under the back skin, which providedMBat a dose of 0.5 mg/kg/day 1 hr afterCOexposure. The results showed thatMBsignificantly suppressed oxidative damage and expression of pro‐inflammatory factors, including tumour necrosis factor‐α and interleukin (IL)‐1β.MBtreatment also suitably modulated mitochondrial fission and fusion, which is helpful in the preservation of mitochondrial function. Furthermore,MBdramatically attenuated apoptosis and neuronal death. Lastly, behavioural studies revealed thatMBtreatment preserved spatial learning and memory in the Barnes maze test. Our findings indicated thatMBmay have protective effects against DEACMP.

Transnitrosylation is an important mechanism by which nitric oxide (NO) modulates cell signaling pathways. For instance, SNO-caspase-3 can transnitrosylate the X-linked inhibitor of apoptosis (XIAP) to enhance apoptosis. XIAP is a potent antagonist of caspase apoptotic activity. Decrease in XIAP activity via nitrosylation results in SNO-XIAP-mediated caspase activation. Considering the functional liaison of procaspase-9 and XIAP, we hypothesized that procaspase-9 nitrosylates XIAP directly. Our data confirmed that cerebral ischemia-reperfusion induced XIAP nitrosylation, procaspase-9 denitrosylation and cleavage. Interestingly, the time courses of the nitrosylation of procaspase-9 and XIAP were negatively correlated, which was more prominent after cerebral ischemia-reperfusion, suggesting a direct interaction. The nitrosylation of XIAP, as well as the denitrosylation and cleavage of procaspase-9, were inhibited by DNCB, TrxR1 AS-ODNs, or TAT-AVPY treatment. Meanwhile, DNCB, TrxR1 AS-ODNs, or TAT-AVPY also inhibited the decrease in hippocampal CA1 neurons induced by ischemia-reperfusion in rats. The denitrosylation and cleavage of procaspase-9 induced by OGD/reoxygenation in SH-SY5Y cells were inhibited when cells were co-transfected with wild-type procaspase-9 and XIAP mutant (C449G). These data suggest that cerebral ischemia-reperfusion induces a transnitrosylation from procaspase-9 to XIAP via the Trx system to consequently cause apoptosis. Additionally, Cys325 is a critical S-nitrosylation site of procaspase-9.

Aims: The basolateral amygdala (BLA) plays an integral role in anxiety disorders (such as post traumatic stress disorder) stem from dysregulated fear memory. The excitability of glutamatergic neurons in the BLA correlates with fear memory, and the afterhyperpolarization current (I_AHP) mediated by small‐conductance calcium‐activated potassium channel subtype 2 (SK2) dominates the excitability of glutamatergicneurons. This study aimed to explore the effect of MPP2 interacts with SK2 in the excitability of glutamatergic neurons in the BLA and the extinction of conditioned fear in mice.Methods: Fear memory was analyzed via freezing percentage. Western blotting and fluorescence quantitative PCR were used to determine the expression of protein and mRNA respectively. Electrophysiology was employed to measure the excitability of glutamatergic neurons and I_AHP.Results: Fear conditioning decreased the levels of synaptic SK2 channels in the BLA, which were restored following fear extinction. Notably, reduced expression of synaptic SK2 channels in the BLA during fear conditioning was caused by the increased activity of protein kinase A (PKA), while increased levels of synaptic SK2 channels in the BLA during fear extinction were mediated by interactions with membrane‐palmitoylated protein 2 (MPP2).Conclusions: Our results revealed that MPP2 interacts with the SK2 channels and rescues the excitability of glutamatergic neurons by increasing the expression of synaptic SK2 channels in the BLA to promote the normalization of anxiety disorders and provide a new direction for the treatment.