Amyloid beta induces neuronal cell death through ROS-mediated ASK1 activation

High-Resolution Digital Panorama of Multiple Structures in Whole Brain of Alzheimer's Disease Mice

Simultaneously visualizing Amyloid-β (Aβ) plaque with its surrounding brain structures at the subcellular level in the intact brain is essential for understanding the complex pathology of Alzheimer's disease, but is still rarely achieved due to the technical limitations. Combining the micro-optical sectioning tomography (MOST) system, whole-brain Nissl staining, and customized image processing workflow, we generated a whole-brain panorama of Alzheimer's disease mice without specific labeling. The workflow employed the steps that include virtual channel splitting, feature enhancement, iso-surface rendering, direct volume rendering, and feature fusion to extract and reconstruct the different signals with distinct gray values and morphologies. Taking advantage of this workflow, we found that the denser-distribution areas of Aβ plaques appeared with relatively more somata and smaller vessels, but show a dissimilar distributing pattern with nerve tracts. In addition, the entorhinal cortex and adjacent subiculum regions present the highest density and biggest diameter of plaques. The neuronal processes in the vicinity of these Aβ plaques showed significant structural alternation such as bending or abrupt branch ending. The capillaries inside or adjacent to the plaques were observed with abundant distorted micro-vessels and abrupt ending. Depicting Aβ plaques, somata, nerve processes and tracts, and blood vessels simultaneously, this panorama enables us for the first time, to analyze how the Aβ plaques interact with capillaries, somata, and processes at a submicron resolution of 3D whole-brain scale, which reveals potential pathological effects of Aβ plaques from a new cross-scale view. Our approach opens a door to routine systematic studies of complex interactions among brain components in mouse models of Alzheimer's disease.

Intrinsic disorder in proteins associated with oxidative stress-induced JNK signaling

The c-Jun N-terminal kinase (JNK) signaling cascade is a mitogen-activated protein kinase (MAPK) signaling pathway that can be activated in response to a wide range of environmental stimuli. Based on the type, degree, and duration of the stimulus, the JNK signaling cascade dictates the fate of the cell by influencing gene expression through its substrate transcription factors. Oxidative stress is a result of a disturbance in the pro-oxidant/antioxidant homeostasis of the cell and is associated with a large number of diseases, such as neurodegenerative disorders, cancer, diabetes, cardiovascular diseases, and disorders of the immune system, where it activates the JNK signaling pathway. Among different biological roles ascribed to the intrinsically disordered proteins (IDPs) and hybrid proteins containing ordered domains and intrinsically disordered protein regions (IDPRs) are signaling hub functions, as intrinsic disorder allows proteins to undertake multiple interactions, each with a different consequence. In order to ensure precise signaling, the cellular abundance of IDPs is highly regulated, and mutations or changes in abundance of IDPs/IDPRs are often associated with disease. In this study, we have used a combination of six disorder predictors to evaluate the presence of intrinsic disorder in proteins of the oxidative stress-induced JNK signaling cascade, and as per our findings, none of the 18 proteins involved in this pathway are ordered. The highest level of intrinsic disorder was observed in the scaffold proteins, JIP1, JIP2, JIP3; dual specificity phosphatases, MKP5, MKP7; 14-3-3ζ and transcription factor c-Jun. The MAP3Ks, MAP2Ks, MAPKs, TRAFs, and thioredoxin were the proteins that were predicted to be moderately disordered. Furthermore, to characterize the predicted IDPs/IDPRs in the proteins of the JNK signaling cascade, we identified the molecular recognition features (MoRFs), posttranslational modification (PTM) sites, and short linear motifs (SLiMs) associated with the disordered regions. These findings will serve as a foundation for experimental characterization of disordered regions in these proteins, which represents a crucial step for a better understanding of the roles of IDPRs in diseases associated with this important pathway.

Anti-Amyloidogenic and Fibril-Disaggregating Potency of the Levodopa-Functionalized Gold Nanoroses as Exemplified in a Diphenylalanine-Based Amyloid Model

The phenomenon of proteins/peptide assembly into amyloid fibrils is associated with various neurodegenerative and age-related human disorders. Inhibition of the aggregation behavior of amyloidogenic peptides/proteins or disruption of the pre-formed aggregates is a viable therapeutic option to control the progression of various protein aggregation-related disorders such as Alzheimer's disease (AD). In the current work, we investigated both the amyloid inhibition and disaggregation proclivity of levodopa-functionalized gold nanoroses (GNRs) against various peptide-based amyloid models, including the amyloid beta peptide [Aβ (1-42) and Aβ (1-40)] and the dipeptide phenylalanine-phenylalanine (FF). Our results depicted the anti-aggregation behavior of the GNR toward FF and both forms of Aβ-derived fibrils. The peptides demonstrated a variation in their fiber-like morphology and a decline in thioflavin T fluorescence after being co-incubated with the GNR. We further demonstrated the neuroprotective effects of the GNR in neuroblastoma cells against FF and Aβ (1-42) fiber-induced toxicity, exemplified both in terms of regaining cellular viability and reducing production of reactive oxygen species. Overall, these findings support the potency of the GNR as a promising platform for combating AD.

Paeoniflorin inhibits proliferation and promotes autophagy and apoptosis of sweat gland cells

Axillary bromhidrosis is sweat excreted by apocrine glands in the armpits, mouth corners and other parts. The clinical manifestation includes excessive sweating and heavy odor, leading to the growth of bacteria and skin disease. The present study investigated the mechanism underlying the effect of paeoniflorin (PF) in the treatment of bromhidrosis. PF was injected into the feet of rats, and the foot skin was dissected for histological analysis. Primary human sweat gland cells (hSGCs) were isolated from patients with bromhidrosis. After 24 h treatment with PF or 3-methyladenine, the production of reactive oxygen species (ROS), autophagy, apoptosis, proliferation and cell cycle distribution were determined. PF induced nuclear pyknosis in rat SGCs. In vitro PF treatment inhibited cell proliferation with a 25% inhibitory concentration of 9.530 µM. Treatment with 9.530 µM PF for 24 h significantly increased apoptosis, ROS production and autophagy in hSGCs. PF promoted LC3B and Beclin 1 expression, but inhibited p62, phosphorylated (p)-PI3K and p-Akt expression. 3-methyladenine treatment reversed PF-induced changes in hSGCs. PF-induced inhibition of hSGC proliferation was associated with ROS production, apoptosis, and autophagy. These findings provide a basis for treating bromhidrosis.

Structural Insights Support Targeting ASK1 Kinase for Therapeutic Interventions

Apoptosis signal-regulating kinase (ASK) 1, a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family, modulates diverse responses to oxidative and endoplasmic reticulum (ER) stress and calcium influx. As a crucial cellular stress sensor, ASK1 activates c-Jun N-terminal kinases (JNKs) and p38 MAPKs. Their excessive and sustained activation leads to cell death, inflammation and fibrosis in various tissues and is implicated in the development of many neurological disorders, such as Alzheimer’s, Parkinson’s and Huntington disease and amyotrophic lateral sclerosis, in addition to cardiovascular diseases, diabetes and cancer. However, currently available inhibitors of JNK and p38 kinases either lack efficacy or have undesirable side effects. Therefore, targeted inhibition of their upstream activator, ASK1, stands out as a promising therapeutic strategy for treating such severe pathological conditions. This review summarizes recent structural findings on ASK1 regulation and its role in various diseases, highlighting prospects for ASK1 inhibition in the treatment of these pathologies.

High-Phytate Diets Increase Amyloid β Deposition and Apoptotic Neuronal Cell Death in a Rat Model

Amyloid-β (Aβ) accumulation in the hippocampus is an essential event in the pathogenesis of Alzheimer's disease. Insoluble Aβ is formed through the sequential proteolytic hydrolysis of the Aβ precursor protein, which is cleaved by proteolytic secretases. However, the pathophysiological mechanisms of Aβ accumulation remain elusive. Here, we report that rats fed high-phytate diets showed Aβ accumulation and increased apoptotic neuronal cell death in the hippocampus through the activation of the amyloidogenic pathway in the hippocampus. Immunoblotting and immunohistochemical analyses confirmed that the overexpression of BACE1 β-secretase, a critical enzyme for Aβ generation, exacerbated the hippocampal Aβ accumulation in rats fed high-phytate diets. Moreover, we identified that parathyroid hormone, a physiological hormone responding to the phytate-mediated dysregulation of calcium and phosphate homeostasis, plays an essential role in the transcriptional activation of the Aβ precursor protein and BACE1 through the vitamin D receptor and retinoid X receptor axis. Thus, our findings suggest that phytate-mediated dysregulation of calcium and phosphate is a substantial risk factor for elevated Aβ accumulation and apoptotic neuronal cell death in rats.

