Andrographolide Protects PC12 Cells Against β-Amyloid-Induced Autophagy-Associated Cell Death Through Activation of the Nrf2-Mediated p62 Signaling Pathway

Andrographolide mitigates neurotoxicity induced by lipopolysaccharide or amyloid-β through modulation of miR-222-mediated p62 and NF-κBp65 expression

MicroRNA-222 (miR-222) plays a crucial role in neurodegeneration and is up-regulated in Alzheimer's disease (AD) patients. Andrographolide (Andro) has been reported to have anti-inflammatory and neuroprotective effects, showing potential for treating AD. The relationship between Andro's anti-AD mechanism and the regulation of miR-222 was discussed in this study. Andro protected against cytotoxicity induced by lipopolysaccharide (LPS) or amyloid-β, accompanied by upregulating p62 and Nrf2 mRNA and protein, downregulating TLR4 and NF-κBp65 mRNA and protein, and increasing LC3Ⅱ protein in vitro. miRNA and mRNA sequencing results showed that Andro downregulated miR-222 and upregulated sqstm1/p62. Andro was observed to inhibit the expression of miR-222 and the phosphorylation of NF-κBp65, while simultaneously enhancing the levels of p62 and LC3Ⅱ proteins, decreasing Aβ levels, and attenuating the release of inflammatory factors in the 3xTg-AD mice. MiR-222 mimic increased NF-κBp65 mRNA and protein levels in LPS-induced cells, while miR-222 inhibitors increased p62 mRNA and protein levels as well as Nrf2 and LC3Ⅱ protein, and decreased p-NF-κBp65 protein level in LPS-induced cells. Furthermore, miR-222 mimic reversed the increase in p62 and LC3Ⅱ protein and the decrease in NF-κBp65 mRNA and protein, as well as the decrease in Tau protein levels induced by Andro in LPS-induced cells. These findings suggest that Andro plays a neuroprotective role through downregulation of miR-222 to promote p62 expression while inhibiting NF-kB p65 expression, providing new insights into the mechanism of action of Andro for treating AD.

Andrographolide Improves ApoE4-Mediated Blood-Brain Barrier Injury by Alleviating Inflammation

The pathological and physiological studies of Alzheimer's disease (AD) have been in-depth, and apolipoprotein E4 (ApoE4) has been proven to be highly correlated with AD, and clinical and experimental data show that ApoE4 can cause blood-brain barrier (BBB) injury, and the change of BBB permeability is an important factor affecting the development of AD. Andrographolide (Andro), as the active component of the natural plant Andrographis paniculata, has been proven to have anti-inflammatory and antioxidant effects, which have potential neuroprotective effects. To verify the protective effect of Andro on BBB in a short term, our research group used atorvastatin (Atorva)-mediated zebrafish brain injury model and the ApoE4-mediated cell co-culture model of BBB injury to explore the protective effects and mechanisms of Andro on BBB injury. Studies have shown that Andro can inhibit the activation of CypA/NF-κB/MMP-9 signaling pathway and has achieved the effect of antagonizing the inhibition of ApoE4 on intercellular tight junction proteins (occludin, claudin-5, and ZO-1). At the same time, Andro can inhibit the secretion of cell adhesion molecules (VCAM-1 and ICAM-1) in cells, thereby delaying the occurrence and progression of neuroinflammation and playing a protective role in BBB. In conclusion, Andro is a potent natural product which can protect the blood-brain barrier.

Therapeutic effect of nicotinamide mononucleotide on Alzheimer's disease through activating autophagy and anti-oxidative stress

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the deposition of β-amyloid (Aβ) plaques and neurofibrillary tangles composed of tau protein in the brain. These neuropathological hallmarks contribute to cognitive impairment by inducing neuronal loss in the cerebral cortex and hippocampus. Unfortunately, current therapeutic approaches only target symptomatic relief and do not impede disease progression. Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD+), has emerged as a promising candidate for the treatment of age-related neurodegenerative disorders. NMN supplementation could restore NAD+ levels, thereby alleviating neuronal damage and slowing the progression of AD and other aging-associated diseases. AD is closely associated with autophagic impairment and oxidative stress. Our in vivo experiments demonstrated that NMN could ameliorate pathological and behavioral impairments in AD mice. Specifically, NMN enhanced autophagy and promoted p-tau clearance. Meanwhile, NMN could activate the Nrf2/Keap1/NQO1 pathway, thereby reducing the oxidative stress. Immunofluorescence results demonstrated that NMN could alleviate neuronal damage in AD mice. Furthermore, in vitro results showed that the p-tau clearance and antioxidant stress effects of NMN were suppressed by autophagy inhibitor, chloroquine (CQ) or bafilomycin A1 (BafA1), in Aβ-induced PC12 cells. Lastly, when Nrf2 was knocked down, the antioxidant stress, autophagy enhancement, and p-tau clearance effects of NMN were all inhibited. In conclusion, our research indicates that NMN exerts therapeutic effect against AD by activating autophagy and the Nrf2/Keap1/NQO1 pathway through a mutual regulating mechanism of autophagy and antioxidative stress. These findings highlight the promising potential of NMN for the treatment of AD.

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.

A novel neuroprotective peptide YVYAETY identified and screened from Flammulina velutipes protein hydrolysates attenuates scopolamine-induced cognitive impairment in mice

Flammulina velutipes protein hydrolysates are known for their abundant amino acids and excellent developmental values. This study aimed to identify and screen neuroprotective peptides from F. velutipes protein hydrolysates in vitro and validate the protective effects of YVYAETY on memory impairment in scopolamine-induced mice. The F. velutipes protein was hydrolyzed by simulated gastrointestinal digestion, followed by purification through ultrafiltration and gel chromatography. The fraction exhibiting the strongest neuroprotective activity was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The main identified peptides (SDLKPADF, WNDHYY, YVYAETY, and WFHPLF) effectively mitigated excessive ROS production by increasing SOD and GSH-px activities while inhibiting cell apoptosis and mitochondrial membrane potential (MMP) collapse against oxidative stress in Aβ25-35-induced HT22 cells. By molecular docking, the interaction between peptides and the active site of the Keap1-Kelch domain reveals their capacity to regulate the Keap1/Nrf2/HO-1 pathway. In vitro, the peptide YVYAETY had the best effect and can be further validated in vivo. The behavioral tests showed that YVYAETY improved scopolamine-induced cognitive impairment in mice. YVYAETY also alleviated neuron damage including neuron vacuolation and pyknotic nuclei in the hippocampus. Furthermore, it significantly inhibited oxidative stress and suppressed the activation of the Nrf2 pathway. Therefore, this study revealed that YVYAETY had the potential to serve as a novel neuroprotective agent.

