Huperzine A (HupA), a novel alkaloid isolated from the Chinese herb Huperzia serrata, is a potent, highly specific and reversible inhibitor of acetylcholinesterase (AChE). Compared with tacrine, donepezil, and rivastigmine, HupA has better penetration through the blood-brain barrier, higher oral bioavailability, and longer duration of AChE inhibitory action. HupA has been found to improve cognitive deficits in a broad range of animal models. HupA possesses the ability to protect cells against hydrogen peroxide, β-amyloid protein (or peptide), glutamate, ischemia and staurosporine-induced cytotoxicity and apoptosis. These protective effects are related to its ability to attenuate oxidative stress, regulate the expression of apoptotic proteins Bcl-2, Bax, P53, and caspase-3, protect mitochondria, upregulate nerve growth factor and its receptors, and interfere with amyloid precursor protein metabolism. Antagonizing effects of HupA on N-methyl-D-aspartate receptors and potassium currents may also contribute to its neuroprotection as well. Pharmacokinetic studies in rodents, canines, and healthy human volunteers indicated that HupA was absorbed rapidly, distributed widely in the body, and eliminated at a moderate rate with the property of slow and prolonged release after oral administration. Animal and clinical safety tests showed that HupA had no unexpected toxicity, particularly the dose-limiting hepatotoxicity induced by tacrine. The phase IV clinical trials in China have demonstrated that HupA significantly improved memory deficits in elderly people with benign senescent forgetfulness, and patients with Alzheimer disease and vascular dementia, with minimal peripheral cholinergic side effects and no unexpected toxicity. HupA can also be used as a protective agent against organophosphate intoxication.

Huperzine A, a reversible and selective acetylcholinesterase (AChE) inhibitor, has been reported to display neuroprotective properties. The present study investigated the protective effects of huperzine A in a rat model of transient focal cerebral ischemia created by middle cerebral artery occlusion (MCAO). Huperzine A (0.1 mg/kg), administrated intraperitoneally at the onset of occlusion and 6 h later, markedly restored regional cerebral blood flow, reduced infarct size, and decreased neurological deficit score at 24 h after reperfusion. Along with inhibiting AChE activity, huperzine A inhibited nuclear translocation of transcription factor nuclear factor‐kappa B, decreased overexpression of proinflammatory factors in both ipsilateral cortex and striatum, and suppressed activation of glial cells in the ischemic penumbra. Neurological deficit and glial cells activation were also reduced by daily administration of huperzine A for 14 days. Mecamylamine, a nicotinic acetylcholine receptor (nAChR) antagonist, totally abolished the inhibitory effects of huperzine A on ischemia‐induced glial cells activation. Meanwhile, mecamylamine partially reversed the infarct size‐reducing effects of huperzine A. In conclusion, our results demonstrate that huperzine A exhibits neuroprotective effects against transient focal cerebral ischemia‐induced brain injury and suggest that the protection mechanism may involve a cholinergic anti‐inflammatory pathway, in which nAChR plays an essential role.

Vascular dementia (VaD) is a progressive neurodegenerative disease with a high prevalence. Several studies have recently reported that VaD patients present cholinergic deficits in the brain and cerebrospinal fluid (CSF) that may be closely related to the pathophysiology of cognitive impairment. Moreover, cholinergic therapies have shown promising effects on cognitive improvement in VaD patients. The precise mechanisms of these cholinergic agents are currently not fully understood; however, accumulating evidence indicates that these drugs may act through the cholinergic anti-inflammatory pathway, in which the efferent vagus nerve signals suppress pro-inflammatory cytokine release and inhibit inflammation, although regulation of oxidative stress and energy metabolism, alleviation of apoptosis may also be involved. In this paper, we provide a brief overview of the cholinergic treatment strategy for VaD and its relevant mechanisms of anti-inflammation.