Specific Activation of the CD271 Intracellular Domain in Combination with Chemotherapy or Targeted Therapy Inhibits Melanoma Progression

CD271 (NGFR) is a neurotrophin receptor that belongs to the tumor necrosis receptor (TNFR) family. Upon ligand binding, CD271 can mediate either survival or cell death. Although the role of CD271 as a marker of tumor-initiating cells is still a matter of debate, its role in melanoma progression has been well documented. Moreover, CD271 has been shown to be upregulated after exposure to both chemotherapy and targeted therapy. In this study, we demonstrate that activation of CD271 by a short β-amyloid-derived peptide (Aβ^(25-35)) in combination with either chemotherapy or MAPK inhibitors induces apoptosis in 2D and 3D cultures of eight melanoma cell lines. This combinatorial treatment significantly reduced metastasis in a zebrafish xenograft model and led to significantly decreased tumor volume in mice. Administration of Aβ^(25-35) in ex vivo tumors from immunotherapy- and targeted therapy-resistant patients significantly reduced proliferation of melanoma cells, showing that activation of CD271 can overcome drug resistance. Aβ^(25-35) was specific to CD271-expressing cells and induced CD271 cleavage and phosphorylation of JNK (pJNK). The direct protein-protein interaction of pJNK with CD271 led to PARP1 cleavage, p53 and caspase activation, and pJNK-dependent cell death. Aβ^(25-35) also mediated mitochondrial reactive oxygen species (mROS) accumulation, which induced CD271 overexpression. Finally, CD271 upregulation inhibited mROS production, revealing the presence of a negative feedback loop in mROS regulation. These results indicate that targeting CD271 can activate cell death pathways to inhibit melanoma progression and potentially overcome resistance to targeted therapy. SIGNIFICANCE: The discovery of a means to specifically activate the CD271 death domain reveals unknown pathways mediated by the receptor and highlights new treatment possibilities for melanoma.

3D hydrogel models of the neurovascular unit to investigate blood-brain barrier dysfunction

The neurovascular unit (NVU), consisting of neurons, glial cells, vascular cells (endothelial cells, pericytes and vascular smooth muscle cells (VSMCs)) together with the surrounding extracellular matrix (ECM), is an important interface between the peripheral blood and the brain parenchyma. Disruption of the NVU impacts on blood-brain barrier (BBB) regulation and underlies the development and pathology of multiple neurological disorders, including stroke and Alzheimer's disease (AD). The ability to differentiate induced pluripotent stem cells (iPSCs) into the different cell types of the NVU and incorporate them into physical models provides a reverse engineering approach to generate human NVU models to study BBB function. To recapitulate the in vivo situation such NVU models must also incorporate the ECM to provide a 3D environment with appropriate mechanical and biochemical cues for the cells of the NVU. In this review, we provide an overview of the cells of the NVU and the surrounding ECM, before discussing the characteristics (stiffness, functionality and porosity) required of hydrogels to mimic the ECM when incorporated into in vitro NVU models. We summarise the approaches available to measure BBB functionality and present the techniques in use to develop robust and translatable models of the NVU, including transwell models, hydrogel models, 3D-bioprinting, microfluidic models and organoids. The incorporation of iPSCs either without or with disease-specific genetic mutations into these NVU models provides a platform in which to study normal and disease mechanisms, test BBB permeability to drugs, screen for new therapeutic targets and drugs or to design cell-based therapies.

Amyloid peptide exerts a rapid induction of Dicer1 protein in neuron via reducing phosphorylation

A growing number of evidence suggests that altered microRNA network in the brain contributes to the risk of Alzheimer's disease(AD). Dicer1 is a type III riboendonuclease which cleaves pre-microRNA into functional microRNA. Reduction of Dicer1 or Dicer1 mutation has been involved in cancer, aging or age-related macular degeneration. Recently, we found a possible link between Dicer1 and AD. In particular, Dicer1 protein and Dicer1 mRNA is reduced in the hippocampus and the cortex of an animal model of AD and exposure to Aβ42 oligomer(AβO) longer than 6 h reduces the transcription of Dicer1 gene in neuron, via depletion of NF-E2-related factor-2. In this study, exposure to AβO at shorter time increased Dicer1 protein in neuron in a dose-dependent mode; but the mRNA level remained unaltered. Under this treatment regime,AβO reduced phosphorylation level of Dicer1 and of its binding partner, transactivation response element RNA-binding protein(TRBP). Addition of a JNK inhibitor,SP600125, or an ERK inhibitor,U0126, further increased Dicer1 protein compared to Aβo treatment alone, with simultaneaous reduction of phospho-Dicer1, but with different effects on phospho-TRBP. Finally, an inhibitor of calcineurin,FK506, further increased Dicer1 protein compared to Aβo treatment alone. Thus, phosphorylation of Dicer1 and TRBP was determined by mitogen activated protein kinases JNK,ERK, and protein phosphatase 2B(calcineurin) which together determined Dicer1 stability. In summary, reduced phosphorylation of Dicer1 accounted for the rapid induction of Dicer1 by AβO. This study highlights a novel way by which AβO regulates Dicer1.

The selective degradation of sirtuins via macroautophagy in the MPP+ model of Parkinson's disease is promoted by conserved oxidation sites

The sirtuin (SIRT) protein family has been of major research interest over the last decades because of their involvement in aging, cancer, and cell death. SIRTs have been implicated in gene and metabolic regulation through their capacity to remove acyl groups from lysine residues in proteins in an NAD⁺-dependent manner, which may alter individual protein properties as well as the histone–DNA interaction. Since SIRTs regulate a wide range of different signaling cascades, a fine-tuned homeostasis of these proteins is imperative to guarantee the function and survival of the cell. So far, however, how exactly this homeostasis is established has remained unknown. Here, we provide evidence that neuronal SIRT degradation in Parkinson’s disease (PD) models is executed by autophagy rather than the proteasome. In neuronal Lund human mesencephalic (LUHMES) cells, all seven SIRTs were substrates for autophagy and showed an accelerated autophagy-dependent degradation upon 1-methyl-4-phenylpyridinium (MPP⁺) mediated oxidative insults in vitro, whereas the proteasome did not contribute to the removal of oxidized SIRTs. Through blockade of endogenous H₂O₂ generation and supplementation with the selective radical scavenger phenothiazine (PHT), we could identify H₂O₂-derived species as the responsible SIRT-oxidizing agents. Analysis of all human SIRTs suggested a conserved regulatory motif based on cysteine oxidation, which may have triggered their degradation via autophagy. High amounts of H₂O₂, however, rapidly carbonylated selectively SIRT2, SIRT6, and SIRT7, which were found to accumulate carbonylation-prone amino acids. Our data may help in finding new strategies to maintain and modify SIRT bioavailability in neurodegenerative disorders.