Andrographolide derivative Andro-III modulates neuroinflammation and attenuates neuropathological changes of Alzheimer's disease via GSK-3β/NF-κB/CREB pathway

Andrographolide has anti-inflammatory and neuroprotective effects, making it a potential therapeutic option for Alzheimer's disease (AD). Our research group optimized its structure in a previous study to minimize the risk of renal toxicity, which would beneficial for future clinical research. This study aims to examine the impact of Andro-III on enhancing cognitive learning ability in 3xTg-AD mice, as well as the mechanisms involved. Andro-III improved spatial learning ability, prevented the loss of Nysted's vesicles, reduced the accumulation of β-amyloid (Aβ) and tau proteins, and suppressed microglial activation. Further research found that the expression of nuclear factor kappa-B RelA (NF-κB p65) expression and glycogen synthase kinase-3β (GSK-3β) activity were inhibited, while CREB was upregulated in brain tissue treated with Andro-III. Moreover, Andro-III downregulated the expression of IBA1 and inflammatory factors in microglial cells of mice induced by Aβ. The regulation of the GSK-3β/NF-κB/CREB pathway was similar to that observed in 3xTg-AD mice. Therefore, Andro-III modulates neuroinflammation and attenuates neuropathological changes of AD via the GSK-3β/NF-κB/CREB pathway.

Therapeutic potential of natural products against Alzheimer's disease via autophagic removal of Aβ

The pathological features of Alzheimer's disease (AD), a progressive neurodegenerative disorder, include the deposition of extracellular amyloid beta (Aβ) plaques and intracellular tau neurofibrillary tangles. A decline in cognitive ability is related to the accumulation of Aβ in patients with AD. Autophagy, which is a primary intracellular mechanism for degrading aggregated proteins and damaged organelles, plays a crucial role in AD. In this review, we summarize the most recent research progress regarding the process of autophagy and the effect of autophagy on Aβ. We further discuss some typical monomers of natural products that contribute to the clearance of Aβ by autophagy, which can alleviate AD. This provides a new perspective for the application of autophagy modulation in natural product therapy for AD.

Andrographolide induced heme oxygenase-1 expression in MSC-like cells isolated from rat bone marrow exposed to environmental stress

BACKGROUND AND OBJECTIVES

Mesenchymal stem cells (MSC-like cells) are the most important stem cells that are used in transplantation clinically in various applications. The survival rate of MSC-like cells is strongly reduced due to adverse conditions in the microenvironment of transplantation, including environmental stress. Heme oxygenase-1 (HO-1) is a member of the heat shock protein, as well as a stress-induced enzyme, present throughout the body. The present study was conducted to investigate the effect of andrographolide, an active derivative from andrographolide paniculate, on HO-1 expression in mesenchymal stem cells derived from rat bone marrow.

MATERIALS AND METHODS

The rat bone marrow-derived mesenchymal stem cells (BMSC-like cells) were extracted and proliferated in several passages. The identity of MSC-like cells was confirmed by morphological observations and differential tests. The flow cytometry method was used to verify the MSC-specific markers. Isolated MSC-like cells were treated with different concentrations of andrographolide and then exposed to environmental stress. Cell viability was assessed using the MTT colorimetric assay. A real-time PCR technique was employed to evaluate the expression level of HO-1 in the treated MSC-like cells.

RESULTS

Isolated MSC-like cells demonstrated fibroblast-like morphology. These cells in different culture mediums differentiated into osteocytes and adipocytes and were identified using alizarin red and oil red staining, respectively. As well, MSC-like cells were verified by the detection of CD105 surface antigen and the absence of CD14 and CD45 antigens. The results of the MTT assay showed that the pre-treatment of MSC-like cells with andrographolide concentration independently increased the viability and resistance of these cells to environmental stress caused by hydrogen peroxide and serum deprivation (SD). Real-time PCR findings indicated a significant increase in HO-1 gene expression in the andrographolide-receiving groups (p < 0.01).

CONCLUSION

Our results suggest that andrographolide creates a promising strategy for enhancing the quality of cell therapy by increasing the resistance of MSC-like cells to environmental stress and inducing the expression of HO-1.

Research Progress on the Preparation and Function of Antioxidant Peptides from Walnuts

Food-derived peptides have good antioxidant activity and are highly safe for humans; consequently, there has been continuous growth in research on antioxidants, with potential applications in food, medicine, cosmetics, and other fields. Among food-derived peptides, walnut-derived peptides have attracted increasing attention as food-derived peptides rich in eight essential amino acids. This review summarizes the progress made in the development and identification of antioxidant peptides in walnut proteins. This article mainly describes the interaction between reactive oxygen species and cellular antioxidant products, modulation of enzyme content and activity, and regulation of the redox signaling pathways and analyzes the mechanisms of reduction in oxidative stress. Finally, the complex structure-activity relationships of walnut-derived peptides are analyzed based on their amino acid composition and secondary structure of the polypeptides. This review provides a theoretical basis for the production of walnut-derived antioxidant peptides and could help promote the development of the walnut industry.

Exploring the therapeutic potential of natural compounds for Alzheimer's disease: Mechanisms of action and pharmacological properties

Alzheimer's Disease (AD) is a global public health priority characterized by high mortality rates in adults and an increasing prevalence in aging populations worldwide. Despite significant advancements in comprehending the pathogenesis of AD since its initial report in 1907, there remains a lack of effective curative or preventive measures for the disease. In recent years, natural compounds sourced from diverse origins have garnered considerable attention as potential therapeutic agents for AD, owing to their anti-inflammatory, antioxidant, and neuroprotective properties. This review aims to consolidate the therapeutic effects of natural compounds on AD, specifically targeting the reduction of β-amyloid (Aβ) overproduction, anti-apoptosis, autophagy, neuroinflammation, oxidative stress, endoplasmic reticulum (ER) stress, and mitochondrial dysfunction. Notably, the identified compounds exhibiting these effects predominantly originate from plants. This review provides valuable insights into the potential of natural compounds as a reservoir of novel therapeutic agents for AD, thereby stimulating further research and contributing to the development of efficacious treatments for this devastating disease.

The Role of Fucoxanthin as a Potent Nrf2 Activator via Akt/GSK-3β/Fyn Axis against Amyloid-β Peptide-Induced Oxidative Damage

