Inhibition of microfold cells ameliorates early pathological phenotypes by modulating microglial functions in Alzheimer's disease mouse model.

BACKGROUND: The gut microbiota has recently attracted attention as a pathogenic factor in Alzheimer's disease (AD). Microfold (M) cells, which play a crucial role in the gut immune response against external antigens, are also exploited for the entry of pathogenic bacteria and proteins into the body. However, whether changes in M cells can affect the gut environments and consequently change brain pathologies in AD remains unknown. METHODS: Five familial AD (5xFAD) and 5xFAD-derived fecal microbiota transplanted (5xFAD-FMT) naïve mice were used to investigate the changes of M cells in the AD environment. Next, to establish the effect of M cell depletion on AD environments, 5xFAD mice and Spib knockout mice were bred, and behavioral and histological analyses were performed when M cell-depleted 5xFAD mice were six or nine months of age. RESULTS: In this study, we found that M cell numbers were increased in the colons of 5xFAD and 5xFAD-FMT mice compared to those of wild-type (WT) and WT-FMT mice. Moreover, the level of total bacteria infiltrating the colons increased in the AD-mimicked mice. The levels of M cell-related genes and that of infiltrating bacteria showed a significant correlation. The genetic inhibition of M cells (Spib knockout) in 5xFAD mice changed the composition of the gut microbiota, along with decreasing proinflammatory cytokine levels in the colons. M cell depletion ameliorated AD symptoms including amyloid-ß accumulation, microglial dysfunction, neuroinflammation, and memory impairment. Similarly, 5xFAD-FMT did not induce AD-like pathologies, such as memory impairment and excessive neuroinflammation in Spib-/- mice. CONCLUSION: Therefore, our findings provide evidence that the inhibiting M cells can prevent AD progression, with therapeutic implications.

Aerial part of Houttuynia cordata reverses memory impairment by regulating amyloid beta accumulation and neuroinflammation in Alzheimer's disease model.

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by amyloid-ß (Aß) deposition, accompanied by neuroinflammation and memory dysfunction. Houttuyniae Herba (aerial parts of Houttuynia cordata, also known as fish mint; HH), an herbal medicine traditionally used to treat fever, urinary disorders, and pus, is revealed to protect neurons from Aß toxicity and regulate cholinergic dysfunction in AD models. In this study, we aimed to investigate the effects of HH on excessive accumulation of Aß followed by neuroinflammation, synaptic degeneration, and memory impairment. Two-month-old 5xFAD transgenic mice were administered HH at 100 mg/kg for 4 months. We observed that HH treatment ameliorated memory impairment and reduced Aß deposits in the brains of the mice. HH directly inhibited Aß aggregation in vitro using the Thioflavin T assay and indirectly suppressed the amyloidogenic pathway by increasing alpha-secretase expression in the mice brain. In addition, HH exerted antineuroinflammatory effects by reducing of glial activation and p38 phosphorylation. Moreover, HH treatment increased the expression of synaptophysin, a presynaptic marker protein. Overall, HH alleviates memory impairment in AD by facilitating nonamyloidogenic pathway and inhibiting neuroinflammation. Therefore, we suggest that HH can be a promising herbal drug for patients with AD requiring multifaceted improvement.

A novel nutritional mixture, MBN, prevents memory impairment via inhibiting NLRP3 inflammasome formation in 5xFAD transgenic mice.

