Sarsasapogenin-AA13 ameliorates Aβ-induced cognitive deficits via improving neuroglial capacity on Aβ clearance and antiinflammation

NLRP3/1-mediated pyroptosis: beneficial clues for the development of novel therapies for Alzheimer's disease

The inflammasome is a multiprotein complex involved in innate immunity that mediates the inflammatory response leading to pyroptosis, which is a lytic, inflammatory form of cell death. There is accumulating evidence that nucleotide-binding domain and leucine-rich repeat pyrin domain containing 3 (NLRP3) inflammasome-mediated microglial pyroptosis and NLRP1 inflammasome-mediated neuronal pyroptosis in the brain are closely associated with the pathogenesis of Alzheimer's disease. In this review, we summarize the possible pathogenic mechanisms of Alzheimer's disease, focusing on neuroinflammation. We also describe the structures of NLRP3 and NLRP1 and the role their activation plays in Alzheimer's disease. Finally, we examine the neuroprotective activity of small-molecule inhibitors, endogenous inhibitor proteins, microRNAs, and natural bioactive molecules that target NLRP3 and NLRP1, based on the rationale that inhibiting NLRP3 and NLRP1 inflammasome-mediated pyroptosis can be an effective therapeutic strategy for Alzheimer's disease.

Unveiling the impact of aging on BBB and Alzheimer's disease: Factors and therapeutic implications

Alzheimer's disease (AD) is a highly prevalent neurodegenerative condition that has devastating effects on individuals, often resulting in dementia. AD is primarily defined by the presence of extracellular plaques containing insoluble β-amyloid peptide (Aβ) and neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau protein (P-tau). In addition, individuals afflicted by these age-related illnesses experience a diminished state of health, which places significant financial strain on their loved ones. Several risk factors play a significant role in the development of AD. These factors include genetics, diet, smoking, certain diseases (such as cerebrovascular diseases, obesity, hypertension, and dyslipidemia), age, and alcohol consumption. Age-related factors are key contributors to the development of vascular-based neurodegenerative diseases such as AD. In general, the process of aging can lead to changes in the immune system's responses and can also initiate inflammation in the brain. The chronic inflammation and the inflammatory mediators found in the brain play a crucial role in the dysfunction of the blood-brain barrier (BBB). Furthermore, maintaining BBB integrity is of utmost importance in preventing a wide range of neurological disorders. Therefore, in this review, we discussed the role of age and its related factors in the breakdown of the blood-brain barrier and the development of AD. We also discussed the importance of different compounds, such as those with anti-aging properties, and other compounds that can help maintain the integrity of the blood-brain barrier in the prevention of AD. This review builds a strong correlation between age-related factors, degradation of the BBB, and its impact on AD.

Rutin prevents pyroptosis and M1 microglia via Nrf2/Mac-1/caspase-1-mediated inflammasome axis to improve POCD

BACKGROUND

Neuroinflammation following peripheral surgery plays a key role in postoperative cognitive dysfunction (POCD) development and there is no effective therapy to inflammation-mediated cognitive impairment. Recent studies showed that rutin, a natural flavonoid compound, conferred neuroprotection. However, the effects and mechanisms of rutin on cognition of surgical and aged mice and LPS-induced BV2 need deeper exploration.

METHODS

The effect of rutin in vivo and vitro were evaluated by Morris water maze test, HE stainin, Golgi-Cox staining, IF, IHC, RT-PCR, Flow Cytometer and Western blotting. In vivo, aged mice were treated with rutin and surgery. In vitro, rutin, Nrf2 knockdown, MAC-1 overexpression and VX765, a caspase-1 inhibitor, were administration on BV2 microglial cells.

RESULTS

Surgery led to compensatory increase in nuclear Nrf2 and rutin could further increase it. Neural damage was accompanied with high level in MAC-1, caspase-1-mediated pyroptosis and M1 microglia, while rutin recovered the process. Nrf2 inhibition abolished the effect of rutin with the increase of MAC-1, caspase-1-mediated pyroptosis and M1 microglia. Activation of MAC-1 abrogated protection of rutin by increase in pyroptosis and M1 microglia. Finally, we found that treatment with VX765 improved injury and increased M2 microglia against overexpression of MAC-1.

CONCLUSIONS

Our study indicated that rutin may be a potential therapy in POCD and exerted neural protection via Nrf2/ Mac-1/ caspase-1-mediated inflammasome axis to regulate pyroptosis and microglial polarization.

Glibenclamide-Loaded Engineered Nanovectors (GNVs) Modulate Autophagy and NLRP3-Inflammasome Activation

Activation of the NLRP3 inflammasome in response to either exogenous (PAMPs) or endogenous (DAMPs) stimuli results in the production of IL-18, caspase-1 and IL-1β. These cytokines have a beneficial role in promoting inflammation, but an excessive activation of the inflammasome and the consequent constitutive inflammatory status plays a role in human pathologies, including Alzheimer's disease (AD). Autophagic removal of NLRP3 inflammasome activators can reduce inflammasome activation and inflammation. Likewise, inflammasome signaling pathways regulate autophagy, allowing the development of inflammatory responses but preventing excessive and detrimental inflammation. Nanotechnology led to the development of liposome engineered nanovectors (NVs) that can load and carry drugs. We verified in an in vitro model of AD-associated inflammation the ability of Glibenclamide-loaded NVs (GNVs) to modulate the balance between inflammasome activation and autophagy. Human THP1dM cells were LPS-primed and oligomeric Aß-stimulated in the presence/absence of GNVs. IL-1β, IL-18 and activated caspase-1 production was evaluated by the Automated Immunoassay System (ELLA); ASC speck formation (a marker of NLRP3 activation) was analyzed by FlowSight Imaging flow-cytometer (AMNIS); the expression of autophagy targets was investigated by RT-PCR and Western blot (WB); and the modulation of autophagy-related up-stream signaling pathways and Tau phosphorylation were WB-quantified. Results showed that GNVs reduce activation of the NLRP3 inflammasome and prevent the Aß-induced phosphorylation of ERK, AKT, and p70S6 kinases, potentiating autophagic flux and counteracting Tau phosphorylation. These preliminary results support the investigation of GNVs as a possible novel strategy in disease and rehabilitation to reduce inflammasome-associated inflammation.