Increasing evidence is suggesting that amyloid-β peptide (Aβ), a characteristic of Alzheimer’s disease (AD), induces oxidative stress and mitochondrial dysfunction, leading to neuronal death. This study aimed to demonstrate the antioxidant and anti-apoptotic effects of fucoxanthin, a major marine carotenoid found in brown algae, against neuronal injury caused by Aβ. Non-toxic dose range of fucoxanthin (0.1–5 µM) were selected for the neuroprotective study against Aβ25–35. The PC12 cells were pretreated with different concentrations of fucoxanthin for 1 h before being exposed to 10 µM Aβ25–35 for another 24 h. The present results showed that fucoxanthin inhibited Aβ25-35-induced cell death by recovering cell cycle arrest and decreasing intracellular reactive oxygen species (ROS) level. The compound enhanced mitochondrial recovery and regulated apoptosis related proteins including B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) from Aβ25-35-induced oxidative stress. Concomitantly, fucoxanthin increased the expression of nuclear factor E2-related factor 2 (Nrf2) and its downstream phase II detoxifying enzymes including NADPH: quinone oxidoreductase-1 (NQO-1), glutamate cysteine ligase modifier subunit (GCLm), and thioredoxin reductase 1 (TrxR1), whereas it decreased the expression of cytoplasmic Kelch-like ECH-associated protein 1 (Keap1). Moreover, pretreatment of fucoxanthin reduced Fyn phosphorylation via protein kinase B (Akt)-mediated inhibition of glycogen synthase kinase-3β (GSK-3β), which increased the nuclear localization of Nrf2, suggesting that the compound enhanced Nrf2 expression by the activation of upstream kinase as well as the dissociation of the Nrf2-Keap1 complex. Further validation with a specific phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 demonstrated that the fucoxanthin-mediated Nrf2 antioxidant defense system was directly associated with the Akt/GSK-3β/Fyn signaling pathway. In silico simulation revealed that the oxygen groups of fucoxanthin participated in potent interactions with target markers in the Nrf2 signaling pathway, which may affect the biological activity of target markers. Taken together, the present results demonstrated that the preventive role of fucoxanthin on Aβ-stimulated oxidative injury and apoptosis via Akt/GSK-3β/Fyn signaling pathway. This study would provide a useful approach for potential intervention for AD prevention.

Natural product-based bioactive agents in combination attenuate neuroinflammation in a tri-culture model

Introduction: Neuroinflammation is an important pathological event contributing to the onset and progression of neurodegenerative diseases. The hyperactivation of microglia triggers the release of excessive proinflammatory mediators that lead to the leaky blood-brain barrier and impaired neuronal survival. Andrographolide (AN), baicalein (BA) and 6-shogaol (6-SG) possess anti-neuroinflammatory properties through diverse mechanisms of action. The present study aims to investigate the effects of the pair-combinations of these bioactive compounds in attenuating neuroinflammation. Methods: A tri-culture model with microglial N11 cells, microvascular endothelial MVEC(B3) cells, and neuroblastoma N2A cells was established in a transwell system. AN, BA and 6-SG used alone (25 µM) or in pair-wised combinations (12.5 + 12.5 µM) were subjected to the tri-culture system. Upon the stimulation of lipopolysaccharides (LPS) at 1 μg/mL, tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6) levels were determined by ELISA assays. Immunofluorescence staining was applied to investigate the nuclear translocation of nuclear factor kappa B p65 (NF-κB p65) on N11 cells, expressions of protein zonula occludens-1 (ZO-1) on MVEC cells and phosphorylated tau (p-tau) on N2A cells, respectively. The endothelial barrier permeability of MVEC cells was assessed by the Evans blue dye, and the resistance from the endothelial barrier was measured by transepithelial/endothelial electrical resistance (TEER) value. Neuronal survival of N2A cells was determined by Alamar blue and MTT assays. Results: Combinations of AN-SG and BA-SG synergistically lowered the TNF and IL-6 levels in LPS-induced N11 cells. Remarkably, the combined anti-neuroinflammatory effects of AN-SG and BA-SG remained significantly greater compared to their individual components at the same concentration level. The molecular mechanism of the attenuated neuroinflammation was likely to be mediated by downregulation of NF-κB p65 translocation (p < 0.0001 vs. LPS stimulation) in N11 cells. In the MVEC cells, both AN-SG and BA-SG restored TEER values, ZO-1 expression and reduced permeability. Furthermore, AN-SG and BA-SG significantly improved neuronal survival and reduced expressions of p-tau on N2A cells. Discussion: The AN-SG and BA-SG combinations showed greater anti-neuroinflammatory potential than those used alone in mono- and tri-cultured N11 cells, thereby further protecting endothelial tight junction and neuronal survival. Taken together, AN-SG and BA-SG may provide improved anti-neuroinflammatory and neuroprotective activities.

Regulation of mitochondrial dysfunction induced cell apoptosis is a potential therapeutic strategy for herbal medicine to treat neurodegenerative diseases

Neurodegenerative disease is a progressive neurodegeneration caused by genetic and environmental factors. Alzheimer’s disease (AD), Parkinson’s disease (PD), and Huntington’s disease (HD) are the three most common neurodegenerative diseases clinically. Unfortunately, the incidence of neurodegenerative diseases is increasing year by year. However, the current available drugs have poor efficacy and large side effects, which brings a great burden to the patients and the society. Increasing evidence suggests that occurrence and development of the neurodegenerative diseases is closely related to the mitochondrial dysfunction, which can affect mitochondrial biogenesis, mitochondrial dynamics, as well as mitochondrial mitophagy. Through the disruption of mitochondrial homeostasis, nerve cells undergo varying degrees of apoptosis. Interestingly, it has been shown in recent years that the natural agents derived from herbal medicines are beneficial for prevention/treatment of neurodegenerative diseases via regulation of mitochondrial dysfunction. Therefore, in this review, we will focus on the potential therapeutic agents from herbal medicines for treating neurodegenerative diseases via suppressing apoptosis through regulation of mitochondrial dysfunction, in order to provide a foundation for the development of more candidate drugs for neurodegenerative diseases from herbal medicine.

Deconvoluting the Complexity of Reactive Oxygen Species (ROS) in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are becoming a serious public health concern as the world’s population continues to age, demanding the discovery of more effective therapies. Excessive formation of reactive oxygen species (ROS) can result in oxidative stress (OS), which can be regarded as one of the common causes of neurodegenerative diseases (NDs). Thus, in this review, we focus on summarizing the consequences of ROS NDs, while taking the four prevalent NDs as examples, including Alzheimer’s disease (AD), Parkinson’s disease (PD), Amyotrophic lateral sclerosis (ALS), and Huntington’s disease (HD), to illustrate the key signaling pathways and relevant drugs. Together, these findings may shed new light on a field in which ROS-related pathways play a key role; thereby setting the groundwork for the future therapeutic development of neurodegenerative diseases.

Redox signaling at the crossroads of human health and disease

Redox biology is at the core of life sciences, accompanied by the close correlation of redox processes with biological activities. Redox homeostasis is a prerequisite for human health, in which the physiological levels of nonradical reactive oxygen species (ROS) function as the primary second messengers to modulate physiological redox signaling by orchestrating multiple redox sensors. However, excessive ROS accumulation, termed oxidative stress (OS), leads to biomolecule damage and subsequent occurrence of various diseases such as type 2 diabetes, atherosclerosis, and cancer. Herein, starting with the evolution of redox biology, we reveal the roles of ROS as multifaceted physiological modulators to mediate redox signaling and sustain redox homeostasis. In addition, we also emphasize the detailed OS mechanisms involved in the initiation and development of several important diseases. ROS as a double-edged sword in disease progression suggest two different therapeutic strategies to treat redox-relevant diseases, in which targeting ROS sources and redox-related effectors to manipulate redox homeostasis will largely promote precision medicine. Therefore, a comprehensive understanding of the redox signaling networks under physiological and pathological conditions will facilitate the development of redox medicine and benefit patients with redox-relevant diseases.

