Acetylcholinesterase-independent protective effects of huperzine A against iron overload-induced oxidative damage and aberrant iron metabolism signaling in rat cortical neurons

Huperzine A ameliorates neurological deficits after spontaneous subarachnoid hemorrhage through endothelial cell pyroptosis inhibition

Spontaneous subarachnoid hemorrhage (SAH) is a kind of hemorrhagic stroke which causes neurological deficits in survivors. Huperzine A has a neuroprotective effect, but its role in SAH is unclear. Therefore, we explore the effect of Huperzine A on neurological deficits induced by SAH and the related mechanism. In this study, Evans blue assay, TUNEL staining, immunofluorescence, western blot analysis, and ELISA are conducted. We find that Huperzine A can improve neurological deficits and inhibit the apoptosis of nerve cells in SAH rats. Huperzine A treatment can improve the upregulation of brain water content, damage of blood-brain barrier, fibrinogen and matrix metalloprotein 9 expressions and the downregulation of ZO-1 and occludin expressions induced by SAH. Huperzine A inhibit the expressions of proteins involved in pyroptosis in endothelial cells in SAH rats. The increase in MDA content and decrease in SOD activity in SAH rats can be partly reversed by Huperzine A. The ROS inducer H 2O 2 can induce pyroptosis and inhibit the expressions of ZO-1 and occludin in endothelial cells, which can be blocked by Huperzine A. In addition, the increase in the entry of p65 into the nucleus in endothelial cells can be partly reversed by Huperzine A. Huperzine A may delay the damage of blood-brain barrier in SAH rats by inhibiting oxidative stress-mediated pyroptosis and tight junction protein expression downregulation through the NF-κB pathway. Overall, Huperzine A may have clinical value for treating SAH.

Microneedles: A Versatile Drug Delivery Carrier for Phytobioactive Compounds as a Therapeutic Modulator for Targeting Mitochondrial Dysfunction in the Management of Neurodegenerative Diseases

Neurodegenerative disease (ND) is the fourth leading cause of death worldwide, with limited symptomatic therapies. Mitochondrial dysfunction is a major risk factor in the progression of ND, and it-increases the generation of reactive oxygen species (ROS). Overexposure to these ROS induces apoptotic changes leading to neuronal cell death. Many studies have shown the prominent effect of phytobioactive compounds in managing mitochondrial dysfunctions associated with ND, mainly due to their antioxidant properties. The drug delivery to the brain is limited due to the presence of the blood-brain barrier (BBB), but effective drug concentration needs to reach the brain for the therapeutic action. Therefore, developing safe and effective strategies to enhance drug entry in the brain is required to establish ND's treatment. The microneedle-based drug delivery system is one of the effective non-invasive techniques for drug delivery through the transdermal route. Microneedles are micronsized drug delivery needles that are self-administrable. It can penetrate through the stratum corneum skin layer without hitting pain receptors, allowing the phytobioactive compounds to be released directly into systemic circulation in a controlled manner. With all of the principles mentioned above, this review discusses microneedles as a versatile drug delivery carrier for the phytoactive compounds as a therapeutic potentiating agent for targeting mitochondrial dysfunction for the management of ND.

Huperzine A-Liposomes Efficiently Improve Neural Injury in the Hippocampus of Mice with Chronic Intermittent Hypoxia

Background

Chronic intermittent hypoxia (CIH) could cause neuronal damage, accelerating the progression of dementia. However, safe and effective therapeutic drugs and delivery are needed for successful CIH therapy.

Purpose

To investigate the neuroprotective effect of Huperzine A (HuA) packaged with nanoliposomes (HuA-LIP) on neuronal damage induced by CIH.

Methods

The stability and release of HuA-LIP in vitro were identified. Mice were randomly divided into the Control, CIH, HuA-LIP, and HuA groups. The mice in the HuA and HuA-LIP groups received HuA (0.1 mg/kg, i.p.), and HuA-LIP was administered during CIH exposure for 21 days. HuA-LIP contains the equivalent content of HuA.