Protective effect of sargahydroquinoic acid against Aβ25-35-evoked damage via PI3K/Akt mediated Nrf2 antioxidant defense system

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by memory loss and cognitive impairment. β-Amyloid (Aβ) is widely accepted as the main neurotoxin that triggers mitochondrial-associated oxidative stress, leading to neuronal death in AD. Following our preliminary research on the neuroprotective effects of the brown alga Sargassum serratifolium, its major compounds, including sargaquinoic acid, sargahydroquinoic acid (SHQA), and sargachromenol, were investigated to elucidate the antioxidant and anti-apoptotic properties of Aβ_25-35-stimulated PC12 cells. SHQA exhibited the most potent effect on Aβ-induced mitochondrial-associated oxidative stress and apoptosis. In addition, the compound enhanced the expression and translocation of nuclear factor-E2-related factor 2 (Nrf2), while reducing the expression of cytoplasmic Kelch-like ECH-associated protein 1 (Keap1). Furthermore, the compound upregulated the expression of Nrf2-regulated antioxidant enzymes, including HO-1, NQO1, GCLc, GCLm, and TrxR1. Co-treatment with SHQA and LY294002, a specific PI3K inhibitor, inhibited nuclear Nrf2 expression and Akt phosphorylation, demonstrating that SHQA-mediated Nrf2 activation was directly associated with the PI3K/Akt signaling pathway. Mechanistic studies indicate that activation of the PI3K/Akt/Nrf2 pathway is the molecular basis for the neuroprotective effects of SHQA. In silico docking simulation revealed that SHQA established specific interactions with the key amino acid residues of PI3K, Akt, and Nrf2-Keap1 via hydrogen bonding and van der Waals interactions, which may affect the biological capacities of target markers. Overall, this is the first report of this novel mechanism of SHQA as a Nrf2 activator against Aβ-mediated oxidative damage, suggesting that the compound might be a potential agent for the prevention of AD.

Low-grade peripheral inflammation affects brain pathology in the AppNL-G-Fmouse model of Alzheimer's disease

Alzheimer’s disease (AD) is a chronic neurodegenerative disease characterized by the accumulation of amyloid β (Aβ) and neurofibrillary tangles. The last decade, it became increasingly clear that neuroinflammation plays a key role in both the initiation and progression of AD. Moreover, also the presence of peripheral inflammation has been extensively documented. However, it is still ambiguous whether this observed inflammation is cause or consequence of AD pathogenesis. Recently, this has been studied using amyloid precursor protein (APP) overexpression mouse models of AD. However, the findings might be confounded by APP-overexpression artifacts. Here, we investigated the effect of low-grade peripheral inflammation in the APP knock-in (App^NL-G-F) mouse model. This revealed that low-grade peripheral inflammation affects (1) microglia characteristics, (2) blood-cerebrospinal fluid barrier integrity, (3) peripheral immune cell infiltration and (4) Aβ deposition in the brain. Next, we identified mechanisms that might cause this effect on AD pathology, more precisely Aβ efflux, persistent microglial activation and insufficient Aβ clearance, neuronal dysfunction and promotion of Aβ aggregation. Our results further strengthen the believe that even low-grade peripheral inflammation has detrimental effects on AD progression and may further reinforce the idea to modulate peripheral inflammation as a therapeutic strategy for AD.

The NLRP3 Inflammasome in the Pathogenesis and Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia. Although AD is one of the most socioeconomically devastating diseases confronting humanity, no "curative" disease modifying drug has been identified. Recent decades have witnessed repeated failures of drug trials and have called into question the utility of the amyloid hypothesis approach to AD therapeutics design. Accordingly, new neurochemical processes are being evaluated and explored as sources of alternative druggable targets. Among these newly identified targets, neuroinflammation is emerging as a front-runner, and within the realm of neuroinflammation, the inflammasome, particularly the NLRP3 complex, is garnering focussed attention. This review summarizes current data and approaches to understanding the role of the NLRP3 inflammasome in neuroinflammation and AD, and systematically identifies and evaluates multiple targets within the NLRP3 inflammasome cascade as putative drug targets.

Inhibition of sEH via stabilizing the level of EETs alleviated Alzheimer's disease through GSK3β signaling pathway

Alzheimer's disease (AD) is the most common neurodegenerative disorder characterized by dementia. Inhibition of soluble epoxide hydrolase (sEH) regulates inflammation involving in central nervous system (CNS) diseases. However, the exactly mechanism of sEH in AD is still unclear. In this study, we evaluated the vital role of sEH in amyloid beta (Aβ)-induced AD mice, and revealed a possible molecular mechanism for inhibition of sEH in the treatment of AD. The results showed that the sEH expression and activity were remarkably increased in the hippocampus of Aβ-induced AD mice. Chemical inhibition of sEH by TPPU, a selective sEH inhibitor, alleviated spatial learning and memory deficits, and elevated levels of neurotransmitters in Aβ-induced AD mice. Furthermore, inhibition of sEH could ameliorate neuroinflammation, neuronal death, and oxidative stress via stabilizing the in vivo level of epoxyeicosatrienoic acids (EETs), especially 8,9-EET and 14,15-EET, further resulting in the anti-AD effect through the regulation of GSK3β-mediated NF-κB, p53, and Nrf2 signaling pathways. These findings revealed the underlying mechanism of sEH as a potential therapeutic target in treatment of AD.

Protein misfolding, ER Stress and Chaperones: An approach to develop chaperone-based therapeutics for Alzheimer's Disease

Alzheimer's disease (AD) is a heterogeneous neurodegenerative disorder with complex etiology that eventually leads to dementia. The main culprit of AD is the extracellular deposition of β-amyloid (Aβ) and intracellular neurofibrillary tangles. The protein conformational change and protein misfolding are the key events of AD pathophysiology, therefore endoplasmic reticulum (ER) stress is an apparent consequence. ER, stress-induced unfolded protein response (UPR) mediators (viz. PERK, IRE1, and ATF6) have been reported widely in the AD brain. Considering these factors, preventing proteins misfolding or aggregation of tau or amyloidogenic proteins appears to be the best approach to halt its pathogenesis. Therefore, therapies through chemical and pharmacological chaperones came to light as an alternative for the treatment of AD. Diverse studies have demonstrated 4-phenylbutyric acid (4-PBA) as a potential therapeutic agent in AD. The current review outlined the mechanism of protein misfolding, different etiological features behind the progression of AD, the significance of ER stress in AD, and the potential therapeutic role of different chaperones to counter AD. The study also highlights the gaps in current knowledge of the chaperones-based therapeutic approach and the possibility of developing chaperones as a potential therapeutic agent for AD treatment.

Molecular functions of ASK family in diseases caused by stress-induced inflammation and apoptosis

VCells are constantly exposed to various types of stress, and disruption of the proper response leads to a variety of diseases. Among them, inflammation and apoptosis are important examples of critical responses and should be tightly regulated, as inappropriate control of these responses is detrimental to the organism. In several disease states, these responses are abnormally regulated, with adverse effects. Apoptosis signal-regulating kinase (ASK) family members are stress-responsive kinases that regulate inflammation and apoptosis after a variety of stimuli, such as oxidative stress and endoplasmic reticulum stress. In this review, we summarize recent reports on the ASK family in terms of their involvement in inflammatory diseases, focussing on upstream stimuli that regulate ASK family members.

Natural Phyto-Antioxidant Albumin Nanoagents to Treat Advanced Alzheimer's Disease

Phytotherapeutic approaches are of immense value in the treatment of advanced Alzheimer's disease (AD) because of their diverse biological components and potential multitarget mechanisms. In this study, quercetin, a natural neuroprotective flavonoid, was encapsulated in human serum albumin to obtain HSA@QC nanoparticles (HQ NPs) as a natural phyto-antioxidant albumin nanoagent for the treatment of advanced AD. HQ NPs showed excellent antioxidant effects and protected PC12 cells from H2O2-induced oxidative damage. The intranasal administration of HQ NPs in 11-month-old APP/PS1 mice, which represented advanced AD, effectively prevented the loss of body weight, increased survival rates, and significantly reduced oxidative stress, Aβ aggregation, neuronal apoptosis, and synaptic damage in the brain. It also ultimately reversed severely impaired cognitive function. In addition to their favorable anti-AD effects, HQ NPs exhibited excellent biosafety and biocompatibility owing to their natural composition and are expected to become an ideal choice for future drug development and clinical applications.

