Zhang Xiaoqin, Zhang Yiping, Zhang Ting, Wang Jing, Liu Chang, Shang Qing, Wei Xiaojie, Zhu Huaqiang, Shen Haowei, Sun Binggui
Department of Pharmacology, Health Science Center of Ningbo University, Ningbo, Zhejiang Province, 315211, China.
Department of Anesthesiology of the Children's Hospital and School of Brain Science and Brain Medicine, Zhejiang University School of Medicine and National Clinical Research Center for Child Health; NHC and CAMS Key Laboratory of Medical Neurobiology, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou, Zhejiang Province, 310058, China.
Alzheimers Res Ther. 2025 Feb 27;17(1):55. doi: 10.1186/s13195-025-01704-y.
Abnormal excitability of hippocampal neurons may lead to dysfunction of neural circuits and then causes cognitive impairments in Alzheimer's disease (AD). However, the underlying mechanisms remain to be fully elucidated.
Electrophysiology was performed to examine the intrinsic excitability of CA1 neurons and the activity of the hyperpolarization-activated cyclic nucleotide-gated ion channels (HCNs) of CA1 neurons in wild type (WT) and hAPP-J20 mice. The activity of CA1 pyramidal neurons (PNs) was modulated with chemogenetics. The activity of HCNs was regulated with nonselective facilitator (cAMP) or inhibitor (ZD7288) of HCNs. Immunohistochemical staining or western blotting were performed to examine the expression of HCN1 and HCN2 in the hippocampus of WT and hAPP-J20 mice, or AD patients and non-AD controls. AAVs were injected to specifically modulate the expression of HCN2 in dorsal CA1 (dCA1) PNs. Cognitive performance of mice was assessed with behavioral tests.
dCA1 PNs were more excitable in hAPP-J20 mice, but the excitability of PNs in the ventral CA1 (vCA1) or PV neurons was comparable between WT and hAPP-J20 mice. The activity of the HCNs was reduced in dCA1 PNs of hAPP-J20 mice, and pharmacologically increasing the activity of HCNs attenuated the hyperexcitability of dCA1 PNs in hAPP-J20 mice, suggesting that the reduced activity of HCNs is associated with the hyperexcitability of dCA1 PNs in hAPP-J20 mice. The expression of HCN2 but not HCN1 was reduced in the hippocampus of hAPP-J20 mice, and the expression of HCN2 was also reduced in the hippocampus of AD patients, suggesting that dysregulation of HCN2 is associated with the reduced activity of HCNs in AD. Overexpressing HCN2 rescued the activity of HCNs, attenuated the hyperexcitability of dCA1 PNs and improved memory of hAPP-J20 mice, and knocking down HCN2 impaired the function of HCNs, increased the excitability of dCA1 PNs and led to memory deficits in WT mice.
Our data suggest that dysregulation of HCNs, particularly HCN2, contributes to the abnormal excitability of CA1 PNs in AD mice and probably in AD patients as well, and thus provide new insights into the mechanisms underlying the aberrant activity or excitability of hippocampal neurons in AD.
海马神经元的异常兴奋性可能导致神经回路功能障碍，进而引起阿尔茨海默病（AD）中的认知障碍。然而，其潜在机制仍有待充分阐明。
采用电生理学方法检测野生型（WT）和hAPP-J20小鼠中CA1神经元的内在兴奋性以及CA1神经元的超极化激活环核苷酸门控离子通道（HCNs）的活性。用化学遗传学方法调节CA1锥体神经元（PNs）的活性。用HCNs的非选择性促进剂（cAMP）或抑制剂（ZD7288）调节HCNs的活性。进行免疫组织化学染色或蛋白质印迹法检测WT和hAPP-J20小鼠、AD患者和非AD对照者海马中HCN1和HCN2的表达。注射腺相关病毒（AAV）以特异性调节背侧CA1（dCA1）PNs中HCN2的表达。用行为测试评估小鼠的认知能力。
hAPP-J20小鼠中的dCA1 PNs兴奋性更高，但WT和hAPP-J20小鼠腹侧CA1（vCA1）或PV神经元中PNs的兴奋性相当。hAPP-J20小鼠dCA1 PNs中HCNs的活性降低，药理学上增加HCNs的活性可减弱hAPP-J20小鼠dCA1 PNs的过度兴奋性，这表明HCNs活性降低与hAPP-J20小鼠dCA1 PNs的过度兴奋性有关。hAPP-J20小鼠海马中HCN2而非HCN1的表达降低，AD患者海马中HCN2的表达也降低，这表明HCN2失调与AD中HCNs活性降低有关。过表达HCN2可恢复HCNs的活性，减弱dCA1 PNs的过度兴奋性并改善hAPP-J20小鼠的记忆，敲低HCN2则损害HCNs的功能，增加dCA1 PNs的兴奋性并导致WT小鼠出现记忆缺陷。
我们的数据表明，HCNs，特别是HCN2的失调，促成了AD小鼠以及可能AD患者中CA1 PNs的异常兴奋性，从而为AD中海马神经元异常活动或兴奋性的潜在机制提供了新见解。