Results

We prepared a novel formulation of HuA-LIP that had good stability and controlled release. First, HuA-LIP significantly ameliorated cognitive dysfunction and neuronal damage in CIH mice. Second, HuA-LIP elevated T-SOD and GSH-Px abilities and decreased MDA content to resist oxidative stress damage induced by CIH. Furthermore, HuA-LIP reduced brain iron levels by downregulating TfR1, hepcidin, and FTL expression. In addition, HuA-LIP activated the PKAα/Erk/CREB/BDNF signaling pathway and elevated MAP2, PSD95, and synaptophysin to improve synaptic plasticity. Most importantly, compared with HuA, HuA-LIP showed a superior performance against neuronal damage induced by CIH.

Conclusion

HuA-LIP has a good sustained-release effect and targeting ability and efficiently protects against neural injury caused by CIH.

Role of Cholinergic Signaling in Alzheimer's Disease

Acetylcholine, a neurotransmitter secreted by cholinergic neurons, is involved in signal transduction related to memory and learning ability. Alzheimer’s disease (AD), a progressive and commonly diagnosed neurodegenerative disease, is characterized by memory and cognitive decline and behavioral disorders. The pathogenesis of AD is complex and remains unclear, being affected by various factors. The cholinergic hypothesis is the earliest theory about the pathogenesis of AD. Cholinergic atrophy and cognitive decline are accelerated in age-related neurodegenerative diseases such as AD. In addition, abnormal central cholinergic changes can also induce abnormal phosphorylation of ttau protein, nerve cell inflammation, cell apoptosis, and other pathological phenomena, but the exact mechanism of action is still unclear. Due to the complex and unclear pathogenesis, effective methods to prevent and treat AD are unavailable, and research to explore novel therapeutic drugs is various and active in the world. This review summaries the role of cholinergic signaling and the correlation between the cholinergic signaling pathway with other risk factors in AD and provides the latest research about the efficient therapeutic drugs and treatment of AD.

A Synopsis of Multitarget Potential Therapeutic Effects of Huperzine A in Diverse Pathologies-Emphasis on Alzheimer's Disease Pathogenesis

Numerous challenges are confronted when it comes to the recognition of therapeutic agents for treating complex neurodegenerative diseases like Alzheimer's disease (AD). The perplexing pathogenicity of AD embodies cholinergic dysfunction, amyloid beta (Aβ) aggregation, neurofibrillary tangle formation, neuroinflammation, mitochondrial disruption along with vicious production of reactive oxygen species (ROS) generating oxidative stress. In this frame of reference, drugs with multi target components could prove more advantageous to counter complex pathological mechanisms that are responsible for AD progression. For as much as, medicinal plant based pharmaco-therapies are emerging as potential candidates for AD treatment keeping the efficacy and safety parameters in terms of toxicity and side effects into consideration. Huperzine A (Hup A) is a purified alkaloid compound extracted from a club moss called Huperzia serrata. Several studies have reported both cholinergic and non-cholinergic effects of this compound on AD with significant neuroprotective properties. The present review convenes cumulative demonstrations of neuroprotection provided by Hup A in in vitro, in vivo, and human studies in various pathologies. The underlying molecular mechanisms of its actions have also been discussed. However, more profound evidence would certainly promote the therapeutic implementation of this drug thus furnishing decisive insights into AD therapeutics and various other pathologies along with preventive and curative management.

Involvement of Hepcidin in Cognitive Damage Induced by Chronic Intermittent Hypoxia in Mice

Obstructive sleep apnea (OSA) patients exhibit different degrees of cognitive impairment, which is related to the activation of reactive oxygen species (ROS) production by chronic intermittent hypoxia (CIH) and the deposition of iron in the brain. As a central regulator of iron homeostasis, whether hepcidin is involved in OSA-induced cognitive impairment has not been clarified. In order to simulate OSA, we established the mouse model by reducing the percentage of inspired O₂ (FiO₂) from 21% to 5%, 20 times/h for 8 h/day. We found hepcidin was rising during CIH, along with increasing iron levels and neuron loss. Then, we constructed a mouse with astrocyte-specific knockdown hepcidin gene (shHamp). During CIH exposure, the shHamp mice showed a lower level of total iron and neuronal iron in the hippocampus, via stabilizing ferroportin 1 (FPN1) and decreasing L-ferritin (FTL) levels, when compared with wild-type (WT) mice. Furthermore, the shHamp mice showed a decrease of ROS by downregulating the elevated NADPH oxidase (NOX2) and 4-hydroxynonenal (4-HNE) levels mediated by CIH. In addition, the shHamp mice presented improved cognitive deficit by improving synaptic plasticity and BDNF expression in the hippocampus when subjected to CIH. Therefore, our data revealed that highly expressed hepcidin might promote the degradation of FPN1, resulting in neuronal iron deposition, oxidative stress damage, reduced synaptic plasticity, and impaired cognitive performance during CIH exposure.