The Specific Connexin 43-Inhibiting Peptide Gap26 Improved Alveolar Development of Neonatal Rats With Hyperoxia Exposure

Bronchopulmonary dysplasia (BPD) is a common devastating pulmonary complication in preterm infants. Alveolar maldevelopment is the crucial pathological change of BPD highly associated with oxidative stress–mediated excessive apoptosis. Cellular injury can be propagated and amplified by gap junction (GJ)–mediated intercellular communication. Connexin 43 (Cx43) is the most ubiquitous and critical GJ protein. Gap26 is a specific Cx43 mimic peptide, playing as a Cx43-GJ inhibitor. We hypothesized that Cx43-GJ was involved in alveolar maldevelopment of BPD via amplifying oxidative stress signaling and inducing excessive apoptosis. Neonatal Sprague Dawley rats were kept in either normoxia (21% O₂) or hyperoxia (85% O₂) continuously from postnatal day (PN) 1 to 14 in the presence or absence of Gap26. Moreover, RLE-6TN cells (type II alveolar epithelial cells of rats) were cultured in vitro under normoxia (21% O₂) or hyperoxia (85% O₂). RLE-6TN cells were treated by N-acetyl cysteine (NAC) (a kind of reactive oxygen species (ROS) scavenger) or Gap26. Morphological properties of lung tissue are detected. Markers associated with Cx43 expression, ROS production, the activity of the ASK1-JNK/p38 signaling pathway, and apoptotic level are detected in vivo and in vitro, respectively. In vitro, the ability of GJ-mediated intercellular communication was examined by dye-coupling assay. In vitro, our results demonstrated ROS increased Cx43 expression and GJ-mediated intercellular communication and Gap26 treatment decreased ROS production, inhibited ASK1-JNK/p38 signaling, and decreased apoptosis. In vivo, we found that hyperoxia exposure resulted in increased ROS production and Cx43 expression, activated ASK1-JNK/p38 signaling, and induced excessive apoptosis. However, Gap26 treatment reversed these changes, thus improving alveolar development in neonatal rats with hyperoxia exposure. In summary, oxidative stress increased Cx43 expression and Cx43-GJ–mediated intercellular communication. And Cx43-GJ–mediated intercellular communication amplified oxidative stress signaling, inducing excessive apoptosis via the ASK1-JNK/p38 signaling pathway. The specific connexin 43–inhibiting peptide Gap26 was a novel therapeutic strategy to improve the alveolar development of BPD.

Gene Expression Profile in Different Age Groups and Its Association with Cognitive Function in Healthy Malay Adults in Malaysia

The mechanism of cognitive aging at the molecular level is complex and not well understood. Growing evidence suggests that cognitive differences might also be caused by ethnicity. Thus, this study aims to determine the gene expression changes associated with age-related cognitive decline among Malay adults in Malaysia. A cross-sectional study was conducted on 160 healthy Malay subjects, aged between 28 and 79, and recruited around Selangor and Klang Valley, Malaysia. Gene expression analysis was performed using a HumanHT-12v4.0 Expression BeadChip microarray kit. The top 20 differentially expressed genes at p < 0.05 and fold change (FC) = 1.2 showed that PAFAH1B3, HIST1H1E, KCNA3, TM7SF2, RGS1, and TGFBRAP1 were regulated with increased age. The gene set analysis suggests that the Malay adult's susceptibility to developing age-related cognitive decline might be due to the changes in gene expression patterns associated with inflammation, signal transduction, and metabolic pathway in the genetic network. It may, perhaps, have important implications for finding a biomarker for cognitive decline and offer molecular targets to achieve successful aging, mainly in the Malay population in Malaysia.

Mitochondrial dysfunction in Alzheimer's disease - a proteomics perspective

Mitochondrial dysfunction is involved in Alzheimer's disease (AD) pathogenesis. Mitochondria have their own genetic material; however, most of their proteins (∼99%) are synthesized as precursors on cytosolic ribosomes, and then imported into the mitochondria. Therefore, exploring proteome changes in these organelles can yield valuable information and shed light on the molecular mechanisms underlying mitochondrial dysfunction in AD. Here, we review AD-associated mitochondrial changes including the effects of amyloid beta and tau protein accumulation on the mitochondrial proteome. We also discuss the relationship of ApoE genetic polymorphism with mitochondrial changes, and present a meta-analysis of various differentially expressed proteins in the mitochondria in AD.Area covered: Proteomics studies and their contribution to our understanding of mitochondrial dysfunction in AD pathogenesis.Expert opinion: Proteomics has proven to be an efficient tool to uncover various aspects of this complex organelle, which will broaden our understanding of mitochondrial dysfunction in AD. Evidently, mitochondrial dysfunction is an early biochemical event that might play a central role in driving AD pathogenesis.

RIPK1 inhibitor ameliorates the MPP+/MPTP-induced Parkinson's disease through the ASK1/JNK signalling pathway

Receptor-interacting protein kinase 1 (RIPK1) is up-regulated in patients with neurodegenerative diseases. Our study aimed to explore the underlying mechanisms that involved in the neurotoxic function of RIPK1 in Parkinson's disease (PD). MPP+/MPTP-induced PD cellular and mice models were used in this study. The results showed that RIPK1 was high expressed and activated in MPP+-treated SH-SY5Y cells and MPTP-induced PD mice. Overexpression of RIPK1 facilitated cell apoptosis, necrosis, inflammation response, ROS production and mitochondrial dysfunction in MPP+- treated SH-SY5Y cells, while the RIPK1 inhibitor Nec-1s has an opposite effect. In addition, the Apoptosis-signaling kinase-1 (ASK1)/c-Jun N-terminal kinase (JNK) signalling pathway was activated during the overexpression of RIPK1, and inhibiting the ASK1/JNK signal by the ASK1 inhibitor partially reversed the decline of cell viability, the increase of cell apoptosis, necrosis and inflammation induced by RIPK1 overexpression in MPP+-treated SH-SY5Y cells. Further studies suggested that the inhibition of RIPK1 by Nec-1s largely alleviated the behavioural impairment in PD mice. Hence, our study indicated that the RIPK1 inhibitor Nec-1s has neuroprotective effects against PD through inactivating the ASK1/JNK signalling pathway.

FBXW11 deletion alleviates Alzheimer's disease by reducing neuroinflammation and amyloid-β plaque formation via repression of ASK1 signaling

Alzheimer's disease (AD) is a neurodegenerative disease with a complicated pathogenesis. F-box and WD-40 domain protein 11 (FBXW11), as a component of the SCF (Skp1-Cul1-F-box) E3 ubiquitin ligase complex, regulates multiple different signaling pathways. However, the effects of FBXW11 on AD progression and the underlying mechanisms have not been studied. In this study, we found that FBXW11 expression was markedly increased in microglial cells stimulated by amyloid-β (Aβ). Immunofluorescence staining showed that FBXW11 was co-localized with Iba-1 in microglial cells, suggesting its potential in regulating neuroinflammation. Meanwhile, significantly elevated expression of FBXW11 was detected in hippocampus of AD mouse models. Then, our in vitro studies showed that FBXW11 deletion considerably ameliorated inflammatory response in Aβ-incubated microglial cells through suppressing nuclear transcription factor κB (NF-κB) signaling. We further found that FBXW11 physically interacted with apoptosis signal-regulating kinase 1 (ASK1) and promoted its ubiquitination, which led to the aberrant activation of NF-κB and mitogen-activated protein kinase (MAPK) signaling pathways. Importantly, promoting ASK1 significantly abolished the effects of FBXW11 knockdown to repress inflammation and MAPKs/NF-κB activation in Aβ-treated microglial cells. Subsequently, our in vivo experiments demonstrated that hippocampus-specific knockout of FBXW11 dramatically alleviated Aβ plaque load, neuronal death, and microglial activation in AD mice. Furthermore, hippocampal deficiency of FBXW11 markedly mitigated neuroinflammation in AD mice through restraining ASK1/MAPKs/NF-κB signaling, along with alleviated cognitive deficits. Together, our findings demonstrated that FBXW11 may be a functionally important mediator of ASK1 activation, which could be a novel molecular target for AD treatment.