OBJECTIVES: Amyloid beta (Aß)-induced abnormal neuroinflammation is recognized as a major pathological factor of Alzheimer's disease (AD), which results in memory impairment. Inhibition of excessive neuroinflammation mediated by Aß is considered a promising strategy to ameliorate AD symptoms. To regulate the inflammatory response, nutritional and dietary supplements have been used for centuries. Based on this idea, we investigated whether MBN, a novel nutritional mixture including cassia bark, turmeric root, and ginkgo leaf, can prevent AD progression through neuroinflammatory regulation. METHODS: MBN (10, 30, or 100 µg/ml) and Aß1-42 monomer were incubated together, and the degree of Aß aggregation was measured using Thioflavin T assay. The effects of MBN on Aß pathology in vivo were evaluated by orally administering MBN (40 mg/kg/day for 16 weeks) to five familial AD (5xFAD) mice. RESULTS: We found that treatment with MBN inhibited Aß aggregation in vitro. Next, MBN treatment significantly inhibited the activation of microglia induced by aggregated Aß in 5xFAD mice. Caspase-1 activation, which plays an important role in the maturation of interleukin-1ß, was markedly reduced by MBN. We also found that oral administration of MBN in 5xFAD mice alleviated memory decline. Taken together, our findings demonstrate that MBN suppresses neuroinflammation by downregulating the caspase-1 expression, thereby ameliorating memory impairment in 5xFAD mice. DISCUSSION: Based on these results, we suggest that MBN may be a preventive and therapeutic supplement for AD through the regulation of neuroinflammation.

Transplantation of gut microbiota derived from Alzheimer's disease mouse model impairs memory function and neurogenesis in C57BL/6 mice.

Alzheimer's disease (AD) is a neurodegenerative disease that causes memory and cognitive decline. Although many studies have attempted to clarify the causes of AD occurrence, it is not clearly understood. Recently, the emerging role of the gut microbiota in neurodegenerative diseases, including AD, has received much attention. The gut microbiota composition of AD patients and AD mouse models is different from that of healthy controls, and these changes may affect the brain environment. However, the specific mechanisms by which gut microbiota that influence memory decline are currently unclear. In this study, we performed fecal microbiota transplantation (FMT) to clarify the role of 5xFAD mouse-derived microbiota in memory decline. We observed that FMT from 5xFAD mice into normal C57BL/6 mice (5xFAD-FMT) decreased adult hippocampal neurogenesis and brain-derived neurotrophic factor expression and increased p21 expression, resulting in memory impairment. Microglia in the hippocampus of the 5xFAD-FMT mice were activated, which caused the elevation of pro-inflammatory cytokines (tumor necrosis factor-α and interleukin-1ß). Moreover, we observed that pro-inflammatory cytokines increased in the colon and plasma of 5xFAD-FMT mice. The gut microbiota composition of the 5xFAD-FMT mice was different from that of the control mice or wild type-FMT mice. Collectively, 5xFAD mouse-derived microbiota decreased neurogenesis by increasing colonic inflammation, thereby contributing to memory loss. Our findings provide further evidence concerning the role of gut microbial dysbiosis in AD pathogenesis and suggest that targeting the gut microbiota may be a useful therapeutic strategy for the development of novel candidates for the treatment of AD.

Phytohormone Abscisic Acid Improves Memory Impairment and Reduces Neuroinflammation in 5xFAD Mice by Upregulation of LanC-Like Protein 2.

Alzheimer's disease (AD), a type of dementia, is the most common neurodegenerative disease in the elderly. Neuroinflammation caused by deposition of amyloid ß (Aß) is one of the most important pathological causes in AD. The isoprenoid phytohormone abscisic acid (ABA) has recently been found in mammals and was shown to be an endogenous hormone, acting in stress conditions. Although ABA has been associated with anti-inflammatory effects and reduced cognitive impairment in several studies, the mechanisms of ABA in AD has not been ascertained clearly. To investigate the clearance of Aß and anti-inflammatory effects of ABA, we used quantitative real-time polymerase chain reaction and immunoassay. ABA treatment inhibited Aß deposition and neuroinflammation, thus resulting in improvement of memory impairment in 5xFAD mice. Interestingly, these effects were not associated with activation of peroxisome proliferator-activated receptor gamma, well known as a molecular target of ABA, but related with modulation of the LanC-like protein 2 (LANCL2), known as a receptor of ABA. Taken together, our results indicate that ABA reduced Aß deposition, neuroinflammation, and memory impairment, which is the most characteristic pathology of AD, via the upregulation of LANCL2. These data suggest that ABA might be a candidate for therapeutics for AD treatment.