Nutraceuticals-based therapeutic approach: recent advances to combat pathogenesis of Alzheimer's disease

Introduction: Alzheimer's disease (AD) is a progressive neurodegenerative disease accompanying memory deficits. The available pharmaceutical care has some limitations mostly entailing side effects, shelf-life, and patient's compliance. The momentous implications of nutraceuticals in AD have attracted scientists. Several preclinical studies for the investigation of nutraceuticals have been conducted.Areas covered: This review focuses on the potential use of a nutraceuticals-based therapeutic approach to treat and prevent AD. Increasing knowledge of AD pathogenesis has led to the discovery of new therapeutic targets including pathophysiological mechanisms and various cascades. Hence, the present contribution will attend to the most popular and effective nutraceuticals with proposed brief mechanisms entailing antioxidant, anti-inflammatory, autophagy regulation, mitochondrial homeostasis, and more. Therefore, even though the effectiveness of nutraceuticals cannot be dismissed, it is essential to do further high-quality randomized clinical trials.Expert opinion: According to the potential of nutraceuticals to combat AD as multi-target directed drugs, there is critical importance to assess them as feasible lead compounds for drug discovery and development. To the best of the authors' knowledge, modification of blood-brain barrier permeability, bioavailability, and features of randomized clinical trials should be considered in prospective studies.

An optically active isochroman-2H-chromene conjugate potently suppresses neuronal oxidative injuries associated with the PI3K/Akt and MAPK signaling pathways

Increasing evidence suggests that the use of potent neuroprotective agents featured with novel pharmacological mechanism would offer a promising strategy to delay or prevent the progression of neurodegeneration. Here, we provide the first demonstration that the chiral nonracemic isochroman-2H-chromene conjugate JE-133, a novel synthetic 1,3-disubstituted isochroman derivative, possesses superior neuroprotective effect against oxidative injuries. Pretreatment with JE-133 (1-10 μM) concentration-dependently prevented H2O2-induced cell death in SH-SY5Y neuroblastoma cells and rat primary cortical neurons. Pretreatment with JE-133 significantly alleviated H2O2-induced apoptotic changes. These protective effects could not be simply attributed to the direct free radical scavenging as JE-133 had moderate activity in reducing DPPH free radical. Further study revealed that pretreatment with JE-133 (10 μM) significantly decreased the phosphorylation of MAPK pathway proteins, especially ERK and P38, in the neuronal cells. In addition, blocking PI3K/Akt pathway using LY294002 partially counteracted the cell viability-enhancing effect of JE-133. We conclude that JE-133 exerts neuroprotection associated with dual regulative mechanisms and consequently activating cell survival and inhibiting apoptotic changes, which may provide important clues for the development of effective neuroprotective drug lead/candidate.

Huperzine A, reduces brain iron overload and alleviates cognitive deficit in mice exposed to chronic intermittent hypoxia

Chronic intermittent hypoxia (CIH) is a consequence of obstructive sleep apnea (OSA), which increases reactive oxygen species (ROS) generation, resulting in oxidative damage and neurocognitive impairment. This study was designed to determine whether abnormal iron metabolism occurs in the brain under conditions of CIH and whether Huperzine A (HuA) could improve abnormal iron metabolism and neurological damage. The mouse model of CIH was established by reducing the percentage of inspired O₂ (FiO₂) from 21% to 9% 20 times/h for 8 h/day, and Huperzine A (HuA, 0.1 mg/kg, i.p.) was administered during CIH exposure for 21 days. HuA significantly improved cognitive impairment and neuronal damage in the hippocampus of CIH mice via increasing the ratio of Bcl-2/Bax and inhibiting caspase-3 cleavage. HuA considerably decreased ROS levels by downregulating the high levels of NADPH oxidase (NOX 2, NOX 4) mediated by CIH. There was an overload of iron, which was characterized by high levels of ferritin (FTL and FTH) and transferrin receptor 1 (TfR1) and low levels of ferroportin 1 (FPN1) in the hippocampus of CIH mice. Decreased levels of TfR1 and FTL proteins observed in HuA treated CIH group, could reduce iron overload in hippocampus. HuA increased PSD 95 protein expression, CREB activation and BDNF protein expression to protect against synaptic plasticity impairment induced by CIH. HuA acts as an effective iron chelator to attenuate apoptosis, oxidative stress and synaptic plasticity mediated by CIH.