Investigation of Anti-Alzheimer's Mechanisms of Sarsasapogenin Derivatives by Network-Based Combining Structure-Based Methods

Alzheimer's disease (AD), a neurodegenerative disease with no cure, affects millions of people worldwide and has become one of the biggest healthcare challenges. Some investigated compounds play anti-AD roles at the cellular or the animal level, but their molecular mechanisms remain unclear. In this study, we designed a strategy combining network-based and structure-based methods together to identify targets for anti-AD sarsasapogenin derivatives (AAs). First, we collected drug-target interactions (DTIs) data from public databases, constructed a global DTI network, and generated drug-substructure associations. After network construction, network-based models were built for DTI prediction. The best bSDTNBI-FCFP_4 model was further used to predict DTIs for AAs. Second, a structure-based molecular docking method was employed for rescreening the prediction results to obtain more credible target proteins. Finally, in vitro experiments were conducted for validation of the predicted targets, and Nrf2 showed significant evidence as the target of anti-AD compound AA13. Moreover, we analyzed the potential mechanisms of AA13 for the treatment of AD. Generally, our combined strategy could be applied to other novel drugs or compounds and become a useful tool in identification of new targets and elucidation of disease mechanisms. Our model was deployed on our NetInfer web server (http://lmmd.ecust.edu.cn/netinfer/).

Revisiting the intersection of microglial activation and neuroinflammation in Alzheimer's disease from the perspective of ferroptosis

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by chronic neuroinflammation with amyloid beta-protein deposition and hyperphosphorylated tau protein. The typical clinical manifestation of AD is progressive memory impairment, and AD is considered a multifactorial disease with various etiologies (genetic factors, aging, lifestyle, etc.) and complicated pathophysiological processes. Previous research identified that neuroinflammation and typical microglial activation are significant mechanisms underlying AD, resulting in dysfunction of the nervous system and progression of the disease. Ferroptosis is a novel modality involved in this process. As an iron-dependent form of cell death, ferroptosis, characterized by iron accumulation, lipid peroxidation, and irreversible plasma membrane disruption, promotes AD by accelerating neuronal dysfunction and abnormal microglial activation. In this case, disturbances in brain iron homeostasis and neuronal ferroptosis aggravate neuroinflammation and lead to the abnormal activation of microglia. Abnormally activated microglia release various pro-inflammatory factors that aggravate the dysregulation of iron homeostasis and neuroinflammation, forming a vicious cycle. In this review, we first introduce ferroptosis, microglia, AD, and their relationship. Second, we discuss the nonnegligible role of ferroptosis in the abnormal microglial activation involved in the chronic neuroinflammation of AD to provide new ideas for the identification of potential therapeutic targets for AD.

A review of the botany, ethnopharmacology, phytochemistry, pharmacology, toxicology and quality of Anemarrhena asphodeloides Bunge

ETHNOPHARMACOLOGICAL RELEVANCE

The rhizomes of Anemarrhena asphodeloides Bunge., belonging to the family Liliaceae, are named 'Zhi-mu' according to traditional Chinese medicine theory. It is a medicinal plant that has long been used as a tonic agent in various ethnomedicinal systems in East Asia, especially in China, and also for treating arthralgia, hematochezia, tidal fever, night sweats, cough, dry mouth and tongue, hemoptysis, etc. THE ARM OF THE REVIEW: The review aims to provide a systematic overview of botany, ethnopharmacology, phytochemistry, pharmacology, toxicology and quality control of Anemarrhena asphodeloides and to explore the future therapeutic potential and scientific potential of this plant.

MATERIALS AND METHODS

A comprehensive literature search was performed on Anemarrhena asphodeloides using scientific databases including Web of Science, PubMed, Google Scholar, CNKI, Elsevier, SpringerLink, ACS publications, ancient books, Doctoral and master's Theses. Collected data from different sources was comprehensively summarised for botany, ethnopharmacology, phytochemistry, pharmacology, toxicology and quality control of Anemarrhena asphodeloides.

RESULTS

A comprehensive analysis of the literature as mentioned above confirmed that the ethnomedical uses of Anemarrhena asphodeloides had a history of thousands of years in eastern Asian countries. Two hundred sixty-nine compounds have been identified from Anemarrhena asphodeloides, including steroidal saponins, flavonoids, phenylpropanoids, alkaloids, steroids, organic acids, polysaccharides, benzophenones and other ingredients. Studies have shown that the extracts and compounds from Anemarrhena asphodeloides have extensive pharmacological activities, such as nervous system activity, antitumour, anti-inflammatory, antidiabetic, antiosteoporotic, antiallergic, antiplatelet aggregation, antimicrobial, antiviral, anti-ageing, hair growth promoting, preventing cell damage, etc. Evaluating the quality and toxicity of Anemarrhena asphodeloides is essential to confirm its safe use in humans.

CONCLUSION

Anemarrhena asphodeloides is widely used in traditional medicine and have diverse chemical constituents with obvious biological activities. Nevertheless, more studies should be carried out in animals and humans to evaluate the cellular and molecular mechanisms involved in its biological activity and confirm its safe use.

