Objective: To investigate the effects of astaxanthin on neuronal injury in hippocampus of rats after acute carbon monoxide poisoning(ACMP) and the relationship with NF-κB inflammatory signaling pathway. Methods: Male SD rats screened by water maze were randomly divided into three group(n=50): control group (NC group), CO poisoning group (COP group), CO poisoning+ astaxanthin group (AST group) . ACMP rat model was established by static inhaled exposure method. Meanwhile, rats in AST group were further given astaxanthin twice a day by gavage.At 1 day, 7 days, 14 days, 21 days and 28 days after CO poisoning (10 rats in each group were selected), the learning and memory abilities were evaluated by Morris water maze test. The pathological changes of the neurons in hippocampal CA1 region were observed by hematoxylin-eosin(HE) staining.The expression and activation of NF-κB in hippocampus were detected by immunoblotting and immunofluorescence, and the expression of TNF-α and IL-6 protein in hippocampus were examined by ELISA. Results: Morris water maze test showed that there were no significant difference in escape latency and crossing platform times between the three groups (P>0.05). Compared with NC group, the escape latency of COP group was prolonged at 14, 21 and 28 days after CO poisoning (t=-6.04, -6.28, -8.18, all P<0.05), and the number of crossing platform was decreased (t= 5.96, 7.85, 6.51, all P<0.05). Compared with the COP group, the escape latency of the rats in AST group at the 14, 21 and 28 days was shortened (t=4.74, 4.82, 5.98, all P<0.05), and the number of crossing platform was increased (t=-3.72, -4.45, -6.53, all P<0.05). Compared with NC group, the number of NF-κ B positive cells in CA1 area of hippocampus in COP group increased at every time point (t=-8.62, -18.00, -16.67, -11.15, -6.22, all P<0.05); the number of NF-κ B positive cells in CA1 area in AST group decreased at 7 d, 14 d, 21 d and 28 d after CO poisoning, the difference was statistically significant (t= 6.55, 6.96, 4.40, 4.17; all P<0.05). Western blot showed that the changes of NF-κB protein was similar to that of immunofluorescence. After 7 days of CO poisoning, the level of NF-κB protein in hippocampus of COP group was (1.44±0.08), it was higher than that of NC group (t=-20.07, P<0.05), while that of AST group was (0.68±0.10), it was lower than that of COP group (t=10.23, P<0.05). The results of Elisa showed that TNF-α and IL-6 in the hippocampus of COP group were higher than those of NC group at every time point(all P<0.05), while compared with COP group, TNF-α and IL-6 in AST group were lower (all P<0.05). After 7 days of CO poisoning, TNF -α in COP group ((39.04±5.29) pg/ml)was higher than that in NC group ((14.13±2.12) pg/ml) (t=-7.58, P<0.05); TNF -α in AST group ((25.77±3.31) pg/ml) was lower than that in COP group (t=3.69, P<0.05). After 7 days of CO poisoning, the level of IL-6 in COP group ((181.79±9.12) pg/ml)was higher than that in NC group ((73.12±11.04) pg/ml) (t=-8.24, P<0.05), and the level of IL-6 in AST group ((121.47±9.80) pg/ml) was lower than that in COP group (t=7.80, P<0.05). Conclusion The excessive inflammatory response which mediated by NF-κB signaling pathway is involved in ACMP-induced neuronal damage in hippocampus.Astaxanthin can down-regulate the expression of NF-κB inflammatory signaling pathway related proteins, and pave a way for the treatment of ACMP brain damage and cognitive dysfunction.

Objective To investigate the role of nuclear transcription factor kappa B (NF-κB) -matrix metalloproteinase-9 (MMP-9) signaling pathway in delayed encephalopathy after acute carbon monoxide poisoning (DEACMP). Methods 150 male SD rats were randomly assigned to air control group (AC group) , CO poisoning group (CO group) , pyrrolidine thiocarbamate (PDTC) + CO poisoning group (PC group). DEACMP model was reconstructed by modified intraperitoneal injections. The 1, 3, 7, 14, and 21 d after intraperitoneal injection were observed here by different approaches. Morris water maze test was used to test the learning and memory ability of rats.HE staining was used to observe the morphology of hippocampal CA3 cells. Immunofluorescence and Western Blot methods were used to detect the expression of NF-κB and MMP-9. RT-PCR was used to measure the expression of MMP-9 mRN A. Transmission electron microscopy was used to observe the ultrastructure of synapses. Results After14 days, the average intubation period of CO group was longer than that of AC group (P < 0.05) , and that of PC group was shorter than that of CO group (P < 0.05). However, average intubation period of PC group was longer than that of AC group (P< 0.05). In CO group, the expression of NF-κB in hippocampus increased (day 1). At day 3, the expression of NF-κB rapidly increased. The expression of MMP-9 gene and protein increased in the first three days and then decreased thereafter. The expression of NF-κB and MMP-9 in PC group was lower than that in CO group (P < 0.05) , while it was higher than AC group (P < 0.05). The peak value of apoptosis in CO group was delayed to 7-14 d after exposure, the apoptotic cells in PC group decreased significantly, and it was obvious on the 14 th day.Electron microscopy showed that the damage of synapses ultrastructure in CO group was significantly heavier than that in PC group on the 14 th day. Conclusions NF-κB-MMP-9 signal pathway leads to DEACMP, and PDTC could alleviate the impairment of learning and memory ability in rats with acute CO poisoning.