Huperzine A ameliorates obesity-related cognitive performance impairments involving neuronal insulin signaling pathway in mice

Type 2 diabetes (T2D) and Alzheimer's disease (AD) share several common pathophysiological features. Huperzine A (Hup A), a Lycopodium alkaloid extracted from the Chinese herb moss Huperzia serrata, is a specific and reversible inhibitor of acetylcholinesterase, which is clinically used for the treatment of AD. In this study, we investigated whether Hup A improved the metabolic and cognitive functions in the high fat-induced (HFD) obese mice and genetic ob/ob mice. HFD and ob/ob mice were treated with Hup A (0.1, 0.3 mg · kg-1 · d-1, ig) for 3 months. Body weight was monitored and glucose tolerance tests were performed. Novel object recognition test and Morris water maze assay were conducted to evaluate the cognitive functions. We found that the Hup A treatment had no significant effect on peripheral metabolism of obese mice, whereas Hup A (0.1, mg · kg-1 · d-1) improved both the abilities of object recognition and spatial memory in HFD-fed mice, but not in ob/ob mice. Furthermore, Hup A treatment significantly upregulated the insulin and phosphorylated Akt levels in the cortex of HFD-fed mice, but not ob/ob mice. In addition, Hup A (0.3, mg · kg-1 · d-1) significantly decreased cortical β-secretase (BACE1) expression. In conclusion, these results demonstrate that treatment with Hup A (0.1, mg · kg-1 · d-1) can effectively improve the cognitive functions, at least in diet-induced obese mice.

Pharmacokinetics, excretion and metabolites analysis of DL0410, a dual‑acting cholinesterase inhibitor and histamine‑3 receptor antagonist

DL0410, a dual‑action cholinesterase inhibitor and histamine‑3 receptor antagonist with a novel structural scaffold, may be a potential candidate for the treatment of Alzheimer's disease (AD). To the best of the authors' knowledge, this is the first study to demonstrate a reliable method for the measurement of DL0410 in rat plasma, brain, bile, urine and feces samples, and identification of its primary metabolites. The pharmacokinetic properties of DL0410 were analyzed by liquid chromatography‑mass spectrometry at oral doses of 25, 50 and 100 mg/kg and intravenous dose of 5 mg/kg. The investigation of the excretion and metabolism of DL0410 was determined following liquid‑liquid extraction for biliary, urinary and fecal samples. Finally, the cytochrome (CY)P450 isoforms involved in the production of DL0410 metabolites with recombinant human cytochrome P450 enzymes were characterized. The results suggested that DL0410 was not well absorbed; however, was distributed to the entorhinal cortex and hippocampus of the brain. A total of two common metabolites of the reduction of DL0140 in the bile, urine and feces were identified and CYP2D6 was involved in this reaction. The pharmacokinetic results of DL0410 provided information for the illustration of its pharmacodynamic properties, mechanism of action and promoted its continued evaluation as a therapeutic agent for AD treatment.