Intranasal interferon-beta alleviates anxiety and depressive-like behaviors by modulating microglia polarization in an Alzheimer's disease model

Alzheimer's disease (AD) patients frequently experience neuropsychiatric symptoms (NPS), which are linked to a lower quality of life and a faster rate of disease progression. A growing body of research indicates that several microglial phenotypes control the inflammatory response and are crucial in the pathophysiology of AD-related NPS. Given the crucial role played by inflammatory mediators produced by microglia in developing of NPS, interferon-beta (IFNβ), a cytokine with anti-inflammatory capabilities, maybe a successful treatment for NPS caused by AD. In this investigation, using a rat model of AD, we examined the impact of intranasal treatment of IFNβ on anxious/depressive-like behavior and microglial M1/M2 polarization. The rat hippocampus was bilaterally injected with lentiviruses harboring mutant human amyloid precursor protein. Rats were given recombinant IFNβ1a (68,000 IU/rat) via the intranasal route, starting on day 23 following viral infection and continuing until day 49. On days 47-49, the elevated plus maze, forced swim, and tail suspension tests were applied to measure anxiety- and depressive-like behavior. Additionally, qPCR was utilized to quantify the expression of M1 markers (CD68, CD86, and CD40) and M2 markers (Ym1, CD206, Arg1, GDNF, BDNF, and SOCS1). Our findings demonstrated that decreased M2 marker expression is accompanied by anxious/depressive-like behavior when the mutant human APP gene is overexpressed in the hippocampus. In the rat model of AD, IFNβ therapy reduces anxious/depressive-like behaviors, at least in part by polarizing microglia towards M2. Therefore, IFNβ may be a viable therapeutic drug for reducing NPS in the context of AD.

Targeting gut microbiota to alleviate neuroinflammation in Alzheimer's disease

The gut microbiota came into focus within the last years regarding being associated with or even underlying neuropsychiatric diseases. The existence of the gut-brain-axis makes it highly plausible that bacterial metabolites or toxins that escape the intestinal environment or approach the vagal connections towards the brain, exert devastating effects on the central nervous system. In Alzheimer's disease (AD), growing evidence for dysbiotic changes in the gut microbiota is obtained, even though the question for cause or consequence remains open. Nevertheless, using modulation of microbiota to address inflammatory processes seems an attractive therapeutic approach as certain microbial products such as short chain fatty acids have been proven to exert beneficial cognitive effects. In this review, we summarize, contemporary knowledge on neuroinflammation and inflammatory processes within the brain and even more detailed in the gut in AD, try to conclude whom to target regarding human microbial commensals and report on current interventional trials.

Chronic cerebral hypoperfusion and blood-brain barrier disruption in uninjured brain areas of rhesus monkeys subjected to transient ischemic stroke

Blood-brain barrier (BBB) disruption is a pivotal pathophysiological process in ischemic stroke. Although temporal changes in BBB permeability during the acute phase have been widely studied, little is known about the chronic phase of cerebrovascular changes that may have a large impact on the long-term outcome. Therefore, this study was aimed to measure cerebral vascular abnormalities using CT perfusion in nine rhesus monkeys subjected to transient middle cerebral artery occlusion (tMCAO) for ≥1 year (MCAO-1Y+). The level of cerebral perfusion demonstrated by mean transit time was significantly higher in the ipsilateral caudate nucleus, white matter, thalamus, hippocampus, and contralateral thalamus in MCAO-1Y+ compared with the other nine age-matched control monkeys. The increase in BBB permeability measured through the permeability surface was found in the same ten regions of interest ipsilaterally and contralaterally. We also found decreased levels of Aβ 42/40 ratio in the cerebrospinal fluid (CSF), suggesting a potential link between post-MCAO cognitive decline and Aβ metabolism. Overall, we demonstrated significant cerebral hypoperfusion, BBB disruption, and CSF Aβ decrease during the rehabilitation stage of ischemic stroke in a non-human primate model. Future studies are needed to elucidate the cause-effect relationship between cerebrovascular disruptions and long-term neurological deficits.

Eriodictyol and Homoeriodictyol Improve Memory Impairment in Aβ25–35-Induced Mice by Inhibiting the NLRP3 Inflammasome

(1) Alzheimer’s disease (AD) is a neurodegenerative disorder, and it is now widely accepted that neuroinflammation plays a key role in its pathogenesis. Eriodictyol (Eri) and homoeriodictyol (Hom), dihydroflavonoids extracted from a variety of plants, have been confirmed to display a relationship with neuroprotection. (2) Methods: An AD mouse model was constructed by intracerebroventricular (ICV) injection of the Aβ_25–35 peptide, and Eri and Hom were administered orally for 4 weeks. UPLC-MS/MS was used to determine whether Eri and Hom cross the blood–brain barrier to exert their therapeutic effects. Histological changes in the brain and levels of Aβ were evaluated, and Y-maze and new object recognition experiments were conducted to assess the effects of Eri and Hom on Aβ_25–35-induced memory impairment in mice. The levels of oxidative stress and apoptosis in peripheral immune cells and progenitor cells in the hippocampal region were analyzed by flow cytometry and in vitro assays. Western blotting and enzyme-linked immunosorbent assays (ELISA) were used to measure the expression levels of NLRP3 inflammasome-related proteins and inflammatory factors in the brain. The effect of nigericin (an agonist of the NLRP3 inflammasome) on Eri and Hom intervention in LPS-induced N9 microglia was examined using a High Content Screening System. (3) Results: Eri and Hom reduced neuronal damage in mouse brain tissue, decreased Aβ levels in the brain, downregulated oxidative stress and apoptosis levels, and improved learning and memory capacity by crossing the blood–brain barrier to exert its effects. Moreover, Eri and Hom inhibited NLRP3 inflammasome activation and ameliorated immune cell disorder. Furthermore, the effect of Eri and Hom on LPS-induced N9 microglia disappeared after the addition of nigericin to agonize NLRP3 receptors. (4) Conclusions: Eri and Hom improved Aβ_25–35-induced memory impairment in mice by inhibiting the NLRP3 inflammasome.

Chemistry, Biosynthesis and Pharmacology of Sarsasapogenin: A Potential Natural Steroid Molecule for New Drug Design, Development and Therapy

Sarsasapogenin is a natural steroidal sapogenin molecule obtained mainly from Anemarrhena asphodeloides Bunge. Among the various phytosteroids present, sarsasapogenin has emerged as a promising molecule due to the fact of its diverse pharmacological activities. In this review, the chemistry, biosynthesis and pharmacological potentials of sarsasapogenin are summarised. Between 1996 and the present, the relevant literature regarding sarsasapogenin was obtained from scientific databases including PubMed, ScienceDirect, Scopus, and Google Scholar. Overall, sarsasapogenin is a potent molecule with anti-inflammatory, anticancer, antidiabetic, anti-osteoclastogenic and neuroprotective activities. It is also a potential molecule in the treatment for precocious puberty. This review also discusses the metabolism, pharmacokinetics and possible structural modifications as well as obstacles and opportunities for sarsasapogenin to become a drug molecule in the near future. More comprehensive preclinical studies, clinical trials, drug delivery, formulations of effective doses in pharmacokinetics studies, evaluation of adverse effects and potential synergistic effects with other drugs need to be thoroughly investigated to make sarsasapogenin a potential molecule for future drug development.