Trans-Cinnamaldehyde Alleviates Amyloid-Beta Pathogenesis via the SIRT1-PGC1α-PPARγ Pathway in 5XFAD Transgenic Mice.

Abnormal amyloid-ß (Aß) accumulation is the most significant feature of Alzheimer's disease (AD). Among the several secretases involved in the generation of Aß, ß-secretase (BACE1) is the first rate-limiting enzyme in Aß production that can be utilized to prevent the development of Aß-related pathologies. Cinnamon extract, used in traditional medicine, was shown to inhibit the aggregation of tau protein and Aß aggregation. However, the effect of trans-cinnamaldehyde (TCA), the main component of cinnamon, on Aß deposition is unknown. Five-month-old 5XFAD mice were treated with TCA for eight weeks. Seven-month-old 5XFAD mice were evaluated for cognitive and spatial memory function. Brain samples collected at the conclusion of the treatment were assessed by immunofluorescence and biochemical analyses. Additional in vivo experiments were conducted to elucidate the mechanisms underlying the effect of TCA in the role of Aß deposition. TCA treatment led to improvements in cognitive impairment and reduced Aß deposition in the brains of 5XFAD mice. Interestingly, the levels of BACE1 were decreased, whereas the mRNA and protein levels of three well-known regulators of BACE1, silent information regulator 1 (SIRT1), peroxisome proliferator-activated receptor γ (PPARγ) coactivator 1α (PGC1α), and PPARγ, were increased in TCA-treated 5XFAD mice. TCA led to an improvement in AD pathology by reducing BACE1 levels through the activation of the SIRT1-PGC1α-PPARγ pathway, suggesting that TCA might be a useful therapeutic approach in AD.

A Novel and Selective p38 Mitogen-Activated Protein Kinase Inhibitor Attenuates LPS-Induced Neuroinflammation in BV2 Microglia and a Mouse Model.

Neuroinflammation is an important pathological feature in neurodegenerative diseases. Accumulating evidence has suggested that neuroinflammation is mainly aggravated by activated microglia, which are macrophage like cells in the central nervous system. Therefore, the inhibition of microglial activation may be considered for treating neuroinflammatory diseases. p38 mitogen-activated protein kinase (MAPK) has been identified as a crucial enzyme with inflammatory roles in several immune cells, and its activation also relates to neuroinflammation. Considering the proinflammatory roles of p38 MAPK, its inhibitors can be potential therapeutic agents for neurodegenerative diseases relating to neuroinflammation initiated by microglia activation. This study was designed to evaluate whether NJK14047, a recently identified novel and selective p38 MAPK inhibitor, could modulate microglia-mediated neuroinflammation by utilizing lipopolysaccharide (LPS)-stimulated BV2 cells and an LPS-injected mice model. Our results showed that NJK14047 markedly reduced the production of nitric oxide and prostaglandin E2 by downregulating the expression of various proinflammatory mediators such as nitric oxide synthase, cyclooxygenase-2, tumor necrosis factor-α and interleukin-1ß in LPS-induced BV2 microglia. Moreover, NJK14047 significantly reduced microglial activation in the brains of LPS-injected mice. Overall, these results suggest that NJK14047 significantly reduces neuroinflammation in cellular/vivo model and would be a therapeutic candidate for various neuroinflammatory diseases.

Piperlongumine inhibits neuroinflammation via regulating NF-κB signaling pathways in lipopolysaccharide-stimulated BV2 microglia cells.