Iron Exposure and the Cellular Mechanisms Linked to Neuron Degeneration in Adult Mice

Although the causal relationship between Alzheimer's disease (AD) and iron overload remains unclear, iron dyshomeostasis or improper transport mechanisms are speculated to lead to the accumulation of this neurotoxic metal in the hippocampal formation and other cerebral areas related to neurodegenerative diseases, resulting in the formation of reactive oxygen species (ROS) and, ultimately, cell death. In this study, exposure to high dietary iron (HDI) revealed no significant difference in the number of iron-positive cells and iron content in the cortex and hippocampal region between wild-type (WT) and APP/PS1 mice; however, compared with the control mice, the HDI-treated mice exhibited upregulated divalent metal transporter 1 (DMT1) and ferroportin (Fpn) expression, and downregulated transferrin receptor (TFR) expression. Importantly, we confirmed that there were significantly fewer NeuN-positive neurons in both APP/PS1 and WT mice given HDI, than in the respective controls. Moreover, this iron-induced neuron loss may involve increased ROS and oxidative mitochondria dysfunction, decreased DNA repair, and exacerbated apoptosis and autophagy. Although HDI administration might trigger protective antioxidant, anti-apoptosis, and autophagy signaling, especially in pathological conditions, these data clearly indicate that chronic iron exposure results in neuronal loss due to apoptosis, autophagy, and ferroptosis, hence increasing the risk for developing AD.

Iron dysregulates APP processing accompanying with sAPPα cellular retention and β-secretase inhibition in rat cortical neurons

Amyloid precursor protein (APP) and iron both play pivotal roles in the central nervous system, but whether and how iron influences the processing of endogenous APP in neurons remain unclear. Here, we investigated the regulatory effects and underlying mechanisms of iron on non-amyloidogenic and amyloidogenic processing of APP in rat primary cortical neurons. Treatment of the neurons with ferric ammonium citrate (FAC, 100 μmol/L) markedly facilitated the non-amyloidogenic processing of APP, as evidenced by a robust increase in α-secretase-derived carboxy-terminal fragment α (CTFα). Furthermore, the distribution of sAPPα was altered after iron treatment, and sAPPα remained in the cellular lysates instead of being secreted into the extracellular milieu. Moreover, the levels of APP amyloidogenic products, including sAPPβ and Aβ were both decreased. We further revealed that FAC did not alter the expression of β-secretase, but significantly suppressed its enzymatic activity in iron-treated neurons. In a cell-free β-secretase activity assay, FAC dose-dependently inhibited the activity of purified β-secretase with an IC₅₀ value of 21.67 μmol/L. Our data provide the first evidence that iron overload alters the neuronal sAPPα distribution and directly inhibits β-secretase activity. These findings shed light on the regulatory mechanism of bio-metals on APP processing.

Assessment of Enzyme Inhibition: A Review with Examples from the Development of Monoamine Oxidase and Cholinesterase Inhibitory Drugs

The actions of many drugs involve enzyme inhibition. This is exemplified by the inhibitors of monoamine oxidases (MAO) and the cholinsterases (ChE) that have been used for several pharmacological purposes. This review describes key principles and approaches for the reliable determination of enzyme activities and inhibition as well as some of the methods that are in current use for such studies with these two enzymes. Their applicability and potential pitfalls arising from their inappropriate use are discussed. Since inhibitor potency is frequently assessed in terms of the quantity necessary to give 50% inhibition (the IC50 value), the relationships between this and the mode of inhibition is also considered, in terms of the misleading information that it may provide. Incorporation of more than one functionality into the same molecule to give a multi-target-directed ligands (MTDLs) requires careful assessment to ensure that the specific target effects are not significantly altered and that the kinetic behavior remains as favourable with the MTDL as it does with the individual components. Such factors will be considered in terms of recently developed MTDLs that combine MAO and ChE inhibitory functions.

Isolation and characterization of phthalates from Brevibacterium mcbrellneri that cause cytotoxicity and cell cycle arrest

Bacteria belonging to the family Brevibacterieae are ubiquitous Gram positive organisms that are responsible for the feet odour and cheese aroma. Brevibacterium mcbrellneri is a relatively new member belonging to Brevibacterieae. In the current manuscript we discuss isolation of biologically active metabolites from Brevibacterium mcbrellneri. Two aromatic esters were isolated from Brevibacterium mcbrellneri by “Bioassay guided fractionation strategy” and identified as di-(2-ethylhexyl) phthalate and dibutyl phthalate by chemical characterization using biophysical techniques. The phthalate compounds show broad spectrum antibacterial activity and mosquito larvicidal activity. Mosquito larvicidal activity has been attributed to inhibition of acetylcholinesterase enzyme activity. These compounds were found to be cytotoxic in multiple cell lines causing cell cycle arrest in G1 phase.