A Pivotal Role of Nrf2 in Neurodegenerative Disorders: A New Way for Therapeutic Strategies

Clinical and preclinical research indicates that neurodegenerative diseases are characterized by excess levels of oxidative stress (OS) biomarkers and by lower levels of antioxidant protection in the brain and peripheral tissues. Dysregulations in the oxidant/antioxidant balance are known to be a major factor in the pathogenesis of neurodegenerative diseases and involve mitochondrial dysfunction, protein misfolding, and neuroinflammation, all events that lead to the proteostatic collapse of neuronal cells and their loss. Nuclear factor-E2-related factor 2 (Nrf2) is a short-lived protein that works as a transcription factor and is related to the expression of many cytoprotective genes involved in xenobiotic metabolism and antioxidant responses. A major emerging function of Nrf2 from studies over the past decade is its role in resistance to OS. Nrf2 is a key regulator of OS defense and research supports a protective and defending role of Nrf2 against neurodegenerative conditions. This review describes the influence of Nrf2 on OS and in what way Nrf2 regulates antioxidant defense for neurodegenerative conditions. Furthermore, we evaluate recent research and evidence for a beneficial and potential role of specific Nrf2 activator compounds as therapeutic agents.

Synthesis and Characterization of Andrographolide Derivatives as Regulators of βAPP Processing in Human Cells

Alzheimer's disease (AD) is a devastating neurodegenerative disorder, one of the main characteristics of which is the abnormal accumulation of amyloid peptide (Aβ) in the brain. Whereas β-secretase supports Aβ formation along the amyloidogenic processing of the β-amyloid precursor protein (βAPP), α-secretase counterbalances this pathway by both preventing Aβ production and triggering the release of the neuroprotective sAPPα metabolite. Therefore, stimulating α-secretase and/or inhibiting β-secretase can be considered a promising anti-AD therapeutic track. In this context, we tested andrographolide, a labdane diterpene derived from the plant Andrographis paniculata, as well as 24 synthesized derivatives, for their ability to induce sAPPα production in cultured SH-SY5Y human neuroblastoma cells. Following several rounds of screening, we identified three hits that were subjected to full characterization. Interestingly, andrographolide (8,17-olefinic) and its close derivative 14α-(5',7'-dichloro-8'-quinolyloxy)-3,19-acetonylidene (compound 9) behave as moderate α-secretase activators, while 14α-(2'-methyl-5',7'-dichloro-8'-quinolyloxy)-8,9-olefinic compounds 31 (3,19-acetonylidene) and 37 (3,19-diol), whose two structures are quite similar although distant from that of andrographolide and 9, stand as β-secretase inhibitors. Importantly, these results were confirmed in human HEK293 cells and these compounds do not trigger toxicity in either cell line. Altogether, these findings may represent an encouraging starting point for the future development of andrographolide-based compounds aimed at both activating α-secretase and inhibiting β-secretase that could prove useful in our quest for the therapeutic treatment of AD.

Andrographolide emeliorates maltol aluminium-induced neurotoxicity via regulating p62-mediated Keap1-Nrf2 pathways in PC12 cells

CONTEXT

Andrographolide (Andro) has a neuroprotective effect and a potential for treating Alzheimer's disease (AD), but the mechanism has not been elucidated.

OBJECTIVE

The efficacy of Andro on p62-mediated Kelch-like ECH-associated protein 1(Keap1)-Nuclear factor E2 related factor 2 (Nrf2) pathways in the aluminium maltolate (Al(mal)₃)-induced neurotoxicity in PC12 cell was explored.

MATERIALS AND METHODS

PC12 cells were induced by Al(mal)₃ (700 μM) to establish a neurotoxicity model. Following Andro (1.25, 2.5, 5, 10, 20, 40 μM) co-treatment with Al(Mal)₃, cell viability was detected with MTT, protein expression levels of β-amyloid precursor protein (APP), β-site APP cleaving enzyme 1 (BACE1), Tau, Nrf2, Keap1, p62 and LC3 were measured via western blotting or immunofluorescence analyses. Nrf2, Keap1, p62 and LC3 mRNA, were detected by reverse transcription-quantitative PCR.

RESULTS

Compared with the 700 μM Al(mal)₃ group, Andro (5, 10 μM) significantly increased Al(mal)3-induced cell viability from 67.4% to 91.9% and 91.2%, respectively, and decreased the expression of APP, BACE1 and Keap1 proteins and the ratio of P-Tau to Tau (from 2.75- fold to 1.94- and 1.70-fold, 2.12-fold to 1.77- and 1.56-fold, 0.68-fold to 0.51- and 0.55-fold, 1.45-fold to 0.82- and 0.91-fold, respectively), increased the protein expression of Nrf2, p62 and the ratio of LC3-II/LC3-I (from 0.67-fold to 0.93- and 0.94-fold, 0.64-fold to 0.88- and 0.87-fold, 0.51-fold to 0.63- and 0.79-fold, respectively), as well as the mRNA expression of Nrf2, p62 and LC3 (from 0.48-fold to 0.92-fold, 0.49-fold to 0.92-fold, 0.25-fold to 0.38-fold). Furthermore, Nrf2 and p62 nuclear translocation were increased and keap1 in the cytoplasm was decreased in the presence of Andro. Silencing p62 or Nrf2 can significantly reduce the protein and mRNA expression of Nrf2 and p62 under co-treatment with Andro and Al(mal)₃.

DISCUSSION AND CONCLUSIONS

Our results suggested that Andro could be a promising therapeutic lead against Al-induced neurotoxicity by regulating p62-mediated keap1-Nrf2 pathways.

Lipopolysaccharide exacerbates chronic restraint stress-induced neurobehavioral deficits: Mechanisms by redox imbalance, ASK1-related apoptosis, autophagic dysregulation

Major depressive disorder (MDD) is the foremost leading psychiatric illness prevailing around the globe. It usually exists along with anxiety and other clinical conditions (cardiovascular, cancer, neurodegenerative diseases, and infectious diseases). Chronic restraint stress (RS) and LPS-induce neurobehavioral alterations in rodent models however their interaction studies in association with the pathogenesis of MDD are still unclear. Therefore, the current study was aimed to investigate the LPS influence on chronic RS mediated redox imbalance, apoptosis, and autophagic dysregulation in the hippocampus (HIP) and frontal cortex (FC) of mice brain. Male Balb/c mice were exposed to 28 days consecutive stress (6h/day) with a single-dose LPS challenge (0.83 mg/kg, i.p.) on the last day (Day 28). In addition, we also carried out separate study to understand physiological relevance, where we used the DSS (dextran sulfate sodium), a water soluble polysaccharide (negatively charged) and studied its influence on RS induced neurobehavioral and certain neurochemical anomalies. The obtained results in RS and RS + LPS animal groups showed significant immune dysfunction, depleted monoamines, lowered ATP & NAD level, elevated serum CORT level, serum and brain tissues IL-1β/TNF-α/IL-6, SOD activity but reduced CAT activity. Furthermore, the redox perturbation was found where significantly upregulated P-NFκB p65, Keap-1, Prx-SO3 and downregulated Nrf2, Srx1, Prx2 protein expression was seen in RS + LPS mice. The apoptosis signaling (P-ASK1, P-p38 MAPK, P-SAPK/JNK, cleaved PARP, cleaved Caspase-3, Cyto-C), autophagic impairment (p62, LC3II/I) were noticed in HIP and FC of RS and RS + LPS grouped animals. Our new findings provide a complex interplay of chemical (LPS) and physical (RS) stressors where both single dose LPS challenge and 3% DSS in drinking water (for 7 days) exaggerated chronic RS-induced inflammation, lowered redox status, increased apoptosis and dysregulated autophagy leading drastic neurobehavioral alterations in the mice.