Inflammatory processes in the central nervous system are feature among biological reactions to harmful stimuli such as pathogens and damaged cells. In resting conditions, microglia are involved in immune surveillance and brain homeostasis. However, the activation of abnormal microglia can be detrimental to neurons, even resulting in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and Huntington's disease. Therefore, normalization of microglial activation is considered a promising strategy for developing drugs that can treat or prevent inflammation-related brain diseases. In the present study, we investigated the effects of piperlongumine, an active component of Piper longum, on lipopolysaccharide (LPS)-induced neuroinflammation using BV2 microglial cells. We found that piperlongumine significantly inhibited the production of nitric oxide and prostaglandin E2 induced by LPS. Piperlongumine also reduced the expression of inducible nitric oxide synthase and cyclooxygenase-2 as well as proinflammatory cytokines such as tumor necrosis factor-α and interleukin-6. Piperlongumine exerted its anti-neuroinflammatory effects by suppressing the nuclear factor kappa B signaling pathway. These findings suggest that piperlongumine could be a candidate agent for the treatment of inflammation-related neurodegenerative diseases.

Bardoxolone Methyl Suppresses Hepatitis B Virus Large Surface Protein Variant W4P-Related Carcinogenesis and Hepatocellular Carcinoma Cell Proliferation Via the Inhibition of Signal Transducer and Activator of Transcription 3 Signaling.

Bardoxolone methyl (CDDO-me) is a synthetic triterpenoid that has been shown to suppress various cancers and inflammation. It has been implicated for the suppression of signal transducer and activator of transcription 3 (STAT3)-mediated signaling, which plays crucial roles in the development and progression of hepatocellular carcinoma (HCC). Previously, we showed that hepatitis B virus (HBV) large surface protein (LHB) variant W4P promotes carcinogenesis and tumor progression through STAT3 activation. Thus, we examined the anti-cancer activity of CDDO-me against HCC using W4P-LHB-expressing NIH3T3 cells and HepG2 and Huh7 HCC cell lines. CDDO-me exerted cytotoxic activity against W4P-LHB-expressing NIH3T3 cells, HepG2 cells, and Huh7 cells, and induced apoptotic cell death in a dose-dependent manner, demonstrating its anti-cancer activity against HCC. Sublethal concentrations of CDDO-me suppressed STAT3 activation by W4P-LHB ectopic expression and interleukin-6 treatment in W4P-LHB-NIH3T3 and Huh7 cells respectively. The suppression of STAT3 activation by CDDO-me in W4P-LHB-NIH3T3 cells was further confirmed by decreased cyclin D1 protein levels and increased p21 and p53 mRNA synthesis. In addition, CDDO-me treatment resulted in decreased cell migration and colony formation in in vitro assays using W4P-LHB-NIH3T3, HepG2, or Huh7 cell lines, supporting its anti-cancer activity through STAT3 inhibition. Furthermore, -CDDO-me administration significantly suppressed tumor growth induced by W4P-LHB-expressing NIH3T3 cells in nude mice, confirming its anti-cancer activity. Collectively, our findings demonstrated that CDDO-me is capable of suppressing STAT3 activation in HCC cells and cells transformed by the natural variant of HBV protein. The results suggest that CDDO-me can be a potential therapeutic agent against HCC, especially tumors related to HBV mutations.

Effects of Rhei Undulati Rhizoma on lipopolysaccharide-induced neuroinflammation in vitro and in vivo.

Neuroinflammation plays a critical role in the pathogenesis of degenerative brain diseases such as Alzheimer's disease and Parkinson's disease. Microglia are the major components of the brain immune system that regulate inflammatory processes. Activated microglia release pro-inflammatory factors and cytokines, resulting in neuronal cell death. We focused on inhibiting the activation of microglia from a stimulus as a strategy to search for neuroprotective drugs. Rhei Undulati Rhizoma (RUR) is traditionally used to treat various inflammatory disorders. In this study, we investigated whether RUR modulates inflammatory processes in lipopolysaccharide (LPS)-stimulated BV2 microglia cells and the mouse brain. RUR exerted anti-neuroinflammatory effects by inhibiting the production of nitric oxide and reactive oxygen species induced by LPS via the downregulation of transcription factors such as inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) without causing cytotoxicity. RUR also regulated mitogen-activated protein kinase pathway by inhibiting phosphorylation of p38 and c-Jun N-terminal kinases and translocation of nuclear factor kappa B. Moreover, RUR attenuated LPS-induced glial activation and COX-2 expression in the substantia nigra and hippocampus of the mouse brain. These results indicate that RUR is a potential candidate to treat neurodegenerative diseases by regulating neuroinflammation.