Linalool Alleviates Aβ42-Induced Neurodegeneration via Suppressing ROS Production and Inflammation in Fly and Rat Models of Alzheimer's Disease

Terpenes are vital metabolites found in various plants and animals and known to be beneficial in the treatment of various diseases. Previously, our group identified terpenes that increased the survival of Alzheimer's disease (AD) model flies expressing human amyloid β (Aβ) and identified linalool as a neuroprotective terpene against Aβ toxicity. Linalool is a monoterpene that is commonly present as a constituent in essential oils from aromatic plants and is known to have anti-inflammatory, anticancer, antihyperlipidemia, antibacterial, and neuroprotective properties. Although several studies have shown the beneficial effect of linalool in AD animal models, the mechanisms underlying the beneficial effect of linalool on AD are yet to be elucidated. In the present study, we showed that linalool intake increased the survival of the AD model flies during development in a dose-dependent manner, while the survival of wild-type flies was not affected even at high linalool concentrations. Linalool also decreases Aβ-induced apoptosis in eye discs as well as the larval brain. Moreover, linalool intake was found to reduce neurodegeneration in the brain of adult AD model flies. However, linalool did not affect the total amount of Aβ42 protein or Aβ42 aggregation. Rather, linalool decreased Aβ-induced ROS levels, oxidative stress, and inflammatory response in the brains of AD model flies. Furthermore, linalool attenuated the induction of oxidative stress and gliosis by Aβ_1-42 treatment in the rat hippocampus. Taken together, our data suggest that linalool exerts its beneficial effects on AD by reducing Aβ42-induced oxidative stress and inflammatory reactions.

PERK Pathway and Neurodegenerative Disease: To Inhibit or to Activate?

With the extension of life span in recent decades, there is an increasing burden of late-onset neurodegenerative diseases, for which effective treatments are lacking. Neurodegenerative diseases include the widespread Alzheimer’s disease (AD) and Parkinson’s disease (PD), the less frequent Huntington’s disease (HD) and Amyotrophic Lateral Sclerosis (ALS) and also rare early-onset diseases linked to mutations that cause protein aggregation or loss of function in genes that maintain protein homeostasis. The difficulties in applying gene therapy approaches to tackle these diseases is drawing increasing attention to strategies that aim to inhibit cellular toxicity and restore homeostasis by intervening in cellular pathways. These include the unfolded protein response (UPR), activated in response to endoplasmic reticulum (ER) stress, a cellular affliction that is shared by these diseases. Special focus is turned to the PKR-like ER kinase (PERK) pathway of the UPR as a target for intervention. However, the complexity of the pathway and its ability to promote cell survival or death, depending on ER stress resolution, has led to some confusion in conflicting studies. Both inhibition and activation of the PERK pathway have been reported to be beneficial in disease models, although there are also some reports where they are counterproductive. Although with the current knowledge a definitive answer cannot be given on whether it is better to activate or to inhibit the pathway, the most encouraging strategies appear to rely on boosting some steps without compromising downstream recovery.

Aspirin eugenol ester ameliorates paraquat-induced oxidative damage through ROS/p38-MAPK-mediated mitochondrial apoptosis pathway

Paraquat (PQ) is an effective and commercially important herbicide that is widely used worldwide. However, PQ is highly toxic and can cause various complications and acute organ damage. Aspirin eugenol ester (AEE) is a potential new compound with anti-inflammatory and antioxidant stress pharmacological activity. The present study was to reveal the therapeutic effects and the protective effect of AEE against PQ-induced acute lung injury (ALI) with the help of PQ-induced oxidative damage in A549 cells and PQ-induced lung injury in rats. AEE might have no significant therapeutic effect on PQ-induced lung injury in rats. However, AEE had a significant protective effect on PQ-induced lung injury in rats. AEE pretreatment significantly reduced the stimulatory effect of PQ on malondialdehyde (MDA), the inhibitory effect of PQ on catalase (CAT) activity, superoxide dismutase (SOD) activity, glutathione peroxidase (GPx) activity, the ratio of GSH/GSSH, the activity of caspase-3 and the overexpression of p38 mitogen-activated protein kinase (MAPK) phosphorylation in vivo. In vitro, A549 cells were treated with 250 μM PQ for 24 h. Incubation of A549 cells with PQ led to apoptosis, and increased the level of superoxide anions, reactive oxygen species (ROS), malondialdehyde and the activity of caspase-3 and up-regulation of phosphorylated p38-MAPK, reduced mitochondrial membrane potential (ΔΨm) and the activity of SOD. However, after 24 h on AEE pretreatment of A549 cells, the above-mentioned adverse reactions caused by PQ were significantly alleviated. In addition, AEE pretreatment reduced p38-MAPK phosphorylation in PQ-treated A549 cells. SB203580, the specific p38-MAPK inhibitor, and p38-MAPK shRNA attenuated the activation of the p38-MAPK signaling pathway. N-acetylcysteine (NAC) reduced the level of phosphorylated p38-MAPK and the production of intracellular ROS and inhibited apoptosis. The results showed that AEE may inhibit PQ-induced cell damage through ROS/p38-MAPK-mediated mitochondrial apoptosis pathway.

Platycodon grandiflorum Root Protects against Aβ-Induced Cognitive Dysfunction and Pathology in Female Models of Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by irreversible cognitive dysfunction. Amyloid beta (Aβ) peptide is an important pathological factor that triggers the progression of AD through accumulation and aggregation, which leads to AD-related pathologies that consequently affect cognitive functions. Interestingly, several studies have reported that Platycodon grandiflorum root extract (PGE), besides exhibiting other bioactive effects, displays neuroprotective, anti-neuroinflammatory, and cognitive-enhancing effects. However, to date, it is not clear whether PGE can affect AD-related cognitive dysfunction and pathogenesis. Therefore, to investigate whether PGE influences cognitive impairment in an animal model of AD, we conducted a Y-maze test using a 5XFAD mouse model. Oral administration of PGE for 3 weeks at a daily dose of 100 mg/kg significantly ameliorated cognitive impairment in 5XFAD mice. Moreover, to elucidate the neurohistological mechanisms underlying the PGE-mediated alleviative effect on cognitive dysfunction, we performed histological analysis of hippocampal formation in these mice. Histopathological analysis showed that PGE significantly alleviated AD-related pathologies such as Aβ accumulation, neurodegeneration, oxidative stress, and neuroinflammation. In addition, we observed a neuroprotective and antioxidant effect of PGE in mouse hippocampal neurons. Our findings suggest that administration of PGE might act as one of the therapeutic agents for AD by decreasing Aβ related pathology and ameliorating Aβ induced cognitive impairment.

The Heart of the Alzheimer's: A Mindful View of Heart Disease

Purpose of Review: This review summarizes the current evidence for the involvement of proteotoxicity and protein quality control systems defects in diseases of the central nervous and cardiovascular systems. Specifically, it presents the commonalities between the pathophysiology of protein misfolding diseases in the heart and the brain. Recent Findings: The involvement of protein homeostasis dysfunction has been for long time investigated and accepted as one of the leading pathophysiological causes of neurodegenerative diseases. In cardiovascular diseases instead the mechanistic focus had been on the primary role of Ca2+ dishomeostasis, myofilament dysfunction as well as extracellular fibrosis, whereas no attention was given to misfolding of proteins as a pathogenetic mechanism. Instead, in the recent years, several contributions have shown protein aggregates in failing hearts similar to the ones found in the brain and increasing evidence have highlighted the crucial importance that proteotoxicity exerts via pre-amyloidogenic species in cardiovascular diseases as well as the prominent role of the cellular response to misfolded protein accumulation. As a result, proteotoxicity, unfolding protein response (UPR), and ubiquitin-proteasome system (UPS) have recently been investigated as potential key pathogenic pathways and therapeutic targets for heart disease. Summary: Overall, the current knowledge summarized in this review describes how the misfolding process in the brain parallels in the heart. Understanding the folding and unfolding mechanisms involved early through studies in the heart will provide new knowledge for neurodegenerative proteinopathies and may prepare the stage for targeted and personalized interventions.