Roles of traditional chinese medicine regulating neuroendocrinology on AD treatment

The incidence of sporadic Alzheimer's disease (AD) is increasing in recent years. Studies have shown that in addition to some genetic abnormalities, the majority of AD patients has a history of long-term exposure to risk factors. Neuroendocrine related risk factors have been proved to be strongly associated with AD. Long-term hormone disorder can have a direct detrimental effect on the brain by producing an AD-like pathology and result in cognitive decline by impairing neuronal metabolism, plasticity and survival. Traditional Chinese Medicine(TCM) may regulate the complex process of endocrine disorders, and improve metabolic abnormalities, as well as the resulting neuroinflammation and oxidative damage through a variety of pathways. TCM has unique therapeutic advantages in treating early intervention of AD-related neuroendocrine disorders and preventing cognitive decline. This paper reviewed the relationship between neuroendocrine and AD as well as the related TCM treatment and its mechanism. The advantages of TCM intervention on endocrine disorders and some pending problems was also discussed, and new insights for TCM treatment of dementia in the future was provided.

N6-methyladenosine modification of TGM2 mRNA contributes to the inhibitory activity of sarsasapogenin in rheumatoid arthritis fibroblast-like synoviocytes

BACKGROUND

Developing alternative targets and drugs for rheumatoid arthritis (RA) treatment is currently an urgent issue. The relationship between TGM2 and the abnormal immune microenvironment in synovium tissues, as well as the specific role of TGM2 in RA are yet to be elucidated. Sarsasapogenin (Sar) is a sapogenin extracted from the Chinese medical herb Anemarrhena asphodeloides Bunge. and served as a representative anti-inflammatory drug capable of ameliorating inflammatory responses in several human diseases. However, the therapeutic effect of Sar on RA remains unknown.

PURPOSE

This investigation aims to elucidate the role of TGM2 in RA and investigate whether Sar is a candidate drug to target TGM2 of fibroblast-like synoviocytes (FLS).

METHODS

Bioinformatics analyses were applied for elucidating the role of N(6)-methyladenine (m6A) RNA methylation in RA and identifying the specific target regulated by m6A methylation in RA-FLS. Methylated RNA immunoprecipitation, CCK8 assay, Edu assay, flow cytometry, RT-qPCR and Western blot were utilized to investigate the function of Sar and TGM2 in RA-FLS.

RESULTS

Bioinformatics analyses emphasized the importance of m6A RNA methylation in RA and identified an m6A methylation-mediated gene TGM2. Interestingly, both m6A RNA methylation and TGM2 expression in RA synovium tissues correlated with activated immuno-inflammatory phenotype and associated with clinical characteristics and therapy response of RA patients. TGM2 served as a promoter of RA-FLS proliferation by inducing DNA replication and cell cycle transition and inhibiting apoptosis through activating NF-κB signaling. Intriguingly, Sar could impair m6A methylation of TGM2 mRNA and downregulate TGM2 expression. Downregulated TGM2 contributed to the suppressive role of Sar in DNA replication and the stimulatory role of Sar in cell cycle arrest and apoptosis of RA-FLS. Mechanically, Sar inhibited the expression of key regulators in DNA replication, cell cycle, and apoptosis by impairing NF-κB signaling, thus abolishing FLS proliferation to ameliorate RA progression.

CONCLUSIONS

This cross-validated work based on three independent datasets is detailedly delineated using cell lines and clinical samples, recognizing that TGM2 can be an attractive target and Sar might be a novel anti-RA drug.

Microglia Polarization in Alzheimer's Disease: Mechanisms and a Potential Therapeutic Target

Neuroinflammation regulated by microglia is one of the important factors involved in the pathogenesis of Alzheimer’s disease (AD). Activated microglia exhibited phenotypes termed as M1 and M2 phenotypes separately. M1 microglia contribute to the development of inflammation via upregulating pro-inflammatory cytokines, while M2 microglia exert anti-inflammation effects through enhancing the expression of anti-inflammation factors. Moreover, M1 and M2 microglia could be mutually transformed under various conditions. Both M1 and M2 microglia are implicated in AD. Amyloid-β (Aβ) and hyperphosphorylated tau are two major components of AD pathological hallmarks, neuritic plaques, and neurofibrillary tangles. Both Aβ and hyperphosphorylated tau were involved in microglial activation and subsequent inflammation, which further contribute to neuronal and synaptic loss in AD. In this review, we summarized the roles of M1 and M2 microglia in AD and underlying mechanisms, which will provide an insight into the role of microglia in the pathogenesis of AD and highlight the therapeutic potential of modulating microglia.

Mechanisms Involved in Microglial-Interceded Alzheimer's Disease and Nanocarrier-Based Treatment Approaches

Alzheimer's disease (AD) is a common neurodegenerative disorder accountable for dementia and cognitive dysfunction. The etiology of AD is complex and multifactorial in origin. The formation and deposition of amyloid-beta (Aβ), hyperphosphorylated tau protein, neuroinflammation, persistent oxidative stress, and alteration in signaling pathways have been extensively explored among the various etiological hallmarks. However, more recently, the immunogenic regulation of AD has been identified, and macroglial activation is considered a limiting factor in its etiological cascade. Macroglial activation causes neuroinflammation via modulation of the NLRP3/NF-kB/p38 MAPKs pathway and is also involved in tau pathology via modulation of the GSK-3β/p38 MAPK pathways. Additionally, microglial activation contributes to the discrete release of neurotransmitters and an altered neuronal synaptic plasticity. Therefore, activated microglial cells appear to be an emerging target for managing and treating AD. This review article discussed the pathology of microglial activation in AD and the role of various nanocarrier-based anti-Alzeihmenr's therapeutic approaches that can either reverse or inhibit this activation. Thus, as a targeted drug delivery system, nanocarrier approaches could emerge as a novel means to overcome existing AD therapy limitations.