Butterbur Leaves Attenuate Memory Impairment and Neuronal Cell Damage in Amyloid Beta-Induced Alzheimer's Disease Models.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease, and is characterized by the accumulation of amyloid beta (Aß) as a pathological hallmark. Aß plays a central role in neuronal degeneration and synaptic dysfunction through the generation of excessive oxidative stress. In the present study, we explored whether leaves of Petasites japonicus (Siebold & Zucc.) Maxim. (PL), called butterbur and traditionally used in folk medicine, show neuroprotective action against Aß25⁻35 plaque neurotoxicity in vitro and in vivo. We found that PL protected Aß25⁻35 plaque-induced neuronal cell death and intracellular reactive oxygen species generation in HT22 cells by elevating expression levels of phosphorylated cyclic AMP response element-binding protein, heme oxygenase-1, and NAD(P)H quinine dehydrogenase 1. These neuroprotective effects of PL were also observed in Aß25⁻35 plaque-injected AD mouse models. Moreover, administration of PL diminished Aß25⁻35 plaque-induced synaptic dysfunction and memory impairment in mice. These findings lead us to suggest that PL can protect neurons against Aß25⁻35 plaque-induced neurotoxicity and thus may be a potential candidate to regulate the progression of AD.

Dangguijakyak-san ameliorates memory deficits in ovariectomized mice by upregulating hippocampal estrogen synthesis.

BACKGROUND: Dangguijakyak-san (DJS) is an herbal formulation that has been clinically applicable for treating postmenopausal symptoms and neurological disorders. It is reported that hippocampal estrogen attenuates memory impairment via neuroprotection and synaptogenesis. However, the effect of DJS on hippocampal estrogen synthesis remains unknown. In this study, we explored the effect of DJS and its neuroprotective mechanism against memory impairment in ovariectomized (OVX) mice, with respect to hippocampal estrogen stimulation. METHODS: Cell cultures were prepared from the hippocampi of 18-day-old embryos from timed pregnant Sprague-Dawley rats. The hippocampi were dissected, collected, dissociated, and plated in 60-mm dishes. The cells were treated with DJS for 48 h and the supernatant was collected to determine estrogen levels. Female ICR mice (8-weeks-old) were housed for 1 week and ovariectomy was performed to remove the influence of ovary-synthesized estrogens. Following a 2-week post-surgical recovery period, the mice were administrated with DJS (50 and 100 mg/kg/day, p.o.) or 17ß-estradiol (200 µg/kg/day, i.p.) once daily for 21 days. Hippocampal and serum estrogen levels were determined using enzyme-linked immunosorbent assay kit. Memory behavioral tests, western blot, and immunohistochemical analyses were performed to evaluate the neuroprotective effects of DJS in this model. RESULTS: DJS treatment promoted estrogen synthesis in primary hippocampal cells and the hippocampus of OVX mice, resulting in the amelioration of OVX-induced memory impairment. Hippocampal estrogen stimulated by DJS treatment contributed to the activation of cAMP response element-binding protein and synaptic protein in OVX mice. CONCLUSION: DJS may attenuate memory deficits in postmenopausal women via hippocampal estrogen synthesis.

White Ginseng Protects Mouse Hippocampal Cells Against Amyloid-Beta Oligomer Toxicity.