Aspirin Eugenol Ester Protects Vascular Endothelium From Oxidative Injury by the Apoptosis Signal Regulating Kinase-1 Pathway

Aspirin eugenol ester (AEE) is a new potential pharmaceutical compound possessing anti-inflammatory, anti-cardiovascular disease, and antioxidative stress activity. The pharmacological activities of AEE are partly dependent on its regulation of cell apoptosis. However, it is still unclear how AEE inhibits cell apoptosis on the basis of its antioxidative stress effect. This study aimed to reveal the vascular antioxidative mechanism of AEE in response to H₂O₂-induced oxidative stress in HUVECs and paraquat-induced oxidative stress in rats. In the different intervention groups of HUVECs and rats, the expression of ASK1, ERK1/2, SAPK/JNK, and p38 and the phosphorylation levels of ERK1/2, SAPK/JNK, and p38 were measured. The effects of ASK1 and ERK1/2 on the anti-apoptotic activity of AEE in the oxidative stress model were probed using the corresponding inhibitors ASK1 and ERK1/2. The results showed that in the HUVECs, 200 μM H₂O₂ treatment significantly increased the phosphorylation of SAPK/JNK and the level of ASK1 but decreased the phosphorylation of ERK1/2, while in the HUVECs pretreated with AEE, the H₂O₂-induced changes were significantly ameliorated. The findings were observed in vitro and in vivo. Moreover, inhibition of ASK1 and ERK1/2 showed that ASK1 plays a vital role in the protective effect of AEE on H₂O₂-induced apoptosis. All findings suggested that AEE protects the vascular endothelium from oxidative injury by mediating the ASK1 pathway.

TNFAIP1 Is Upregulated in APP/PS1 Mice and Promotes Apoptosis in SH-SY5Y Cells by Binding to RhoB

Alzheimer's disease (AD) poses a significant threat to human life and health. The intraneuronal accumulation of β-amyloid (Aβ) plaques in the brains of AD patients results in neuronal cell death, which is a key factor that triggers multiple changes in the pathogenesis of AD. The inhibition of Aβ-induced neuronal cell death may potentially help in the intervention and treatment of AD. Our previous study reported that tumor necrosis factor α-induced protein 1 (TNFAIP1) is induced by and promotes Aβ_25-35-induced neurotoxicity in mouse neuronal cells, but the roles and regulatory mechanisms of TNFAIP1 are still largely unknown. In this study, our experimental results show that TNFAIP1 and p-TNFAIP1 (phosphorylation of TNFAIP1 at Ser280) are overexpressed in the neurons of the cortex and hippocampus in the brains of APP/PS1 mice, and the transcription factor NF-κB is involved in the Aβ-induced upregulation of TNFAIP1. Moreover, our results suggest that TNFAIP1 contributes to the Aβ-induced reactive oxygen species (ROS) production, decreased mitochondrial membrane potential (∆Ψm), and neuronal cell death in human SH-SY5Y cells. We further revealed that Aβ increases the binding of TNFAIP1 to RhoB, and knockdown of RhoB attenuates the TNFAIP1-induced apoptosis of human SH-SY5Y cells. These data suggest that TNFAIP1 is closely associated with AD pathogenesis, and overexpression of TNFAIP1 in the neurons of the brains of AD patients plays a role in apoptosis, at least in part, via RhoB signaling.

Neuroprotective Effects of Baicalein, Wogonin, and Oroxylin A on Amyloid Beta-Induced Toxicity via NF-κB/MAPK Pathway Modulation

Amyloid beta (Aβ) peptide, one of the most important pathogenic traits of Alzheimer’s disease (AD), invokes a cascade of oxidative damage and eventually leads to neuronal death. In the present study, baicalein, wogonin, and oroxylin A, main active flavones in Scutellaria baicalensis, were evaluated for their neuroprotective effects against Aβ_25–35-stimulated damage. All tested compounds decreased Aβ_25–35-induced ROS generation and cell cycle arrest. In particular, baicalein exhibited the strongest antioxidant activity. In addition, these compounds suppressed apoptosis by attenuating mitochondrial dysfunction such as loss of membrane potential, Ca²⁺ accumulation and Bax/Bcl-2 ratio. Furthermore, all tested flavones inhibited the expression of iNOS and COX-2, which resulted in suppressing inflammatory cytokines including TNF-α, NO, and PGE₂. Noticeably, all compounds exhibited the anti-inflammatory effects through downregulating NF-κB/MAPK pathway. Especially, oroxylin A was effective against both p65 and IκBα, while wogonin and baicalein were suppressed phospho-p65 and phospho-IκBα, respectively. Taken together, baicalein, wogonin, and oroxylin A can effectively relieve Aβ_25–35-stimulated neuronal apoptosis and inflammation in PC12 cells via downregulating NF-κB/MAPK signaling pathway.

Are Heat Shock Proteins an Important Link between Type 2 Diabetes and Alzheimer Disease?

Type 2 diabetes (T2D) and Alzheimer’s disease (AD) are growing in prevalence worldwide. The development of T2D increases the risk of AD disease, while AD patients can show glucose imbalance due to an increased insulin resistance. T2D and AD share similar pathological features and underlying mechanisms, including the deposition of amyloidogenic peptides in pancreatic islets (i.e., islet amyloid polypeptide; IAPP) and brain (β-Amyloid; Aβ). Both IAPP and Aβ can undergo misfolding and aggregation and accumulate in the extracellular space of their respective tissues of origin. As a main response to protein misfolding, there is evidence of the role of heat shock proteins (HSPs) in moderating T2D and AD. HSPs play a pivotal role in cell homeostasis by providing cytoprotection during acute and chronic metabolic stresses. In T2D and AD, intracellular HSP (iHSP) levels are reduced, potentially due to the ability of the cell to export HSPs to the extracellular space (eHSP). The increase in eHSPs can contribute to oxidative damage and is associated with various pro-inflammatory pathways in T2D and AD. Here, we review the role of HSP in moderating T2D and AD, as well as propose that these chaperone proteins are an important link in the relationship between T2D and AD.

SQSTM1/ p62 oligomerization contributes to Aβ-induced inhibition of Nrf2 signaling

SQSTM1/p62, also known as sequestosome 1 (SQSTM1) or p62, is an intracellular protein induced by stress and functions as an adaptor molecule in diverse cellular processes. Oxidative damage induced by overproduction of amyloid-β (Aβ) and the impairment of endogenous antioxidant Nrf2 signaling have been documented in the brains of Alzheimer's disease (AD) patients. The causes of the inactivation of Nrf2 signaling under Aβ-induced oxidative stress are unclear, and p62 might be involved in this process. In this study, APP/PS1 transgenic mice, Aβ intrahippocampal injection rat model, and SH-SY5Y cells were used to reveal that the alterations in the oligomeric state of p62 participated in the regulation of Nrf2 signaling under Aβ insult. The present in vivo and in vitro studies revealed that short-term treatment of Aβ activated Nrf2 signaling, while long-term Aβ treatment inhibited it through either canonical or noncanonical Nrf2 activation pathway. p62 oligomerization was largely attenuated under long-term Aβ treatment. The reduction of p62 oligomerization weakened p62 sequestration to Keap1, leading to Nrf2 signaling inhibition. Our findings provide a better understanding of p62-mediated modulation on Nrf2 activity and highlight a potential therapeutic target of p62 in AD.

Axonal Degeneration in AD: The Contribution of Aβ and Tau

Alzheimer's disease (AD) represents the most common age-related neurodegenerative disorder, affecting around 35 million people worldwide. Despite enormous efforts dedicated to AD research over decades, there is still no cure for the disease. Misfolding and accumulation of Aβ and tau proteins in the brain constitute a defining signature of AD neuropathology, and mounting evidence has documented a link between aggregation of these proteins and neuronal dysfunction. In this context, progressive axonal degeneration has been associated with early stages of AD and linked to Aβ and tau accumulation. As the axonal degeneration mechanism has been starting to be unveiled, it constitutes a promising target for neuroprotection in AD. A comprehensive understanding of the mechanism of axonal destruction in neurodegenerative conditions is therefore critical for the development of new therapies aimed to prevent axonal loss before irreversible neuronal death occurs in AD. Here, we review current evidence of the involvement of Aβ and tau pathologies in the activation of signaling cascades that can promote axonal demise.

Surface Charge-Dependent Cytotoxicity of Plastic Nanoparticles in Alveolar Cells under Cyclic Stretches

Polystyrene nanoparticles (PS-NPs) derived from both environmental and occupational sources are an important class of ultrafine particles associated with human pulmonary disorders. The effects of surface charges of particle internalization and toxicity to alveolar cells, especially under conditions comparable to those found during breathing, have not been examined. Here, we applied cyclic stretches (CS) to human alveolar cells during nanoparticle exposure and show an enhanced accumulation of positively charged polystyrene nanoparticles as compared to similar negatively charged particles. The cellular uptake of the positive particles into live cells was visualized with three-dimensional optical diffraction tomography (3-D ODT). The simultaneous application of both periodic stretching as well as positively charged nanoparticles led to blebbing morphology and activation of apoptotic signaling compared to control cells. Our findings provide a better understanding of how surface charge mediates the uptake and toxicity of nanoplastics under the dynamical mechanical conditions relevant for breathing exposures.