Sarsasapogenin attenuates Alzheimer-like encephalopathy in diabetes

BACKGROUND

A crosstalk exists between diabetes and Alzheimer's disease (AD), and diabetic encephalopathy displays AD-like disorders. Sarsasapogenin (Sar) has strong anti-inflammatory efficacy, showing neuroprotection and memory-enhancement effects.

PURPOSE

This study aims to verify the ameliorative effects of Sar on diabetic encephalopathy in vivo and in vitro, and to clarify the mechanisms from attenuation of AD-like pathology.

METHODS

Streptozotocin-induced type 1 diabetic rats and high glucose-cultured SH-SY5Y cells were used in this study. After Sar treatment (20 and 60 mg/kg) for consecutive 9 weeks, Morris water maze and novel object recognition tasks were performed. Hematoxylin-eosin staining was used for examining loss of neurons in CA1 area and ki67 expression for reflecting neurogenesis in DG area of hippocampus. Aβ production pathway and tau phosphorylation kinase cascade were examined in these two models.

RESULTS

Sar improved learning and memory ability, loss of neurons and reduction of neurogenesis in the hippocampus of diabetic rats. Moreover, Sar suppressed Aβ overproduction due to up-regulation of BACE1 in protein and mRNA and tau hyperphosphorylation from inactivation of AKT/GSK-3β cascade in the hippocampus and cerebral cortex of diabetic rats and high glucose-cultured SH-SY5Y cells, and PPARγ antagonism abolished the effects of Sar on key molecules in the two pathways. Additionally, it was found that high glucose-stimulated Aβ overproduction was prior to tau hyperphosphorylation in neurons.

CONCLUSION

Sar alleviated diabetic encephalopathy, which was obtained through inhibitions of Aβ overproduction and tau hyperphosphorylation mediated by the activation of PPARγ signaling. Hence, Sar is a good candidate compound for AD-like disorders.

New insights in drug development for Alzheimer's disease based on microglia function

One of the biggest challenges in drug development for Alzheimer's disease (AD) is how to effectively remove deposits of amyloid-beta (Aβ). Recently, the relationship between microglia and Aβ has become a research hotspot. Emerging evidence suggests that Aβ-induced microglia-mediated neuroinflammation further aggravates the decline of cognitive function, while microglia are also involved in the process of Aβ clearance. Hence, microglia have become a potential therapeutic target for the treatment or prevention of AD. An in-depth understanding of the role played by microglia in the development of AD will help us to broaden therapeutic strategies for AD. In this review, we provide an overview of the dual roles of microglia in AD progression: the positive effect of phagocytosis of Aβ and its negative effect on neuroinflammation after over-activation. With the advantages of novel structure, high efficiency, and low toxicity, small-molecule compounds as modulators of microglial function have attracted considerable attention in the therapeutic areas of AD. In this review, we also summarize the therapeutic potential of small molecule compounds (SMCs) and their structure-activity relationship for AD treatment through modulating microglial phagocytosis and inhibiting neuroinflammation. For example, the position and number of phenolic hydroxyl groups on the B ring are the key to the activity of flavonoids, and the substitution of hydroxyl groups on the benzene ring enhances the anti-inflammatory activity of phenolic acids. This review is expected to be useful for developing effective modulators of microglial function from SMCs for the amelioration and treatment of AD.

Sarsasapogenin ameliorates diabetes-associated memory impairment and neuroinflammation through down-regulation of PAR-1 receptor

Sarsasapogenin (Sar), a natural steroidal compound, shows neuroprotection, cognition-enhancement, antiinflammation, antithrombosis effects, and so on. However, whether Sar has ameliorative effects on diabetes-associated cognitive impairment remains unknown. In this study, we found that Sar ameliorated diabetes-associated memory impairment in streptozotocin-induced diabetic rats, evidenced by increased numbers of crossing platform and percentage of time spent in the target quadrant in Morris water maze tests, and suppressed the nucleotide-binding domain and leucine-rich repeat containing protein 1 (NLRP1) inflammasome in hippocampus and cerebral cortex. Furthermore, Sar inhibited advanced glycation end-products and its receptor (AGEs/RAGE) axis and suppressed up-regulation of thrombin receptor protease-activated receptor 1 (PAR-1) in cerebral cortex. On the other hand, Sar mitigated high glucose-induced neuronal damages, NLRP1 inflammasome activation, and PAR-1 up-regulation in high glucose-cultured SH-SY5Y cells, but did not affect thrombin activity. Moreover, the effects of Sar were similar to those of a selective PAR-1 antagonist vorapaxar. Further studies indicated that activation of the NLRP1 inflammasome and NF-κB mediated the effect of PAR-1 up-regulation in high glucose condition by using PAR-1 knockdown assay. In summary, this study demonstrated that Sar prevented memory impairment caused by diabetes, which was achieved through suppressing neuroinflammation from activated NLRP1 inflammasome and NF-κB regulated by cerebral PAR-1. HIGHLIGHTS: Sarsasapogenin ameliorated memory impairment caused by diabetes in rats. Sarsasapogenin mitigated neuronal damages and neuroinflammation by down-regulating cerebral PAR-1. The NLRP1 inflammasome and NF-κB signaling mediated the pro-inflammatory effects of PAR-1. Sarsasapogenin was a pleiotropic neuroprotective agent and memory enhancer in diabetic rodents.