Amyloid-beta oligomer (AßO) is a soluble oligomer form of the Aß peptide and the most potent amyloid-beta form that induces neuronal damage in Alzheimer's disease. We investigated the effect of dried white ginseng extract (WGE) on neuronal cell damage and memory impairment in intrahippocampal AßO (10 µM)-injected mice. Mice were treated with WGE (100 and 500 mg/kg/day, p.o.) for 12 days after surgery. WGE improved memory impairment by inhibiting hippocampal cell death caused by AßO. In addition, AßO-injected mice treated with WGE showed restoration of reduced synaptophysin and choline acetyltransferase intensity and lower levels of ionized calcium-binding adaptor molecule 1 in the hippocampus compared with those of vehicle-treated controls. These results suggest that WGE reverses memory impairment in Alzheimer's disease by attenuating neuronal damage and neuroinflammation in the AßO-injected mouse hippocampus. Copyright © 2017 John Wiley & Sons, Ltd.

An experimental study on providing a scientific evidence for seven-time alcohol-steaming of Rhei Rhizoma when clinically used.

BACKGROUND: Rhei Rhizoma (RR) has been widely used as laxative and processed to alter its therapeutic actions or reduce its side effects. In this study, we evaluated experimentally the clinical application guideline that RR should be alcohol-steamed seven times before being used in elderly patients, as described in Dongeuibogam, the most famous book on Korean traditional medicine. METHODS: Unprocessed RR (RR-U) was soaked in rice wine, steamed and then fully dried (RR-P1). The process was repeated four (RR-P4) or seven times (RR-P7). Reversed-phase high-performance liquid chromatography was used to determine the RR-U, RR-P1, RR-P4 and RR-P7 (RRs) constituents. To evaluate the effect of RRs on liver toxicity, human hepatoma cells (HepG2) were treated with RRs at 100 µg/mL for 4 h and then cell viabilities were measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. To confirm the effects in vivo, 5-week-old male Sprague-Dawley rats were treated with RRs at 3 g/kg/day for 21 days. Body weight and serum biochemical parameters were measured and liver histology was assessed. RESULTS: The levels of sennosides decreased in processed RRs in an iteration-dependent manner, while the emodin level was unaffected. In HepG2 cells, cell viability was reduced with RR-U, while the toxicity decreased according to the number of processing cycles. The changes in body weight, relative liver weight and liver enzymes of RR-U-treated rats were reduced in processed RRs-treated rats. Histopathological analysis indicated swelling and cholestasis improved following seven times alcohol-steaming cycles. CONCLUSIONS: These results provide experimental evidence that RR-P7 almost completely reduces RR hepatotoxicity.

Survivin enhances hippocampal neurogenesis and cognitive function in Alzheimer's disease mouse model.

AIMS: Cognitive impairment is associated with reduced hippocampal neurogenesis; however, the causes of decreased hippocampal neurogenesis remain highly controversial. Here, we investigated the role of survivin in the modulation of hippocampal neurogenesis in AD. METHODS: To investigate the effect of survivin on neurogenesis in neural stem cells (NSCs), we treated mouse embryonic NSCs with a survivin inhibitor (YM155) and adeno-associated viral survivin (AAV-Survivin). To explore the potential role of survivin expression in AD, AAV9-Survivin or AAV9-GFP were injected into the dentate gyrus (DG) of hippocampus of 7-month-old wild-type and 5XFAD mice. Cognitive function was measured by the Y maze and Morris water maze. Neurogenesis was investigated by BrdU staining, immature, and mature neuron markers. RESULTS: Our results indicate that suppression of survivin expression resulted in decreased neurogenesis. Conversely, overexpression of survivin using AAV-Survivin restored neurogenesis in NSCs that had been suppressed by YM155 treatment. Furthermore, the expression level of survivin decreased in the 9-month-old 5XFAD compared with that in wild-type mice. AAV-Survivin-mediated overexpression of survivin in the DG in 5XFAD mice enhanced neurogenesis and cognitive function. CONCLUSION: Hippocampal neurogenesis can be enhanced by survivin overexpression, suggesting that survivin could serve as a promising therapeutic target for the treatment of AD.