Andrographolide: A review of its pharmacology, pharmacokinetics, toxicity and clinical trials and pharmaceutical researches

Andrographis paniculata (Burm. f.) Wall. ex Nees, a renowned herb medicine in China, is broadly utilized in traditional Chinese medicine (TCM) for the treatment of cold and fever, sore throat, sore tongue, snake bite with its excellent functions of clearing heat and toxin, cooling blood and detumescence from times immemorial. Modern pharmacological research corroborates that andrographolide, the major ingredient in this traditional herb, is the fundamental material basis for its efficacy. As the main component of Andrographis paniculata (Burm. f.) Wall. ex Nees, andrographolide reveals numerous therapeutic actions, such as antiinflammatory, antioxidant, anticancer, antimicrobial, antihyperglycemic and so on. However, there are scarcely systematic summaries on the specific mechanism of disease treatment and pharmacokinetics. Moreover, it is also found that it possesses easily ignored security issues in clinical application, such as nephrotoxicity and reproductive toxicity. Thereby it should be kept a lookout over in clinical. Besides, the relationship between the efficacy and security issues of andrographolide should be investigated and evaluated scientifically. In this review, special emphasis is given to andrographolide, a multifunctional natural terpenoids, including its pharmacology, pharmacokinetics, toxicity and pharmaceutical researches. A brief overview of its clinical trials is also presented. This review intends to systematically and comprehensively summarize the current researches of andrographolide, which is of great significance for the development of andrographolide clinical products. Noteworthy, those un-cracked issues such as specific pharmacological mechanisms, security issues, as well as the bottleneck in clinical transformation, which detailed exploration and excavation are still not to be ignored before achieving integration into clinical practice. In addition, given that current extensive clinical data do not have sufficient rigor and documented details, more high-quality investigations in this field are needed to validate the efficacy and/or safety of many herbal products.

5,6,7,4'-Tetramethoxyflavanone attenuates NADPH oxidase 1/4 and promotes sirtuin-1 to inhibit cell stress, senescence and apoptosis in Aß25-35-mediated SK-N-SH dysfunction

Amyloidogenesis is a fundamental step of amyloid beta (Aβ) generation-induced toxicity that is commonly reported to disrupt neuronal circuits, function and survival in Alzheimer's disease (AD). The neuroprotective effect of 5,6,7,4'-tetramethoxyflavanone (TMF) from Chormolaela odorata extract on brain degeneration and amyloidogenesis has previously been demonstrated. However, the mechanistic evidence for TMF's effects is still unclear. In this study, we evaluated the neuroprotective effect of TMF in Aβ_25-35-induced toxicity in SK-N-SH neuroblastoma cells. Herein, we demonstrated that TMF exhibited potent antioxidant activity and significantly increased cell viability and decreased ROS production in a dose-dependent manner. Moreover, TMF reversed the effect of Aβ_25-35, which caused energy deprivation and apoptosis, by decreasing the ratio of Bax/Bcl-x_L and reducing mitochondrial membrane potential (Δψ_m), caspase-3 expression, apoptotic cells, and attenuating glucose transporter (Glut-3) expression. In addition, TMF protected against Aβ_25-35-induced cellular senescence by attenuating β-galactosidase, p-21 and p-53 expression and promoted the expression of Sirt-1 and p-Rb. In addition, the effects of TMF on Aβ_25-35 toxicity were related to the upregulation of phase II antioxidant and nuclear factor erythroid 2-related factor-2 (Nrf2) signaling, including superoxide dismutase (SOD), heme oxygenase (HO)-1, and nuclear translocation of Nrf2. Finally, we also found that TMF attenuated Aβ_25-35-reduced synaptic plasticity by increasing the expression of synaptophysin and PSD-95, which was correlated with a decrease in acetylcholine esterase (AChE). Importantly, we found that the protective effects of TMF on Aβ_25-35 were bidirectional, including marked inhibition of NADPH oxidase (NOX)-4 activity and partial activation of Sirt-1, which occurred prior to a reduction in the negative responses. Therefore, TMF may be useful for treating Aβ toxicity in AD.

β-Asarone Attenuates Aβ-Induced Neuronal Damage in PC12 Cells Overexpressing APPswe by Restoring Autophagic Flux

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by progressive memory damage and cognitive dysfunction. Studies have shown that defective autophagic flux is associated with neuronal dysfunction. Modulating autophagic activity represents a potential method of combating AD. In Chinese medicine, Acori Tatarinowii Rhizoma is used to treat dementia and amnesia. β-Asarone, an active component of this rhizome can protect PC12 cells from Aβ-induced injury and modulate expression of autophagy factors. However, its cytoprotective mechanisms have yet to be discerned. It is unclear whether β-asarone affects autophagic flux and, if it does, whether this effect can alleviate Aβ cell damage. In the present study, we constructed APPswe-overexpressing PC12 cell line as a cell model of Aβ-induced damage and assessed expression of autophagic flux-related proteins as well as the number and morphology of autophagosomes and autolysosomes. Our results show that β-asarone decreases the expression levels of Beclin-1, p62, LC3-Ⅱ, and Aβ_1-42. β-Asarone reduced the number of autophagosomes and increased the number of autolysosomes, as determined by confocal laser scanning microscopy and transmission electron microscopy. Our results suggest that β-asarone can protect PC12 cells from Aβ-induced damage by promoting autophagic flux, which may be achieved by enhancing autophagosome-lysosome fusion and/or lysosome function.