Design, synthesis, and biological evaluation of diosgenin-indole derivatives as dual-functional agents for the treatment of Alzheimer's disease

The complex pathogenesis of Alzheimer's disease (AD) has become a major obstacle in its treatment. An effective approach is to develop multifunctional agents that simultaneously target multiple pathological processes. Here, a series of diosgenin-indole compounds were designed, synthesized and evaluated for their neuroprotective effects against H₂O₂ (hydrogen peroxide), 6-OHDA (6-hydroxydopamine) and Aβ (beta amyloid) damages. Preliminary structure-activities relationship revealed that the introduction of indole fragment and electron-donating group at C-5 on ring indole could be beneficial for neuroprotective activities. Results indicated that compound 5b was the most promising candidate against cellular damage induced by H₂O₂ (52.9 ± 1.9%), 6-OHDA (38.4 ± 2.4%) and Aβ_1-42 (54.4 ± 2.7%). Molecular docking study suggested the affinity for 5b bound to Aβ_1-42 was -40.59 kcal/mol, which revealed the strong binding affinity of 5b to Aβ_1-42. The predicted values of brain/blood partition coefficient (-0.733) and polar surface area (85.118 Å²) indicated the favorable abilities of BBB permeation and absorption of 5b. In addition, 5b significantly decreased ROS (reactive oxygen species) production induced by H₂O₂. In the following in vivo experiment, 5b obviously attenuated memory and learning impairments of Aβ-injected mice. In summary, compound 5b could be considered as a promising dual-functional neuroprotective agent against AD.

The involvement of NLRP3 inflammasome in the treatment of neurodegenerative diseases

In an ageing society, neurodegenerative diseases have attracted attention because of their high incidence worldwide. Despite extensive research, there is a lack of conclusive insights into the pathogenesis of neurodegenerative diseases, which limit the strategies for symptomatic treatment. Therefore, better elucidation of the molecular mechanisms involved in neurodegenerative diseases can provide an important theoretical basis for the discovery of new and effective prevention and treatment methods. The innate immune system is activated during the ageing process and in response to neurodegenerative diseases. Inflammasomes are multiprotein complexes that play an important role in the activation of the innate immune system. They mediate inflammatory reactions and pyroptosis, which are closely involved in neurodegeneration. There are different types of inflammasomes, although the nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is the most common inflammasome; NLRP3 plays an important role in the pathogenesis of neurodegenerative diseases. In this review, we will discuss the mechanisms that are involved in the activation of the NLRP3 inflammasome and its crucial role in the pathology of neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and multiple sclerosis. We will also review various treatments that target the NLRP3 inflammasome pathway and alleviate neuroinflammation. Finally, we will summarize the novel treatment strategies for neurodegenerative disorders.

The involvement of NLRP3 inflammasome in the treatment of Alzheimer's disease

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases, and it is characterised by progressive deterioration in cognitive and memory abilities, which can severely influence the elderly population's daily living abilities. Although researchers have made great efforts in the field of AD, there are still no well-established strategies to prevent and treat this disease. Therefore, better clarification of the molecular mechanisms associated with the onset and progression of AD is critical to provide a theoretical basis for the establishment of novel preventive and therapeutic strategies. Currently, it is generally believed that neuroinflammation plays a key role in the pathogenesis of AD. Inflammasome, a multiprotein complex, is involved in the innate immune system, and it can mediate inflammatory responses and pyroptosis, which lead to neurodegeneration. Among the various types of inflammasomes, the NLRP3 inflammasome is the most characterised in neurodegenerative diseases, especially in AD. The activation of the NLRP3 inflammasome causes the generation of caspase-1-mediated interleukin (IL)-1β and IL-18 in microglia cells, where neuroinflammation is involved in the development and progression of AD. Thus, the NLRP3 inflammasome is likely to be a crucial therapeutic molecular target for AD via regulating neuroinflammation. In this review, we summarise the current knowledge on the role and regulatory mechanisms of the NLRP3 inflammasome in the pathogenic mechanisms of AD. We also focus on a series of potential therapeutic treatments targeting NLRP3 inflammasome for AD. Further clarification of the regulatory mechanisms of the NLRP3 inflammasome in AD may provide more useful clues to develop novel AD treatment strategies.

Sarsasapogenin Suppresses RANKL-Induced Osteoclastogenesis in vitro and Prevents Lipopolysaccharide-Induced Bone Loss in vivo

INTRODUCTION

Osteoclasts are giant polynuclear cells; their main function is bone resorption. An increased number of osteoclasts and enhanced bone resorption exert significant effects on osteoclast-related bone-lytic diseases, including osteoporosis. Given the limitations of current therapies for osteolytic diseases, it is urgently required to develop safer and more effective alternatives. Sarsasapogenin, a major sapogenin from Anemarrhena asphodeloides Bunge, possesses potent antitumor effects and inhibits NF-κB and MAPK signaling. However, the manner in which it affects osteoclasts is unclear.

METHODS

We investigated the effects of anti-osteoclastogenic and anti-resorptive of sarsasapogenin on bone marrow-derived osteoclasts.

RESULTS

Sarsasapogenin inhibited multiple RANKL-induced signaling cascades, thereby inhibiting the induction of key osteoclast transcription factor NFATc1. The in vivo and in vitro results were consistent: sarsasapogenin treatment protected against bone loss in a mouse osteolysis model induced by lipopolysaccharide.

CONCLUSION

Our research confirms that sarsasapogenin can be used as a new treatment for osteoclast-related osteolytic diseases.