Dextran sodium sulfate (DSS)-induced colitis is alleviated in mice after administration of flavone-derived NRF2-activating molecules.

Inflammatory Bowel Disease (IBD) is a chronic and relapsing inflammatory condition characterized by severe symptoms such as diarrhea, fatigue, and weight loss. Growing evidence underscores the direct involvement of the nuclear factor-erythroid 2-related factor 2 (NRF2) in the development and progression of IBD, along with its associated complications, including colorectal cancer. The NRF2 pathway plays a crucial role in cellular responses to oxidative stress, and dysregulation of this pathway has been implicated in IBD. Flavones, a significant subclass of flavonoids, have shown pharmacological impacts in various diseases including IBD, through the NRF2 signaling pathway. In this study, we conducted a screening of compounds with a flavone structure and identified NJK15003 as a promising NRF2 activator. NJK15003 demonstrated potent NRF2 activation, as evidenced by the upregulation of downstream proteins, promoter activation, and NRF2 nuclear translocation in IBD cellular models. Treatment with NJK15003 effectively restored the protein levels of tight junctions in cells treated with dextran sodium sulfate (DSS) and in DSS-treated mice, suggesting its potential to protect cells from barrier integrity disruption in IBD. In DSS-treated mice, the administration of NJK15003 resulted in the prevention of body weight loss, a reduction in colon length shortening, and a decrease in the disease activity index. Furthermore, NJK15003 treatment substantially alleviated inflammatory responses and apoptotic cell death in the colon of DSS-treated mice. Taken together, this study proposes the potential utility of NRF2-activating flavone compounds, exemplified by NJK15003, for the treatment of IBD.

Eugenol relieves the pathological manifestations of Alzheimer's disease in 5×FAD mice.

BACKGROUND: Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by the accumulation of amyloid-ß (Aß) and excessive neuroinflammation, resulting in neuronal cell death and cognitive impairments. Eugenol, a phenylpropene, is the main component of Syzygium aromaticum L. (Myrtaceae) and has multiple therapeutic effects, including neuroprotective and anti-inflammatory effects, through multimodal mechanisms. PURPOSE: We aimed to investigate the effect of eugenol on AD pathologies using a 5× familiar AD (5×FAD) mouse model. METHODS: Eight-month-old 5×FAD and wild-type mice were administered with eugenol (10 or 30 mg/kg/day, p.o) for 2 months. Y-maze and Morris water maze tests were performed to assess the cognitive function of mice. After the behavioral test, molecular analysis was conducted to investigate the therapeutic mechanism of eugenol. RESULTS: Our findings indicate that eugenol treatment effectively mitigated cognitive impairments in 5×FAD mice. This beneficial effect was associated with a decrease in AD pathologies, including neuronal cell loss and Aß deposition. Specifically, eugenol inhibited necroptosis activation and increased microglial phagocytosis, which were the underlying mechanisms for the observed reductions in neuronal cell loss and Aß deposition, respectively. CONCLUSION: Overall, our data suggest that eugenol would be a potential therapeutic candidate for AD.

