Objective: To explore whether the cholinergic anti-inflammatory pathway is involved in the neuroprotective effect of acetylcholinesterase inhibitor huperzine A (HupA) on sepsis-associated encephalopathy (SAE) by observing the effect of HupA on the expressions of choline acetyltransferase (CHAT) and cholinergic muscarinic receptor M1 (CHRM1) of sepsis rats.
Methods: Fifty-four male Wistar rats, 8 weeks old, were divided into three experimental groups according to random number table:control group,sepsis group, and HupA group, with 18 rats in each group. The rat model of sepsis was reproduced by intraperitoneal injection of 10 mg/kg lipopolysaccharide (LPS,1 mL),and the rats in control group were given the same volume of normal saline. The rats in HupA group were intraperitoneally administered with HupA 0.04 mg/kg (1 mL) at 30 minutes before model reproduction, while the rats in control group and sepsis group were treated with the same volume of saline instead. At 3,12,and 24 hours after model reproduction,6 rats in each group were sacrificed after clinical manifestation observation, and cerebral cortex tissue was collected. Pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1 β) in cerebral cortex were determined with enzyme linked immunosorbent assay (ELISA),along with the measurement of neuronal apoptosis by caspase-3 and neuronal nuclear antigen (NeuN) immune double standard staining. The mRNA expressions and positive expressions of ChAT and CHRM1 were detected by real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR) and immunofluorescence methods.
Results: Clinical manifestations of sepsis rats were present at 3 hours and reached a peak at 12 hours, including lethargy,vertical hair and lazy to move. Over-expression of pro-inflammatory cytokines TNF-α and IL-1β was found in sepsis group, and apoptotic neurons marked by two fluorescences were significantly increased in sepsis rats ,in comparison with deficient ChAT and CHRM1 proteins marked by red fluorescence, and low-expressed ChAT and CHRM1 mRNA as well. The differences between sepsis group and control group were statistically significant [12-hour TNF-α (ng/L):84.97±31.84 vs.40.31 ± 10.37,12-hour IL-1 β (ng/L):1 095.98± 127.09 vs.622.62± 117.25,12-hour ChAT mRNA (2-△△Ct):1.34 (0.67,1.86) vs.1.92 (1.12,2.87),12-hour CHRM1 mRNA (2-△△Ct):0.65±0.12 vs.1.16±0.42,all P ＜ 0.05].The septic symptoms were relieved after HupA administration,as well as the reduction of pro-inflammatory cytokines and the neuronal apoptosis, which might attribute to the increased expressions of ChAT and CHRM1.The differences between HupA group and sepsis group were statistically significant [12-hour TNF-α (ng/L):48.38 ± 12.62 vs.84.97 ± 31.84,12-hour IL-1 β (ng/L):718.13 ± 163.33 vs.1 095.98 ± 127.09,12-hour ChAT mRNA (2-△△Ct):18.04 (17.22,19.23) vs.1.34 (0.67,1.86),12-hour CHRM1 mRNA (2-△ △Ct):1.46 ± 0.69 vs 0.65 ± 0.12,all P ＜ 0.05].The clinical manifestations and neuroinflammation mainly recovered at 24 hours.
Conclusions: The cortical cholinergic neurons dysfunction and the abnormal inflammatory response are involved in the onset of SAE process. HupA plays a protective role in SAE through recovering the function of cholinergic neurons and cholinergic anti-inflammatory pathway.