A Cationic Gallium Phthalocyanine Inhibits Amyloid β Peptide Fibril Formation

BACKGROUND

Amyloid β (Aβ) peptide deposition is considered as the main cause of Alzheimer's disease (AD). Previously, we have shown that a Zn containing neutral phthalocyanine (Zn-Pc) inhibits Aβ fibril formation.

OBJECTIVE

The objective of this study is to investigate the effects of a cationic gallium containing Pc (GaCl-Pc) on Aβ fibril formation process.

METHODS AND RESULT

Aβ fibril formation was induced by incubating synthetic Aβ peptides in a fibril forming buffer, and the amount of fibril was evaluated by ThT fluorescence assay. GaCl-Pc dosedependently inhibited both Aβ1-40 and Aβ1-42 fibril formation. It mainly inhibited the elongation phase of Aβ1-42 fibril formation kinetics, but not the lag phase. Western blotting results showed that it did not inhibit its oligomerization process, rather increased it. Additionally, GaCl-Pc destabilized preformed Aβ1- 42 fibrils dose-dependently in vitro condition, and decreased Aβ levels in the brain slice culture of APP transgenic AD model mice (J20 strain). Near-infrared scanning results showed that GaCl-Pc had the ability to bind to Aβ1-42. MTT assay demonstrated that GaCl-Pc did not have toxicity towards a neuronal cell line (A1) in culture rather, showed protective effects on Aβ-induced toxicity. Moreover, it dosedependently decreased Aβ-induced reactive oxygen species levels in A1 culture.

CONCLUSION

Thus, our result demonstrated that GaCl-Pc decreased Aβ aggregation and destabilized the preformed fibrils. Since cationic molecules show a better ability to cross the blood-brain barrier, cationic GaCl-Pc could be important for the therapy of AD.

Single and combined effects of carbamazepine and copper on nervous and antioxidant systems of zebrafish (Danio rerio)

Various pollutants co-exist in the aquatic environment such as carbamazepine (CBZ) and copper (Cu), which can cause complex effects on inhabiting organisms. The toxic impacts of the single substance have been studied extensively. However, the studies about their combined adverse impacts are not enough. In the present study, zebrafish were exposed to environmental relevant concentrations of CBZ (1, 10, and 100 μg/L), Cu (0.5, 5, and 10 μg/L) and the mixtures (1 μg/L CBZ + 0.5 μg/L Cu, 10 μg/L CBZ + 5 μg/L Cu, 100 μg/L CBZ + 10 μg/L Cu) for 45 days, the effects on nervous and antioxidant systems of zebrafish were investigated. The results demonstrated that, in comparison with single exposure group, the combined presence of CBZ and Cu exacerbated the effect of antioxidant system (the ability of inhibition of hydroxyl radicals (IHR), superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST)) but not nervous system (Acetylcholinesterase [AChE]). The qPCR results supported the changes of corresponding enzymes activities. Hepatic histopathological analysis verified the results of biomarkers. Our work illustrated that the toxicity of mixed pollutants is very complicated, which cannot simply be inferred from the toxicity of single pollutant, and calls for more co-exposure experiments to better understanding of the co-effects of pollutants on aquatic organisms.

Seeding and Growth of β-Amyloid Aggregates upon Interaction with Neuronal Cell Membranes

In recent years, the prevalence of amyloid neurodegenerative diseases such as Alzheimer's disease (AD) has significantly increased in developed countries due to increased life expectancy. This amyloid disease is characterized by the presence of accumulations and deposits of β-amyloid peptide (Aβ) in neuronal tissue, leading to the formation of oligomers, fibers, and plaques. First, oligomeric intermediates that arise during the aggregation process are currently thought to be primarily responsible for cytotoxicity in cells. This work aims to provide further insights into the mechanisms of cytotoxicity by studying the interaction of Aβ aggregates with Neuro-2a (N2a) neuronal cells and the effects caused by this interaction. For this purpose, we have exploited the advantages of advanced, multidimensional fluorescence microscopy techniques to determine whether different types of Aβ are involved in higher rates of cellular toxicity, and we measured the cellular stress caused by such aggregates by using a fluorogenic intracellular biothiol sensor. Stress provoked by the peptide is evident by N2a cells generating high levels of biothiols as a defense mechanism. In our study, we demonstrate that Aβ aggregates act as seeds for aggregate growth upon interacting with the cellular membrane, which results in cell permeability and damage and induces lysis. In parallel, these damaged cells undergo a significant increase in intracellular biothiol levels.

Cell death and survival pathways in Alzheimer's disease: an integrative hypothesis testing approach utilizing -omic data sets

Whether a cell lives or dies is controlled by an array of intercepting and dynamic molecular pathways. Although there is evidence of neuronal loss in Alzheimer's disease (AD) and multiple programmed cell death (PCD) pathways have been implicated in this process, there has been no comprehensive evaluation of the dominant pathway responsible for cell death in AD. Likewise, the relative dominance of survival and PCD pathways in AD remains unclear. Here, we present the results of hypothesis-driven bioinformatic analysis of PCD and survival pathway activation in paired methylation and expression data from the middle temporal gyrus (MTG) as well as expression from laser-captured cells from the MTG and hippocampus. The results not only indicate activation of cell death pathways in AD-of which apoptosis is responsible for the largest fraction of upregulated genes-but also of cell survival pathways. These results are indicative of a complex balance between survival and death pathways in AD that future studies should work to delineate at a single cell level.

Senescence as an Amyloid Cascade: The Amyloid Senescence Hypothesis

Due to their postmitotic status, the potential for neurons to undergo senescence has historically received little attention. This lack of attention has extended to some non-postmitotic cells as well. Recently, the study of senescence within the central nervous system (CNS) has begun to emerge as a new etiological framework for neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). The presence of senescent cells is known to be deleterious to non-senescent neighboring cells via development of a senescence-associated secretory phenotype (SASP) which includes the release of inflammatory, oxidative, mitogenic, and matrix-degrading factors. Senescence and the SASP have recently been hailed as an alternative to the amyloid cascade hypothesis and the selective killing of senescence cells by senolytic drugs as a substitute for amyloid beta (Aß) targeting antibodies. Here we call for caution in rejecting the amyloid cascade hypothesis and to the dismissal of Aß antibody intervention at least in early disease stages, as Aß oligomers (AßO), and cellular senescence may be inextricably linked. We will review literature that portrays AßO as a stressor capable of inducing senescence. We will discuss research on the potential role of secondary senescence, a process by which senescent cells induce senescence in neighboring cells, in disease progression. Once this seed of senescent cells is present, the elimination of senescence-inducing stressors like Aß would likely be ineffective in abrogating the spread of senescence. This has potential implications for when and why AßO clearance may or may not be effective as a therapeutic for AD. The selective killing of senescent cells by the immune system via immune surveillance naturally curtails the SASP and secondary senescence outside the CNS. Immune privilege restricts the access of peripheral immune cells to the brain parenchyma, making the brain a safe harbor for the spread of senescence and the SASP. However, an increasingly leaky blood brain barrier (BBB) compromises immune privilege in aging AD patients, potentially enabling immune infiltration that could have detrimental consequences in later AD stages. Rather than an alternative etiology, senescence itself may constitute an essential component of the cascade in the amyloid cascade hypothesis.

Discovery and development of ASK1 inhibitors

Aberrant activation of mitogen-activated protein kinases (MAPKs) like c-Jun N-terminal kinase (JNK) and p38 is an event involved in the pathophysiology of numerous human diseases. The apoptosis signal-regulating kinase 1 (ASK1) is an upstream target that gets activated only under pathological conditions and as such is a promising target for therapeutic intervention. In the first part of this review the molecular mechanisms leading to ASK1 activation and regulation will be described as well as the evidences supporting a pathogenic role for ASK1 in human disease. In the second part, an update on drug discovery efforts towards the discovery and development of ASK1-targeting therapies will be provided.