Hesperidin Improves Memory Function by Enhancing Neurogenesis in a Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is an irreversible neurodegenerative disease characterized by memory and cognitive impairments. Neurogenesis, which is related to memory and cognitive function, is reduced in the brains of patients with AD. Therefore, enhancing neurogenesis is a potential therapeutic strategy for neurodegenerative diseases, including AD. Hesperidin (HSP), a bioflavonoid found primarily in citrus plants, has anti-inflammatory, antioxidant, and neuroprotective effects. The objective of this study was to determine the effects of HSP on neurogenesis in neural stem cells (NSCs) isolated from the brain of mouse embryos and five familial AD (5xFAD) mice. In NSCs, HSP significantly increased the proliferation of NSCs by activating adenosine monophosphate (AMP)-activated protein kinase (AMPK)/cAMP-response element-binding protein (CREB) signaling, but did not affect NSC differentiation into neurons and astrocytes. HSP administration restored neurogenesis in the hippocampus of 5xFAD mice via AMPK/brain-derived neurotrophic factor/tropomyosin receptor kinase B/CREB signaling, thereby decreasing amyloid-beta accumulation and ameliorating memory dysfunction. Collectively, these preclinical findings suggest that HSP is a promising candidate for the prevention and treatment of AD.

Yomogin, Isolated from Artemisia iwayomogi, Inhibits Neuroinflammation Stimulated by Lipopolysaccharide via Regulating MAPK Pathway.

Neuroinflammation causes various neurological disorders, including depression and neurodegenerative diseases. Therefore, regulation of neuroinflammation is a promising therapeutic strategy for inflammation-related neurological disorders. This study aimed to investigate whether yomogin, isolated from Artemisia iwayomogi, has anti-neuroinflammatory effects. First, we evaluated the effects of yomogin by assessing pro-inflammatory mediators and cytokines in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. The results showed that yomogin inhibited the increase in neuroinflammatory factors, including nitric oxide, inducible nitric oxide synthase, cyclooxygenase-2, interleukin-6, and tumor necrosis factor-α, and suppressed phosphorylation of c-Jun N-terminal kinase, extracellular signal-regulated kinase and p38, which participate in the mitogen-activated protein kinase (MAPK) pathway. To confirm these effects in vivo, we measured the activation of astrocyte and microglia in LPS-injected mouse brains. Results showed that yomogin treatment decreased astrocyte and microglia activations. Collectively, these results suggest that yomogin suppresses neuroinflammation by regulating the MAPK pathway and it could be a potential candidate for inflammation-mediated neurological diseases.

Artemisiae Iwayomogii Herba inhibits lipopolysaccharide-induced neuroinflammation by regulating NF-κB and MAPK signaling pathways.

BACKGROUND: Neuroinflammation plays a major role in the development of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. The regulation of microglia is an efficient therapeutic approach to controlling neuroinflammation. PURPOSE: In this study, we aimed to determine whether Artemisiae Iwayomogii Herba (AIH), which is herbal medicine traditionally used for inflammation-related disorders, controls neuroinflammatory responses by regulating the microglia-mediated signaling pathway. METHODS: BV-2 microglial cells were treated with AIH and lipopolysaccharides (LPS), then various pro-inflammatory mediators were analyzed using griess reaction, quantitative reverse-transcription polymerase chain reaction, or western blotting. C57BL/6 J mice were orally administered by AIH for 17 days and intraperitoneally injected with LPS for the last 14 days. The brains were collected and the microglial activation and nucleotide-binding oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing 3 (NLRP3) expression in the cortex and hippocampus were analyzed using immunohistochemistry or western blotting. RESULTS: In BV-2 microglial cells, we found that AIH inhibited nitric oxide (NO) production induced by LPS. AIH also suppressed the expressions of pro-inflammatory mediators, including inducible NO synthase, cyclooxygenase-2, tumor necrosis factor-α, and interleukin-6. The study also revealed that the effects of AIH are related to the regulation of the nuclear factor kappa B (NF-κB) and the mitogen-activated protein kinase (MAPK) signaling pathway. Additionally, we found that AIH prevented the formation of NLRP3 inflammasomes. Consistent with the results of in vitro studies on the brains of LPS-injected mice, we observed that AIH suppressed microglial activation and NLRP3 expression. CONCLUSION: Taken together, these results suggest that AIH attenuates neuroinflammation by regulating the NF-κB and MAPK pathways, and it may be used for treating neurological diseases.