[Role of mitophagy in neonatal rats with hypoxic-ischemic brain damage]

OBJECTIVE

To investigate mitophagy in an animal model of hypoxic-ischemic brain damage (HIBD) and its role in HIBD.

METHODS

A total of 120 neonatal Sprague-Dawley rats aged 7 days were divided into three groups: sham-operation, HIBD, and autophagy inhibitor intervention (3MA group). The rats in the HIBD group were treated with right common carotid artery ligation and then put in a hypoxic chamber (8% oxygen and 92% nitrogen) for 2.5 hours. Those in the 3MA group were given ligation and hypoxic treatment at 30 minutes after intraperitoneal injection of 2 μL 3MA. Those in the sham-operation group were not given ligation or hypoxic treatment. Single cell suspension was obtained from all groups after model establishment. Immunofluorescence localization was performed for mitochondria labeled with MitoTracker, autophagosomes labeled with LysoTracker, and autophagy labeled with LC3 to observe mitophagy. After staining with the fluorescent probe JC-1, flow cytometry was used to measure mitochondrial membrane potential. TTC staining was used to measure infarct volume. Cytoplasmic proteins in cortical neurons were extracted, and Western blot was used to measure the expression of mitophagy-related proteins.

RESULTS

Compared with the sham-operation group, the HIBD group had a significant reduction in mitochondrial membrane potential (P<0.05), a significant increase in mitophagy (P<0.05), a significant increase in the expression of the proteins associated with the division of the mitochondrial Drp1 and Fis1 (P<0.05), and a significant reduction in the expression of the mitochondrial outer membrane protein Tom20 and the mitochondrial inner membrane protein Tim23 (P<0.05). Compared with the HIBD group, the 3MA group had a significantly greater reduction in mitochondrial membrane potential (P<0.05), but showed significantly reduced mitophagy (P<0.05). In addition, the 3MA group had a significantly increased degree of cerebral infarction compared with the HIBD group (P<0.05).

CONCLUSIONS

HIBD can increase the degree of mitophagy, and the inhibition of mitophagy can aggravate HIBD in neonatal rats.

[Role of mitophagy in neonatal rats with hypoxic-ischemic brain damage]

OBJECTIVE

To investigate mitophagy in an animal model of hypoxic-ischemic brain damage (HIBD) and its role in HIBD.

METHODS

A total of 120 neonatal Sprague-Dawley rats aged 7 days were divided into three groups: sham-operation, HIBD, and autophagy inhibitor intervention (3MA group). The rats in the HIBD group were treated with right common carotid artery ligation and then put in a hypoxic chamber (8% oxygen and 92% nitrogen) for 2.5 hours. Those in the 3MA group were given ligation and hypoxic treatment at 30 minutes after intraperitoneal injection of 2 μL 3MA. Those in the sham-operation group were not given ligation or hypoxic treatment. Single cell suspension was obtained from all groups after model establishment. Immunofluorescence localization was performed for mitochondria labeled with MitoTracker, autophagosomes labeled with LysoTracker, and autophagy labeled with LC3 to observe mitophagy. After staining with the fluorescent probe JC-1, flow cytometry was used to measure mitochondrial membrane potential. TTC staining was used to measure infarct volume. Cytoplasmic proteins in cortical neurons were extracted, and Western blot was used to measure the expression of mitophagy-related proteins.

RESULTS

Compared with the sham-operation group, the HIBD group had a significant reduction in mitochondrial membrane potential (P<0.05), a significant increase in mitophagy (P<0.05), a significant increase in the expression of the proteins associated with the division of the mitochondrial Drp1 and Fis1 (P<0.05), and a significant reduction in the expression of the mitochondrial outer membrane protein Tom20 and the mitochondrial inner membrane protein Tim23 (P<0.05). Compared with the HIBD group, the 3MA group had a significantly greater reduction in mitochondrial membrane potential (P<0.05), but showed significantly reduced mitophagy (P<0.05). In addition, the 3MA group had a significantly increased degree of cerebral infarction compared with the HIBD group (P<0.05).

CONCLUSIONS

HIBD can increase the degree of mitophagy, and the inhibition of mitophagy can aggravate HIBD in neonatal rats.