Protective Effects and Mechanism of Hyperoside in PC12 Cells Against Oxidative Stress Injury Induced by Hydrogen Peroxide

As the aging phenomenon continues to increase, the incidence of neurodegenerative diseases continues to increase annually. As one of the significant contributive factors of neurodegenerative diseases, oxidative stress damage has received extensive attention in recent years. Oxidative stress plays an important role in neuronal damage through various apoptotic mechanisms related to neurodegenerative diseases. The use of natural antioxidants to combat oxidative stress may be a useful approach in delaying disease progression. In this study, we explored the neuroprotective effect of hyperoside on rat pheochromoma (PC12) cells. Specifically, the antioxidant effect and mechanism of hyperoside in hydrogen peroxide (H2O2)-induced cellular cytotoxicity were investigated. Our results showed that hyperoside could significantly increase the survival rate of rat PC12 cells when exposed to H2O2. In addition, hyperoside regulated the expression of genes and proteins in the corresponding pathways by up-regulating the phosphatidylinositol-3-kinase (PI3K), protein kinase B (Akt), and light chain 3β (LC3B) pathways and down-regulating the nuclear factor-ᴋ-gene binding (NF-κB), Bcl2-associated X (Bax), cysteinyl aspartate specific proteinase 3 (Caspase 3), and P62 pathways, thereby inhibiting cell apoptosis. Therefore, hyperoside can effectively inhibit H2O2-induced oxidative stress damage by regulating inflammation, autophagy, and apoptosis-related pathways.

Andrographis paniculata (Burm. f.) Wall. ex Nees: An Updated Review of Phytochemistry, Antimicrobial Pharmacology, and Clinical Safety and Efficacy

Infectious disease (ID) is one of the top-most serious threats to human health globally, further aggravated by antimicrobial resistance and lack of novel immunization options. Andrographis paniculata (Burm. f.) Wall. ex Nees and its metabolites have been long used to treat IDs. Andrographolide, derived from A. paniculata, can inhibit invasive microbes virulence factors and regulate the host immunity. Controlled clinical trials revealed that A. paniculata treatment is safe and efficacious for acute respiratory tract infections like common cold and sinusitis. Hence, A. paniculata, mainly andrographolide, could be considered as an excellent candidate for antimicrobial drug development. Considering the importance, medicinal values, and significant role as antimicrobial agents, this study critically evaluated the antimicrobial therapeutic potency of A. paniculata and its metabolites, focusing on the mechanism of action in inhibiting invasive microbes and biofilm formation. A critical evaluation of the secondary metabolites with the aim of identifying pure compounds that possess antimicrobial functions has further added significant values to this study. Notwithstanding that A. paniculata is a promising source of antimicrobial agents and safe treatment for IDs, further empirical research is warranted.

Natural products as pharmacological modulators of mitochondrial dysfunctions for the treatments of Alzheimer's disease: A comprehensive review

Alzheimer's disease (AD) is the most common progressive neurodegenerative disorder characterized by neuronal loss and cognitive impairment that harshly affect the elderly individuals. Currently, the available anti-AD pharmacological approaches are purely symptomatic to alleviate AD symptoms, and the curative effects of novel anti-AD drugs focused on Aβ target are disappointing. Hence, there is a tremendous need to adjust AD therapeutic targets and discover novel anti-AD agents. In AD, mitochondrial dysfunction gradually triggers neuronal death from different aspects and worsens the occurrence and progress of AD. Consequently, it has been proposed that the intervention of impaired mitochondria represents an attractive breakthrough point for AD treatments. Due to chemical diversity, poly-pharmacological activities, few adverse effects and multiple targeting, natural products (NPs) have been identified as a valuable treasure for drug discovery and development. Multiple lines of studies have scientifically proven that NPs display ameliorative benefits in AD treatment in relation to mitochondrial dysfunction. This review surveys the complicated implications for mitochondrial dysregulation and AD, and then summarizes the potentials of NPs and their underlying molecular mechanisms against AD via reducing or improving mitochondrial dysfunction. It is expected that this work may open the window to speed up the development of innovative anti-AD drugs originated from NPs and improve upcoming AD therapeutics.

Novel target for treating Alzheimer's Diseases: Crosstalk between the Nrf2 pathway and autophagy

In mammals, the Keap1-Nrf2-ARE pathway (henceforth, "the Nrf2 pathway") and autophagy are major intracellular defence systems that combat oxidative damage and maintain homeostasis. p62/SQSTM1, a ubiquitin-binding autophagy receptor protein, links the Nrf2 pathway and autophagy. Phosphorylation of p62 dramatically enhances its affinity for Keap1, which induces Keap1 to release Nrf2, and the p62-Keap1 heterodimer recruits LC3 and mediates the permanent degradation of Keap1 in the selective autophagy pathway. Eventually, Nrf2 accumulates in the cytoplasm and then translocates into the nucleus to activate the transcription of downstream genes that encode antioxidant enzymes, which protect cells from oxidative damage. Since Nrf2 also upregulates the expression of the p62 gene, a p62-Keap1-Nrf2 positive feedback loop is created that further enhances the protective effect on cells. Studies have shown that the p62-activated noncanonical Nrf2 pathway is an important marker of neurodegenerative diseases. The p62-Keap1-Nrf2 positive feedback loop and the Nrf2 pathway are involved in eliminating the ROS and protein aggregates induced by AD. Therefore, maintaining the homeostasis of the p62-Keap1-Nrf2 positive feedback loop, which is a bridge between the Nrf2 pathway and autophagy, may be a potential target for the treatment of AD.

Nrf2: a dark horse in Alzheimer's disease treatment

Alzheimer's disease (AD), an age-dependent neurodegenerative disorder, is the main cause of dementia. Common hallmarks of AD include the amyloid β-peptide (Aβ) aggregation, high levels of hyperphosphorylated tau protein (p-tau) and failure in redox homeostasis. To date, all proposed drugs affecting Aβ and/or p-tau have been failed in clinical trials. A decline in the expression of the transcription factor Nrf2 (nuclear factor-erythroid 2-p45 derived factor 2) and its driven genes (NQO1, HO-1, and GCLC), and alteration of the Nrf2-related pathways have been observed in AD brains. Nrf2 plays a critical role in maintaining cellular redox homeostasis and regulating inflammation response. Nrf2 activation also provides cytoprotection against increasing pathologies including neurodegenerative diseases. These lines of evidence imply that Nrf2 activation may be a novel AD treatment option. Interestingly, recent studies have also demonstrated that Nrf2 interferes with several key pathogenic processes in AD including Aβ and p-tau pathways. The current review aims to provide insights into the role of Nrf2 in AD. Also, we discuss the progress and challenges regarding the Nrf2 activators for AD treatment.