Redundant role of ASK1-mediated p38MAPK activation in human platelet function

Apoptosis signal-regulating kinase 1 (ASK1) is a member of mitogen-activated protein kinase kinase kinase (MAP3K) family, which recently has been implicated in the regulation of p38 MAPK/PLA2/thromboxane (TxA2) generation, as well as P2Y12 signalling in murine platelets. ASK1 has therefore been proposed as a potential target for anti-thrombotic therapy. At present it is unknown whether ASK1 also contributes to TxA2 formation and platelet function in human. In this study we therefore examined the role of ASK1 using the ASK1 inhibitor selonsertib (GS-4997). We established that ASK1 is responsible for p38 phosphorylation and TxA2 formation in murine platelets, with both GS4997 and p38 inhibitors reducing TxA2 formation. Similar to murine platelets, activation of human platelets resulted in the rapid and transient phosphorylation of ASK1 and the MAP2Ks MMK3/4/6. In contrast, phosphorylation of p38 and its substrate; MAPKAP-kinase2 (MAPKAPK2) was much more sustained. In keeping with these findings, inhibition of ASK1 blocked early, but not later p38/MAPKAPK2 phosphorylation. The latter was dependent on non-canonical autophosphorylation as it was blocked by the p38 inhibitor; SB203580 and the SYK inhibitor; R406. Furthermore, ASK1 and p38 inhibitors had no effect on PLA2 phosphorylation, TxA2 formation and platelet aggregation, demonstrating that this pathway is redundant in human platelets. Together, these results demonstrate that ASK1 contributes to TxA2 formation in murine, but not human platelets and highlight the importance of confirming findings from genetic murine models in humans.

Elucidating Critical Proteinopathic Mechanisms and Potential Drug Targets in Neurodegeneration

Neurodegeneration entails progressive loss of neuronal structure as well as function leading to cognitive failure, apathy, anxiety, irregular body movements, mood swing and ageing. Proteomic dysregulation is considered the key factor for neurodegeneration. Mechanisms involving deregulated processing of proteins such as amyloid beta (Aβ) oligomerization; tau hyperphosphorylation, prion misfolding; α-synuclein accumulation/lewy body formation, chaperone deregulation, acetylcholine depletion, adenosine 2A (A2A) receptor hyperactivation, secretase deregulation, leucine-rich repeat kinase 2 (LRRK2) mutation and mitochondrial proteinopathies have deeper implications in neurodegenerative disorders. Better understanding of such pathological mechanisms is pivotal for exploring crucial drug targets. Herein, we provide a comprehensive outlook about the diverse proteomic irregularities in Alzheimer's, Parkinson's and Creutzfeldt Jakob disease (CJD). We explicate the role of key neuroproteomic drug targets notably Aβ, tau, alpha synuclein, prions, secretases, acetylcholinesterase (AchE), LRRK2, molecular chaperones, A2A receptors, muscarinic acetylcholine receptors (mAchR), N-methyl-D-aspartate receptor (NMDAR), glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) and mitochondrial/oxidative stress-related proteins for combating neurodegeneration and associated cognitive and motor impairment. Cross talk between amyloidopathy, synucleinopathy, tauopathy and several other proteinopathies pinpoints the need to develop safe therapeutics with ability to strike multiple targets in the aetiology of the neurodegenerative disorders. Therapeutics like microtubule stabilisers, chaperones, kinase inhibitors, anti-aggregation agents and antibodies could serve promising regimens for treating neurodegeneration. However, drugs should be target specific, safe and able to penetrate blood-brain barrier.

ASK1 inhibition: a therapeutic strategy with multi-system benefits

p38 mitogen-activated protein kinases (P38α and β) and c-Jun N-terminal kinases (JNK1, 2, and 3) are key mediators of the cellular stress response. However, prolonged P38 and JNK signalling is associated with damaging inflammatory responses, reactive oxygen species-induced cell death, and fibrosis in multiple tissues, such as the kidney, liver, central nervous system, and cardiopulmonary systems. These responses are associated with many human diseases, including arthritis, dementia, and multiple organ dysfunctions. Attempts to prevent P38- and JNK-mediated disease using small molecule inhibitors of P38 or JNK have generally been unsuccessful. However, apoptosis signal-regulating kinase 1 (ASK1), an upstream regulator of P38 and JNK, has emerged as an alternative drug target for limiting P38- and JNK-mediated disease. Within this review, we compile the evidence that ASK1 mediates damaging cellular responses via prolonged P38 or JNK activation. We discuss the potential benefits of ASK1 inhibition as a therapeutic and summarise the studies that have tested the effects of ASK1 inhibition in cell and animal disease models, in addition to human clinical trials for a variety of disorders.

Chinese medicine Di-Huang-Yi-Zhi protects PC12 cells from H2O2-induced apoptosis by regulating ROS-ASK1-JNK/p38 MAPK signaling

Background

Oxidative stress mediates the nerve injury during the pathogenesis of Alzheimer’s disease (AD). Protecting against oxidative stress damage is an important strategy to prevent and treat AD. Di-Huang-Yi-Zhi (DHYZ) is a Chinese medicine used for the treatment of AD, but its mechanism remains unknown. This study is aimed to investigate the effect of DHYZ on H₂O₂ induced oxidative damage in PC12 cells.

Methods

PC12 cells were treated with H₂O₂ and DHYZ. Cell proliferation was detected by Cell counting kit-8 (CCK-8) assay. Cytotoxicity of H₂O₂ was measured by lactate dehydrogenase (LDH) release assay. Apoptosis were identified by Annexin V-FITC/PI staining. Caspase 3 activity was detected by commercial kit. Mitochondrial membrane potential (MMP) was detected by JC-1 staining. Reactive oxygen species (ROS) was 2′, 7′-Dichlorodihydrofluorescein diacetate (DCFH-DA) staining. Protein expression and phosphorylation was identified by western blot.

Results

The results showed that DHYZ antagonized H₂O₂-mediated cytotoxicity and proliferation inhibition. DHYZ reduced ROS production, stabilize mitochondrial membrane potential, inhibit Caspase-3 activity and apoptosis induced by H₂O₂. In addition, DHYZ inhibited the phosphorylation of ASK1, JNK1/2/3 and p38 MAPK which were up-regulated by H₂O₂.

Conclusions

The present study suggested that DHYZ protected PC12 cells from H₂O₂-induced oxidative stress damage and was related to inhibition of ROS production and ASK1-JNK/p38 MAPK signaling. The present study provides experimental evidence for the application of DHYZ for the management of oxidative stress damage and AD.

Polystyrene Nanoparticles Reduced ROS and Inhibited Ferroptosis by Triggering Lysosome Stress and TFEB Nucleus Translocation in a Size-Dependent Manner

Though plastic nanoparticles have already raised much concern for their potential impact on health, our understanding of their biological effects is still utterly limited. Here we demonstrate for the first time that carboxyl-modified polystyrene nanoparticles (CPS) could effectively inhibit ferroptosis as a result of reduced cellular ROS which was triggered by transcription factor EB (TFEB) nucleus translocation. In this process, CPS first entered cells via macropinocytosis, then CPS-containing macropinosomes fused with lysosomes and expanded into abnormal lysosome-like large vacuoles in vacuolar-type H⁺-ATPase (V-ATPase) and aquaporins (AQPs) in a dependent way. These large vacuoles were detected both in vitro and in vivo, which was found to be a sign of lysosome stress. The lysosome stress induced deactivation of mammalian target of rapamycin (mTOR) which led to nucleus translocation of TFEB. Then, TFEB-dependent enhanced expression of lysosomal proteins and superoxide dismutase (SOD) which ultimately led to ROS reduction and inhibition of ferroptosis. Knockout of TFEB-enhanced ferroptosis was triggered by Erastin and abolished the effect of CPS on ROS and ferroptosis. In summary, our results reveal a novel mechanism whereby CPS reduced ROS and inhibited ferroptosis in a TFEB-dependent way. These findings have important implications for understanding the biological effects of polystyrene nanoparticles and searching for new anti-ROS and antiferroptosis particles or reagents.