β-Lapachone attenuates cognitive impairment and neuroinflammation in beta-amyloid induced mouse model of Alzheimer's disease

Oxidative stress and neuroinflammation are critically involved in amyloid beta (Aβ) induced cognitive impairments. β-Lapachone (β-LAP) is a natural activator of NAD(P)H quinone oxidoreductase 1 (NQO1) which has antioxidant and anti-inflammatory properties.This study investigated the effect of β-LAP administration on Aβ-induced memory deficit, oxidative stress, neuroinflammation, and apoptosis cell death in the hippocampus. Forty BALB/c mice were allocated into control, sham, β-LAP (βL), Aβ, and Aβ + βL groups. Intracerebroventricular injection of Aβ_1-42 was used to induce Alzheimer's disease (AD) model. Mice in the βL and Aβ + βL groups were treated with β-LAP (10 mg/kg, i.p) for 4 days. Results revealed that β-LAP attenuated memory impairment in the Aβ-received mice, as measured in the novel object recognition (NOR) and Barnes maze tests. Moreover, Aβ resulted in inflammasome activation evident by enhanced caspase-1 immunoreactivity and interleukin-1 beta (IL-1β) protein levels. However, β-LAP could markedly reduce reactive oxygen species (ROS) production and down-regulate mRNA expression of NLRP3 inflammasome and protein levels of cleaved caspase 1 and IL-1β. Additionally, β-LAP-treated mice showed increased SIRT1 levels and NAD⁺/NADH ratio in the hippocampus. These results were followed by fewer number of TUNEL-positive cell, reduced hippocampal atrophy and neuronal loss in the hippocampal dentate gyrus (DG). These results indicated that the protective effect of β-LAP against AD-associated cognitive deficits is partially through its strong antioxidant and anti-inflammatory actions.

A validated UPLC-MS/MS method for quantitative determination of a potent neuroprotective agent Sarsasapogenin-AA13 in rat plasma: Application to pharmacokinetic studies

Sarsasapogenin-AA13(AA13), a sarsasapogenin derivative, exhibited good neuroprotective and anti-inflammatory activities in vitro and therapeutic effects on learning and memory dysfunction in amyloid-β-injected mice. A sensitive UPLC-MS/MS method was developed and validated to quantitatively determine AA13 in rat plasma and was further applied to evaluate the pharmacokinetic behaviour of AA13 in rats that were administered AA13 intravenously and orally. This method was validated to exhibit excellent linearity in the concentration range of 1-1000 ng/mL. The lower limit of quantification was 1 ng/mL for AA13 in rat plasma. Intra-day accuracy for AA13 was in the range of 90-114%, and inter-day accuracy was in the range of 97-103 %. The relative standard deviation of intra-day and inter-day assay was less than 15%. After a single oral administration of AA13 at the dose of 25 mg/kg, C_max of AA13 was 1266.4 ± 316.1 ng/mL. AUC_{0-48 h} was 6928.5 ± 1990.1 h·ng/mL, and t_1/2 was 10.2 ± 0.8 h. Under intravenous administration of AA13 at a dosage of 250 μg/kg, AUC_{0-48 h} was 785.7 ± 103.3 h⋅ng/mL, and t_1/2 was 20.8 ± 7.2 h. Based on the results, oral bioavailability (F %) of AA13 in rats at 25 mg/kg was 8.82 %.

Mitochondria-targeted TPP-MoS2 with dual enzyme activity provides efficient neuroprotection through M1/M2 microglial polarization in an Alzheimer's disease model

Alzheimer's disease (AD) is one of the most common age-associated brain diseases and is induced by the accumulation of amyloid beta (Aβ) and oxidative stress. Many studies have focused on eliminating Aβ by nanoparticle affinity; however, nanoparticles are taken up mainly by microglia rather than neurons, leading poor control of AD. Herein, mitochondria-targeted nanozymes known as (3-carboxypropyl)triphenyl-phosphonium bromide-conjugated 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)-2000]-functionalized molybdenum disulfide quantum dots (TPP-MoS₂ QDs) were designed. TPP-MoS₂ QDs mitigate Aβ aggregate-mediated neurotoxicity and eliminate Aβ aggregates in AD mice by switching microglia from the proinflammatory M1 phenotype to the anti-inflammatory M2 phenotype. TPP-MoS₂ QDs cross the blood-brain barrier, escape from lysosomes, target mitochondria and exhibit the comprehensive activity of a bifunctional nanozyme, thus preventing spontaneous neuroinflammation by regulating the proinflammatory substances interleukin-1β, interleukin-6 and tumor necrosis factors as well as the anti-inflammatory substance transforming growth factor-β. In contrast to the low efficacy of eliminating Aβ by nanoparticle affinity, the present study provides a new pathway to mitigate AD pathology through mitochondria-targeted nanozymes and M1/M2 microglial polarization.

Icariin Attenuates M1 Activation of Microglia and Aβ Plaque Accumulation in the Hippocampus and Prefrontal Cortex by Up-Regulating PPARγ in Restraint/Isolation-Stressed APP/PS1 Mice

Background

Studies have shown that psychosocial stress is involved in Alzheimer's disease (AD) pathogenesis; it induces M1 microglia polarization and production of pro-inflammatory cytokines, leading to neurotoxic outcomes and decreased β-amyloid (Aβ) clearance. Icariin has been proven to be an effective anti-inflammatory agent and to activate peroxisome proliferator-activated receptors gamma (PPARγ) which induces the M2 phenotype in the microglia. However, whether restraint/isolation stress reduces the clearance ability of microglia by priming and polarizing microglia to the M1 phenotype, and the effects of icariin in attenuating the inflammatory response and relieving the pathological changes of AD are still unclear.

Methods

APP/PS1 mice (male, aged 3 months) were randomly divided into a control group, a restraint/isolation stress group, and a restraint/isolation stress + icariin group. The restraint/isolation stress group was subjected to a paradigm to build a depressive animal model. Sucrose preference, open field, elevated plus maze, and Y maze test were used to assess the stress paradigm. The Morris water maze test was performed to evaluate spatial reference learning and memory. Enzyme-linked immunosorbent assay and immunohistochemistry were used to identify the microglia phenotype and Aβ accumulation. Western blotting was used to detect the expression of PPARγ in the hippocampus and prefrontal cortex (PFC).

Results

Restraint/isolation stress induced significant depressive-like behaviors in APP/PS1 mice at 4 months of age and memory impairment at 10 months of age, while 6 months of icariin administration relieved the memory damage. Restraint/isolation stressed mice had elevated pro-inflammatory cytokines, decreased anti-inflammatory cytokines, increased Aβ plaque accumulation and more M1 phenotype microglia in the hippocampus and PFC at 10 months of age, while 6 months of icariin administration relieved these changes. Moreover, restraint/isolation stressed mice had down-regulated PPARγ expression in the hippocampus and PFC at 10 months of age, while 6 months of icariin administration reversed the alteration, especially in the hippocampus.