Attenuation of Nrf2/Keap1/ARE in Alzheimer's Disease by Plant Secondary Metabolites: A Mechanistic Review

Alzheimer’s disease (AD) is a progressive neuronal/cognitional dysfunction, leading to disability and death. Despite advances in revealing the pathophysiological mechanisms behind AD, no effective treatment has yet been provided. It urges the need for finding novel multi-target agents in combating the complex dysregulated mechanisms in AD. Amongst the dysregulated pathophysiological pathways in AD, oxidative stress seems to play a critical role in the pathogenesis progression of AD, with a dominant role of nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein-1 (Keap1)/antioxidant responsive elements (ARE) pathway. In the present study, a comprehensive review was conducted using the existing electronic databases, including PubMed, Medline, Web of Science, and Scopus, as well as related articles in the field. Nrf2/Keap1/ARE has shown to be the upstream orchestrate of oxidative pathways, which also ameliorates various inflammatory and apoptotic pathways. So, developing multi-target agents with higher efficacy and lower side effects could pave the road in the prevention/management of AD. The plant kingdom is now a great source of natural secondary metabolites in targeting Nrf2/Keap1/ARE. Among natural entities, phenolic compounds, alkaloids, terpene/terpenoids, carotenoids, sulfur-compounds, as well as some other miscellaneous plant-derived compounds have shown promising future accordingly. Prevailing evidence has shown that activating Nrf2/ARE and downstream antioxidant enzymes, as well as inhibiting Keap1 could play hopeful roles in overcoming AD. The current review highlights the neuroprotective effects of plant secondary metabolites through targeting Nrf2/Keap1/ARE and downstream interconnected mediators in combating AD.

Wnt Signaling Pathway Dysregulation in the Aging Brain: Lessons From the Octodon degus

Wnt signaling constitutes a fundamental cellular and molecular pathway, necessary from proper embryogenesis to function-maintenance of fully developed complex organisms. In this regard, Wnt pathway plays a crucial role in both the development of the central nervous system and in maintaining the structure and function of the neuronal circuits, and it has been suggested that its dysregulation is critical in the onset of several pathologies including cancer and neurodegenerative disorders, such as Alzheimer's disease (AD). Due to its relevance in the maintenance of the neuronal activity and its involvement in the outbreak of devastating diseases, we explored the age-related changes in the expression of Wnt key components in the cortex and hippocampus of 7 to 72-months-old Octodon degus (O. degus), a Chilean long-living endemic rodent that has been proposed and used as a natural model for AD. We found a down-regulation in the expression of different Wnt ligands (Wnt3a, Wnt7a, and Wnt5a), as well as in the Wnt co-receptor LRP6. We also observed an increase in the activity of GSK-3β related to the down-regulation of Wnt activity, a fact that was confirmed by a decreased expression of Wnt target genes. Relevantly, an important increase was found in secreted endogenous Wnt inhibitors, including the secreted-frizzled-related protein 1 and 2 (SFRP-1 and SFRP-2) and Dickkopf-1 (Dkk-1), all them antagonists at the cell surface. Furthermore, treatment with Andrographolide, a labdane diterpene obtained from Andrographis paniculata, prevents Wnt signaling loss in aging degus. Taken together, these results suggest that during the aging process Wnt signaling activity decreases in the brain of O. degus.

Andrographis Paniculata and Its Bioactive Diterpenoids Protect Dermal Fibroblasts Against Inflammation and Oxidative Stress

Andrographis paniculata (Burm.f.) has long been used in ayurvedic medicine through its anti-inflammatory properties. However, its protective effect of skin aging has not been studied in vitro. This study aimed to investigate the anti-aging effects of methanolic extract (ME), andrographolide (ANDRO), neoandrographolide (NEO), 14-deoxyandrographolide (14DAP) and 14-deoxy-11,12-didehydroandrographolide (14DAP11-12) on human dermal fibroblasts (HDFa) under pro-oxidant or pro-inflammatory condition. The in vitro anti-aging capacity of ME, ANDRO, NEO, 14DAP, and 14DAP11-12 (1, 2.5 and 5 µg/mL) was performed in HDFa. Oxidative stress and inflammation were induced by hydrogen peroxide and lipopolysaccharide/TNF-α, respectively. Reactive oxygen species (ROS) production was measured by the fluorescence of DCF-DA probe and cytokines were quantified by ELISA (IL6 and IL8) or RTqPCR (TNF-α). Procollagen type I production was determined by an ELISA. Our results showed a decrease in ROS production with ME and 14DAP at 5 µg/mL and 1 µg/mL, respectively. Furthermore, IL-6 production and TNF-α expression decreased under ANDRO and ME at 5 µg/mL. Our data indicated that ME and 14DAP protect from oxidative stress. Additionally, ME and ANDRO decreased an inflammation marker, IL-6. This suggests their potential natural treatment against skin damage. Hence, their applications could be of interest in cosmetics for preventing skin ageing.

Traditional Chinese Medicine: Role in Reducing β-Amyloid, Apoptosis, Autophagy, Neuroinflammation, Oxidative Stress, and Mitochondrial Dysfunction of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive age-related neurodegenerative disease characterized by memory loss and cognitive impairment. The major characteristics of AD are amyloid β plaques, apoptosis, autophagy dysfunction, neuroinflammation, oxidative stress, and mitochondrial dysfunction. These are mostly used as the significant indicators for selecting the effects of potential drugs. It is imperative to explain AD pathogenesis and realize productive treatments. Although the currently used chemical drugs for clinical applications of AD are effective in managing the symptoms, they are inadequate to achieve anticipated preventive or therapeutic outcomes. There are new strategies for treating AD. Traditional Chinese Medicine (TCM) has accumulated thousands of years of experience in treating dementia. Nowadays, numerous modern pharmacological studies have verified the efficacy of many bioactive ingredients isolated from TCM for AD treatment. In this review, representative TCM for the treatment of AD are discussed, and among these herbal medicines, the Lamiaceae family accounts for the highest proportion. It is concluded that monomers and extracts from TCM have potential therapeutic effect for AD treatment.

A network-based analysis of key pharmacological pathways of Andrographis paniculata acting on Alzheimer's disease and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Andrographis paniculata (AP) is a native plant with anti-inflammatory and antioxidant properties and used as an official herbal medicine. Recently more and more researches have indicated that AP shows pharmacological effects on Alzheimer's disease (AD) but its mechanism is unclear.

AIMS OF THE STUDY

Network pharmacology approach combined with experimental validation was developed to reveal the underlying molecular mechanisms of AP in treating AD.

MATERIALS AND METHODS

The compounds of AP from TCM database, the AD-related targets from disease database and the targets corresponding to compounds from swissTargetPrediction were collected. Then DAVID database was used for annotation and enrichment pathways, meanwhile the compound-target, protein-protein interaction from String database and compound-target-pathway network was constructed, molecular modeling was performed using Sybyl-x. Okadaic acid (OKA)-induced cytotoxicity model in PC12 cells was established to verify the mechanism of AP and the key proteins were detected by western blotting.

RESULTS

28 AP components were identified after ADME filter analysis and 52 targets were gained via mapping predicted targets into AD-related proteins. In addition, after multiple network analysis, the 22 hub target genes were enriched onto pathways involved in AD, such as neuroactive ligand-receptor interaction, serotonergic synapse, Alzheimer's disease, PI3K-Akt and NF-kB signaling pathway. Interestingly, molecular docking simulation revealed that the targets including PTGS2, BACE1, GSK3B and IKBKB had good ability to combine with AP components. Experimental validation in an in vitro system proved that AP treatment obviously increased in levels inactive of p-GSK3β (P < 0.05) and decreased in levels of BACE (P < 0.05), PTGS2 (namely COX2, P < 0.05) and NF-kB protein (P < 0.05) compare with OKA treated group.