Conclusion

Restraint/isolation stress induced depressive-like behaviors and spatial memory damage, over-expression of M1 microglia markers and more severe Aβ accumulation by suppressing PPARγ in APP/PS1 mice. Icariin can be considered a new treatment option as it induces the switch of the microglia phenotype by activating PPARγ.

Development and validation of a UPLC-MS/MS method for determination of Sarsasapogenin-AA22 in rat plasma and its application to a pharmacokinetic study

A sarsasapogenin derivative, sarsasapogenin-AA22 (AA22), with cyclobutylamine at the 3-hydroxyl position of sarsasapogenin, has great neuroprotective activity in PC12 cells and NO production inhibitory activity in RAW264.7 cell lines. A method was developed to determine AA22 in rat plasma which was further applied to evaluate the pharmacokinetics of AA22 after taking a single dose of AA22. Liquid chromatography tandem mass spectrometry was used in the method, while diosgenin was used as internal standard. A simple protein precipitation based on acetonitrile was utilized. A simple sample cleanup promoted the throughput of the method considerably. The method was validated over the range of 1-1000 ng/mL with a correlation coefficient > 0.99. The lower limit of quantification was 1 ng/mL for AA22 in plasma. Intra- and inter-day accuracies for AA22 were 92-111 and 100-103%, respectively, and the inter-day precision was <15%. After a single oral dose of 25 mg/kg of AA22, the mean peak plasma concentration of AA22 was 2114 ± 362 ng/mL at 6 h. The area under the plasma concentration-time curve was 196,098 ± 69,375 h ng/mL, and the elimination half-life was 8.7 ± 2.2 h.

Design, synthesis and biological evaluation of 3-piperazinecarboxylate sarsasapogenin derivatives as potential multifunctional anti-Alzheimer agents

A series of multifunctional 3-piperazinecarboxylate sarsasapogenin derivatives were designed and synthesized against Alzheimer's disease (AD). The protection against H₂O₂-triggered oxidative stress in PC12 cells, and inhibition on LPS-induced NO production in RAW264.7 cell lines in vitro by these derivatives were firstly evaluated. Most of the compounds showed better antioxidant and antiinflammatory activities compared with sarsasapogenin, especially AA34 and AA36. Structure-activity relationships revealed that benzyl group, electron-donating group and intramolecular hydrogen bond might be beneficial to enhancing their neuroprotective activities. Moreover, Aβ42 was the optimum predicted target based on the high 3D molecular similarity between compound AA36 and caprospinol. In the following experiments, AA36 significantly protected PC12 cells from Aβ-induced damage and improved learning and memory impairments in Aβ-injected mice. Thus AA36 is regarded as a potent anti-AD agent and N-substituted piperazinecarboxylate can be served as a promising structural unit for anti-AD drug design.

Astrocytes mediated the nootropic and neurotrophic effects of Sarsasapogenin-AA13 via upregulating brain-derived neurotrophic factor

Rhizoma Anemarrhena, a widely used traditional Chinese medicine, has previously been shown to have neuroprotective effect. Sarsasapogenin-AA13 (AA13) is a novel synthetic derivative of Sarsasapogenin, which is extracted from Rhizoma Anemarrhena. The aim of this study is to investigate the nootropic and neurotrophic effects of AA13 and underlying mechanisms. In vitro, cell viability of rat primary astrocytes treated with AA13 and neurons cultured with conditioned medium of AA13-treated rat primary astrocytes was tested by MTT assays. In vivo, a pharmacological model of cognitive impairment induced by scopolamine was employed and spatial memory of the mice was assessed by Morris water maze. This study found that AA13 increased cell viability of primary astrocytes and AA13-treated astrocyte-conditioned medium enhanced the survival rate of primary neurons. Interestingly, AA13 markedly enhanced the level of BDNF in astrocytes. Furthermore, AA13 (6 mg/kg) improved the cognitive deficits in animal models (p<0.05) and BDNF and PSD95 levels were increased in brain. Therefore, we hypothesize that AA13 exerts nootropic and neurotrophic activities through astrocytes mediated upregulation of BDNF secretion. The results suggest that AA13 could be a potential compound for cognitive impairment after further research.

Sarsasapogenin-AA13 ameliorates Aβ-induced cognitive deficits via improving neuroglial capacity on Aβ clearance and antiinflammation

AIMS

Sarsasapogenin has been reported to improve dementia symptoms somehow, probably through modulating the function of cholinergic system, suppressing neurofibrillary tangles, and inhibiting inflammation. However, the role of sarsasapogenin in response to beta-amyloid (Aβ) remains to be delineated. This study aimed to determine the therapeutic effect of sarsasapogenin-13 (AA13, a sarsasapogenin derivative) on learning and memory impairments in Aβ-injected mice, as well as the role of AA13 in neuroglia-mediated antiinflammation and Aβ clearance.

METHODS

Focusing on the role of AA13 in regulating glial responses to Aβ, we conducted behavioral, morphological, and protein expression studies to explore the effects of AA13 on Aβ clearance and inflammatory regulation.

RESULTS

The results indicated that oral administration of AA13 attenuated the memory deficits of intracerebroventricular (i.c.v.) Aβ-injected mice; also, AA13 protected neuroglial cells against Aβ-induced cytotoxicity. The further mechanical studies demonstrated that AA13 reversed the upregulation of proinflammatory M1 markers and increased the expression of antiinflammatory M2 markers in Aβ-treated cells. Furthermore, AA13 facilitated Aβ clearance through promoting Aβ phagocytosis and degradation. AA13 modulated the expression of fatty acid translocase (CD36), insulin-degrading enzyme (IDE), neprilysin (NEP), and endothelin-converting enzyme (ECE) in neuroglia.

CONCLUSION

The present study indicated that the neuroprotective effect of AA13 might relate to its modulatory effects on microglia activation state, phagocytic ability, and expression of Aβ-degrading enzymes, which makes it a promising therapeutic agent in the early stage of Alzheimer's disease (AD).