CONCLUSION

Our data provided convincing evidence that the neuroprotective effects of AP might be partially related to their regulation of the APP-BACE1-GSK3B signal axis and inflammation, which should be the focus of study in this field in the future.

Neuroprotection by Walnut-Derived Peptides through Autophagy Promotion via Akt/mTOR Signaling Pathway against Oxidative Stress in PC12 Cells

Natural-derived peptides are effective substances in attenuating oxidative stress. However, their specific mechanisms have not been fully elucidated, especially in peptide-mediated autophagy. In the present study, TWLPLPR, YVLLPSPK, and KVPPLLY, novel peptides from Juglans mandshurica Maxim, prevented reactive oxygen species (ROS) production, elevated glutathione peroxidase (GSH-Px) activity and adenosine 5'-triphosphate (ATP) levels, and ameliorated apoptosis in Aβ_25-35 (at a concentration of 50 μM for 24 h)-induced PC12 cells (P < 0.01). Both western blot and immunofluorescence analysis illustrated that the peptides regulated Akt/mTOR signaling through p-Akt (Ser473) and p-mTOR (S2481) and promoted autophagy by increasing the levels of LC3-II/LC3-I and Beclin-1 while lowering p62 expression (P < 0.01). The autophagy inhibitor (3-methyladenine, 3-MA) and inducer (rapamycin, RAPA) were combined used to confirm the contribution of peptide-regulated autophagy in antioxidative effects. Moreover, the peptides increased the levels of LAMP1, LAMP2, and Cathepsin D (P < 0.05) and promoted the fusion with lysosomes to form autolysosomes, accelerating ROS removal. These data suggested that walnut-derived peptides regulated oxidative stress by promoting autophagy in the Aβ_25-35-induced PC12 cells.

Exploring the bi-directional relationship between autophagy and Alzheimer's disease

Alzheimer's disease (AD) is characterized by β-amyloid (Aβ) deposition and Tau phosphorylation, in which its pathogenesis has not been cleared so far. The metabolism of Aβ and Tau is critically affected by the autophagy. Abnormal autophagy is thought to be involved in the pathogenesis of AD, regulating autophagy may become a new strategy for AD treatment. In the early stage of AD, the presence of Aβ and Tau can induce autophagy to promote their clearance by means of mTOR-dependent and independent manners. As AD progress, the autophagy goes aberrant. As a result, Aβ and Tau generate continually, which aggravates both autophagy dysfunction and AD. Besides, several related genes and proteins of AD can also adapt autophagy to make an effect on the AD development. There seems to be a bi-directional relationship between AD pathology and autophagy. At present, this article reviews this relationship from these aspects: (a) the signaling pathways of regulating autophagy; (b) the relationships between the autophagy and the processing of Aβ; (c) Aβ and Tau cause autophagy dysfunction; (d) normal autophagy promotes the clearance of Aβ and Tau; (e) the relationships between the autophagy and both genes and proteins related to AD: TFEB, miRNAs, Beclin-1, Presenilin, and Nrf2; and (f) the small molecules regulating autophagy on AD therapy. All of the above may help to further elucidate the pathogenesis of AD and provide a theoretical basis for clinical treatment of AD.

Andrographolide Protects Against Adverse Cardiac Remodeling After Myocardial Infarction through Enhancing Nrf2 Signaling Pathway

Adverse cardiac remodeling after myocardial infarction (MI) is associated with extremely high mortality rates worldwide. Although optimized medical therapy, Preservation of lusitropic and inotropic function and protection against adverse remodeling in ventricular structure remain relatively frequent. This study demonstrated that Andrographolide (Andr) significantly ameliorated adverse cardiac remodeling induced by myocardial infarction and improves contractile function in mice with LAD ligation compared with the control group. Briefly, Andr markedly attenuated cardiac fibrosis and relieved inflammation after myocardial infarction. Specifically, Andr significantly blocked oxidative stress and the nuclear translocation of p-P65 following myocardial infarction. At the mechanistic level, antioxidant effect of Andr was achieved through strengthening antioxidative stress capacity and attributed to the activation of Nrf2/HO-1 Signaling. Consistently, H9C2 administrated with Andr showed a decreased oxidative stress caused by hypoxia precondition, but treatment with specific Nrf2 inhibitor (ML385) or the silence of Nrf2 blunted the activation of Nrf2/HO-1 Signaling and removed the protective effects of Andr in vitro. Thus, we suggest that Andr alleviates adverse cardiac remodeling following myocardial infarction through enhancing Nrf2 signaling pathway.

Andrographolide, a Natural Antioxidant: An Update

Traditionally, Andrographis paniculata has been used as an herbal remedy for lung infection treatments. Its leaves contain a diterpenoid labdane called andrographolide responsible for a wide range of biological activities such as antioxidant, anti-inflammatory, and anti-cancer properties. This manuscript is a brief review of the antioxidant mechanisms and the regulation of the Nrf2 (nuclear factor (erythroid-derived 2)-like 2) signaling pathway by andrographolide.

Andrographolide enhances hippocampal BDNF signaling and suppresses neuronal apoptosis, astroglial activation, neuroinflammation, and spatial memory deficits in a rat model of chronic cerebral hypoperfusion

Andrographolide is a medical herbal compound with documented anti-inflammatory activity and therapeutic efficacy in animal models of Alzheimer's disease, traumatic brain injury, and ischemic stroke. The present study examined the potential therapeutic effects of andrographolide on chronic cerebral hypoperfusion (CCH)-induced hippocampal neuronal damage and cognitive dysfunction. A CCH model was established in male Sprague Dawley (SD) rats using 2-vessel occlusion (2VO). After 4 weeks of CCH, spatial learning and memory were assessed in the Morris water maze and structural damage to the hippocampus by hematoxylin and eosin (HE) staining. Astrocyte activation was examined by immunohistochemical staining and Western blotting for glial fibrillary acid protein (GFAP), while expression levels of the pro-inflammatory cytokine-tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β), the apoptosis effector cysteinyl aspartate specific proteinase-3 (caspase-3), and the neuroprotectant brain-derived neurotrophic factor (BDNF) and the TrkB receptor were estimated by Western blotting. After 4 weeks of CCH, the hippocampus of 2VO rats exhibited marked neurodegeneration as well as elevated GFAP, TNF-α, IL-1β, and caspase-3 compared to Sham controls. In addition, spatial learning was impaired compared to Sham controls. Andrographolide treatment during CCH suppressed astrocyte activation as evidenced by reduced GFAP expression, enhanced expression of BDNF and TrkB, improved impaired spatial learning and memory, and reversed upregulated TNF-α, IL-1β, and caspase-3 expression. These results reveal a potential neuroprotective effect of andrographolide on hippocampal neuronal damage and cognitive impairment from CCH due to suppression of astrocyte activation and enhancement of BDNF-TrkB signaling.